Site Assessment and Remediation Handbook, Second Edition

Lake and Pond Management Guidebook

Lake and Pond Management Guidebook

LEWIS PUBLISHERS A CRC Press Company Boca Raton London New York Washington, D.C.

Cover image courtesy of Dr. Ramesh Venkatakrishnan and Waste Management Inc.

Library of Congress Cataloging-in-Publication Data Sara, Martin N., 1946Site assessment and remediation handbook / Martin N. Sara. --[2nd ed.]. p. cm. Includes bibliographical references and index. ISBN 1-56670-577-0 (alk. paper) 1. Groundwater--Sampling. 2. Groundwater flow--Measurement. 3. Hazardous waste. Treatment facilities--Evaluation. 4. Refuse disposal facilities--Evaluation. I. Title. GB1001.72.S3S27 2003 628.1'68-dc21

2002043473

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Visit the CRC Press Web site at www.crcpress.com © 2003 by Chapman & Hall/CRC CRC Press LLC St. Lucie Press Lewis Publishers Auerbach is an imprint of CRC Press LLC No claim to original U.S. Government works International Standard Book Number 0-56670-577-0 Library of Congress Card Number 2002043473 Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 Printed on acid-free paper

for my teacher who left before his time, Richard O. Stone

to my parents Martin C. Sara and Nancy Sara,

and to Martin James, Nicole, Amy, Amanda and most of all Terrie

FOREWORD From my viewpoint, the highest order of devotion to duty in the professions is when a seasoned practitioner writes a useful book dealing with the true elements of professional practice. Marty Sara has already paid his dues to the profession in many ways, not the least of which was the First Edition of Standard Handbook for Solid & Hazardous Waste Assessment, 1993. Now Marty has produced a complete revision and renaming of his powerful 1993 tome. In order to appreciate the substance of this book, you need to know something about the author. Marty received degrees from two fine institutions (University of Illinois at Chicago and the University of Southern California). His grasp of geology is fine and he has honed that appreciation in 33 years of “hard” practice, every day of it in private sector firms facing and meeting real deadlines and issues representing financial imperatives to his clients. Martin Sara is the embodiment of the professional geologist and he manages to deport himself at the highest ethical standards in an increasingly difficult market buffeted by commoditization and bid-shopping for those professional services. Additionally, Marty has participated for many years in the deliberations of the American Society for Testing & Materials toward standardization of site characterization efforts. This latest book of guidance is a blend of Marty’s sense that some form of standardization is necessary for not only the protection of the consumer of geoenvironmental services and design, but that the increased difficulty of the practice calls for such so that qualified, competent practitioners survive to deliver these services. This book actually is Marty’s “third” edition, as it all began with his Site Assessment Manual (“SAM”) produced as an internal document for Waste Management, Inc. (WMI) in 1987. Marty had returned from 8 years’ duty in South Africa managing the Johannesburg office of Dames & Moore, premier international consultants, and found himself facing a considerable variance in the competence behind the body of consultant reports tendered to WMI. As WMI’s Chief Hydrogeologist, the buck stopped with Marty when it came to the quality of observations, findings, interpretations and predictions that could be made from those consultant reports. Marty was impressed by some of the work and frightened by the remainder. That year was 1985 and Marty resolved to gather and present a key to the proper conduct of site characterization. As he worked the problem of competence and presentation Marty became one of the national supporters of that theme and the concept of the “site conceptual geologic model.” This is not a “model” of mathematical fantasy; rather the graphic, three-dimensional representation of what has been observed and how it likely fits together in geologic reality. In the process of creating the model Marty counsels us to define and to search for what also “might be” expected based on geologic principles. In fact, I view Marty as the “father” of that Site Model movement, which has been strictly North American in character but which has been adopted as the state of the art worldwide. You will see here in the Second edition, a true menu for each of us to follow, irrespective of the depth and breadth of our own training. It is suitable for entry-level geologists and engineers (geological, geotechnical, environmental and general civil) alike. The geologists will learn the practical rationale that they likely were never taught. The engineers will have a masterful checklist to set out on their desks when they call for Site Assessments and they will have a direct comparative checklist on the quality and completeness of the tendered work product. In neither case do you find Marty telling you “what” to do at your site. Rather, his menu will guide your own geologic and engineering judgment toward the right pathway. Marty Sara is of the school that calls for direct geologic interaction with the ground; that is, careful planning before letting the exploration contract and careful collection, assessment, interpretation and evaluation of the data that come in from the field. Marty likes the graphic approach and he is a master at developing and pushing the limits of graphic presentation. He personally drew many of the illustrations and the writing is all his own. He has “been there” and “done that” and we can believe in what he has to say to us. The strength of this book stems from Marty’s personal experience and convictions and his ability to show you a graphic representation toward which you can apply your expertise to meet the unique site characterization situation before you.

In this book, and in countless other ways, Martin N. Sara has served his profession as well as the best interests of the environment. Allen W. Hatheway, HM, AEG Environmental Litigation & Forensics Consultant Rolla, Missouri & Big Arm, Montana Past-Chairman, Engineering Geology Div., Geol. Society of America (1980) Past-President, Association of Engineering Geologists (1985)

PREFACE This book is the result of many years of trying to evaluate the physical reality of ground-water flow in geologic materials. This text concentrates on practical aspects of hydrogeology and was designed as a working tool to be used to evaluate the heterogeneities of subsurface units. The key to understanding the conceptual basis of a particular geologic environment is building the geologic models from known regional systems and adding site facility knowledge to the regional picture. I have tried to build a conceptual basis for understanding geologic and hydrogeologic systems using traditional methods, some dating back over fifty years. These traditional evaluation methods provide a systematic basis for sorting out some very difficult field problems. Rather than taking a total cookbook approach, I have tried to keep professional insights as an integral part of the site assessment process. One should not lose sight that excessive drilling to evaluate a particular property should not be substituted for a knowledgeable, targeted, cost-effective evaluation. Experience in conducting site investigations in a specific geologic environment must always be an important consideration. Since assessment methods may be dramatically different, I have tried to provide illustrative guidance on the procedural aspects of site investigations for both primary and secondary porosity systems. Low hydraulic conductivity geologic environments provide special challenges to the investigative hydrogeologist. No hydrogeologic system provides so many problems (and has been so thoughly miss evaluated) as the low hydraulic conductivity geologic environment. This book provides a number of evaluation methods for these geologic materials that often represent important confining units for waste disposal facilities. The case examples used in the text are presented for illustrative purposes and the actual locations are generally irrelevant. As such I have removed locational references as much as possible and wish to focus only on the technical aspects of the presentations. These examples are presented as evidence that one can use these illustrations for working out the conceptual understanding of geologic environments. I have used, whenever possible, a form of structured graphics that I refer to as pictographics. These organization charts provide a systematic view of a particular group of evaluation methods, inter-method relationships and references are preserved within the pictographic.

ACKNOWLEDGMENTS The generation of a text such as this requires the efforts of many individuals who have provide both illustrative and textural materials for which I am indebted. Versions of the original Site Assessment Manual (SAM) and the first edition text Standard Handbook for Solid and Hazardous Waste Facility Assessments, which served as the root documents for this text, were reviewed by three of the most capable professionals I have ever had the pleasure to work with: Dr. Lee C. Atkinson, Professor Allen W. Hatheway and Dr. Travis H. Hughes. The first edition had a cover conceptual model artistic rendering by Dr. Ramesh Venkatakrishnan. The figure acknowledgment was unfortunately, with my sincere apologies, contained on an errata sheet. Dr. Venkatakrishnan remains one of the most skilled practitioners in incorporating both technical and artistic elements within geologic conceptual models. The continued support of the above professionals was critical to the concepts and guidance presented herein. The concepts presented in Chapter 11 relative to statistical evaluation of ground-water data are the product of the work of Professor Robert Gibbons; his contributions to the science of statistical evaluation of ground-water parameters have made detection monitoring possible for solid and hazardous waste disposal facilities. Special recognition is given to John Baker, who provided many insights into the detection and assessment monitoring methods presented in this text. Special recognition must also be given to the following individuals: Richard C. Benson, for the concepts associated with geophysics and scale relationships of site investigations; Michael R. Noel, for the conceptual process as applied to numerous geologic environments; Harry Morris, for the three-dimensional conceptual process as applied to detection monitoring; James F. Quinlan (now deceased), for Karst hydrogeology and monitoring; Frank Jarke, for text describing concepts of MCLs in Chapter 11; Richard C. F. King, for several pump testing discussions and especially for fractured-rock illustrative figures; John F. Clerici, for development of procedures for testing of confining units; Professor F. D. I. (Frank) Hodgson, for conceptual development of ground-water flow in fractured rock; David D. Slaine, for the many photographs in Chapter 3 that illustrate geophysical field applications; John E. Scaife, for illustrative presentations in Chapter 3 on GPR and reflection seismic techniques; Dave Burt, for the flow diagrams on Subtitle D and Jack Dowden, for fast-track Superfund investigative processes. Many consulting companies provided both their expertise and professional support in the example materials presented within the various sections. These contributions are referenced below the illustration or in the text describing the figure. Special recognition is given to the following organizations: Canonie Environmental, Dames & Moore, (now URS), Donohue (now Earthtech), Eckenfelder Inc., EMCON Associates (now URS), Gartner Lee, Golder Associates Inc., GZA GeoEnvironmental, Kerfoot and Associates, Meredith/Boli & Associates, Inc., multiVIEW Geoservices Inc., P. E. LaMoreaux & Associates, Patrick Engineering Inc., Simon Hydro-Search, Inc. and Solinst. The value of the text has been greatly increased by the contributions of the following individuals: Florin Gheorghiu, Lawrence E. Annen, David Nielsen, Les G. McMillion, Sam Brown, Phil Wagner, Louis Lindsay, Henry B. Kerfoot, Paul Sanborn, A. S. (Tony) Burgess, Donald J. Miller, Richard S. Williams, Dennis G. Fenn, Lome G. Everett, Charles O. Riggs, Robert V. Colangelo, Douglas R. Fraser, Dirk Kassenaar, John Luttinger, Pedro Fierro, Dennis Goldman, John V. A. Sharp, Mike D. Shotton, Russell H. Plumb, Jr., Joe D’Lugosz, Michael J. Mann, David Nielsen, David B. Kaminski, Bashir A. Memon, J. W. LaMoreaux, Lori C. Huntoon, Timothy D. Lynch, Ronald Schalla, George Gillespie, Vadat Batu and especially Jeff Shanks and Dan Kellerher. This work represents a particular perspective of site investigations and the individuals above are exempt from any responsibility for whatever omissions or errors may be present within this document. Source information credit has been provided, whenever a source was known. If omissions are present, they are unintentional and will be corrected in later printings. I would like readers to bring to my attention any such credits, where considered significant. Finally this book could not have been completed without the high technical goals set by Dave Burt and Chuck Williams as part of the Waste Management Inc. (WMX) extensive Environmental Monitoring Program. I would also like to thank Henry Goyette, Dave Edwards, Dick Brown and Andy Huggins for their support at Environmental Resource Management (ERM) during the preparation of this text.

LIST OF TABLES Table 1-1 Table 2-1 Table 2-2 Table 2-3 Table 2-4 Table 2-5 Table 2-6 Table 2-7 Table 2-8 Table 2-9 Table 2-10 Table 2-11 Table 2.12 Table 2-13 Table 2-14 Table 2-15 Table 3-1 Table 3-2 Table 3-3 Table 3-4 Table 3-5 Table 3-6 Table 3-7 Table 3-8 Table 3-9 Table 4-1 Table 4-2 Table 4-3 Table 4-4 Table 4-5 Table 4-6 Table 4-7 Table 4-8 Table 4-9 Table 4-11

Proportional Costs for Site Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Types of Phase I Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Phase I — Program Summaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Basic Data Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Topographic Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Geologic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 Geophysical Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Remote Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Hydrology Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 Climatic Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Phase I Basic Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 Greenfield Siting Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 Example Output from Map Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 Businesses that Signal Strong Potential for Phase II Recommendation . . . . . . . . . . . . . . . . . . . . . .67 Situations Likely to Drive Need for Phase II. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68 Sources of Information for Background Levels of Inorganics in Soils and Sediments. . . . . . . . . . .71 Phase II Work Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 General Lithological Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96 Phase Il Work Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 Summary of Geophysical Methods for Assessing Geologic and Hydrogeologic Conditions . . . . . .100 Summary of Geophysical Methods for Locating Buried Objects . . . . . . . . . . . . . . . . . . . . . . . . . . .101 Geophysical Methods for Delineating Residual and Floating Product . . . . . . . . . . . . . . . . . . . . . . .102 Depth Penetration EM-34-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 Example Well Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132 Comparison of U.S. Fault Criteria for Critical Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 Example Borehole Plan with Justification of Drilling and Piezometer Installation . . . . . . . . . . . . .152 Recommend Rational for Minimal Allocation of Borings for a Landfill Expansion . . . . . . . . . . . .153 Unified Soil Classification System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171 Facies Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172 Lithofacies and Sedimentary Structures of Low Sinuosity and Glaciofluvial Deposits . . . . . . . . . .173 Diagnostic Criteria for Recognition of Common Matrix-Supported Diamict Lithofacies . . . . . . . .176 Field Borehole Log Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180 Causes of Low RQD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190 Quality Control Guidelines for Determination of RQD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190 Piezometer Selection Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229

Table 4-12

Summary of Methods for Manual Measurement of Well Water Levels Nonflowing and Flowing Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240 Hydrogeologic Well Tests and Measurement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273 Estimates of Distances for Radius of Influences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275 Estimates of Specific Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .276

Table 5-1 Table 5-2 Table 5-3

Table 5-4 Table 5-5 Table 5-6 Table 5-7 Table 5-8 Table 5-9 Table 6-1 Table 6-2 Table 6-3 Table 6-4 Table 6-5 Table 6-6 Table 6-7 Table 7-1 Table 7-2 Table 7-3 Table 7-4 Table 9-1 Table 10-1 Table 10-2 Table 10-3a Table 10-3b Table 10-4a Table 10-4b Table 10-5 Table 10-6 Table 10-7 Table 10-8 Table 10-9 Table 10-10 Table 10-11 Table 10-12 Table 10-13 Table 10-14 Table 10-15a Table 10-15b Table 10-16 Table 10-17 Table 10-18 Table 11-1 Table 11-2

Predicted Drawdowns in Aquitard Piezometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283 Maximum Recommended Time Intervals for Aquifer Test Water Level Measurements . . . . . . . . .288 Typical Plasticity Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303 Soil Density Relationships. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .304 Representative Values of Dry Bulk Density, Total Porosity and Effective Porosity for Common Aquifer Matrix Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .315 Porosity, Residual Saturation and Effective Porosity of Common Soils . . . . . . . . . . . . . . . . . . . . . .316 Comparison of Granular-Dual Porosity and Discrete Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .330 General Fracture Key Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338 Piteau Roughness Categories (1971) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .342 Hardness Classification for Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343 Information Typically Recorded on Fractured Rock Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346 Downhole Measurement and Sampling Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355 Rock Parameters Obtainable from Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409 Components of a Phase II Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .433 Fluctuations in Ground Water Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .463 Values of Dry Bulk Density, Total Porosity and Effective Porosity for Common Aquifer Matrix Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .470 Aquifer Testing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .482 Conceptual Model of the Hydrogeologic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .663 Conceptual Components of Site Assessments for Remedial Projects . . . . . . . . . . . . . . . . . . . . . .699 Initial Complexity Issues in Remedial Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .704 Statistical Methods Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .719 Tests for Evaluating Normality of Datasets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .720 Primary Soil Characteristic for CERCLA Decision-Making Process . . . . . . . . . . . . . . . . . . . . . . . .726 Ancillary Soil Parameters for the CERCLA Decision-Making Process . . . . . . . . . . . . . . . . . . . . . .727 Ancillary Soil Parameters for the CERCLA Decision-Making Programs . . . . . . . . . . . . . . . . . . . .728 Examples of Regression Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .738 Parameters for Regression Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .739 Vapor Pressure and Henry’s Law Constant of Various Organic Compounds At 20°C . . . . . . . . . . .742 Summary of General Active Soil-Gas Sampling Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .743 Advantages and Limitations of Passive Soil-Gas Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .743 Advantages and Limitations of Active Soil-Gas Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .748 Applications for Active and Passive Soil-Gas Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .749 Concentrations of Inorganics in Surface Soils of the U.S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .752 Average Soil Contamination Inorganic Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .754 Site Data Can Indicate If DNAPLs Are Present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .763 DNAPL Organic Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .763 DNAPL Organic Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .766 Industrial Processes or Waste Disposal Practices with a High Probability of Historical DNAPL Releases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .767 Important Site / DNAPL Characteristics to Remember During a Site Investigation. . . . . . . . . . . . .768 Example Indicator Parameters for Sanitary Landfills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .799 A Complete Water Quality Parameter List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .800

Table 11-3 Table 11-4 Table 11-5 Table 11-6 Table 11-7 Table 11-8 Table 11-9 Table 11-10 Table 11-11 Table 11-12 Table 11-13 Table 11-14 Table 11-15 Table 11-16 Table 11-17 Table 11-18 Table 11-19 Table 11-20 Table 11-22 Table 12-1 Table 13-1 Table 13-2 Table 13-3 Table 13-4 Table 13-5 Table 13-6 Table 13-7

Laboratory Quality Assurance Program Plan Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .801 Examples of Laboratory and Cross-Contamination Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . .806 Application of Intervals to Regulatory Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .829 Factors (k) for Constructing Two-Sided and One-Sided Normal Tolerance Limits (x ± ks and x + ks) 5% Confidence that 95% of the Distribution is Covered. . . . . . . . . . . . . . . . . . .832 One-Sided 95% Poisson Prediction Limits for r Additional Samples Given Background Sample of Size n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .833 Values of t for Obtaining One-Sided 95% Poisson Prediction Limits for r Additional Samples Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . .834 Values of t for Obtaining One-Sided 95% Poisson Prediction Limits for r Additional Samples Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . .835 Factors for Obtaining Two-Sided 95% Prediction Limits for r Additional Samples Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .836 Factors for Obtaining Two-Sided 95% Prediction Limits for r Additional Samples Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .837 Factors for Obtaining Two-Sided 95% Prediction Limits for r Additional Sample Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .838 Method 624 Volatile Organic Compounds and Published Method Detection Limits . . . . . . . . . . . .844 One-Sided 95% Poisson Prediction Limits for r Additional Samples Given Background Sample of Size n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .845 Factors for Obtaining Two-Sided 95% Prediction Limits for r Additional Samples Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .846 Values of t for Obtaining One-Sided 95% Poisson Prediction Limits for r Additional Samples Given a Background Sample of Size n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .847 Probability That a Single Sample Will Be below the Maximum of n Background Measurements at Each of k Monitoring Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .849 Probability That at Least One Out of Two Samples Will Be below the Maximum of n Background Measurements at Each of k Monitoring Wells . . . . . . . . . . . . . . . .850 Probability That at Least One Out of Three Samples Will Be below the Maximum of n Background Measurements at Each of k Monitoring Wells . . . . . . . . . . . . . . . .851 Comparison of Exact and Approximate Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .852 Example Total Metal Confidence Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .870 QA Principles for Geologic Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .885 Factors to Consider in Evaluating General Applicability of MNA . . . . . . . . . . . . . . . . . . . . . . . . . .905 Degradation of Common Chlorinated Solvents under Aerobic and Anaerobic Conditions . . . . . . .908 Common Patterns of Chlorated Solvents in Ground Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .909 Data Collection Tiers for Evaluation and Implementation of Natural Attenuation . . . . . . . . . . . . . .912 Elements of the Long-Term Natural Attenuation Monitoring Plan . . . . . . . . . . . . . . . . . . . . . . . . . .918 Examples of Geochemical Indicators for Destruction of Common Organic Contaminants . . . . . . .919 Natural Attenuation Pathways for Inorganics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .920

LIST OF FIGURES Figure 1-1 Figure 1-2 Figure 1-3 Figure 1-4 Figure 1-5 Figure 1-6 Figure 1-7 Figure 1-8 Figure 1-9 Figure 1-10 Figure 1-11 Figure 2-1 Figure 2-2 Figure 2-3 Figure 2-4 Figure 2-5 Figure 2-6 Figure 2-7 Figure 2-8 Figure 2-9 Figure 2-10 Figure 2-11 Figure 2-12 Figure 2-13 Figure 2-14 Figure 2-15 Figure 2-16 Figure 2-17 Figure 2-18 Figure 2-19 Figure 2-20 Figure 3-1 Figure 3-2 Figure 3-3 Figure 3-4 Figure 3-5 Figure 3-6

Summary Ground-Water Monitoring Design Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Variations in Hydraulic Conductivity of Seven Orders of Magnitude Can Occur Within a Few Feet in Glacial Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Flow Chart from Kiersch (1958) That Defined the Procedure for Site Assessments Still Relevant Today. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Evolution of Site Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 Hvorslev's Site Assessment Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 Regional to Site-Specific Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Site Geologic Complexity Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Levels of Environmental Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Intrinsic Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Monitoring wells require protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Example of an Integrated Site Remediation Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 Phase I Program Summary for Site Assessments and Remediation . . . . . . . . . . . . . . . . . . . . . . . . .20 Regional Base Map Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Site Location and Topography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Regional Cross-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Regional Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Regional Geology of Grayson County, Texas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 Regional Geologic Map, Grayson Co. TX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Local Soils Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 Regional Quaternary Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 100-Year Flood Plain Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Phase I Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 Phase I Conceptual Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Simple Conceptual Flow Model Cross-Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 Environmental Issues Can Cause Strong Reactions among Local Land Owners . . . . . . . . . . . . . . .49 Topographic Map Downloaded from the Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52 This is not a Downhole TV Camera! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 Distance Target Figure for Phase I Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60 Historic Aerial Photo Can Be Evaluated beginning in the 1930s . . . . . . . . . . . . . . . . . . . . . . . . . . .62 Sanborn Maps Provide Site Conditions Back to the 19th Century . . . . . . . . . . . . . . . . . . . . . . . . . .66 Fast Track Superfund RI/FS Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70 Ground-Water Monitoring Flow Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 Vadose and Saturated Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81 Phase II Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82 Example Phase II Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86 Example Site Base Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87 Soil Classification Schemes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89

Figure 3-7 Figure 3-8 Figure 3-9 Figure 3-10 Figure 3-11 Figure 3-12 Figure 3-13 Figure 3-14 Figure 3-15 Figure 3-16 Figure 3-17 Figure 3-18 Figure 3-19 Figure 3-20 Figure 3-21 Figure 3-22 Figure 3-23 Figure 3-24 Figure 3-25 Figure 3-26 Figure 3-27 Figure 3-28 Figure 3-28 Figure 3-29 Figure 3-30 Figure 3-31 Figure 3-32 Figure 3-33 Figure 3-34 Figure 3-35 Figure 3-36 Figure 3-37 Figure 3-38 Figure 3-39 Figure 3-40

Geologic Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92 Surfical Geologic Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93 Facility Geologic Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 Local Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95 Example Aerial Photo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97 Regional to Core Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98 Geophysics Geotechnical Purposes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 Gravity Geoid/Reference Spheroid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104 Gravity Curve Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105 Seismic Geophysical Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106 Bison Seismic Collecting Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107 Example Refraction Dataset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108 Example Refraction Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109 Metal Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109 Magnetometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110 Frequencies Used in Electrical Geophysical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111 GPR Geophysical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112 GPR Geophysical Method in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112 GPR Trace in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113 EM-31 Method in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 Geonics EM-34 Electromagnetic Induction Geophysical Method . . . . . . . . . . . . . . . . . . . . . . . . . .115 Resistivity Geophysical Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 HNU Equipment Used in Soil Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117 GPR Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118 GSSI 120-Mhz GPR Antenna Being Pulled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118 Relationship of Geophysical Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 Seismic Reflection for Mining Purposes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120 Location of EM Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121 EM Results for Leachate Plume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121 GPR Survey Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122 Vertical Gradient Mag Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 EM Conductivity Survey for Landfill Wastes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124 Annual Wind Rose Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126 Precipitation at Sherman, Texas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126 Precipation Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127

Figure 3-41 Figure 3-42 Figure 3-43 Figure 3-44 Figure 3-45 Figure 3-46 Figure 3-47 Figure 4-1

Rainfall Water Level Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128 Off-Site Drainage Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 Well Census Figure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 Current Land Use Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 Wetlands Mitigation Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135 Principal Plant Communities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 Exploration Trench Mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 Borehole Geologic Interpretations B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146

Figure 4-2 Figure 4-3 Figure 4-4 Figure 4-5 Figure 4-6 Figure 4-7 Figure 4-8 Figure 4-9 Figure 4-10 Figure 4-11 Figure 4-12 Figure 4-13 Figure 4-14 Figure 4-15 Figure 4-16 Figure 4-17 Figure 4-18 Figure 4-19 Figure 4-20 Figure 4-21 Figure 4-22 Figure 4-23 Figure 4-24

Borehole Geologic Interpretations A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146 Borehole Geologic Interpretations C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 Spatial Variability in Site Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149 Borehole Guidance for Drilling and Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151 Fractures in Clays Represent a Secondary Porosity Flowpath . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153 Trial Pit Log. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 Drilling Performance Comparison. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155 Drilling Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156 Landfill Gas Coming from Augered Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 Solid Stem Auger Rig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 Hollow Stem Drilling Is the Most Common Method Used in Environmental Projects . . . . . . . . . .158 Rotary Drilling Rig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 Rotary Drilling with Plain Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159 Drilling with Foam May Be Necessary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 Inclined Auger Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161 Mechanics of Rotosonic Drilling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162 Continuous Core Sample from Sonic Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 Rotosonic Rig Work Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164 Sampling with Rotosonic Rig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .165 Soil Sampling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 Split Spoon Sampling was the Most Common Sampling Technique (before Direct Push) . . . . . . .167 Common Methods of Soil Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168 Soil Logging Must Be Done by Direct Observation, Grading Curves Are Generated from Laboratory Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174 Figure 4-25 Grading Curve for Till (Diamict) #1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174 Figure 4-26 Grading Curve for Till (Diamict) #2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174 Figure 4-27 Comparison of Outwash and Till (Diamicts). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 Figure 4-28 Use of Lithostratigraphic Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177 Figure 4-29 Use of Grading Curves to Evaluate Site Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 Figure 4-30 Example Soil Field Classification System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 Figure 4-31 Example Borehole Field Log. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185 Figure 4-32 Example Borehole Edited Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186 Figure 4-33 Example Monitoring Well Construction Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187 Figure 4-34 Core Logging Must be Done in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 Figure 4-35 Example RQD calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 Figure 4-36 Pictograph of in situ Borehole Field Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192 Figure 4-37 Comparison of in situ Field Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 Figure 4-38 Taking SPT Tests through a Hollow Stem Auger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 Figure 4-39 Direct Push Rig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Figure 4-40 Potential Areas for Use of Piezocone Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199 Figure 4-41a DP Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201 Figure 4-41b Types of Direct Push Soil Sampling Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201 Figure 4-42 Types of Direct Push Ground-Water Sampling Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204

Figure 4-43 Figure 4-44 Figure 4-45 Figure 4-46 Figure 4-47 Figure 4-48 Figure 4-49 Figure 4-50 Figure 4-51 Figure 4-52 Figure 4-53 Figure 4-54 Figure 4-55 Figure 4-56 Figure 4-57 Figure 4-58 Figure 4-59 Figure 4-60 Figure 4-61 Figure 4-62 Figure 4-63 Figure 4-64 Figure 4-65 Figure 4-66 Figure 4-67 Figure 4-68 Figure 4-69 Figure 4-70 Figure 5-1 Figure 5-2 Figure 5-3 Figure 5-4 Figure 5-5 Figure 5-6 Figure 5-7

Direct Push Testing Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206 Direct Push Chart of Correlations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209 Example Dataset from Piezocone Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210 DP Equipment with MIPs Probe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212 MIPs Direct Push Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214 Plan View of MIP Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 Example Cross-Section Results for MIPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .216 Waterloo DP Sampling Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .217 CPT Probe Index Measurements of Hydraulic Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .217 CPT Probe Index Measurements of Hydraulic Conductivity Compared to Analytic Results . . . . . .217 Example Water Quality Along Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218 Example Results of Waterloo Direct Push Profiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218 Grouting of DP Hole Using a Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220 DP Slug Testing Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222 Example of Slug-Test Pneumatic Initiation Method Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222 Well Completion Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226 Piezometer Classifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228 Installation of multipoint Piezometers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228 Hydrostatic Time Lag - Piezometer Response Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .230 Dummy Used To Improve Response Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231 Terms Used in Pressure Water Level Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236 Hydrograph of Tides and Water-Level Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236 Hydrograph of Water-Level Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .237 Barometric Efficiency Determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .238 Manual Dipping of Wells Is The Most Common Technique Used Today . . . . . . . . . . . . . . . . . . . . .239 Hydrograph for a 14-Day Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .241 Summary Documentation of Boreholes and Monitoring Wells/Piezometers . . . . . . . . . . . . . . . . . .242 Decommissioning of Boreholes and Monitoring Wells/Piezometers . . . . . . . . . . . . . . . . . . . . . . . .244 Pictograph Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252 Pictograph Hydraulic Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .253 Vadose-Saturated Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .254 Pictograph Saturated Hydraulic Conductivity of Vadose Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . .255 Borehole Permeameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .257 Double-Ring Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .258 Large Area Double-Ring Infiltrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .258

Figure 5-8 Figure 5-9 Figure 5-10 Figure 5-11 Figure 5-12 Figure 5-13 Figure 5-14 Figure 5-15

Double-Tube Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259 Air-Entry Permeameter Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .260 Gypsum Crust-Cube Set-up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .260 Moisture Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262 Unsaturated Hydraulic Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263 Soil Characteristic Curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264 Instantaneous Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .264 Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266

Figure 5-16 Figure 5-17 Figure 5-18 Figure 5-19 Figure 5-20 Figure 5-21 Figure 5-22 Figure 5-23

Figure 5-28 Figure 5-29 Figure 5-30 Figure 5-31 Figure 5-32 Figure 5-33 Figure 5-34 Figure 5-35

Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267 Pump-In Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269 Pump-Out Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269 Falling Head Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .270 Rising Head Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .270 Pump Testing Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .272 Observation Well Layout Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 Example Test Site Showing Baseline, Pumping Test and Recovery Water Level Measurements in One of the Wells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 Example of Large Volume Flow Measurement Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280 Pre-test Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283 Pressure Test Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292 Type Curve of the Function F(a, b) against the Product Parameter _` (after Bredehoeft and Papadopulos, 1980) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 Borehole Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294 Ratio Method Type Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296 Packer Permeability Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297 Laboratory Testing Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299 Grain Size Distribution for Example Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302 Index property Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303 Pressure Cell Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308 Consolidation Permeameter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308

Figure 5-36 Figure 5-37 Figure 5-38 Figure 5-39 Figure 6-1 Figure 6-2 Figure 6-3 Figure 6-4 Figure 6-5 Figure 6-6 Figure 6-7 Figure 6-8 Figure 6-9 Figure 6-10 Figure 6-11 Figure 6-12 Figure 6-13 Figure 6-15 Figure 6-14 Figure 6-16 Figure 6-17

Triaxial Test Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309 Consolidation Cell Test Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310 Masch and Denny Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .313 Powers Curves for Density and K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 Dual Porosity Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .323 Scale Factors in Fractured Rock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324 Scale of Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324 Design for Evaluation of Ground-Water Flow in Fractured Rocks. . . . . . . . . . . . . . . . . . . . . . . .325 Example Fractured-Rock Design Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .326 Comprehensive Fractured Rock Phase II Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329 Fracture Trace Surface Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331 Local Discharge from Fracture Set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .332 Spring Produced from Fracture Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333 GPR Trace Showing Fracture Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 Trenches Must Be Safe before Entering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339 Design Fracture Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341 Core Indenter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343 Core Section Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344 Oriented Core Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344 Example Borehole Log. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347 Example Edited Borehole Log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .350

Figure 5-24 Figure 5-25 Figure 5-26 Figure 5-27

Figure 6-18 Figure 6-19 Figure 6-20 Figure 6-21 Figure 6-22 Figure 6-23 Figure 6-24 Figure 6-25 Figure 6-26 Figure 6-27 Figure 6-28 Figure 6-29 Figure 6-30 Figure 6-31 Figure 6-32 Figure 6-33a Figure 6-33b Figure 6-34 Figure 6-35a Figure 6-35b Figure 6-36 Figure 6-37 Figure 6-38 Figure 6-39 Figure 6-40 Figure 6-41 Figure 6-42 Figure 6-43 Figure 6-44 Figure 6-45 Figure 6-46 Figure 6-47 Figure 6-48 Figure 6-49A Figure 6-49B Figure 6-50 Figure 6-51 Figure 6-52 Figure 6-53A Figure 6-53B Figure 6-54 Figure 6-55

Core Storage Box Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351 Core Box Storage Must Be Organized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352 Example Core Box Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352 Relationship between Fracture Orientation and ATV Log Trace . . . . . . . . . . . . . . . . . . . . . . . . .353 CCTV Probe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .356 Example Composite Flow Zone Evaluation Obtained for 1981 Investigation . . . . . . . . . . . . . . .357 Borehole Geophysics Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358 Well Deviation Trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358 A Modern Computer-Produced Borehole Geophysical Log Can Summarize Many Aspects of the Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359 Setup for Flow Meter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .360 Pictograph of Flow Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .361 Heat-Pulse Flow Meter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .361 ATV Computer Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .361 Composite Geophysical Logs Used in Flow Meter Evaluations. . . . . . . . . . . . . . . . . . . . . . . . . .362 CCTV Example Fracture Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363 Comparison of Geophysical and Optical Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .364 Caliper Geophysical Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365 Geophysical Logging Used to Define Flow Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365 Internal Liners Reduce Potential Inter-Fracture Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366 Geophysical Tool Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366 Planar Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366 Joint Azimuth Rose Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367 Comparison between Surface Fractures and Deep Borehole Fractures. . . . . . . . . . . . . . . . . . . . . . .368 Depth/Hydraulic Conductivity Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368 Depth/Hydraulic Conductivity Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 Stereographic Projections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370 Stereographic Polar Projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .371 Equal Area Projection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .371 Stereographic Projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372 Equal Area Pole Projection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 Discontinuities Projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 Stereogram Foliation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .374 Stereograms of Cleavage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .374 Composite Stereogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .375 Point Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .375 Bias in Borehole Drilling Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 Frequency Distribution for Rock Dip Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 Factors That Control Head Level Measurements in Fractured Rock . . . . . . . . . . . . . . . . . . . . . . . .378 Mass Averaging Approach Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .383 Discrete Approach Conceptual Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .383 Shape of Dewatering Cone in Fractured Rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 Cooper-Jacob Solution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .387

Figure 6-56 Figure 6-57 Figure 6-58 Figure 6-59 Figure 6-60 Figure 6-61 Figure 6-62 Figure 6-63 Figure 6-64 Figure 6-65 Figure 6-66 Figure 6-67 Figure 6-68 Figure 6-69 Figure 6-70 Figure 6-71 Figure 6-72 Figure 6-73 Figure 6-74 Figure 6-75 Figure 6-76 Figure 6-77 Figure 6-78 Figure 6-79 Figure 6-80 Figure 6-81 Figure 6-82 Figure 7-1 Figure 7-2 Figure 7-3 Figure 7-4 Figure 7-5 Figure 7-6 Figure 7-7 Figure 7-8

Walton Solution Type Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .388 Boulton Solution Type Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .388 Variable Fractured Media Drawdowns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .389 Fractured Rock Drawdown Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390 Impermeable Boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 Recharge Boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 Main Portions of Data Plots in Fractured Rock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393 Skin Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .394 Data Plots with Significant Dewatering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .396 Example Fractured Rock Data Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .397 Dewatering Estimates Using Step Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .398 Test Arrangement for Field Packer Hydraulic Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399 Hydraulic Conductivity Conversions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .402 Friction Loss Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .403 Test Arrangement for Friction Loss Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .404 Graphical Solution for Packer Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405 Configuration of Test Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .407 Downhole Test Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .408 Type Curve Analysis Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409 Stepped Constant-Rate Field Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410 Three Types of Multipoint Piezometers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .412 Multipoint Equipment before Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .413 Multipoint Equipment during Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .414 FLUTe 15 Port Surface Completion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .415 FLUTe Cross-Section View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .415 FLUTe Installation with Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .416 Conceptual Models for Fractured Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .418 Spatial Variability Assessment Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .430 Components of a Phase II Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .432 Alternative Interpretation of Geologic Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .435 Schematic Site Stratigraphy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .437 Typical Stratigraphic Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .437 Geologic Structural Map Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .439 Structural Geologic Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .440 Contouring Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441

Figure 7-9a Figure 7-9b Figure 7-9c Figure 7-9d Figure 7-10 Figure 7-11 Figure 7-12 Figure 7-13

Contour Method Basic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .443 Contour Method Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .443 Contour Method Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .443 Contour Method Example 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .443 Bedrock Contour Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .445 Cross-Section Construction Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .446 Schematic Development of Site Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .449 Cross-Section Location Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .452

Figure 7-14 Computer-Generated Cross-Section Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .453 Figure 7-15 Hand-Drawn Version of Figure 7-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .454 Figure 7-16 Hand-Drawn Conceptual Model of Glacial Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .455 Figure 7-17 Hydrogeologic Cross-Section of a New York Site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .456 Figure 7-18 Isopach Maps That Depict the Geologic Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458 Figure 7-19 Ground-Water Contour Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .460 Figure 7-20a Ground Water Contours Example - Plan View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .461 Figure 7-20b,c Ground-Water Contours Example (Expanded to 10 and 50 Times Scales). . . . . . . . . . . . . . . . . . . .462 Figure 7-21 Potentiometric Surface Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .464 Figure 7-22 Ground-Water Surface Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .465 Figure 7-23 Tidal Processes Observed in Monitoring Wells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .466 Figure 7-24 Components of Hydraulic Heads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .468 Figure 7-25 Basis for Calculation of Gradients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .469 Figure 7-26a Hvorslev Equations for Common Field Situations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .474 Figure 7-26b Use of Hvorslev Equations for Falling-Head Field Situations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .476 Figure 7-27a Geometry and Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .478 Figure 7-27b Curves Relating Coefficients A, B, and C to L/rw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .478 Figure 7-27c Plot of y vs. t for Bouwer and Rice Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .478 Figure 7-28 Match Point Curves Cooper-Bredehoeft Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .479 Figure 7-29 Pneumatic Data Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .479 Figure 7-30 Overdamped Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .480 Figure 7-31 Overdamped Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .480 Figure 7-32 Underdamped Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .480 Figure 7-33 Pump Test Curve Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .483 Figure 7-34 Applicability of Basic Type Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .484 Figure 7-35 Corrected Depth to Water vs. Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .485 Figure 7-36a Data Plotting Method for Determining Pump Test Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .486 Figure 7-36b Data Plotting Method for Determining Pump Test Values (con.) . . . . . . . . . . . . . . . . . . . . . . . . . . .487 Figure 7-37 Distance-Drawdown Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .490 Figure 8-1 The Conceptual Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .495 Figure 8-2 Cross-Sectional Information on Regional Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .497 Figure 8-3 Final Boring Log Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .498 Figure 8-4 Cross-Sectional View of Site Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .499 Figure 8-5 Fence Diagram of Site Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .500 Figure 8-6 Final Conceptual Model of Facility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .501 Figure 8-7 Regional Conceptual Flow Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .502 Figure 8-8 Regional Conceptual Flow Pattern in Glacial Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .503 Figure 8-9 Cross-Sectional Stratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .504 Figure 8-10 Cross-Sectional View without Vertical Exaggeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .505 Figure 8-11 Flownet Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .505 Figure 8-12 Horizontal Flowthrough System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .506 Figure 8-13 Horizontal and Vertical Variability of Geologic Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .506 Figure 8-14A-EConceptual Cartoons of Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .507

Figure 8-15 Figure 8-16 Figure 8-17 Figure 8-18 Figure 8-19 Figure 8-21 Figure 8-20 Figure 8-22 Figure 8-23 Figure 8-24 Figure 8-25 Figure 8-26 Figure 8-27 Figure 8-28 Figure 8-29 Figure 8-30 Figure 8-31 Figure 8-32 Figure 8-33 Figure 8-34 Figure 8-35 Figure 8-36 Figure 8-37 Figure 8-38 Figure 8-39 Figure 8-40 Figure 8-41 Figure 8-42 Figure 8-43 Figure 8-44 Figure 8-45 Figure 8-46 Figure 8-47 Figure 8-48 Figure 8-49

Fence Diagram Example A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .508 Conceptual Model Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .510 Fence Diagram Example B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .512 Conceptual Model of Claystone/Sandstone Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .515 Fence Diagram Example D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .518 Conceptual Oblique Flow Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .521 Example of Oblique Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .521 Example of Oblique Flow Conditions in Granular Environments. . . . . . . . . . . . . . . . . . . . . . . . . . .522 Conceptual Model of Granular Geologic Conditions with Oblique Flow. . . . . . . . . . . . . . . . . . . . .523 Composite Conceptual Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .524 Sources and Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .525 Composite Conceptual Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .525 Geologic and Conceptual Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .527 Vadose Zone Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .528 Hubert’s Regional Flow Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .529 Sand Tank Flow Model Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .530 Reflection of Flowthrough Materials with Variable Hydraulic Conductivity . . . . . . . . . . . . . . . . . .531 Downward Ground-Water Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .531 Regional Flow through Geologic Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .533 One-, Two-, and Three-Dimensional Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .534 Flow Line Construction Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .535 Horizontal and Vertical Flow Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .536 Simple Flownet Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .536 Curvilinear Net Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .537 Four Types of Heterogeneous Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .538 Recharge/Discharge Piezometer Head Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .539 Boundary Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .540 Flownet Model Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .542 Flownet Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .543 Flow Lines in Geologic Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .544 Flowthrough Variable Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .544 Lithologic Cross-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .545 Lithologic and Head Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .546 Plotting of Equipotential Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .546 Initial Flownet Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .547

Figure 8-50 Figure 8-51 Figure 8-52 Figure 8-53a Figure 8-53b Figure 8-54 Figure 8-55a Figure 8-55b

Silty Sand and Sand Layer Flownet Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .548 Example Flownet Construction Three Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .549 Example Flownet Construction, Three Layers with Downward Flow . . . . . . . . . . . . . . . . . . . . . . .549 Transformation of the Flownet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .550 Transformation of the Flownet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .550 Original Dimensions of the Section for a Homogeneous Anisotropic System . . . . . . . . . . . . . . . . .550 Transformed Section of Equipotential Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .551 Flownet Construction in Silty Sand Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .551

Figure 8-56 Figure 8-57 Figure 8-58 Figure 8-59 Figure 8-60 Figure 8-61 Figure 8-62 Figure 8-63 Figure 8-64 Figure 8-65 Figure 8-66 Figure 8-67 Figure 8-68 Figure 8-69 Figure 8-70 Figure 8-71 Figure 8-72 Figure 8-73 Figure 8-74 Figure 8-75 Figure 8-76 Figure 8-77 Figure 8-78 Figure 8-79 Figure 8-80 Figure 8-81 Figure 8-82 Figure 8-83 Figure 8-84 Figure 8-85 Figure 8-86 Figure 8-87 Figure 8-88 Figure 8-89 Figure 8-90

Flownet Returned to Original Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .552 Number of Geologic Cross-Sections for Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .553 Geologic Cross-Section for Flownet Interpretation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .555 Potentiometric Heads Shallow Unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .556 Potentiometric Heads Medium Depth Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .556 Potentiometric Heads Deep Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .556 Hydrogeological Flownet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .557 Seepage Face Conditions Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .560 Flownet for Seepage Face Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .561 X and h(x) for Dupuit-Forchheimer Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .562 Cross-Section for Free-Surface Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .562 Cross-Section for Free-Surface Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .562 Symbols Used in Areal Flownet Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .563 Flownet from Stream to Discharging Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .563 Vertical Leakage to a Confined Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .564 Low Hydraulic Conductivity Materials with Channel Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . .565 Alternative Flownet Construction - Layered Rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .567 Anticline Regional Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .568 Dipping Bedrock Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .568 Vadose, Unconfined and Confined Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .569 Shallow Flow System Discharge to a Large River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .570 Shallow Flow System Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .571 Cross-Section of Site Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .572 Head Levels in Piezometers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .574 Conceptual Model of Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .575 Relationship between Fractures and Piezometer Response. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .577 Conceptual Cross-Section of Example Site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .578 Multilevel Ground-Water Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .579 Relationship Between Ground Water Surface and Conceptual Models of Vertical Flow . . . . . . . . .581 General Site Stratigraphic Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .585 Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .587 Trilinear Diagram of Example Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .588 Pre-Tertiary Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .592 Tertiary Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .594 Development of Karst System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .595

Figure 8-91 Figure 8-92 Figure 8-93 Figure 8-94 Figure 8-95 Figure 8-96 Figure 8-97 Figure 8-98

Modern Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .596 Initial Triple Tube Percussion Drilling to 100 ft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .597 Extend the 10 3/4" Triple Tube Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .597 Extend the 10 3/4" Triple Tube Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .597 Pre-well Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .598 Well Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .598 Well Construction/Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .598 TCE Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .599

Figure 8-99 1,1,1 TCE Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .599 Figure 8-100 Fractures Bypassing Double Casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .600 Figure 9-1 Regulatory Context of Detection Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .608 Figure 9-2a Unconfined Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .610 Figure 9-2b Confined Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .610 Figure 9-2c Unconfined/Confined Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .611 Figure 9-3 Monitoring System Design Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .613 Figure 9-4 Flow Diagram Monitoring System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .615 Figure 9-5 Potential Target Monitoring Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .616 Figure 9-6 Cross-Section of Target Monitoring Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .616 Figure 9-7a Losing Stream Target Monitoring Zones. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .618 Figure 9-7b Losing Stream Target Monitoring Zones, Plan View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .618 Figure 9-8 Steep Gradient Facilities Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .619 Figure 9-9 Conceptual Model of Local Flow Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .620 Figure 9-10 Map View of Local Flow Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .620 Figure 9-11 Unconfined/Confined Flownets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .621 Figure 9-12a-b Regional Ground-Water Flow in Confined Aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .621 Figure 9-13 Confined Aquifer Piezometer Nest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .622 Figure 9-14 Unconfined Aquifer Piezometer Nest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .622 Figure 9-15 Shallow Discharging Ground-Water System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .623 Figure 9-16 Low-Hydraulic-Conductivity Environments with Nondischarging Sand Lenses . . . . . . . . . . . . . . .624 Figure 9-17a Conceptual Model with Nondischarging Sand Lenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .625 Figure 9-17b Conceptual Model with Nondischarging Sand Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .625 Figure 9-17c Conceptual Model with Discharging Sand Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .626 Figure 9-17d Conceptual Model with Discharging Sand Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .626 Figure 9-18 Conceptual Model of Discharging Sand Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .627 Figure 9-19 Gradient Comparisons for Recharging and Discharging Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . .628 Figure 9-20 Conceptual Recharging Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .628 Figure 9-21 Example Leachate Water Quality Plume, Field Determined . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .629 Figure 9-22 Time Sequence for Leachate Plume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .630 Figure 9-23 Conceptual Flow in Layered Deposits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .631 Figure 9-24 Conceptual Model in Layered Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .632 Figure 9-25 Computer Flow Results Model in Layered Deposits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .632 Figure 9-26 Two-Layer Flow Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .633 Figure 9-27 Three-Layer Flow Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .634 Figure 9-28 Figure 9-29 Figure 9-30 Figure 9-31 Figure 9-32 Figure 9-33 Figure 9-34 Figure 9-35

Effect of Drains on Low-Hydraulic-Conductivity Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .635 Channel Deposits in Low-Hydraulic-Conductivity Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .636 Low-Hydraulic-Conductivity Materials with Weathered Upper Units . . . . . . . . . . . . . . . . . . . . . . .637 Structural Control of Ground-Water Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .638 Perched Structural Control of Ground-Water Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .639 Ground Water Discharge through More Permeable Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .640 Various Forms of Ground-Water Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .640 Fractured Rock Control of Ground-Water Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .641

Figure 9-36 Figure 9-37 Figure 9-38 Figure 9-39 Figure 9-40 Figure 9-41 Figure 9-42 Figure 9-43 Figure 9-44 Figure 9-45 Figure 9-46 Figure 9-47 Figure 9-48 Figure 9-49 Figure 9-50 Figure 9-51 Figure 9-52 Figure 9-53 Figure 9-54 Figure 9-55 Figure 9-56 Figure 9-57 Figure 9-58 Figure 9-59 Figure 9-60 Figure 9-61 Figure 10-1 Figure 10-2a Figure 10-2b Figure 10-2c Figure 10-3a Figure 10-3b Figure 10-3c Figure 10-4 Figure 10-5

Fractured-Rock Localized Flow Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .642 Fractured Rock - Evenly Distributed Flow Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .643 Karst Rock Localized Flow Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .644 Gradient-Controlled Ground-Water Surface Contours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .646 Hydrogeological Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .646 Plan View of Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .647 Conceptual Model of Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .648 Cross-Section View of Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .648 Ground-Water Contour Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .649 Flownet Construction for Facility C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .649 Density Consideration in Facility Monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .651 Vadose and Ground-Water Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .652 Example Vadose Monitoring Placement in Facility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .652 Layout of Boreholes at Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .656 Piezometric Levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .656 Conceptual Hydrogeologic Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .657 Site Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .658 Cross-Section of Geology for Example Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .659 Location of Exploration Points for Example Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .661 Conceptual Model for Example Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .662 Potentiometric Surface of Overburden Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .664 Potentiometric Surface of Fractured Rock Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .665 Potentiometric Surface of Competent Bedrock Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .667 Example Cross-Section Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .669 Example Cross-Section Conceptual Model Answer A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .671 Example Cross-Section Conceptual Model (Answer B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .672 Comparisons of Remedial Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .678 RCRA Detection Monitoring Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .683 RCRA Subtitle D Assessment Monitoring Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .684 RCRA Subtitle D Corrective Action Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .685 General Steps in the Superfund Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .690 General Steps in the Superfund Process (cont.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .691 Enforcement Steps in the Superfund Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .692 The Superfund Investigative Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .694 Example Sites Requiring Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .697

Figure 10-6 Figure 10-7 Figure 10-8 Figure 10-9 Figure 10-10 Figure 10-12 Figure 10-11 Figure 10-14

Alternative Superfund Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .700 Site Complexity Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .702 Conceptual Model of a Layered Rock System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .705 Various levels of Ground-Water Flow Discharges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .707 Summary of Selection of Ground-Water Monitoring Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . .709 Location of Monitoring Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .712 Example Site Assessment Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .712 Locate Assessment Monitoring Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .713

Figure 10-13 Figure 10-15 Figure 10-16 Figure 10-17 Figure 10-18 Figure 10-19 Figure 10-20 Figure 10-21 Figure 10-22 Figure 10-23 Figure 10-24 Figure 10-25 Figure 10-26 Figure 10-27 Figure 10-28 Figure 10-29 Figure 10-30 Figure 10-31 Figure 10-32 Figure 10-33 Figure 10-34 Figure 10-35 Figure 10-36 Figure 11-1 Figure 11-2 Figure 11-3 Figure 11-4 Figure 11-5 Figure 11-6 Figure 11-7 Figure 11-8 Figure 11-9 Figure 11-10 Figure 11-11 Figure 11-12 Figure 11-13 Figure 11-14 Figure 11-15 Figure 11-16 Figure 11-17 Figure 11-18

Water Quality of Monitoring Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .713 Keep a Regional Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .714 Example of Target Isocontours Around Monitoring Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .715 Alternative Soil Sampling Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .723 Soil Sampling Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .724 Calculation of Isotherm Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .734 Relationship between Koc and Kow for a Coarse Silt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .740 Correlation of Aqueous Solubility with Octanol Water partition Coefficient . . . . . . . . . . . . . . . . . .740 Example of Typical Soil-Gas Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .748 Codisposal Environmental Pathways. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .759 Remedial Technologies Used at Codisposal Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .761 Conceptual Flow Models for NAPL Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .762 Conceptual Models for DNAPL Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .765 Residual DNAPL Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .769 Conceptual Model of Hydrocarbons in Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .770 Measuring DNAPLs Levels in Boreholes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .771 DNAPL Collection in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .771 Targeted Conceptual Model Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .772 Intergration of Risk Assessment and the RI/FS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .776 Evaluation of a Risk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .777 Streamlined RI/FS Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .782 Continuous Horizontal Wells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .785 Blind Horizontal Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .785 General Monitoring Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .796 Sources of Variability in Ground Water Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .797 Relationship of LOD and LOQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .804 Typical Water Quality Tabular Dataset for Inorganic Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . .808 Isocontours, Closed Isopleths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .809 Isocontours - Open Isopleths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .810 Isocontours - Total Organic Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .811 Time Series Comparisons for Six Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .812 Time Series Comparisons with Sliding Scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .813 Time Series Comparisons for Chloride and Water Levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .814 Time Series Comparisons with Box Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .814 Error Bar Plot Compared to Box and Whisker Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .815 Histogram of Metals Data for Individual Boreholes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .815 Histogram of Leachate Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .816 Histograms Used to Check Data Normality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .817 Probability Plot for Raw and Log Transformed Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .818 Trilinear Datasets Used for Comparisons of Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .819 Simple Time Series Dataset for Organic Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .820

Figure 11-19 Statistical Error in Hypothesis Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .822 Figure 11-20 Methodology for Subtitle D Ground Water Evaluations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .825

Figure 11-21 Figure 11-22 Figure 11-23 Figure 11-24 Figure 11-25 Figure 11-26 Figure 11-27 Figure 11-28 Figure 11-29 Figure 11-30 Figure 11-31 Figure 11-32 Figure 11-33 Figure 11-34 Figure 12-1 Figure 12-2 Figure 12-3 Figure 12-4 Figure 12-5 Figure 12-6 Figure 12-7 Figure 12-8 Figure 12-9 Figure 12-10 Figure 12-11 Figure 13-1 Figure 13-2 Figure 13-3 Figure 13-4 Figure 13-5 Figure 13-6 Figure 13-7 Figure 13-8 Figure 13-9 Figure 13-10

Random Sampling Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .830 Statistics for Parameters That Have Detectable Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .831 Background Well Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .839 Methods for 90 to 100% Nondetects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .843 Evaluation Procedure where Resampling is Allowed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .855 Sampling Used for Ground-Water Comparisons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .860 Frozen Ground May Cause Increased Gas Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .861 The Statistics of Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .863 Single PAOC Comparisons to a Standard/Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .864 Multiple PAOC Comparison to a Standard/Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .865 Comparison of Mean Concentrations of Entire Site to a Standard/Criteria . . . . . . . . . . . . . . . . . . .866 Evaluation of Ground Water Concentrations of Entire Site. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .866 Evaluation of Ground Water to Determine Compliance with GSI Criteria . . . . . . . . . . . . . . . . . . . .867 Comparison to a Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .870 Example of Proposal Title Page. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .877 Example Proposal Transmittal Letter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .878 Example Proposal Table of Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .879 Example of a Simple Proposal Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .880 Example of a Proposal Organization Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .882 Example of a Proposal’s Manpower Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .883 Example of a Proposal Rebillables Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .884 Example of a Progress Report Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .887 Example of a Financial Status Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .888 Report Table of Contents Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .893 Common Mistakes of Professional Liability Claims. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .897 Flow Chart for Initial Screening Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .906 Flow Chart for Evaluating Monitored Natural Attenuation of Chlorinated Solvent . . . . . . . . . . . . .907 General Conceptual Model of MNA Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .910 Target Areas for Collecting Screening Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911 Example of a Complex Geological Situation That Would Form Multiple Plumes . . . . . . . . . . . . . .911 Basis for Development of MNA Criteria (a Shrinking Plume) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .923 Example of Concentration vs. Distance Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .927 Example of Geochemical Footprint Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .928 Example of Concentration vs. Time Graphs.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .929 Example of Geochemical Footprints Plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .930

Figure 13-11 Figure 13-12 Figure 13-13 Figure 13-14 Figure 13-15 Figure 13-16

Concentration vs. time rate constant calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .932 Example of a Conservative Calculation for Plume Length Comparisons . . . . . . . . . . . . . . . . . . . . .934 Example of Remediation Time Frame Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .935 Diagram of Steps in Computer Flow Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .937 Diagram of Steps in Transport Computer Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .938 Development of Attenuation Action Levels (AALs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .941



 7$%/(2)&217(176 &+$37(5,1752'8&7,21 ,1752'8&7,21726,7($66(660(176 6&23( +,6725,&%$&.*5281'726,7($66(660(176 2%-(&7,9(6$1'$3352$&+  $QDO\VLVRI([LVWLQJ,QIRUPDWLRQ3KDVH,  6XSSOHPHQWDO3KDVH,, 6LWH,QYHVWLJDWLRQV   ,1752'8&7,2172,175,16,&5(0(',$7,21  7KH'1$3/,VVXH  8VLQJD7RROER[$SSURDFK  ,1129$7,9(&+$5$&7(5,=$7,21722/6 &267())(&7,9(6,7(5(0(',$7,21 +$1'%22.&+$37(5&217(176  5()(5(1&(6 &+$37(53+$6(,,19(67,*$7,216 ,1752'8&7,21723+$6(,678',(6 3+$6(,678',(6  6LWH6SHFL¿F&RPSOLDQFHDQG2ZQHU2SHUDWRU'DWD 5HJLRQDO%DVH0DS  *HRORJ\*HRSK\VLFV*URXQG:DWHU 6RLOV 6XUIDFH:DWHU  &OLPDWRORJ\ (FRORJLFDO6WXGLHV  +LVWRULFDODQG$UFKDHRORJLFDO5HVRXUFHV /DQG8VH  +RORFHQH)DXOWLQJ$QDO\VLV %DVLF'DWD&KHFNOLVW  6,7(5(&211$,66$1&(  35(/,0,1$51

Total Plotted

< 1/8

1/8 - 1/4

1/4 - 1/2

1/2 - 1

1.000 1.000 0.500 0.250 1.000 0.500 0.250 0.250 TP

0 0 0 0 0 0 0 1 NR

1 0 1 0 0 0 1 5 NR

1 0 1 NR 2 1 NR NR NR

0 0 NR NR 7 NR NR NR NR

NR NR NR NR NR NR NR NR NR

2 0 2 0 9 1 1 6 0

1.000 0.500 0.500 0.250 1.000

0 0 1 1 0

0 0 2 2 0

1 0 6 NR 1

0 NR NR NR 0

NR NR NR NR NR

1 0 9 3 1

1.000 1.000 1.000 TP TP TP 0.250 TP TP TP TP TP TP

0 0 0 NR NR NR 0 NR NR NR NR NR NR

0 1 0 NR NR NR 0 NR NR NR NR NR NR

0 0 0 NR NR NR NR NR NR NR NR NR NR

0 0 0 NR NR NR NR NR NR NR NR NR NR

NR NR NR NR NR NR NR NR NR NR NR NR NR

0 1 0 0 0 0 0 0 0 0 0 0 0

0.500 1.000

0 1

0 0

0 0

NR 3

NR NR

0 4

Coal Gas 1.000 0 AQUIFLOW - see EDR Physical Setting Source Addendum

0

0

0

NR

0

FEDERAL ASTM STANDARD

NPL Proposed NPL CERCLIS CERC-NFRAP CORRACTS RCRIS-TSD RCRIS Lg. Quan. Gen. RCRIS Sm. Quan. Gen. ERNS

X

STATE ASTM STANDARD

State Haz. Waste State Landfill LUST UST CAT FEDERAL ASTM SUPPLEMENTAL

CONSENT ROD Delisted NPL FINDS HMIRS MLTS MINES NPL Liens PADS RAATS TRIS TSCA FTTS

X

STATE OR LOCAL ASTM SUPPLEMENTAL

IL NIPC SRP EDR PROPRIETARY DATABASES

TP = Target Property NR = Not Requested at this Search Distance * Sites may be listed in more than one database

61

PHASE I INVESTIGATIONS

evidence of excessive soil moisture, seeps, erosion and gullying and lineaments/fracture trends. Investigation of sequential aerial photography makes it possible to obtain a better understanding of natural conditions and man-made changes over the years. This enables investigators to identify historic conditions at the site and determine if changing conditions could cause adverse effects on surface- and ground-water hydrology. Typically,

such an investigation would first address an overview of general site conditions during the periods covered by the flights. The majority of the historical aerial photo analysis should consist of an assessment of the chronological changes in site conditions and the potential effects of such changes on the disposal of waste. The investigation should identify potential problem areas that may affect monitoring of surface or ground waters. The text of the investigation

Figure 2-18 Historic Aerial Photo Can Be Evaluated beginning in the 1930s

62

PHASE I INVESTIGATIONS

should include actual aerial photographs with pertinent annotations made on mylar overlays, which are registered to individual photographic frames. This is not a job for amateur aerial photo interpreters! In those cases where questions arise about depths of excavation, topographic contours (down to several foot intervals) can be generated by commercial aerial photo laboratories, even on sites flown 30 to 40 years ago (see Figure 2-18). The technique can be much more cost effective in comparison with drilling or surface geophysics. If review of historic airphoto data locates questionable disposal areas, they can be confirmed by further Phase II field assessment techniques such as geophysics, direct push, hand augering and, if necessary, borehole drilling, sampling and chem ical analysis of ground-water samples. Some labs offer 24- to 48-hour turnaround times for indicator parameters, hazardous metals and volatile organic chemicals (VOCs) to quickly establish if significant ground-water contamination is present at the site. 2.8.2 Phase I Field Reconnaissance for Environmental Audits and Acquisitions A major field component of environmental audits and acquisitions is conducting interviews with current and past employees. For commercial and industrial properties, a review of site records and interviews should be conducted with long-time facility employees. Maintenance engineers and plant managers can provide a wealth of information on plant practices. A tour of the site should also be conducted with a facility or site representative. Table 2-10 provides areas that should receive special reconnaissance effort that may pose potential environmental liabilities to the prospective purchaser. Inspection of the facility may include careful examination of physical plant structures, piping, material and liquid handling procedures (Bernath, 1988). Key containment features of product storage or use areas such as the condition of flooring in chemical storage or handling areas (e.g., cracked floors) should be examined for possible release to the underlying soils. The areas near sumps, drains and trenches should also be examined for evidence of leakage through cracks or exposed soil areas. Underground piping can represent major leakage points that are very difficult to evaluate fully in a simple site reconnaissance. Although one can expect that former and current owner/operators may be somewhat hesitant to discuss important environmental information about the site, interviews with these individuals may be used to determine past processes, raw and manufactured materials handled, locations of underground storage tanks and the availability of site borings and water well logs. The local fire chief, town engineer, public works department and governing officials

can also provide valuable historical information on the site and should be contacted during the interview process. During site acquisition activities, the prospective purchaser may try to conceal adverse environmental or historical information which is important to the overall environmental assessment. This may occur because the purchaser wants to hide negative environmental facts from the financial lender or the insurance carrier (see Bernath, 1988). For this reason, it is recommended that the assessment or audit team obtain access to all parts of the facility and perform the assessment as independently as possible from the purchaser. 2.8.3 Supplemental Field Characterization for Property Acquisitions Site assessments for property acquisitions may include a number of Phase I and II field data collection components. The extent of field collection activities is dependent on the time available for the acquisition review, the extent of previous site activities and the overall size of the facility. Field characterization activities may also be necessary to confirm suspected contaminated areas or impacted ground water. This Phase I supplemental field characterization depends upon surface geophysical techniques and direct sampling of soils and ground water for analytical testing. Surface Characterizations Some field data collection activities, such as surface geophysical surveys, can be performed rapidly. Other field collection activities, such as installing monitoring wells, take a number of weeks to complete, with additional weeks to obtain and analyze ground-water samples. However, if reliable wells are available, these wells can be sampled and analyzed (at a premium cost) within a week. These existing wells must be adequately documented as to the zone being sampled and the well construction details. Following the review of air photography, a magnetometer or electro-magnetic (EM) ground conductivity survey can be used to delineate disturbed areas that may contain buried ferromagnetic debris, such as drums and abandoned underground storage tanks (USTs). False-color infrared photography can provide excellent coverage for disturbed areas, springs and distressed vegetation. These points should be checked in the field with a geophysical survey and, if possible, backhoe reconnaissance trenches. The position of drains leaving the site buildings can often be located through aerial photo and geophysical techniques. These surface profile methods can also locate abandoned well casings that require later costly decommissioning. A variety of different types of geophysical equipment are available for evaluation of sites. They can range from

63

PHASE I INVESTIGATIONS

simple metal detectors to sophisticated depth-penetrating radar. For most surveys a port battery-operated magnetometer or metal detector can be used to locate shallow buried iron and steel objects. These devices are light weight and respond audibly when a difference in the magnetic field (or the actual metal object) is detected between the receiving and transmitting sensors. Electromagnetic (EM) ground conductivity meters measure the apparent conductivity of shallow earth materials. The instrument has a self-contained dipole transmitter and receiver with a spacing that can be varied for different depth penetration. Some of the meters provide output in a single survey, both ground conductivity and the location of buried ferrometallic debris. The inductive EM method allows rapid survey of subsurface materials without the time-consuming ground contact probes necessary in electrical resistivity surveys. As with any technique reliant on conductivity, man-made surface features such as power lines, fences and railroad tracks can greatly affect performance of the technique. Ground-penetrating radar (GPR) provides detailed reflection records of the subsurface which can be used to identify the size, shap and depth of buried debris. This equipment is most useful in areas of sandy soil and where shallow, detailed stratigraphy is needed in the assessment. Interpretation of the features observed in GPR can be particularly difficult in soils containing predominant clays. Subsurface Characterizations Environmental assessments for real estate transactions may require some level of borings or backhoe trenches to gather detailed site information in a relatively quick operation. Conducting subsurface exploration is important for a number of reasons: •

To characterize the general geologic conditions of the site

•

To evaluate the nature and thickness of fill materials

•

To provide soil samples profiles for chemical screening

Although shallow soil samples can be obtained using hand soil samplers and coring devices, truck or trailermounted drilling rigs are usually more efficient in the short time periods typically available for real estate transactions. Additional soil gas survey techniques can be combined with the soil collection methods (see Marrin and Kerfoot, 1988). Such boring and backhoe trenches will always require some level of negotiations for access rights. If the stratigraphy of the site is poorly documented from previous investigation, some number of soil borings

64

may be required to establish if geologic or man-made pathways provide hydrological connection with underlying aquifers or discharge to surface water. Before any borings are drilled, a full Phase I literature search investigation should be completed to define regional geology and target drilling areas. A common practice is to target likely areas of contamination by increasing the density of borings or backhoe pits in areas near USTs, near drain systems which have contacted hazardous materials and in areas of obvious surfical impact (stained soils, stressed vegetation, surface refuse, etc.) that were observed in historic aerial photo review and surface reconnaissance (Chereremisinoff et al., 1986). Depth of borings and soil sampling should be based on site conditions and the product stored on site historically. This would consist of drilling down to confining units for tank areas handling dense non-aqueous phase liquids (DNAPLs) or down to the watertable for tanks handling less dense (than water, LNAPLEs) gasoline products. Special care is needed when drilling through areas where DNAPLs have been disposed of as a product spill. Considerations not to cross-contaminate deeper aquifers by inadvertently drilling through perched DNAPL product zones must be applied during the drilling and sampling project phase. Ground-Water Sampling Representative “grab” samples of ground water can be quickly collected at sites with a shallow watertable and permeable soils by using any one of a series of “real time” sampling methods. A screened auger method (while drilling borings) or using a direct push hydro-punch system (see Chapter 5) can offer access to saturated permeable subsurface materials. Installation of new monitoring wells in borings may be essential to provide sufficient information on lithology and ground water contained in areas with low or highly variable hydraulic conductivity soils. Installation of the more traditional monitoring wells may not be possible with the typical time constraints imposed during acquisitions. As a general rule in areas where there exists a potential for LNAPLEs hydrocarbon contamination, the well screens should extend above the watertable to allow entry of floating hydrocarbons. Remember, however, that the thickness of product in the well will be greater than the product thickness in the aquifer, (see Chapter 4 for details). In low hydraulic conductivity environments such as clays or glacial tills, sufficient time must be allowed for the ground water to enter the open hole and reach reasonably static watertable levels. Estimates of this time can be made using Hvorslev’s 90% hydrostatic time lag calculations (see Chapter 5). Special care must be exercised in determining the potential for these low hydraulic conductivity units to be fractured. Secondary porosity

PHASE I INVESTIGATIONS

fractures in normally confining units can cause unexpected vertical hydraulic conductivity between shallow and deep units. The vertical component of flow can be determined from small-diameter, nested piezometers installed in soil borings. Adequate care must always be exercised to seal the piezometers in permeable zones that will hydraulically react quickly. As with the previous examples of Phase I investigations the results of the project should be fully described in the Phase I report. The report format will be somewhat different depending upon the requirements of the purchaser or the state regulatory agency. In any case the conclusions of the investigation should be expressed in less than 30 pages of text with appropriate supporting documentation. Phase I and II Investigations for Property Transferals A Phase I investigation required for a property transferal differs from that for site investigation by the amount of attention placed on historic site usage. The property transferal Phase I has been defined by an ASTM standard passed by Subcommittee E-50. This standard has been the highest selling ASTM standard for the last several years and has turned these investigation into commodity consulting. The Phase I applied to property transferal have taken automated database services into every Phase I investigation. These services provide the basic search capabilities to address the individual requirements of the ASTM standard E1527-00 for a property transferal Phase Is. These databases include for example, an aerial photography print service. This image database is a screening tool designed to assist professionals in evaluating potential liability on a target property resulting from past activities. ASTM E152700, Section 7.3 on Historical Use Information, identifies the prior use requirements for a Phase I environmental site assessment. The ASTM standard requires a review of reasonably ascertainable standard historical sources. Reasonably ascertainable means information that is publicly available, obtainable from a source with reasonable time and cost constraints and practically reviewable. To meet the prior use requirements of ASTM E 152700, Section 7.3.2, the following standard historical sources may be used: aerial photographs, fire insurance maps, property tax files, land title records (although these cannot be the sole historical source consulted), topographic maps, city directories, building department records or zoning/land use records. ASTM E1527-00 requires: “All obvious uses of the property shall be identified from the present, back to the properties obvious first developed use or back to 1940, whichever is earlier. This task requires reviewing only as many of the standard historical sources as are necessary and

that are reasonably ascertainable and likely to be useful (ASTM E 1527-00, Section 7.3.2, page 11). Radius Map Report This map-based report identifies sites with real or potential environmental issues. Environmental databases are searched within a radius as defined by ASTM E-1527 or tailored to client specifications. Each Radius Map Report should include an overview and detail map to help in the location of the sites. Additional features shown on maps can include sensitive receptors, waterways and major roads, NPL site boundaries, wetlands, coal gas sites, oil and gas lines, powerlines and 100- and 500- year flood zones. These Radius map reports often include relative site elevation data, proprietary historical data and detailed information on each site. These interactive mapping service provide their reports using delivery as PDF files through the Internet. Sanborn® Maps EDR’s Sanborn collection dates from 1866 and includes over 1.2 million Sanborn maps chronicling the history of approximately 12,000 American cities and towns. Since acquiring the Sanborn Map Company collection in 1996, EDR has revolutionized the fire insurance map research process. The original Sanborn collection has been digitized and can be searched from the desktop through EDR’s website. EDR’s Sanborn Search Engine is the only system to search the collection using latitude and longitude and provide instant site-specific search results. If maps are available for a target property, you have the option of Sanborn map delivery via email (see Figure 2-19 for a series of Sanborn maps). Going from Phase I to Phase II The Phase I site assessment process requires the environmental professional to conduct sufficient research (within the scope of services) to conclude whether or not recognized environmental conditions (RECs) have been discovered and to provide an opinion on their impact. As defined in the ASTM E1527-00 Phase I standard, a REC is “an environmental condition that indicates an existing release, a past release or material threat of a release, unless the condition can be considered de minimis.” The Phase I practice is therefore extremely important for use in identifying potential sources of contamination, the specific contaminants involved and their location. Once the Phase I is completed, the environmental professional may recommend that a Phase II investigation be performed to confirm

65

PHASE I INVESTIGATIONS

1890

1885 Æ

Æ

The Sanborn Library, LLC

This SanbornÆ Map is a certified copy produced by Environmental Data Resources, Inc. under arrangement with The Sanborn Library, LLC. Information on this SanbornÆ Map is derived from Sanborn field surveys conducted in:

The Sanborn Library, LLC This SanbornÆ Map is a certified copy produced by Environmental Data Resources, Inc. under arrangement with The Sanborn Library, LLC. Information on this SanbornÆ Map is derived from Sanborn field surveys conducted in:

Copyright ©

1890

The Sanborn Library, LLC

Year

Copyright ©

1885

CHP

The Sanborn Library, LLC

Year

CHP EDR Research Associate

Reproduction in whole or in part of any map of The Sanborn Library, LLC may be prohibited without prior

EDR Research Associate

written permission from The Sanborn Library, LLC.

Reproduction in whole or in part of any map of The Sanborn Library, LLC may be prohibited without prior written permission from The Sanborn Library, LLC.

1969

1907 Æ

The Sanborn Library, LLC

This SanbornÆ Map is a certified copy produced by Environmental Data Resources, Inc. under arrangement with The Sanborn Library, LLC. Information on this SanbornÆ Map is derived from Sanborn field surveys conducted in: Copyright ©

1907 Year

The Sanborn Library, LLC

CHP EDR Research Associate

Reproduction in whole or in part of any map of The Sanborn Library, LLC may be prohibited without prior

Æ

Sanborn Maps Used With Permission Environmental Data Resources, Inc

The Sanborn Library, LLC This SanbornÆ Map is a certified copy produced by Environmental Data Resources, Inc. under arrangement with The Sanborn Library, LLC. Information on this SanbornÆ Map is derived from Sanborn field surveys conducted in:

written permission from The Sanborn Library, LLC.

Copyright ©

1969 Year

The Sanborn Library, LLC

CHP EDR Research Associate

Reproduction in whole or in part of any map of The Sanborn Library, LLC may be prohibited without prior written permission from The Sanborn Library, LLC.

Figure 2-19 Sanborn Maps Provide Site Conditions Back to the 19th Century

66

PHASE I INVESTIGATIONS

the existence and evaluate the extent of contamination prior to evaluating cleanup options and preparing remediation cost estimates. Typically, the results of 10 to 20% of Phase I site assessments recommend further investigation under a Phase II assessment. What are the most common Phase I findings that lead to Phase II? What factors should the environmental professional consider when making a Phase II recommendation? The following discussion summarizes the most common findings that have triggered a Phase II recommendation, as well as some guidelines for making a Phase II recommendation. Site Conditions Likely to Lead to a Phase II Table 2-13 summarizes the types of REC findings that commonly signal the need for a Phase II. In general, a Phase II is recommended whenever there has been an untreated known or suspected hazardous substance release on the property or on any adjacent site, that could impact the target property. In some cases, a REC is obvious, such as the release of a hazardous substance to groundwater. In other cases, the Phase I may identify a number of potential RECs that would require further investigation to accurately assess. Litigation case studies from past editions of the Environmental Site Assessments (ESA) report indicate that old industrial operations, dry cleaners and unregistered USTs are frequently missed environmental conditions that should have been included in a Phase I report. If the soil or building on the target property is stained, the environmental professional must assess whether the staining is significant, investigate what the cause might be and, ultimately, determine whether the staining is expected to have a material impact on the property. If there have been environmental violations on the property, the key areas to explore involve identifying what

the violations were, whether they are related to a release onto the property, when the violations occurred and how or whether they have been addressed. In cases where contaminated fill dirt may have been transported to the site, a Phase II is highly likely. The environmental assessment must determine whether the volume or location of fill dirt brought to the property can be expected to impact the property. If the Phase I historical research indicates that there are or have been, under- or above-ground storage tanks on or near the target property, key considerations are whether the tanks were used to store hazardous substances or petroleum products, the age and construction of the tanks, whether the tanks are still in use, whether leak detection equipment has been installed, results of past testing (if available) and whether there is any history of spills from the tanks. If there is evidence that operations on the target property involved the discharge of wastewater the nature and volume of the discharge must be assessed, as well as where the wastewater is discharged and whether the discharge contains or contained hazardous constituents or petroleum products. High Risk Operations A key component of Phase I involves identifying the past and present use of the target and adjoining property and collecting data to determine whether the operations could have materially impacted the target property. Obviously, there are certain types of industrial and commercial operations that signal strong potential for a Phase II recommendation by the Phase I consultant. Table 2-14 lists common high-risk businesses that, if uncovered on a target property or adjacent property, are most likely to trigger a recommendation for a Phase II. During Phase I, particular attention should be paid to

Table 2-13 Businesses that Signal Strong Potential for Phase II Recommendation

Automotive dealership Automobile maintenance, repair shops Automotive storage and salvage lots

Industrial/manufacturing facilities Machine/equipment/appliance servicing Any industries involved in the storage and disposal of hazardous wastes

Dry cleaning operations that used perchloroethylene Commercial printing Farmland used for intensive agricultural operations Golf courses, fertilizer use

Oil distribution facilities Gasoline service stations

67

PHASE I INVESTIGATIONS

Table 2-14 Situations Likely to Drive Need for Phase II High Likelihood to Lead to Phase II Known or suspect contamination at upgradient/adjoining site

Known or suspect contamination onsite Likely plume migration to target property Known or suspect presence of underground storage tanks on the property Property discharges known or suspected wastewater (other than storm water and sanitary waste) into a storm water drain Fill dirt suspected to have been brought to the property that originated from a contaminated site Existence of a former dry cleaner on the property

identifying the presence of facilities involved in any of these operations. If the assessment involves properties with tenants, such as shopping centers, all prior tenants should be identified to determine whether any past operations present a potential REC. The Phase I consultant may recommend that a Phase II investigation be carried out as part of due diligence on a specific property due to the presence of any of the operations listed in the Table. In general, it is safe to assume that most pre-CERCLA operating industrial facilities that handled hazardous substances or petroleum products would be expected to have multiple RECs that can only be assessed by a Phase II investigation. Recommending a Phase II The ASTM E1527-00 standard does not automatically require that a Phase II investigation be conducted if a REC is identified. Rather, the standard requires the environmental professional to identify all RECs and provide supporting documentation, as well as an opinion of their impact on the target property. If during the course of conducting a Phase I, a REC is identified and Phase II is deemed necessary, all relevant information supporting this recommendation should be provided to the client. Whether to include all potential RECs and make a

68

Moderate Likelihood to Lead to Phase II Adjoining property is or has been used for industrial/manufacturing operations substance to groundwater Property has an environmental lien on it Earlier ESA indicated the potential for contamination Evidence of hazardous waste storage on site

Visible staining on the property Contaminants exceeding drinking water standards detected in private well serving the property Notices of violation have been issued

Equipment on the property may contain PCBs

Phase II recommendation is up to the professional discretion of the environmental professional conducting the Phase I. If information is uncovered during the Phase I investigation that indicates the possibility of a REC, the Phase I report should state this and a recommendation made to the client, preferably under separate cover, on how to evaluate the REC. There is no doubt that the Phase I market can uncover more lucrative Phase II opportunities. If done well, ESAs can open the door to other consulting services for the same clients, such as Phase II soil and groundwater investigations, compliance audits, geotechnical assessments, building condition surveys, asbestos and lead surveys and remediation projects. Some consultants will recommend Phase II investigations to avoid liability and in the hopes of securing future Phase II work. Ultimately, the environmental professional must decide whether a Phase II recommendation serves the needs of the client. For instance, a Phase II may be warranted to prevent a client from paying market price for a contaminated or potentially contaminated parcel of real estate. The decision about whether or not to conduct a Phase II is obviously up to the discretion of the client, but providing the client with data to support the Phase II recommen-

PHASE I INVESTIGATIONS

dation can only be to the environmental professional's benefit. This will protect the consultant from a claim of negligence in the event that his/her client opts not to do the Phase II and contamination is later discovered during development. Phase I Environmental Site Assessments The true value of the Phase I ESA is that it allows the consultant to assess whether additional investigation is necessary to either protect the client from future liability or assist in avoiding paying market price for a contaminated parcel of land. In conducting a Phase I, all reasonably ascertainable sources of information should be checked and the results used to reconstruct past history. Historical city directories can be a valuable historical resource to identify former uses of a property, such as the presence of a gasoline service station that do not show up in fire insurance maps during the prior use investigation. Historical aerial photographs may also reveal the former presence of high risk facilities that do not show up in other historical sources. Both underground storage tanks and dry cleaners are the most common reasons for conducting a Phase II on a piece of commercial property today after a Phase I has been performed. The site investigation and remediation potential is considerable. Only a quality Phase I that incorporates a comprehensive historical investigation will uncover such potential. Dry Cleaners Dry cleaners operate either on their own property or as a tenant on someone else’s property. By far the most common location for dry cleaners is at a shopping center (or strip center). Dry cleaners may be either the drop-off type or the type that have dry cleaning performed on site. However only dry cleaners with cleaning operations onsite represent a soil and groundwater contamination risk. There are approximately 40,000 shopping centers in the U.S. today. Typically, an owner holds this type of property for between 3 and 7 years. Assuming an average 5-year ownership period before the property is sold, about 8,000 shopping center transactions could take place annually. Experience at firms which specialize in the acquisition of shopping centers suggests that approximately 70% have today or have had in the past, a dry cleaner using perchloroethylene operating on the property. Of those shopping centers which have or have had, a dry cleaner operating on the property, experience also has shown that almost 90% will have some level of either soil contamination alone or a combination of soil

and groundwater contamination. This means that 8,000 dry cleaners (70%) or as many as 5,600 shopping centers each year would be likely candidates for a Phase II investigation and that some level of perchloroethylene contamination would be expected at approximately 5,000 shopping centers. This represents considerable potential for Phase I firms which also have Phase II and Phase III expertise. Underground Storage Tanks Underground storage tanks are widely believed to be the most common Phase I finding leading to a Phase II, particularly at sites which were gas stations prior to, but not after, 1980 (before RCRA and the UST regulations were passed). Prior research focused on intersections in commercial zones which did not have gas stations operating on any of the four corner properties after 1980. Today these properties have many other uses (e.g., fast food restaurants, shopping centers, strip centers, etc). Using Sanborn fire insurance maps as the principal investigative tool, approximately 240,000 former gas station sites existed on at least one of the four corners of such intersections. These 240,000 sites represent a significant Phase II and Phase III opportunity (if they have been identified in the Phase I) 2.9 ASSESSMENT MONITORING PHASE I PROGRAMS Assessment monitoring programs represent both a technically difficult and potentially costly site evaluation process. At least two federal programs (Superfund and RCRA) and many state-level assessment monitoring regulations currently exist for hazardous and solid waste land disposal facilities. Although procedural and format differences exist between these various programs, the technical site evaluation process is essentially equivalent for any type of assessment monitoring program (see Frost, 1988) for a review on strict liability under Superfund). The following discussion will first briefly describe both Superfund and RCRA assessment programs and then describe similar Phase I evaluations that address this important planning phase of work. Further Phase II scopes of work for these assessment monitoring programs, addressed in Chapter 10 of this text, continue the goals of direct evaluation of site conditions in order to design an appropriate clean-up of the site to protect human health and the environment. 2.9.1 General Superfund Procedure Superfund represents both a legal and procedural process that is tied to a series of federal laws: the Superfund

69

PHASE I

CONSENT ORDER & STATEMENT OF WORK NEGOTIATIONS

FEASIBILITY STUDY

REMEDIAL INVESTIGATION

TASK I INVESTIGATION SUPPORT & DESCRIPTION OF CURRENT SITUATION

TASK 2 INVESTIGATION

PHASE II

SOURCE CHARACTERIZATION

TASK 0 WORK PLAN PREPARATION

CONTAMINANT CHARACTERIZATION MIGRATION PATHWAY ASSESSMENT

PHASE III

TASK 3 INVESTIGATIVE ANALYSIS

TASK 5 DRAFT RI REPORT

TASK 9 DRAFT FS REPORT

TASK 8 REMEDIAL ALTERNATIVES EVALUATION

TASK 2 SUPPLEMENTAL SITE INVESTIGATION TASK 0 SUPPLEMENTAL WORK PLAN PREPARATION

TASK 7 REMEDIAL ALTERNATIVES SCREENING

TASK 5 FINAL RI REPORT TASK 4 BENCH / PILOT STUDIES

Figure 2-20 Fast Track Superfund RI/FS Program

TASK 9 FINAL FS REPORT

PHASE I INVESTIGATIONS

70 WORK PLAN

PHASE I INVESTIGATIONS

Table 2-15 Sources of Information for Background Levels of Inorganics in Soils and Sediments Supporting Background Source

Information

Locations

Contact point

Bureau of Land Management (BLM)

Provides data on areas in the country that have naturally occurring substances that pose a hazard to humans or the environment

Mostly western U.S.

BLM Service Center Denver Federal Center Lakewood, CO 80225 (303) 236-0142

National Park Service (NPS)

Inventory and monitoring of trace levels of inorganics in soils in natural areas

Nationwide

Local NPS Headquarters

U.S. Geological Survey

Several reports on the concentration of inorganics in the environment

Nationwide

Water Resources Information Center (703) 648-6818

Background geochemistry of some rocks, soils, plant and vegetables in the conterminous U.S. "Geological Survey," professional paper 574-F, 1975 Summary of determination between natural and anthropogenic contributions— shows natural values vary widely and are highly site specific and regionally dependent.

Nationwide

National Technical Information Service (NTIS) U.S. Department of Communication (703) 487-4650

An accounting of pesticides in soils and ground water in the Iowa River Basin, 1985-88 (IA 86-055)

Midwest

NTIS

U.S. Geological Survey

Aerial photographs of sites

Nationwide

USGS, Salt Lake City ESIC 8105 Federal Bldg. 125 South State St. Salt Lake City, UT 84138-1177 (801) 524-5652/Fax: (801) 524-6500

USDA- Agricultural Stabilization and Conservation Service (ASCS/SCS)

Aerial photographs of current and previous land use and soils types including erosion potential

Nationwide

ASCS/SCS Aerial Photography Field Office P.O. Box 30010 Salt Lake City, UT 84130-0010 (801) 975-3503/Fax: (801) 975-3532

National Ocean Service (NOS)

Coastal and Geodetic Surveys including aerial photographs

Coastal areas

National Ocean Service Coast and Geodetic Survey Support Sec. N/CG23 6 SSMC#3, Rm. 5212 1315 East-West Highway Silver Spring, MD 20910 (301) 713-2692/Fax: (301) 713-0445

71

PHASE I INVESTIGATIONS

TABLE 2-15 Sources of Information for Background Levels of Inorganics in Soils and Sediments (Continued) Supporting Background Source

Information

Locations

National Archives Research Administration/National Air Survey (NARA/NASC)

Series of infrared Landsat photographs for mid-1970s by state.

Nationwide

NARA/NASC National Air Survey 4321 Baltimore Ave. Bladensburg, MD 20710 (301) 927-7180/Fax: (301) 927-5013

U.S. Forest Service (FS)

Often has data on trace elements as part of soils inventory and monitoring program.

Nationwide

Nearest FS experiment station

U.S. Department of Energy (DOE )

Collects and publishes data on trace metals and radionuclide concentrations around DOE facilities and for reference sites.

Nationwide

Nearest DOE office, Environmental Monitoring Division

Oak Ridge National Laboratory

The background soil characterization project provides background levels of selected metals, organic compounds, and radionuclides in soils from uncontaminated sites at the Oak Ridge Reservation. Also a good approach for evaluating background for use in baseline risk assessments

Local Roane County, TN

D.R. Watkins Oak Ridge Reservation Environmental Restoration Div. P.O. Box 2003 Oak Ridge, TN 37831-7298 (615) 576-9931 See ref. ORNL 1993.

National Climatic Data Center

Provides data on wind roses and climate parameters for most areas of the country.

Nationwide

User Service Branch Asheville, NC (704) 259-0682

U.S. EPA

Most complete source of data that includes U.S. EPA and other agency information on hazard ID, doseresponse, and risk characterization.

Nationwide

EPA/540/1-86/061 (EPA 1986)

Approach useful nationwide

STORET (physical and chemical parameters in soils and sediments).

Journal articles

Can provide local, regional or national background concentration values. Can be accessed via literature searches, but usually need to be searched by element or media.

Amendments and Reauthorization Act (SARA) and the National Contingency Plan (NCP). When looking at the process of Superfund, many organizational and planning activities are directly related to the phased investigation approach. The first step of the Superfund process is the

72

Contact point

EPA Office of Water and Hazardous Material (202) 382-7220 Commercial product— more user friendly, EarthInfo: (303) 938-1788 Local to National

Selected references: (1) Metals in Determining Natural Background Concentrations in Mineralized Areas, 1992 (Runnells et al., 1992), and (2) Sediment Quality and Aquatic Life Assessment (Adams et al., 1992).

identification of potentially hazardous sites that may require remedial action and their entry in a database known as CERCLIS. At this point or at any time thereafter, an emergency removal action may be conducted by the EPA at a site due to environmental conditions requiring rapid response

PHASE I INVESTIGATIONS

actions or because the situation at the site may significantly worsen before a full-scale remedial action can be implemented. In the pre-remedial process, sites undergo a preliminary assessment (PA) and a site inspection (Sl) which usually culminates in a scoring by the hazard ranking system (HRS). Currently, if a site scores over 28.5 on the HRS, it is placed on the National Priority List (NPL) where it becomes eligible for funding of investigative programs (remedial investigation/feasibility study [RI/FS]) and possible remedial action. Approximately 10% of all sites which are initially identified are finally listed on the NPL. Concomitant with this, the Agency for Toxic Substances Disease Registry (ATSDR) conducts a health assessment to determine if an imminent health threat exists or if further community public health studies (e.g., epidemiology and biological monitoring) are necessary for the site. Once a site or, in some cases regional areas, are listed on the NPL, they eventually undergo an RI/FS to determine the nature and extent of contamination and to evaluate alternatives for remedial action. The RI/FS program is shown in Figure 2-20. This program is divided into a series of tasks and phases. The RI and FS usually overlap in time as shown in Figure 2-20; for example, there can be initial scoping of alternatives while field data are being collected. The RI starts off with the preparation of a series of QA/QC, sampling and work plans. On-site test results may also be compared to background soils from database sources (see Table 2-15). This process is an evaluation of all data previously collected (e.g., during the PA/SI or by other investigation) and an in-depth cost and time proposal for the conduct of the RI/FS. A Phase I investigation as described in this text would be extended to include a number of these planning documents. The Phase I scope is similar to the preliminary assessment (PA) site inspection (SI) tasks of the formal Superfund investigation. The PA/SI also sets the stage for development of planning documents. A preliminary risk assessment, identification of applicable or relevant and appropriate requirements (ARARs) boring and sampling plans, determination of data quality objectives (DQOs) and an initial screening of remedial alternatives often support the work plan. Once the components of the documents are approved by federal and state regulatory agencies, actual investigative work commences at the site. Unfortunately, the majority of this work at the typical Superfund RI project involves the collection of samples for chemical analysis rather than directing the investigations toward fully understanding the site geologic conditions. Chapter 10 contains a full discussion into the goals and methods of the RI/FS investigation with suggested streamlining assessment techniques to concentrate on evaluation of site geologic and hydrogeologic conditions. These

results are used to determine or estimate the nature and extent of contamination. During the time when field data are being collected, the initial screening of alternatives is performed by the investigation staff. After the analytical data leave the laboratory, they go through a process of data validation to ensure that the data meet the U.S. EPA’s QA/ QC requirements. The field and analytical data are then used in the RI report to describe the nature and extent of contamination. Another use of analytical results obtained from site samples is in the human health risk assessment or the public health evaluation performed as part of the RI/FS. The stated objective of the risk assessment is to assist the U.S. EPA in making remedial alternative decisions that have a public health basis. Additionally, during this time, the FS progresses through its final evaluation of alternatives, with the result that one alternative is recommended to the U.S. EPA, Two additional risk assessment activities accompany the FS. The first assessment is a determination of preliminary remediation goals (clean-up levels) for contaminants in various media at the site; this determination takes health effects and ARARs into account. The second assessment is a health-based screening of remedial alternatives which accompanies evaluations of long- and short-term effectiveness and reduction of toxicity as required by SARA. Following the completion of the RI/FS, the U.S. EPA issues a Record of Decision (ROD) which states the chosen remedy, justifies its choice and responds to comments received from the public on the RI/FS. The ROD may also decide on a no-action alternative. Additionally, a ROD may be issued for a portion or single operable unit at a site. After the issuance of a ROD, the site proceeds to the remedial design (RD) stage which sets out the details of construction for remediation. This step may be preceded by a conceptual design, and experience shows that most Superfund investigations require additional sampling and analysis over what was performed for the RI/FS. Once the RD is approved, the remedy is implemented as a remedial action (RA). When an effective clean-up has been completed, the site is removed from the NPL. If hazardous materials are left onsite in a form where they are still toxic and potentially mobile, the site may be revisited every 5 years by the EPA to ensure that the clean-up remains effective. 2.9.2 Technical Approach to RCRA Site Remediation Program The RCRA Facility Investigation (RFI) is generally equivalent in technical scope to the Superfund remedial investigation (RI/FS). Units are areas of concern that are determined in the RFI to be a likely source of significant continuing releases of hazardous wastes or hazardous constituents. The regulatory means of requiring the RFI is

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either through RCRA permit conditions (operating or closure/post-closure) or via enforcement orders [e.g., 3008 (h)]. Because of the Hazardous Substance Waste Act (HSWA) statutory language, the agencies must focus the RFI requirements on specific solid waste management units or known or suspected releases that are considered to be routine and systematic. The HSWA permit conditions or enforcement orders can range from very general (e.g., “evaluate the soil at.”) to highly specific instruction (e.g., a specified number, depth, location of monitoring wells with samples analyzed for a given set of constituents at a set frequency). Since the USEPA in the RFI process is not required to positively confirm a continuing release, but merely determine that the “likelihood” of a release exists, the scope of the RFI can range from a single limited specified activity to a complex multimedia study. The investigation may be phased, initially allowing for confirmation or rebuttal of the suspected continuing releases through continual sampling. If release to the environment is verified, the second phase of investigation typically consists of release characterization. This second phase of a RCRA RFI is much like a Superfund RI and includes: •

The type and quantity of hazardous wastes or constituents within and released from the unit

•

The media affected by the release(s)

•

The current extent of the release

•

The rate and direction at which the releases are migrating

Inter-media transfer of releases where applicable (e.g., sediment or surface water releases) is also addressed during the RFI. The responsible regulatory agency will typically interpret the RFI program and release findings. The agency will also evaluate the data quality of the RFI (i.e., do location criteria, sampling and analytical data quality objectives for the completed project agree with planning documents?). The analytical results of the RFI are then compared against established human health and environmental criteria. These criteria or “action” levels can be established for each environmental medium and exposure pathway, using the toxicological properties of the waste constituent and standardized exposure model assumptions. At this stage, in the RCRA facility investigation, if the continuing release of hazardous wastes is determined to be a potential short-term or longterm threat to human health or the environment, the regulatory agency may require either interim corrective measures or a corrective measures study. This evaluation of human health and the environment risk factors is a crucial stage in the RCRA corrective action process. Identifying and implementing interim corrective mea74

sures for the facility may be conducted at any time during the RFI. This procedure may be used in a case where exposure to hazardous constituents is currently occurring or is imminent. In those sites where interim corrective measures may be needed, both the owner/operator and the regulator agency have a responsibility to identify and respond to these interim corrective action situations. The owner/operator and the regulatory agency must work together to assure the adequacy and acceptance of the data collected during the RFI and the final evaluation of those data. 2.9.3 Phase I Assessment Programs Many common Phase I goals are important tasks in any assessment monitoring program. These “desktop” activities represent the early steps that permit full-scale planning of the field activities that follow the Phase I scope of work. Both Superfund and RCRA have a number of required planning, documentation and safety documents that describe the overall process to be followed during the assessment program. Although planning documents (such as generation of the quality assurance quality control (QAPP) are specific to the individual remedial program, a number of basic Phase I tasks can greatly enhance the planning process to target drilling locations of boreholes and the sampling process during later parts of the second phase field program. Although most RCRA and Superfund sites will have some historic ground-water monitoring, these monitoring systems may be poorly constructed or documented or screened in the wrong locations and depths to fully evaluate the “rate and extent” of ground-water contamination at the facility. Often these sites or facilities have a minimum “detection” monitoring system that must first be evaluated and then supplemented by a significantly expanded assessment program beyond the traditional detection monitoring program. Unless the facility has had a comprehensive Phase I investigation completed as part of a detection monitoring or SI/PA program, it is recommended that a full Phase I scope of work be completed for every assessment monitoring project within the early planning process. An investigation of releases from unregulated hazardous disposal areas or affected RCRA disposal units requires various types of technical information. This information is specific to the waste disposed or managed, unit type, design and operation of the environment surrounding the unit or facility and the environmental medium to which contamination is being released. Although each medium (e g., ground water, surface water, sediments) will require specific data and methodologies, the following represents general guidance for Phase I investigation of several important elements: one is “desktop” in nature and the other focuses on field reconnaissance data collection. The technical approach of a full assessment monitoring program requires the investigator to examine extensive data

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on the site area and specific disposal practices. These data generally can be divided into the following categories: • Regulatory history • Facility and unit design • Waste characteristics • Environmental setting • Pollution migration pathways • Evidence of release • Environmental receptors • Previous release events Investigative efforts will vary depending on which environmental pathway medium is considered most vulnerable. For example, unlined RCRA units are more likely to have soil and ground-water releases than lined units. A site’s environmental setting will determine which media are of concern (e.g., shallow ground water or fractured subsoils). As such, the phase investigation approach must be based on regional understanding of the subsurface pointing toward the more direct site based Phase II geologic and hydrogeologic field data gathering effects. The scope of work for Phase I investigations, where an existing monitoring system is in place, should begin with: •

Review of the facility disposal practices

•

Historic aerial photo review

•

When present onsite, an evaluation of the current environmental monitoring system and the data acquired

•

Well census

•

Initial conceptual geologic or site model

•

Phase I report

•

Surface investigative plan

•

Subsurface investigative plan

Formulation and implementation of field investigations, sampling and analysis and/or monitoring procedures are designed to verify or rebut suspected releases (Phase I) (see Zirschky and Gilbert, 1984) and to evaluate the nature, extent and rate of migration of verified releases (Phase II). The latter phase can in turn be divided into logical technical steps. Assessment monitoring programs typically have goals to evaluate the environment, establish the extent of contam-

ination present at site, propose a technically correct and cost effective remedial solution. The above eight tasks provide the raw material to adequately plan virtually any site remedial investigation for state or federal compliance. Additional documentation will be necessary for meeting program format submittals, such as, the quality assurance project plan (QAPP) or the project sampling plan. Each state and federal program has slightly different reporting requirements and the relevant programs must be rigorously followed. However, the eight-point Phase I program should be followed as the basic scope and included as part of the assessment planning process. Documents such as the Superfund sampling plan should logically follow completion of the Phase I report or be composed essentially from the Phase I data. No matter what program is followed, at least, the above eight points should be performed for the project area before selection of the relevant sampling points in the various planning documents required by Superfund. A strong case can be made to “hold off” the specific locating of sampling points for ground-water monitoring until the full Phase II study has been completed. Many of these projects spend most of the investigative dollars taking ground-water quality samples and then trying to figure out what the parameters’ values really mean. If the project establishes the geology and hydrogeology first selection of appropriate monitoring locations is relatively easy. The following text describe or reference important tasks within the eight points. Review of the Facility Disposal Practice Phase I review of the facility disposal practices should consist of development of a series of datasets based on the characterization of potential leachate. Much of the data should be available for review if the facility represents an operational facility with some form of leachate collection and treatment. The mode of disposal or codisposal of waste materials can be particularly relevant for construction of migration pathway conceptual models. Closed disposal cells within more modern waste disposal facilities are often filled-in previously excavated gravel or construction material source areas. If source areas were stopped at the watertable, at clay confining units (for gravel or sand pits) or at saturated sandy soils (for a clay brick manufacturing site), contact of the waste with the ground-water surface can have a significant impact on the potential for leachate generation and migration. Much of this information can be established through the site interview process described in this chapter. Particular care should be taken to ask specific questions dealing with base grade conditions present at the facility when the disposal practice began. If this occurred before the current or available staff was hired, records of preexist-

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ing conditions should be evaluated based on later regional geologic/hydrogeologic conditions established in the Phase I literature review. Historic Aerial Photo Analysis Historic aerial photo analysis can be the most efficient and cost-effective technique available for Phase I monitoring evaluation of post disposal practices, base grade elevations, saturated or unsaturated conditions, fill rates and virtually any visually relevant information (see Zirschky and Gilbert, 1984). Chapter 3 describes further aerial photo review activities which can span the range of structural interpretations of geology (fracture trace analysis) to direct topographic mapping of surface features with 2-foot contours of historic pit and excavation depths. Evaluation of Current Monitoring Programs During assessment monitoring programs one is often required to review data gathered from previous environmental monitoring. These data may be the primary cause for initiation of the assessment monitoring project. Chapter 2 provides the methods to review data generated from earlier environmental monitoring programs. Well Census An accurate well census of potable ground- and surface-water users is an important Phase I tasks associated with an assessment monitoring program (or any environmental assessment or monitoring where ground water is involved). Well census data gathering can take a number of alternative directions. In those states where good well drilling data are available, (typically required by law), the location, logs and depths of local potable water wells are found at state geological surveys, department of health or departments of the environments, depend on state regulations. Unfortunately these data often include ground-water wells drilled only over the last 40 years and older water well logs may not be available (see WDNR, 1985). Recent aerial photo reviews should form part of the well census work to evaluate the location of residences with potential to be locally affected by the facility under investigation. Discussions should also be held with local drillers on areas using ground-water sources and information on target aquifers for the area. These discussions are extremely important in the Phase I project work. They point the direction for Phase II field assessment work and provide important interpretations for conceptual modeling, (i.e., discharge areas, first water contacts, target monitoring zones, etc.), for both the Phase I and Phase II investigations.

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Although the raw data gathered from driller’s logs filed at state offices are typically very rough, they often provide relative depths to bedrock, clay/sand interfaces, soil depths and types of bedrock contacted. These data can be quickly evaluated for usefulness and for how pertinent the data will be to the assessment monitoring program. These data should be always be arranged into at least two formats: 1. A map showing the location of each well relative to the facility 2. Tabular presentations of the available driller log information If sufficient regional geologic information is available for the area (and the geology merits such presentations), cross-sectional presentations should be produced showing the relationship between perceived upgradient and downgradient potable water wells and the facility of interest. This initial cross-section should assist the Phase II field investigation scoping for site-specific drilling and sampling and evaluation work. All adjacent potable water wells should be evaluated by a site visit to evaluate the current conditions and use of the wells. Particular care should be taken to evaluate nearby wells for potential for contamination through facility leachate migration. If any potential exists it is highly recommended that potentially affected downgradient ground-water users be provided with bottled water until adequate testing of the potable well can be completed. Phase I Assessment Report Phase I reports for assessment monitoring programs should cover many of the same aspects as other Phase I reports. However, additional format requirements specific to the federal or state program may require a significant increase in the planning efforts of later Phase II field investigations and the proposed interpretative and analytical programs. One should clearly define the deliverables necessary for the particular assessment monitoring program so that timely and complete documentation is available for the Phase I report. Although these documents, such as, sampling plans, Quality Assurance Project Plans, ARARs and risk assessments are necessary relative to assessment project deliverables, the raw data that feed into much of these documents are developed within the classical Phase I project scope of work. A properly conducted Phase I investigation with the resultant report will greatly assist the production of the required state and federal deliverables. Without the focusing of the Phase I data interpretations later expensive field data gathering efforts can collect irrelevant or redundant data. Often the somewhat random

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analytical results obtained from the unfocused sample collection results in point values of water or soil chemical data without knowledge of what exactly the value means in context to the whole site environment. In addition, reliance on sample collection specifically for analytical laboratory evaluation renders the gathering of important site characterizations necessary for remediation of the facility as secondary and incomplete. No matter what assessment monitoring program is applied to a facility, the goal of the investigation must be to fully evaluate the facility, geologic and hydrogeologic environment before selection of location for ground-water or soil monitoring. The application of the various recommendations provided in this chapter and in later chapters on Phase II field programs can provide significant savings in both the assessment monitoring program design and implementation of the various remedial activities required for the facility. REFERENCES Benson, R., 1988. Hazardous Materials Control, Vol. 1, No. 4. Bernath, T., 1988. Environmental audit and property liability assessment: Pollution Engineering, Vol. XX, No. 9, pp. 110-l l S. Bleiweiss, S. J., 1987. Legal considerations in environmental audit decisions: Chemical Engineering Progress, Vol. 83, No. 1, pp. 15-19. Chereremisinoff, P. N.; J. G. Casana; and H. W. Prichard, 1986. Special Report: Update on Underground Tanks: Pollution Engineering, Vol. XVIII, No. 8, pp. 12-25. Fed. Regist. 1982, 47(143, July 26), 32291. Fed. Regist. 1982, 47(143, July 26), 32295. Fed. Regist. 1982, 47(143, July 26), 32299. Fitzsimmons, M. P. and J. K. Sherwood, 1987. The Real Estate Lawyer’s Primer (and more) to Superfund: the Environmental Hazards of Real Estate Transactions: Real Property Probate and Trust Journal, Vol. 22, No. 4, pp. 765-790. Frost, E. B., 1988, Strict Liability as an Incentive for Clean-up of Contaminated Property: Houston Law Review, Vol. 25, pp. 96l-962.

Harrington, A. J. and J. M. Van Lieshout, 1987. Environmental Concerns in Commercial Real Estate Transactions. In Hazardous/Solid Waste Meeting. October 14: Federation of Environmental Technologists: Milwaukee, Wl (unpublished oral presentation). Kaplan, S.R., 1965. Mining Minerals and Geosciences, Vol. 2, Interscience/Wiley. King, S. M., 1988. Lender’s Liability for Clean-up Costs: Environmental Law, Vol. 18, No. 2, pp. 241-292. Marrin, D. L. and K. B. Kerfoot, 1988. Soil Gas Surveying Techniques: Environmental Science and Technology, Vol. 22, No. 7, pp. 740-745. Peterson, S., 1987. Historical Risk Assessment of Environmental Liabilities at Former Industrial Properties, In Superfund 87' Proceedings, 8th National Conference: Hazardous Materials Control Research Institute, Washington, DC, pp. 45- 47. Roy, M. J. B., 1987. Corporate Successor Liability for Environmental Torts, In Superfund ‘87 Proceedings, 8th National Conference: Hazardous Materials Control Research Institute, Washington, DC, pp. 48-52. U.S.EPA, 1983. Applicants’ Guidance Manual for Hazardous Waste Land Storage, Treatment and Disposal facilities; EPA: Washington, D.C., p. GW-13. U.S.EPA, 1983. Treatability Manuals, EPA-600/2-82-001A: Office of Research and Development, Washington, D.C., 5 volumes. U.S. EPA, 1994. Procedures Manual for Groundwater Monitoring at Solid Waste Disposal facilities; EPA: Washington, D.C. Ward, Dederick, C., and R.A. Bier, 1972. Geological Reference Sources: A Subject and Regional Bibliography of Publications and Maps in the Geological Sciences, Scarecrow Press, Metuchen, NJ, pp. 453. Wisconsin Dept of Natural Resources, 1985. Priorities for Abandoned Waste Site Investigations, an Addendum to Locating and Repairing Abandoned Waste Sites: Wisconsin Department of Natural Resources, Madison, Wl, 32 p. Willman, H. B., 1971. Handbook of Illinois Stratigraphy, Bulletin 95, Illinois Geological Survey, 260 p. Zirschky, J. and R. 0. Gilbert, 1984. Detecting hot spots at hazardous waste sites: Chemical Engineering, Vol. 91, No. 14, pp. 97-100.

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CHAPTER 3 PHASE II SURFICAL FIELD INVESTIGATIONS

A thorough understanding of the geologic and hydrologic regime is essential in a site assessment. For new sites, it is important to define existing hydrogeologic conditions so that the proposed facility may be properly constructed to minimize possible contamination of the ground water. For acquisitions or expansions to existing facilities, it is important to understand the hydrogeology of the region and the site so that the extent of any prior releases to the environment can be determined and proper corrective action implemented. Assessment monitoring programs under Superfund or RCRA also require full evaluation of hydrogeologic conditions to quantify the rate and extent of contamination. Many of the aquifer characteristics established in the Phase II field assessment program will be directly applicable to design of the remediations for the facility. Phase II field investigations are the first third of the site characterization and design of the ground-water monitoring system, as illustrated in Figure 3-1. Chapter 3 describes surface evaluation techniques. Chapter 4 discusses subsurface evaluation methods and Chapter 5 looks at assessment testing methods for the field and laboratory. These three chapters serve as the basis for Phase II field investigations in primary porosity geologic environments. Chapter 6 extends site assessment techniques to fractured rock. Chapters 7 to 9 describe data analysis, development of the conceptual models and design of the monitoring system. The field investigation always provides data used for both design of the groundwater monitoring system and engineering design of the site or the remediation. Data from existing sources and on-site investigations serve as the basis for determining locations, numbers and depths of monitoring wells that are most appropriate to a particular facility. In general, a Phase II description of the area should include a discussion of the following factors: • •

• •

• •

Natural fractures in bedrock or over-consolidated site soils Chemical and physical properties of underlying strata (soil and rock), including lithology, mineralogy and hydraulic properties Soil characteristics, including soil type, distribution and attenuation properties Ground-water regime, including depth to the potentiometric surface, aquifer types, flow paths and flow rates

Important climatic aspects of the area (e.g., precipitation and infiltration) Structural attitude, fracturing and distribution of bedrock and overlying strata Figure 3-1 Ground-Water Monitoring Flow Diagram

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•

Anomalous geomorphic or structural geologic features that could represent potential contaminant flow paths Environmental and human resources in the area

•

This section identifies the many levels of technical information typically necessary to characterize a site for both assessment and detection ground-water monitoring and landfill design, beginning with an understanding of the surface of the site. Complete Phase II characterization is required for siting and development of most major solid or hazardous waste facilities. However, if the quality of ground water beneath the site is relatively poor (i.e., is not a current or potential future source of drinking water) or if a qualified engineer or geologist can show that there are no pathways for contamination of ground water, investigative and data gathering efforts can be appropriately reduced from those described in this chapter. 3.1 PHASE II COMPONENTS This section summarizes the investigative techniques used to collect data for site assessments. The purpose of this section is to provide the project investigator with an overview of these assessment techniques. Much of the information identified for characterizing the hydrogeology associated with a site will probably be obtained through extensive laboratory and field investigations, including hydrogeologic, geologic, soil and water budget analyses, conducted by qualified professionals thoroughly familiar with such methods. Environmental information, if so required by the individual state regulation also should be included to complete a single comprehensive investigation. 3.1.1 Field Parameters Prior to specifying or initiating field work, all existing geologic and hydrologic data should be collected, compiled and interpreted. This scope of work is described in the Phase I study (Chapter 2). After compiling and thoroughly reviewing the collected data, the investigator can properly begin planning a field investigation for Phase II. Some on-site investigation methods may be appropriate in one geologic setting but not in another. A combination of methods will likely be needed in most cases. The Phase I investigation “sets the stage” or scope through development of an evolving conceptual understanding of the site conditions. This conceptual understanding will direct the investigator to evaluate the respective components of the hydrogeologic regime. These pertinent assessment components may include both saturated and unsaturated eval-

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uations. Vadose zone evaluations are especially important for land disposal facilities where thick unsaturated deposits separate the facility base grades from aquifer units. The vadose zone extends from the land surface to the water table. It has also been referred to as the zone of aeration, variably saturated zone and unsaturated zone. Use of the latter term should be discouraged since the vadose zone contains moisture up to 100% saturation; and therefore, the term unsaturated could lead to misunderstanding of overall ground-water flow. In the humid areas, the normal vadose zone may be only a few feet thick, disappearing during high recharge periods when the water table is high. In arid areas, the vadose zone can be several hundred feet or more thick dependent on subsurface geologic units. One should not assume the presence of deep water tables in all desert environments, however, without adequate Phase I regional data. Because the vadose zone overlies the saturated zone, facility releases at or near the land surface must pass through the vadose zone before reaching the ground-water surface. Both detection and assessment monitoring programs on occasion require both the vadose zone and the saturated zone for saturated and unsaturated hydrogeologic conditions. As will be discussed later, the vadose zone can be more difficult to characterize due to complex localized flow conditions than are found in the saturated zone. On the other hand, because it is nearer to land surface, remedial actions may not require complete characterization of the vadose-zone flow system for certain site conditions and contaminants if the majority of the affected soils will be removed or treated in place. The vadose zone can be divided (from the top) into three layers: (l) zone of soil water, (2) intermediate zone and (3) capillary fringe (Davis and DeWiest, 1966). The zone of soil water (see Figure 3-2) extends from the land surface down to where soil moisture changes are minimal. Since it contains the root zone of plants, evapotranspiration is the major active process affecting recharge events. The amount of water and air in the saturated and vadose zones varies both spatially and temporally. This is one reason for the complex nature of the vadose-zone flow system. In general terms when precipitation, falls to the land surface portions of the flow runs-off via overland flow and some percentage infiltrates into the ground. Evaporation and transpiration reduce the quantity of infiltrating water. Evaporation can be defined as the process that converts the water at or near the land surface to vapor. Transpiration is the process by which plant roots absorb water and release water vapor back to the atmosphere through their leaves and stems. These two processes are combined into the term evapotranspiration. In a typical hydrologic system a significant part of the infiltrating water is consumed by evapotranspiration. The water that

PHASE II SURFICAL FIELD INVESTIGATIONS

Figure 3-2 Vadose and Saturated Zones

is not incorporated in evapotranspiration will eventually reach the ground-water surface as recharge. However, as the vadose zone geologic profile gets finer or less permeable (for example, in areas of glacial clays and tills), the downward movement of recharge slows down to where it may take thousands of years for recharge to penetrate through overburden units to the bedrock. This observation has been confirmed through carbon 14 dating of ground water contained in sand lenses that were encapsulated within glacial till materials. Vadose zone characterization may be important to (l) help understand recharge events and how release events may move through the vadose zone and (2) use in design of land disposal unit caps for limiting infiltration and recharge to an uppermost aquifer. The capillary fringe (at the base of the vadose zone) by definition extends upward from the water table until there is a decrease in soil moisture. Portions of this zone can be at 100% saturation. This zone can be expected to change in elevation as recharge/discharge causes the water table to fluctuate. The capillary fringe is formed due to a capillary rise effect caused by the surface tension between air and water; therefore, capillary zone thickness is dependent on the grain size of the geologic units. Fine-grained materials such as clays may have a capillary rise on the order of 10 feet (3 meters) while coarse sands may have a capillary rise of only a few inches. An important field parameter in any site assessment is the hydraulic head present at any particular point in the

vadose and saturated zones. As part of the conceptual process of understanding ground-water flow, hydraulic head relationships must be known in the context of the threedimensional geologic environment. Hydraulic head is made up of two components: an elevation head and a pressure head (see Figure 3-2). At the water table, the pressure head is zero (i.e., equal to atmospheric pressure). It increases below the water table and decreases above the water table. That is, pressure head is negative in the vadose zone, which is sometimes referred to as soil tension or suction; this negative pressure head is also characterized relative permeability. Relative permeability varies between zero and one and represents the nonlinear function of saturation. Thus, for the vadose zone, in addition to determination of the saturated hydraulic conductivity, the relative permeability function must also be known to fully characterize shallow ground-water flow. The following sections describe applicable assessment techniques and test methods that can be used for both vadose and saturated zone evaluations. As such, care should be exercised to use appropriate methods for the hydraulic system under study. However, for most investigations one should concentrate on the saturated zone since these fully saturated units represent the most likely area for significant lateral flow offsite to potential down gradient ground-water users. 3.1.2 Field Task Components Figure 3-3 is a flow diagram illustrating the types of activities and analyses used in selecting locations for monitoring wells at the conclusion of the Phase II investigations. Each illustration is referenced to a Handbook chapter or section number for easy referral. The important concept presented in the diagram is the linkage between individual project producibles (such as a geologic map or boring log) and collection of field data. All data should be collected for a purpose and should be displayed in easily understood formats to aid interpretation. Not all presentations illustrated in Figure 3-3 may be required for a specific site characterization; however, the logical progression of collecting field data, data analysis and conceptualization should be followed, in order to design the monitoring system or an aquifer remediation Subsequent sections provide a general discussion of the types of data necessary for characterizing the geology and hydrogeology of a site and the types of investigative techniques that will likely be used to collect such data. Additional sources of information on investigative techniques can be found in the references included in this chapter. The investigator should realize that the amount of information and field efforts needed to fully characterize a site may be extensive. However, such assessments are

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critical to evaluating both the design of the ground-water monitoring program and other environmental issues related to location, operation and ultimate remediation of both hazardous and solid-waste landfill facilities. A variety of investigative techniques are available to collect data for characterization of hydrogeology. The site-specific investigative program should include direct methods (e.g., borings, piezometers, geochemical analysis of soil samples) for determining the hydrogeology. Indirect methods (e.g., aerial photography, ground-penetrating radar, earth resistivity borehole geophysical studies) also may provide valuable sources of additional information (such as porosity). Thus, the investigator should combine the use of direct and indirect techniques in the investigative program to produce an efficient and complete characterization of the facility. Different types of investigations, such as greenfield siting or expansions of existing facilities, may require somewhat different Phase II work components. Table 3-1 shows the potential components of a

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Phase II investigation for greenfield, site expansions, remedial investigation/feasibility studies for Superfund or RCRA remediation projects and investigations where fractured rock aquifers are present. The list only provides a general reference for comparison and for collection of field data. Phase II investigations must be of sufficient intensity to determine the conditions that may, for example, influence the design and construction of both the landfill and the ground-water monitoring system (see Figure 3-4). The extent of geologic investigation required for a particular site depends on: (1) complexity of the site conditions; (2) size of the landfill and (3) potential damage, if there is functional failure in the containment. This chapter has been divided into eleven subsections. Section 3.2 summarizes investigative techniques that are basic to data gathering efforts and the development of base maps upon which site data can be illustrated. Section 3.3 describes the types of soil classification

Figure 3-3 Phase II Flow Diagram

PHASE II SURFICAL FIELD INVESTIGATIONS

Table 3-1 Phase II Work Components

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Table 3-1 Phase II Work Components (Cont.)

systems used to describe both surface and subsurface materials. Sections 3.4 and 3.5 discuss regional and sitespecific data required to characterize surfical geology and geophysics. Section 3.6 discusses climatic and hydrologic information needed to assess the effects of surface water patterns. Section 3.7 describes aspects of the surface- and ground-water quality water quality and land use that

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should be assessed during the investigation. Section 3.8 summarizes field ecology surveys to evaluate endangered species in and around site areas. Section 3.9 provides general procedures for historical and archaeological surveys. Methods and tools of Holocene faulting investigations important for documentation of site conditions are provided in Section 3.10.

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While this chapter is intended to give the investigator an idea of and a guide to, the extent of potentially necessary data-gathering efforts, it should not be viewed as a “checklist” for the completeness of a site characterization. The specific types and amounts of information that must be collected and presented will vary from site to site (e.g., states with more stringent assessment requirements would require more information to characterize the facility). Evaluation of any site requires a consideration of the geologic or hydrogeologic features that may affect ground-water flow. Figure 3-4 illustrates the building process used to characterize a glacial till for hydraulic conductivity features. Those features that would cause directional or enhanced flow must be evaluated for the particular site in question. In the case of the glacial till environment, sand layers, weathered zones and potential fractures, if present, must be fully evaluated for effects on ground-water flow. The individual components of a Phase II investigation are linked to the overall complexity of the site. Figure 1-7 (in Chapter 1) provides a conceptual basis for planning site assessments referenced to the overall complexity of the geologic and hydrogeologic environment. It is highly recommended that the investigator work out the Phase II components on the basis of the Phase I regional information. In other words, link the extent of the investigation on the complexity of the system. 3.2 TOPOGRAPHIC MAP The intent of requiring a topographic map as part of a Phase II investigation is to provide a base for information collected in the Phase II field investigation, and it provides some of the required site-assessment parameters, such as contours, scale, date, etc. Two types of topographic maps are usually prepared for Phase II investigations: • •

Regional Base Map Detailed Base Map of the Site

The regional base map, used for site location and general area features, was described in Chapter 2. These base maps are easily obtained from published sources and can be used directly for illustrative purposes. These maps, however, have limited use for the engineering design and location of environmental sampling points of a facility; hence, a detailed base map of the site is normally required for Phase II investigations. 3.2.1 Site Topographic Map The topographic map of the site should contain 2-foot or 5-foot contour intervals. USGS maps (7.5-minute quad-

rangles) generally have contour intervals of 10 feet or more; therefore, a more detailed contour map may generally have to be produced for each site. Methods applicable to producing or obtaining the necessary topographic maps include: • • •

•

Obtaining a map from local town offices On-site surveying to gather exact elevations and preparation of a contour map Use of a photogrammetric survey company to fly the site and develop a map with a specified contour interval The use of a USGS map, when it meets the required qualifications

Often, local town offices, such as the Building Department or Board of Assessors, have compiled largescale maps which might be helpful in meeting the topographic map requirements. Municipal tax maps, available from town clerks at local Town/City Halls, may provide useful information for a base map (e.g., boundary lines, rights of way, structures, pipelines). Such a map could be used as a base map if the contour intervals are 2 or 5 feet. If no suitable topographic map of the proposed site location exists, it may be necessary to measure and plot land elevations by conducting a stadia survey. This technique will provide the information necessary for plotting any desired contour interval. The base map may be prepared, in part, from information from stereoscopic aerial photos (photogrammetry) yielding pertinent information on location of surface features. Departments of Transportation, Departments of Environmental Protection and County Planning Departments generally catalog such state or regional aerial photos. Agricultural, landscape design and other related academic departments at colleges and universities throughout the country also maintain aerial photographs. Section 2.1 provides information on sources of aerialphoto base maps. Another and more typical method that the investigator might choose to meet the topographic map requirements entails the use of a photogrammetric survey company to target the site and then photograph the area and produce the required maps. Such companies are available throughout the U.S. Their abilities include planning and scheduling the flight to collect data for the map, performing the flight, analyzing the results and compiling a final topographic map. These companies can provide the topographic data in the form of mylars or digital format for later use in CAD/CAM systems. In addition, the investigator could request that this company take the aerial photos needed for location of faults or other geologic

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Figure 3-4 Example Phase II Characterizations

information, thus fulfilling several site-assessment requirements at one time. The project staff should carefully consider use of 2- or 5-foot contours in areas that have significant relief. If 2foot contours are required (as in California) for submittals to state agencies, costs for photogrammetric surveys escalate quickly to $20,000 (2002 costs). This would provide

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flight services and production of a 1-inch to 200-foot (1:2400 scale) topographic map for a 1,200-acre site. 3.2.2 Site Base Map In order to verify that the requirements for location of upgradient and downgradient wells are met, the prepara-

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tion of a site base map is mandatory. The base map can be used throughout the process of locating wells to summarize and display information (see Figure 3-5). In addition to its use for contour maps of the ground-water surface, a base map should also be used during planning and executing the on-site investigation, as well as to serve for facility design. The area to be covered by the base map, should be selected to best represent the significant features at the facility. The base map should extend beyond the facility boundaries to cover other areas that may be affected by

disposal activities, such as off-site surface-water supply wells, references to thematic maps and watershed runoff drainage paths onto the site. USGS topographic quadrangles and aerial photographs may help in deciding how far to extend the base map. Dependent on the size of the facility, an appropriate scale for a base map is 1 inch equal to 200 feet (1:2400; approaching 1:2000, but not 1:3000), unless other factors override. (Note: The USGS, in converting to metric representations, commonly employs a scale of 1:2500, which is

Figure 3-5 Example Site Base Map

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also a useful scale.). Although available aerial photographs do not usually provide this level of detail (1 inch equals 2,000 feet is a commonly available scale for aerial photographs), information obtained on land surface features and man-made structures is very useful in base map preparation. The selection of scale should be based on placement of the site features on a single sheet of 24" x 36" or 11" x 17". Very large sites may require smaller scales to properly fit within the base map sheet. Important features which should be identified and located on the base map include: •

Facility-related structures (e.g., buildings, roads, parking lots, existing wells, pipelines, benchmarks, soil and water sampling areas, borrow pits and quarried, stockpiled soil or rock, and foundation exploratory borings); Potential, adjacent sources of contamination (e.g., impoundments, other landfills, storage areas, septic tanks and drain fields) and adjacent waste management facilities; Direction of surface water bodies, drainage, and discharge points (e.g., streams, ponds, drainage patterns and divides); Withdrawals (e.g., wells, springs); and Vegetation.

•

•

• •

An essential component of site mapping is to compare existing site configurations with the predevelopment topography and man-made features. This may be critical for interpretation of effects of prior land use on the ground-water system. Scale keys should always appear on the base map so that later reductions or enlargements are reflected in the size of the key. 3.3 SOILS Soils data provide a basic source of information on the extent, thickness and physical properties of suitable geotechnical construction materials for liners, drains and daily and final cover. Such data also provides a fundamental basis for decisions on the viability of soils at the facility base grade to contain or restrict the ground-water movement in or out of the site. Although published soils maps and aerial photographs of an area may provide useful information, detailed exploration of on-site soils may be necessary. This information is typically obtained through the use of the same investigative measures discussed later in Chapter 4 under subsurface geotechnical investigative methods and by laboratory analyses of the samples collected. These surveys are especially important in areas of heterogeneous material that show significant variations in physical properties and/or stratigraphy. At least some of the soils information will be acquired

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through borings conducted to investigate the subsurface stratigraphy. This section includes discussion of soil characteristics that should be investigated at each site. These characteristics include: • •

Soil types and area extent as illustrated on soil maps Physical and chemical properties of each soil, such as organic carbon content, percentage clay and moisture content

In analyzing the surfical soils at homogeneous sites, published or otherwise available maps may be helpful if soils are undisturbed. While less likely to be available in adequate detail, published sources may also provide information about subsurface soils. If soils at the site surface have been disturbed, a soil survey may be conducted to determine the distribution of each type of soil. The first step in a soil investigation is identifying and classifying soil types. The U.S. Department of Agriculture's soil classification scheme (see Figure 3-5), based on soil grain-size distribution, is the typical presentation format. Most of the National Cooperative Soil Survey (NCSS) maps or in common language, “agricultural soil survey” maps, in the U.S. have been published since 1899 by the Soil Conservation Service of the U.S. Department of Agriculture in cooperation with several federal and state agencies, particularly in cooperation with state Agricultural Experiment Stations. Some soil surveys are also published by certain state organizations. The list of federally published soil surveys for the entire U.S., together with a brief introduction, is periodically issued by the Soil Conservation Service of the Federal Department of Agriculture (SCS, 1972). More up-to-date listings are frequently available from the local State Soil Conservation Surveys and related offices. The state listing frequently contains important information on completed but still unpublished soil surveys and surveys in progress. Mailing addresses of the state offices are included in the Federal List of Published Soil Surveys. All soil survey maps are accompanied with a more or less explicit text describing topography, climate, agriculture and soil series in the study area. Some initial general soil surveys are of a reconnaissance character and cover a large area but have relatively brief descriptive text. Most of the surveys published prior to 1957 are on a scale of 1:62,500 and 1:125,000 (1 in. equaling 1 or 2 mi) and their descriptive text is also rather brief. Most of the soil maps after 1957 are to scales of 1:24,000; 1:20,000 and 1:15,840. In general, these maps are much more detailed than many available published geologic maps. Many modern soil maps are printed on aerial photographs (ortho quads) and the associated text contains detailed data on climate, soil formation, topography, agriculture, irrigation, drainage, conservation, etc. Some

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surveys have useful diagrammatic profiles and tabulations showing the relationship between soil series and topographic units. 3.3.1 Classification System Main units shown on soil survey maps and identified by letter number indices or colors are the so-called soil series or “soil series association” in which mapping units combine several soil series. These series are frequently subdivided into smaller units or phases. Different systems of pedological classification have been developed and are being employed at the present time (see Figure 3-6). Most useful for the engineer and others dealing with shallow foundations in the U.S. and

cooperating countries is the Thorp and Smith (1949) formulation of the original Marbut system (USDA, 1938). Marbut lists the following features as essential for the definition of a soil unit: number, color, texture, structure, thickness, chemical and mineral composition, relative arrangement of the various horizons and the geology of the parent material. An individual soil unit, the soil type, has at least two names: a series or family name and a class (texture) name (for example, Sassafras loam). A soil series is comprised of all soils that have the same: •

Parent material: (a) solid rock (igneous, sedimentary, metamorphic), (b) loose rock (gravels, sands, clays, other sediments)

Figure 3-6 Soil Classification Schemes 89

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•

Special features of parent geologic material (residual or transported by wind, water, ice or combinations or parent geologic formation)

•

Topographic position (rugged to depressed)

•

Natural drainage (excessive to poor)

•

Profile characteristics

The different series usually have geographic names indicative of the location where they were first recognized and described (e.g., Sassafras, Putnam, Cecil). The soil series are important to the geotechnical engineer and are described in detail and mapped by the U.S. Soil Service. A list of published soil surveys of the U.S. and its territories is available through the SCS. Identification of a soil in the field as belonging to a certain series makes automatically available the information already gathered regarding this soil. By conducting a soil survey, the extent of soil types at the site can be identified. Results should be presented on a plan-view soil map. To supplement the surface analysis, a cross-sectional analysis of the soils underlying a site can also be conducted. Results should be presented via maps showing soil thicknesses, types and extents (lateral). The information needed to prepare these cross-sections should be available from soil borings or test pits compiled in the field program. The location of each borehole or backhoe pit should be identified on each soil survey map. 3.3.2 Soil Properties and Geology Soil properties that are important to measure or determine for understanding the engineering, physical and chemical properties include: porosity (total and effective), hydraulic conductivity, moisture content organic carbon content, cation and anion exchange capacity and grainsize distribution. These parameters should be available for each significant soil zone (i.e., several soil types having similar characteristics) underlying a site and should be presented in the site assessment report as a table summarizing soil information. The geologic interpretation of soil maps typically used by investigators is based essentially on the: (l) composition of source (or parent) material for the different soil series; (2) age of the soil series, which controls the degree of development of the soil profile; and (3) topographic-geomorphic location of the different soil series. The first and probably the most difficult step in geologic interpretation of soil maps is to establish the sequence of geomorphic geologic units in the area and their engineering characteristics. Many soil survey publications have a generalized profile showing the major geomorphic units

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and their relationship to the soil series. The geologic interpretation of some soil surveys, however, is sometimes difficult due to occasional differences in terminology used in pedelogy and geology. The engineer must make the translation from soil survey nomenclature to engineering nomenclature for soil surveys to provide the optimum use (see Figure 3-5). Generally, these analysis efforts can provide keys to identifying underlying geologic materials, especially in residual soil areas. Engineering data available from an interpretation of soil maps may sometimes be of greater interpretative value than data obtained from a review of common geologic maps. Particularly important are data on the presence and composition of the B horizon and on distribution of soluble salts illustrated on soil maps, but missing on geologic maps. The presence of the B horizon may cause serious operation-maintenance problems in facility excavations. For example, perched water bodies developed on B horizons can cause both numerous slides and slumps in cut banks These perched water tables also confuse ground-water monitoring system design. 3.4 GEOLOGIC MAPPING Mapping the surfical geology of the site and adjacent areas represents an important early Phase II task. On the basis of the information obtained during the Phase I regional geology investigation, appropriate field mapping should be performed to define the general geology of the site, including soil conditions. The goal of this investigation is to identify the geologic conditions that may affect location of the facility monitoring system and those geologic conditions that may influence ground-water occurrence, movement and recharge. The primary purpose of the mapping is to aid in selection of locations for exploration borings, piezometers and later location of monitoring wells. This geologic mapping must be performed early in the Phase II work activity since geologic conditions have an important influence on the ultimate location and success of the monitoring well system. Sufficient time should be allowed to evaluate the geologic conditions before selecting subsurface investigation methods. The resultant geologic maps generated from this task should be refined after the Phase II drilling program to address three-dimensional distribution of the geologic and earth materials exposed or inferred within the area. This work is best based upon both geologic and geophysical interpretations of the site area. In areas underlain by overconsolidated soil or fractured bedrock, secondary porosity may provide the major source of hydraulic conductivity. Here the geologic mapping program should include a detailed analysis of the orientation and distribution of fracture joints and joint sets.

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Fractures are characterized on the basis of information obtained from mapping of surface outcrops, tunnels, excavations, mines, adits, core drilling and logging. Among the parameters most commonly recorded are the locations orientation, size, opening and nature of infilling of individual fractures and parameters describing the spatial relationships between fractures such as spacing and density. The data are then given a geometrical representation in the form of schematic diagrams, fracture maps, depth profiles, parametric stereograms and polar or cyclographic stereograms or a statistical representation in the form of histograms and statistical stereograms (also known as rose diagrams or rosettes). Chapter 6 specifically reviews the fractured rock environment where secondary porosity is the primary mode for ground-water movement. 3.4.1 Geological Map of the Site Production of site geologic maps requires that some level of standardization be employed so that subsequent evaluations can build on the field interpretation toward final conceptualization of ground-water flow. A standard for engineering geologic mapping was issued by the Geologic Society of London (U.K.) in its Quarterly Journal of Engineering Geology. “The preparation of maps and plans in terms of engineering geology” was developed in the United Kingdom by the Geological Society Engineering Group Working Party (1972). Although somewhat modified later, this 89-page report was the first comprehensive work in English on the whole spectrum of engineering geology methodology, including what to do in the field, how to do it and cartography of maps at scales of 1:10,000 or smaller and of engineering geologic plans at larger scales. Further comment about the Working Party report symbols for lithology was made by Dearman (1974). In 1968, the International Association of Engineering Geologists (IAEG) established as its first commission the Working Group on Engineering Geological Mapping. The commission, composed of seven internationally known experts, produced its first major work—Engineering Geological Maps, A Guide to Their Preparation (Commission on Engineering Geological Mapping of the International Association of Engineering Geology, 1976). This is a comprehensive volume and is well illustrated by examples from actual maps in a variety of scales. These maps are reproduced in color and in black and white. Although not specifically designed for surface geologic mapping, the classifications of rock developed by the International Society for Rock Mechanics (Commission on Classification of Rocks and Rock Masses) and of soil by the American Society for Testing and Materials are

pertinent sources of basic site mapping information. Various rock classification schemes were reviewed by Bieniawski (1988), who concluded that there was a need for limited standardization but that there are advantages to having several systems available for comparison on a given project and for application to various engineering requirements. A simplified system that does appear applicable to field classification, has been presented by Williamson (1984). 3.4.2 Geologic Mapping Examples Figure 3-7 is a regional geologic map of a California facility. The map includes recent unconsolidated alluvium and pre-Holocene faults. Figure 3-8 is a map of the subsurface geology at a site in Pennsylvania. Details of pre-Holocene faulting are given along with surface features of the site. Relating surface and facility features to the underlying geology is a powerful analytical tool in site characterization studies. Combining topographic map features with geology also offers a useful tool to understand the surface outcrop pattern and potential recharge/discharge patterns. Figure 3-9 shows the regional bedrock geology of an area containing fractured rock in Pennsylvania. The figure includes a detailed geologic description of the site and a frequency diagram of the strike of subvertical joints observed in exposures and quarries. Figure 3-10 is a map of the local surfical geology near a site in California. Holocene, Pleistocene, Miocene andppre-Cretaceous geologic units are mapped along with urban features adjacent to the site. 3.4.3 Mapping Procedure The first objective of a site assessment where geology is visible from the surface is the production of a general geological map for the site area, describing the rock type distribution, faults and tectonic structure. A site geological map is developed by using existing regional geological information (from Phase I work), photogeology, obtained from historic recent flights and by onsite geological mapping. Available geologic maps obtained during the Phase I investigation can greatly help in planning a site-specific geologic survey. The following advice can be provided in reviewing geologic maps that apply to planning an additional site geologic survey: 1. Determine the regional setting by referring to a smallerscale map that shows the relationships of the area in question to surrounding previously mapped areas. 2. Read the legend and other marginal information of the

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map to be studied, noting in particular the conventional symbols that are used. 3. Base your conclusions of detailed study on the evidence of more than one area or part of a map—it is quite common for a particular outcrop or exposure to represent a local anomaly or deviation from the general pattern. 4. Study the regional map as a whole, for example, by viewing it from a distance of a few yards, in order to rec-

ognize the broad pattern of rock relations that are shown in the area. 5. Relate your interpretation of the map to the historic environments and processes that created the rock/sand/clay structures that you are studying. In this way the geology of the area shown by the regional map will fit in the context of the specific site mapping area. Approaches to geological mapping vary according to

Figure 3-7 Geologic Map

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the amount of natural outcrops, complexity of geological structure, time constraints and goals of the project. Topographical control of geological observations must be developed from topographical maps and aerial photographs or for detailed work with the aid of a plane table and survey data. Investigations of these various geologic features must be as systematic and quantitative as possible. In general, the following requirements must be satisfied (Compton, 1962): • •

•

The stratigraphic frame of reference for measurements must be well understood. Rock names and descriptions should be quantitative and based as much as possible on characteristics that have genetic meaning. Small structures must be observed to determine conditions of sedimentation as well as stratigraphic sequence.

•

Methods of sampling and measuring must be precise enough to permit accurate correlation of data.

A single comprehensive study is generally preferred to several partial ones, for some data can be interpreted only in the light of others. Many projects, however, must be limited in scope and must therefore be organized carefully in order to meet their special purposes. Lithologic descriptions (such as shown on Table 3-2) are more usable if recorded in a fairly systematic way, as by the outline (Compton, 1962) that follows. Care must be used in determining the colors, induration and mineralogy of units that are weathered almost everywhere; otherwise, their “typical” recorded lithology can be totally unlike descriptions of the same unit in drill cores or mine samples. This does not mean that weathered materials should not be examined; weathering may make it possible to see structures and minerals that cannot be

Figure 3-8 Surfical Geologic Map

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Figure 3-9 Facility Geologic Map seen readily in fresh rock. Mapping approaches can be divided into traverse mapping or area mapping depending on the level of exposure. In addition, significant discussion is provided in Chapter 6 on fracture or discontinuity mapping. Such data are necessary for hydraulic conductivity assessments and conceptual modeling which require knowledge on orienttion components of the fractures present in the facilities’ bedrock. Area Geologic Mapping Area geologic mapping is recommended if the site possesses less than about 10% of natural outcrop. These mapping programs require every available outcrop delineated on the area base map, with geological observations plotted within these outlines. The end product is a drawing on which the geology and orientation measurements are plotted on a series of outcrop islands. As typical for these types of presentations, geological features between outcrops must be interpolated as inferred conditions with dashed lines One should provide clear explanations in the accompanying map text what geologic data were inferred from observed conditions. The Manual of Field Geology by R.R. Compton or Field Geology by Lahee should be

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consulted for further advice on general geological mapping. Traverse Geologic Mapping Sites with thin overburden and considerable rock exposure should have systematic mapping of geology to provide representative coverage of the area early in the project work tasks. These geologic site assessments are performed by laying out a system of parallel traverses across the area, about 100 ft to (30 m) to 1000 ft (300 m) apart, dependent on outcrop conditions. The traverses are located on the project base map and surveyed in the field. The required observations along these traverses are documented by the geologists, and the observation locations are either paced out or measured by more accurate survey activities. Connections between traverses are typically made by interpolation and are clearly shown as dashed lines on the final geologic map. Due to the effects on ground-water flow at waste disposal sites, areas of complex geology, rock type boundaries and faults have to be clearly mapped and described for later potential field drilling work. The general geological map of a facility or proposed waste disposal site provides essential background infor-

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mation for decision making on general facility conditions but is insufficient for developing either detection or assessment ground-water monitoring programs. Rock and overburden materials should not only be known by geological names but also provide an estimate of potential primary porosity flow paths and hydraulic conductivity. Fractured rock and, in some cases, partially fractured confining units require that the discontinuities be described in more detail than is the case in general geological mapping. This discontinuity or fracture-set mapping procedure is described in Chapter 6. The geologic map should clearly delineate the facility location and should show structural attitude, distribution and lithology of surfical engineering geologic (soil) units, as well as bedrock types. Faults on or near the site should be located on the map and (along with geologic information) discussed in the geologic narrative of the reports, keeping in mind the potential of such features to act as pathways or barriers for the movement of ground water or the migration of leachate. While published sources will be of use (generally at scales of 1:24,000 or smaller), the level of detail needed (usually 1:2,400 or larger) for gaining this information will probably require limited field and mapping (outcrop) surveys. Trenching and backhoe trenching may be needed to accurately document the location of Holocene ( 80 Hz) geophones and by filtering the low-frequency end of the signal. The cross-sections obtained from seismic reflection programs look very similar to ground penetrating radar (GPR) data, in that they provide a picture-like cross-section. Reflection is very useful for mapping the top of bedrock, bedrock channels and alluvial and fluvial deposits and for identification of important secondary hydraulic conductivity features such as fractures and channels. Seismic reflection data can also display phantom horizons in a manner similar to GPR traces and care should be used in their interpretation as lithologic boundaries. Shallow reflections require special evaluation techniques to design the field testing program. The details of the “optimum window” and “optimum offset” shallow seismic reflection techniques utilizing a 12-channel seismograph are presented in a series of papers by Hunter et al., 1982 and 1984. The “optimum window” refers to the space in time when the subsurface reflector can be observed with minimum interference. The near side of the “optimum window” is located beyond the zone of “ground-roll” interference. Ground-roll is a term related to low-frequency vibrations traveling along the ground surface (Slaine, 1989). The far side of the “optimum

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window” is usually the point where other events such as shallow overburden reflections start to interfere with the deeper or bedrock reflections. Within the “optimum window,” a “common offset” is chosen, meaning that the seismic section is shot one trace at a time with the same source to geophone spacing. Individual channels on a 12-channel seismograph are then shot one at a time while maintaining the chosen offset. Data are stored on tape or in the memory of the seismograph for subsequent analysis. Computer processing of seismic records involves: •

Data enhancement with bandpass filtering, trace gain normalization, automatic gain control, gain tapering and muting

• •

Alignment using static corrections for variations in the first arrival refraction Velocity analysis using normal move out corrections as described by Gagne et al., (1985) to convert velocity data to depth measurements

Figure 3-19 shows the result of a reflection study (Slaine, 1989) Metal Detection Metal detectors have been extensively used in site investigations since they are important tools for detecting and delineating boundaries of filled areas or trenches containing metallic drums or other metallic waste (see Figure 3-20). A metal detector is a continuously sensing instru-

Figure 3-18 Example Refraction Dataset

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Figure 3-19 Example Refraction Results ment displaying metered results as the investigator walks along a traverse line. The range of these instruments is relatively short; their response is proportional to the crosssection of the target (thickness of the target is relatively unimportant) and inversely proportional to the sixth power of the distance to the target (Benson et al. 1984). Although metal detectors can be affected by pipes, fences, cars, etc., they have been used on many site assessments to effectively define trench boundaries and locate buried drums, utility lines and tanks. They also can be used to select drilling locations clear of metal obstructions or hazardous drum disposal areas.

field called induced magnetization. Magnetometers use a measurement of the intensity of the Earth’s magnetic field to detect the presence at waste disposal sites of buried ferrous metals by magnetic variations. The magnetometer’s response is proportional to the mass of the ferrous target and inversely proportional to the cube of the distance to the target. A single drum has been reported (Benson,

Magnetometry Mapping of the intensity of the Earth’s magnetic field and interpretation of variations in its intensity over a study area is an important geophysical technique used primarily in mineral and petroleum exploration in many types of geologic environments. These variations, called magnetic anomalies, are the distortions of the regional magnetic field of the Earth produced by materials of magnetic properties in the subsurface (shown in Figure 3-21). Magnetic anomalies important to site assessments are due to the magnetization induced in a rock by the Earth’s magnetic

Figure 3-20 Metal Detection

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1988) detected as deep as ten feet with large masses of drums detectable down to thirty feet. The use of magnetic surveys in hard rock terrain for geologic assessments is limited practically to the regions of igneous and metamorphic rocks. The sedimentary rocks are non-magnetic, hence most common hard rock aquifers such as sandstone and carbonate rock show little benefit from magnetic surveys. Because of the extreme sensitivity of the Earth’s magnetic field to micro-scale anomalies, magnetometer works best in rural areas away from urban magnetic perturbations (fences, power lines, underground pipes). Two types of electrical magnetic instruments use different measurement techniques to obtain magnetic mapping data. Flux gate magnetometers use the frequency of the magnetic momentum of hydrogen ions after relaxing a strong magnetic field. The proton procession magnetometer directly measures the total intensity of the magnetic field present at a survey point. The proton procession magnetometer is based on a transducer that converts the Earth’s magnetic field strength into an alternating voltage, which has a frequency proportional to the field strength. Proton procession magnetometers require the operator to stop for each measurement; fluxgate gradiometer magnetometers permit continuous data acquisition as the instrument is moved across the site (Figure 3-20). Continuous coverage is typically more suitable for detailed surveys and for mapping areas where complex anomalies are expected. Using an appropriate instrument is essential because the effectiveness of some magnetometers can be reduced or totally inhibited by noise or interference from time-variable changes in the Earth’s magnetic field, magnetic minerals in the soil or iron and steel debris, pipes, buildings, passing vehicles, etc. Electrical Geophysical Methods The electrical conductivity of Earth’s materials can be studied by measuring the electrical potential distribution produced at the surface by an electric current supplied into the ground by means of electrodes; this is called the resistivity method. Another method detects the low frequency electromagnetic field produced by an alternating current introduced into the ground and is called the electromagnetic method. The range of electrical geophysical techniques are shown in Figure 3-22. The study of the decaying potential difference, when the injected electrical current was turned off, is known as the induced polarization method. Very-short-time duration electromagnetic pulses measured as reflected energy are used in the ground-penetrating radar geophysical method. Electrical methods use a number of physical properties of rocks:

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Figure 3-21 Magnetometer

1. The specific electrical conductivity of rocks (i.e., their ability to conduct direct and low-frequency electrical currents) 2. Induced polarization which occurs when an electrical current is passed through them and then interrupted 3. The permittivity of rocks (i.e. their ability to conduct high-frequency electrical current as applied by the ground-penetrating radar mapping system). Figure 3-22 shows the various frequencies used by electrical geophysical methods both for laboratory evaluations and field site assessments. Ground-Penetrating Radar (GPR) GPR provides the greatest resolution of all the surface geophysical methods. High-frequency, very-short-time duration electromagnetic impulses in the 100-MHz to GHz range are transmitted through an antenna system into the Earth (shown in Figure 3-23). GPR impulses are reflected at interfaces where a dielectric constant change exists in the geologic units. The GPR reflected impulses are received at the surface and reflection depths are defined by the travel time from the surface to the reflecting surface and back again. The final graphic presentation is a cross-section displaying the reflecting surfaces. Varia-

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Figure 3-22 Frequencies Used in Electrical Geophysical Methods tions in the return signal are continuously recorded to produce a cross-sectional profile of shallow subsurface conditions. Many different types of Earth radar instruments are available under different trade-names but the basic principle is the same as represented in Figure 3-23. An interpretable profile is produced by moving the GPR antenna over a ground surface and a cross-section representation is made up from a collection of many pulses transmitted and received along the profile (Figure 3-24). An interface between soil and rock units having sufficiently different electrical properties (dielectric and conductive) will show up in the radar profile. The profile will also show differences caused by buried waste materials, drums or buried pipes and cables.

Radar performance and depth of penetration are highly site-specific because of attenuation due to the higher electrical conductivity of subsurface materials or scattering. Generally, better overall penetration is achieved in dry, sandy or rocky areas; poorer results are obtained in clay or conductive soils. Radar penetration in soil and rock to 30 feet is typical, with special GPR systems reading to 70 feet under optimum conditions, but penetration may be considerably less in some cases. Where saturated silts and clays are present, GPR penetration may be less than 3 ft, under dry conditions, with computer enhancement of the datasets, radar penetration depth may reach 45 feet. The ground-water surface will be detected in coarse-grained materials, though probably not in finer grained materials.

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The continuous profile (Figure 3-25) produced by GPR permits data to be gathered rapidly, thereby providing a large amount of data with substantial detail. This detail can, however, be difficult to interpret and only experienced staff should attempt to analyze the results from these surveys. Since the profiles can be generated quickly in GPR, many lines can be run across a site to cross-check the profiles. Lower frequencies of GPR (80 MHz) provide greater depths of penetration. Higher frequencies can provide better resolution. However, care must be exercised in the interpretation, since even strong reflectance features are often not discernible in samples collected by drilling or backhoe trenching programs. Electromagnetic (EM) The electromagnetic geophysical methods have become one of the more popular techniques used in site assessment, since they provide a rapid measurement the electrical conductivity of subsurface soil, rock and ground water. The EM methods induce a current in the ground without ground-contact by placing an alternating current in a coil placed over the ground surface. Changes in phase and magnitude of the individual currents are measured by

Figure 3-23 GPR Geophysical Methods

Figure 3-24 GPR Geophysical Method in the Field

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Figure 3-25 GPR Trace in the Field a receiver coil. By varying the frequency, “depth sounding” can be produced without changing electrode distances. For EM resistivity methods, the exploration depth depends on the transmitter receiver spacing and the coil configuration. Electrical conductivity is a function of the type of soil or rock, the porosity and permeability of the rock and the fluids filling the pore spaces. Because the EM fields are attenuated strongly in conductive media, EM fields have a certain (effective) depth of penetration or skin depth. The effective exploration depth depends on the frequency of the EM field used and the resistivity of the ground. The conductivity (specific conductance) of the pore fluids contained in the soil or rock may dominate the EM field measurement. EM field programs are, therefore, useful for assessing natural hydrogeologic conditions and migration of higher conductivity facility leachate. Waste trench boundaries, drums and metallic utility lines can also be located with EM techniques. The primary limitations of EM methods are the narrow range of sensitivity, susceptibility of the electromagnetic signal to interference and sensitivity of the instrument to misalignment. Detection and correction of alignment errors are part of the

standard operating procedure for those EM devices that are sensitive to misalignment. In general, standard EM mapping lacks the resolution and depth penetration of resistivity mapping but has the advantage of being rapid and less expensive. Recent advances in high-resolution EM techniques now allow the collection of massive numbers of quadrature and in-phase readings for site assessment mapping. The Geonics EM31-DL device is used to simultaneously map the quadrature (terrain conductivity) and in-phase (metallic) response of the shallow subsurface. The EM-31 operates on the principle of electromagnetic induction and has an approximate depth of exploration of 4 m (13 feet). The unit creates an oscillating primary magnetic field in the earth through a transmitter coil. The primary magnetic field (Hp) creates a secondary magnetic field (Hs) that is detected by the receiver coil. Geonics Limited attached a data logger system of the EM-31 model, which permits data to be digitally recorded and stored on-site. The data logger transmits information to a laptop computer where the data are initially analyzed on-site and stored on floppy disk. A data logger system

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Figure 3-26 EM-31 Method in the Field tied to the geophysical device increased the amount of data one is able to measure during a survey along with increasing the overall efficiency of the system. The absolute apparent conductivity of the geologic materials and contained ground water are not necessarily diagnostic in themselves; however, variations in conductivity, observed both laterally and with depth, is the interpretation tool. EM anomalies in the data arrays (typically shown as contour maps of apparent resistivity) enable the investigator to define potential problem areas. Lateral variations in conductivity can be mapped by a field technique called EM profiling. Profiling measure-

Table 3-7

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Depth Penetration EM-34-3

ments have been reported by Benson (1988) being effective to depths ranging from 2.5 to 200-feet (see Table 3-7 and Figure 3-27). These profile methods use frequency domain EM systems by applying a continuous alternating current of a fixed frequency. Continuous profiling measurement by EM can be obtained for shallow surveys (down to 50 feet). This method allows increased rates of data acquisition to improve resolution of small hydrogeologic features. Resistivity Resistivity geophysical methods measure the electrical resistivity of subsurface soil, rock and ground water by applying a direct current (DC) or alternating current (AC) of very low frequency. Resistivity is the reciprocal of conductivity, the parameter measured by the EM technique. The resistivity method is based in principle on the contrast in resistivities of rocks, rather than on absolute resistivity values. In most rocks, electricity is conducted electrolytically by the interstitial fluid and resistivity is controlled more by porosity, water content and water quality than by the resistivities of the solid matrix. Clay minerals, however, are capable of conducting electricity and the flow of current in a clay layer is both electronic and electrolytic.

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Figure 3-27 Geonics EM-34 Electromagnetic Induction Geophysical Method The conductive water film is very thin in coarse-grained sands and pebbles, thus the effect of saturation is very large on their resistivities. In fine-grained clays, however, where the water film fills the pore volume almost completely, resistivity changes little. These clay resistivity lows (or conductivity highs) also confound EM measurements. Resistivity contrasts, however, are sharp enough for practical site assessment purposes and they exist locally in most cases in spite of a wide range of regional variations. The resistivity method pumps electrical current into the ground using a pair of surface electrodes (Figure 328). The resulting ground potential (voltage) is then measured at the surface between a second pair of electrodes. The potential distribution within a homogeneous and isotropic rock containing the current electrodes at the surface is shown in Figure 3-28. The subsurface resistivity is calculated from the separation and geometry of the electrode positions, the applied current and the measured voltage. The typical difference in the electric resistivity of aquifers and confining unit rocks (Figure 3-28) points toward the applicability of resistivity methods in site assessments. Resistivity methods have been used successfully in stratigraphic as well as in structural ground-water assessments. Horizontal profiling is used to determine the

variations of the apparent resistivity in the horizontal direction within a pre-selected range. This method uses a fixed electrode spacing set on the basis of studying the results of electrical soundings. The whole resistivity electrode array is moved along a profile after each measurement is made. The value of apparent resistivity is plotted, generally, at the geometric center of the electrode array. The method of horizontal profiling is very suitable to the study of hard rock terrain. The technique of vertical electrical sounding (VES) is the process by which depth investigations are made by a series of resistivity measurements. Electrical sounding is based on the distance between the source electrodes and measurement of the potential difference between receiver and ejector points thus allowing the penetration of the resistivity technique; this is irrespective of the many alternative electrode arrays that may be used. The depth of probing also depends on the distance between the two current electrodes when linear arrays are used. As expressed previously, specific resistivity of soil units and rocks (Figure 3-28) varies widely. It is a very sensitive parameter, but there is no general correlation between the specific rock types and resultant resistivities.

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Thus, as the current electrode separation is increased during VES, the electrical potential distribution on the surface should be affected relatively more by the deep strata. The first step in the interpretation of sounding field data is to prepare a graph in which the calculated apparent resistivities are plotted on the ordinates and variable parameters (dependent on the array used) are plotted on the graph abscissa. A significant difficulty in interpretation of resistivity sounding curves is the complexity of the curves. VES curve interpretation is one of the most intricate techniques in applied geophysics and should only be attempted by professionals with considerable experience in the technique. There are some rules, however, which can serve as a basis for most cases in site assessment to define geologic conditions: • • • •

Sediments are less resistive than igneous rocks. Basic igneous types are better conducting than the acidic ones. Clayey rocks possess lower resistivity than sandy types. Stratified and schistose rocks display electric anisotropy; that is, their specific resistivity is higher in the direction normal to the plane of schistosity than parallel to it.

Although time consuming, resistivity profiling has been a useful technique for mapping lateral changes in the subsurface. This field technique has been used to delineate leachate plumes and detecting changes in natural hydrogeologic conditions. Resistivity sounding requires considerable space; for example, to obtain data from a depth of 100 feet could require an overall array length (distance between the outermost pair of electrodes) of 900 to 1,200 feet. This method is often constrained due to property fence lines and power lines in built-up areas. Although they measure similar physical properties, when comparing EM and resistivity survey data from the same site, you can expect some differences in the results due to variance in the geometry of the measurement methods. The two techniques can be used for much the same purposes and though both are affected by buried metal pipes, metal buildings and fences, etc. it is believed that the resistivity technique may be less sensitive to these sources of error (Benson et al., 1984). Induced Polarization (IP) Method This less familiar method of electrical survey passes a direct current into the ground through two current electrodes for a period of several seconds, after which time the current is interrupted. The potential difference measured

Figure 3-28 Resistivity Geophysical Method 116

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across the two potential electrodes does not drop to zero instantaneously, but after falling to a value of Vo that is a small fraction of V, the charging voltage, it decays slowly over a period of several seconds. This phenomenon is known as induced polarization. Its magnitude is most commonly expressed by a parameter termed the chargeability, which is the ratio V/Vo (millivolts per volt). The ratio of these voltages characterizes the decay of the “over voltage.” The ground becomes polarized by the primary electric current. When the polarizing current is turned off, the ground will gradually discharge and return to equilibrium. The procedure for measuring induced polarization response in the field is very similar to that used in direct current resistivity prospecting. Polarization is excited by galvanic current of a square wave form driven into the ground by two current electrodes. The effect of polarization is measured by noting the potential decay measured between two potential electrodes following the end of the exciting pulses. Induced polarization may be applied over a broad band from 100 to 10-2 Hz or within a “normal” band width of 10 to 10-1 Hz. Although the greatest use of IP is in mineral exploration, this technique finds application in hydrogeological surveys where it may be employed to distinguish between pure sands of high hydraulic conductivity (no IP effect) and sands with disseminated clays of lower hydraulic conductivity (high IP effect, e.g.,) Vacquier et al., 1957).

• • •

Screening the head space of soil and water samples for organics Evaluating cuttings for sampling while drilling to prescribe proper disposal Determining which samples will require further organic and physical laboratory analysis

3.5.3 Field Application of Geophysics The most widely used geophysical technique to map lateral variations in soil and rock (such as fractures, Karst features, sand and clay lenses and buried channels) are continuous profile GPR (see Figures 3-29 and 3-30 and EM. The EM technique has been applied in almost every environment and can often provide deeper information than GPR. Recently EM survey methods have included data loggers to allow more rapid data collection during field surveys. Increased quantities of data collected in a more efficient manner greatly increase the mapping resolution of the technique. An example of a resultant high resolution EM survey (Slaine, 1989) was provided as a color contoured figure with contaminated soils, metallic

Organic Vapor Analysis Although geophysical site assessment technique do not normally consider measurement of organic vapors, the various field methods used in reconnaissance mapping of organic vapors in samples of soil rock or fluids are becoming important field techniques for assessment monitoring programs. These organic vapor analysis (OVAs or HNUs, see Figure 3-28A) detectors produce a measured current that is proportional to the concentration of vapor in the sample. Some portable OVA units have the capability to perform a gas chromatography scan that can also determine the type of organic compound present. OVAs have found use during site assessment sampling and drilling operations including: •

Establishing organic contamination (both vadose and ground water) at specific depths using a hollow Dutch cone type of probe (the Dutch Cone penetrometer method is discussed in the following chapter)

Figure 3-28 HNU Equipment Used in Soil Sampling

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Figure 3-29 GPR Results objects and undisturbed soils all showing different colors and overall saturation of colors. Thousands of individual EM readings were incorporated by Slaine to produce the color contour output. The purpose of the geophysical survey at this 16-acre site was to map buried wastes on the property so the site could be remediated prior to a property transfer. The data were continuously recorded along lines that were spaced 10 feet apart. Seismic reflection (although somewhat expensive) can provide good lateral and vertical information at much greater depths than GPR or the frequency domain

Figure 3-30 GSSI 120-Mhz GPR Antenna Being Pulled

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EM (see Figure 3-32). Slaine et al. (1990) reported the results of a seismic reflection survey run to determine the integrity of a clay aquitard beneath a proposed hazardous waste site in southern Ontario. Continuity of the confining unit was demonstrated down to 35 meters along a 10-km transit line. A stratified gravel aquifer was defined for depth, thickness and lateral extent using high-frequency seismic reflection techniques. The geophones were spaced at 3meter intervals and shotgun shells were used as the energy source. The processed common-offset seismic reflection section is shown in Figure 3-28. The four 1000-foot-long transects defined the vertical and horizontal extent of the stratified gravel aquifer within the bedrock valley. High hydraulic conductivity units, such as the gravel aquifer in this case, are extremely important to fully establish in assessment monitoring programs since these features can have the potential to discharge some distance away from the facility. They can greatly affect the local movement of leachate plumes preferentially toward and into the high hydraulic conductivity units. This preferred flow path will typically confound attempts to establish rate and extent of leachate migration, unless the locations of these features are fully established during the Phase II field investigation. Various geophysical methods provide different subsurface “pictures” of lithology. Figure 3-31 shows seismic and

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Figure 3-31 Relationship of Geophysical Methods

resistivity profiles compared to a generalized geologic section (edited borehole log) and actual logging data from an auger borehole. Each representation of a subsurface condition provides reasonable correlation and also some significant differences in both the geophysics and logging profiles. Under optimum conditions GPR profiles can define complete stratigraphic sequences. Figure 3-29 illustrates a GPR survey using 100-MHZ antennas on a 10-meter spaced line. The sequence of aeolian and fluvial sands overlying the bedrock is well visualized by this method. This exceptional GPR processed radar section shows the sands to have a maximum thickness of over 20 meters. Reflecting horizons in the sand indicate erosional unconformities which have a direct effect on the hydraulic conductivity. A complete ground-water flow model was successfully developed from the radar stratigraphy defined by the survey. Downhole geophysical techniques have found wide use to improve the interpolation of geologic conditions between borings or to complement surface geophysical techniques. Geophysical logging between borings (holeto-hole techniques) increases the volume of material sampled and may reduce the need for additional borings. These downhole techniques are covered in Chapter 6. The following subsections provide examples of the use of geophysics in site assessments. They were selected as much for a clear presentation of geophysical data as for

demonstration of the results of the actual technique. One of the greatest difficulties in gaining full acceptance of geophysical surveys to support field investigations is the typical poor illustrative quality of the results of the geophysical survey. Often the inexperienced investigator will produce geophysical traces that require more than squinting at the figure to see what was interpreted from the data. Even relatively “standard” seismic refraction surveys can be presented in an easily understood format by preparing informative presentations. Seismic refraction survey data combined with selective drilling were used to map bedrock surface elevation. These data were used to define bedrock topography prior to shaft sinking and first level drifting in order to ensure sufficient rock cover above proposed mine workings (Scaife, 1990). Bedrock topography data as illustrated in Figure 3-32 provide mining engineers with a basis for mine development design. A contour map and surface plot of the bedrock elevation data along with an isopach map of overburden thickness were delivered to the client within 30 days of project commencement. The resultant geophysical survey should be presented in a clear format that a normally technically conversant individual from the sciences or engineering profession could understand by looking at the illustrations.

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Figure 3-32 Seismic Reflection for Mining Purposes Detection of Inorganics Inorganic parameters are often the key to evaluation of organics contained in ground water. This is especially relevant in landfill leachate migration projects. These inorganic indicator parameters, such as chlorides, iron, and manganese and many additional leachate parameter, can raise the specific conductance of pore fluids within the area of the plume. Geophysical techniques that observe differences in subsurface conductivity often point toward potential target ground-water monitoring well locations. EM and resistivity methods have been the traditional geophysical methods for detecting and mapping inorganic plumes. EM, however, has been the method of choice for site assessments because the rapid, non-contact nature of the method and the continuous data record (see Figures 333 and 3-34). Both EM and resistivity methods can be greatly affected by noise interference from nearby fence lines, railroad tracks, buried pipes or power lines. In these cases, if the geologic conditions are favorable (sandy soil), GPR methods may be applied successfully to shallow investigations. A GPR survey (Figure 3-35) was conducted to establish the orientation, lateral extent and depth of a landfill

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leachate plume. The radar survey clearly indicated the horizontal extent of the leachate plume along a survey line perpendicular to the regional ground-water flow direction. The high-conductivity leachate plume absorbs the radar energy. Zones where radar reflections disappear indicate the presence of the signal-absorbing leachate plume. Zones where pore water conductivity obtained from existing monitoring wells and exceeded a value of 10 mS/m correlated with the areas of high radar attention. The stratigraphy of unaffected areas of the site were mapped down to 20-meters using the GPR technique. Geophysical survey equipment in the hands of experienced geophysics can provide many keys to site conditions as much by what is not observed as by what is observed in the survey. Assessment monitoring situations typically require that the “rate and extent” of contamination be determined. Rather than punching in numerous monitoring points, EM geophysical data can be obtained very rapidly in the field to aid in locating the edge of leachate contamination. The results of 385 EM measurements are illustrated in Figure 3-33. The contoured EM data show a plume-like anomaly migrating to the southwest from the landfill (Slaine, 1989). The results are shown in Figure 3-33 as decibels (Greenhouse and Saine, 1983, 1986) A decibel can be

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Figure 3-33 Location of EM Station

defined as a unit that describes a logarithmic ratio. The ratio for this contouring is a conductivity (resistivity) ratio normalized to a background conductivity (resistivity) value. The contours presented in Figure 3-34 are values only above background values. The method also, through the log scale, reduces congestion of contour lines in the immediate vicinity of the landfill or contaminant source. The EM survey was then used to locate assessment monitoring wells (as shown in Figure 3-34). Resistivity geophysical methods cannot produce continuous profile measurements as does the EM method, due to the necessity of electrode movement. Resistivity methods may also be severely limited due to concrete or asphalt surfaces or due to highly resistive surface materials such as dry sand. Assessment monitoring programs should include a geophysical component that looks at depth conductivity/ resistivity relationships. Both vertical sounding resistivity and EM methods can be used to assist in determining the depth of an inorganic leachate plume that may be generated by an unlined disposal facility. Geophysical applications used in the detection of contaminated ground water should be reliable down to several hundred feet, a depth frequently involved in ground-water assessment. The frequency domain EM method is limited to about 200 feet, the depth the requirements for many assessment projects. Transient EM and resistivity depth criteria are virtually unlimited in the context of contamination site assessments, since, these methods can be accurate from a few hundred to a few thousand feet (Benson et al., 1984).

Figure 3-34 EM Results for Leachate Plume

The physical length of the resistivity arrays or the EM coil separation necessary to measure the required depth can, however, be a limiting factor in these methods. The overall length of a resistivity array will typically be 9 to 12 times the depth of interest so to measure to a depth of 200 feet, the array may need to be 2000-feet long. Longer arrays are also more subject to noise interference from electrical lines and such lengths can present access problems. EM coil separations only require about two times the depth of interest, therefore, EM methods can be used in much tighter sites than possible with resistivity methods. Organic Detection Geophysical surveys have been used to map organic contamination for many projects reported in the literature. However, direct measurement of the organics present in the subsurface by direct geophysical techniques has not been fully demonstrated even to 2003. Indirect geophysical techniques for measurement of organics, however, is well described in the literature. Since a thin layer of hydrocarbons has the effect of compressing the capillary zone of the water table to a level that it can be detected by GPR, Olhoeft (1986) described a GPR investigation over a pipeline in Minnesota. He reported a marked contrast in the reflective character of the radar records between undisturbed areas and zones where outwash was saturated with hydrocarbons. If the oily layer is thick enough, GPR

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Figure 3-35 GPR Survey Results may allow the hydrocarbon thickness to be estimated. Surface and downhole electrical methods may also be used to detect and map thicker floating product spills. Cosgrave (1987) reported on a survey of a sandy aquifer near North Bay, Ontario. A landfill leachate plume was reported imaged by the attenuation pattern of the radar record. Vertical resolution was 15 cm and the 100-MHz radar record illustrated two areas of leachate movement adjacent to the facility. Although direct evidence of detection of organic (not inorganic related) plumes is sparse in the literature, Saunders and Cox (1987) described the use of EM-31 conductivity surveys across a suspected leak of JP-4 aircraft fuel from an underground airport pipeline. The free product was believed sitting on a shallow water table in a sandy aquifer. The resultant EM in-phase and quadrature-phase responses were cited as direct evidence of detection of the fuel. The authors, however, acknowledged that this may be the result of volatile-related chemical changes in the vadose zone above the fuel. Location of Buried Wastes Site assessments commonly require the location of waste areas in and out of property boundaries. Buried wastes, disposal trenches, tanks and utilities can be located using many different geophysical methods. GPR, EM, metal detection and magnetometer methods can be used to quickly locate utilities and underground storage tanks before drilling on a property.

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When metal is present in the form of trash, drums, tanks, pipes or cables, the application of both metal detectors and magnetics becomes the primary approach to locate shallow drum disposal areas. Figure 3-36 illustrates the use of a vertical gradient magnetometer collected on 3-meter centers across a property. The data clearly show a linear series of isolated fluctuating magnetic anomalies which inferred the location of a buried drum-filled trench. Upon test excavation, isolated magnetic anomalies were found to be generated by small targets such as individual pieces of rebar and a roll of metal strapping located 1.5 meters below surface. The site engineers were comfortable that no larger features such as buried drums or tanks were located at the site. The final report including processed magnetic data was delivered 7 working days after project commencement. These methods are unaffected by most soil types or the presence of other contaminants. All geophysical methods that rely on resistivity or conductance of subsurface materials can be made ineffective if buried non-hazardous wastes are present, for example, in a co-disposal facility that contains large volumes of municipal waste. Although GPR can be used to find drums, the method has some limitations, such as shallow depth of penetration, inability to detect drums due to orientation or geometry problems and confusion due to other objects that give a similar response. Where GPR can penetrate, a good evaluation of drain depths can be made. Depths of trenches and landfills can be determined by resistivity, seismic refraction, gravity and magnetics. If borings or wells exist, downhole geophysical logs may be

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Figure 3-36 Vertical Gradient Mag Results used. In limited cases, radar may be useful for determining the depth of a shallow trench, if relatively nonconductive materials are present. Pit or trench slopes can also be estimated with radar; this can be used to extrapolate depth. Metal detectors and EM will respond to ferrous and nonferrous metals. As shown in Figure 3-37, EM conductivity surveys can effectively delineate the area of buried landfill debris. The area of fluctuating electromagnetic conductivity values infers the presence of buried refuse, while the flat area of electromagnetic conductivity data indicates natural, undisturbed soils. A magnetometer will respond only to ferrous metals. It is helpful, therefore, to review the site history to evaluate which metals to expect so that the proper instruments may be used. Assessing Geological and Hydrogeological Conditions All geophysical methods are capable of providing information about geologic and/or hydrogeologic conditions. By assessing the subsurface investigators can make judgments about where contamination is likely to be located and the direction in which it is likely to migrate. This information is also critical in the design of appropriate remediation technologies. Geophysical methods are, of course, not always necessary for determining the geo-

logic and hydrogeological conditions of underground storage tanks (UST) sites; however, when adequate background information does not exist and site geology is complicated, geophysical methods may be a cost-effective means of supplementing intrusive methods of characterization (e.g., soil logging). Geophysical methods can be helpful in resolving depth to groundwater; determining depth, thickness and composition of soil and rock layers; and mapping local features such as permeable zones, joints, faults, Karst and buried stream channels. The following text summarizes the most useful methods for these tasks and explains their applicability. The geophysical methods most likely to be useful at UST sites include ground-penetrating radar (GPR), seismic refraction (SR), electrical resistivity (ER) and electromagnetics (EM). Although all of these methods may on occasion be useful in determining the depth to the saturated zone, they all require sharp boundaries to be successful. As a result, when there is a large capillary fringe, they may not distinguish the saturated zone from the vadose zone. Magnetometry, very-low-frequency electromagnetics (VLF-EM), self-potential (SP) and seismic reflection are other surface geophysical methods that may provide additional information; however, they are not discussed in detail because they are rarely useful at UST sites for assessing geologic and hydrogeologic conditions because

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Figure 3-37 EM Conductivity Survey for Landfill Wastes of sensitivities to cultural interferences, cost or applicability for rare conditions. Magnetometry and VLF-EM methods can be useful for delineating faults and large fracture zones. SP surveys, although sensitive to interferences, can be used to assess Karst, fractures and groundwater recharge. Borehole methods may also be useful for logging soil types and fracture characterization. Borehole methods that have been adapted to direct push technologies are discussed in Chapter 4, which summarizes the application of each of the major surface geophysical methods used for subsurface characterization of geologic and hydrogeologic conditions. One of the most difficult aspects of a site assessment is delineating the extent of contamination. Although geophysical tools are not helpful in mapping the extent of dissolved product at a site, in some situations they can play an important role in mapping the location of residual product in the vadose zone and floating product above groundwater. This is an area of active research and many issues involved with the uses of appropriate methods remain unresolved. In general, hydrocarbons are difficult to detect because they are resistive compounds that often cannot be

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distinguished from the surrounding soils and rock layers. However, among the hydrocarbons, light non-aqueous phase liquids (LNAPLs) (e.g., gasoline, jet fuel, diesel fuel) are the most likely hydrocarbons to be detected because they float and form a distinct layer above the ground water. For some geophysical methods, the LNAPL layer must be several feet thick for detection. Some detection methods may detect older spills more easily than newer spills because the natural rise and fall of a water table will “smear” the product over a greater area. In addition, the natural lateral geologic variations will interfere with the interpretation of geophysical plots for all methods because distinguishing between changes due to geology or LNAPLs may be difficult. There are several surface geophysical methods that have the potential to detect LNAPLs in the subsurface. Ground-penetrating radar (GPR) and electrical resistivity (ER) are currently the best documented methods and are discussed in the following text. A summary of the effectiveness of these two methods for delineating residual or floating product is presented in Table 3-6.

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Other methods that are undergoing research but that are not yet appropriate for routine use include electromagnetic methods (EM), induced polarization (Olhoeft, 1986) also known as complex resistivity) and ultrasonic imaging (Geller and Myer, 1995), a type of seismic method. Borehole methods are extremely useful for the purpose of determining the thickness of floating product because they provide exact in situ measurements that cannot be accomplished with any other means. These methods are discussed in detail in Direct Push Technologies, Chapter 4. Ground-Penetrating Radar Occasionally, GPR can provide an indication of the presence of hydrocarbons, although success may be difficult to predict and the reasons for the observed reflections are not yet completely understood. There are several observations reported in scientific literature. In most cases, interpretation requires a boring log to compare reflection depths with actual soil types. One study (Daniels et al., 1995) reports that in areas of petroleum hydrocarbon contamination, radar waves will not necessarily reflect back to the GPR receiver. This effect causes a “halo” (i.e., decrease in reflection) over the area of contamination which contrasts with neighboring areas of reflection. A similar result was observed in a controlled kerosene spill in Canada (DeRyck et al., 1993). However, in another controlled spill experiment (Campbell et al., 1996), a bright spot (i.e., an increase in the reflected GPR signal) was observed. The reason for these contradictory results has not yet been adequately explained. In addition, Benson and Yuhr (1995) observed that, on occasion, a small amount of petroleum can cause the groundwater capillary fringe to collapse. If the water table is located in a zone of low permeability soils that create a large capillary fringe (e.g., clays), then a drop in the location of the groundwater reflection compared with the surrounding area may be observed. The amount of floating product required for these observations and understanding the conditions that cause them require further research. As a result, the use of GPR to detect contamination is still experimental. Electrical Resistivity Electrical resistivity surveys are primarily used for determining site stratigraphy. On occasion, as a secondary aspect of the survey, this method may present evidence of LNAPL contamination (DeRyck et al., 1993). In order for this method to be successful, a number of conditions must exist at a site. Ground water must be no more than 15 feet deep, conductive soils must be present in the contaminated zone and floating product must exist (although the

minimum quantity is unknown). Because this method is relatively expensive and success in locating hydrocarbon contamination is not predictable, it is not typically used for the sole purpose of locating petroleum plumes. 3.6 HYDROLOGY 3.6.1 Meteorology and Climatology This section describes the types of meteorological and climatic information typically collected during Phase II investigations. Meteorological stations are commonly erected on site to measure wind direction, wind speed and temperature at a height of approximately 10 meters. An example of a wind rose format for direction and wind speed is shown in Figure 3-38. Impacts of rainfall patterns can be divided into two categories: (1) surface-water dilution potential and (2) runoff potential. Surface-water dilution potential affects the ability of nearby surface water to assimilate discharges and consequently reduce parameter concentrations. Runoff potential affects the potential transport of landfill materials to surface waters and the surrounding land. Some of the elements that define the climatic characteristics and hydrology of a region include precipitation (e.g., rainfall), temperature, evaporation, runoff and infiltration. The type of information necessary to assess these phenomena are described below. Precipitation Monthly and annual precipitation with snowfall expressed as equivalent rainfall can be obtained from the National Oceanic and Atmospheric Administration (NOAA) or the National Weather Service. Daily records of rainfall and snow are published in “Climatological Data” and “Hourly Precipitation” by the U.S. Environmental Data Service. Regional precipitation data may be presented and used if they were generated within a reasonably close distance to the site (approximately 15 km) and are representative of rainfall and/or snowmelt conditions at the site. Regional data collected at greater distances from the site should be correlated with available on-site data. The monthly mean and range of these data, the specific time period from which the data came and the location of the rain gauge(s) in relation to the facility should be provided. Precipitation data can be presented in Tables showing monthly and yearly averages over a period of time or as precipitation events, as shown in Figure 3-39. Precipitation is measured as a depth of water and is defined as the total amount of water that reaches land surface. It is measured with various rain gauges (see pictographic

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Figure 3-40). These data can also be used to relate rainfall and elevation of ground water in wells and piezometers as is shown in Figure 3-41. This information should be available from the Federal Insurance Administration (FIA) in the form of maps or other data. If the facility design includes any special flood prevention devices (e.g., dikes, berms), these devices could also be shown on a site map. Any special site conditions that affect infiltration and runoff should also be discussed. Temperature Ambient air temperature (degree) data can be useful in the general assessment of the climatic setting of a site

and may be useful in the assessment of potential volatilization of gases. This regional information should be available from sources similar to those used to obtain precipitation information. Temperature is generally reported as monthly and annual averages over the period of record and is important in assessing evaporation. Evaporation Evaporation and transpiration (evapotranspiration) rates (depth of water per unit time) reflect the amount of precipitation returned to the air. Evaporation rates are measured by NOAA and evapotranspiration rates can be estimated from these data. Evapotranspiration rates can also be obtained through site studies (preferably using tensiometers) or through published sources if the nearest dataset (collected at a gauging station) is representative of the site conditions. There are two major methods for defining evapotranspiration: the water balance methods and micro-meteorological methods. Standard pan evaporation equipment can be a component of the site weather station if required; however, these devices require daily attention. Runoff Surface runoff is of interest in assessing the transport of sediments over the land surface. Specifically, overland flow (i.e., the part of surface runoff that flows over the land surface toward channels) is of interest. The project engineer should identify the potential of overland flow to transport landfill wastes to land areas of particular interest (e.g., agricultural land) and surface water. This potential

Figure 3-38 Annual Wind Rose Results

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Figure 3-39 Precipitation at Sherman, Texas

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depends on the surrounding surface characteristics (e.g., slope, soil type, vegetation, paved areas). If the potential for the transport of materials is significant, then the engineer will likely have to conduct a detailed analysis of overland flow (i.e., the identification of the quantity and quality of overland flow). Such an analysis would likely require the use of a runoff simulation computer model such as the Storm Water Management Model (SWMM). Infiltration The maximum rate at which precipitation can enter the soil is the infiltration rate (depth of water per unit time). During precipitation events, all the water will infiltrate if the rainfall intensity is less than the infiltration capacity. If this capacity is exceeded, the excess rain cannot infiltrate and will produce surface runoff. The infiltration capacity can vary greatly due to the soil surface cover. If a soil is completely covered by a crop canopy, evaporation losses are negligible and transpiration is the principal process by which water is lost from the root zone. The same environmental factors that control evaporation also control the potential transpiration.

Infiltration rates (average annual) can be important in the determination of the velocity of ground water moving downward through soil, as recharge to ground water and hence, in the modeling and determination of potential leachate transport rates. Records of estimated infiltration rates for an area may be available from sources such as the U.S. Department of Agriculture (Soil Conservation Service). However, it will probably be necessary to estimate this value by taking the average precipitation rate (average annual) and subtracting evapotranspiration and runoff rates (average annual). Actual field measurements of infiltration, through tensiometers in the vadose zone, are rarely performed. They are very expensive, difficult to perform correctly and even more difficult to interpret. 3.6.2 Surface-Water Hydrology The purpose of surface-water hydrology studies is to describe the drainage systems, flow characteristics and quality of the streams and water bodies and to aid in determining the ground-water/surface-water relationships. This information documents baseline conditions and forms the basis of assessing any future environmental impacts of the

Figure 3-40 Precipation Measurement

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Figure 3-41 Rainfall Water Level Relationships facility on surface water bodies. The typical Phase II scope of work for surface-water studies includes site reconnaissance by a combined hydrology/geology team, a stream gauging program and various engineering analyses of hydrologic and streamflow characteristics for a 12-month minimum time period with careful long-term extrapolation. A review of pertinent literature published by federal, state and local agencies (such as the U.S. Geological Survey, the U.S. Soil Conservation Service and the various state departments of natural resources) will be normally included in the Phase I report. Phase II tasks typically supplement the information from literature sources with more site-specific information. Periodic discharge measurements normally are made at selected stream sites using a standardized Price or pygmy current meter and standard U.S. Geological Survey techniques, as described by USGS publications. These data are correlated with any continuous gauging stations operated by the U.S. Geological Survey along major sur-

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face water streams. All staff gauges should be leveled to the U.S. Geological Survey datum (NGVD) and nearby reference points should be established as permanent site monitoring stations. Lateral and longitudinal stream profiles are typically constructed where appropriate for the investigation. For a comprehensive investigation when surfacewater features and flow play important roles in the site assessment, staff gauges in streams are normally monitored weekly by the field personnel, with staff gauges in lakes read on a monthly basis. Precipitation data must be correlated with lake levels and with streamflow data. Stage-discharge relationships should be determined for each stream gauging station. Drainage areas and basin boundaries can typically be determined from USGS 1:24,000-scale topographic maps. In order to calculate potential surface-water flows in and around the site, a map of the drainage area should be prepared based on site development topography (1:2,400) and stream flows. Figure 3-42 shows a drainage area map for an arid region in south-central Arizona. Each drainage area boundary is shown, along with soils of each drainage area. These data are used for evaluation of erosion potential storm runoff volumes and peak rates of runoff. The major goal of such an analysis is to provide design criteria Other goals include: (1) managing off-site drainage from up-slope areas for subsequent down-slope release under non-damaging conditions; and (2) detaining on site, for a specific period, a specific volume of runoff produced within the property boundaries following a design basis storm. The flow characteristics and flooding potential of streams should be established by means of the field gauging program, by correlation to any nearby long-term station operated by government agencies and by use of standard engineering techniques. The relevant state regulatory agencies should be contacted to determine the current design requirements for flood frequency or probable maximum precipitation criteria for design of required site flood control structures. The 10-, 25-, 50- and 100-yearfrequency floods and the flooding potential should be addressed as appropriate requirements for design. A generalized water budget should be prepared so that the average annual rate of water movement into and out of the project area can be evaluated. Sampling points may be established on streams in the area to monitor total suspended solids (TSS) as a function of stream flow. Selection of the number and specific location of each sampling point may be affected by the activities at the project. The sampling stations should be located at or near staff gauges. Factors that should be considered in the final selection of sample points include size of the drainage basin, slope of the land surface, topography, relief, height of vegetative canopy and flow channel char-

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Figure 3-42 Off-Site Drainage Areas

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acteristics. Turbidity should be measured using a turbidimeter at the time sediment samples are collected from each station. Sediment samples should be collected using a suspended sediment sampler. For comprehensive investigations, sampling may be required during periods of high precipitation or high runoff from snow melt. The frequency of turbidity measurements and collection of sediment samples should be increased to as often as daily or even hourly, as appropriate for selected stations. Measurement of total suspended solids within a given drainage basin provides a basis for calculating the erosion rates. As land is disturbed by project activities, monitoring of total suspended solids will provide information from which subsequent changes in the erosion rate can be evaluated. Monitoring points established to evaluate the rate and volume of erosion (see Figure 3-42) during the baseline period will provide information to assist in design of effective site- or cell-closure reclamation plans. In addition, these points can be used for monitoring, during and after completion of the project. During and following the field data collection, baseline information should be compiled and evaluated. A section on surface water should be prepared to document existing conditions and should be included in the site assessment report.

3.7 SURROUNDING LAND USE, WATER USE AND WATER-QUALITY CHARACTERISTICS This section presents guidance on identifying and obtaining relevant information about water quality, water use and land use. The Phase II program may require an extension of the preliminary Phase I studies, such as is often necessary for environmental impact analysis or risk assessments. These factors can be grouped into three general categories: ground-water use and ground-water quality, surface-water use and surface-water quality and characteristics of land use in the vicinity of the site. Accordingly, this section is organized into three basic sections. Section 3.7.1 discusses use of ground water and its quality characteristics, Section 3.7.2 discusses surfacewater use and quality characteristics and Section 3.7.3 discusses land use of the surrounding area. Within each section, the type of recommended information is presented first, followed by a brief discussion of potential sources of information, suggestions for presenting the information and how the information should be used in the assessment process. This section presents separate discussions of the information needed to characterize ground water and sur-

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face water, both for uses and quality as well as land use of the area, recognizing, of course, that uses of ground water, surface water and surrounding land are all interrelated. Therefore, although this section provides a sequential discussion of quality and use of the ground water, surface water and surrounding land, in practice it will probably be necessary for the investigator to obtain some information in all three of these areas before completing an evaluation of any one particular area. It is usually desirable to present data and findings in matrix form, for clarity and assimilation by the reader. Not all of the water-quality, water-use and land-use parameters discussed in this chapter will require characterization at all sites. The investigator should exercise professional judgment, given the general guidelines presented in this section, in determining which water use and waterquality parameters are relevant for the facility and in determining the level of detail necessary to adequately support the environmental impact report (EIR) or riskbased assessments. 3.7.1 Ground-Water Use and Quality Existing quality of ground water and current and potential future uses of ground water must be considered by the engineer in evaluating the present and potential hazard to human health and the environment posed by a potential release of leachate from a waste management facility. Characterizing existing quality of ground water is an important task for two reasons. First, existing groundwater quality normally establishes the baseline conditions for evaluating risks to human health and the environment throughout the facility operational and post-closure periods. Second, existing ground-water quality, in part, determines current uses and affects future uses. In addition, determining ground-water uses is an important initial step in identifying potential pathways of exposure for risk assessment studies. Proximity and Withdrawal Rates of Ground-Water Users The proximity and withdrawal rates of ground water by users within the site area are important factors in determining the potential adverse effects of a release on human health and the environment. The proximity of groundwater users will affect both the time it takes a leachate to reach the user and the concentration of parameters in the ground water. The withdrawal rate (i.e., the daily or annual volume of water pumped from an aquifer) is used to assess the total amount of contaminants to which the user is exposed and, in some cases, any influence the rate has on the direction and magnitude of ground-water flow.

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Figure 3-43 shows a map of well locations for a region. Well notations are keyed into tables (Table 3-8), providing information about individual wells. For each ground-water user identified in the surrounding area, the following information should be provided: • • • •

•

Well location and distance from potential point of release Well construction Well depth Type of user: - potable (municipal and residential) - Domestic nonpotable (e.g., lawn watering) - Industrial - Agricultural - Artificial recharge Estimated withdrawal rates (daily peak, annual and seasonal)

The above information can be presented using a map and an accompanying summary sheet. Possible sources

for information relating to proximity and withdrawal rates of ground water include local and regional water districts or companies, state agencies, federal agencies (USEPA, U.S. Geological Survey, U.S. Department of Agriculture), and various databases of state, federal and private organizations. A detailed list of these sources is contained in Phase I sections of this book. Existing Background Quality of Site-Area Ground Water The existing quality of ground water affects current and potential uses of ground water and also provides a baseline for evaluating the incremental potential for risk to human health and the environment due to a possible release of leachate from the facility. The quality of ground water can be affected by both naturally occurring sources (such as leaching of minerals from the aquifer medium) and human sources (such as leaking of petroleum or chemical products from underground storage tanks or the downward migration of pesticides and fertilizers from agricultural areas). The primary purpose of this subsection

Figure 3-43 Well Census Figure

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Table 3-8 Example Well Information

is to define guidelines for characterization of existing background quality of ground water in the site area (i.e., the ambient quality of the ground water prior to project implementation). In evaluating background water quality of the site area, the investigator must consider not only possible background concentrations of the selected indicator chemicals, but also the background concentrations of other potential hazardous constituents from leachate. Existing contamination associated with indicator chemicals or other RCRA hazardous constituents may be due to:

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• • •

Natural conditions in the area Prior or present releases from the unlined old landfill areas Prior or present releases from other upgradient sources in the surrounding area

Assessing background concentrations of constituents is necessary to establish an existing baseline of groundwater quality to which the incremental effects of potential release can be added.

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In cases where sufficient historical monitoring data are unavailable, the investigator may need to install an upgradient ground-water monitoring system or add to an existing system in order to adequately assess background quality of ground water. At a minimum, background water quality should be determined based upon at least two separate confirmatory samplings of existing or newly installed monitoring wells. 3.7.2 Surface Water Use and Quality Existing quality and current uses of surface water must be considered in evaluating the design of surfacewater control systems and discharges to surface water. Characterizing existing quality and current and future uses of surface water may be required in site assessments directed toward evaluation of risk to: (1) establish the baseline conditions for evaluating risks to human health and the environment and (2) determine probable water uses for identifying potential exposure pathways in surface water. In assessing surface-water use and quality characteristics, the investigator should evaluate those surface waters that might possibly become contaminated by a release, based on the hydrogeologic characterization discussed in this chapter. For example, it is unlikely that surface waters upgradient and distant from the facility would be contaminated by a release from the facility to be permitted. The investigator should consider the possibility of surface-water contamination via both surface runoff and ground-water flow via springs, seeps or into gaining streams. The following subsections explain what types of information relating to surface waters may be required and how this information may be used in evaluating the quality of surface waters, in identifying current uses and drainage and in predicting future water uses. Existing Quality of Surface Water Surface-water quality parameters are both physical and chemical in nature. Physical parameters of surfacewater quality, such as temperature and turbidity, may already have been measured when evaluating the hydrologic characteristics of surrounding surface water. The investigator should provide data of conventional surface-water quality parameters, such as suspended solids, nutrients (e.g., nitrogen and phosphorous), total suspended sediment, oxygen-demand, salinity, hardness, alkalinity, pH, fecal coliform and dissolved solids. Data on these parameters may be helpful in evaluating potential

surface-water uses and providing the base line for future impacts on surface water quality. For example, highly saline or turbid water may be unsuitable for drinking without extensive treatment. In many cases, state or local environmental agencies may already have obtained current data for these parameters for specific surface-water bodies. If such data are unavailable for the area, water quality testing may be required. The results of water quality testing should be submitted in a clear, concise format along with necessary supporting documentation relating to conditions of sampling and analyses. In both traditional site assessments and risk assessments, current users of water, state and local government agencies (such as water authorities) and natural resource management agencies should be contacted. In remote areas, nearby residents may also be able to supply useful information. If a surface-water body has been assigned a “designated use” or “sole source” status, the investigator should identify the designated use or uses and determine which of the designated uses are considered to be currently active. 3.7.3 Current and Future Uses of Surrounding Land To some extent, current and future uses of surrounding land will have already been determined when identifying current and future uses of ground water and surface water. The purpose of obtaining information on the current and future uses of surrounding land in this section is to characterize surrounding agricultural, commercial and residential land use (see Figure 3-44) and to identify any ecologically sensitive areas that could be adversely affected by operation of a proposed facility. Such ecologically sensitive areas may include: • • • • •

State, federal and local parks Wildlife refuges Wilderness areas Critical habitats for endangered and threatened species Wetlands

Agricultural, commercial and industrial land uses can usually be identified by contacting local land use regulatory authorities, such as planning and/or zoning boards and reviewing appropriate land use plans and maps. Identifying ecologically sensitive areas may be more difficult. While some of these ecologically sensitive areas may be marked on U.S. Geological Survey topographic or other

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maps, many may not be marked. In particular, the location and boundaries of some critical habitats are not published or made readily available to the public. To verify the existence of ecologically sensitive areas and to identify areas under consideration for protection, relevant state and federal government agencies (such as state and federal park agencies, fish and wildlife agencies and private conservation groups (e.g., The Nature Conservancy) should be contacted. A list of potential agencies and organizations that may be able to provide information on surrounding land use is included in Chapter 2. The investigator should include a brief narrative description of current and projected future uses of surrounding land in the Phase II report. The use of all land in the immediate surrounding area of the site should be carefully described. The engineer should devote special attention to mapping any ecologically sensitive habitats in the surrounding area. Two maps of the surrounding area, one identifying current land use and another identifying known or reasonably projected future land uses, should be provided as part of the project documentation. 3.8 FIELD ECOLOGY SURVEYS

•

•

•

Establishment of water-quality monitoring programs in areas potentially affected by development of the disposal areas An assessment of potential impacts on aquatic resources caused by construction and operation of the disposal facility An evaluation of potential measures for mitigating (see Figure 3-45) or eliminating deleterious effects on the aquatic resources in the vicinity of the disposal site

The scope of the study should be flexible so as to allow such modifications in the program as may become apparent as on-site experience is gained and design concepts become formalized.

3.8.2 Terrestrial Ecology The terrestrial ecology program should be designed to identify and describe the major terrestrial communities within the proposed facility areas and to provide a baseline for analyzing potential impacts resulting from site

Field ecological surveys are very specialized technical investigations that must be scoped directly to the facility area. These surveys supplement the land use data collected in the previous investigations. Field ecology surveys can make the difference between project success or failure depending on the adequacy of the program. Endangered species are typically defined in Phase I activities; however, Phase II comprehensive ecological surveys are are long term (at least a year) and are expensive investigations that should be handled by specialists in the field. These investigations are normally divided into two areas: aquatic and terrestrial ecology. 3.8.1 Aquatic Ecology Studies of aquatic ecology are designed to define, in detail sufficient for assessment purposes, the aquatic ecosystems on and adjacent to the proposed facility areas. The work normally required to assess impacts to aquatic systems could include: • •

A description of the biological baseline conditions in surface-water bodies near the proposed site The biological baseline conditions for surface-water bodies in the immediate vicinity of the candidate disposal areas

Figure 3-44 Current Land Use Map 134

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development. Information developed within this program should include: • • •

• •

Identification of important floral and fauna species including rare and endangered species, if present Distribution and relative abundance of important biota A map showing the distribution of the principal plant communities (see Figure 3-46) and the habitats of important fauna species Site usage and tropic interrelationships of important biota, including habitat requirements Regional importance of the site’s fauna and flora populations based on a comparison of site data with a literature search describing the regional ecology

Field studies of vegetation, mammals, birds, reptiles and amphibians can all be part of a terrestrial ecology investigation. The exact nature and scope of the investigation should be based on the Phase I literature search and site reconnaissance. An example illustration of principal plant communities is provided in Figure 3-46. These data can then be used to establish impacts and mitigation analyses required by individual state environmental programs. Figure 3-46 shows proposed wetland enhancement, revegetation and plant community mitigation areas. Such detailed plans for site environmental care can significantly reduce project development impacts.

Figure 3-45 Wetlands Mitigation Map

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3.9 HISTORICAL AND ARCHAEOLOGICAL SURVEYS A regional overview of the area is typically developed based primarily on literature review in Phase I. In addition, a reconnaissance survey may be required to confirm the presence or absence of significant historical or archaeological sites on or adjacent to the facility. Reconnaissance surveys typically include the deployment of multiple transects and involve systematic examination of samples of subsurface conditions at regular intervals (for example at 15-meter intervals). Standard survey procedures also include visual examination of all

disturbed earth areas such as road cuts, farmers’ fields, spoil from rodent burrows, etc. These procedures are typically necessary in heavily forested areas with significant groundcover conditions. These procedures result in field verification of known or suspected locations of archaeological and historical sites. They may also result in the discovery of previously unknown sites. The precise locations (on-site topographic scale of about 1:2,400 or larger) of these new sites, together with maps which indicate areas which failed to produce evidence of remains, should be prepared for inclusion in the Phase II report. All recovered archaeological and historical debris should be washed, marked, cata-

Figure 3-46 Principal Plant Communities

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loged and deposited with an appropriate museum department of anthropology. All newly discovered archaeological and historical remains should be recorded with the State Archaeologist and, if required, appropriate archaeological site codification numbers should be applied for. A period of laboratory analysis is typically scheduled to follow the field work in order to process materials and inventory and to evaluate cultural remains and to prepare maps and photographs of these data. 3.10 METHODS AND TOOLS OF HOLOCENE FAULT INVESTIGATIONS The methods and tools for conducting a comprehensive geologic investigation for Holocene faulting (within the last 11,000 to 13,000 years) include a review of published data, aerial reconnaissance, interpretation of aerial photographs, ground reconnaissance and subsurface investigations. These tools are used to identify faults and lineations (linear features that suggest the presence of a fault) and to verify whether or not there has been fault displacement in Holocene time; if so, such faults would be classified as “active” or “capable” (identical meanings). Federal regulations and many states, require consideration of faulting as a potential “fatal flaw” in a site considered for waste disposal. Proving a particular site does not contain Holocene faulting can represent a significant commitment in time and expense that requires carefully planned field evaluation techniques. This section contains a detailed description of these field evaluation techniques due to the complexity and difficulty in demonstrating that no Holocene faults are present within areas of waste disposal. 3.10.1 Review of Existing Data A review of existing data is directed toward obtaining information on the seismicity of the site area (to a radius of 5 miles). Preliminary data on geology were gathered in the Phase I program. Any available information on the geology, recent fault activity and earthquakes should be reviewed to determine if Holocene faults have been identified in the project area. During this effort, it is important to further identify any structural geologic trends or geomorphic features that may be related to faulting. Seismicity data should include information about epicenter concentrations and depths of “felt” and instrumented earthquake activity, historical accounts of major earthquakes and any related surface effects of faulting in the area. Such data may indicate the presence and location of faults. In general, these fault investigations will be required

only in regions identified by the National Oceanographic and Atmospheric Administration (NOAA) as Zone 3 (Algemissan and Perkins, 1976). Information on the location of faults near the site and a record of their activity may exist as published data. Because fault-related studies of a particular site will not exist in many cases, geological information from a wider area than the specific local facility must be reviewed. The Phase I investigation establishes the potential for faulting in the facility area. After this assessment, one can determine if a Phase II field investigation (e.g., aerial reconnaissance, ground reconnaissance, borings) must be conducted to demonstrate compliance with a seismic location standard. 3.10.2 Analysis of Aerial Photographs Studies of aerial photographs and other remote images are an essential part of an investigation for Holocene faults. Experience has shown that aerial photographs may be of limited use in forested areas or in areas that were developed before the photographs were taken. However, in many cases, features of faults can be observed on aerial photographs that could not be readily identified during land-based studies. The traces of some faults can be easily identified through preliminary review of aerial photography. In some cases, surface features of some faults seen on the aerial photographs may be so small and relatively insignificant from surface inspection that they can only be recognized as faults by experienced geologists with considerable background in studying active faults and in interpretation of aerial photographs. There is a large element of experience and judgment in the interpretation of aerial photographs; this is particularly true in the interpretation of Holocene fault activity. This is not a job for amateur photo-interpreters! Much of the U.S. has been photographed in black and white at scales of 1:30,000 to 1:60,000. These photographs are especially useful for preliminary regional investigations. More detailed investigations require scales of 1:12,000 to 1:20,000, and stereoscopic coverage is absolutely necessary for interpretation of fault traces. Aerial photographs not taken specifically for fault studies are usually taken during midday. However, it is recommended that aerial photography flown specifically for detection of active faults should utilize low-sun-angle photography taken at different times of the day and sometimes in different seasons of the year depending on the trend of the fault and the azimuth of the sun. The purpose of the photography is to record shadows cast from subtle surface irregularities representing fault scarps of sufficient vertical relief and/or youth as to yet remain detectable. Optimum lighting for fault analysis is obtained when the sun angle is nearly perpendicular to the trend of the fault,

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in the direction from the uphill side of the fault scarp toward the downhill side, at an angle slightly lower than the average slope of the scarp (usually 10 to 25 degrees). The most useful scale is about 1:12,000, with scales of 1:6,000 and 1:3,000 applicable for detailed analyses. While it may be beneficial to repeat the photography in both the early morning and late afternoon, experience shows that photographs taken either in the early morning or late afternoon provide most of the detail that can be obtained by flying at both times. Other types of remote images that may be helpful include infrared and color images, photographs from satellites and high-altitude aircraft photographs. The following points summarize fault analysis through aerial photography: •

The most useful type of photograph is the black-andwhite, low-sun-angle, vertical aerial photograph. When photographs are taken for the purpose of a fault study, low-sun-angle, black-and-white aerial photographs are superior to color photographs under the same conditions, which, in turn, are superior to black-and-white photographs taken at midday.

•

•

Infrared photography can occasionally give a better indication of differences in near-surface groundwater level or contrasts in vegetation on the opposite sides of a fault with minimal surface expression, but low-sun-angle photographs are better for analyzing historic fault activity that has resulted in geomorphic evidence of displacement. Satellite and high-altitude aircraft images (both types at scales >1:60,000) can be useful for regional identification of geologic structures that may require additional evaluation using low-sun-angle photography or field studies.

•

Documentation of analysis of aerial photographs should include sources of photographs, photograph numbers, dates photographs were taken, type of photographs and either copies of photographs or overlays on which analysis is made. Superfund image interpretation portfolios produced by the USEPA Environmental Monitoring Systems Laboratory (Las Vegas, Nevada) are of state-ofthe-art quality. 3.10.3 Surface Geologic Reconnaissance A surface geologic reconnaissance is made to observe geomorphic and geological features that have been noted in the literature or detected on aerial photographs and that may be associated with Holocene or older faults. If a fault has experienced Holocene activity, geomorphic evidence of faulting can be expected to occur at a number of locations along its trace. Confidence in conclusions drawn

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from a ground reconnaissance can be enhanced by: • •

•

•

Extending the reconnaissance into the site area (5+ mile radius). Examining locations of known faults in the area to determine type of faulting and evidence of Holocene activity. Examining lineations or suspicious features identified during the aerial reconnaissance or as such appear on aerial photographs. Describing any evidence of stratigraphic continuity that would demonstrate a lack of Holocene fault activity in the vicinity of the site.

Ground reconnaissance should be documented by plotting geotechnical observations on a topographic map or photo overlay and by providing 35-mm slides of observations, with photo location (station) and axis of view noted on an original geologic map prepared for the evaluation. 3.10.4 Subsurface Mapping The purpose of mapping the subsurface is to demonstrate (1) the presence or absence of active faults within 200 feet (lateral distance) of portions of the facility where disposal of waste will be conducted, and (2) to determine if these faults have had displacement during Holocene time. Subsurface exploration may consist of: •

•

•

Geophysical investigations of subsurface conditions along traverses selected so as to cross suspected fault traces at nearly perpendicular orientations Exploratory trenching and other extensive excavations to permit detailed and direct subsurface observations Borings and backhoe pits to permit collection of data at specific locations and depths

Geophysical methods are indirect methods to detect anomalies and variations in subsurface strata. These anomalies and variations may represent faults. Therefore, they require specific knowledge of subsurface conditions for reliable interpretation. Geophysical methods alone do not prove the absence of a fault, nor do they provide the age of fault activity. Geophysical methods used for fault studies may include seismic refraction, seismic reflection, ground-penetrating radar, magnetism, resistivity or gravity. These methods are described in standard textbooks on applied geophysics. The purpose of any geophysical investigation

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Figure 3-47 Exploration Trench Mapping is to detect and locate subsurface geological structures or masses. During the investigation, measurements of variations in subsurface properties are obtained. These data are analyzed to surmise the causes of each variation. Borings have traditionally been much less informative than exploratory trenching for locations of faults. Faulted zones are often rubbly and do not provide intact core well. Conversely, some faults are represented by only a single-rupture plane or offset that cannot be easily observed from cores. Exploratory excavations (see Figure 3-47) are the most positive and definitive method to establish the location and potential activity of faults at a given location. The excavation is commonly made by a backhoe, a dozer or some other means of exposing subsurface materials. Selection of the excavation equipment depends upon accessibility, depth of excavation, difficulty of excavation, cost, length of time the excavation is to remain open and the potential environmental impact of the excavation. Guidelines as to scale, manner of recording detail and logistics are presented by Hatheway and Leighton (1979). The purpose of the excavation is to expose the subsurface materials below weathered soils at a depth sufficient for geologists to make a detailed evaluation of the excavation walls for inspection of potential age-determinable

fault features. Excavations are expensive; hence, to ensure that the maximum amount of information is obtained from each excavation, the following procedures are recommended: •

•

•

Although each site is different, the excavation may be at least 10 to 20 feet deep. It will probably be necessary to excavate the trench below the depth influenced by man-made activities and weathering and soil-forming processes in order to expose materials that will show age-determinable fault offset. The excavation should be perpendicular to the suspected trend of known faults, lineations or suspicious features since additional faults generally occur parallel to other faults. Thus, maximum coverage can be obtained by such trenches. The excavation must be constructed with worker safety in mind and comply with local, state and federal requirements for safety. All permits for such excavations must be secured before excavation. Most excavations require shoring or walls laid back to reduce the potential for collapse.

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•

•

The trench should be inspected and logged by experienced individuals as significant fault features may be difficult to recognize. Sufficient time should be allowed to inspect, log and photograph the excavation. After the excavation is backfilled, the excavation and photographic log are the only evidence of the investigation. It is very important that the log reflect the significant geotechnical details observed in the excavation. The graphic log should show scale, the length and depth of the trench, the contacts between various subsurface materials, representative strike and dip of bedding and/or joints, shear planes and faults, lithology and continuous unfaulted material within the length of the trench. Figure 3-47 shows an example of a trench log prepared for a Holocene fault evaluation.

•

The excavations should extend beyond the limits of the fault and the proposed facility boundary to identify parallel fault planes. In California, the required width of consideration is a 1/4-mile band for all potentially active faults identified by the State Division of Mines and Geology and so depicted on their open-file quadrangle maps (1:24,000 scale).

Generally, more than one excavation should be made across a fault or suspected fault to determine conclusively its location and relative activity. The number of trenches will depend on size of the facility (small or large), tectonic environment (active or inactive), style of faulting (strikeslip, normal or reverse), type of surface materials (rockHolocene materials) and results of initial trenching (simple to complex). One trench might be sufficient for a small

Table 3-9 Comparison of U.S. Fault Criteria for Critical Structures

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site with a simple, narrow, well-defined fault in the subsurface; well-recognized surface features; and continuous Holocene deposits. At least two trenches should be used at large sites; at sites with no evidence of subsurface faulting, but surface lineations or Holocene faults within 300 feet; at sites with a wide or complex fault pattern; when a fault changes width, direction or pattern; or for thrust or normal faults. Three, four or more trenches may be needed to adequately locate a fault zone across a site, to demonstrate that the site is unfaulted and/or to show that any faults that cross the site have not had displacement in Holocene time. The logging of exploratory excavations and the observations of “active” faults in exploratory trenches are discussed by Taylor and Cluff (1973). 3.10.5 Age Determinations Age determination of faults is a relatively new field that presents many challenges for the investigator. Beyond simple geological mapping of trenches and excavations for fault features, the investigator should seek to identify and collect direct evidence of age of movement through carbon 14 (14C) analysis of deposited wood chips and roots located directly above the offset strata. This data collection requires that at least small pieces of carbon based material be present in an undisturbed (by faulting) layer overlying the faulted strata. Typically, small chips can be found in boundary areas between rock canyons and stream valleys. 14C can now be used successfully for ages of up to 55,000 years. 3.10.6 Results The results of the geologic study should be presented in a report and be of a technical quality acceptable to a geologist experienced in identifying and evaluating faults. The report should represent and describe the observations made during the investigation and be based on defensible geologic evidence. Contents of the report should include, but not be limited to, the following: • • • • • • •

Location and map of study area Sources of available data List of key scientists/engineers conducting study Description of geologic setting and site conditions Investigative methods and approaches Aerial photographs or remote images interpreted (type, scale, source, index number) Trench logs (showing details, not diagrammatic), if appropriate

• • •

• •

Photographs of the classified fault features Geologic map with exploration locations (1 inch = 200 feet, for example), if appropriate Site area geologic map (1 inch = 1,000 feet, for example) Regional geologic map (1 inch = 2,000 feet, for example) Results, conclusions and basis of findings References cited

Often, the data gathered must draw conclusions as to the probability of the site being located above a Holocene fault. Unfortunately, much of the data gathered in these investigations are inconclusive in defining the absence of Holocene faults. Hence, the report must try to draw conclusions by using supporting evidence of regional geologic-tectonic settings and the local characteristics of regional Holocene faults. To accomplish this, the investigator must first define the regional setting and then define the physical characteristics of the Holocene faulting as to the following: • • • • • • •

Orientation (example: NW-trending, right-lateral, strike slip) Length (example: 5 to 10 miles long) Rock displacements (example: Miocene rocks offset 1,000 ft) Loci of earthquakes (example: 1889 MMI 6.0 Antioch, CA, earthquake) Results of field investigation (example: results of trenching study) Surface geomorphic expression (example: recent faulting indicated by disturbed beds) Regulatory classification (example: identified as Holocene-aged fault by CDMG)

The data should be placed on convenient base maps showing the physical characteristics of the Holocene faulting activity. The characteristics of the Holocene faults should then be compared with features observed from mapping the surface and trenches. Tables of comparisons can be developed using the site characteristics established during the Holocene fault investigation. 3.11 ADDITIONAL FIELD SURVEYS 3.11.1 Acoustics Equipment used in waste disposal operations make noise; as such, assessment of the effects of noise can play

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PHASE II SURFICAL FIELD INVESTIGATIONS

an important part in defining acceptance of the overall project in a community. For comprehensive environmental impact analysis, it is important to document the pre-operation ambient sound levels at the proposed site. Through assessment, by a comparison of the pre-operation and estimated post-operation data, the impact of a proposed facility on noise-sensitive land use areas is established. Baseline sound levels are normally obtained by sampling the ambient sound as a function of time of day, season and geographic location. To optimize the assessment, data are obtained at noise-sensitive (human, domestic animals and wildlife) land use locations.

The estimated sound levels resulting from construction and operation of the proposed facility are then compared with applicable state, federal and local noise regulations. They can also be evaluated using the current federal (Environmental Protection Agency) ambient sound-level descriptor, day/night equivalent sound-level decibel number (Ldn), to assess the impact on the neighboring residents and workers. The assessment of impacts should consist of: • •

Baseline Surveys)

Assessment

(Winter

and

Summer

The following baseline studies should be conducted during a comprehensive acoustic study: •

•

• • •

The proposed site and surrounding area should be reviewed through use of aerial photographs, USGS quadrangle maps and other available maps. Potential noise-sensitive land use areas should be identified by size, distance from the site and other important parameters. Locations for measurement should be selected. Ambient sound levels should be recorded on tape. The recorded data must be analyzed.

Ambient sounds are recorded on magnetic tape during representative sampling periods at each selected location. Field equipment typically consists of a sound-level meter and octave-band analyzer with accessories and a magnetic recorder. Tape-recorded data are then returned to an appropriate acoustics laboratory for analysis, using a real-time analyzer and a mini-computer. Each recording is used to construct an A-weighted sound-level histogram and cumulative distribution for a typical measurement period. Octave-band statistical distributions are normally obtained as well. To evaluate the effect of the proposed facility on the sound climate of the area, octave-band sound pressure levels of principal noise-producing operations and equipment should be obtained from an existing facility, architect/ engineer data, equipment manufacturers and engineer files. These data would be extrapolated to the measurement positions initially used and added to the baseline sound-level data.

142

• • •

Analysis of construction methodology and equipment Analysis of operation noise, producing operations and equipment Estimation of community sound-level contribution by facility construction and operation Comparison of estimated levels with current or proposed federal, state or local noise regulations Assessment of the proposed facility on public health and welfare

When appropriate, general noise-abatement procedures should be suggested in the report to mitigate any adverse impact. REFERENCES Algemissan, S. T. and D. M. Perkins, 1976. A Probabilistic Estimate of Maximum Acceleration in Rock in the Contiguous United States, U.S.G.S. Open File Report 76-416, U.S. Government Printing Office, Washington D.C. 45p. ASTM, 1996. Standard guide for using the seismic refraction method for subsurface investigation, D5777-95. Annual Book of ASTM Standards. Philadelphia. Benson, R., 1988. Hazardous Materials Control, Vol. 1, No. 4. Benson, R.C. and L. Yuhr, 1995. Geophysical Methods for Environmental Assessment. In The Geoenvironmental 2000, 1995 ASCE Conference and Exhibition, New Orleans. Benson, R.C., R.A., Glaccum, and M.R. Noel, 1982. Geophysical Techniques for Sensing Buried Waste and Waste Migration. U.S.EPA Enviromental Monitoring Systems Laboratory, Office of Research and Development, Las Vegas, 236p. Benson, R.C., R. Glaccum and M. Noel. 1984. Geophysical Techniques for Sensing Buried Wastes and Waste Migration (NTIS PB84-198449). Prepared for U.S. EPA Environmental Monitoring Systems Laboratory, Las Vegas, 236 p. Beres, M., Jr. and F.P. Haeni, 1991. Application of Ground-Penetrating-Radar Methods in Hydrogeologic Studies. Gr. Water, vol. 29, no. 3: 375-86.

PHASE II SURFICAL FIELD INVESTIGATIONS

Bieniawski, Z. T., 1988. Engineering Rock Mass Classifications, John Wiley and Sons, New York, N. Y., 311 p. Campbell, D.L., J.E. Lucius, K.J. Ellefsen, and M. Deszez-Pan, 1996. Monitoring of a Controlled LNAPL Spill Using Ground-Penetrating Radar. In Proceedings of the symposium on the application of geophysics to engineering and environmental problems, Denver. Commission on Classification of Rocks and Rock Masses of the International Society for Rock Mechanics, 1981. Recommended Symbols for Engineering Geological Mapping: International Association of Engineering Geology Bulletin, No. 24, pp. 227-234. Commission on Engineering Geological Mapping of the International Association of Engineering Geology, 1976. Engineering Geological Maps, A Guide to Their Preparation: The UNESCO Press, Paris, France, 79 p. Compton, R. R., 1962. Manual of Field Geology, John Wiley and Sons, New York, NY, 378 p. Cosgrave, T. M., 1987. An Investigation of Shallow Stratigraphic Reflections From Ground Penetrating Radar. Unpublished M.Sc. thesis. Department of Earth Science, University of Waterloo. Daily, W., A. Ramirez, D. LaBrecque, and W. Barber. 1995. Electrical Resistance Tomography Experiments at Oregon Graduate Institute. J. of Appl. Geophys., vol. 33: 227-37. Daniels, J.J., R. Roberts, and M. Vendl, 1995. Ground Penetrating Radar for the Detection of Liquid Contaminants. J. of Appl. Geophys., vol. 33, no. 33: 195-207. Darracott B. W. and D. M. McCann, 1986. Planning Engineering Geophysical Surveys, in Site Investigation Practice: Assessing BS 5930, Geological Society Engineering Geology Special Publications, No. 2, pp. 85-90. Davis and DeWiest, 1966. Hydrogeology, Wiley, New York. Dearman, 1974. Presentation of Information on Engineering Geological Maps and Plans: Quarterly Journal of Engineering Geology, Vol. 7, No. 3, pp. 317-320. DeRyck, S.M., J.D. Redman, and A.P. Annan. 1993. Geophysical monitoring of a controlled kerosene spill. In Proceedings of the symposium on the application of geophysics to engineering and environmental problems, San Diego. Dobecki, T.L. and P.R. Romig. 1985. Geotechnical and Groundwater Geophysics. In Geophys., vol. 50, no. 12: 2621-36. Dobrin, M. B. & C. H. Savit, 1988. Introduction to Geophysical Prospecting: McGraw-Hill Book Co., New York, N. Y. 867 p. Erdélyi M., and J. Gálfi, 1988. Surface and Subsurface Mapping in Hydrogeology, Wiley-Interscience Publications, 383 p. Gagne, R. M., S. E. Pullan, and J. A. Hunter, 1985. A Shallow Seismic Reflection Method for Use in Mapping Overburden Stratigraphy: Proc. 2nd NWWA Conference on Surface and Borehole Geophysical Methods in Ground Water Investigations, 132-145. Garland, G. D., 1965. The Earth’s Shape and Gravity, Pergamon Press, New York. Geller, J.T. and L.R. Myer, 1995. Ultrasonic imaging of organic liquid contaminants in unconsolidated porous media. J. of Contam. Hydrology, vol. 19.

Goldstein, N.E., 1994. Expedited Site Characterization Geophysics: Geophysical methods and tools for site characterization. Prepared for the U.S. Department of Energy by Lawrence Berkeley Laboratory, Univ. of California. 124 p. Greenhouse, J. P. and D. D. Saine, 1983. The Use of Reconnaissance Electromagnetic Methods to Map Contaminant Migration. Ground Water Monitoring Review, Vol. 3(2), pp. 47-59. Greenhouse, J. P. and D. D. Saine, 1986. Geophysical Modeling and Mapping of Contaminated Ground Water Around Three Waste Disposal Sites in Southern Ontario, Canadian Geotechnical Journal, Vol. 23(3), pp. 372-384. Griffiths D. H., and R.F. King, 1981. Applied Geophysics for Geologists and Engineers: Elements of Geophysical Prospecting, Pergamon Press, New York, N.Y., 230 p. Haeni, F. P., 1985. Applications of Continuous Seismic Reflection Methods in Hydrologic Studies, Ground Water 24, 23-31. Hammer, S., 1939. Terrain Corrections for Gravimeter Stations. Geophysics, V. 4, pp. 184-194. Hatheway, A and B. Leighton, 1979. Exploratory Trenching, In: Hathaway, A. W. and C. R. McClure Jr. (editors),.Geology in the Siting of Nuclear Power Plants, Reviews in Engineering Geology, Vol. 4, The Geologic Society of America, Boulder, CO. Hunter, J. A.and Hobson, 1977. Reflections on Shallow Seismic Reflection Records; Geoexploration, V. 15, p. 183-193. Hunter, J. A., R. A. Burnes, R. L. Good, H. A. MacAulay and R. M. Gagne, 1982. Optimum Field Techniques for Bedrock Reflection Mapping with the Multichannel Engineering Seismograph: in Current Research. Part B, Geol. Surv. of Canada, Paper 82-1B, 131-138. Hunter, J. A., S. E. Pullan, R. A. Burnes, R. M. Gagne and R. L. Good, 1984, Shallow Seismic Reflection Mapping of the Overburden-bedrock Interface with the Engineering Seismograph, Some Simple Techniques, Geophysics, 49, 1381-1385. Lahee, 1952. Field Geology Lennox, D. H. and V. Carlson, 1967. Geophysical Exploration for Buried Valleys in an Area North of Two Hills, Alberta, Geophysics, Vol. 32, p. 331-362. Morey, R.M., 1974. Continuous Subsurface Profiling by Impulse Radar. In Proceedings: Engineering foundation conference on subsurface exploration for underground excavations and heavy construction. Henniker, NH, American Society Civil Engineers. Mota, L., 1954. Determination of Dips and Depths of Geological Layers by the Seismic Refracrion Method. Geophysics, v. 19, p 242-254. NORCAL Geophysical Consultants, Inc., 1996. Product Literature. 1350 Industrial Avenue, Suite A. Petaluma, CA. Office of Research and Development, Washington, DC. U.S. EPA. 1993. Use of Airborne, Surface and Borehole Geophysical Techniques at Contaminated Sites: A reference guide, EPA/625/R-92/007. Office of Research and Development, Washington, DC. Olhoeft, G.R., 1986. Direct Detection of Hydrocarbon and

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Organic Chemicals with Ground Penetrating Radar and Complex Resistivity. In Proceedings of the National Water Well Association/American Petroleum Institute conference on petroleum hydrocarbons and organic chemicals entitled Ground Water - Prevention, Detection and Restoration. Houston. Olhoeft, G.R., 1992. Geophysical Advisor expert system, version 2.0, EPA/600/R-92/ 200. U.S. EPA Environmental Monitoring Systems Laboratory, Las Vegas: 21 pages and a floppy disk. Olhoeft, G.R., 1986. Direct Detection of Hydrocarbon and Organic Chemicals with Ground Penetrating Radar and Complex Resistivity: in Proc. of the NWWA~API Conf. on Petroleum Hydrocarbons and Organic Chemicals in Ground Water, 1986, Houston, p. 284-305. Palmer, D., 1980. The Generalized Reciprocal Method of Seismic Refraction Interpretation, K. B. S. Burke, Ed., Dept of Geology, University of New Brunswick, Fredericton, Canada, 104 pp. Pitchford, A.M., A.T. Mazzella and K.R. Scarbrough, 1988. Soil-gas and geophysical techniques for detection of subsurface organic contamination, EPA/600/4-88/019. (NTIS PB88-208194). 81 p. Robinson, E. S. and C. Coruh, 1988. Basic Exploration Geophysics, John Wiley and Sons Inc., New York, N.Y., 562 pp. Saunders, W. R. and S. A. Cox, 1987. Use of an Electromagnetic Induction Technique in Subsurface Hydrocarbon Investigations, in Proceedings of the First National Outdoor Action Conference, The National Water Well Assoiciation, Las Vegas, Nevada, May 18-21. Scaife, J., 1990. Personal Communication Slaine, D. D., 1989. Applying Seismic Reflection Techniques to Hydrogeological Investigations, Slaine, D. D. and D. G. Leask, 1988. Gravity—Chapter in Guide to the Use of Geophysics in Engineering Geology, International Association of Engineering Geologists Commission on Site Investigations, Delft, Netherlands. Slaine, D. D., P. E. Pehme, J. A. Hunter, S. E. Pullan and J. P. Greenhouse, 1990. Mapping Overburden Stratigraphy at a Proposed Hazardous Waste Facility Using Shallow Seismic Reflection Methods, Society of Exploration Geophysicists Three Volume Special Publication on Environmental Geophysics, Salt Lake City, Utah, Volume II: Environmental and Groundwater, pp. 273-280. Soil Conservation Service, 1972. List of published soil surveys. U.S. Department of Agriculture, Washington, D.C. Taylor, C. L. and L. S. Cluff, 1973. Fault Activity and its Significance Assessed by Exploration, Conference on Tectonic Problems on the San Andreas Fault System Proceedings, Geologic Sciences, v. 13, School of Earth Sciences, Stanford Univ., Stanford, CA. Telford, W. M., L. P. Geldart, R. E. Sheriff and D. Keys, 1976. Applied Geophysics, Cambridge University Press, New York, N.Y., 860 pp. Thorp, J. and G. D. Smith, 1949. Higher Categories of Soil Classification order, Suborder and Great Soil Groups, Soil Science 67, pp. 117-126.

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U.S. Department of Agriculture, 1938. Soils and man. Yearbook of Agriculture, U.S. Department of Agriculture, Washington, D.C. U.S. EPA. 1993. Subsurface Characterization and Monitoring Techniques: A desk reference guide. Volume 1: Solids and groundwater, EPA/625/R-93/003a. U.S. EPA, 1995. Accelerated Leaking Underground Storage Tank Site Characterization Methods. Presented at LUST Site Characterization Methods Seminar sponsored by U.S. EPA Region 5, Chicago. 108 p. USDA, 1938. Marbut system, Soils and Man, Yearbook of Agriculture, Washington, D.C. Vacquier, V. C., R. Holmes, P. R. Kintzinger and M. Lavergne, 1957. Prospecting for Ground-water by Induction Electrical Polarization, Geophysics 12, No. 3, 660 pp. Ward, S.H. 1990. Resistivity and Induced Polarization Methods. Geotech. and Environ. Geophys. vol. 1, no. 1. Williamson, D. A., 1984. Unified Rock Classification System, Bulletin of the Association of Engineering Geologists, Vol. XXI, No. 3 pp. 354-354.

PHASE II SUBSURFACE INVESTIGATIONS

CHAPTER 4 PHASE II SUBSURFACE INVESTIGATIONS 4.1 INTRODUCTION Determination of the location, depth and total number of wells and borings is typically difficult within any site assessment project. Beyond pure technical needs for subsurface information there are often regulatory mandated requirements for coverage of subsurface data. Some states require minimal borings/layouts on a grid pattern, using specific criteria for spacing; other states impose minimum numbers based on acreage. State and local facility permit requirements should be reviewed before determining soil/ rock borings to be installed during the site investigation. Regardless of the state requirements, the number and location of borings should be sufficient to adequately characterize the geologic and ground-water conditions beneath the site, with respect to the types of material, uniformity, potential leachate pathways, hydraulic conductivity, porosity and depth to ground water. The extent of the investigation for site assessments is determined by the character and variability of the subsurface and ground water, the type or importance of the project and the amount of existing information. It is important that the general character and variability of the site area be established before deciding on the basic principles of the design of the waste disposal facility. Investigations may include a range of methods, e.g., excavations, boreholes and in situ testing. The factors determining the selection of a particular method are discussed below. In general, the recommendations apply irrespective of the method adopted and the term exploration point or borehole is used to describe a position where the subsurface is to be explored by any particular method. Each combination of project and site is likely to be unique and the following general points should therefore be considered as guidance in planning the ground investigation and not as a set of rules to be applied rigidly in every case. Flexibility in approaching site investigation work can often provide for a successful final result. The technical development of the project should be kept under continuous review since decisions on the design often influence the extent of the investigation. It cannot be too strongly emphasized that subsurface investigation work must always be considered supplemen-

tary to and conditioned by previous studies of the local geological structure. The greater the natural variability of the ground or subsurface, the greater will be the extent of the investigation required to obtain an indication of the character of the site. The depth of exploration is generally determined by the nature of the facility projected, but it may be necessary to explore to greater depths at a limited number of points (called in this text stratigraphic borings) to establish the overall geological structure. Brief consideration of the possibility of complex structures existing beneath relatively simple-looking ground surfaces will confirm the validity of the following recommendations. It is an especially important consideration in areas previously subjected to glacial action, where glacial drift now covers an original rock surface that might be totally unrelated to present-day topography. Even without the existence of glacial conditions, however, disastrous results have been known to occur when reliance was placed on the results of test boreholes that had not been correlated with the local and regional geology (Legget, 1962). Consider as an example the conditions shown in Figure 4-1. Cursory surface examination of exposed rock in the immediate vicinity of the proposed facility would show outcrops of shale only. Stratigraphic borings drilled as shown to confirm what these rock outcrops appear to suggest would give an entirely false picture of the actual subsurface conditions across the valley. A geological survey made of this site should include, at least, a general surface reconnaissance of the area geologic conditions. The fault and more permeable sandstones are the important target features in this investigation, since they have significant influence over area ground-water flow. Observation of the outcrops along the river bed or evaluation of changes in local topography may have detected the fault. Even if this were not done directly, a detailed examination of shale outcrops on the two sides of the valley would potentially show differences between the two deposits, through variations in color or bedding thickness or perhaps fossil contents. The geologic mapping should be sufficient to show that they were not the same formation and thus would indicate some change in structure between the two sides of the valley. Regional data may point toward the potential for a major fault, but the absence of previously docu-

145

PHASE II SUBSURFACE INVESTIGATIONS

Figure 4-1 Borehole Geologic Interpretations A mented structural features should not discount adequate surface mapping of the geologic units. This mapping can direct the location and depths required for Phase II drilling programs. Figure 4-2 illustrates a case where the strata dip steeply across the site. Correlating the strata found in one drill hole (3) with those pierced by the adjacent hole (2) shows only shale overlying limestone. Often shale and

limestones look quite similar in core, hence, it would be possible to confuse shale A/limestone A with shale B/ limestone B. If borehole and surface mapping are not correlated and hole 3, for example, had been put down only as far as the point shown, the existence of the fault and highly permeable sandstone would have been undetected, unless it were discovered through surface geological investigations. In the case of suficial residual soils (units

Figure 4-2 Borehole Geologic Interpretations B

146

PHASE II SUBSURFACE INVESTIGATIONS

Figure 4-3 Borehole Geologic Interpretations C C and D), geologic mapping would be difficult without some prior knowledge of local faulting. As shown in Figure 4-2 relatively minor surface exposure differences can develop into major structural complexity in the subsurface. Experience and knowledge of the region provide the best keys to being able to evaluate these types of dipping geologic umits. Figure 4-3 shows a case in which casual surface examinations and the use of the subsurface information provided by the boreholes shown would be misleading because of the existence of folds in the strata, which are covered by glacial sediments. The permeable sand channel deposits would go undetected from the pattern of borings shown in Figure 4-3. The examples illustrated in the three sections are not intended to show that stratigraphic borings and similar investigations are often faulty. Such a conclusion would, in fact, be incorrect, because in the cases cited the results from the boreholes may have been correct, but their interpretation might not have been if the results were not correlated with the local geology. The structural complexity shown by the three examples has significant implication for ground-water monitoring issues for both detection and assessment monitoring programs. From the study of the cases described and many other similar instances, the following general guides from Legget (1962) were prepared for subsurface exploratory work. (For convenience, the word boreholes will be used to describe all such subsurface work.) 1. No boreholes should be put down before at least a general geological survey of the area has been made. 2. Boreholes should always be located in relation to the local geological structure.

3. Boreholes should, whenever necessary, be carried to sufficient depths that they will definitely correlate the strata observed in adjacent holes by an overlap into at least one hydrostratigraphic unit. 4. In exploring superficial and glacial deposits, at least one borehole should, whenever possible, be carried to bedrock. 5. In all cases of superficial deposits extending to no great depth, test borings should be taken into the rock for some specified distance, never less than 2 m (6 ft), but more than this if the nature of the work warrants the extra cost or if large boulders are liable to be contacted. 6. Unusual care must be exercised in putting down test borings in areas known to have been subjected to glacial action, especially with regard to checking all rock found during drilling (as in item 5) and for the possible existence of buried river valleys. 7. The three-dimensional nature of the work must always be remembered; for example, three boreholes properly located will define exactly the thickness, dip and strike of any continuous buried stratum having a uniform dip. 8. Planning and contractual arrangements for the conduct of all test boring and drilling must be kept flexible, so that changes can be made immediately at the site, as the picture of the underground conditions gradually unfolds. 9. Special attention must be paid to ground water observed in test holes, careful observations being made of levels before work starts each day in holes that are in the process of being put down.

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PHASE II SUBSURFACE INVESTIGATIONS

10. At least one test hole on every site should be cased and fitted with the necessary screen and filter arrangements, so that it may serve as an observation well for ground-water for the longest possible duration. Legget (1962) made these recommendations some 40 years ago and they are as true today as the day he organized these guidelines. These 10 points should form the basis of both stratigraphic and geotechnical borings used in site investigations Methods adopted for penetrating unconsolidated materials and solid rock are naturally different, even though they may often have to be employed in the same hole. Detailed information concerning subsurface conditions can best be obtained through an adequate drilling program where at least the first few holes are continuously logged. The adequacy of a drilling program can become subjective in any site assessment. One should, however, use Legget’s guidance to evaluate depth of drilling. Location criteria are addressed in the following paragraphs. The objective of this subsurface program is to characterize the soil and bedrock beneath the site to depths sufficient to establish geologic and ground-water conditions and to plan the effective location, design and installation of piezometers and monitoring wells. Furthermore, it is important to realize that the detailed geology of a site can be no more than inferred from aerial photography, surface outcrops and subsurface information at the positions of the exploration points. The above examples illustrate the possibility that significant undetected variations or discontinuities can exist, including lateral or vertical variations within a given stratum. The uncertainties in any site investigation can be reduced but, except by complete excavation, can never be wholly eliminated by a more intensive investigation. This is why a composite understanding of the variability of site conditions should be obtained through comparitive assessment techniques as illustrated in Figure 4-4. The overall goal is to understand the site conditions sufficiently to meet the project requirements but not to overkill the technical components of the investigation. One may require X number of ecplorations to fully evaluate site conditions; 2X or 3X exploration may not necessarily provide significantly more information and may also affect the project negatively. This is especially true for holes drilled through confining units where later borehole completions and decommissioning work may leave the vertical containment of the unit in question. The investigator will need to present a thorough characterization of surfical and subsurface geology at a site for both engineering design and ground-water monitoring. In order to describe in detail the geology beneath and adja-

148

cent to the site and, therefore, be able to identify potential pathways for migration of leachate, the investigator (using qualified professionals) must collect and analyze individual strata beneath and adjacent to a site. To assess the geologic properties of strata beneath a site that are likely to influence the migration of ground water, the investigator will require results of a multifaceted subsurface stratigraphic investigation including, as necessary: •

Exploratory borings

•

Backhoe pit excavations

•

Rock coring

•

Static probing devices

•

Borehole visual and geophysical logging

•

Sample collection

•

Geophysical surveys

•

Laboratory analyses

In addition to the types of information discussed in Section 4.4 these investigations will also provide information on site features such as soil and aquifer characteristics. 4.2 BORING PLAN A boring plan should be prepared by the geologist or geotechnical engineer in charge of the investigation. The plan should include proposed locations and anticipated depths of boreholes and the type and frequency of required soil and rock sampling. Determination of when to terminate boreholes and/or when additional boreholes are needed is dependent upon additional data that may require consideration of site-specific hydrogeologic factors. For example, a near-surface (10–3 cm/s) hydraulic conductivity where evaluation of storage and boundary conditions are important, multi-well pumping tests are preferred. Multiple-well tests, more commonly referred to as pumping tests, are performed by pumping water from one well and recording the resulting drawdown in nearby observation wells. Tests conducted with wells screened in the same water-bearing formation provide hydraulic conductivity data. Tests conducted with wells screened in different water-bearing zones furnish information concerning hydraulic communication between units. The most reliable type of aquifer test usually conducted is a pumping test. In addition, some site studies involve the use of short-term slug tests to obtain estimates of hydraulic conductivity, usually for a specific zone or very limited portion of the aquifer. It should be emphasized that slug tests provide very limited information on the hydraulic properties of the aquifer and often produce estimates that are only accurate within an order of magnitude. Heterogeneity in aquifer materials will cause variations in hydraulic conductivity that should be evaluated and, if possible, quantified. Additionally, hydraulic conductivity may show variations with the direction of measurement. It is important that measurements define hydraulic conductivity, both vertically and horizontally, as components of the vector(s) of ground-water flow across the site. In assessing the completeness of hydraulic conductivity measurements, the investigator should also consider geologic characterization information from the boring program. Zones of high hydraulic conductivity or discontinuities identified from drilling logs should also be considered in the determination of hydraulic conductivity. Depending on the requirements, the designed well performance test will allow determination of some or all of the following points: 1. Yield characteristics and flow potential of the well or piezometer 2. Efficiency of the installation performance as an indication of its hydraulic condition 3. Confirmation of the aquifer type 4. Determination of the hydraulic properties of the aquifer system 5. Prediction of the effect(s) of present and/or future ground-water withdrawal from the piezometer or

271

ENVIRONMENTAL TESTING

well based on hydrogeologic conditions in the aquifer The first two items are best derived from a test procedure in which pumping is increased incrementally, while the remaining items require a constant withdrawal rate of reasonable duration, preferably using one or more observation wells. To gather information on all the items specified, it is necessary to combine into a single test schedule two types of pumping: a multiple-rate performance test and a constant-rate aquifer test. Figure 5-21 illustrates the various pumping schedules for typical field testing for hydraulic conductivity. The determination of accurate estimates of aquifer hydraulic characteristics is dependent on the availability of reliable data from an aquifer test. This section outlines the planning, equipment and test procedures for designing and conducting an accurate aquifer test. The design and operation of a slug test is included in other section of this document. The slug test information can be very useful in developing the aquifer test design (see ASTM D-18 Committee, D4050 and D4104). If an accurate conceptual model of the site is developed and the proper equipment, wells and procedures are selected during the design phase, the resulting data should be reliable. The aquifer estimates obtained from analyzing the data will, of course, depend on the method of analysis. The analysis and evaluation of pumping test data is adequately covered by numerous texts on the subject (Dawson and

Istok, 1991; Kruseman and de Ridder, 1991; Walton, 1962; and Ferris et al., 1962). It should be emphasized, however, that information on the methods for analyzing test data should be reviewed in detail during the planning phase. This is especially important for determining the number, location and construction details for all wells involved in the test. Typically, the piezometer to be tested may be located in an individual exploratory borehole. In this case, it will probably be a small-diameter hole drilled primarily to evaluate the lithological sequence, but the test can also be used with certain limitations for an aquifer test. In the case of the aquifer test designed for establishing area-wide properties, the hole is likely to be of medium to large diameter, capable of accommodating a pump. Although a number of submersible pumps can fit down a 2-inch well, at least a 4-inch and preferably larger diameter casing is required to conduct a full-scale pump test. If concerned solely with maximizing yield, the test may be restricted to a performance test with steps or stages, each of several hours or more duration. With this length of duration, there may be no need to conduct a separate aquifer test for determination of aquifer properties. For individual pumping wells without observation piezometers, only the transmissivity and not the storativity of the aquifer can be calculated. Where the test well is an investigation type with accompanying observation point(s) or a production well associated with others in a well field,

Figure 5-21 Pump Testing Schedule 272

ENVIRONMENTAL TESTING

then it is possible to identify and determine a much wider range of parameters than is possible with the single-well situation. The full scale pumping test schedule can be used see scale Table 5-1, which summarizes the type of test and resulting parameters. A simple pump (specific capacity) test involves the pumping of a single well with no associated observation wells. The purpose of a pump test is to obtain information on well yield, observed drawdown, pump efficiency and calculated specific capacity. The information is used mainly for developing the final design of the pump facility and water delivery system. The pump test usually has a duration of 2 to 12 hours with periodic water level and discharge measurements. The pump is generally allowed to run at maximum capacity with little or no attempt to maintain constant discharge. Discharge variations are often as high as 50%. Short-term pump tests with poor control of discharge are not suitable for estimating parameters needed for adequate aquifer characterization. If the pump test, however, is run in such a way that the discharge rate varies less than 5% and water levels are measured frequently, the test data can also be used to obtain some reliable estimates of aquifer performance. It should be emphasized that an estimate of aquifer transmissivity obtained in this manner will not be as accurate as that obtained using an aquifer test including observation wells. By controlling the discharge variation and pumping for a sufficient duration, it is possible to obtain reliable estimates of transmissivity using water level data obtained during the pump test. However, this method does not provide information on boundaries, storativity, leaky aquifers and other information needed to adequately characterize the hydrology of an aquifer. For the purpose of this document, an aquifer test is defined as a controlled field experiment using a discharging (control) well and at least one observation well. The aquifer test is accomplished by applying a known stress to an aquifer of known or assumed dimensions and observing the water level response over time. Hydraulic characteristics that can be estimated if the test is designed and implemented properly include the coefficient of stor-

age, specific yield, transmissivity, vertical and horizontal permeability and confining layer leakage. Depending on the location of observation wells, it may be possible to determine the location of aquifer boundaries. If measurements are made on nearby springs, it may also be possible to determine the impact of pumping on surface-water features. Test Design Adequate attention paid to the planning and design phase of the aquifer pumping test will ensure that the effort and expense of conducting a test produce useful results. Individuals involved in designing an aquifer test should review the relevant ASTM Standards relating to: (1) appropriate field procedures for determining aquifer hydraulic properties (D4050 and D4106); (2) selection of aquifer test method (D4043); and (3) design and installation of ground water monitoring wells (D5092). The relevant portions of these standards should be incorporated into the design. All available information regarding the aquifer and the site should be collected and reviewed at the commencement of the test design phase. This information will provide the basis for development of a conceptual model of the site and for selecting the final design. It is important that the geometry of the site, location and depth of observation wells and piezometers and the pumping period agree with the mathematical model to be used in the analysis of the data. A test should be designed for the most important parameters to be determined and other parameters may have to be de-emphasized. Numerous published formulae for calculating hydraulic conductivity or permeability from these tests are available many of them partly empirical. Those given by Hvorslev (1951), reproduced in Section 5.7, are much used and cover a large number of conditions. They are based on the assumption that the effect of soil compressibility is negligible. The method given in Gibson (1963) for the constant-head test is also shown. This gives a more accurate result with compressible soils.

Table 5-1 Hydrogeologic Well Tests and Measurement Parameters

Type of Test

Pumping Well, Multiple Rate Yield Potential 3 Well Efficiency 3 Aquifer Type – Aquifer Limits – Transmissivity – Hydraulic Conductivity – Storativity – Leakage – Drawdown Prediction 3

Well, Constant Rate – – 3 – 3 3 – – 3

Piezometers Constant Rate – – 3 3 3 3 3 3 3

Slug Tests – – – – 3 3 – – 3 273

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It must be emphasized that the formulae given in Chapter 7 are steady-state equations suitable for calculation of hydraulic conductivity when the test is carried out below the ground-water surface. In site assessments for waste disposal projects it is often necessary to measure hydraulic conductivity above the watertable. In this case, the steady-state equations can only be used if the time over which the test is conducted becomes very long. 5.4.5 Aquifer Pump Test Procedures Site assessments commonly require application of larger scale pump testing to evaluate potentially complex problems of ground-water extraction and replenishment. Examples of these larger scale problems include optimum location of extraction wells, reliability of confining units to control vertical leakage, artificial recharge, determination of available storage, boundary conditions and directional hydraulic conductivity. All of these field questions can be resolved using mathematical methods developed over the last 120 years. The results obtained from these mathematical methods are highly dependent on field-derived values of the hydraulic characteristics with initial and boundary conditions. Wrong assumptions or poor field techniques will lead to incorrect evaluations of the parameters of interest. The pump test, where water is extracted at a constant rate and drawdowns are observed in nearby observation points, was first evaluated by Thiem (1870) using formulae to derive aquifer properties from the resultant aquifer stresses (drawdown). Since the work of Thiem many pump test formulae and procedures have been derived to evaluate aquifer properties from pump testing. General discussion is provided below on test design and execution not covered by previous publications more specific to pump testing, such as Kruseman and deRidder (1976), Rosco Moss Company (1990) and Walton (1987). A specific application of these guidelines is applied to testing of a confining unit to derive values of leakage, an important concept for waste disposal sites. Test Design and Execution Any aquifer stress or well performance test must be planned with an appreciation of the prevailing hydrogeological conditions, by utilizing all existing information to develop a conceptual model for the aquifer system. Then, by adopting a reasonable range of values for the variable parameters in the Theis (1935) equations for non-steadystate solutions for drawdown, one can derive a set of pretest data that will provide a basis for selection of pumping well discharge, duration of the test and location of observation piezometers. This pretest design is important to establish the eventual water level drawdown and, hence, the

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required location distances of the observation piezometers. This pretest analysis is required to: • Avoid drilling observation piezometers in areas where drawdown will be less than a few inches • Establish pumping rates and test durations sufficient to obtain significant drawdown in existing piezometers An example of pretest analysis is provided for a special case of evaluation of a confining unit. The pretest procedures are similar (but may be less rigorous) for the typical full-scale pump test. The importance of generation of a conceptual model and pretest evaluation should not be ignored in any aquifer evaluation.The initial element of the test design, formulating a conceptual model of the site, involves the collection and analysis of existing data regarding the aquifer and related geologic and hydrologic units. All available information on the aquifer itself, such as saturated thickness, locations of aquifer boundaries, locations of springs, information on all on-site and all nearby wells (construction, well logs, pumping schedules, etc.), estimates of regional transmissivities and other pertinent data, should be collected. Detailed information relating to the geology and hydrology is required to formulate the conceptual model and to determine which mathematical model should be utilized to estimate the most important parameters. It is also important to review various methods for the analyses and evaluation of pumping test data (Ferris et al., 1962; Kruseman and de Ridder, 1976; Walton, 1962, 1970). Information relating to the various analytical methods and associated data needs will assist the hydrologist in reviewing the existing data, identifying gaps in information and formulating a program for filling any gaps that exist. The conceptual model of the site should be prepared after carrying out a detailed site visit and an evaluation of the assembled information. The review of available records should include files available from the U. S. Geological Survey, appropriate state agencies and information from local drillers with experience in the area. Formulation of a conceptual model should include a brief analysis of how the local hydrology/geology fits into the regional hydrogeologic setting. Duration of testing should theoretically continue until sufficient data have been gathered for the purpose of the test. In practice, the test is run for periods of time specified in advance, such as one or two days, as much as one or two weeks for large-scale or difficult situations. Tests carried out on confined aquifers will probably require a shorter time duration than those representative of unconfined (water table) conditions. The distance to observation

ENVIRONMENTAL TESTING

wells can be estimated through a number of key aquifer criteria: • The greater the hydraulic conductivity the greater the distance to the observation well (R). • For the same hydraulic conductivity, R (unconfined) < R (confined).

influence, however, none is reliable under every field circumstance. For estimation of radius of influence for evaluation of drawdown at observation points before the execution of the pump test, the Kozeny formula may provide acceptable values. R =

12t QK -------- -------Sy /

water table system

Equation 5-2

R =

12t QK -------- -------S /

confined system

Equation 5-3

• To avoid the effect of partial penetration R > 1.5 * m KH/KV. • If a distance-drawdown method will be used, then three observation wells should provide at least one logarithmic cycle of the distance-drawdown data. Typical spacing is 100, 400 and 1,000 feet (Walton, 1967). Table 5-2 illustrates some estimates of distances to observation points for various types of geologic/hydrogeologic systems. The distance values provided in the table are applicable if no other recommendation or supporting information are available for the particular aquifer system. After selecting the distance (with particular reference to distance II and III observation points), check whether the radius of influence is greater than the distance concerned. Several equations have been developed to estimate the radius of

R = radius of influence [m] t = time of projected pumping (unsteady state) [s] Q = anticipated discharge rate [m3/S] Sy = specific yield [percentage] S = storativity [specific storage * thickness] Table 5-3 provides representative value ranges of specific storage for a number of geologic materials. This simple computation to evaluate drawdown-radius of influence is developed further in following sections on pre pump test evaluations.

Table 5-2 Estimates of Distances for Radius of Influences

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Table 5-3 Estimates of Specific Storage

Specific Storage (1/m) -3 6 * 10 - 2 * 10-4 3 * 10-4 - 1 * 10-5 2 * 10-5 - 1 * 10-6

Materials Clay Sand and gravel Rock, fractured

Water levels should be measured in each piezometer or well from a distinctly marked datum point by means of manual or automatic devices that should have been calibrated beforehand in order that readings can be made to the nearest 0.1 inch. Where measurements are to be made within the pumping well, it is desirable that a narrowdiameter (say, 0.1. If _ < 0.1 the following steps should be taken: • Prepare a family of type curves, one for each _, of F(_, `) against, ` on semilogarithmic paper. A table giving the value of F(_, `) as function of _ and, ` is presented by Bredehoeft and Papadopulos (1980).

• Plot observed values of H/Ho versus time t on another semilog paper of the same scale as the type curves. • Match the observed curve with one of the type curves keeping the ` and axes coincident and moving the plots horizontally. • Note the value of a of the matched type curve and the values of ` and t from the match point. • Calculate values of S and T from the definitions of a and ` given by Equations (5-16) and (5-17). The above method is not suitable for _ > 0.1. In this range of _, this method can only give the product of transmissivity and storage coefficient, TS. This product may be calculated by matching the field curve of H/Ho versus time t with a type curve family of F(_, `) versus the product _` (Figure 5-27). The major assumption employed in this method is that volumetric changes due to expansion and contraction of other components of the system are negligible. In other words, expansion of the pipes and contraction of the rock in the test zone are negligible relative to those of water. This assumption may introduce large errors into the calculation of hydraulic conductivity. Neuzil (1982) has referred to a test in which the compressibility in the shut-in well

Figure 5-26 Pressure Test Arrangement

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was approximately six times larger than the compressibility of water. The other major assumption is employed in this method is that before the system was pressurized, either the water level in the well has come to a near equilibrium condition with the aquifer or that the observed trend could be extended throughout the test. Neuzil (1982) has pointed out that this assumption may lead to erroneous results. He argues that the pressure changes due to non equilibrium conditions before shut-in become much more rapid after the well is pressurized. Neuzil (1982) has proposed the following modifications in the setup and procedure for performing the test. • Modify the test equipment to that shown in Figure 528. • Fill the borehole with water and set two packers near each other. • Set up two pressure transducers as shown in Figure 528. • Close the valve, shutting in the test section and monitor the pressures in both sections until they are changing very slowly. • Open the valve, pressurize the test section by pumping

in a known volume of water and reclose the valve. • Measure the net pressure decay (slug) by subtracting the decline due to transient flow prior to the test from the measured total pressure. • Analyze data using the technique prepared by Bredehoeft and Papadopulos (1980) as was mentioned before, except that the term for the compressibility of water Cw is replaced by the ratio c, defined as c = (6V/v)/6P

Equation 5-18

where: v = the volume of the shut-in section 6V = the volume of water added to generate a pressure change of 6P Neuzil (1982) indicates that a rise in pressure measured by the transducer between the two packers may indicate leakage upward from the test section. However, two other phenomena may cause some rise of pressure in the middle section. One is increase of pressure inside the formation adjacent to the test section, which may or may not be significant. The other reason is the possibility of transfer of pressure by the packer itself, from the test section to

Figure 5-27 Type Curve of the Function F(_, `) against the Product Parameter _` (after Bredehoeft and Papadopulos, 1980)

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the middle section. The following problems are inherent in all single well tests (U.S. EPA, 1993): • The hydraulic conductivity measured by these tests is only representative of a small zone around the testing interval. A thin lens of very small permeability located between injection and measuring zones could lead to an erroneously low vertical hydraulic conductivity, even if it is only locally present. This problem may be overcome by conducting several tests within the total thickness of a given formation; however, the lateral variation of vertical hydraulic conductivity could be another problem which requires either other types of testing or performance of a number of single-well tests. • Because the horizontal hydraulic conductivity of sedimentary materials is usually much larger than the vertical hydraulic conductivity, flow lines generated by either injection or pumping in these tests are predominantly horizontal. Therefore, a long time may be required to detect significant pressure disturbances in measuring intervals located vertically above or below the flow zone. A small pressure change together with leakage behind the casing due to poor cementing will result in an increased degree of uncertainty in the credibility of these tests in tight formations.

mation. Unfortunately, these tests often cannot be directly used within the formation of interest once the hydraulic conductivity of that formation becomes very low. Wells completed in very low hydraulic conductivity materials are unable to produce fluid for the required test period and pressure heads take long periods of time to be transmitted through the unit. Even by injecting fluid into these wells it could take years before any useful response can be measured in observation wells at a distance of 5 to 10 m. One would then have an interesting time separating out natural variations in head level from stress induced head changes. Neuman and Witherspoon’s “ratio method”: Data from a pumping test to determine the effects of leakage through aquitards (confining units) can be analyzed using what is commonly referred to as the ratio method. Although the theory behind the ratio method is somewhat complex (see Neuman and Witherspoon, 1972), its use with applicable field problems is actually very easy. In fact, it is simpler and much less subjective than many of the aquifer test methods which require curve matching. Neuman and Witherspoon’s ratio method is based on the assumption that flow in the aquitard is vertical. The hori-

• Measurement of change of pressure due to pumping or injection in single-well tests is another source of uncertainty. This is because the test may often start before the pressure at the measuring interval has stabilized. One way to handle this problem is to minimize the volume of the measurement cavity in the well with the help of extra packers. This will shorten the time required for pressure stabilization. • In a single-well test, injection is preferred over pumping unless the well will flow without artificial lift. In a tight formation, injection is the only feasible way to test. • The injection or pumping zone should be packed off to minimize well bore storage. 5.5.11 Tests with Two or More Wells Those tests involving two or more wells can measure the response of a much larger volume of rocks or soils than tests for a single well. Therefore, the value of hydraulic conductivity obtained from multiple-well tests is usually more representative of the large-scale behavior of the for-

294

Figure 5-28 Borehole Instrumentation

ENVIRONMENTAL TESTING

zontal hydraulic gradients in a permeable aquifer in areas near the pumped well will be relatively large and, therefore, flow in the aquitard will deviate somewhat from the vertical. Fortunately, the ratio method is robust in that it is not sensitive to such small deviations from the assumed conditions. If nonvertical flow were really important and could affect the value of hydraulic conductivity in the confining unit, a more exact analysis using numerical modelling could be carried out. In practice, the most critical parameter in application of the ratio method is often the value of Z, the height of the confining unit piezometer above the top of the aquifer. If the interface between the aquifer and the aquitard is irregular or takes the form of a gradual transition, there may be considerable uncertainty as to the value of Z that should be used in the ratio method calculations. In any case, this means that careful attention should be paid to the elevation and nature of the interface between the aquifer and confining unit. A brief summary of the application of the ratio method to the test of a confining unit is as follows. Using values of transmissivity, T (ft2/day) and storativity, S (dimensionless), for the aquifer derivable with data from observation wells b and c (Figure 5-25), the aquifer dimensionless time parameter is calculated by Equation 519 Kvt tv D = -----------2 Sv s z

Equation 5-19

The time parameter establishes which of the type curves is to be used (see Figure 5-26). For each of the confining units piezometers included in the test, the ratio between their measured drawdown, s’ (ft) and the drawdown in the aquifer, s (ft), at the same radial distance at the same time: s' / s

Equation 5-20

is provided. Drawdown in the aquifer at an equivalent distance is either interpolated or extrapolated from the drawdown vs. distance (logarithmic) plot provide by the drawdowns in observation piezometers b and c. Although the assumed linear drawdown vs. distance (logarithmic) relationship is not absolutely valid for a leaky aquifer (Neuman and Witherspoon, 1972, the error over these relatively closely spaced piezometers would be considered minor. The value of the aquitard dimensionless time parameter can be evaluated by using the following equation: tT t D = ------2 r s

where for Equations 5-19 to 5-21: K’ = vertical hydraulic conductivity of the aquitard (ft2/day) S’s = specific storage of the aquitard (ft) z = vertical distance of the piezometer above the top of the aquifer (ft) t = time (days) r = radial distance from the pumping well (ft) tD the aquifer time parameter is then simply read off the horizontal axis of the graph in Figure 5-29 for the point at which the value of the drawdown ratio (S’/S) intersects the selected type curve. Inserting the appropriate values of t and z into Equation 5-21 the value of hydraulic diffusivity for the aquitard can be calculated by the derived equation: K' / S's

Equation 5-22

Laboratory consolidation tests can provide a representative value of compressibility of aquitard material. The specific storage can be calculated from S’s = 0.305 [lg (_+ n`)]

Equation 5-23

where: l = density of the water (kg/m3) g = gravitational constant, m/s) _ = compressibility of the aquitard, (m s2/kg) n = porosity of the aquitard (dimensionless) ` = compressibility of the water (m s2/kg)

Assuming the constant values for l, g and ` given in the previous section, Equation 5-23 can be re-written as S’s = 3.0 x 103_+ 1.3 x lO-l0n

Equation 5-24

Values of compressibility for clays are in the range of 10-6 to 10-8 m s2/kg and the porosity of clays is typically in the range of 0.4 to 0.7 (Freeze and Cherry, 1979). If the tested properties of the confining unit fall into such typical ranges, the second term in Equation 5-24 becomes insignificant when compared to the first term. Consequently, the specific storage of the confining unit would be able to be calculated simply from

Equation 5-21

295

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Svs = 3.0 × 103

Equation 5-25

The remaining unknown term, the effective vertical hydraulic conductivity Kv of the confining unit can be obtained by substituting the value derived in Equation 5-25 (or 5-24, if necessary) into Equation 5-22. Another version of leakance analysis is given in Walton (1987). However, Walton’s method is not very explanatory, uses very cumbersome units and relies on less than precise interpolation between values given in a table to determine tD; however as a check, one should use this or other methods to confirm the results of the test. Relevant case histories applying the ratio method to field problems involving confining units (glacial till) are presented in Keller et al. (1986) and Grisak and Cherry (1975). 5.5.12 Packer Hydraulic Conductivity Tests Packer tests provide a means of assessing permeability of earth materials surrounding a definite, preselected test interval. The technique is particularly useful in rock exhibiting only secondary hydraulic conductivity, due to the presence of discontinuities. The procedure used for packer hydraulic conductivity tests depends upon the condition of the rock. Figure 5-30 shows the arrangement for performing packer tests in consolidated material where the tests are completed in stages (A) and (B) with a single packer arrangement and (C) and (D) where a double packer system is used. In rock that is not subject to cave-in, the following double packer method is used. After the borehole has been completed, it is filled with clear water, surged and washed out. The double packer test apparatus is then inserted into the hole until the top packer is at the top of the rock. Both packers are then expanded and water under pressure is introduced into the hole, first between the packers and then below the lower packer. Observations of the elapsed time and the volume of water pumped at different pressures are recorded as detailed in the section on pumping. Upon completion of the test, the packer apparatus is lowered a distance equal to the space between the packers and the test is repeated. This procedure is continued until the entire length of the hole has been tested or until there is no measurable loss of water in the hole below the lower packer. If the rock in which the hole is being drilled is subject to cave-in, the pressure test is conducted after each advance of the hole for a length equal to the maximum permissible unsupported length of hole or the distance between the packers, whichever is less. In this case, the test is limited, of course, to the zone between the packers. In jointed and/or bedded or foliated rock, packer intervals should be selected to incorporate individual disconti-

nuities or clusters of such fractures, so that an accurate representation of secondary hydraulic conductivity may be obtained. Regardless of which procedure is used, a minimum of three pressure increments should be used for each section tested. The magnitude of these pressures are commonly 15, 30 and 45 psi above the natural piezometric level. However, in no case should the excess pressure above the natural piezometric level be greater than 1 psi per foot of soil and rock overburden above the upper packer. This limitation is imposed to prevent possible heaving and hydrofracture damage to the foundation rock. In general, each of the above pressures should be maintained for 10 minutes or until a uniform rate of flow is attained, whichever is longer. If a uniform rate of flow is not reached in a reasonable time, the investigator must use personal discretion in terminating the test. The quantity of flow for each pressure increment should be recorded at 1, 2 and 5 minutes after the start of the test and for each 5 minute interval thereafter. Upon completion of the tests at 15, 30 and 45 psi, the pressure should be reduced to 30 and 15 psi and the rate of flow and elapsed time should once more be recorded in a similar manner for each of these pressure increments. Observation of the water inflow quantities, taken with increasing and decreasing pressure, permits evaluation of the nature of open discontinuities in the rock. For example, a linear variation of flow with pressure indicates openings that neither increase or decrease in size. If the curve of

Figure 5-29 Ratio Method Type Curve

296

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flow versus pressure is concave upward, it indicates the openings are enlarging; if convex, the openings are becoming plugged. Additional data required for each test are as follows: (1) depth of hole at time of each test, (2) depth to bottom of top packer, (3) depth to top of bottom packer, (4) depth to water level in borehole at frequent intervals, (5) elevation of piezometric level, (6) length of test section, (7) borehole radius, (8) length of packer, (9) height of pressure gauge above ground surface, (10) height of water swivel above ground surface and (11) description of geologic host material being tested in each interval. Item (4) is important because a rise in water level in the borehole may indicate leakage around the packers. 5.6 LABORATORY ANALYSES 5.6.1 Soils Laboratory tests of soils collected during the field drilling task define four basic properties of soils and their

suitability for use on waste disposal sites. These soil characteristics can be summarized as: • Index and mechnical properties • Strength and compressibility • Hydraulic conductivity • Chemistry Laboratory test procedures for these groupings are provided in Figure 5-31 for a number of standard reference documents or standards developed by various standards organizations. The use of standard technical methods in the development or measurement of site assessment data should never be overlooked in any project. Determination of soil physical and chemical properties in site characterizations is a major part of the remedial investigation/feasability study (Rl/FS) process at hazardous wastes sites, where it is essential for evaluating the fate and transport of contaminants in the soil system. Fate and transport studies of soil contaminants are directly used for

Figures 5-30 Packer Permeability Tests

297

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developing exposure assessments, risk assessments and remedial design strategies. The purpose of soil sample collection with the RI/FS may be to evaluate a wide variety of geochemical reactions such as chemical leaching to ground water, retardation within the soil column, leaching/retardation within caps, resuspension of contaminated soil as dust and chemical retardation within the aquifer matrix. The interrelation of soil chemical and physical processes in the soil system is complex. Sorption of chemicals can vary with concentration, pH, moisture content and sorbent. This is further complicated by the contact of the chemical contaminant on specific soil properties and interactions with other chemical contaminants. The movement of solutes in the unsaturated zone is dependent on soil physical properties and infiltration which must be evaluated as a total system. Soil systems can also extremely heterogeneous and anisotropic. A chemical or physical property measured or determined in one location may not adequately characterize the entire site. Care must be taken that values such as hydraulic conductivity, fraction of organic carbon (foc), pH, soil moisture, sorption coefficients and bulk density are representative of field conditions and adequately describe the total volume of soil under consideration within the assessment. Statistical techniques may be required to establish this correlation due to the typical heterogeneity of soil existing on a site. The following laboratory tests are designed to provide information on the quantity and physical characteristics of soil located on project sites. For specific waste disposal projects individual tests must be selected to evaluate both borrow and landfill cut areas for greenfield and facility expansion projects. Guidelines for the numbers of tests are given below for typical waste disposal projects; however, good engineering judgment must be applied to adequately describe the quality and quantity of the individual soils located on the property. RI/FS investigations are too specific to site disposal history for general guidelines on the quantity of tests necessary to evaluate the remediations. Chapter 10 includes general descriptions of geostatistical methods for the evaluation of quantifies of soil tests for RI/ FS investigations under assessment monitoring programs. The Phase II investigations for disposal projects will generally consist of: (1) either drilling and sampling soil borings or excavating shallow exploratory pits, (2) obtaining bulk samples of representative soils and (3) evaluating these samples for use as borrow material. Establishment of borrow material is an important part of many Phase II programs for waste disposal. Although not currently available (2002), it is anticipated that both the American Society for Testing Materials (ASTM) and the American Society of Agronomy will be compiling specific methods directly relevant for contaminated soils in the near future. The specific

298

references for the analytical methods discussed are cited. The purpose of the methods and limitations of the methods are briefly discussed in this section. It is not the intent of this section to give a detailed description or procedure for each method, as that information is available in the references cited. It is the intent rather to list various methods that are generally the most applicable for selection within accepted laboratory testing programs. The Representative Sample The difficulties of obtaining a representative soil sample for laboratory evaluation has been recognized for at least forty years. Hvorslev (1949) classified five basic types of potential disturbances to soil that range from slight disturbance to severe: • Changes in stress conditions • Changes in water content and void ratio • Disturbance of the soil structure • Chemical changes • Mixing and segregation of the soil constituents These five classes or levels of disturbances are still important today as site assessments results may be greatly affected by any one of the above points. The simple (or complex) act of sampling and transporting soil samples to the laboratory can affect any or all of the above classes of soil disturbance. Recent reviews of ground-water sampling procedures (Nielsen, 1991) have looked at sampling and transportation difficulties of pulling water quality samples from monitoring wells and moving them to the analytical laboratory. Obtaining representative soil samples has conceptually similar, but very different real operational problems beginning with the act of sampling through to soil laboratory tests and concluding with the data evaluations. It is expected that by the time the sample has arrived in the laboratory it has been fully logged according to descriptive standards, USCS and Facies Codes as required for the project. Additional classification may be conducted at the laboratory based on the results of grading and index tests, but the basic classification work must be completed in the field. Mechanical Index Properties Evaluation of waste disposal sites must incorporate an organized sampling and testing program of the facility subsoils to fully understand site geologic conditions. Grading curves, plasticity index properties (called Attenberg limits), and many additional physical properties of the soil and bedrock are normally evaluated as the first step of the

ENVIRONMENTAL TESTING

299

Figure 5-31 Laboratory Testing Procedures

ENVIRONMENTAL TESTING

design of new facilities or expansions to waste disposal sites. The evaluation of physical properties are also important for remedial projects, where long-term stability of the design must be assured for predictable time periods into the future. Soil Moisture Content The gravimetric oven-drying procedure is the standard by which all methods of measuring soil moisture content are compared. Oven-dry water content is expressed on a weight or volume basis, producing gravimetric (Og) and volumetric (Ov) content values. The water contents of soils commonly range from 5% to 35%. However, for soil types that contain a high percentage of clay or organic material, very high water content may be observed; sometimes unconsolidated muds can show moisture contents in excess of 100%. In general, the water content depends on void ratio, particle size, clay minerals organic content and ground-water conditions. Soil moisture content determinations are essential for fate and transport estimations. The soil moisture content (% pore water) is one test used in vadose transport equations to modified water input from infiltration. Soil moisture has a direct influence on the sorption processes and should be considered in sorption studies or estimations. Soil moisture determinations also allow conversion of soil masses and chemical concentrations on a wet weight basis to dry weight equivalent masses and concentrations. ASTM Method D-2216 determines the free water or pore water content as a percentage based on moist and oven-dried soil weight differences. Method D-2216 may generate erroneous information for soils with a high organic material content, high clay content (halloysite, smectite and illite/smectite), high gypsum content or a high salt content in the pore water. Additional problems may be observed with the oven-drying method as oven temperatures may vary significantly and convectional temperature differences may introduce a systematic error. Relative Density The unit weight or density of a material is defined as the weight of material divided by its volume, including solids, liquids and voids. The in-place density of soils is considered a function of deposition, gradation and loading history. For example a fine grained soil deposited by wind or water and not subsequently subjected to loading will be relatively loose; if subsequently consolidated by the weight of overlying soil deposits or glacial action, the soil density will be materially increased. In general, when measuring the degree of compaction of a soil, the dry density-weight of solids divided by total

300

volume is used. Typical ranges of density of various soil types are shown in Table 5-6. The relative density value offers a convenient measure of the degree of compactness of a soil in a fill or embankment and also provides a significant indication of the susceptibility of the soil to liquefaction. The relative density of a soil is the density relative to the limiting values described as its loosest state and its densest state. A soil in its loosest state has a relative density of zero and a soil in its densest state has a relative density of 100%. Because the density of a soil is directly related to the void ratio, the relative density, Dr., can be expressed in terms of the void ratios: e max – e D r = ------------------e min

Equation 5-26

where: emax is the void ratio of the loosest state; emin is the void ratio of the densest state; and, e is the void ratio of the soil as it exists. The specific gravity of a rock or soil may be defined as the ratio between the unit weight of the substance to the unit weight of pure water at 40°C. Classification of Soils for Engineering Purposes (ASTM D2487-69) Test method ASTM D2487 classifies soils from any geographic location into categories representing the results of prescribed laboratory tests to determine the particle-size characteristics, the liquid limit and the plasticity index. The assigning of a group name and symbol(s) along with the descriptive information required in ASTM practice D2488 can be used to describe a soil to aid in the evaluation of its significant properties for engineering use. The various groupings of this classification system have been devised to correlate in a general way with the engineering behavior of soils. This test method provides a useful first step in any field or laboratory investigation for geotechnical engineering purposes. Additional classification methods to further describe soil samples, included in Chapter 4, may be more important in hydrogeologic investigations than pure engineering classifications as represented by D2487. Particle Size Analysis of Soils (ASTM D422) Particle size information is used to generate soil classifications, size distribution curves and textural classifications (e.g., USDA and USCS classification) for both engineering and descriptive purposes. Particle size and

ENVIRONMENTAL TESTING

distribution determinations aid in characterizing the physical soil environment where migration can occur. This information can also aid in lithologic correlations. To some extent, the grain size curve for sands can be related to engineering behavior such as soil hydraulic conductivity, frost susceptibility, angle of internal friction, bearing capacity and liquefaction potential Particle or grain size determinations are either visually estimated or determined by sieving in the field. In the laboratory, grain or particle size is determined by sieving (>75 mm) and hydrometer techniques for the fine fraction ( 0.1 Sce , and preferably: t > 3 Sce then verify β < 0.01

t1 t2

If the time required is too long for a pump test then there is no point in doing the test to determine c' Use same approach to estimate pumping time required to obtain any other formation parameters.

4.

Leaky

Evaluate appropriate distance (r) to observation piezometers for spread of β values for measurable drawdown (s). Observation piezometers

Unconfined

If t . 0.1 ce the r/L > 1.0

Estimate Drawdowns

If r/L > 1.0

should be spaced to obtain r/L values greater than 1.0 t2

t2

6.

Generate Composite Plot of Corrected Drawdown (s) versus t/r2

10

Pump Test Q

Field Test Data 5.0

2.0

t1

W(u) 1.0

t2

0.5

= Piezometer p23 = Piezometer p12 = Piezometer p29

0.2

5. Perform Pump Test PROCEDURE BASED ON VAN DER KAMP (1985)

0.1 -4

10

2

5

10

2

2

5

10

3

2

5

r2 2 t ft /min

Figure 7-36a Data Plotting Method for Determining Pump Test Values

486

10

4

2

5

10

5

PHASE II DATA ANALYSIS

10

PUMP TEST EVALUATION PROCEDURE (B)

Field Test Data

5.0

1) Generate composite plot of corrected drawdown versus t/r 2 from data from two or more piezometers.

2.0

W(u)1.0 = Piezometer p23 = Piezometer p12 = Piezometer p29

0.5

2) Compare hydrogeologic model to field data to begin selection of appropriate type curve.

0.2 0.1 -4

2

5

10

10

2

2

5

10

2

3

5

4

10

r2 2 t ft /min

2

5

10

5

APPLICABILITY OF WELL FUNCTIONS AND TYPE CURVES BOULTON β < 0.01

"A"

NEUMAN

THEIS

or

C' = 0 F = W (UA,η )

f = W (UB )

= W(U , r/L) T, S, c e

(T,S y )

T, S, c

THEIS

"B"

BOULTON β < 0.01 f = W (UB, r/L )

β < 0.01 f = W (UA) T , S, β

NEUMAN C' = 0 f = W (UB, η ) T, c, S y (?)

or

T , S , S y, (?)

3) Select appropriate type curve from master curve figure such that the type curve values of b or r/L are in proportion to the value of r ( if only one piezometer is available then plot s (vertical) and t (horizontal).

STEADY STATE f = 2K (r/L) 0 T, ce

HANTUSH > 0.01 f = H(UA, β) (T, S, β )

TIME 0.1S' c'

0.1 S ce

3 S ce

0.1 Syce

3S y ce

THEIS CURVE

log (h - h)

THEIS CURVE

log(t) Modified from van der Kamp (1985)

4) The type curve selected is plotted W (u ) versus values of u, (or alternatively values of W (u) for values of 1/u).

10 Theis Curve

5.0

2.0

W(u)1.0 0.5

5) Superimpose the field-data curve on the type-curve sheet, Keeping coordinate axes parallel to a point of best fit of observed points to the type curve.

Type Curve

0.2 0.1 -4

2

5

10

10

-3

10

-2

10

-1

10

0

u 10

6) Select an arbitary match point and record coordinates s, r 2/t, and W(u). Determine formation parameters through substitution of the coordinates into pertinate equations.

Field Test Data

5.0

T = 114.6 Q W(u)/s = 665,419 gpd/ft S = T u/(1.87 r /t) 2= 0.032

Theis Curve

2.0 Q = 1000 Gal/min

1.0

Match Point W(u) = 1.8 u = 0.1 s = 0.31 ft r 2/t = 780

0.5

W(u)

7) Critical times for type curves should be re-calculated to confirm initial calculations.

0.2 0.1 2

5

10

10

2

5

5

10

2

3

5

10

r2 2 t ft /min

Type Curve

-4

2

2

-3

2

5

-2

2

5

-1

2

5

0

4

2

5

5

10

8) Evaluate if additional test constraints require adjustment of values (ie) nearfield skin effects, partial penetration, or farfield boundaries require additional data or curve adjustments or interpretations.

u

Figure 7-36b Data Plotting Method for Determining Pump Test Values (con.)

487

PHASE II DATA ANALYSIS

an assumption that the pumping well and the observation well are perforated throughout the entire saturated thickness of the aquifer; therefore, the drawdown in the observation well is given by: Q s ( r, t ) = -------------- • S D 4 T

s r t Q T sD

Equation 7-31

= drawdown = radial distance from the pumping well = time since pumping started = pumping rate = transmissivity = dimensionless drawdown represented numerically by an integral function

Two sets of type curves were developed by Newman, expressed in terms of three independent dimensionless parameters: , ts (dimensionless time with respect to the specific elastic storage) or ty (dimensionless time with respect to the specific yield). The dimensionless time parameters are related to each other by the equation: ty =

• ts

and

Equation 7-32

were defined by Neuman (1975) as follows:

= S/Sy, = KD

r2

Equation 7-33 /b2

Equation 7-34

The dimensionless time parameters are defined as follows: Tt t s = ---------2 Ss r Tt t y = ---------2 Sy r

The key to this method is when approaches zero (S is much less than Sy) only two independent variables remain and sD can be integrated for different values of . The results are two asymptotic families of type curves: type A (sD versus ts) and type B (sD versus ty). Both A and B type curves approach a set of horizontal asymptotes, the length of which depend on the value of . The procedure used to determine aquifer parameters is as follows: • Plot the family of Neuman type curves SD versus ts and ty for a practical range of values on log-log paper; • Plot the corrected drawdown (s) against the corresponding time for a given observation well at a distance r from the pumped well on another sheet of loglog paper, with the same scale as was used to plot the type curves. • Superimpose the time-drawdown field data curve on type B curves. Keep the coordinate axes parallel at all times, so that the sD axis is parallel with the s axis and the ts/v axis is parallel with the t axis. The overlying datasets used and type curves must be adjusted until, as much as possible late time-drawdown field data fall on one of the type B curves. Record the value of the selected type B curve. • Select an arbitrary point B and record the coordinates Sd, ty and s, t. • Calculate the transmissivity (T) and the specific yield (Sy) using the equations:

Equation 7-35

114.6Qs T = -----------------------Ds

Equation 7-37

Equation 7-38

Equation 7-36

0.1337Tt S y = ---------------------2 ty r

where: S: storage coefficient = Ss b Ss: specific elastic storage (Ft-1) Sy: specific yield b: initial saturated thickness of the aquifer KD: degree of vertical anisotropy = Kz (vertical hydraulic conductivity)/Kr (horizontal hydraulic conductivity) r: radial distance from the pumping well;

488

b: initial saturated thickness of the aquifer

Q is in gpm and the other parameters in gallons per day per foot system. The early time data should also be evaluated for the elastic storage coefficient using the following procedures: • As before, superimpose the field data on the type A curves, keeping the coordinate axes of both graphs parallel to each other and matching as much of the earliest time drawdown data to a particular type curve as possible. The value corresponding to this type curve must be the same as that obtained previously from the type B curves.

PHASE II DATA ANALYSIS

• Select an arbitrary point A on the superimposed curves and note its coordinates sD, ts and s, t.

•

• Calculate the transmissivity and the elastic storage coefficient:

• lD = ratio between distance from the initial water table to bottom of the screen in pumping well (l) and initial saturated aquifer thickness (b) = l/b.

0.1337Tt S = ---------------------2 ts r

Equation 7-39

• In practice the transmissivity, is taken as the average of the early and late data, unless boundary effects are evident in the data the horizontal hydraulic conductivity (Kr) can be calculated with the formula: Kr = T/b

Equation 7-40

• Vertical anisotropy (KD) us evaluated from the value of according to: 2

b K D = ------------2 r

Equation 7-41

• Values of Kr and KD, obtained previously, can be used to determine the vertical hydraulic conductivity (Kz) with the following relationship: Kz = KD Kr

Equation 7-42

The parameter SIGMA ( ) is calculated from: S = ----Sy

Equation 7-43

Specific storage of the aquifer can be calculated from: S S s = --b

Equation 7-44

Unconfined aquifers are often thick and piezometers are compiled in the unit as partially penetrating. When either the pumping well or the observation well is screened only through a portion of the saturated thickness of the aquifer the extended Neuman model requires additional parameters be taken into account. The integral function for partially penetrating conditions that describes the dimensionless drawdown (sD) is expressed in terms of six independent dimensionless parameters: , , lD, dD, ZlD, Z2D and ts or ty where:

, , ts and ty have the same definition as the fully saturated model described above.

• dD = ratio between distance from the initial water table to top of the screens in pumping well (d) and initial saturated aquifer thickness (b) = d/b. • ZlD = ratio between the vertical distance from the bottom of the aquifer to bottom of the screens in the pumping well and initial saturated aquifer thickness. • Z2D = ratio between the vertical distance from the bottom of the aquifer to top of the screens in the pumping well and initial saturated aquifer thickness. Fully penetrating condition allows the number of independent parameters to be reduced from three to two by letting approach zero. Partially penetrating conditions allow the same parameter reduction procedure provided that the geometric factors (lD, dD ZlD Z2D) are known. A special set of theoretical curves must be developed to use this procedure in accordance with the geometrical distribution and construction of the pumping well and the observation wells. Driscoll (1987) considers that at a distance from the pumping well equal to twice the aquifer thickness, the effect of partial penetration is no longer observed in the observation piezometers. The effect of partial penetration on the drawdown in an unconfined aquifer decreases with radial distance from the pumping well and with the ratio KD = Kz/Kr Neuman (1974). At distances greater than r = b / KDl/2 this effect disappears completely when time exceeds t = 10 Sy r2/T and the drawdown data follow the late Theis curve in terms of ty. If the condition is not satisfied a set of theoretical type curves have to be used. 7.6.7 Distance-Drawdown Analysis Distance-drawdown analysis can be performed using a number of wells at variable distances between the pumping well and observation point. Usually three wells are used to produce the graphs of drawdown versus distance. The formulae used to determine the transmissivity (T) and the storage coefficient (S) are given below. 528Q T = ------------S

Equation 7-45a

489

PHASE II DATA ANALYSIS

0.3Tt S = ------------- (b) 2 r0

Equation 7-45b

where: T = transmissivity in gpd/ft Q = pumping rate in gpm S = slope of the distance-drawdown graph expressed as the change in drawdown, in feet, between any two values of distance on the log scale whose ratio is 10 t = time since pumping started in days ro2 = intercept of the extended straight line at 0 (drawdown, in feet An example of the graphs of drawdown versus logarithm of distance are presented in the Figures 7-37. As can be seen at 2000 minutes since the pumping started, the corresponding drawdowns for the considered wells fall along a straight line on the semilogarithmic graphs. This moment of the pumping test was used in the distance-drawdown analysis.

can be used to assess radial anisotropy of an aquifer because the analysis generates the average hydraulic conductivity along a line of piezometers. By comparison of lines of observation points along perpendicular lines of wells, one can calculate a value for anisotropy. Distance drawdown analysis performed along several sets of observation wells set along the strike of geologic formations and perpendicular to the strike represent the major axis of hydraulic conductivity. The degree of radial anisotropy in the vicinity of a pumping well (KR) is typically calculated as the ratio between the hydraulic conductivity along the major resultant axis of anisotropy and the hydraulic conductivity along the minor axis of anisotropy. The shape of drawdown cones (measured from many piezometers) provide large-scale views of the anisotropic hydraulic conductivity conditions. In general, one should plot the shape of drawdown cones at a series of time steps. Anisotropic conditions should be evident by the shape of the drawdown cones. Often initial anisotropic-shaped drawdown cones later develop fully radial shapes at long time periods. These shapes can be back calculated to define porosity values from the total volume of geologic material dewatered divided by the total discharge during the test period.

7.6.8 Aquifer Radial Anisotropy Recovery Analysis The Neuman model takes into account the vertical anisotropy of the aquifer. The distance-drawdown analysis

To confirm results obtained during a pump test, recovery data can also be analyzed using the Theis recovery method. The results obtained using the Theis recovery analysis should be the same order of magnitude as those determined for the unsteady-state condition during the pumping period. The formula used to determine the transmissivity (T) is: 264Q T = ------------s

Equation 7-46

where: T = transmissivity in gpd/ft Q = pumping rate in gpm s = slope of the distance-drawdown graph expressed as the change in drawdown, in feet, between any two values of distance on the log scale with a ratio of 10 Summary of the Results

Figure 7-37 Distance-Drawdown Graph

490

One should always include summary ranges of the average hydrogeological parameters obtained by the various analysis methods for the area influenced by the pumping test.

PHASE II DATA ANALYSIS

Conclusions At the conclusions of the Phase II field and office studies, the physical, geologic and hydrogeologic setting of the site should be well established. The following data should be available for inclusion into the conceptual model: • Topographic maps • Boring logs • Interpretative cross-sections • Interpretative analysis of geophysical studies • Material test results and interpretations • Narrative description of ground water with flow patterns • Piezometric or potentiometric maps with interpreted flow lines • Analysis of aquifer characterization tests • Structural contour maps of uppermost aquifer and confining layers in plan view These data are then used to construct the unified conceptual hydrogeologic models and flownets which are then used to design the monitoring system for the facility. The following chapter addresses the process of geologic conceptualization and flownet construction techniques specific to geologic models and ground-water monitoring programs. These models and flownet construction are important for both detection and assessment monitoring design as well as aquifer remediation design elements.

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PHASE II DATA ANALYSIS

Paper 708, 70 pp. Lutenegger, A.J. and D.J. DeGroot, 1995. Techniques for Sealing Cone Penetrometer Holes. Canadian Geotech. J, October. McCall, W, J. J. Butler, Jr., J. M. Healey, A. A. Lanier, S. M. Sellwood and E. J. Garnett, 2002. A Dual-Tube Direct-Push Method for Vertical Profiling of Hydraulic Conductivity in Unconsolidated Formations. Environmental & Engineering Geoscience, in press. GSA, Denver, CO. Meinzer, 0. E., 1939. Ground Water in the United States. U.S. Geological Survey Water-Supply Paper 836-D, pp 157229. Michalak, P., 1995. A Statistical Comparison of mobile and Fixed Laboratory Analysis of Groundwater Samples Collected using Geoprobes Direct Push Sampling Technology. In Proceedings of the 9th National Outdoor Action Conference. National Ground Water Association, Columbus, OH. Mines, B.S., J.L. Davidson, D. Bloomquist and T.B. Stauffer. 1993. Sampling of VOCs with the BATS Ground Water Sampling System. Gr. Water Mon. & Remed., vol. 13, number 1: 115-120. Morley, D.P., 1995. Direct Push: Proceed With Caution. In Proceeding of the 9th National Outdoor Action Conference. National Ground Water Association, Columbus, OH. Neuman, S.P., 1972. Theory of Flow in Unconfined Aquifers Considering Delayed Response of the Water Table. Water Resources Research, Vol. 8, No. 4, pp. 1031-1045. Neuman, S.P., 1974. Effect of partial penetration on flow in unconfined aquifers considering delayed gravity respone, Water Resources Research, Vol. 10, No. 2, pp. 303-312. Neuman, S.P., 1975. Analysis of pumping test data from anisotropic unconfined aquifers considering delayed gravity response. Water Resources Research, Vol. 11, No. 2, pp. 329-342. New Jersey Department of Environmental Protection, 1994. Alternative Ground Water Sampling Techniques Guide. Trenton, 56 p. Nielsen, D.M., 1991. Practical Handbook of Ground Water Monitoring. Lewis Publishers, Boca Raton, FL. Nguyen, V. and G. F. Pinder, 1984. Direct Calculation of Aquifer Parameters in Slug Test Analysis. In: Groundwater Hydraulics, J. Rosenshein and G Bennett (eds.) American Geophysical Union Water Resources Monograph (Washington, DC, pp. 222-239. Pitkin, S., R.A. Ingleton and J. A. Cherry, 1994. Use of a Drive Point Sampling Device for Detailed Characterization of a PCE Plume in a Sand Aquifer at a Dry Cleaning Facility. In Proceedings of the 8th National Outdoor Action Conference. National Ground Water Association, Columbus, OH. Prosser, D.W., 1981. A Method of Performing Response Tests on Highly Permeable Aquifers. Ground Water, Vol. 19, No. 6, pp 588-592. NGWA, Westerville, OH. Reed, J. E., 1980. Type Curves for Selected Problems of Flow to Wells in Confined Aquifers. U.S. Geological Survey Techniques of Water-Resources Investigations, Book 3, Ch. B 3, 106 pp. Robertson, P.K. and R.G. Campanella, 1989. Guidelines for Geotechnical Design Using the Cone Penetrometer Test and

CPT with Pore Pressure Measurement. Hogentogler & Company, Inc., Columbia, MD. Roscoe Moss, 1990, Handbook of Ground Water Development. Wiley Interscience, 493 pp. Siegrist, R.L. and P.D. Jenssen, 1990. Evaluation of Sampling Method Effects on Volatile Organic Compound Measurements in Contaminated Soils, Environ. Sci. and Tech. vol. 24: 1387-92. Smolley, M. and J.C. Kappmeyer, 1991. Cone Penetrometer Tests and Hydropunch Sampling: A Screening Technique for Plume Definition. Gr. Water Mon. Rev., vol. 11, no. 3: 101-6. Springer, R.K. and L.W. Gelhar, 1991. Characterization of Large Scale Aquifer Heterogeneity in Glacial Outwash by Analysis of Slug Tests with Oscillatory Response, Cape Cod, MA. In U.S. Geol. Surv. Water Res. Invest Rep. 914034, pp 36-40. Stallman, R. W., 1971. Aquifer-test Design, Observation, and Data Analysis. U.S. Geological Survey Techniques of Water-Resources Investigations, Book 3, Chap. B1, 26 p. Theis, C.V., 1935. The relationship between the lowering of piezometric surface and the rate and duration of discharge of a well using ground-water storage. Am. Geophys. Union Trans., Vol. 14, Pt. 2, pp. 519-524. Todd, D.K., 1980. Ground Water Hydrology. Second Edition, John Wiley & Sons, NY, 535 pp. van der Kamp G., 1985. Brief Quantitative Guidelines for the Design and Analysis of Pumping Tests. Hydrogeology in the Service of Men, Memoires of the 18th Congress of the International Association of Hydrogeologists, Cambridge, pp. 197-206. Walton, W. C., 1962. Selected Analytical Methods for Well and Aquifer Evaluation. Illinois Department of Registration and Education Bulletin 49. 81 pp. Walton, W. C. 1987. Groundwater Pumping Test: Design and Analysis, Lewis Publishers, Chelsea, MI. Weeks, E. P. 1964. Field Methods for Determining Vertical Permeability and Aquifer Anisotropy. U.S. Geological Survey Professional Paper 501-D, pp. D193-DI98. Weeks, E. P., 1969. Determining the Ratio of Horizontal to Vertical Permeability by Aquifer-test Analysis. Water Resources Research. Vol. 5, No. 1, p 196-214. Weekes, E. P., 1977. Aquifer Tests – The State of the Art in Hydrogeology, Proceedings of the Invitational Well Testing Symposium, Berkeley, CA, Oct. 19-21, 1977, Lawrence Berkeley Laboratory, pp. 14-26.

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CHAPTER 8 THE CONCEPTUAL MODEL

8.1 INTRODUCTION TO CONCEPTUAL MODELS The two objectives in the use of conceptual models for the evaluation of ground-water flow in site assessments are: • Site characterization –– To develop a sound and informed understanding of the geology and geohydrology, the natural hydraulic character and chemical evolution of the ground-water system, and ground-water flow directions and rates. • Prediction –– To forecast or predict the nature, rate and volume of movement of leachate organic residuals, or ground-water contamination treatment solutions into ground-water monitoring zones. The site characterization and prediction process is explained in this chapter, as it employs data gathered in the Phase I and Phase II programs. These data are formatted into additional visual presentations, such as the maps and cross-sections that were discussed in Chapter 7. Review of these derivative presentations naturally leads to completion of the conceptual hydrogeologic model for the facility of interest. Figure 8-1 illustrates an overview of the model conceptualization process using data developed during the Phase II investigation, displayed as derivative maps, cross-sections and fence diagrams. The conceptual model of the physical geologic and hydrogeologic system can be represented by more than the typical two- or three-dimensional drawings common in the literature. These representations of the real-world field conditions can also be enhanced by including within the conceptualization process ground-water flownet constructions. These composite evaluations provide the investigator with important insight into directional components and rates of flow of the system under investigation. Review of data leads to a conceptual model of the ground-water system and its interaction with surface water bodies and human activities. The term conceptual

model is a convenient designation for visualization of the physical system, which is formed in the mind of a geohydrologist. It is always an idealization and simplification of the actual physical situation. There are many types of conceptual models available to illustrate aspects of groundwater conditions present. An aquifer is a complex, three-dimensional geologic system containing water. The aquifer is bounded by other geologic units, the ground surface and/or bodies of surface water. At many locations, for example, it is entirely appropriate to represent this concept as a single layer of finite horizontal extent. This is done by applying an averaging process to the third dimension, the vertical,

Figure 8-1 The Conceptual Process

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resulting in what is sometimes known as the vertically integrated approach. Editing of borehole logs and conversion into a final geologic column is a similar process; however, unified conceptual and flownet models should include both geologic and hydraulic conditions contributing to ground-water movement. Many of the major contributions to the field of ground-water hydrology are the Theim equation, Theis equation, Hantush-Jacob leaky equation, Dupuit-Forcheimer equation, the Dupuit approximation, etc. are based on the approach of integrating average conditions into an analytical conceptual model. The unified conceptual/flow model must incorporate all the essential features of the physical system under study. With this constraint, conceptualization is tailored to an appropriate level or sophistication to describe the environment under study. The degree of accuracy required for various geologic conditions differs. For example, an unconfined aquifer in a permeable, homogeneous, sandy lithology may require only simple cross-sections to illustrate the conceptual system. If there is a significant and identifiable three-dimensional gradient with more than a single permeable layer, more complex geologic models, including complex flownet construction, may be necessary to illustrate the system. The conceptual process may require consideration of facies or depositional models to fully understand the geologic system. These models are supported in Phase II field lithostratigraphic mapping and logging procedures. Phase I studies involve less time and money, fewer data and require only a fair accuracy in their predictions of the conceptual system. Consequently, a much simpler conceptual model is required. Design of the final conceptual model for important facilities and/or large-scale ground-water restoration projects involving significant financial investments or risks requires complete information, more time and money and a more sophisticated manner of conceptualization. The following subsections first review the geologic model, where the principal emphasis is placed on arriving at a correct interpretation of the geologic environment. A conceptual geologic model often is developed over time with many alternative configurations of the model tried and discarded. This process is developed to illustrate the common procedure typically employed in these cases. The geologic conceptual model is then further supported by hydrogeologic data developed by field gathered hydraulic head levels. Flownets are developed as pertinent to geologic systems. The integration of geologic data with flow data completes the process leading to selection of target zones for ground-water monitoring system design. Flownet construction may only be an initial step toward full computer modeling using numerical techniques. These

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flownet constructions, however, can be completed in a matter of hours and would even be recommended as a preliminary step before extensive computer modeling to serve as a guide and cross check of the numerical work. These flownet constructions can provide steady state results that are often sufficiently accurate for many ground-water issues that arise during site assessment projects. Conceptual hydrogeologic models can range between everything from very simple drawings to artist renderings of the rock soil and ground-water flow. Each type of conceptual models is evaluated in this chapter along with recommendations for when to apply the alternative presentations.

8.2 REGIONAL AND SITE GEOLOGY In order to define the geologic environment of a specific area, the regional and site-specific geology must be thoroughly characterized. These data must establish the properties and features of individual geologic units beneath and near the site, through use of all the data available to the investigator: • Regional geologic maps and cross-sections that are used to characterize area-wide geologic units, facies, and depositional and structural features, to depths incorporating probable groundwater movement as it could impact or be impacted by facility construction and operation • Topographic maps used to characterize site-specific topographic relief • Stratigraphic maps and cross-sections used to characterize detailed site-specific geologic conditions • Aerial photography, as used to illustrate information such as vegetation, springs, gaining or losing stream conditions, wetland areas and important elements of geologic structure The above data have been gathered within the Phase I and Phase II programs. Cross-sections and stratigraphic maps should be prepared so that a clear technical basis is used to derive the conceptual geologic and hydrogeologic models. The entire process of geologic conceptualization is built-up by regional data to establish the geologic setting, thereby gradually building an understanding of geologic conditions at the site from the drilling program. Interpretation of data through cross-sections and maps strengthens the conceptual model until a final picture of the geology is established. The final conceptual geologic model is a sitespecific representation of the geologic system under and

CONCEPTUAL MODELS

adjacent to the facility. Geologic information used to construct conceptual geologic models typically consists of the following: • Depth, thickness and area extent of each stratigraphic unit, including weathering horizons • Stratigraphic zones and lenses within the nearsurface zone of saturation • Stratigraphic contacts between significant formations/strata • Significant structural features such as discontinuity sets, faults and folds • Zones of high hydraulic conductivity or shearing/faulting Several cross-sections may be required to depict significant geologic or structural trends and to reflect geologic/structural features in relation to local and regional ground-water flow. The area and vertical extent of the geologic units can be presented in several ways. For complex settings, the most desirable presentation is a series of structure contour maps representing the physical character

of the tops and/or bottoms of each unit. Cross-sections and isopach maps can also be used because they are generally good graphic supplements to the structure contour maps. These cross-sections can be combined into a fence diagram (three-dimensional) that can serve as the basis for conceptualization of the geology. Conceptualization is a way of achieving a graphic idealization of the actual geologic conditions; the investigator must, therefore, consider the geologic features that would affect ground-water flow and ground-water quality. Minor features that are not important to the overall picture should not be transferred to representations of the conceptual model. The conceptualization process is illustrated in Figures 8-2 through 8-6. Figure 8-2 provides a cross-section showing regional bedrock and ground-water flow for an area in upstate New York. The conceptualization was developed entirely from a Phase I literature search and geologic experience in the region. The regional cross-section shows the site to be located over the dipping Vernon Shale and unconsolidated glacial deposits. The regional ground-water discharges into the Erie Canal. The deeper bedrock units are also

Source: Wehran Engineering

Figure 8-2 Cross-Sectional Information on Regional Scale

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shown discharging ground water from depths beneath the Appalachian Plateau, through the Vernon Shale and into the Erie Canal. This information allowed the investigators to plan a program to drill to the Vernon Shale and confirm the depth of glacial deposits, ice contact deposits and weathering in the shale. Figure 8-3 is an example of a final boring log from the drilling program. The lithology of glacial

till deposits, residual soil and weathered/fractured bedrock was confirmed by the detailed description of splitspoon samples taken during boring effort. A series of borings is presented on a cross-section in Figure 8-4. Boring B-8 illustrates the geologic section down to competent shale. The conceptualization process was started in this figure because many of the minor sand lenses are grouped within the till body as undifferentiated

Source: Wehran Engineering

Figure 8-3 Final Boring Log Example

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till deposits. If the unit contained significant sand layers, as represented in boring B-2 as glacial outwash, these units should be shown on the cross-section. The conceptualization process goes further, as shown in the Figure 8-5 fence diagram, which includes many cross-section views. These diagrams are three-dimensional representations constructed using several cross-sections that are helpful in presenting an area view of geologic and ground-water conditions. As with cross-sections, they are based on the logs of the field borings, measurements of ground-water levels and topography. However, the conceptual process required one additional step to aid in the evaluation of the site. The final step in the conceptualization process is reduction of the information on cross-sections or fence diagrams to the essential elements of geology. The picture should be a clear and concise conceptualization of the geology, presenting all important features necessary for understanding the interrelationships between geology and ground-water flow below the site. Note that each of these

presentations tries to use physical data collected for the field drilling program. Figure 8-6 presents the final conceptual model of the geology and the preliminary ground-water flow directions for the facility. The arrows do not represent an actual flownet; however, the directional components shown provide the target monitoring zone for the site. Weathered and unweathered basal tills are shown as separate conceptual elements, due to inherent differences in hydraulic conductivity of the two units. Residual soil overlying the fractured and weathered contact with the Vernon Shale is not identified because it has a hydraulic conductivity similar to that of unweathered tills. In such an instance, the geologic unit nomenclature should show the combined names (lacking in this figure). Weathered and fractured bedrock are, however, distinguished from competent bedrock due to its differences in hydraulic conductivity. This system is integrated in this chapter with a flownet to fully evaluate potential for alternative detection and assessment monitoring well location.

Source: Wehran Engineering

Figure 8-4 Cross-Sectional View of Site Data 499

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Source: Wehran Engineering

Figure 8-5 Fence Diagram of Site Geology

8.3 CHARACTERISTICS OF THE SATURATED ZONE Each of the significant stratigraphic units in the zone of saturation should be characterized by determination of its hydrogeologic properties such as hydraulic conductivity (vertical and horizontal) and effective porosity. These parameters describe aquifer characteristics that control ground-water movement and the ability of the aquifer to retain or pass potential leachate. Both are needed for a general understanding of the hydrogeologic setting at a site and for completing the conceptual hydrogeologic model for design of ground-water monitoring systems. Typically, the amount of data necessary to complete a conceptual hydrogeologic model will differ for each geologic environment in question.

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For example, an aquifer in extensive, homogeneous beach sand (SP under the Unified Soil Classification system) will require less investigation than a glacial unit consisting of lenticular deposits of outwash interbedded with clayey till (GW/CL). The USC system should be supplemented by lithostratigraphic descriptions (Facies codes); for example, is the sediment in question clast supported or matrix supported? When fine-grained sediments reach 20% within a particular sandy unit the sand-size clasts lose contact and the unit becomes matrix supported. Hydraulic conductivity drops significantly when this point is reached in a particular unit (Hughs, 1991). This drop in hydraulic conductivity can range as much as three to four orders of magnitude. There are two types of fundamental aquifer characteristics required to define a hydrogeologic conceptual model: characteristics of the aquifer and char-

CONCEPTUAL MODELS

Note: that this conceptual mode takes hydraulic, flow and geologic information to develop a rational model of the ground-water flow system

Zone a

Zone a represents the potential target monitoring zone.

Source: Wehran Engineering

Figure 8-6 Final Conceptual Model of Facility acteristics of ground-water flow. Aquifer characteristics for each hydrogeologic unit should include:

• Flow directions • Flow rates

• Hydraulic conductivity • Effective porosity • Specific yield/storage (as required for the project) Additional aquifer characteristics such as transmissivity and chemical attenuation properties can be derived, and estimated dispersivity values may be necessary for ground-water transport modeling to estimate ultimately (long-term) concentrations at points of exposure. These aquifer characteristics support ground-water flow characteristics used to define the quantity and the direction of ground-water flow. Both aquifer and flow characteristics are necessary to define the conceptual movement of ground water away from a facility and toward a monitoring point. In order to define the general flow characteristics necessary to develop conceptual hydrogeologic models, the following data are required: • Boundaries and zones of recharge/discharge

Each of these flow characteristics provides components necessary to evaluate the geologic units likely discharging from the facility and to select target zones for monitoring. 8.3.1 Boundaries and Recharge/Discharge Zones To aid in the understanding of the ground-water flow regime and identification of potential pathways to target for monitoring, the location of any proximate zones of recharge or discharge should be identified within the hydrogeologic conceptual model. This identification is determined in part by the general site location in the watershed. Figure 8-7 shows regional discharge/recharge areas from Hubbert (1940) for an unconfined aquifer. The investigator probably does not need to quantify such information in detail; rather, a general indication of discharge or recharge characteristics is used as part of the conceptualization process.

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For unconfined aquifers, recharge areas are usually topographic highs. Discharge/recharge areas also indicate relative depth to unconfined ground water. In discharge areas, ground water is found close to or at the land surface; while at recharge areas, there is often a deep unsaturated zone between the unconfined ground-water surface and the land surface. Discharge areas may be represented by streams, springs, rivers, swamps or ultimately the ocean. Discharge areas may also be related to more permeable aquifers, dry streambeds (with a subsurface discharge to thalweg) or areas of wetland-type vegetation. Freeze and Witherspoon (1967) concluded in a computer based analysis that discharge areas within a particular basin are smaller than recharge areas. They estimated that in studies with three dimensional models the actual percentage of discharge area represented approximately 7% of the total area of the basins. Further discussion of computer based flownet-based discharge-recharge is contained in Section 8.4 on flownet construction. A ground-water contour map can be used to help locate these areas. Recharge and discharge in confined aquifers are typically more complex than for unconfined aquifers. Discharge and recharge may occur where the aquifer is exposed. Some discharge may also occur in the form of upward leakage in areas of upward hydraulic gradient and leaky confining units. Recharge can also occur by downward ground-water flow through leaks in the confining layers (aquitards). Topographic information can provide significant insight into ground-water movement; however, topography can also mislead an investigator, when aquifers are confined or perched. Ground water in such aquifers can often move in unexpected directions. The investigator must pay particular attention to potential mounding of ground water and directional complexities that may be covered by low hydraulic conductivity subgrade materials. Specific conditions can only be discerned through analysis of lithology (perhaps through depositional models) and measurement of piezometric hydraulic heads, which should be obtained in the Phase II field program.

tain for use in determination of ground-water flow directions include: • Depth to ground water • Potentiometric surfaces • Hydraulic gradients • Vertical components of flow Each of these parameters was defined in Chapters 3, 4 and 5 of this manual; the following text will describe use of these data in development of the conceptual hydrogeologic model.

8.3.2 Ground-Water Flow Directions The Phase II investigations include a program for precise monitoring of the area and temporal variations in ground-water levels. This program involves the measurement of water levels or hydraulic head levels in piezometers installed for the purpose of investigating the saturated zone. These data are used to define ground-water flow directions during development of the ground-water monitoring system. Parameters necessary to measure or ascer-

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Source: Hubbert (1940)

Figure 8-7 Regional Conceptual Flow Patterns

CONCEPTUAL MODELS

Figure 8-8 shows the potentiometric surface of a glacial outwash sand and gravel (SW) unit that has facilitywide extent. Piezometers are located on the map, which also provides water levels measured on a single day during stable barometric conditions. Because the unit is confined within a fine-grained lodgment till (or diamict), water level readings are affected mainly by changes in barometric pressure. Interpretations of ground-water

flow-direction (for the geologic unit measured) should always be based on water level measurements from a single, continuous, permeable unit. This unit can be classed as a hydrostratigraphic unit. Much of the inconsistencies observed in potentiometric contour maps are due to piezometers installed in different hydrostratigraphic zones or in thick, low-hydraulic conductivity confining units that have strong downward gradients. Slight variations in

Source: Golder Associates

Figure 8-8 Regional Conceptual Flow Pattern in Glacial Environment 503

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piezometer tip depth can result in large inconsistencies in observed hydraulic head level for such confining units. Cross-sectional stratigraphic data are provided in Figure 8-9. A cross-section without vertical exaggeration is provided in Figure 8-10. Cross-sections without exaggerated vertical scales are helpful for conceptualizing the zones that will serve as discharge points. Such a view provides a perspective on relative thickness and regional extent of the units. The data provided in Figure 8-9 were used in conjunction with hydraulic conductivity data to sketch a flownet for the cross-section (Figure 8-11). The flownet provides the conceptual ground-water movement for the facility from which the potential target monitoring zones can be determined. Two zones, above and below the till units, would probably represent the target zones for monitoring areas, as based on the nearly horizontal flow regime at the site. Constructing piezometric or potentiometric contour maps from raw data, then combining the data with stratigraphic cross-sections to develop flownets, can be a tedious effort when geologic systems become complex; however, these derived illustrations of ground-water flow are essential for selection of target monitoring zones and design of the monitoring system.

8.4 CONCEPTUAL GEOLOGIC MODELS Much of the conceptualization process for hydrogeologic systems was developed from the traditional engineering approach for water balance evaluations. This can be simply illustrated as a layered aquifer system with both recharge (from the surface) and flow horizontally through the geologic block diagram shown in Figure 8-12. Each pertinent layer of the site geologic units is represented in the diagram with relative thickness, including values for hydraulic conductivity. The illustration represents an idealized system with little variability in geologic unit lateral thickness and unit hydraulic conductivity. Although actual field situations will normally vary somewhat (or can vary widely), the conceptualization process dictates that the model represents an idealization and simplification of the actual physical situation. If the actual field data showed significant differences in thickness of the lithology in the site crosssection from one end of the site to the other, the model should include some concept as to this spatial variability. The concept of unit thickness variability may not have any relevance to the model unless the observed variability exceeds some acceptable limits. These limits depend on the overall size of the model and may only be important if the thickness has relevance to the overall model.

Source: Golder Associates

Figure 8-9 Cross-Sectional Stratigraphy 504

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Source: Modified from Golder Associates

Figure 8-10 Cross-Sectional View without Vertical Exaggeration One can expect that there will be considerable variability in the results of hydraulic conductivity testing due to both variability in the test procedure and to the natural variability of the geologic units. As with minor thickness variability in the field testing program, if the hydraulic conductivity of a single hydrostratigraphic unit can be represented as a normal curve of values with similar hydraulic conductivity across the unit, then the unit can be considered as a single hydrostratigraphic unit. Any geologic unit can be expected to show both horizontal and

vertical variability as illustrated in Figure 8-13. The illustrations represent an obvious layering of the geologic units; however, the bell-shaped curves of horizontal hydraulic conductivity show the natural ranges expected in naturally occurring materials. Although unit B shows two orders of magnitude variations in average hydraulic conductivity from borehole L to bore N, an individual measurement of K (in layer B) could range from 10-2 cm/s to 10-4 cm/s in borehole L to 10-4 cm/s to

Source: Modified from Golder Associates

Figure 8-11 Flownet Construction

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Figure 8-12 Horizontal Flowthrough System

10-6 cm/s in borehole N. Because layer A averages around 5*10-6 cm/s, some confusion can result when one depends only on determinations of hydraulic conductivity as the deciding factor in the geologic conceptual model formulation. The decision process of developing a conceptual geologic model for a site must include the geologic information gathered from the literature, where typical type sections can point toward proper interpretation of lithological data gathered during the field boring program. However, specific site conditions can also change radically from conditions depicted in regional studies. Type sections are the starting point where further site work derives the specifics that develop the conceptual model.

Figure 8-13 Horizontal and Vertical Variability of Geologic Units

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This tuning in of the site to regional data represents one of the first tasks in developing an conceptual model. Previously defined hydrostratigraphic units may be already available for inclusion in the site-specific conceptual model. These hydrostratigraphic units may be formations, units, or individual stratigraphic zones that represent likely confining or more highly conductive zones. Probably the best guidance in this area is to consider the scale of the features. First evaluate which features or geologic units would have some effects on ground-water flow in the area of interest. These should be defined in the borehole drilling and logging process. The conceptualization process also must consider the structure of the geologic system in the Phase I investigation so that areas that may require investigation can be targeted in the Phase II field program. Lateral variations, such as facies changes, should be included in the conceptualization process if these changes affect the flow of ground water through the geologic units present on site. Examples of the building process of hydrogeologic conceptualization are shown in Figure 8-14A through 814E. These five illustrations represent a process of conceptualization from early missteps to later more acceptable realization of the relatively uncomplex hydrogeologic system. Illustration 8-14E represents the first attempt in construction of a conceptual model for a landfill located on coastal deposits. The figure shows a landfill composed of typical solid waste with a significant level of leachate. The geologic units serving as the landfill base-grade consists of fine to medium clean sand with a number of separated clay units. This type of representation is typically called a cartoon due to the unrealistic representations of real-world geologic and site features. The foundation sand and gravel of the facility are shown as somehow able to contain a significant height of leachate within a mass of solid waste (with a probable waste hydraulic conductivity somewhere between 10-4 to 10-5 cm/s). It is unlikely that the highly permeable sand would contain (like a bathtub) leachate within the landfill limit, given that the landfill is most likely unlined. The water level (or water table) shown on the figure is also too flat for the suggested leachate migration suggested in the cartoon. Finally, the physical form of the clay layers reflects a lack of insight by the illustrator in to likely geologic processes. The same cross-section was modified at a later date (shown in Figure 8-14B) to include bedrock and the formation names of the unconsolidated deposits (PotomacRariton Magothy formations) Three different water levels are shown draining presumably from point A toward the landfill. Although this representation is probably better than the first attempt, local lithologic variations in the

CONCEPTUAL MODELS

unconsolidated formations are provided, but little insight into why we are viewing three separate water levels is provided by the model. As with the previous model, leachate levels in the landfill are shown above regional water levels. As with the previous cartoon, given that the regional aquifer consists of highly permeable sands it would be unlikely that the leachate levels shown could be maintained at the levels shown. The model is also static with little consideration into ground-water flow. Geologic model figure 8-14C has greatly improved cross-sectional information tied into the regional water surfaces. Although the various clay units are shown in a more realistic manner, the water table shown (with a date 10-27-83) does not show any deflection downward over the area without clay (between well 6 and well 5). It is unlikely that the ground-water level could maintain the heads shown over this area given the wide variations between the region water table and the local piezometric surface. One would expect a downward deflection in head levels in the ground-water level in the window area and an upward deflection (or interconnection) of the piezometric surface with the regional ground-water level. Conceptual models must always show logical solutions to the interconnections between geologic units and ground-water flow systems. Occasionally, conceptualization of both geologic and ground-water flow systems requires more than one illustration to fully transmit an understanding of site conditions. Figures 8-14D and 8-14E show two conceptual models of the site previously described in 8-14A to 814C. Figure 8-14D shows the relationship between shallow clay units and perched shallow ground water discharging into the deeper aquifer. Figure 8-14E shows a different perspective of the same site area. Historic records of both water tables (dating back to 1956) show the regional ground-water level lowering through 1990 due to water supply pumpage. As with any conceptual model one must consider the regional and local geologic and hydrogeologic conditions and express these relationships in an easily understood pictorial representation. Conceptual models are, however, more than simple illustrations of the lithology. Conceptual models are constructed from detailed knowledge of the geologic and hydrogeologic conditions present on site. The following section provides examples of conceptual geologic models constructed from an understanding of the processes that formed the geologic units present on site. Each conceptual model is first introduced by a short description of the geologic/hydrogeologic conditions. Then the geologic conceptual model is described and a review of the evaluation of the model relative to ground-water conditions at site is provided.

Figure 8-14A-E Conceptual Cartoons of Geology

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Source: Modified from Hydro-Search, Inc.

Figure 8-15 Fence Diagram Example A 8.5

EXAMPLES OF GEOLOGIC CONCEPTUAL MODELS

8.5.1 Glacial Geologic Model Site A is located in pre-Illinoian glacial drift and alluvium and includes recent alluvial and aeolian deposits. Figure 8-15 shows a fence diagram of the site area. Shallow pre-Illinoian aquifer materials consist of the wellsorted sand of the Sankoty Member of the Banner Formation. Recent alluvial and aeolian deposits include the Cahokia alluvium and Parkland Sands. The Cahokia allu-

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vium consists of sands, silts and gravels deposited by recent rivers and streams. Regionally, the Cahokia alluvium is present as recent sediment deposited in the Illinois River Basin. The thickness of these deposits in the Illinois River drainage ways is unknown, but the deposits commonly are less than 50 feet thick (Willman et al., 1975). The Parkland Sands consist of wind-blown sands also deposited along the Illinois River Basin. The thickness of these deposits along the Illinois River drainage way is unknown, but the deposits have been noted to average 20 to 40 feet thick (Willard et al., 1975). Parkland Sands is

CONCEPTUAL MODELS

Figure 8-15 Fence Diagram Example A (continued) noted here as a potential shallow aquifer material because of its permeable character, but it may not be an actual water-bearing unit because of its physical elevation at or above existing watertable conditions. In the site area, the thicknesses of the glacial aquifer materials overlying bedrock are estimated to be 100 to 150 feet. The elevation of ground water at the site ranges from approximately 508 ft mean sea level (msl) at the eastern portion of the site to approximately 500 ft msl at the western edge of the area. Therefore, ground water has been established to flow east to west across the site.

Regionally, recharge to the Sankoty is expected to occur from upland areas east of the area. Local flow is expected to discharge to creeks approximately one-half mile to the west of the site. Intermediate components of flow may discharge to the Illinois River 4 to 5 miles to the west of the site where the stage of the river is approximately 440 ft msl. Ground water that occurs in Illinois and Wisconsinaged glacial tills in the immediate area of the facility exists under perched conditions. Where glacial and post glacial erosion has dissected outwash units of these

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Source: Modified from ADS

Figure 8-16 Conceptual Model Example glacial tills, ground water within these units discharges to the surface as it seeps along the dissected drainage ways. Movement of residual water within these units, however, is also dependent upon the hydraulic conductivity of the outwash units. In areas eastern and northeastern of areas where Wisconsin- and Illinoian-aged tills have not been dissected by glacial and/or port-glacial erosion, water bearing outwash units of the till materials may be usable aquifers.

manent ground-water surface is found within the Sankoty Sand Aquifer. A conceptual hydrogeologic model for the site is presented in Figure 8-16. The following sections include discussion for the hydrogeologic system relating to historic development of the geology and hydrogeology to the present.

Bedrock

Deposition of glacial till and outwash units appears to have occurred in a layer-cake fashion with younger units being deposited conformably on top of each older unit (Figure 8-15). Exceptions to this appear near edges of the existing bluff slopes where the glacial units appear to have been deposited on sloping surfaces. The phenomenon is best defined near the southwest corner of the facility in Figure 8-15 where the current topography appears to mimic the paleogeography. Geologically, glacial till units of the Radnor and Vandalia Tills appear to have been deposited from advancing ice fronts. Silt, sand and sand and gravel deposits within specific till units may have also been deposited from advancing ice fronts. Outwash deposits, such as the unnamed sand and gravel, the sand unit above the Vandalia Till and the Sankoty Sand appear to have been deposited by water processes. These three deposits appear to be laterally continuous from borehole information for the site. Silt deposits of the Wisconsin stage and the unnamed silt appear to have been deposited by aeolian or wind processes.

Pennsylvanian-aged sandstone and limestone are possible bedrock aquifer materials. Bedrock in the area is at an elevation of approximately 400 ft msl. None of the water well records shows completion within the Pennsylvanian-aged bedrock. Conceptual Hydrogeologic Model The geology of the site can be described as a layered system consisting of variable thicknesses of Wisconsinaged loess overlying Illinoian-stage glacial tills and outwash units; which in turn overlie pre-Illinoian-aged till of predominantly outwash deposits. Subsequent to deposition, the glacial materials have been dissected by the processes of glacial and post-glacial erosion, creating the glacial plateau on which the facility is currently situated. Perched ground-water conditions have been found in outwash deposits of the Illinoian-aged glacial tills. The per-

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Evaluation of Geology and Hydrogeology

CONCEPTUAL MODELS

The present day geomorphology of the site is predominantly a result of glacial meltwaters dissecting the unconsolidated glacial materials of the Wisconsin, Illinoian and pre-Illinoian stages of glaciation along the southern extent of the glacial bluff. In essence, the glacial and post-glacial activities of the current creek drainage basin have removed the Wisconsin-stage loess and the till and outwash units of the Illinoian stage to expose the underlying Sankoty Sand Aquifer. The creek drainage basin appears to have been one of a number of glacial tributaries which eventually discharge to the major river system. Subsequent to formation of the glacial bluff areas and subsidence of glacial meltwaters, it would appear that water within outwash units of unnamed sand and gravel and the outwash unit overlying the Vandalia Till would have been allowed to freely drain along the dissected bluff areas. Figure 8-15 indicates that potential drainage pathways of the outwash units will be dependent upon the geometry and slope of the unit and whether or not the unit has been dissected by former erosion activities. Referencing Figure 8-16, areas of perched water or potentially perched waters occur in two different areas: (1) in silts, sands, or sand and gravel deposits included within major glacial till units or (2) in more laterally contiguous outwash units overlying less permeable glacial till units. As previously noted and as depicted in Figure 8-16, the presence or absence and flow direction of water within the units is a function of the slope and geometry of the confining till unit and whether or not the outwash unit is exposed along glacial bluff areas. Recharge of perched water to the outwash units may occur in several ways. The primary source of recharge is anticipated to be the release of connate water from overlying glacial till units. Another source of perched water may result from infiltration due to precipitation. This type of recharge is greatest where perched outwash units are exposed to a continuous source of water, such as a stream. Watertable conditions occur within the Sankoty Sand Aquifer below the landfill site. Referencing Figure 8-15, Sankoty Sand Aquifer is along the creek drainage basin where the Sankoty Sand is exposed near the surface. Primary recharge to the Sankoty is relatively near the surface. Secondary recharge to the Sankoty may occur where overland runoff from upland areas may be discharged to lowland areas during the release of perched water from overlying glacial tills. Referencing Figure 8-16, local components of ground-water flow are expected to discharge to the creek. Intermediate and regional component ground-water flow is from east to west near the site. Descriptions of the regional and site geologic and

hydrogeologic conditions provide the basic data for making decisions on ground-water monitoring of the facility. The descriptive hydrogeologic model offers the kind of information that points toward target monitoring zones. Such data include recharge areas and discharge areas for both perched and deeper ground-water level aquifers. Even though this is an extremely complete description of the local hydrogeologic conditions, additional evaluation of the need to monitor perched ground-water systems (as the upper most aquifer) must be included in the design approach. One can appreciate through inspection of the conceptual model that this is geologically a complex site. However, relatively simple decisions can be made on the locations of background (or upgradient) monitoring wells in the continuous Sankoty aquifer. Downgradient monitoring wells would be indicated in the Sankoty aquifer on the western side of the site. Evaluations as to screening depth would be necessary, beyond the data presented above, to further target the monitoring wells. 8.5.2 Unconsolidated Deposits Conceptual Model The purpose of the site B investigation was to review the regional geology to confirm the subsurface conditions and to provide an interpretation of the hydrogeological conditions particularly as they affect the design of the facility. The geological fence diagram shown in Figures 8-17a and 8-17b confirmed that the site lies within the Prairie Formation (Late Quaternary). As such, the property generally is underlain by fine grained cohesive sediments laid down during the Mississippi River delta building process. In addition, the site is traversed by three channel sands that have been termed Lower, Middle and Upper. The depths to the three sands are typically 37 ft, 20 ft and 6 ft, respectively. The piezometric levels in the channel sands indicate that the lower and middle sands are not hydraulically connected whereas the middle and upper units probably are connected. Superimposed on this pattern is a system of random local sand stringers generally located less than 20 ft deep. The site is underlain by thick beds of competent, plastic and relatively impervious subsoil. These fine-grained cohesive materials are incised by local channel sands and sand stringers. The cohesive units display a broad range of plasticity and can be classified on that basis into organic clay, clay, silty clay and clayey silt. In general, the thickness of the individual beds for the latter three units varies from 10 to 15 ft. Ground surface is generally underlain by a silty clay unit that overlies a clay stratum. The organic clay constitutes a marker horizon and is located at depth.

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Source: Modified from Soil Testing Engineers, Inc.

Figure 8-17 Fence Diagram Example B Clayey silt and silt deposits, where observed, generally flank the channel sands and represent overbank deposits of the channel units. Regarding ground-water conditions, the potentiometric surface is typically 6 to 8 ft below ground surface with seasonal fluctuations of a few feet. The flow direction across the site is from northeast to southwest. The ground water level in the Middle Channel Sand decreases across

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the site at a gradient of about 0.0012. The flow velocity within this unit is estimated to range from 4 to 19 ft/year. Interpreted Site Geology The site location, based on the Phase I literature review, is landward of the estimated position of sea level during the Late Quaternary in which the Prairie Formation

CONCEPTUAL MODELS

was being deposited. The sediments observed on site are believed predominantly non-marine to marginally marine and exhibit characteristics associated with deltaic aggradation (delta building) processes and not coastal or offshore marine processes. Typical features of this type of system initially consist of braided streams becoming meandering streams as the river gradient decreases. As different deltas were built into the Gulf of Mexico, broad

meander belts developed. Also associated with this environment are organic-rich back-swamp deposits that lie adjacent to meander belts and natural levees. Phase II site investigation soil borings and cone penetrometer testing validate the model described above. There have been three significant sands observed at different elevations across the site. An organic clay (OH), probably indicative of a back-swamp deposit, can be

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found with reasonable consistency across the site at elevations of 11 to 12 ft. This bed serves as an excellent timestratigraphic marker. In addition, most borings adjacent to the three sands show a sand/silt mixture indicative of natural levee or near-river overbank deposits. The three significant channel sands found on the site occur at different elevations with respect to their organic clay marker bed. These sands are designated the Lower, Middle and Upper channel sands, in reference to their relative position in the stratigraphic column. The Lower Channel sand unit was found in the northern part of the site at about msl elevation -10 to 3 ft. This unit trends generally east-west, apparently meandering across the northern edge of the site. The largest of the three sands, the Middle Channel sand, can be found in the central part of the site at about msl elevation 7 to 22 ft. The sand trends east-west and apparently does not meander significantly within the borders of the site. It has incised into the OH bed, removing it altogether. The upper channel sand is found in the southwest corner of the site at about MCL elevation 20 to 34 ft. Little can be inferred about the trend or shape of this sand because of its relatively small area of intersection with the site borders. Several other significant sands have been found at different elevation across the site. These are probably indicative of smaller tributary channels that are often quite numerous in the dendritic drainage pattern commonly associated with deltaic deposits. The relationship of the Lower, Middle and Upper channels to each other is not clearly understood at this time. A plausible explanation of their formation is that they represent three meander scars of the same river. However, ground water levels indicate that the hydrostatic head of the Lower and Middle channel sands differ by about 3 to 4 ft, the Middle sand having the higher hydrostatic head. If these sands were a result of a continuous meander pattern, one would expect that there would be hydraulic connection between the sands and the heads would be similar. The hydraulic difference may indicate that one or more of the meander channels have been cut off, resulting in the formation of oxbow lakes. The discussion of the geologic conceptual model provides lithologic and sedimentary relationships of unconsolidated Quaternary sediments. These silty to clayey deposits can be extremely difficult to evaluate without detailed continuous field logging of boreholes. The fence diagram in Figure 8-17 is the result of data from over fifty boreholes. Additional borehole information would probably not have made any difference in the interpretation or in the conceptual model. In fact, the conceptual geologic model could have been adequately constructed with Phase

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I regional information and one half to one fourth of the drilling completed on site. Once the basic conceptual model is established (in this case deltaic non-marine with sand channel stream deposits), additional borehole examination of the subsurface should be used to validate the model. Excessive overdrilling of a site to gather redundant subsurface data for waste disposal investigations can significantly cross-connect hydrostratigraphic units. Although grouting-off of boreholes is commonly required, one cannot guarantee that there will be complete sealing of the borings. Once these penetrations are made through confining units, vertical hydraulic conductivity can be significantly affected by excessive over-drilling of a site to demonstrate the existence of a continuous confining unit. 8.5.3 Consolidated Bedrock Conceptual Model Site C conceptualization began with a review of the geology of the site, including the major stratigraphic units and must include ground-water occurrence and potentiometric heads. This information is then combined to develop a conceptual model depicting the general hydrogeology of the site. Such a model may assist the understanding of site conditions by providing a framework for placing the site into general hydrogeologic perspective. The following represents a conceptual geologic model of a relatively simple layered consolidated rock site where fracturing does not greatly affect the interpretation of the geologic model. Figure 8-18 is an idealized hydrogeologic profile (i.e., a conceptual model) for the site. The above described hydrostratigraphic units are fundamentally a reflection of Appalachian plateau geology with alternating lithologies of varying hydraulic conductivity, resulting in multiple zones of saturation. Vertical and horizontal lithologic variations (or facies changes) make it difficult to correlate lithologic units between borings. The basis for identification of the hydrostratigraphic units described above is the general lithologic characteristics from borehole samples, albeit with variations, as well as the tendency for piezometric heads to occur or be missing from discreet elevation zones. Figure 8-18 also shows an inset enlargement of local conditions along the site margin where mine spoil has been cast beyond the limits of the No. 5 Clay. In these areas, test pits and borings show either an absence of the No. 5 Clay or its occurrence at elevation below the normal or expectable top surface elevation. The basic hydrostratigraphic units are indicated in descending order as follows: Mine Spoil: The mine spoil is readily distinguished by its physical appearance in borehole samples, test pits

CONCEPTUAL MODELS

Source: Modified from Soil Testing Engineers, Inc.

Figure 8-18 Conceptual Model of Claystone/Sandstone Site and outcrops. The mine spoil has a thickness which varies from 15 to 48 feet and a hydraulic conductivity of 10-5 to 10-6 cm/s. This unit is predominantly unsaturated except for a thin, perched ground-water zone at its base. The predominant flow direction appears to be horizontal, as indicated by plan view head relations, seeps and springs along lateral margins and a dry, crumbly texture for the bulk of the underlying No. 5 Clay. Piezometric heads in the mine spoil and deeper saturated zones indicate a potential for downward flow, although whether or not such flow exists has not been established. If downward flow does occur, it most likely would be in the form of quantitatively small amounts of leakage. No. 5 Clay: This unit represents the regionally described No. 5 Clay and the underlying weathered zone. Because these materials are difficult to distinguish by their appearance, they are combined (Note: conceptual models often combine similar materials). The contact between the true clay and the weathered bedrock is gradational. The No. 5 Clay was identified in all borings and test pits except locally along the site margins where it was removed by erosion or mining. The thickness of the No. 5 Clay generally ranges from about ten ft in the central por-

tions of the site to in excess of 30 ft along the margins. As already noted, the No. 5 Clay is generally unsaturated, except for the upper few feet. Slight dampness or moisture was also found along small scale heterogeneity (stratification or textural/structural variations) in core samples. Shale/Mudstone Bedrock: The No. 5 Clay grades downward into consolidated bedrock. Core samples show an upper zone that is predominantly shale or mudstone, but with interbedded layers or lenses of sandstone. This unit includes a saturated zone (or multiple zones) with head elevations in wells screened in this unit of about 1165 to 1175 ft (msl). Lateral head differences in the few wells screened in this unit suggest southwesterly flow. Vertical head differences between this unit and deeper strata indicate a potential for limited downward flow. Unsaturated Sandstone: Beneath the shale/mudstone strata is a sandstone unit, the upper portion of which trends to be unsaturated. Three wells screened in this unit indicate that the unsaturated zone extends over an elevation range of 1148 to 1172 feet. Saturated Sandstone: The lower most hydrostratigraphic unit is a saturated sandstone. Wells screened in this unit have head elevations on the order of 1135 to 1145 ft. Lateral head differences suggest a flow to the South-

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east, although the degree of data control points is limited in this unit. In summary, the conceptual model shown in Figure 818 and described here depicts the general conditions bearing on site suitability for landfilling. The mine spoil is relatively easily identified and is everywhere laterally continuous, extending out to the site margins. The No. 5 Clay is likewise relatively easily identified and is similarly laterally continuous, except for local gaps along the site margin. Because this investigation focused on the saturated, more permeable zones, there is relatively little information on the permeability of this unit and any hydraulic heads. The top of the No. 5 Clay occurs characteristically at an elevation of approximately 1200 feet (msl). The bottom surface of the unit is variable in elevation due to greater thicknesses along the lateral margins. The bedrock stratigraphy is primarily established on the basis of general lithologies and especially elevation differences in piezometric heads for wells screened in the different units. Although leakage through the No. 5 Clay has not been quantified, the upper saturated bedrock zone in the shale mudstone potentially represents the uppermost aquifer beneath the facility. The above geologic conceptual model agrees with a general description of Appalachian claystone and siltstone. The vertical hydraulic conductivity is extremely limited in this environment, as long as secondary fracture systems do not breach the shale/mudstone units. Indication of the limited vertical flows are the spring systems occurring at major lithologic boundaries such as the No. 5 Clay. Field observation of the integrity of the clay or mudstone units should always form part of the Phase II geologic mapping tasks. Visual examination of fractures and lithological continuity must verify the presence of the confining units and provide reasonable assurance that secondary porosity does not provide vertical pathways for ground-water movements. 8.5.4 Consolidated Channel Deposits Conceptual Model Site D is underlain by a sedimentary rock sequence more than 13,000 feet thick that exists within the Denver Basin. This structure, a north-south trending asymmetrical basin with a gently dipping east flank, was formed during late Cretaceous and early Tertiary time. During its formation, the basin was the site of fluvial deposition of sediments eroded from the mountains to the West. The upper six formations beneath the site (with a combined thickness of over 8,000 ft) are the Dawson, Denver, Arapahoe, Laramie, Fox Hills Sandstone and Pierre Shale. The regional dip of the sedimentary units

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beneath the site is toward the west at approximately 1 degree. The two formations of primary interest to this investigation are the Dawson and Denver Formations. The lower approximately 100 ft of the Dawson Formation forms the near-surface bedrock at the site. The lithology of this formation is complex, consisting of interbedded claystone, siltstone and lenticular sandstone. Some of these materials contain reworked sediments from the underlying Denver Formation. Tracing distinguishable lithologic units for lateral distances in excess of a few hundred feet is difficult within the Dawson. A weathering profile has developed within the upper 25 to 50 ft of the bedrock that is identifiable by a dominance of mottling, brown and orange-brown colors, friability and iron and manganese oxide stained fractures. In general, the depth to unweathered bedrock is greatest near the tops of ridges and is shallowest along stream drainages. The unweathered Dawson Formation tends to have a dark to blue-gray color, is without evident mottling, has an absence of fractures and oxide straining, and is less friable. The underlying Denver Formation is similar to the Dawson Formation in that it consists of interbedded claystone, siltstone and sandstone. The main distinguishable difference between the two formations is color. The Dawson is generally gray beneath the weathered zone, whereas the Denver exhibits a darker greenish-gray color. This darker color reflects the presence of altered volcanic debris in the rock. The thickness of the Denver Formation is estimated to be about 800 ft beneath the site. Regional Hydrogeology The principle water-bearing formations within the Denver Basin are Dawson, Denver, Arapahoe and Laramie-Foxhills (the latter two are usually considered to be a single hydrostratigraphic unit). It should be noted that the USGS and Colorado Department of Natural Resources (which includes the office of the State Engineer) use the term aquifer synonymously with formation in referring to these geologic units. With the exception of the Laramie-Foxhills, the true aquifers (in a hydrogeologic sense) are individual beds or groups of beds of sandstone and conglomerate within the predominantly argillaceous sequences of sediments. Nonetheless, the term aquifer has been used for entire formations for regulatory (e.g., for the issuance of water rights) purposes and in much of the literature on the water resources of the Denver Basin. This conceptual description, however, will use the term aquifer in the more limited and technically correct sense only when referring to primary water-yield-

CONCEPTUAL MODELS

ing geologic units. The water-bearing formations of primary interest are the Dawson and Denver sedimentary units. The units within the Dawson Formation that comprise the true aquifers beneath the site consist primarily of coarse-grained and poorly to moderately well-consolidated sandstone and conglomerate. These represent the channels in the fluvial depositional environment that existed in this area in the late Cretaceous and early Tertiary time. Overall, the Dawson Formation on a regional basis is estimated to contain an average of 45% sandstone, conglomerate and siltstone. Site Geology The stratigraphic conditions beneath the facility as defined by all coreholes and boreholes drilled to date are shown in a fence diagram in Figure 8-19. The complex fluvial stratigraphy has been depicted according to the predominant lithology in each portion of the sections. Therefore, a rock sequence with a generalized description of claystone may contain some relatively thin units of coarse-grained materials. Similarly, a sequence identified as sandstone may contain some claystone or siltstone layers. Interbedded sequences are shown in the cross-sections as a mixture of sandstone and claystone. As indicated in the fence diagrams, argillaceous sediments comprise the actual majority of the geologic materials beneath the facility (note that regional geology may differ significantly from actual specific site conditions). Within this fine-grained matrix, however, there are three distinct sandstone (with some gravel) units which, based on lateral variation in grain size, are most likely east-west trending buried stream channels. The uppermost sandstone occurs at a depth of 10 to 20 ft on the north side of the facility and pinches out to the south. The intermediate sandstone, which is as much as 40 to 80 ft, is primarily beneath the western side of the facility. The largest sandstone unit is the lower sandstone channel which is located at a depth between 80 to 140 ft. This gravel, representing the center of this channel deposit, is the key hydrostratigraphic unit beneath the facility and should be the primary target for ground-water monitoring. Hydrogeologic Framework Ground-water levels have been monitored in eight piezometers and in nine wells. Together with the regional hydrogeology and the well-defined local stratigraphy, head data describe the following hydrogeologic framework (shown schematically in Figure 8-19) for the shallow ground-water system in the vicinity of the ponds:

1. The site is located within the regional recharge area of the Dawson-Denver aquifer system characterized by deeper stratigraphic units having lower potentiometric surfaces. This is evidenced by the 5690 ft ground-water elevation (msl) in the lower sandstone and the 5682 ft ground-water elevation of the coal. 2. Based on all data collected to date, the intermediate sandstone is unsaturated. This indicates that it is above the ground-water level and that the limited vertical flux through the sandstone is not great enough to impound or perch ground water at the base of the unit. 3. The upper sandstone on the north side of the site does contain perched ground water. This is because the rate of vertical infiltration to the unit is greater than the rate at which ground water can leak out through the bottom of the sandstone. 4. It is not known whether the perched water in the upper sandstone results in a ground-water mound on the north that is connected to the lower sandstone by continuously saturated claystone or whether there is a wetting front below the perched water and a zone of unsaturated material between it and the lower sandstone. In either case, there is a hydraulic gradient from the upper sandstone southward and downward into the lower sandstone. This downward infiltrating ground water will move primarily in the claystone and not laterally into the unsaturated intermediate sandstone. This is because the saturated hydraulic conductivity of the claystone most likely would be greater than the unsaturated hydraulic conductivity of the intermediate sandstone. 5. The lower sandstone is the uppermost saturated zone beneath the ponds. Based on current water levels, this sandstone channel is an unconfined aquifer bordered by less permeable units with lower water levels. The gradient within the unit is from east to west. This suggests the channel could be cross-cutting hydrogeologic feature whose recharge zone may be along the creek at an elevation greater that 5691 ft msl and whose discharge point could be along the creek at some lower elevation.

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Note: These isometric cross-sections are sometimes difficult to visualize and may require significant experience to develop. Computer drawing software may be helpful in the development of these presentations.

Source: Modified from Hydro-Search, Inc. and Golder and Associates. Inc.

Figure 8-19 Fence Diagram Example D

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6. Although the predominant direction of groundwater flow through the unsaturated zone in this recharge area is downward, the lower fully saturated sandstone (which has a significantly higher hydraulic conductivity than the surrounding claystone) acts as a short circuit in the flow system and permits lateral flow where sandstones discharge to areas of lower head. The previous subsections that describe heterogeneity in the geologic materials can have widely variable ground-water flow directions from the expected patterns. For example, the channel deposits described in the Denver-Dawson Formations can represent lateral drains to the low hydraulic conductivity claystone deposits. The localized flow would be similar in cross-section to Figures 5.8(b) and 5.9(b) and (c) in Freeze and Cheery (1979, pp. 176 and 177). The discharge to the single point (the channel) would then discharge along the channel deposit to areas of lower hydraulic head. The Denver-Dawson channel and mudstone deposits present a series of problems for ground-water monitoring design. Locating a monitoring well in the claystone would provide a highly ineffective monitoring location. The well could take several months to recover after purging before water quality sampling efforts are begun. Given the USEPA’s general sampling guidance (SW 846) to purge and resample within twenty-four hours, the accurate evaluation of water quality from such low-hydraulic-conductivity environments would be highly problematical. In addition, locating specific monitoring wells in more highly permeable sand channel deposits can also be difficult due to the localized condition of these deposits. Depth area and discharge directional criteria for the sand channel deposits must be understood sufficiently to define background and downgradient locations for monitoring system design. Only with sufficient geologic understanding supported by piezometer hydraulic head data and possibly geophysical data will provide sufficient information to locate ground-water monitoring wells. 8.5.5 Oblique Flow to Hydraulic Gradient A number of the previous examples may be complicated by oblique flow to the expected ground-water flow directions. These complications can be due to high hydraulic conductivity channel type deposits that may not be detected through the normal site investigation. By definition, ground-water flow is perpendicular to the hydraulic gradient in aquifers that are homogeneous and isotropic. Because many aquifer conceptualizations are based on homogeneous and isotropic conditions, it has become common place to use the term direction of

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ground-water flow interchangeable with direction of hydraulic gradient. In most cases, however, the aquifers exhibit heterogeneous and anisotropic conditions that result in ground-water flow being tangential or oblique to the prevailing hydraulic gradient. This condition must be considered when evaluating ground-water flow systems for the design of ground-water monitoring networks and/ or the restoration of contaminated aquifers. In evaluating and developing conceptual models of site ground-water systems, several basic factors may be helpful in predicting the occurrence of flow oblique to gradient. The first factor is that the hydraulic gradient is primarily controlled by the position and geometry of the recharge and discharge areas. The flow, on the other hand, is controlled generally by geologic or subsurface features that serve to restrict, redirect or concentrate the flow of ground water. It must be remembered that ground water, like electricity, will seek the path of least resistance (i.e., the highest hydraulic conductivity material in the ground-water flow path) in response to a pressure differential. This phenomenon is most pronounced in geologic formations that are fractured due to secondary weathering or orogenic processes or in materials that by their depositional nature are graded and sorted. In most environments, the hydraulic gradient of the uppermost aquifer is consistent with the gradient of the land surface, as evidenced by topographic contours. In these environments, the ground-water recharge areas generally coincide with areas of higher elevation, whereas the discharge areas coincide with the lower elevations in the watershed, generally identified by the presence of streams, rivers and lakes. In the vertical dimension, the presence of upward or downward gradients can be predicted by identifying the position of the site within the ground-water flow system. Again, by definition, a recharge area is one in which hydraulic heads decrease with depth; a discharge area, conversely, is one in which heads increase with depth. Therefore, by determining the location of the site relative to the overall ground-water flow system, the hydrogeologist or geologist can estimate the general pattern of lateral and vertical gradients at a site. The geologic factors that may result in a flow oblique to gradient can also be predicted by prior evaluation of the site geology and depositional history. Generally, continental depositional environments (fluvial, glacial, pluvial, colluvial, aeolian) tend to produce deposits that are graded and poorly sorted and which exhibit pronounced anisotropic conditions. These deposits are particularly suited to lithostratigraphic mapping techniques that can link depositional models to the observed anisotropic geology. These anisotropic conditions generally persist through the processes of rock consolidation and solidifi-

CONCEPTUAL MODELS

cation. Therefore, by evaluating the depositional history of a site and the orientation of the geologic processes that resulted in the deposition, the geologist or hydrogeologist can often predict the general direction of anisotropy within a given deposit. In consolidated rock environments, the initial fabric or structure of the deposit may be altered by secondary physical and chemical processes. These processes result in apertures or openings in the rock matrix that may provide preferential pathways for groundwater migration. Prediction of the direction of these apertures or fractures can be extremely difficult, particularly in geologic units that have a complex orogenic history. In rock formations that have been deformed by only a single event, the fractures are generally most pronounced along the strike of the rock. Secondary fractures are also common at 60% angles from the strike. In formations that have undergone multiple orogenic events and are intensely fractured and folded, prediction of anisotropic orientation is generally not possible without extensive background drilling and testing data. In developing the conceptual model at the end of

Figure 8-21 Conceptual Oblique Flow Conditions

Figure 8-20 Example of Oblique Flow

Phase I, one should expect a reasonable prediction of the occurrence of flow oblique to gradient and, if possible, the direction of that flow. Examples of the conceptualization of flow oblique to gradient are provided in Figures 8-20 and 8-21. Hydrogeologic reports should allow one to distinguish between upgradient/downgradient and upflow/ downflow. It is the author’s position that ground-water monitoring wells should be located in accordance with the prevailing direction of ground-water flow and not the prevailing direction of hydraulic gradient, particularly in those conceptual cases where flow can be oblique to gradient. Confirmation of anisotropic and heterogeneous conditions can best be obtained through detailed analysis of borehole data and reconstruction of the depositional environment. Geophysical and piezometric data can often confirm or supplement the stratigraphic interpretations. However, qualification of anisotropic conditions can

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generally only be accomplished through intensive pump testing programs. Such programs are generally undertaken only when aquifer restoration is being considered as a remedial action. In fractured rock environments, the installation of angle boring and the acquisition of oriented core are necessary to determine fracture frequency and orientation. These data provide the geologic insight into the formulation of a conceptual model that addresses the heterogeneity and resultant ground-water flow directions. 8.5.6 Unconsolidated Deposits with Oblique Flow Conceptual Model The following section describes a geologic environment when heterogeneity affects the general ground-water flow directions. These highly varied geologic units are described to illustrate the field conditions that lead to an unexpected ground-water flow direction. Glacial deposits can range in hydraulic conductivity from greater than 102 (gravels) to < 10-7 cm/s. Such a great range of hydraulic conductivity offers potential for ground water flow oblique to the expected ground-water direction. The geologic history of the glacial deposits is first discussed, then the evaluation of ground-water flow. Approximately 1.5 to 2 million years ago, thick ice sheets developed in northeast Canada and expanded into

the United States. Four primary advances and recessions have been established from geologic mapping of deposits along the edge of the glacial advances. During the first three advances, the Nebraskan, Kansan and Illinoian, hundreds of feet of sediments were stripped from the landscapes of Canada, Wisconsin, Minnesota and the Dakotas and redeposited in broad till plains stretching from Indiana to Colorado. Beginning about 75,000 years ago, after a prolonged warm period, the Laurantide Ice Sheet expanded again from its center west of Hudson Bay and advanced southward across Minnesota. This signified the beginning of the last major glacial advance in Wisconsin. In Minnesota, the Wisconsin glaciation is marked by six major advance and recession cycles with the major landforms and deposits being attributable primarily to the last two of these cycles. Deposits from the three earlier glaciations were removed, buried or reworked by the Wisconsin glaciation. Approximately 30 to 35,000 years ago, renewed growth of the Rainey-Superior Lobes sent a thick sheet of ice from northeastern Minnesota and the Lake Superior Basin into central Minnesota to a point 35 to 40 miles southwest of the site. As this advance stalled, the prominent St. Croix moraine was formed at its margin. As the ice sheet melted, high velocity streams at the bottom of the ice cut tunnel valleys into the frozen, unconsolidated

Source: Modified from Foth and Van Dyke

Figure 8-22 Example of Oblique Flow Conditions in Granular Environments

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Figure 8-23 Conceptual Model of Granular Geologic Conditions with Oblique Flow

sediments beneath the glacier. The trace of these valleys can often be interpreted by mapping lineations on aerial photographs and topographic maps (Wright, 1973). These valleys are commonly associated with linear strings of lakes, wetland depressions and eskers, the latter of which commonly have crests at the level of the adjacent till plain. The presence of these eskers, commonly bounded by marginal troughs as depicted in Figure 8-22, indicate that the subglacial streams responsible for the initial cutting of the tunnel valleys eventually lost energy and changed from erosional to depositional environments. As the Rainey-Superior Lobe melted, a blanket of reddish, poorly graded material, the Superior Till was left as ground moraine over the entire area of inundation. Further melting as the lobe retreated caused an outwash plain of sands and gravels to form at the ice margin. Before all of the ice remnants of the Rainey-Superior Lobe melted, the Grantsburg sublobe blocked southward drainage from the Rainey-Superior Lobe and glacial Lake Grantsburg was formed. As the Grantsburg ice sheet melted a second till was deposited over the area. This till is characteristically a gray, fine-grained calcareous material and is generally visually distinct from the red Superior Till and appears to have been chemically reduced upon burial and has been converted to a dark gray color. In these locations the Grantsburg and Superior tills can be distinguished only by texture and gradation.

The glacial Mississippi River maintained its position along the front margin of the Grantsburg Sublobe throughout its melting and retreat. As the river migrated southwestward to its present-day course it deposited a thick mantle of outwash sand known as the Sand Plain. This unit forms what is referred to as the Upper Sand unit in Figure 8-22. As documented previously several tunnel valleys were traced in east central Minnesota, including one immediately to the east and southeast of the site. Test drilling and photo interpretations have generally defined the presence and geometry of this valley. The Phase II drilling also established the presence within the valley of an esker that has been buried under the Anoka Sand Plain. The surface expression of the tunnel valley and esker is shown by the location and orientation of the lakes and surface depressions near the site. These depressions are the result of the melting of remnant ice blocks that were buried during the retreat of the Rainey-Superior Lobe. In spite of the uncertainty regarding the exact time of origin, the presence of a tunnel valley, bounded vertically by till plains, partially filled with an esker and covered by the Sand Plain, is an accurate conceptual model. The esker is believed to be continuous from north of East Lake to where the esker and tunnel valley would likely be truncated by the Mississippi River valley train deposits. Figure 8-23 illustrates the separation of permeable aquifers and much less permeable aquitard/confining units. The range in hydraulic conductivity for this conceptual model was over seven orders of magnitude; hence, a clear understanding of the extent of the aquifer/confining units was important before analysis of potential flow directions. In this case, the tunnel valley aquifer, with hydraulic conductivity of 10-1 cm/s, provided a preferred pathway for ground-water movement from the site. Subsequent to the conceptual model formulation, it was believed that ground water moved directly in a west to east direction. These directional flow estimates were based on simple ground-water contour maps developed from numerous monitoring wells. The highly permeable tunnel valley deposit, however, represented a groundwater flow pathway that is discharging to areas of lower hydraulic heads. The actual ground-water flow from the facility was some 90 degrees different from what would be expected from interpretation of the ground-water contour map of the site area. Difficulties arise in the flattening of the contours within the high permeability feature. Placement of piezometers within the permeability feature would have shown the very low head levels in the tunnel gravels, however, difficulties in locating these features result in few actual measurement points being placed in these deposits.

523

CONCEPTUAL FLOW MODELS

8.5.7 Using Conceptual Models in the Remedial Process The conceptual modeling process has been incorporated into the entire Hanford remedial process. The conceptual model serves to consolidate Hanford Site data (e.g., geologic, hydraulic, transport and contaminant) into a set of assumptions and concepts that can be quantitatively evaluated. The quantitative model will be used to estimate transport of contaminants through the groundwater pathway on the Hanford Site. Hanford Site geology and ground-water hydrology have been studied extensively for approximately 50 years. Since establishing the Hanford Site in the early 1940s, there have been several attempts to predict contaminant transport in the unconfined aquifer. These studies have supported several objectives, ranging from an impact assessment for the operations or remediation of a discrete facility to assessing the cumulative impacts from all Hanford waste sources. The various objectives have often resulted in differing approaches with respect to conceptualization, implementation and spatial and temporal discretization of numerical processes. The underlying groundwater conceptual models for these various assessments have continually evolved with the addition of new data and adaptation of more powerful computers, which has led to larger and more complex problems. The ground-water conceptual model used by the Hadford investigators is an interpretation or working description of the characteristics and dynamics of the physical hydrogeologic system. The ground-water element takes the results of the analyses from the vadose zone technical element in the form of contaminant flux from various waste sources. In addition to the influx from the vadose zone element, the ground-water model requires data that define the physical characteristics of the hydrologic system, transport parameters and recharge and discharge rates. Each of the boxes shown in Figure 824 has conceptual models developed for sorting out technical elements. Definition of the hydrologic system was based on previous subsurface investigations that have collected data on the hydrologic units, unit boundaries, hydraulic conductivity, hydraulic heads, storativity and specific yield for the Hanford facility. Transport parameters were based on both site-specific work done during previous investigations and on published literature values for parameters including effective porosity, dispersivity, contaminant-specific retardation coefficients and vertical and horizontal anisotropy. Data critical to the groundwater flow and transport model also include estimates of natural recharge rates and locations and magnitude of

524

artificial recharge to the hydrologic system, which are available from historic records and direct measurements. Establishing model domain boundaries for the flow system will be based on site-specific knowledge and output data requirements. Boundaries were established along the northern and eastern portion of the site corresponding to the course of the Columbia River and along the southeastern portion of the model along the course of the Yakima River. Basalt ridgelines and the Cold Creek Valley will form the western model domain boundaries. Lower flow boundaries will be established between the confined basalt aquifer system and the overlying unconfined aquifer. The output from the ground-water element feeds the Columbia River model along the course of the river as concentrations of contaminants through time at the boundary of the groundwater/river mixing zone. The groundwater model also feeds information in the form of predicted estimates of contaminant distribution into the risk model, which will be evaluated based on selected risk metrics. Estimates of contaminant concentrations for four mobility classes of radionuclides and two chemicals will be provided as input data to the Columbia River and risk and impacts model elements. Verification of the estimated contaminant flux through the ground water will

Figure 8-24 Composite Conceptual Models

CONCEPTUAL MODELS

Figure 8-25 Sources and Pathways be made by comparing estimates of contaminant flux to the extent of contaminant distribution observed in groundwater through groundwater monitoring. The ground-water conceptual model, which is the subject of this section, is the uppermost saturated zone on the Hanford Site that offers a pathway for contaminants released from past, present and future site activities. This uppermost-satu-

rated zone is termed the unconfined aquifer, although semi-confined conditions may exist in certain locations. The contaminant pathways may be wholly contained within the unconfined aquifer (e.g., the contaminants may be sorbed to the sediments and remain fixed at a location) or they may lead to points of discharge (i.e., along the Columbia River, to a water supply well or to the

Figure 8-26 Composite Conceptual Models

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CONCEPTUAL FLOW MODELS

underlying confined aquifer). Thus, the extent of the conceptual model must include both current and potential future downgradient areas from the sources to the pathway end points. The ground-water conceptual model includes the Hanford Site areas that are east and south of the Columbia River. These areas lie within the Pasco Basin, a structural depression that has accumulated a relatively thick sequence of fluvial, lacustrine and glaciofluvial sediments. Detailed summaries are provided in DOE (1988), Delaney et al. (1991), Lindsey et al. (1992), Lindsey (1995) and Cushing (1995). The ground-water segment of the overall contaminant pathway links sources and source areas with potential receptors. Radioactive and hazardous chemicals have been released at the Hanford Site from a variety of sources, including ponds, cribs, ditches, injection wells (locally referred to as reverse wells), surface spills and tank leaks, as illustrated in Figure 8-25. Many of these sources have already impacted the ground water and some may yet cause an impact in the future. Driving forces, including natural recharge from precipitation and artificial recharge from waste disposal activities (Figure 8-26), contribute to the movement of the contaminants through the vadose zone and into the ground water of the unconfined aquifer. Several processes, including first order radioactive decay, chemical interactions with the water and sediments and contaminant density control the fate and transport of the contaminants in the groundwater. Once in the ground water, the contaminants move along the pathways of least resistance, moving from higher elevations to lower elevations where some contaminants may ultimately discharge into the Columbia River. The Hanford Site and adjacent areas north and east of the Columbia River lie within the Pasco Basin, a structural depression that has accumulated a relatively thick sequence of fluvial, lacustrine and glaciofluvial sediments. The Pasco Basin and nearby anticlines and synclines initially developed in the underlying Columbia River Basalt Group, a sequence of continental flood basalts covering more than 160,000 km2 (DOE, 1988). These basalt flows erupted as a fluid, molten lava during the late Tertiary Period. The most recent, laterally extensive basalt flow underlying the Hanford Site is the Elephant Mountain Member of the Saddle Mountains Basalt Formation, although the younger Ice Harbor Member is found in the southern part of the Hanford Site (DOE 1988). Sandwiched between various basalt flows are sedimentary interbeds collectively called the Ellensburg Formation. The Ellensburg Formation includes fluvial and lacustrine sediments consisting of mud, sand and gravel which, along with the porous basalt flow tops and bottoms, form confined basalt aquifers across the basin. The

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Rattlesnake Ridge Interbed is the uppermost laterally extensive interbed and confined basalt aquifer of the Ellensburg Formation (Spane and Vermeul, 1994). Overlying the basalt within the Pasco Basin are fluvial and lacustrine sediments of the Ringold Formation (Newcomb and Strand, 1953; DOE, 1988; Lindsey et al., 1992). Figure 8-27 shows the generalized geologic column for the Hanford Site. The ancestral Columbia River and its tributaries flowed into the Pasco Basin, depositing coarsegrained sediments in the migrating river channels and fine-grained sediments (silt and clay) in the overbank flood deposits. On at least two occasions, these river channels were blocked, forming a lake in the Pasco Basin and depositing extensive layers of fine-grained sediments within the Ringold Formation. The Plio-Pleistocene unit, consisting of a paleosol/calcrete and/or basaltic sidestream sediments and the early Palouse soil, an eolian sand and silt deposit, overlie the Ringold Formation, but are present only in the western portion of the Pasco Basin. The uppermost sedimentary unit covering much of the Hanford Site is the Hanford Formation, a complex series of coarse- and fine-grained sediments deposited by cataclysmic floods (called the Missoula floods) during the last ice age. For the most part, the fine-grained sediments are found near the margins of the basin and in areas protected from the main flood currents, which deposited the coarsegrained sediments. A thin veneer of eolian sands and/or recent fluvial deposits cap the Hanford formation in many areas. There are two major areas from which uncertainty in the conceptual groundwater model arise: • Model uncertainty or the chance that the conceptual ground-water model is inappropriate (e.g., has assumed inappropriate processes such as linear sorption isotherm process for transport or that there is no communication with the underlying basalts) • Parameter uncertainty associated with prescribed processes, hydrogeologic features, boundary conditions, stresses imposed on the system, hydraulic parameters and transport parameters that are not known everywhere in the model domain. Model uncertainty can be estimated with select test cases. The process involves (1) identifying alternative conceptual ground-water models; (2) establishing a set of test cases where the metric would include such things as time versus concentration of a contaminant at selected points in the domain; (3) expressing the alternative conceptual models numerically; (4) calculating the appropriate metric values; and (5) comparing results. The process would likely be iterative, as results are obtained and additional combinations of alternative realizations are considered.

CONCEPTUAL MODELS

The movement of ground water within any aquifer (with significant primary porosity) is controlled by hydraulic conductivity, which is closely related to the sediment texture. Texture is a function of the grain-size distribution, sorting and consolidation/cementation. Sediments for this example were differentiated into either coarse or fine texture groups, then split into individual hydrogeologic units based on stratigraphic position, color and distinctive markers such as ash horizons. Normally, identifying geologic units also uses depositional environment and relative time of deposition to define contacts between units. Because the prime interest is in the movement of ground water, the important geologic information is targeted to the movement of ground water. Figure 8-27 shows a comparison of a geologic stratigraphic column and the proposed units for the base conceptual model. The two are very similar, but it is

important to clarify the difference. An example is the lower part of the upper Ringold, as defined by Lindsey (1992), which in some places becomes progressively more sandy with depth. Where sand is the only (or overwhelmingly dominant) grain size, it was grouped with the underlying coarse-grained Unit 5. Although this may not conform to standard geologic classification, the sandy base of the upper Ringold is probably hydraulically connected with and hydrologically similar to Unit 5, with which it is proposed to be grouped in the base conceptual model. Generally, sands were grouped with sandy gravels and silt was grouped with clay, assuming similar hydraulic conductivities. The nine hydrogeologic units identified for this example conceptual model are similar to those in the previous facility reports, with some differences in the location of unit contacts in places, as shown in Figure 8-27. The

Modified from Lindsey (1995)

Figure 8-27 Geologic and Conceptual Models 527

CONCEPTUAL FLOW MODELS

column on the left side of Figure 8-27 shows the hydrogeologic layering for the base case ground-water conceptual model, where the individual layers are established based on similarities in their hydraulic characteristics rather than their geology. The column on the right is the standard Hanford Site stratigraphic column and the dashed lines connecting the two columns illustrate how the nine hydrogeologic layers map to the standard Hanford Site stratigraphy. The vadose zone, (see Figure 8-28) is the hydrogeologic region that extends from the soil surface to the watertable (DOE-RL 1998b). The geographic focus is on areas at the Hanford Site that (1) underlie liquid waste disposal sites and tanks; (2) have the potential for leaks or leaching; and (3) have experienced past leaks and spills. Selected areas away from the focus areas are also included (i.e., areas representative of background conditions and areas that have the potential to become contaminated in the future). Figure 8-28 illustrates a general system conceptual model as presented in the Groundwater/Vadose Zone Integration Project Specification (DOE-RL 1998b). Figure 8-

28 illustrates the role of the vadose zone technical element and its primary linkages with other technical elements. The vadose zone element relies on input from the inventory and release elements. This needed input includes the spatial and temporal distributions of waste releases and the mass flux and concentrations of these releases. Other required inputs would come from existing databases and/ or future predictions/operational plans. These plans would include infiltration rates from both natural events (e.g., precipitation, snowmelt run-on) and operational activities (e.g., pipe leaks, dust suppression, sanitary discharges), the effectiveness and timing of planned remedial activities (e.g., excavation, capping, soil vapor extraction) and the hydrostratigraphy and associated physical and chemical parameter distributions. Output from the vadose zone element would feed the ground water and/or the risk elements. This output would be primarily in the form of spatial and temporal distributions of the mass flux and concentration of contaminants. Wilson (1995) described flow within the vadose zone as dynamic and characterized by periods of unsaturated flow at varying degrees of partial saturation punctuated by

Figure 8-28 Vadose Zone Model 528

CONCEPTUAL MODELS

episodes of preferential, saturated flow in response to hydrologic events or releases of liquids. Specific topics of interest to the Hanford Site include: (1) subsurface contamination (i.e., characteristics of past disposal and leakage, including chemistries, volume and distribution); (2) surface hydrologic features and processes (e.g., winter rain and snowmelt, water line leaks, infiltration, deep drainage and evaporation rates); and (3) subsurface geologic and hydraulic features and processes (e.g., stratigraphy, structures, physical properties, geochemistry and microbiology of the sediments above the watertable) (DOE-RL 1998b). 8.6 THE FLOWNET Construction of flownets offers a direct method for defining the most likely direction of ground-water movement. flownets are the basic tool used in site assessment and monitoring well system design to illustrate regional and local flow patterns that may require monitoring or later aquifer remediation. A flownet is a two-dimensional model of the ground-water system that identifies groundwater flow directions and head levels. These are a means of portraying a graphic solution to the Laplace equation that governs steady state flow. Flownets can also be conveniently used to identify suitable locations for monitoring wells, as well as, screened intervals of the wells.

solutions to many flow problems. For one variation of this method, the hydraulic head distribution in the geologic media is unknown in cross-section and is determined by solving for ground-water flow paths. To determine the solution, a family of curves parallel to the flow direction called flow lines are drawn orthogonally to another family of curves, equipotential lines. Each flow line represents the path a fluid particle would follow through a porous medium and successive flow lines are constructed so that an equal quantity of discharge is contained between each flow path. The first set is referred to as equipotential lines, which are locations of equal hydraulic head, (see Figure 8-29). Equipotentials represent the height of the potentiometric surface of a confined aquifer or the piezometric height of the unconfined water above a reference datum plane; or, alternatively, a discharge elevation. Because ground water moves in the direction of the highest hydraulic gradient, the resultant flow line in isotropic geologic systems is perpendicular to equipotential lines. Hence, flow lines cross equipotential lines at right angles.

8.6.1 Introduction Flownet analysis is a graphical method of solution for several different kinds of ground-water flow and seepage problems. This text will concentrate on the use of these flownet constructions for selection of the target monitoring zones for assessing the performance of land disposal facilities. Descriptive models of regional and local steady state ground-water flow in an unconfined aquifer was first presented by Hubbert (1940), who demonstrated that the hydraulic head at a point in a potential field represents the elevation to which water will rise in a piezometer that is open only at that point. At the point where an equipotential line intersects the potentiometric surface, water in the piezometer will rise to the ground-water surface. Elsewhere, water in a piezometer intersecting the equipotential line may be above or below the ground-water surface, depending upon the relative hydraulic potential (see Figure 8-29). Flownets are particularly useful because they illustrate the principles of fluid motion and the influence of various types of boundary conditions on flow patterns. They also provide a solution that does not require specialized mathematical procedures for obtaining approximate

Figure 8-29 Hubert’s Regional Flow Model 529

CONCEPTUAL FLOW MODELS

One general limitation on this method lies in the amount of time needed to obtain a solution because these flownet constructions require trial and error sketching of flow lines and equipotential lines. This limitation becomes especially severe for free-surface problems having complicated boundaries and involving more than one hydraulic conductivity. Flow lines represent an additional conceptualization of ground-water movement in a geologic system; as such, only a relatively few of these sets must be drawn during the analysis. A reasonable level of effort in many geologic environments can achieve sufficient conceptual understanding of ground-water flow to select relatively accurate monitoring well locations from these flownet constructions. This method can also be useful for calculation of flow rates and quantities for selected geologic sections. Another variant of the method uses a contour map of either a potentiometric surface or ground-water surface that has been constructed from known water-level data. Pairs of flow lines are drawn orthogonally to the contour lines only at selected points, then discharge differences can be computed between several cross-sections, each bounded by the pair of flow lines and oriented parallel to the contours. Differences between the discharges at two or more of the cross-sections can be related to withdrawals by wells, recharge, changes in ground-water storage or other phenomena. Knowing all but one of these variables, the remaining one can be computed. If all of these variables are known, it is also possible to use the discharge difference to estimate transmissivity. Hubbert’s model was for an unconfined aquifer of great depths. Additional models were later presented by Toth (1962, 1963) and Freeze and Witherspoon (1967). These flow models extend the flow path concepts to more complex hydrologic systems and allow direct analysis of small basins to define areas of recharge and discharge. A number of popular texts review the basics of flownet construction for site-specific, small-scale flow systems. Cedergren (1967), Freeze and Cherry (1979) and Todd (1980) all describe the basic criteria for generation of flownets and provide the mathematical derivations. A more recent publication of the U.S. Environmental Protection Agency (U.S EPA, 1986) provides additional information on ground-water flownets and flow line construction related to the time-of-travel calculations. These methods of flownet construction are part of the traditional instruction in undergraduate hydrogeology and soil engineering courses and must be used in establishing ground-water flow directions for monitoring well system design. Sand tank constructions have been used since the 1950s to illustrate ground-water flow. C.V. Theis, H. Skibiski and J. Lehr developed the use of sand tank models to represent a wide variety of subsurface flow and lithologic

530

conditions. More recently, these physical models were used by a Swiss Researcher to represent dense non aqueous phased liquids (DNAPLs) flow in both vadose and fully saturated conditions. These physical models use dyed water to represent ground-water flow paths. They provide an unparalleled instructional technique to illustrate the interaction between lithology and ground-water recharge and discharge points. The National Water Well Association markets a series of 35-mm slides that show time-lapse sequence photographs of various geologic flow situations. Figure 8-30 illustrates ground-water discharge to a gaining stream. The boundary conditions of a constant head at the recharge (ends of the model) and discharge at the stream (in the center of the model) where water is removed and finally the no-flow boundary at the bottom of the model causes the resultant flow lines as shown on the model. Ground water as shown in the dye traces moves from higher to lower hydraulic pressure. Especially important is the area of no flow directly below the discharge point in the sand tank model. The flowing dye lines discharge to the lowest hydraulic head levels, as shown, and cannot cross over to the other side of the model due to the higher head levels present across the stream area. The only way ground-water flow lines could cross the discharge area shown in the model would be for a lower (than the model’s constant head discharge point) discharge point to be present. Such lower head points could be due to a highly transmissive geologic unit discharging to a lower hydraulic head area. This lower head level is present within the physical model. This recharge/ discharge relationship is the basis for many decisions that must be made on both detection and assessment monitoring design. Figure 8-31 illustrates the deflections of the flow lines as the ground water moves through varable lay-

Source: J. Lehr

Figure 8-30 Sand Tank Flow Model Example

CONCEPTUAL FLOW MODELS

Source: J. Lehr

Figure 8-31 Reflection of Flowthrough Materials with Variable Hydraulic Conductivity ers of hydraulic conductivity. Sand tank models can also provide insight into the localized effects of aquifer heterogeneity and groundwater flow. Figure 8-32 illustrates a downward groundwater flow through various fine- and coarse-grained layers. Although deflections (according to the tangent law) are observed these course sand units are not discharging in a horizontal direction. The lowest hydraulic head at the bottom of the model attracts the flow lines as represented by the dye traces. Questions regarding flow in minor sandy units are common during evaluation of ground water monitoring systems. If these small more permeable sandy units are not connected to a discharging unit, these units will not have the low hydraulic heads necessary to "attract" the ground-water flow. Sand tank models can be extremely illustrative in representing local recharge and discharge relationships. Regional ground-water flow in nonhomogeneous, anisotropic systems can be investigated by means of both analytical and numerical methods. Toth (1962, 1963) used analytical solutions to evaluate models for basin wide flow patterns. Freeze and Witherspoon (1967) evaluated basins using variations of watertable configurations and hydraulic conductivity variations. They developed a series of two dimensional cross-sectional views. These series of illustrations, which were later reprinted in Back and Freeze (1985), provide excellent insight into groundwater basin flow conditions. Only a few of these illustrations are reproduced here; however, they accurately portray many of the issues that must be addressed in

Source: J. Lehr

Figure 8-32 Downward Ground-Water Flow

531

CONCEPTUAL FLOW MODELS

development of flownet constructions. Computer-based cross-sectional presentations extend the applicability of simple sand tank models to more complex geologic and hydraulic situations. The effect of ground-water surface configuration on regional ground-water flow through homogeneous isotropic geologic units is illustrated in Figure 8-33A and 833B. Variable hydraulic conductivity flownets are shown in Figure 8-33C. 8.6.2 Darcy’s Equation and Flownets Flownets are practical solutions to Laplace equations. As such, they require that Darcy’s law is valid and essential assumptions of flow apply to the system. In order to introduce the concept of flownet constructions, the development and validity of Darcy’s law are reviewed as fundamental to the understanding of ground-water flow. As described in Chapter 5, Darcy’s law provides the means for determining hydraulic conductivity of soils and rock both in the field and laboratory. The relationship has been defined in a series of forms: Q=kiA Q=kiAt q=kiA=VdA

Equation 8-1

In these expressions, Q or q is the seepage quantity, t is time, k is Darcy's coefficient of permeability, i is the hydraulic gradient that is also equivalent to: v = ki = q/A = Vd Vs = ki/ne

Equation 8-2

A is the total cross-sectional area normal to the direction of flow, including both void spaces and solids, Vd (or v) is the discharge velocity and Vs is the seepage velocity. The effective porosity is defined as the ratio of the actual volume of pore spaces through which water is seeping to the total volume. Discussions as to effective porosity and velocity calculations are further developed in Chapter 5. Darcy’s law has been the focus of ground-water flow analysis since the recognition of the difficulties of further development of Newton’s law of friction together with the classical Navier-Stokes equations of hydrodynamics to describe the behavior of fluids under motion in porous media (Cedergren, 1967). Darcy’s development in 1859 of the quantitative representation of the simple relationships of fluids flowing in porous media provided the basic

532

understanding that has been used in the intervening years. Muskat (1937), Taylor (1948), Leonards (1962) and Cedergren (1967) have presented discussions of permeability (or hydraulic conductivity) and Darcy’s law. Each of these references defines the valid ranges of Darcy’s law for a range of sediment sizes and gradients. The fundamental consideration of the nature of flow in porous media, as pointed out by Cedegren (1967) have led investigators to conclude that Darcy’s law of proportionality of macroscopic velocity and hydraulic gradient is an accurate representation of the law of flow as long as the velocity is low. Taylor (1948) has described the slow transition states from laminar flow (i.e., Darcian flow) to a slightly turbulent condition (where Darcy flow does not apply). He concludes that uniform sand with a grain size of 0.5 mm or less will always have laminar flow for gradients of 100%. Even with gradients as high as 800%, the flow will remain laminar for sands with particle diameters below 0.25 mm. Very low gradients have also been investigated by Fishel (1935) for validity with respect to Darcy’s law. He reported that under heads as low as 2 to 3 in. to the mile in sands, Darcy’s law fully applied. Seepage solutions that require validity to Darcy’s law include: •

Flownets for steady state seepage

•

Calculations for the velocity of water masses

•

Approximation solutions to non-steady seepage for moving saturation lines using flownets

•

Seepage quantity determinations in saturated soil and rock

The first of the above four bullets represents the focus of the practical solution of seepage through geologic cross-sections of material with different hydraulic conductivity for both isotropic and anisotropic conditions. flownets for steady state seepage conditions provide investigators a tool for selection of target monitoring zones where seepage from the facility would move most rapidly and meet regulatory criteria for immediate detection of discharges from the facility. 8.6.3 Flownets Flownet construction is a graphical method for solving forms of streamline flow that can be represented by the Laplace equation. The Laplace equation for flow of water through porous media requires a series of assumptions that the following conditions apply: •

The soil is homogeneous.

CONCEPTUAL FLOW MODELS

Source: Freeze and Witherspoon, 1967

Figure 8-33 Regional Flow through Geologic Units (From Freeze, A. and P. A. Witherspoon, Water Resources Research, 3:623–634, 1967. With permission.)

•

The media is fully saturated.

•

Consolidation and expansion of the media are not factors.

•

The geologic media and water are incompressible.

•

Ground-water flow is laminar (hence, Darcy’s law is valid).

Flownets are very useful because they illustrate the principles of fluid motion and the influence of various types of boundary conditions on the fluid flow patterns. As water flows through porous geologic materials, ground water moves through all the interconnected pore spaces. The path of the water particles can be represented by individual flow lines. An infinite number of flow lines are possible; however, only those that provide sufficient details for satisfactory construction accuracy are drawn on the flownet. Each flow line represents the path a fluid particle would follow through a porous geologic medium and successive flow lines are constructed so that an equal quantity of discharge is contained between each flow line segment.

A simple illustration of flow lines is shown in Figure 8-34. The saturated sand contained within a horizontal tube with two end reservoirs provides the nature of flow lines. The driving force for the model consists of the differential head h between the two reservoirs. This flow from left to right is highlighted by dye streaks in the illustration. These streaks represent flow lines. All flownet constructions could be represented through similar sand tank models where dye traces could represent flow lines. However, construction of sand tank models is very tedious and flownets can be drawn on paper that can represent the flow conditions (dye traces) in sand tank models. Flow through the model can be either horizontal or vertical as shown in Figure 8-35. 8.6.4 Flownet Theory A fundamental rule is that each flow path in a flownet must transmit the same quantity of water. Therefore, the total flow of ground water through the system (Q) is equal to the flow quantity in each flow path (q) multiplied by the total number of flow paths (F). Also, the total head loss, 533

CONCEPTUAL FLOW MODELS

(h), experienced in moving through one flow path of the entire flownet, is equivalent to the head loss experienced in passing through any equipotential space multiplied by the number of equipotential spaces (N). The total quantity of water that flows through a given mass of geologic material is equal to the sum of the quantities of water through each flow path in the flownet. Flow (q) through any path in a flownet is defined by Darcy’s law: q=kiA

Equation 8-3

where k is the coefficient of hydraulic conductivity (cm/s or ft/day), i is the hydraulic gradient (dimensionless) and A is the cross-sectional area through which flow occurs (m2 or ft2) The value of q obtained from the equation is for a unit width in the third dimension perpendicular to the crosssection. Hence, the units of q are meters cubed/s per meter of width. The total flow through a single flow path is found by multiplying q by the width of interest. When one considers a flownet consisting of squares of dimension s * 1 with head loss, h, through a single equipotential space (U.S. EPA, 1986), Darcy’s law reduces to: q = khs/l

to the number of equipotential spaces. Each equipotential line represents a line of equal hydraulic head and these lines are drawn so that there is an equal head loss between each successive segment. The second type of lines used in flownet construction are the equipotential lines. These lines are shown in Figure 8-36. Each equipotential line represents a line of equal hydraulic head. These lines are drawn so that there is an equal head loss between each successive line. As represented in Figure 8-37, the gradual frictional loss of energy between the two reservoirs can be quantified through head levels in piezometers located with the sand mass. Piezometers located along an equipotential line will show equal head levels. Because the model has an impermeable top and bottom (no flow), the equipotential lines are perpendicular

Equation 8-4

The flownet is by definition composed of rectilinear spaces that approximate squares; hence, s = 1 and: q=k*h

Equation 8-5

As defined: h = H/N so that: q=H/K

Equation 8-6

Equation 8-7

Because the flow, q, through any square is described by: q=Q/F

Equation 8-8

where F is the total number of flow paths, the total flow Q can be calculated as follows: Q = kHF/N

Equation 8-9

Therefore, the total quantity of water that will pass through a unit width of a given subsurface geologic unit can be calculated by using a flownet for the cross-section using the hydraulic conductivity multiplied by the total head difference and the ratio of the number of flow paths

534

Source: J. Cherry

Figure 8-34 One-, Two-, and Three-Dimensional Model

CONCEPTUAL FLOW MODELS

to the boundaries. If the flow lines of Figure 8-35 are combined with the equipotential lines of Figure 8-36, a very simple flownet is obtained (Figure 8-37). Although this flownet is extremely simple, it possesses the properties of a true flownet. The flow lines intersect the equipotential lines at right angles and the net is composed of squares. Most flownets are composed of curves and the square figures are not true squares but curvilinear squares. The strict requirement that a net must be composed of square figures is met only if the average width of an area is equal to its average length. As pointed out by Cedergren (1967), water will rise to the same level in piezometers installed anywhere along a given equipotential line. This is mandatory because the same energy level exists everywhere along a given equipotential line. As with the flow lines, equipotentials are independent of the orientation of the geologic element, and vertical (Figure 8-38) or any other equipotential lines can be illustrated by flownets. Flow lines and equipotential lines are then combined to form the construction components of flownets. All flownets must meet a number of base requirements: 1. Flow lines and equipotentials should intersect at right angles and form geometric figures that are squares. The requirement for squares can be met with any length-to-width ratio.

squares except at seepage boundaries where the net is cut off. 5. At any point in the flownet, the spacing of adjacent lines is inversely proportional to the hydraulic gradient (i) and the seepage velocity (Vs). The requirement for flownet constructions that represents squares can be easily understood for simple models presented so far; however, most flownets will not have the impermeable boundaries represented in these models (that cause simple, parallel flow lines). Most flow consists of curved lines that are more difficult to picture as a series of squares, but rather curvilinear squares. Casagrande (1937) provided a simple illustrative procedure (Figure 838) to demonstrate the actual square nature of curvilineal geometric figures. The simple requirement that a net must be composed of square figures is met if the average width of an area equals the average length. For example, if the distance between points 9 and 10 equals the distance between points 11 and 12, then the area represents a square (a circle could be drawn within Figure 8-38 points 1, 2, 3 and 4). The square nature of the figure becomes clear if subdividing lines (and squares) are drawn connecting the 1, 2, 3 and 4 points of the figure.

2. All boundary conditions must be satisfied: a. Equipotential lines must meet impermeable boundaries at right angles. b. Equipotential lines must be parallel to constant head boundaries. 3. Adjacent equipotential lines represent equal head losses. This would apply to the series of successive equipotential drops. The flownet should be drawn to contain a whole number of stream tubes. The number of equipotential drops depends on the physical shape of the cross-section of interest. The last drop at each end or both ends of the net may have a fractional drop. 4. The number of stream tubes must remain the same throughout the constructions. An equivalent discharge must flow between adjacent pairs of flow lines. As with the previous rule, a stream tube near a boundary may be fractional, but this fraction should be the same everywhere. This rule guarantees that the flownet will be composed of

Figure 8-35 Flow Line Construction Example

535

CONCEPTUAL FLOW MODELS

ceptual flow system, the resultant equipotential lines and flow lines constitute a flownet. A flownet can be later used to determine the distribution of heads, velocity distribution, flow paths, flow rates and the general flow pattern in a ground-water system (McWhorter and Sunada, 1977). One should always remember that two-dimensional representations of three-dimensional flow provides only part of the picture. Several cross-sections orthogonal to each other or true three-dimensional representations of flow may be necessary to fully describe local flow conditions at site. Four basic types of ground-water systems exist (U.S. EPA, 1986), based on the distribution of hydraulic conductivity: •

Homogeneous and isotropic

•

Homogeneous and anisotropic

•

Heterogeneous and isotropic

•

Heterogeneous and anisotropic

Figure 8-39 is a graphical representation of the four types of systems, where the hydraulic conductivity (hori-

Figure 8-36 Horizontal and Vertical Flow Examples

8.6.5 Application of Flownets to Conceptual Models A flownet is a two-dimensional model of a groundwater system that identifies ground-water flow directions and can be used to calculate ground water flow rates and quantity of flow. Flownets can also be used to identify suitable locations for monitoring wells as well as the target monitoring zone for the most appropriate depth for the screened interval of the wells. The conceptual hydrogeologic model of a site can be linked with a flownet construction. The combined model can then be tested (similar to verifying a computer flow model) by installing additional piezometers at selected locations and comparing the actual head values at these locations with those predicted by the flownet construction. Any ground-water system in the field can be represented by the three-dimensional set of equipotential surfaces and orthogonal flow lines. If a plan view or a twodimensional cross-section is drawn to represent this con-

536

Figure 8-37 Simple Flownet Construction

CONCEPTUAL FLOW MODELS

zontal and vertical) is represented in vector form and shown at two different locations within each aquifer. Although geologic (or any other) material can have variable hydraulic conductivity in any of three dimensions, hydraulic conductivity measurement has dictated the horizontal and vertical conventions. Through laboratory measurements (vertical) and field in situ hydraulic conductivity tests (horizontal measurements) two directional orientations are provided for flownet construction. Geologic materials are homogeneous if the hydraulic conductivity does not vary spatially, whereas such materials are heterogeneous if hydraulic conductivity does vary spatially. If the hydraulic conductivity varies with the direction of measurement at a point (for example, when the vertical hydraulic conductivity is different from the horizontal conductivity), the geologic material is anisotropic at that measurement point. Decisions on Use of Flownets Flownets may not always be appropriate in every site assessment project. There are a number of geologic and hydrogeologic situations in which the accurate construction and use of flownets are difficult or impossible. These conditions occur when there are scaling difficulties within complex geologic settings under conditions of few threedimensional hydrologic data for the ground-water system and when ground-water flow conditions do not sufficiently conform to Darcy’s law. One has physical scaling difficulties when the aquifer and/or geologic hydrostragraphic layers associated with a particular ground-water system are thin in relation to the length of the flownet. Unless the scale is exaggerated the flownet for this condition will be made up of squares that are too small to accurately. A common problem with flownet construction obtained from monitoring well data is the lack of threedimensional hydrologic data or hydrologically equivalent data for a ground-water flow system. Hydrologic testing must be available at various depths within an aquifer. Monitoring wells that screen wide portions of an aquifer can provide only integrated hydraulic head data rather than point values. If, however, flow is horizontal in the aquifer (or hydrostratigraphic unit), then the almost vertical equipotential line could be fairly represented by the monitoring well water level. One should fully consider the reliability of using such data sources before including them in the project database. You must also obtain values for both the vertical and horizontal hydraulic conductivity and the vertical and horizontal gradient in the aquifer to provide reliable interpretive results. These data must be

Figure 8-38 Curvilinear Net Construction available before a flownet can be constructed. Questions can arise for two types of ground-water systems regarding the applicability of Darcy’s law. The first is a system in which ground-water flows through materials with low hydraulic conductivity under extremely low gradients (Freeze and Cherry, 1979) and the second is a system in which a large amount of flow passes through materials with very high hydraulic conductivity. Because Darcy’s law expresses linear relationships and requires that flow be laminar, a system with high hydraulic conductivity can have turbulent flow conditions. Turbulent flow can be characteristic of Karst limestone and dolomite, cavernous volcanics and some fractured rock systems (U.S. EPA, 1986). Construction of flownets for areas of turbulent flow would not provide accurate results. The concept of time of travel (TOT) has been used in federal guidance decision models for site location criteria. The flow path of least resistance can usually be identified by inspection once a flownet is constructed for the site in question. This particular application of flownets provides a very conservative approach to assessing ground-water vulnerability beneath a waste management or unregulated disposal site. However, these time of travel calculations are useful to define relative rates of ground-water flow under site-specific constraints. 8.6.6 Hydrologic Considerations In using flownets for ground-water monitoring well design problems, it should be recognized that the solutions are no better than the idealized cross-sections drawn. For a given section, however, the flownet can give an accurate solution for flow quantities. To enable proper construction of a flownet for use with a conceptual geologic model, certain hydrologic parameters of the groundwater system must be known, including:

537

CONCEPTUAL FLOW MODELS

Source: Freeze and Cherry, 1979

Figure 8-39 Four Types of Heterogeneous Conditions (From Freeze, R. A. and J. A. Cherry, Groundwater, Prentice Hall, Englewood Cliffs, NJ, 1979. With permission.)

•

Distribution of vertical and horizontal head

•

Vertical and horizontal hydraulic conductivity of the saturated zone

•

Thickness of saturated layers

•

Boundary conditions

Facility Head Distribution Piezometers installed during the Phase II field tasks are used to determine the distribution of head throughout the site area. Head measurements made for the flownet construction must be time equivalent; that is, all piezometric measurements must be made coincidentally. Alternatively, all head measurements must be made under the same ground-water conditions. Piezometers should be spatially distributed and placed at varying depths to determine the existence and magnitude of vertical and horizontal gradients (actually the three-dimensional components of flow). When significant vertical flow components exist in the system, the flow direction cannot be derived simply based on inspection of the potentiometric surface in two dimensions. Three-dimensional views of the potentiometric surface would be required to fully interpret the flow direction. Ground water will flow, however, from areas of high hydraulic head to areas of low hydraulic head. Figure 8-40 illustrates the hydraulic heads in a series of piezometers located in recharging and discharging geologic

538

environments. In recharging zones, deeper piezometers show lower ground-water levels. This is due to the lowering of equipotentials with depth in recharge areas. In discharging environments, deeper piezometers show higher water levels or heads, as illustrated in Figure 8-40. The reader should study carefully the reasons for the relative downward hydraulic heads in the recharge area and the upward hydraulic heads in discharging areas. This relationship controls ground water flow at many overburden sediments and fractured rock sites. Simple homogeneous, isotopic systems, as illustrated, require consideration of depth below the ground-water surface to correctly use the head data. Strong recharge/discharge systems require full understanding of both the vertical and horizontal gradients. Special care should be maintained to not mix piezometer readings from different hydrostratigraphic units or unrelated elevations in generating ground-water contour maps. Aquifer Thickness and Extent The physical location and thickness of an aquifer (or any geologic strata) are determined during the Phase II field program by evaluation of geologic logs or by geophysical techniques. Geologic logs generated from boreholes show changes in lithology (the characteristics of the geologic material) indicating the relative hydraulic conductivity of materials. Various geophysical techniques, both downhole and surface (discussed in Chapter 3) can

CONCEPTUAL FLOW MODELS

be used to assist in the evaluation of the thickness and extent of geologic units. The observed geologic materials establish the physical framework to establish flownets and conceptual models for the facility.

many thousands of times less in aquifers than in aquitards. Therefore, lateral flow in aquitards usually is negligible and the flow lines concentrate in aquifers and run parallel to aquifer boundaries.

Hydraulic Conductivity

Boundary Conditions The boundary conditions of the area of investigation must be known to properly construct a flownet. The boundary conditions are used as the boundaries of the flownet. The four general types of boundaries are (1) impermeable boundaries, (2) constant-head boundaries and (3) unconfined aquifer boundaries (Freeze and Cherry, 1979) and (4) surface of seepage. Ground water will not flow across an impermeable boundary; it flows parallel to these boundaries. Unfractured granite is an example of an impermeable boundary (Figure 8-41a). A boundary where the hydraulic head is constant is termed a constant head boundary. Ground-water flow at a constant-head boundary is perpendicular to the boundary.

Vertical and horizontal hydraulic conductivity is a primary component of Phase II site assessment tests. Several laboratory and field methods can be used to determine the saturated and unsaturated hydraulic conductivity of soils, including tracer tests, auger-hole tests and pumping tests of wells. Most ground-water systems consist of mixtures of aquifer and aquitard units. Flow path analysis must consider ground-water movements through aquifers and across aquitards. The relative hydraulic conductivity of these units can vary many orders of magnitude; hence, aquifers offer the least resistance to flow. This results in a head loss per unit of distance along a flow line ten to

Figure 8-40 Recharge/Discharge Piezometer Head Relationships 539

CONCEPTUAL FLOW MODELS

Examples of constant-head boundaries are lakes, streams and ponds (Figure 8-41b). The unconfined ground-water boundary is the upper surface of an unconfined aquifer and is a surface of known and variable head. Flow can be at any angle in relation to the piezometric surface due to recharge and the regional ground-water gradient (Figure 8-40c). The surface of seepage boundary is where water leaves the porous medium as seepage and enters the open air. The pressure at this boundary is considered constant. Because h - z = o, constant, equipotential lines will intersect the boundary at constant intervals. This boundary cannot be considered either an equipotential or a flow line in the construction of the flownet. The boundary conditions of an aquifer can be determined after a review of the hydrogeologic data for a site and then considering the flow system within the conceptual model framework. Boundary conditions of a particular cross-section must be established through regional and specific investigation of site conditions. After assessing the hydrologic

parameters of the ground-water system at the site of concern, the necessary data should be available to construct flownets and resultant determination of ground water flow direction from the facility to potential downgradient receptor points. 8.6.7 Basic Guidance on Flownet Construction The most basic flownet construction consists of a homogeneous and isotropic system relative to hydraulic conductivity. The homogeneous and isotropic geologic medium although rarely occurring in nature can serve to describe the basic rules of flownet construction. The basic rules must be applied for all hydrogeologic media, with necessary modifications made to account for heterogeneity or anisotropic conditions of the system under examination. The fundamental rules (U.S. EPA, 1986) and properties of flownets are summarized below: 1. Equipotential lines and flow lines must intersect at 90 degree angles. 2. The geometric figures formed by the intersection of equipotential lines and flow lines must approximate squares. 3. Equipotential lines must be parallel to constanthead boundaries (constant-head boundaries are equipotential lines). 4. Equipotential lines must meet impermeable boundaries at right angles (impermeable boundaries are analogous to flow lines). 5. Each flow path in a flownet must transmit the same quantity of water (q). 6. The head difference (h) between any pair of equipotential lines is constant throughout the flownet. 7. At any point in the flownet, the spacing of adjacent lines is inversely proportional to the hydraulic gradient (i) and the seepage velocity (Vs).

a

b

Flownet sketching can be sufficiently accurate for assessing most ground-water flow condition relative to water quality monitoring issues. Patience and a certain degree of intuition will develop with practice in construction of these nets. Even with the difficulties in generation of accurate flownets, the precision associated with these sketches is likely comparable to that associated with the measurement of field and laboratory values for hydraulic conductivity of the various site geologic units.

c

Flownet Construction Steps

Figure 8-41 Boundary Conditions

540

Relatively few flow lines are necessary to adequately characterize flow conditions at any particular site. The use of three to five flow lines will generally be sufficient for

CONCEPTUAL FLOW MODELS

most investigations. With this in mind, the following steps should be used to construct a flownet: 1. Draw a geologic cross-section at a 1:1 scale of the geologic units of concern in the direction of flow. At times, expanded vertical scales may be useful, but with the consideration that some changes will occur in flow lines and equipotential interception angles. 2. Establish all points of known hydraulic head from the Phase II data and draw tie lines between them by traversing the shortest possible distances and avoiding crossing of lines. 3. The tie lines constructed in Step 2 should be used to interpolate other hydraulic head values for the purpose of sketching equipotential contour lines. The accuracy of this interpolation procedure will depend upon the number and location of piezometer points for assessment of known hydraulic head. 4. With the known geologic data, establish two boundary flow lines. 5. By trial and error, sketch intermediate flow and equipotential lines; consistent right angles and squares should be formed in the sketching process. 6. Continued to sketch these lines until inconsistent shapes (i.e., angles other than right angles or rectangles that are not squares) start to develop in the flownet construction. 7. Continue successive trials until the flownet is fully consistent. Each inconsistency noted will indicate the direction and magnitude of change for the next trial. One obtains the most effective results if only a few lines should be used in constructing the flownet. Any transitions that exist in the net should be smooth and the size of the spaces should change gradually. The following steps should be viewed as additional suggestions for drawing flownets and not as fixed rules. The experience of each individual will determine what methods are most beneficial to the analysis technique. 1. The cross-section to be studied should be drawn on

one side of tracing paper and the flownet construction should be drawn on the other side. It can then be traced onto the former side or onto another sheet of paper. 2. Just enough flow lines and equipotential lines should be used to bring out the essential features of the site. If detail needs to be emphasized in some parts of the flownet (i.e., facility features), flow lines and equipotential lines in those parts can be subdivided after the flownet is completed. 3. The scale of the drawing should be just large enough to draw essential details. If necessary a long flownet construction (e.g., 1 to 1 cross-section with an extensive horizontal dimension) can be subdivided into regions that will fit on single sheets of paper. 4. The boundary conditions, especially prefixed flow lines and equipotential lines, should be plotted before starting to draw the full flownet. 5. Either the number of streamtubes or the number of equipotential drops should be made a whole number to simplify flownet construction; however, if necessary, both streamtubes can be fractional on the ends of the net. 6. The overall shape of the flownet should be kept well in mind while working on details of the system. Because the shape of each section of a flownet affects the rest of the construction, a small portion should never be refined before the net is almost completed. At most facilities, vertical and horizontal head data are obtained from well and piezometer measurements and from free surfaces such as springs, lagoons, ponds and swamps. Data gathered from sources not related to the controlled area evaluated in the site assessment should be inspected carefully before use. Often, potable water supply wells (used for water level measurement) have long, open screened sections or have slotting at variable elevations below the ground-water surface for measurement of fluid pressure. These measurement devices provide very different head data from piezometers with short screened zones. As general guidance the open interval on a piezometer should be as short as possible with the midpoint of the interval being the measuring point for use in the flownet construction.

541

CONCEPTUAL FLOW MODELS

Preexisting wells with long screened sections may be used to obtain approximate metric levels if the midpoint of the open interval is used. The head measured in such a well is the integrated average of all the different heads over the entire length of the open interval. In this instance, it is important to note that if vertical gradients are present, the measured head can be a function of the screened length of the well and the variable depths of the screening. This must be considered when piezometric data are collected from such wells to be interpreted for the purpose of establishing hydraulic head conditions.

lines. The flownet in Figure 8-42b is the simplest representation that can be drawn for the system. A more detailed flownet (Figure 8-42c) can be constructed for this system, but the calculated flow rate is the same. From the flownet in Figure 8-42c, there are 5 flow paths and 20 equipotential spaces. Thus, the calculated flow rate is: Q = (10-6 m/s)(5)(2m) / 20 Q = 5 * 10-7 m3/s per meter of width

8.6.8 Example Flownet Constructions

and is equal to the value calculated from the flownet in Figure 8-42b.

Homogeneous Isotropic Flow System Figure 8-42a is an introduction to flownet analysis procedures shows a cross-section of a homogeneous, isotropic system with no vertical hydraulic gradients. As a typical example, the cross-section has been drawn parallel to the direction of flow. The water level elevation is 122 m in Well A and 120 m in Well B. The aquifer consists of fine sand with a hydraulic conductivity of 10-4 cm/s. The top and bottom of the aquifer are considered in these cases as impermeable (no-flow) boundaries and, as such, represent flow lines. The flow lines in this figure form a single flow path, which is sufficient in this flownet example. For this example, it is assumed that flow is the vertical equipotential lines are drawn at Wells A and B due to the horizontal flow. Intermediate equipotential lines are drawn by equally dividing the space between Wells A and B into squares (Figure 8-41b). Once the flownet has been constructed, the flow rate can be calculated using the equation: Q = kFH / N

a

b

Equation 8-10

where: Q = flow rate k = coefficient of hydraulic conductivity = 10-4 cm/s = 10-6 m/s F = number of flow paths = 1 H = total head drop = 2 m N = number of equipotential spaces = 4

c

Using the flownet constructed for this problem, Q = (10-6 m/s) (1) (2m) / 4 Q = 5 * 10-7 m3/s per meter of width N is the number of equipotential spaces in one flow path rather than the number of equipotential lines; therefore, N is one less than the number of equipotential

542

Figure 8-42 Flownet Model Construction

CONCEPTUAL FLOW MODELS

Heterogeneous, Isotropic Systems Few ground-water flow systems can be adequately studied as a section with a single hydraulic conductivity. Natural geologic materials can have over seven orders of magnitude variation in hydraulic conductivity within a few feet (for example, glacial out-wash gravels underlying till). As a general rule greater head loss should be expected to occur in materials with low hydraulic conductivity than in materials with high hydraulic conductivity. Flow lines tend to follow or parallel zones of contact between materials that have differences in hydraulic conductivity of 100 (two orders of magnitude) or more. Flownets drawn for materials with a difference in hydraulic conductivity of a factor of 100 will look the same if the ratio of conductivity is 10-7 to 10-5 or 10-3 to 10-1. However, variations will be evident in the quantity of flow and the calculated time of travel. Directional differences in hydraulic conductivity within the same geologic layer (i.e., anisotropy) are also of importance in flownet construction. Construction of flownets must consider not only hydraulic conductivity differences between layers, but also variations in horizontal and vertical hydraulic conductivity. Horizontal and vertical hydraulic conductivity are convenient representations for the test results from in situ field tests (horizontal hydraulic conductivity) and laboratory permeability or triaxial tests (as vertical hydraulic conductivity). In reality, hydraulic conductivity of geologic material can be represented in any direction but test methods have formalized the concept of vertical and horizontal conductivity. Beginning with a layered system with two different hydraulic conductivities water flowing through the two materials will have flow lines that bend at the boundary. This phenomenon of bending of flow lines at changes in hydraulic conductivity is due to the conservation of energy, where the flow (or any natural energy such as light rays) is deflected when passing through boundaries. Cedergren (1967) describes flow between materials of different hydraulic conductivity: “All factors being equal, the higher the permeability, the smaller the area required to pass a given volume of water.” Conversely, the lower the hydraulic conductivity, the greater the area required." This relationship is also applicable to the energy necessary for water to flow through porous media. Water level contour maps often show the effects of variations in hydraulic conductivity from point to point. Because the rate or loss in energy is related to the steepness of the hydraulic gradient, steep gradients are often observed in areas of lower hydraulic conductivity and flatter gradients in areas of higher hydraulic conductivity. The deflection (and velocity change) of flow through geologic boundaries is derived through use of Darcy’s law

and by geometry described by the Law of Tangents. This relationship is described by the ratio of the hydraulic conductivity of two different materials as equal to the ratio of the tangents of the two angles formed by the ground water flow lines so that: tan e k1 ----- = -------------2 k2 tan e 1

Equation 8-11

The relative shape of this flow line deflection is shown in Figure 8-43. Figure 8-43a shows flow from higher conductivity and back again to the original higher hydraulic conductivity. Figure 8-43b shows flow from low hydraulic conductivity to higher and again back to lower conductivity material. In these illustrations, both flow lines and equipotential lines are similarly deflected. The areas formed by the intersecting flow and equipotential lines also can be described by ratios of the two hydraulic conductivities by the following equation: c/d = k2/k1

Equation 8-12

The relationship of longer or shorter rectangles based on the ratio of the two hydraulic conductivities can be visualized by considering the energy necessary to push water through geologic materials. The cross-sectional area required for water to flow from low hydraulic conductivity units to high hydraulic conductivity units is less; hence, the rectangles will stretch out in the higher hydraulic conductivity material. This stretching effect will be demonstrated by lower resultant gradients. Flow from higher hydraulic conductivity to lower conductivity,

a

b

Figure 8-43 Flownet Refraction

543

CONCEPTUAL FLOW MODELS

results in a shortening of the geometric figures shorten, because steeper gradients are required and more crosssectional area is required to pass the flow. Because conservation of mass applies in the flow between the two materials, the ratios will hold according to Equation 8-11. Heterogeneous, isotropic ground-water systems usually consist of two or more layers of materials with different lithologies and hydraulic conductivity. This heterogeneity may result from vertical layering, sloping strata, fault zones, igneous injection or the existence of man-made structures such as slurry walls to control rates of seepage. Ground-water flow in heterogeneous, isotropic systems is controlled both by the hydraulic conductivity of the layers as well as by boundaries within the system. The rules for construction of flownets for heterogeneous, isotropic systems are the same as for homogeneous, isotropic systems, except that the tangent law (see above) must be satisfied at geologic boundaries of variable hydraulic conductivity. If squares are created in one portion of a formation, squares must be created throughout that formation and throughout other formations that have the same hydraulic conductivity. Rectangles will be created in associated formations that have different hydraulic conductivity (Freeze and Cherry, 1979). Flow lines tend to be parallel to the zone of contact between materials in the medium with higher hydraulic conductivity and perpendicular to contacts between materials in the medium with lower hydraulic conductivity (Figure 8-44).

Source: Freeze and Cherry, 1979

Figure 8-44 Flow Lines in Geologic Model Figure 8-44a shows the deflection of a flow line passing from a material of higher hydraulic conductivity (sand) to one of lower hydraulic conductivity (silt). Deflection of a flow line passing from a low to a high hydraulic conductivity zone is shown in Figure 8-44b. The illustration also shows the shape of the rectangles that exist in the downstream material. Equipotential lines are also deflected when they cross conductivity boundaries because they are perpendicular to flow lines. It is impossible to construct a flownet for a heterogeneous, isotropic system in which only squares are created. However, the

a

b

Figure 8-45 Flowthrough Variable Materials 544

CONCEPTUAL FLOW MODELS

still form right angles (the flownet will consist of squares and rectangles). Before beginning construction of the flownet for heterogeneous, isotropic systems, one should look for the dominating parts of the cross-section and determine whether the hydraulic conductivities are in series or parallel. The system is in series when the cross-section perpendicular to the flow direction is of one hydraulic conductivity and different hydraulic conductivity regions occur sequentially in the flow direction (Figure 8-45a). Conversely, hydraulic conductivities are in parallel when more than one region occurs perpendicular to the flow direction and most flow lines remain in the same region throughout the net (Figure 8-45b). For geologic systems where hydraulic conductivity is in series, draw a preliminary flownet choosing one region to have squares and making length-to-width ratios in the other region as nearly correct as possible. If the flownet has a free surface, the slope of the free surface will be greater in the region of lower conductivity (Figure 8-45b). Repeated adjustments will be necessary to yield the final flownet. When seepage occurs through two hydraulic conductivity zones that are basically in parallel, flow through the more pervious zone usually dominates the flow pattern (Figure 8-45b). A flownet can be constructed for the more pervious part assuming temporarily that the other part is impermeable. The equipotential lines are then extended into the less permeable zone and, by repeated adjustments, the flownet is completed. This process works best

when the hydraulic conductivities to be compared are much different, for example, at least one order of magnitude. A check on accuracy for all composite sections can be made by subdividing the rectangles into a number of parts equal to the number of times the conductivity is higher (or lower than the hydraulic conductivity in the region where squares are drawn. Each subdivision should be a square. Whether the subdivisions are of the flow tubes or the equipotential drops depends on whether the conductivity is lower or higher, respectively, than in the region of I squares (Figure 3-45a and 3-45b). To obtain the quantity of seepage through any composite section, count the total number of equipotential drops and streamtubes and use Equation 8-10. The conductivity used should be the one for the region of squares. Example of a Heterogeneous Isotropic Ground-Water System The example target waste disposal area (Figure 8-46) is located in a recharge area over a heterogeneous aquifer. The conceptual geology of the site is based on two geologic units as shown on the lithological cross-section. The upper unit is a 20-m thick layer of silt sand with a hydraulic conductivity of 5*10-7 m/s (k1). The lower layer is a 10 m thick layer of sand with a hydraulic conductivity of 1*10-5 m/s (k2). The flownet is constructed using the following procedures:

Figure 8-46 Lithologic Cross-Section 545

CONCEPTUAL FLOW MODELS

Figure 8-47 Lithologic and Head Data •

Construct a conceptual model cross-section on a 1:1 scale.

•

Add the location of screens, head levels and a base line vertical scale.

•

Draw tie lines between the measured head levels (as between 16-m heads in p-17b and p-18a, 12-m heads between p-19a and p-18b).

•

Using the constructed lines, interpolate the equipotential head values for the cross-section (18 m, 14 m and 10 m equipotential).

•

Construct the initial flownet lines perpendicular to the equipotentials as shown in Figure 8-47.

•

Equipotential lines that do not originate at a head measurement point should be determined from the ratio 36 m / 2 m = x / 1 m.

Figure 8-48 Plotting of Equipotential Lines

546

CONCEPTUAL FLOW MODELS

In the case of the example provided in Figure 8-48 the distance is from the intersection of the equipotential and the flow line to the measuring point. The distance in Figure 8-48 is calculated at 18 m. •

Continue plotting equipotential lines along the tie lines until all points of equal head are connected.

•

Construct flow lines at right angles to the equipotential lines to form squares.

•

As ground water flows into the more permeable sand layers, an acute angle, m1, is formed by the flow lines. This angle is used in the tangent law calculations to determine the angle of deflection m2.

•

Enter the hydraulic conductivity of each geologic unit and the tangent of m1, to calculate the tangent of m2.

•

After calculating of m2 in degrees, the angle of refraction is used to plot flow lines into the sand layer, (the example is 12.1°).

•

The ratio of the adjacent units hydraulic conductivities is used to define the dimensions of the rectangles in the sand layer. Equation 8-12 is used to calculate the dimensions using c as the length of the rectangle and d as the width.

Figure 8-49 shows the width, d, of the rectangles in the sand equal to 1 m and the length c equal to 20 m. In order to evaluate the flow path for the facility to be monitored one should plot flow lines from the edges of the dis-

posal area to select the depth-location relationships. The resultant flownet will directly show the most direct target monitoring zone of the facility.

Heterogeneous Isotropic Ground-Water Systems (Three Layers) The previous example of a heterogeneous isotropic ground-water system with two units represents a simple layered case. Real-world ground-water flow systems often consist of three layers, with overburden on top of a weathered or highly fractured bedrock overlying a much less fractured or unweathered deeper bedrock. These three-layer systems can be evaluated in a similar Phase II program as described in Chapters 3 and 4. Lithology, hydraulic conductivity, hydraulic heads, along with physical boundary conditions provide the necessary tools to construct the flownet for a three-layered system. Especially important and often overlooked, is the evaluation of deeper bedrock conditions. If the deeper bedrock has a much lower hydraulic conductivity than overlying units it will act effectively as a traditional confining unit; however, this must be first proven if reliance is to be placed on the bedrock to act as a very limited flow zone. Very deep bedrock having overlying units with much higher hydraulic conductivity (say, three orders of magnitude) may be considered as confining units. However, each site must be individually evaluated for potential deep bedrock ground-water movements. In addition, density flow conditions, such as DNAPL product spills, may

Figure 8-49 Initial Flownet Construction 547

CONCEPTUAL FLOW MODELS

cause even deep lying low hydraulic conductivity bedrock to be contaminated. These density controlled pure product flow conditions must include both stratigraphic surface consideration (i.e., high density liquids flow stratigraphically downhill on confining unit), as well as traditional flownet constructions to evaluate the soluble water-borne product flow. This diluted contaminate flow will generally move in a similar manner as normal ground water. The procedure described above for the two-layer system must be extended to include flow components of the deeper unit. Hydraulic heads of the deeper unit provide the directional components necessary to construct the flownet. Figure 8-57 shows a three-layered system with hydraulic conductivity of 5*10-7 m/s, 1*10-5 m/s and 1*10-7 m/s, respectively, from top to bottom. Hydraulic heads are downward in all units. The flownet is extended through the various units down into the third layer with the appropriate reflection angles calculated from Equation 8-9. In the case of Figure 8-51, the angle of reflection is calculated as: 5*10-5 m/s / 1 * 10-7 m/s = Tan 66 ° / Tan x = 6.4° The refraction angle for the deep unit is 2.1°. Flow lines should be continued into the deeper layer using the calculated refraction angle. Scale considerations are important in these constructions. The 1:1 scale allows evaluation of facility boundary flow lines for monitoring system design. If the facility boundary flow lines enter

the third geologic unit before reaching the facility edge (where it can be sampled with traditional monitoring wells) considerations must be made to include the deeper unit within the monitoring program. This decision must also include evaluation of the relative hydraulic conductivity of the deepest unit; whether this unit is sufficiently permeable to represent a target monitoring zone. Low hydraulic conductivity geologic materials that represent confining units rarely provide good locations for groundwater monitoring (see ASTM D5092). If the deeper units show higher hydraulic heads, as illustrated in Figure 8-51, then an upward flow must be accounted for in the flownet construction. The procedures for construction of these nets are as above based on use of the tangent law. The completed construction shown in Figure 8-51 represents a flownet for a silty-sand and sand and bedrock units with the bedrock having upward gradients. Because the middle sand unit is acting as a discharging zone, it represents a target monitoring zone. Deeper bedrock (with upward gradients) probably represents a discharging environment from upgradient recharging areas such as bedrock upland areas. One must be sure to evaluate the recharge and discharge areas of the bedrock to be sure that the facility is not locally recharging the deeper bedrock unit in upland areas. This will probably require multipoint piezometer evaluations to assure that consistent upward gradients exist throughout the bedrock surrounding the facility area. As with the consistent downward ground-water flow conditions, as shown in Figure 8-52, discharging units provide the target monitoring

Figure 8-50 Silty Sand and Sand Layer Flownet Construction

548

CONCEPTUAL FLOW MODELS

Figure 8-51 Example Flownet Construction Three Layers

Figure 8-52 Example Flownet Construction, Three Layers with Downward Flow

549

CONCEPTUAL FLOW MODELS

Figure 8-53a Transformation of the Flownet

zone for the facility. If the discharging unit is very thick, the facility boundary flow lines may be contained within only a portion of the strata. In this case the detection monitoring wells can be designed with partial penetration of the discharging unit. However, local variations in hydraulic conductivity and piezometric heads may cause the flow to preferentially move into deeper portions of the discharging strata. With reasonably thick units (say 10 to 40 ft), a fully penetrating monitoring well screen probably represents a prudent target monitoring strategy. Homogeneous, Anisotropic Systems The hydraulic conductivity within the flow system as illustrated in the previous example was the same in all directions; at any given point this system was both homo-

Figure 8-53b Transformation of the Flownet

geneous and isotropic. In some sediments, such as clays and silts, microscale anisotropy is due to flat particles deposited in sheet-like beds. These tabular deposits decrease vertical hydraulic conductivity and result in relatively higher horizontal hydraulic conductivity. Aniso tropy (large-scale) can also result from lenses, channels or pockets of material of different hydraulic conductivity within a matrix. A medium that is predominantly clay but includes sand stringers or varved deposits (alternative graded bedding) will have a higher horizontal conductivity than clay without the sand stringers. When constructing flownets for anisotropic media,

Figure 8-54 Original Dimensions of the Section for a Homogeneous Anisotropic System

550

CONCEPTUAL FLOW MODELS

one must decrease the dimensions of the cross-section in the direction of the higher hydraulic conductivity or increase the dimension of the cross-section in the direction of the lower hydraulic conductivity. With a horizontal hydraulic conductivity kh greater than the vertical hydraulic conductivity kv , one must then reduce the reconstructed section to a narrower horizontal dimension or expanded to increase the vertical dimension. If the reverse is true (kv > kh), the cross-section after construction of the flownet is modified by dividing the transformed dimension by the expression used in the transformak kh

k kv

tion ----v- or ----h- . After the cross-section has been returned to its original dimensions, the flownet is reconstructed using the same number of flow lines and equipotential lines. Transformation such as this does not change the ratio of F to N and will not change any of the calculations made on the transformed section. The new flownet is composed of rectangles elongated in the direction of high hydraulic conductivity. Due to the reconstruction of the

Figure 8-55a Transformed Section of Equipotential Lines

net the intersections between flow lines and equipotential lines may not necessarily be at right angles. Figure 8-54 illustrates the procedure of returning a flownet to its original dimension, a value of horizontal hydraulic conductivity four times greater than the value of vertical hydraulic conductivity is used for the transformation. Figure 8-55b is the transformed flownet and Figure 8-56 is the flownet in the original scale. After transformation, the flownet must be rechecked to be sure that a reasonable construction is obtained. As a key to this reality check, the rectangles should be elongated in the direction of greatest hydraulic conductivity. As with the previous example the ratio of F to N will remain the same and

k v k h is used as the effective

hydraulic conductivity for construction with the transformed section. Example of a Homogeneous Anisotropic Flow System An example of a homogeneous anisotropic flow

Figure 8-55b Flownet Construction in Silty Sand Layer

551

CONCEPTUAL FLOW MODELS

system with the geology and system orientation of the site the same as that shown earlier in Figure 8-46 provides a simple case to evaluate. This example uses the same head distribution but has different hydraulic conductivity from that shown in Figure 8-47. Because this example only requires the additional consideration of the anisotropic silt layer we will only consider the flow construction in the silt layer. The silt layer had field hydraulic conductivity (slug tests) ten times the laboratory-obtained vertical hydraulic conductivity. The hydraulic properties of the silt layer are: kv= 5*10-7 m/s kh = 5*10-6 m/s ne = 0.25 The value of the square root of kv/kh for the section is 0.316. Several alternative adjustments can be used to obtain the necessary scale changes. The horizontal scale can be reduced to 31.6 percent of the original and/or both the horizontal and vertical scales could be increased or decreased so that the ratio of these dimensions is 0.316. In this example, the horizontal scale is 1 in. = 6 m and the vertical scale is 1 in. = 1.896 m (note that 1.896/6 =

0.316). The transformed geologic section is shown in Figure 8-55a. The flownet is constructed as if the sediments are isotropic, as shown in Figures 8-55 and 8-56. Figure 8-56 illustrates the boundary flow lines that originate in the facility area. Flownet Construction in Heterogeneous, Anisotropic Systems The process of conceptualization of a ground-water system requires bringing together much of the data gathered during the Phase II study. Several examples of this data organization are provided below. Subsurface information gathered during field drilling are typically edited into final boring logs and cross-sections as shown in Figure 857. These cross-sections, constructed through edited borehole logs, go through a second conceptual process of a generalized cross-section as shown in Figure 8-58. A generalized cross-section for the example area in the following subsection fully links conceptual hydrogeologic models and flownets to provide targeted monitoring locations for site assessment projects. This method provides the necessary location and depth information for both detection and assessment monitoring design. A descriptive conceptual model for an example site area will first introduce the conceptual process followed by the incorporation of flownet evaluations for the site area constructed as shown in Figure 8-58. The stratigraphic section contains five separate layers ranging from loose sand

Figure 8-56 Flownet Returned to Original Dimensions

552

CONCEPTUAL FLOW MODELS

to clay overlying limestone. A series of water level measurements was taken for shallow and deep unconsolidated aquifers and the limestone bedrock aquifer illustrated in Figures 8-59 to 8-61. The descriptive conceptual site hydrogeologic model developed from the geology, the potentiometric data, hydraulic characteristic test data and a general water balance has the following characteristics: 1. The system includes an anisotropic unconfined aquifer (sand unit with silts and clays) separated from a limestone aquifer by a semi-confining clay/

marl unit. There was strong evidence for a layer at shallow depth within the unconfined aquifer. 2. The unconfined aquifer may be considered to closely mirror the ground surface, as the variability in hydraulic conductivity is not significantly greater than one order of magnitude vertically or horizontally. Values of hydraulic conductivity in the aquifer vary from 10–3 cm/s and greater in the sand portions, to 10–4 cm/s in the hard, calcified zone.

Figure 8-57 Number of Geologic Cross-Sections for Site

553

CONCEPTUAL FLOW MODELS

3. The semi-confining aquitard separating the unconfined aquifer and the limestone aquifer is primarily a clay with hydraulic conductivity in the range of 10–5 cm/s. This unit is hydraulically discontinuous (leaky). 4. The limestone aquifer is fractured and/or dissolutioned and, therefore, quite heterogeneous. 5. The overall hydraulic conductivity of the limestone aquifer is on the order of 10–2 cm/s, but varies locally depending on the secondary hydraulic conductivity of the discontinuities (dissolution-widened joints). 6. Recharge for the area is occurring across the plateau where the landfill is located and discharge is in the valleys of the adjacent river system. 7. Ground-water flow in the site area is predominantly vertical down to the limestone and then horizontal toward the stream valleys. The conceptual hydrogeological model is based on the descriptions of site and vicinity conditions developed during Phase I and II investigations. Modifications in the flownet analysis have been made to account for variability of soil conditions within the unconfined aquifer, particularly downgradient from the site, in the northeast and east directions, where the available data indicate the surfical material to contain a greater clay content. The conceptual model was tested using flownet analyses and water balance estimates in selected flow tubes. Method of Analysis Figure 8-62 shows the geological section and hydrogeological parameters for the flownet analysis. The method used to define the hydrogeological flow regime near the facility is the graphical construction technique to account for heterogeneity and anisotropy in the system and using interpolated hydraulic heads based on field measurements. This construction was totally hand drawn without support of a numerical computer model of the system. The method used to develop the flownet shown in Figure 8-62 is described in Freeze and Cherry (1979, p. 174) and follows the procedure described below. Pertinent flownet calculations and the construction method for flow lines are shown in Figures 8-58 and 8-62.

554

Discussion of Flownet/Conceptual Model Results Once the linked conceptual hydrogeologic model is combined with a flownet construction, an important next step is evaluation of the results of the conceptual/flownet drawings. The facility site described above in the previous subsection provides sufficient data to fully evaluate the area flow system. The flownet analysis described above has shown the following: 1. Flow lines in the vicinity of the landfill are relatively steep (vertical) in the unconfined aquifer and horizontal in the limestone, indicating short flow paths to the limestone from higher elevations in the aquifer. This scenario is consistent with a recharge area having no significant topographic variations and a high hydraulic conductivity zone underlying a lower hydraulic conductivity semi-confining zone. Close to the discharge zone, the flow lines became more horizontal in the unconfined aquifer. 2. Average travel times for water movement from the facility, down through the unconfined aquifer, into the limestone and then to the vicinity of boreholes A-2 and A-3 is about 4.7 years through the unconfined aquifer and 2.5 years through the limestone, for a total of about 7 years. Travel times for other parts of the downgradient system, from surface to the limestone, are greater than 5 years, reflecting the lower hydraulic conductivity of the downgradient system. 3. The flow lines show that, under natural gradients, potential seepage from the facility would enter the limestone upgradient of wells A-2 or A-3 and should not be detected in the potentiometric surface zone at these well locations. A surface source of contaminants in the vicinity of wells A-2 and A3 would take some 3 to 4 years to reach the 50-foot level in either borehole. Thus, contamination of wells A-2 and A-3 is more likely due to activities in the areas of the wells than due to the facility. As described above the combination of conceptual models and flownets provide a powerful tool for evaluation of site ground-water movements and predictions of potential leachate flow directions so that geologic units can be targeted for the monitoring well design described in Chapter 9. The progression from simple homogeneous systems to more complex flownet constructions follows the basic progression as outlined above. Heterogeneous and anisotropic systems must include the additional factor

CONCEPTUAL FLOW MODELS

Figure 8-58 Geologic Cross-Section for Flownet Interpretation

of the ratio between vertical hydraulic conductivity and horizontal hydraulic conductivity in the uppermost layer of the system must be assumed to be representative of the directional ratio of conductivity in the lower layers. This assumption of kh>kv is based on unconsolidated or semiconsolidated geologic material. This assumption would apply for most unconsolidated sedimentary deposits with one exception. This one unconsolidated strata exception would be for vertically fractured glacial tills. Consolidated bedrock must also be evaluated for directional hydraulic conductivity. To begin construction of the flownet with heterogeneous anisotropic conditions separate flownets would have to be constructed for each hydrostratigraphic layer in the system by using information from the upper layer as the starting point for construction of a lower layer. Additionally, the dimensions of this new flownet would have to be adjusted to the conductivity ratio in the next layer and so on throughout the system. The following provides an example of the calculations and net constructions for a heterogeneous, anisotropic layered system.

Mass Balance Calculations Step 1. A typical geological section line (Figures 857 and 8-58) was chosen as the representative hydrogeological section for flownet construction. The section was divided into three subsections (for construction convenience), based on the geological interpretation of lateral variations in the soils in the unconfined aquifer. The subsections A, B and C are shown in Figure 8-58 and are based on an apparent increase in silt, clay and “mudstone” content in the soils towards the northeast. The division between the subsections is somewhat arbitrary because the geological log descriptions by various investigations were difficult to correlate. However, the divisions used correspond to descriptive changes in the lithology of the unconfined aquifer. Step 2. The geologic units in each subsection of the geological section are then assigned a hydraulic conductivity (Figure 8-58). In subsection A, the values correspond approximately to those

555

CONCEPTUAL FLOW MODELS

measured by field pump testing; in subsections B and C, the hydraulic conductivities were decreased to correspond to the increasing silt, clay and mudstone content of the geologic units. The values chosen are considered consistent with the geologic unit observed in field sampling programs. Step 3. Hydraulic heads for the upper unconfined zone, the lower unconfined zone and the limestone were interpolated from the potentiometric data shown in Figures 8-59 to 8-61 and are plotted on the geological section in Figure 8-58. The assumption is made that the limestone and unconfined zone are hydraulically connected, as there is no strong evidence at the facility for a continuous confining layer. Generally, the data indicate a slight ground-water mound near the facility, causing almost vertical flow and an increase in verticality of the equipotential lines toward the discharge zones to the northeast; this results in an increase in localized horizontal flow.

Figure 8-59 Potentiometric Heads Shallow Unit

Figure 8-60 Potentiometric Heads Medium Depth Unit

556

Step 4. Each subsection of the unconfined zone in the geologic cross-section was resolved as a homogeneous, anisotropic system by calculating a horizontal (Kh) and vertical (Kv) equivalent

Figure 8-61 Potentiometric Heads Deep Unit

CONCEPTUAL FLOW MODELS

hydraulic conductivity from:

Equation 8-13

Equation 8-14 The hydrogeological flownet is shown in Figure 8-62 where: b = total thickness of unconfined zone, ft bi = thickness of layer i in unconfined zone, ft Ki = hydraulic conductivity of layer i, ft/s. (assumed homogeneous & isotropic) n = number of layers

Step 6. For each subsection of the conceptual hydrogeologic section, the parameters required to calculate flow velocity, flow rate and travel times within flow tubes are computed. These parameters are; Ks~ the system hydraulic conductivity resolved from the hydraulic conductivity ellipse as shown below:

The calculations are shown in Figure 8-58, which also shows the conceptual model resulting from this approach. Step 5. Flow lines for each subsection were resolved, taking account of nonorthogonality with equipotential lines using the method of hydraulic conductivity ellipse constructions as described by Bear and Dagin (1965), Liakopoulos (1965) and Maasland (1957).

2

2

l Cos e Sin e ------ = ---------------- + -------------Ks Kx Kz

Equation 8-15

Source: Modified from Golder Associates

Figure 8-62 Hydrogeological Flownet 557

CONCEPTUAL FLOW MODELS

•

n, the material effective porosity, estimated as 0.20 in the water table zone and semiconfining unit.

•

i, the hydraulic gradient, computed as the change in head within the flow tube between the piezometric surfaces in the water table zone and in the limestone divided by the length of flow tube (LWT) above the limestone.

•

A, the area of the flow tube, taken as the thickness of the flow tube per unit width.

Equation 8-20

where: KLST = hydraulic conductivity in the limestone = 2*10-2 cm/s n = effective porosity of the limestone (0.1) i = hydraulic gradient in the limestone = 0.0027 Flow rate, QLST = AKi

Thus: where: A = area of limestone per unit width = 25 ft/ft

Average flow velocity =

Equation 8-21

Equation 8-16

where: LLST = distance from northeast corner of the facility to borehole clusters EMW-3.

Travel time =

Equation 8-17 Flow rate = Qwt = AKs • i ft3/year

Equation 8-18

Step 7. Potential recharge rate into the flow tubes is calculated using the flow rate in the flow tubes from: Q WT - ft / year r = ---------AS

Equation 8-19

where r = Potential recharge rate/flow tube in the saturated unconfined unit (ft/year) As = Surface area over each flow tube available for recharge (ft2) per unit width. The potential recharge rate/flow tube is checked against the published values for the site area of 10 to 16 in. per year. If the r values indicate each subsection is capable of taking this recharge, the calculation is considered acceptable. Step 8. Flow velocity, flow rates and travel times in the limestone unit are then calculated from:

558

8.6.9 Flownets in Special Settings Several special cases of construction of flownets for seepage face conditions and free surface/water table conditions are developed below. Because these conditions are important for interceptor trench design and discharge into excavations, the governing equations and construction procedures are important for many types of site assessments. Seepage Face Conditions Seepage face conditions developed in a saturated/ unsaturated flow system are typically considered a free outflow boundary, such as an excavation. Freeze and Cherry (1979) describe this phenomenon and analysis techniques for drawing seepage face flownets. The intersection of the ground-water surface and the ground surface at the excavation face defines the upper boundary of the seepage face. An example is a waste disposal site located adjacent to a riverbank (U.S.EPA, 1986). A shallow upgradient groundwater surface introduces water that passes through the waste area and flows through a layer of sand and silt that forms the top portion of the river bank. The watertable and river bank intersect at the top of the seepage face at an elevation of 315 m. A confining bedrock boundary is located below the sand and silt deposits. A piezometer located upgradient from the waste disposal area facility in an adjacent upland area shows that the

CONCEPTUAL FLOW MODELS

ground-water level is 10 ft (3 m) below ground surface during the high rainfall summer months. A conceptual model based on the cross-section shown in Figure 8-63 provides the basis for ground-water discharge calculation into the river. The flownet (Figure 8-64) uses the hill top as a constant-head boundary. The underlying bedrock is considered as a confining unit (impermeable boundary) and the water flows out of the seepage face. The exact top of the seepage face (see Figure 8-65) is unknown; however, trial and error estimates or approximate locations from observations in the field are the complicating factors in evaluating this type of field problem. The flow through a unit width represented by the cross-section is determined from the basic equation for flownet quantity calculations: Q = KFH/N

Flow lines are assumed to be horizontal and equipotential lines are assumed to be vertical.

•

The hydraulic gradient is assumed to be equal to the slope of the free water surface and to be invariant with depth.

An empirical approximation under these assumptions can be used to calculate flow, as follows: Q = k h(x) dv/dx

Equation 8-23

where: h(x) is the elevation of the ground-water surface above the datum used for the flow system at x.

Equation 8-22

where, in this example: F=3 K = 1*10-5 m/s H = 18 m N = 11

•

(from flownet) (from data) (from flownet) (from flownet)

Therefore: Q = (1*10-5m/s) (3) (18 m) /11 Q = 4.9*10-5 m3/s per meter of width Free Surface/Water Table Flow Conditions If the ground-water surface itself approximates a flow line, it represents a boundary and no vertical gradient exists is referred to as free surface flow. There are two methods (USEPA, 1986) that can be used to calculate flow for free surface flow conditions: •

Solve the flow problem using the Dupuit-Forchheimer theory to construct a flownet

•

Calculate the flow as in the previous sections

With a simple flownet construction method, however, the position of the entire free surface may not be known and errors may develop in the construction. To solve the flow problem where freesurface conditions are important the Dupuit-Forchheimer theory of free surface flow is used. This theory is based on two assumptions (U.S. EPA, 1986):

The gradient (dh/dx) is the slope of the free surface, Dh/ Dx at x (Figure 8-65). This equation in theory is representative of a free surface that forms a parabola. The DupuitForchheimer theory is believed to produce the most accurate calculated results when the slope of the free surface is small and when the depth of the unconfined aquifer is shallow (Freeze and Cherry, 1979). Figure 8-66a shows a simple conceptual cross-section in the direction of ground-water flow at a site where there is significant free-surface flow. To better illustrate the freesurface flow the figure is vertically exaggerated by a factor of 100. Dupuit-Forchheimer flownet is then constructed on the basis of the conceptual cross-section One flow path is used with each equipotential line representing the same drop in head (Figure 8-66b). The flow rate is calculated using the Dupuit-Forschheimer solution at point X1, where h(x) = 3.9 m. The quantity dh/dx, at Xl, is measured from the figure, resulting in dh = 0.6 m and dx = 115 m. Therefore, dh/dx = 5.2*10-3 m/m. Using the equation: Q = Kh(x) dh/dx

Equation 8-24

Q = (1*10-5 m/s)(3.9 m)(5.2*10-3 m/m)(l m) Q = 2*10 m /s 8.6.10 Area Flownets The flownet construction process described up to this point has been of vertical cross-sections, most useful for target monitoring zone selection. However, two-dimensional flownet analysis can also be conducted on water

559

CONCEPTUAL FLOW MODELS

table or piezometric surfaces: •

•

If it is assumed that there is no variation in hydraulic head vertically in the aquifer (Ferris et al., 1962, pp. 139-144).

Q = total discharge through the flownet q = discharge per unit thickness b = average saturated thickness of the aquifer The resulting relationship is:

If it is assumed that each equipotential line represents the mean in the vertical.

It is also required that the saturated thickness of the aquifer be constant for each of the above points because any variation in thickness from point to point causes a change in velocity from point to point. As an example, in order for discharge from the section to remain constant along each flow tube, the flownet would be composed of rectangles of varying length-to-width ratios. This would be a very difficult flownet to draw. A constant aquifer thickness is rarely observed in site assessments; however, sufficiently accurate flownets can be drawn where the variation in saturated thickness is small compared with the total saturated thickness. In these cases, an average thickness should be used to compute the discharge through the flownet. The equation: q = KH nt/nd

Equation 8-25

can be rewritten for area ground-water flow analysis using the relation: Q = qb where:

Equation 8-26

Equation 8-27 where: T = aquifer transmissivity nt = the number of stream tubes H = the total head loss through the region nd = the number of potential or head drops in the flownet If the area transmissivity is found to be anisotropic, the flownet can be transformed as described earlier for homogeneous anisotropic systems. Area-based nonhomogeneous regions can also be analyzed, but if more than two regions the flownets are difficult to draw and numerical models may be required to fully evaluate the flow system. Figure 8-66. represents a flownet of ground-water flow from a perennial stream to a discharging well (modified from Ferris et al., 1962, p. 142) An example of a flownet drawn for a discharging well located between a recharge boundary (a perennial stream) and a barrier boundary is shown in Figure 8-68. The well acts as an internal boundary of known head; therefore, the value of each equipotential drop is determined from the head difference between the perennial stream and the well.

Figure 8-63 Seepage Face Conditions Example

560

CONCEPTUAL FLOW MODELS

Figure 8-64 Flownet for Seepage Face Example

Modified Area Flownet Analysis A modified method of area flownet analysis can be developed using a map of either ground-water surface or piezometric contours. For each area being studied in a given region, two flow lines are drawn and used as limits for vertical cross-sections along selected contours (Figure 8-64). As with the previous area flownet analysis the assumption must be made that hydraulic head and conductivity do not vary with depth to compute flow through the aquifer at the selected cross-sections. A flownet made of exact squares does not have to be drawn, so aquifer conductivity and saturated thickness can vary somewhat within each area being studied. Also, unsteady-state cases can be analyzed approximately. It is convenient to position each cross-section at the average distance between two successive contours. In order to compute the flow across each cross-section, a convenient form of Darcy’s law was developed by Foley et al. (1953) from the form Q = TiW by defining: i = C / La

Equation 8-28

where: La = Axy / W c = contour interval for equipotential Axy = surface area bounded by the two successive contours and the limiting flow lines W = average width (i.e., parallel to contours) within Axy. Figure 8-68 illustrates two cross-sections bounded by

two flow lines. In this case flow across both cross-sections would be computed. The surface area of the total area being studied in Figure 8-68, AQ is represented by the vertical line pattern. The areas, (Axy)1 and (Axy)2 are represented by the diagonal line patterns. The subscripts, 1 and 2, refer to the two cross-sections across which flow is being computed. If there is vertical leakage into or from an aquifer bounded by a confining bed above or below, it can be computed from Walton (1962, p. 22): Qc = K'Ac 6h / b'

Equation 8-29

where: Qc = leakage through the leaky confining bed K' = vertical hydraulic conductivity of the leaky confining bed Ac = area of leaky confining bed within the study area 6h = difference between the head in the aquifer and the head at the distal surface of the confining bed b' = the thickness of the confining bed As with cross-sectional net constructions, flow lines are refracted across a conductivity boundary. If the conductivity contrast is large enough, the 90o refraction implied by horizontal flow in the aquifer and vertical flow in the confining bed (or aquitard) is a good approximation. A simple construction where vertical leakage take place between units is shown in Figure 8-69. The conceptual model shows leakage from aquifer A to aquifer B through the confining bed. Leakage occurs because the watertable is higher than the piezometric surface for aquifer B.

561

CONCEPTUAL FLOW MODELS

Al = the map areas between the two assumed flow cross-section and the limited flow lines in ml2 (see Figure 8-69). If a leaky confining bed is present then Al = Ac. S = coefficient of storage (dimensionless). This will equal Sy for an unconfined case. an average rate of water table or piezometric surface rise in ft/day calculated as: (average h in the area at time t2 - average h in area at time tl)/(t2 - tl), t2> tl). The quantity will be negative for a decline. I = discharge rate in the section in gpd. Rs = net recharge rate in gpd/mi2. This variable is assumed to represent the balance between the actual average recharge rate and the average ground-water evapotranspiration rate over the interval of time, 6t.

Figure 8-65 X and h(x) for Dupuit-Forchheimer Calculations A general water balance or continuity equation can be formulated to apply to the section of aquifer between the limiting flow lines and two cross-sections. This equation is derived from Equation 8-29. Q1 - Q2 = AlSf(t)6h/6o + D - R

Equation 8-30

The last term in Equation 8-31, Qc, is positive for leakage from the aquifer. Equation 8-31 contains several assumptions. The most important ones are:

It represents a modification of one presented in Walton (1962, p. 22) and is stated as:

•

Ql - Q2 ' = 2.1*108 AlS 6h/6t + D - RsAl + Qc Equation 8-31

Vertical flow exists through confining beds and horizontal flow exists through the aquifers (see Figure 865).

•

Dupuit’s simplifying assumptions hold for analysis of watertable aquifers. In this case, T = Kb where b = f(h)

•

Conductivity at all elevations in the aquifer or confining beds is equal.

•

No changes in storage in the confining bed(s) takes place during the time interval Dt.

where: Ql - Q2 = average difference in discharge in gpd between the two cross-sections during the time interval t computed using Equation 8-24. The discharge Ql is upstream from Q2.

Figure 8-66 Cross-Section for Free-Surface Flow 562

Figure 8-67 Cross-Section for Free-Surface Flow

CONCEPTUAL FLOW MODELS

•

Darcy’s law is valid.

•

The coefficient of storage for the aquifer is constant.

The above assumptions are rarely fully met in practice and average values are assumed to be constant numbers. As with any assumptions used for hydrogeologic evaluations, large deviations from the assumptions can produce large errors. This method is very useful where the assumptions are appropriately met and where all but one of the quantities in Equation (8-30) are either known are can be shown to be negligible. Unknown values can be computed for a number of areas in the region covered by the watertable or piezometric maps and geological data. The method also can be used to check the consistency of data when all of the quantities can be estimated using other methods. The equation should approximately balance for all areas in the region. 8.7 FLOWNET/CONCEPTUAL MODEL FORMULATION IN EXAMPLES The process of conceptualization of a ground-water system requires bringing together much of the data gathered during the Phase II study. Several examples of this data organization are provided below. Subsurface information gathered during field drilling is typically edited into final boring logs and cross-sections as shown in previous

Figure 8-68 Symbols Used in Areal Flownet Analysis

sections. These cross-sections, constructed through edited borehole logs, go through a second conceptual process of a generalized cross-section. A generalized cross-section for each of the example areas fully links conceptual hydrogeologic models and flownets to provide targeted monitoring locations for site assessment projects. This method provides the necessary location and depth information for both detection and assessment monitoring design. A descriptive conceptual model for any example site area will first introduce the conceptual process followed by the incorporation of flownet

Figure 8-69 Flownet from Stream to Discharging Well 563

CONCEPTUAL FLOW MODELS

evaluations for the site area. The descriptive conceptual site hydrogeologic model is developed from the geology, the potentiometric data, hydraulic characteristic test data and a general water balance. Once the linked conceptual hydrogeologic model is combined with a flownet construction, an important next step is evaluation of the results of the conceptual/flownet drawings. The facility sites described in the following subsections provide sufficient data to fully evaluate the area flow system using the descriptive visual drawings. These images range from flat two-dimensional representations to full-color artist renderings. While such involved images may not be necessary for basic Phase II reports, drawings prepared by specialized technical illustrators can give the public the basic idea of ground-water flow in complicated hydraulic systems. The following section provides conceptual models that range from consolidated rock to Karst limestone. Each example describes the geology and hydrogeology through text and illustrations. Each of these examples is for illustration purposes and should not be confused with actual facilities as these data support the illustrative example. 8.7.1 Example of Consolidated Rock An example of the conceptual model building and linkage with flownet construction in consolidated rock provides insight into the process of conceptual model building. The following example is based on semiconsolidated deltaic sandstone and claystone bedrock with sand channel deposits. The geologic units on site consist of unconsolidated deposits and bedrock of the Denver and Arapahoe Forma-

tions. The upland area along the north and east portions of the site area typically consists of surfical materials (alluvium, colluvium, residual soil and weathered bedrock). These consist of silty clays and clayey sands with isolated cemented layers. Underlying the surfical materials (exposed on the cliff face) are interbedded claystone, siltstone and sandstone of the Denver Formation. Underlying the Denver Formation is the Arapahoe Formation, locally characterized by coarse sandstone and conglomerate with interbedded siltstone and claystone. The contact between the Arapahoe and Denver Formations is believed to be near the base of the topographic expression of the site’s cliff face. In an earlier geologic study of the area, investigators divided the bedrock exposed along the cliff face into the upper and lower units of the Dawson Group. Because the northern portion of the face has been covered with solid waste materials (see Figure 8-71) since the time of the previous study, their description of the two units is highly descriptive of the facility lithology repeated as follows: The Upper Unit is well exposed on the site and is characterized by an interbedded series of sandstones, claystones and siltstones. It is estimated that sandstone comprises 60% of this unit while the siltstone and claystone comprise about 40%. The sandstone within this unit is characteristically tan to light brown in color and varies from arkosic and medium to coarse grained to fine to medium grained and silty to micaeous. Scattered throughout the unit is petrified wood and carbonaceous debris.

Figure 8-70 Vertical Leakage to a Confined Aquifer

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THE CONCEPTUAL MODEL

Within this unit are a few resistant, ledge-forming sandstones which range in thickness from only a few inches to an estimated 20 ft. Although these resistant ledges and cliff formers dominate the topography by virtue of the ledges and cliffs that they form, it is estimated that they make up 10% or less of the exposed unit. The sandstone in this Upper Unit typically exhibits laminations from magnetite grains and small to large scale cross-bedding. A few of the thicker sandstones are lenticular in nature and can be seen to pinch out or are reduced from thicknesses of 20 ft to somewhat less than 2 ft within the perimeter of the site. Other sandstones are more or less tabular and can be traced for considerable distances across the site. The thicknesses of the various sandstone beds range from only a few inches to approximately 20 ft. The claystones and siltstones that are interbedded with the sandstones in the upper unit are typically gray to brown to tan in color and range from a few inches to about 8 ft in thickness. Only about 20 to 30 ft of the Lower Unit is exposed onsite. The contact between the Upper and Lower Units is drawn at the base of a distinctive white sandstone marker bed that is well exposed on the ridge crest in the south/cen-

A

tral portion of the site. Although this white marker bed is not entirely continuous and dies out in the central portion of the site in the main canyon area, it also occurs west of the main drainage on the prominent ridge. The lower unit may correspond to the Arapahoe Formation as referred to in this report. Regardless, because the Denver Formation is reported to be about 200 ft in this area, it is probable that the Arapahoe Formation bedrock underlies the surfical deposits on the canyon floor area of the site. surfical deposits at the site below the cliff face consist primarily of alluvium. The majority of the site topography at the base of the cliff topographic feature has been altered due to site activities. Prior to site regarding activities, alluvium occurred at the base of the cliff face and along the former surface drainage features. Conceptual Hydrogeologic Model A conceptual flownet of the site is presented in crosssection in Figure 8-71. The site is characterized as a ground-water recharge area for the Denver Formation beneath the upland area of the site and the Arapahoe For-

Predominately vertical flow through near surface fractures in the finegrained siltstones and claystones

Isolated seeps occur where the perched ground-water flows in the sandstone intercept stream canyons walls

Perched ground-water. Predominately horizontal flow in coarse-grained sandstones where discharging to the local stream systems

P-6

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TYPICAL SECTION THROUGH FACILITY LOOKING NORTH MUNICIPAL REFUSE

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Primary lateral flow through thin zone of saturation in the alluvium P-5 P-2

E TION) FLOW LINANT FLOW DIREC (RESULT

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B

Individual perched water zones in isolated sandstone units. If no discharge point, predominately vertical flow

Figure 8-71 Low Hydraulic Conductivity Materials with Channel Deposits

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THE CONCEPTUAL MODEL

mation on the canyon floor beneath the landfill. Figure 8-71 presents an approximation of the uppermost water table. The water level data indicate that the cliff face causes a localized alteration of the regional flow system in that a watertable divide is present near the crest of the ridge. To the east and north of the ground-water divide, the primary direction of flow in the Denver Formation is laterally toward the southeast through erratically distributed, more permeable sandstone lenses. To the south and west of the ground-water divide near the cliff face, the direction of ground-water flow in the Denver Formation is toward the site cliff face. An enlarged view of the flow paths is presented in Figure 8-71. Anisotropic geologic conditions cause ground water to flow toward the cliff face laterally within more permeable sandstone lenses. Vertical leakage occurs beneath the sandstone layers through subvertical fractures within less permeable siltstone and claystone units. As observed during cliff face reconnaissance, vertical leakage occurs at a greater rate near the cliff face because fracture frequency and width increase towards the cliff face due to stress relief from natural erosion. The results of in situ testing during the field program indicated that the hydraulic conductivity of subgrade materials on the excavation bench is about 6* 10-6 cm/s. This value is greater than the average hydraulic conductivity value as measured in the canyon floor 1*10-6 cm/s. As shown in Figure 8-71b, the resultant direction of flow along the cliff face roughly parallels the cliff face. The conceptual flownet shown in Figure 8-71b has been constructed to reflect differences in hydraulic conductivity in the horizontal and vertical directions of flow. The ratio of 100 horizontal to 1 vertical is used to represent the anisotropic conditions within the stratified sedimentary rocks typical of those occurring at the landfill (Freeze and Cherry, 1979). As a result of the transformation, streamlines and equipotentials are not orthogonal, but rather are deformed in the direction of the observed higher hydraulic conductivity. 8.8 CORRELATION OF FLOWNETS AND GEOLOGIC STRUCTURES Structural effects on ground-water flow are often misinterpreted in site assessments. While the effect of layered strata of different hydraulic conductivity on the flow system is represented by the tangent law, dipping beds of variable hydraulic conductivity require considerable care in the linkage between the conceptual model and flownet construction.

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8.8.1 Dipping Geologic Structures Figure 8-72 illustrates alternative flownet constructions for dipping heterogeneous rock. Section B-B (Figure 872a) was originally drawn using the head levels observed from a series of multiple point piezometers located along the cross-section line. This flownet shows almost vertical equipotentials and the resultant almost horizontal flow lines. If the site geology were composed of relatively homogeneous/isotropic units this interpretation would be acceptable; however, the real world geologic conditions are alternative shales and sandstones with significantly different hydraulic conductivities. Although the equipotentials drawn in Figure 8-72a agree with the head levels observed in the section’s piezometers, this construction is not unique and requires further consideration to obtain a more representative flownet. Figure 8-72b shows a redrawn net, where consideration of the variable hydraulic conductivity has refracted the flow lines to represent the tangent rule. The equipotential lines have been drawn to reflect the likely head loss through the lower hydraulic conductivity geologic units. The redrawn net provides a more consistent example of flow conditions represented by the dipping alternative shales and sandstones. This is especially important for consideration of the depth required to screen monitoring wells for both detection and assessment monitoring design. Alternatively layers of dipping bedrock must be evaluated for the effects of fracturing as a modifying feature to the geologic units variable hydraulic conductivity. In some cases the resultant effective hydraulic conductivity (which is a combination of primary and secondary porosity) can modify flow conditions so that relative recharge/discharge relationships can hold true. For example, although unfractured hydraulic conductivity of the sandstone/shale geologic units of the section would vary 3 to 4 orders of magnitude, the fractures interconnecting the two units have modified the effective hydraulic conductivity of the units to one order of magnitude. Hence, ground water can discharge through the various layers to downgradient discharge points along the section shown. This model is especially important for sites with old (pre-1980s) cells that were likely constructed unlined or for sites with uncontrolled disposal as you may find with RCRA corrective actions or Superfund sites. In those cases where fractures are not significant as a modifying factor for increasing the effective hydraulic conductivity, the discharge along strike of the geologic units would be more likely flow directions for ground water. Figure 8-73 illustrates a regional conceptual model of an anticlinal structure source to depths of 2 km deep based on oil and gas explorations. A facility based on a limb of the anti-

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Figure 8-72 Alternative Flownet Construction - Layered Rock

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567

THE CONCEPTUAL MODEL

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THE CONCEPTUAL MODEL

ied hydraulic conductivity. In effect, if one could show head elevations behind the two-dimensional surfaces of the paper you would see lower hydraulic head elevation in each of the sandstone units. Respectively, a similar view in front of the paper’s surface would also show a lower hydraulic head value for each of the sandstone units monitored. We, therefore, have at least locally a mounding condition along the strike of the sandstone units. Hence, ground-water flow is parallel to the strike of the bedding and flownets must consider the individual sandstone units as bounded by the claystone confining units. Because mounding exists in this particular hydrogeologic environment, flow conditions should be represented by a localized flow cell discharging in either nearby adjacent areas or down toward the regional discharge flow system. Additional flow considerations with layered dipping bedrock systems must also address down-dip movement of ground water, if the down-dip strata are discharging to a lower head aquifer system or to a lower surface water discharge point. The particular example used above was part of a major deep-seated basin of highly saline brines that were neither connected to potable water aquifers nor discharging to surface waters. In this case, downward movement of the ground water down dip was considered as not important because the overall majority of the ground-water flow was along the strike of the sandstone units. This conceptual model illustrates the importance of a rigorous understanding of the site geology and hydrogeology before designing a monitoring program. Without adequate understanding of hydraulic head conditions, in a

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Figure 8-73 Anticline Regional Structure

cline could be expected to overlie dipping rocks as shown in Figure 8-73. The individual beds consist of alternating claystone and sandstone layers that have at least three orders of magnitude different hydraulic conductivities. Fractures are not significant in this particular situation so flow conditions can be expected to be highly modified by the layered rocks. This condition is highlighted by site piezometer data that show inconsistent head level data for each of the sandstone units monitored. Although the head levels have higher elevations in the upgradient piezometers, monitoring head levels in intermediate sandstone units illustrates the inconsistencies in the flow system due to the highly var-

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Figure 8-74 Dipping Bedrock Structure

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Site Formation Water Surface

THE CONCEPTUAL MODEL

• Strong upward vertical gradients are observed in piezometer sets near surface water discharge points. • Similar strong upward gradients are found on the opposite side of the surface water. Unsaturated Vadose Zone Piezometric Surface

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Figure 8-75 Vadose, Unconfined and Confined Conditions three-dimensional sense, it would have been highly unlikely that a resultant monitoring system with widely screened zones would have sorted out the overall components of flow. Dipping heterogeneous rocks must have piezometers installed in lithologic borings with very accurate logging and testing data to evaluate the potential for ground-water flow parallel to the strike of the rock mass. Additional complications such as secondary porosity through fracturing must also be fully evaluated before any consideration is given as to the position of the facility monitoring well system. 8.8.2 Flownets Discharging to Streams and Wetlands The discharge of a ground-water aquifer to surface water bodies is an important situation that must be evaluated to define the potential limits for assessment monitoring investigations. As was illustrated in sand tank and computer numerical models, discharge to areas of low hydraulic head represents the area to which neutral density leachate plumes must move. Figure 8-76 illustrates a flownet of a system that fully discharges to the local stream system between the elevations of 1300 to 1400 ft msl. Keys to the interpretation of these flow systems can be listed as follows: • Very low or neutral vertical gradients are observed in piezometer sites in upland areas. • Strong horizontal gradients are typically found.

• Confining units may be found underlying the shallow flow cell which limit downward movement of ground water. Figure 8-77 shows a classical case of almost complete discharge of the cross-sections flow to the stream discharge zone. In this case because discharge passes by the stream deeper monitoring may be required to evaluate if this flow may be affected by contamination. Considering this illustration represents a 10:1 scale from horizontal to vertical, the actual flownet would have been virtually flat within the area of the net construction. Deeper piezometers extending down to a regional flow system may have shown groundwater flow lines moving beyond the local discharge area of the stream. This condition is shown in Figure 8-76, where the shallow flow systems discharge to larger rivers. Keys to interpretations for these systems must be based on: • Stronger downward gradients than observed in a fully discharging system • Downward gradients in deeper piezometers adjacent to local streams • High density leachates that have moved to deeper systems • Unbounded systems where no confining units exist at depth The importance of establishing the limits of these discharging cells cannot be overemphasized. The scope of the investigative program, risk assessments, assessment monitoring system design, remedial system design and well census data collection activities is directly related to the potential for affected ground water to move past a local discharge boundary. 8.8.3 Example Facility with Structural Complications The basic goals of data analysis and interpretation are to increase one's knowledge and understanding of site conditions, both surfical and subsurface, through evaluation of data collected during Phase I and Phase II projects. The following example represents the logical development of the

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THE CONCEPTUAL MODEL

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Figure 8-76 Shallow Flow System Discharge to a Large River

monitoring target zones for a large facility with a number of geologic complications. These analyses and interpretation efforts attempt to define the actual field conditions and hydrogeologic processes based on the necessarily limited sampling and observation points used during the field program. Site assessment projects may have many data analysis aspects. They may include identification of conceptual physical models of the subsurface, definition of previously unknown conditions, and establishment of recurring physical patterns and ultimately determination of the physical or chemical causes of the phenomenon under investigation. This example facility has developed a consistent picture of the geologic and hydrogeological site conditions through the Phase II investigations conducted over a two-year period. These data combined with the regional literature provide a comprehensive evaluation of the facility's ground-water flow system sufficient to protect human health and the environment under Texas Natural Resources Conservation Commission (TNRCC), now the Texas Commission on Environmental Quality (TECQ) requirements.

570

The data elements used to develop the conceptual model for this Texas example were developed through many lines of investigation to understand the subsurface spatial variability. For example, in Chapter 7, Pictograph Figure 7-1, spatial variability is established through a number of alternative evaluation techniques (e.g., logging lithology, hydraulic conductivity testing, hydrochemical testing). Each technique gathers independent data on the conceptual model representing the site. Site assessments require the analysis and interpretation of large volumes of data; however, much of the data can be distilled into a conceptual model of the facility that addresses what is seen in the field and interpreted in the evaluation techniques. These models greatly aid in the establishment of geologic and hydrogeologic criteria that ultimately support design components of placement, design of the ground-water monitoring system, and evaluation of potential remediations. Many of the deliverables of a Phase II study are developed and refined during data analysis and interpretation. Data analysis begins in the field during collection of the basic geologic and hydrogeologic data within the various

THE CONCEPTUAL MODEL

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Figure 8-77 Shallow Flow System Discharge surface and subsurface mapping tasks. This analysis and integration continue in the office where raw field data are reduced and combined with laboratory-derived information. The resultant data are combined into various tabular, map, or cross-sectional presentations relating observed field conditions with important site criteria that affect potential disposal actions at the site. The specific conceptual model issues important for the design of the ground-water monitoring system at the example facility can be addressed as a series of questions: • Is the nature of ground-water flow at the example facility due to primary (intergranular) or secondary (fractures) porosity? • What is the ability of the saturated units to yield water to monitoring wells and potentially to the excavation? • Does the marker unit (in this example a unit called the Glauconitic Sands) represent a potential flow path?

• Do the geologic faults mapped on site represent potential flow paths? These questions are typical for site assessments that would normally by addressed by the data obtained from the Phase II investigation. These can be specifically answered by the conceptual model developed for the facility. What is the Mode of Ground-Water Flow at the Example Facility? Establishment of the mode of ground-water flow at the example facility was one of the main goals of the Phase II investigations. Every site assessment will have this issue as one of the important aspects of the site that must be understood before designing a monitoring system or remediation. The project included extensive field and laboratory techniques to establish this most basic of conceptual understanding. The example facility regional area is geologically well described in the literature and local geological conditions have been evaluated through numerous exploration boreholes, as described in this section. The data gathered from individual boreholes were linked together as cross-

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THE CONCEPTUAL MODEL

marker zone

Figure 8-78 Cross-Section of Site Area sections and fence diagrams. These lithological datasets provided the initial evaluation required for designing ground-water monitoring systems under Subtitle D standards. The second supporting dataset was developed from piezometer and monitoring well hydraulic heads obtained from hydrostratigraphic layers. Figures (photographs) should be provided to illustrate the nature of the subgrade materials present at the example facility when making the case to the state regulatory staff. These photographs of the core are obtained during the expansion drilling program to show the fine-grained matrix of the geologic units. This core would then be used in a series of laboratory tests for both hydraulic conductivity and particle size grading curves to show the very limited potential for primary porosity ground-water flow at the example facility. The particle size analysis results show two types of grading curves. These curves show that 90% of these representative geologic materials under the site are composed of silt and clay-sized particles. The matrix hydraulic conductivity of these units is very low, probably on the order of 10-8 cm/s.

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The second characteristic type of grading curve represents a sandy fraction with significant silt and clay fractions. Despite having more than 50% sand-sized particles, the considerable fine-grained fraction fills in the void spaces between the sand grains in this unit. The resultant geological units have very low hydraulic conductivity, which was confirmed through a geotechnical test for hydraulic conductivity at a depth of 90 ft below ground surface. This test showed a hydraulic conductivity of 7*10-8 cm/s. A second line of information on the likely mode of ground-water flow is the core data collected during the Phase II investigation. Visual inspection of the core data shows the importance of fractures in the movement of ground water at the example facility. The core collected showed fractures with oxidized surfaces and weathered clay adjacent to the fractures. These data link the groundwater flow to fractures rather than intergranular flow through the geological units. In conclusion, the field and lab data confirm that ground-water movement at base-grade depths at the example facility are likely due to fracture flow in fractures that

THE CONCEPTUAL MODEL

are generally filled with weathered clays or secondary minerals.

Piezometers and wells installed in the expansion area do provide sufficient points of information to establish the ability of the geological units to yield water to monitoring wells at the example facility. Figure 8-79 shows a comparison of a number of piezometer readings. These comparative head level data provide some of the most useful information collected in field collection activities. In general terms, the target monitoring zones for the expansion area must be located in fractures connected to the base grades. These fractures will likely be saturated approximately at the basegrade elevation, but will yield ground water only sparingly to monitoring wells. The excavation down to base-grade elevations will provide the final evaluation of the ability of the interconnected fractures to yield ground water to the excavation. The excavation slopes and base in this case would be cleaned off and fully mapped for fractures and potential ground-water inflow points. This inspection allows for the location of required excavation treatments for control of fracture flow and selection of points for drilling of environmental monitoring wells at base-grade depths. It was expected through evaluation of the disposal methods, that fractures will rarely provide significant ground-water inflows to the excavation due to the low porosity of the fractured units. The carbon-14 results collected to establish flow rates demonstrated that very little ground-water flows occur at the depths of the proposed excavation. Age dates at depths of only 85 ft below the ground surface showed the ground water on the order of 6,000 to 14,000 years old. An important point here is to back up the environmental data in as many ways as possible. This example has important implications to remediation projects in that alternative methods other than the repeated collection of water quality samples should be evaluated to support the primary line of field data. The important lines of evidence must be specific to the site in question, because the unique geology and hydrogeology of the site combined with the target compounds disposed and the mode of disposal go back to the geology and hydrogeology of the site area.

the Glauconitic sands (gray zone labeled Marker Zone in Figure 8-78) shows the ground-water occurrence in the sands. There are four main points regarding the evaluation of the Glauconitic marker sands as a potential target monitoring zone for this facility: (1) Is the sand present throughout the basegrades of the expansion? (2) Is the Glauconitic marker sand saturated?. (3) Do the Glauconitic marker sands have sufficient hydraulic conductivity to serve as potential target monitoring zone. (4) Will the sand be excavated out to reach base-grade depths? Taking points one and four first, the Glauconitic marker sand unit is either missing (due to a northwest trending fault that crosses the site) or will be removed during the excavation process for the majority of the expansion area. In addition, only a few saturated areas would remain adjacent to the base grades of the facility and even if saturated, the Glauconitic sands have such low hydraulic conductivity that they would not yield ground water in sufficient quantities to provide an effective monitoring system. Only two piezometers located in the Glauconitic sands showed any significant piezometric head levels. The sandy unit, in addition to the above, is located above the proposed base grades by at least 20 ft and would be removed from the excavation area. One piezometer showed the only significant saturated Glauconitic marker sand unit in the expansion area with 26 ft of head. Under normal circumstances this completion would serve as a target monitoring zone; however, two factors make this location questionable. First, the Glauconitic marker sand is unsaturated up the dip slope (stratigraphically uphill from the monitoring point at PP-7XD), hence ground water flows are not necessarily coming from the area of the expansion. Second, the Glauconitic sands are so impermeable with a large proportion of clay intermixed with the sand that wells completed in this zone are expected to produce only limited quantities of ground water. As such the Glauconitic sands would not make acceptable target monitoring points for the expansion area. This aspect of understanding the low hydraulic conductivity of the unit has implications for alternative remedial methods that may be applied to the marker zone if this unit was a target for remediation. The remedial technology to be applied, the methods used to make that application and the time it may take to remediate the target are all rolled into the hydraulic conductivity of the specific unit to be remediated.

Does the Glauconitic Sands Marker Unit Represent a Potential Flow Path?

Do the Geologic Faults Mapped on Site Represent Potential Flow Paths?

Because this marker unit represents the only potential zone that contains sandy sediments, it became the center of interest for agency staff. Figure 8-78 shows the thickness of

Geological cross-sections trending north-south all show an interpreted fault line through the expansion property. These data show the interruption of the marker sands unit

What Is the Ability of the Saturated Units to Yield Water to Monitoring Wells and Potentially to the Excavation?

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THE CONCEPTUAL MODEL

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Date of Reading

Figure 8-79 Head Levels in Piezometers due to the throw of the fault. Faults in general terms can serve as pathways through increased fracturing or as barriers to ground-water flow. In the context of the example facility, we have not seen positive indications as to the fault serving as either a preferential pathway or as a barrier to ground-water flow. The piezometers placed adjacent to the fault do not show unusually high or low hydraulic heads and the fault looks as though it is hydraulically neutral to ground-water flow. The handling of hydraulic heads adjacent to faults are the best way to establish if structural units such as faults are flow zones or barriers to ground-water flow. The excavation process down to base-grade elevations provides the most effective mapping of the fault and associated fracture systems. The excavation was mapped geologically and the orientations of all significant fracture systems were recorded before installation of the liner. These data were used to evaluate the potential ground-water yielding ability of the fractures associated with the faulting. These data also were directly used for design of the environmental monitoring system.

574

Conceptual Ground-Water Flow Sufficient data were gathered to verify that, in general terms, consistent downward ground-water gradients present at the example facility expansion property. Because the overall hydraulic conductivity for the base-grade bedrock is generally less than 10-7 cm/s (and are typically measured in the 10-8 and 10-9 ranges), the movement of recharge ground water to deeper geologic units is very slow. Carbon-14 age dating measurements for the example facility deep piezometers ranged from 6,200 to 14,000 years before the present. These data were collected from piezometers completed at 100 ft. Deeper ground water would be expected to have significantly older age dates. The only potential for somewhat faster ground-water movement would be within interconnected fracture sets associated with regional structural stresses and near-surface shrink-swell fractures (see Figure 8-79 and Figure 8-80). Piezometer P-8S was completed between 26.50 and 31.50 ft below the ground surface in a shallow fracture zone. The age of the ground water from this shallow piezometer was established as less than 8 years old. A well screen com-

Ground Water Is Recharged Along Fracture Sets Main Fracture

(a.)

Stratum Flow Alon

g Top of

I

Clay

Recharge of fracture during wet season into clay

(b.)

(e.)

Fractures Transmit Ground-Water Heads to Deeper Piezometer Completions

1m Stratum

Fracture Hydraulic Head Level Transmitted to both Piezometers with Minor Head Loss but Restricted Flow Along Fracture

II

Depth of Exploration Approx. 150 ft Lower Ground Water Surface Stratum

I

Str a

tum

3m Fractures Become Tighter with Depth

Stratum

Str a

II

Flow Alon

II

tum

I

III

Fr a Tig ctu r Du hter es B Mi e to withecom ne Se D ra co ep e liz ati nda th on ry

Increased Fractures Adjacent to Structure Causes Ground water to be Found at Lower Levels

Increased Fracture Sets Adjacent to Structure Cause a Lower Ground-Water Surface

tum

Stra

g Top of

Claystone

tum tra

I

S

a Str

tum tum

P-8D

(d.)

P-8S

II Stratum I

Young Ground Water < 8 Years Old

III

a Str

10 m Stratum II Stratum III

Ground Water 6210 Years Old Deeper Ground Water is Very Old (14,000 Years)

14C

Age Dating Results Agree With Conceptual Flow Model

Stratum StratumI I

Young Ground Water

10 m (c.) Few fractures Continue Through Stratum II Stratum II

Not to Scale

Shallow Ground Water Circulation Is More Rapid Due To More Fractures Near Stratum II Top

Figure 8-80 Conceptual Model of Flow

Regional Studies Show Claystone Extends to Depth

Conceptual Model of Ground-Water Primary and Secondary Flow Systems

575

THE CONCEPTUAL MODEL

Ground Water Circulation Very slow

THE CONCEPTUAL MODEL

pleted 75.30 to 80.30 ft below the ground surface showed a carbon-14 age date of 6,210 years. These data show that it took 6,000 additional years for the ground water to move 50 ft down from the shallow zone at this location through the matrix of this unit. Figure 8-80 and Figure 8-81 together illustrate the conceptual model for ground-water flow at the example facility. Piezometers could be completed in either a fracture set or within essentially unfractured bedrock matrix. The performance of the piezometer is a direct result of the connectability of the screened area of the piezometer to a fractures that provides secondary porosity to the bedrock matrix. The observed ground-water head levels in the piezometers completed at the example facility and the expansion area are in effect a direct result of the density of interconnected fractures adjacent to the piezometer completion. Piezometers were completed in a shallow system where the flow is almost equivalent to a primary porosity (granular) system. Head levels may be reasonably stable (as in piezometer P-8D) or have many rapid fluctuations as seen in piezometer P-7S shown in Figure 8-79. In shallower stratum zones where there are fewer fractures, one can observe rising water levels during wet seasons and conversely during dry seasons, falling ground-water head levels due to the lower effective porosity of these areas. In general terms the shallow units would have very young ground waters as confirmed by carbon-14 age dates from piezometer P-8S. In deeper zones of stratum II, where there are more fractures adjacent to the piezometer completion the rise and fall of heads can be much more rapid (see Figure 8-79) piezometers P-7D and P-8D) than in relatively less fractured areas. Farther away from a fracture, the ground-water hydraulic heads rise or fall much more slowly. For piezometer completions finished in true matrix bedrock (unfractured) the ground water pressure heads remain stable throughout the year (see Figure 8-80, piezometer P-9). Because the overall hydraulic conductivity for the base-grade bedrock is typically less than 10-7 cm/s, the localized hydraulic heads are a result of the density of fracturing occurring within a particular geologic unit. The stratum II zone has many more fractures in the upper levels and these fractures die out toward the base of stratum II. Because of the higher density of fractures in stratum II piezometers completed in this zone typically show slowly falling head levels during the dry season. The drilling program confirmed that there are fewer fractures in the stratum III zone than occur in the upper strata I and II. Therefore, we see piezometers completed in stratum III that have stable hydraulic heads, with little seasonal variation in water levels.

576

Conclusions The conceptual model as described represents a geological and hydrogeological system that can provide confusing results when viewed from individual datasets rather than using a composite approach that includes geology, hydraulic heads from piezometers, age dating and experience with low permeability units. For example pneumatic piezometers PP-6I, PP-6D and PP-6XD show hydraulic heads ranging from 11 to more than 20 ft high. These pneumatic piezometers are, however, completed in thick claystone, and the hydraulic heads have little potential to yield ground water to either monitoring wells or the excavation due to the low hydraulic conductivity of the base-grade materials. This linkage between hydraulic heads, hydraulic conductivity and lithology dictate the ability for geologic units to yield ground water and for any remediation that might be applied to similar geologic units. 8.8.4 A Conceptual Model with Multiple GroundWater Surfaces In general terms, the mass of subsurface data collected example facility is truly impressive. With literally hundreds of borings/piezometers/monitoring wells, the facility has developed a detailed knowledge of the site from the disposal areas south to an adjacent canyon. The project goals were to evaluate the mass of data currently available and address the primary issues relevant to permitting these expansions. The procedure used in the review process relied heavily on development of a conceptual model of the site geology and hydrology as the basis of comparing the reliability of the current data and the questions still surrounding the ground-water flow system. At this point, the majority of the investigative work was completed and a relatively focused technical scope was necessary for the permit modifications. A multi-path technical evaluation technique offered the best choice to build acceptance of the expansion’s groundwater monitoring program. Geophysical surface and borehole techniques tied to a limited drilling and piezometer installation program provide two pathways to data verification (hydraulic head and lithological data). Water quality evaluation and age-dating of the ground-water masses provide two additional pathways to the confirmation of groundwater flow direction and rates of flow. Each of these methods builds the basis for selection of the correct location of downgradient and background monitoring wells. Each of these pathways provides the components of the conceptual model. The following text describes the regional and site-specific hydrogeology that represents the most likely

Main Fracture Stratum I

Ground-Water Recharges Along Fracture Sets During Wet Season. Fractures Fill-up with Recharge & then Swell Closed

Flow Alon

g Top of Cl aystone

Stratum II Recharge of fracture during wet season into clay

1m

Hydrograph P-7S Showing Fracture Flow System Ground-Water Head Level Changes

560.00

one

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yst

Flow Downward in Rock Mass

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Cla

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y/

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Cla

600.00

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(b.)

610.00

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(e.)

620.00

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Monitoring well "A"

630.00

03/12/94

Limited Recharge Causes Stable Matrix Head Levels

640.00

01/15/94

Monitoring well "B"

Ground-Water Elevation (ft. MSL)

Deeper Piezometer Points Show Deeper Hydraulic Heads

02/26/94

660 650 640 630 620 610 600 590 580 570 560 550 540 530 520

Recharge Causes Changes in Fracture Head Levels (f.)

02/12/94

640 630 620 610 600 590 580 570 560 550 540 530 0 52 510 500

Actual Hydraulic Pressure Heads of Unit

Elevation (ft. MSL)

(a.)

Date of Reading

Be

dro

ck

Deeper Piezometer Points Show Deeper Hydraulic Heads

(d.)

Flow (mm/year) in Rock Mass

Geologic Unit Mass Hydraulic Heads May Show Downward Gradients Toward Deep Discharging Units

PP-2I

PP-2D

Fracture Hydraulic Head Level Transmitted to both Piezometers with Minor Head Loss

Example Hydrograph of Matrix Flow System Ground-Water Head Level Changes

PP-2S

650.00

Piezometers Located in Same Fracture Sets Show Similar Head Levels

620.00 610.00

PP-2S

600.00 590.00

(c.)

PP-2I

580.00 570.00

PP-2D

560.00 550.00 540.00

Date of Reading

577

Figure 8-81 Relationship between Fractures and Piezometer Response

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07/30/95

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530.00 01/01/94

Not to Scale

630.00

Conceptual Model of Claystone Site with Primary and Secondary Flow Systems

THE CONCEPTUAL MODEL

Ground-Water Elevation (ft. MSL)

640.00

600

650

700

T.D. 27.5'

750

800

850

900

950

Well N

SOUTHWEST H'

conditions present at the example facility as an example with multiple layered ground-water flow system. The text does not include specific references (which would be normally included in a geologic or hydrogeologic description) because the text is for illustrative purposes of what a site geological description would contain.

1000

THE CONCEPTUAL MODEL

578

T.D. 147.5'

2

T.D. 261.5'

Tpr1 T.D. 205.0'

Ter

Tevt

Excavation

Tes

2

Tds

Tdc

1 1a

Well H Well 3Q

4

3

2

Tes

1

Tds

T.D. 331.0'

Tes

2

1

T.D. 321.0'

Tevt

Tdc

Tds

2

T.D. 210.0'

Tdg

Fill

Tpr1

1

Qgf

2

T.D. 185.0'

1

Tes

Tevt

Tdc Well 2M

T.D. 140.0'

1 2

Tes

T.D. 136.0'

2

Qgf

T.D. 212.0' ?

600

650

700

750

800

850

900

950

Tcp

Tpr1

T.D. 190.0'

(dry)

Tes

?

(dry) ?

?

?

Tevt Tdc Ql Well W1

1000

Figure 8-82 Conceptual Cross-Section of Example Site

T.D. 240.0'

Well 2Z Well B Well 2Q Fill Well 2V Well R Well 2I Well Z Northwest H

Conceptual Cross Section

Boring P7-1 Boring P7-2 Well (projected) 3C

N-S Lineament

The facility and surrounding areas are underlain by a series of basalt flows and sedimentary interbeds. The basalt flows are part of the Columbia Plateau geological flood-basalt province of Miocene to lower Pliocene age (8 to 17 million years old). This province covers much of eastern Washington and northeastern Oregon. The dominant physiographic features for the site and immediately surrounding area were produced by folding the bedrock and differential erosion during the Spokane floods at the end of the Pleistocene. The features include the closed depressions in the north part of the site; the low, streamlined mounds scattered throughout the site area and the fans of glaciofluvial sand and gravel that were deposited downstream of obstructions to the glacial floods. Varved sand and silt (Touchet Beds) were deposited in a lake that formed during flood peaks. Partially masking these flood caused or modified features is a layer of aeolian (winddeposited) silty sand and silt (loess) which varies from a few inches to several ft in thickness. Stratigraphic units in the site area include three formations that belong within the Unit C Basalt Group. Pleistocene glaciofluvial, colluvial and alluvial and Holocene aeolian deposits locally mantle the bedrock units (see Figure 8-82). The major Basalt Member consists of two to six large and several smaller basalt flows. Geologic mapping shows that in the site area only two basalt flows are present. The two flows are generally separated by an interbed. The regional mapping indicates a thickness of approximately 140 to 170 ft for the member in the regional basin. Upper Basalt Flow (Tbm1): The upper basalt flow varies from approximately 60 to 95 ft in thickness in boreholes at the site. This thickness range is consistent with that determined in the area by regional geologic mapping. In outcrops in a canyon southwest of the site, the Upper Basalt flow could be characterized by well developed columnar jointing. Regionally exceptionally large-diameter columns are typical of the basalt flows and this feature assists identification of this unit in outcrops. Generally they range from 4 to 8 ft in diameter and rise from the base of the flows for two-thirds to three-fourths the total thickness. The columns, which are usually nearly vertical and roughly hexagonal in cross-section, are cut into sections by subhorizontal cross-joints with variable spacing (0.5 to 10 ft). Randomly oriented joints frequently extend through the upper part of the colonnade.

Fill

Regional Geology

THE CONCEPTUAL MODEL

The Upper Basalt flow generally consists of hard, darkgray to greenish-gray basalt. The upper few feet of the Upper Basalt flow consist of vesicular basalt, flow breccia or scoria that are moderately weathered or decomposed. The weathered basalt consists of soft to medium hard rock with the consistency of a clayey, sandy siltstone because of alteration of the feldspars to kaolinitic clay and of the pyroxene and olivine to chlorite and iron-rich clays. This weathered zone ranges from at least 2 ft to more than 10 ft in cores recovered at the site. The weathered zone is readily distinguished from the overlying Shallow Member by the relict igneous texture, by the presence of amygdules and by its brownish to reddish-brown color. The weathered zone grades downward into fresh to slightly weathered basalt over a distance of a few inches to about 2 ft. The fresh basalt is moderately to closely jointed and locally displays vesicular texture. Joints and vesicles in the upper flow are almost always lined with blue-gray or green secondary alteration products. Analysis of similar joint linings indicates that they are generally a mixture of chlorite and nontronitic clays.

Lower Basalt Flow (Tbm2): The upper part of the Lower Basalt flow and the basalt interbed are exposed in several outcrops north of the site and in a creek southwest of the site. They were also found in 12 of the boreholes, as well as in a site water-supply well SW-l. The lower flow is approximately 45 ft thick in SW-l. It is similar to the upper flow with respect to petrography, jointing and joint linings. However, in most of the boreholes, the lower flow has an “aa” flow-top breccia. This breccia consists of fragments of scoria and vesicular basalt that were rafted along on top of the flow. These fragments range in size from microscopic to several feet. The breccia is often loose; however, in some places it is slightly welded or cemented to form a relatively competent rock. The breccia typically has open voids throughout the site area. The voids are evident in outcrops and can be inferred in local water-well logs. In some boreholes at the site, the voids are infilled with fine-grained sedimentary material. Basalt Interbed: The interbed between the two basalt flows extends throughout the regional basin. It varies from

W DR 1-2 Y

W 854.6-2 25 W 863. 4-2 47

6K 851. -2 58

3B-2 866. 02

A-2 866. 01 6G 852. -2 79

W9856. 2 91

2H-2 862. 44

2J 853. -2 83

X847. 2 59

3C 842. -2 22

S-2 858. 46 Sa 853.-2 R-2 60 845. 66 3V 846. -2 10

3M 836.-2 35

2O 828.-2 73

3E 834.-2 18 2W 831. -2 46 4H 832.-2 18

3H-2 83 3.20

3P 832.-2 91

2V 827. a-2 89 2Vb827. 2 74 3L 827.a-2 45

30-2 83 1.10

Surface Features

I-2 848. 29

2N 851.2 28

6I-2 853. 67 2M 850. -2 65

852K -2 1.89

2L 851.-2 58 6H 859. -2 40 -2 85Sb 4.52

2B 861. -2 07

3F-2 85 9.41

2I-2 875. 44 -2 863C 1.55

3Ka827. 42 2

2V-2 827. 49

4K-2 828. 18

5D 826. -2 73 4Ba825. 2 30

4J-2 824. 48

2X 795. -2 95

Va 79 -2 V-2 2.27 793. 98

Shallow Level 1 Ground-water Surface 84

835

860

0

850

855

866G -1 6.59

845

5

86

860 865

Vb-2 79 3.59

855

850 845 835

830

840 830 825 820 815 810

800 795

865 860

805

865

865

Shallow Level 2 Ground-water Surface

870

865 860

860 855

850845

84035 8

840

845

83

0

850

860

845

840 835 830

835

830

825 820 815 810 805 800 795

Figure 8-83 Multilevel Ground-Water Surface

579

THE CONCEPTUAL MODEL

nearly 30 ft thick to only a few inches thick in several localities. It is between 2 and 12 ft thick in boreholes at the site. Typically, the interbed is a tuffaceous siltstone. However, at the site it is quite variable in lithology. It is made up of clayey silt, silty clay, weathered hyaloclastite and clayey silty sandstone. Regardless of its original lithology, the interbed is now largely weathered to clay and silt. Shallow Member: The Shallow Member of the Unit E Formation occurs as an interbed between two Basalt Members throughout the Columbia Plateau. It is comprised of weathered volcanic ash (tuff) and ash-rich sediments that accumulated in a broad shallow lake or flood plain during the volcanic hiatus between extrusion of the two Basalts. At the site, the Shallow Member varies from approximately 115 to 160 ft in boreholes where the top has not been eroded in channels of Dalles or glaciofluvial gravel. Originally, the Shallow Member averaged approximately 140 feet in thickness. Generally, it thickens toward the south and thins across the axis of an east-west trending anticline. After deposition of the Shallow Unit and the overlying tuff, the top of the member locally was eroded by the stream channels that deposited the Dalles Formation. Erosion during the Spokane floods at the end of Pleistocene time also carved channels and potholes through the Dalles into the top of the Shallow Unit. Within the adjacent canyon, these floods totally removed the Shallow Unit. For the purpose of this investigation the Shallow Unit consists of four recognizable intervals that appear to be correlative throughout the site. These are: (l) a bottom interval composed of interbedded clays, pebbly sands and welded tuffs, (2) a lower-middle interval comprised of clayey silt, sand and sandy silt, (3) an upper middle interval comprised of interbedded clay, silt and sandy silt and (4) an upper interval comprised of interbedded sand, sandy silt and clay. Weathering, zeolitization and clay alteration of the Shallow Member often inhibit recognition of the original lithologies of these intervals in outcrop and downhole samples. These divisions are believed to be best evident in the geophysical cross-sections conducted at the facility. In building a conceptual model of a facility the discussion of the geological units represents one of the first tasks in the design of a monitoring progran or in the potential remediation of the bedrock. Regional Hydrogeology The principal aquifers within the Plateau are associated with zones of fractured, rubbly, scoriaceous and/or vesicular basalt (interflow zones) within the the three basalt members. The interflow zones within the Columbia River Basalts typically have high to very high hydraulic conductivity and low storativity. Stratigraphically adjacent interflow zones are

580

often hydraulically isolated over large geographic areas due to the generally impervious nature of intervening dense competent basalt and/or sedimentary tuffaceous interbeds. Site Hydrogeology The hydrogeologic setting at the example facility consists of a thick, heterogeneous, unsaturated or vadose zone; a thin, heterogeneous, low-yield saturated zone within the lower portion of the Shallow Member; and regional aquifers within three basalt aquifers. Vadose Zone An unsaturated zone of layered sedimentary and volcanic rocks, approximately 150 to 200 ft thick, is present below the existing ground surface of the plateau on which the facility is located. The permit application reported as many as several unsaturated layers above the Shallow Member of the Unit E Formation. These layers overlay the unsaturated portion of the Shallow Member. It is likely that these layers show a wide range in vertical and horizontal unsaturated hydraulic conductivity both within and between layers. This contrast in unsaturated hydraulic conductivity can have a predominant effect on the movement of water within the unsaturated zone. Water in the unsaturated zone will move primarily vertically downward in zones/layers of higher unsaturated hydraulic conductivity and would likely have a large component of horizontal movement (down the geologic dip) when encountering a zone/layer of lower unsaturated hydraulic conductivity. Direct observations during exploratory drilling did not indicate potential perched water zones. However, analysis of water-level elevation data from closely spaced wells and piezometers suggests that perched water zones may be present within the unsaturated Shallow Member. Shallow Member Saturated Zone The uppermost zone of saturation consistent with ASTM D5092 standards for a detection monitoring program at the example facility is located above the top of the Basalt within the lower portion of the Shallow Member of the Unit E Formation. This zone of saturation occurs approximately 150 to 200 ft below the existing ground surface. Extensive site investigations have shown the Shallow Member to be highly variable with regard to its lithologic and hydraulic characteristics. In general, the saturated portion of the Shallow Member is a heterogeneous, low-yield, groundwater system that exhibits both locally unconfined and confined conditions. The occurrence of a saturated zone within the lower portion of the Shallow Member is associated with low to very low hydraulic conductivity within the basal sec-

Variable Heads in Shallow Member Through Transmittal of Higher Pressure Heads Through More Permeable Zones in the Gray Soil W1 -2 DR Y

W6 854.2-2 5 W4 863.4 -2 7

6G 852.7-2 9

W9 -2 856.9 1

Surfac

6K 851.5-2 8

3B-2 866.0 2

A-2 866.0 1

2I-2 875.4 4 3C 861.5-2 5

2J-2 853.8 3

X847.52 9

3C-2 842.2 2

3H-2 833.2 0

Transmittal of Higher Pressure Heads Through More Permeable Zone of Gray Soil

3P-2 832.9 1

3K 827.4a-2 2

2V-2 827.4

9

5D-2 826.7 3 4Ba-2 825.3 0

4K-2 828.1 8 4J-2 824.4

8

Shallo w Me Groun mber Leve l1 d wate r Surf ace

2X-2 795.9 5

Va 79 -2 V-2 2.27 793.9 8

Level 1 Selah

Head Level Observed in Well (Combined Heads of Shallow Member Level 1 and Selah Level 2)

Gray Weathered Surface

845

Level 2 Shallow Member Level 2 Shalow Menber

835

84

860

Actual Ground Water Surface Shallow Member for Level 1&2

0

850

855

5

86

860 865

Vb-2 79 3.5 9

3E-2 834.1 8 2W -2 831.4 6 4H-2 832.1 8

Shallow Member

2O -2 828.7 3

8

3M -2 836.3 5

3La-2 827.4 5

30-2 83 1.1 0

tures

I-2 848.2 9

S-2 858.4 6 Sa-2 853.6 R0 845.6 2 6 3V-2 846.1 0 2V 827.8 a-2 9 2Vb-2 827.7 4

Upward Gradients Between Shallow Member Levels 1 and 2 Can Be Explained by Three Alternative Conceptual Models

2B-2 861.0 7

2N2 851.2

6I-2 853.6 7 2M 850.6-2 5

852K 1.8-2 9

2L-2 851.5 8 6H-2 859.4 0 Sb 854.5-2 2

e Fea

2H-2 862.4 4 3F-2 859.4 1

855

850 845 835

2-10 foot Low Hydraulic Conductivity Weathered Surface of Basalt

830

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Basalt

Conceptual Model C

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Variable Heads in Shallow Member Through Transmittal of Higher Pressure Heads Through Sand Channel Zones in the Shallow Member

845

835 830

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825

Variable Heads in Shallow Member Through Transmittal of Higher Pressure Heads Through Zones Where the Gray Soil Has Beem Eroded

820 815 810

Shallow Member

Shallow Member

Actual Ground Water Surface Shallow Member for Level

Level 1 Selah

1&2 Actual Ground Water Surface Shallow Member for Level 1&2

Gray Weathered Surface Sand Channel

Level 2 Shallow Member

Level 2 Shallow Member

Head Level Observed in Well (Combined heads of Shallow Member Level 1 and Shallow Member Level 2) Level 1 Selah

Level 1 Shallow Member

Gray Weathered Surface

2-10 foot Low Hydraulic Conductivity Weathered Surface of Basalt

Level 2 Shallow Member

Level 2 Shallow Member

2-10 foot Low Hydraulic Conductivity Weathered Surface of Basalt

Conceptual Model B Basalt

Figure 8-84 Relationship Between Ground Water Surface and Conceptual Models of Vertical Flow 581

THE CONCEPTUAL MODEL

Conceptual Model A Basalt

Transmittal of Higher Pressure Heads Through Eroded Section of Gray Soil

THE CONCEPTUAL MODEL

tion. In the west-central portion of the site, the saturated thickness at the base of the Shallow Member is in excess of 50 ft. Unsaturated zones at the base of the Shallow Member are present in the north portion of the site along the crest of the east-west trending anticline and possibly locally along the south margin of the facility property, adjacent to the canyon. The absence of a saturated portion of the Shallow Member along the anticline is associated with a structural topographic high and possibly with preferential leakage into the underlying basalt due to the geologic structure in this area. The absence of a saturated portion of the Shallow Member adjacent to the canyon is considered to be associated with well construction, evapotranspiration, leakage to the basalt and discharge to the valley colluvium.

site, in the vicinity of Wells V and 2X, continuous saturation appears to exist from the base of the Shallow Member downward to the top of the interbed. Ground water also occurs under both confined and water table conditions within the interflow zone at the top of the lower basalt flow. In general, ground water within the interflow zone beneath the south-central portion of the site is confined or partially confined. In the northern portion of the site where the interbed rises toward the crest of the anticline, ground water exists under water table conditions. Flow within the vadose zone is predominantly vertical downward, whereas flow within the saturated zone at the base of the Shallow Member is predominantly horizontal. Water Level Trends

Level 1 Water Level A water table contour map for the saturated zone at the base of the Shallow Member (Level l) is shown in Figure 883. The configuration of the water table roughly parallels the structural dip of the top of the basalt south of the anticline. Within the southern two thirds of the site, the water table slopes relatively uniformly to the south and southeast. Within the northwestern third of the site, however, the saturated zone at the base of the Shallow Member is less uniform. Tension fracturing along the crest of the anticline is inferred to contribute to greater vertical hydraulic conductivity in these areas which, in conjunction with the rise in the elevation of the top of the basalt, results in the apparent thinning or absence of the zone or saturation at the base of the Shallow Member. In summary, ground water occurs under water table conditions at the base of the Shallow Member; it also occurs under both water table and partially confined conditions within the upper basalt flow above the interbed between the upper and lower flows and within the interflow zone between the two basalt flows. The uppermost zone of saturation is located physically within the Shallow Member of the Unit E Formation and above the top of the Basalt. This saturated zone is continuous across the southern twothirds of the site (north of canyon). It is thin or absent beneath the northwestern corner of the site in the vicinity of Wells E, Z, 2F and Wl and in the northcentral part of the site in the area of Well 2N (see Figure 8-83). Beneath the northern two thirds of the site and along its southern margin, an unsaturated zone exists within the upper part of the upper basalt flow. The thickness of this unsaturated zone ranges from a few feet near the southern boundary of the property to greater than 80 ft in the northern portion of the site. The lower portion of the upper basalt flow is saturated. In the southeastern portion of the

582

Water table and potentiometric data for the saturated zone at the base of the Shallow Member indicate that almost everywhere within the site boundary a downward vertical hydraulic gradient is present, in addition to the lateral or horizontal gradient. Locally, vertically upward hydraulic gradients are recorded at locations where a semicontinuous, confining bed, often a subunit of the gray clay, is present between vertically discrete monitoring well screens that are completed within transmissive zones. The dip of the confining beds causes the apparent hydraulic head in the lower zones to be greater than that in the overlying zone, as shown in Figure 8-84. Although significant vertical gradients exist within the saturated zone at the base of the Shallow Member, the ratio of horizontal to vertical hydraulic conductivity (Kh:Kv 175:1 to 500:1) results in an effective horizontal movement of ground water that is ten times greater than that in the vertical direction. These factors, combined with the overall low hydraulic conductivity of the Shallow Member, result in slow, predominantly horizontal ground-water flow. Horizontal and Vertical Hydraulic Conductivity In situ and laboratory permeability tests indicate that horizontal and vertical hydraulic conductivity for the saturated portion of the Shallow Member range over at least four orders of magnitude (1*10-8 to 1*10-4 cm/s). This range of variability is characteristic of stratified sedimentary interbeds in the Columbia Plateau region. The ratio of horizontal to vertical hydraulic conductivity is at least 175:1 and locally, could be greater than 500:1. Storativity values obtained from long-term pump tests show a wide range that spans those typical of both unconfined and confined aquifer conditions. Slug Tests: In situ, falling-head permeability (slug)

THE CONCEPTUAL MODEL

tests in open boreholes terminated at the base of the Shallow Member and at the top of the basalt indicate that the horizontal hydraulic conductivity at the base of the Shallow Member range over two orders of magnitude from about 1*10-6 to 1*10-4 cm/s. Laboratory Testing: Laboratory testing on undisturbed cores from the saturated zone at the base of the Shallow Member indicate the vertical hydraulic conductivity ranges from 1*10-8 to 1*10-5 cm/s. The difference between field horizontal hydraulic conductivity and laboratory vertical hydraulic conductivity may be attributed, in part, to the difference in measurement techniques. Packer Tests: Packer tests conducted within the basalt indicate wide variation in horizontal hydraulic conductivities. The measured horizontal hydraulic conductivity in the basalt range from less than 1*10-8 cm/s to greater than 1*10-3 cm/s. The Shallow Member pumping tests conducted at Wells V, 2V and S entailed pumping from the base of the Shallow Member and monitoring the response to pumping at the base of the Shallow Member, at an intermediate depth between the base and the water table and at the water table. The calculated horizontal hydraulic conductivity of the Shallow Member from the pump test results range from 1*10-6 to 1*10-4 cm/s. These values are based on the timedrawdown responses, which closely follow the Theis curve predictions. The horizontal hydraulic conductivity values calculated from slug tests and pumping tests conducted in the same well indicates slug tests and pump tests produced essentially the same horizontal hydraulic conductivity and transmissivity values when the inherent inaccuracies of the tests are considered. This condition exists within the transmissive zones of the saturated portion of the Shallow Member. The dominant mode of ground-water flow is down dip parallel to bedding (l to 2 degrees from horizontal). This is due to the confining beds that are a naturally occurring portion of the bedding and the anisotropy. The Shallow Member is anisotropic in that the horizontal hydraulic conductivity is greater than vertical hydraulic conductivity. However, due to the discontinuous and lenticular nature of much of the saturated portion of the Shallow Member, combined with hydraulic head conditions and inferred hydraulic conductivity differences, a component of cross-bed flow can occur. In some portions of the saturated zone of the Shallow Member, stratigraphic conditions are such that confining bed dip can locally induce hydraulic heads which are greater than that of the overlying hydraulic head. Structural Influences: The dominant geologic structural feature at the subject facility is an east-west trending anticline that is present in the northern portion of the site.

This and other structural features associated with the anticline exert a strong influence on the occurrence and movement of ground water in the Shallow Member. Specifically, tension fractures along the crest of the anticline may increase the vertical hydraulic conductivity, resulting in local discharge from the Shallow Member to the basalt interflow zones. This interpretation is consistent with the unsaturated zones that are present along the crest of the anticline. Other geologic structures that affect the flow of ground water are monoclinal folds, wrench faults and shear zones. These structures tend to form areas of reduced hydraulic conductivity within the saturated portion of the Shallow Member by creating offset bedding, by smearing of the geologic units and by remolding clayey beds and fault gouge materials. Ground-Water Velocity Estimates in the Shallow Member The average horizontal and vertical ground-water flow velocities in the Shallow Member can be estimated from the following relationship: • The horizontal hydraulic conductivity is estimated to range from 1*10-6 to 1*10-4 cm/s. • The average horizontal hydraulic conductivity is estimated to be at least 175 to 500 times greater than the vertical hydraulic conductivity based on hydraulic conductivity tests performed in the lab on core samples. • The horizontal hydraulic gradient is estimated to range from 0.01 to 0.04 ft/ft and the vertical hydraulic gradient from 0.04 to 0.5 ft/ft. • The effective porosity is assumed to range from 0.20 to 0.30. • The estimated average horizontal and vertical ground-water flow velocities are approximately 6 ft/year and 0.2 ft/year, respectively. Water Quality In general, major ion chemical data show ground water in the uppermost saturated zone at the base of the Shallow Member to be a calcium carbonate (bicarbonate) type with minor chloride and potassium. In some locations at depth, sulfate becomes dominant over carbonate, sodium becomes dominant over calcium and chloride increases. This probably reflects greater maturity resulting from increased reaction between ground water and the Shallow Member. Magnesium is also a significant component of the ground

583

THE CONCEPTUAL MODEL

waters; it is likely derived from weathering of basalt or volcanic clasts in the Shallow Member. Ground-water isotopic data suggest slow meteoric recharge. Tritium data clearly show that water in the Shallow Member has been isolated from the atmosphere for at least thirty years, with no identifiable admixture of younger water. Limited Carbon-14 data suggest an age in excess of 70 years for Shallow Member ground water. Stable isotope data (for example deuterium and H30) are also compatible with a meteoric origin for the ground water, with no apparent contribution from geothermal or evaporite sources.

The uppermost bedrock unit underlying the site was found at depths ranging from 160 to 205 ft below ground surface and is believed to represent upper portions of the Cretaceous Blackleaf formation. The formation consists of interbedded marine sandstones, siltstones, and shales. The contact between the overlying unconsolidated materials and the bedrock is marked by a yellowish grey clay containing fragments of weathered sandstone. The clay is interpreted to represent a zone of weathered bedrock. The thickness of this weathered contact may be up to 10 f;, however; it does not appear to be continuous across the site.

General Comments on the Conceptual Model

Site Hydrogeology

The conceptual model as described above provides an explanation of the observed ground-water head levels in the Shallow Member and the basalt. Where the confining layer at the top of the basalt is more permeable, the Shallow Member is not able to maintain the 20- to 40-ft ground-water surface within the silt units. Away from the overthrust/anticline trace the head levels reestablish the typical downgradient flow toward the southeast. The detection monitoring programs on the current facility units are far enough south not be affected by the gradients toward the north near the overthrust feature. This example provided a lot of data that were acquired through the application of significant research.

The hydrogeologic setting at the example facility consists of a thick, heterogeneous, unsaturated or vadose zone; a thin, heterogeneous, low-yield saturated zone within the lower portion of the Selah Member; and regional aquifers within the Priest Rapids, Frenchman Springs and Grande Ronde Basalt.

8.8.5 Characterization of Ground Water in FineGrained Rocks This example shows the importance of including into site investigations geochemical and isotope evaluations linked to site geotechnical data. In this example the facility was applying for a no-migration petition through the state-led program. A generalized stratigraphic column of the site soils and rock is presented in Figure 8-85. Site geologic materials have been separated into three primary units - two upper unconsolidated units and an underlying bedrock unit. The unconsolidated materials are subdivided on the basis of color and clay content. The upper unit consists primarily of a dark yellowish brown clayey silt with occasional lenses of fine sand. Gravel is scattered throughout the matrix of the unit. Salt precipitates and gypsum crystals are present in small pockets or vugs. The thickness of the upper unit generally ranges from about 10 ft or less beneath the base of the coulee to approximately 75 ft. The lower unit consists of from 100 to 140 ft of an olive grey silty clay with scattered gravel, cobbles and gypsum crystals. A narrow band of interbedded grey and brown clay has been observed at the transition between the upper and lower units.

584

Vadose Zone An unsaturated zone of layered sedimentary and volcanic rocks, approximately 150 to 200 ft thick, is present below the existing ground surface of the plateau on which the facility is located. The permit application reported as many as several unsaturated layers above the Selah Member of the Ellensburg Formation. These layers overlay the unsaturated portion of the Selah Member. It is likely that these layers show a wide range in vertical and horizontal unsaturated hydraulic conductivity both within and between layers. This contrast in unsaturated hydraulic conductivity can have a predominant affect on the movement of water within the unsaturated zone. Water in the unsaturated zone will move primarily vertically downward in zones/ layers of higher unsaturated hydraulic conductivity and would likely have a large component of horizontal movement (down the geologic dip) when encountering a zone/ layer of lower unsaturated hydraulic conductivity. Direct observations during exploratory drilling did not indicate potential perched water zones. However, analysis of water-level elevation data from closely spaced wells and piezometers suggests that perched water zones may be present within the unsaturated Selah Member. Shallow Member Saturated Zone The uppermost zone of saturation consistent with ASTM D5092 standards for a detection monitoring program at the example facility is located above the top of the Basalt within the lower portion of the Shallow Member of

THE CONCEPTUAL MODEL

the Unit E Formation. This zone of saturation occurs approximately 150 to 200 ft below the existing ground surface. Extensive site investigations have shown the Shallow Member to be highly variable with regard to its lithologic and hydraulic characteristics. In general, the saturated portion of the Shallow Member is a heterogeneous, low-yield, ground-water system that exhibits both locally unconfined and confined conditions. The occurrence of a saturated zone within the lower portion of the Shallow Member is associated with low to very low hydraulic conductivity within the basal section. In the west-central portion of the site, the saturated thickness at the base of the Shallow Member is in excess of 50 ft. Unsaturated zones at the base of the Shallow Member are present in the north portion of the site along the crest of the east-west trending anticline and possibly locally along the south margin of the facility property, adjacent to the canyon. The absence of a saturated portion of the Shallow Member along the anticline is associated with a structural topographic high and possibly with preferential leakage

into the underlying basalt due to the geologic structure in this area. The absence of a saturated portion of the Shallow Member adjacent to the canyon is considered to be associated with well construction, evapotranspiration, leakage to the basalt and discharge to the valley colluvium. Level 1 Water Level A water table contour map for the saturated zone at the base of the Shallow Member (Level l) is shown in Figure 8-83. The configuration of the water table roughly parallels the structural dip of the top of the basalt south of the anticline. Within the southern two thirds of the site, the water table slopes relatively uniformly to the south and southeast. Within the northwestern third of the site, however, the saturated zone at the base of the Shallow Member is less uniform. Tension fracturing along the crest of the anticline is inferred to contribute to greater vertical hydraulic conductivity in these areas which, in conjunction with the rise in the elevation of the top of the basalt, results in the apparent

GENERALIZED SITE STRATIGRAPHIC COLUMN GEOLOGIC UNIT UNIT 1: Unconsolidated Quarternary Glaciolacustrine Deposits UNIT 2: Unconsolidated Quarternary Glaciolacustrine Deposits

UNIT 3: Consolidated Cretaceous Marine and Deltaic Deposits

Stratigraphic Approximate Unit Thickness (feet)

50-75

100-140

Average Elevation (MSL)

3359

3296

Dark yellowish brown clayey silt with trace sand and gravel.

Gray silty clay with scattered gravel/cobbles and gypsum crystals Yellowish clay

< 10

> 300

Description

3187

Gray to dark gray sandstone, siltstone and shale

Note: 1. Thickness and descriptions are based on exploratory drilling and inference from site topography. 2. Geologic units are based on USGS descriptions.

Figure 8-85 General Site Stratigraphic Column

585

THE CONCEPTUAL MODEL

thinning or absence of the zone or saturation at the base of the Shallow Member. In summary, ground water occurs under water table conditions at the base of the Shallow Member; it also occurs under both water table and partially confined conditions within the upper basalt flow above the interbed between the upper and lower flows and within the interflow zone between the two basalt basalt flows. The uppermost zone of saturation is located physically within the Selah Member of the Unit E Formation and above the top of the basalt. This saturated zone is continuous across the southern two thirds of the site (north of canyon). It is thin or absent beneath the northwestern corner of the site in the vicinity of Wells E, Z, 2F and Wl and in the northcentral part of the site in the area of Well 2N (see Figure 8-83). Beneath the northern two thirds of the site and along its southern margin, an unsaturated zone exists within the upper part of the upper basalt flow. The thickness of this unsaturated zone ranges from a few feet near the southern boundary of the property to greater than 80 ft in the northern portion of the site. The lower portion of the upper basalt flow is saturated. In the southeastern portion of the site, in the vicinity of Wells V and 2X, continuous saturation appears to exist from the base of the Shallow Member downward to the top of the interbed. Ground water also occurs under both confined and water table conditions within the interflow zone at the top of the lower basalt flow. In general, ground water within the interflow zone beneath the south-central portion of the site is confined or partially confined. In the northern portion of the site where the interbed rises toward the crest of the anticline, ground water exists under water table conditions. Flow within the vadose zone is predominantly vertical downward, whereas flow within the saturated zone at the base of the Shallow Member is predominantly horizontal. Water Level Trends Water table and potentiometric data for the saturated zone at the base of the Shallow Member indicate that almost everywhere within the site boundary a downward vertical hydraulic gradient is present, in addition to the lateral or horizontal gradient. Locally, vertically upward hydraulic gradients are recorded at locations where a semicontinuous, confining bed, often a subunit of the gray clay, is present between vertically discrete monitoring well screens that are completed within transmissive zones. The dip of the confining beds causes the apparent hydraulic head in the lower zones to be greater than that in the overlying zone, as shown in Figure 8-84.

586

Although significant vertical gradients exist within the saturated zone at the base of the Shallow Member, the ratio of horizontal to vertical hydraulic conductivity (Kh:Kv 175:1 to 500:1) results in an effective horizontal movement of ground water that is ten times greater than that in the vertical direction. These factors, combined with the overall low hydraulic conductivity of the Shallow Member, result in slow, predominantly horizontal ground-water flow. Horizontal and Vertical Hydraulic Conductivity In situ and laboratory permeability tests indicate that horizontal and vertical hydraulic conductivity for the saturated portion of the Shallow Member range over at least four orders of magnitude (1*10-8 to 1*10-4 cm/s). This range of variability is characteristic of stratified sedimentary interbeds in the Columbia Plateau region. The ratio of horizontal to vertical hydraulic conductivity is at least 175:1 and locally could be greater than 500:1. Storativity values obtained from long-term pump tests show a wide range that spans those typical of both unconfined and confined aquifer conditions. Slug Tests: In situ, falling-head permeability (slug) tests in open boreholes terminated at the base of the Shallow Member and at the top of the basalt indicate that the horizontal hydraulic conductivity at the base of the Shallow Member range over two orders of magnitude from about 1*10-6 to 1*10-4 cm/s. Laboratory Testing: Laboratory testing on undisturbed cores from the saturated zone at the base of the Shallow Member indicate the vertical hydraulic conductivity ranges from 1*10-8 to 1*10-5 cm/s. The difference between field horizontal hydraulic conductivity and laboratory vertical hydraulic conductivity may be attributed, in part, to the difference in measurement techniques. Packer Tests: Packer tests conducted within the basalt indicate wide variation in horizontal hydraulic conductivities. The measured horizontal hydraulic conductivity in the basalt range from less than 1*10-8 cm/s to greater than 1*103 cm/s. The Shallow Member pumping tests conducted at Wells V, 2V and S entailed pumping from the base of the Shallow Member and monitoring the response to pumping at the base of the Shallow Member, at an intermediate depth between the base and the water table and at the water table. The calculated horizontal hydraulic conductivity of the Shallow Member from the pump test results ranges from 1*10-6 to 1*10-4 cm/s. These values are based on the timedrawdown responses, which closely follow the Theis curve predictions. The horizontal hydraulic conductivity values calculated from slug tests and pumping tests conducted in the

14C Age Date

NW

14C Age Date

11,200 YBP

21,300 YBP MW-4

14C Age Date

MW-1

14C Age Date

29,200 YBP

19,400 YBP

3400

SE 3450

PZ-1S

PZ-1D MW-2 MW-3A

3400

Brown clayey silt with gravel

3300

Fill

MW-5

Local ground-water surface

3300 3200

Fine grained sandstone

Gray silty clay with gravel

Olive gray mudstone Yellowish clay Potentiometric Surface of Bedrock Unit

Elevation Above Sea Level

Elevation Above Sea Level

3450

3200

Sand Interval Well Screen Interval 0

200

400

Horizontal Scale (ft.)

3360 3350 3340 3330 3320 3310 3300 3290 3280 3270 3260 3250 3240 3230 3220

3360 3350 3340 3330 33200 331 3300 3290 32800 327 3260 0 3254 32 0 3230

587

Deeper Piezometer Points show Deeper Hydraulic Heads in Glacial Units

Figure 8-86 Conceptual Model

THE CONCEPTUAL MODEL

Potentiometric Surface ? Inferred Contacts

MSL Elevation

LEGEND

Note: Head Levels in Glacial Materials Near MW-2 Show Downward Gradients in the Low Hydraulic Conductivity Sediments

Actual Hydraulic Pressure Heads of Units

Olive gray mudstone

THE CONCEPTUAL MODEL

Structural Influences: The dominant geologic structural feature at the subject facility is an east-west trending anticline that is present in the northern portion of the site. This and other structural features associated with the anticline exert a strong influence on the occurrence and movement of ground water in the Shallow Member. Specifically, tension fractures along the crest of the anticline may increase the vertical hydraulic conductivity, resulting in local discharge from the Shallow Member to the basalt interflow zones. This interpretation is consistent with the unsaturated zones that are present along the crest of the anticline. Other geologic structures that affect the flow of ground water are monoclinal folds, wrench faults and shear zones. These structures tend to form areas of reduced hydraulic conductivity within the saturated portion of the Shallow Member by creating offset bedding, by smearing of the geologic units and by remolding clayey beds and fault gouge materials.

same well indicate slug tests and pump tests produced essentially the same horizontal hydraulic conductivity and transmissivity values when the inherent inaccuracies of the tests are considered. This condition exists within the transmissive zones of the saturated portion of the Shallow Member. The dominant mode of ground-water flow is down dip parallel to bedding (l to 2 degrees from horizontal). This is due to the confining beds that are a naturally occurring portion of the bedding and the anisotropy. The Shallow Member is anisotropic in that the horizontal hydraulic conductivity is greater than vertical hydraulic conductivity. However, due to the discontinuous and lenticular nature of much of the saturated portion of the Shallow Member, combined with hydraulic head conditions and inferred hydraulic conductivity differences, a component of cross-bed flow can occur. In some portions of the saturated zone of the Shallow Member, stratigraphic conditions are such that confining bed dip can locally induce hydraulic heads which are greater than that of the overlying hydraulic head.

CO 3)

)

g (m m siu 20

Su lf 20 ate ( S

e gn Ma 40

O 40 4 ) + C

+ a) 60

(C

hlo 60 ride

(C l 80 )

um lci Ca 0 8

MW01 MW02 MW03 MW04 MW05 RP01

(H + B 40 40 ica rb o 20 20 nate

Ca rb 80 80 ona te ( 60 60 CO 3)

g) (m

60

ium es

40

gn Ma

20

20

%meq/L

60 40 Chlorine (Cl)

ANIONS

Figure 8-87 Trilinear Diagram of Example Site

588

) 4 (SO te 40

SO4 HCO3-CO3 20

lfa

CATIONS

20

60

60 40 Calcium (Ca)

Su

80

SO4 80

Ca

) 80m (K 0 8 siu 60 otas 0 +P 6 40 (Na) 0 4 ium 20Sod 0 2

80

Mg

80

C

THE CONCEPTUAL MODEL

Ground-Water Velocity Estimates in the Shallow Member The average horizontal and vertical ground-water flow velocities in the Shallow Member can be estimated from the following relationship: • The horizontal hydraulic conductivity is estimated to range from 1*10-6 to 1*10-4 cm/s. • The average horizontal hydraulic conductivity is estimated to be at least 175 to 500 times greater than the vertical hydraulic conductivity based on hydraulic conductivity tests performed in the lab on core samples. • The horizontal hydraulic gradient is estimated to range from 0.01 to 0.04 ft/ft and the vertical hydraulic gradient from 0.04 to 0.5 ft/ft. • The effective porosity is assumed to range from 0.20 to 0.30. • The estimated average horizontal and vertical ground-water flow velocities are approximately 6 ft/year and 0.2 ft/year, respectively. Water Quality In general, major ion chemical data show ground water in the uppermost saturated zone at the base of the Shallow Member to be a calcium carbonate (bicarbonate) type with minor chloride and potassium. In some locations at depth, sulfate becomes dominant over carbonate, sodium becomes dominant over calcium and chloride increases. This probably reflects greater maturity resulting from increased reaction between ground water and the Shallow Member. Magnesium is also a significant component of the ground waters; it is likely derived from weathering of basalt or volcanic clasts in the Shallow Member. Ground-water isotopic data suggest slow meteoric recharge. Tritium data clearly show that water in the Shallow Member has been isolated from the atmosphere for at least thirty years, with no identifiable admixture of younger water. Limited Carbon-14 data suggest an age in excess of 70 years for Shallow Member ground water. Stable isotope data (for example, deuterium and H30) are also compatible with a meteoric origin for the ground water, with no apparent contribution from geothermal or evaporite sources. General Comments on the Conceptual Model The conceptual model as described above provides an explanation of the observed ground-water head levels in

the Shallow Member and the basalt. Where the confining layer at the top of the basalt is more permeable, the Shallow Member is not able to maintain the 20- to 40-ft ground-water surface within the silt units. Away from the overthrust/anticline trace the head levels reestablish the typical downgradient flow toward the southeast. The detection monitoring programs on the current facility units are far enough south not be affected by the gradients toward the north near the overthrust feature. This example provided a lot of data that were acquired through the application of significant research. This example shows the importance of including into site investigations geochemical and isotope evaluations linked to site geotechnical data. In this example the facility was applying for a no-migration petition through the state-led program. A generalized stratigraphic column of the site soils and rock is presented in Figure 8-85. Site geologic materials have been separated into three primary units - two upper unconsolidated units and an underlying bedrock unit. The unconsolidated materials are subdivided on the basis of color and clay content. The upper unit consists primarily of a dark yellowish brown clayey silt with occasional lenses of fine sand. Gravel is scattered throughout the matrix of the unit. Salt precipitates and gypsum crystals are present in small pockets or vugs. The thickness of the upper unit generally ranges from about 10 ft or less beneath the base of the coulee to approximately 75 ft. The lower unit consists of from 100 to 140 ft of an olive grey silty clay with scattered gravel, cobbles and gypsum crystals. A narrow band of interbedded grey and brown clay has been observed at the transition between the upper and lower units. The uppermost bedrock unit underlying the site was found at depths ranging from 160 to 205 ft below ground surface and is believed to represent upper portions of the Cretaceous Blackleaf formation. The formation consists of interbedded marine sandstones, siltstones, and shales. The contact between the overlying unconsolidated materials and the bedrock is marked by a yellowish grey clay containing fragments of weathered sandstone. The clay is interpreted to represent a zone of weathered bedrock. The thickness of this weathered contact may be up to 10 ft; however, it does not appear to be continuous across the site. Site Hydrogeology Geologic materials underlying the site can be broadly divided into two types: the unconsolidated finegrained glacio-lacustrine deposits and the underlying bedrock materials of the Blackleaf formation (Figure 887). The bedrock is generally found at depths of about

589

THE CONCEPTUAL MODEL

160 to 205 ft below ground surface in the vicinity of the site. The unconsolidated materials are further subdivided into two units based largely on color and clay content with an upper unit of primarily dark yellowish brown clayey silt and a lower unit of olive grey silty clay. Gravel, salt precipitates and gypsum crystals are scattered throughout the matrix of the two unconsolidated units. The thickness of the upper unit generally ranges from about 10 ft or less beneath the base of the coulee to approximately 75 ft. The lower unit is from about 100 to 140 ft in thickness. Two water-bearing zones have been identified during field investigations undertaken at the site. These consist of a discontinuous, perched zone located just above or at the contact between the upper brown silt and lower grey clay and a lower bedrock aquifer. Ground-Water Monitoring System The initial geologic site assessment conducted by previous consultants indicates the occurrence of both a discontinuous perched ground-water zone in the upper unconsolidated, glacio-lacustrine units and a more extensive ground-water zone in the lower bedrock. The bedrock ground-water zone lies within the Cretaceous bedrock unit known as the Blackleaf formation located at a depth of approximately 170 to 190 ft below ground surface at the site. The five ground-water monitoring wells were completed in the upper sandstone and shale member of the Blackleaf formation. Water level measurements in each of the monitoring wells suggest that the bedrock water table is relatively flat with local hydraulic gradients ranging from approximately 0.0024 ft/ft in the northwest portion of the site and flattening somewhat to approximately 0.0019 ft/ft in the southeastern portions of the site. The mean hydraulic gradient across the site is approximately 0.0021 cm/cm. Slug tests performed by the consultant on wells MW-l and MW-3 indicated an estimated hydraulic conductivity of 4.6*10-5 cm/s and 9.5*10-5 cm/s, respectively. Estimated average linear horizontal ground-water velocities within the bedrock aquifer range from 2.4*10-7 cm/s to 5*l0-7 cm/s. Ground-water quality was found to be poor with estimated total dissolved solids exceeding the secondary maximum contaminant levels set for public water systems. The discontinuous perched ground-water zone(s) observed at two of the six boreholes lies at the contact between the upper brown clayey silt and the underlying grey silty clay. It is not considered an aquifer because of

590

its limited extent and low estimated yield (no perched ground-water zones were noted by investigators during the drilling of the MW-I and PB4 boreholes or by the second investigators during the drilling and installation of wells MW-4 and MW-5). Water level readings suggest that a hydraulic gradient of approximately 0.01 ft/ft exists in the perched ground-water zone between wells MW-2 and MW-3 (if it is assumed that there is a continuous perched zone between these two wells). Laboratory testing performed by the soil laboratory indicated that the vertical hydraulic conductivities ranged from 2.4*10-9 cm/s to 5.7*10-9 cm/s in samples of the unconsolidated materials collected during the drilling operations. With the very low vertical hydraulic conductivities within the unconsolidated units, deep infiltration to the bedrock ground-water zone is believed to be minimal with the grey silty clay overlying the bedrock serving as an effective aquitard, hydraulically isolating the perched ground water and any surface water from the bedrock aquifer. Investigative drilling suggests that the contact between the brown and grey units may have a slightly higher percentage of sand or cobbles, possibly due to reworking of the surface of the grey unit. However, because of the low vertical hydraulic conductivity of the overlying soils, recharge to this zone most likely occurs where these soils are thin or where there is significant secondary porosity. During periods of no runoff or recharge the perched ground-water zone most likely loses water from evapotranspiration through the soil. Potential Contaminant Migration Pathways The generation of leachates at the site would most likely be the result of precipitation or intermittent surface water percolating through the fill, potentially picking up organic and inorganic contaminants in the process. Migration of these leachates from the site through the subsurface environment is dependent upon the hydraulic properties and potential hydraulic pathways within the fill, the underlying unconsolidated units and the bedrock downgradient of the site. The extremely low vertical hydraulic conductivities of the unconsolidated silty clays and clayey silts appear to make it unlikely that any leachate generated within the landfill will be able to migrate vertically to the bedrock aquifer within the confines of the site (see Figure 8-86). The majority of leachate generated within the fill will have only a limited ability to migrate downward and will probably follow the contact between the fill and the underlying brown clayey silt to the toe of the landfill where it

THE CONCEPTUAL MODEL

would discharge onto the floor of the coulee. Any leachate that did infiltrate the clayey silts would most likely have a much greater horizontal component of flow than vertical as expressed by the higher horizontal hydraulic conductivities noted above (glacio-lacustrine deposits are frequently anisotropic with higher horizontal permeabilities than vertical). In areas below the fill or in areas where leachate may collect on the surface, the brown clayey silt unit may be relatively thin and leachate could conceivably recharge the perched water zones which lie above the grey silty clay unit. If this zone is continuous across the site, the hydraulic gradient suggests that the leachate would migrate to the southeast towards the toe of the landfill, following the slope of the coulee. However, given the low estimated groundwater velocities within the perched zone(s), it is unlikely that any leachate could migrate off of the site for several hundred years. For example, leachate recharging the perched zone at a point midway between wells MW-I and MW-2 would require approximately 273 years to migrate downgradient to well MW-3. In a similar fashion, leachates that were able to recharge the bedrock aquifer the same point beneath the landfill would take nearly 4,100 years to migrate horizontally to well MW-3, based on current knowledge of the site. Geochemical Characterization Major anions and cations (Ca, Mg, Na, K, SO4, Cl) and alkalinity, were sampled in ground water and leachate at select monitoring wells. These geochemical parameters are useful in determining if mixing is occurring between adjacent aquifers or water bearing zones or if hydraulic connection has occurred vertically between aquifers or different water bearing zones. The landfill and leachate is considered to be a separate “water bearing unit” from the underlying ground water because it is lined. Similar patterns on Stiff diagrams suggest water of the same origin or ground-water bearing zone while waters with different patterns most likely are from unique geologic water bearing zones. Trilinear diagrams (see Figure 8-87) are also plotted for the major anions and cations. Ground water that shows distinct aquifers or distinct origins will plot in separate clusters. Mixing of two different water bearing zones will be shown as a straight line joining the clusters of data on different areas of the diagram (Piper, 1944; Hill, 1940). Leachate data are plotted as a distinct water bearing zone and evaluated as in Baedecker and Back, 1979. These methods also can be used to observe geochemical changes laterally along ground-water flowpaths from recharge to discharge areas. According to Freeze and

Cherry (1979), recharge of rain or snowmelt that infiltrates through the soil zone (or vadose zone) undergoes a net loss of mineral matter to the flowing water. As groundwater moves along flowlines in the aquifer matrix (i.e., soil and/or rock) from recharge to discharge areas, its chemistry is altered by the effects of a variety of geochemical processes. These geochemical processes are described in detail in Chapter 7 of Freeze and Cherry (1979). In general, ground water in a recharge area is lower in total dissolved solids than ground water in the discharge area in the same aquifer or water bearing geologic unit. As ground-water ages from transport through the flowpath, mineralization occurs from the soil and/or rock in the water-bearing geologic unit. Natural Isotopes The stable and radioactive isotopes greatly assist in interpreting the geochemistry at the example facility. Stable isotopes are useful in determining if ground water in different lateral or vertical locations has been derived from precipitation from different climatic periods over geologic time. The use of natural isotopes in investigating a variety of groundwater issues is discussed in detail in Szpakiewicz (1990). Isotopes are atoms of the same element that have a different number of neutrons in the nuclei and therefore different atomic weights (shown as a superscript in front of the element’s symbol). Isotopes may be stable or radioactive. Environmental isotopes generally include the isotopes of carbon (12C, 13C, 14C), hydrogen (H, 2H, 3H), oxygen (16O, 18O) and other elements not included in this study. The average terrestrial abundance for the isotopes of these three elements are: Carbon-12................98.89% Carbon-13................ 1.11% Carbon-14................trace% (radioactive) Hydrogen (H)...........99.984% Deuterium (2H).......... 0.015% Tritium (3H)............trace% (radioactive) Oxygen-16................99.76% Oxygen-18................ 0.2% Stable Isotopes: The concentrations of stable isotopes of an element in coexisting chemical phases or reacting chemical compounds vary slightly because of the differences in the mass of the isotopes. In general, for those elements undergoing transitions from the solid, liquid and gaseous phases over a range of temperature, the

591

THE CONCEPTUAL MODEL

Figure 8-88 Pre-Tertiary Ground-Water System heavier isotope will be concentrated in the solid phase where it is more strongly bound. Heavier isotopes also tend to be concentrated in the more oxidized phase of an element. Isotopic distributions in biological systems (such as photosynthesis or bacterial reactions) are primarily a result of kinetic effects or, in other words, differences between the reaction rates of the isotopes. In general, the lighter isotope will have the faster reaction rate and will be concentrated in the main reaction product relative to the source materials. Carbon-13: The 13C of dissolved carbonate species (mostly bicarbonate) in the ocean is about 0 per mill (0/00) and of atmospheric CO2, about -7 per mill. The 13C/12C

592

ratio (referred to the Peedee belemnite carbonate or PDB standard) is subject to fractionation effects in living organisms; thus this ratio indicates not only whether dissolved carbon is of organic origin (light) or inorganic origin (heavy) but also the relative concentrations of each type to mixtures. Baedecker and Back (1979) also have shown that 13C is enriched in landfill leachates showing delta 13C levels up to +30 0/00 (most natural groundwater in lithology similar to High Plains should have delta 13C levels from -12 to -20 0/00). Landfill impacts to ground water tend to enrich background ground water and shift 13C into positive readings at

THE CONCEPTUAL MODEL

impacted wells. Oxygen and Hydrogen Isotopes: The processes of evaporation, condensation and precipitation as well as the temperature at which these processes take place significantly affect the isotopic composition (2H/H and 18O/16O) of meteoric water. Oxygen and hydrogen isotopes in precipitation from around the world follow a consistent relationship characteristic of latitude and climatic conditions (Craig, 1961). This relationship results in a straight line represented by the following equation: 2H/H

= 8(18O/16O) + 10

This line is referred to as the meteoric water line. The 18O and 2H values are generally preserved in meteoric water after it enters the soil zone and infiltrates to the ground-water table. Significant deviations from the meteoric line are caused by physical and chemical processes which affect the isotopic composition of the water subsequent to precipitation. The conservative nature of 18O and 2H allows these isotopes to be used in leakage or mixing studies between two reservoirs of water that may be isotopically distinct. Paleoclimatic and seasonal effects can be also be seen from these data in changes along the meteoric line. Data plotted in the more positive reaches of the line (or towards 0 for both parameters) indicate water of origins from warmer climates whereas data plotted along the meteoric line towards more negative values may indicate water from colder climates. Ground water present from the glacial periods may indicate more negative results than more recent groundwater or precipitation. In a relative sense, these parameters can be used to age-date the groundwater. Tritium: This radioactive isotope has been most commonly applied in environmental studies. Understanding the regional and time-dependent distribution of all atmospheric environmental isotopes in rainfall is crucial for their application as a quantitative or semiquantitative tool in studies of aquifer pollution. Average tritium concentration in precipitation, corrected for radioactive decay since 1963, was very different in northern and southern hemispheres until 1968. Peak values for the thermonuclear tritium 3H in rainfall reached several thousand tritium units (TU) during the 1960s. The global distribution of the yearly average tritium concentration in precipitation during 1969 has varied. The tritium levels have not declined to less than 100 TU in temperate latitudes of the northern hemisphere. If tritium is detected at or near detection limits, the ground water is older than 40 years. Detectable tritium above background levels indicates water aged between the present and 40 years ago. The

half-life of tritium is 12.5 years. Studies conducted by other facilities of landfill leachates from older sites has shown tritium levels ranging from 200 to 10,000 tritium units. Since background ground-water and surface water tritium in Michigan probably is in the range of 10 to 35 TU, impacts from landfill leachate will greatly elevate these levels in downgradient wells. Results of a Geochemical and Isotopic Ground-Water Study Leachate was sampled from the older portion of the landfill to identify the geochemical and isotopic fingerprint of this potential source of ground water contamination. A boring through the landfill at the lower portion of the site was made until saturated refuse was found. Because the landfill was completed within the overlying till, the leachate and landfill are treated as a separate water-bearing zone compared to the underlying bedrock aquifer that is monitored by ground-water wells. Trilineal Diagrams: The trilinear plots of the leachate and the ground-water monitoring wells show distinct distributions of anions and cations in leachate from the ground-water monitoring wells (see Figure 887). Upgradient well MW04 also shows a different plot from the cluster formed by the other monitoring wells. This may be due to differences in overlying lithology (see cross-section in Figure 8-86) and the fact the MW04 is unconfined (i.e., ground-water level is within the bedrock). MW04 may be in a recharge location because it is located on a hillside. The downgradient wells and the other upgradient well, MW01, lie on a flowline from MW04. These wells have similar overlying lithology (silty tills) and are confined (i.e., ground-water levels are above the top of bedrock). If any of the downgradient wells were impacted by leachate, they would plot in a flowline between the upgradient wells and the leachate as end members and show a mixing effect (Baedecker and Back, 1979). Since leachate plots well away from the flowline, it is concluded that no mixing is occurring. Isotopes: (Deuterium vs. Oxygen-18) Ground water and leachate data show extreme differences in the ratio of deuterium and 18O. Leachate data plots above the meteoric line showing methanogenesis (Baedecker and Back, 1979). No ground-water wells show this affect and plot parallel to the meteoric line. The origin of ground water with the level of depletion shown for these isotopes has been age dated to over 10,000 years old. This indicates meteoric water from glacial or pre-glacial periods from a colder climate than present as the origin of this groundwa-

593

THE CONCEPTUAL MODEL

ter. Chloride and Alkalinity vs. 13C: These two graphs are useful in determining if mixing lines are occurring, similar to the trilinear diagrams. The leachate data and the upgradient well data are the end members of the line. If ground water was mixing with leachate, then downgradient wells would plot between the upgradient well, MW01 and leachate. The data show downgradient wells have 13C below the level of MW01 and similar to lower levels of the leachate indicator parameters, chloride and alkalinity. Chloride is a conservative parameter that moves with ground water without attenuation, biodegradation or precipitation. Alkalinity also is a good indicator of methanogenesis due to production of carbon dioxide that is soluble in groundwater. Elevated 13C is also evident of methanogenesis due to depletion of dissolved inorganic carbon as

methane that is outgassed. This enriches the delta 13C in leachate. There is no evidence of leachate impacting or mixing with ground water, because these levels are at or below background. Radioactive Isotopes: The results of tritium and 14C show extremely old ground water in both upgradient and downgradient wells. Leachate is enriched in tritium, indicating modern water from precipitation and luminescent paints. Tritium is an excellent tracer of ground water movement since it is part of the water molecule. The lack of tritium in ground water and the depletion of 14C well below 100 per cent modern carbon (PMC) show the lack of any leachate impact or release from the facility. The 14C results have been age-date corrected by 13C

81.1'

Surface Depression Begins

81.2'

Ground-water Surface Shallow (20 ft. Down)

81.0'

81.3' 81.4'

Surfical Sediments

Clay

Sand Clay

ndy to Sa

Clay

nd

y Sa Claye

Hawthorn Formation

y y Cla

Sand

Ocala Formation (Floridan Aquifer System)

stone

Lime

Sediments Gradually Move down into Limestone Void Spaces

Figure 8-89 Tertiary Ground-Water System 594

THE CONCEPTUAL MODEL

(Mazor, 1991). 13C accounts for dead carbon that may be present in the lithology that would bias the ground-water age if it were derived from shales, coals or dissolved naturally occurring methane. These sources are millions of years old and have no 14C, as its half life is over 5700 years. 14C age dating confirms the flowpath in that MW01 is the youngest ground water with an age of while the ages of the downgradient wells varies from 19,000 to 21,000 years old. Conclusions

quality from the facility. The statistical differences in downgradient quality from upgradient prediction limits are due to natural spatial geochemical differences. It is recommended that site-specific analytes be substituted for the RCRA Subtitle D, Appendix I metals for future detection monitoring. Also, due to the age of the ground water, an alternate liner (especially the in situ till) is suitable for a landfill in this environment. A demonstration of alternate liner design should be submitted to the state for formal approval as well as an alternate monitoring program consisting of alternative parameters and intra-well comparisons using control charts.

The results of the geochemical and isotope study show that there are no current impacts to ground-water

Surface Depression Intersects Water Table Surface Surface

Water Table Surfical Sediments

Clay

Sand Clay

ndy to Sa

Hawthorn Formation

y y Cla

Clay

Sand

nd

y Sa Claye

Ocala Formation (Floridan Aquifer System)

stone

Lime

Sediments Fall as a block into Limestone

Development of Karst Terrain and Internal Drainage to Sinkhole Lakes Figure 8-90 Development of Karst System 595

THE CONCEPTUAL MODEL

8.8.6 A Conceptual Model That Requires Historic Geology Interpretations to Establish Monitoring Zones This section describes the regional physiographic, geologic and hydrogeologic setting of a complicated geologic system that required evaluation of historic geological information to establish the most correct ground-water monitoring locations. Information was used from previous investigations for a basis of the site-specific geologic and

hydrogeologic setting. The state of Florida, the location of the example site, is divided into three topographic regions: (1) the low lying regions, less than 35 ft msl, (2) the intermediate regions, from 35 ft msl to 105 ft and (3) highland regions, above 105 ft msl (Lichter et al., 1968). The site is located in the highland regions associated with the Apopka Upland physiographic subdivision.

Lake Serves as Evaporative Surfical Sediments Flow Field Discharge Surface for Ground Water Lowest Head Between Sinkhole & Recycling Center Surfical Sediments Flow Field Horizontal Across Sinkhole Shallow Ground-water Flow Into Surface Depression 81'

N

82'

80' 70' 60'

Surfical Sediments

Clay Sand C

andy C lay to S

lay Sandy C

lay

Clay

Sand Clayey

lay

Sandy C

Regional Ground-water Flow to the Northeast

Ocala Formation (Floridan Aquifer System)

ne

Limesto

Modern Ground-water Flow System

Figure 8-91 Modern Ground-Water System 596

Hawthorn Formation

Slight Downward Gradients & Minor Flows into Ocala Formation Between Sinkhole and Soil Recycling Cente due to Deflections of Ground-water Flow Field to Below Dipping Clays

THE CONCEPTUAL MODEL

Drilling Methods Employed that Breached the Low Permeability Weathered Tuff e Several Inches of Leachat Organic Vapors

inated Soils Organic Residuals Contam

Weathered Silt

Silt thered

-65 ft.

Wea

Tuff

-100 ft.

Tuff

Target Unit

Three Phase Contaminated Zone at -65 feet Triple Tube Drilling Continued through the Perched Contaminated zone above Tuff Without Sealing off Unit by Double Casing the Hole

Leachate, Contaminated Soils and Vapors can Move Down Along Annular Space in Borehole

Actual Ground Water Surface Target Unit for Level 1 & 2

Southeastern coastal sediments can be grouped into two general categories: (1) clastic rocks that contain minor amounts of limestone and extend eastward and southward from southern Georgia to the Atlantic Ocean and Gulf of Mexico and (2) a thick, continuous sequence of shallow-water platform carbonate rocks underlying the Florida peninsula. In northcentral Florida, the clastic and carbonate rocks interfinger with one another; accordingly, lithofacies changes in this area are abrupt and complex. Stratigraphic Framework

Vitric Tuff Gray Weathered Surface

Level 2

2-10 foot Low Hydraulic Conductivity

-220 ft.

Target Unit

Weathered Surface of Bedrock Basalt

-245 ft.

Bedrock Basalt

Figure A

1st Drilling Phase

Figure 8-92 Initial Triple Tube Percussion Drilling to 100 ft Regional Geologic Setting The geologic materials of concern to this study are the unconsolidated to semiconsoldiated sedimentary rocks of Tertiary age which underlie the Coastal Plain province of Florida. The nomenclature used in this section is that of the previously established site stratigraphy and the Florida Geological Survey (Bond, 1996; Scott, 1993). The regional rock stratigraphic units include highly prolific carbonate aquifers which thicken southeastward from a feather edge in northern Florida, where they crop out, overlying older crystalline rocks to more than 5,500 meters thick in southern Florida. Locally, the general lowangle seaward dip of the Coastal Plain rocks is interrupted by faults or gentle folds.

Three regional stratigraphic units mapped by the Florida Geological Survey are identified beneath the site, in ascending order: (1) the Ocala Formation, (2) the Hawthorn Formation and (3) the undifferentiated Cypress Head Formation (Scott, 1993). Figure 8-88 shows the preTertiary ground-water system present at the site. The Ocala Formation consists of limestones composed of different textures deposited on a carbonate platform. Much of the limestone has been dolomitized to varying degrees. Anhydride and gypsum occur locally as beds and as pore-filling minerals, mostly in central and south Florida. The Hawthorn Formation overlies the Ocala Formation. It consists of Miocene-age clay, clayey sand and sandy clay with lenses of phosphorite and limestone. The lower part of the Hawthorn Formation generally contains more limestone than the upper part. The limestone commonly contains lithofacies transitions of sandstone known locally as “salt and pepper rock” (Lichter et al., 1968). The uppermost sediments in the region are referred to as the undifferentiated Cypresshead Formation. The Cypresshead Formation consists of Tertiary-age surfical quartz sands with minor clay associated with marine terNX Core Drilling Methods Were Conducted Through Ungrouted Casing Set at 100 Feet

Drilling Methods Breach the Geologic Unit and Push Multi-Component Contamination Into Target Monitoring Zone Sand Units 10 3/4" Hole is Extended by Triple Tube Percussion Drilling Along NX Core Hole Down to Bottom of Target Monitoring

Silt thered

-65 ft.

Wea

Tuff Unit

Leachate and Vapors can be Pushed into Targer Monitoring Zone Sand Seams by Air Pressure

Target Monitoring r Zone

2nd Drilling Phase - Core Drilling Through 1st Phase Borehole

Triple Tube Drilling Continued through the Perched Contaminated zone above Tuff Without Sealing off Unit by Double Casing the Hole

Leachate, Vapors and Contaminated Soils can Move Down Along Annular Space in Borehole

lt ered Si

Weath

-65 ft.

Tuff

Shallow Member r

5 inch Steel Casing is Set in the 10 3/4" Borehole and NX Coring is Taken Down to -245 feet

Target Unit

Organic Residuals

Weathered Silt

Actual Ground Water Surface Shallow Member for Level

NX (4") Core drilled Down 245 feet into Top of Priest Rapids

Level 2

-220 ft. 2-10 foot Low Hydraulic Conductivity

3rd Drilling Phase Bedrock Basalt

Figure 8-93 Coring into Bedrock

Contaminated Soils Remain at Bottom of Borehole

-245 ft.

Level 2 Shallow Member

2-10 foot Low Hydraulic Conductivity Weathered Surface of Basalt

Weathered Surface of Bedrock Basalt

-245 ft.

Tuff

1&2

Gray Weathered Surface Level 1

Gray Weathered Surface

-220 ft.

Several Inches of Leachate with Potential for Migration Down Borehole

Organic Vapor

Triple Tube Drilling Continued through the Perched Contaminated zone above Tuff Unit Without Sealing off Unit by Double Casing the Hole

Actual Ground Water Surface Target Monitoring Zone for Level 1 & 2

Organic Vapor Migrates Down Open Borehole

Basalt

5" Steel Casing used in Core Drilling set in 10 3/4" Open Hole

Soil Particles Contaminated with Organic Residuals Fall down Open Borehole

Figure B

Figure C

Figure 8-93 Extend the 10 3/4" Triple Tube Drilling

Figure 8-94 Extend the 10 3/4" Triple Tube Drilling

597

THE CONCEPTUAL MODEL

Open Hole allows Leachate to Move Down Borehole and Push Further Into Tabular Sand Units

Well Completion and Development Phase Leaves Residual Organics in Monitoring Well

In this Phase Drilling is Complete, but the Open Hole is not Protected from Perched Leachate, Vapors or Contaminated Soil Particles Moving Downward in Annular Space Between Outer Tube and Borehole Wall. These Contaminated Materials Mix with Ground Water in Target Unit lt ered Si

-65 ft.

Weath

Well Development Consists of Using Surge Blocks, Compressed Gas or Direct Pumping of the Well That Causes Agitation of the Filter Pack and the Drilled Area Adjacent to the Filter Pack. Resultant Water Quality Temporarily Improves.

Well Development Phase

Tuff

Weath

Tuff

Leachate & Vapors Move Down Along Annular Space in Borehole

Target Monitoring r Unit

Triple Tube Drilling Continued through the Perched Contaminated zone above Tuff Without Sealing off Unit by Double Casing the Hole

t ered Sil

- 65 ft.

Non-Drilling Phase (Pre-well Construction)

Shallow Member r

Target Unit

Well Development washes Organics away from direct contact with Filter Pack But leaves Residual Organics in Sand Lenses of Target Unit

Target Monitoring Zone

Actual Ground Water Surface Target Unit for Level 1 & 2

Actual Ground Water Surface Target Unit for Level 1 & 2

Leachate Residuals Further Pushed Into Sand Seams in Target Unit

Organic Vapors Pushed Into Sand Seams in Target Unit

Level 1

Level 1

Gray Weathered Surface

Gray Weathered Surface Level 2

Level 2

-220 ft.

- 220 ft.

2-10 foot Low Hydraulic Conductivity

2-10 foot Low Hydraulic Conductivity Weathered Surface of Bedrock Basalt

Weathered Surface of Bedrock Basalt

Leachate Pushed Into Sand Seams in Target Unit

-245 ft.

Soil Residuals That fell DownHole Remain at Hole Bottom

Bedrock Basalt

- 240 ft. Bedrock Basalt

Soil Residuals Adjacent to Screen Temporally Washed Away

Leachate Residuals Adjacent to Screen Temporally Washed Away

Figure E

Figure D

Figure 8-96 Well Construction

Figure 8-95 Pre-well Construction

race deposits (Scott, 1993). Regional Hydrogeologic Setting Structure The general low-angle southward dip of the Coastal Plain rocks is disturbed with a few faults or gentle folds. The nearest fault to the site is located approximately 75 miles away in Seminole County. The bedrock surface is undulatory ranging from 0 ft msl beneath the site to 50 ft msl near Orlando. Sinkholes are conspicuous throughout the county by the abundance of sinkhole lakes. Sinkholes are enclosed hollows of moderate dimensions originating because of dissolution of the underlying bedrock (Wilson, 1995). One of the lakes present at the site is a result of a buried sinkhole.

Well Sampling Phase Draws Residual Organics Back into Monitoring Well Well Sampling Consists of Direct Pumping of the Well that Cause Organic Residuals to be Drawn into the Filter Pack and included in the Sampling Process.

Well Sampling Phase t ered Sil

- 65 ft.

Weath Tuff

Target Unit

Leachate Residuals Adjacent to Screen Move Down Gradient

r

Well Development washes Organics away from direct contact with Filter Pack But leaves Residual Organics in Sand Lenses of Target Unit

Actual Ground Water Surface Target Unit for Level 1 & 2

Target Unit

Level 1

Gray Weathered Surface

Level 2

- 220 ft.

2-10 foot Low Hydraulic Conductivity Weathered Surface of Bedropck Basalt

- 245 ft. Bedrock Basalt

Leachate Residuals Pushed Back Toward Screens by Ground water Movement Through Sand Seams in Target Unit They are also Pulled into the Well During Sampling.

Organic Soil Residuals at Base of Screens Pulled into the Well During Sampling.

Figure 8-97 Well Construction/Sampling

598

Figure F

The regional hydrostratigraphic units are mapped regionally based on rock-stratigraphic water-bearing or confining properties. The regional aquifer is the Floridan Aquifer system overlain by a confining unit (Hawthorn Formation). The confining units is overlain by a surfical sand that is water bearing under water table conditions. The following subsections are a summary of each regional hydrostratigraphic unit. Hydrostratigraphic Framework The regional aquifer consists of a sequence of highly permeable hydraulically interconnected carbonate rocks collectively referred to as the Floridan Aquifer System. The Floridan Aquifer System underlies the entire state and supplies potable ground water in all but southernmost and westernmost Florida (Franks, 1982). The principal stratigraphic units comprising the Floridan Aquifer System include the Ocala, Avon Park, Lake City and Oldsmar Formations of Eocene age and Suwannee Formation of Oligocene age. The Floridan Aquifer System can be divided in most places into an Upper and Lower aquifer that is separated by a less permeable rock. The Upper Floridan aquifer is generally more permeable than the Lower Floridan aquifer, except where the latter contains extensive zones of paleokarst. Its thickness ranges from 2100 ft in the northwest corner of the county to 2500 ft in the southeast corner (Johnston and Miller, 1988; Franks, 1982). The natural recharge, flow and discharge of the Flori-

THE CONCEPTUAL MODEL

dan Aquifer System are mostly controlled by the geometry and distribution of the overlying confining layer (Johnston and Miller, 1988). The regional potentiometric surface from 1980 indicates ground-water flow direction in the county is northeast with potentiometric head values about 52 ft msl in the vicinity of the site. Overlying the Floridan Aquifer System is a confining to semiconfining unit associated with the Hawthorn Formation. It consists of clayey sands with interbedded limestone ranging in thickness from 60 to 300 ft (Knochemus, 1975). Surfical aquifers include numerous surfical sediments of sand and shell associated with the Cypresshead Formation. The contact between the surfical sand and the underlying confining unit is gradational; the beds become finer with depth (Knochemus, 1975). Site Geologic Setting The site geologic setting was determined from existing boring logs, piezocone and monitoring well construction summaries. The surfical sediments described in previous facility reports were classified stratigraphically as the Cypress Head Formation. Site boring logs describe the surfical sand ranging from mostly brown, loose, dry, poorly graded sand (SP) to gray, medium dense, dry, silty clay (CL-ML). These sediments range in thickness from less than 10 ft beneath the limits of refuse to greater than 50 ft beneath Circle Lake. Underlying the surfical sediments at the site is a vertical gradation to sandy clay and fine-grained clayey sand with a few interfingering limestone beds. This heterogeneous mixture of sediments was classified stratigraphically as the Hawthorn Formation. Site boring logs describe this unit ranging from loose to well-cemented

poorly graded sand (SP) to green-gray lean clay (CL) to buff phosphatic limestone. These sediments range in thickness on site from 20 ft to 45 ft. Underlying the Hawthorn Formation at the site is limestone bedrock with interfingering clay beds. This rock stratigraphic unit was classified as the Ocala Formation. Site boring logs indicate this unit is soft, cream to tan, granular limestone with occasional clay lenses. Regional information suggests that the Ocala Formation is approximately 450 ft thick. Site Hydrogeologic Setting The site hydrogeologic setting consists of two waterbearing hydrostratigraphic units separated by a semiconfining unit. The uppermost water-bearing unit is the surfical sediments of the Cypresshead Formation. It is underlain by a semiconfining unit of cohesive and semicohesive sediments of the Hawthorn Formation. Beneath the confining unit is limestone of the Floridan Aquifer. Currently, the ground water beneath the site is monitored in the surfical sediments, the water-bearing sand lenses within the Hawthorn Formation and the Floridan Aquifer. The Floridan Aquifer is monitored by FL-series wells. The surfical sediments and the water-bearing sand lenses within the Hawthorn Formation are monitored collectively as a single hydrostratigraphic unit. The unit is monitored at three different zones: (1) the shallow zone designated by the A-series wells, (2) the intermediate zone designated by the B-series wells and (3) the deep zone designated by the C-series wells. Although most of the Hawthorn Formation is a semiconfining unit, the upper water-bearing sands of this unit are monitored with the surfical sands and are referred to in this report as the surfical aquifer.

1,1,1 TCE vs Time

TCE vs Time

650

400 600 550

350

1, 1, 1 Trichloethlene (μg/l)

Trichloethlene (μg/l)

500

300 250 200 150 100

450 400 350 300 250 200 150 100

50

1/15

50

2/16

3/12

4/15

5/13

Sample Dates in Months

Figure 8-98 TCE Results

6/18

7/12

1/15

2/16

3/12

4/15

5/13

6/18

7/12

Sample Dates in Months

Figure 8-99 1,1,1 TCE Results

599

THE CONCEPTUAL MODEL

Double Cased Section of Borehole(s) was not Deep Enough to Seal out Contamination Before Drilling Open Hole.

Detail of Cross Contamination From Shallow Fractures into Drilled Borehole

Bedrock Fracture

Weeping from Fractures(s) into Open Boring Especially During Drilling & Purging

Overburden Contamination can move Easily Down Open Hole

Figure 8-100 Fractures Bypassing Double Casing Ground-Water Flow System Potentiometric surface maps were constructed for the Floridan Aquifer and the surfical aquifer. The potentiometric surface map of the Floridan Aquifer System indicates ground-water flow direction beneath the facility is northeastward. The regional potentiometric surface map for the Floridan Aquifer agrees with the site map. A mound is observed on the potentiometric surface based on the water level measured in site wells. The mound is likely due to the recharge contribution from the overlying surfical aquifer. The potentiometric surface map for the surfical aquifer indicates that ground-water flow direction beneath the facility is related to pre-construction ground surface topography. Ground-water flow converges toward the approximate area of the site lake. Hydrographs Hydrographs generated in this project illustrate the results of measuring the head level elevations of the MW-

600

01 piezometer cluster for three points that are situated at 20, 40 and 60 ft, respectively, below ground surface over a one-year period. The three head levels track almost exactly along the same line. One would conclude that the ground water flow through this area would be horizontal with no vertical flow component. In order to evaluate the potential for vertical flow in the remaining well clusters surrounding the site lake all surfical piezometers adjacent to Circle Lake were plotted on a single hydrograph. This resulted in all twelve piezometers tracking along the same line as the MW-01 well cluster. We would conclude that ground-water flow surrounding the site lake has little if any downward (or upward) flow component as it moves across the lake. Surfical Aquifer Ground-Water Flow Direction The relative head levels of ground water in these hydrographs can be used for the evaluation of up-todown gradient relationships. Hydrographs provide information on how consistent the surfical aquifer groundwater flow is throughout the year. Data for new wells

THE CONCEPTUAL MODEL

located at the Soil Recycling Center (although only measured in 1996) show the most downgradient point in the surfical aquifer is between Circle Lake and the Soil Recycling Center. Floridan Aquifer Ground-Water Flow Direction Hydrographs for the Floridan Aquifer show how consistent the hydraulic flow relationships between the various Floridan piezometers are maintained during the year. These spatial data were used to evaluate flow directions in potentiometric maps for the Floridan Aquifer. These data show that ground water flow in the Floridan Aquifer is to the northeast. Relationships between the lake level and adjacent piezometers show that the lake is typically the same or slightly higher than the adjacent ground water surface. This is not surprising considering the high hydraulic conductivity of the sediments surrounding the lake and the potentially high evaporation rates of the lake surface during most of the year. Conceptual Hydrogeologic Model A series of four conceptual illustrations that represent the geologic and hydrogeologic formation of the groundwater flow systems at site are provided in Figures 8-88 to 8-91. These illustrations are based on both regional and site-specific data. Figure 8-88 shows the layered sediments existing before the development of sinkhole caused modification to the layered materials. Figure 8-89 shows how the layered sediments first gradually moved downward into the limestone voids, causing warping of sediments and eventually causing a surface depression. Figure 8-90 continues the development of the sinkhole formation process into both a downward movement of cohesive pieces of the Hawthorn formation and infilling of sandy surfical materials. This development of a geomorphic Karst terrain effected both the surface settlements and formation of an internal drainage pattern for the surfical ground-water system. The gradual formation of lakes due to the depression of the ground surface to below the ground-water table probably aided the formation of the internal drainage patterns in the Florida Lake District. Figure 8-91 shows the modern day ground-water flow system present at the example facility. This flow system is marked by an internal drainage system that moves in the surfical aquifer radially inward toward an area adjacent to Circle Lake where ground-water in the shallow unit shows downward gradients to the Floridan Aquifer. This downward gradient most likely represents flow between clay

blocks in sandy sediments with more permeable zones that interconnect to the Floridan Aquifer. Ground water also evaporates from (and rainfall recharges to) the surface of Circle Lake during much of the year, but this evaporation (and recharge) does not cause significant upward (or downward) gradients in adjacent surfical aquifer sediments. Ground Water Monitoring System Design The design of the ground-water monitoring system for the example facility was based on the use of all the geologic and hydraulic data gathered over the last ten years. This includes regional and site based information for seasonal, spatial, geomorphic and hydrodynamic flow analysis for the facility. One of the primary tools in this evaluation is the multiple hydrographs. They provide the basic directional information on the composite groundwater flow field represented in the conceptual models and flownet presentations. The following main points were used to design the recommended ground-water monitoring system for the facility: • Ground-water flow in the surfical aquifer is radial inward toward an area between the Site Recycling Area and the site lake (see ground-water contour maps and conceptual models) • Ground-water flow in the Floridan Aquifer is to the northeast toward Wekeva Springs; both site and regional data illustrate this flow direction. • The ground-water flow path (target monitoring zone) for the surfical aquifer is represented by radial flow toward the area between Circle Lake and the Site Recycling Area. This interception of the surfical aquifer flowpath is by wells to the southwest of the lake such as the MW-03 C, MW 12B and MW-11B. Since the flow is radially inward these three wells meet the state criteria for downgradient wells on a 500 foot spacing pattern.

The basis for an alternative well design is due to the well-defined directional and high flow rates in the Floridan Aquifer and other specific site conditions including the nature of the waste (C & D with low health risk); the statistical methods do not require additional background wells and the geomorphic-related internal flow of the surfical aquifer favors this alternative placement of wells. 8.8.7 Conceptual Models to Illustrate Specific Issues Conceptual models can be used for supporting or

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explaining observed water quality or hydraulic head data from a piezometer or well. This section presents a series of conceptual models that illustrate how actions used in the process of drilling and well installation can be combined with geologic and observed water quality to solve a specific site assessment issue. Figures 8-92 to 8-96 do not represent an specific site and are used for illustrative purposes only of the development of a series of conceptual model to explain observed conditions. The conceptual understanding of this particular hydrogeology was initially difficult to follow and had to be broken down into the basic scientific principals of ground-water flow. The well in question had for many years (10 years) seen low levels of VOCs gradually Over the years the VOCs reached a point where a detailed investigation of the particular well was conducted to evaluate if there was a good technical reason why the well showed the observed values. The basic question to answer is: are the analyical results due to problems with the well or the downward movement of the VOCs through the geological units? Following the drilling and well installation procedure by using conceptual models can explain the results obtained in the targeted site investigation. The consultant elected to use a triple-tube percussion method to advance the hole down to the saturated zone. This was different from the traditional method used on site of double casing the vadose zone and then advancing the boring down to the saturated zone to install the monitoring well screen. •

•

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Figure 8-92. The initial drilling of the assessment well down to -100 ft below ground surface (BGS) provided the first contact with a known organic contaminated zone existing between -60 and -80 ft (BGS) and the top of the unit that represents the target monitoring zone for the facility. The contaminated zone likely consisted of a three phase; vapor, contaminated soils and potentially a thin saturated zone above the weathered silt unit. The triple tube percussion method used in this drilling effort most likely did not seal off the contaminated zone during the downward drilling into the target monitoring zone. The illustration shows how portions of the phased contamination could move downward at this time in the annular space between the borehole wall and the outer drill stem casing. This is the point at which the borehole would normally have been double cased and grouted to seal off the shallow contamination zone from deeper drilling activities. Figure 8-93 illustrates the lowering of a 5-inch steel casing into the 10 3/5” hole and using this pipe to drill and sample down to 245 ft. This would have been several tens of feet into the underlying basalt.

As shown in Figure 8-93 the smaller casing most likely left room for significant contamination to move down into the hole during the core drilling process that took two to three days to complete. Having an open hole in contact with known zones of phased organic contamination is a recipe for real problems. The resultant water quality obtained for the completed well provided classical drag down analytical results. •

Figure 8-94. This second drilling phase with the triple tube system takes the hole down to the target monitoring zone in the geological unit (which has two target monitoring zones 1 or 2). Since the contaminated zone above the Target Monitoring Zone was not double cased, contaminated soil, vapor and liquids could move down the borehole at any time in the drilling process. The high air pressures used in the drilling process could also have forced contaminated liquids and vapors into the more permeable sandy units in the target monitoring zones at the bottom of the target monitoring zone.

•

Figure 8-95. This period of time after drilling and before well construction potentially could allow any of the phased contamination to move down the well borehole to the bottom of the hole when the air pressure used during drilling was not in place.

•

Figure 8-96. This phase includes the completion and development of the well inclusive of screen placement, primary filter packs, primary bentonite seals, final grouting, development and surface completion. None of this work would have been able to remove contaminated soil residuals that fell into the hole, nor leachate residuals that would have been pushed into the sidewalls of the borehole. Although, redevelopment could temporally lower contamination observed in the well, the high organic parameter levels will always return once the ground water flow or well sampling pulls residuals back into the screens. This conclusion has been confirmed through the resultant water quality observed in this hole over a two year period.

•

Figure 8-97. This phase includes the direct sampling of the affected wells inclusive of well purging and sampling. Leachate residuals, during this phase, are pulled into the well sampling zone from the affected sand seams in the lower Shallow Member. The analytical results show the ability of the contaminated residuals to continue to provide significant levels of organic parameters to the well screen sampling zone. The downgradient movement of contaminated residuals can also affect an adjacent well’s water quality.

THE CONCEPTUAL MODEL

Under these conditions one cannot trust water quality results from any adjacent wells, since purging before sampling can cause ground water to flow in almost any direction toward the pumping (purging) well. A ground-water sample collected from the well installed in this investigation reported the presence of seven VOCs, ranging from a few μg/l to a few hundred μg/ l. Additional sampling events were obtained from the well in March, April and May of a single year. These data for two parameters include time trend graphs. Several of these graphs are reproduced as Figures 8-98 and 8-99. Figure 8-99 shows the relationships between 1,1,1trichloroethane vs. time over a six-month sampling period. Considering the comparatively high level of 1, 1, 1-TCE found in February, the level shown in May represents more than a 50 times reduction in concentration for this parameter. Figure 8-98 also shows a similar major reduction in parameter concentration levels as illustrated in Figure 8-99. Other time/trend graphs or organic parameters also show either (1) initially high organic parameters that reduce significantly to less than 20 ppb or, (2) persistent low levels of organic parameters that remain at just detection levels. The organic signature illustrated in these graphs represents a classical example of drag-down water quality obtained from an affected well. Initial high levels of organic parameters incorporated into the well’s grout and filter packs through organic residuals attached to soil particles are gradually reduced as the well is developed or just through sampling of the well. The resultant water quality never totally cleans-up, because the contained soil particles organic residuals can contribute 10 to 30 ppb levels of organics to the well screen zones for years. If the well in question was completed into contaminated ground water, the well would not show initial high levels of organic parameters that drop radically through sampling or development. Monitoring wells are not pumped during the sampling process sufficient to cause dilution to the low levels observed for the data gathered for this facility if the contamination came from the Shallow Member. This unit has too low hydraulic conductivity to produce the quantity of ground water to the point where dilution could come into play. Only production wells where very large volumes of water are pumped out of an aquifer with a small contaminated zone would sufficient mixing and dilution occur to reduce the organic parameters from hundreds of ppb to less than 20 ppb. The initial high levels of organics observed can only be due to drag-down of contaminated soil during the drilling process that became incorporated into the well construction.

Cross-Contamination Illustrative Example Figure 8-100 shows a conceptual model to address the potential for double casing of a well at a bedrock/ overburden surface. The example shows how fractured rock can potentially require extension of double casing down much further into the bedrock than would be normally expected. The key to this evaluation was the use of a downhole video camera to document flow into the open borehole from fractures dipping down into the well. The conceptual model provides the investigator options for displaying technical ideas that words alone would leave the reviewers scratching their heads. The illustrations show clearly and to the point of this issue at hand. 8.9 CONCLUSIONS This chapter developed the integration of flownet constructions and conceptual models. Just as some sites are not amenable to computer modeling, some of these sites are also difficult to draw reasonably accurate flownets. It is recommended that conceptual models be generated for all project sites even if an integrated flownet construction is difficult or impossible for the geologic environment. The conceptual model can provide the key to an effective ground-water monitoring program or aquifer remediation. As such, conceptual models should form part of the overall site interpretation before designs of the facility monitoring or aquifer remediation.

REFERENCES Administrative Rules of Montana (ARM) Title 36, Chapter 21. Administrative Rules of Montana (ARM) Title 16, Chapter 14, Sub-Chapters 5 and 7. Administrative Rules of Montana (ARM) Title 16, Chapter 14, Sub-Chapters 5 and 7. Alpha, W.C., 1932. Tectonic History of North-Central Montana, in Sweetgrass Arch. Disturbed Belt, Montana, P.T. Lewis (ed), 6th Annual Field Conference Guidebook; Billings Ged. Soc., pp. 129-142. ASTM, 2002. Annual Book of ASTM Standards D5092 (Designing and Installation of Ground Water Monitoring Wells in Aquifers); Annual Book of ASTM Standards, American Society for Testing and Materials, Philadelphia, vol. 04.08, pp Back, W., and R. A. Freeze, 1985. Physical Hydrogeology Baedecker, M. J., and Back, W., 1979. Hydrogeological Processes and Chemical Reactions at a Landfill: Ground Water, v. 17, pp 429-437. Bear, J. and G. Dagan, 1965. The Relationship Between Solutions of Flow Problems in Isotropic and Anisotropic Soil. J. Hydrol., 3.

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Bond, P., 1996, Personal Communication, District Geologist, Florida Geological Survey. Budinger and Associates, Inc., 1984. Field and Laboratory Investigation, City Transfer and Disposal Inc., Site C, Great Falls, Montana. Casagrande, A., 1937. Seepage Through Dams, Harvard University Pub. 209, reprinted from Journal of the New England Water Works Assoc., June, 1937. Cedergren, H.R., 1967. Seepage, drainage and flownets. John Wiley & Sons, New York, pp. 184–204. Code of Federal Regulation, 1990. Title 40. Part 143. National Secondary Drinking Water Regulations. Office of the Federal Register. National Archives and Records Administration. US Government Printing Office, Washington, D.C. Cooley, R. L. et. al., 1972. Hydrologic Engineering Methods for Water Resources Development, Vol.10; Principles of Ground-Water Hydrology, Corp. of Engineers, Davis California. Craig, H., 1961. Isotopic Varations in Meteoric Waters, Science 133, pp. 1702-1703. Cushing, C. E., ed., 1995, Hanford Site National Environmental Policy Act (NEPA) Characterization, PNL-6415, Rev. 7, Pacific Northwest Laboratory, Richland, Washington. Delaney, C. D., K. A. Lindsey, and S. P. Luttrell, 1991. Geology and Hydrology of the Hanford Site: A Standardized Text for Use in Westinghouse Hanford Company Documents and Reports, WHC-SD-ER-TI-003, Rev. 0, Westinghouse Hanford Company, Richland, Washington. DOE, 1988. Consultation Draft, Site Characterization Plan, Reference Repository Location, Hanford Site, Washington, DOE/RW-0164, Vols. 1 and 2, U.S. Department of Energy, Richland, Washington. DOE-RL, 1998b, Groundwater/Vadose Zone Integration Project Specification, DOE/RL-98-48, Draft C, U.S. Department of Energy, Richland Operations Office, Richland, Washington Domenico P.A. and F.W. Schwartz, 1990. Physical and Chemical Hydrogeology, Wiley Publishers, New York. Ferris, J.G., D.B. Knowles, R.H. Brown and R.W. Stallman. 1962. Theory of aquifer tests. U.S. Geol. Survey Water– Supply Paper 1536–E, pp. 69–174. Fishel, V. C., 1935. Further Tests of Permeability with Low Hydraulic Gradients, Transactions, American Geophysics Union, p. 503. Foley, F. C., W. C. Walton and W. J. Dreschler, 1953. Groundwater Conditions in the Milwaukee-Waukesha Area, Wisconsin, U.S. Geological Survey Water Supply Paper 1229. Ford, D.C., A.N. Palmer and W.B. White, 1988. Landform Development, Karst, in Back, W., Rosenshein, J.S. and Seaber, P.R., eds. Hydrogeology, The Geology of North America; Geological Society of America DNAG Vol. O-2. Franks, B.J., 1982. Map of Principal Aquifers in Florida; United State Geological Survey Water-Resources Investigation Open-File Report 82-255. Freeze, R.A. and J.A. Cherry. 1979. Ground water. Prentice– Hall, Inc., NJ, 604 pp. Freeze, R.A. and P.A. Witherspoon, 1967. Theoretical analysis of regional ground water flow. American Geophysical

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Union, Water Resources Research, 3, pp. 623–634. Hill, R. A., 1940. Geochemical Patterns in Coachella Valley, California: American Geophysical Union Transactions v. 21, pp. 46-49 Hubbert, M.K. 1940. Theory of ground water motion. J. Geol., 48, pp. 785–944. Hughs, T., 1991. Personal Communication. Hvorslev, M.J., 1951. Time Lag and Soil Permeability in Groundwater Observations, U.S. Army Corps of Engineers Water vays Exp. Sta. Bull. 36, Vicksburg, Mississippi. J. Geophys. Res., 68, pp. 4796–4812. (Also published in Natl. Res. Council Canada, Proc. Hydrol. Symp. 3, Ground Water, pp. 75–96, 1963.) Johnston, R.H. and J.A. Miller, 1988. Region 24, Southeastern United States in Back, W., Rosenshein, J.S. and Seaber, P.R., eds. Hydrogeology, The Geology of North America; Geological Society of America DNAG Vol. O-2. Jordan, A.N. and D.E. Mekeel, 1995. Bibliography of Index of Graduate Theses and Dissertations on Florida Geology Through 1991 Including Abstracts; Florida Geological Survey, Special Publication No. 29. Knochemus, D.D., 1975. Hydrologic Concepts of Artificially Recharging the Floridan Aquifer in Eastern Orange County, Florida; Florida Department of Natural Resources Report of Investigations No. 72. Krieger, H.L. and E.L. Whittkar 1980. Prescribed Procedures for Measurements of Radioactivity in Drinking Water. Ed., EMSL. EPA-600-4-80-032 p. 49. Lehr, J., 1962. Ph.D. Thesis, University of Arizona. Lemke, R.W., 1977. Geologic Map of the Great Falls Quadrangle, Montana; U.S. Geological Survey Open-File Map. Lemke, R.W. and S. Maughan, 1977. Engineering Geology of the City of Great Falls and Vicinity, Montana; U.S. Geologic Survey Miscellaneous Investigations Map I-1025. Lemke, R.W., E.K. Maughan and D. Erskine. 1954. Preliminary Geologic Map of the Portage Quadrangle, Montana; U.S. Geologic Survey Open File Map OFR 54-166. Leonards, G. A., 1962. Foundation Engineering, McGraw-Hill Book Co., New York, pp. 107-39. Liakopoulos, A.C., 1965. Variation of the Permeability Tensor Ellipsoid in Homogeneous Anisotropic Soils, Water Resources Research, l. Lichter, W.F. W. Anderson and B.F. Joyner, 1968. Water Resources of Orange County, Florida, Florida Department of Natural Resources Report of Investigations No. 50. Lindsey, K. A., B. N. Bjornstad, J. W. Lindberg, and K. M. Hoffman, 1992. Geologic Setting of the 200 East Area: An Update, WHC-SD-EN-TI-012, Westinghouse Hanford Company, Richland, Washington. Lindsey, K. A., 1995. Miocene- to Pliocene-Aged Suprabasalt Sediments of the Hanford Site, South-Central Washington, BHI-00184, Rev. 00, Bechtel Hanford, Inc., Richland, Washington. Maasland, M., 1957. Soil Anisotropy and Land Drainage. Drainage of Agricultural Lands, J.N. Luthin, ed. American Society of Agronomy, Madison, Wis. Marcus, H. and Evenson, D.E., 1968. Directional Permeability

THE CONCEPTUAL MODEL

in Anisotropic Porous Media. Water Resources Center Contribution No. 31., Univ. of California, Berkeley. McWhorter and Sunada, 1977. Ground-Water Hydrology and Hydraulics, Water Resources Publications, Fort Collins, CO. Miller, J.A., 1988, Coastal Plain Deposits, in Back, W., Rosenshein, J.S. and Seaber, P.R., eds. Hydrogeology, The Geology of North America; Geological Society of America DNAG Vol. O-2. Montana Administrative Code, Title 16, Chapter 2, Sub-Chapter 5. Muskat, M., 1937. Flow of Homogeneous Fluids Through Porous Media. McGraw-Hill Book Co., 139 pp. Newcomb, R. C. and J. R. Strand, 1953. Geology and GroundWater Characteristics of the Hanford Reservation of the U.S. Atomic Energy Commission, Washington. U.S. Geological Survey Administrative Report WP-8, U.S. Geological Survey, Washington, D.C. Piper, A. M., 1944. A Graphic Procedure in the Geochemical Interpretation of Water Analysis, Trans Amer. Geophys. Union, 25, pp 914-923. Phelps, G.G., K.P. Rohrer and St. Johns River Water Management District, 1987. Hydrogeology in the Area of a Freshwater Lens in the Floridan Aquifer System, Northeastern Seminole County, Florida; United States Geological Survey Water-Resources Investigations Report 864078. Qubain, B.S., E.J. Seksinsky and E.G. Aldin, 1995, Techniques to Investigate and Remedy Sinkholes, in Beck B., ed., Karst Geohazards, Balkema Publishers, Rotterdam. Sara, M.N., 1993. Standard Handbook for Solid and Hazardous Waste Facility Assessments, Lewis Publishers, Boca Raton, FL. Scott, T., 1993, Geologic Map of Orange County, Florida, Florida Geological Survey, Map Series No. 47. Sinclair, W.C. and J.W. Steart, 1985, Map of Sinkhole Type, Development and Distribution in Florida, Florida Geological Survey, Map Series 110. Spane, Jr., F. A. and V. R. Vermeul, 1994, Summary and Evaluation of Hydraulic Property Data Available for the Hanford Site Upper Basalt Confined Aquifer System, PNL-10158,

Pacific Northwest Laboratory, Richland, Washington. Stojic, P., M. Milicevic, P. Milanovic and E.B. Trebinje, 1976. Use of Piezometers for Karst investigations in Yejvevich, V., Karst Hydrology and Water Resources, Vol. 1; Water Resources Publications, Boulder, Colorado. Szpakiewicz M., 1990. Application of Natural Isotopes in Groundwater for Solving Environmental Problems, National Institute for Petroleum and Energy Research, Bartlesville, Oklahoma, NTIS, NIPER-450, DE90000223 Taylor, D. W., 1948. Fundamentals of Soil Mechanics, John Wiley and Sons, New York, pp. 97-123. Tibbals, C.H., 1975. Map of Recharge Areas of the Floridan Aquifer in Seminole County and Vicinity, Florida, Map Series No. 68. Todd, D.K., 1980. Groundwater Hydrology (2nd edition). John Wiley and Sons. 535 pp. Toth, J.A., 1962. Journal of Geophysical Research, 67:4375– 4387. Toth, J., 1963. A Theoretical Analysis of Ground-Water Flow in Small Drainage Basins. U.S. EPA, 1986. Criteria for Identifying Areas of Vulnerable Hydrogeology Under the Resource Conservation and Recovery Act, Appendix B, Interm Final. PB86-224979. U.S. EPA, 1986. Ground-Water flownet/Flow Line Construction and Analysis, Appendix B, Criteria for Identifying Areas of Vulnerable Hydrogeology Under the Resource Conservation and Recovery Act; PB89-224979. U.S.G.S., 1980. (photorevised), 7.5-minute Quadrangle Map, Apopka, Florida. Walton, W.C., 1962. Selected Analytical Methods for Well and Aquifer Evaluation, Illinois Department of Registration and Education Bulletin 49. 81 pp. Willman et al., 1975. Handbook of Illinois State Geologic Survey Bulletin 95, Urbana, Illinois 261 pp. Wilson, W.L., 1995. Sinkhole and Buried Sinkhole Densities and New Sinkhole Frequencies in Karsts of Northwest Peninsular Florida, in Beck B., ed., Karst Geohazards, Balkema Publishers, Rotterdam.

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CHAPTER 9 MONITORING SYSTEM DESIGN 9.1 INTRODUCTION TO MONITORING DESIGN There are at least three different types of monitoring programs commonly applied to site assessment and remediation projects. These may begin with area reconnaissance monitoring of wide areas and then focus down to detection monitoring of a specific facility. Assessment monitoring includes program elements from RCRA subtitles C and D, and many aspects of ground-water monitoring under the Superfund program. Chapter 2 described the regulatory requirements of these programs, and this chapter builds on the design elements important to locating monitoring points optimum for the purpose of the program. The discussion will begin with detection monitoring programs, and addresses design aspects of assessment monitoring programs. The area-wide reconnaissance programs may have very different design goals as compared to the more regulatory driven detection/assessment programs. To design an optimum or ideal ground-water monitoring system in a detection program, a wish list of system attributes can be formulated: • Three-dimensional array of monitoring points for discrete sampling and hydraulic testing • Continuous real-time measurements of chemical parameters of chemical parameters and hydraulic head at each monitoring point • As few as possible holes penetrating the facility area • Sufficient monitoring points so that complex geology will not confound detection of potential releases from the facility • Significant releases observable by sufficiently frequent measurements of indicator parameters • Reliable installations to maintain reproducibility and representativeness of the sampling • Convenient maintenance and quality auditing

These seven attributes of an ideal ground-water monitoring system are not obtainable by current technology; however, many aspects of these points can be approached through a well-designed monitoring system using a conceptual understanding of the geologic conditions present on the target site. Because the majority of ground-water systems move slowly and in predictable pathways (if you understand the subsurface environment sufficiently!), the attributes of continuous monitoring at many points can be achieved if the target monitoring zone (ASTM D 5092, 2002) is carefully selected and a reasonable sampling period is established. Techniques provided in previous chapters of this manual combined with those described in the ASTM D 5092 standard Practice for the Design and Installation of Ground Water Monitoring Wells in Aquifers will effectively address the remaining 5 points expressed above. Selection of the proper locations for monitoring wells should be based on a holistic approach to the evaluation of a specific site. The placement of the wells in this process must weigh and balance data collected in the field, laboratory and office. The question “How much detection monitoring is enough?” when answered in the context of the number of monitoring wells required at a site, will be entirely site specific. In general, the monitoring system designer should ensure that convincing evidence is established for each assumption and for demonstrating the basic capability of the system to produce ground-water samples representative of both upgradient (background) and downgradient conditions. General rules of thumb are provided in this chapter, but the reader should bear in mind that “enough” is a subjective determination for the questions of how much monitoring is necessary to provide a monitoring system capable of detecting ground-water contamination and how much demonstration is required to convince a regulatory agency of that capability. The key to most regulatory programs that require ground-water monitoring is demonstration that the system is capable. The owner or operator of a facility required to

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monitor ground water must install and implement a monitoring system capable of determining the facility’s impact on ground water; it must be capable of yielding representative ground-water samples for analyses. The number, locations and depths of the detection monitoring wells must be such that the system is capable of the prompt detection of any statistically significant differences in indicator parameters. The monitoring system designer must base decisions on sufficient numbers and locations of monitoring wells on performance-oriented criteria to describe a sufficient monitoring system, as it will be a very unusual monitoring situation in which as few as several downgradient wells would ensure system capability. Some very simple geologic environments can be effectively monitored with the U.S. EPAspecified minimum system of one upgradient and three downgradient wells; however, this level of monitoring may be representative of very few sites. It is not uncommon for monitoring systems to employ many sampling points in detection monitoring. This is especially true for sites located in heavily regulated states. This is also true for facilities in operation over long periods of time and consisting of multiple cells or expansions. 9.2 REGULATORY CONCEPTS IN FACILITY MONITORING Many regulatory concepts surround monitoring of all types of facilities, but specifically hazardous and solid Land Surface

waste management facilities evolve around compliance with U.S. EPA regulations on ground-water monitoring. Specifically RCRA regulations (40 CFR 264.97) set requirements for ground-water monitoring at hazardous waste sites. For example, the owner or operator of a hazardous waste management facility must comply with the following requirements for any ground-water monitoring program developed to satisfy §264.98, §264.99 or §264.100: (a) The ground-water monitoring system must consist of a sufficient number of wells, installed at appropriate locations and depths to yield ground-water samples from the uppermost aquifer that: (1) Represent the quality of background (upgradient) ground water that has not been affected by possible leakage from a facility; and (2) Represent the quality of ground water downgradient of the facility. (b) If a facility contains more than one regulated unit, separate ground-water monitoring systems are not required for each regulated unit provided that provisions for sampling the ground water in the uppermost aquifer will enable detection and measurement at the compliance point of hazardous constituents from the regulated units that have entered the ground water in the uppermost aquifer.

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Figure 9-1 Regulatory Context of Detection Monitoring 608

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MONITORING SYSTEM DESIGN

Many millions of dollars and millions of words in reports and meetings have been spent on defining exactly what these relatively few lines of text really mean in the context of actual monitoring of hazardous waste sites. Both RCRA Subtitle C (hazardous waste) and Subtitle D (solid municipal waste) facilities are required to meet these basic points of detection monitoring programs. This federal rule can be depicted in a single figure that illustrates the concept of detection monitoring. Figure 9-1 shows a conceptual presentation of the §264.97 guidance on placement of detection monitoring wells. The RCRA Ground-Water Monitoring Technical Enforcement Guidance Document (TEGD) provided additional guidance on placement and number of upgradient or background wells by recommending that these wells are: • Located beyond the upgradient extent of possible contamination from the hazardous waste management unit so that they reflect background water quality. • Screened at the same stratigraphic horizon(s) as downgradient wells to ensure comparability of data. • Of sufficient number to account for heterogeneity in background ground-water quality. The conceptual homogeneous unconfined uppermost aquifer, Figure 9-1, would still meet the above three TEGD requirements; however, this conceptual hydrogeologic condition is seldom observed in the field as such a simple unconfined aquifer flow system. RCRA Subtitle D (Oct. 13, 1991) includes many components specific to ground-water monitoring. Section 258.51 (ground-water monitoring systems) requires that: (a) A ground-water monitoring system must be installed that consists of a sufficient number of wells, installed at appropriate locations and depths, to yield ground-water samples from the uppermost aquifer (as defined in Section 258.2) that:

(I) Sampling at other wells will provide an indication of background groundwater quality that is as representative or more representative than that provided by the upgradient wells; and (2) Represent the quality of ground water passing the relevant points of compliance specified by the Director of an approved State under Section 258.40(d) or at the waste management unit boundary in unapproved States. The downgradient monitoring system must be installed at the relevant point of compliance specified by the Director of an approved State under Section 258.40(d) or at the waste management unit boundary in unapproved States that ensures detection of ground-water contamination in the uppermost aquifer. When physical obstacles preclude installation of ground-water monitoring wells at the relevant point of compliance at existing units, the down-gradient monitoring system may be installed at the closest practicable distance hydraulically downgradient from the relevant point of compliance specified by the Director of an approved State under Section 258.40 that ensures detection of ground-water contamination in the uppermost aquifer. The Director of an approved State under Section 258.51 (d) may approve a multi-unit ground-water monitoring system instead of separate ground-water monitoring system meets the requirement of Section 258.5 (a) and will be as protective of human health and the environment as individual monitoring systems for each MSWLF unit, based on the following factors: 1. Number, spacing and orientation of the MSWLF unite 2. Hydrogeologic setting 3. Site history 4. Engineering design of the MSWLF units 5. Type of waste accepted at the MSWLF units

(1) Represent the quality of background ground water that has not been affected by leakage from a unit. A determination of background quality may include sampling of wells that are not hydraulically upgradient of the waste management area where:

RCRA Subtitle, D Section 258.51 in section (2) goes on to require that in subsection (d) the number, spacing and depths of monitoring systems shall be:

(i) Hydrogeologic conditions do not allow the owner or operator to determine what wells are hydraulically upgradient; or

(1) Determined based upon site-specific technical information that must include thorough characterization of: (i) Aquifer thickness, ground-water flow rates, ground-water flow direction including

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MONITORING SYSTEM DESIGN

Figure 9-2a seasonal and temporal ground-water flow; and,

Unconfined Ground-Water System

fluctuations

in

(ii) Saturated and unsaturated geologic units and fill materials overlying the uppermost aquifer, materials comprising the uppermost aquifer and materials comprising the confining units defining the lower boundary of the uppermost aquifer, including, but not limited to: thicknesses, stratigraphy, lithology, hydraulic conductivities, porosities and effective porosities.

Figure 9-2b 610

The above technical Subtitle D requirements are comprehensive as to the full definition of site geological and hydrogeologic conditions. Many waste disposal facilities are located in complex geologic environments in which preliminary (or very extensive) site assessment investigations are required to properly locate the wells for detection ground-water monitoring systems as described above in the RCRA Subtitle D regulation. Layering of geologic units of significantly different hydraulic conductivity complicates the simple conceptual picture described by the federal rule.

Confined Ground-Water System

MONITORING SYSTEM DESIGN

Figure 9-2c

Unconfined/Confined Ground-Water System

Figures 9-2a and 9-2b show a two-layer system with the uppermost aquifer consisting of homogeneous isotropic sand below a near surface silt/clay unit of lower hydraulic conductivity. In Figure 9-2a, the uppermost aquifer is unconfined, in that water only partly fills an aquifer (i.e., potentiometric surface); the upper surface of the saturated zone is free to rise and decline. Where water completely fills an aquifer that is overlain by a confining bed, as shown in Figure 9-2b, the aquifer is said to be confined by the lower hydraulic conductivity unit. Downgradient well positions are shown as point B in both figures. Both upgradient and background wells are also shown in these figures. The concept of background representing not hydraulically upgradient locations but reflecting general water quality of the uppermost aquifer are represented by point C. In each case, the sand unit should be considered as the uppermost aquifer for the following reasons: • The sand unit has regional extent and is saturated. • The sand unit has sufficient hydraulic conductivity to produce usable quantities of water to springs or wells. • The sand unit would be the zone in which leachate from the facility could migrate horizontally away from the site to potentially affect human health and the environment. Much of the early concern of regulatory agencies with respect to subtitle C detection monitoring programs is with

meeting federal regulations in 40 CFR 265.91, which describes ground-water monitoring system requirements for interim-status hazardous waste disposal facilities. These regulations state: “A ground-water monitoring system must be capable of yielding ground-water samples for analysis and must consist of: (1) Monitoring wells (at least one) installed hydraulically upgradient (i.e., in the direction of increasing static head) from the limit of the waste management area. Their number, locations and depths must be sufficient to yield ground-water samples that are: (i) Representative of background ground-water quality in the uppermost aquifer near the facility; and (ii) Not affected by the facility; and (2) Monitoring wells (at least three) installed hydraulically downgradient (i.e., in the direction of decreasing static head) at the limit of the waste management area. Their number, locations and depths must ensure that they immediately detect any statistically significant amounts of hazardous waste or hazardous waste constituents that migrate from the waste management area to the uppermost aquifer.” This interim status rule on ground-water monitoring has several key features different from §264.97 rules that have been widely used in defining what a detection

611

MONITORING SYSTEM DESIGN

monitoring system should consist of, specifically: • One monitoring well upgradient and three downgradient from a facility • Immediate detection capabilities While immediate detection is open to widely variable interpretation, especially considering the slow movement of ground water, the TEGD provides some additional guidance on how to meet the “immediate” criteria by placing detection monitoring wells immediately adjacent to the waste management unit. The federal Subtitle D regulations proposed for nonhazardous solid waste sites, (early 1989), set 150-m buffer zones (or property boundary, whichever is less) for placement of monitoring wells. This buffer zone was also included in the final rules and might include a compliance boundary set at the edge of the waste management unit. Reducing these federal regulations to a series of criteria based on concepts presented in this text results in a series of technical points. The detection monitoring system should have: • Sufficient wells, both upgradient (background) and downgradient, to detect discharges from the regulated facility • Wells located within a flow path from the regulated facility in the uppermost aquifer Furthermore, the uppermost aquifer should have sufficient hydraulic conductivity and extent so that sampling could be conducted within the waste unit boundary for both hazardous waste Subtitle C facilities and Subtitle D solid waste sites. An adequate detection monitoring program can be designed for any geologic/hydrogeologic environment using the above criteria. The following chapter sections present conceptual models for detection monitoring programs for a wide variety of hydrogeologic environments. Prior to selecting the locations and depths for the screened intervals for ground-water monitoring wells, the ground–water monitoring system designer must have, at a minimum: • Performed a complete site characterization • Established a conceptual hydrogeologic model for the site • Constructed a ground-water flownet • Located facility boundaries and waste disposal areas Each of these tasks provides data that will be used to select the target monitoring zones for the monitoring sys-

612

tem. The remaining sections describe the monitoring system process summarized in Figure 9-3. Examples of the process are included to assist in the design conceptualization process. 9.3 DATA ANALYSIS REQUIRED FOR DESIGN Geologic factors (related chiefly to geologic formations and their water-bearing properties) and hydrologic factors (related to the movement of water in the formations) must be known in some detail to properly design a groundwater monitoring system. These data are normally developed in a field investigation as described elsewhere in this manual The geologic framework of a site includes the lithology, texture, structure, mineralogy and distribution of the unconsolidated and consolidated earth materials through which ground-water flows. The hydraulic properties of these earth materials depend upon the geologic framework. Thus, the geologic framework of the facility heavily influences the design of the ground-water monitoring system. Elements of the hydrogeologic framework and the site hydrogeology that should be considered in ground-water monitoring system design include: • The spatial location and configuration of the uppermost aquifer and its hydraulic properties (e.g., horizontal and vertical hydraulic conductivity, depth and location of ground-water surface, seasonal fluctuations of ground-water surface elevation) • Hydraulic gradient (vertical and horizontal) within the geologic materials underlying the facility • Discharge and recharge areas of the site • Facility operational considerations These data are used to establish the locations of both upgradient and downgradient wells in the uppermost aquifer. Both upgradient and downgradient wells should be located in the direction of ground-water flow along flow pathways most likely to transport ground water and the potential contaminants contained in ground water. These pathways should be identified from data gained from existing information and the phased site investigations. The objectives of the field site investigations and subsequent data analysis and interpretations to provide some or all of the following information: • Lithologic characteristics of the subsurface, including: – Established stratigraphic names – Classification of hydrogeologic units – Extent of hydrogeologic units

MONITORING SYSTEM DESIGN

Figure 9-3 Monitoring System Design Summary

613

MONITORING SYSTEM DESIGN

• Key hydrogeologic characteristics used to describe the site to the conceptual model including: – Hydraulic conductivity (vertical and horizontal) – Porosity – Gradient (vertical and horizontal) – Specific yield • Aquifer characteristics including: – Boundaries – Type of aquifers – Saturated/unsaturated conditions Each piece of data is an important building block in establishing the conceptual hydrogeologic model and targeting zones to be monitored. These data are used in combination to define the uppermost aquifer and hydraulic gradients to allow the construction of a flownet that will provide identification of aquifer flow pathways so that target monitoring zones can be selected. 9.4 SELECT TARGET MONITORING ZONES The first task in the design of a detection ground-water monitoring system is the selection of the target monitoring zone (see ASTM 5092-90). The logic used in selection of the target monitoring zone is illustrated in Figure 9-4. A review of features of the facility to be monitored, used in combination with conceptual models and flownets provide the system designer with the information to select those zones that will provide a high level of certainty that releases from the facility will be immediately detected. The concept of the target monitoring zone was developed as a means of directing the ground-water monitoring system designer toward placement of well screens in the uppermost aquifer at locations and depths that would have the highest likelihood of detecting leakage from a facility. Target monitoring zone is defined in ASTM standard D-5092 as the groundwater flow path from a particular area or facility in which monitoring wells will be installed. The target monitoring zone should be a stratum (strata) in which there is a reasonable expectation that a vertically placed well will intercept migrating contaminants. This target zone usually lies in the saturated geologic unit in which ground-water flow rates are the highest because it possesses the highest hydraulic conductivity of the material adjacent to or underlying the facility of interest. Figure 9-4 illustrates the process of selection of a target monitoring zone using information on facility features, geologic characteristics and hydraulic characteristics gathered during the preliminary field investigations. This selection process can be described as a series of steps:

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Step 1. Locate Site Features on a Topographic Base Map Format: Site features should be compared to information on geologic and soil maps to define the location of important facility components in relation to the distribution of surfical materials. Any likely recharge/discharge areas (streams, wetlands or other surface-water) should be located. Step 2. Cross-Section Construction and Conceptual Model Development: Cross-sections should be constructed, based on boring logs and/or geophysical traverses. These sections should be compared with the location of site features and facility components. The base grades of the facility should be plotted on cross-sections of sensitive geologic units or ground-water flow pathways. A conceptual model should be constructed to establish the site geological framework and to illustrate distribution of geologic materials of differing hydraulic conductivity. Step 3. Use Flownet to Define Likely Direction of Ground-Water Flow: Construction of flownets assists in defining the gradient and direction of ground-water flow in the uppermost aquifer. The rates of flow along flow paths can be calculated from the information provided by the flownet using equations from Chapter 7. Vertical gradients can be used to predict target zones by comparison of relative heads between units. Interconnections between aquifers can be predicted from relationships of relating hydraulic conductivity to hydraulic heads for the units defined in the conceptual models. Step 4. Select Target Monitoring Zones: The zone meeting the regulatory definition of the uppermost aquifer, which also shows primarily horizontal ground-water movement under or adjacent to the facility, would therefore represent the target monitoring zone. This zone would probably represent a permeable unit that is discharging to other permeable units or to local discharge areas. The system designer should be aware of the flow paths within the uppermost aquifer that would represent the most likely zones of ground-water movement away from the facility. These zones, typically those with the highest hydraulic conductivity, would be the focus of the detection monitoring system. If interconnected aquifers are present, these units should be monitored as necessary to provide safeguards of downgradient ground-water users. This four-step procedure for selecting the target monitoring zone must be flexible enough to accommodate environmental effects due to seasonal changes in gradient or due to future plans to expand or alter the configuration of the facility. The target monitoring zone might include only a portion of a very thick aquifer (for example, the top 30 ft) or span several geologic units (as in the case of a thin, permeable, unconsolidated unit overlying weathered and/or fractured bedrock). These target zones represent the proper location for placement of monitoring wells.

MONITORING SYSTEM DESIGN

Figure 9-4

Flow Diagram Monitoring System Design 615

MONITORING SYSTEM DESIGN

9.5 LOCATE BACKGROUND AND DOWN GRADIENT WELLS 9.5.1 Gradients

Figure 9-5 Potential Target Monitoring Areas

The basis for detection monitoring programs is knowledge of the hydraulically upgradient and downgradient direction from the site to be monitored. Figure 9-1 illustrated a simple relationship of ground-water movement from higher potentiometric surface elevations (upgradient) to lower potentiometric elevations (downgradient). This simple conceptual model of a homogeneous aquifer is the basis for much of the regulatory thought on ground-water monitoring. It is also unfortunately rare to find such a simple flow configuration in the real world. After the selection of the target monitoring zone(s), the next step in design of a ground-water monitoring system is locating upgradient or background monitoring wells. The conceptual geologic model and flownet construction will have defined the uppermost aquifer and the relative direction of ground-water flow, both vertically and horizontally. Selection of upgradient wells for analysis should be based not only on this information, but also on other factors mainly relating to the physical presence of the facility. The numbers of upgradient or background wells installed at a site must be based on the size of the facility, the geologic/ hydrogeologic environment and the ability to satisfy statis-

Figure 9-6 Cross-Section of Target Monitoring Zones 616

MONITORING SYSTEM DESIGN

tical criteria for analysis of water quality data. As general guidance, it is very difficult to pass any type of statistical test (applicable under RCRA), unless more than one upgradient well is used in the monitoring system. This is due to the natural spatial variability observed in geologic environments. This spatial variability must be evaluated during the design process so that sufficient background water quality data is available for background to downgradient water quality statistical comparisons. The TEGD defines upgradient wells as “one or more wells that are placed hydraulically upgradient of the site and are capable of yielding ground-water samples that are representative of regional conditions and not affected by the regulated facility.” This usage of the term upgradient is consistent with 40 CFR 265.91, which links background and upgradient for interim RCRA sites. Background wells would meet the 40 CFR 264.97 test to “represent the quality of background water that has not been affected by leakage from a regulated, unit and represent the quality of ground water passing the point of compliance.” The term upgradient can be a difficult concept to demonstrate in ground-water monitoring system design, because field conditions may not match the simple, regulatory models. As a closing statement on the relationship between upgradient and downgradient wells, a correctly designed (located) detection monitoring well will only be placed within the flowpaths from the basegrades of the facility to be monitored. This is due to the placement of the downgradient well screen within the flow path from the facility. The designer must closely consider site-specific hydraulic conditions to accurately locate upgradient monitoring wells because ground water does not always flow as expected in a simple regulatory model, horizontally from upgradient to downgradient areas. Simple single-aquifer flow systems are established by a clear understanding of the directional movements of ground water through evaluation of the ground-water gradients across a site. Figures 9-5 and 9-6 illustrate, in plan view and cross-section, the flow around a gaining stream, where discharging ground water provides the stream’s base flow. Figures 9-7a and 9-7b illustrate flow around a losing stream, where surface water supports adjacent groundwater levels. In each of these cases, this simple system provides directional components to allow the positioning of groundwater monitoring wells. Figures 9-5 and 9-6 illustrate a facility (B) located in a recharge area that discharges to streams on either side of the facility. Ground-water flow lines are shown in plan and cross-section. Because the facility is sitting directly on top of the recharge area, the downgradient flow zone is composed of a wide arc around the facility. This example provides perhaps the simplest gradient controlled system.

Potential target zones for a detection monitoring system are shown in Figure 9-5. Upgradient background water quality target zones should be sufficiently within the recharge area so as not to be affected by the facility. Several conclusions can be drawn from Figures 9-5 and 9-6: • Facility A would have its downgradient monitoring wells located within the ground-water flow lines shown. This facility location would have background monitoring wells located in the central recharge area. • Facility B would have an upgradient or background well in the area indicated. Because the facility is located directly within the local recharge area, this would not be considered an upgradient well, but rather a background well that represents water quality similar to that for a well that would be upgradient from the facility. Actual flow conditions would result in a water table significantly flatter than that shown in Figure 9-6, vertical exaggeration (approximately 125 to 1) makes the flow lines appear to travel deeper than would be represented in real life. The vertical scale indicates that the monitoring wells installed at the site should be screened from 19 to 24 meters below ground surface to intercept the ground-water flow (and any contained contaminants) emanating from beneath the site. Figures 9-7a and 9-7b illustrate a losing stream condition and the resultant monitoring target zones for Facility A. Because the stream in this illustration is recharging ground water and thus represents the highest point of upgradient ground water, target monitoring zones are located along the flow lines shown in Figure 9-7. Depths of screen placement must be based on the projected vertical gradients in the area. One can observe from the example provided that the location of a detection monitoring system is particularly sensitive to whatever the stream is gaining or losing. This relatively simple complication can lead to incorrect location of downgradient detection monitoring wells. Piezometers located perpendicular to the stream and careful evaluation of stream flow can provide the basic data to define the recharge/discharge relationship of the surface and ground-water system. Steep/Flat Gradients Even simple, single-aquifer systems require consideration of local gradients adjacent to the facility of interest. In an area with a relatively flat gradient it is necessary to consider possible ground-water flow in what would normally be an upgradient direction. In an area with steep gradient on the water table surface, as shown in Figure 9-8 (typical of

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MONITORING SYSTEM DESIGN

Figure 9-7a Losing Stream Target Monitoring Zones

Figure 9-7b 618

lower hydraulic conductivity materials), there is little potential for reversal of flow directions. The target monitoring zone in an area with such a steep gradient would normally be much narrower than in the flat gradient environment. The relationship between horizontal and downward gradients are still required to establish the depth of the detection monitoring well screens. Figure 9-8 shows placement of two downgradient piezometers (A and B). A monitoring well screened at B would meet the regulatory criteria of being downgradient from the facility (and from upgradient piezometer C); however, the flow path screened by B would be too deep to intercept flow from the unlined facility. Detection monitoring wells located at the depth of piezometer A would correctly monitor the facility. Figures 9-9 and 9-10 show an unlined landfill within an area where the hydraulic gradient is low. The target monitoring zone is characteristically thicker than it would be in an area with high hydraulic gradient (as shown in Figure 9-8). The discharge directions shown in these figures probably represent a common hydraulic condition for

Losing Stream Target Monitoring Zones, Plan View

MONITORING SYSTEM DESIGN

Figure 9-8

Steep Gradient Facilities Example

unlined facilities. The cross-sectional view (Figure 9-9) shows both intermediate and shallow flow cells. The deeper intermediate flow system, at least in this case, is not affected by the facility. The local independent shallow flow cell is discharging in what could be viewed as both a downgradient and a perceived upgradient direction. The upgradient component is due to the higher heads observed at piezometer D (52.0 m) and lower heads in the other three piezometers (A, B and C). These discharge recharge cell relationships require significant interpretative skills by the designer, as well as sufficient field piezometric data. A plan view of this type system is shown in Figure 9-10. The local shallow ground-water system discharging from the facility causes a disturbance in the regional ground-water system. The actual disturbance may be difficult to establish in the field, so sufficient care should be exercised to locate background monitoring wells out of the local cell influence. The localized flow cells depicted in Figures 6-9 and 6-10 probably represent, more often than not, a typical flownet for a low gradient site. The local flow cells discharging around the topographically higher site would cause downgradient monitoring wells to be located in what would typically be called an upgradient location. Deeper screening of the detection monitoring wells at locations B or C would place the wells in the deeper intermediate flow cell. As such, they

would not represent truly downgradient monitoring of the facility. Procedures for Gradient Controlled Sites Even with simple, single-hydraulic-conductivity environments, care must be taken to fully understand the threedimensional nature of ground-water flow. As general guidance the designer should: 1. Establish lithology and gradients as with singleaquifer systems. 2. Compare natural (baseline) gradients across the site and hydraulic conductivity of aquifer. 3. Select position for upgradient monitoring well, as in position D of Figures 9-9 and 9-10. Gradient Control/Flownets Unfortunately most real-world geologic systems are not composed of simple single layers. Once observed field conditions include stacked, variable hydraulic conductivity layers somewhat more difficult evaluations of how ground

619

MONITORING SYSTEM DESIGN

DISCHARGE

RECHARGE

A

B

C

Unlined Landfill

D

Figure 9-9 Conceptual Model of Local Flow Cells water is affected by the variable geologic materials comes into play. Figure 9-11 shows an unconfined aquifer separated from a confined aquifer by a low hydraulic conductivity confining bed. Ground-water movement through this system involves flow not only through the aquifers but also across the confining bed. The hydraulic conductivity of aquifers are tens to thousands of times greater than those of confining beds; for a given rate of flow, the head loss per unit of distance along a flow line is tens to thousands of times less in aquifers than it is in confining beds. Consequently, lateral flow in confining beds usually is negligible and flow in aquifers tends to be parallel to aquifer boundaries, as shown in Figure 9-11. Differences in the hydraulic conductivity of aquifers and confining beds cause refraction or bending of flow lines at their boundaries, as was described in Chapter 8. As flow lines move from aquifers into confining beds, they are refracted toward the direction perpendicular to the boundary. In other words, they are refracted in the direction that produces the shortest flow path in the confining bed. As the flow lines emerge from the confining bed, they are refracted toward the direction parallel to the boundary (Figure 9-11). Hence, ground water tends to move horizontally in aquifers and vertically in confining beds or low-hydraulic-conduc-

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Figure 9-10 Map View of Local Flow Cells

MONITORING SYSTEM DESIGN

Figure 9-11

Unconfined/Confined Flownets

tivity materials. This observation is important to the design location and depths of the facility detection monitoring system. Lateral flow components in aquifers have direct relevance to ground-water monitoring system design, because the physical location and depth of the wells must correspond to the overall three-dimensional components of flow typically at the edge of the facility. Most detection monitoring programs concentrate on establishing target monitoring zones in the uppermost aquifers beneath a site. These target monitoring zones are directly correlated with the hydros-

Figure 9-12a-b

tratigraphic zone that has the highest rate of flow away from the facility so that immediate detection of leachate migration could be detected from the facility. Some assessment programs may involve monitoring the uppermost aquifer, deeper aquifers and zones between the uppermost and deeper aquifers. As a general statement the threedimensional ground-water flow established by piezometer hydraulic-head relationships is necessary for either detection or assessment monitoring design. The movement of water through aquifer/confining unit systems is controlled by the vertical and horizontal

Regional Ground-Water Flow in Confined Aquifer 621

MONITORING SYSTEM DESIGN

hydraulic conductivity, the thicknesses of the aquifers and confining beds, the recharge and discharge (boundary) areas and hydraulic gradients. Because of the relatively large head loss that occurs as water moves across confining beds, the most vigorous circulation of ground water normally occurs through the shallowest aquifers. Movement generally becomes slower as depth increases. The uppermost aquifers will usually show contamination first (unless a direct conduit for downward movement exists into deeper aquifers) and thus must be served by monitoring efforts. The concentration of flow lines in aquifers is illustrated further by Figures 9-12a and 9-12b (Freeze and Witherspoon, 1967). Aquifers bounded by a sloping confining layer and a flat-lying confining unit, as may present, for example, in glaciated regions where low-hydraulic-conductivity tills overlie higher hydraulic conductivity, outwash sand and gravel aquifers. Nearly vertical flow occurs through the generally thick, low hydraulic conductivity materials, while nearly horizontal flow occurs within the underlying aquifer. The aquifer represents the only zone in which ground water moving away from a facility could be properly intercepted and monitored and thus should be considered the target monitoring zone. This concept is further illustrated in Figure 9-13 where the piezometers installed at increasing depths in the confined aquifer and in the confining zone indicate that a strong downward gradient exists in the fine-grained overburden material. Monitoring wells located in Figure 9-13 at A3 and B3 would represent background and downgradient, respectively. The entire target zone should be screened in both these locations. Figure 9-14 illustrates an unconfined flow system in a recharge area. Recharge areas with strong downward gradients may require special consideration of localized shallow flow cells. Depth-location relationships are especially important in such situations. For example, downgradient monitoring wells in the unconfined aquifer,

Figure 9-13 622

Confined Aquifer Piezometer Nest

shown in Figure 9-14, should be located in a target zone screened at or below the interval screened by piezometer B2. Figure 9-15 illustrates the potential ground-water flow paths to a discharging stream. Both upgradient wells (A and B) and downgradient wells (C) are shown in this simple conceptual illustration. However, even this relatively simple conceptual model can demonstrate how a shallow downgradient well (C) would not intercept potential leachate flow from the unlined waste disposal area. The downgradient ground-water monitoring point for facilities located in discharge areas must be designed on the basis of shallow, nearsurface discharge to wetlands or streams. Upgradient wells should be screened in shallow flow paths, as illustrated by well B. Deeper upgradient wells (as illustrated by well A) would probably suffice, but may not represent groundwater flowing in the target monitoring zone. Ground-water monitoring in complex alluvial deposits often presents difficult problems with respect to identification of target monitoring zones. These deposits often have shallow sandy zones encapsulated within low hydraulic conductivity sediments. Sand tank experiments have shown that these discontinuous sandy deposits do not affect the downward movement of ground water when strong downward gradients exist. Figure 9-16 shows such a conceptual situation. Shallow permeable zones contained within the low hydraulic conductivity materials do not have significant horizontal gradients; vertical gradients usually predominate in such environments. Monitoring points located adjacent to a facility located in these deposits (such as well A) may not represent a target monitoring zone. Only where significant horizontal flow exists, as in the regional (uppermost) aquifer, would a horizontally downgradient target flow path be found. Well B represents a correct downgradient monitoring point for this situation. However, upper permeable units may represent uppermost aquifers if they have suffi-

Figure 9-14

Unconfined Aquifer Piezometer Nest

MONITORING SYSTEM DESIGN

Figure 9-15 Shallow Discharging Ground-Water System cient hydraulic conductivity and are of sufficient extent to serve as a water source for off-site ground-water users. These more permeable, sandy lenses, channels and tabular deposits have been observed in many types of geologic environments. These units can range from recent glacial deposits, such as, tills with interlayered outwash sands, to unconsolidated overbank deposits associated with alluvial river deposits, to consolidated claystone deposits with interbedded channel sandstone deposits. The four important criteria for establishment of the need to monitor saturated sand lenses located within lower hydraulic conductivity units are: • Differential hydraulic conductivity • Directional hydraulic heads • Unit prevalence • Unit thickness Differential hydraulic conductivity refers to the variation in hydraulic conductivity observed between geologic units. Directional hydraulic head refers to the potential flow

directions observed from piezometers located within individual units. Unit prevalence is a qualitative judgment based on the overall site stratigraphic characterization. Unit thickness is defined from the site field drilling program and is based on simple thickness of the observed sandy units. Each of these criteria must be considered in order for a system designer to decide if a particular permeable unit would require monitoring as a target monitoring zone. Differential hydraulic conductivity represents an order of magnitude comparison of the sandy unit to the adjacent matrix materials. Freeze and Cherry (1979, p. 173) state that, “In aquifer-aquitard systems with permeability contrasts of two orders of magnitude or more, flow lines tend to become almost horizontal in the aquifers and almost vertical in the aquitards.” This flow must, however, require that the aquifer discharges into other permeable units, to surface water or is pumped from the system. Directional heads provide an indication as to the discharge potential of the sandy units. If vertical directional heads are discharging upward (from below the unit) and downwards (from above the unit) into the sandy layers, it is likely that the unit discharges into adjacent lower head areas. The unit prevalence criteria

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MONITORING SYSTEM DESIGN

Figure 9-16 Low-Hydraulic-Conductivity Environments with Nondischarging Sand Lenses provide an indication as to how continuous the layer is in the field. These data are gathered during field borehole drilling activity to demonstrate the continuity of the unit in the site area. As general guidance, if all of the Phase II borings (100%) contacted the definable unit at equivalent elevations, it is likely that the geologic stratum is continuous. If this contact percentage falls to 50% or shows an elevation variability, the unit is much less likely to represent a continuous feature that should be monitored. An understanding of the depositional history of the geologic unit probably represents the best method for evaluating the continuity of more permeable deposits that could discharge ground water to downgradient, off-site areas. Channel deposits may have been cut off by agrading streams during the geologic past. However, sufficient stratigraphic data should be established to confirm such assumptions before ruling out discharge through such linear features. The drilling program also establishes the relevant thickness of these units. If the thicknesses of the saturated permeable units are very thick (say, 100 ft), it would be likely that the unit would require monitoring. As the thickness lessens, the other factors or criteria become more important in the overall decision to monitor or not to monitor the unit as the uppermost aquifer. The last criterion, water use of the units, can outweigh all the other factors, assuming that the unit is hydraulically connected between the facility and the downgradient water users. Each of these factors must be weighed in the decision pro-

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cess. A system designer is often required to monitor all potential pathways by regulatory agencies. Rather than blindly installing monitoring wells in every conceivable permeable unit, the author recommends using technical reasoning for flow path interception. Only monitor geologic units that have a reasonable chance for flow toward downgradient receptors. This may include human or biological receptors. Stick to detection monitoring in the classical uppermost aquifer that is discharging off-site. In the majority of cases you will meet both the letter of the law and limit long-term liability issues with this approach. If a discontinuous sand unit with a differential hydraulic conductivity of one order of magnitude shows piezometric heads passing through the unit (i.e., heads continued downward through sandy unit) and few borings contact the approximately 1-ft thick unit, we would not consider the unit as a target monitoring zone. If that unit is 10 ft thick and was contacted by only a few borings, it may be necessary to monitor the unit as the uppermost aquifer or it may not. However, if the saturated unit was 20 ft thick, was penetrated by all borings and showed piezometric heads discharging into the unit from above and below, the unit would probably be monitored as the uppermost aquifer. Figures 9-17a through 9-17d illustrate the use of this concept with a series of conceptual models with various levels of discharge from sandy units. The levels of dis-

MONITORING SYSTEM DESIGN

Figure 9-17a Conceptual Model with Nondischarging Sand Lenses charge range from almost none in Figure 9-17a to significant discharge between the unconsolidated and bedrock systems. The interpretation of site hydrogeologic condition and thus the design of the monitoring system, in each case, would be based on the following key points: • The lateral extent and thickness of the various geologic material present • The hydraulic conductivity of each of the individual

Figure 9-17b

lithologic units • The gradients obtained from piezometers placed in each of the permeable units • The discharge/recharge potentials of the geologic units present on site The conceptualizations and flownet constructions should be based on illustrations with 1-to-1 scales. Figures 9-17a through 9-17d provide some additional keys to

Conceptual Model with Nondischarging Sand Layers 625

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Figure 9-17c Conceptual Model with Discharging Sand Layers

interpretation of the appropriate monitoring locations. The conditions depicted in figures 9-17a and 9-17b would point toward the ground-water detection monitoring only be conducted in the regional (uppermost) aquifer. Ground-water discharges down through the two sandy layers (one discontinuous in 9-17b), into the regional bedrock aquifer. The conditions depicted in Figure 9-17d would indicate that

sandy unit 2 would represent the better detection monitoring target as the uppermost aquifer. The first sandy unit in Figure 9-17d would not represent an effective monitoring location because of its thin, limited discharging nature. Ground-water samples obtained from this unit would only be representative of conditions along the edge of the facility within the flow path shown in Figure 9-17d. While a case

Y Y’

626

Figure 9-17d

Conceptual Model with Discharging Sand Layers

MONITORING SYSTEM DESIGN

Figure 9-18

Conceptual Model of Discharging Sand Units

may be made that a monitoring well located at D may be necessary to evaluate the area along one side of the facility, virtually 95% of the area would be monitored if wells were placed at downgradient locations in sandy units. Figure 9-17c represents a situation in which both the sandy unit and the regional system should be monitored. This decision to monitor both sandy units should be weighed on the basis of additional site characterization work to determine the regional extent and current/future use of the sandy units. If the second sandy unit represents a likely flow path and hence a target monitoring zone from the facility, it should be included in the monitoring program. Detailed evaluations of layered geologic units can be used to define the specific discharging more permeable strata next to a waste disposal area. Figure 9-18 shows a evaluation of a cross-sectional area 40 ft deep and 200 ft wide. The waste disposal area is just to the left of piezometer C. The flownet superimposed on the cross-section was based on both piezometers and wells screened along the cross-section line. Recognizing that widely screened zones provide an integrated hydraulic head value, more validity should be placed on hydraulic data gathered from piezome-

ters. The results of this linked cross-sectional and flownet construction shows the discharging nature of the shallow continuous sandy layer above the unfractured bedrock. Selection was made to monitor at a location within the relatively thin discharging sandy zone. Although there may be some upward movement of ground water from deeper, less permeable units, the flow lines that bound the base grades of the waste disposal areas would probably represent the optimum location and depth for detection monitoring. Multiple Piezometers To Establish Flow Relationships Heads established by multiple piezometers can identify the potential flow paths from a facility in homogeneous materials. Figure 9-19 illustrates an upgradient area of recharge and downgradient discharge point as defined by water levels measured in piezometers. The downgradient piezometers show an upward vertical gradient, while upgradient piezometers show a downward gradient. Figure 9-20 illustrates a recharge condition both in background and downgradient piezometers. The heads shown in monitoring wells A and B represent the average of the equipotential

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Figure 9-19

Gradient Comparisons for Recharging and Discharging Areas

heads contacted by the screened area of the wells. 9.5.2 Geologic Control Geologic controls over ground-water movement represent the most critical factors that should be considered in

Figure 9-20 628

ground-water monitoring network design (see Figure 9-20). The goal, in most cases, is to define the most likely zone in which ground water moves beneath a facility and, hence, the most likely zone for any possible contaminant movement to occur and be detected. The following discussion first addresses simple geologic systems where design of the

Conceptual Recharging Conditions

MONITORING SYSTEM DESIGN

monitoring system is relatively straightforward based on the geology and ground-water flow directions. The discussion then moves to a more complex systems that require significant site assessment and conceptualization to design an appropriate monitoring system. The discussion also includes a design for perched water conditions. Some of the following examples include unlined waste disposal sites where leachate is shown to dramatize the potential flow paths and target monitoring zones. Single Homogeneous Aquifer The single homogeneous aquifer represents the simplest geologic environment in which to design a detection monitoring system. The single homogeneous/isotropic aquifer system requires only the following steps to define the target monitoring zone: 1. Evaluate aquifer geometry, thickness and vertical and horizontal hydraulic conductivity variability by way of continuously sampled stratigraphic borings logged to confirm homogeneous and isotropic conditions within each layer. 2. Prepare a conceptual geologic/hydrogeologic model and plot potential target monitoring zones. 3. Construct flownets using water level/piezometric head information from piezometers or observations wells; and confirming target monitoring zones. 4. Install wells to monitor potential contaminant flow paths.

Figure 9-20 illustrates the subsurface movement of leachate from an unlined solid waste facility in a humid environment. Selection of appropriate screen depths for down gradient wells is relatively simple using the procedure above. Figure 9-21 (Freeze and Cherry, 1979) represents isoconcentrations of chloride next to an unlined solid waste landfill. The contours were based on water quality obtained from numerous, closely spaced sampling points screened at various depths. The location of the target monitoring zone here would be the center line of the chloride plume. The center point, with the highest chloride concentrations, represents the most direct flow path away from the landfill. Monitoring wells located in this zone (along the highest chloride contour) would provide the earliest detection of leachate excursion away from the facility. Figure 921 (field determined flow fields) and Figure 9-20 constructed from a flownet provide essentially the same solution to ground-water flow for this particular hydrogeologic site environment. Single Aquifer of Variable Hydraulic Conductivity Differences in hydraulic conductivity due to changes in stratigraphy with depth can point the way toward establishment of an effective monitoring system. The procedure for design would likely include the following steps: 1. Determine the horizontal extent and thickness of individual geologic units by evaluating geologic logs of continuously sampled stratigraphic borings to a depth of least 25 ft below base of the facility. This suggested depth is used as a rule of thumb and actual depths may vary based on site conditions.

Taken from Freeze and Cherry, (1979)

Figure 9-21 Example Leachate Water Quality Plume, Field Determined (From Freeze, R. A. and J. A. Cherry, Groundwater, Prentice Hall, Englewood Cliffs, NJ, 1979. With permission.) 629

MONITORING SYSTEM DESIGN

Figure 9-22 Time Sequence for Leachate Plume

2. Establish hydraulic conductivity for each unit from results of field and laboratory tests confirming isotropic conditions. 3. Construct a flownet based on observed hydraulic heads (from piezometers) and a conceptual geologic hydrogeologic model to select target monitoring zone(s). 4. Install monitoring wells based on defined target zones that represent primarily horizontal movement of ground water. If anisotropic conditions are observed in the difference between laboratory and field hydraulic conductivity test results, the procedures for construction of anisotropic and heterogeneous conditions will be necessary to properly draw the flownet. As a general rule the difference between hydraulic conductivity measurements in the field, as compared to those evaluated in the laboratory, may not be a result of actual isotropic aquifers. Because laboratory measurements are made from relatively small volume samples and field hydraulic conductivity measurements are made on screened sections of 5 ft or more, some natural variations in hydraulic conductivity should be expected. A comparison of the values obtained from the field and laboratory should be made in conjunction with both the samples collected and

630

logs of the lithology. If the comparisons of the values show little reason for a wide variation in hydraulic conductivity then conduct an inspection of the samples provided to the laboratory. Special care should be taken that the majority of the samples collected in the field represent the typical lithology, rather than exceptions to the typical field conditions. In any case it is probably rare to obtain exactly the same hydraulic conductivity from an individual field and laboratory test. Because we are sampling a range of hydraulic conductivities of the geologic strata, the smaller the sample tested, the more likely the sample is to test differently from an average value as obtained from field tests of screened sections of the units. For these reasons it is recommended that sufficiently large numbers of laboratory samples be collected from each hydrostratigraphic unit to provide a representation test value. As a rule of thumb, three laboratory samples for each hydrostratigraphic unit should provide a minimum value for comparison to field obtained hydraulic conductivity. For large or complex sites many additional laboratory determinations may be necessary. Figure 9-22 depicts a time sequential leachate plume from an unlined solid waste facility. Leachate movement in the system is represented by primarily vertical flow in the lower hydraulic conductivity units and the horizontal excursion in more permeable silty sands and gravel zones. The monitoring system for this facility would consist of wells screened in the silty sand unit directly next to the

MONITORING SYSTEM DESIGN

Figure 9-23

Conceptual Flow in Layered Deposits

facility, in the gravel or in both units. The extent of the geologic units, the potential for off-site migration and the current or potential use of the water contained in the units are some of the deciding factors in the actual system design. If the silty sand is discontinuous, the gravel would be the primary monitoring target zone. However, if the silty sand extended beyond the site boundaries and sufficient horizontal flow exists to be monitored effectively at the edge of the facility, both the silty sand and the gravel would be targets for ground-water monitoring. The silty sands represent the probable first affected unit and the gravel would most likely represent a water supply for off-site downgradient water users. An important key is the potential for horizontal migration in the silty sand unit. If flownets show discharge of the silty sand unit to downgradient receptors then this unit would likely represent the uppermost aquifer. As such, detection monitoring should be conducted within this unit. Conversely if this silty unit shows strong downward gradients and does not discharge (as shown in the Figure 9-22), then little would be gained from monitoring the silty sand unit. Figure 9-23 shows a sand and gravel unit as the uppermost aquifer beneath two tills. Typical of near-surface, low hydraulic conductivity units, ground-water flow is nearly vertical in the tills. Ground water then flows horizontally in the much higher hydraulic conductivity sand and gravel aquifer. This sand and gravel unit is the only potential target monitoring zone for a facility located in this type of environment. The dominance of vertical flow in low hydraulic conductivity deposits and horizontal flow in continuous, permeable zones is very typical. In glaciated regions, deeper sand and gravel, valley fill or outwash deposits are

often in direct contact with underlying weathered or highly fractured bedrock. Such systems would represent a composite target monitoring zone. Small lenses of sand within a mass of low conductivity material, however, do not represent adequate targets for monitoring. Thin or discontinuous, sand lenses will not provide the low heads necessary for horizontal movement of ground water away from a facility. Figures 9-24 and 9-25 represent the idealized cross-section of a facility located in a clay till above a bedrock aquifer. A series of discontinuous sand seams was present within the clay till. Numerical modeling of the system provided the velocity vector and concentration contour plots shown in Figure 9-25. A point source of contamination was simulated in the modeling project. The point source produced a plume that moved horizontally in near-surface material (the jointed till), vertically downward through the clay till and sand lenses, and finally horizontally in the underlying dolomite bedrock. The dolomite represents the target monitoring zone in this situation due to the following factors: • The near-surface, jointed till is shallow and does not represent a flow path away from the base of the facility. • The near-surface tills can be influenced by vertical recharge events that are not associated with ground water passing beneath the facility (i.e., not in the flow path). • The thick clay tills and the minor sand lenses do not represent aquifers. • The thick clay till and enclosed sand lenses, when considered as composite units, have primarily vertical ground-water flow components.

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MONITORING SYSTEM DESIGN

Figure 9-24

Conceptual Model in Layered Deposits

• The dolomites can yield water to monitoring wells and do represent a horizontal flow path from the facility. Therefore, the dolomites would represent the target monitoring zone for the facility. Multiple Aquifers Multiple aquifers represent a challenge to the groundwater monitoring system designer. Ground water in layered aquifers often moves in different directions. Thus multiple

aquifers require a more complex understanding of the three-dimensional hydrogeologic data to accurately establish a capable monitoring system. Figure 9-26 shows a two-aquifer system with groundwater flow in opposite directions. Such a geologic environment would require significant geologic and hydrogeologic characterization to establish target flow paths from the facility. The following procedure is recommended to establish a ground-water monitoring system for a two-aquifer system as is shown in Figure 9-26:

Figure 9-25 Computer Flow Results Model in Layered Deposits

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Figure 9-26

Two-Layer Flow Model

1. Install stratigraphic borings using continuous sampling techniques from the surface through all overburden units down to competent bedrock. 2. Complete piezometers in each aquifer so that vertical and horizontal gradients can be established for the each of the aquifers. 3. Establish hydraulic conductivity for each unit by conducting field in situ and laboratory hydraulic conductivity test. 4. Construct flownet constructions for each aquifer. 5. Establish the target monitoring zones. If the goal of the monitoring system is to provide immediate detection of any contamination released from a facility (i.e., as in a detection monitoring program), the target monitoring zone should be the unconfined uppermost aquifer. If the goal of the system is to assess the extent of contamination emanating from a site (i.e., as in an assessment monitoring program), defining the rate and extent of contaminant movement would require monitoring in both the upper and lower aquifers. If a nearby surface stream serves as a base flow discharge point for one of the aquifers, the stream would probably also require water quality monitoring. The monitoring program should also define if there is underflow beneath the stream. Figure 9-27 shows a three-aquifer system including a deep, interconnected, fractured bedrock aquifer. As with the two-aquifer system, the assessment technique should be as

follows: 1. Install borings to take soil samples sufficient to characterize the unconsolidated materials down to competent bedrock. Determine if continuous sampling and logging techniques are necessary for the geologic environment. The presence of fractured bedrock indicates that rock core drilling would be required to evaluate fractures and bedrock hydraulic conductivity. 2. Complete a series of piezometers in each geologic unit to establish hydraulic gradients. 3. Establish hydraulic conductivity (horizontal or vertical) for each geologic unit, including confining units. 4. Construct flownets and piezometric contour maps for each aquifer. 5. Develop a geologic/hydrologic conceptual modes and establish target monitoring zones. 6. Install monitoring wells. Assessment monitoring wells in deeper units should be double-cased through the overlying units as necessary to prevent cross-communications between units. As with the two-aquifer system, a monitoring system installed for the purpose of detecting contamination would

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focus on the uppermost aquifer to provide immediate detection of leachate from the facility. The shaded area in Figure 9-27 represents widespread contamination that provides many challenges in assessment monitoring programs. Typically if assessment programs require full project planning at the project start (such as in the Superfund program), these deeper contamination zones are often not included in sampling programs. A phased program that includes full geologic conceptualization and flownet construction should be completed before generation of sampling plans for ground-water quality. Chapter 10 provides additional guidance for assessment monitoring evaluations. Low Hydraulic Conductivity Environments Probably the most difficult (and error prone) geologic environment in which to design a ground-water monitoring system is thick, low hydraulic conductivity materials overlying an aquifer at depth. Much of the controversy surrounding ground-water monitoring of hazardous waste sites is based on the difficulties in interpreting ground-water movement in low hydraulic conductivity environments. Figure 9-28 illustrates a facility located in a thick low hydraulic conductivity clay overlying a high-hydraulic-conductivity sand. The sand is confined and the clay contains

minor sand lenses, acting as a subdrain to the adjacent low hydraulic conductivity clay thus masking the directional components of the shallow ground-water flow. Piezometers should be installed within the clay and the uppermost aquifer (the lower sand) in order to define vertical gradients and to assist in selection of the target monitoring zones. Geologic environments that consist of primarily low hydraulic conductivity units containing higher hydraulic conductivity deposits of significant lateral extent require comprehensive preliminary hydrogeologic investigations to define the target monitoring zone(s). An example of the kind of conceptual geologic descriptions necessary for evaluating generally low-hydraulic-conductivity environments is provided below. The shallow, unconfined ground-water surface is affected by a facility leachate collection system that acts as an underdrain. Figure 9-29 illustrates a conceptual model of a buried channel located in much less permeable claystone. One example of this type of lithologic system is the Cretaceous Dawson Formation in the Denver, Colorado area, which was deposited in a fluvial, deltaic environment. The Dawson stratigraphic sequence consists of depth-uncorrelatable, vertically stacked sandstone channel deposits, each of which is isolated within a fine-grained claystone that originated as backswamp deposits in the Cretaceous delta.

Double cased assessment monitoring wells

C

B

A

Vadose Zone

Water Table Saturated Zone

Figure 9-27

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Three-Layer Flow Model

D

MONITORING SYSTEM DESIGN

Thin, isolated sandstone lenses (as viewed in crosssections) are present in the sequences that are characteristic of levee splay deposits and minor overbank deposits. The majority of geologic materials in such a sequence are matrix-supported diamicts that have very low hydraulic conductivity. The channel deposits represent clast supported units. These channel deposits can provide discharge pathways both to recent alluvial materials present in ephemeral stream channels and to adjacent claystone units. On the basis of on evaluation of the depositional environment, through detail core analysis using Facies codes, the Dawson Formation deposits were determined to be laid down in a delta that gradually was uplifted by ancestral Rocky Mountain tectonics in early Tertiary time. Different depositional characteristics of each of the sand sequences observed in cored boreholes emphasize that sands were deposited by separate and different stream systems and, therefore, not vertically interconnected. Minor sand lenses, such as the levee splay deposits or overbank matrix-supported sands that were deposited in backswamps, also have limited area extent. They are connected horizontally over short distances and are vertically separated from other sandstone in the system by the intervening claystone. Near-surface Dawson claystones are typically weathered and can become seasonally saturated as a perched ground water system with sufficient hydraulic conductivity to comprise a target monitoring zone. This weathered zone can be easily defined by shallow (1*10-3) material exists near the surface with less permeable material below, then perched water bodies are more likely. The lower the amount of recharge, the less likely that the hydraulic conductivity contrast will act as a significant perching mechanism. Monitoring beneath the perched zone

for rate and extent qualification would concentrate, in this case, on the first aquifer beneath the perched zone rather than on the perched zone itself. Although the potential may be present on a site for individual clay units to perch ground water, the limited extent or continuity of the perching unit may not require the definition of the individual low hydraulic conductivity units. Figure 9-33 illustrates a conceptual cross-section/ flownet of unconsolidated deposits overlying a regional confining unit. In this example the individual clay units

Figure 9-34 Various Forms of Ground-Water Flow 640

MONITORING SYSTEM DESIGN

were limited horizontally so ground water could flow through windows of the clay deposits. A single unconfined water surface was established with little or no perching conditions. Flow path A discharges from around piezometers D-15 toward the southeast working through and around the various flat-lying clay units. Alternative flow paths could be constructed from the D-15 area to the northwest, as this location represents a recharge-upland area. Discharge is toward streams (gaining streams) cutting into the Coopers formation to the northwest and southeast of the facility area. The projected flow path A would be perhaps best monitored in the area of D-13 as the majority of flow for the system passes below the clay unit at this location. To the northwest, monitoring of the zone between 50-60 ft above NGDV would provide a secondary flow path target from the site area. Secondary Hydraulic Conductivity The three basic types of ground-water occurrence and movement are shown in Figures 9-34a through 9-34c. Figure 9-34a shows primary porosity where ground water moves through the interstices (voids) between sand-sized grains. Figure 9-34b shows ground-water movement through fractures that represent secondary porosity. Figure 9-34c shows ground-water movement through solution channels developed in a carbonate rock, another type of secondary porosity. A particular geologic environment could consist of any or all of these media. The preliminary

field investigation should determine the dominant flow mechanism beneath the facility to be monitored so that the appropriate locations for monitoring wells can be selected. Fractured or solution-channeled carbonate rocks provide special problems in ground-water monitoring system design. Often there will be highly directional ground-water movement along discontinuities or dissolution-widened joints. The success of any monitoring system in a fractured or solution-channeled environment requires knowledge of the joint or fracture patterns. In some instances, remote image interpretation and special field techniques (e.g., tracer tests) can point toward the target monitoring zone in a secondary porosity environment. Most consolidated rocks (with the exception of some indurated sandstone and conglomerates) have few primary intergranular openings for ground-water flow and usually have much lower hydraulic conductivity value than their unconsolidated equivalents. Ground-water flow in bedrock aquifers often takes place through secondary openings such as fractures (joints, bedding planes) and/or solution-channels. The investigator designing a monitoring system should fully identify areas in which this factor is important and should do so at an early stage in the preliminary site investigation. Although regional flow patterns should be well established in preliminary investigation, it is often very difficult to predict ground-water flow through a set of fractures or solution channels on a site-specific scale (e.g., in the vicinity of a monitoring well). Thus, facilities located over bedrock aquifers should employ additional

Figure 9-35 Fractured Rock Control of Ground-Water Flow

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investigative techniques (e.g., fracture-trace analysis, geologic mapping and pumping tests specifically designed to evaluate anisotropy) to adequately determine likely groundwater flow pathways. Fractured rock environments require consideration of specific flow paths to define the target zone monitoring system design. Chapter 4 discusses the Phase II field investigation tasks for a fractured-rock environment. Figure 9-35 shows the individual ground-water flow paths in a fractured rock environment of a single rock type. Leachate is shown moving down from an unlined landfill toward a series of fracture sets that control local ground-water flow. Detection monitoring system design would place screened zones both upgradient and downgradient of the facility. Individual screen depths must be based on the results of the boring program and the observed fractures or weathered zones rather than on only observed head levels. In an assessment monitoring situation, long (say, >15 feet) screened zones should be avoided to reduce the potential for cross-contamination caused by leachate entering an upper zone and mov-

ing downward into uncontaminated zones. Fracture patterns can be highly localized and unpredictable, as shown in Figure 9-36 or more evenly distributed and predictable as illustrated in Figure 9-37. Often, both primary and secondary porosity are present in bedrock units, as illustrated by Figure 9-38, so the preliminary site assessment must include measurement of the hydraulic and geologic parameters for each of the media present at the site. The approaches for design in a fractured geologic environment should follow the recommended procedures: 1. Evaluate fracture patterns using background information, aerial photographs (fracture trace analysis) and measurement of fractures at surface exposures. 2. Establish a core drilling program at the site that may include use of rock quality designation (RQD), fracture orientation of core, borehole video logging and detailed visual logging. Packer hydraulic conductivity tests should be considered for use

Figure 9-36 Fractured-Rock Localized Flow Pathways

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in the assessment, in which packer intervals should be selected to test specific, observed discontinuities. Consideration should also be given to including angle core drilling in those areas where vertical fractures may be present. 3. Implement borehole geophysical surveys, such as caliper logs, flow logs and temperature surveys. 4. Install multiple piezometers or multipoint completions for assessment of hydraulic conditions in individual fracture zones detected in the coring and geologic logging process. 5. Measure piezometric heads and gradients in relationship to joint patterns (fracture sets). 6. Establish a conceptual model defining the target flow zones in plan and cross-section.

Figure 9-37

A detection monitoring system can be effective in a fractured-rock environment if the wells are screened in highly permeable fractures (those flowing into the borehole) downgradient from the facility. These systems can react very quickly (say, days to weeks) to leachate releases from the facility. Solution-channeled bedrock (Karst) terrain presents additional challenges to the designer of a ground-water monitoring network because monitoring wells can miss permeable solution channel joints and may even end up as dry holes. Quinlan (1990) provided a full description of ground-water monitoring in Karst terrain. Karst environments require considerations of where to locate both background and downgradient wells and springs as well as when to monitor the extremely fast reacting system. Quinlan (1990) recommends the following procedures for design of monitoring systems in Karst terrain: •

Review the regional and local geologic and hydrogeologic literature for the area in question.

Fractured Rock - Evenly Distributed Flow Pathways

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MONITORING SYSTEM DESIGN

•

Evaluate topographic and geologic maps.

•

Conduct a survey of springs.

•

Map regional and local potentiometric surface.

•

Organize a dye-tracing study based on references above.

•

Perform the first dye-trace, preferably during moderate flow conditions.

•

Evaluate the results of the first dye trace and modify if necessary the design of the tracing study.

•

Determine whether local springs to the facility are characterized by conduit or diffuse flow.

•

Perform additional dye-traces during moderate flow conditions, always modifying the tracing plan, as necessary, in light of the results of the previous trace results. For most facilities it is necessary to perform only two dye traces during moderate flow conditions.

•

Repeat selected traces during base flow and flood flow conditions.

•

Integrate dye-tracing results, available potentiometric data, and conductivity and turbidity data used to discriminate between conduit and diffuse flow into a monitoring plan.

•

Have the entire project area reviewed. General guidance for detection monitoring in Karst ter-

Figure 9-38

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rain must also include consideration of background well locations. In general terms, background well locations must be based on: •

Negative results from dye tracing tests

•

Locations in similar rocks and geochemistry as downgradient sites

•

Locations selected in similar cultural environments

Sampling for water quality in Karst terrain also does not meet the typical regulatory model for biannual or quarterly sampling periods. Quinlan (1990) recommends sampling based on storm and meltwater events. Figure 9-38 illustrates monitoring of an unlined facility in a Karst area, where sinkholes are present beneath and next to the facility. Normally, such a setting is not easy to monitor, but a monitoring system can be developed to determine the facility’s impact on the environment. The assessment monitoring procedure would be similar to that used above with the possible addition of other surface geophysical surveys. Ground-penetrating radar, electromagnetic conductivity and seismic refraction surveys can help identify some zones of solution channeling and deep weathering within the rock mass. Selection of target monitoring zones in the plan view and cross-section should be prepared before any installation of any monitoring wells. In Karst systems, gradients are typically very low and require very accurate surveys for directional definition of ground-water flow.

Karst Rock Localized Flow Pathways

MONITORING SYSTEM DESIGN

9.6 SEPARATION OF ADJACENT MONITORING PROGRAMS New landfills built to state-of-the-art design criteria are commonly being constructed next to traditional disposal areas, many of which do not have liners and leachate collection systems. Even with extensive double composite liners the new facilities must demonstrate the long-term engineering performance of the new cells through groundwater detection monitoring programs. Selection of the proper locations for detection monitoring wells should be based on a holistic approach to the evaluation of a specific site. The placement of the ground-water wells in this process must weigh and balance data collected in the field, laboratory and office. This is especially true for multiple facilities located on adjacent properties. The target monitoring zones are further useful for the separation of detection ground-water monitoring systems from adjacent facilities that may have been unlined or are currently impacting water quality. The following three case histories illustrate how ground-water flow concepts can be effectively used to evaluate the optimum locations and depths of a detection monitoring system. Simple Gradient Control: Facility A represents a relatively simple condition where the existing 20-acre landfill is located in a downgradient position from a 25-acre expansion as shown in Figure 9-39. The expansion has a 60-mil HDPE liner and leachate collection. Ground-water surface contours, shown in Figure 9-39, when combined with the hydrogeological cross-section (Figure 9-40) show the target monitoring zone to be the Pleistocene Terrace deposits of interlayered sand and clayey sands. The underlying Choctawhatchee formation was not judged to be significantly more permeable than the Terrace deposits and both formations are underlain by the locally non-water-bearing Hawthorn formation. As such, ground-water would not have a significantly downward movement adjacent to the site and detection monitoring wells should be located between the two facilities. The flatness of the ground-water contours as they pass under the site shows that there is not significant mounding in the existing facility. This facility would not cause the area between the two facilities to be discharge points for the existing site. Wells located between the facilities with the observed ground-water flow conditions would monitor the expansion. At least two background wells are located between the 65’ and 70’ ground-water contour line. The well depths should be completed between the base grade of the expansion and the base of the Terrace deposits. Gradient and Lithology Control: Site B represents a slightly more complex example where a ground-water divide and lithology complicate ground-water monitoring conditions. Figure 9-41 shows a 16-acre lined cell with leachate collection next to a 5-acre closed commercial and

large closed county landfill. The hydrogeologic cross-section (Figure 9-42) illustrates the lithology and base grade configurations for the site. The site’s geology/hydrogeology is dominated by the thick 100 ft Cooper formation that acts as a regional confining unit. The shallow aquifer Pleistocene sands and clays have a generally unsaturated upper sands unit with an intervening clay unit overlying a saturated lower sands unit. The hydrogeologic cross-section, as presented, is insufficient to fully evaluate the localized flow conditions for selecting locations for detection monitoring wells. Cross-section G-G’ (Figure 9-43) must be evaluated in combination with watertable contours shown in Figure 941. The water table contours show a ground-water divide occurring along a natural ridge area. The new lined cell is located along the nose of the ridge and on top of the ground-water divide. Monitoring of sites located on ground-water divides requires almost a three-sided approach. If the cell was located directly on top of a hill downgradient could be in all four directions and monitoring background ground-water quality would be generally more complicated. Background water quality for the example B site would, however, be along the ridge line in the locations shown between MW-7 and MW-6. Downgradient locations would be located from MW-1A clock-wise around through MW-5. Because the site has sufficient ground-water gradients from the new cell toward the old closed county and commercial sites, local discharge between the old and new sites would not be considered a problem. The cross-section of G-G’ illustrates a combined conceptual model of the geology site cross-section and the observed ground-water flow paths. Flow path A represents a potential flow line from below the lined facility in one direction toward a local creek discharge point. A flow path could also be drawn in the opposite direction (as represented by the ground-water divide shown in Figure 9-43). The well screen depths that would most effectively cover the facility in a detection monitoring system should be located in the sandy unit above the Coopers Formation, directly below the first saturated Pleistocene clay unit. Downgradient detection monitoring wells should be located in both cross-section directions as indicated by the groundwater flow arrows. Information on local lithology and ground-water flownets makes selection of potential depths for well screens a relatively straightforward task. The previous two examples represent primarily horizontal groundwater flow conditions; the following example site C, however, represents a more complex three-dimensional example requiring complete linkage of flow and lithology. Complex Ground-Water Flow Conditions: Site C represents a new 70-acre lined site with leachate collection next to a closed 80-acre MSW landfill (Figure 9-44). The closed site is unlined without leachate collection facilities.

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Figure 9-39

Gradient-Controlled Ground-Water Surface Contours

Figure 9-40

646

Hydrogeological Conceptual Model

MONITORING SYSTEM DESIGN

Figure 9-41

Plan View of Facility

The uppermost aquifer as shown in Figure 9-45 is Pleistocene alluvium (35 ft thick). The underlying Garber-Wellington Formation (300 to 400 ft thick) is the main regional aquifer. The Garber-Wellington Formation shows hydraulic conductivity similar to the overlying alluvium, so simple horizontal flow conditions cannot be assured for detection monitoring purposes. The ground-water contour plan (Figure 9-44) shows that complex localized flow conditions exist at site due to the effects of the inactive sand and gravel operations (now full of water) and the river to the west of the site. Ground-water movement is generally from the southwest to the west of the new facility, however, local discharges also occur to the east of the closed facility. The physical condition of having an unlined site generally upgradient of a new facility can make interpretation and comparison of background and downgradient water quality very difficult. The ground-water flow conditions are furthered complicated by having no confining units to separate the uppermost aquifer (alluvium) from deeper regional aquifers. This site must be evaluated through use of a linked conceptual model and flownet construction cutting an eastwest cross-section. Figure 9-45 illustrates site flow conditions through the uppermost aquifer into the Garber-Wellington and discharging in two directions (west and east). The lined site’s potential flow path discharges to the river and as such, can be monitored with wells completed to between 1080 ft and 1130 ft above msl. This 50-ft zone rep-

resents the most likely flow path for potential discharges from the lined facility. Completion of deeper monitoring wells would intercept flow paths coming from the unlined facility and, as such, would not represent true downgradient conditions from the active disposal site. Background wells must also be carefully chosen relative to adjacent facilities and the overall geology and ground-water flow conditions. The example C monitoring wells are located between the new facility and the river in an arc down to the sand and gravel operation south of the lined cell. Background wells are located between the closed site and the new facility. As with the downgradient detection monitoring wells the background water-quality monitoring points must be carefully selected relative to depth of the well screens. They probably should be no deeper than being screened between elevation 1140 ft and 1130 ft above msl. As with any detection ground-water monitoring system located next to an unlined facility, the wells must be entirely screened below the seasonal low watertable. This is to ensure that landfill gas potentially moving in the vadose zone from the unlined site would not enter a monitoring well and cross-contaminate ground-water samples taken from the well. This type of cross-contamination can greatly confuse detection monitoring analytical results. Gas movement in the vadose zone should be monitored through a separate gas monitoring network designed especially for the purpose.

647

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Figure 9-42

Figure 9-43

Conceptual Model of Facility

Cross-Section View of Facility

9.7 DENSITY CONTROL In this discussion, various monitoring system designs will be reviewed to illustrate some of the major implications of density and immiscibility in the design of ground water sampling networks. In the preceding monitoring well system designs, it was assumed that the waste solutions were miscible in water and that the density of the water was not altered by the presence of the solutes. Although typical leachates from codisposal, hazardous waste and solid waste disposal facili-

648

ties fit this profile, there are a number of monitoring situations for which these neutral density assumptions are not appropriate. In particular, waste such as brines or other water-based industrial effluents can be miscible in water but have a density significantly greater than water. Oily wastes and other organic-based fluids may also contribute to the waste solutions that are immiscible in water. Physical properties of waste solutions can result in transport characteristics quite unlike those normally associated with such neutral density leachates.

MONITORING SYSTEM DESIGN

Figure 9-44 Ground-Water Contour Map

Figure 9-45

Flownet Construction for Facility C 649

MONITORING SYSTEM DESIGN

Figure 9-46a shows a contaminant plume developing as a result of seepage of a dense miscible fluid into the ground water zone. As shown, the contaminants tend to move vertically downward to the bottom of the aquifer. Once on the bottom, the movement of the plume is governed largely by the topography of the confining unit below the aquifer, thus the direction of flow will not necessarily be in the direction of regional ground-water flow. Due to dispersion, diluted contaminants near the edge of the plume will be contributed to the local ground-water flow system. Thus, several areas of contamination may be present, the major plume of dense fluid and the adjacent ground-water zone contaminated by diluted levels of dense fluid as a result of dispersion at the perimeter of the plume. Establishing the area of contaminated ground water would require typical methods of investigations as for any assessment monitoring design. Locating the major pool of contamination, the dense plume would require knowledge of the surface of the lower permeability layer and the installation of sampling points near the bottom of the aquifer. In the case of high density miscible fluids over a period of time, the density would decrease to the point where the plume would migrate according to the local ground water flow conditions. In the case of a dense immiscible fluid, soluble constituents would be contributed to the local flow system; however, the denser immiscible plume would likely remain at the bottom of the aquifer for a prolonged period of time moving according to gravity. Figure 9-46b presents the migration of a miscible phase having a density less than that of water. In this case, the major zone of contamination occurs near the top of the saturated zone and migration is controlled by the directional slope of the watertable. As a result of dispersion, contaminants would be contributed to the regional flow system and the plume would gradually be dissipated over potentially long distances. In the case of miscible, less dense (than water) product spills, monitoring points should be concentrated in the upper part of the aquifer if vertical flow components are not significant. Figure 9-46c presents the infiltration and migration of an immiscible fluid having a density less than or similar to that of water. In this case, the main area of contamination occurs near the top of the saturated zone and the plume is dispersed in the direction of ground-water flow. As the immiscible phase moves through a porous medium, a residual amount of fluid is retained in the medium in a relatively immobile state to slowly leak into ground water as it flows past the residual contaminated units. Immiscible fluids have soluble constituents that will tend to be leached from the fluid and migrate as part of the regional ground-water flow system. In addition, volatile constitu-

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ents could be contributed to the gas phase in the zone above the watertable. Figure 9-46d presents a neutral-density miscible fluid moving from an unlined landfill into a local ground-water aquifer. Because the leachate plume moves in a manner similar to that of the ground-water flow in the aquifer, monitoring would be based on target monitoring zones and three-dimensional ground-water flow components. Ground-water monitoring system design for the above contaminants should use both conceptual models and flownet constructions along with consideration of the leachate density. This presentation is designed to present information regarding the conceptual design and implementation of a vadose zone monitoring system. Definitions and a brief discussion of the assumptions and properties governing vadose zone transport are presented. Step-by-step guidelines and procedures for designing a vadose zone monitoring system follow this discussion.

9.8 FUNDAMENTAL MONITORING CONCEPTS OF THE VADOSE ZONE An important point for any type monitoring programs is the regulatory requirement to install the system. OMB rewrote Part B of RCRA to require Vadose Zone Monitoring. The Revised Part B was published in the Federal Register in June 1991. The law required Vadose Zone Monitoring in any reauthorized Part B permit. Subtitle D requires vadose zone monitoring to be determined at the state level for MSW facilities. The California Legislature introduced the Calderon Bill that required retrofitting all Subtitle C and Subtitle D sites with a Vadose Zone Monitoring System. California promulgated under the California Code of Regulations (CCR) Title 23, Chapter 15, article 5 that required vadose zone monitoring for solid waste disposal sites. The following provides a summary of major aspects of vadose zone monitoring, Looney and Falta (2000) provides many of the details associated with vadose zone monitoring. 9.8.1 Definitions and Units of Measurement The vadose zone (also called the zone of aeration or unsaturated zone as shown in Figure 9-47) is defined as the geologic column that extends from the ground surface to the first major saturated formation. A soil or unconsolidated sediments can be conceptualized as a three-phase system composed of liquids, solids, and gases. The solid phase consists of mineral and organic matter, while the liquid

MONITORING SYSTEM DESIGN

Figure 9-46 Density Consideration in Facility Monitoring

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phase occupies the pore space. The liquid phase is often referred to as soil pore water. The soil solution may partially fill the soil pores in the unsaturated case; the liquid exists as thin films along particle surfaces, as liquid wedges around the particle contacts or as isolated bodies in small pore spaces. The matric potential (also referred to as capillary potential, tension, and soil suction) is the result of capillary and adsorptive forces acting on the soil matrix. The matric potential is a negative pressure and can be measured in unsaturated soils by tensiometers. As a soil becomes wet, for example, the matric potential increases from a very low (negative value) to zero value (i.e., saturated). The soil suction can be measured with a tensiometer and is reported in units of bars or centibars (l bar equals 0.987 atmosphere = 1017 cm of H20 = 10-1 megapascal). Soil suction can range from 0, which means the soil is saturated, to as high as 600 bars, as found in some extremely dry soils. This becomes important when discussing poreliquid samplers or suction Iysimeters, because unsaturated pore-liquid movement takes place only in the 0- to 20-cbar range. A pore-liquid sample can be obtained only in the 0to 60-cbar range. If the soil suction is greater than 60 cbars, then the suction lysimeter will not work. The soil water potential is the observation that liquid flows in the vadose zone as a function of its potential and kinetic energy. Because vadose water movement is slow, the kinetic energy is normally considered negligible. There-

Figure 9-47 Vadose and Ground-Water Zones fore the primary energy source is that which determines the state and movement of soil water. Potential energy is determined by the liquid position and drive of vadose soil water to move to a lower potential energy state. Soil water potentials are often expressed in terms of the height of a reference body of water that will develop an equivalent pressure

Figure 9-48 Example Vadose Monitoring Placement in Facility 652

MONITORING SYSTEM DESIGN

or suction. Units used in describing tension and energy of the soil water potential include the bar. A common unit conversion is that 1 cbar is roughly equal to 1 kPa that is roughly equal to 100 cm of H20. The soil moisture distribution dictates the unsaturated hydraulic conductivity. Because the soil moisture almost always varies, the unsaturated hydraulic conductivity may be highly variable, even in a homogeneous lithology. A common observation in vadose zone flow systems is the movement of pore liquids through fine-grained soils rather than coarse-grained materials. Richard’s principle says that in unsaturated flow (0 to 20 bars) pore liquids will not readily move from a finegrained to a coarse-grained material. The contact will act as a boundary and fluids will build up or mound, before entering the coarse-grained material (if they enter at all). As the liquid enters the coarse-grained material fingers of flow referred to as Taylor Instabilities develop. These fingers appear to form as the result of some preferential flow path force; however, the actual cause is unknown. If the soil is completely dried and then rewetted, the fingers of flow develop at new locations. These Taylor instabilities result in unpredictable flow patterns that make vadose zone modeling difficult. 9.8.2 Implementation of a Vadose Zone Monitoring System Designing a vadose zone monitoring system can be reduced to five major tasks: •

Project scoping

•

Site characterization

•

Equipment selection

•

Equipment placement

•

Documentation

Each of these steps is briefly discussed here. Project Scoping Defining the purpose or objective of the monitoring program is required prior to designing the system. The objectives and expectations need to be realistically defined as part of a project scoping effort. Monitoring objectives must become part of the conceptual understanding of the site. Vadose zone monitoring programs require a clear understanding of site geology because the ability of the

proposed system to obtain a sample of pore liquids or measure changes in soil moisture is directly related to subsurface conditions. These data are gathered during site characterization activities. Site Characterization Site characterization for a vadose zone detection monitoring system consists primarily of collecting soil/geologic and hydrogeologic information: •

Textural information of major soil groups

•

Depth, stratification sequence, estimated porosity

•

Depth to ground water and seasonal ground-water flux

•

Saturated hydraulic conductivity of major soil groups

These data are required to design a vadose zone monitoring system to assess the applicability of the various sampling and evaluation techniques to the specific site. This is accomplished best by obtaining continuous cores of the entire vadose zone or to an appropriate depth, at a specified number of locations depending on size of the site. The matrix potential of these core samples can be measured top to bottom in the field by use of a quick-draw tensiometer. This tool is simply pushed into the sidewall of the core and takes approximately three minutes to equilibrate. The soil moisture may vary significantly at lithology changes. Soil Vapor Sampling/Monitoring Soil vapor hydraulic conductivity should not be measured in the lab by forcing the liquids out of the sample before running the test. The lab K (vapor) should be run on the sample at the same soil tension as was measured in the field. This will assure that the core is not wet or dried out relative to actual formation moisture content. Time domain reflectometry (TDR) can be used to measure the formation water content independent of lithology. This is accomplished by measuring the capacitance of the soil. Soil psychrometers are typically used to measure the relationship between negative soil-water potential and the relative humidity of soil water. Typical scopes of work for vadose zone monitoring system design may include: •

Unsaturated hydraulic conductivity of major soil groups (field and laboratory; as expected, the field measurement is more representative)

•

Drying branch of a soil moisture characteristic curve for each major soil type

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•

Estimated or field measured unsaturated hydraulic conductivity (Bouma et al., 1974)

•

Gas (air) permeability of major soil types as measured in the field

•

Grain size distribution of major soil groups

•

Identification of major textural interfaces or gradations (mean grain size diameter >1.5 times greater than adjoining soils)

•

Saturated hydraulic conductivity of all major soil types

Once this subsurface information is collected, a conceptual or graphical model of the soils at the facility should be developed in a fashion similar to that used for saturated monitoring programs. This model will begin to provide one with an intuitive sense of optimum equipment locations for placement. Uncertainties associated with soil moisture transport through the vadose zone identify the most probable location to detect a facility release (i.e., optimum equipment placement location). For example, it might be qualitatively determined that placement of any device at a depth less than 5 ft below the ground surface may be impractical due to a preponderance of roots, earthworm activity, burrowing animals, etc. At the conclusion of this step, the optimum locations for equipment placement for the purpose of leak detection can be identified and prioritized based on the purpose of the monitoring system. Vadose Zone Equipment The purpose of the vadose zone monitoring system, leachate properties and characterization of the subsurface environment will dictate the most suitable technology for the site. Many types of vadose monitoring equipment may be employed in conjunction with saturated monitoring equipment as shown in Figure 9-48. For example, if pore water collection is desired, an active system such as lysimeters in combination with a passive, non-sampling system such as tensiometers may be the most appropriate design. Both depth and location issues should be considered in the vadose zone detection monitoring program. In some cases new facilities or cells will have sump areas for leachate collection systems. These sumps are at the lowest portion of the facility or cell and represent likely points of limited area that can concentrate vadose zone monitoring. Some base grades are often designed to be located 5 to 10 ft above seasonal ground-water high. Large-pan lysimeters located between sump base grades and the ground-water highs have a high likelihood of detecting leakage from these sumps. There will be cases when the limiting factors of the geo-

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logic and hydrogeologic systems will dictate a single system. In most cases, there will be a threshold at which more money does not buy an appreciable increase in detection probability for a given technology. Various pore-liquid sampling equipment are appropriate for vadose systems including BAT samplers, suction lysimeters, pan lysimeters, gypsum blocks, resistivity measurements, magnetometry and neutron moderation. Some of the important systems are discussed below: Soil psychrometers: measure the relationship between negative soil-water potential and the relative humidity of soil water. The use of psychrometers is commonly associated with erroneous data. This is because an insignificant change in relative humidity, which the instrument measures, are associated with a significant change in both water content and soil tension. This is illustrated by the following chart: Relative Bars 0.1 1.0 5.0 10.0 15.0

Humidity

Water Content (% by weight)

99.9926 99.926 99.637 99.26 98.89

15% 6% 3% 2% 1.5%

Neutron Moderation: At a site where the soil suction is greater than 2 bars, the neutron probe is the best monitoring choice. The probe is 2 in. in diameter and 1-ft long. It has a 50-mC americium beryllium high-energy, neutronemitting source. The probe emits the neutrons and measures the moderated or slowed down, neutrons that return. The number of moderated neutrons correlates to the hydrogen ion concentration in a 32-cm radius around the probe. Because the mass of the hydrogen ion is very close to the mass of the neutrons, the collision of these results in the maximum energy loss. Therefore, the maximum amount of energy loss is a function of the formation’s hydrogen concentration. Thus, the neutron probe measures the concentration of water. In the presence of water and methane, the gas will have little influence on the reading because the hydrogen concentration of the methane is very low compared to that of the water. Also, the neutron probe will work through PVC, HDPE or stainless steel casing and can penetrate through up to two ft of cement and/or bentonite grout. The particular technology selected for the vadose system should be field tested in a few units at the site. Calibration techniques over the anticipated range of conditions for example soil moisture content can provide assurances that the selected system does, in fact, look as designed. These trial tests allow refinements or modifications to be evalu-

MONITORING SYSTEM DESIGN

ated before actual installation of the final system. The final installation may also require considerable assembly and calibration efforts before final equipment check-out. 9.8.3 Vadose Equipment Location Location of the equipment in the optimum or prioritized target monitoring zone is usually the least difficult of the various steps. Whenever possible the vadose monitoring system should be installed as part of a new cell or facility, rather than as an afterthought. Because the majority of flow in the vadose zone is vertical, location of vadose zone monitoring technology has to be primarily under portions of the facility. External sumps are facility design features that allow for reasonably effective vadose system design. Retrofitting vadose monitoring systems may present the least optimum condition, as these installations probably require access below the facility. A key task performed during this process is position of the drilling rig to access the target zone. For example, one may bulldoze a trench next to a surface impoundment so that the drill rig can drill horizontally under a surface impoundment rather than slant boring. Borehole location and documentation of the angle of drilling (if used) should be recorded throughout the installation process. Extensive logging of the soil layers using continuous sampling techniques should be performed during the drilling. Continuous sampling and logging form the basis for adjusting the target zone during installation. If the actual target zone once reached consists of coarse-grained rather than fine-grained sands (as originally believed from the early site characterization phase), placement of the vadose monitoring system can be adjusted so that it is installed in a material with the physical attributes closer to that required by the equipment selected. Once the target zone is reached the devices are placed at the appropriate depth(s), the hole is backfilled with the correct annular sealant, and the unit is fully tested prior to moving to the next installation. For example, if a porous cup sampler is installed, a vacuum should be drawn at the surface and sample collected. A gypsum block requires that an electrical signal be compared to the calibration curve prepared for that unit at the approximated moisture content of the backfill. If the device is shown to be fully functioning, the borehole can be completed and the above ground tubing/wires, etc. permanently labeled. Documentation The final but important step in the vadose zone monitoring process is the documentation of each installation. One should not lose sight that monitoring programs are

built with proper documentation. Such information should include all installation data (field notes, survey information, types of units, depth of installation, etc.), maintenance problems encountered after installation, calibration data for each unit and the name of manufacturer and model number of all equipment installed in the borehole. 9.9 Examples of Monitoring Design 9.9.1 Interpreted Site Geology The site is considered to be landward of the estimated position of sea level during the time in which the Prairie Formation was being deposited (Late Quaternary). Therefore, it is expected that the sediments found on site would be predominantly non-marine to marginally marine and would exhibit characteristics associated with deltaic aggradation (delta building) processes and not coastal or offshore marine processes. Figure 9-49 shows the layout of borings used in the investigations for the facility. Typical features of this type of system initially consist of braided streams becoming meandering streams as the river gradient decreases. As different deltas were built into the Gulf of Mexico, broad meander belts developed. Also associated with this environment are organic-rich back-swamp deposits which lie adjacent to meander belts and natural levees. Examination of false-color infrared aerial photographs revealed no surfical expressions of these features. Thus, it was necessary to rely on the results of subsurface investigations. The results of a hydrogeological investigation for the proposed landfill are shown in Figures 9-49 through 9-51. The purpose of the investigation was to review the geology of the site, to confirm the subsurface conditions as determined previously at the site by others, and to provide an interpretation of the hydrogeological conditions particularly as they affect the design of the landfill. The geological review confirmed that the site lies within the Prairie Formation. As such, the property generally is underlain by fine-grained cohesive sediments laid down during the delta building process. In addition, the site is traversed by three channel sands which have been termed lower, middle and upper. The depth to the three sands is typically 37 ft, 20 ft and 6 ft, respectively. The piezometric levels in the channel sands indicate that the lower and middle sands are not hydraulically connected, whereas the middle and upper units probably are connected. Superimposed on this pattern is a system of random local sand stringers generally located less than 20 ft deep. To augment previous geotechnical data, a field investigation was undertaken. This involved five sampled bore-

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zone that would show contamination if there should be a release from the facility. In summary, the target monitoring zone is represented by the sand channel that crosses the site and serves as a local discharge system for the site area.

holes, nine cone penetrometer tests, one test trench and the installation of six piezometers. In general, the site is underlain by thick beds of competent, plastic, and relatively impervious subsoil. These materials are incised by local channel sands and sand stringers. The cohesive units display a broad range of plasticity and have been classified on that basis into organic clay, clay, silty clay, and clayey silt. In general, the thickness of the individual beds for the latter three units varies from 10 to 15 ft. Ground surface is generally underlain by a silty clay unit which overlies a clay stratum. The organic clay constitutes a marker horizon and is located at depth. Clayey silt and silt deposits, where encountered, generally flank the channel sands and are believed to be overbank deposits. Regarding ground-water conditions, the potentiometric surface is typically 6 to 8 ft below ground surface with seasonal fluctuations of a few feet. The flow direction across the site is from northeast to southwest in the deep unit and west to east in the middle/shallow unit. The ground-water level in the middle channel sand decreases across the site at a gradient of about 0.0012, and this low gradient can at times during seasonal recharge reverse directions as shown in Figure 9-50. The flow velocity within this unit is estimated to range from 4 to 19 ft/year.

As a basis for the selection of either compliance or assessment monitoring locations, one would first turn to the site assessment reports generated for the facility. The previous eight chapters provided the scope of work and interpretation methods that should give the investigator the information necessary to develop a full picture of the three-dimensional picture of the ground-water flow conditions at the site. The decisions to be made in order to define specific ground-water monitoring locations are explained in this example problem. This problem was used as part of the EPA’s Superfund University Training Institute (SUTI) that was held at the University of Nevada over a 7-year period. The discussion provides a background dataset for making decisions on the placement of monitoring points. This example provides conflicting flow directions from a multiple layered system.

9.9.2 Monitoring System Design

9.10.1

Once the conceptual hydrogeologic model is constructed fully based on the data gathered during the Phase II investigation, design of the detection monitoring system is relatively simple. The flow into the sand channel units represents the most rapid and significant target monitoring

To put the site into perspective within the larger geologic framework of the region and to describe the geologic history which led to the formation of the strata, a brief discussion of the regional geology was presented as Figures 8-2 to 8-5 in Chapter 8. This discussion is based upon the published geo-

Figure 9-49 Layout of Boreholes at Facility 656

9.10 ON DESIGN OF GROUND-WATER MONITORING SYSTEMS PROBLEM

Site Investigation Report

Figure 9-50

Piezometric Levels

MONITORING SYSTEM DESIGN

logic data for the region, as well as upon the results of the hydrogeologic investigation conducted at the facility. The geology of the site is then described in detail in Sections 9.10.3 and 9.10.4, based upon the interpretation of the existing data. Of particular importance is the conceptual model of the hydrogeologic system described in Section 9.10.5. In Section 9.10.6, the results of the various hydraulic conductivity testing programs are described and summarized. In Section 9.10.7, the hydrogeologic conditions observed at the facility are discussed in detail. Ground-water flow in the overburden and in the bedrock is discussed in Section 9.9.8 and recommendations as to the monitoring system are contained in Section 9.10.9. 9.10.2 Instructions Based on the following information the reader should try to work out the three-dimensional patterns of ground

water flow for the problem at hand. Then, based on the flownet one must then select the appropriate locations for ground-water monitoring of the site. The SUTI students were given three different target monitoring cross-sections for use in the problem, dependent on the experience and background of the student. However, only one cross-section is presented in this chapter. A flownet representative of the head levels observed provide the data necessary to define potential monitoring points. These levels provide the equipotential points to base the drawing of the equipotential lines and subsequent flow lines. Based on the nets and baseline water quality, the reader would be expected to complete the following: 1. Define the wells or piezometers that would monitor the facility, as both background and downgradient wells.

Figure 9-51 Conceptual Hydrogeologic Model

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Figure 9-52 Site Location Map 2.

Locate the cross-sectional locations (depths) of the most effective facility monitoring points.

9.10.3 Regional Geologic Setting

3.

Select both organic and inorganic indicator parameters that would monitor the facility.

The study area is located within the central lowlands province as described by Fenneman (1938). The dominant feature of the province is a relatively flat surface that rises from an elevation of approximately 400 ft in the north to

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600 ft at the southern boundary of the province. Superimposed upon the relatively flat surface are the north-south striking drumlins which rise to heights of 100 to 300 ft above the surrounding plain (see Figure 9-52). Interspersed between the drumlins are various other glacially derived features such as moraines, kames, eskers, deltas and glacial stream deposits. These glacially derived features dominant the area and are the results of the advancing and retreating Wisconsin ice mass which covered most of New York State. Figure 9-53, a cross-section, summarizes the stratigraphic sequence of bedrock formations which underlie the region. The bedrock underlying this area consists of shale, siltstone, sandstone, limestone and dolomite. All of these rock units contain recognizable layers or beds ranging from less then one inch to several feet in thickness and some contain significant deposits of salt and/or gypsum. Formation of these bedrock units began approximately 350 to 440 mil-

lion years ago during the Devonian and Silurian periods, when much of North America was inundated by the seas. During the late Silurian time period the seas oscillated over broadly exposed mud flats resembling the coastal plains of today. This process left highly saline embayments and lagoons, many of which were entirely landlocked. Whenever evaporation exceeded the inflow of water, thick deposits of salt and gypsum were precipitated. The deposited sediments consolidated over time and were eventually uplifted above sea level and partially eroded away. This uplift has resulted in a regional dip to the south of approximately 50 ft/mi. The most striking glacial feature in northwestern New York, particularly east of Rochester, is the drumlins. These subglacial deposits consist of dense till, which are certainly depositional in origin as opposed to being erosional features. The typical drumlin form is an elongated oval, with

Source: Eckefelder, Inc

Figure 9-53 Cross-Section of Geology for Example Facility

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steep convex side slopes and its long axis running parallel to the direction of ice movement. The majority of the drumlins consist of till throughout their thickness; however, a few have been found to have cores of soft shale and have been termed rock drumlins. As the drumlins are formed beneath the ice they typically predate the glacial fluvial deposits within the area. As such, they were obstructions to established flow patterns and the inter-drumlin areas generally indicate some form of glacial drainage features. For example, it is typical to find outwash deposits adjacent to the northern slopes of the drumlin where a glacial stream was diverted from its path. As mentioned above, the interdrumlin areas typically contain some form of glacial drainage features; this is not to say, however, that these are the dominant deposits. On the contrary, the most dominant deposit, by far, is the glacial till, which not only comprises the drumlins but underlies the other glacial deposits at almost every location in the area and in some areas is the only unconsolidated deposit covering the bedrock in upland areas. Glacial till deposits in the area have been found in excess of 200 ft in thickness. 9.10.4 Site Geology Detailed descriptions of the materials encountered on site were presented on the boring and test pit logs gather during the site investigation. An example of a boring log is shown on a log presented in Chapter 8, as 8-3. The soil descriptions were based upon visual examination, the results of laboratory grain-size analyses and index testing. The geologic strata are depicted on the geologic crosssection presented in Figure 9-53, based on boreholes and test pits located in Figure 9-54. The general character, areal extent and significance of the major geologic strata will be discussed in the following sections. The strata are described in chronological order based upon their relative ages, beginning with the oldest unit, the Vernon Shale. Vernon Shale The oldest geologic unit encountered during this investigation was the Vernon Shale of late Silurian age. The Vernon Shale generally consists of red, green and gray-black shale, gray gypsiferous shales and gray dolomitic shales. Bedding was observed to be predominantly plane-parallel. Fractures intersected during the drilling and coring were predominantly associated with the bedding planes with occasional 45 degree fractures. Both horizontal and sub vertical fractures within the formation were generally found to be filled with gypsum deposits. The Vernon Shale

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has been broken down into five lithofacies in order of decreasing abundance, described briefly below: Red Shale Lithofacies: This is an argillaceous rock with subordinate quartz of silt size. Minor amounts of gypsum, anhydrite, euhedral dolomite, secondary calcite and black organic matter occur. There is little to no visible stratification within this facies. Grayish Green Lithofacies: This is an argillaceous rock with green ferrous oxide coating the ground mass. It is slightly calcareous and angular quartz silt averages 10 to 15 percent of the volume. The beds are commonly laminated. Medium Dark Gray Shale Lithofacies: The shale is essentially a clay paste with varying amounts of recrystallized calcite, rare quartz silt and rare pyrite. This lithofacies is far less common than the two described above. Dolomite Lithofacies: This is a conchoidal fracturing fine-grained dolomite with some interstitial silica, infrequent grains of pyrite and opaque black specks. This lithofacies occurs as rare thin beds usually associated with the gray shale where it is transitional into the green shale. Greenish-black Shale Lithofacies: This lithofacies is also referred to as the discontinuous Pittsford Shale. The rock consists of argillaceous, carbonaceous and dolomitic material with much disseminated pyrite and some angular quartz. The rock core collected during the investigation consisted primarily of red and green Shales with varying amounts of gypsum. The gray shales described above were also encountered but to a much lesser degree. Surfical Geology Residual Soil: The residual soil is an in-place remnant of the bedrock surface, that underlies the majority of the site and can generally be described as a clayey soil containing visible remnant bedding planes and occasional intact pieces of shale. The residual soil is the result of in place weathering of the Vernon Shale prior to glaciation. It is presented and discussed under the subheading of surfical geology because it most truly represents a soil in its character. The residual soil can generally be described as a gray-green silt & clay, sand, little to trace gravel in the modified Burmister soil classification system. In the Unified Soil Classification System, it could generally be described as a SM to SC-SM soil. The distribution of the residual soil beneath the site is presented on the geologic cross-sections A-A' (Figure 953). The soil ranges in thickness from 0 to approximately 31 ft beneath the site. The top of this unit is generally a mirror image of the top of rock structural contour map. It should be noted, however, that the thickness of the residual

MONITORING SYSTEM DESIGN

soil does vary as it, too, is an erosional surface as a result of glaciation. Glacial Till: Glacial till is by far the predominant unconsolidated material beneath the facility. It underlies all the other glacial deposits found at the site and ranges in thickness from approximately 10 ft in the northcentral portion of the site to greater than 135 ft at the crest of the drumlin. Its distribution throughout the site is also graphically portrayed in the geologic cross-sections. Glacial till is defined as a heterogeneous, non-stratified sediment depos-

ited directly by the action of glacial ice and typically includes particle sizes in the range of clay to boulders. The till encountered at the site represents a classical example of a dense lodgement till. In general the till can be classified as a SC-SM to CL-ML soil in the Unified Soil Classification System. Occasional layers of sand and gravel were observed in several test pits and borings. However, these infrequent layers are of limited thickness and extent. Over much of the site, near-surface geological processes have served to

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Figure 9-54 Location of Exploration Points for Example Facility 661

MONITORING SYSTEM DESIGN

alter the character of the till. This alteration has included oxidation of the upper 5 to 10 ft of the till and disturbance of the soil structure by roots and by jointing or fracturing. Of these factors, jointing is perhaps of greatest significance. In recent years, several case studies have been published that address the occurrence origin and hydrologic implications of fractured glacial till (Williams and Farvolden, 1967; Grisak and Cherry, 1975; Hendry, 1982; Desaulniers et al., 1981). These studies suggest that jointed glacial till is a common occurrence from New York State westward to the Rocky Mountains. Shallow, closely spaced fractures are attributed primarily to desiccation and to disturbance by cyclical freezing and thawing. Deeper fractures are believed to be the result of deformation due to crustal rebound following the retreat of the glacial ice. The consensus has been that the presence of significant fracturing can increase the bulk hydraulic conductivity of the glacial till by as much as one to three orders of magnitude; typically, however, increases in the range of one order of magnitude can be anticipated. Glacial Outwash Deposits: Glacial outwash deposits are associated with glacial meltwaters and are typically composed of poorly sorted to moderately well sorted sand and gravels. Glacial outwash deposits were observed in channels eroded into the underlying glacial till along the perimeter of the drumlin. The thickness of the outwash deposits and their configuration are illustrated on geologic cross-sections A-A’ (Figure 9-53). The channel type deposition and the steepness of the channel walls, particularly

along the drumlin, is most evident in the cross-sections. The grain size of these deposits varies greatly with coarse sand and gravel found in the deepest portions of the channel and fine sand and silt found near the edges. Also visible on the cross-sections are limited buried outwash deposits, mentioned above, which do not correlate with the surfical deposits. 9.10.5 Conceptual Model of the Hydrogeologic System A conceptual model of the hydrogeologic system at the site has been developed using the geologic, hydrogeologic and geochemical data collected during the investigation. The conceptual model built from Figures 8-3 to 8-6 in Chapter 8 describes the various hydrostratigraphic units in which lateral flow occurs, as well as the lower permeability units in which vertical flow dominates. The conceptual hydrogeologic model for the site consists of three water-bearing zones and two lower permeability units as shown in Figure 9-55 and Table 9-1. In descending order, the units include an overburden waterbearing zone contained primarily in the surfical glacial outwash deposits and the weathered glacial till, an aquitard within the unweathered glacial till and residual soils, a water-bearing zone within the upper fractured rock, an aquitard consisting of relatively unfractured shale and a water-bearing zone contained within a laterally continuous interval within the competent shale (competent rock

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Figure 9-55 Conceptual Model for Example Site 662

MONITORING SYSTEM DESIGN

water-bearing zone). Groundwater flow paths and gradients are predominantly vertically downward through the glacial till and predominantly vertically upward through the competent rock, with the fractured rock water-bearing zone acting as the discharge point with essentially horizontal flow paths. 9.10.6 Hydraulic Conductivity Determinations A number of independent methods were employed for determining the hydraulic conductivity of the various geologic deposits found at the site. In this section, the results of these various testing programs are described. The result of the laboratory tests performed on the glacial till indicated that the till is typically classified as a CL-MC to SC-SM soil. The silt and clay size fraction range from 14% to 86% with an arithmetic mean of 47.8%. The liquid limits ranged from 10 to 20 with an arithmetic mean of 15.6% to plasticity index ranged from 4% to 9% with an arithmetic mean of 5.6%. In this section, the results of the various hydraulic conductivity testing programs are summarized and representative values for each hydrostratigraphic unit are assigned.This part of the development of an concetual model is extremely important for the investigator to establish the likely zones of ground-water flow. For the defined water-bearing zones, lateral hydraulic conductivity values are presented. The lower permeability units that occur between the water-bearing zones are assigned vertical hydraulic conductivity values.

Glacial Outwash Although no water table wells were screened exclusively within the glacial outwash, a lateral hydraulic conductivity can be determined from wells screened in both glacial outwash and weathered glacial till. Due to the higher hydraulic conductivity of the outwash, hydraulic conductivity values determined from these wells would yield a reasonable approximation of the glacial outwash hydraulic conductivity. Therefore, based upon in situ variable head recovery tests, the geometric mean lateral hydraulic conductivity of the glacial outwash is 1.2*10-3 cm/s. Glacial Till Based upon in situ variable head recovery tests, the geometric mean lateral hydraulic conductivity of the weathered glacial till is 1.7*10-5 cm/s. The results of laboratory testing of the sample of basal glacial till indicates a vertical hydraulic conductivity of 7.1*10-7 cm/s. One undisturbed sample was obtained in the basal till in a previous study by Wehran Engineering (1986a) yielding a vertical hydraulic conductivity of 2.1*10-6 cm/s. Residual Soil No wells were completed in the residual soil during this investigation. However, lateral hydraulic conductivity

Table 9-1 CONCEPTUAL MODEL OF THE HYDROGEOLOGIC SYSTEM Hydraulic Conductivity (ft/day)

Hydraulic Conductivity (cm/s)

0-18

3.45

1.22 x 10-3**

WBZ*

0-40

4.8 x 10-2

1.71 x 10-5**

Aquitard

10-78

1.1 x 10-2

3.95 x 10-6***

43.0

1.52 x 10-2**

Hydrostratigraphic

Type Unit

Glacial Outwash

WBZ*

Weathered Glacial Till Basa Glacial Till/ Residual Soil Fractured Rock Upper Vernon Shale Competent Rock

Thickness (ft)

WBZ*

7-35

Aquitard

0-60

1.4 x 10-4

5.0 x 10-8***

WBZ*

10-30

1.9 x 10-1

6.6 x 10-5**

Note: WBZ indicates water-bearing zone Lateral hydraulic conductivity Vertical hydraulic conductivity

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values for the residual soil were determined in a previous investigation by the consultant. Based upon in situ variable head recovery test conducted on one well screen within the residual soil, the lateral hydraulic conductivity was 1.2*10-3 cm/s. Correlative grain size analysis indicates that the hydraulic conductivity is 5.0*10-6 cm/s. The geometric mean of these values is 2.7*10-5 cm/s.

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Fractured-Rock Water-Bearing Zone Based upon in situ variable head recovery testing, the geometric mean lateral hydraulic conductivity of the fractured-rock water-bearing zone is 1.5*10-2 cm/s.

Figure 9-56 Potentiometric Surface of Overburden Zone

MONITORING SYSTEM DESIGN

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Figure 9-57 Potentiometric Surface of Fractured Rock Zone

Competent Rock Aquitard Based on packer testing, the geometric mean lateral hydraulic conductivity of the competent rock aquitard is 6.0*10-7 cm/s. The vertical hydraulic conductivity was assessed from information in published literature. Walton (1984) presents a range of field-scale vertical hydraulic

conductivity for shale of 5*10-l2 cm/s to 5*10-8 cm/s. For a conservative estimate, the higher value of 5*10-8 cm/s was chosen to represent the vertical hydraulic conductivity of competent rock aquitard.

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MONITORING SYSTEM DESIGN

Competent Rock Water-Bearing Zone The in situ variable head recovery testing program yielded a geometric mean lateral hydraulic conductivity of 1.8*10-5 cm/s for the competent rock water-bearing zone. The results of the packer testing program provided a geometric mean lateral hydraulic conductivity of 5.3*10-5 cm/s for this zone. To ensure that the highest permeability zones are fully represented, the two datasets were combined and the maximum hydraulic conductivity at each location was selected as the representative estimate (Table 9-1). The geometric mean lateral hydraulic conductivity for the combined data set is 6.6*10-5 cm/s. 9.10.7 Hydrogeologic Conditions The geology of the site has been described in previous sections of this chapter. In this section, the conditions under which ground water is contained within the various geologic deposits is described. The conceptual model for the proposed site consists of three water-bearing zones and two lower permeability units. In descending order, these units include the unconfined water-bearing zone consisting of weathered glacial till and glacial outwash, an aquitard consisting of unweathered glacial till and residual soils, a water-bearing zone within the upper highly fractured bedrock, an aquitard consisting of relatively unfractured shale bedrock and a water-bearing zone within a laterally continuous zone of increased hydraulic conductivity within the competent rock. Each hydrostratigraphic unit is described individually below. Competent Rock Water-Bearing Zone The deepest laterally continuous water-bearing zone encountered during this investigation occurs at elevations ranging from approximately 365 to 380 ft (msl). This zone (see Figure 9-58) is correlated on the basis of the gamma response and by an increase in hydraulic conductivity. The correlation between a specific stratigraphic interval and increased hydraulic conductivity may be a result of two factors. The first possibility is that this zone is associated with a number of small bedding planes which, collectively, promote an increase in hydraulic conductivity. The second possibility is that the increased hydraulic conductivity is a result of the dissolution of gypsum beds within the shale. This form of secondary porosity within the Vernon Shale is documented by Crain (1975). In all likelihood, the increased hydraulic conductivity is a result

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of the combination of these two factors as neither is clearly indicated upon examination of the collected core. The degree to which hydraulic conductivity enhancement occurs at this stratigraphically controlled horizon is variable. Increased hydraulic conductivity is associated with this horizon across laterally extensive areas of the site. However, the magnitude of the increase varies considerably from borehole to borehole and at location P-106 was noticeably absent. Nonetheless, the increased hydraulic conductivity does represent a mappable water-bearing horizon. The piezometric surface ranged from 475.04 ft to 462.82 ft (msl) on the date when all the wells and piezometers were measured. The flow direction indicated from all the accumulated data is generally north to south with a consistent, typical, hydraulic gradient of 0.008. The depiction of the piezometric surface in Figure 958 was completed by excluding the water elevations measured at location P-112C and P-114C as the water levels in these two piezometers were judged not to be representative of static head. A review of the hydrographs for each of the wells indicates that the water levels in both of these piezometers are still rising in an attempt to reach static conditions. Furthermore, an attempt to contour these water elevations provides an unrealistic representation of the piezometric surface and, in fact, would indicate a complete reversal in the ground-water flow direction. As such, these data points have been excluded from the mapping and a consistent hydraulic gradient has been assumed at these locations. While the hydraulic conductivity governs the volume of ground-water flow through a particular water-bearing zone, the velocity of flow, particularly in a fractured rock environment, is strongly controlled by the effective porosity, ne. The average linear velocity (seepage velocity, Vs) is directly proportional to the hydraulic conductivity and gradient and is inversely proportional to the effective porosity as presented in the above relationship. Accordingly, as the effective porosity decreases, the seepage velocity increases. In unconsolidated sediments, the effective porosity may range from a few percent to 40% or more. In a fractured media, however, the effective porosity may be as low as 1*10-5 (0.001%) and is usually less than 1*10-1 (10%) (Freeze and Cherry, 1979). The seepage velocity in a fractured rock may therefore be thousands of times more rapid than in a porous, unconsolidated material of equivalent hydraulic conductivity. A review of the literature indicates that the typical range of fracture porosity in sedimentary rocks is on the order of 1*10-3 to 5*10-3 (Streltsova, 1976; Walter and Thompson, 1982; Smith and Vaughan, 1985; Kelley et al., 1987). Streltsova (1976) reports fracture porosities of 1*10-3 to 2*10-3 for sandy shale petroleum reservoirs and

MONITORING SYSTEM DESIGN

a range of 1*10-3 to 5*10-3 for fissured reservoirs in general (Streltsova, 1976). Walter and Thompson (1982) noted a fracture porosity of 2*10-3 for the Conasauga Shale of Tennessee based upon field tracer studies. Yurochko (1982) reported a range in fracture porosity from 1*10-3 to 5*10-3 for siliceous reservoirs. Based upon aquifer test analysis, Smith and Vaughan (1985) concluded

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that the fracture porosity of the Nolichucky Shale in Tennessee was on the order of 1*10-3. Kelley et al. (1987) reported a fracture porosity of 2*10-3 for the Culebra Dolomite of New Mexico. In light of the above and for the purposes of the calculations and estimates presented in this report, an estimated fracture porosity of 2.5*10-3 (.0025) will be used to

Figure 9-58 Potentiometric Surface of Competent Bedrock Zone

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calculate the flow velocities for each of the bedrock waterbearing zones. This value is chosen as it is within the typical ranges cited in the literature. The seepage velocity calculations are therefore, as follows: .186 ft/day x (.008) = .56 ft/day Therefore, the lateral seepage velocity within the competent water-bearing zone is on the order of 205 ft per year. Upper Vernon Shale Aquitard (Competent Rock) The upper Vernon Shale aquitard occurs between the fractured rock water-bearing zone and the competent rock water-bearing zone. The upper surface of this unit is controlled by the depth of weathering (i.e., fracturing) of the Vernon Shale and is thus somewhat variable. The base of this unit is somewhat more consistent and is stratigraphically controlled by the occurrence of the competentwater-bearing zone. The thickness of this unit thus varies from 10 to 60 ft. As presented and discussed in Section 9.9.5, the vertical hydraulic conductivity of the competent Vernon Shale aquitard is conservatively estimated at 5*10-8 cm/s (1.4*10-4 ft/day). The geometric mean lateral hydraulic conductivity of this unit, as determined from borehole packer testing is 6*10-7 cm/s. The vertical seepage velocity is determined by the relation: Vs =ki/ne Where k, i and ne are as previously defined and the seepage velocity is calculated as follows: Vs = (1.4*10-4 ft/day)(.14)/.0025 =.008 ft/day Therefore, the vertical seepage velocity through the competent Vernon Shale aquitard is on the order of 2.9 ft/year. Fractured-Rock Water-Bearing Zone The uppermost bedrock water-bearing zone is found at elevations ranging from 384 ft to 472 ft. The occurrence of this top of rock zone is controlled by the erosional surface that defines the top of the bedrock and by the depth to which extensive fracturing has occurred. The ground water occurrence within this zone is by an interconnected network of fractures which more closely resembles a classical porous medium rather than a limited number of discrete fractures. The fact that highly to moderately fractured rock behaves as a classical porous media and

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can be modeled as such has been well documented in the literature and in particular by Thackston et al. (1989) and Merin (1989). The potentiometric surface ranges from 463.61 ft to 478.70 ft and indicates an overall south to southeast trending flow direction. The most striking features of this potentiometric surface map are the significant change in hydraulic gradients between the northwest corner of the site (notably wells P-201 and P-202) and the remainder of the site and the lobate shape of the 464 ft elevation contour. With respect to the lobate 464 ft contour it should be noted that this pattern may or may not exist in the actual system as the elevation data from the monitoring wells used to create this plot are all within 0.20 ft of each other. These 0.20-ft differences in elevation could easily be attributed to a combination of survey error, water level measurement error, a poor reference elevation on the well casing or possibly even a barometric efficiency change in water levels that occurred between the measurement of one well versus another. On the other hand, the variations in the transmissivity throughout the fractured-rock water-bearing zone, as discussed below, could account for just such a lobate pattern. The sudden change in hydraulic gradient is likely a result of two significant factors. First, a review of the hydrostratigraphic cross-sections indicate that the elevation of the top of rock water-bearing zone dips to an elevation consistent with that of the competent rock waterbearing zone (approximately 380 ft msl). This merging of these two water-bearing zones is further illustrated by the projection of the stratigraphic marker beds as indicated by the downhole gamma log responses. Furthermore, a review of the water elevations measured in wells P-201 and P-202 reveals that the elevations are generally consistent with what one would expect to find within the competent rock water-bearing zone at these locations. Thus the seemingly anomalous high water elevations found at well locations P-201 and P-202, which are screened within the fractured rock water-bearing zone, are simply a reflection of the fact that the competent rock water-bearing zone is intersecting the fractured-rock water-bearing zone. The second factor relating to the sudden change in hydraulic gradient is the varying hydraulic conductivities and changing thickness of the fractured rock water-bearing zone. Hydraulic conductivity varies from a low of 4.6*10-5 cm/s at location MW-102 to a high of 1.2*l0-l cm/s at location P-116. As presented on the cross-section (Figure 9-53), the thickness of this zone varies from 7 ft at location MW-102 to 35 ft at location MW-101. The approximate thickness of this water-bearing zone, as presented on the cross-sections, was based in packer test hydraulic conductivity values within the upper portion of the bedrock and on rock quality designation (RQD) values from individual rock cores. The packer test-

MONITORING SYSTEM DESIGN

ing proved to be the most diagnostic criterion for determining the lower limits of this fractured rock waterbearing zone. A hydraulic conductivity value of 1.0*10-5 cm/s was used to define the lower limit of this zone. In the absence of hydraulic conductivity values, RQDs from individual rock cores were utilized. A noticeable increase in RQD indicated an increase in the competence of the rock. Unconfined Overburden Water-Bearing Zone Ground water occurs under unconfined water table conditions within the glacial outwash, glacial till and residual soils beneath the proposed site. Due to the relatively low hydraulic conductivity of the glacial till and residual soils, ground water contained within these geologic units is restricted to vertical flow paths at a relatively slow rate of movement. This relationship is depicted graphically in hydrogeologic cross-section Figure 9-59.

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The jointing and weathering within approximately the upper 10 ft of the glacial till have served to increase the hydraulic conductivity by generally at least one order of magnitude as compared to the unweathered till found at depth below the site. As such, the weathered till in conjunction with the outwash deposits is characterized by a lateral flow of ground water. This scenario is depicted in Figure 9-56. The potentiometric surface map reveals that the flow direction throughout the majority of the site is to the south and southwest with radial flow from the area of mounding which is associated with the drumlin in the northeast corner of the site. Lateral gradients range from approximately .33 on the east side of the drumlin to a low of .009 near the center of the site. As lateral flow occurs primarily in the upper weathered zone of the glacial till an average saturated thickness of approximately 10 ft will be used for the purposes of flow calculations. The geometric mean lateral hydraulic conductivity of the glacial till is on the order of 1.7*10-5

Figure 9-59 Example Cross-Section Conceptual Model

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MONITORING SYSTEM DESIGN

cm/s or 0.36 gpd/ft2. The lateral volumetric flow rate for the weathered glacial till is then calculated as follows: Q = KIA = 0.36 gpd/ft2 There are also saturated zones of outwash which, at present, convey ground water off the site. The lateral volumetric flow rate for these deposits are calculated based upon the average thickness of saturated outwash deposits and a geometric mean lateral hydraulic conductivity of 1.2*10-3 cm/s. The calculation is as follows: Q = KIA Combining the lateral volumetric flow from the glacial till and the saturated glacial outwash deposits one calculates approximately 2,500 gallons of water per day to be moving laterally through the weathered till and outwash deposits. The lateral seepage velocity in the weathered till, assuming an effective porosity of.20, is calculated as follows: Vs = (4.9*10-2 ft/day (.024) /.20 = 5.8*10-3 ft/day The seepage velocity within the saturated outwash deposits, assuming an effective porosity of.35 is given as: Vs = (3.5 ft/day (.009) /.35 =.09 ft/day Lateral ground-water discharge from the unconfined water-bearing zone is to the small streams and springs which are found bordering the site. Basal Glacial Till/Residual Soil Aquitard As discussed above, the relatively low hydraulic conductivity of the unweathered glacial till and residual soils restricts the flow to vertical flow paths. The vertical hydraulic conductivity of these units will thus control the rate of vertical recharge to the bedrock underlying the residual soil. The geometric mean of the undisturbed samples collected during this and previous investigations is 1.2*10-6 cm/s. The lateral hydraulic conductivity for the unweathered glacial till and residual soils as reported by Wehran (1986b) is 4*10-6 cm/s and 2.8*10-5 cm/s, respectively. 9.10.8 Three-Dimensional Patterns of GroundWater Flow The case site investigation report has discussed each of the hydrostratigraphic sections individually and in

670

detail. The objective of this section is to integrate this information in order to accurately describe and understand the three-dimensional ground-water flow patterns beneath the site. This understanding will dictate the ground-water monitoring plan described later in this solution. The three-dimensional patterns of ground-water flow are most accurately depicted in hydrogeologic cross-sections. These sections were constructed using the static water levels collected from the monitoring wells and piezometers, as well as the calculated heads from the pneumatic piezometers. As in the construction of the potentiometric surface map for the competent rock waterbearing zone discussed previously, the water levels at locations P-112C and P-114C were deemed not representative of static conditions and were thus not used in the construction of the hydrogeologic cross-sections. As such, a consistent gradient was assumed and presented on the sections. An additional point with respect to these sections is the fact that, due to the scale of the sections, the lateral component of flow within the weathered glacial till and outwash deposits is not accurately portrayed. Nonetheless, the sections do provide a good illustration of the overall pattern of ground-water flow within the study area and the relationship between the various hydrostratigraphic units. A review of the sections indicates a downward gradient through the glacial till which discharges into the fractured-rock water-bearing zone and an upward gradient in the competent-rock water-bearing zone which also discharges in to the fractured-rock zone. This condition exists throughout the area proposed for the facility. Some deviation from this model occurs immediately west of the proposed site beneath the facilities operations parcel of land. Hydrogeologic cross-section (Figure 9-61, Answer B) indicates a reversal of the flow direction within the glacial till, thus indicating a discharge area, as opposed to a recharge area, as is found beneath the site area. This reversal in flow direction is a result of the high head values found within the fractured rock unit as discussed previously in Section 9.10.6. The overall effect of this flow reversal on the hydrogeologic regime is to create a ground-water stagnation zone within the glacial till just west of the proposed landfill property line. Ground water within this immediate vicinity would, as a result of the extremely low hydraulic gradient and relatively low hydraulic conductivity, move at an almost imperceptible rate. An apparent deviation also occurs at cluster 106 where the static heads indicate a slight downward component of flow from the fractured-rock zone to the competent-rock zone. The slightly lower head in the competentrock zone is considered to be a result of a number of factors. First, there is a limited vertical separation distance

MONITORING SYSTEM DESIGN

between the screened intervals in either water-bearing zone, potentially making any gradient that was there difficult to see. Secondly, the projected elevation of the bedrock surface to the south of location 106 indicates that the interval screened at P-106C very likely intersects the fractured rock water-bearing zone within approximately 200 ft. This, plus the fact that a review of the packer test results indicates a distinct zone of less than 10 ft of lower hydraulic conductivity rock between the two screened intervals, would tend to mask any difference in head which may exist. Furthermore, P-106C is screened at a stratigraphically higher position then any other competent rock piezometer on the site. This scenario is not present at any of the other locations throughout the site. In all likelihood, a piezometer screened at a stratigraphically correlative position and separated from the fractured rock zone by a greater thickness of lower hydraulic conductivity rock, would exhibit an upward component of flow. The ultimate discharge point for the ground water

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within the vicinity of the site has, in the past, been considered the canal, as this is the only significant surface water feature in the area. A conceptual cross-section incorporating the proposed site and the canal, however, indicates two other possible scenarios. Utilizing data generated during this investigation, the two conceptual cross-sections presented as Answer A and Answer B have been constructed. This conceptual diagram may indicate that not all ground water contained within the competent or fractured-rock water-bearing zones is discharging into the barge canal. Therefore, indicating that a discharge point may exist further to the south. The two conceptual cross-sections differ in the projected hydraulic gradient used in the fractured-rock zone. If one uses an hydraulic gradient of .001, consistent with that of the central portion of the proposed site, the conceptual model indicates a reversal in flow direction between the fractured and competent rock zones as presented in Figure 9-60, Answer A. This would indicate that recharge

Figure 9-60 Example Cross-Section Conceptual Model Answer A

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MONITORING SYSTEM DESIGN

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Figure 9-61 Example Cross-Section Conceptual Model (Answer B)

conditions are occurring south of the site and that ground water from the fractured-rock water-bearing zone is moving downward into the competent rock zone. The scenario presented in Figure 9-61 (Answer B), however, uses an hydraulic gradient consistent with that found in the northwest corner of the proposed site and indicates that discharge conditions prevail. In other words, ground water is moving upward from the competent rock to the fractured-rock water-bearing zone and a limited amount of discharge is occurring from the fractured rock zone to the canal. In both cases the top of rock surface has been projected based upon the site-specific information and indicates that the top of rock is approximately 70 ft below the ground surface in the vicinity of the canal. This was done as a very conservative approach and may or may not be true as all the regional literature discussed in Section 9.10.2 indicate that the bedrock is typically shallow along the trace of the canal. If one assumes this scenario to be correct then discharge from the fractured-rock to the canal would be occurring.

672

Although the ground-water flow paths south of the site are of interest, their definition with respect to the site investigation at the site is of little importance. The presented information clearly demonstrates that groundwater flow is downward through the glacial till and residual soils and upward from the competent rock to the fractured rock water-bearing zone. Thus limiting any potential impact from the site to the clearly defined fractured rock water-bearing zone. The ground water within this unit is readily monitored and, if circumstances should require, easily remediated at the site boundary prior to potentially entering the regional flow system. 9.10.9 Environmental Monitoring Plan An important component of any site-based detection or assessment environmental monitoring program is to be able to monitor and detect any impacts the facility may have upon the environment. This is true for both facility monitoring and to establish the impact of natural attenuation sites on human health and the environment. The

MONITORING SYSTEM DESIGN

monitoring plan addresses the various requirements for determination of existing water quality and for development and implementation of a comprehensive detection or assessment monitoring system. In addition to specifying standard methods and procedures for sampling and analysis, the plan also provides recommended locations for surface water monitoring stations and ground-water monitoring wells. The monitoring plan was predicated upon the technical criteria outlined below. Monitoring System Design Criteria The successful implementation of an effective environmental monitoring system is dependent upon a number of technical factors. For example, monitoring wells must be properly located, constructed of appropriate materials and properly installed. Similarly, samples must be carefully obtained, properly analyzed and the data clearly reported and interpreted. These factors collectively represent the criteria which must be considered in the design of a comprehensive and effective monitoring system. The design criteria identified and utilized in the development of a ground-water monitoring plan are outlined below. •

Monitoring Network Design Criteria - Recommended locations and specifications for monitoring wells and surface water sampling stations based upon an analysis of potential migration pathways

•

Sampling Protocol - Sampling instrumentation and approved methodologies, sampling frequency, sample storage and preservation requirements and chain-ofcustody procedures

•

Analytical Protocol - Parameter selection, approved field and laboratory methods and quality assurance/ quality control procedures

•

Data Management Criteria - Recommended procedures for data statistical analyses and data reporting

References Aguileia, R. and H.K.Van Poden, 1978. How to Evaluate Naturally Fractured Reservoirs from Various Well Logs. The Oil and Gas Journal, December. 1978, pp. 202-208. Basham, R.B. and W. Macune, 1952, The Delta-Log, a Differential Temperature Surveying Method, Petroleum Trans., AIME, V. 195, pp. 123-128. Bouma, Baker and Veneman, 1974. Measurement of Water Movement in Soil Pedons Above the Watertable. University of Wisconsin Extension. Geological and Natural History Survey, Information Circular Number 27. Bouwer, H., 1989. The Bower and Rice Slug Test - An Update,

Groundwater, Vol. 27, No. 3, pp. 304-309. Brooks and Corey, 1975. Drainage characteristics of a soil. Soil Science Society of America Proceedings. 39:251-255. Burmister, D.M., 1958. Suggested Methods of Tests for Identification of Soils, Procedures for Testing Soils, ASTM. Cedergren, J.R., 1977. Seepage, Drainage and Flownets. John Wiley & Sons, New York, New York, 68 pp. CH2M Hill, Inc., May 1985. Site Investigation/Feasibility Study - Sand and Gravel Mining at High Acres Sanitary Landfill. Crain, L.J., 1974. Ground-Water Resources of the Western Oswego River Basin, New York. U.S. Geological Survey Report for State of New York Department of Environmental Conservation, Basin Planning Report ORB-5, 137 pp. Crain, L.J., 1975. Chemical Quality of Ground Water in the Western Oswego River Basin, New York. U.S. Geological Survey Report for State of New York Department of Environmental Conservation, Basin Planning Report ORB-3, 69 pp. Davis, S.N. and R.J.M. DeWiest 1967. Hydrogeology, John Wiley and Sons, New York, 463 pp. Dax, A., 1987. A Note on the Analysis of Slug Tests, Journal of Hydrology, Vol. 9, pp. 153-177. Desaulniers, D.E., J.A. Cherry, and P. Fritz, 1981. Origin, Age and Movement of Pure Water in Argillaceous Quaternary Deposits at Four Sites in Southwestern Ontario, Jnl. of Hydrology, Vol. 50, pp. 231-257. Diment, G. and K. Watson, 1983. Stability Analysis of Water Movement in Unsaturated Porous Materials. 2. Numerical studies. Water Resources Research. 19(4) 1002-1010. Diment, G. and K. Watson, 1985. Stability Analysis of Water Movement in Unsaturated Porous Materials: Experimental studies. Water Resources Research. 21:979-984. Driscoll, F. G., 1986. Groundwater and Wells. Johnson Division, St. Paul, Minnesota. Dunnicliff, J., 1988. Geotechnical Instrumentation for Monitoring Field Performance, John Wiley and Son, New York, 575 pp. Fairchild, H.L., 1895. Glacial Lakes of Western New York, Bulletin of the Geological Society of America, Vol. 6, pp. 353-374. Fairchild, H.L., 1913. Pleistocene Geology of New York State, Bulletin of the Geological Society of America, Vol. 24, pp. 133-162. Fairchild, H.L., 1932. New York Moraines, Bulletin of the Geological Society of America, Vol. 43, pp. 627-662. Fenneman, N.M., 1938. Physiography of Eastern United States. New York, McGraw-Hill Book Co., Inc., 691 pp. Fisher, D.W., 1955. Lithology, Paleocology and Paleontology of the Vernon Shale (Late Silvrian) in the Type Area, New York State Museum and Science Service, Bull. 364, 31 p. Flint, R.F., 1971. Glacial and Quarternary Geology. John Wiley and Sons, New York. Freeze, R.A. and J.A., Cherry, 1979. Groundwater, PrenticeHall, New Jersey, 604 pp. Freeze, R.A. and P.A. Witherspoon, 1967. Water Resources Research, 3:623–634.

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Gardner, W. and J. Chatelain, 1947. Thermodynamic potential and soil moisture. Soil Science Society of America Proceedings. 11:100-102. Germann, P. and K. Beven, 1981a. Water Flow in Soil Macropores I. An experimental approach. Journal of Soil Science. 31:1-13. Germann, P. and K. Beven, 1981b. Water Flow in Soil Macropores II. A Combined Flow Model. Journal of Soil Science, 32:15-29. Glass, R., T. Steenhuis and J. Parlange, 1988. Wetting front instability as a rapid and far-reaching hydrologic process in the vadose zone. Journal of Contaminant Hydrology. 3:207-226. Grisak, G.E. and Cherry, J.A., 1975. Hydrologic Characteristics and Response of Fractured Till and Clay Confining Shallow Aquifer. Canadian Geotechnical Journal, Vol. 12, No. 23, pp. 23-43. Griswold, R.E., 1951. The Ground Water Resources of Wayne County, New York. U.S. Geological Survey Bulletin 6W29, Albany, New York. Guarino, J., 1985. Pore Pressure Changes Due to Bentonite Pellet Seals, Project. Rep. for M.S. Degree, University of Massachusetts, Amherst. Heffner, R.F. and S.D. Goodman, 1973. Soil Survey of Monroe County, New York, United States Department of Agriculture. 173 p. Hem, J.D., 1985. Study and Interpretation of the Chemical Characteristics of Natural Water. Third Edition. U.S. Geological Survey Water-Supply Paper 2254. Hendry, James, M., 1982. Hydraulic Conductivity of a Glacial Till in Alberta, Groundwater, Vol. 20, No. 2, pp. 162-169. Hvorslov, M.J., 1951. Time-Lag and Soil Permeability in Groundwater Observations, U.S. Army Corps. of Eng., Water Exp. Stn., Bull. 36, 50 p. Kantrowitz and Snavely, 1982. Availability of Water from Aquifers in Upstate New York, U.S. Geological Survey, Open File Report 82-437. Kelley, V.A., J.F. Pickens, M. Reeves, and R.C. Beauheim, 1987. Double- Porosity Tracer-Test Analysis for Interpretation of Fracture Characteristics of Dolomite Formation, in Proc. of the Solving Groundwater Problems with Models Conference, NWWA, February, 1987, Denver, CO, p. 147- 169. Kirkham, D. and W. Powers, 1972. Advanced Soil Physics. WileyInterscience, New York. Klute, A., 1972. The Determination of the Hydraulic Conductivity and Diffusivity of Unsaturated Soils. Soil Science. 113:264-276. Looney, B.B. and R.W. Falta, 2000. Vadose Zone Science and Technology Solutions, Battelle Press Columbus OH, 1540 p. Merin, I.S., 1989. Characterization of Fractures in Devonian Siltstones, Northern Appalachian Plateau: Implications for Ground Water Flow, Proceeding of the Third National Outdoor Action Conference on Aquifer Restoration, Ground Water Monitoring and Geophysical Methods, Assoc. of Groundwater, Sci. & Eng., May 22-25, 1989 Orlando, FL.

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Miller, E., 1975. Physics of swelling and cracking soils. Journal of Colloid and Interface Science. 52t3)434-443. Miller, T. S., 1987. U.S. Geological Survey in cooperation with the New York State Department of Environmental Conservation. Unconsolidated Aquifers in Upstate New York. Finger Lakes Sheet. Muralem, Y., 1976. A catalogue of the hydraulic properties of unsaturated soils. Haifa, Israel. Israel Institute of Technology. National Oceanic and Atmospheric Administration, 1988. Local Climatological Data, Annual Summary with Comparative Data, Rochester, New York, 7 p. Nelson, P.H., 1982. Advances in Borehole Geophysics for Hydrology, Recent Trends in Hydrogeology, USGS, Special Paper 189, T.N. Narasimhan, ed., p. 207-219. New York State Department of Environmental Conservation, 1987. Final Upstate New York Groundwater Management Program. New York State Department of Environmental Conservation, May 1987. Upstate New York Groundwater Management Program. New York State Department of Environmental Conservation, December, 1988. 6 NYCRR Part 360 Solid Waste Management Facilities. Norris, S.E., 1972. The Use of Gamma Logs in Determining the Character of Unconsolidated Sediments and Well Construction Features, Groundwater, V. 10, No. 6, p. 14-21. Quinlan, J.F., 1990. Special Problems of Ground-water Monitoring in Karst terrains in Ground Water and Vadose Zone Monitoring, Nielsen and Johnson ed. ASTM STP 1053, Philadelphia, PA 19103, pp. 275-307. Rbhabhirama, A. and C. Kridakorn, 1968. Steady downward flow to a watertable. Water Resources Research. Vol. 4. Richards, L., 1931. Capillary conduction of liquids through porous mediums. Physics. Vol. 1. Scott and Clothier, 1983. A transient method for measuring soil water diffusivity and unsaturated hydraulic conductivity. Soil Science Society of America Journal. 47:1068-1072. Simpson T. and R. Cunningham, 1982. The occurrence of flow channels in soils. Journal of Environmental Quality. 1(1):2930. Smith, E.D. and N.D. Vaughan, 1985. Experiences with Aquifer Testing and Analysis in Fractured Low-Permeability Sedimentary Rocks Exhibiting Non-Radial Pumping Response, Hydrogeology of Rocks of Low Permeability, Intn'l Assoc. of Hydrogeologists, January 1985, pp. 137149. Steenhuis, T. and J. Parlange, 1988. Simulating preferential flow of water and solutes on hillslopes. Conference on Validation of Flow and Transport Models for the Unsaturated Zone. Ruidoso, New Mexico. May 23-26. pg. 11. Streltsova, T.D., 1976, Hydrodynamics of Groundwater Flow in a Fractured Formation, Water Resources Research, Vol. 12, No. 3, pp. 405-414. Taylor, A., 1950. The instability of liquid surface when accelerated in a direction perpendicular to their planes. Proceedings of the Royal Society. 201:192-195.

MONITORING SYSTEM DESIGN

Thackston, J., Y. Meeks, J. Strandberg, and H. Tuchfeld, 1989. Characterization of a Fractured Flow Groundwater System at a Waste management Facility, Proceeding of the Third National Outdoor Action Conference on Aquifer Restoration Ground Water Monitoring and Geophysical Methods, Assoc. of Groundwater, Sci. & Eng., May 2225, 1989. Orlando, FL. United States Department of Agriculture, Soil Conservation Service 1973. Soil Survey, Monroe County, New York. United States Department of Agriculture, Soil Conservation Service 1975. Soil Survey of Wayne County, New York. United States Environmental Protection Agency, 1983. Guidance on Implementation of Subpart F Requirements for Statistically Significant Increases in Indicator Parameter Values, Agency Memorandum. Walter, G.R. and G.M. Thompson, 1982. A Repeated Pulse Technique for Determining the Hydraulic Properties of Tight Formations, Groundwater, V. 20, No. 2, pp. 186193. Walton, W.C., 1970. Groundwater Resources Evaluations, McGraw-Hill, New York, 664 pp. Walton, W.C., 1984. Handbook of Analytical Groundwater Models Short Course. Practical Analysis of Well Hydraulic and Aquifer Pollutions, Intnl Groundwater Modeling Center, Holcomb Research Institute, Bulter University, April 9-13, 1984. Warner, G. and J. Nieber, 1988. CT scanning of macropores in soil columns. Winter Meeting of American Society of Agricultural Engineers. Paper No. 88-2632. Presented at the International Winter Meeting at the Hyatt Regency, Chicago, Dec. 13-16, 1988. p. 13. Wehran Engineering, 1986a. Draft Environmental Impact Statement for the Expansion of the Sanitary Landfill. Wehran Engineering, 1986b. Hydrogeologic Investigation for the Expansion of the Sanitary Landfill. Wehran Engineering, 1988. Supplemental Phase II Report for the Sanitary Landfill, Volumes 1 and 2. White, R., 1985. The influence of macropores on the transport of dissolved and suspended matter through soil. Advances in Soil Science, Vol 3., Springer Verlag New York Inc., pp. 95-113. Williams, Roy E., and R.N. Farvolden, 1967 The Influenced Joints on the Movement of Ground-water Through Glacial Till. Journal of Hydrology, Vol. 5, No. 2, pp. 163-170. Yurochko, A.I., 1982. in North, F.K., Petroleum Geology, Allen & Unwin, Boston, MA, 607 pp.

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CHAPTER 10 ASSESSMENT MONITORING DESIGN

Assessment monitoring programs typically are employed once the owner/operator of the facility has detected a statistically valid increase in indicator parameters in his detection monitoring program. Assessment monitoring activities may also be initiated due to previous hazardous waste disposal activities that may nominate the site through a state or federal regulatory program as a significant risk to human health and the environment. Federal and state regulations have codified assessment monitoring programs throughout the Resource Conservation and Recovery Act (RCRA), Subtitles C and D and Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) Superfund regulations. Although it may seem like a daunting task to review assessment monitoring programs for such complex regulations, the actual scope of the site evaluation technical work components is essentially similar to the scope presented in the previous discussion, only with more rigorous documentation requirements. These federal programs are compared in Figure 10-1 for major goals of assessment investigations. These goals can be summarized into the following points: • Identify releases needing further investigations. • Characterize nature, extent and rate of release. • Evaluate alternatives and identify remedies. • Propose selected remedy. • Include public participation. • Authorize selected remedy. • Design and implement chosen remedy. These federal programs are followed by very similar state remedial action programs that could easily be categorized into the same set of goals. Hence, assessment programs go beyond pure evaluation of rate and extent of ground-water contamination to include definition of all contaminated media and the selected remedy.

These regulations place considerable reliance on collection of soil and ground-water quality samples to determine both the source area and the rate and extent of contaminant movement. Once these data are established, appropriate corrective actions could range from just continued monitoring (such as Monitored Natural Attenuation, see Chapter 13) to an aggressive aquifer and site remediation program. Unfortunately, federal and state mandated programs have primarily relied on the collection of extensive organic and hazardous metal contaminant parameters lists, to the detriment of gathering sufficient geologic data to both define the extent of affected ground water and establish the basic hydrogeologic characteristics sufficient to design a remediation for the facility. The technical difficulties in design of assessment monitoring programs that follow the above seven points can be eased through application of a site assessment program based on a phased approach similar to the analysis used in detection monitoring. An investigation program that puts understanding the geology and hydrogeology first allows the remaining five assessment goals be addressed in a more direct manner. The following sections summarize some of the common aspects of federal and state assessment monitoring programs and details program guidance for both specific determination of the extent of affected aquifers or soils and acquisition of sufficient data to design appropriate aquifer restoration techniques. The guidance provided below evaluates site complexity and general program components applicable for such evaluations. Because soil contamination is typically an important aspect in remedial studies for both organic and hazardous metals contamination, components of soil and soil gas programs are provided below. These data are typically used in source reduction efforts. This chapter also includes an introduction to risk assessment, because assessment of risk now forms an important part of most remedial studies. Special guidance is also provided for site evaluations specific to nonaqueous phase liquids (NAPLs) as

677

ASSESSMENT MONITORING DESIGN

RCRA / CERCLA COMPARISON RCRA

GOAL

CERCLA

Subtitle C Hazarous Waste

Subtitle D Solid Waste

Identify Releases Requiring Further Investigation

RCRA Facility Assessment (FRA)

Phased Detection Monitoring

Preliminary Assessment/ Site Investigatioin (PA/SI)

Characterize Nature, Extent, and Rate of Release

RCRA Facility Investigation (RFI)

Facility Assessment

Remedial Investigation (RI)

Evaluate Alternatives and Identify Remedy(s)

Corrective Measures Study (CMS)

Superfund

Corrective Measures Study (CMS)

Feasibility Study (FS)

Propose Selected Remedy

Draft Permit Modification

(State) Permit Modification

Proposed Plan

Conduct Public Participation

Public Comment

Evaluation of Public Acceptance

Public Comment

Authorize Selected Remedy

RCRA Permit

State Selection of Remedy

Record of Decision

Design and Implement Chosen Remedy

Corrective Measures Implementation (CMI)

Corrective Action Program

Remedial Design/ Remedial Action (RD/RA)

Figure 10-1 Comparisons of Remedial Programs density may have a significant effect on the scope of a facility assessment. 10.1 RCRA ASSESSMENT MONITORING PROGRAMS Congress significantly expanded the federal role in controlling the management of waste materials in the United states with the passage of the RCRA of 1976. Subtitle C of RCRA required the U.S. Environmental Protection Agency (USEPA) to establish a comprehensive regula-

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tory program to ensure proper management of hazardous waste. Subtitle D of RCRA established a cooperative framework for involving federal, state, and local governments in solid waste disposal. The federal role in the Subtitle D is to provide technical assistance to states and regions for planning and developing waste management practices and to furnish financial assistance to enable states to implement these measures. The planning and implementation of solid waste programs under Subtitle D will remain primarily a state and local function.

ASSESSMENT MONITORING DESIGN

Much of the monitoring technology used to date has been based on RCRA Technical Enforcement Guidance Document (TEGD). While this document is used as a basis for RCRA monitoring programs, a number of important issues regarding ground-water monitoring have made portions of the TEGD outdated. The TEGD, which was issued in 1986, is far from the last word in the rapidly developing field of ground-water monitoring technology. For example, the TEGD indicates that “fluorocarbon resins or stainless steel should be specified for use in the saturated zone when volatile organics are to be determined.” Moreover, according to the TEGD, “PVC is appropriate only for trace metals and nonvolatile organics.” Superfund investigations even to the date of this 2nd edition (2003) would require stainless steel casing and screens for the assessment monitoring system. There is no scientific data to suggest that PVC is not appropriate for use in ground-water monitoring wells when used for detection monitoring programs and, in fact, there is substantial data to support such use. Indeed, the recently revised ASTM Committee D-18 “Recommended Practice for Design and Installation of Ground Water Monitoring Wells in Aquifers” (D 5092-02) specifies that well screens and risers can be composed of PVC, stainless steel, fiberglass or fluoropolymer materials. Another example of the TEGD’s obsolescence is the use of statistical analysis of ground-water monitoring data to determine if a release has actually occurred. The TEGD recommends that Cochran’s approximation to the Behrans-Fisher (CABF) t-test be used as the statistical test for a detection monitoring program. Since issuing the TEGD, the U.S. EPA itself expressed doubt regarding the validity of the CABF t-test for ground-water monitoring programs in the October 11, 1988 final rule, Statistical Methods for Evaluating Ground-Water Monitoring Data from Hazardous Waste Facilities. The U.S. EPA concluded that the this statistical methodology was not appropriate for use because: (l) the replicate sampling method required under the then-current Part 264 Subpart F regulations was not appropriate for the CABF procedure; (2) the CABF procedure did not adequately consider the number of comparisons that must be made under the regulations; and (3) the CABF did not control for seasonal variation. Moreover, the CABF test generates an unacceptable rate of false positives and has placed facilities in compliance monitoring programs when, in fact, no releases has actually occurred. Since the original issuance of the TEGD several draft revisions corrected some of the main incorrect points in the 1986 document; however, as of 2003 the U.S. EPA has not issued a final version of this document. Ground-water remedial programs should always be based on using solutions that provide a reasonable assurance that the affected media will actually reach some acceptable clean-up level. This may sound like a given for

conducting any remedial project; however, there are circumstances when (because of widespread ground-water contamination stemming from numerous other sources), performing a corrective action remedy at a waste disposal facility will produce no measurable improvement in ground-water quality. Experience over the past few years has shown that most, if not all, contaminated aquifers cannot, at present, be restored to a condition compatible with national health-based water quality standards. Several recent studies support this conclusion. For example, the U.S. EPA (1990) released a study involving 19 Superfund sites where ground-water pump-and-treat systems have been in operation for up to 10 years. This study concluded that, in most cases, although the initial phases of remediation had achieved significant mass removal of contaminants, there had been little success in reducing concentrations to target levels. Typically, these systems achieved an initial drop in concentrations by factors ranging from 2 to 10, followed by a leveling off with no further decline in contaminant concentrations. Similarly, an independent analysis completed by the Oak Ridge National Laboratory concluded that restoration of contaminated aquifers to health-based levels may be impossible. In addition, leading environmental and ground-water scientists have predicted that continuous pumping for 100 to 200 years may be necessary to reduce contaminant concentrations by a factor of 100 (assuming ideal conditions) and that for sites with light or dense nonaqueous phase liquid (LNAPL or DNAPL) contaminants, restoration to drinking water standards may simply be unachievable. For this reason, the incorporation of the concept of risk is included into the remedial evaluation process. This allows investigators flexibility to address the protection of human health and the environment in the evaluation process. Although implementation of remedial programs is the ultimate goal for the federal and state programs discussed in this chapter, one should not lose sight of the reality in the extreme difficulty of evaluating and actually successfully cleaning-up affected aquifers. 10.1.1 RCRA Subtitle C The passage of the revised RCRA legislation in 1984 detailed assessment monitoring of waste disposal facilities within several sections of 10 CFR for hazardous waste sites. Sections 265.93(d)(4), 270.14(c)(4) and 270.14(c)(2) provide enforcement officials with the regulatory authority needed to review an owner/operator’s assessment monitoring program. These sections describe the following criteria: • 265.93(d)(4) An assessment monitoring plan must be capable of determining:

679

ASSESSMENT MONITORING DESIGN

(i) Whether hazardous waste or hazardous waste constituents have entered the ground water, and (ii) The rate and extent of migration of hazardous waste or hazardous waste constituents in the ground water. • 270.14(c)(4) The Part B applicant must include in the submittal a “description of any plume of contamination that has entered the ground water from a regulated unit at the time the application was submitted that: (i) Delineates the extent of the plume, and (ii) Identifies the concentration of each Appendix VIII... constituent... throughout the plume...” • 270.14(c)(2) The Part B applicant must submit, among other things, an “identification of the uppermost aquifer and aquifers hydraulically interconnected beneath the facility property, including ground water flow direction and rate and the basis for such identification (i.e., the information obtained from hydrogeologic investigations of the facility area).” Technical Approach RCRA Site Remediation Program The RCRA facility investigation (RFI) is generally equivalent in technical scope to the CERCLA remedial investigation. Units are areas of concern that are determined in the RCRA Facility Assessment (RFA) to be a likely source of significant continuing releases of hazardous wastes or hazardous constituents. The regulatory means of requiring the RFA is either through RCRA permit conditions (operating or closure/post-closure) or via enforcement orders [e.g., 3008(h)]. Because of the Hazardous and Solid Waste Act (HSWA) statutory language, the agencies must focus the RFI requirements on specific solid waste management units or known or suspected releases that are considered to be routine and systematic. The HSWA permit conditions or enforcement orders can range from very general (e.g., “characterize the ground water at...”) to very specific (e.g., a specified number, depth, location and frequency of samples analyzed for a given set of constituents). Because the regulatory agency in the RFA, is not required to positively confirm a continuing release, but merely determine that the “likelihood” of a release exists, the scope of the RFI can range from a limited specified activity to a complex multimedia study. The investigation may be phased, initially allowing for verification or rebuttal of the suspected continuing release(s). If release to the environment is verified, the second phase of investigation typi-

680

cally consists of release characterization. This second phase of a RCRA RFI is much like a Superfund RI, and includes: (1) the type and quantity of hazardous wastes or constituents within and released from the unit, (2) the media affected by the release, (3) the current extent of the release, and (4) the rate and direction at which the releases are migrating. Inter-media transfer of releases (e.g., evaporation of organic compounds from contaminated soil to the atmosphere) may also be addressed where applicable during the RFI. Investigation of potential releases from RCRA units requires establishment of various types of technical information early in the RFI. This information is specific to the RCRA waste managed, the unit type (for example, lagoon or landfill), design and operation of the facility, the environment surrounding the unit or facility and the environmental medium to which contamination may be released. Although each medium (i.e., ground water, surface water, sediments) will require specific data and methodologies to investigate a release, the following represents a general strategy for a RCRA RFI project. The technical approach of the RFI requires the investigator to examine extensive data on the facility and specific units at the facility. These data generally can be divided into the following categories: • Regulatory history

(Typically estab-

• Facility and unit design

lished in Phase I

• Waste characteristics

work)

• Previous release events • Environmental setting • Pollution migration pathways

(Typically estab-

• Evidence of release

lished in Phase II

• Environmental receptors

field investigations)

Specific factors in each category that must be considered will vary depending on which environmental pathway medium is considered most vulnerable. For example, unlined in-ground units are more likely to have soil and ground-water releases than lined units or waste disposal in clay will retard the movement of contaminants. A facility’s environmental setting will determine which media are of concern (e.g., shallow ground water or fractured subsoils). As such, the phase investigation approach must first be based on a regional understanding of the subsurface that points toward a more direct site-based Phase II geologic and hydrogeologic field data gathering. RCRA Facility Investigation Assessment monitoring programs as detailed later in this chapter can be used to define the various site indices

ASSESSMENT MONITORING DESIGN

that provide for direct evaluation of the potential release and the remediations required by RCRA (see Figure 10-1). In reviewing the RFI Phase I and II investigative efforts, the regulatory agency will typically interpret the release findings. The first interpretive emphasis of the investigation is primarily on the data quality (i.e., were location criteria, sampling and analytical data quality objectives defined and accomplished according to planning documents?). The results of the RFI are then compared against established human health and environmental criteria. It is important to remember that the direct assessment techniques described in this chapter will typically provide water quality values that are directly within the main part of the migration pathway. These targeted analytical values are generally much higher than the somewhat random or soil residual values obtained from typical assessment programs. The more concentrated values produce higher criteria or “action” levels for each environmental medium and exposure pathway, using the toxicological properties of the waste constituent and standardized exposure model assumptions. At this stage in the RCRA facility investigation, if the continuing release of hazardous wastes is determined as a potential short-term or long-term threat to human health and the environment, the regulatory agency may require either interim corrective measures or a corrective measures study. This evaluation of human health and the environment risk factors is a crucial stage in the RCRA corrective action process. Because the assessment monitoring points are placed directly within ground-water flow lines from the facility in question, these values allow better evaluation of migration pathway risk assessment, potential receptors and worst-case water quality parameter leads. With the data gathered within the targeted field assessment program, water quality values and remedial design criteria are available early in the program. In addressing releases from Solid Waste Management Units (SWMUs) to the environment, the RFI is followed by corrective measures; that is, a release or source of contamination has been identified and the owner/operator must initiate a remedial response. As in the Superfund program, remedial action objectives of a particular corrective action are site specific; therefore, quantitative goals that define the level of cleanup are required to achieve the response objectives. These goals include any preliminary cleanup levels for environmental media affected by a release, the area of attainment, and the remedial time-frame. The above objectives are accomplished through the corrective measures study (CMS) and the corrective measures implementation (CMI) by identifying, designing and implementing the appropriate remedial strategy, all in

accordance with published guidance. The CMS serves as a recommendation to the U.S. EPA or the state, while the CMI is the allowed time frame for the actual corrective measures. Corrective Measures Studyy (CMS) The first step in the CM phase is the development and implementation of the CMS to determine the most effective remedial option to correct potential or actual environmental impact and human exposure threats posed by releases of hazardous wastes or constituents. Regardless of whether the remedial response effort is conducted under CERCLA or RCRA authority, the objectives of the RCRA CMS or Superfund feasibility study, are to utilize technical knowledge and propose actions to control the source of the contamination (by preventing or mitigating the continued migration of contamination by removing, stabilizing, and/ or containing the contaminants) and/or actions to abate problems posed by the migration of substances from their original source into the environment. Through the CMS, the owner/operator must technically demonstrate that the response action proposed effectively abates the threats to human health and the environment posed by the release(s). This typically requires the analysis of several remedial technologies in detail sufficient to show that the recommended measures effectively remove the threats posed by the release. To do so, the owner/operators must assess these alternatives in terms of their technical feasibility (including reliability and requirements for long-term operation and maintenance), their ability to meet public health protection requirements and their ability to protect the environment and any adverse environmental effects of the measures. The owner/operator also should consider any institutional constraints to implementation of the measures, such as off-site capacity problems and potential public opposition. The RCRA approach to assessing the level of remedial action required for environmental media is similar to that of CERCLA and generally is based on the following criteria: • Overall protection of human health and the environment • Compliance with regulatory programs (e.g., CERCLA or RCRA) • Short-term effectiveness • Long-term effectiveness and permanence • Reduction of toxicity, mobility, or volume of hazardous wastes and/or waste constituents • Implementability

681

ASSESSMENT MONITORING DESIGN

• Cost • U.S. EPA and/or state acceptance • Community acceptance The first two criteria are the basic regulatory requirements, while the next five criteria are interactively used to analyze and compare the options. The final two criteria are considerations in the overall evaluation. In some cases, it is possible for owner/operators to analyze and present to the agency or state only a single alternative that meets public health and environmental requirements. This situation is often the case at facilities that have taken “interim corrective measures” and thus have had an opportunity to evaluate the remedial strategy and the associated operations to determine their effectiveness. The RCRA final remedies will be required to meet applicable, possibly current, health and environmental standards promulgated under RCRA and other laws. For example, at regulated units, ground-water releases are subject to the ground-water protection standards, possibly consisting of the following: • Constituent specific maximum concentration limits (MCLs) • The background level of that constituent in ground water • An approved alternate concentration limit (ACL) where approval would be based on criterion set forth in the RCRA regulatory framework For soil, soil gas, surface water, ground water and air emissions problems that cannot be addressed by existing health based or regulatory standards, the U.S. EPA currently is assessing the appropriate technical approach. One possible alternative is to establish appropriate health-based standards on a case-by-case basis. Once the owner/operator proposes the remedial strategies) for addressing releases to environmental media and the SWMU itself, the US EPA or the state will evaluate the owner/operator recommendation and approve or disapprove it. During the review process, the owner/operator must be prepared to provide the technical support for his or her proposition and must be open to negotiations. The views of the public on the proposed measures and the financial assurance demonstration also will normally be considered by the state and U.S. EPA in making these technical and cost decisions.

682

Corrective Measures Implementation Once the U.S. EPA, the state and the owner/operator agree on the remedial approach, the owner/operators must design and construct the selected response action. After construction, the appropriate measures needed to operate, maintain and monitor the remedy will be taken by the owner/operators. These activities will be called out by permit condition or a compliance order and these activities must be completed by the owner/operators with some level of oversight by the U.S. EPA or state. Because the actual remedial operations serve to provide data concerning the effectiveness of the corrective action, it is essential that these data are used as criterion in determining whether the operations should be modified over time to meet the project cleanup objectives. 10.1.2 RCRA Subtitle D In developing the corrective action provision of RCRA Subtitle D, Subpart E, for solid waste facilities, the U.S. EPA reviewed the processes, approaches and historical experiences gained through CERCLA remedial actions and the corrective action program under the hazardous waste regulations of RCRA Subtitle C. The assessment process contain in 40 CFR §258.56 is begun when the ground-water trigger levels have been verified exceeded during Phase II monitoring as shown in Figure 10-2. Components of the 1991 RCRA Subtitle D assessment monitoring and remedial actions sections of these regulations are provided below in italics referenced section by section, and illustrated in Figures 10-2a to 10-2c. Assessment Monitoring Program (§258.55) Within 90 days of triggering an assessment monitoring program and annually thereafter, the owner or operator must sample and analyze the ground-water for all constituents identified in Appendix II. A minimum of one sample must be collected and analyzed during each sampling event. For any constituent detected in the downgradient wells as a result of the complete Appendix II analysis, a minimum of four independent samples from each well (background and downgradient) must be collected and analyzed to establish background for the constituents. The Director of an approved state may specify an appropriate subset of wells to be sampled and analyzed.

ASSESSMENT MONITORING DESIGN

Ground-Water Monitoring Programs

DETECTION, ASSESSMENT MONITORING AND CORRECTIVE ACTION FOR SOLID WASTE FACILITIES UNDER RCRA SUBTITLE D

• Install Monitoring System (258.51) • Establish Sampling and Analysis Programs (258.53)

Detection Monitoring Programs (258.54) • Semi Annual Monitoring (258) • Detection Monitoring for Appendix I Constituents (258)

Assessment Monitoring (258.55) • Sample for All Appendix II Constituents. Is There a Statistically Significant Increase in Appendix I Constituents ?

Yes

• Set Ground-water Protection Standards for Detected Appendix II Constituents. • Resample for Detected Appendix II Constituents and All Appendix I Constituents Semi-annually. • Repeat Annual Monitoring for All Appendix II Constituents.

No

• Characterize Nature and Extent of Release.

Continue / return to Detection Monitoring Yes

Are all Appendix II Constituents below Background ?

No o

Is There a Statistically Significantt Increase in Appendix II Constituents Over G ou d Ground-Water ate Protection otect o Standards ?

Yes

No Continue Assessment Monitoring

Corrective Action • Assess Corrective Measures • Evaluate Corrective Measures and Select Remedy (258.57) SOURCE: 40 CFR 258.50 -258.58

• Implement Remedy (258.58)

Figure 10-2a RCRA Detection Monitoring Programs

683

ASSESSMENT MONITORING DESIGN

From m Detection Monitoring Program Progra

Figure 10-2b Assessment Monitoring Program (258.55)

Sample for Appendix II • Within 90 Days of SSI Report • Constituents at All Downgradient Wells

Any Appendix II Constituents Detected ?

No

Second Sampling of Wells Sample All Downgradient Wells for Appendix II Constitutes for Second Sampling Event

No

(A)

Are Detected Appendix II Constituents Above GWPS ?

Yes

Background Water Quality Collect 4 Independent Samples from Each Well to Establish Background for Each Detected Constituent

(B) Yes

Ye es

b))

Update Operating Record Within 14 Days of (B) Place Notice in Operating Record

Within 14 D

Any Appendix II Constituents Detected in Second Sampling g Event ? No

A) Place

I.D. Appendix II Constituents (258 55(d)(1)) (258.55(d)(1))

Suspected Yes Source of Exceedance, Sampling, Sam ling, or Statistical Error ?

Establish Ground-Water Protection Standards (GWPS) (258.55(h))

With

No

Nature & Extent of Release Characterize the Nature and Extent of the release by: (1) Installing additional Wells as Necessary. (2) Install at least one well at Downgradient Boundary. (3) Notify adjacent landowners of off-site migration.

wells for Appendix I & Detected Appendix II Constituents (258.55(b)) and Perform Annual Monitoring for all Appendix II Constituents in Downgradient wells (258.55(d)(2))

Return to Detection Monitoring

N Note: We Recommend a Second Sampling Ev vent be Completed Before Conducting Saampling Pursuant to 258.55(d)(2).

Yes

Report on Water Quality

Report Successful ?

Submit Report Demonstrating Findings Certified by a Ground-Water Professional No

Corrective Measures Assessment Within 90 Days of (B), Initiate Assessment of Corrective Measures

Are Site C Sit Conditions diti Amendable to Monitored Natural Attenuation ?

No Yes

Establish Traditional Assessment Monitoring/Corrective Action Program. g Establish Natural Attenuation Assessment Monitoring/Corrective Action Program.

Figure 10-2b RCRA Subtitle D Assessment Monitoring Program 684

ASSESSMENT MONITORING DESIGN

From Assessment Monitoring Program Continue Assessment Monitoring

Figure 10-2c Corrective Action Program (258.56-256.58)

Continue Assessment Monitoring in Accordance with (258.55). (258.55(b))

Initial Effectiveness Check Analyze the Effectiveness of Potential Corrective Measures (initially within 90 Days of (B)). (258 55(c)) (258.55(c))

Hold Public Meetings Hold Public Meeting to Discuss Results of Corrective Measures Assessment

Implement Corrective Actions Implement Corrective Action Program Based on Schedule Identified in Report "Selected Remedy" Under Program (1) Establish & Implement Corrective Action Groundwater Monitoring Program. (2) Implement the Corrective Action Remedy. (3) Take any Interim Measures To Protect Human Health & the Environment.

( (258.58(d)) ( ))

Select a Remedy (258.57(b))

Return to Detection Monitoring

Within 14 days Notify Director That a Remedy Is Selected

(258.58)

Within 14 Days Present Certification of Completed Remedy to Director Check on Achievability Obtain Approval from Certified Ground-Water Professional or Director that the Requirement Cannot be Achieved.

Alternative Measures

No

Can Compliance Under Requirements in "Remedy Selection" Report be Achieved Using Currently Available Methods?

Yes

Implement Alternative Measures To Protect Human Health & the Environment, and Control Sources of Contamination.

Notify Director Within 14 days Notify Director That a Report Justifying Revised Measures Is in Operating Record.

Any Appendix II WQPS Exceedance for 3 Consecutive Years at All Points Within the Plume & Beyond the Detection Monitoring System? Have All Actions Required To Complete the Remedy been Satisfied?.

No

Yes

Figure 10-2c RCRA Subtitle D Corrective Action Program 685

ASSESSMENT MONITORING DESIGN

The Director of an approved state may delete any Appendix II monitoring parameters.

the constituent established from the (background) wells

• The Director of an approved state may establish an alternate frequency for repeated sampling and analysis considering the factors in §258.55(c)(1) through (6).

- For constituents for which the background level is higher than the MCL or health-based level (identified under §258.55(i)(1)), the background concentration

(Note: Specifying a subset of wells, deleting Appendix II parameters and establishing an alternate frequency for assessment monitoring are not available options in unapproved states.) • After obtaining the results from the initial or subsequent sampling events, the owner or operator must: - Within 14 days, place a notice in the operating record identifying the constituents that have been detected and notify the state Director that the notice has been placed in the operating record. - Within 90 days and on at least a semi-annual basis thereafter, resample all wells, conduct analyses for all constituents in Appendix I (or alternative list) and for the Appendix II constituents that are detected per §258.55(b). The Director of an approved state may specify an alternate monitoring frequency for the constituents referred to in §258.55(d)(2). (Note: An alternative monitoring frequency is not an available option in an unapproved state.) - Establish background concentrations for any constituents detected. - Establish ground-water protection standards for all constituents detected. The ground-water protection standards shall be set according to the following: The owner or operator must establish a ground-water protection standard for each Appendix II constituent detected in the ground water. The protection standard shall be:

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• The Director of an approved state may establish an alternative ground-water protection standard for constituents for which MCLs have not been established. (Note: An alternative ground-water protection standard for constituents without MCLs cannot be established unless in an approved state). • If the concentrations for all Appendix II constituents are shown to be at or below background values, using the statistical methods defined in §258.53(g), for two consecutive sampling events, the owner or operator must notify the state Director and may return to detection monitoring. • If the concentrations of any Appendix II constituents are above background values, but all concentrations are below the ground-water protection standard using the statistical procedures in §258.53(g), the owner or operator must continue assessment monitoring. • If one or more Appendix II constituents are detected at statistically significant levels above the ground-water protection standard in any sampling event, the owner or operator, within 14 days of this finding, must place a notice in the operating record identifying the Appendix II constituents that have exceeded the ground-water protection standard and notify the state Director and all appropriate local government officials. The owner or operator must also: - Characterize the nature and extent of the release by installing additional monitoring wells as necessary. - Install at least one additional monitoring well at the facility boundary in the direction of contaminant migration and sample the well in accordance with §258.55(d)(2).

- For constituents for which a maximum contaminant level (MCL) has been promulgated under Section 1412 of the Safe Drinking Water Act under 40 CFR 141, the MCL for that constituent

- Notify all persons who own land or reside on the land that directly overlies any part of the plume of contamination if contaminants have migrated offsite if indicated by sampling of wells.

- For constituents for which MCLs have not been promulgated, the background concentration for

- Initiate an assessment of corrective measures within 90 days (see below).

ASSESSMENT MONITORING DESIGN

- Demonstrate that a source other than a MSWLF unit caused the contamination or that a statistically significant increase resulted from an error in sampling, analysis, statistical evaluation or natural variation in ground-water quality. A report documenting alternate source or error must be certified by a qualified ground-water scientist or approved by the Director of an approved state and be placed in the operating record. If a successful demonstration is made, the owner or operator must continue monitoring in accordance with the assessment monitoring program and may return to detection monitoring if the Appendix II constituents are at or below background (§258.55(e)).

actual or potential receptors or • The constituent is present in ground water that: – Is not currently or reasonably expected to be a source of drinking water. – Is not hydraulically connected with waters to which the hazardous constituents are migrating or are likely to migrate in a concentration that would exceed ground-water protection standards. – Remediation of the release is technically impracticable. – Remediation results in unacceptable cross-media impacts.

During the assessment phase, a range of alternative remedies is evaluated by the facility owner or operator; the state responsible then selects the remedy from those evaluated. While the assessment process is conducted, the facility continues monitoring according to the Phase II requirements. The proposed criteria revisions in §258.56(b), however, allow for ground-water monitoring in addition to the Phase II requirements, as necessary, to characterize the plume of contamination and to demonstrate the effectiveness of the corrective action program. Hence, an assessment monitoring program is addressed within the RCRA Subtitle D regulations for solid waste facilities.

(Note: Demonstration that remediation of a release is not necessary is not an available option unless in an approved state.)

Selection of Remedy (§258.57)

The U.S. EPA (1989b) provides some generic examples of conditions that may require additional monitoring:

Based on the results of the corrective measures assessment, the owner or operator must select a remedy that, at a minimum, meets the standards listed in §258.57(b). The owner or operator must notify the state Director, within 14 days of selecting a remedy, that a report describing the selected remedy and how §258.57(b) is satisfied, has been placed in the operating record. • The owner or operator shall specify as part of the selected remedy, a schedule for initiating and completing remedial activities. • The Director of an approved state may determine that remediation of a release of an Appendix II constituent from a MSWLF unit is not necessary if the owner or operator demonstrates to the satisfaction of the Director of the approved state that: – The ground water is additionally contaminated from a source other than a MSWLF unit and those substances are present in concentrations such that a cleanup of the release from the MSWLF unit would provide no significant reduction in risk to

• A determination by the Director of an approved state shall not affect the authority of the state to require the owner or operator to undertake source control measures or other measures that may be necessary to eliminate or minimize further releases to the ground water or to remedy the ground water to concentrations that are technically practicable and significantly reduce threats to human health or the environment.

• Facilities that have not determined the horizontal and vertical extent of the contaminant plume • Locations with heterogeneous or transient groundwater flow regimes • Mounding associated with MSWLF units Once a contaminant release has been detected and confirmed via the various phases of monitoring, the owner or operator may be requested by state regulatory agencies to implement a more aggressive monitoring program capable of delineating the horizontal and vertical extent of contamination. Implementation of the Corrective Action Program (§258.58) • Based on the schedule established under §258.57(d) for initiation and completion of remedial activities, the owner or operator must:

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ASSESSMENT MONITORING DESIGN

– Establish and implement a corrective action ground-water monitoring program that: – Meet the requirements of an assessment monitoring program (§258.55), – Indicate the effectiveness of the corrective action remedy and – Demonstrate compliance with ground-water protection standard pursuant to §258.58(e). – Implement the corrective action remedy selected under §258.57 and – Take any interim measures necessary to ensure the protection of human health and the environment. • An owner or operator may determine, based on information developed after implementation of the remedy has begun or other information, that compliance with §258.57(b) is not being achieved. In such cases, the owner or operator must implement other methods or techniques that could practicably achieve compliance with the requirements, unless the owner or operator makes the determination discussed below. • If compliance with §258.57(b) cannot be practically achieved with any currently available methods, the owner or operator must: – Obtain certification of a qualified ground-water scientist or approval by the Director of an approved state that compliance with requirements under §258.57(b) cannot be practically achieved with any currently available methods. – Implement alternate measures to control exposure of humans or the environment to residual contamination. – Implement alternate measures for control of the sources of contamination or for removal or decontamination of equipment, units, devices or structures. – Notify the state Director within 14 days that, prior to implementing the alternate measures, a report justifying the alternate measures, has been placed in the operating record. • All solid wastes that are managed pursuant to a remedy or an interim measure, shall be managed in a man-

688

ner that is: – Protective of human health and the environment – Complies with applicable RCRA requirements. • Remedies selected shall be considered complete when: – The owner or operator complies with the groundwater protection standards established under §258.55(h) or (i) at all points within the plume of contamination that lie beyond the ground-water monitoring well system. – Compliance with the ground-water protection standards established under §258.55(h) or (i) has been achieved by demonstrating that concentrations of Appendix II constituents have not exceeded the ground-water protection standard(s) for a period of three consecutive years using the statistical procedures and performance standards in §258.53(g) and (h). The Director of an approved state may specify an alternate length of time during which the owner or operator must demonstrate that concentrations of Appendix II constituents have not exceeded the ground-water protection standard(s). (Note: An alternate length of time for demonstrating that concentrations have not exceeded ground-water protection standards is not an option in an unapproved state.) – All actions required to complete the remedy have been satisfied. • Upon completion of the remedy, the owner or operator must notify the state Director within 14 days that a certification that the remedy has been completed in compliance with the requirements of §258.58(e) has been placed in the operating record. This certification must be signed by the owner or operator and by a qualified ground-water scientist or approved by the Director of an approved state. Upon completion of the certification, the owner or operator determines that the corrective action remedy has been completed in accordance with the requirements under §258.58 (e), the owner or operator shall be released from the requirements for financial assurance for corrective action under §258.73.

ASSESSMENT MONITORING DESIGN

10.2 CERCLA (SUPERFUND) REGULATIONS Superfund represents both a legal and procedural process for dealing with past hazardous waste disposal practices, tied to a series of federal laws; the Superfund Amendments and Reauthorization Act (SARA) and the National Contingency Plan (NCP). When evaluating the process of Superfund, many organizational and planning activities are directly related to the phased investigation approach. The first step of the Superfund process is the identification of potentially hazardous sites which may require remedial action and their entry in a database known as CERCLIS. The Superfund program continues to make progress in cleaning up hazardous waste sites to protect human health and the environment. Since 1980, the national program, along with state and tribal partners, has assessed nearly 44,259 sites. To date (2003), 32,929 sites (74% of the listed sites) have been removed from the Superfund inventory to help encourage economic redevelopment, while 11,330 sites remain active with the site assessment program or are on the National Priorities List (NPL). The current Superfund statistics are as follows: • 74 sites have been proposed to the NPL (46 have construction activity.) • 1,479 sites are final or deleted from the NPL. • 1,220 sites are final on the NPL. • 259 sites (18%) have been deleted from the NPL Pipeline of the 1,479 final and deleted NPL sites. • 823 sites are construction completed or deleted, of which 32 are federal facilities (FF). • 818 (55%) sites are construction completed (includes 254 deleted sites). • 5 sites have been deleted and referred to another authority. • 656 (44%) sites with construction needed or ongoing, of which 138 (21%) sites are FF. • 390 sites have remedial construction underway. • 248 sites have study or design underway (151 sites with removal activity) 18 sites are pending study or design (9 sites with removal activity). Of the 1,479 final and deleted NPL sites: • 1,373 sites (93%) have had construction activity, are completed or deleted. • 1,089 sites (74%) have all final cleanup plans approved.

Of the 818 construction completed sites: • 551 sites have post-construction activity underway (e.g., institutional controls, 5-year reviews, operation and maintenance, long-term response actions, optimization of remedies). Enforcement of the Superfund program is an important aspect of the remedial program. U.S. EPA publishes data on the enforcement activities of the agency. Enforcement Settlements Cumulative value of private party commitments since inception of the program is over $20 billion; since FY92, responsible parties have performed over 70% of nonfederal remedial actions. • De Minimis Parties: Settled out over 24,700 de minimis parties in over 475 settlements. • Prospective Purchaser Agreements: U.S. EPA has signed more than 170 prospective purchaser agreements. • Orphan Shares: Offered $217.2 million in orphan share compensation at 134 sites across the United states between FY96 - FY01. • Site-Specific Special Accounts: Through FY2001 the U.S. EPA collected over $878 million, established 197 accounts and accrued over $135 million in interest for a total of over $1 billion. In the pre-remedial process, sites undergo a preliminary assessment (PA) and a site inspection (SI) which usually culminates in a scoring under the hazard ranking system (HRS). Currently, if a site scores over 28.5 on the HRS, it is placed on the National Priority List (NPL, where it becomes eligible for funding of investigative programs (Remedial Investigation/Feasibility Study [RI/FS]) and possible remedial action. Approximately 10% of all sites initially identified under CERCLIS are finally listed on the NPL. The Agency for Toxic Substances Disease Registry (ATSDR) also conducts a health assessment once a site is listed on the NPL to determine if an imminent health threat exists or if further community public health studies (e.g., epidemiology and biological monitoring) are necessary. A listing of a site on the NPL will cause a site to undergo an RI/FS by either federal superfund contractors or by the potentially responsible parties (PRPs) to determine

689

ASSESSMENT MONITORING DESIGN

STEPS FOR CLEANING UP A SUPERFUND SITE The general approach taken by EPA to clean up a Superfund site is detailed below. Each box represents a different step in the process

SITE DISCOVERY

rocess begins when a hazardous substance elease (e.g., spill, abandoned site) is identified and reported o U.S. EPA.

CERCLIS

Site is listed in the Comprehensive Environmental Response Compensation and Liability Information System (CERCLIS), which inventories and tracks releases providing comprehensive information to response agencies.

PRELIMINARY ASSESSMENT (PA)

SITE INSPECTION (SI)

REMOVAL ACTION*

HAZARD RANKING SYSTEM (HRS) PACKAGE

NPL LISTING

This is the first stage of a site assessment. Preliminary Assessments are conducted to determine if an emergency removal action is necessary, and to establish site inspection priorities.

The second stage of a site assessment involves on-site nvestigations to ascertain the extent of a release or potential or release. The Site Inspection usually involves sample collection nd may also include the installation of ground-water monitoring wells.

A short-term, fast-track federal response to prevent, minimize, or mitigate damage at sites where hazardous materials have been released or pose a threat of release. Removal actions may occur at any step of the response process.

Site assessment information is then used in the Hazard Ranking System (HRS). HRS is a screening system to evaluate nvironmental hazards of a site.

The NPL is a list of abandoned or uncontrolled hazardous substance sites that are the national priorities for long-term cleanup, making them eligible for federal cleanp funds.

Figure 10-3a General Steps in the Superfund Process the nature and extent of contamination and to evaluate alternatives for remedial action. The Superfund program is shown in flow diagrams Figure 10-3a to 10-3c. The site investigation program in Superfund is divided into a series of tasks and phases. The RI and FS usually overlap in time

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as shown in Figure 10-4; for example, there can be initial scoping of alternatives while field data are being collected. The RI starts off with the preparation of a series of QA/QC, sampling and work plans. This process is an evaluation of all data previously collected (e.g., during the SI/PA or by

ASSESSMENT MONITORING DESIGN

REMEDIAL INVESTIGATION/ FEASIBILITY STUDY (RI/FS)

RECORD OF DECISION (ROD)

O Once a site has been placed on the NPL, a Remedial Investigation ((RI) and Feasibility Study (FS) are conducted. The purpose of the RI is to collect data necessary to assess risk and support the R selection of response alternatives. The FS is a process for s developing, evaluating, and selecting a remedial action. d

O Once an RI/FS is completed, a Record of Decision (ROD) is generated, which outlines cleanup actions planned for a site. g

REMEDIAL DESIGN (RD)

T Remedial Design (RD) is the set of technical plans and The specifications for implementing the cleanup actions chosen s in the ROD.

REMEDIAL ACTION (RA)

R Remedial Action (RA) is the execution of construction and other work necessary to implement the chosen remedy. o

CONSTRUCTION COMPLETION

OPERATION AND MAINTENANCE (O&M)

DELETION FROM NPL

C Construction completion occurs when physical construction of all cleanup remedies is complete, all immediate threats have a been addressed, and all long-term threats are under control. b

Operation and maintenance are activities conducted at a site after remedial construction activities have been completed to ensure the cleanup methods are working properly.

When EPA, in conjunction with the state, has determined that all appropriate response actions have been implemented and no further remedial measures are necessary, a Notice of Final Action to Delete is published in the Federal Register. If U.S. EPA receives no significant adverse or critical comments from the public within the 30-day comment period, the site is deleted from the NPL.

Figure 10-3b General Steps in the Superfund Process (cont.) other parties) and an in-depth cost and time proposal for the conduct of the RI/FS. A Phase I investigation, as described in Chapter 2 of this text, can be extended to include a number of these planning documents fundamental to the Superfund program. A preliminary risk assessment, identification of applicable or relevant and appropriate requirements

(ARARs), boring and sampling plans, determination of data quality objectives (DQOs) and an initial screening of remedial alternatives often support the work plan. Once the components of the documents are approved by federal and state regulatory agencies, actual investigative work commences at the site. The Superfund process has developed a

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ASSESSMENT MONITORING DESIGN

STEPS FOR ENFORCEMENT AT SUPERFUND SITES The general approach taken by EPA for enforcement a Superfund site is detailed below. Each box represents a different step in the process

INITIATE PRP SEARCH

ISSUE GENERAL NOTICE LETTERS

EXCHANGE INFORMATION

ISSUE SPECIAL NOTICE LETTERS (SNLs)

NEGOTIATE SETTLEMENT

To search for individuals, companies, or other parties potentially liable for cleanup costs, U.S. EPA reviews State and Federal agency records, conducts title searches, interviews site operators, and performs PRP financial assessments.

U.S. EPA notifies identified PRPs of their potential liability, usually through General Notice Letters.

U.S. EPA begins an informal information exchange concerning site conditions, PRP connections to the site, and the identification of other PRPs.

Special Notice Letters (SNLs) are issued to PRPs identifying the names and addresses of other PRPs as well as, if available, the volume and nature of substances each PRP contributed.

Issuance of SNLs triggers a moratorium, ceasing U.S. EPA response and abatement actions for 60 days. The goal of the moratorium is to reach a settlement in which all the PRPs agree to conduct or finance response activities. NEGOTIATION SUCCESSFUL?

YES.... Consent Decree and PRP Cleanup Response

NO.... Issue UAO

When negotiations are successful, U.S. EPA and the PRPs enter into a Consent Decree setting forth the cleanup requirements.

f settlement negotiations fail, U.S. EPA may issue a Unilateral Administrative Order (UAO) to force liable parties to conduct the response action.

Figure 10-3c Enforcement Steps in the Superfund Process bias for the collection of large numbers of water quality samples as back-up for the future potential litigation process.

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Bias for Sample Collection The majority of this work at the typical Superfund RI project involves the collection of samples for chemical

ASSESSMENT MONITORING DESIGN

analysis. These results are generally used to determine or estimate the nature and extent of contamination. The Superfund process is geared toward establishing guilt of PRP’s in a fashion that provides evidence usable in court actions for cost recovery. The inflexibility of this type of planning often results in multiple phases of additional rounds of sampling collections. Since the passage of the initial Superfund legislation in 1980, engineers and scientists have striven to devise a uniform, yet cost-effective methodology for characterizing sites that are or are suspected of, releasing contaminants to the environment. The U.S. EPA’s initial remedial investigation guidance (U.S. EPA, 1985) focused site characterization efforts primarily on determining the area, extent and magnitude of contamination, i.e., plume delineation. This has commonly necessitated multiple drilling, sampling and analysis episodes to develop the database required to support a site-specific risk assessment and to evaluate the appropriate remedial actions. In recent years, it has become increasingly apparent that this approach is not an efficient utilization of limited financial and investigative resources. To address this issue, throughout the 1990s the U.S. EPA, U.S. Air Force, U.S. Army Corps of Engineers, etc. issued a series of technical guidance manuals that have attempted to standardize the investigation process. After the analytical data leave the laboratory, they go through a process of data validation to ensure that the data meet the U.S. EPA’s QA/QC requirements. The field and analytical data are then used in the RI report to describe the nature and extent of contamination. Another use of analytical results obtained from site samples is in the human health risk assessment or the public health evaluation performed as part of the RI/FS. The stated objective of the risk assessment is to assist the U.S. EPA in remedial alternative decisions which have a public health basis. Additionally, during this time, the FS progresses through its final evaluation of alternatives, with the result that one alternative is recommended to the U.S. EPA. Two additional risk assessment activities accompany the FS. The first assessment is a determination of preliminary remediation goals (cleanup levels) for contaminants in various media at the site; this determination takes health effects and applicable or relevant ARARs into account. The second assessment is a health-based screening of remedial alternatives which accompanies evaluations of long and short-term effectiveness and reduction of toxicity as required by SARA. Following the completion of the RI/FS, the U.S. EPA issues a Record of Decision (ROD) which states the chosen remedy, justifies its choice and responds to comments

received from the public on the RI/FS. The ROD may decide on a no-action alternative. Additionally, a ROD may be issued for a portion or single operable unit at a site. After the issuance of a ROD, the site proceeds to the remedial design (RD) stage which sets out the details of construction for remediation. This step may be preceded by a conceptual design and experience shows that most Superfund investigations require additional sampling and analysis over what was performed for the RI/FS. Once the RD is approved, the remedy is implemented as a remedial action (RA). When an effective cleanup has been completed, the site is removed from the NPL. If hazardous materials are left on site in a form where they are still toxic and mobile, the site may be revisited every five years by the U.S. EPA to insure that the clean-up remains effective. The U.S. EPA proposed in the 1989 National Contingency Plan revision to emphasize (53 FR 51423) a “bias for action” and to use the principle of “streamlining” in managing the Superfund program as a whole and in conducting individual remedial action projects. It is the author’s experience that most Superfund actions develop into field data collection and office documentation exercises with little bias for action to place into effect reasonable solutions for dealing with real risks to human health and the environment. In 1993, U.S. EPA began a series of reforms to make the Superfund program “faster, fairer and more efficient.” Building on the 90-Day and 30-Day Studies, SACM and the “Enforcement First” policy, the first round of Superfund Reforms consisted of 17 initiatives that improved the effectiveness of cleanups and increased enforcement fairness. The First Round also focused on expanding state and public involvement in cleanup decisions. In Round 2, U.S. EPA introduced an additional 12 reforms and tested many of them through pilot projects. Round 3 consisted of 20 initiatives and took a common sense approach to reforming the program. Rounds 2 and 3 were introduced in 1995 and together they strengthened the Superfund program by attempting to reduce litigation and transaction costs; make cleanup decisions more cost-effective; encourage the redevelopment of cleaned up sites; get states, tribes and communities more involved; and encourage innovative technologies. The National Academy of Public Administration (NAPA) conducted an in-depth examination of the Superfund reforms. In a June 2000 report, NAPA concluded that “the reinvention effort successfully addressed the key challenges facing Superfund” and “implementation of the reforms has been accompanied by substantial improvement in aggregate measures of program output.”

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Site Characterization

Treatability Investigation

Conduct Field Investigation n.

Perform Bench or Pilot Treatability Tests As Necessary.

Define nature and extent of contamination (waste typ pes s, concentrations, distribution ns

CURRENT SUPERFUND PROCESS

Identify Federal/State Contamination and Location Specific ARARs. Conduct Baseline Risk Assessment.

Project Planning

Refine Remedial Action Goals.

Collect and Analyze Existing Data Identify Initial Project/ Operable Unit. Likely ResponseScenarios & Remedial Action Objectives.

Design Investigation

Monitoring

Perform Treatability Studies . Collect Addition Field Data

Collect Data During Implementation.

Perform Additional Support Services.

Initiate Federal/State ARAR Identification. Prepare Project Plans.

Development of Alternatives Identify Potential Treatment Technologie es,

Screening of Alt ti s to

Detailed Analysis of Alternatives

Record of Decision

Remedial Design

Record of Decision

Further Refine Alternatives As Necessary..

Select Remedy.

Design Details.

Prepare Bid Documents.

Solicit Public Comment.

Perform Additional Support Activities.

Construct Action.

to Detailed Analysis. Preserve Approximate Range of Options. Action-Specific ARARs s.

Analyze Alternatives Against the Nine Criteria.

Screen Technologies. Assemble Technologie es into Alternatives.

FEASIBIL FEASIBILITY SIBILITY STUDY Y

Figure 10-4 The Superfund Investigative Process

Operate Action.

ASSESSMENT MONITORING DESIGN

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REMEDIAL REMEDI L INVEST INVESTIGATION NVEST TIG TION

ASSESSMENT MONITORING DESIGN

Enhancing Cleanup Effectiveness and Consistency The U.S. EPA has initiated several ongoing reforms to ensure that cleanups are cost effective and reflect the most recent advances in science and technology. Partially because of these reforms, three times as many Superfund sites have been cleaned up in the past 7 years than in all the prior years of the program combined. Some of the more significant advances in cleanup effectiveness and consistency are described below in the next subsection. SARA established a preference for treatment of hazardous wastes and created a demand for alternatives to land disposal. New innovative treatment technologies grew from this demand to provide more permanent, less costly solutions for dealing with contaminated materials. The Superfund Innovative Technology Evaluation (SITE) Program was established to meet this increased demand for alternative technologies. The SITE Program has provided demonstrations of new technologies at particular sites, resulting in average cost savings of over 70 percent per site. The total cost savings for innovative treatment as opposed to conventional treatment was estimated at $2.1 billion by the federal agency. Technologies Used to Make Sites Safe

• STABILIZATION: Inducing chemical reactions between a stabilizing agent (such as lime, Portland cement, fly ash or kiln dust) and the contaminants to reduce their mobility. • BIOREMEDIATION: Breaking down toxic contaminants by using natural microorganisms. • CHEMICAL TRANSFORMATION: Detoxifying contaminants by transforming their chemical structure. • NATURAL ATTENUATION: Using natural biotransformation processes such as dilution, dispersion, volatilization, biodegradation, adsorption and chemical reactions to reduce contaminant concentrations to acceptable levels. • INCINERATION: Using extremely high temperatures (1,600-2,200°F) to render organic contaminants harmless. Seeking to improve consistency and to streamline cleanups, U.S. EPA implemented the use of presumptive remedies. Presumptive remedies provide guidance on how to address certain recurring situations at sites, thereby standardizing the response. Presumptive remedies have been developed for the following four types of sites: • Municipal landfills • Volatile organic chemicals (VOCs) in soils

Today, there are as many ways to clean up a Superfund site as there are types of sites. U.S. EPA tailors the techniques and technologies to community needs and to individual problems posed by different areas of a site. Here are some of the cleanup techniques that U.S. EPA developed to make sure that all areas of a site have acceptable levels or risk to human health and the environment: • REMOVAL: Physically removing toxic contaminants from the site to a facility that can safely handle the waste. • TREATMENT: Treating the waste at the site to remove the toxic contaminants from the soil, sediment or ground water. • RECYCLING: Treating or converting toxic waste material to make it safe and reusing it for other purposes. • CONTAINMENT: Placing covers over or barriers around waste to prevent migration and to keep people from coming into contact with the waste. • SOLIDIFICATION: Physically binding or enclosing toxic contaminants within a stabilized mass such as cement.

• Wood treater sites • Contaminated ground water Reform of the program is ongoing. The reforms are being refined and improved, and their impact is becoming broader. U.S. EPA’s national policy is to consistently address stakeholders’ criticisms to attempt to develop new ways to make Superfund work faster, fairer and more efficiently. However, given the size of the program and that many RODs were written using outdated technology, it can be difficult to obtain regulatory acceptance for use of more modern technology at the older sites. Once the RI/FS process is complete and a Record of Decision (ROD) is issued, additional data are commonly gathered during various design phases. Because the majority of data gathered in the RI/FS is of ground-water quality, the design stage of the RD (after the ROD) often requires additional site aquifer characterization work that could have been easily gathered in the RI. Figure 10-4 illustrates the typical RI/FS project where following the site assessment program as described in Chapters 2 to 9 would greatly ease the RD field assessment programs and provide for more cost-effective site solutions. This more direct program is discussed further after this section.

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ASSESSMENT MONITORING DESIGN

10.3 STATE REGULATIONS AND ASSESSMENT MONITORING A number of states have instituted comprehensive regulation of both unregulated waste disposal, such as leaking underground tanks or dry cleaner and degreasing solvents. For example, Massachusetts regulations specific to assessment monitoring have assessment components similar to RCRA and Superfund regulations. The purpose of the Massachusetts Contingency Plan (MCP) is to “insure the protection of health, safety, public welfare and the environment.” The MCP provides: • A list of oils and hazardous materials and a description of the characteristics of hazardous materials subject to the MCP • Procedures and requirements for notifying the responsible department of a release

Each state may develop its own format for assessment of facilities that fail statistical or some specified maximum levels of indicator parameters. It is expected that RCRA Subtitle D will form the basis for such monitoring and assessment activities with some level of variation from state to state. Almost every state has some form of state-lead remediation program. Many such as Illinois incorporate risk analysis as part of the evaluation 10.4 ASSESSMENT MONITORING ANALYSIS The previous subsection described a number of alternative regulatory approaches to assessment of facilities where an exceedance was verified for indicator parameters or health-based standards. Each of these approaches has common relationships to a series of goals of site assessments to define the extent of affected ground water. These goals can be defined as follows:

• Procedures and requirements whereby the extent and nature of a release can be addressed

• Definition of physical site characteristics

• Procedures for involvement of potentially responsible parties

• Establishment of background concentrations of parameters

• Procedures for the public involvement in response actions

• Identification of the source of the release

• Cost recovery procedures Massachusetts 310 CMR 40.000 provides specific details for each of these points. We will, however, focus on the third point, the procedures and requirements whereby the extent and nature of a release can be addressed. Section 40.532 of the MCP requires a number of phases of remedial response actions. The sequence of these phases is intended to ensure the comprehensive assessment of the nature, extent and risk of harm posed by a disposal site. The MCP requires that phases of a remedial response action occur in the following sequence: • Preliminary Assessment • Phase I, Limited Site Investigation • Phase II, Comprehensive Site Assessment • Phase III, Development of Remedial Response Alternatives and Final Remedial Response Plan • Phase IV, Implementation of the Approved Remedial Response Alternatives

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• Establishment of the characteristics and extent of the release • Identification of exposure points and risk to human health RCRA Subtitle C and D, CERCLA and many state waste management regulations all have these common points within their assessment programs. These waste management regulations then go through various site clean-up procedures that implement remedial actions leading to the ultimate reduction of risk to human health and the environment. Much of the experience associated with assessment programs (since RCRA solid waste Subtitle D and hazardous waste Subtitle C remediation programs) has evolved around the CERCLA Superfund program. Since passage of CERCLA in 1980, the assessment program expenditures in the Superfund program have risen to $2.0 billion per year at over 1300 sites (U.S. EPA, 2002). However, many of these sites still have problems with ground water contaminants. It is believed that few, if any sites with contaminated groundwater aquifers have been confirmed to be cleaned to healthbased water quality standards. The new class of Superfund

ASSESSMENT MONITORING DESIGN

site will likely be the super site where regional aquifers are contaminated with organic chemicals to levels that will require some form of remediation as a natural resource damage issue. Categories of Sites Requiring Remediation Sites requiring assessment programs can be divided into three major categories: point sources (PT), multiple point sources (MPS) and large volume/low toxicity (LV/ LT) sites. These sites are illustrated in Figure 10-5. PT sites may represent product spills of organics or soil contaminated by heavy metals or residual organics. MPTs represent industrial areas that have had numerous areas of hazardous waste disposal that contribute to a regional water quality problem. LV/LT sites may be represented by areas containing a municipal landfill that received hazardous wastes or a mine tailings site. Each of these site categories requires somewhat different assessment methodologies for the timely implementation of a remedial assessment program. The experiences learned from the Superfund program point toward more effective use of assessment techniques to obtain targeted and timely remediations. The concern of the U.S. Congress on the slow progress of the Superfund clean-

up process has brought into focus the inefficiencies of the initial RI/FS process. This prompted the U.S. EPA to initiate a series of reforms as described in Section 10.2. Federal guidance and review documents concentrate on field collection and chemical analysis of large numbers of samples. Remedial Investigations (RIs) conducted pursuant to CERCLA/SARA are primarily designed to delineate the spatial distribution of contaminants with respect to receptor populations and institutional boundaries. This has been traditionally accomplished by assembling a soil and water quality database, the size and scope of which is influenced by non technical factors such as community sensitivity and cost-recovery litigation requirements. Analytical costs can reach to 30 to 40% of the total RI assessment costs and 40% of the remaining costs are devoted to the management and execution of field sampling of the soil and water samples provided to the analytical labs. Although site-specific hydrogeologic conditions exert the main control on contaminant migration in the subsurface, hydrogeologic data are generally relegated to secondary importance (the remaining estimated 10 to 20% of the RI costs) with respect to the water quality data. The databases resulting from this investigative methodology typically do not adequately support detailed analysis of the

COMPARISON OF LARGE-VOLUME CODISPOSAL & LOW-VOLUME HIGH-TOXICITY SITES DrumExamples: disposal y product spill

Point Source

High-Volume/ Low-toxicity Site Soil Residuals High Toxicity Leachate

Examples : Municiple co-disposal tailing disposal

Multip

Examples: Super Sites Industrial areas, Multiple Spill Environmental Impairment of Major Potential Drinking Water Aquifers

Multiple oint Sour

High-toxicity Leachate

Low-toxicity Super Volume Leachate

Figure 10-5 Example Sites Requiring Remediation

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ASSESSMENT MONITORING DESIGN

predominant contaminant transport mechanisms and may be of limited value for evaluating and designing effective remedial actions. The classical geotechnical site characterization process was defined by Ralph B. Peck in six steps back in 1975: • Conduct an investigation of sufficient scope to establish the general characteristics of the site. • Assess the most probable conditions and the deviations from them. • Develop a design based on the most probable conditions. • Determine what courses of action should be taken if the conditions deviate from predictions. • Measure and evaluate actual conditions during construction. • Modify the design, as needed, to suit actual conditions. While this site characterization process must be modified to provide a basis for reducing facility uncertainties to levels acceptable to regulatory bodies, the general observational approach can from the basis for site assessments. The observational method to hazardous waste site remediation problems has been described by researchers to provide a more direct method to evaluate site for remedial actions. The steps described below seek to identify the most probable model of the site and the reasonable deviations from that model according to the method of Ralph B. Peck, (Peck, 1975). 1. Gather existing information on general site conditions and set remedial goals and general responses. The purpose of this step is to decide on a general set of remediation objectives and suitable responses. This step is basically the Phase I investigation as defined in Chapter 2 of this text. This will give direction to the Phase II investigations and analyses that provide the basis for all the assessment and design activities that follow. Existing information developed for the Phase I scope is used to make initial estimates of waste quantities and contaminant concentrations present at the site. This assumes that a reasonable level of prior information is available on the facility. The Phase I work should define the scope of work that will be executed in the next step. 2. Gather information and refine knowledge of general site conditions and nature and extent of contaminants. This is an information-gathering

698

step to identify the general nature and extent of contamination, receptors, pathways, remedial objectives, treatment discharge standards, aquifer characteristics and general site properties within a somewhat extended Phase II scope of work. Phase II investigations are complete when it is possible to differentiate among alternatives, set design criteria and identify reasonable deviations. 3. Establish the most probable site conditions and reasonable deviations. The most probable conditions as defined by the field and office evaluations require significant technical experience in site assessment to know when you have acquired sufficient information. The decision of when to quit is perhaps the most difficult task in using the observational method. The purpose of this third step is to develop a recommendation and a conceptual design leading to the Superfund Record of Decision (ROD). Conceptual designs for handling reasonable deviations from the expected conditions are included in this step. In order to determine the most likely model of the site and the set of reasonable deviations, one must make reasonable assumptions on what potential deviations are likely for the waste disposed and geologic conditions present at site. This is often a step requiring a significant experience level on such projects. 4. Design the remedial action based on the most probable conditions and reasonable deviations. After the remedy selection, typically designs proceed beyond the conceptual level. These consist of remedial designs based on the most probable site conditions, plus designs covering contingencies for the agreed-upon reasonable deviations. 5. Select quantities to observe during remediation to detect deviations during construction and operation. The key environmental indicators are selected during this step for observation during remediation for both expected and deviant conditions. These environmental indicators may include chemical parameters, hydraulic head values, geologic strata expected during excavations, etc. The purpose of this step is to identify what will be used to indicate where the actual site conditions do not match the assumed site conditions and to determine the level of deviation that will trigger a response. If a model of the most probable conditions and reasonable deviations cannot be confidently established or if key indicators cannot be defined, then

ASSESSMENT MONITORING DESIGN

the observational method may not be appropriate for the project. In such a situation, alternative choices can be: (1) design the remedy to meet the worst-case scenario (often an expensive choice!), (2) continue to collect and analyze more site data in an attempt to better define the probable site model and deviations (such steps must be careful evaluated to have some opportunity to control costs) or (3) wait until better technology is available (rarely acceptable to state or federal regulators). 6. In advance, select a course of action or design modification for each reasonable deviation. The purpose of this step is to establish contingency plans for what to do if a deviation is detected. This is an extremely important step, to control the potential for errors or unexpected conditions affecting the outcome of the program 7. Implement the remedial alternative. Measure the selected parameters during remediation and make the necessary modifications should a deviation occur. Once the remedial action is under way, project staff must work closely with the constructors, looking for deviations. Decisions on changes to the remediation will be made based on detected deviations and the preplanned responses. All deviations and modifications to the design must be fully documented. The data necessary for an effective characterization of site flow conditions for determination of rate and extent (assessment monitoring) is typically the same data required for design of the ground-water remediation system. In order to develop a cost-effective process of linking water quality

data with the more traditional geotechnical / hydrogeologic data, a new way of conducting RI/FS investigation is described below using the observational methods tied conceptual geology and hydrology to target more cost-effective site assessments and the resulting facility remediations. The following subsection proposes a phased approach to the site characterizations that link basic observational geotechnical techniques to traditional hydrogeologic site analysis. These methods have often been forgotten in the rush to collect water quality information for Superfund investigations. This methodology would hold-off installation of ground-water monitoring wells until a site is adequately characterized for basic hydrogeologic conditions. The thesis of this procedure is that significant time and cost savings can be recognized if the focus of assessment is shifted from laboratory analysis of statistically representative quantities of environmental samples (i.e., “saturation” sampling) to sampling and analysis schemes which are predicated on a thorough understanding of the physical geologic and hydrologic systems (i.e., “smarter” sampling). 10.4.1 Traditional RI Methodology It has become standard practice to begin remedial investigations with generation of massive planning documents for the establishment of monitoring points and the acquisition and analysis of environmental samples (air, soils, sediments and ground and surface waters). The primary emphasis of this approach is placed on defining the type, magnitude and spatial and temporal distribution of contamination (i.e., rate and extent). Table 10-1 provides the conceptual basis for this approach and alternative evaluation methods discussed in this chapter. The parameters that exert the primary control on contaminant transport, such as the media geometry and ambient flux, are estimated during

Table 10-1 Conceptual Components of Site Assessments for Remedial Projects Conceptual Component

Technical Component

Methodology

• Transmitter

Source evaluation • Characteristics of release

• Historical Records • Air photo - Historical sequences • Leachate /water characteristics

• Media

Extent of release • Physical Site Investigations

• Assessment Phase II characteristics • Air/surface & ground - Background • Water background Concentrations

• Receptors

Exposure points analysis • Risk assessment

• Well census • Exposure assessments • Toxicity assessments

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ASSESSMENT MONITORING DESIGN

Comparison of Superfund Assessment Techniques PLUME DELINEATION METHOD

CONCEPTUAL ANALYSIS METHOD Review Data & Literature

Review Data & Literature

Develop Conceptual Mode el Identify Critical Parameterrs Install Monitor Wells

Collect & Analyze Ground-watte er Samples

Install Stratigraphic Borings & Piezometers & Define Hydraulic Parameters

No

Data A An nalysis & Red duction

No

Sufficient data?

Flow mechanisms well defined ? Y Yes

Install Monitor Wells & Sample for Indicator Parameters

Yes

Feasibility Study

Design

Feasibility Study

Data sufficient for design? g

Design

Implementation of Design

Implementation of Design

Long Term Performance Monitoring

Long Term Performance Monitoring

Figure 10-6 Alternative Superfund Methods

700

Remedial Investigation Analysis & Assessment

ASSESSMENT MONITORING DESIGN

the sampling or monitoring points installation activities. As a result, the location of these monitoring points is generally predicated on the general knowledge of site conditions derived from topographic gradients, aerial surveys, historical accounts of disposal activities and a variable amount of site-specific technical data. In those rare cases where moderate to extensive technical databases exist prior to the initiation of the RI, strict program quality control and documentation requirements often limit the use of such data in the RI. Frequently, the results of these initial sampling events showed that the contamination has migrated beyond the initial limits of the study area and/or the concentration gradients cannot be sufficiently interpreted within the constraints of the existing database. In either case, the typical response to this situation has been to establish additional sampling points and collect and analyze more environmental samples. Investigations that follow this track rapidly degenerate into “plume chases” wherein the goal gradually shifts away from the definition and quantification of exposure pathways to locating the leading edge of the plume. This approach has been more formally referred to as the plume delineation method (Dowden, 1988). The records of traditional assessment monitoring investigations commonly show three or more major field exercises to define the limits of contamination and the primary exposure pathways. In many of these cases, the site complexities justify a phased or staged analysis. However, in too many of these situations, the continued reliance on repetitive well installation and sampling did not adequately address the site complexities or significantly increase the understanding of the contaminant transport mechanisms. The first column in Figure 10-6 shows a flow diagram of the alternative traditional assessment monitoring process. The second column shows a conceptual analysis method to allow depiction and quantification of site ground-water flow conditions. The accurate depiction and quantification of these flow mechanisms are crucial in estimating potential exposure concentrations beyond the known limits of the plume and in evaluating and designing effective groundwater remedial actions. Without targeted geotechnical and hydrogeologic assessment techniques, the investigations are always required to go back for additional field data for later feasibility and design phases. This plume delineation methodology has been gradually improved through the use of direct push technology using detection and sampling probes described in Chapter 4 of this text. However the basic collection of site-specific geologic information should not be forgotten in the rush to collect water quality data.

10.4.2 Alternative Methodology: Understand the Geology First An alternative approach to remedial investigations would be to postpone environmental sampling until the site hydrogeologic flow paths and mechanisms are adequately understood. In ground-water investigations, the traditional ground-water assessment approach (before Superfund) involves a thorough evaluation of all preexisting data and aerial photographs, performance of geophysical surveys, drilling of stratigraphic boreholes, installation of piezometers and measurement of heads, performance of in situ hydraulic conductivity tests and evaluation of hydraulic connections between aquifers and confining beds. All of the information derived from these activities can then be utilized to construct stratigraphic and hydrostratigraphic cross-sections, vertical and plan view flownets and to develop rate and extent of migration predictions. In complex hydrogeologic settings, numerical modeling may be required to attain the appropriate level of quantitative analysis. These predictions, combined with a relatively small amount of information on the nature and history of the source(s), can be used to develop a rational and efficient environmental sampling and analysis plan. These more linear investigations are shown in the second column of Figure 10-6. Because the pre-Superfund assessment methods yield more data on the physical controls of the ground-water transport system, the relevance and significance of the environmental sampling results can be more readily interpreted. An additional advantage is that the environmental sampling results can be utilized to refine and recalibrate the predicative analyses based on the physical site characterization. The proposed bias for action and streamlining should also include consideration of the flow diagram (Figure 106). This diagram details the activities necessary to fully define the geologic and hydrogeologic conditions before selection of sampling location to confirm real risks to human health and the environment. Once sampling locations were selected, only a volatile organic analysis (VOA) scan would be performed assuming that the site’s target contamination are VOCs. If VOAs were detected at statistically determined levels, full hazardous constituent sampling would be performed only on those wells showing VOAs. Because this proposed bias for action program stresses collection of geologic and hydrogeologic data, the information necessary for design of the remediation would be available at an early point in the remedial process. Decisions made within the feasibility study can establish the special situations where it may not be practicable to

701

ASSESSMENT MONITORING DESIGN

actively restore ground water. The type of geotechnical and geologic information necessary to select the assessment monitoring points would also provide the design information for the pump and treat systems normally required to remediate contaminated aquifers that are affecting human health and the environment. These data include flownets and target monitoring zones, transmissivity and storage coefficients, cross-sections and structural maps of the site. The data gathered during the phased investigation would

home in on the geology and hydrogeology first before going into a significant sample collection program. Figure 10-6 illustrates the process of defining the geology/hydrogeology first and then working out the required sampling program. Few Superfund or, for that matter, state assessment investigations collected too much geotechnical and geologic information; rather, these RI/FS projects (and state analogs to Superfund) are based on extensive soil and ground-water sample collection with limited interpretation

DEVELOPMENT OF SITE COMPLEXITY UNCOMPLICATED ISOLATED WASTES

LOW HYDRAULIC CONDUCTIVITY GEOLOGY

COMPLICATED SURFACE RUNOFF SOIL STAINS

BURIED DRUMS

ODORS

VERY COMPLICATED A SOIL STAINS

LEAKAGE

GROUND-WATER AQUIFERS

EXTREMELY COMPLICATED MULTIPLE SOURCES

AIRBORN EMISSIONS MIXED WASTE

SURFACE PONDING

WATER WELL

B

A

MULTIPLE AQUIFERS

SOURCE: Modified from "SCOPER'S NOTES"

Figure 10-7 Site Complexity Issues

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DEPOSITS FISH KILLS SEDIMENTS

OFF-SITE IMPACTS

ASSESSMENT MONITORING DESIGN

of the data and understanding of the site geology and hydrogeology. It is these data collection programs that should be tailored and focused as proposed in the above discussion.

composition of the release. 2. It provides a mechanism for obtaining data necessary to the information requirement process of most federal and state regulations.

10.5 ASSESSMENT MONITORING TECHNIQUES The procedures and techniques used in development of an assessment program should be designed to define each of the three components of facility, environment and potential receptors. This relationship can be summarized in the conceptual model of the television station microwave/air transmitting media/local antenna receivers. Each of these three components should be thoroughly evaluated to establish the assessment goals outlined in the previous section. Each of these components can be addressed by following a phased assessment program that follows the detection monitoring program with selective additional technical components directed toward determination of extent of affected media and risk to receptors. Specific federal or state assessment programs may have requirements such as QA/QC plans or detailed work plans that must be completed to meet aspects of these regulations. Key technical components of an assessment program that meet the general assessment standards of federal and state programs are presented in the following subsections. 10.5.1 Preliminary Assessment Procedures The extent of the preliminary assessment procedures are directly dependent on previous analysis performed at the facility in question. If the detection monitoring program was designed on the basis of a detailed hydrogeologic analysis that located the ground-water wells within target flow paths from the facility, additional preliminary assessment procedures should be directed toward source and receptor analysis. Much of the level of effort required in assessment programs is based on the level of complexity of the site. Figure 10-7 (U.S. EPA, 1990) illustrates various site complexity issues typical for Superfund projects. The scoping efforts are the most difficult part of the preliminary procedures employed on assessment projects. Table 10-2 (U.S. U.S. EPA, 1990) provides a first look in development of site complexity. As the site becomes more complex, additional components must be included in the conceptual model and within the scope of work. Most initial state and federal regulations require some form of planning to document the owner/operators assessment program. This document serves a number of purposes: 1. It presents a descriptive procedure for determining the rate of migration, extent and the constituent

3. It provides a mechanism for obtaining data necessary for subsequent corrective actions at facilities. The owner/operator should include a number of elements in the assessment monitoring plan: • Narrative discussion of the hydrogeologic conditions at the site • Identification of potential contaminant pathways • Description of the facility detection monitoring system • Description of the approach to be used to make the first determination (false–positives rationale) • Description of the approach to be used to characterize rate and extent of affected media • Identification and discussion of investigatory phases • Discussion of the number, location, depth and rationale of borings that will be used to assess the affected media • Information on design and construction of piezometers and wells • Description of the sampling and analytical program to be used to obtain and analyze geologic and groundwater hydraulic data • Description of data collection and analysis procedures the owner/operator plans to employ • Schedule for the implementation of each phase of the assessment program Although planning is important it should not consume inordinate time and cost in its production. Flexibility must be built into the document so that the plan is not defeated by unexpected variations in site conditions. The components of such plans should not require hundreds of pages of text and tables; rather short documents of less than 30 pages of text should be sufficient for the planning of the majority of assessment programs. 10.5.2 Conceptualization Using Regional and Site Geology In order to define the geologic environment of a specific area, the regional and site-specific geology must be thoroughly characterized. These data must establish the

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Table 10-2 Initial Complexity Issues in Remedial Projects RANGE

EXPOSURE RISK FACTORS Significant closest population Working drinking water wells Offsite sensitive areas Adjacent agriculture land use

1500m no no no

500m

100m yes yes yes

20 >1 >1 rocky >1 heavy heavy >1 yes

no no no no 25 many many yes

no no no no 30

yes yes yes

some some some

no no no

yes simple

poor

unknown complex

SITE SURFACE FACTORS Area in acres Access (for equipment) Topographic variation in feet Ponds or lagoons Streams on site Soil type Rock outcrops Vegetation on site Evident soil erosion Utility easements on site Safety precautions necessary ESTIMATED MEDIA(S) CONTAMINATED Soil stains Odors Wind blown particulate Buildings, structures Watertable depth Offsite complaints (fishkills) Discolored sediment deposits Multiple aquifers WASTE CONDITION Drums Container corrosion Storage tanks Known high hazard substances Annual rainfall Prevailing wind direction EXISTING INFORMATION Previous site study results Local official records Local informal sources SUBSURFACE FEATURES Established geology Hydrogeology

SITE COMPLEXITY IS ESTIMATED BY THE NUMBER OF CHECKS APPEARING IN EACH VERTICAL COLUMN. COMPLEX SITES WILL RANGE TO THE RIGHT.

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ASSESSMENT MONITORING DESIGN

properties and features of individual geologic units beneath and near the site, through use of: • Regional geologic maps and cross-sections that are used to characterize area-wide geologic units and structural features to depths incorporating probable ground-water movement • Topographic maps used to characterize site-specific topographic relief • Stratigraphic maps and cross-sections used to characterize detailed site-specific geologic conditions • Aerial photography, as used to illustrate information such as vegetation, springs, gaining or losing stream conditions, wetland areas and important elements of geologic structure The above data will have been gathered within the field assessment programs. Cross-sections and stratigraphic maps should be prepared so that a clear technical basis is used to derive the conceptual geologic and hydrogeologic

SUBSURFACE FLOW DOWN CREEK

models. The entire process of geologic conceptualization is built up by using regional data to establish the general geologic setting and then by gradually building an understanding of geologic conditions at the site from the drilling program. Interpretation of data through cross-sections and maps strengthens the conceptual models until a final picture of the geology is established. The final conceptual geologic model is a site-specific representation of the geologic system under and adjacent to the facility or waste disposal area. Figure 8-1 (Chapter 8) illustrates an overview of the site conceptual model process and the linkage between geology and hydrogeology. Geologic information used to construct conceptual geologic models typically consists of the following: • The depth, thickness and area extent of each stratigraphic unit, including weathering horizons • Stratigraphic zones and lenses within the near-surface zone of saturation

LATERAL SECONDARY GROUND-WATER FLOW IN SHALLOW CHANNEL DEPOSIT CONCEPTUAL TEST AREA #2 BASED ON GROUND-WATER FLOW IN SHALLOW WEATHERED UNITS Disposal Area

AS

AN

DS

CONCEPTUAL TEST AREA #1 BASED ON GROUND-WATER FLOW ALLUVIAL UNITS

C

SA

ND S

BS AN DS

CONCEPTUAL TEST AREA #3 BASED ON GROUND-WATER FLOW IN SHALLOW CHANNEL DEPOSIT

ARROW SIZE INDICATES RELATIVE QUANTITY OF GROUND-WATER FLOWS IN CONCEPTUAL MODEL

Figure 10-8 Conceptual Model of a Layered Rock System

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ASSESSMENT MONITORING DESIGN

• Stratigraphic contacts between significant formations/ strata

characteristics of ground-water flow.

• Significant structural features such as discontinuity sets, faults and folds

10.5.4 Aquifer Characteristics

• Zones of high hydraulic conductivity or shearing/faulting Several cross-sections may be required to depict significant geologic or structural trends and to reflect geologic/ structural features in relation to local and regional groundwater flow. The area and vertical extent of the geologic units can be presented in several ways. For complex settings, the most desirable presentation is a series of structure contour maps representing the physical character of the tops and/or bottoms of each unit. Cross-sections and isopach maps can also be used because they are generally good graphic supplements to the structure contour maps. These cross-sections can be combined into a fence diagram (three-dimensional) that can serve as the basis for conceptualization of the geology. Figure 10-8 shows the conceptualization of the geology and hydrogeology of a layered rock with both perched and regional potentiometric surfaces. Conceptualization is a means of achieving a graphic idealization of the actual geologic conditions; the investigator must, therefore, consider the geologic features that would affect ground-water flow and ground-water quality. Minor features that are not important to the overall picture should not be transferred to representations of the conceptual model. 10.5.3 Characteristics of the Saturated Zone Each of the significant stratigraphic units in the zone of saturation should be characterized by determination of its hydrogeologic properties such as hydraulic conductivity (vertical and horizontal) and effective porosity. These parameters describe aquifer characteristics that control ground-water movement and, hence, the ability of the aquifer to retain or pass contamination. Both are needed for a general understanding of the hydrogeologic setting at a site and for completing the conceptual hydrogeologic model for design of ground-water monitoring systems. Typically, the amount of data necessary to complete a conceptual hydrogeologic model will differ for each geologic environment in question. For example, an aquifer in extensive, homogeneous beach sand (SP) will require less investigation than a glacial unit consisting of lenticular deposits of outwash interbedded with clayey till (GW/CL). The data gathered, however, will be similar. There are two types of fundamental aquifer characteristics required to define a hydrogeologic conceptual model: characteristics of the aquifer and

706

Aquifer characteristics should be determined for each of the significant stratigraphic units in the zone of saturation including property variations in the geologic unit. Aquifer characteristics, for each hydrogeologic unit, should include: • Hydraulic conductivity • Effective porosity • Specific yield/storage (as required for the project) Additional aquifer characteristics, such as transmissivity and attenuation properties, can be derived, and estimated dispersivity values may be necessary for groundwater transport modeling to estimate ultimate (long-term) concentrations at points of exposure. These aquifer characteristics support ground-water flow characteristics used to define the quantity and the direction of ground-water flow as necessary to define the conceptual movement of ground water away from a facility and toward a monitoring point. Hydraulic Conductivity Hydraulic conductivity is a measure of the ability of an earth material to transmit water. Several laboratory and field methods can be used to determine the saturated and unsaturated hydraulic conductivity of soils, including tracer tests, auger-hole tests and pumping tests of wells. Most ground-water systems consist of mixtures of aquifer and aquitard units. Flow path analysis must consider groundwater movements through aquifers and across aquitards. The relative hydraulic conductivity of these units can vary many orders of magnitude; hence, aquifers offer the least resistance to flow. This results in a head loss per unit of distance along a flow line ten to many thousands of times less in aquifers than in aquitards. Therefore, lateral flow in aquitards usually is negligible and the flow lines concentrate in aquifers and run parallel to aquifer boundaries. Figure 10-9 illustrates the refraction of ground-water flow lines between sand and clay for various discharge points. If the individual geologic units are relatively isotropic (i.e., horizontal hydraulic conductivity is reasonably equivalent to vertical hydraulic conductivity), flownet construction is relatively straightforward. However, if anisotropic hydraulic conductivity conditions are established, the investigator must use transformation techniques as described by Cedergren (1967) and Freeze and Cherry (1979).

ASSESSMENT MONITORING DESIGN

10.5.5 Ground-Water Flow Directions The RI field investigations should include a program for precise monitoring of the area and temporal variations in ground-water levels. This program involves the measurement of water levels in piezometers installed for the purpose of investigating the saturated zone. These data are used to define ground-water flow-directions during development of the ground-water monitoring system. Parameters necessary to measure or ascertain for use in determination of ground-water flow directions include:

most likely direction of ground-water movement. Flownets are the basic tool used in site assessment and monitoring well system design to illustrate regional and local flow patterns that may require monitoring. In using flownets for ground-water monitoring well design problems, it should be recognized that the solutions are no better than the idealized cross-sections drawn. For a given section, however, the flownet can give an accurate solution for flow quantities. To enable proper construction of a flownet for use with a conceptual geologic model, certain hydrologic parameters of the ground-water system must be known, including:

• Depth to ground water • Potentiometric surface

• Distribution of vertical and horizontal head

• Hydraulic gradients

• Vertical and horizontal hydraulic conductivity of the saturated zone

• Vertical components of flow Constructing piezometric or potentiometric contour maps from raw data, then combining the data with stratigraphic cross-sections to develop flownets, is a tedious effort; however, these derived illustrations are essential for selection of target monitoring zones and design of the assessment monitoring system. The process of flownet construction is fully described in Chapter 5 of this text. Construction of flownets offers a direct method for defining the

• Thickness of saturated layers • Boundary conditions Head Distribution Piezometers are used to determine the distribution of head throughout the area of interest. To be valid, head measurements must be time equivalent; that is, all piezometric measurements must be made coincidentally or all

Figure 10-9 Various levels of Ground-Water Flow Discharges

707

ASSESSMENT MONITORING DESIGN

measurements must be made for the same ground-water conditions. Piezometers should be spatially distributed and placed at varying depths to determine the existence and magnitude of vertical gradients. If vertical flow components exist, the flow direction cannot be derived simply based on inspection of the potentiometric surface in two dimensions. A three-dimensional representation of the potentiometric surface would be required to interpret the flow direction. Ground water will flow, however, from areas of high hydraulic head to areas of low hydraulic head. Figure 10-9 illustrates the hydraulic heads in a series of piezometers located in recharging and discharging geologic environments where sandy zones show variable levels of interconnection and discharge. In recharging zones, deeper piezometers show lower ground-water levels. This is due to the lowering of equipotentials with depth in recharge areas. The deeper bedrock can also have a discharge direction significantly different than the overburden soils. In discharging environments, deeper piezometers show higher water levels or heads, as illustrated in Figure 10-9d. Simple homogeneous, isotopic systems, as illustrated, require consideration of depth below the ground-water surface to correctly use the head data. Strong recharge/discharge systems require full understanding of both the vertical and horizontal gradients. Special care should be maintained not to mix piezometer readings from different elevations in generating ground-water contour maps. Aquifer Thickness and Extent The thickness of an aquifer or any geologic strata can be determined by evaluation of geologic logs or by geophysical techniques. Geologic logs generated from boreholes show changes in lithology (the characteristics of the geologic material) indicating the relative hydraulic conductivity of materials. Various geophysical techniques, both downhole and surface, can be used to determine the thickness and extent of geologic units. These thicknesses and extents of geologic materials are used to establish flownets and conceptual models for the facility. Boundaries and Recharge/Discharge Zones To aid in the understanding of the ground-water flowregime and to aid in identification of potential pathways to target for monitoring, the location of any proximate zones of recharge or discharge should be identified within the hydrogeologic conceptual-model. This identification is determined in part by the general site location in the watershed. The investigator probably does not need to quantify such information; rather, a general indication of discharge

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or recharge characteristics could be used as part of the conceptualization process. For unconfined aquifers, recharge areas are usually topographic lows. Discharge/recharge areas also indicate relative depth to unconfined ground water. In discharge areas, ground water is found close to or at the land surface, while at recharge areas, there is often a deep unsaturated zone between the unconfined ground-water surface and the land surface. A ground-water contour map can be used to locate these areas. Recharge and discharge in confined aquifers is typically more complex than for unconfined aquifers. Discharge and recharge may occur where the aquifer is exposed. Some discharge may also occur in the form of upward leakage in areas of upward hydraulic gradient and leaky confinement. Recharge can also occur by downward flow through leaks in the confining layers (aquitards). Topographic information can provide significant insight into ground-water movement; however, topography can also mislead an investigator, when aquifers are confined or perched. Ground water in such aquifers can often move in unexpected directions. The investigator must pay particular attention to potential mounding of ground water and directional complexities that may be covered by low hydraulic conductivity subgrade materials. Caution must always be used in drawing ground-water surface (watertable) or poteniometeric level contour maps. Ground-water flow will generally be uniform, but one must understand the system flow fields. Specific conditions can only be discerned through analysis of lithology and measurement of piezometric heads, which was gathered in the RI field program. 10.5.6 Linkage of the Conceptual Model and Flownets The diagram in Figure 10-10 illustrates the selection of the target monitoring zones using facility geologic and hydrologic information gathered during the RI field investigation prior to selection of locations of assessment monitoring points. The selection process can be described as a series of steps: Step 1. Locate Site Features on a Topographic Map Format: The location of site features including previous disposal areas, stained soils, pipelines or underground storage tanks, should be compared to geologic and soils maps to define preferential flow map areas. Any recharge/ discharge areas should be defined conceptually. Step 2. Cross-Section and Conceptual Model Assessment: Cross-sections based on geologic borings should be available for comparison to site features and facility location. Base grades of the actual facility should be

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CONCEPTUAL MODELS AND CROSS-SECTIONS • Prepare cross section with lithology • Define facility base grades Compare base grades with permeable units Establish most likely uppermost aquifer

GROUND-WATER FLOW DIRECTIONS • Plot piezometric and potentiometric heads • Define relative head differences between aquifers Check for interconnection between aquifers Calculate rates of ground-water movement Plot flow directions using flow lines and equipotentials • Establish if vertical gradients would predict target zone

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SELECT TARGET MONITORING ZONES Vertical heads in unit A Horizontal flow in unit B Unit C confining (aquitard) with upward gradients

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LOCATION OF SITE FEATURES Topographic map format T Plot all pertinent site features on map Surficial soil units should be sampled for analysis Define recharge and discharge areas on map Establish ambient water quality and likely source areas

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LOCATE ASSESSMENT POINTS Place assessment points in likely flow zones Begin along flow lines from affected areas • Target likely source areas with monitoring wells

EVALUATE RATE AND EXTENT OF PLUME Estimate plume configuation from all data Complete rate and extent evaluation

Figure 10-10 Summary of Selection of Ground-Water Monitoring Locations

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plotted on cross-sections to establish potential facility and permeable unit contacts or ground-water flow paths. Conceptual models should be constructed to idealize cross-sections to establish overall site conditions and to illustrate distribution of permeable /less permeable units. Step 3. Use Flownet(s) to Define Likely Ground Water Movements: The flownet will define the watertable and piezometric heads between saturated units. The rates of flow along flow paths can be calculated from the flownets. Vertical gradients can predict target zones by comparison of relative head between units. Interconnections between aquifers can be predicted by relating hydraulic conductivity to hydraulic heads for the units defined in the conceptual model. Step 4. Select Target Monitoring Zones: The flow zones most likely to represent pathways from the waste disposal area sand show ground-water movement from under or adjacent to the waste disposal areas would represent the target monitoring zone(s). These areas would be selected for assessment monitoring well placement. This four step procedure for defining the target monitoring zones must be flexible to include environmental effects due to seasonal changes in gradient or other man-induced flow modifications. The target zone might include only a portion of a very thick aquifer or span several geologic unit as in the case of a thin permeable unconsolidated unit overlying weathered fractured bedrock. These target zones represent the depthlocation criteria for placement of monitoring well screens. 10.6 SYSTEM DESIGN AND OPERATION Assessment monitoring programs under either RCRA or Superfund have many similar features. The following discussions first evaluate evaluation programs typically experienced with large-volume/low toxicity, codisposal facilities. These unlined facilities typically show significant leachate plumes of dilute organic and inorganic parameters. These sites are typically remediated through containment (cover and cut-off areas of discharge from the site) and pump and treat techniques are customarily used to deal with the resultant ground-water plume. Additional single or multiple point source contaminated sites, as illustrated in Figure 10-4, may require alternative field evaluation techniques, as these low volume/high toxicity sites require more focused procedures. Special considerations relative to DNAPLs and LNAPLs will be reviewed later in this section. The degree of site characterization necessary to design an effective ground-water extraction system depends on the objectives of the remediation. In cases where well-head treatment is the objective, it may be sufficient simply to characterize contamination to the extent necessary to design the treatment system. The site charac-

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terization requirements for an aquifer restoration system are likely to be far more extensive. Before designing an aquifer restoration program, it is generally necessary to characterize: l. Hydrogeologic properties of the geologic layers involved 2. Types and distributions of contaminants 3. Location of sources and their potential for continued contamination of the saturated zone 4. Contaminant migration properties of the contamination in the affected aquifers In addition, successful operation of the system requires that the actual performance of the implemented design be monitored so that adjustments can be made to optimize performance. 10.6.1 Hydrogeologic Information Whatever the remedial objective of the ground-water extraction system, its functional purpose is to establish some form of control over ground-water flow in the vicinity of the pumping wells. To design a system of wells that can establish this control requires an adequate understanding of the hydrogeologic characteristics of the site. For the design of an extraction system, the necessary hydrogeologic information includes the stratigraphy, the hydraulic conductivity of aquifer layers, the leakance of semi-confining layers and the natural distribution of potentiometric head. Stratigraphy It is necessary to identify the number and thickness of the aquifers potentially affected by contamination at the site. It is also important to know the lateral extent and continuity of any confining or semiconfining layers as shown in Figure 10-8. Any local gaps in the confining layers that occur within the area of concern can have an important effect on the success of the aquifer remediation. These open window areas are especially important in DNAPL contaminated sites as local holes in clay layers between upper and lower aquifers permit DNAPLs to enter a lower uncontaminated aquifer. It is also very important to establish the bottom of the zone involved in the remediation because shallow groundwater control designs can leave deeper unknown contamination uncontrolled. No matter what type of contamination is present at site, one must fully understand the subsurface geology to have any chance to evaluate aquifer restoration. Adequate investigation of site stratigraphy requires

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installation and appropriate logging of sufficient exploratory borings to characterize the site. The number of borings ultimately required depends on the complexity of the subsurface geologic environment. Aquifer Hydraulic Properties In relatively homogeneous aquifers the main reason for investigating the transmissivity is to predict the extent of the capture zone that can be established by wells and the rate of pumping that will be required. While detection monitoring program design would rarely require the expense of a full-scale pump test, aquifer remediation requires good field data. Chapters 5 through 7 provide background information setting-up and the evaluation of aquifer test data. When the stratigraphy is well defined and good transmissivity estimates can be made through pump tests, the depth-averaged hydraulic conductivity can be provided to the design of the extraction system. Depthaveraged hydraulic conductivity estimates arising from aquifer test results may be deceptive if the aquifer is vertically heterogeneous. In general, insufficient effort is expended to determine hydraulic conductivity variations in aquifer systems requiring remediation. Determination of vertical hydraulic conductivity variations within an aquifer unit requires special testing methods. In consolidated openhole bedrock wells this can be done by packer testing or stressed flowmeter logging. In unconsolidated materials, individual slug tests on wells screened at different depths combined with grain size/hydraulic conductivity analyses can be used to estimate vertical permeability variations in aquifer properties. One should use sufficient care in evaluation of aquifers with complex heterogeneity, because conventional aquifer tests can be very difficult to interpret. Long-term aquifer tests in which a large number of observation wells are monitored can provide adequate detail, dependent on the scope of the test and the ability of the aquifer to transmit pressure head changes throughout the system in question. A practical system to evaluate complex hydrogeologic systems is phased pilot testing of extraction wells. Because this usually involves incremental design of the extraction system as successive components are installed and tested, the design elements must be sufficiently flexible to accommodate changes to the system on the basis of observed hydraulic heads. The thickness and hydraulic conductivity of semiconfining layers separating individual aquifers in multilayered hydrogeologic systems can have an important influence on the effectiveness of ground-water extraction systems. Interaquifer leakage in response to the pumping of extraction wells can drastically reduce the radius of influence of the

wells. Chapter 5 reviews pump testing procedures applicable to inter-aquifer testing so that accommodation can be made to system design elements. Leakage through semiconfining layers also permits contaminants to move between aquifers. Evaluation of storage coefficients is of secondary importance in aquifer remediations, as the extraction system operation is usually analyzed as a steady-state phenomenon. Potentiometric Gradients Ground-water extraction systems achieve their remedial goals primarily through the manipulation of groundwater flow patterns (hydraulic heads) in the contaminated aquifers. The hydraulic pressure heads or gradients produced by the extraction system must also control or contain the large-scale regional gradient that may be moving the contaminants in an undesired direction. These regional gradients may be due to natural recharge and discharge relationships or they may be the result of nearby production wells that affect local flow systems. The design of the extraction system must take both natural and anthropogenic systems into account. Installation and monitoring of piezometers or water level monitoring wells must be part of the overall design of the hydraulic control system. Natural gradients can change seasonally, so water levels must be measured enough times during the year to determine gradients for potential reversals in flow. 10.6.2 Contaminant Source Characteristics The nature of the ground-water contamination problem is generally established by determination of the number and identity of the contaminant compounds present, their concentration and spatial distribution in the aquifer and their mobility characteristics. This is the basis of the assessment monitoring program. Based on Figure 10-11, a series of figures (Figures 10-12 to 10-15) are presented below that describe the process of defining the source of an observed exceedance in a detection monitoring program. This procedure would follow the basic goals of tracking down the source of the observed hit in a monitoring well. This process is greatly extended in the typical remedial program where there may be multiple sources present or unknown historic source of persistent inorganic of organic residuals. Identification of Contaminants This is probably the aspect of the site investigation that is routinely most thoroughly covered in a typical assessment program. It is important in the design of an extraction

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Figure 10-11 Example Site Assessment Process

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system because of the different mobility and toxicity of the various contaminants and because of the special handling and treatment problems associated with some compounds. The vast majority of remedial assessment projects will be concerned with volatile organics. Whether working with codisposal, point source or multiple point source volatile organics will drive the assessment monitoring risk assessments and ultimate remedial design (unless the site is specific to metallic wastes only). These organic compounds have relatively high mobility as dissolved species in ground water. Do not, however, lose sight of the fact that inorganic parameters, many of which are not health based, can provide the fingerprint of the leachate. Establishing the specific water quality fingerprint must represent a project goal in assessment monitoring. Once establishing the leachate parameter fingerprint, the investigator must stick with using the indicator parameter finger print to trace flow path water quality. Figures 10-11 and 10-12 illustrate a simple disposal site with a typical minimum downgradient detection program of three wells and two upgradient or background wells. The observed water quality in downgradient well 5 (which could have been installed as an assessment or detection installation), was found to exceed regulated parameters A, B, C, and D. This would have caused a preliminary assessment or resampling of the detection of assessment wells present at the site. The water quality fingerprint for several of the on-site sampling locations is shown in Figure 10-13. In addition to the chemical fingerprint identity of the

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Figure 10-12 Location of Monitoring Points compounds, it is also important to determine whether they are present in a nonaqueous phase. If NAPL contamination is involved, it is unlikely that aquifer restoration by a simple extraction system will be successful (i.e., lower resident water quality to below health-based risk levels) over any reasonable time period. More than likely hydraulic containment objectives will be the main control technique used for DNAPL contaminated sites. The presence of LNAPL (floating products) contamination presents a number of special problems for the investigator; because of interfacial tension effects, NAPLs that are present in an aquifer at relatively low saturation may not flow into a normally constructed monitoring well. Therefore, the presence of NAPLs cannot be ruled out just because they have not been seen as a separate phase in any of the ground-water samples. A reasonably reliable way to detect NAPL contamination is to take soil samples during installation of the piezometer or monitoring wells (e.g., split-spoon or Shelby tube samples) or as part of a U.S. EPA soil boring program. In fractured rock aquifers, diamond rock coring can be used to collect aquifer samples but this may not conclusively rule out NAPL presence. Contaminant Distribution and Concentration Knowledge of the spatial distribution of contaminants in the aquifer is obviously very important for the design of

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example, to keep it simple, we have drawn the contaminate plume directly through and ending near well 6. In real life this solution may not be so easy. With the many unknowns and uncertain geologic and hydrogeologic conditions it is always important to keep a regional perspective as shown in Figure 10-15. In the design of plume containment and well-head treatment systems it may not be essential to establish the upgradient extent of the contaminant plume. But, the downgradient and lateral extent of the area in which health-based standards are exceeded must be known for the data to complete the rate and extent evaluation. In an assessment monitoring program accurate measurement of contaminant concentrations is important for a number of reasons:

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• Aquifer restoration goals are typically expressed in terms of individual contaminant concentrations, so the boundaries of the contaminated region must be determined.

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the assessment monitoring system, as the rate and extent values determine the area in which one must establish control of ground-water flow. The general problem an assessment monitoring program must deal with is essentially to determine the boundaries of the contaminant plume. This generally requires during the investigation that monitoring wells be installed both inside and outside the contaminated area. This presents the general problem with any traditional (RCRA or Superfund) assessment monitoring design; you must know the location of the contaminate plume during the planning stage of these federal programs. However, you do not actually know the true rate and extent of the plume until the wells are installed and sampled. Often the wells are either installed in the wrong location (out of the plume) or all of the wells are inside the contaminated area, so the plume edge cannot be located. Figure 10-14 shows the results of the assessment monitoring to confirm the source of the exceedance was from the sump area of the facility in question. Well 7 shows the same parameters as well 5 (although high levels) and well 6 shows diluted similar parameter as wells 5 and 7. This is not to say that the diluted parameters stop near well 6, as the narrow plume could have moved up or down or changed directions slightly to only graze the open screens of well 6. In this

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Figure 10-14 Locate Assessment Monitoring Points

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Figure 10-15 Keep a Regional Perspective • Predictions of the contaminant concentrations in the extracted ground-water are required in the design of the treatment system. • Measurement of the progress of aquifer remediation is best handled by periodic comparison of the contaminant concentration distribution using the initial preremediation parameter distribution. Data on concentration distributions defined in assessment monitoring are usually described by drawing contour maps of the contaminant plume. These contaminant contour maps are prepared for defining the initial site conditions and for meeting clean-up goals during the remediation period. Assessment monitoring programs often ignore layered water quality conditions. This is especially true for isocon-

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tour presentations developed from single-point monitoring wells. When interpreting concentration contour maps it is important to understand how vertical variations in aquifer contaminant concentration have been accounted for. Assessment programs result in data presentations that require summarization to improve understanding of the vast datasets. Contour maps offer the investigator the tools to evaluate and display reasonable numbers of indicator parameters. Unfortunately, isocontour maps can misrepresent the actual indicator parameters, as they are only a twodimensional presentation of a three-dimensional system. Figure 10-16 shows a poorly drawn isocontour map of observed organic indicator parameters that are difficult to defend. Because the detection or assessment wells were screened in different target monitoring zones, the circular

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isocontours should not have been drawn in this map presentation. Contour maps may be developed directly from the analytical results without regard to the depth from which the samples were taken or the length of the screened intervals in the monitoring wells. This presentation can give false impression of the distribution of contaminants in the aquifer. These isocontour presentations may also show target contours drawn around monitoring points. This is a direct result of either too little data, incorrect selection of indicator parameters or having wells located in and out of the containment flow path. If the samples were taken from fully penetrating monitoring wells, the results can be interpreted as a permeability-weighted, depth-averaged concentration. Such a parameter concentration measurement is useful in predicting the contaminant concentrations that will be produced by fully penetrating extraction wells. However, concentrations measured in this way will probably be lower than the maximum concentrations in the aquifer and may produce incorrect estimates of total contaminant mass. Estimates of the total contaminant mass in the aquifer are sometimes used within assessment programs to express

the magnitude of the containment problem. Because a goal of aquifer restoration may be to remove 99% of the contaminant mass in the aquifer over some period of time, evaluation of the remediation depends heavily on the accurate estimation of this contaminant mass. The only effective way to do this in an assessment program is to understand the three-dimensional distribution of contaminant concentration in the aquifer, which may only be obtained by multilevel assessment sampling system. Both dissolved and sorbed contaminants must be accounted for in estimates of the total contaminant mass. Contaminant Mobility Characteristics One of the most common explanations for underestimation of the time required for aquifer remediation is that the effects of adsorptive retardation were not accounted for. The retarding effects of contaminant sorption are typically estimated using the concept of multiple pore volumes that must be extracted before the contamination concentrations are reduced to the necessary regulatory standards. Quantitative estimates of contaminant retardation

Figure 10-16 Example of Target Isocontours Around Monitoring Point

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developed in assessment programs are usually based on the total organic carbon content of the aquifer materials and tabulated values of partition coefficients for organic compounds. These programs must include measurement of total soil organic carbon as part of the assessment sampling scope. Soil samples can also be taken from beneath a contaminant source area to evaluate the partitioning of contaminants between soil and water. Sampling below source areas, however, should be very selective and not cause further additional cross contamination. These data are used to support analysis of the continued leaching of contaminants from the vadose zone into the underlying aquifer. Laboratory testing of site materials for partition coefficients is fairly rare at ground-water contamination sites, but the information obtained from such tests may be quite useful in the calculation of total containment mass (U.S. EPA, 1990). Contaminant Sources Characterization of the sources of contamination is important in the design of any assessment program. While establishing a containment source is relatively easy when viewing a large codisposal landfill with little additional potential source areas, one should not forget that the main target of the investigation may be entirely or only partially the source of the observed contamination. Short-sighted assessment programs do a disservice to long-term goals of protecting human health and the environment. Continued contaminant discharge from alternative sources can defeat the ground-water cleanup efforts and risk further negative environmental effects. Even with the original source removed, it is important to evaluate the potential for continued leaching of contaminants from the remaining contaminated areas. 10.6.3 Performance Monitoring The performance of aquifer remediation systems must be monitored at regular intervals to ensure that the desired containment is being maintained over the ground-water flow patterns and the resultant movement of contaminants. Monitoring of the hydraulic performance of the system is performed by regular head measurement of water levels in piezometers and monitoring wells throughout the area of remediation. Potentiometric surface maps are then drawn for each of the aquifers of concern to show maintenance of the desired capture zones. In multiple-aquifer situations the potentiometric gradients between aquifers should also checked using these maps. Performance monitoring of the aquifer cleanup can be demonstrated in several ways:

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• A common, but not very reliable approach is to monitor the flow rate and contaminant concentrations produced by the extraction wells. • Integration of the product of flow and concentration over time gives a rough estimate of the mass of contaminants removed. This method does not, however, provide a direct measure of the reduction in contaminant concentrations in the aquifer. • A more accurate method is to take samples simultaneously from enough monitoring wells in the remediation area to permit plume maps to be drawn. Plume isocontour maps can be used to determine when the aquifer remediation is complete. In general samples taken from the extraction wells may not be reliable for prediction of remedial goals, as these wells generally show considerable dilution of indicator parameters through their hydraulic effects on the aquifer. In monitoring plume containment systems, it is important that some monitoring wells be located downgradient of the extraction wells. This is necessary so that flow reversal downgradient of the well can be demonstrated to show containment of the contamination. Even though hydraulic head measurements are the primary data sources to demonstrate containment, periodic water quality sampling should be conducted to ensure that contaminants are not escaping by passing under or between the extraction wells. The bottom line to any assessment program is knowledge of the geologic and hydrogeologic system. The appearance of complete hydraulic capture on the basis of potentiometric heads can be deceptive if the true hydrogeologic nature of the aquifer is not well understood. 10.6.4 Post-Remediation Monitoring Most assessment monitoring require some form of post-remediation monitoring. Performance monitoring of the aquifer restoration sites should continue even after the extraction system has been turned-off due to meeting remediation goals. It should be expected to see low contaminant concentrations measured toward the end of the remedial action rebounding after the extraction system pumpage has been terminated. Several reasons for this effect can be established: • The ground-water flow patterns generated by the extraction system can cause dilution of the concentrations sampled at monitoring wells.

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• Residual contaminants stored in low permeability zones of the aquifer sorbed to the aquifer materials or retained as NAPLs, may cause the concentrations to rise when the extraction is terminated. • The recovery of water levels after system shutdown may resaturate contaminated soils and thus release additional parameter mass to the ground water.

10.7 SOIL SAMPLING AND ANALYSIS DESIGN The goals of collecting samples for VOAs may include source identification, spill delineation, fate and transport modeling, risk assessment, enforcement, remediation or post-remediation confirmation. The intended purpose of the sampling effort drives the selection of the appropriate sampling approach and the devices to be used in the investigation. Soil investigation may include surface (two dimensions) or subsurface (three dimensions) environments, hot spots, a parameter concentration greater or less than a health or regulatory-based action limit or simply the area around a leaking underground storage tank. Statistical approaches used to evaluate the soils data should be established during the development of a sample and analysis design. Statistics typically used in such soil sampling programs include average analyte concentration and the variance about the mean (statistics that compare whether the observed level is significantly above or below an action level) as well as temporal and spatial trends. An excellent user’s guide on quality assurance in soil sampling is Barth et al. (1989) and the U.S. EPA’s (1987) document for the development of data quality objectives for remedial response activities provide guidance for setting Data Quality Objectives (DQOs) for soil sampling activities. DQOs can be defined as “qualitative and quantitative statements of the level of uncertainty a decision maker is willing to accept in making decisions on the basis of environmental data.” Large errors in one part of an investigation will set the level of error for the rest of the particular sampling effort. For example, if the error associated with the sample collection or preparation step is large, then the best laboratory quality assurance program will be inadequate. The greatest emphasis should be placed on the phase that contributes the largest component of error. For the analysis of soils for VOCs, the greatest sources of error are the sample collection and handling phases. Field sampling personnel should coordinate with laboratory analysts to ensure that samples of a size appropriate to the analytical method are collected. Field-screening procedures provide an effective means of locating sampling locations and obtaining real-time data.

The benefits of soil field-screening procedures are: • Near real-time data to guide sampling activities • Concentration of Contract Laboratory Program (CLP) sample collection in critical areas • Reduced need for a second visit to the site • Reduced analytical load on the laboratory Limitations of field-screening procedures are: • Prior knowledge of VOCs present at the site is needed to accurately identify the compounds. • Methodologies and instruments are in their infancy and procedures for their use are not well documented. • More stringent level of quality assurance and quality control (QA/QC) must be employed to ensure accurate and precise measurements. The potential benefits and limitations associated with soil-screening procedures must be carefully weighed and compared to the DQOs. The approaches described in this document, for the most part, combine discussion of issues generic to soils and sediments. Step 1. Evaluation of Land Use History and Existing Data Early in a hazardous waste site investigation, site history should be determined by examining available records and by interviewing personnel familiar with the site. This information can be used to assess the types of contaminants associated with past operations that may be of concern and may be compared to Appendix IX, Superfund and Priority Pollutant Compounds, lists which identify the inorganic contaminants of concern. Evaluation of site history can provide important data when determining those compounds for which background concentrations need to be established. For example, if releases of cadmium and lead are suspected at a hazardous waste site and the site is located in a heavily industrialized area, there is high potential that metals such as mercury, lead and cadmium may be present and elevated in soils and sediment from offsite contributions. An initial evaluation of on-site data should be sensitive to the issue of elevated background so that off-site contributions can be properly accounted for. Another advantage of evaluating existing hazardous waste site data is to determine if pre-site operation values are available for inorganics in sediments or soil. These data can be obtained from site records or other existing

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sources discussed later in this chapter. NRCS soil surveys should be checked both for aerial photographs for previous land use on or near the site, and evaluate data for average physical and chemical properties for soils at and around the site. Local agents, including state, county, and federal environmental quality officials, are also sources of information on local emissions or previous sampling data that may be used to establish background concentrations. U.S. EPA or state regulators of chemical storage, use, and emission databases of local industries may be a good source of chemicals used or stored in the local area. Step 2. Establishment of Data Quality Objectives The DQO process is described in Standard Practice for Generation of Environmental Data Related to Waste Management Activities: Development of Data Quality Objectives (ASTM, 1995) and is summarized in a companion issue paper titled Characterizing Soils for Hazardous Waste Site Assessments (Breckenridge et al., 1991), which explains how to classify soils when faced with different classification systems and what data need to be considered when establishing DQOs. U.S. EPA’s external working draft, Guidance for Data Quality Assessment U.S. EPA, 1995), is helpful in discussing the role of statistics in the DQO process. This document has a companion PC-based software program to help support the document. Because this is designed as a living document, contact the Quality Assurance Division [Fax number (202) 260-4346] in the Office of Research and Development (401 M Street, SW, Washington, D.C. 20460) to obtain the latest version. Step 3. Determining Sample Location and Numbers to Collect A number of options are available in sampling design that determine where to collect samples from a hazardous waste site to compare against a background site. The investigator needs to discuss the DQOs with a statistician to select the appropriate design. Numerous design options are available. One option is for those areas where the soil and sediment matrix and distribution of suspected contaminants appear to be homogeneous. Establishing a consistent grid (i.e., systematic sampling grid) across the entire site and sampling at set locations should provide a reasonable characterization of the contamination values across the site. A second option may apply if certain parts of a site are suspected of being contaminated due to historical use. In this case, bias sampling or intensifying the grid in highly suspected areas could be considered. This approach maximizes the possibility of determining whether contaminant concentrations at a site are above background and minimizes the risk of not taking action at

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a hazardous waste site. There is a wealth of guidance on soil sampling. One document that is useful because of its coverage of soil sampling methods and design for reducing various sources of sampling error is titled Preparation of Soil Sampling Protocols: Sampling Techniques and Strategies U.S. EPA, 1992c). This document also provides information for those uncertain about sampling design options and composite collection techniques. The following discussion points should be considered when selecting and designing the sampling plan. For a given site, there may be several areas of concern based on known or suspected past site activities. Once these areas are identified, a sampling plan can be developed. Historical data should be identified and evaluated early in the process to determine their use in identifying areas of concern or if the entire site needs to be sampled. Historical and land use information identified from Step 1 plays a key role in determining the degree of bias in the sampling plan. Factors such as location of tanks, piping, staging areas, disposal ponds and drainage areas (e.g., sumps) should be considered when designing a sampling plan. Several soil properties or processes that govern the mobility of contaminants can also bias sample location. Step 4. Sample Collection, Preservation, Handling, Analysis and Data Reporting 1. All sample collection, preservation, preparation, handling and analytical methods should follow standard methods, e.g., U.S. EPA SW-846, Test Methods for Evaluating Solid Waste, Physical/ Chemical Methods (U.S. EPA 1986). It is important that all samples are handled using comparable methods when preparing for and during analysis. For example, using different digestion methods can change results significantly. 2. For inorganics, it is recommended to use a total metals procedure with results reported in mg/kg (a percent for iron) on a dry weight basis. This minimizes additional sources of variation, as these constituents are often naturally occurring. To assess the bioavailability of metals in anoxic sediments, acid volatile sulfide and simultaneously extracted metals should be determined (Di Toro et al., 1990, 1992). Step 5. Statistical Comparison of Hazardous Waste and Background Sites The following discussion outlines some basic statistical concepts in the context of background data evaluation.

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A general statistics textbook such as Statistical Methods for Environmental Pollution Monitoring (Gilbert, 1987) should be consulted for additional detail. Also, Table 103a may be useful. Numerous statistical approaches that are applicable when collecting, assessing and analyzing background data. The approaches presented here have been adopted by the State of Michigan (Michigan, 1990, 1991b) and modified based on the author’s experience. They are readily understandable and easy to use. However, it is recommended that investigators consult a statistician to assist in the design or review of a sampling plan prior to collecting samples. Careful consideration must be given to the selection of a statistical procedure based on site-specific factors. These include the size of the background database and the number of samples available for comparison, variability of soil type and coefficient of variation of data. The following are some statistical methods that can be used if data from the site follow a normal distribution. Some environmental sample sets are normally distributed. However, the majority of environmental contamination datasets are not normally distributed. Some of the more commonly used tests of normality are presented in Table 10-3b. Tests should be conducted on all data to determine if the data meet the assumption of normality. If the data are not normally distributed, log or other types of transformations should be conducted to approximate normality prior to using the datasets in statistical comparisons, such as t-tests or analysis of variance (ANOVA) procedures. If the data cannot be normalized, additional attention needs to be given to selecting appropriate statistical tests and the situation needs to be discussed with a statistician. Special statistical consideration may be warranted if samples are composited and the data are needed to support regulatory requirements. 10.7.1 Soil Sampling Objectives Soil or sediment sampling represents a common tool used in assessment programs to establish “in place” levels of contaminated materials. These soil sampling procedures represent a very different type of problems to investigators as compared to ground-water flow path analysis. While flow path analysis requires consideration of hydraulic head levels in subsurface units, soil and sediments remediation programs represent traditional area sampling where both material sampling theory and geostatistical concepts can be used to locate and optimize sampling points. Even with this basis for soil sampling, targeted sampling programs can greatly increase the cost effectiveness of the program.

Table 10-3a Statistical Methods Guidance

Basic Statistical Methods for Environmental Pollution Monitoring, (Gilbert 1987). Guidance for Data Quality Assessment (U.S. EPA, 1995). Soils Sampling Quality Assurance Guide (U.S. EPA 1989d). Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA (U.S. U.S. EPA 1988a) U.S. EPA's Guidance Manual: Bedded Sediment Bioaccumulation Tests, pp. 82-91 (Lee et al., 1989). Statistical Guidance for Ecology Site Managers, Washington State Department of Ecology (WDOE 1992). Risk Assessment Guidance for Superfund, Volume 1: Human Health Evaluation Manual (Part A), pp. 45 to 4-10 U.S. EPA 1989c). Advanced Gibbons, R. D. Statistical Methods for Groundwater Monitoring, Wiley, New York, 1994. Gibbons R. D. and Coleman D. E. Statistical Methods for Detection and Quantification of Environmental Contamination, John Wiley & Sons, 2001. Estimation of Background Levels of Contaminants (Singh and Singh, 1993). Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities (U.S. EPA1992d). Background and Cleanup Standards Methods for Evaluating the Attainment of Cleanup Standards, Volume 1: Soils and Solid Media, (U.S. U.S. EPA 1989b) (detailed statistical discussion). Note: If time and resources are limited, Gilbert (1987), Hardin and Gilbert (1993) and U.S. EPA (1995a) provide some of the most relevant statistical information.

Soil sampling designs or strategies should be based on pre-specified sampling objectives. These strategies must, however, be based on some level of site-specific data, such as prior disposal patterns, air photo target sites or known contamination. The sampling design or strategy chosen will largely depend on the objectives of sampling. Without clearly stated program objectives, sampling efforts can lead

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Table 10-3b Tests for Evaluating Normality of Datasets Test Shapiro Wilk W test

Sample Size (N)

Notes on Use

Reference

50

Highly recommended.

Gilbert (1987) U.S. EPA (1992c)

Filiben’s statistic

100

Highly recommended.

U.S. EPA (1995a)

Studentized range test

1000

Highly recommended.

U.S. EPA (1995a)

Lilliefors KolmogorovSmirnoff test

>50

Useful when tables for other tests are not available.

Madansky (1988)

Coefficients of Skewness and kurtosis tests

>50

Useful for large sample sizes.

U.S. EPA (1995)

Geary’s Tests

>50

Useful when tables for other tests are not available.

U.S. EPA (1995)

50

Use only to discard assumption of normality quickly.

U.S. EPA (1995)

Coefficient of variation test Chi-square test

Large a

Useful for group data and when the comparison distribution is known.

Introductory Statistics Books

a

The necessary sample size depends on the number of groups formed when implementing this test Each group should contain at least five observations. SOURCE: U.S. EPA (1995)

to unusable or unnecessary data and result in costly or misdirected remedial actions. Sampling objectives can be reduce to the following actions: Detecting evidence of contamination: During initial phases of site investigation the source of contaminated soil may not be known either because the contamination is buried beneath the soil surface or because the contamination has not expressed itself by visible discoloration or other distinctive observational features at the soil surface. This objective only requires that evidence of contamination be determined, not how much is present or its pattern of distribution. Estimating the mean, variance and confidence intervals of soil properties in a volume of soil: One of the primary purposes of soil sampling is to estimate the mean value of a soil mass and associated confidence limits for a pre-specified volume of soil. These data provide input for exposure assessment modeling. Such information may also be necessary to determine whether a level of contamination in site soils exceeds an average background soil concentration level or is less than some specified action level. Determining the spatial structure of soil properties: Site characterization studies require understanding the spatial structure of important soil properties including the spatial distribution of contaminants. Spatial distribution of soil contamination is necessary to optimize removal or remediation of contaminated soils at reasonable costs.

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During a preliminary investigation of a hazardous waste site, it may be necessary to determine whether or not there is soil or sediment contamination. Where there is no visible evidence of surface contamination and if contamination is thought to be distributed at random or is thoroughly dispersed, a systematic sampling strategy has been reported as more efficient than a random sampling strategy for detecting small localized areas of contaminated soil or hot spots or in finding buried tanks and wastes (Parkhurst, 1984; Greenberg, 1987). One should, however, evaluate the potential for use of geophysical methods to target the contaminated soils (especially for tanks and metallic contamination), before conducting an extensive soil sampling program. Disturbed soils can also be evaluated through false-color IR air photos to assist in targeting the soils investigation. By using non-sampling methods to target the potential soil contamination the probability of detecting a soil or sediment hot spot will obviously increase by increasing sampling density (i.e., the number of sampling locations per unit area) in a surface evaluation program. Targeting the sampling program allows one to use available project funds more effectively. Singer (1972, 1975) has developed a computer program for determining the grid spacing (or sampling density) needed to hit an elliptical hot spot of a given size with a specified confidence. Subsequently, Zirschky and Gilbert (1984) developed monographs for determining the same. The selection of the proper grid spacing depends

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on the following assumptions (Gilbert, 1987): • The hot spot is circular or elliptical and has no preferred orientation.

contaminated soil as sources of risk to human health and the environment. Specifically, soil sampling efforts can be designed and conducted to:

• Samples or measurements are taken on a square, rectangular or triangular grid.

• Determine the extent to which soils act as either sources or sinks for air or water pollutants

• The distance between sampling locations is much greater than the dimensions of the sampling unit.

• Determine the risk to human health and/or the environment from soil contamination by selected pollutants

• The definition of a hot spot is clear and unambiguous, that is, the types of measurement and the levels of contamination that result in a detection are clearly defined.

• Determine the presence and concentration of specified pollutants in comparison to background levels

• There are no measurement misclassification errors; that is, there are no errors associated with the determination of a detection. Where the cost of analysis exceeds the cost of sampling, it may be desirable to use composite sampling methods. However, the criteria for determining whether a hot spot has been hit may have to be decreased by a factor equivalent to the number of sampling units that are composites. For example, if the criteria for a hit is 100 ppm of some substance in soil, then the criteria would have to be reduced to 20 ppm if five sampling units were composited. If a hit is found in the composite, then the original sampling locations may have to be resampled to determine which one or more of the subsampling locations contributed to the hit. Optionally, if representative portions of each of the original sampling units were left uncomposited, then the uncomposited portions of the sampling units could be analyzed individually using the predetermined criteria for a hit. Where the criteria for a hit is at or near the detection limit, one would then have to weigh the risk of not detecting contamination when it is present (i.e., consumer’s risk) against the increased coverage offered by taking more samples. If subsamples are to be composited, the subsamples should have the same dimensions and orientation and be obtained from comparable geologic strata or, if the location of the geologic strata have been masked by soil disturbances, from similar depth intervals below the original land surface. If subsamples do not have the same dimensions and orientation, the average value of a soil property for the composited sample may be biased toward the larger sized sample. 10.7.2 Purposes for Soil Sampling As a general goal of CERCLA, concentrations of hazardous pollutants in soils or sediments should not exceed levels established as being adequately protective of humans and the environment. From a contaminated soil perspective within assessment programs, one needs to establish the role of soils as sources or sinks for selected pollutants. There are numerous techniques used within RI projects to evaluate

• Determine the concentration of pollutants and their spatial and temporal distribution • Measure the efficacy of control or removal actions • Obtain measurements for validation or use of soil transport and deposition models • Determine the potential risk to flora and fauna from specific soil pollutants • Identify pollutant sources, transport mechanisms or routes and potential receptors • Meet the provisions and intent of environmental laws such as the Resource Conservation and Recovery Act (RCRA), the Comprehensive Environmental Response, Compensation and Liability Act, (CERCLA), the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and the Toxic Substances Control Act (TSCA) As a general definition, the term soils encompasses the mass (surface and subsurface) of unconsolidated mantle of weathered rock and loose material lying above solid rock. The soil component can be defined as all mineral and naturally occurring organic material 2 mm or less in particle size, the size normally used to distinguish between soils (e.g., sands, silts and clays) and gravels. Organic matter is often found as an integral part of the soil. An additional component that must also be addressed during the sampling effort consists of the non-soil fraction (e.g., automobile fluff, wood chips, various absorbents, and mineral/organic material greater than 2 mm). This component may contain a greater amount of contaminant than the associated soil. At sites in which this occurs reporting contaminant levels only in the soil fraction will ultimately lead to inappropriate and incorrect decisions on project remedial design. Pollutant behavior in the soil environment is a function of both the pollutant’s and soil’s physical and chemical properties. Soil sorption (the retention of substances by adsorption or absorption) is related to properties of the pollutants (e.g., solubility, viscosity, heats of solution and vapor pressure) and to properties of soils (e.g., clay content organic content, texture, hydraulic conductivity, pH,

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particle size, specific surface area, ion exchange capacity, water content, temperature). The soil components that are most associated with sorption are clay content and organic matter. The soil particle surface characteristics thought to be most important in adsorption are surface area and cation exchange capacity (U.S. EPA, 1989). The extreme complexity and variability of soil necessitates a multitude of sampling/monitoring approaches must be incorporated into soil investigations. Both field and laboratory tests are necessary to understand the presence and behavior of soil contaminates. Field tests primarily provide information for soil classification in order to relate nearsurface environmental conditions. Laboratory tests supply analytical data on the type and quantity of a pollutant present in the soil sampled in the program. If significant quantities of selected pollutants are found to be associated with soils initially and then released slowly over relatively long periods of time, the soils, in essence, act as pollutant sources. If significant quantities of contaminant(s) become permanently attached to soil and remain biologically unavailable, the soils may constitute a sink. Pollutant control needs in these cases may be reduced by the amounts by which the soils reduce the pollutant availability. Underestimating the ability of soils to act as a sink might lead to source control requirements more stringent than necessary, whereas overestimating might lead to less stringent control requirements than necessary. Soil sampling to measure the efficacy of control or removal actions must be preceded by the establishment of unacceptable concentrations of pollutants of concern in soil. A critical consideration in this instance will be the depth and surface area extent of the soil sample on the basis of which the soil concentration will be calculated. Determination of risk to human health and the environment from contaminated soils involves several investigative steps. The soil/sediment evaluation must determine exposure and dose distributions to the most sensitive populations or receptors via all significant exposure pathways. This may include possible soil-related exposure from other media such as air or water, exposure from the soils themselves either through ingestion, inhalation or skin absorption, as well as exposure through ingestion of foods contaminated directly or indirectly from the soils. It is important within these investigations to measure or estimate the extent to which the soils act as sources (through contacting air surface and ground-waters) for the pollutant(s) of concern. Underestimating the extent to which soils act as contaminant sources will lead to inappropriate and insufficient controls of other additional sources, whereas overestimating may lead to expensive soil removal to a greater degree than necessary. Remediation through soil removal involves extensive testing of the soils and evaluation of proposed

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disposal options to evaluate the most cost-effective option with the least environmental impact. 10.7.3 Sample Design Once a site must be sampled, sampling decisions must be made for the soil programs. Initial decisions must be made on the type of sampling design and sampling density. In most cases development of a statistical basis for the sampling is an early goal. The prime objective of a statistically based sampling design are either to provide the necessary site information for a fixed survey cost or to minimize survey cost for a fixed amount of information. Secondary concerns in sampling design are simplicity of resulting data analysis and simplicity of field operations in performing the survey. A design used in many soil assessment programs is the simple random sample design (see Figure 10-18). Sampling units in these designs are determined by random selection. The random design for site investigation simplifies the statistical analysis; however, it is typically very expensive due to sampling many uncontaminated site areas. A deviation of simple random sampling is the stratified random design. This design partitions the region to be sampled into subregions (strata) on the basis of suspected differences in level of pollutant, on cost of sampling, on the basis of equal strata areas or on some combination of the above. Once subregions are established, simple random sample is then taken from each stratum. An example of this design would establish sufficient information to divide the site into strata where the level of pollutant concentrations is either far above action level, near action level or far below action level. Typically you would expend most of the sampling effort (i.e., high sample density) on the strata that are near action level, so that decisions can be made with a high level of accuracy on the area needing remediation. Stratification ensures that all subregions of the site will be sampled, which may not be the case with a simple random sample of the site. The stratification design uses scientific or historical knowledge based on a number data sources that the pollutant concentrations are quite different in identifiable segments of the site area. This targeting improves the subsequent estimate of the mean concentration over the entire site. Another criterion that may be useful in stratification for sediment sampling is distance from known point sources. Simple random sampling and stratified random sampling designs are among a class of designs originally developed for the sampling of units that are discrete objects so that statistical analysis techniques associated with these designs can provide an estimation of population means. Both stratified random sample and simple random sample

ASSESSMENT MONITORING DESIGN

Figure 10-17 Alternative Soil Sampling Design procedures were developed for sampling of discrete sampling units and may not adequately take into account the spatial continuity and spatial correlation of soil or geologic properties. Samples taken at locations that are close together tend to give redundant information and are therefore wasteful of resources. For this reason, some type of sample selection grid (systematic design as shown in Figure 10-17) is often used to assure that sample locations will not be close to one another. The grid may be radial, triangular, rectangular, hexagonal, etc. Systematic grid designs provide many of the advantages of stratification plus the avoidance of redundant samples. They thereby improve statistical precision and power. Investigations of the efficiencies of the grid designs show that the hexagonal grid is the most efficient given certain assumptions about the spatial distribution of the pollutant, but the square or rectangular grid is easier to use in practice. The radial grid may have some advantages in investigating the distribution of a pollutant near a point source. A grid pattern is best oriented in the direction of flow of the pollutant, which may relate to site topography or a wind rose. Once the sampling density (grid spacing) and the orientation of the grid have been determined, selection of one sample location will completely determine the locations of all sample locations. The systematic grid designs are more closely related to

the sampling of continuous media such as soil, air and sediment. The statistical analyses associated with the results of these surveys of continuous media are typically aimed at estimating the spatial distribution of a property of the media such as a pollutant concentration or in finding hot spots within the region or site being sampled. When a grid (systematic) design is used one finds many of the actual sample locations will not be at the grid locations because of the presence of obstructions such as roads, houses, rocks and trees. If the field crew cannot sample at a specified location, they should have instructions to take a sample at the nearest point in a prespecified direction from the original point, provided that the location is within a specified distance (usually less than half the grid spacing) of the original point. Many of the statistical techniques used in the analysis of data from surveys of continuous media fall into a category called geostatistics. For sample surveys involving random selection of sampling units, the statistical procedures are usually formed on a probability base provided by the randomization, while in geostatistics, the statistical inferences are based on what is known as a random field model. In general terms, geostatistics is an application of classical statistical theory to geological measurements that takes into account the spatial continuities of geological variables in estimating the distribution of variables. In

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many ways, geostatistics is for measurements taken in two-, three-, and four-dimensional space (the three spatial dimensions and the time dimension), what a time series is for measurements taken in one-dimensional space, time. However, a principal use of time series is in forecasting; in geostatistics, the principal emphasis is on interpolation. 10.7.4 Device Selection Criteria The selection of a sampling device and sampling procedures requires the consideration of many factors including

the number of samples to be collected, available funds, soil characteristics, site limitations, ability to sample the target domain, whether or not screening procedures are to be used, the size of sample needed and the required precision and accuracy as given in the DQOs. The number of samples to be collected can greatly affect sampling costs and the time required to complete a site characterization. If many subsurface samples are needed, it may be possible to use soil-gas sampling coupled with on-site analysis as an integrated screening technique to reduce the area of interest and thus the number of samples needed. Such a sampling approach

Figure 10-18 Soil Sampling Design 724

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may be applicable for cases of near-surface contamination. Ultimately, the sampling, sample handling, containerizing and transport of the soil sample should minimize losses of volatiles and should avoid contamination of the sample. Soil sampling equipment should be readily decontaminated in the field if it is to be reused on the job site. Decontamination of sampling equipment may require the use of decontamination pads that have impervious liners, wash and rinse troughs and careful handling of large equipment. Whenever possible, a liner should be used inside the sampling device to reduce potential cross contamination and carryover to other sampling points. Decontamination procedures take time, require extra equipment and ultimately increase site characterization costs. Ease and cost of decontamination are thus important factors to be considered in device selection. Several soil-screening procedures are in use that include headspace analysis of soils using organic vapor analyzers: water (or NaCl-saturated water) extraction of soil, followed by static headspace analysis using an organic vapor analyzer (OVA) or gas chromatograph (GC); colorimetric test kits; methanol extraction followed by headspace analysis or direct injection into a GC; and soil-gas sampling (U.S. EPA, 1988a). Field measurements may not provide absolute values but often may be a superior means of obtaining relative values.

10.7.5 Soil and Site Characteristics The facility setting may have important controls on the methods and techniques used in the soil sampling program. For example, the remoteness of a site and the physical setting may restrict site access; factors as vegetation, steep slopes, rugged or rocky terrain, overhead power lines or other overhead restrictions and lack of roads can also contribute to access problems. The presence of underground utilities, pipes, electrical lines, tanks and leach fields can also affect selection of sampling equipment. If the location or absence of these hazards cannot be established, it may be desirable to conduct a nonintrusive survey of the area and select a sampling approach that minimizes hazards. For example, for shallow small-scale soil sampling hand tools and a backhoe are more practical than a large, hollow-stem auger. The selection of a sampling device may be influenced by other contaminants of interest such as pesticides, metals, semivolatile organic compounds, radio nuclides and explosives. The presence of ordnance, drums, concrete, voids, pyrophoric materials and high-hazard radioactive materials may preclude some sampling and may require development of alternate sampling designs or even reconsideration of project objectives.

The characteristics of the soil material being sampled have a marked effect upon the selection of a sampling device. An investigator must evaluate soil characteristics, the type of VOCs and the depth at which a sample is to be collected before selection of a proper sampling device. Specific characteristics that must be considered are: 1. Is the soil compacted, rocky or rubble filled? If the answer is yes, then either hollow-stem augers or pit sampling must be used. 2. Is the soil fine grained? If yes, use split spoons, Shelby tubes, liners or hollow-stem augers. 3. Are there flowing sands or water-saturated soils? If yes, use samplers such as piston samplers that can retain these materials.

10.7.6 Important Soil Characteristics in Site Evaluations Soil pH: A quick check using a field test kit can identify if the pH of the soil is in a range to mobilize contaminants. In acid soils (pH 1 and C/CS parachor (Pr) >> other methods. • The foc, Kow, S and pr and other property values for the contaminant/soil system should fall within the range of values used to derive the selected regression equation for estimating a Koc. Often, experimentally derived values for Koc are unavailable in the literature and partition-based empirical

737

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Table 10-6 Examples of Regression Equations

also adapted from Lyman et al. (1982), lists the parameters required for each equation, the range of values for each parameter and the range of Koc values calculated with each equation. Regression equation selection has been recommend by Lyman et al. (1982) using as a basis data available about the chemical, the chemical classes covered by each regression equation and the range of Koc and input parameter values covered by each regression equation. In general terms the following points should be considered in the evaluation process: • One should always place the highest priority on the most accurate data from actual measurements. • If data are available for all equation input parameters, a regression equation using Kow is preferred to an equation using S. • If one must make election of a regression equation on the basis of chemical classes, high priority should be given to the equation which was derived from the same chemical class as the chemical being modeled. However, if there is no clear match of chemical classes, Lyman et al. (1982) suggest using Equations 10-1 or 10-4 or Table 10-6 because they are derived from the widest variety of chemicals. • Selection of a regression equation on the basis of the range of Koc and input parameter values, the values should be within the range originally covered by the regression equation.

regression estimates of Koc have been used. A large array of regression equations are found in the literature (Lyman et al., 1982; Bednarz et al., 1983; Dragun, 1988). The reliability of the theoretical method for calculating the adsorption coefficient depends on several factors. Regression equations are experimentally derived from a specific data set that represents particular classes of chemicals and ranges of parameters. The reliability of the Koc value is directly related to the correlation between the dataset of the model and the dataset from which the regression equation was derived. Therefore, care must be taken when selecting a regression equation. Also, the regression equation method is only valid in porous media with greater than 0.1% organic carbon content (Lyman et al., 1982). Regression equation methods consider organic carbon as the primary adsorbent; however, below an organic carbon content of 0.1%, inorganic surfaces are the dominant adsorbent (Pennington, 1982). Table 10-6, adapted from Lyman et al. (1982), includes examples of various regression equations, the source of each equation and the classes of organic chemicals for which each equation was derived. Table 10-7,

738

• The use of the parameter values or estimation of Koc values outside the range Or the original dataset will subject the estimated Koc and, therefore, the estimated retardation coefficient, to greater uncertainty. • Selection of a regression equation to estimate a Koc should be based on the dataused to derive the regressions and the contaminant’s chemical properties. • The value of the chemical property on which the selected regression equation is based should be the most accurate value available. • If chemical property values are equally accurate then the order of preference would be Kow * 5 > pr. • Regression equations derived from chemicals similar to the compound in question should be used. • For an appropriate application of Koc estimation, the data used to derive the regression must encompass the case under consideration (foc, Kow, S, pr, etc.). Some of the regression equations have been experimentally derived from high foc content and low contami-

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nant concentrations; and may not be applicable for Koc estimations at high concentrations typically encountered in contaminated soils.

Table 10-7 Parameters for Regression Equations

Estimation of Koc from Kow (n-octanol/water) Partition Coefficient The n-octanol/water partition coefficient (Kow) has often been used to estimate Koc values for estimating adsorption. The common method for determining the partition coefficient is by mixing the chemical in a two-phase octanol/water system and determining the concentrations in one or both phases at equilibrium. Reverse-phase high performance liquid chromatography (HPLC) has also been used to determine partitioning based on retention values and regression with better accuracy for low concentration ranges. Examples for determining Koc from Kow are presented in Lyman et al. (1982) and Dragun (1988), who also list many of the regression equations. The next step in this process is the determination of Koc. This is usually accomplished using an equation with the general form: Log Koc = alog (Sw or Kow) + b

Equation 10-17

where: Sw = aqueous solubility of a compound Kow = octanol water partition coefficient (ratio of concentration of solute in octanol phase to concentration of solute in aqueous phase) a = slope on log-log plot b = minimum value of log Koc (intercept of log-log plot) Many studies of various chemical groups have been conducted. Karickhoff et al. (1979) related Koc to the octanol water partition coefficient and to the water solubility by the following relationships: Koc = 0.63 Kow

Equation 10-18

Koc = 0.54 log Sw + 0.44

Equation 10-19

and

where: Sw = aqueous solubility of a compound (expressed as a mole fraction). The water solubilities of the compounds examined ranged from 1 ppb to 1000 ppm. Hassett et al. (1980) found a similar relationship between Koc and Kow for organic

energy-related pollutants. Figure 10-20 shows the data relationships from both these studies. Chiou et al. (1979) also investigated the relationship between octanol water partitioning and aqueous solubilities for a wide variety of chemicals including aliphatic and aromatic hydrocarbons, aromatic acids organochlorine and organophosphate pesticides and polychlorinated biphenyls. Their results, shown in Figure 10-21, cover more than eight orders of magnitude in solubility and six orders of magnitude in the octanolwater partition coefficient. The regression equation based on these data is: log Koc = -0.670 log Sw + 5.00

Equation 10-20

where: Sw = aqueous solubility of a compound, in mmol/l Brown and Flagg (1981) have extended the work of Karickhoff et al. (1979) by developing an empirical relationship between Kow and Koc for nine chloro-s-triazine and dinitroaniline compounds. They plotted their results, along with those of Karickhoff et al. (1979), as shown in Figure 10-21. The combined dataset produces the following correlation: log Koc = 0.937 log Kow -0.006

Equation 10-21

The correlation between Koc and Kow for the compounds studied by Brown and Flagg (1981) has a larger factor of uncertainty than those studied by Karickhoff et al. (1979). The octanol water partition coefficient and the solubility of an organic compound are generally available or may

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equation correlations with structural activity relations (SARs) using chemical fragments or physical properties such as solubilities constants (aqueous solubility and parachor) are the most dominant. Additionally, specific regressions are available relating Kow to Koc to estimate adsorption. Estimation of Koc from Solubility (S) A wide variety of regression equations have been formulated relating aqueous solubility (S) of an organic compound to a Koc value. In these equations, solubility has been expressed in various forms (mol/L ppm or mole fraction). The most extensive list of organic chemical Koc values determined by solubility regressions and from experimental data is from Kenaga (1980). The reader should be aware that cited solubility values can have a wide range per compound and should be used with care. Examples are presented for many of the regression equations, listed in Lyman (1982) and Dragun (1988). Figure 10-20 Relationship between Koc and Kow for a Coarse Silt be calculated. Leo et al. (1971) have compiled a list of octanol water partition coefficients. For organic compounds, Verschueren (1983) provides many common properties. Lyman et al. (1982) provide methods of calculating solubilities and octanol water partition coefficients. A wide variety of methods are available in the literature for estimating Kow for organic chemicals based on chemical structures or physical properties. Regression

Estimation of Koc from SARs (Structure Activity Relationships) When Kow and Koc partitioning information and solubility are unavailable, chemical structure activity relationships (SARs) have been used to estimate adsorption. These estimation techniques are based on structural parameters and are not considered as reliable as partitioning information. Substituting constants such as p constants and hydrophobic fragments and other structural activities such as molecular conductivity indices and parachor properties

Figure 10-21 Correlation of Aqueous Solubility with Octanol Water Partition Coefficient

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ASSESSMENT MONITORING DESIGN

have been used to estimate Koc. Parachor estimation techniques are the most dominant method. Inorganic Elemental and Ionic Compounds Adsorption Estimation Though adsorption to organic material dominates total soil sorption for low solubility organic compounds for soils with greater than 1% organic material, clay mineral (illite, illite/montmorillonite, saprolite, vermiculite, chlorite, kaolinite, halloysite, etc.) and zeolite mineral adsorption usually dominates for inorganic compounds, cationic species and ionically charged organic compounds, irrespective of the soil. This adsorption process is pH dependent because cation exchange and protonation are pH dependent. Generally, as pH increases, the adsorption of heavy metal cations such as Pb2+, Cd2+, Zn2+, Cu2+, Hg2+ and Cr6+ increases and adsorption decreases for Cr6+, As3- and Se4-. Ionic organic compound adsorption may also be pH dependent. Ionic organic compound sorption is dependent on whether the compound is an acid or a base and the affinity of the ionic form for organic sites relative to the affinity of non-ionic form for lipophilic sites. Other factors that influence the adsorption of cationic species and organic ionic molecules are moisture content, fixation as insoluble complexes, selective competition and ionic strength of soil pore water. Clay particles and clay minerals with high cation exchange capacities (CECs) have been shown to have high adsorption capabilities for cationic species. There is a preferential order of ion replacement progressing from higher valence state to lower. Organic material also demonstrates some ionic exchange capabilities. CEC determinations are usually total soil determinations without segregation of effective sorbents. Bonazountas and Hartge (1984) and many other sources, document a method based on soil CEC determinations (uncontaminated) and the mass and valence of contaminant compound for estimating the maximum soil concentration of contaminants. This method does not consider pH, redox and complexation affects and may only serve as a gross approximation of maximum adsorption. Additionally, CEC determination methodologies have inherent problems in design such as carbonate mineral effects and incomplete ion exchange with some clay minerals. 10.9 SOIL-GAS SURVEYS Soil-gas measurements have particular relevance to soil contamination by organic product spills and can serve a

variety of screening purposes in soil sampling and analysis programs, from initial site reconnaissance to remedial monitoring efforts. Soil-gas measurements should be used for screening purposes only and not for definitive determination of soil-bound VOCs. Field analysis is usually by handheld detectors, portable GC or GC/MS, infrared detectors, ion mobility spectrometers (IMS), industrial hygiene detector tubes and fiber optic sensors. Soil-gas measurements may several potential applications. Summarized in Table 10-4, these include in situ soilgas surveying, measurement of headspace concentrations above containerized soil samples and scanning of soil contained in cores collected from different depths (see Figures 10-4a, 10-4b and Table 10-5). Currently, no standard protocols exist for soil-gas analysis; many investigators have devised their own techniques, which have varying degrees of efficacy. Independently, the American Society for Testing and Materials (ASTM) and U.S. EPA EMSL-LV are preparing guidance documents for soil-gas measurement. The required precision and accuracy of site characterization, as defined in the DQOs, affect the selection of a sampling device. Where maximum precision and accuracy are required, sampling devices that collect an intact core should be used, particularly for more volatile VOCs in nonretentive matrices. Augers and other devices that collect highly disturbed samples and expose the samples to the atmosphere can be used if lower precision and accuracy can be tolerated. Collection of a larger number of samples to characterize a given area, however, can compensate for a less precise sampling approach. The closer the expected contaminant level is to the action or detection limit, the more efficient the sampling device should be for obtaining an accurate measurement. Soil-gas surveys can provide relatively rapid and cost-effective site data that can help direct more costly and invasive techniques. Although they are typically performed early in the expedited site assessment (ESA) process, soil-gas surveys can also be used to monitor underground storage tanks (USTs) for releases, to evaluate remediation effectiveness and to assess upward migration of vapors into buildings for risk assessments. Two basic types of soil-gas surveys are commonly performed during UST site assessments. The first type is the active soil-gas survey in which a volume of soil gas is pumped out of the vadose zone into a sample collection device for analysis. The second type is the passive soilgas survey in which a sorbent material is left in the ground so that contaminant vapors can be selectively adsorbed over time using the ambient flow of soil gas. Active soilgas surveys can be completed in as little as one day and are most commonly used for sites with volatile organic

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Table 10-8 Vapor Pressure and Henry’s Law Constant of Various Organic Compounds At 20o C Compound

Vapor Pressure (mm Hg)

Compound

Henry’s Law Constant (dimensionless)

n-Butane

1560

n-Hexane

36.61

Methylt-butyl ether

245

n-Butane

25.22

n-Hexane

121

Ethylbenzene

0.322

Benzene

76

Xylenes

0.304

Toluene

22

Toluene

0.262

Ethylbenzene

7

Benzene

0.215

Methyl-butyl ether

0.018

Naphthalene

0.018

Xylenes Naphthalene

6 0.5

* Values above dotted line indicate active active soil-gas sampling methods are appropriate.

compounds (VOCs). Passive soil-gas surveys take several days or weeks to complete and are most useful where semivolatile organic compounds (SVOCs) are suspected or when soils prevent sufficient air flow for active sampling. This section provides a discussion of soil-gas principles affecting soil-gas surveys, the applicability and the essential elements of both active and passive soil-gas surveys and case studies illustrating the effective use of both soil-gas surveying methods. Details on soil-gas sampling equipment are provided in Chapter 4. Applicability of Soil-Gas Sampling In order to understand the applicability and design of soil-gas surveys, it is important to first understand the parameters that control the migration of contaminants through the vadose zone. The primary controlling parameters are the physical and chemical properties of the contaminant, the site geology and biological processes. This section contains brief descriptions of these parameters, how they affect various contaminants and how they relate to the applicability of active and passive soil-gas sampling. Physical and Chemical Properties of Hydrocarbons To assess whether soil-gas sampling is applicable to characterize subsurface contamination at a UST site, the

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potential for the contaminant to be present in the vapor phase first needs to be evaluated. Petroleum products stored in USTs, such as gasoline, diesel fuel and kerosene, are complex mixtures with more than 100 different compounds, each with a different degree of volatility. Therefore, individual constituents must be assessed independently. The degree to which a chemical will partition into the vapor phase is primarily controlled by the compound's vapor pressure and its Henry’s law constant. Vapor Pressure Vapor pressure is one of the most important constituent characteristics for determining if a particular hydrocarbon can be detected as a gas in the source area. The vapor pressure of a constituent is a measure of its tendency to evaporate. More precisely, it is the pressure that a vapor exerts when it is in equilibrium with its pure liquid or solid form. As a result, the higher the vapor pressure of a constituent, the more readily it evaporates into the vapor phase. As a general rule, vapor pressures higher than 0.5 mm Hg are considered to be detectable with active methods. Occasionally, constituents with lower vapor pressures can be detected, but the soil concentrations must be high and the geological formation should be permeable. If the contaminant is dissolved in ground water or soil moisture, Henry’s law constant must be considered along with the vapor pressure to determine the potential for detection (see below). Table 10-8 lists the vapor pressures of selected petroleum constituents. Gasoline contains a number of hydrocarbons that have sufficient vapor pressures to be easily sampled with active soil-gas surveying methods. Jet fuel diesel fuel and kerosene contain SVOCs that can be actively sampled only under optimal conditions. Lubricating and waste oils contain mainly low volatility compounds and cannot be directly sampled through active methods. Passive sampling methods, which are more successful in detecting SVOCs, may be successful in detecting some low volatility compounds. Henry’s Law Constant (Water to Vapor Partitioning). Henry’s law constant is a measure of a compound’s tendency to partition between water and vapor. This constant can be used to estimate the likelihood of detecting a constituent in the vapor phase that had dissolved in soil moisture or ground water. There are several ways to express this constant, but the most useful way is in the

ASSESSMENT MONITORING DESIGN

dimensionless form. Henry’s law constant can be obtained by dividing the equilibrium concentration of a compound in air with the equilibrium concentration of the compound in water (at a given temperature and pressure). Because the units on both values are the same, the resulting constant is dimensionless. Compounds with a greater tendency to exist in the vapor phase have a Henry’s law constant greater than 1, compounds with a greater tendency to exist in water have a Henry’s law constant less than 1. Henry’s law constants for several common constituents found in petroleum products are shown in Table 10-9.

Degree of saturation < 80%

vapor phase. Consequently, if equal volumes of alkanes and aromatics have been spilled on a site, in the source area alkanes will be found in much higher concentrations in the soil gas. However, because alkanes partition out of the dissolved phase to a greater extent, aromatics are more likely to provide an indication of dissolved contaminant plumes. In addition, vapor phase concentrations of compounds such as methyl tert-butyl ether (MTBE) or naphthalene will not be useful indicators of contamination in soil gas outside the source area because they tend to remain dissolved in water. In general, compounds with Henry’s law constants greater than 0.1 are considered to be detectable with active soil-gas sampling if the vapor pressure is also sufficient and geologic conditions are favorable. Constituents with slightly lower values may also be detectable if initial concentrations are high. Passive soil gas techniques are able to detect compounds with lower Henry’s law constants; however, a precise limit of detection cannot be estimated because site conditions, exposure times and product sensitivities will vary.

Sampling zone is free of clay

Geologic Factors

Table 10-9 Summary of General Active Soil-Gas Sampling Criteria

Vapor pressure > 0.5 mm Hg Henry’s law constant > 0.1

Notice that alkanes (chained hydrocarbons [e.g., butane, hexane] commonly found in gasoline) have Henry’s law constant values two orders of magnitude greater than aromatics (ringed hydrocarbons [e.g., benzene, toluene]). In a state of equilibrium, 36 molecules of hexane will exist in the vapor phase for every molecule of hexane dissolved in water. For every five molecules of benzene dissolved in water, only one will be found in the Table 10-10 Advantages and Limitations of Passive Soil-Gas Sampling Advantages

Limitations

A wide range of VOCs, SVOCs, and low volatile mixtures can be detected.

The data cannot be used to estimate contaminant mass.

More effective than active sampling in low permeability and high moisture soils.

The vertical distribution of contaminants is typically not assessed.

From 40 to 100 devices can be installed in a day.

The time required to collect and analyze samples is typically 3 to 6 weeks.

There is minimal disturbance to subsurface and site operations.

Sorbent desorption may destroy some compounds.

Easy to install.

Measurements are time weighted and are not directly comparable to soil and groundwater laboratory methods. Impervious layers and changes in the thickness of clay layers can create misleading information.

The most important geologic factor in the movement of soil gas through the vadose zone is soil permeability, a measure of the relative ease with which rock, soil or sediment will transmit a gas or liquid. Soil permeability is primarily related to gain size and soil moisture. Soils with smaller gain sizes and hence smaller pore spaces are less permeable. Clays having the smallest grain size significantly restrict soil vapor migration. Soil moisture decreases permeability because moisture trapped in the pore space of sediments can inhibit or block vapor flow. Because soil moisture content varies seasonally and geographically, effective air permeabilities are often unknown prior to sampling. For active soil-gas surveys, soil-air permeability testing should be conducted in vertical profiles at select locations in order to optimize sampling depth. For passive soil-gas surveys, soil-air permeability is important but usually not determined because additional equipment is required. In addition, several other soil factors can create misleading information about the location of contamination. Preferential pathways (e.g., tree roots, soil cracks, utilities, backfill) and vapor impervious layers (e.g., clay layers, foundations, buried pavement, perched ground water) are features that should be evaluated. Moreover, adsorption of hydrocarbons on soils with high percentages of clay or organic matter can limit partitioning of contaminants into the vapor phase. Although active soil-gas sampling is applicable for all soil types except tight clays, it is generally ineffective

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when the soil moisture is above 80 to 90% saturation (Corey, 1986) because of the absence of connected airfilled pores. High soil moisture conditions can be overcome with sampling procedures (e.g., minimizing sample volume, increasing the air volume around the tip, waiting for equilibrium to take place), but these procedures can often be very time consuming. Passive soil-gas sampling is generally useful in all soil types and conditions; however, sediments with low intrinsic permeabilities and high degrees of saturation can affect both the quantity of contaminants coming into contact with the sampler and the quantity of contaminant that is adsorbed. For example, the presence of a dense moist clay lense will reduce the amount of vapor that contacts a sampler directly above it. In addition, Werner (1985) demonstrated that activated carbon, a common soil-gas adsorbent, will adsorb significantly less TCE with increasing relative humidity levels. Other contaminants may, therefore, also be adsorbed to a lesser degree under humid conditions. Although passive soil-gas sampling remains more sensitive to contaminant detection than active soil-gas sampling under low permeability and high humidity, geologic heterogeneities in the subsurface can also affect passive soil-gas results. Biodegradation Biodegradation of VOCs in the vadose zone can reduce the ability to detect the contaminants in soil gas. Petroleum hydrocarbons are readily degraded by microorganisms to produce increased levels of numerous gases (e.g., carbon dioxide, hydrogen sulfide, methane) while decreasing the concentration of oxygen. The rate of biodegradation is controlled by several factors, including soil moisture content, concentration of electron acceptors (e.g., oxygen), available nutrients in the soils, contaminant type and soil temperatures. Sampling for soil gases affected by biodegradation (e.g., oxygen, carbon dioxide, methane, hydrogen sulfide) can provide useful information about the contaminant source area and plume, provided background samples are collected in a neighboring uncontaminated area. Measurement of these parameters is most useful when active soilgas sampling is being employed and the contaminant is a semi volatile or non-volatile compound or if a volatile contaminant is known to exist but has not been directly detected. Summary Detection of individual constituents by both active and passive soil-gas sampling methods is limited by the

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physical and chemical properties of hydrocarbons. General parameters for selecting active soil-gas sampling are presented in Table 10-11. Passive soil-gas sampling methods are more sensitive than active soil-gas sampling, but individual manufacturers should be contacted for specific compounds that can be detected. Vapor pressure and Henry’s law constant are indicators of the potential of a method to detect a specific constituent. For active sampling, the vapor pressure should be above 0.5 mm. Hg. If contamination is dissolved in soil moisture or ground water, the Henry’s law constant should also be above 0.1. Geologic factors (e.g., clay layers, high soil moisture content) will affect both active and passive sampling capabilities, but passive sampling will generally provide more sensitive results under these conditions. In addition, the by-products of biodegradation can provide valuable information in active soil-gas sampling for indirect detection of contaminants. Active sampling may still be useful for the indirect detection of contaminants below these vapor pressure and Henry’s law constant values. 10.9.1 Active Soil-Gas Sampling Methods Of the two soil-gas sampling methods, active and passive active soil-gas sampling is the method typically used for site investigations where VOCs are the primary constituents of concern. This method allows for rapid soil-gas collection from specific depths by analyzing soil gas that has been pumped from the ground through probe holes. The samples are typically analyzed on-site so that realtime data can be used to direct further sampling. VOCs can be detected directly with soil-gas sampling methods, while SVOCs and low volatility organic compounds may be detected indirectly through the measurement of gases (O2, COD H2S, CH4) influenced by biogenic processes. Active soil-gas surveying was initially utilized by the oil industry in the 1960s to monitor gas control systems, track gas migration off-site and evaluate resources. It was first applied to VOC site assessments in the early 1980s and rapidly gained popularity as a screening tool to detect and delineate subsurface contamination. Samples are collected by inserting a sampling device into a borehole, usually with a slam bar, a direct push system or a hollow-stem auger. Most sampling devices consist of screens or ports that are pushed directly into the ground or inserted through the insides of drill rod or pipe. Soil gas is drawn through the port or screen through plastic (primarily polyethylene or TeflonTm) or metal tubing and into a collection vessel using a vacuum device. The port or screen, tubing, sample vessel and vacuum source are collectively referred to as the “sample train.” For a

ASSESSMENT MONITORING DESIGN

more detailed discussion of soil-gas sampling equipment refer to Chapter 4, subsection on Direct Push Technologies. As active soil-gas sampling has evolved and become more cost effective through the application of direct push technology, on-site analysis of soil-gas samples by mobile laboratories utilizing transportable gas chromatographs has become more common. Mobile laboratories provide quantitative chemical data with rapid turnaround time and do not necessitate the packaging and shipping of samples. Other useful pieces of analytical equipment include total organic vapor detection instruments, such as photo ionization detectors (PID) and flame ionization detectors (FID), field portable gas chromatographs and detector tubes. Assessment objectives must be considered in the selection of analytical methods because capabilities and limitations are extremely variable. Applications for Active Soil-Gas Sampling Active soil-gas sampling can be an important aspect of an ESA because it provides the ability to assess many different aspects of a site in a short period of time, typically in 1 to 3 days. Active soil-gas sampling can help the investigator:

to provide a three-dimensional conceptualization of the contaminant distribution and allows for calculation of upward and downward contaminant fluxes. Active Soil-Gas Survey Design Although active soil-gas surveys are a rapid and effective way to focus subsequent assessment methods, several procedures are needed to ensure that the data provided are valid. The following section describes some of the essential elements required for a successful active soil-gas survey. Review Existing Site Information Investigators should review and evaluate existing site information in order to make an initial determination of the applicability of active soil-gas sampling (refer to previous section). If active sampling is appropriate, this information will also help the investigator select sampling locations. Information to be reviewed may include: • Type of contaminant and suspected release mechanism (e.g., spills, leaks) • Estimates of volume of contaminant discharged

• Identify releases.

• Length of time contaminant has been present

• Identify sources of contaminants.

• Stratigraphy of the site

• Identify the types of VOCs present in the vadose zone.

• Depth of ground water, direction and rate of flow

• Provide an indication of the magnitude of VOC and SVOC contamination.

• Map of site facility with subsurface structures (e.g., tanks, sewers, piping, wells)

• Infer contaminant distribution of SVOCs and low volatility organic hydrocarbons by measuring indicators of biodegradation.

• Reports of site inspectionsf

• Optimize the placement of soil borings and monitoring wells. • Monitor potential off-site sources. • Collect data that could be useful in the design of soil vapor extraction (SVE) or bioventing systems. • Assess the potential for upward migration of vapors in buildings. • Monitor the effectiveness of remedial systems. One major advantage of active soil-gas sampling is that data can be collected from discrete depths for vertical profiling of contaminant concentrations and relative air permeabilities in the vadose zone. This information helps

Preliminary Measurements For Soil-Gas Sampling Three conditions should be assessed prior to sampling to determine how soil-gas samples should be extracted and to ensure that the samples are representative of subsurface conditions: relative soil-air permeability, purge volume and rates and subsurface short circuiting. Relative Soil-Air Permeability Testing Relative soil-air permeability can help to assess the influence of geologic materials and the moisture content at the locations tested. An estimate can be calculated by comparing airflow data with the corresponding vacuum pressure or more accurately by using a pressure

745

ASSESSMENT MONITORING DESIGN

transducer. Low-permeability zones should be identified to help interpret the data. Purge Volume and Rates Prior to initiating sampling at a site, tests should be conducted to optimize the purge volume and rates. Generally, these tests should be conducted in various soil types encountered at the site and in the areas of suspected elevated VOC concentrations. The tests are performed by varying the purge volume and rates at a single location while samples are being taken. Optimal sampling conditions occur when contaminant concentrations stabilize. Subsurface Short-Circuiting Purge volume and rate tests should also be used to check for subsurface short-circuiting with the aboveground atmosphere. This condition is indicated when contaminant levels decrease rapidly or when atmospheric gases (e.g., atmospheric oxygen levels) are detected. Sometimes indicator VOCs (e.g., pentane) are placed on a rag near the probe hole. In order to prevent short circuiting, it is important to seal the probe hole, typically with wet bentonite. In addition, the drive point should not be larger than the diameter of the probe because the open space created by the drive point would provide a conduit for atmospheric gases to travel. Initial Sampling Initial sampling points are usually located in potential source areas. The proposed sampling locations should be located on a facility map with subsurface structures noted. Additional sampling points need to be considered along possible conduits (e.g., sewer lines, trenches, utility vaults, pipelines) where contaminants may preferentially migrate. Sampling may also be organized along a standard orthogonal grid. Sampling Depth The depth of sampling will vary depending on the depth to ground water and the stratigraphy of the site. Active soil-gas sampling in a vertical profile is necessary to determine the permeable horizons and vertical contaminant distributions. Initial profiles should be completed in known or suspected source areas and in areas where elevated VOCs are detected. If liquid-phase hydrocarbon delineation is the objective, soil-gas surveys should be collected just above the watertable.

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Sample Spacing Sample spacing depends primarily on the objectives of the investigation, the size of the site and the size of potential contaminant sources. At 1- or 2-acre USTs sites, initial spacing is generally between 10 and 50 ft. When trying to track down the source at a major industrial site, spacing may be as great as 400 or 500 ft. Sufficient soil-gas data from shallow and deeper vadose zone horizons should also be collected to provide a three-dimensional distribution of the contaminants. The spacing between vertical samples depends primarily on the depth to ground water and the objectives of the investigation. Data should be integrated into maps and contoured in the field to determine if additional sampling locations are necessary. As a general rule, if two sampling points have a two- to three-orders of magnitude change, samples should be collected in the area between the two points. Sample Containers There are four commonly used sample containers, each with different advantages and limitations. Stainless steel canisters are durable, but they can be difficult to decontaminate. Glass bulbs are easy to decontaminate, but they are breakable and may have leakage through the septa. Tedlar bags are easy to handle and leakage is readily apparent, but some contaminants may sorb onto the bag (for the primary gasoline constituents, however, this is not a problem). Syringes are inexpensive and allow for easy collection of samples, but they have short holding times and are difficult to decontaminate. Although no sampling container is perfect, problems are minimized by analyzing samples as soon as possible after collection. Quality Assurance/Quality Control Procedures Numerous QA/QC procedures must be undertaken during an active soil-gas survey to ensure that the samples are representative of subsurface conditions. The following list is not comprehensive for all site conditions or equipment; rather, it contains the primary issues that regulators should check when they evaluate active soil-gas survey reports. All soil-gas surveys should be collected following the same procedures. Sampling should be completed in a relatively short period of time (e.g., hours, days) because temporal variations such as temperature, humidity, barometric pressure and rain can affect contaminant concentrations. Decontamination procedures should be practiced to prevent contaminant gain or loss that results from adsorption onto sampling equipment.

ASSESSMENT MONITORING DESIGN

The insides of the sample train components should be as dry as possible because water can raise or lower contamination values. Ambient air present in the sample train must be purged prior to sample collection. When sampling directly through probe rods, the sample train connections should be checked prior to collecting each sample to ensure they are air-tight. Annular space between the side of the borehole and the installation device (e.g., probe rod) should be sealed at the ground surface with a bentonite paste or similar material. Blank samples should be tested regularly to ensure that decontamination procedures are adequate and to determine background VOC levels. Duplicate soil-gas samples should be collected each day (generally 1 for every 10 samples) to assess the reproducibility of the data. Sample containers should be monitored for leakage.

benzene) to total VOCs to determine the relative length of time a contaminant has been present. Since the pre-benzene constituents of gasoline migrate more rapidly than other hydrocarbons, a relatively high ratio will indicate a more recent release while a low ratio will indicate an older release. Because there are many factors that affect the absolute ratio, the ratios can only be used to compare multiple releases at a single site. An additional issue that is important for interpretation of results is analysis of the units of measurement. Commonly, two types of units are used for reporting soil-gas data: volume per volume (e.g., ppm or ppb or mass per volume (e.g., gg/L or mg/mL). Although for water, gg/L is equivalent to ppb, this is not true for gases. If concentrations are reported in gg/L, a conversion may be required. For samples analyzed at 200C and 1 atm. pressure:

Interpretation of Active Soil-Gas Data

2.447 × 10 ppbv = mg/L* -----------------------------------------------------------------molecular weight of the gas

A thorough understanding of the capabilities of the active soil-gas sampling methods and the site conditions is necessary for avoiding over interpretation of the soil-gas survey results. Soil-gas concentrations must be compared with stratigraphic and cultural features in order to determine how soil-gas migrates and how contaminants are distributed. Subsurface barriers (e.g., clay lenses, perched ground water, infrastructure, buildings) and secondary pathways (e.g., utility trenches, animal burrows) can cause soil-gas distribution to be significantly different than soil and ground-water contamination. As a result, stratigraphic cross-sectional maps should be used to evaluate vertical concentrations. Trends noted should be evaluated to assess whether they are associated with soil types, chemical migration, influence of diffusion from ground water, potential preferential pathways or obstructions. Interpretation of the soil-gas data should begin in the field. Posting the data on a site map as the results are reported will help to direct and refine the sampling program. The final results of the soil-gas survey are usually presented in maps showing contours of gas concentrations at various subsurface depths. Sample depths should be corrected for site elevation changes so that the contour represents a horizontal layer. By creating several horizontal contours, data can be analyzed in three dimensions. Plotting total VOCs is often the easiest method, but it is important to evaluate if differing sources exist by examining the distribution of individual constituents. An example of this type of analysis is the use of the ratio between prebenzene hydrocarbons (i.e., constituents that pass through a gas chromatograph column prior to

4

Equation10-22

Active Soil-Gas Surveys Because the sampling and analytical equipment used in active soil-gas surveys varies considerably according to site conditions, survey objectives and investigator preferences, the cost will also vary considerably. Most soil-gas surveys are performed using direct push (DP) technology. The cost of collecting active soil-gas surveys with truckmounted DP ranges from $1,000 to $2,000 per day. In some cases, DP can be deployed manually, which may be less expensive. Typically, 10 to 30 samples can be collected per day depending primarily on soil type, sampling depths and sampling method. Numerous field analytical methods are applicable for soil-gas surveys; however, portable and transportable gas chromatographs are most common because of their high data quality level capabilities. Samples are rarely sent off-site to a fixed laboratory because on-site information is often used for determining subsequent sample locations and delays in analysis can affect data quality. Active soil-gas survey sampling can be completed in as little as 1 day at a 1-acre site and should rarely require more than 3 days. As a result, the cost of a complete soil-gas survey with a report will typically range from $3,000 to $15,000. A summary of the advantages and limitations of active soil-gas surveys is presented in Table 10-11. 10.9.2 Passive Soil-Gas Sampling Methods Of the two soil-gas sampling methods (active and passive) soil-gas sampling techniques are typically used

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ASSESSMENT MONITORING DESIGN

when SVOCs or low volatility compounds are the primary constituents of concern. Passive soil-gas surveys utilize probes that are placed in the ground for days or weeks to adsorb soil-gas constituents on sorbent material using the ambient flow of vapors in the subsurface. After the probe is removed from the ground, it is sent to a laboratory where contaminants are desorbed and analyzed. An example of a passive soil-gas sampler is presented in Figure 10-22.

Table 10- 11 Advantages and Limitations of Active Soil-Gas Sampling Advantages

Limitations

Samples can be analyzed on site for "real time" data reporting.

Not effective for identifying SVOCs or low volatility compounds.

Extensive QA/QC must be From 10 to 30 samples can typically be collected and analyzed followed. per day.

Applications for Passive Soil-Gas Sampling

Can delineate contaminant source Cannot be easily conducted in area and plume of VOCs. very low permeability or saturated soils.

Passive soil-gas surveys are not considered an expedited site assessment method because of the extended time required to collect and analyze the data. However, in certain applications, the passive devices may be used as a screening tool to help determine the soil and ground-water sampling location needed to complete a site assessment. Generally, passive sampling is most applicable when SVOCs are a primary concern, when numerous unknown compounds are suspected (e.g., a Superfund site) or when subsurface conditions do not permit adequate penetration with DP methods for active soil-gas sampling. Capabilities of passive soil-gas surveys include providing an initial screening at very large sites; screening the site for potential leakage from a UST or product line; providing data on the types of contaminants present in the vadose zone, including a wide range of VOCs, SVOCs and complex mixtures; providing information the lateral distribution of contaminants in the vadose zone; identifying sources of contaminants; and tracking a ground-water plume.

SVOCs and heavy petroleum product contamination can be inferred indirectly by measuring products of biodegradation.

Analytical equipment selected may not be capable of identifying all constituents present.

Passive Soil-Gas Survey Design The specific survey design will vary between sites for a number of reasons including the size of the site, the survey objectives and the capabilities of the sampler; however, some generalities can be presented. Sampling devices are placed just below the surface (between 3 in. and 4 ft) and can be quickly installed (between 2 and 15 minutes per device). A grid design is used because all sampling devices are analyzed at the same time (i.e., analytical results do not affect sampling locations). The number of samples and their spacing vary but, in general, 15 to 30 samples are sufficient for a 1- to 2-acre gasoline station survey. Sampling devices are left in the ground for 3

Soil Sampling Techniques

Sample Cap

Vacuum Pump

Filter Retaining Ring

Temperature Readout

Silicone Gasket

Vacuum Gauge

Quartz-Fiber Filter

Syringe/Canister Sampling Port

Inlet

Real Time Analyzer

Filter Support Screen

Outlet Line

Ground Surface

Filter Holder (part 2)

Section of Hollow Steel Pipe Vadose Zone

lass Cartridge etaining Screen

Expendable Point Holder Void Where Gas Vapor is Drawn From Expendable Drive Point

orbent etained Screen

Cut Away to Show Sweep Air Inlet Line and the Outlet Line

licone Gasket

Passive Tube

Suma Canister

Resin Cartridge

Figure 10-22 Example of Typical Soil-Gas Techniques

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18"

Cartridge Holder (part 1)

Water Table T

Direct Push

Stainless Steel or Plexiglas

Silicone Gasket

Flux Chamber

ASSESSMENT MONITORING DESIGN

to 21 days and then removed and typically shipped to the manufacturer’s laboratory for analysis. Individuals installing the sampling devices must ensure that contamination does not occur prior to installation or after removal. Field blanks are, therefore, a necessary check on field procedures. Interpretation of Passive Soil-Gas Data A report can usually be developed 2 to 3 weeks after removal of the sampling devices. The results are reported in the amount of contaminant detected per sorbent device. It is not possible to quantify the concentration of contaminants present in the soil gas using passive sorbent devices because the volume of gas contacting the sorbent material is unknown. The relative concentrations of analytes on the sorbent may be related more to differences in the affinity of individual VOCs for the sorbent (as well as sorbent capacity for that VOC and vapor flow rates than to the relative VOC concentrations in soil gas. In addition, passive soil-gas surveys typically collect samples from a single depth which will provide only a two-dimensional view of contaminant distribution. Usually there is not sufficient site-specific geologic information to make a judgment about the actual distribution of contaminants. For example, perched watertables may appear as clean zones and changes in the data may be related to changes in the thickness of clay layers rather than changes in subsurface contaminant concentrations. As a result, although passive soil-gas surveys are an effective screening method, interpretation of the data is more limited than active soil-gas surveys.

Table 10-12 Applications for Active and Passive Soil-Gas Designs Application Detect presence of VOCs

Active 

Passive  

Detect presence of SVOCs Infer assessment of hydrocarbon presence through the measurement of indicators of biodegradation



Identify specific compounds



Evaluate (indirectly) contaminant concentrations in soil



Evaluate 2-dimensional contaminant distribution



Evaluate 3-dimensional contaminant distribution



Evaluate remedial options



Monitor remedial system effectiveness









Cost of Passive Soil-Gas Surveys The cost of passive soil-gas surveys varies among manufacturers of sampling devices, ranging from $75 to $225 per sample (including analysis). Because analytical costs for UST sites tend to be on the low end of this range and because sampling 15 to 30 locations is typical for a 1acre site, most gasoline stations can be screened for between $1,200 and $3,000. Soil-Gas Sampling Applications Active soil-gas surveys are more appropriate than passive soil-gas surveys for most petroleum UST expedited site assessments because active soil-gas surveys provide more information, more rapidly and often at a cost that is comparable to that of passive soil-gas surveys. Data collected with active soil-gas surveys can be used immediately to direct additional sampling and analysis so that the site assessment can be completed in a single mobilization. Active soil-gas surveys also provide three-dimensional information about the distribution of contaminants and subsurface stratigraphy which allows for better interpretation of data than is possible with passive soil-gas surveys. Passive soil-gas surveys are most useful as a screening tool when SVOCs and low volatility compounds are known or suspected to be present at a site. In addition, passive soil-gas surveys may also be useful in real estate transactions because passive soil-gas surveys provide valuable screening information which can be obtained during time-consuming negotiations without more expensive, intrusive techniques. Because of their high sensitivity to contaminant vapors, passive soil-gas surveys can provide accurate information about the specific compounds present and their relative concentration in two dimensions. A summary and comparison of the applications of these two soil-gas sampling methods are provided in Table 10-12. 10.10 BACKGROUND SOIL CONCENTRATION Regulations have been based on the concept that hazardous waste sites, where toxic substances have been released may pose a threat to human health and the environment. The hazardous substances at a site may originate from either on-site (i.e., resulting from releases attributable to site-specific activities) or off-site (i.e., resulting from sources not on site). These off-site substances may result either from natural sources (e.g., erosion of naturally occurring mineral deposits) or anthropogenic sources (e.g., widespread lead contamination from auto-

749

ASSESSMENT MONITORING DESIGN

mobile exhaust in urban areas) (U.S. EPA, 1992a). To determine the appropriate action to take at a hazardous waste site, the investigator must distinguish between substances directly attributable to the hazardous waste site (i.e., site contaminants) and those attributable to natural background concentrations. Statistics play a major role in establishing background concentration levels and methods vary widely in their degree of complexity. Some general guidance is presented to acquaint the reader with issues that should be discussed with a statistician early in the design of a study. Statistics should be used throughout the development of a sampling plan in the same manner as quality assurance. Sampling objectives, design, data analysis and reporting can an be influenced by statistical considerations. Almost any investigator involved with hazardous waste site evaluations will at some time be involved in determining background concentrations of inorganics at a site. There are two issues to be considered when addressing background. The first is whether the site and local area have a high natural variability in concentrations of inorganics. The second is to differentiate between natural and anthropogenic sources at a site with high background concentrations (e.g., lead in soil due to automobile emissions). The broad range in concentrations of naturally occurring inorganics may lead to the erroneous conclusion that an area has been contaminated with inorganics. Establishment of background concentrations based on adequate site-specific sampling data and comparison to normal background ranges for a specific area and land use can help resolve the confusion. The basis for the development of the information contained in this section was taken from several different approaches to the development of background levels. The approach was developed by the U.S. EPA as reported in the Engineering Forum (1995) for the determination of background concentrations of inorganics in soils and sediments at hazardous waste sites. Additional procedures as employed by the State of Michigan (Michigan 1990, 1991b) provides one of the most straightforward and scientifically sound strategies that, in combination with U.S. EPA documents (U.S. EPA 1989a, 1989b) and scientific literature (Kabata-Pendias and Pendias, 1984), form the basis for this section. This section discusses the generic issues from various strategies that should be considered when addressing the background issue. However, information presented here may need to be modified to meet site-specific soil and sediment or data-quality objective concerns. The term background concentration is defined in this document as the concentration of inorganics found in soils or sediments surrounding a waste site, but which are not

750

influenced by site activities or releases. A background site should be a site that is geologically similar and has similar biological, physical and chemical characteristics (e.g., particle size, percent organic carbon, pH) compared to the contaminated site (ASTM, 1990) but also should be upstream, upgradient or upwind of the site. Samples taken from a site to determine background concentrations will be referred to as background samples. U.S. EPA in its Risk Assessment Guidance for Superfund: Volume 1, Human Health Evaluation Manual (Part A) (often referred to as RAGS) (U.S. EPA, 1989c) discusses two categories of background: 1. Naturally occurring substances present in the environment in forms that have not been influenced by human activity. 2. Anthropogenic-natural and manmade substances present in the environment as a result of human activities not specifically related to the CERCLA site. In some locations, the background concentrations resulting from naturally occurring or anthropogenic sources may exceed contaminant-specific standards promulgated to protect human health (U.S. EPA, 1992a). The background concentration defined in this document includes both the naturally occurring and local/regional anthropogenic contributions. Background concentrations are needed when deciding whether a site is contaminated. Knowledge of background concentrations helps address issues such as (1) the effects of past land use practices on levels of inorganics in soil and sediment and (2) establishing lower limits when conducting risk assessments for soil and sediment contamination. Determining the effect of past land use practices on levels of inorganics in soils and sediments is an important initial step toward quantifying the potential threat to human health and the environment. Information obtained from this step can provide the first indication that background concentrations may be elevated. Preliminary site investigations should be carefully planned so that high-quality data can be gathered to gain an understanding of the nature and degree of threat posed by a site and to determine whether immediate response is required. In general terms it is often best to compare mean concentrations between groups of similar samples from the hazardous waste and background sites. Mean values can be developed for a soil series or an operable unit. The operable unit is usually the smallest area that would be considered under a remediation plan (e.g., 10 in. × 10 in. if a bulldozer is used to remove the top 6 in. of soil).

ASSESSMENT MONITORING DESIGN

However, there may be cases when it is important to know if a single sample has a high probability of exceeding background. In this case, the single value can be compared to the background maximum limit (mean background concentration plus three standard deviations), which is discussed later. 10.10.1 Background Concentration Numerous natural and anthropogenic sources influence background concentrations and need to be accounted for during an initial hazardous waste site investigation. Proper accounting of these sources is important when establishing cleanup standards and are critical if discussions about ARARs develop. It is often not feasible to establish a single universal background concentration for soils or sediments; it is more useful to discuss the range of background concentrations for a contaminant. Single values are hard to establish because concentrations vary depending on how physical, chemical and biological processes and anthropogenic contributions have affected parent geological material at a site. If a site has various soil or sediment textures (e.g., sands, loams), a range in inorganic concentrations should be developed for different soil series or textural groupings. Thus, physical and chemical parameters need to be identified when investigating a site to ensure that soils or sediments with similar parameters are compared. This is important because there are often different soil types at a site and sediments differ depending on where (e.g., in a pool or main channel) and when samples are collected. The following parameters should be similar when comparing paired hazardous waste site samples to background samples: • pH/Eh • salinity • cation exchange capacity (CEQ • percent organic carbon • particle size and distribution • thickness of horizon (soil) • soil type, structure (soil) • sample design • depth of sampling • sampling equipment and compositing regime (if applicable)

• number of samples • digestion/analytical method • acid volatile sulfide concentrations (sediment) • simultaneously extracted metal concentrations (for determining sediment toxicity) At times some of these soil parameters such as percent organic carbon, pH and salinity may be altered by hazardous waste site activities. These changes in soil chemistry could falsely imply that the hazardous waste site and background site soil/sediment matrices are totally very comparable. For example, if oil were released at a hazardous waste site where mercury is of a concern the percent organic carbon values could be much higher than at the background site. This could lead to an incorrect conclusion that the sites are not similar for comparison of inorganic concentrations. Many of these soil parameters can be obtained by contacting the local Natural Resources Conservation Service (NRCS) Office and requesting a soil survey report for the county (usually free of charge) where the site is located. Most soils on private lands in the U.S. have been mapped by the NRCS. By using a soil survey report, the field personnel can evaluate how the soils were originally classified and gain access to average values for the soil series located at the site. By consulting with a soil scientist and comparing current site soils to those previously mapped, an assessment can be made of the amount of change and disturbance that has occurred to the soil profile. Aerial photographs used to map soils are also helpful in evaluating past land use, locating stream channels, determining parent material for sediment loading and determining site factors that affect movement of contaminants (e.g., low percolation rate). More detail on how and why to characterize soils at hazardous waste sites can be found in Breckenridge et al. (1991). A special case occurs for hazardous waste sites that contain fill. Fill areas may be present around construction or disposal areas and should be suspected if the site is located in areas frequently inundated with water. Sites where dredge material (e.g., sediments from shipping areas) is suspected to have been used as fill should be given additional attention because the dredge material may have elevated levels of contaminants. A soil scientist can usually identify fill locations and areas disturbed by construction because of the disturbed nature of the sod profile.

751

Elements As Soil

Range

Ba Mean

Range

Co Mean

Range

Cr Mean

Range

Cu Mean

Range

Hg Mean

Range

Mean

Sandy soils and lithosols on sandstones

50,000 Trend of Chemical Evolution

Source: Hydro-Search, Inc

Figure 11-17 Trilinear Datasets Used for Comparisons of Water Quality shown in Figure 11-18; however, more complex statistical treatments of analytical data are necessary when state and federal performance standards are required for a waste disposal or remedial clean-up sites. Federal regulations have been established for statistical determination of compliance for RCRA facilities. Both existing and new hazardous waste facilities are covered by Subtitle C of the Resource Conservation and Recovery Act (RCRA) and regulated by 40 CFR Parts 264 and 265. When first issued, Part 264 Subpart F required that Cochran’s approximation to the Behrens Fisher Student’s t-test (CABF) or an alternative statistical procedure

approved by U.S. EPA be used to determine whether there is a statistically significant exceedance. This Part 264 Subpart F regulation and in particular the CABF procedure, generated significant technical criticism over use of these statistical procedures for use with ground-water quality data and U.S. EPA proposed a new regulation in response to these concerns. The proposed regulation was revised based on comments EPA received and was then made final (U.S. EPA, October 11, 1988). The final regulation (October 1988) describes five performance standards that a statistical procedure must meet. The federal regulations do recommend four types of

819

1993 μg/L 12,000 U 12,000 U 2,200 J 6,200 U 9,200 U* 1,500 UR 6,200 U 1,200 U 2,500 U 860 J 6,200 U 1,200 U 750 U 350 UR 1,000 U 6,200 U 1,200 U 1,200 U 2,500 U 1,200 U 3,800 U 2,500 U 620 U 2,500 U 1,200 U 2,500 U 13,000 720 UR 2,500 U 620 U 1,200 U 52,000 J 6,200 U 2,700 J 1,200 U 14,000 6,200 U 6,200 U 12,000 U 5,000 UR 2,500 U

1996 μg/L 1,000 U 1,000 U 1,000 U 1,000 U 2,000 U 3,100 R 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 3,700 J 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 1,000 U 3,000 J 5,000 U 1,000 U 1,000 U 1,000 U 14,000 1,000 U 1,700 1,000 U 8,700 1,000 U 1,000 U 1,000 U R 2,500 U

1997 μg/L 250 J 2,500 UJ 650 J 2,500 U 2,500 U* 21,000 R 2,500 U 2,500 U 320 J 620 J 2,500 U 2,500 U 2,500 U 19,000 J 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 920 J 2,500 U 2,500 U 14,000 R 2,500 U 2,500 U 2,500 U 30,000 2,500 U 2,700 2,500 U 12,000 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U

MW-16S 1998 μg/L 2,500 U 2,500 U 2,500 U 2,500 U 5,000 U* 22,000 U* 2,500 U 2,500 U 2,500 U 2,500 2,500 U 2,500 U 2,500 U 19,000 U* 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 13,000 R 2,500 U 2,500 U 2,500 U 44,000 2,500 U 2,500 2,500 U 13,000 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U

1999 μg/L 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 11,000 J 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 11,000 J 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U 8,300 J 12,000 U 2,500 U 2,500 U 2,500 U 34,000 2,500 U 2,900 2,500 U 16,000 2,500 U 2,500 U 2,500 U 2,500 U 2,500 U

2000 μg/L 500 U 500 U 120 J 500 U 500 U 2,900 500 U 500 U 110 J 500 U 500 U 500 U 500 U 3,000 J 2,500 U 500 U 500 U 500 U 500 U 500 U 500 U 500 U 500 U 83 J 500 U 500 U 3,400 230 J 500 U 500 U 500 U 13,000 500 U 1,600 500 U 9,900 500 U 500 U 500 U 500 U 500 U

2001 μg/L 100 U 100 U 250 100 U 380 2,500 J 11 J 100 U 260 110 17 J 100 U* 100 U 2,100 2,500 U 100 U 100 U 100 U 38 J 100 U 100 U 100 U 100 U 140 100 U 100 UJ 3,700 430 100 U 100 U 100 U 12,000 100 U 1,800 100 U 11,000 100 U 100 U 100 U 100 UJ 100 UJ

Key: J= U= U* = UJ =

1993 μg/L 10 U 10 U 2U 19 J 7 U* 7J 5U 1U 2U 0.7 J 5U 1U 0.6 U 2J 5 1 1 2 1 0.8 2 0.5 3 1 2 5 50 2 0.5 1 17 5 3 1 17 5 5 10 4

U U U U U J U U U U U UR U U U U J U U U U UR

1996 μg/L 1U 1U 1U 4 2.0 U* R 1U 1U 1U 1U 0.4 J 1U 1U R 1U 1U 1U 1U 1U 1U 1U 1U 1U 0.8 J 1U 1U 5U R 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U R

MW-16D 1997 1998 μg/L μg/L 0.1 J 1U 1U 1U 0.2 J 1U 6J 3J 1 U* 2 U* 7 U* R 1U 1U 1U 1U 1U 1U 1U 1U 0.5 J 1U 1U 1U 0.3 J 1U 2J R 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1 1 1U 1U 1U 1U 5U 5U R R 1U 1U 1U 1U 1U 1U 1 U* 1 U 1U 1U 1 UJ 1 U 1U 1U 5U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U

The concentration is approximate due to limitations identified during the quality assurance review Indicates the compound was analyzed but not detected. The associated value is the sample quantitation limit The compound should be considered "not detected" since it was detected in a blank at a similar concentration level Indicates the compound was analyzed but not detected. The associated value is an estimated sample quantitation limit based on a bias identified during the quality assurance review R = The results were considered unusable during the quality assurance review Blank = The compound was not analyzed for _______________________ (1) Values shown are the highest detected between the investigative sample and its unpreserved, duplicate, reanalysis, or dilution sample.

Figure 11-18 Simple Time Series Dataset for Organic Parameters

1999 μg/L 1 UJ 1U 1U 8 2 U* R 1U 1U 1U 1U 1U 1U 1U R 1U 1U 1U 1U 1U 1U 1U 1U 1U 1 1U 1U 5U 5U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U 1U

2000 μg/L 1U 1U 1U 7 2 U* 5 U* 1U 1U 1U 1U 1U 1U 1U R 1U 1U 1U 1U 1U 1U 1U 1U 1U 1 1U 1U 5U 5U 1U 1U 1U 1 U* 1U 1U 1U 1U 1U 1U 1U 1U 1U

2001 μg/L 1 U* 1U 1U 6J 1J 5 U* 1U 1U 1U 1U 1U 0.4 J 1U 10 U 1 UJ 1U 1 UJ 1U 1U 1U 1U 1U 1U 1 1U 1U 5 UJ 5 UJ 1U 1 UJ 1U 0.1 J 1U 1U 1U 1U 1U 1U 1U 1U 1U

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

820

Well Number: Collection Date : Units: Chloromethane Bromomethane Vinyl chloride Chloroethane Methylene chloride Acetone Carbon disulfide 1,1-Dichloroethene 1,1-Dichloroethane cis-1,2-Dichloroethene trans-1,2-Dichloroethene Chloroform 1,2-Dichloroethane 2-Butanone Bromochloromethane 1,1,1-Trichloroethane Carbon tetrachloride Bromodichloromethane 1,2-Dichloropropane cis-1,3-Dichloropropene Trichloroethene Chlorodibromomethane 1,1,2-Trichloroethane Benzene trans-1,3-Dichloropropene Bromoform 4-Methyl-2-pentanone 2-Hexanone Tetrachloroethene 1,1,2,2-Tetrachloroethane 1,2-Dibromoethane Toluene Chlorobenzene Ethyl benzene Styrene Xylenes (total) 1,3-Dichlorobenzene 1,4-Dichlorobenzene 1,2-Dichlorobenzene 1,2-Dibromo-3-chloropropane 1,2,4-Trichlorobenzene

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

statistical procedures to evaluate performance of RCRA facilities for releases to ground water. In addition, EPA issued (October 1991) amendments to Subtitle D of RCRA to include criteria for municipal solid waste landfills (MSWLFs). The number of samples collected to establish ground-water quality data must be consistent with the appropriate statistical procedures (discussed below). The sampling procedures are defined in the applicable sections for detection monitoring (§258.54(b)), assessment monitoring (§258.55(b)) and corrective action (§258.56(b)). • Owner or operator must specify in the operating record one of the following statistical methods to be used in evaluating ground-water monitoring data for each hazardous constituent. The statistical test chosen shall be conducted separately for each hazardous constituent in each well. - A parametric analysis of variance followed by multiple comparisons procedures to identify statistically significant evidence of contamination. - An analysis of variance based on ranks followed by multiple comparisons procedures to identify statistically significant evidence of contamination. - A tolerance or prediction interval procedure in which an interval for each constituent is established from the distribution of the background data and the level of each constituent in each compliance well is compared to the upper tolerance or prediction limit. - A control chart approach that gives control limits for each constituent. - Another statistical test method that meets the performance standards discussed immediately below. • Any statistical method chosen shall comply with the following performance standards, as appropriate: - The statistical method shall be appropriate for the distribution of chemical parameters or hazardous constituents. - If an individual well comparison procedure is used to compare an individual compliance well constituent concentration with background constituent concentrations or a ground-water protection standard, the test shall be done at a Type I error level no less than 0.01 for each testing period. If a multiple comparisons procedure is used, the Type I experiment wise error rate for each testing period shall be no less than 0.05; however the Type I error of no less than 0.01 for individual well comparisons must be maintained. - If a control chart approach is used to evaluate ground-water monitoring data, the specific type of control chart and its associated parameter values shall be protec-

tive of human health and the environment. - If a tolerance interval or a prediction interval is used to evaluate ground-water monitoring data, the levels of confidence and, for tolerance intervals, the percentage of the population that the interval must contain, shall be protective of human health and the environment. - The statistical method shall account for data below the limit of detection with one or more statistical procedures that are protective of human health and the environment. Any practical quantitation limit (PQL) that is used in the statistical method shall be the lowest concentration level that can be reliably achieved within specified limits of precisions and accuracy during routine laboratory operating conditions that are available to the facility. - If necessary, the statistical method shall include procedures to control or correct for seasonal and spatial variability as well as temporal correlation in the data. • The owner or operator must determine whether or not there is a statistically significant increase over background values for each parameter or constituent required in the particular ground-water monitoring program that applies to the MSWLF unit. - In determining whether a statistically significant increase has occurred, the owner or operator must compare the ground-water quality of each parameter or constituent at each monitoring well to the background value of that constituent. - Within a reasonable period of time after completing sampling and analysis, the owner or operator must determine whether there has been a statistically significant increase over background at each monitoring well. The statistical test requirements are the same as the RCRA Subtitle C final regulation as the solid waste rules recommend the same four types of procedures. The performance standards in these federal rules allow flexibility in designing statistical procedures to sitespecific considerations. Selection of an appropriate statistical test must be made based on the quality of the data available, the hydrogeology of the site and the theoretical properties of the test. As expressed in previous sections, ground-water quality data can be expected to vary temporally and spatially due to natural effects and the results are also affected by sampling and analytic errors. Due to natural variability observed in ground water, the determination of a significant change in water quality is linked to statistical probability theory.

821

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

In order to define if there has been a significant change in water quality, comparison must be made between supposedly “clean” background data and possibly impacted data. Both of these ground-water classes are subject to temporal and spatial variability as well as sampling and analytic error. Hence, the problem becomes one of evaluation of variable water quality in time and space with potential statistical inferences. A statistical hypothesis is used to compare water quality: Null Hypothesis: Ho:

No contamination exists therefore, the facility is in compliance

Alternative Hypothesis: H1:

Contamination exists; facility is in violation

A statistical test is made on the null hypothesis and a conclusion is reached that either the facility is or is not in violation. The null hypothesis starts out with the assumption that there is no real difference between the quality of up- and downgradient ground water. The assumption is that they are all from the same population. Thus, the difference between the means of the two samples would be just one possible difference from the theoretical distribution where the mean difference is zero. The assumption is called the null hypothesis because it attempts to nullify the difference between the two sample means by suggesting or forming a hypothesis it is of no statistical difference. If the statistical difference between the two sample means turns out to be too big to be explained by the kind of variation that would often occur by chance between random samples, then one must

reject it (the null hypothesis), as it will not explain our observations. The typical alternative hypothesis would be that the two water quality population means are not equal. In this context, a violation implies that water quality is significantly different from background. Figure 11-19 illustrates the two types of errors associated with hypothesis testing. Significant technical discussions surround whether a site has observed a false positive indicating contamination. Type I error (false positive) occurs when a site (or well) is actually in compliance but the statistical test is triggered that decides it is in violation. The probability of a Type I error (or) is defined as the controllable significance level of the test. Usually, this is set at 0.05, giving a 1/20 chance that a false positive conclusion of contamination will occur. Type II error (false negative) occurs when contamination exists but is not detected. The probability of a false negative conclusion is more difficult to control, is often difficult to calculate and is dependent on many factors that may include sample size, the overall magnitude of change in parameter concentration and choice of statistic tested in the decision process. Statistical hypothesis testing can be divided into two general categories: (1) parametric, those which rely on the estimation of parameters of a probability distribution (usually the mean and standard deviation of the normal distribution); and (2) nonparametric, those which do not fit a normal distribution. Nonparametric methods usually rely on test statistics developed from the ordered ranks of the data. The simplest nonparametric evaluation is the median or middle value of a dataset. Both parametric and nonparametric statistical tests are reviewed in the context of ground-water monitoring events in later subsections of this chapter. In general terms, the type of statistical test to use for a facility regulated under Federal laws should be consistent with U.S. EPA (1988) 40 CFR Part 264, Statistical Methods for Evaluating Ground-Water Monitoring from Hazardous Waste Facilities; final rule. (Federal Register, 53, 196, 39720-39731). Both RCRA solid waste (Subtitle D) and hazardous waste (Subtitle C) are keyed into this code. 11.7.1 Data Independence

Figure 11-19 Statistical Error in Hypothesis Testing

822

Independence of data collected in environmental programs must be evaluated by determining if the data show serial correlation. Serial correlation of ground-water sampling data is most likely to occur from very slow groundwater flow. Even with reasonably permeable aquifers (say with hydraulic conductivity > 10-3 cm/s) low gradients can slow ground-water velocity to less than 20 feet per

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

year. When ground-water quality measurements are collected too frequently to be independent of each other, one can observe serial correlation in the data. Independence can often be achieved by increasing the time between observations. Several tests have been reported in the literature to evaluate the presence of serial correlation in ground-water quality data. Montgomery et al. (1987) chose the Lag 1 auto correlation function (ACF). Goodman and Potter, (1987) also used this method as well as the nonparametric autorun test (AR). The application of the ACF test to ground-water quality data is described in detail by Harris et al. (1987). The AR test was applied to hydrologic data by Sen (1979). Most advanced statistics texts and computer packages include these tests. An example of data that show serial correlation is provided in Figure 11-8. These results indicate that serial correlation may exist in ground-water quality data even though the sampling was at intervals of 3 months. The reality of most sampling programs dictates the sampling period required by regulatory standards or permit requirements. It is probably sufficient that one is aware of the potential difficulties associated with serial correlation of the data so that independence of the observations can be checked to help in the selection of the statistical test used in the evaluation of the data. 11.7.2 Data Normality The normal distribution is perhaps the single most important and widely used probability modal in applied statistics. This is because many real systems fluctuate normally about a central mean; i.e., measurement error of a random variable is symmetric about a true mean and has a greater probability of being small (close to the mean) than large in the tail of the distribution. The U.S. EPA’s statistical RCRA regulations (40 CFR 264 Subpart F) do not require tests for normality or other distributional assumptions unless: 1. A data transformation is made. 2. Nonparametric statistical tests are applied. Data transformations are commonly used to normalize skewed data for parametric tests. Many environmental systems are modeled using the lognormal distribution because (1) it has a lower bound of zero and (2) it is positively skewed, allowing high values to be included (Benjamin and Cornell, 1970). The hypothesis of normality can be evaluated through any number of statistical goodness-of-fit tests. These tests are used to mathematically compare the shape of the normal distribution to the dataset. Care should be taken to

only apply these tests to independent, stationary datasets. In the ground-water quality literature, Montgomery et al. (1987) tested the normality of ground-water quality data using graphical methods, the chi square test and the skewness test. Harris et al. (1987) recommend the skewness test for general use with ground-water quality data. 11.7.3 Evaluation of Ground-Water Contamination A main objective of a ground-water detection monitoring program is to determine if the facility is affecting ground water. Owner/operators are required in federal rules to place detection monitoring wells in both upgradient (background) and downgradient locations around the facility and to monitor those wells at regular intervals, typically quarterly or twice per year, for a series of indicator parameters. Subtitle D defines in [§258.53] (Groundwater Sampling and Analysis Requirements) that: “The ground-water monitoring program must include consistent sampling and analysis procedures that are designed to ensure monitoring results that provide an accurate representation of ground-water quality at the background and downgradient wells. The owner or operator must notify the State Director that the sampling and analysis program documentation have been placed in the operating record and the program must include procedures and techniques specified in §258.53(a)(1) through (5): • The ground-water monitoring program must include sampling and analytical methods that are appropriate for ground-water sampling and that accurately measure hazardous constituents and other monitoring parameters in ground-water samples. Ground-water samples shall not be field filtered prior to laboratory analysis. • Ground-water elevations must be measured in each well immediately prior to purging each time groundwater is sampled. Ground-water elevations must be measured within a period of time short enough to avoid temporal variations in ground-water flow that could preclude accurate determination of groundwater flow rate and direction. • The owner or operator must establish background ground-water quality in a hydraulically upgradient or background well(s) for each of the monitoring parameters or constituents required in the particular groundwater monitoring program that applies to the MSWLF unit. • The number of samples collected to establish groundwater quality data must be consistent with the appropriate statistical procedures (discussed below). The

823

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

sampling procedures are defined in the applicable sections for detection monitoring (§258.54(b)), assessment monitoring (§258.55(b)) and corrective action (§258.56(b)).” The logic of this sampling strategy is that upgradient water quality represents the background conditions for that particular region and downgradient water quality represents background water quality, plus any influence produced by the facility. Section 258.40 states, “The relevant point of compliance specified by the Director of an approved State shall be no more than 150 meters from the waste management unit boundary and shall be located on land owned by the owner of the MSWLF unit.” This sets the stage for defining a boundary zone in which to locate the monitoring wells. The detection monitoring program as described in subtitle D for solid waste (§258.54) then defines the following: • Detection monitoring is required at MSWLF units at all ground-water monitoring wells specified in §258.51(a)(1) and (2) [background and downgradient]. At a minimum, the constituents from Appendix I must be included in the program. • The Director of an approved State may delete any of the Appendix I constituents if it can be shown that the removed constituents are not reasonably expected to be in or derived from the waste contained in the unit. • A Director of an approved State may establish an alternative list of inorganic indicator parameters for a MSWLF unit, in lieu of some or all of the heavy metals in Appendix I. Note: Deletion of Appendix I constituents or establishing alternative inorganic parameters is not possible unless the state is approved by the U.S. EPA. • The monitoring frequency shall be at least semiannual during the active life of the facility (including closure) and the post-closure period. A minimum of four independent samples from each well (background and downgradient) must be collected and analyzed during the first semi-annual sampling event. At least one sample from each well (background and downgradient) must be collected and analyzed during subsequent semi-annual events. The Director of an approved State may specify an alternative frequency during the active life (including closure) and the postclosure care period. The alternative frequency shall be no less than annual.

824

Note: An alternative monitoring frequency is not an option unless the state is approved by the U.S. EPA. • If the owner determines that there is a statistically significant increase over background for one or more of the constituents in Appendix I or an approved alternative list, the owner or operator must: - Within 14 days of the finding, place a notice in the operating record indicating which constituents have shown statistically significant changes from background levels and notify the State Director that the notice was placed in the operating record. - Establish an assessment monitoring program within 90 days unless the owner or operator can demonstrate that a source other than a MSWLF unit caused the contamination or that a statistically significant increase resulted from an error in sampling, analysis, statistical evaluation or natural variation in ground-water quality. A report documenting alternate source or error must be certified by a qualified ground-water scientist or the Director of an approved State and placed in the operating record. As described in Chapter 9 the issue of the regulatory concept of the simple upgradient and downgradient model is rarely observed in real world monitoring programs; however, the use of background wells as representative of upgradient water can be used in statistical comparisons. In many cases, particularly when adequate background data are available prior to the installation of the facility, intrawell comparisons may be the most successful technique to use (i.e., each well compared to its own history). The major advantage of this approach is that it eliminates the spatial component of variability from the comparison. One is left with evaluating the local effects on the well installation, such as construction, maintenance and nearby vertical interferences to water quality (such as wells located near roads that are salted during winter, local spills, etc.). The statistical methodology is illustrated in Figure 11-20, which graphically portrays the variable bases for statistical comparisons between wells and for intra-well statistical comparisons. Detection monitoring programs at waste disposal facilities require not only that a release to the environment has occurred, but also that the release observed is directly due to discharges from the facility. Water quality standards are commonly used as a basis for judging if a release to the environment. Yet, even a water quality standard exceedance must be compared to background water quality to conclude that the facility is responsible for the

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Figure 11-20 Methodology for Subtitle D Ground Water Evaluations 825

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

ground-water impact. In reviewing facility data one can expect a number of water quality standards (especially non-organic parameters) to be exceeded in natural ground water. Thus, comparison of downgradient water quality to known background water quality is an important part of any detection monitoring program. It is imperative that detection monitoring programs not rely on only one background well as the basis for comparisons to downgradient wells. Spatial variability within the geologic environment can significantly affect the statistical comparisons necessary for detection monitoring programs. Evaluation and knowledge of ground-water flow and geology sufficient to design detection monitoring systems, together with time series graphs of ground-water quality, may clearly show a release. Statistical tests applicable to water quality evaluations currently recommended by U.S. EPA with other methods proposed in the water quality literature can be used as evaluation tools for the following example facilities:

ity. Confidence intervals also set limits for average background water quality. Control charts are widely used graphical methods for industrial engineering quality control and are similar to the prediction, tolerance and confidence intervals. To evaluate water quality data, a series of questions must be formulated to select the appropriate statistical tests to evaluate the data. These statistical tests are designed to evaluate whether or not a significant difference exists between the historical mean/median of background water quality and the mean/median of each downgradient well. The ability of these tests to detect ground-water contamination quickly, (i.e., when applied quarterly with detection within one or two quarters after a release occurs) depends on the choice of the statistical test and other dataset factors including:

• Existing municipal solid waste landfills (MSWLFs), new facilities, and existing facilities with historically clean water quality

• Magnitude of the increase in concentration due to the release

• RCRA Subtitle C hazardous waste disposal sites, industrial waste disposal sites, land disposal sites for waste water

Regulatory requirements for immediate detection of releases to the environment can be extremely difficult to demonstrate even with the monitoring well screen located directly within the ground-water flow path from the facility. Also of interest in a detection monitoring program is to establish if specific water quality standards have been exceeded. If a sample value exceeds a regulatory standard such as maximum contaminant level (MCL) under the Clean Water Act (accounting for sampling and analytic variability), then a determination of a violation may be made by state or federal regulators. In this situation, a violation means only that a mandated concentration level has been exceeded, not that certain actions must be taken. The problem of regulatory violation of a standard is acute when state or federal standards are at or approach the level of detection of the contaminant, as is the case with some volatile organic compounds. Possible decision approaches may include:

• Superfund-type evaluations for assessment and aquifer remediation projects for federal and state clean-up programs 11.7.4 Types of Statistical Tests The four general categories of statistical methods used for facility compliance comparisons with groundwater quality RCRA regulations are: • Tests of central tendency (location) • Tests of trend • Prediction, tolerance and confidence intervals

• Length of the unaffected water quality record • Variability in the datasets

• Control charts • Statistical tests of central tendency are used to compare the mean or median of two or more sets of data and establish if they are significantly different. Tests of trend evaluate significant increase or decrease in water quality over time. Prediction and tolerance intervals are statistical methods that set limits for acceptable background water quality based on historic datasets. These interval tests also can be used to define the number of background measurements required to fully establish background water qual-

826

A regulatory mandated “hard” limit where no data should exceed the water quality standard with consideration given to sampling and laboratory error

• The more flexible historic mean concentration at a well where the water quality standard should not exceed this regulatory limit • The moving window approach where the last-year’s mean concentration should not exceed the limit • The statistical limits where 95 percent of the population must be below the standard

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

The above provide a number alternative decision paths for water quality evaluation or for making decisions on analytical sample values close to a water quality standard. Comparison of downgradient water quality to the standard is conceptually straightforward. The indicator parameter is plotted on a simple item series graph and compared to the concentration called out in the water quality standard. Background concentrations should be plotted to evaluate if the background water quality levels exceed the particular standard. If background parameter levels do exceed the relevant standard, the downgradient well parameter concentrations must be evaluated statistically against the background rather than comparing the well data to the water quality standard. In those cases where background does not exceed the standard, downgradient concentration cable compared to the standard. Parameter trends (especially for inorganic indicator variables) can serve as a useful management tool for implementing corrective actions before primary drinking water standards are exceeded. Once water quality standards are clearly exceeded and verified through resampling, a release to the environment is confirmed. In the second and third approaches, confidence limits on the mean (where the standard must be below the lower confidence level) can provide the evaluation tool. The last approach can effectively use tolerance interval tests for evaluation of exceedances. After evaluation of the issues or questions to be answered statistically, the next step is to choose a specific test that answers the question. The test must not only have an appropriate experimental design (i.e., answer the right question) but the implicit assumptions of the test must not be grossly violated. As previously discussed, groundwater quality data may grossly violate the assumption of normality, even after appropriate data transformation. A detection monitoring data evaluation must be based on the variable regulatory issues that can change from state to state and from site to site. Some facilities may have specific permit requirements for statistical tests or specified parameter lists that can be significantly different from site to site within a single state. In the following sections, potential releases to ground water can be evaluated using three general types of statistical methods: 1. Tests of central tendency (location) 2. Tests of trend 3. Prediction, tolerance and confidence intervals In each subsection emphasis is placed on the situations where the type of test is appropriate. The types of

water quality questions these tests can answer are discussed. Tests of Central Tendency (Location) The statistical mean and median of water quality datasets are the most common estimates of central tendency. Tests that compare the mean or median of two or more sets of data are tests of central tendency or tests of location. The U.S. EPA had previously required that Cochran’s Approximation to the Student’s t-test be applied between pooled background water quality data and each downgradient compliance well. Significant criticism of this procedure (see U.S. EPA, Oct. 11, 1988; Miller and Kohout (undated); Silver, 1986; and McBean and Rovers, 1984) resulted in the Agency change to a parametric one-way analysis of variance (ANOVA) or the nonparametric analog called the Kruskal-Wallis test (U.S. EPA, 1988). Unfortunately the ANOVA test also suffers from a high false-positive error rate when many multiple comparisons must be done for sites with, for example, more than five or six compliance wells (see Fisher and Potter, 1989) Tests of Trend Tests of trend are commonly used in detection monitoring programs to evaluate whether water quality parameter values are increasing or decreasing with time. Trend analysis is also useful for evaluating changes in background water quality. Trends in data could be observed as a gradual increase (usually modeled as a linear function) or a step function or even cyclical on a seasonal basis. Trend evaluations have traditionally been performed by inspection of graphed time concentration plots. Time series plots also can be used in conjunction with box plots to evaluate trends and seasonal fluctuations. A number of statistical methods can be applied to datasets to evaluate for trends and seasonality. Example procedures such as the Mann-Kendall test for trend evaluates the relative magnitudes of the concentration data with time (Goodman, 1987). The length of time recommended to obtain adequate long-term trends is two years of data (Doctor et al., 1986); for seasonal trends, a much longer period dataset may be necessary. Goodman (1987) using a modified Mann-Kendall test found that at least 10 years of quarterly data were required for obtaining adequate power to detect seasonal trends. Although few facilities have such a long period of data, the long (post) closure requirements in state and federal regulations of 10 to 30 years will make such evaluations for seasonal trends possible. Statistical trend tests alone cannot be used to

827

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

determine compliance with ground-water quality regulations. These tests can only answer the question, “Does a positive or negative trend exist?” The presence of a minor trend should not be construed to mean there has been a release from the facility. Therefore, if a test of trend is used to support the hypothesis of a release, the results must be linked to exceedance of water quality standards and to likelihood of the release based on review of potential cross-contamination and interferences. Tests of trend have been commonly used in evaluating the expected effectiveness of remedial action. However, tests of trend should not be used to predict when a target concentration will be reached since aquifer restoration is usually not a linear but rather an asymptotic process. A common use of trend tests is to evaluate if background water quality is significantly (gradually) changing in time. Hence, the background water quality represents a moving window that will be compared to down-gradient water quality. In this case, the background trend should be removed prior to further analysis (Harris et al., 1987). An apparent trend at a downgradient well cannot be confirmed as evidence of contamination, unless it can be shown that the same trend does not exist in background or upgradient wells. The nonparametric analogs to the linear regression ftest are Kendall’s tau statistic and Spearman’s (rho) rank correlation coefficient. Usually Kendall’s tau is chosen for water quality data because the test statistic approaches normality at smaller sample sizes than Spearman’s rho (Montgomery et al., 1987). Linear regression is considered a powerful technique of trend, but analysts tend to delete outlying values without physical justification to get a good fit. to the data. Also, some users will wrongly try to make predictions of when concentration will return to normal or when a standard will be exceeded. Reviewers should make sure that deletion of data is physically justified. Also, any predictions made with the regression line should be interpreted as no more than a best guess. Fisher and Potter (1989) reviewed statistical tests for applicability for use in detecting facility ground-water contamination events. They found that tests of central tendency both parametric and nonparametric have severe limitations. At least for the cases reviewed, natural spatial variability did not permit ANOVA results to discern between natural variations in mean and those due to potential contamination. They also observed that groundwater quality data often violated the parametric assumptions of normality for both raw and log transformed datasets. Even nonparametric tests of central tendency (such as Kruskal-Wallis) are not recommended for detecting contamination but rather should be used for evaluating

828

spatial variability (Fisher and Potter, 1989). Statistical tests based on trend can be used in conjunction with other data evaluation techniques to support the conclusion of observed contamination. Prediction interval tests were recommended by Fisher and Potter (1989) as the most theoretically sound approach to setting background levels, and in the author’s opinion interval statistical tests represent the most applicable methods for evaluating detection monitoring programs. As such, the remaining discussion of statistics will concentrate on interval tests. Confidence, Tolerance, and Prediction Intervals Statistical intervals tests are used to set limits using background water quality or for intrawell comparisons. Measurements may be compared to the upper bound of the interval to determine if there has been a release. Both the upper and lower bounds are considered for parameters such as pH that may increase or decrease depending on the type of contamination. Confidence limits on the mean define an interval within which the true mean of the population will fall 90, 95, or 99% of the time. Tolerance limits define a range within which some proportion of the population will fall (90, 95, or 99%) of the time. Usually this proportion is also 90, 95 or 99%. Prediction limits define an interval within which it can be stated that the next k measurements will fall (90, 95, or 99%) of the time. Hahn (1970) explains the difference between these limits: A typical astronaut, who has been assigned to a specific number of flights, is generally not very interested in what will happen on the average in the population of all space flights, of which his happens to be a random sample (confidence interval on the mean) or even what will happen in at least 99 percent of such flights (tolerance interval). His main concern is the worst that will happen in the (next) one, three or five flights in which he will personally be involved (prediction interval). All three (parametric) intervals are symmetric and are calculated based on the models x ± ks (two-sided) or x + ks (one-sided) where k is a constant obtained from tabulated values. The environmental use of these statistics depends on the validity of the assumptions of normality, stationarity and independence. Table 11-5 lists questions asked from a regulatory perspective and the appropriate method(s) in each case. A common mistake observed is the use confidence limits when tolerance intervals or prediction limits will answer the question of concern. In theory, question 6 of Table 11-5 is not applicable for determining compliance with ground-water quality

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Table 11-5 Application of Intervals to Regulatory Questions

QUESTIONS

METHOD

1. What is a reasonable upper limit for background water quality?

Tolerance

2. Are downgradient concentrations outside the allowable range of background water quality?

Tolerance Prediction

3. Do new measurements at downgradient wells come from the background population?

Prediction

4. Has a standard been exceeded based on average water quality over a time period?

Confidence

5. Has a standard been exceeded more than a specified percent of the time?

Tolerance

6. Within what range can we state the mean/median of background water quality falls?

Confidence

regulations. This is because we are not interested in comparisons to average water quality, but rather on comparison of compliance well data to the population of background data. Assumptions—The following statistical methods are suitable for data that are normally distributed, rare event data that have a Poisson distribution or data for which the distribution is unknown and/or atypical (i.e., nonparametric). In addition, normally distributed data that have some proportion (less than 90%) below a detection limit (i.e., nondetects) can also be accommodated. We will refer to such data as “censored” and the corresponding distribution as a “censored-normal” distribution. Given these four choices (i.e., normal, censored-normal, Poisson or nonparametric), the only case that is not covered is when nothing is detected in the background, water quality samples (see Figure 11-21). For this case, we will present a method by which practical quantification limits can be obtained based on an analyte present in a laboratory calibration study. These limits may, in turn, be used as criteria for decisions in detection monitoring (i.e., limits) or substituted for nondetects in other analyses. In addition to selecting the proper sampling distribution, the most critical assumption underlying all of the statistical methods to be presented is the independence of the data. These models strictly assume that observations are the result of a random sampling and that each observation

is an independent random sample from the parent population. In the context of ground-water monitoring, this assumption rules out the use of replicate samples, daily samples and perhaps even monthly samples, given how slowly ground-water moves. As such, the author strongly recommends adoption of a quarterly sampling program as the basis for the detection monitoring program. Statistical Overview—In detection monitoring programs, the investigator obtains a sample from a monitoring well and must decide whether the facility has had an impact on concentrations of a series of indicator parameters. It is critically important to realize that each new measurement is not a mean value, but rather, a single, new observation in a supposedly dynamic (flowing) groundwater system. As such, statistical methods for the comparison of mean values (e.g., Student’s t-test) do not apply. From a statistical perspective, the problem is, therefore, to estimate the probability that each new datum was drawn from the population of pristine, background water quality, for which we only have estimates of mean and variance, as obtained from a limited number of upgradient measurements. If the investigator knew that a particular indicator parameter was normally distributed and somehow had the privileged information of knowing the population mean (μ) and variance (s2), then he/she could construct the interval μ ± 1.96s, which would contain 95% of all individual measurements (not means), which were drawn

829

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Figure 11-21

Random Sampling Statistics

from that population and the job would be finished. However, in practice, the investigator never knows the values of μ and s but only has the sample-based estimates (x and s), obtained from n independent, upgradient measurements. As such, uncertainty is twofold. First, a range of possible values exists when sampling known parameters with a normal distribution and second, there is a range of possible means (x) and standard deviations (s) that could

830

be obtained from drawing a sample, of size n, from a normally distributed population with mean (μ) and variance (s2). This latter source of uncertainty will require a multiplier that is larger than 1.96 if one requires reasonable confidence that 95% of the population is contained within the interval. As the number of background water quality measurements approaches infinity, however, the multiplier once again approaches 1.96. When the sample size is

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Figure 11-22

Statistics for Parameters That Have Detectable Values

831

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Table 11-6 Factors (k) for Constructing Two-Sided and One-Sided Normal Tolerance Limits (x ± ks and x + ks) 5% Confidence that 95% of the Distribution is Covered n 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 30 35 40 50 60 80 100

Two-sided 6.370 5.079 4.414 4.007 3.732 3.532 3.379 3.259 3.169 3.081 3.012 2.954 2.903 2.858 2.819 2.784 2.752 2.723 2.697 2.673 2.651 2.631 2.549 2.490 2.445 2.379 2.333 2.272 2.233

One-Sided 5.144 4.210 3.711 3.401 3.188 3.032 2.911 2.815 2.736 2.670 2.614 2.566 2.523 2.486 2.453 2.423 2.396 2.371 2.350 2.329 2.309 2.292 2.220 2.166 2.126 2.065 2.022 1.965 1.927

small (say n = 8), the required multiplier for 95% confidence that 95% of the population is contained is 3.732 (i.e., x ± 3.732 s). For a sample size of n = 30, 95% confidence is achieved using a multiplier of 2.549; and when n = 100, the multiplier is 2.233. These intervals are known as two-sided tolerance intervals in the statistical literature and are largely due to the work of Wald and Wolfowitz (1946). When one is only concerned with values that are large, one-sided tolerance limits can be constructed as x + ks, where the multiplier k is somewhat smaller than the previous two-sided tolerance-limit factors. Figure 11-22 shows the statistical procedure for evaluation of background and downgradient water quality for parameters that normally have detectable values. For example, for n = 8, the one-sided tolerance

832

limit is obtained as x + 3.188 s; for n = 30, k = 2.220; and for n = 100, k = 1.927. Table 11-6 presents values of the multiplier k for n = 4 to 100 that are required to have 95% confidence that 95% of a normally distributed population are contained in the interval (i.e., two-sided) or is below the limit (i.e., one-sided). Although tolerance intervals are generally quite useful in quality control problems, which are similar to ground-water detection monitoring, even more precise probability statements are possible. For example, in the context of ground-water monitoring, one is generally less interested in what can happen in 95% of all possible samples and more interested in what can happen on the next round of sampling, for which measurements are to be obtained from the monitoring wells at the facility. Because one knows the number of future comparisons (i.e., monitoring wells), we can construct an interval (twosided) or limit (one-sided) that will contain the next r measurements with 95% confidence. If r, in this case the number of monitoring wells, is reasonably small, it will provide a more conservative test than the corresponding 95% confidence and 95% coverage tolerance-interval. For example, for a facility with n = 8 background measurements and r = 3 monitoring wells, the multiplier for a onesided 95% confidence and 95% coverage tolerance-limit is k = 3.188; whereas the corresponding factor for a 95% prediction limit is only k = 2.80. However, if the facility had r = 10 monitoring wells, the tolerance-limit factor is, of course, unchanged, but the prediction limit factor is now k = 3.71, which is considerably larger than the corresponding tolerance-limit factor. In general, for 95% confidence and 95% coverage, tolerance intervals will be more conservative for facilities with r > 10 monitoring wells and prediction limits will be more conservative for facilities with r ) 10 monitoring wells. Given the large number of detection monitoring wells at most modern waste disposal facilities, tolerance intervals may well be the method of choice. Tables 11-7 through 11-9 contain factors for computing one-sided 95% prediction limits based on background samples of n = 4 to 100 and number of monitoring wells of r = 1 to 100. Corresponding twosided 95% prediction interval factors are provided in Tables 11-10 through 11-12 As in the case of tolerance intervals and limits, these factors are applied as x ± ks (interval) and x + ks (limit). A detailed description of prediction limits in the context of ground-water monitoring problems is provided by Gibbons (1987). Selecting the Number of Background Samples—A common question asked of statisticians is: “How many background samples do I need?” This question became even more common when, in previous regulations (40 CFR Part 264), owner/operators were required to demon-

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Table 11-7. One-Sided 95% Poisson Prediction Limits for r Additional Samples Given Background Sample of Size n. Previous n

1

2

3

4

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 60 70 80 90 100

2.63 2.34 2.18 2.08 2.01 1.96 1.92 1.89 1.87 1.85 1.83 1.82 1.81 1.80 1.79 1.78 1.77 1.77 1.76 1.75 1.75 1.74 1.74 1.74 1.73 1.73 1.73 1.72 1.72 1.72 1.72 1.71 1.71 1.71 1.71 1.71 1.71 1.70 l.70 1.70 1.70 1.70 1.70 1.70 1.70 1.69 1.69 1.68 1.68 l.67 1.67 1.67

3.56 3.04 2.78 2.62 2.51 2.43 2 37 2.33 2.29 2.26 2.24 2.21 2.20 2.18 2.17 2.16 2.14 2.13 2.13 2.l2 2.11 2.10 2.10 2.09 2.09 2.08 2.08 2.07 2.07 2.07 2.06 2.06 2.06 2.06 2.05 2.05 2.05 2.05 2.04 2.04 2.04 2.04 2.04 2.03 2.03 2.03 2.03 2.02 2.01 2.00 2.00 1.99

4.18 3.49 3.14 2.94 2.80 2.70 2 63 2.58 2.53 2.49 2.46 2.44 2.41 2.40 2.38 2.36 2.35 2.34 2.33 2.32 2.31 2.30 2.29 2.29 2.28 2.28 2.27 2.27 2.26 2.26 2.25 2.25 2.25 2.24 2.24 2.24 2.23 2.23 2.23 2.23 2.22 2.22 2.22 2.22 2.22 2.21 2.21 2.20 2.19 2.18 2.17 2.17

4.67 3.83 3.42 3.17 3.01 2.90 2 82 2.75 2.70 2.66 2.62 2.59 2.57 2.54 2.53 2.51 2.49 2.48 2.47 2.46 2.45 2.44 2.43 2.42 2.42 2.41 2.40 2.40 2.39 2.39 2.38 2.38 2.37 2.37 2.37 2.36 2.36 2.36 2.35 2.35 2.35 2.35 2.34 2.34 2.34 2.34 2.34 2.32 2.31 2.30 2.29 2.29

Number of New Measurements (r) 5 6 7 8 9 10 11 5.08 4.10 3.63 3.38 3.18 3.05 2.96 2.89 2.83 2.78 2.74 2.71 2.68 2.66 2.64 2.62 2.60 2.59 2.57 2.56 2.55 2.54 2.53 2.52 2.52 2.51 2.50 2.50 2.49 2.49 2.48 2.48 2.47 2.47 2.46 2.46 2.46 2.45 2.45 2.45 2.44 2.44 2.44 2.44 2.43 2.43 2.43 2.41 2.40 2.39 2.38 2.38

5.43 4.34 3.82 3.51 3.32 3.18 3.08 3.00 2.93 2.88 2.84 2.81 2.78 2.75 2.73 2.71 2.69 2.67 2.66 2.65 2.63 2.62 2.61 2.61 2.60 2.59 2.58 2.58 2.57 2.56 2.56 2.55 2.55 2.54 2.54 2.54 2.53 2.53 2.53 2.52 2.52 2.52 2.51 2.51 2.51 2.51 2.50 2.48 2.47 2.46 2.45 2.45

5.74 4.54 3.97 3.65 3.43 3.29 3.18 3.09 3.02 2.97 2.93 2.89 2.85 2.83 2.80 2.78 2.76 2.75 2.73 2.72 2.70 2.69 2.68 2.67 2.66 2.66 2.65 2.64 2.64 2.63 2.62 2.62 2.61 2.61 2.60 2.60 2.60 2.59 2.59 2.59 2.58 2.58 2.58 2.57 2.57 2.57 2.57 2.55 2.53 2.52 2.51 2.51

Tables 11-7 to 11-12 : Source Gibbons (1990) and Factor Equation

6.03 4.73 4.11 3.76 3.54 3.38 3.26 3.17 3.10 3.04 3.00 2.96 2.92 2.89 2.87 2.85 2.83 2.81 2.79 2.78 2.76 2.75 2.74 2.73 2.72 2.71 2.71 2.70 2.69 2.69 2.68 2.67 2.67 2.66 2.66 2.66 2.65 2.65 2.64 2.64 2.64 2.63 2.63 2.63 2.62 2.62 2.62 2.60 2.58 2.57 2.56 2.56

6.29 4.89 4.24 3.87 3.63 3.48 3.34 3.25 3.17 3.11 3.06 3.02 2.98 2.95 2.93 2.90 2.88 2.86 2.85 2.83 2.82 2.81 2.79 2.78 2.77 2.77 2.76 2.75 2.74 2.74 2.73 2.72 2.72 2.71 2.71 2.70 2.70 2.69 2.69 2.69 2.68 2.68 2.68 2.67 2.67 2.67 2.67 2.64 2.63 2.62 2.61 2.60

6.53 5.04 4.35 3.96 3.71 3.54 3.41 3.31 3.23 3.17 3.12 3.07 3.04 3.01 2.98 2.95 2.93 2.91 2.89 2.88 2.87 2.85 2.84 2.83 2.82 2.81 2.80 2.79 2.79 2.78 2.77 2.77 2.76 2.76 2.75 2.75 2.74 2.74 2.73 2.73 2.73 2.72 2.72 2.72 2.71 2.71 2.71 2.68 2.67 2.66 2.65 2.64

6.76 5.18 4.46 4.05 3.79 3.60 3 47 3.37 3.29 3.22 3.17 3.12 3.09 3.05 3.02 3.00 2.98 2.96 2.94 2.92 2.91 2.89 2.88 2.87 2.86 2.85 2.84 2.83 2.83 2.82 2.81 2.81 2.80 2.79 2.79 2.78 2.78 2.77 2.77 2.77 2.76 2.76 2.76 2.75 2.75 2.75 2.74 2.72 2.70 2.69 2.68 2.67

12

13

14

15

6.97 5.31 4.56 4.13 3.86 3.67 3 53 3.42 3.34 3.27 3.22 3.17 3.13 3.09 3.07 3.04 3.02 3.00 2.98 2.96 2.95 2.93 2.92 2.91 2.90 2.89 2.88 2.87 2.86 2.85 2.85 2.84 2.83 2.83 2.82 2.82 2.81 2.8l 2.80 2.80 2.80 2.79 2.79 2.79 2.78 2.78 2.78 2.75 2.74 2.72 2.71 2.71

7.l7 5.44 4.65 4.20 3.92 3.72 3 58 3.47 3.39 3.32 3.26 3.21 3.17 3.13 3.10 3.08 3.05 3 03 3.0l 3.00 2.98 2.97 2.95 2.94 2.93 2.92 2.91 2.90 2.89 2.89 2.88 2.87 2.87 2.86 2.86 2.85 2.85 2.84 2.84 2.83 2.83 2.82 2.82 2.82 2.81 2.8l 2.81 2.78 2.77 2.75 2.74 2.73

7.36 5.55 4.73 4.27 3.98 3.78 3.63 3.52 3.43 3.36 3.30 3.25 3.21 3.17 3.14 3.11 3.09 3.07 3.05 3.03 3.01 3.00 2.99 2.97 2.96 2.95 2.94 2.93 2.92 2.92 2.91 2.90 2.90 2.89 2.B8 2.88 2.87 2.87 2.87 2.86 2.86 2.85 2.85 2.85 2.84 2.84 2.84 2.81 2.79 2.78 2.77 2.76

7.54 5.66 4.81 4.34 4.04 3.83 3 68 3.56 3.47 3.40 3.34 3.28 3.24 3.21 3.17 3.14 3.12 3.10 3.08 3.06 3.04 3.03 3.01 3.00 2.99 2.98 2.97 2.96 2.95 2.94 2.94 2.93 2.92 2.92 2.91 2.91 2.90 2.90 2.89 2.89 2.88 2.88 2.88 2.87 2.87 2.86 2.86 2.84 2.82 2.80 2.79 2.79

Factor = t ( n 10, the approximation is virtually identical to the exact values. These results are consistent for k = 5 and 10 (i.e., 5 or 10 monitoring wells) and m = 2, 3 and 4 (i.e., 1, 2 or 3 resamplings). Even at n = 5, when the exact probability was greater than 0.9, the approximate value differed by no more than 1.5%. Table 11-21 provides the number of resamplings required to achieve at least a 95% confidence level for combinations of n = 4 to 100 and k = 1 to 100. Tables 1117 and 11-21 show that without the action of resampling the failing well, the necessary background sample sizes are generally too large to be of much practical value; however, a single resampling decreases the required number of background samples to within a reasonable range for most waste disposal facilities. Single-background wells do not provide a sufficient statistical basis for detection monitoring programs at waste disposal sites. Typically with small numbers of background measurements and large numbers of downgradient monitoring wells (unfortunately a common monitoring problem), the required number of resamplings will be quite large and will lead to a detection monitoring program with a high false negative rate. Table 11-18 illustrates the effect of various combinations of numbers of background samples and numbers of monitoring wells on the integrity of detection monitoring decisions. Given the requirements of RCRA Subtitle D (ground-water monitoring with set time limits for the review of water quality data), it will be difficult having

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Figure 11-24 Methods for 90 to 100% Nondetects

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ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

sufficient time for more than a single resample (i.e., m = 2; see Table 11-18). General Procedure—In this discussion, a nonparametric approach to constructing prediction limits is described. Specifically, interest is in the probability that at least one of m future measurements in each of k monitoring wells will not exceed the maximum of n previous samples. For example, consider a hypothetical (but not antipodal) facility with two upgradient wells and five downgradient wells for which quarterly monitoring produces relatively independent ground-water measurements. In terms of the upgradient wells, 2 years of quarterly monitoring have taken place, yielding 16 background measurements. This evaluation procedure requires the assumptions that: • The distribution of the indicator parameter is continuous. • The distribution of water quality is the same in the background and monitoring locations. • The measurements are independent. The probability that the five new monitoring values (i.e., one at each of the five downgradient wells) will be less than the maximum of the 16 background measurements is .762, (obtained from Table 11-17, where no resampling is performed and n =16 and k = 5), This result has a high false positive rate (i.e., 1 - .762 =.238 or 23.8% of the time a false positive will be obtained). However, assume that in this example in the 23.8% of the cases in which a false positive result is obtained, the owner/operator is permitted to resample the well and if the new measurement is below the maximum of the 16 background values, the facility could return to normal detection monitoring following the procedure shown in Figure 11-24. With a single resampling, we obtain the probability that at least one out of two measurements at each of the five monitoring wells will be less than the maximum of the 16 background measurements. This probability is given in Table 11-18 by looking up k = 5 and n = 16 as .968 or a false positive rate of only 3.2%. This rate provides both an acceptable false positive rate and is fully protective of the environment. Case X—A new landfill has one year to obtain four quarterly measurements in a single well before operation. State law requires a single resampling. How many monitoring wells should the owner/operator install in order to obtain 95% confidence that at least one of the two measurements at each monitoring well will not exceed the largest of the four background measurements? Inspection of Table 11-18 reveals that it is hopeless; even with a single monitoring well, we can at most have .933 confidence.

844

Table 11-13 Method 624 Volatile Organic Compounds and Published Method Detection Limits Compound Benzene Bromodichloromethane Bromoform Bromomethane Carbon tetrachloride Chlorobenzene Chloroethane Chloroform Chloromethane Dibromochloromethane 1,1-Dichloroethane 1,2-Dichloroethane 1,1-Dichloroethene trans-1,2-Dichloroethene 1,2-Dichloropropane cis-1,3-Dichloropropene trans-1,3-Dichloropropene Ethyl benzene Methylene chloride 1,1,2,2-Tetrachloroethane Tetrachloroethene Toluene 1,1,1-Trichloroethane 1,1,2-Trichloroethane Trichloroethene Trichlorofluoromethane Vinyl chloride

Reported MDL 4.4 2.2 4.7 10.0 2.8 6.0 10.0 1.6 10.0 3.1 4.7 2.8 2.8 10.0 6.0 5.0 10.0 7.2 2.8 6.9 4.1 6.0 3.8 5.0 1.9 10.0 10.0

All values reported in μg/L.

Inspection of Table 11-21 reveals that even with as few as three monitoring wells, three resamplings would be required to achieve a 95% confidence level. Furthermore, from a hydrogeological perspective, characterizing background water quality with a single background well is not a very reasonable choice. From a statistical perspective, a single background well produces a confound between contamination and spatial variability that cannot be resolved without additional background wells. Finally, the selection of monitoring wells should be based on a detailed hydrogeological understanding of the site and not simply statistical optimization. Conversely, placing large numbers of monitoring wells on a site may be of some hydrogeological interest, but it will make it almost

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Table 11-14 One-Sided 95% Poisson Prediction Limits for r Additional Samples Given Background Sample of Size n Previous n 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 60 70 80 90 100

1 2.35 2.13 2.01 1.94 1.89 1.86 1.83 1.81 1.80 1.78 1.77 1.76 1.75 1.75 1.74 1.73 1.73 1.72 1.72 1.72 1.71 1.71 1.71 1.71 1.70 1.70 1.70 1.70 1.70 1.69 1.69 1.69 1.69 1.69 1.69 1.69 1.68 1.68 1.68 1.68 1.68 1.68 1.68 1.68 1.68 1.68 1.68 1.67 1.67 1.66 1.66 1.66

Number of New Measurements (r) 5 6 7 8 9 10 11

2

3

4

3.18 2.78 2.57 2.45 2.36 2.31 2.26 2.23 2.20 2.18 2.16 2.14 2.13 2.12 2.11 2.10 2.09 2.09 2.08 2.07 2.07 2.06 2.06 2.06 2.05 2.05 2.05 2.04 2.04 2.04 2.03 2.03 2.03 2.03 2.03 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.01 2.01 2.01 2.01 2.01 2.00 1.99 1.99 1.99 1.98

3.74 3.19 2.91 2.75 2.64 2.57 2.51 2.47 2.43 2.40 2.38 2.36 2.34 2.33 2.31 2.30 2.29 2.28 2.28 2.27 2.26 2.26 2.25 2.25 2.24 2.24 2.23 2.23 2.23 2.22 2.22 2.22 2.22 2.21 2.21 2.21 2.21 2.20 2.20 2.20 2.20 2.20 2.20 2.19 2.19 2.19 2.19 2.18 2.17 2.17 2.16 2.16

4.18 3.50 3.16 2.97 2.84 2.75 2.68 2.63 2.59 2.56 2.53 2.51 2.49 2.47 2.46 2.44 2.43 2.42 2.41 2.40 2.40 2.39 2.38 2.38 2.37 2.37 2.36 2.36 2.36 .235 2.35 2.34 2.34 2.34 2.34 2.33 2.33 2.33 2.33 2.32 2.32 2.32 2.32 2.32 2.32 2.31 2.31 2.30 2.29 2.28 2.28 2.28

4.54 3.75 3.36 3.14 3.00 2.90 2.82 2.76 2.72 2.68 2.65 2.62 2.60 2.58 2.57 2.55 2.54 2.53 2.52 2.51 2.50 2.49 2.48 2.48 2.47 2.47 2.46 2.46 2.45 2.45 2.44 2.44 2.44 2.43 2.43 2.43 2.43 2.42 2.42 2.42 2.42 2.41 2.41 2.41 2.41 2.41 2.40 2.39 2.38 2.37 2.37 2.36

4.86 3.96 3.53 3.29 3.13 3.02 2.93 2.87 2.82 2.78 2.75 2.72 2.69 2.67 2.65 2.64 2.62 2.61 2.60 2.59 2.58 2.57 2.57 2.56 2.55 2.55 2.54 2.54 2.53 2.53 2.52 2.52 2.51 2.51 2.51 2.50 2.50 2.50 2.50 2.49 2.49 2.49 2.49 2.48 2.48 2.48 2.48 2.46 2.45 2.45 2.44 2.44

Tables 11-14 to 11-16 : Source Gibbons 1990 and Factor Equation

5.14 4.15 3.68 3.41 3.24 3.12 3.03 2.96 2.91 2.86 2.83 2.80 2.77 2.75 2.73 2.71 2.70 2.68 2.67 2.66 2.65 2.64 2.63 2.63 2.62 2.61 2.61 2.60 2.60 2.59 2.59 2.58 2.58 2.57 2.57 2.57 2.56 2.56 2.56 2.56 2.55 2.55 2.55 2.55 2.54 2.54 2.54 2.52 2.51 2.51 2.50 2.49

5.39 4.31 3.81 3.52 3.33 3.21 3.11 3.04 2.98 2.93 2.90 2.86 2.84 2.81 2.79 2.77 2.76 2.74 2.73 2.72 2.71 2.70 2.69 2.68 2.68 2.67 2.66 2.66 2.65 2.65 2.64 2.64 2.63 2.63 2.63 2.62 2.26 2.62 2.61 2.61 2.61 2.60 2.60 2.60 2.60 2.60 2.59 2.58 2.56 2.56 2.55 2.54

5.62 4.47 3.93 3.62 3.42 3.28 3.18 3.11 3.05 3.00 2.96 2.92 2.89 2.87 2.85 2.83 2.81 2.80 2.78 2.77 2.76 2.75 2.74 2.73 2.73 2.72 2.71 2.71 2.70 2.70 2.69 2.69 2.68 2.68 2.67 2.67 2.67 2.66 2.66 2.66 2.65 2.65 2.65 2.65 2.64 2.64 2.64 2.62 2.61 2.60 2.59 2.59

5.84 4.60 4.03 3.71 3.50 3.35 3.25 3.17 3.11 3.05 3.01 2.98 2.95 2.92 2.90 2.88 2.86 2.84 2.83 2.82 2.81 2.80 2.79 2.78 2.77 2.76 2.76 2.75 2.74 2.74 2.73 2.73 2.72 2.72 2.72 2.71 2.71 2.70 2.70 2.70 2.69 2.69 2.69 2.69 2.68 2.68 2.68 2.66 2.65 2.64 2.63 2.63

6.04 4.73 4.13 3.79 3.57 3.42 3.31 3.22 3.16 3.11 3.06 3.02 2.99 2.97 2.94 2.92 2.90 2.89 2.87 2.86 2.85 2.84 2.83 2.82 2.81 2.80 2.80 2.79 2.78 2.78 2.77 2.77 2.76 2.76 2.75 2.75 2.75 2.74 2.74 2.74 2.73 2.73 2.73 2.72 2.72 2.72 2.72 2.70 2.68 2.67 2.67 2.66

12 6.23 4.85 4.22 3.86 3.64 3.48 3.36 3.28 3.21 3.15 3.11 3.07 3.04 3.01 2.98 2.96 2.94 2.93 2.91 2.90 2.89 2.88 2.86 2.85 2.85 2.84 2.83 2.82 2.82 2.81 2.81 2.80 2.80 2.79 2.79 2.78 2.78 2.78 2.77 2.77 2.77 2.76 2.76 2.76 2.75 2.75 2.75 2.73 2.72 2.71 2.70 2.69

13 6.41 4.96 4.30 3.93 3.70 3.53 3.41 3.32 3.25 3.20 3.15 3.11 3.07 3.05 3.02 3.00 2.98 2 96 2.95 2.93 2.92 2.91 2.90 2.89 2.88 2.87 2.86 2.86 2.85 2.84 2.84 2.83 2.83 2.82 2.82 2.81 2.81 2.81 2.80 2.80 2.80 2.79 2.79 2.79 2.78 2.78 2.78 2.76 2.75 2.74 2.73 2.72

14

15

6.58 5.07 4.38 4.00 3.75 3.58 3.46 3.37 3.29 3.23 3.19 3.15 3.11 3.08 3.06 3.03 3.01 3.00 2.98 2.96 2.95 2.94 2.93 2.92 2.91 2.90 2.89 2.89 2.88 2.87 2.87 2.86 2.86 2.85 2.85 2.84 2.84 2.84 2.83 2.83 2.82 2.82 2.82 2.82 2.81 2.81 2.81 2.79 2.77 2.76 2.75 2.75

6.74 5.17 4.45 4.06 3.81 3.63 3.50 3.41 3.33 3.27 3.22 3.18 3.15 3.11 3.09 3.07 3.04 3.03 3.01 2.99 2.98 2.97 2.96 2.95 2.94 2.93 2.92 2.91 2.91 2.90 2.90 2.89 2.88 2.88 2.87 2.87 2.87 2.86 2.86 2.85 2.85 2.85 2.84 2.84 2.84 2.84 2.83 2.81 2.80 2.79 2.78 2.77

Factor = t ( n 5 >5 3 3 3 4 4 4 4 4 4 2 3 3 3 3 3 3 4 4 2 2 2 3 3 3 3 3 3 2 2 2 2 2 3 3 3 3 2 2 2 2 2 2 2 2 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 1 1 2 2 2 2 2 2 2 1 1 1 2 2 2 2 2 2 1 1 1 2 2 2 2 2 2 1 1 1 1 2 2 2 2 2 1 1 1 1 1 2 2 2 2 1 1 1 1 1 1 2 2 2 1 1 1 1 1 1 1 2 2 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1

13 14 15 >5 >5 >5 5 5 5 4 4 4 3 3 3 3 3 3 3 3 3 2 2 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Previous Number of Monitoring Wells (k) n 20 25 30 35 40 45 50 55 60 65 70 75 80 90 100 4 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 5 5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 6 4 5 5 5 5 5 >5 >5 >5 >5 >5 >5 >5 >5 >5 7 4 4 4 4 4 5 5 5 5 5 5 5 5 >5 >5 8 3 3 4 4 4 4 4 4 4 4 5 5 5 5 5 9 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 10 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 11 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 12 2 3 3 3 3 3 3 3 3 3 3 3 3 3 4 13 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 14 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 15 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 16 2 2 2 2 2 2 3 3 3 3 3 3. 3 3 3 17 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 18 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 19 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 20 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 25 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 30 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 35 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 40 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 45 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 50 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 60 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 70 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 80 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 90 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 100 1 1 1 1 1 1 1 1 1 1 1 1

854

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Figure 11-25 Evaluation Procedure where Resampling is Allowed

855

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

s 2y.x =

-

Ž¥ 2 16 £ ² y < yi´ / ( 16 < 2 ) i =1 ¤ i ¦

Equation 11-6

where yi = yi + b (xi – x) is the predicted instrument response for target concentration xi. 8. The method detection limit for n = 16 samples is then computed as:

MDL * = ( 3. 46sy. x / b ) 1 +1 /16 + x 2 /

6 ( xi < x ) -1i =1

2

Equation 11-7a where 3.46 is the a = b = .95 percentage point of the noncentral t-distribution on 16 – 2 = 14 degrees of freedom. To express MDL in the n original metric (example mg/L), compute MDL = (MDL*)2 + 0.632455 MDL*

Equation 11-7b

In the absence of any detected values, this estimated MDL can be used as the corresponding prediction limit for detection monitoring. We note that there are existing published MDLs for many compounds, including the Method 624 VOCs. More recently, practical quantitation limits (PQLs) have also published in the Method SW-846 regulation. These national values were established under idealized conditions in which both presence and spiking concentration were known to the analyst and very questionable statistical computations were performed (see Gibbons et al., 1988). As such, it is quite reasonable that such levels will not be reached in routine laboratory practice and that the procedure described here will provide more realistic estimates that are consistent with attainable standards in the routine application of these methods. This view is reiterated in the 40 CFR 264 statistical regulation. The Appendix IX rule (52 FR 25942, July 9, 1987) listed PQLs that were established from Test Methods for Evaluating Solid Waste (SW-846). SW-846 is the general RCRA analytical methods manual, currently in its third edition. The PQLs listed were U.S. EPA’s best estimate of the practical sensitivity of the applicable method for RCRA ground–water monitoring purposes. However, some of the PQLs may be unattainable because they are based on general estimates for the specific substance. Furthermore, due to site-specific factors, these limits may not be reached. For these reasons the Agency feels that the PQLs listed in Appendix IX are not appropriate for establishing a national baseline value for each constituent for

856

determining whether a release to ground water has occurred. Instead, the PQLs are viewed as target levels that chemical laboratories should try to achieve in their analyses of ground water. In the event that a laboratory cannot achieve the suggested PQL, the owner or operator may submit a justification stating the reasons why these values cannot be achieved (e.g., specific instrument limitations). After reviewing this justification, the Regional Administrator may choose to establish facility specific PQLs based on the technical limitations of the contracting laboratory. Thus, U.S. EPA may allow under 264.97(h) owners or operators to propose facility specific PQLs. These PQLs may be used with the statistical methods listed in 264.97.Summary The statistical methods described here provide a series of general tools by which detection monitoring programs can be designed using indicator parameters that vary from 100% detection to no detection. The methods are completely site specific with the exception of the case of no detection for which they are specific to the monitoring laboratory responsible for the routine analysis of the ground-water samples. The statistical procedures are parametric and nonparametric forms of prediction and tolerance intervals and limits, and as such are consistent with the new RCRA 40 CFR Part 264 statistical regulation. The facility-wide false positive rate is restricted to 5%; therefore, quarterly monitoring should statistically result in one false positive decision every 5 years. Resampling of the well or wells in question should produce even fewer false positive results. Using the suggested sample sizes should produce false negative rates of less than 5% for monitoring requirements in excess of 2 to 3 standard deviation units above the background mean. False positive and false negative results are, therefore, balanced for even modest deviations from background water quality levels. 11.8 VERIFICATION OF EXCEEDANCE When water quality data from a detection monitoring program show a statistically significant increase, a series of steps should be performed to determine if the increase is due to a release from the facility or from non-facilitybased interferences. Three major components of potential exceedance can be defined as: • Site interference – Landfill gas present in well – Grout alkaline pH interferences – Poor well construction or maintenance – Background increase due to upgradient discharge – Natural aquifer interferences • Laboratory interference – Transcription errors

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

– Laboratory contamination – Method or chemical interferences

ther evaluation through additional sampling point comparisons. Data analysis may include other data relationships within the water quality review process:

• Facility release exceedance Each of the above potential pathways can cause a site to go into an exceedance verification analysis. Some of the interferences are relatively simple to define such as transcription errors and laboratory chemical interferences (e.g., persistent low levels of methylene chloride). Other interferences are difficult to define and quantify, such as landfill gas cross-contamination or poor well construction. Each of the site interferences will be briefly discussed in the following subsections.

• Anion-cation balances and relationships to electric conductivity (EC) • Comparison of theoretical and measured electric conductivity/total dissolved solids (EC/TDS) • Demand parameter relationships (biochemical oxygen demand [BOD]/chemical oxygen demand [COD]/total organic carbon [TOC] ratios) • Evaluate trace elements data in terms of potential inter-elemental interferences

11.8.1 Site Evaluation Procedure if Statistical Tests are Triggered

• Logical volatile organic compounds (VOC) degradation patterns (landfill age vs. solvent breakdown product appearances

If three or more parameters tested fail the statistical test, then the following steps will be followed to confirm the statistically increase.

• Confirm the presence or absence of common laboratory contaminants, such as solvents, phthalates, methylene chloride

Review Procedures

• Interpretation of data relative to detection limits and dilutions

Sampling and laboratory procedures may be reviewed to determine if there was a systematic error. Field notes, sample team interviews, chain-of-custody, trip and field blanks and lab quality control data will be reviewed for these types of errors. Laboratory performance verification is directed toward determining the quality of individual analyses. The interpretative technique is designed to review all parameters together to form an overall picture of the data quality. This review process is sometimes an acquired skill; other times, individuals may never be able to develop the cognitive skills to evaluate large databases by visual inspection of the information. There are, however, a number of computer-generated reports described in the next section that can assist in data evaluation. The historical comparison of analytical and field results represents one for the most important potential data sources for the review process. Table 11-17 shows an example of this data format. One should not rely on memory of past results as compared to current data to form conceptual ideas of the changes in water quality. This technique should not be used without access to easily reviewed historical data arrays. Historical comparison reports can provide data at a sampling location for full historic record or for a defined period of time. These reports are tabular arrays of the trend of the data, much in the same sense as a graphical trend analysis of a particular variable. The historical comparison report however, allows the reviewer to compare the entire dataset as a whole. Anomalous data and specific indicator parameters can be targeted for fur-

• Close scrutiny of rare event analytes • Relationship of detected analytes to potential sources contamination (e.g., elevated lead and cadmium near highways or due to the acid digestion of a turbid ground-water sample). Natural Inter-Aquifer Interferences Water quality obtained from aquifers can typically exceed standards for drinking-water quality for many inorganic and some organic indicators. Interferences with detection monitoring programs have been documented for chlorides (shale bedrock discharge). Arsenic has been reported in bedrock wells from Massachusetts, and even organic indicator parameters such as phenols and TOX occur naturally in swamps and near the seashore. The best procedure to follow in assessing these potentially natural indicator parameters is to have adequate upgradient or background monitoring wells. Sufficient numbers of background wells should assist in establishing ambient water quality and provide a better statistical basis for water quality comparisons. Expression of the relationships among ions or of one constituent to the total concentration (such as use of mathematical ratios) is often helpful in identifying similarities and differences among different samples of ground water. These differences can define interferences by indicator parameters that may be naturally present in the aquifer. For most comparisons of this type, concentrations,

857

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

expressed in terms of milliequivalents per liter or moles per liter, are the most useful. Ratios can be useful to establish chemical similarities among waters; for example, by grouping analyses representing a single geologic terrain, upgradient and downgradient waters in a single aquifer or a water-bearing zone. Fixed rules for selection of the most significant parameters to compare cannot be given, but the investigator should consider the sources of ions and the chemical behavior of the parameter. Distinguishing between two sources of contamination usually involves comparison of different ionic ratios, using a variety of graphical methods (i.e., Stiff, Piper or Scholler diagrams). Compare Gas Data The presence of gas from landfills in monitoring wells is probably one of the most significant contamination problems observed at solid waste sites. The typical gas contaminated well shows persistent, low concentrations of vinyl chloride. The well may be sampled through bailing or by bladder pumps. Typically, bailed wells contain higher concentrations of contamination by gas because the bailer passes through the gas as it is removed from the well. When the screened interval in a monitoring well is above the potentiometric surface, landfill gas can enter the well. These gas cross-contamination problems, however, do not relate to true ground-water contamination. In a number of cases, hand-bailed wells showing vinyl chloride hits produced nondetect VOAs once a bladder pump was installed. To define if gas is causing contamination of samples, the following procedure should be considered: • If persistent low levels of VOCs are observed from a well, answer the following questions: – Is the well screened partially in the unsaturated zone? – Is a bailer used to obtain a sample? – Can landfill gas be detected in the well with a methane monitor? – Is vinyl chloride observed in the results of analyses? – Is the well casing cracked or broken in the unsaturated zone (observe with downhole TV camera)? Landfill gas and condensate may be compared to ground-water quality data. The patterns of fingerprint VOCs in gas and condensates can be compared to groundwater quality data patterns of VOCs. Also, VOCs detected

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in well headspace will be evaluated using Henry’s Law to determine whether VOCs have migrated from the vapor phase to the liquid phase or vice versa. The presence of landfill gas cross–contamination would be suspected if any of the above were observed at a VOC detect well. Grout Alkaline Ph Interferences High pH readings are unusual in ground water. Typically, pH above 8.5 would be considered uncommon in natural aquifers (Hem, 1967). However, monitoring wells have been observed producing water in which pH approaches 14. For wells contaminated with cement grout, pH values of 11 to 12 are typical. Grout-contaminated wells are a result of poor well construction, such as not separating the well screen intake area sufficiently from the annular seals of cement/bentonite grout. Some examples of likely environments for grout contamination are: • Wells have been injected into the screened area of the well. • Bentonite seals are either too thin or ineffective. • Fractured rock provides channels for alkaline water to move around bentonite seals. All of the above causes of well contamination can be remedied by proper construction and development of the well using ASTM standard well designs. For those wells already showing high pH, the investigation should redevelop the well until a reasonable pH is obtained. Normal purging of wells during sampling (in low hydraulic conductivity environments) can require many years to reduce pH to background levels. Such wells may have to be replaced with properly constructed wells or continuously pumped at low discharge until acceptable pH readings are obtained. Low pumping rates, however, may not be effective because high pH readings may return after purging ceases. Review Screened Intervals The spatial and seasonal differences may be evaluated by reviewing the screened intervals of the well construction logs, the water levels (i.e., falling or rising water levels that may result in contact with different soil and rock type) and the geochemistry of the soil and/or rock screened and gravel packed. Poor Well Construction and Poor Maintenance Interferences due to inter-aquifer connections or surface water entering the screened zone of the well along

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

the annular space can cause excessive concentrations of indicator parameters. Proper well construction based on monitoring flow paths can target the uppermost aquifer for monitoring. Damaged wells can often be identified through a program of maintenance and inspection. Each monitoring well should be visually inspected before sampling to document the condition of the installation. Background Increase Is Due to Discharge Resolving an exceedance of indicator parameters may require inspection of upgradient areas for visible signs of spills or use of chemicals that can cause high concentrations of the indicator parameters. For example, road salt on upgradient recharge areas can cause a dramatic increase in chlorides in permeable, surfical aquifers. Because chloride is mobile and is present in leachate from landfills, road salt can give false-positive results in downgradient wells. This interference is especially troublesome with poorly defined monitoring systems in which upgradient and downgradient relationships have not been properly identified. Historical Review A historical review of land use patterns may be conducted. The potential for industrial and municipal sludges deposited in the floodplain of the river will be evaluated in addition to the prior uses of the landfill property.

Sample the leachate and affected ground-water well for comparison of major cations and anions – Leachate will normally be sampled in the risers nearest the groundwater monitoring well(s) that failed the statistical test. Ground-water data may be compared to leachate chemistry to determine if leachate has affected ground-water chemistry. Patterns in leachate chemistry will be compared to patterns in ground-water chemistry. For example, bedrock ground water contains a much higher ratio of sodium to chloride than does leachate (sodium is two thirds the concentration of chloride, indicating a sodium chloride origin of natural salt). If leachate was released, the ratio would shift and decrease to that resembling leachate. Also, multivariate statistical tests can be used for this evaluation. A geochemical analysis may be done using trilinear diagrams. An example of a trilinear plot is presented (Figure 11-25) of leachate and ground-water data from another facility to determine if mixing of the two types have occurred. Leachate data are plotted on the trilinear plot in a pattern similar to that observed in Baedecker and Back (1979). Leachate cations shifted to sodium and potassium while ground water primarily was of calcium-magnesium type cations (Baedecker and Back, 1979). Leachate also is generally dominated by alkalinity, chloride, sodium, potassium, ammonia nitrogen and iron. Most ground water is particularly depleted in potassium and ammonia nitrogen. The leachate evaluation may require several additional actions in the facility monitoring program:

11.8.2 Verification of Release

• Expand parameters to include additional VOCs and metals.

If concentrations of indicator parameters exceed a predetermined threshold, steps must be taken to confirm the significant increase. These steps can be reduced to:

• Determine if three or more parameters exceed statistical thresholds during the next two quarters of sampling.

Resample Well – If the previous evaluation steps above do not satisfactorily explain a statistical exceedance, then the well should be resampled for the specific parameters. Evaluate Sources – Evaluation may be made of the data (if it is not a systematic error) by comparing the additional parameters analyzed along with the required parameters to the various potential sources of ground-water quality impacts. The potential sources include leachates, landfill gas, gas condensates, naturally occurring changes (i.e., drought, flooding, spatial or seasonal variations), offsite sources or prior land use impacts. The primary task is to determine if leachate has affected ground-water quality. To determine the potential source of observed contaminants several tasks should be performed: (1) sample leachate and verify the fingerprint of the leachate, and (2) compare fingerprint of the leachate with observed parameters.

If VOCs exceed two times the PQL, then the affected monitoring well should be sampled for landfill gas in the headspace above the ground-water level in the well. VOCs found in the vapor phase can be compared to VOCs found in the ground-water sample and landfill gas sampled from nearby gas collection piezometers. Landfill gas condensates also should be sampled for VOCs. If confirmation of the increase occurs, then the investigation should initiate an assessment monitoring program. Assessment monitoring may include drilling of additional wells, expansion of analytical parameters and additional sampling of the detection monitoring wells. Assessment monitoring is specifically addressed in Chapter 10 where the techniques to evaluate the rate and extent of leachate migration are described. If no Phase I and Phase II investigations were previously performed before beginning an assessment program, the investigator should

859

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

use the phased sequence of defining target pathways. The assessment monitoring system should be fully based on knowledge of the site geology and hydrogeology. 11.9

EDITING AND MANAGING DATA

Analytical data from environmental programs generates massive amounts of tabular data. Evaluations of these large datasets require special techniques to manage, edit and analyze the data. Previous sections of this chapter discussed the graphical techniques appropriate for the visual display of water quality data. There are, however, basic issues of data error control and database management that go beyond the straightforward display of analytical results. These techniques are required to deal with the large volume of analytical result. All scientific data are gathered in ways that result in data not being absolutely correct. Every datum has some inherent uncertainty. Three different types of errors are associated with any collected data: • Systematic errors of determination • Random errors of determination • Blunders Systematic errors consistently bias data away from the correct value in one direction. Data analyzed in micrograms per liter and reported in milligrams is one example;

860

incomplete digestion of metals samples is another. Random errors are those that are as likely to bias a datum in one direction as the other. Reading the needle on a pH meter is as likely to cause a reading 0.1 unit higher as 0.1 unit lower and rainfall estimates are as likely to be 1 inch/ month too high as 1 inch/month too low. Blunders are gross errors — reading the wrong scale, cross-contamination of a sample using the wrong preservative on a water sample or sampling the wrong well. These blunders may also include components of both systematic or random errors in addition to the simple blunder errors. Statistically, random errors are somewhat easier to determine than systematic errors. Blunders are often easiest to determine especially when they violate a boundary condition such as a pH of 356.7 or a 17,547 foot deep surfical aquifer well. There are a number of methods of finding blunders in reported data. The first of these is a set of physical bounds checks done as the data are first received. If the data are received in a digital format, the database can be automatically filtered for a number of key bounds checks. These checks would include pH not less than 1.0 and not greater than 14.0, temperatures above 100°F or less than 0°F, total depth of well not less than cased depth and potentially many others. Additional comparative data manipulation techniques can be used to further evaluate large datasets. Parameters can be ranked and the uppermost and lowermost 10% then compared to file values as a check against data entry error. Any errors determined through these checks are corrected, if possible, before further checks of

Figure 11-26 Sampling Used for Ground-Water Comparisons

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

data are done. Random errors, other than blunders, can be evaluated by outlier determination and these points marked for further examination. Because environmental data often do not fit a normal distribution, one cannot use parametric outlier tests that assume normality. Instead, nonparametric outlier checks may be usable for these evaluations. These tests include parametric checks that have been made distribution independent by the substitution of medians for means and quarter-spreads for standard deviations. Commercially written database management systems are normally used as a front end for maintenance of environmental water quality data. These software programs allow one to manipulate incoming data, do edit checks and reformat the data into a form that allows other commercial software products to further graph and hardcopy display the required data for report generation. Extreme care must be maintained in protecting these large datasets. Multiple copies and various levels of working and protected copies should be maintained for use by project staff as part of QA/QC procedures. 11.9.1 Reporting Water Quality Data to Agencies State and federal regulations require some form of reporting to confirm that the monitoring system is working as required by the codes. Some regulations require the reporting of tabular sets of data on forms or through a formatted electronic media. In general terms all data should

be fully reviewed before transmittal to regulatory organizations. A simple set of guidelines can ease potential errors and embarrassment when submitting water quality data on your facility: • Read the permit or waste discharge requirements and then follow them. • Format data as required in a manner that communicates the data most effectively (so everyone reaches the same conclusions). • If the state requires reporting of exceedances, format the response in a neutral manner: - Talk about the specific exceedance issues. - Relate progress made on defining causes of the exceedance(s). - Propose schedules for establishing the cause of the exceedance or schedules for the remedial actions required. - Provide a summary statement on the level of concern • Maintain consistency and continuity between quarterly reports: - Indicator parameter exceedance changes from quarter to quarter. - New personnel should review past data. - Always cross-check reports from quarter to quarter.

Figure 11-27 Frozen Ground May Cause Increased Gas Migration

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ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

•

Explain why and what will be done with the data.

•

Maintain technical standards and textural reporting consistency between sites; always maintain a consistent standard format for reporting water quality data.

11.10 THE STATISTICS OF REMEDIATION Remedial evaluations require a variety of statistical approaches for assessment, compliance, and corrective action environmental monitoring programs. Although the methods provided below are appropriate and often optimal for many environmental monitoring problems, they do not preclude use of other statistical approaches that may be equally or even more useful for certain site-specific applications. In the following sections, complete details of select statistical procedures used in assessment and corrective action programs for environmental monitoring (soil, ground water, air, surface water and waste streams) are presented. The guide is summarized in Figure 11-28. This figure provides a flow-chart illustrating the steps used in computing the comparisons to regulatory or health based groundwater protection standards (GWPSs) in assessment and corrective action environmental monitoring programs. The principal use of this standard is in assessment, compliance, and corrective action environmental monitoring programs (e.g. for any facility that could potentially contaminate ground water). The significance of the guidance is that it presents a statistical method that allows comparison of ground-water data to regulatory and/or health based limits. Of course, there is considerable U.S. EPA support for statistical methods applied to detection, assessment and corrective action monitoring programs that can be applied to environmental investigations. For example, the 90% upper confidence limit (UCL) of the mean is used in SW846 (Chapter 9) for determining if a waste is hazardous. If the UCL is less than the criterion for a particular hazardous waste code, then the waste is not a hazardous waste even if certain individual measurements exceed the criterion. Similarly, in the U.S.EPA Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities Addendum to the Interim Final Guidance (1992), confidence intervals for the mean and various upper percentiles of the distribution are advocated for assessment and corrective action. Interestingly, both the 1989 and 1992 U.S. EPA guidance documents suggests use of the lower 95% confidence limit (LCL) as a tool for determining whether a criterion has been exceeded in assessment monitoring. U.S. EPA guidance in this area (i.e., the draft U.S. EPA Unified Statistical Guidance) calls for use of the LCL in assessment monitoring and the UCL in corrective action. In this way, corrective

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action is only triggered if there is a high degree of confidence that the true concentration has exceeded the criterion or standard, whereas corrective action continues until there is a high degree of confidence that the true concentration is below the criterion or standard. This is the general approach adopted in this guidance document, as well. There are several reasons why statistical methods are essential in assessment and corrective action monitoring programs. First, a single measurement indicates very little about the true concentration in the sampling location of interest and with only one sample there is no way of knowing if the measured concentration is a typical or an extreme value. The objective is to compare the true concentration (or some interval that contains it) to the relevant criterion or standard. Second, in many cases the constituents of interest are naturally occurring (e.g., metals) and the naturally existing concentrations may exceed the relevant criteria. In this case, the relevant comparison is to background (e.g., off-site soil or upgradient ground water) and not to a fixed criterion. As such, background data must be statistically characterized to obtain a statistical estimate of an upper bound for the naturally occurring concentrations so that it can be confidently determined if onsite concentrations are above background levels. Third, there is often a need to compare numerous potential constituents of concern to criteria or background, at numerous sampling locations. By chance alone there will be exceedances as the number of comparisons becomes large. The statistical approach to this problem can ensure that false positive results are minimized. Statistical methods for detection monitoring have been well studied in recent years (see Gibbons, 1994, 1996; U.S. EPA, 1992; ASTM Standard D6312-98, formerly PS 64-96 authored by Gibbons et al., 1996). Although equally important, statistical methods for assessment monitoring, Phase I and II investigations, ongoing monitoring and corrective action monitoring have received less attention (Gibbons and Coleman, 2001). The guide is summarized in Figure 11-28, which provides a flow-chart illustrating the steps in developing a statistical evaluation method for assessment and corrective action programs. Figure 11-28 illustrates the various decision points at which the general comparative strategy is selected and how the statistical methods are to be selected based on site-specific considerations. 11.10.1 Procedure for Statistical Sampling In the following, the general conceptual and statistical foundations of the sampling program are described. Following this general discussion, media-specific details (i.e., soil, ground water and waste streams) are provided.

Select Constituents for a Particular Onsite Area (PAOC) Corrective Action or Assessmentt Monitoring

If not Already Done, Collect a Minimum of Four Independent Samples per Constituent (e.g., 1 Sample at 4 Locations at Similar Intervals)

Comparison to Standard

Compute Background (i.e., offsite) Normal, Lognormal, or Nonparametric Prediction Limit (PL) for Mean Onsite Concentration

No

Yes

No

Test for Normality and Lognormality

Is N > 7?

Yes

Normality and Lognormality

No

Compare Individual or Mean of m Onsite Samples to the Background PL

Adjust Mean and SD for Nondetects Using Aitchison's Method

Compute 95% Normal UCL Setting NDs to PQL/2

Compare UCL to Standard Yes

FAIL

No FAIL

Ye es

Is UCL > Standard?

Compute Normal, Lognormal, or Nonparametric 95% UCL

Compute 95% Normal LCL Setting NDs to PQL/2

Compare new LCL to Standard

Ye es FAIL

Is LCL > Standard?

PASS No Note: PASS - Standard/Criteria not Exceeded FAIL - Standard/Criteria Exceeded PAOC - Potential Area of Concern

PASS

863

Figure 11-28 The Statistics of Remediation

No PASS

Adjust Mean and SD for Nondetects Using Aitchison's Method

Compute Normal, Lognormal, or Nonparametric 95% LCL

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Yes

Is Onsite Mean > PL?

Compare to Standard

g

Is N > 7?

Determine Standard or Criteria (Standard) for Each Constituent

Is Background PL> > Regulatory Standard

Co orrectiv

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Identify relevant constituents for the specific type of facility, media (e.g., soil, ground water etc.) and area of interest. A facility is generally comprised of a series of subunits or source areas that may have a distinct set of sampling locations and relevant constituents of concern (referred to as a PAOC). The subunit may consist of a single sampling point or collection of sampling points. In some cases, the entire site may comprise the area of interest and all sampling locations are considered jointly. The boundaries of the source area or decision unit should be defined. In all cases, the owner/operator should select the smallest possible list of constituents that adequately characterize the source area in terms of historical use. For each constituent obtain the appropriate regulatory criterion, or standard (e.g., maximum contaminant level or MCL) if one is available. The appropriate criterion or standard should be selected based on relevant pathways (e.g., direct contact, ingestion, inhalation) and appropriate land use criteria (e.g., commercial, industrial, residential). For each constituent that may have a background concentration higher than the relevant health-based criterion, set background to the upper 95% confidence prediction limit (UPL) as described in the Technical Details section. The prediction limits are computed from all available data collected from background or outside source areas that are unlikely to be contaminated, upstream, upwind or upgradient locations only. Henceforth, background refers to any of these types of offsite sources. The

MINIMUM OF 4 INDIVIDUAL SAMPLES PER CONSTITUENT (4 TOTAL SAMPLES PER PAOC)

SB-1 TMW-1

SB-4 TMW-4 GROUND-WATER FLOW

PAOC #1 SB-3 TMW-3

SB-2 TMW-2

SB-5

SB-8 TMW-8

TMW-5

PAOC #2 TMW-7

TMW-6 SB-6

SB-7 PROPERTY BOUNDARY LEGEND SB-# SOIL BORING TMW-# DIRECT PUSH GROUND-WATER SAMPLE

Figure 11-29 Single PAOC Comparisons to a Standard/Criteria

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background data are first screened for outliers and then tested for normality and lognormality: • If the test of normality cannot be rejected (e.g., at the 95% confidence level), background is equal to the 95% confidence normal prediction limit. • If the test of normality is rejected but the test of lognormality cannot be rejected, background is equal to the 95% confidence lognormal prediction limit. If the data are neither normal nor lognormal or the detection frequency is less than 50%, background is the nonparametric prediction limit which is computed as the maximum of the background measurements. Note that, if the detection frequency is zero, background is set equal to the appropriate quantification limit (QL) for that constituent which is the lowest concentration that can be reliably determined within specified limits of precision and accuracy by the indicated methods under routine laboratory operating conditions. If the background is greater than the relevant criterion or standard or if there is no criterion or standard, then comparisons are made to the background prediction limit. If the criterion is greater than background, then compare the appropriate confidence limit to the criterion. Note that if nothing is detected in background, then the background is the QL. If the criterion is lower than the QL, then the criterion is the QL. The number of samples taken depends on whether comparison is to background or a criterion and whether comparisons are made at individual locations or by pooling samples within a source area. If comparison is to background, collect a minimum of one sample from each source area or sampling location. If comparison is to a criterion (i.e., the criterion is greater than background) and interest in a single location, a minimum of four independent samples from each sampling location will be required. If the comparison is to a criterion for an entire source area, a minimum of one sample from each of four sampling locations within the source area is required. If there are fewer than four sampling locations within a given source area, then the total number of measurements from the source area must be four or more (e.g., two sampling locations each with two independent samples). Note that these sample sizes represent absolute minimums necessary for the statistical computations. In general, larger number of samples will be required to obtain a representative sample of the population of interest. If comparison is to a criterion or standard there are two general approaches. In assessment monitoring, where interest is in determining if a criterion has been exceeded, compare the 95% lower confidence limit (LCL) for the mean of at least four samples from a single location, source

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

1 SAMPLE/CONSTITUENT AT EACH OF A MINIMUM OF 4 OCCASIONS

SB-1 TMW-1

GROUND-WATER FLOW

In the following sections, application to specific media and types of sampling and monitoring programs is described. The areas covered include soil, ground water and waste-stream sampling; however, similar approaches can be taken for air and surface-water monitoring. 11.10.2 Soils, Evaluation of Individual Source Areas (PAOCs)

PAOC #1 SB-2 TMW-2

SB-3

TMW-3

PAOC #2 TMW-4 SB-4

PROPERTY BOUNDARY

LEGEND SB-# SOIL BORING TMW-# DIRECT PUSH GROUND-WATER SAMPLE

Figure 11-30 Multiple PAOC Comparison to a Standard/ Criteria area, or the entire site to the relevant criterion. In corrective action sampling and monitoring, where interest is in demonstrating that the onsite concentration is lower than the criterion, compare the 95% upper confidence limit (UCL) for the mean of at least four samples from a single location, source area or the entire site to the relevant criterion. If the background prediction limit is larger than the relevant criterion, then do one of the following: (1) for a single measurement obtained from an individual location, compare this individual measurement to the background prediction limit for the next single measurement from each of k locations; (2) for multiple measurements obtained from a given source area or the entire site, compare the mean of the measurements to the background prediction limit for the mean of m measurements based on the best fitting statistical distribution or nonparametric alternative. Note that, if the background UPL and the regulatory criterion are quite similar, it may be possible for the downgradient mean to exceed the background UPL but the LCL for the downgradient mean may still be less than the regulatory criterion. In this case, an exceedance is not determined. Figure 11-28 presents a decision tree that can be used to step through the statistical analysis approach.

Collect soil samples from the surface to the ground watertable at appropriate intervals in the most likely contaminated location in the source area and screen soils to determine the interval with highest concentration(s). At a minimum of three other nearby borings located in the same source area, collect one sample in the same vertical interval (geologic profile) as the previously identified highest concentration interval (i.e., the first boring in the interval of highest screening concentration). Send the samples from the vertical interval in all four borings to the lab for analysis. As in Section 11.10.1 these intervals and sample sizes represent a minimum required for the statistical computations and larger numbers will typically be required in practice to ensure adequate characterization of the area of interest. Compute the 95% LCL (assessment) or UCL (corrective action) for the mean of the m results to determine if the particular PAOC exceeds the regulatory criterion. If an exceedance is found, assess whether it is naturally occurring (e.g., metals) by obtaining a minimum of eight independent background samples (i.e., offsite soil samples from the same interval) and compute the 95% confidence upper prediction limit (UPL) for the mean of the m onsite/downgradient samples and compare the UPL to the observed mean at each PAOC. An exceedance is determined only if the PAOC mean concentration exceeds both the regulatory criterion and the background UPL. Figures 11-29 and 1130 illustrate the sampling location approaches for this scenario. Eight samples are required because for any fewer, uncertainty in the background mean and variance will lead to unacceptably wide intervals. Soils, Area-Wide or Site-Wide Evaluations For site-based soil sampling programs one can implement different strategies for the design of a soil sampling program. In general terms, we would collect soil samples to be representative of the entire spatial distribution of constituents of concern (a minimum of four samples). For this sampling we then compute the 95% LCL (assessment)

865

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

SB/TMW-1 SB/TMW-3

PAOC #1 SB/TMW-4 SB/TMW-7 SB/TMW-5

SB/TMW-6

PAOC #2

SB/TMW-8

PROPERTY BOUNDARY

SB/TMW-2 GROUND-WATER FLOW

SB/TMW-9

SB/TMW-10 SB/TMW-12

SB/TMW-11

LEGEND SB-# SOIL BORING TMW-# DIRECT PUSH GROUND-WATER SAMPLE NOTES:

1) SAMPLES SHOULD BE DISTRIBUTED ACROSS SITE, INCLUDING PAOCS 2) IF COMPARISON FAILS EXCLUDE DATA FROM PAOCS AND RECALCULATE

Figure 11-31 Comparison of Mean Concentrations of Entire Site to a Standard/Criteria or UCL (corrective action) for the mean of all onsite samples and determine if the area or site as a whole exceeds the regulatory criterion. If an exceedance is found for an indicator parameter our goal would be to ensure that it is not a naturally occurring constituent by obtaining a minimum of eight independent background samples (i.e., offsite soil samples from the same stratigraphic unit) and from this sampling we would compute the 95% confidence UPL. If the level of hazardous substance concentrations at the site is relatively homogeneous, we would compute the UPL for the mean of the m onsite measurements and compare the observed mean to the UPL. If the level of hazardous substance concentrations at the site is heterogeneous, compute the UPL for the m individual onsite measurements and compare each measurement to the UPL. An exceedance is determined only if the area or site-wide mean concentration exceeds both the regulatory criterion and the background UPL. If an exceedance is found, it is possible to exclude PAOCs one at a time until the site minus the selected PAOCs does not exceed criterion. This method may be appropriate only when sufficient sampling of the PAOC has been conducted as part of the site or area-wide evaluation. Figure 11-30 illustrates the sampling location approach for this scenario. Ground-Water Aquifer As in the soil sampling above, if soil sampling and screening or prior ground-water monitoring indicates that

866

ground water may be impacted, then one ground-water sample will be obtained in each of a minimum of four borings using a direct push methodology or from existing ground-water monitoring wells and results will be evaluated statistically to determine if the entire PAOC requires additional assessment. The general methodology previously described for Soil PAOCs can be used here as well, as illustrated in Figures 11-29 and 11-30. To characterize background, a minimum of eight independent, samples must be collected. This can be four samples from each of two locations, two samples from four locations or one sample from each of eight locations. A minimum of two locations are required. Statistical independence implies that the same ground water is not sampled repeatedly and that the background data are representative of the same temporal variation as are the onsite data. This precludes establishing background in the winter and comparing onsite measurements obtained in the summer. As in previous sections, these sampling requirements represent minimum requirements of the statistical procedures and the actual numbers of samples and time frames should be based on geologic criteria (e.g., see Guide for Developing Conceptual Models for Contaminated Sites.) Figure 11-32 illustrates another approach for evaluating ground water at a site. Sampling locations are set up as shown and four independent samples are collected from background locations GW-7 and GW-8 (i.e., eight total background samples). If the background UPL exceeds the appropriate regulatory criterion, then the mean from downgradient samples GW-1 through GW-6 is compared to

2) COMPARE DOWNGRADIENT MEAN TO BACKGROUND UPL OR DOWNGRADIENT LCL TO CRITERIA

1) CALCULATE BACKGROUND CONDITIONS (IN THIS CASE, 4 SAMPLES FROM GW-7 AND GW-8 FOR A TOTAL OF 8 SAMPLES)

PROPERTY BOUNDARY

AT LEAST ONE SAMPLE AT EACH LOCATION (IN THIS EXAMPLE 12 SAMPLES)

GW-7

GW-1 GROUNDWATER FLOW

GW-3 PAOC #1 GW-2

GW-8 GW-4 PAOC #2

GW-5 GW-6

LEGEND GW - # NOTES:

DIRECT-PUSH GROUND-WATER SAMPLE 1) SAMPLES SHOULD BE DISTRIBUTED ACROSS SITE, INCLUDING PAOC'S 2) IF COMPARISON FAILS EXCLUDE DATA FROM PAOCS AND RECALCULATE

EVALUATION OF GROUND-WATER CONCENTRATIONS FOR THE ENTIRE SITE

Figure 11-32 Evaluation of Ground Water Concentrations of Entire Site

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

PROPERTY BOUNDARY

GW-6 GW-1 GW-9 GROUND-WATER FLOW

PAOC #1

GW-2

GW-5 GW-8

GW-3 PAOC #2 GW-4 GW-7 LEGEND GW - #

DIRECT PUSH GROUND-WATER SAMPLE OR MONITORING WELL

1) CHARACTERIZE BACKGROUND (IN THIS CASE, 2 SAMPLES FROM GW-6, GW-7, GW-8 AND GW-9 FOR A TOTAL OF 8 SAMPLES, COMPUTE UPL) 2) DETERMINE IF BACKGROUND OR GSI CRITERIA APPLY. 3A) IF BACKGROUND APPLIES, COLLECT ONE SAMPLE FROM GW-1 THROUGH GW-5 AND COMPARE EACH RESULT TO BACKGROUND UPL 3A) IF GSI APPLIES, COLLECT ONE SAMPLE FROM GW-1 THROUGH GW-5 AND COMPARE LCL (OR UCL FOR CORRECTIVE ACTION MONITORING) TO GSI CRITERIA

EVALUATION OF GROUND-WATER DATA TO DETERMINE COMPLIANCE WITH GSI CRITERIA

Figure 11-33 Evaluation of Ground Water to Determine Compliance with GSI Criteria background UPL to determine if an exceedance exists. If the background UPL is less than the appropriate regulatory criterion, then the downgradient LCL should be compared to the criterion. Another modification to this approach is if an exceedance exists, the m downgradient samples can be compared individually to background to determine if the impact is restricted to a subset of monitoring locations. As previously discussed, if the background UPL and the regulatory criterion are quite similar, it may be possible for the downgradient mean to exceed the background UPL but the LCL for the downgradient mean may still be less than the regulatory criterion. In this case, an exceedance is not determined. This applies equally to all media.

sample from each compliance point) and compare to the appropriate upgradient UPL. If comparison is to regulatory criteria, obtain a minimum of four independent samples from each GSI sampling location (i.e., four samples from each compliance point) and compare the LCL (assessment) or the UCL (corrective action) to the regulatory criterion. If the upgradient UPL is greater than the regulatory criterion for a particular constituent, compare each GSI sampling location to background. Depending on the application, each GSI sampling location can be compared to background or the appropriate regulatory criterion individually or as a group. Figure 1133 illustrates the sampling strategy for this scenario.

11.10.3 Ground-Water/Surface-Water Interface (GSI)

Long-Term Monitoring of Ground Water

Characterize background as described previously. As previously indicated, background is established by obtaining at least eight independent, samples from a minimum of two locations (i.e., to incorporate spatial variability). The background limit is established by computing the UPL from these data (i.e., a minimum of eight background samples). If the only comparison is to background, obtain a single sample from each GSI sampling location (i.e., one

When sampling for long-term monitoring of a plume, compute the 95% confidence normal UCL for the most recent four measurements in each sampling location and compare to the relevant regulatory criteria. Compute Sen’s test to determine if there are increasing or decreasing trends (at a 95% confidence level) at each sampling location (need a minimum of eight measurements per well).

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ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

11.10.4 Natural Attenuation Evaluation of Ground Water

11.11.1 Comparison to a Regulatory Criterion or Standard

Here temporal changes are considered in the mean of all wells within a plume or wells in the relatively higher concentration area of a plume. Obtain a minimum of eight independent samples (e.g., one from each of eight monitoring wells or two from each of four monitoring wells). This should be done either for all wells within the plume or the relatively higher concentration area of the plume. Note that if there is seasonal variability in analyte concentrations four quarterly samples within a period of no less than one year should be obtained from each sampling location. Compute the 95% confidence lower prediction limit (LPL) and the UPL for the mean of all wells in the plume or all wells within the relatively higher concentration area. For example, if there are eight wells, compute the LPL and UPL for the mean of the next eight samples:

Confidence Limits for the Mean or Median Concentration

• If the actual mean exceeds the UPL, there is evidence that the plume is getting significantly worse. • If the actual mean is less than the LPL, there is evidence that the plume is getting significantly better (i.e., natural attenuation is occurring). Compute Sen’s test to determine if there are increasing or decreasing trends (at a 95% confidence level) at each sampling location (need a minimum of eight measurements per well). Waste Stream Sampling To determine if a particular waste stream is hazardous, obtain a series of n * 4 representative samples from the waste stream for all relevant characteristically hazardous criteria. Compute the appropriate 90% UCL for the mean concentration. Note that the 90% confidence level is used based on guidance provided in SW-846 (Chapter 9). If the 90% UCL is less than the regulatory criterion or standard, the waste stream is not hazardous. 11.11 TECHNICAL APPROACH The purpose of this section is to provide a description of the specific statistical methods to be used in assessment and corrective action sampling programs (see Gibbons and Coleman, 2001).

868

The 95% normal LCL (assessment sampling and monitoring) or 95% normal UCL (corrective action) for the mean of at least four measurements is computed and compared to the regulatory criterion or standard. The 95% normal LCL (assessment sampling and monitoring) for the mean of m measurements is computed as s x – t [m – 1,0.95] -------- . m

Equation 11-8

The 95% normal UCL (corrective action) for the mean of m measurements is computed as s x + t [m – 1,0.95] -------- . m

Equation 11-9

If m < 8 , nondetects are replaced by one half of the QL because with fewer than eight measurements, more sophisticated statistical adjustments are not appropriate. Similarly, a normal UCL is used because seven or fewer samples are insufficient to confidently determine distributional form of the data. Use of a lognormal limit with small samples can result in extreme limit estimates; therefore, default to normality for m < 8. If m * 8 , use Aitchison’s (1955) method to adjust for nondetects and test for normality and lognormality of the data using the single group or multiple group version of the Shapiro-Wilk test (see following section for details). The multiple group version of the Shapiro-Wilk test is used when there are multiple measurements from multiple onsite locations (use 95% confidence level). Note that alternatives such as Cohen’s (1961) method can be used, however the reporting limit must be constant for each constituent, which is rarely the case. If m * 8 and the data are neither normally nor lognormally distributed, compute the 95% nonparametric LCL or UCL for the median of m samples (see Hahn and Meeker, 1991, Section 5.2 and Gibbons and Coleman, 2001). Alternatively, if the data are lognormally distributed, compute a lognormal LCL or UCL for the mean (see Land, 1971). The (1- _) 100% lognormal UCL for the mean is:

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

H 1 – _s ¥ £ exp ² y + 0.5s y + ------------------y´ , ¤ m – 1¦

Equation 11-10

The (1 - _) 100% lognormal LCL for the mean is H _s ¥ £ y exp ² y + 0.5s y + ----------------´ , ¤ m – 1¦

Equation 11-11

In general, the LCL or UCL for the mean should be used except in the nonparametric case where it is not defined. In addition, caution should be taken using Land’s method in that it is not robust to departures from lognormality. The factors H are given by Land (1975) and y and sy and the mean and standard deviation of the natural log transformed data (i.e., y = loge(x)). The lognormal LCL or UCL for the median is simply the exponentiated result of computing the normal LCL or UCL on natural log transformed data (see Hahn and Meeker, 1991; Gibbons and Coleman, 2001). Use Sen’s nonparametric trend test to evaluate trends (both increasing and decreasing) to demonstrate the effectiveness of corrective action (see Gibbons, 1994, pp. 175-178). The Mann-Kendall test is also a valid alternative (see Gibbons, 1994 which also discusses methods for seasonal adjustments). Confidence Limits for Other Percentiles of the Distribution For some applications, there may be interest in a LCL or UCL for a specific percentile of the distribution (e.g., 90th, 95th or 99th percentiles of the concentration distribution). Of course, in the nonparametric case, only confidence limits for percentiles are available, such as the 50th percentile of the distribution (i.e., the concept of confidence limits for the mean does not exist without a specific parametric form of the distribution). For those constituents with short-term exposure risks or in those cases in which one may wish to show added environmental protection, confidence limits for upper percentiles of the distribution may be used (e.g., 90th, 95th or 99th percentiles). The interpretation here is that there is 95% confidence that 95% of the distribution is beneath the estimated confidence limit. Both LCLs and UCLs for upper percentiles can be computed and normal, lognormal and nonparametric approaches have been described in general by Hahn and Meeker (1991) and more recently by Gibbons and Coleman (2001) and are closely related to statistical tolerance limits.

11.11.2 Generation of the Background Prediction Limit When the background upper prediction limit exceeds the regulatory criterion or standard, then onsite measurements are compared to the 95% confidence upper prediction limit based on all available background data for that constituent. The following section presents the method by which the prediction limit is computed. Case 1: Compounds Quantified in All Background Samples For ground water, obtain a minimum of four measurements from at least two background sampling locations. For soils, obtain measurements from a minimum of eight different background sampling locations. For ground water, in which measurements are taken repeatedly from the same sampling location (i.e., an upgradient sampling well), test normality of distribution using the multiple group version of the Shapiro-Wilk test (Wilk and Shapiro, 1968) applied to n upgradient or background measurements. The n background measurements refer to all available background measurements obtained at multiple background sampling locations (spatial) and all available sampling events (temporal). The multiple group version of the original Shapiro-Wilk test (Shapiro and Wilk, 1965) takes into consideration that upgradient measurements are nested within different upgradient sampling wells; hence, the original Shapiro-Wilk test does not apply. This computation is described by Gibbons (1994, pp. 228-231). For soils, the n background samples can be tested for normality using the original Shapiro-Wilk test (Gibbons, 1994, pp. 219-222) because each measurement is obtained from a unique background sampling location. If normality is not rejected (i.e., at the 95% confidence level), compute the 95% (i.e., site-wide) prediction limit as: 1 1 x + t [n – 1,1 – _] s ---- + --- , m n

Equation 11-12

where n

x =

xi

- ---n- ,

Equation 11-13

i=1

n

s =

i=1

2

( xi – x ) -------------------- , n–1

Equation 11-14

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ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

where _ is the false positive rate for each individual test, t[n-1,_] is the one-sided (1 - _) 100% point of Student's tdistribution on n - 1 degrees of freedom, n is the number of background measurements and m is the number of measurements from which the onsite source area mean is computed. Note that if individual onsite measurements are to be compared to background (e.g., the most recent measurement from each location), m = 1 and the prediction limit becomes:

Total Chrome For Location HA12A-ROW Exceedance of Standard/ Normal Limit 1.00 0.90 0.80 0.70

Mg/l

0.60 0.50 0.40

1 x + t [n – 1,1 – _] s 1 + --- . n

Equation 11-15

0.30

Key 0.20 Detect 0.10

1 1 exp £ y + t [n – 1,1 – _] s y ---- + --- ¥ ¤ m n¦

,

Equation 11-16

where n

y =

log e ( x i )

- -----------------n

Equation 11-17

,

1996

95% UCL for the Mean

1997

Oct.

Jan.

July

Jan.

April

Oct.

July

April

Oct.

Jan.

Jan.

Samples

July

0.00 Outlier

April

Select _ =.05/k, where k is the number of comparisons (i.e., sampling locations or source areas times the number of constituents). If normality is rejected, take natural logarithms of the n background measurements and recompute the multiple group Shapiro-Wilk test. If the transformation results in a nonsignificant G statistic (i.e., the values loge (x) are normally distributed), compute the lognormal prediction limit as:

ND

1998

1999

Month / Year

Standard

Figure 11-34 Comparison to a Standard If log transformation does not bring about normality (i.e., the probability of G is less than 0.01), compute the nonparametric prediction limit which is an order statistic (i.e., an ordered measurement such as the maximum) of the background concentration measurements. For the case of m = 1, tables are provided by Gibbons (1994, Chapter 2) for

Table 11-22 Example Total Metal Confidence Limits

i=1

Worksheet 2 - Comparison to Standard Total Chrome at HA12A-ROW Normal Confidence Limit mg/L

and Step

n

Sy =

( log e ( x i ) – y )

2

- ----------------------------------n–1

.

Equation 11-18

Equation

Description

1

Percentile = mean of the onsite / downgradient distribution.

2

X = sum[X] / M

Compute the mean of the m onsite / downgradient measurements.

i=1

= 0.924 / 4

For m > 1 this lognormal prediction limit is for the onsite geometric mean or median concentration. To compute an approximate lognormal prediction limit for the onsite arithmetic mean concentration (m > 1) use Land’s method and compute (see Gibbons and Coleman, 2001).

= 0.231

3

S = ((sum[X2] - sum[X]2 / M) / (M-1))1/2 = ((0.357- 0.854 / 4) / (4-1)1/2 = 0.219

4

1/2

UCL = X + tS/M

1/2

= 0.231 + 2.353*0.219/4

1 1 exp £ y + 0.5s y + H 1 – _ s y ---- + --- ¥ . ¤ m n¦

Compute the standard deviation (sd) of the m onsite/ downgradient measurements.

= 0.488

Equation 11-19 5

Compute the upper confidence limit for the mean of the m onsite/ downgradient measurements.

Confidence = 0.95 Confidence level for this location and constituent

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ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

confidence levels based on using the largest (x(n)) or second largest (x(n-1)) measurement as the prediction limit as a function of n and k with and without verification resampling. For m > 1, one-sided nonparametric prediction limits for the median of m onsite measurements are given by Hahn and Meeker (1991, Section 5.5.2). In the context of ground-water monitoring, this general decision tree is described in ASTM D6312-98 (formerly PS64-96). Case 2: Compounds Quantified in at Least 50% of All Background Samples Apply the multiple group Shapiro-Wilk test to the quantified measurements only. If the data are normally distributed compute the mean of the n background samples as: n x = £ 1 – ----0-¥ x' ¤ n¦

Equation 11-21

Where no is the number of samples in which the compound was not detected, n is the total number of measurements and x' is the average of the n - no detected values. The standard deviation is:

s =

n 0 – 1¥ 2' £ 1 – n----0-¥ s 2' + n----0- £ 1 – ------------- x ¤ ¤ ¦ n n–1¦ n

Equation 11-22

where s' is the standard deviation of the n - n0 detected measurements. The normal prediction limit can then be computed as previously described. This method is due to Aitchison (1955). If the multiple group Shapiro-Wilk test reveals that the data are lognormally distributed, replace x' with y' and s' with s'y in the equations for x and s. The lognormal prediction limit for the onsite mean or median concentration may then be computed as previously described. Note that this adjustment only applies to positive random variables. The natural logarithm of concentrations less than 1 are negative and therefore the adjustment does not apply. For this reason, add 1 to each value (i.e., loge(xi + 1) * 0) and subtract 1 from the exponentiated limit. If the data are neither normally or lognormally distributed, compute a nonparametric prediction limit. Case 3: Compounds Quantified in less than 50% of All Background Samples For individual comparisons of the most recent measurement in each sampling location to background (i.e., m

= 1), the nonparametric prediction limit for the next single measurement in each of k sampling locations is the largest concentration found in n background measurements. Gibbons (1990, 1991, 1994) has shown that the confidence associated with this decision rule is a function of the multivariate extension of the hypergeometric distribution. Complete tabulation of confidence levels for n = 4,..., 100, k = 1,..., 100 comparisons (i.e., sampling locations) is presented in Gibbons, 1994 (Table 2.5). To compare the source area median to background (i.e., m > 1), compute a nonparametric prediction limit for the 50th percentile of the distribution of m onsite samples based on n background samples using the method described by Hahn and Meeker (1991, Section 5.5) and Gibbons and Coleman (2001). In the context of ground-water sampling with m = detection 20.8%, this general decision tree is described in ASTM D 6312-98. Detection of Outliers - From time to time anomalous results may be found among background samples due to a laboratory, sampling or clerical error. The net result is that the background prediction limit will be dramatically larger than it should be, leading to a less environmentally conservative sampling program. To eliminate these problems, background data are screened for others using Dixon’s test at the 99% confidence level (see Gibbons, 1994, pp. 254-257). Example This example illustrates the use of statistical procedures at a site undergoing long-term monitoring. At the X Site (Site) manufacturing operations have ceased, all production equipment has been relocated and the Site has been sold to a third party. Hexavalent chromium was detected in soil and ground water in the vicinity of a former chromium plating area located in the southeast quadrant of the facility. Site investigations defined the distribution of chemical constituents and physical characteristics of this area and an interim ground-water remediation system was designed and installed as the primary remedial action component for ground water. The system includes a blasted bedrock trench, a ground-water recovery system with electrical controls, a remote telemetry unit (RTU) and an ion exchange ground-water treatment system which discharges treated ground water to the sanitary sewer system. A baseline sampling event occurred August 1 through 5, 1996, prior to remedial system start-up and permanent operation. After initiation of permanent operation, selected wells were monitored biweekly for the first month of operation and quarterly thereafter. Other selected wells are monitored on an annual basis. The ground-water protection standard for total chromium is 0.05 mg/L (ppm).

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ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Following this guidance (see Section 11.11), compare the 95% UCL for the mean concentration for the last four available measurements for each monitoring well and constituent to the relevant criterion and test for both increasing and decreasing trends in all of the data for each well and constituent using Sen's test. To illustrate the method, data for total chromium in monitoring well HA12A-ROW were analyzed. Figure 11-34 presents the graphical results of the analysis and Table 11-22 presents step by step computational details. Inspection of Figure 11-7 and Table 11-22 reveals that: (1) there is a decreasing trend in the well, which demonstrates the beneficial effects of the remediation; (2) the most current measurement is now close to the cleanup criterion of 0.050 mg/L; and (3) the UCL for the mean concentration is 0.488 mg/L which is still an order of magnitude above the criterion indicating that remediation should continue. REFERENCES 40 CFR Part 264 and FR Vol. 53 No. 196 pp. 39720-39731, October 11, 1988. Aitchison, L., 1955. On The Distribution of A Positive, Random Variable Having a Discrete Probability Mass at the Origin, Journal of the American Statistical Association, 50, 901-908. Baedecker, M. J., and Back, W., 1979. Hydrogeological Processes and Chemical Reactions at a Landfill: Ground Water, v. 17, pp 429-437. Benjamin J. R. and C. A. Cornell, 1970. Probability Statistics and Decision for Civil Engineers. McGraw-Hill Book Company, New York Chou, Y. M. and D. B. Owen, 1986. One-Sided DistributionFree Simultaneous Prediction Limits For Future Samples, Journal of Quality Technology, 18, pp. 96–98. Clayton, C. A.; J. W. Hines; and P. D. Elkins, 1987. Detection Limits With Specified Assurance Probabilities, Analytical Chemistry, 59, pp. 2506–2514. Cohen, A. C., 1961. Tables for maximum likelihood estimates: singly truncated and singly censored samples. Technometrics 3, 535-541. Currie, L. A., 1968. Limits for Qualitative Decision and Quantitative Determination, Analytical Chemistry, 40, pp. 586– 593. Davis, C. B. and R. J. McNicols, 1988. Statistical Issues and Problems in Ground-Water Detection Monitoring at Hazardous Waste Facilities, Ground Water Monitoring Review v. 7, pp. 72-76. Doctor, P. G. et al., 1986. Draft - Statistical Comparisons of Ground-Water Monitoring Data, Ground-Water Plans and Statistical Procedures to Detect Leaking at Hazardous Waste Facilities, PNL-5754, Pacific Northwest Laboratories, Richland Washington 55112. Doctor, P. G., R. O. Gilbert, R. A. Saar and G. Duffield, 1985. An Analysis of Sources of Variation in Ground-Water Monitoring Data of Hazardous Waste Sites, Milestone 1.

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Revised Draft EPA Contract No. 68-01-6871. Battelle Pacific Northwest Laboratories. Richland, WA. Fisher and Potter, 1989. Methods for Determining Compliance with Ground Water Quality Regulations at Waste Disposal Facilities, Wisconsin Dept. of Natural Resources, Jan. 120 pp. Freeze, R. A., and J. A. Cherry, 1979. Ground water, Prentice– Hall, Inc., NJ, 604 pp. Gibbons R. D., and Coleman D. E., 2001. Statistical Methods for Detection and Quantification of Environmental Contamination, John Wiley and Sons, 2001. Gibbons, R. D., 1987. Statistical Models for the Analysis of Volatile Organic Compounds in Waste Disposal Facilities, Ground Water, 25, . Vol. 21, pp. 572-580. Gibbons, R. D. (1990). A General Statistical Procedure for Groundwater Detection Monitoring at Waste Disposal Facilities, Ground Water, 28, 235-243. Gibbons, R. D. (1991). Some Additional Nonparametric Prediction Limits For Groundwater Monitoring at Waste Disposal Facilities. Ground Water., 29, 729-736. Gibbons, R. D., 1994. Statistical Methods for Groundwater Monitoring, Wiley, New York, Gibbons, R. D., 1987. Statistical prediction intervals for the evaluation of ground water quality. Ground Water, 25, pp. 455–465. Gibbons, R. D., 1988. A General Statistical Procedure for Ground Water Detection Monitoring at Waste Disposal Facilities. Ground Water. Gibbons, R. D., 1996. Some Conceptual and Statistical Issues In Analysis of Groundwater Monitoring Data. Environmetrics, 7., 185-199. Gibbons, R. D., and Baker, J. A., 1991. The Properties of Various Statistical Prediction Intervals for Groundwater Detection Monitoring, Environmental Science and Health A26(4), pp. 535-553. Gibbons, R. D., F. H. Jarke and K. P. Stoub, 1988. Method Detection Limits. Proc. Fifth Annual USEPA Waste Testing and Quality Assurance Symp., 2, 292-319. Goodman, I. and K. Potter, 1987. Graphical and Statistical Methods to Assess the Effects of Landfills on Groundwater Quality, Report to Wisconsin Department of Natural Resources, Bureau of Solid and Hazardous Waste,. Goodman, I., 1987. Graphical and Statistical Methods to Assess the Effect of Landfills on Groundwater Quality. M.S. Thesis. University of Wisconsin Madison. Green, W. R., 1985. Computer-Aided Data Analysis, A Practical Guide, John Wiley and Sons, 268 p. Hahn, G. J. and W. Q. Meeker, 1991. Statistical Intervals: A Guide for Practitioners, Wiley, New York. Hahn, Gerald J., 1970a. Statistical Intenals for a Normal Population, Part 1. Examples & Applications, Journal of Quality Technology. Vol. 2, No. 3 (July): 1 15-125. Hamilton, L. F. and Simpson, S. G., 1960. Calculations of Analytical Chemistry McGraw-Hill Book Company. Harris, J., J. C. Loftis and R. H. Montgomery, 1987. Statistical Methods for Characterizing Ground-Water Quality, Ground Water. Vol. 25, No. 2 (March-April): 185193EPA, Oct. 11, 1988.

ORGANIZATION AND ANALYSIS OF WATER QUALITY DATA

Hem, J. D., 1970. Study and Interpretation of the Chemical Characteristics of Natural Water, U.S. Geological Survey Water-Supply Paper 1473, 363 p. Hurd, M., 1986. Personal Communication. Hoaglin, D. C., F. Mosteller and J. W. Tukey, 1983. Understanding Robust and Exploratory Data Analysis, John Wiley & Sons, New York. Hoaglin, D. C., F. Mosteller and J. W. Tukey, 1983. Understanding Robust and Exploratory Data Analysis, John Wiley & Song, Inc. Hubaux, A. and G. Vos., 1970. Decision and Detection Limits For Linear Calibration Curves, Analytical Chemistry, 42, pp. 849–855. Jarke, F., 1990. Is it Possible to Understand MDLs, PQLs, IDLs, EMLRLs, etc. Lab Notes, 2 pp. Land, C. E., 1971. Confidence intervals for linear functions of the normal mean and variance. Annals of Mathematical Statistics, 42, 1187-1205. Land, C. E, 1975. Tables of confidence limits for linear functions of the normal mean and variance. In, Selected Tables of Mathematical Statistics, Vol. III, American Mathematical Society, Providence, RI, pp. 385-419. Loftis, J. C., J. Harris and R. H. Montgomery, 1987. Detecting Changes in Ground Water Qauality at Regulated Facilities. Monitoring Review. (Winter1987): 72-76. McBean, E. and F. A. Rovers, 1984. Alternatives for Handling Detection Limit Data in Impact Assessments. Ground Water Monitoring Review. Vol. 4, No. 2 (Spring): 42-44. McGill, R., J. W. Tukey and W. A. Larsen, 1978. Variations of Box Plots, The American Statistician. Vol. 32, No. 1 (Feb.): 12-16. Meierer, R. E. and R. J. Whitehead, 1989. Making an On-Site Evaluation of an Analytical Services Laboratory, Enviromental Claims Journal, Vol. 1, No. 4, pp. 503-515. Miller, M. D. and F. C. Kohout. (Undated.) RCRA Ground Water Monitoring Statistical Comparisons: A Better Version of Student’s t-Test. Mobil Research and Development Corporation. Paulsboro, NJ. Montgomery, R. H. and J. C. Loftis, 1987. Applicability of the TTest for Detecting Trends in Water Quality Variables, Water Resources Bulletin. Vol. 23, No. 4: 653-662. Montgomery, R. H., J. C. Loftis and J. Harris, 1987. Statistical Characteristics of Ground-Water Quality Variables, Ground Water, Vol. 25, No. 2 (March-April): 176-184. Piper, A. M., 1944. A Graphic Procedure in the Geochemical Interpretation of Water Analysis, Trans Amer. Geophys. Union, 25, pp. 914-923. Rosner, B., 1975. Technometrics, 17, 221-227. Sen, P. K., 1968. Estimates of the regression coefficient based on Kendall’s tau. Journal of the American Statistical Association, 63, 1379-1389. Sen, Z., 1979. Application of the Autorun Test to Hydrologic Data. Journal of llydrology. Vol. 42: 1-7. Sen, Z., 1982. Discussion of Statistical Considerations and Sampling Techniques for Ground-Water Quality Monitoring by J. D. Nelson and R. C. Ward. Vol. 20: 494-495.

Shapiro, S. S. and Wilk, M. B., 1965. An Analysis of Variance Test For Normality (Complete Samples). Biometrika, 52, 591611. Silver, Carl A., 1986a. Statistical Approaches to Groundwater Monitoring, Open File Report #7, University of Alabama, Environmental Institute for Waste Management Studies. U.S. EPA, 1988. Test Method’s for Evaluating Solid Waste, Physical Chemical Methods (SW-846) U.S. EPA, 1988. 40 CFR Part 264: Statistical Methods for Evaluating Ground Water Monitoring from Hazardous Waste Facilities; Final Rule. Federal Register, 53, 196, pp. 39720–39731. U.S. EPA, 1992. Addendum to Interim Final Guidance Document Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities. U.S. EPA, 1989. Interim Final Guidance Document Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities (April). Wald, A. and J. Wolfowitz, 1946. Tolerance Limits for a Normal Distribution, Ann. Math. Statistics, 17, pp. 208–215. Wilk, M. B. and S. S. Shapiro, 1968. The Joint Assessment of Normality of Several Independent Samples, Technometrics, 10, 825-839.

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CHAPTER 12 REPORTING This chapter reviews both proposal preparation guidelines and the overall reporting of technical data in reports and long-term documentation. These guidelines were also prepared to assist engineering and science staff with the assessment of proposals written for site assessments. The guidelines provide formats recommended so that the scope, schedule and costs of technical services are fully documented so that during later execution of the project both the client and the consultant know fully well the expected product of the investigation and the project deliverables. Requests for Proposals (RFPs) are typically the first step in a project. Although the client may have spent tens, hundreds or even thousands of hours preparing the RFP, the consultant’s first contact with a specific project is likely to be through the RFP transmitted from the client. Addressing the specific points of the RFP should be the first goal when the proposal comes into the office. Proposals represent legal agreements between clients and consultants; hence, it is important to document the details of the various components of a proposal just as in a formal contract. As with any contract the terms and limitations are important for protecting both the client and the consultant. The proposal typically consists of four major parts: 1. Introduction. Here the consultant briefly sets down everything needed to inform the reader about the problem being presented. The proposal should be identified. The consultant should explain how the idea originated. The subject matter of the proposed project should be clearly identified. There should also be comments on the importance of the problem. The consultant’s qualifications for the work should be presented. If it can be done briefly, there should be a preview of the proposal. 2. Body. Here we would expect the consultant to develop the substance of the proposal in all necessary detail. This should be the longest section of the proposal, This section would typically be called the “Scope of Work.” For topical contents, see the next section.

3. Conclusion. Here the text should consolidate what the consultant has discussed in the body of the proposal and to encourage acceptance and precipitate action. Again, the consultant may stress the importance of the problem. The consultant may also suggest an interview or assert willingness to modify portions of the proposal if required by unforeseen events. 4. Attachments. Here the consultant can insert display matter and back-up matter that would interrupt the main presentation in the body of the proposal. Possibilities for inclusion here are testimonial letters from previous clients, flow-charts of the intended work program and descriptions of past projects. This guideline focuses on the components of a typical hydrogeological/geotechnical proposal for which a RFP has been prepared and for which the estimate of the consultant’s fee is based on a time and materials contractual arrangement. 12.1 MEET WITH THE CONSULTANT A successful proposal effort should reflect the needs of the client and demonstrate that the expectations are clearly understood. Therefore, a clear understanding of the client’s thinking and expectations is essential to any project. The basic expectations are set forth in the RFP, but frequently the RFP is only the beginning of the proposal effort. After distribution of the RFP, a client would expect to the consultant to contact the responsible engineer. This discussion should clarify the client’s expectations so that the proposal reflects that understanding. 12.2 PROPOSAL CONTENT A typical proposal may conform to the following annotated outline or can vary to a greater of lesser degree. A client may have many consulting companies currently under master agreement contracts, although variations in proposal content should be expected; however, major devi-

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ations from an acceptable standard format should be avoided. 12.2.1 Title Page The title page should show the title, local division and address, proposal number and the date of issue (see Figure 12-1). 12.2.2 Transmittal Cover Letter The cover letter of a proposal should be relatively direct; in most instances, it should not exceed one to two pages. The cover letter should transmit the proposal, citing its title and number of copies submitted. Reference to the RFP and any subsequent contact which may have had a bearing on understanding of the client’s requirements should also be cited. The cover letter should also highlight those aspects of the proposal that may affect the client’s attitude toward the proposal. The consultant, for example, may wish to direct the client’s attention to the strengths of the proposal or explain various alternatives or modifications the client should consider in selecting a consultant that will serve the needs the best. It should be signed by an authorized representative of the consultant who has legal authority to sign. For a sample cover letter, see Figure 12-2. 12.2.3 Table of Contents A simple table of contents should be prepared, containing the major outline headings listed below and adding subheadings as necessary. A list of figures and tables may also be included. See Figure 12-3 for a sample table of contents. 12.2.4 Introduction This section should contain a basic discussion of the proposed work, answering the question, “What is the purpose of the project?” It should include the request for proposal date and repeat the requirements set forth in the RFP. It should indicate general understanding of the problem and the consultant should briefly describe any possible difficulties. This section should also contain a general description of the objectives of the proposed project. 12.2.5 Scope of Work This section should set forth the limits of the technical services by explaining in general what services are to be provided. The scope statement sets boundaries and states what is to be done within these boundaries. In other words,

876

the scope statement establishes the depth, breadth and means of the consultants approach. Also, for everyone’s protection, the consultant may include in it observations regarding what will or will not be done. For example, the Scope of Work section of a hydrogeological proposal might discuss: • • • •

Geophysical survey Field drilling program Laboratory testing installation of monitoring wells Permeability tests evaluation report

Individual scopes of work must be specific to the site in question; guidance for components of Scope of Work is available in this chapter. 12.2.6 Approach This section should state how the work will be done by the consultant who provides a detailed description (methodology) of the proposed work. This section is often subdivided according to phases/tasks and/or disciplines to be considered. All but the simplest projects require a breakdown into tasks. One task may consist of initial exploration and planning, another a search of the literature, another correspondence and interviews and so on. To try to do everything at one time produces confusion and dispersion of effort. Furthermore, one or several tasks may have to be completed before others can be started. Breaking a project into its component tasks also gives some assurance that the total job will be done in an orderly manner and be completed on schedule. These guidelines for RFPs provide significant direction as to the Scope of Work; however, the methodology often requires definition by the consultant as to test methods. 12.2.7 Schedule Each proposal should include a program plan or schedule chart (Figure 12-3). With few exceptions, work proposals and agreements specify the calendar period within which projects are to be completed. The period may extend for days, months or years. Further, the schedule may stipulate that portions of the work are to be done in a stated order and are to be completed by a given date. Time and effort must be carefully allocated; it is common practice to prepare a time-based flow-chart on a wall. Even limited projects require planning for efficient performance to guarantee that work will be completed by target or deadline dates. The amount of detail to be shown should govern the

REPORTING

LEAKY ACRES LANDFILL CO. PROPOSAL ENVIRONMENTAL BASELINE STUDIES FOR A SANITARY LANDFILL PROJECT SUNNY VALLEY, COLORADO

Ewing Consulting Services 55 Alexander Street Dallas, Texas 41735

Figure 12-1 Example of Proposal Title Page 877

REPORTING

Figure 12-2 Example Proposal Transmittal Letter 878

REPORTING

Figure 12-3 Example Proposal Table of Contents

879

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Figure 12-4 Example of a Simple Proposal Schedule

type of presentation. The standard presentation is a bar chart with markers to indicate significant events. With the increased use of PERT, some companies are using PERT charts in place of bar charts. Either method is acceptable for the typical site assessment project. Normally, the text will only supplement the schedule. Therefore, the amount of text in this section will be limited, even in a large program. In any program longer than three

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months, check-points and review points should be noted. This will indicate to the owner that tight operational and fiscal control of the program is planned. If the program is extended (i.e., 2 to 5 years), large expenditures should be phased-in with the the clients funding procedures. The project schedule answers the question, “When will it be done?” Adequate schedule is often the deciding factor in awarding a contract. The project schedule is most effec-

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tively conveyed in the proposal by means of a figure such as that shown in Figure 12-4. The schedule should be simple and easily understandable, conveying the message that the project will be completed in the time specified. The text portion of the proposal should refer to the figure and highlight the importance of the schedule to the overall project. 12.2.8 Project Organization and Schedule The project organization should be presented to the client as a chart showing how the principal investigators have been organized to help the owner’s engineer accomplish the project objectives. The project’s director, principal investigator and project manager should be introduced and their experience discussed. All staff should be detailed within this section (see Figure 12-5). Qualifications and the vitae of key personnel should be appended to the proposal. However, if the consultant cannot guarantee the availability of such persons for the project, their potential contributions should not be stated as a firm promise; otherwise, the contract may be broken on the grounds of misrepresentation.

ment or as promising follow-up maintenance and consulting services free of extra cost. Therefore, a clear and specific statement of products to be delivered, while it commits the consultant, also sets bounds on what are to be delivered. Often it is beneficial to clearly describe in the proposal the deliverables of the project, on a task by task basis so there is no misunderstanding of exactly what will be the products of the work. 12.2.11 Costs The consultant should detail the expected costs associated with the execution of the project using actual labor charges of the people that will be used on the project. Multiple tables should be constructed defining individual costs for labor, reimbursables and support costs as shown in Figures 12-6 and 12-7. The spreadsheet formats allow for rapid costing of the project tasks. Because these spreadsheet programs are available in every engineering office, the use of such programs is essentially mandatory for the project costing efforts.

12.2.9 Previous Experience 12.3 DOCUMENTATION Lack of experience in someone offering a proposal makes a client pause, whereas successful accomplishments in the past promise success in the future. Whenever possible, therefore, the consultant should cite earlier successes with similar problems when preparing the new proposal. It is not essential that the past and present problems be identical, only that they overlap and have major points in common. Dates, contract numbers, names and addresses should be provided so that the client can verify the statements. 12.2.10 Products of the Project Stating what the consultant is to produce throughout a project and at its termination commits the writer of the proposal to definite performance and productiveness. In terms of the typical field investigation, details on the numbers, locations, expected depths and reasons for the exploration provide a clear vision of the expected program. The technical reasons for every borehole should be described in the proposal. While these data may (or even should) change due to unknown field conditions, the reasons for gathering data are an important part of technical proposals. Sometimes the consultant may find it burdensome and costly to satisfy all points of the client’s RFP. By dodging these issues and not specifying exactly what will be produced and supplied, the consultant may create future problems. The owner, for example, may construe the proposal as promising delivery of a working model or prototype equip-

12.3.1 Introduction Much of this Site Assessment and Remediation Handbook revolves around the documentation typically applied to site assessments. Proposals for technical work, quality assurance and both progress and final reports make up much of the documentation for site assessment of a waste disposal facility. It is important for both the consultant and the facility engineer to understand the various technical, schedule and financial elements of the proposed scope of work. The proposal is a legal document committing the consultant to perform the agreed work elements within the schedule given for the cost estimate. The owner is committed to pay the consultant if the agreed-upon price if all elements are performed satisfactorily. This straightforward concept, however, often becomes quite complex in execution. Subsections 12.1 and 12.2 provide detailed information on the form and content of proposals to assist in the review of such documents. The requirement to deal with both real and perceived risk from both sanitary and hazardous waste facilities makes the technical quality of studies performed by consultants of the utmost importance to the long-term success of the owner. Clearly, the only time-tested solution to maintenance of technical quantity to reduce environmental risk is to apply a quality assurance program to the site-based work

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performed by consultants. Quality assurance has been used since the 1950s in aerospace and later for nuclear power plant siting and high level radioactive waste repository site investigations. Many owners and operators currently use modified quality programs in analytical laboratory programs. Quality assurance provides a planned and systematic approach of developing and applying actions necessary to assure the quality of output from work activities. It helps to avoid omissions and oversights that could adversely affect

quality and, hence, increase long-term risk to the owner. Quality assurance for geologic investigations could be defined as follows: the planned and systematic actions necessary to provide adequate confidence that data are valid, have integrity and are preserved and retrievable. The goal of quality assurance is to help achieve success. Its purpose is not to replace established work practices, but to supplement them as necessary to produce an effective control program.

Project Team Organization Chart

Figure 12-5 Example of a Proposal Organization Chart 882

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The quality assurance standard, which the author believes would fit the typical owner’s program, is ANSI/ ASME NQA-1. Based on NQA-1, nine principles of quality assurance have been identified for geologic/hydrogeologic investigations. The principles include practices that are easily associated with geologic work activities: (1) planning and organization of activities, (2) preparation and control of procedures, (3) training and qualification of personnel, (4) control and handling of samples, (5) acquition and protection of data; (6) peer review, (7) identification and correction of deficiencies, (8) use and control of records, and (9) control of purchased items and services. Most investigations do not require a fully formalized QA program be used on non-RI/FS projects; however, some projects may require the addition of QA elements. Reports on the completed scope of work are a major subsection element. Details on format, scope and content are included in the Subsection 12.3. In general, the author believes flexibility is important in the documentation of many site assessments; however, all field based drilling,

logging and well/piezometer installation must be fully documented to stand the test of time. Sample logging and field forms in addition to well/piezometer completion diagrams are provided in Chapter 7 of this text. Requirements for progress reports are also important as the necessity for multitask projects becomes more typical. Documentation often walks a fine line between not enough and too much. In practice, field activities rarely are documented to the extent that it becomes a burden. 12.4 QUALITY ASSURANCE FOR SITE ASSESSMENT INVESTIGATIONS 12.4.1 Introduction Investigations associated with site characterization include a variety of work activities from which data are obtained and analyzed, leading to site selection and permitting of landfills. The quality of data and the validity of the analyses will have a significant influence on the site

Figure 12-6 Example of a Proposal’s Manpower Spreadsheet

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selection and permitting processes. Obtaining acceptable quality will depend, of course, on how well those work activities are performed. The application of appropriate principles of quality assurance will assist in achieving adequate performance, particularly if those principles are effectively integrated into the work activities. Application of the nine principles of quality assurance for hydrogeologic investigations have been selected (see Table 12-1) requires knowledge of the activity’s objective(s), work tasks, constraints, potential sources of loss and failure and the consequences of loss and failure. Also required is an understanding of the principles and how they are used. This process has four steps. The first is to define the technical and programmatic objectives and requirements of the work activity. The second is to identify within the work activity sources of risk and then to evaluate those risks in terms of probability and consequences. The third step is to select the principles of quality assurance that will provide the control needed for successful completion of the activ-

ity. These steps should be carried out early so that quality assurance can be more effectively integrated into the work. The fourth step is implementing the selected principles. Hydrogeological studies involve the following types of activities: • • • • • •

Gathering and evaluating historical data and information Making regional and site geologic, hydrogeologic and geophysical surveys Collecting samples through in situ geologic sampling Gathering and evaluating test and measurement data through laboratory tests and field analyses; Performing field experiments and demonstrations Processing and analyzing geologic data

Much of the data and information obtained from these activities ultimately becomes the technical bases upon which site selections will be made. The quality and unifor-

Figure 12-7 Example of a Proposal Rebillables Spreadsheet 884

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Table 12-1 QA Principals for Geologic Investigations

mity of that data are extremely important. All scientific disciplines have established practices that provide control over various sources of loss and failure that can occur when carrying out experiments and studies. Such practices help to assure the scientists that scientific activities are properly planned and executed so that useful (quality) data are obtained. Comparison of practices used by scientists with quality assurance practices often shows that both types are clearly related. Thus, quality assurance is used by scientists to some degree whether or not they are consciously doing so. Quality assurance provides a planned and systematic approach for developing and applying actions necessary to assure the quality of output from work activities. It helps to avoid omissions and oversights that could adversely affect quality. A generally accepted definition of quality assurance is as follows: the planned and systematic actions necessary to provide adequate confidence that a material, component, system or facility will perform satisfactorily in service. Based on this definition, quality assurance for geologic investigations could be defined as follows: the planned and systematic actions necessary to provide adequate confidence that data are valid, have integrity and are preserved and retrievable. The goal of quality assurance is to help achieve success. Its purpose is not to replace established work practices, but to supplement them as necessary to produce an effective control program. The sources for identifying the planned and systematic actions needed for our program are quality assurance standards. They provide the requirements established or criteria for effectively carrying out such functions associated with work activities as: • • • • • •

Organizing roles and responsibilities of people Preparing and qualifying procedures Training and qualifying personnel Obtaining and preserving information (data) Assessing and improving performance Purchasing items and services

Standards have been developed for nuclear energy and aerospace programs and, although names and arrangements of the standards vary, they all use the same basic logic for controlling work activities. Implementation of an appropriate quality program will provide not only a more reliable gathering of site data and, hence, reduced corporate risk, but also can be an effective marketing and permitting tool. Because these sites can be involved in litigation many years into the future, a quality program with retrievable documentation is the most cost-effective solution for field based studies. 12.4.2 Planning and Organization of Activities Planning and organizing work activities are identified as a principle because a conscious and deliberate planning and organizing effort for each important work activity is essential. Although this principle emphasizes a function that usually precedes the actual conduct of work, there is need to maintain a continuing planning effort until completion of a work activity. This need, unfortunately, can be too easily de-emphasized or overlooked, particularly during the work performance stages where cost and schedule priorities may dominate. The primary purpose of planning and organizing is the clear and specific identification of work requirements and objectives. Planning and organizing should clearly identify objectives, participants organizational interfaces, responsibilities, restraints or limitations and the expected result of the work. 12.4.3 Preparation and Control of Procedures Work activities are carried out in a planned, systematic and controlled manner so that the products or end results will conform to expected outcomes. The process used to produce such an outcome often involves discrete actions taken in a specific order. Any change in an action or in the order without a valid reason most likely will result in an unsatisfactory outcome. To control the processes and avoid effors leading to unsatisfactory results, procedures are written that provide guides for those doing the work. The significance of having a procedure for a specific activity depends on several factors such as the importance of the results to the overall success of the activity or larger project/program, the degree to which an error has an adverse effect on the end result, the state of the training and knowledge of those doing the work, the need to document the process used and the need to substantiate the technical basis of the process used. To be effective and to help provide credibility to the activity being performed, procedures should be well written, complete and correct.

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12.4.4 Training and Qualification of Personnel

12.4.7 Peer Review

An important factor affecting all work activities is the training and qualification of those doing the work. There are very few, if any organizations engaged in work activities that do not provide some type of training. Training can vary from direct, on-the-job training by a more experienced worker to a formal program involving both classroom and on-the-job training. The extent of training required depends on the complexity of the work, education and previous experience requirements, the economics involved and the overall importance of the work to meeting the goals of the organization. Closely associated with training is the concept of qualifying people for a job before beginning work. Qualification includes not only specific training, but also the review and verification of applicable education and experience. Using adequately trained and qualified people should be a requirement for all geologic investigations.

A way to validate practices is through independent peer review. Peer reviews can help validate technical adequacy and, perhaps more importantly, can validate the application of established practices. For those situations when practices are new or beyond the state of the art, independent peer review is essential.

12.4.5 Control and Handling of Samples

12.4.8 Identification and Correction of Deficiencies Deficiencies, as discussed here, include failures, defects, errors, deviations from specified requirements and other conditions considered adverse to quality. Uniform and well-defined practices are required to ensure proper control and disposition of deficiencies. These practices should emphasize the timely or prompt identification and correction of all deficiencies or conditions that might adversely affect the quality of continuing geologic investigations.

A source of data important to site hydrogeologic characterization is the analysis and testing of geologic materials associated with a landfill site. The reliability of the physical and chemical characteristics determined for each type of material depends on the validity of the processes used to analyze those materials and to make experimental tests. As important or even more important, is the integrity of the samples used. Invalid results will be obtained from samples that do not truly represent the materials from which they were taken. Loss of sample integrity can occur from inadequate sampling procedures and from improper control and handling practices once the samples have been taken.

12.4.9 Use and Control of Records

12.4.6 Acquisition and Protection of Data

12.4.10 Control of Purchased Items and Services

The practices used to assure proper acquisition and protection of data are of importance to essentially all facets of geologic investigations. Data are interpreted to include any site-related measurements or recordable observations acquired as a part of geophysical, geochemical or hydrological studies, plus the results of any associated laboratory analyses. In the broadest sense, data include any information generated for use in the technical assessment of site-related evaluations or experiments. The success of site explorations, experiments or any of the R&D-oriented site studies required to determine site landfill suitability depends on obtaining data that are applicable, sufficiently accurate, readily identifiable, retrievable and suitably preserved.

When items and services are required that are not available on-site, purchase of those items and services is usually necessary, which requires that procedures be established and followed to obtain the necessary quality. This will require that procurement actions follow uniform written procurement instructions which provide a systematic approach to the procurement process. It is essential that technical and quality requirements be properly evaluated and control practices be established according to quality needs. Evaluation should consider various factors, including cost and schedule effects, failure consequences, methods of acceptance, programmatic importance and applicable codes or standards.

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The use and control of records are key in providing documentary evidence of technical adequacy and quality for all hydrogeologic investigations. Records provide the direct evidence and support for the necessary technical interpretations, judgments and decisions for site selection. Records preparation and use must be an integral part of ongoing work activities. These records must directly support current or ongoing technical studies and activities and must provide the historical evidence needed for later reviews or analyses, particularly those which might be anticipated as part of the landfill permitting.

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12.5 REPORTS Report writing is a critical portion of any profession and this is particularly true in hydrogeology where word communication often is the only way a reader or client can "see" the problem. 1. Outline: First, make a thorough outline of your report to third- and fourth-order headings. Rework the outline and make certain that a logical sequence is followed and that one entry tends to lead into another. 2. In writing a hydrogeological report, you should have several sources before you: • E.B. White’s A Style Manual • Suggestions to Authors, published by U.S. Geological Survey; and • A recent issue of a Geological Society of America Bulletin, Ground Water or the Journal of Sedimentary Petrology. Almost all questions in form that arise can be answered by examining current articles, and the Geological Society of America Bulletins and Journal of Sedimentary Petrology are doubtless the best. Most clients expect both progress and final reports will be submitted during the course of an investigation. 12.5.1 Progress Reports Time and distance normally separate consultants from those who will make use of their findings. An accounting of progress, whether submitted as a bound report or as a

letter, helps to keep the owner in touch with the work being done. The main and obvious function of any progress report is to give the company an accounting of the work that has been done. It explains how the consultant has spent billable hours and the owner/operator’s money and what has been accomplished as a result of the investment. Though this purpose is dominant, do not lose sight of four other purposes that are discharged by a progress letter or report: 1. It enables the owner/operator to check on progress, direction of development, emphasis of the investigation and general conduct of the research. Thus, the owner/operator can alter the course of the work before too much time and money have been invested. 2. It enables the consultant to estimate work done and work remaining with respect to the total time and effort available. 3. It compels consultants to shape their material and focus their attention. 4. It provides a sample report that helps both the owner and the consultants to decide upon the tone, content and plan of the final report. Work is done and progress is made with the passage of time. This fact gives us a useful clue to the basic nature of every progress report, whether or not the particular format makes time the dominant element. However, the progresswith-time philosophy is clearly evident in the following scheme of reporting progress.

Figure 12-8 Example of a Progress Report Format

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The opening sections, Introduction and Project Description, seldom vary from one progress report to another in a series dealing with the same project. In fact, these two parts of a succeeding progress report are often created by correcting (updating) these parts of the preceding progress report. If changes have been made in the con-

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tractual agreement, the Project Description (also called Work Statement or Contractual Requirements) has to be updated to accord with the most recent agreement. This description spells out what the researcher is required to do and produce. That is, it represents the total job he is prepared to undertake.

Figure 12-9 Example of a Financial Status Spreadsheet

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The work done sections are of chief interest in most progress reports, for these sections describe, for better or worse, what has been accomplished during the work period (or periods) just closing. Progress, schedule and financial status documents are important components to progress reports. Figures 12-8 and 12-9 are easy to prepare and provide documentation that the consultant is in control of the costs of the project. For our purposes here, we can regard every progress report as having three main ingredients in the body: (1) the consumption or passage of time and the order of events throughout that time, (2) the allocation of effort from the task point of view, and (3) the activity or problem point of view.

•

12.5.2 Requirements for Independent Technical Reviews

Records preparation and control must be an integral part of ongoing work activities. The following items provide a series of steps for the use of records associated with site investigations. These points are important for the management of projects and the control of the completed data and reports. One should establish documentation and management actions to achieve the following:

For written reports or recommendations produced as final contractual deliverables, a detailed technical review will be performed by a qualified reviewer who is independent from the preparation of the document. At a minimum, independent technical reviews shall be documented by a standard review memo. Guidelines for using the memo are as follows: •

•

•

The review draft is complete when presented for review. Incorporation of informal comments sought when possible during the development of the review draft, but no informal comments are accepted after the draft is submitted for review. All calculations are documented and checked prior to final review; where standard engineering practices are involved, checks are performed to the full extent required. Where appropriate, calculation sheets include a brief description of the scope of the checks made and the methods used. Calculation sheets or drawings are signed and dated by the preparer and checker and are attached to the review form when presented to the reviewer. The reviewer ensures that all calculations have been adequately checked to the extent appropriate for the standard practices involved and as appropriate for the type and purpose of the calculations. The reviewer signs and date the calculation sheets or drawings if acceptable. Review comments may be mandatory or nonmandatory. All mandatory comments shall be numbered in the reviewed text; the review memo should be marked appropriately whenever mandatory comments have been made. Unnumbered comments shall be considered nonmandatory and may be incorporated at the discretion of the author. All mandatory comments must be documented and resolved.

The review form is filed along with the as-reviewed draft, completed calculation check-sheets and the final approved text.

Independent technical review requirements do not apply categorically to interim recommendations or other types of technical communications that are based on work in process, provided that any associated uncertainties are addressed by appropriate disclaimers. However, independent technical reviews of these and other types of documents may be requested at the project manager's discretion at any time. 12.5.3 Control of Documents

1. Procedures for recording pre-engagement activities and communications. a. Require that working files adequately record client-furnished information and other data on which the project proposal was based. b. Identify guidelines and responsibility for project acceptance and for proposal review, as well as procedures for recording such approvals. 2. Provide procedures for recording the performance and review of project activities. a. Require that project files provide a reasonably complete chronological record of project activity, including planning documents, telephone calls, letters, conferences, calculations, field and laboratory data and progress reports. b. Require that all information originating within the firm be identified as to job, date, and name of persons originating each work item. c. Develop guidelines for review process. 3. Provide procedures for retiring, storing and/or purging project files. a. Assign responsibility for closing an active file.

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b. Identify appropriate form and content for closed files. c. Provide for duplicate storage or other method of safekeeping of essential documents. d. Develop guidelines for terminating or retiring files. 12.5.4 Final Report Content: Subsurface Investigation Introduction Detailed subsurface investigations must be of sufficient intensity to determine the conditions that may influence the design and construction of the monitoring system. The extent of geologic investigation required for a particular site depends on: (1) complexity of the site conditions, (2) size of the landfill construction and (3) potential damage if there is functional failure in the liner. Detailed exploration and location of the monitoring system typically consists of three components: (1) determining and interpreting subsurface conditions, (2) taking samples for soil and rock tests and (3) installing the monitoring wells. During the first work component, test holes must be put down and logged in the foundation and borrow areas. These test holes must be deep enough to penetrate all pertinent materials. The number and spacing of test holes must be adequate for correlation in both longitudinal and transverse directions for complete interpretation of any condition that may influence the local permeabilities. Geologic structural features, such as faults, folds and joints, should be documented and information must be obtained on soils to classify them and to determine their location, thickness and extent. Test holes can be put down by drilling or by excavating pits or trenches for areas of shallow soils. In the second work component of the detailed site investigation, the data gathered in the first work component are analyzed on the site and behavior characteristics and engineering significance of the materials and conditions are evaluated. From this analysis and evaluation, the geologist and the engineer determine what materials are to be sampled and what laboratory analyses are needed. This determines the kind, number and size of samples. The necessary samples are obtained by using appropriate sampling procedures. Any additional or special in-place field tests should be made. In practice, these work components are not usually consecutive. Where the geologist is familiar with the area and knows generally the materials and conditions that will be found, sampling and field testing proceed concurrently

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with the drilling program. The third component, location of the monitoring wells, would proceed from the knowledge gained from the first two work components. The federal RCRA requirement of three downgradient and one upgradient monitoring wells is the minimum acceptable for sanitary landfills. In practice, the owner/operator often has numerous piezometers and monitoring wells in excess of the minimums. Actual numbers of monitoring wells can be expected to range from the required three to in excess of a dozen wells. Location of Monitoring Wells for Detection Monitoring The actual location and depth of wells for detection monitoring must be based on two major factors: 1. The direction of ground-water flow 2. The first or uppermost aquifer depth The wells to be installed under Phase II detection monitoring work must be designed to intercept potential landfill leachate downgradient of the waste area in the first continuous saturated and permeable zone adjacent to the waste disposal area. All the technical work to be performed in Phase II effort must be directed toward this goal. The final performance assessment of the consultant and peer review will be directed toward determining if the consultant has met this goal. Field Investigation Report Content The field based investigation is aimed at several goals: (1) documenting field conditions found at the site, (2) documenting the location and acceptability of the monitoring wells. These goals may differ for investigations directed toward expansions or permitting new sites and those required within RI/FS projects. However, reporting of technical observations in final reports have many similar components as given in the following sections. Reports on ground water also differ greatly in their subject matter and objectives and they have a highly diversified group of readers. Although no general outline can be given that will be suitable for all, a report that gives a systematic description of the ground water conditions in a specified area is the most typical and should comprise the following parts: Introduction — Introductions to site assessment reports seldom have subheadings. However, analysis of these reports reveals that the contents of the introduction could be sorted and placed under these headings:

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• • • • •

Reasons for the investigation Some historical background Purpose and objectives of the investigation Scope and limitations of the work Plan of development (if unconventional)

In other words, the introduction provides the reader with a backdrop against which the new data is to be seen and appraised. Setting — Setting should include regional and local description of geographic matters, such as climate, rainfall, flooding, runoff and drainage, attitude, land use and agricultural soils, surface geology, topography and other factors. A description of the general characteristics of the site is also an important step. Because surface attributes of the facility will directly and indirectly affect the subsurface environment, these attributes need to be identified. Information is needed on the climactic factors of precipitation, temperature and evapotranspiration. Locational factors for which information is needed include topography, accessibility, site size, proximity to surface water and proximity to population centers. Additional comments on each of these factors are as follows: 1. Precipitation: In most cases, precipitation will dictate both the amount and rate at which leachate from a site moves into the groundwater. This is especially important for solid waste disposal areas. Precipitation also affects the recharge rate of an aquifer. 2. Temperature: Surface temperature will become an important factor in determining the feasibility of certain surface treatment strategies. 3. Evapotranspiration: The amount of water lost to the atmosphere through transpiration and evaporation can be important when considering the ultimate use of a site. For example, surface capping of a landfill relies in part on evapotranspiration from the vegetative cover to reduce the amount of water infiltrating to the solid waste. 4. Topography: The general topography of the site will affect the infiltration rate and the feasible solutions. Areas of steep gradients will have little infiltration and will be subject to high erosion rates. 5. Accessibility: Related to topography is the accessibility of the site. Areas of rugged terrain or limited

access will present not only construction problems but could also hamper any subsequent operation and maintenance activities. 6. Site Size: The size of the site refers to the actual surface areal extent. This factor will affect the fill design solutions in that many of the technologies are size specific. 7. Proximity to Ground-water Users: All potential users of groundwater adjacent to the site should be identified in the site assessment study. Facility Description — This section should locate the site on a regional map (first figure), describe the site features, land use, land surface elevations, local drainage patterns and slopes. Existing Monitoring Well Locations and Procedures — Identification of existing monitoring well locations and the parameters monitored can save both study time and costs. In addition to providing immediate data, existing monitoring wells can, in some cases, become permanent parts of a monitoring network or converted to piezometers. Regional Hydrogeology and Ground-water Quality — This section should include a discussion of the major aquifers, their usage, stratigraphy and ground-water conditions gradient directions and magnitudes and elevation of the ground-water surface. An indication of regional ground-water quality and related issues should be included. This section should include a systematic description of each of the successive geologic formations in the area, including its water-bearing properties and the quality of its water. These should also be either detailed descriptions of subareas, such as counties, townships or geomorphic units; or a detailed discussion of the hydrology of the area as a whole, with emphasis on recharge, discharge and potential availability of groundwater. Results: Site Hydrogeology and Ground-water Quality — Site hydrogeology and ground-water quality should provide locations of borings and piezometers (second figure) and include discussions of the site stratigraphy, subsurface profiles (additional figures) and shallowest water-bearing soils. Shallow ground-water conditions, gradient directions and magnitude, elevation of water table or piezometric surface, should be covered in detail. This section should also include a description of local ground-water quality, with significant anomalies and frequencies and seasonal fluctuations noted. Some areas of information and

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reasons for their interest are as follows: 1. Geologic Setting and Generalized Soil Profiles: Determination of the types of soils is important for determining the capacity of the leachate to move through the subsurface. Certain soils will possess higher tendencies to attenuate the leachate(s) (through adsorption, precipitation, filtration, etc.) than others. Likewise, certain soils will be amenable to certain leachate collection strategies while others are not. 2. Soil Physical-Chemical Characteristics: Once a general soil type has been identified, it is then necessary to characterize this type both physically and chemically. Physical characterization of the soil type will provide information on the ability of the soil to filter landfill leachate. The physical characterization will also give an idea as to the workability of the soil for different containment designs. Chemical characterization will provide information on the ability of the soil to chemically remove a given chemical through adsorption, precipitation, etc. 3. Depth to Ground Water and Bedrock: The depth to ground water in conjunction with the soil physical/ chemical characterization will give insight as to how long generated leachate will take to actually reach the aquifer, if in fact it will. If sufficient depth to the ground water exists in a highly attenuating soil, minimal ground water impacts can be expected. The depth to bedrock is needed to assess the feasibility of some leachate containment strategies. 4. Ground-water Flow Patterns and Volumes: The flow patterns and volume of ground water threatened will play a vital role in determining the feasible solutions to the problem. 5. Recharge Areas and Rates: Identifying recharge areas and rates will play an important role in aquifer protection plans. Information on recharge areas and rates for the case of an existing site will be important for a number of reasons. First, it should be determined whether or not the source(s) is in a recharge area. Solutions to problems located in recharge areas will most likely be more elaborate that those not located in recharge areas and should include leachate removal, if possible. Second, recharge rates will give insight into the rate of leachate movement and leachate dilution.

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6. Aquifer Characteristics: Identification of aquifer characteristics will be essential for any analysis of ground-water flow and chemical transport. This information becomes extremely important if ground-water modeling studies are to be initiated. 7. Background Water Quality Data: Background water quality data is important in determining the severity of the problem and the appropriate remedial actions. Interpretation or Discussion — In the interpretation or discussion section, the consultant reviews and analyzes the data presented in the preceding section. The discussion is one of the most important sections of physical research reports and, unfortunately, often one of the most poorly handled. The consultant should, therefore, take special pains with this section and must try to step back from the work and findings to reflect upon them before putting the whole story together. In site assessment reports, the discussion sometimes does little more than translate numbers into words. Justification for this practice may lie in the fact that all report users are not equally capable of digesting data presented in tabular or graphic form. At other times and more commonly, the discussion must do far more than provide a prose recapitulation. Are there blanks in the data? Were some of the data projected from actual test data? Were the data subjected to mathematical processing? Do the data contain puzzling irregularities? Were all the data taken with the same equipment? Do the data, when considered in their entirety, lead to a significant conclusion? Were there recognized inaccuracies in measuring and recording? Points such as these must be dealt with in the discussion. Analysis and interpretation are frequently needed to qualify and illuminate raw data. Assessment, in any case, should combine the hydraulic analysis of the site hydrogeology and the analysis of the site’s soils and geology. A reasonable picture of the potential for contaminant migration from the waste facility from seepage and horizontal or vertical movement through and off the site should be produced. Imminent and potential ground-water quality risks to the public must be identified. An important part of the interpretation is if the observed geologic/hydrogeologic features match the conceptual model generated during Phase I studies. If not, why not; and how should the conceptual model be changed to fit the observed geology, hydraulic heads, aquifer characteristics and water quality? This section is where the consultant can provide real insight into the monitoring well system design.

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Figure 12-10 Report Table of Contents Alternatives

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Summary, Conclusions and Recommendations — In the Summary section, you extract and extrapolate from the preceding sections of the report what you consider the outcome and final worth of the investigation. You may comment on the reliability and validity of the results and you may suggest new approaches to the problem for later use. Recommendations should refine the quality of the hydraulic and water-quality analysis and evaluate the synthesis of hydrogeologic and geologic analysis and work towards statistical significance, if needed. Recommendations should be presented in a natural and supportive way so that the client is logically drawn toward them. Typically, the consultant must answer requirements of the state issuing the permit. These requirements often are as follows:

the base map should be specifically indicated. For operating landfills, the base map should be the same as that to be used for the tentative map or grading plan. 6. Mapping by the geologist should reflect careful attention to the lithogy, structural elements and three-dimensional distribution of the earth materials exposed or inferred within the area. In most hillside areas, these materials will include both bedrock and surfical deposits. A clear distinction should be made between observed and inferred features and relationships.

1. Determine the availability, quality and quantity of on-site soil for cover material.

7. A detailed large-scale map normally will be required for a report on a small expansion, as well as for a report on a smaller area in which the geologic relationships are not simple.

2. Evaluate the influence that geologic factors, such as ledge, would have on the ease of excavation and potential for ground water and surface water pollution.

8. Where three-dimensional relationships are significant but cannot be described satisfactorily in words alone, the report should be accompanied by one or more appropriately positioned structure sections.

3. Determine the maximum high ground-water surface elevation and ground-water flow patterns.

The locations of test holes and other specific sources of subsurface information should be indicated in the text of the report or, better, on the map and any sections that are submitted with the report.

4. Determine background water quality of ground water at the site and of surface water at the most likely discharge area.

12.6.1 Captions, Titles and Headings

3. Areal photos (originals or suitable copies) should be included to document any discussion on landslides and faults.

We use the term captions to refer to the various headings and titles that may be used to display the report’s coordination and subordination to the reader. The caption itself is a phrase that describes what is discussed in the paragraph or paragraphs that follow it. Coordination and subordination are shown by a consistent use of various typefaces and positions for different level captions. There are several systems used for headings in a geologic report. The main or first heading is centered and is in capital letters; the second-order heading is centered, first letter capitalized and remainder lower case; the third-order heading is the same as the second heading only it is underlined; fourth-order headings are indented three spaces from the left margin, followed by a colon and the text follows the colon after a double space. This heading is also underlined. For example,

4. The method(s) of field analysis should be discussed in a lucid manner.

INTRODUCTION

5. Evaluate the importance of the ground-water resource that might be affected by the operation of a landfill facility. 12.6 DOCUMENTATION 1. All materials in the report should be relevant to the purpose of the report. 2. All statements should be documented by references or by accurate field observations.

5. All mapping should be based on a base with satisfactory horizontal and vertical control - in general, a detailed topographic map. The nature and source of

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Rainfall

Distribution: Rainfall is principally in the winter months, but on rare occasions... Quite often, in order to facilitate reference back and forth in a report or book, a numbering system is combined with the captions. The three systems in most common use are the traditional outline system, the century-decade-unit system (often called the Navy System) and the multipledecimal system. The traditional and multiple-decimal systems that are acceptable to most clients are shown in Figure 12-10. 12.6.2 Figures and Plates There are several views on the difference is between a figure and a plate. The author’s view is that all items in the text are considered to be figures and those placed in a jacket at the end of the report, plates. Every figure or plate must be accompanied by a complete title and description beneath the figure. A somewhat abbreviated or shortened title is used in the list of illustrations. Do not simply copy the captions into the illustrations compilation; shorten them. All figures should read righthanded (i.e., the bottom of the figure is toward the reader or on the right-hand side of the page). North should almost always be at the top of the figure. A good report makes constant reference to the figures and plates in the body of the text and an illustration should never be included that is not referred to in the written text. Where the illustrations are included in the body of the text, they should appear on the page following the page where they are first mentioned. If two (or four or five) are mentioned on a single page, they should appear in proper sequence following that page. Citing Figures and Plates in Your Text: If reference to a figure or plate is made parenthetically (Fig. 6), then the abbreviations Fig., Pl. or Figs. 6 and 7 or Pls. 8 and 9 are used. If the writer refers to a figure or plate and it is expressed as part of the sentence, then the word is spelled out. For example: On Plate 7 the dendritic pattern is evident and in Figure 3 the location is shown. Arrangement of this page should be much like the Contents page. A brief sample is outlined below and note that only the first letter of the first word of the proper nouns are capitalized: Figures should include a vicinity map, site plan with boring and monitoring well locations, two subsurface profiles (N-S and E-W) and a local geohydrologic column at a

minimum. The site plan should show the location of the subsurface profiles and the direction and magnitude of the gradient. If ground-water anomalies are clearly present, additional figures may highlight this through anomaly maps that overextend the size of anomalies because of sparse and distant control points. 12.6.3 References Cited This section may also be entitled “List of References” or “References.” The term “Bibliography” is customarily used when references other than those actually cited in the report are listed for the reader. Generally, only those references cited in the text are included in this section. The purpose of the bibliography references is to show the reader the source of the reference and to enable him to locate supplementary material. Also, citing a reference in the text allows the reader to recognize that the work is not your own. References should include all cited literature, the consultant’s and client’s files, conversations with agency personnel and client reports. Confidential reports completed for other clients with nearby facilities should not be explicitly cited. Several different systems of recording bibliographic references are in use, but the most commonly accepted one is the form of the Geological Society of America. The form followed by the GSA is: 1. Name of author, last name first and then initials. 2. Year of publication, set off with a comma. 3. Title of paper, in full. First letter of first word and only geographical and formation names have first letter capitalized. At end of title, a colon is used. 4. Series of publication, or publisher, with standard abbreviations. (Standard abbreviations are listed in Suggestions to Authors.) 5. Volume and page reference. The items are listed alphabetically by authors. Where more than one paper by the same author is cited, each is listed chronologically under his name. On the second listing, the name is not rewritten but is indicated by a solid line. Below are some typical examples of a reference listing: Daly, R.A., 1933. Igneous rocks and the depths of the earth: McGraw Hill, New York, 598 pp.

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Donnelly, M., 1934. Geology and mineral resources of the Julian district, San Diego Co., California: Calif. Jour. Mines Geol., v. 30, pp. 331-370. King, W.B.R., 1951. The influence of geology on military operations in northwest Europe: Adv. Sci., v. 8, n. 30, pp. 131-137. McIntyre, D.B., 1951. Lineation in Highland schists: Geol. Mag., v. 88, pp. 150-151. — 1954. The Moine Thrust, its discovery, age, and tectonic significance: Geol. Assoc. Proc., v. 65, pp. 203-233. Scheidegger, A.E., 1953. Examination of the physics of theories of orogenesis: Geol. Soc. America Bull., v. 65, pp. 127- 150. Alternatively, the title name may have the first letter of each word capitalized (called the “Title Case”). References are used in the text by enclosing the author's name, the date of publication, and, where necessary, the page numbers in parentheses. Never use the footnote system of referencing. Below are several examples of how references may appear in a text. 1. The rocks fit into the eugeosynclinal category, as defined by Stille (1941) and Kay (1951). 2. Flint (1953) referred to casehardening of friable limestone to explain the origin of certain limestone ridges in Okinawa. 3. The Military Geology unit of the U. S . Geological Survey (Hunt, 1950) made a substantial contribution during World War II. 4. With regard to this important point, Allen C. Tester (Personal Communication) states: “Die geological significance, etc...” 5. ... such crystallization is shown by the orbicular and nodular structure (Miller, 1938, pp. 1224, Lawson, 1904). 6. ... so that they were not covered by a thick volcanic cover (Lindgren, 1911, pp. 37-39). 7. The name applied by Miller (1937) will be used. Appendices should include any available field exploration and soil laboratory testing, ground-water monitoring network, ground-water sampling and analysis plans, and

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analyses of ground-water samples. Specific tables, such as logs of borings, summary of ground-water level measurements, well completion data, soil laboratory tests, field water-quality analyses, laboratory water-quality analyses, and chain of custody records, are appropriate. Personnel involved and procedures utilized in the various phases of the project should be identified. Examples include notations such as “water levels were measured with a steel tape by ...”, “field measurements were made conductivity meter, pH meter, and thermometer by ...,” etc. Data should be reported to significant figures. Basic data collected during the investigation must be provided so that client can perform an independent assessment of the information generated by the investigation. The draft and final reports should be thoroughly reviewed for technical accuracy and editorial consistency. Reports should be checked for numerical, citation, and typographical errors; as well as tone, consistency, emphasis, and logic. A poorly- written report will erode credibility, diminish future opportunities, and cause later expense and embarrassment. 12.6.4 Report Presentation The client should be given sufficient copies of the draft final report to review. The owner/operator may correct any facility-related or procedural errors that the consultant has made; hence, this draft must be as clear and accurate as possible. It is generally more vivid, and consequently more effective, for the consultant to review the report in the physical presence of the client. 12.7 PROFESSIONAL LIABILITY CONTROL All professionals in the geosciences must strive to reduce needless exposure to professional liability. Lawsuits and other form of litigation rarely benefit the professional involved in the legal action. Control of professional liability must be a daily inbred set of actions that begins at the proposal stage and works itself throughout the project and final report. One can assume responsibility for items that are beyond the Scope of Work if observations or recommendation are made either in the field or in the office through report text, even when you are only doing a favor for the client in providing such information. A series of common mistakes that have caused professional liability claims are provided in Figure 12-11. These common mistakes cause the majority of the professional liability claims and should be committed to memory by every professional geoscientist practicing in the environmental market. Because loss prevention begins at the proposal stage the following three subsections provide check-off lists for

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Figure 12-11 Common Mistakes of Professional Liability Claims

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reviewing both proposals and the reports. These lists (Dames & Moore, 1985) provide a firm handle on the potential common mistakes made in professional liability claims

2.

Are clauses indicating the accuracy of location and elevation of borings, test pits, samples, etc., included in report?

3.

Are clauses regarding ground-water variation, and conditions at and between borings or samples included in the report?

4.

Are clauses regarding reinterpretation included in the report such as limitation of data for particular site and time, review of plans and specifications, and limitation of data to use of current client?

12.7.1 Proposal and Contract Check-Off List 1.

Has the type of study (e.g., preliminary, feasibility, investigation) been clearly defined?

2.

Have the project requirements and conditions been clearly defined?

3.

Were the purposes of the study clearly defined?

5.

Are clauses included in the report regarding changed conditions during construction?

4.

Are the scopes of investigation and testing appropriate for the types and nature of the project and conclusions to be reached?

6.

Are clauses included in the report recommending use of the soils engineer during construction?

5.

Is the scope of services clearly defined?

7.

6.

Are the items of work clearly and specifically spelled out?

Are appropriate notes on the boring logs and drawings regarding ground water, interpolation between borings, nature and exactness of descriptions, etc?

8. 7.

Has a clause regarding warranty been included?

Have taboo words been eliminated from the text; for example, words such as supervise, certify, assure, control, required, etc.?

8.

Are clauses delineating responsibility of the engineer and/or engineering geologist included?

9.

Does the report volunteer any recommendations that are not a part of the scope of work?

9.

Have limitations of the study been discussed?

10. Have taboo words, such as complete, thorough, supervise, certify, assure, control, etc. been avoided? 11. Have limitations of cost estimates been discussed? 12. Was the proposal well worded to avoid misunderstanding?

10. Has the report indicated the inexactness of our science by eliminating words such as complete, final, obvious, best, etc., and by using rounded numbers for settlement, shear strength, permeability, etc.? 11. Does the report limit the scope of work to satisfy intended purposes? 12. Are recommendations consistent with the scope of work?

13. Was limitation of liability addressed? 14. What is your overall evaluation of the proposal?

13. Has the report indicated that it was prepared only for intended purpose, such as design, feasibility, etc.?

12.7.2 Part A: Loss Prevention Wording and Clauses 1.

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Has a clause regarding warranty been included in the Report (i.e., “Report prepared in accordance with generally accepted soil and foundation engineering practice. No other warranty expressed, ... etc.”)?

14. Has the nature and extent of the project been described adequately? 15. What is your overall evaluation of the loss prevention part of this report?

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12.7.3 Part B - Technical Matters 1.

Was the type of project, its nature and the scope of work discussed?

2.

Were the limits of the site and the existing site conditions discussed?

3.

Was the general geology and soil stratigraphy discussed?

4.

If applicable, were ground water/seepage and seismicity addressed?

5.

Did the engineer and/or engineering geologist limit himself to his own area of expertise?

6.

Were drilling, sampling, and testing done in accordance with the standard procedures and/or adequately described?

7.

Were the sampling and testing sufficient to draw conclusions when integrated with general site conditions and prior site experience?

8.

Was all test data adequately considered or used in the analysis?

9.

Did the recommendations and conclusions reflect the field and laboratory data obtained?

2.

Was the report self-contained with complete references to auxiliary work?

3.

Were the choice of words and explanation of terms consistent with the client and user of the report (layman, architect, engineer, etc.)?

4.

Were the exhibits, data, and written material integrated to form a well-organized presentation?

5.

Were the standard clauses wordings well integrated at the appropriate places in the report?

6.

Were the choices of words, grammar, sentence structure, and length appropriate?

7.

Were the drawings clear with sufficient notes for a quick grasp of the information portrayed?

8.

Were the data sheets or tabular data clear and understandable?

9.

Did the report exhibit competence and completeness and create an atmosphere of confidence, such that good client relations would exist under possible future unforeseen difficulties on the project?

10. What is your overall evaluation of the composition part of this report? 12.7.5 Part D - Overall Evaluation

10. Where applicable, was there a discussion of the feasible solutions in terms of financial or practical consequences?

Your overall evaluation may differ from that indicated by the previous three parts. Provide an overall rating of the report.

11. If applicable, were alternatives discussed? 12. If applicable, was the seismicity addressed?

12.8 CONCLUSIONS

13. Were recommendations, conclusions, data and information presented for all significant features?

The use of the correct wording in reports and proposals are developed over a long professional career of many individual letters, proposals and reports. The guidance provided above can provide a shorter and less error-filled route for the professional.

14. Were the methods of analysis appropriate, well documented, and adequate? 15. Was the report technically up to date? 16. What is your overall evaluation of the technical part of this report? 12.7.4 Part C-Report Writing and Presentation 1.

Were statements clear and concise?

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CHAPTER 13 MONITORED NATURAL ATTENUATION

13.1 INTRODUCTION TO MNA Throughout the 1990s, the scientific understanding of natural attenuation processes evolved rapidly to the point where monitored natural attenuation evaluation now receives attention as a cost-effective means of restoring contaminated ground water once immediate threats to public health from drinking contaminated ground water are not considered as an environmental issue. Natural attenuation is being used at sites with a wide range of contaminants, including chlorinated solvents; benzene, toluene, ethylbenzene and xylene (BTEX) compounds; polycyclic aromatic hydrocarbons; phenols; polychlorinated biphenyls; pesticides; and inorganics. The use of natural attenuation at underground storage tank sites with petroleum releases increased significantly in the early 1990s. As of 1995, natural attenuation is the second most popular option for sites with contaminated soils; it is being used at roughly 29,000 sites or at 28% of the active contaminated soil universe. Natural attenuation is the most common treatment option at sites with contaminated ground water; it is being used at 17,000 sites or about 47 % of the active contaminated ground water universe. Inevitably, natural attenuation was first perceived by many as a “walk-away” approach to achieving remedial objectives at site. However, the U.S. EPA published its monitored natural attenuation (MNA) policy directive (U.S. EPA, 1999a) in part to assure skeptics and critics of MNA that U.S. EPA does not consider MNA, when applied appropriately, as a “no action” approach. Many states now included MNA as part of volunteer site cleanup programs (see Texas Guidance for MNA in TNRCC RG-366/TRRP-26), especially when combined with risk assessment techniques. In general terms MNA can be protective when it can attain remedial objectives in a reasonable time frame and the prescribed data collection protocols are followed. The protocols described in this chapter and in the chapters of this text can provide the keys to defining MNA for facilities.

Monitored natural attenuation may be an appropriate cleanup option (U.S. EPA, 1996) when the facility can demonstrate that the remedy is capable of achieving facility-specific ground-water cleanup levels in a reasonable cleanup time frame. Facilities should evaluate and justify monitored natural attenuation remedies using recommended threshold and balancing criteria discussed in the Final Cleanup Goal section of this Handbook. Monitored natural attenuation should be justified on a facility-specific basis and compared with, where appropriate, other plausible options. In general, monitored natural attenuation proposals are more likely to be acceptable to regulators when: • The facility can demonstrate that monitored natural attenuation will beable to achieve ground-water cleanup objectives. • Measures for source control of ground-water contamination are already in place. • The dominant natural attenuation processes cause degradation or destruction of contaminants, as opposed to those processes that merely dilute contamination or prevent its movement. • The contaminant plume is already stable or shrinking in extent. • The estimated cleanup time frame to meet cleanup levels is reasonable considering factors such as groundwater use and time frames required for other remedies and the time frame is comparable to that which could be achieved through active remediation (U.S. EPA, 1990b - NCP preamble page 8734). • The facility uses monitored natural attenuation in conjunction with an active remedial system or as a followup measure. For a more complete list of recommended factors, a list of advantages and disadvantages of monitored natural attenuation remedies and additional policy and technical guidance, refer to U.S. EPA (1999d, 1998). You can also

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find additional information concerning monitored natural attenuation in a report developed by the National Research Council (NRC, 2000). In most projects, the regulator would normally determine whether monitored natural attenuation will be acceptable for offsite contaminated ground water based on the data submitted for the project. In making this determination, the regulator should consider facility-specific circumstances, as well as any applicable federal and state requirements and guidance. One important situation where a regulator might accept a monitored natural attenuation remedy is where no one is currently exposed to unacceptable levels of contamination and the plume is not expanding (i.e., the facility meets U.S. EPA’s short-term protection goals). Federal guidance suggests that other very important factors to consider when deciding whether to rely on monitored natural attenuation for off-site contamination include the thoroughness of public participation, the ability to conduct long-term monitoring and prevent exposures and whether the facility is controlling the source of the ground-water contamination. The acceptable remedial time frame is dependent on site-specific conditions, including the nature and extent of groundwater contamination, usability of the aquifer, existing and potential future impact on human and environmental receptors, existing and potential development of the area and availability of a public water supply. The potentially adverse effect of residual NAPLs and other contaminant sources on remedial time frames has been well documented in the literature, as these residual sources can produce long-term (hundreds of years) contamination of ground-water sources far beyond water quality standards. Therefore, the author recommends that, particularly at sites where MNA is under consideration, remedial actions include the removal and treatment of source materials once an understanding of the physical and chemical situation of the site has been obtained (U.S. EPA, 1999a). Furthermore, largely due to the uncertainty associated with the potential effectiveness of monitored natural attenuation to meet remedial objectives that are protective of human health and the environment, source control and performance monitoring are fundamental components of any monitored natural attenuation remedy. Of all potential alternatives for site remediation MNA requires extensive knowledge of the geologic and hydrogeologic systems and the locations and residual concentrations of the source areas If a facility or site decides to go this route as the selected remedy or as a component in the overall remedial solution, the investigator should be prepared to collect significant hydrogeologic and water quality data to defend this remedy.

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The term “monitored natural attenuation”, as used in this text, refers to the reliance on natural attenuation processes (within the context of a carefully controlled and monitored site cleanup approach) to achieve site-specific remedial objectives within a time frame that is reasonable compared to that offered by other more active methods. The natural attenuation processes that are at work in such a remediation approach include a variety of physical, chemical or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume or concentration of contaminants in soil or ground water. These in situ processes include biodegradation, dispersion, dilution, sorption, volatilization, and chemical or biological stabilization, transformation or destruction of contaminants. When relying on natural attenuation processes for site remediation, regulatory agencies traditionally prefer those processes that degrade contaminants and for this reason acceptance of the use of monitored natural attenuation will be most appropriate at sites that have a low potential for plume generation and migration. Other terms associated with natural attenuation in the literature include “intrinsic remediation,” “intrinsic bioremediation,” “passive bioremediation,” “natural recovery and “natural assimilation.” While some of these terms are synonymous with “natural attenuation,” others refer strictly to biological processes, excluding chemical and physical processes. Therefore, it is recommended that for clarity and consistency, the term “monitored natural attenuation” (MNA) be used throughout this chapter unless a specific process (e.g., reductive dehalogenation) is being referenced. Specifically, this chapter: • Defines natural attenuation. • Explains how MNA can be applied under most groundwater conditions. • Establishes technical processes to apply MNA. • Illustrates the technical demonstrations to establish sufficient evidence for MNA. Most contaminated ground-water plumes are formed under one or more of three different organic contamination source scenarios: 1. Aqueous-phase release to subsurface 2. Leaching from source material in the vadose zone 3. Nonaqueous phase liquid (NAPL) release to the saturated zone For the second and third source mechanisms, there often is a continuing release of organic contamination to

MONITORED NATURAL ATTENUATION

ground water from source materials. If natural attenuation processes cannot be demonstrated to decontaminate the ground-water source materials in a reasonable time frame, then MNA would likely not be appropriate as a sole remedy. Experience has shown that if there are any NAPLs present in the ground water, then the readily recoverable NAPLs must be recovered in order to preclude the NAPLs from spreading horizontally or vertically. In these cases, MNA may not be solely adequate for addressing high levels of NAPLs in the subsurface. This chapter explains how natural attenuation occurs and how the data necessary to evaluate natural attenuation processes should be collected during the site assessment process. Additionally, this document will focus on the application of MNA in ground water. 13.2 CHLORINATED SOLVENTS Chlorinated solvents, such as trichloroethylene, represent another class of common contaminants that may also biodegrade under certain environmental conditions. The remediation of chlorinated solvents has been one of the primary driving force in the use of MNA. Recent research has identified some of the mechanisms potentially responsible for degrading these solvents, furthering the development of methods for estimating biodegradation rates of these chlorinated compounds. However, the hydrologic and geochemical conditions favoring significant biodegradation of chlorinated solvents may not often occur. Because of the nature and distribution of these compounds, natural attenuation may not be effective as a remedial option. If they are not adequately addressed through removal or containment measures, source materials can continue to contaminate ground water for decades or even centuries. Cleanup of solvent spills is also complicated by the fact that a typical spill includes multiple contaminants, including some that are essentially nondegradable. Extremely long dissolved solvent plumes have been documented that may be due to the existence of subsurface conditions that are not conducive to natural attenuation. 13.3 INORGANICS Monitored natural attenuation may, under certain conditions (e.g., through sorption or oxidation-reduction reactions), effectively reduce the dissolved concentrations and/or toxic forms of inorganic contaminants in groundwater and soil. Both metals and non-metals (including radionuclides) may be attenuated by sorption reactions such as precipitation, adsorption on the surfaces of soil minerals, absorption into the matrix of soil minerals or partitioning into organic matter. Oxidation-reduction

(redox) reactions can transform the valence states of some inorganic contaminants to less soluble and thus less mobile forms (e.g., hexavalent uranium to tetravalent uranium) and/or to less toxic forms (e.g., hexavalent chromium to trivalent chromium). Sorption and redox reactions are the dominant mechanisms responsible for the reduction of mobility, toxicity or bioavailability of inorganic contaminants. It is necessary to know what specific mechanism (type of sorption or redox reaction) is responsible for the attenuation of inorganics because some mechanisms are more desirable than others. For example, precipitation reactions and absorption into a soil’s solid structure (e.g., cesium into specific clay minerals) are generally stable, whereas surface adsorption (e.g., uranium on iron-oxide minerals) and organic partitioning (complexation reactions) are more reversible. Complexation of metals or radionuclides with carrier (chelating) agents (e.g., trivalent chromium with EDTA) may increase their concentrations in water and thus enhance their mobility. Changes in a contaminant’s concentration, pH, redox potential and chemical speciation may reduce a contaminant’s stability at a site and release it into the environment. Determining the existence and demonstrating the irreversibility of these mechanisms are key components of a sufficiently protective monitored natural attenuation remedy. 13.4 NATURAL ATTENUATION AND MONITORED NATURAL ATTUNUATION In this chapter, the applicable definitions that will be used for natural attenuation and monitored natural attenuation are those provided by the U.S. EPA. The evaluation of sites where chlorinated VOCs are the primary source of contamination will form the basis for the majority of the following discussion. Inorganic parameters make up a minority of the current MNA projects; however, the procedures and methods would also apply to this sites. Natural attenuation (NA) is the reduction in mass or concentration of a chemical of concern over time or distance from the source of a chemical of concern due to naturally occurring physical, chemical and biological processes, such as biodegradation, dispersion, dilution, adsorption and volatilization. Monitored natural attenuation (MNA) is the use of natural attenuation within the context of a carefully controlled and monitored response action to achieve protective concentration levels at the point of exposure. The U.S. EPA’s technical protocol (1999a), for evaluating natural attenuation of chlorinated solvents also advocates NAPL source removal, treatment or containment to shorten the time frame needed for natural processes to attain remedial objectives (U.S. EPA, 1998). The

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document recommends that “where removal of mobile NAPL is feasible, it is desirable to remove this source material and decrease the time required to reach cleanup objectives. Where removal or treatment of NAPL is not practicable, source containment may be practicable and necessary for MNA to be a viable option” (U.S. EPA, 1998). Site characterization in defense of a monitored natural attenuation design should include collecting data to define (in three spatial dimensions over time) the nature and distribution of contamination sources as well as the extent of the ground-water plume and its potential impacts on receptors. However, where monitored natural attenuation will be considered as a remedial approach, certain aspects of site characterization may require more detail or additional elements. For example, to assess the contributions of sorption, dilution and dispersion to natural attenuation of contaminated ground water, a very detailed understanding of aquifer hydraulics, recharge and discharge areas and volumes and chemical properties is required. Where biodegradation will be assessed, characterization also should include evaluation of the nutrients and electron donors and acceptors present in the groundwater, the concentrations of co-metabolites and metabolic byproducts and perhaps specific analyses to identify the microbial populations present. The findings of these and any other analyses pertinent to characterizing natural attenuation processes, should be incorporated into the conceptual model of contaminant fate and transport developed for the site. Monitored natural attenuation may not be appropriate as a remedial option at many sites for technological or economic reasons. For example, in some complex geologic systems, technological limitations may preclude adequate monitoring of a natural attenuation remedy. A related consideration for site characterization is how other remedial activities at the site could affect natural attenuation. For example, the capping of contaminated soil could alter the type of contaminants leached to ground water, as well as their rate of transport and degradation. Therefore, the impacts of any ongoing or proposed remedial actions should be factored into the analysis of natural attenuation’s effectiveness. When considering source containment/treatment together with natural attenuation of chlorinated solvents, the potential for cutting off sources of organic carbon (which are critical to biodegradation of the solvents) should be carefully evaluated.

to evaluate the efficacy of monitored natural attenuation as a remedial approach. A somewhat traditional approach has been taken by a number of regulatory agencies in the classification of data used to evaluate the case for allowing natural attenuation as a site remediation choice. Three types of site-specific information or “lines of evidence” can be used in such an evaluation:

13.5 LINES OF EVIDENCE

Unless U.S. EPA or the implementing state agency determines that historical data (type 1 above) are of sufficient quality and duration to support a decision to use monitored natural attenuation, U.S. EPA has expressed in

Once the site characterization data have been collected and a conceptual model developed, the next step is

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1. Historical ground-water and/or soil chemistry data that demonstrate a clear and meaningful trend of decreasing contaminant mass and/or concentration over time at appropriate monitoring or sampling points (classified as primary line of evidence). In the case of a ground-water plume, decreasing concentrations should not be solely the result of plume migration. In the case of inorganic contaminants, the primary attenuating mechanism should also be understood. 2. Hydrogeologic and geochemical data that can be used to demonstrate indirectly the type(s) of natural attenuation processes active at the site and the rate at which such processes will reduce contaminant concentrations to required levels (called secondary line of evidence). For example, characterization data may be used to quantify the rates of contaminant sorption, dilution or volatilization or to demonstrate and quantify the rates of biological degradation processes occurring at the site. 3. Other lines of evidence that MNA is occurring at the site most often consists of predictive modeling studies and other lab/field studies that demonstrate an understanding of the natural attenuation process(es) occurring at the affected property and their effectiveness in controlling protective concentration limit exceedance plume migration and decreasing contaminates of concern (COCs) concentrations. (other lines of evidence) These data from field or microcosm studies (conducted in or with actual contaminated site media) may directly demonstrate the occurrence of a particular natural attenuation process at the site and its ability to degrade the contaminants of concern (typically used to demonstrate biological degradation processes only).

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guidance that data characterizing the nature and rates of natural attenuation processes at the site (type 2 above) should be provided. Where the latter are also inadequate or inconclusive, data from microcosm studies (type 3 above) may also be necessary. In general, more supporting information may be required to demonstrate the efficacy of monitored natural attenuation at those sites with contaminants that do not readily degrade through biological processes (e.g., most non-petroleum compounds, inorganics), at sites with contaminants that transform into more toxic and/or mobile forms than the parent contaminant or at sites where monitoring has been performed for a relatively short period of time. The amount and type of information needed for such a demonstration will depend upon a number of site-specific factors, such as the size and nature of the contamination problem, the proximity of receptors and the potential risk to those receptors and other physical characteristics of the environmental setting (e.g., hydrogeology, ground cover or climatic basis).

13.6 WHEN CAN MNA BE APPLIED AS A REMEDY? MNA in ground water is only one of many remedial alternatives that can be used to address ground-water contamination. Like any remedial alternative, if MNA can be shown to be fully protective of human health and the envi ronment and meet the response objectives in the time frame that is established to be reasonable for an affected property, then MNA can be applied as the initial and sole response or in combination with other remedial alternatives.

Also, as with any remedial alternative, selection of MNA requires appropriate planning, evaluation and supporting data. When considering potential application of MNA to an affected property, the person is encouraged to develop a conceptual model of the affected property that integrates data collection and guides investigative and remedial actions. Figures 13-1 and 13-2 illustrate a systematic process for how MNA can be evaluated as a remedial alternative. Later sections of this chapter explain in detail the evaluation process presented in Figures 13-1 and 13-2 but in short, the appropriateness of MNA is based on conditions at the affected property, the amount of data that are available and how much time is available to collect additional data. Figure 13-1 shows an initial screening process to evaluate if MNA should be considered as a potential remedy. First, a series of general factors, shown in Table 13-1, is assessed to evaluate the general appropriateness of MNA to an affected property. For example, if preliminary affected property data show that ground-water users are now being exposed to organic contaminant concentrations exceeding water quality standards, then MNA alone will not be an appropriate remedy. MNA is most appropriate where exposure potential over the remedial period is low. This screening process also anticipates that some affected properties may be amenable to an MNA remedy but lack the necessary historical water quality data to fully evaluate MNA processes. More specifically, evidence of MNA is best documented by a trend of water quality data showing reduced concentrations over time and distance (see Section 13.6 for a discussion of the amount of historical data needed to evaluate MNA). However, when data are insufficient, no such trend may be verifiable. At some of

Table 13-1 Factors to Consider in Evaluating General Applicability of MNA

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Figure 13-1 Flow Chart for Initial Screening Process 906

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Figure 13-2 Flow Chart for Evaluating Monitored Natural Attenuation of Chlorinated Solvent 907

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Table 13-2 Degradation of Common Chlorinated Solvents under Aerobic and Anaerobic Conditions

these “no trend data” affected properties the selection of a remedy may be delayed to compile the required trend data. At other affected properties with no established trend data, other factors such as potential risks to nearby receptors, commercial issues such as real estate transactions that may require a near-term remedy and other timesensitive drivers will preclude use of MNA as a potential remedy because there is not time to collect water quality trend data.

13.7 ADVANTAGES AND DISADVANTAGES OF MONITORED NATURAL ATTENUATION

• Lower overall remediation costs than those associated with active remediation The potential disadvantages of monitored natural attenuation include: • Longer time frames may be required to achieve remediation objectives, compared to active remediation. • Site characterization may be more complex and costly. • Toxicity of transformation products may exceed that of the parent compound. • Long-term monitoring will generally be necessary.

Monitored natural attenuation has several potential advantages and disadvantages and its use should be carefully considered during site characterization and evaluation of remediation alternatives. Potential advantages of monitored natural attenuation include: • As with any in situ process, generation of lesser volume of remediation wastes, reduced potential for cross-media transfer of contaminants commonly associated with ex situ treatment and reduced risk of human exposure to contaminated media • Less intrusion as few surface structures are required • Potential for application to all or part of a given site, depending on site conditions and cleanup objectives • Use in conjunction with or as a follow-up to, other (active) remedial measures 908

• Institutional controls may be necessary to ensure longterm protectiveness. • Potential exists for continued contamination migration and/or cross-media transfer of contaminants. Decisions to employ monitored natural attenuation as a remedy or remedy component should be thoroughly and adequately supported with site-specific characterization data and analysis. In general, the level of site characterization necessary to support a comprehensive evaluation of natural attenuation is more detailed than that needed to support active remediation. Site characterizations for natural attenuation generally warrant a quantitative understanding of source mass; ground-water flow; contaminant phase distribution and partitioning between soil, ground-

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Table 13-3 Common Patterns of Chlorated Solvents in Ground Water

water and soil gas; rates of biological and non-biological transformation; and an understanding of how all of these factors are likely to vary with time. This information is generally necessary as contaminant behavior is governed by dynamic processes that must be well understood before natural attenuation can be appropriately applied at a site. Table 13-3 provides the common patterns of chlorinated solvent presence and distribution in ground water along with suggested data collection tiers to support natural attenuation. Demonstrating the efficacy of this remediation approach likely will require analytical or numerical simulation of complex attenuation processes. Such analyses, which are critical to demonstrate natural attenuation’s ability to meet remedial action objectives, generally require a detailed conceptual site model as a foundation. A conceptual site model is a three-dimensional representation that conveys what is known or suspected about contamination sources, release mechanisms and the transport and fate of those contaminants. The conceptual model provides the basis for assessing potential remedial technologies at the site. “Conceptual site model” is not synonymous with “computer model;” however, a computer model may be helpful for understanding and visualizing current site conditions or for predictive simulations of potential future conditions. Computer models, which simulate site processes mathematically, should in turn be

based upon sound conceptual site models to provide meaningful information. Computer models, including spreadsheet analytical models, typically require a lot of data and the quality of the output from computer models is directly related to the quality of the input data. Because of the complexity of natural systems, models necessarily rely on simplifying assumptions that may or may not accurately represent the dynamics of the natural system. Calibration and sensitivity analyses are important steps in appropriate use of models. Even so, the results of computer models should be carefully interpreted and continuously verified with adequate field data. Numerous U.S. EPA references on models are listed in the reference section at the end of this chapter.

13.8 METHODS This section provides the reader with a step-wise framework that can be used to review data for a given chlorinated solvent site, evaluate whether the natural attenuation of chlorinated VOC is occurring, identify and collect additional data that support the three lines of evidence of natural attenuation and integrate natural attenuation into a long-term site remediation/management strategy. It is anticipated that these activities can be

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Figure 13-3 General Conceptual Model of MNA Components conducted concurrent with other investigation and remediation planning activities. Figure 13-2 summarizes this information in a flowchart format. This strategy follows the U.S. EPA steps in several of the current guidance documents associated with monitored natural attenuation, (see U.S. EPA, 1999a). Step 1. Phase I Review Available Site Data The first step in evaluating natural attenuation is to review available site data typically gathered as a Phase I type evaluation. For Superfund sites, data typically available from remedial investigation (RI), risk assessment and feasibility study (FS) documents. For Resource Conservation and Recovery Act (RCRA) facilities, data typically will be available from RCRA Facility Investigation (RFI) and Corrective Measures Study (CMS) documents and/or RCRA Alternate Concentration Limit Demonstration reports. Monitoring reports for existing remediation systems may also be available for review. It is important to identify potential receptor exposure points (e.g., drinking water wells, surface or groundwater discharge points) at this time if not yet identified. Site characterization is necessary for sites with insufficient data. Chapters 2 to 8 of this text references site

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investigation protocols appropriate for establishing important site criteria for MNA. Evaluating natural attenuation should be incorporated into the site investigation at uncharacterized sites as the costs of collecting the additional data to evaluate natural attenuation are outweighed by the cost savings that may be realized if natural attenuation is integrated into the long-term site remediation strategy. Step 4 discusses the level of natural attenuation data that should be collected at uncharacterized sites. Step 2. Generate the Site Conceptual Model Once the Phase I data are generated you should be able to determine whether a reasonably accurate site conceptual model would fit the criteria for a MNA solution. The site conceptual model should be fully representative of the site-specific ground-water flow and solute transport system for the site. This model (U.S. EPA, 1998) is typically used to: • Present and explain chemical distributions in the site ground water in relation to ground-water flow and transport processes. • Facilitate the identification of risk assessment elements

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used in exposure analysis, including sources, release mechanisms, transport pathways, exposure points and potential receptors as shown in Figure 13-3. RI documents typically present a site conceptual model that is based on available geological, hydrogeological and chemical data. These models should follow the guidance described in Chapter 8 of this text. These models generally do not adequately integrate chemical fate due to degradation (biological and abiotic) processes and these processes are very site specific for chlorinated solvents. However, as they exist, site conceptual models are useful to identify: • Reduction of chemical mass in relation to groundwater flow and transport • Locations at the site (relative to sources, receptors or site boundaries) where additional data are required to document reduction of chemical mass and presence of geochemical indicators of natural attenuation processes

Figure 13-4 Target Areas for Collecting Screening Data

• Specific types of data that should be collected at the locations selected. A site conceptual model is necessary if it is not presented in the available site documents. Chapter 8 references protocols for conceptual model development.

processes that are promoting the attenuation. Screening for natural attenuation can be conducted by reviewing the information and answering the following questions:

Step 3. Develop Hypothesis To Explain the Attenuation Processes through Screening the Data for Evidence of Natural Attenuation.

1. Do the existing data provide evidence for reduction of chemical mass (line of evidence #1)?

The available site data and site conceptual model should be screened both to assess whether natural attenuation is occurring and to develop a hypothesis regarding the

2. Have concentrations of known or suspected parent chlorinated solvents decreased over time? Do observed chlorinated solvent distributions differ (decrease along the flow path) from distributions predicted from expected transport in ground water? 3. Do the existing data provide evidence for the presence of geochemical or biochemical indicators of natural attenuation (line of evidence #2)? 4. Are known degradation products (e.g., cis-1,2DCE, VC or ethene at a TCE site, see Table 13-3) present in the ground water? Have ratios of dechlorination daughter products to parent solvents increased over time and is cis-1,2-DCE the predominant DCE isomer?

Figure 13-5 Example of a Complex Geological Situation That Would Form Multiple Plumes

5. Do available data indicate production or consumption of carbon sources or production of inorganic constituents consistent with known biodegradation reactions (e.g., increased alkalinity, chloride and/or dissolved iron concentrations in source area wells)?

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Table 13-4a: Data Collection Tiers for Evaluation and Implementation of Natural Attenuation

Yes answers to any/all of these questions typically indicate that biodegradation processes are occurring and should be further evaluated following Steps 4 through 9 (U.S. EPA, 1998). Figures 13-4 and 13-5 provide examples of several common patterns of chlorinated solvent biodegradation in anaerobic and sequential anaerobic/aerobic systems, respectively. Sites where screening does not indicate the occurrence of these biological processes may still be candidates for natural attenuation, depending on the results of exposure pathways analysis and should be further evaluated by advancing to Step 8. Step 4. Develop Basis for Additional Supporting Data Identification and selection of additional data to test the natural attenuation hypothesis and support the lines of evidence approach are site-specific processes. However, the process can generally be conducted as follows: 1. Compare the conceptual model for the given site to the common patterns of chlorinated solvent presence and distribution presented in Table 13-3. Select the pattern that best approximates condi912

tions at the given site and identify the suggested data collection tier. Using Table 13-4, identify the specific data parameters that correspond to the selected data collection tier. As an example, the conceptual model for a site having 1,2-DCE and VC in the ground water near a TCE storage or disposal area should be similar to Pattern 3 and would warrant collection of Tier 2 data. 2. Select locations for additional data collection based on the site conceptual model. For sites having significant vertical flow components, locations should be selected to represent the vertical profile as well. The adequacy of existing well coverage to test/support the natural attenuation hypothesis should be evaluated. Locations should be selected to represent upgradient (background), lateral, source and several downgradient conditions, including at least one well beyond the terminus (toe) of the VOC plume. Additional monitoring locations may need to be installed to adequately test/support the natural attenuation hypothesis. For example, the capacity of the natural system to

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Table 13-4b: Data Collection Tiers for Evaluation and Implementation of Natural Attenuation

degrade chlorinated hydrocarbons that are directly oxidized is almost totally dependent on the amount of electron acceptors in background groundwater just as it is with petroleum hydrocarbons; therefore, the need for a true “background” well is important. However, the installation of new wells in what might be considered the “source area” at a DNAPL site is highly discouraged (see Chapter 13 of Pankow and Cherry, 1996). 3. Microcosm studies may be important for making the case for MNA. Microcosm studies provide direct microbiological evidence and are used to: (1) confirm specific chlorinated solvent biodegradation processes and/or (2) estimate site-specific biodegradation rates that cannot be conclusively demonstrated with field data alone. Because microcosm studies are both expensive and time consuming, they should only be performed when the information cannot be obtained from field data. Microcosm studies are designed using aquifer sediment and ground-water samples collected from the site and should provide direct evidence for natural attenuation of chlorinated solvents

under simulated redox conditions that occur at the site. If these studies are required, they can also be used to characterize: a) Soil adsorption potential b) Mass balance c) Role of available electron donors/co-metabolites in supporting natural attenuation processes d) Factors that may affect/inhibit natural attenuation over time, including the ability to enhance the natural processes. For uncharacterized sites, a minimum of Tier I data should be collected during site characterization to evaluate the potential for natural attenuation. An evaluation of site use history should indicate whether Tier II or Tier III data should also be collected. For example, if site records indicate that waste solvents (e.g., TCE) were used and disposed of along with sewage, petroleum hydrocarbons or other solvents (e.g., acetone, methanol, methylene chloride), then it is likely that some degree of intrinsic biodegradation has occurred; therefore, collection of Tier II or III

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data during site characterization may be warranted. Step 5. Additional Data Collection Data should be collected following appropriate protocols to ensure the quality and integrity of the data. The reader is referred to ASTM standards as resource guiddance for accepted protocols for well installation and development, well purging and sampling, field parameter measurement, chemical and microbial analyses and QA/ QC procedures. Step 6. Refine the Site Conceptual Model The site conceptual model should be refined by incorporating new data and reinterpreting site conditions as indicated below. Chapters 3 through 6 reference protocols for tasks listed below (e.g., calculation, modeling). Reconstruct:

• Potentiometric surface ( watertable) maps with updated data and data from any new monitoring points to assess lateral components of ground-water flow. • Hydrogeologic cross-sections parallel and perpendicular to the ground-water flow path with updated data and data from new monitoring points to assess vertical (upward/downward) components of ground-water flow. • Plots of concentration versus time or concentration versus distance for key ground-water chemistry parameters for wells located on the ground-water flowpath(s). • Isopleth contour maps and vertical cross-sections (if warranted) of key groundwater chemistry parameters. Maps existing for the initial site conceptual model (e.g., VOC, possibly anions) should be updated to include new data. Maps should be prepared for new data parameters [e.g., degradation products, redox

Table 13-4c Data Collection Tiers for Evaluation and Implementation of Natural Attenuation

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Table 13-4d: Data Collection Tiers for Evaluation and Implementation of Natural Attenuation

parameters, electron donors/co-metabolites, electron acceptors, conservative tracers (chloride)].

of electron donors/acceptors/co-metabolites promoting degradation).

Estimate:

Conduct:

• Mass balance for parent and daughter products, including both metabolic intermediates (e.g., DCE, VC) and final products (e.g., ethene, ethane, methane, inorganic chloride). • Flux of parent and daughter products and, if possible, electron donors, electron acceptors and co-metabolites. • Sorption and retardation of chemicals (from literature or laboratory tests). • Biodegradation kinetics such as half-life or degradation rate constants. Biodegradation kinetics can be estimated by evaluating field data (changes in concentration over distance) or laboratory microcosm studies. • Estimate the long-term capacity of the aquifer to sustain natural attenuation (e.g., half-life/degradation rate

• Fate and transport modeling if the site hydrogeology is complex enough to warrant the effort to better understand the flow regime. Ground-water fate and transport models are currently available to simulate groundwater flow and solute transport. Models incorporating biodegradation kinetics for natural attenuation of chlorinated solvents are currently under development. • Perform a sensitivity analysis for key geological, hydrogeological and attenuation factors. Assess the need to refine the available data. • Compare concentration profiles generated for various time intervals in model simulations conducted with and without incorporating biodegradation kinetics.

Step 7. Refine Conceptual Model

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Review the refined site conceptual model and determine whether the data fit this conceptual model. If the data support the natural attenuation hypothesis developed in Step 3 (i.e., distributions of parent and daughter products are consistent with redox and distribution of electron donors/acceptors, metabolic products and site hydrogeology), then exposure pathways analysis should be conducted (Step 8). If data do not support the hypothesis developed in Step 3 (i.e., the redox and/or distributions of electron donors/acceptors or metabolic products do not support the distribution of parent and daughter products), then the hypothesis should be refined and re-tested. In most cases, the available data is sufficient to test new or refined hypotheses. However, some additional data collection (a return to Step 4) may be required to test new/refined hypotheses at complex sites. Step 8. Exposure Pathway Analysis

The refined conceptual model should be examined in association with identified human and ecological risks and the following questions should be answered: Are the rates of natural attenuation processes sufficient to reduce risk (now and in the future) to human and ecological receptors to acceptable levels? If yes, then the site is a strong candidate for a natural attenuation alternative and implementation of natural attenuation should be considered as discussed in Step 9. If no: Can other engineering controls or technologies control or further reduce this risk such that natural attenuation is sufficient? If yes, then these options should be further evaluated/ implemented. Integration of natural attenuation into the

Table 13-4e: Data Collection Tiers for Evaluation and Implementation of Natural Attenuation

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Table 13-4f: Data Collection Tiers for Evaluation and Implementation of Natural Attenuation

overall remediation strategy should then be considered where it may be cost effective. If implementation of engineering controls is technically impracticable (e.g., at some DNAPL sites), then natural attenuation may be the primary mechanism of risk reduction and therefore natural attenuation should be incorporated into the long-term site management strategy. Step 9. Develop a Long-Term Site Management Strategy to Include the MNA process The long-term prognosis of natural attenuation should be assessed by answering the following question: Can factors promoting natural attenuation be sustained over the long-term (e.g., is the amount of available electron donor/acceptor/co-metabolite sufficient to maintain intrinsic degradation or will additional electron donor need to be added at a later date and when)? If yes, then develop a strategy for long-term management that incorporates monitoring and process validation to ensure that regulatory requirements are met (e.g., no adverse impact). If no, evaluate whether it will be possible to enhance the naturally occurring processes in the future (at such time that this is required) or whether other remediation technologies can be implemented currently or at a later date to support natural attenuation. A backup reme-

dial technology should be selected at a conceptual level along with natural attenuation even when natural attenuation is selected as the sole remedy. Findings and the proposed strategy should be presented to regulatory agencies (and the public where appropriate) and final acceptance should be pursued. Upon acceptance, a natural attenuation strategy should be implemented. In the future, when natural attenuation is as accepted a technology as others currently in use, this step will belong here. In the interim, it is highly recommended that any proponent of natural attenuation actively seek the involvement of regulatory agencies and other stakeholders as early as possible in the process. Involvement should ideally occur after Step 2 or 3, when the proponent has convinced themselves that natural attenuation is worth investigating, but prior to collection of additional data. Acceptance by regulatory agencies at this point will ensure that money is not wasted on additional investigation and that all required data is collected efficiently. Table 13-7 contains the elements of a long-term monitoring plan. 13.9 SITES WHERE MONITORED NATURAL ATTENUATION MAY BE APPROPRIATE Monitored natural attenuation is appropriate as a remedial approach only where it can be demonstrated capable of achieving a site’s remedial objectives within a time frame that is reasonable compared to that offered by

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918 Table 13-5: Elements of the Long-Term Natural Attenuation Monitoring Plan

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Table 13-6 Examples of Geochemical Indicators for Destruction of Common Organic Contaminants

Source: TNRCC (2001)

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Table 13-7 Natural Attenuation Pathways for Inorganics

Source: Adapted from Brady and Borns (1997)

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other methods and where it meets the applicable remedy selection criteria for the particular regulatory program. U.S. EPA and state lead programs expect that monitored natural attenuation will be most appropriate when used in conjunction with active remediation measures (e.g., source control) or as a follow-up to active remediation measures that have already been implemented. In determining whether MNA is an appropriate remedy for soil or ground water at a given site, the invesitgator should consider the following: • Whether the contaminants present in soil or ground water can be effectively remediated by natural attenuation processes • Whether the resulting transformation products present a greater risk than do the parent contaminants • The nature and distribution of sources of contamination and whether these sources have been or can be adequately controlled • Whether the plume is relatively stable or is still migrating and the potential for environmental conditions to change over time • The impact of existing and proposed active remediation measures upon the MNA component of the remedy • Whether drinking water supplies, other ground waters, surface waters, ecosystems, sediments, air or other environmental resources could be adversely impacted as a consequence of selecting MNA as the remediation option • Whether the estimated time frame of remediation is reasonable (see below) compared to time frames required for other more active methods (including the anticipated effectiveness of various remedial approaches on different portions of the contaminated soil and/or ground water) • Current and projected demand for the affected aquifer over the time period that the remedy will remain in effect (including the availability of other water supplies and the loss of availability of other ground-water resources due to contamination from other sources) • Whether reliable site-specific vehicles for implementing institutional controls (i.e., zoning ordinances) are available and if an institution responsible for their monitoring and enforcement can be identified For example, evaluation of a given site may determine that, once the source area and higher concentration portions of the plume are effectively contained or remediated, lower concentration portions of the plume could

achieve cleanup standards within a few decades through MNA, if this time frame is comparable to those of the more aggressive methods evaluated for this site. Also, MNA would more likely be appropriate if the plume is not expanding, nor threatening downgradient wells or surface water bodies and where ample potable water supplies are available. The remedy for this site could include source control, a pump and treat system to mitigate only the highly contaminated plume areas and MNA in the lower concentration portions of the plume. In combination, these methods would maximize ground water restored to beneficial use in a time frame consistent with future demand on the aquifer, while utilizing natural attenuation processes to reduce the reliance on active remediation methods (and reduce cost). Of the above factors, the most important considerations regarding the suitability of MNA as a remedy include whether the ground-water contaminant plume is growing, stable or shrinking and any risks posed to human and environmental receptors by the contamination. MNA should not be used where such an approach would result in significant contaminant migration or unacceptable impacts to receptors. Therefore, sites where the contaminant plumes are no longer increasing in size or are shrinking in size, would be the most appropriate candidates for MNA remedies. 13.9.1 Reasonableness of Remediation Time Frame The longer remediation time frames typically associated with monitored natural attenuation should be compatible with site-specific land and ground-water use scenarios. Remediation time frames generally should be estimated for all remedy alternatives undergoing detailed analysis, including monitored natural attenuation. Decisions regarding the “reasonableness” of the remediation time frame for any given remedy alternative should then be evaluated on a site-specific basis. While it is expected that MNA may take longer to achieve remediation objectives than would active remediation, the overall remediation time frame for a remedy which relies in whole or in part on MNA should not be excessive compared to the other remedies considered. Furthermore, subsurface conditions and plume stability can change over the extended time frames that are necessary for monitored natural attenuation. Defining a reasonable time frame is a complex and site-specific decision. Factors that should be considered when evaluating the length of time appropriate for remediation include:

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• Classification of the affected resource (e.g., drinking water source, agricultural water source) and value of the resource • Relative time frame in which the affected portions of the aquifer might be needed for future water supply (including the availability of alternate supplies) • Uncertainties regarding the mass of contaminants in the subsurface and predictive analyses (e.g., remediation time frame, timing of future demand and travel time for contaminants to reach points of exposure appropriate for the site) • Reliability of monitoring and of institutional controls over long time periods • Public acceptance of the extended time for remediation • Provisions by the responsible party for adequate funding of monitoring and performance evaluation over the period required for remediation Finally, individual states may provide information and guidance relevant to many of the factors discussed above as part of a Comprehensive State Ground Water Protection Program (CSGWPP). Where a CSGWPP has been developed, it should be consulted for ground-water resource classification and other information relevant to determining required cleanup levels and the urgency of the need for the ground water. Also, EPA remediation programs generally should defer to state determinations of current and future ground water uses, when based on an U.S. EPA-endorsed CSGWPP that has provisions for sitespecific decisions (U.S. EPA, 1997). Thus, U.S. EPA or other regulatory authorities should consider a number of factors when evaluating reasonable time frames for monitored natural attenuation at a given site. These factors, on the whole, should allow the regulatory agency to determine whether a natural attenuation remedy (including institutional controls where applicable) will fully protect potential human and environmental receptors and whether the site remediation objectives and the time needed to meet them are consistent with the regulatory expectation that contaminated ground waters will be returned to beneficial uses within a reasonable time frame. When these conditions cannot be met using monitored natural attenuation, a remedial alternative that does meet these expectations should be selected instead. Information typically included in presentations to demonstrate MNA includes: • Map illustrating the sampling network and the COC flow pattern • Time series concentration data indicating that COC

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concentrations are declining (Type I data) • Appropriate geochemical indicator data as warranted to substantiate decontamination • Technical basis for the estimated remedial time frame and supporting degradation rate calculations • Performance measures to monitor remedial effectiveness and a proposed schedule for submission of response action • Contingencies to be implemented in the event the remedy is ineffective If the facility decides use MNA, then this alternative would normally be proposed within a remedial action plan (RAP) document. Each state has variable reporting requirements; however, these submittals will always require approval from the regulatory agency before implementation. Performance measures to monitor remedial effectiveness, a schedule for submission of water quality results and contingencies to be implemented in the event the remedy is ineffective are normally included in the documents submitted to the agencies. During the monitoring period the regulatory agencies can be expected to review the results of the performance of the attenuation performance and if the agency determines that MNA is not satisfactorily progressing to attainment of the response objectives, then you should expect that the regulatory agency will require an alternative remedy to be implemented. State agencies have set up methods for measuring the performance of MNA remediations. Once these MNA remedies are selected all reporting requirements should be closely followed. 13.9.2 Plume Status The majority of programs require that MNA will be used only where a contaminant plume zone is shrinking in extent or in combination with another decontamination remedy. If the plume is either stable or expanding, it can be very difficult to make a case for its use as a sole remedy, as response objectives would be very difficult to meet. Figure 13-6 shows how plumes can change over time and would represent a shrinking plume. Each state has various lines of evidence (see Section 13.5) and requires complicated data collection activities that typically would be needed to support MNA as a control remedy. Note that in most states the data requirements are different depending on whether the plume is smaller than or larger than the limits of the site property, as well as, if the plume is shrinking, stable or expanding. An attenuation monitoring point is a monitoring point

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established within the migration pathway of a organic contaminant that is used to verify that a critical water quality standard will not be exceeded at the ground water point of exposure. An attenuation action level is the maximum concentration of a organic contaminant that can be present in an attenuation monitoring point and not result in the critical water quality standard being exceeded at the ground-water point of exposure over time. Guidance presented later in this chapter will discuss factors to consider when selecting the location of attenuation monitoring points. Each state can be expected to require a sometimes complicated basis of allowing the use of MNA solutions for a facility. Before proposing this alternation the investigation should be well versed in the state regulations and requirements used in these programs. 13.9.3 Reasonable Time Frame An MNA demonstration must address the requirement that remedial goals be achieved in a reasonable time frame. This can be done by: (1) comparing times required

using other remedial alternatives at the same affected property under similar conditions, or (2) developing estimates of how long MNA will take to achieve the cleanup goals (see Section 13.10). In order to lessen the estimated time frame required to complete the MNA, investigators may consider the use of amendments such as nutrients or oxygen agents to stimulate microbial activity. However, ensure that all regulatory approvals, registrations, or permitting requirements are met for the injection action or use of injection wells. 13.10 MNA METHODS Monitored natural attenuation is demonstrated using lines of evidence approach. The most direct demonstrations for the natural attenuation remediation option are those that utilize existing historical ground-water monitoring data that, if appropriately obtained, indicate that the zone of contamination plume is stable or shrinking. Monitored stability or shrinkage in the zone of contamination is the primary line of evidence that should be documented as part of the report presentations. Affected

Figure 13-6 Basis for Development of MNA Criteria (a Shrinking Plume) Source: U. S. EPA 1997a

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properties at which evidence of decontamination is needed or where the historical ground-water organic contaminant analytical monitoring data do not conclusively demonstrate control can be evaluated further by utilizing secondary alternative evidence. Geochemical data provide information on the current status of natural attenuation at the affected property. Such lines of evidence include plume zone geochemistry and determinations of natural attenuation rates. At some affected properties, more detailed information from calculations or modeling studies may be required to help predict the future behavior of a zone of contamination. Table 13-6 summarizes qualitatively the types of demonstrations for the natural attenuation option. 13.10.1 Data Considerations The property characteristics and the remedy standard dictate data requirements. You should, at a minimum, consider these property characteristics when determining data requirements: • Response objective to be achieved • Proximity to point of exposure • Organic contaminant levels • Ground-water flow velocity and direction, including variations in ground-water conditions • Hydrogeologic setting Examples of how these considerations can influence different data collection matters are discussed next. 13.10.2 Amount/Quality of Data When the ground-water zone of contamination is in close proximity to receptors, more detailed monitoring data and alternative lines of evidence are needed to make a case for natural attenuation as a response action. This is especially crucial if potential receptors, such as drinking water wells or surface water, are proximate to and downgradient of a ground-water contamination plume. Additionally, situations where receptors do not currently exist in proximity to the documented contamination but are reasonably likely to develop in the future warrant gathering more data for the affected properties. Typically, MNA studies will have contamination plume maps from different time intervals, concentration vs. time plots from different individual wells and concentration vs. distance plots. The Texas Natural Resources Conservation Committee (TNRCC) has described in state regulatory guidance

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documents that a strong case can be made for monitored natural attenuation based on monitoring data using a minimum of four sampling events spaced evenly over the course of a year (see TNRCC guidance document Compliance Sampling and Monitoring, RG-366/ TRRP-30) to check the effect variations in ground-water conditions may have on MNA if the affected property is well understood. Four quarters of time series data represent the minimum sampling requirements for relatively simple affected properties or affected properties that are well understood. 13.10.3 Monitoring Points Regardless of the ground-water response objective or property characteristics, multiple ground-water attenuation monitoring points should be placed along the groundwater flow path to evaluate MNA. This will allow for proper measurement of contaminant concentrations and comparison to the attenuation action levels that will be established in the state regulatory program. Moreover, multiple monitoring points along the flow path facilitate gathering data necessary for making decisions on the potential facility remedy. In the context of decontamination, plume shrinkage along the ground-water flow path is usually the best indicator of contamination zone shrinkage as a whole. 13.10.4 Daughter Products The majority of organic chlorinated solvents degrade into daughter products under natural conditions. For example, 1,1,1-trichloroethane (1,1,1-TCA) can chemically degrade to 1,1-dichloroethylene (1,1-DCE), 1,1dichloroethane (1,1-DCA), vinyl chloride and chloroethane. Daughter products of these common organic chlorinated solvents are also traditionally included in state remediation programs because they are themselves considered to be contaminants of ground-water systems. As such, PCLs are assigned to daughter products. As discussed in Section 13.8, the presence of the daughter products is considered as alternative evidence that degradation of the parent organic chlorinated solvent is occurring. Table 13-6 lists some common daughter products. Additionally, understanding the formation and presence of daughter products can also be important because in some instances they are more toxic than the parent organic chlorinated solvent. For example, vinyl chloride is more toxic than the parent 1,1,1-TCA. Therefore, for both of the reasons mentioned, concentrations of the original (parent) organic chlorinated solvent and daughter products must be monitored. In most cases state regulatory agency staff will exercise reasonableness in determining

MONITORED NATURAL ATTENUATION

how far to carry the evaluation of daughter products. For example, if the maximum concentration of the parent organic chlorinated solvents is stable or declining and less than the PCL of the daughter product and the concentration of the daughter product does not exceed its PCL, then there would be little need to be further concerned with the daughter product. In this case even if all of the parent organic chlorinated solvent were transformed to the daughter product, the daughter product PCL could not be exceeded. The spatial distribution of daughter products may need to be presented as part of the demonstration of acceptable contamination plume and ground-water flow behavior. 13.10.5 Geochemistry / Modeling

13.10.7 Level of Information In general, more information (for example, more wells, more samples, more lines of evidence) could be required for MNA demonstrations at affected properties with these conditions: • Karst ground-water-bearing units • Fractured-rock ground-water-bearing units • Potable water supply Class 1 ground-water-bearing units • Complex, multilayered hydrogeology • Organic concentrations much greater than PCLs • Organics that yield daughter products of concern

When implementing decontamination, ground-water geochemistry data should be collected as necessary to demonstrate the improvements in water quality. The types of geochemical analyses should be tailored to the organic contamination being addressed by natural attenuation. For example, for chlorinated hydrocarbons it may be necessary to collect data for potential competing electron acceptors (dissolved oxygen, nitrate, sulfate), indirect indicators of competing electron acceptors (ferrous iron and methane), potential fermentation substrates (total organic carbon), chlorides, alkalinity and dechlorination end products, such as ethane and ethene. Other lines of evidence, specifically ground-water computer modeling or conservative calculations, may be needed to predict plume behavior. To develop an acceptable ground-water model to act as other evidence for natural attenuation, sufficient data should be gathered to calibrate the ground-water model. 13.10.6 Field Measurements In summary, the following data should be derived from field measurements for most MNA demonstrations: • Hydraulic conductivity data from slug tests, pump tests or other aquifer tests • Ground-water flow maps based on data from at least four monitoring wells • Fraction organic carbon (foc) measurements of clean ground-water-bearing unit material (not organics measurements from at least four wells that are appropriately located) • Daughter products measurements, if present, at the affected property

• Affected properties with persistent organics at high concentrations • NAPLs • Receptors near plume boundaries • Affected properties with hydrogeologic conditions that change over time In general, less information (for example, fewer wells, fewer samples, fewer lines of evidence) could be required for MNA demonstrations at affected properties with these conditions: • Single-layer unconsolidated ground-water-bearing units • Industrial, Class 3 ground-water-bearing units • Affected properties with only BTEX (benzene, toluene, ethyl benzene and xylenes) COCs • Affected properties with organic concentrations near PCLs • Contaminants that do not yield daughter products of concern • No free-phase NAPLs • No receptors near PCLE zone boundaries • Affected properties with hydrogeologic conditions that do not appear to change over time In all cases, however, the data must be sufficient to demonstrate that MNA will serve as an effective remedy at an affected property.

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13.10.8 How to Analyze and Present Water Quality Data as Evidence for MNA Each MNA demonstration should have a discussion of the conceptual model of the affected property with a review of the source mechanisms, key fate and transport processes that can contribute to natural attenuation and the ultimate fate of organics in the subsurface. Other key factors include: • Potential receptors • Ground-water flow paths • Sources that discharge organic contamination to ground water • Natural attenuation processes that decontaminate or control the migration of COCs in ground water • Transformations of COCs into other COCs through natural processes, such as reductive dechlorination Chemical evidence of two types can be used to document the occurrence of biodegradation. The first type of evidence is graphical and is provided by the electron acceptor and metabolic by-product maps discussed in the following sections. The second line of evidence involves using a conservative tracer. 13.10.9 Isopleth Maps The extent and distribution of contamination relative to electron acceptors and metabolic byproducts can be used to qualitatively document the occurrence of biodegradation. Depleted dissolved oxygen concentrations in areas with fuel hydrocarbon contamination indicate that an active zone of aerobic hydrocarbon biodegradation is present. Depleted nitrate and sulfate concentrations in areas with fuel hydrocarbon contamination indicate that an active zone of anaerobic hydrocarbon biodegradation is present and that denitrification and sulfate reduction are occurring. Elevated iron (II) and methane concentrations in areas with fuel hydrocarbon contamination indicate that an active zone of anaerobic hydrocarbon biodegradation is present and that iron reduction and methanogenesis are occurring. Isopleth maps of contaminants, electron acceptors and metabolic byproducts can be used as evidence that biodegradation of fuel hydrocarbons is occurring.

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13.10.10 Data Set Normalization In order to calculate biodegradation rates accurately, measured contaminant concentrations must be normalized for the effects of dispersion, dilution and sorption. A convenient way to do this is to use compounds or elements associated with the contaminant plume that are relatively unaffected or predictably affected by biologic processes occurring within the aquifer. At sites where commingled fuel hydrocarbon and chlorinated solvent plumes are present, the trimethylbenzene (TMB) isomers, which can be biologically recalcitrant under some geochemical conditions, have proven useful when estimating biodegradation rates for BTEX and chlorinated solvents. At sites where TMB data are not available, the chloride produced as a result of biodegradation or the carbon nucleus of the chlorinated compound can be used as a tracer. Measured concentrations of tracer and contaminant from a minimum of two points along a flow path can be used to estimate the amount of contaminant that would be expected to remain at each point if biodegradation were the only attenuation process operating to reduce contaminant concentrations. The fraction of contaminant remaining as a result of all attenuation processes can be computed from the measured contaminant concentrations at two adjacent points. The fraction of contaminant that would be expected to remain if dilution and dispersion were the only mechanisms for attenuation can be estimated from the tracer concentrations at the same two points. The tracer is affected by dilution and dispersion to the same degree as the contaminant of interest and is not affected by biologic processes. The following equation uses these assumptions to solve for the expected downgradient contaminant concentration if biodegradation had been the only attenuation process operating between two points along the flow path: T C B, corr = C B £ -----A-¥ ¤T ¦ B

Equation 13-1

where: CB,corr = corrected contaminant concentration at a point B downgradient CB = measured contaminant concentration at point B TA = tracer concentration at a point A upgradient TB = tracer concentration at point B downgradient

MONITORED NATURAL ATTENUATION

This equation can be used to estimate the theoretical contaminant concentration that would result from biodegradation alone for every point along a flow path on the basis of the measured contaminant concentration at the origin and the dilution of the tracer along the flow path. This series of normalized concentrations can then be used to estimate a first-order rate of biodegradation 13.10.11 Maps and Graphs Maps and graphs are useful in analyzing and presenting primary evidence of natural attenuation. Graphical comparisons of contaminate plume size over time will show if the contaminate plume is shrinking, stable or expanding. These graphical comparisons can be of the plume as a whole over time. The gross contaminate plume outline for sequential monitoring events can be compared to determine plume behavior. For decontamination organic mass estimates over time may be graphically ana-

Source: TNRCC 2001

lyzed and presented to demonstrate contaminant destruction. Graphs of organic concentrations along groundwater flow paths can be compared for sequential monitoring events. This will often show whether the contaminate plume is shrinking, stable or expanding. Plots of single well concentrations vs. time are useful in determining whether plumes are stable or shrinking. Under a control response action, a number of plots of concentrations vs. time from individual wells may be useful in determining whether a plume that has been expanding within a facility property area has now stabilized. In summary, key graphics that should be included at a minimum in MNA demonstration for affected properties with data over time are: • A sufficient number of historic plume maps vs. time that represent the overall dynamic of the plume (Figure 13-4). • A sufficient number of concentration vs. time plots for individual monitoring wells (for at least two wells

Figure 13-7 Example of Concentration vs. Distance Plots

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from the source and leading edge along the centerline of the plume over the entire sampling record) that represent the overall dynamic of the plume (Figures 13-4 and 13-6). • Concentration vs. distance plot for wells (along the centerline of the plume) (Figure 13-7). Optional graphics include mass estimates for the dissolved phase contamination within the plume vs. time plots There are a number of statistical methods that can be used with ground water monitoring evidence. Statistical methods are most compelling when used in conjunction with graphics. Some statistical methods, such as MannKendall, are useful for discerning trends that may not be apparent graphically. Other statistical data such as the confidence factor and the coefficient of variation can be used to determine plume trends (for example, the Air Force’s MAROS system). Other statistical methods, such as linear regression and Sen’s test, may be accepted statistical methods for evaluating plume trends. 13.10.12 How To Analyze and Present Data MNA Proper analysis and presentation of data indicating that MNA will be an effective remedy are important. This

section discusses the water quality data typically used to support MNA evaluations and provides guidance for how to present the information in order to substantiate MNA as a remedy. Show Destruction with Geochemical Footprints For some affected properties, ground-water geochemical indicator data should be evaluated and displayed in the MNA demonstration to show that organic contamination remediation is occurring. Where decontamination is occurring, a pattern or footprint for the geochemical indicator data will commonly be present that relates to the location of the contaminant plume. For example, there will often be a pattern or footprint of depressed dissolved oxygen concentrations in ground water that coincides with BTEX plumes that are indicative of aerobic microbial degradation of the BTEX. Several protocols discuss the collection and interpretation of geochemical indicators, Table 13-4 provides recommended analytical methods. Note that in Table 13-4 the sample collection method varies according to a qualitative well depth of shallow, medium or deep. This is related to the feasibility of sample collection as a function of well depth and there is no intent to provide specific definitions of these depths. Table 13-6 provides a brief summary of key geochemical indicators for common types of organic chlorinated solvents and BTEX and the affected properties for

Figure 13-8 Example of Geochemical Footprint Map

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Source: TNRCC 2001

Figure 13-9 Example of Concentration vs. Time Graphs.

these contaminants. Chief geochemical indicators are the ones expected at most affected properties with each particular organic contaminant that is undergoing natural attenuation processes. Supplemental geochemical indicators are less commonly used (non-routine) or are not observed as prominently as the chief indicators or are more difficult to interpret. Note this list is not meant to be inclusive, but only provides a summary of more prominent geochemical indicators. Geochemical indicator data are commonly presented in maps (Figure 13-8) and/or graphs (Figure 13-9). Note that some organic chlorinated solvents (1,2DCA, DCE, VC) can biodegrade in either anaerobic or aerobic conditions and therefore indicators of these conditions could be used to support the conclusions that geochemical conditions are appropriate for destruction. Rate Calculations An additional line of evidence for the demonstration of natural attenuation is determination of the rate of deg-

radation of organic chlorinated solvents measured within the plume. Contamination plume attenuation rate calculations comprise two different methods, each of which is capable of producing quantitative data that can demonstrate the progress of and provide support for, the natural attenuation remedial option. Additionally, the organic contaminant attenuation rate is required information in cases when predictive modeling is used to estimate the time necessary to meet remedial goals. The methods entail: (1) organic contaminant concentrations versus time and (2) organic contaminant concentrations vs. distance. However, each method of rate calculation is applicable only to a specific condition of ground-water plume dynamics as described below. Caution is advised in the use of these methods as they are not strictly applicable to families of organic contaminant which undergo sequential reactions that produce decay products (daughters) of a precursor (parent) organic contaminant, such as occurs with some chlorinated solvents.

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Source: TNRCC 2001

Figure 13-10 Example of Geochemical Footprints Plot Organic Contaminant Concentration vs. Time Attenuation Rate Constant. Documentation of a reduction of organic contaminant in a shrinking contaminant plume is established through previous monitoring of the size and location through direct measurement of ground-water quality. The rate of organic contamination degradation occurring within the plume is determined using the concentration versus time relationship. Rate calculations are needed only to support the case where the monitoring data are not sufficient to determine if MNA will work. In the case of a shrinking plume, the rate of organic contamination attenuation is greater than the rate of organic contamination added to the plume. As with a large number of processes, the change in a solute’s concentration in ground water over time often can be described using a first-order rate constant. A first-order approximation, if appropriate, has the advantage of being easy to calculate and simplifies fate and transport modeling of complex phenomenon. In one dimension, first-order decay is described by the following ordinary differential equation:

dC ------- = – kt dt

930

Equation 13-2

where: C = concentration at time t [M/L3] k = overall attenuation rate (first-order rate constant)[1/T] Solving this differential equation yields: C = Coe-kt

Equation 13-3

This equation can also be expressed as: C(t) = Cie -(ktime t)

Equation 13-4

where: C(t) = concentration (such as mg/L) as a function of time, t (such as years) Ci = concentration at t = 0 (such as mg/L or μg/L) t = time (in units such as years; the units will determine the units of k time) ktime = first-order attenuation rate constant (such as per year) The overall attenuation rate groups all processes acting to reduce contaminant concentrations and includes advection, dispersion, dilution from recharge, sorption and biodegradation. To determine the portion of the overall attenuation that can be attributed to biodegradation, these

MONITORED NATURAL ATTENUATION

effects must be accounted for and subtracted from the total attenuation rate. Aronson and Howard (1997) have compiled a large number of attenuation rate constants for biodegradation of organic compounds in aquifers. Graphically, the regression method requires log COC concentration to be plotted against time for each monitoring well. A first-order organic contamination attenuation will plot as a straight line. The slope of the regressed line (ktime) gives the decay rate constant, the y-intercept gives the initial concentration (Ci) (Figure 13-9). This is potentially a daughter product if this organic contamination was not part of the source materials in the original release. For late-time plume data that have reached asymptotic concentrations or when there is a need to confirm a long-term asymptotic concentration, the following equation can be employed: C(t) = (Ci – Ca)e -(ktime t) – Ca

Equation 13-5

where: Ca is the asymptotic concentration In summary, concentration vs. time rate constants: • Can be used to show attenuation is occurring. • Can be used to predict how long organic contamination will persist in the subsurface. • Can be used for evaluating if MNA can achieve remediation goals in a reasonable time frame). • Cannot be used as a biodegradation rate in a fate and transport model. Using these equations, the overall attenuation rate can be estimated based on the changes over time in contaminant concentration in ground-water samples collected from individual monitoring wells at a site. The procedure consists of plotting the natural log of the ratio C/C0 vs. time and calculating the slope of the best fitting line. Because biodegradation is the most important destructive attenuation mechanism, estimating the sitespecific biodegradation rate is critical to documenting loss of contaminants. To determine the portion of the overall attenuation rate that can be attributed to biodegradation, the effects of abiotic processes such as advection, dispersion, dilution from recharge and sorption must be subtracted from the total attenuation rate. These effects can be subtracted out through data analysis or by using biodegradation rates measured during microcosm studies. In their technical protocol, U.S. EPA states that microcosms should be used to estimate biodegradation rates only when it is impossible to estimate the rate of attenuation based on data obtained from monitoring wells in the plume.

U.S. EPA’s technical protocol presents two methods of calculating biodegradation from data from monitoring wells in the plume. One method involves the use of a normalized data set (i.e., a set of data that has been corrected to exclude the effects of abiotic processes) to compute a decay rate. The second method was derived by Buscheck and Alcantar (1995) and is valid for steady-state plumes. Others, have suggested the use of screening solute transport models such as BIOSCREEN, BIOCHLOR and BIOPLUME III to iteratively fit plume characteristics as a means of calculating biodegradations rates. Organic Contamination Concentration vs. Distance Attenuation Rate Constant When the long organic contamination indicates the constant long organic contamination concentrations of a stable plume (i.e. organic contamination concentrations which remain constant over time in each monitoring well) a different type of attenuation rate can be determined using the concentration vs. distance relationship (Buscheck and Alcantar, 1995). Again, rate calculations are needed only to support the case where the ground-water monitoring data are not sufficient to determine if MNA will work. In a stable plume, the rate of attenuation is equal to the rate of dissolved-phase organic contamination mass loading to the ground-water-bearing unit from the source. The organic contamination source influx rate is controlled by a organic contamination’s effective solubility and the flow rate of ground water through the source area. In the following relation, time t, is described in terms of the ground-water seepage velocity (also called pore water velocity or linear velocity), v (L/T) and distance traveled, x (L): x t = -v

Equation 13-6

where: x -v

=

residence time for pore water to move a distance, x, from the source, in units such as ft or the pore water velocity (groundwater seepage velocity in units such as ft/ yr)

The first-order attenuation rate equation can be rewritten for concentration as a function of distance: C(x) = C0e-kdist(x/v)

Equation 13-7

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where:

• Can be used to show attenuation is occurring.

C(x) = concentration as a function of distance, x (such as in ft) C0 = concentration at x = 0 (such as in mg/L or μg/L) kdist = first-order attenuation rate constant (yr-1) A minimum of three monitoring wells placed along the ground-water flow direction is necessary for this method. Data are plotted as log organic contamination concentration vs. distance. For multiple sampling event data, the plotted concentrations are the average concentration over time for each well. The slope of the line is k/v(L-1), the reciprocal of the attenuation distance. The attenuation rate constant, kdist (T -1), is obtained by multiplying the slope (k/v) by the ground-water velocity, v (L/T). The kdist /v term also can be useful for selecting downgradient monitoring well locations whose placement must be a function of travel time. In summary, concentration vs. distance constants:

Source: TNRCC 2001

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• Can be used for predicting concentrations along any point of the center line of the plume or at some point beyond the current monitoring system (Figure 13-10). • Cannot be used to estimate how long (how many years) the plume will persist in the subsurface. • Cannot be used as a biodegradation rate in a fate and transport model. Organic Contamination Biodegradation Rate Constants The last type of rate constant is a biodegradation rate constant. It represents how quickly ground-water contamination organic parameters are decontaminated by biodegradation alone (no effects of dispersion or retardation). They can be calculated using concentration vs. distance data and simple modeling relationships (Buscheck and Alcantar, 1995) by comparing organic contamination con-

Figure 13-11 Concentration vs. time rate constant calculation.

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centrations to no-or low-biodegradable tracers (Rifai et al., 2001) or by calibrating a ground-water model to groundwater organic contamination concentration vs. distance data). Buscheck and Alcantar (1995) derive a relationship that allows calculation of first-order decay rate constants for steady-state plumes. This method involves coupling the regression of contaminant concentration (plotted on a logarithmic scale) vs. distance downgradient (plotted on a linear scale) to an analytical solution for one-dimensional, steady-state, contaminant transport that includes advection, dispersion, sorption and biodegradation. For a steady-state plume, the first-order decay rate is given by (Buscheck and Alcantar, 1995): vc £ k - 1 + 2_ x £ ----¥ h = -------¤v ¦ 4_ x ¤ x

2

– 1¥ ¦

Equation 13-8

where: h = first-order biological rate constant vc = retarded contaminant velocity in the x-direction ax = dispersivity k/vx = slope of line formed by making a ln-linear plot of contaminant concentration versus distance downgradient along flow path A biodegradation rate constant: • Can be used to show attenuation is occurring. • Can be used in a fate and transport model for predicting concentrations along any point of the center line of the plume or at some point beyond the current monitoring system. • Cannot be used to estimate how long (how many years) the plume will persist in the subsurface. The first step is to confirm that the contaminant plume has reached a steady-state configuration. This is done by analyzing historical data to make sure that the plume is no longer migrating downgradient and that contaminant concentrations are not changing significantly through time. This is generally the case for older spills where the source has not been removed. The next step is to make a plot of the natural logarithm of contaminant concentration vs. distance downgradient (see Figure 13-7 for an example). Using linear regression, y in the regression analysis is the contaminant concentration, x is the distance downgradient from the source and the slope of the ln-linear regression is the ratio k/vx that is entered into Equation 13-8.

Other Lines of Evidence When the ground-water monitoring data and geochemical data are insufficient to definitively demonstrate the adequacy of MNA as a response action, other alternative evidence may be generated to support an application for a MNA. This section discusses examples of these methods that can be considered. Demonstrate MNA Processes with Modeling Ground-water models are typically used to support conclusions drawn from an analysis of the ground water monitoring data and in some cases evaluation of geochemical evidence that: • Attenuation is occurring. • The plume is either shrinking, stable or will not expand beyond the facility boundary. and can provide the: • Estimated time of organic contamination transport to the point of exposure • Estimated concentration(s) of organic contamination at the point of exposure Ground-water modeling includes (1) conservative calculations; (2) natural attenuation factor (NAF) calculations, and (3) the use of computer fate and transport models. To help demonstrate that attenuation is occurring, conservative calculations or NAF calculations can be applied. One type of conservative calculation is to compare a theoretical plume length to the actual measured length of the plume. If the theoretical plume length is significantly longer than the actual measured length, then attenuation processes (dispersion, sorption and/or degradation) are shown to be active at the affected property (Figure 13-14). Natural attenuation factor (NAF) calculations based on a ground-water model (the lateral transport Domenico solution) are described more fully in many state guidance documents (see TNRCC document RG-366/TRRP-26). The resulting NAF can be used to demonstrate that natural attenuation processes reduce organic contamination concentrations after they leave the source zone. Alternatively, biodegradation rate constants can be calculated by calibrating a fate-and-transport model against concentration vs. distance data to yield a biodegradation rate constant. If

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a model with a decaying source is used, a concentration vs. time rate constant can also be determined. Reporting rate constants in an MNA demonstration support the conclusion that attenuation is occurring. Computer modeling requires an additional level of sophistication compared to NAF calculations or hand calculations. One approach for applying either analytical or numerical computer models in MNA demonstrations is to: 1. Select a model. In general, one should use the simplest model that simulates the key natural attenuation processes that are occurring. In many cases, a simple analytical model can serve as a cost-effective approach for incorporating modeling into MNA demonstration as long as conservative assumptions are used to account for processes that are not incorporated into the model. The use of complicated numerical models should be reserved for more complex affected properties.

2. Collect and enter input parameters. In some cases field data will be required (e.g., hydraulic conductivity, hydraulic gradient, fraction organic carbon organic contamination data, source dimensions, release data). Partition coefficients are obtained from the applicable state rules or from site-specific data (see TNRCC guidance document. Toxicity Factors and Chemical/Physical Properties (RG366/TRRP-19 for examples of these coefficients). In other cases, rules of thumb or literature values are used for parameter estimation (for example, dispersivity, bulk density, porosity, rate constants). 3. Calibrate the model to affected property data. The calibration parameters will vary for different models, but typically first order rate constants, dispersivities or the source data are used to calibrate fate and transport models.

Source: TNRCC 2001

Figure 13-12 Example of a Conservative Calculation for Plume Length Comparisons

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4. Increase the simulation time by some time frame, such as 100 years. The resulting plume prediction is compared to the calibrated actual plume to see if the model indicates that the plume is expanding or stable (if a constant-source model is used) or the plume is expanding, stable or shrinking (if a decaying source model is used). 5. Perforn a sensitivity analysis. Several of the key parameters in the model are adjusted (e.g., increased by 50% and then decreased by 50%) to determine if the predicted contaminant plume trend in Step 4 is consistent even if key input data are changed. 6. Verify the model using the long-term monitoring

data. If the verification shows that the actual measured plume is significantly longer or has higher concentrations than the plume predicted by the model, then the model work should be revised to update and correct the model. If the verification shows that the actual measured plume is significantly shorter or has lower concentration than the plume predicted by the model, then this should be noted in any state regulatory submittals, but does not mean the modeling work has to be revised. In summary, computer fate and transport models can be applied in the following ways: 1. A constant-source model can show that natural attenuation processes control the plume if the

Source: TNRCC 2001

Figure 13-13. Example of Remediation Time Frame Calculation

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modeled plume is stable over time or does not expand beyond the property boundary. 2. A decaying-source model can show that natural attenuation processes: (a) decontaminate the plume if the modeled plume shrinks over time; or (b) control the plume if the modeled plume is stable, shrinks or does not expand beyond the property boundary; or (c) achieve remediation goals in a reasonable time frame. Other types of models include source lifetime models that show that the source materials are being attenuated for the purpose of decontamination or for evaluating remediation time frames. Modeling studies are more important for affected properties with little or no historical record of organic contamination concentrations and may be critical for evaluating if expanding plume will meet State regulatory requirements. Ground-Water Flow Modeling Concepts To aid in the design and predictions of the performance of a MNA system, it is recommended that a ground-water flow model be constructed using the sitespecific geologic and hydrogeologic data collected as part of the site characterization effort. The model can be used to assess the area of influence, optimize the design and design the performance monitoring network for the MNA system. A complete description of ground-water flow modeling and the mathematics involved is provided in Wang and Anderson (1982) and Anderson and Woessner (1992). The steps involved in model construction and execution are discussed in the following subsections. Figure 13-14 (from Batu, 1997) shows a flow diagram of the typical steps of a computer flow model, Figure 13-15 extends the model to a solute transport function. Conceptual Model Development The first step in any modeling effort is the development of the conceptual model. Chapter 8 describes the components of conceptual models that are directly applicable to use within computer models. The conceptual model is a three-dimensional (3-D) representation of the ground-water flow and transport system based on all available geologic, hydrogeologic and geochemical data for the site. A complete conceptual model will include geologic and topographic maps of the site, cross-sections depicting the site geology/hydrogeology, a description of the physical and chemical parameters associated with the aquifer(s)

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and contaminant concentration and distribution maps. The purpose of the conceptual model is the integration of the available data into a coherent representation of the flow system to be modeled. The conceptual model is used to aid in computer model selection, model construction and interpretation of model results. Model Selection Many ground-water flow modeling codes currently on the market meet the above requirements. A comprehensive description of nonproprietary and proprietary flow and transport modeling codes can be found in the United States Environmental Protection Agency (U.S. EPA) document titled Compilation of Ground-Water Models (van der Heijde and Elnawawy, 1993). Depending on the project’s needs, the designer of a MNA system may want to apply a contaminant transport code (see Figure 13-15) that can use the calculated hydraulic-head distribution and flow field from the flow modeling effort. If flow and transport in the vadose zone are of concern, a coupled or uncoupled, unsaturated/saturated flow and transport model should be considered. Model Construction and Calibration Model construction consists primarily of converting the conceptual model into the input files for the numerical model. The hydrostratigraphic units defined in the conceptual model can be used to define the physical framework or grid mesh of the numerical model. In both finitedifference models (such as MODFLOW) and finite-element models (such as FRAC3DVS), a model grid is constructed to discretize the lateral and vertical space that the model is to represent. The different hydrostratigraphic units are represented by model layers, each of which is defined by an array of grid cells. Each grid cell is defined by hydraulic parameters (e.g., K, storativity, cell thickness, cell top and cell bottom) that control the flow of water through the cells. Model boundaries are simulated by specifying boundary conditions that define the head or flux of water that occurs at the model grid boundaries or edges. These boundary conditions describe the interaction between the system being modeled and its surroundings. Three types of boundary conditions generally are used to describe ground-water flow: specified-head (Dirichlet), specified flux (Neumann) and head-dependent flux (Cauchy) (Anderson and Woessner, 1992). Internal boundaries or hydrologic stresses, such as wells, rivers, drains and recharge, also may be simulated using these conditions. Boundary conditions are used to include the effects of the hydrogeologic system outside the area being

MONITORED NATURAL ATTENUATION

Source: Batu 1997

Figure 13-14 Diagram of Steps in Computer Flow Model 937

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Source: Batu 1997

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Figure 13-15 Diagram of Steps in Transport Computer Model

MONITORED NATURAL ATTENUATION

modeled and also to make possible isolation of the desired model domain from the larger hydrogeologic system. Calibration of a ground-water flow model refers to the demonstration that the model is capable of producing field-measured heads and flows, which are used as the calibration values or targets. Calibration is accomplished by finding a set of hydraulic parameters, boundary conditions and stresses that can be used in the model to produce simulated heads and fluxes that match field-measured values within a preestablished range of error (Anderson and Woessner, 1992). Model calibration can be evaluated through statistical comparison of field-measured and simulated conditions. Model calibration often is difficult because values for aquifer parameters and hydrologic stresses typically are known in relatively few locations and their estimates are influenced by uncertainty. The uncertainty in a calibrated model and its input parameters can be evaluated by performing a sensitivity analysis in which the aquifer parameters, stresses and boundary conditions are varied within an established range. The impact of these changes on the model output (or hydraulic heads) provides a measure of the uncertainty associated with the model parameters, stresses and boundary conditions used in the model. To ensure a reasonable representation of the natural system, it is important to calibrate with values that are consistent with the field-measured heads and hydraulic parameters. Calibration techniques and the uncertainty involved in model calibration are described in detail in Anderson and Woessner (1992). Model Execution After a model has been calibrated to observed conditions, it can be used for interpretive or predictive simulations. In a predictive simulation, the parameters determined during calibration are used to predict the response of the flow system to future events, such as the decrease in K over time or the effect of pumping in the vicinity of the MNA. The predictive requirements of the model will determine the need for either a steady-state simulation or a transient simulation, which would accommodate changing conditions and stresses through time. Model output and hydraulic heads can be interpreted through the use of a contouring package and should be applied to particle-tracking simulations in order to calculate ground-water pathways, travel times and fluxes through the cell.

MNA Simulation Models MODFLOW and Associated Programs Perhaps the most versatile, widely used and widely accepted groundwater modeling code is the United States Geological Survey’s (USGS’s) modular, 3-D, finite-difference ground-water flow model, commonly referred to as MODFLOW (McDonald and Harbaugh, 1988). MODFLOW simulates 2-D and quasi- or fully 3-D, transient ground-water flow in anisotropic, heterogeneous, layered aquifer systems. MODFLOW calculates piezometric head distributions, flow rates and water balances and it includes modules for flow toward wells, through riverbeds and into drains (other modules handle evapotranspiration and recharge). Various textual and graphical pre- and postprocessors are available on the market that make it easy to use the code and analyze the simulation results. These include GMS (Groundwater Modeling System), ModelCad386 (Rumbaugh, 1993), Visual MODFLOW (Waterloo Hydrogeologic, Inc., 1999b) and Groundwater Vistas. Other Evidence: Microcosm and Molecular Bioassay Studies Other lines of evidence include microcosm studies. Although these types of studies were done more frequently in the past, many MNA protocols now recommend that microcosm studies be performed only under special circumstances. Microcosm studies are generally not required to demonstrate biodegradation or abiotic degradation under the majority of state remediation programs. However, microcosm studies may provide useful site-specific evidence of biodegradation or abiotic degradation where literature indicates that organic contamination is persistent or little or no degradation data are available. Other technologies are now emerging where molecular approaches are used to define beneficial bacteria for MNA processes. 13.10.13 Methods for Demonstrating Compliance with the Proposed or Approved Reasonable Time Frame The general process for establishing and proposing a reasonable time frame for remediation requires the facility to demonstrate that the proposed remedial alternative will complete the remediation within a reasonable time frame.

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MONITORED NATURAL ATTENUATION

The establishment of what is considered as reasonable must be based on the level of data available for assisting the state regulatory agency staff in accepting the time period proposed and if the schedule can be met. This section discusses methods that can be employed to estimate the remedial time frame of MNA in order to determine if the proposed remedial time frame can be met with the use of MNA. Empirical Data The simplest approach and probably the most accurate if data are available, is to calculate a concentration versus time rate constant (see discussion under Section 13.10.12) and then use the rate constant to determine the time when concentrations reach the required response objective goal (PCL or attenuation action level). To perform this calculation, the concentration versus time rate constant (ktime) is determined from a plot of the natural log of organic contamination concentration versus time (Figure 13-16).

tion some form of a completion report is submitted to the state agency. Typically the state agency will then issue a letter of no further action. The monitoring required to document natural attenuation is typical defined in state remediation programs. Requirements for Decontamination To evaluate the effectiveness of MNA as a method to remediate organic contamination, a routine monitoring program should be established as part of the program documentation. In most cases, the routine monitoring will focus on the change in organic contamination over time as they trend toward the required cleanup levels. This routine monitoring might not require the sampling of all the monitoring wells or all the organic contamination at a particular location, but uses the most important wells/organic contamination to ensure that a correct slope of of remediation is being maintained to achieve the desired remedial cleanup levels. Requirements for Control

t = - ln (Cgoal / Ci) / ktime

Equation 13-9 Monitoring requirements for the MNA remediation have been defined to:

where, Cgoal =

Ci = ktime = t

=

response objective goal (concentration units such as mg/L) as a function of time, t (in units such as years) concentration at t = 0 (such as mg/L) time-based first order attenuation rate constant (such as per year) time to reach response objective goal (such as years)

This calculation should not be performed with the concentration vs. distance (kdist) rate constant. Source Lifetime Models Selected fate and transport models have simple source decay terms that can be used to evaluate the size of the plume zone lifetime questions. 13.10.14 Evaluating the Effectiveness of MNA after Remedy Selection After MNA is selected as a remedy, monitoring is required to determine when the water quality goals for the selected response objective are achieved. These analytical monitoring results are normally reported in a state level remedial program. Following completion of the remedia-

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• Ensure compliance with state level requirements • Document actual progress of remediation • Compare progress of remediation in relation to the predicted schedule for meeting the remedial objective • Trigger contingency plans upon detection of unauthorized plume migration Integral to the documentation of MNA are (1) establishment of cleanup action levels and (2) locations of the attenuation monitoring point. Establishing Attenuation Cleanup Action Levels Attenuation cleanup action levels can be defined as the “… maximum concentration of a chemical of concern which can be present at an attenuation monitoring point and not exceed the applicable critical protective concentration level at the points of exposure over time.” Two potential methods for establishing these levels are presented below. Method One. Method one is a graphical technique based on an analysis of empirical data obtained from ground-water monitoring events that indicate the status of the ground-water plume dynamics (plume zone is expanding, stable or shrinking). Organic contamination concentrations are plotted against distance (x) from the source to

MONITORED NATURAL ATTENUATION

Source: TNRCC 2002

Figure 13-16 Development of Attenuation Action Levels (AALs)

the groundwater point of exposure using monitoring data. A horizontal line is drawn across the graph that is equivalent to the critical PCL value at the down gradient point of exposure. A first-order curve is fit from a point near the source zone (after accounting for natural variability) to the point of exposure (see Figure 13-16). The concentrations represented by this line at several key locations on the x-axis with wells are calculated and represent the attenuation action levels. The data used to develop the curves should be selected so that the method accounts for routine variations in the data due to seasonal effects or sampling variability, such as by (1) using the upper range of historical data to construct the action levels first order line; or (2) accounting for some level of exceedances; or (3) using a moving average over the long-term monitoring data in each well; or (4) some other method. Method Two. Method two utilizes the application of an analytic model, such as the ground-water contaminant

fate and transport Natural Attenuation Factor (NAF) model of Domenico (1987) or its equivalent. These action level are developed using the NAF transport equation to back-calculate the maximum concentration of a organic contamination from the point of exposure at each attenuation monitoring point located at a known distance (x) from the source in the downgradient direction. In this method, the maximum attenuation action levels is determined by back-calculating from a point of exposure which has been assigned a presumed concentration equal to the critical water quality criteria. The result is maximum parameter attenuation levels at locations in the ground-water plume allowed by the model that do not result in exceeding the applicable critical ground-water quality standard at the designated ground-water point of exposure. Again, the modeling approach should account for seasonal effects and natural variability (see Method one, above).

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MONITORED NATURAL ATTENUATION

Determining Locations of Attenuation Monitoring Points An attenuation monitoring point is defined as a “… location within the migration pathway of a chemical of concern which is used to verify that the critical PCL will not be exceeded at the points of exposure.” In a site situation, monitoring ground-water plume attenuation will typically require a minimum of four monitoring points within the plume and along axis the axis of the plume. You need three monitoring points properly located within a plume to ensure that first-order curves can be fit to the data. Ideally, the wells located internal to the plume should be distributed purposefully within the area of the plume. Although this may sound like a simple task, in application this can represent a difficult task if the source area of the contamination is ill defined. Theoretically, one monitoring point should be located at or very near to the source, in a downgradient location; another attenuation monitoring point (AMP) should be located close to, but within, the downgradient edge of the associated plume; and at least one other well should be positioned in the plume between the first two. The fourth AMP is required to be located within the same ground-waterflow zone, but upgradient of the groundwater source area. Monitoring Considerations A monitoring plan to evaluate remedial effectiveness of the MNA response action should include the following components: periodic collection and laboratory analysis for concentrations of selected key organic contamination and degradation products in the source area (it may not be necessary to monitor the selected organic contamination) along the center line of the plume to the leading edge or branches, if applicable and along the boundary of the plume. In most cases the monitoring will likely continue until the critical water quality standards are achieved. In the instance of plume control, the monitoring will continue until the remedial objectives are met and the hydrogeologic dynamics are demonstrated to be such that the plume will be permanently contained within the facility boundaries. Other data such as ground-water gradient maps, plume maps and organic contamination concentration versus time graphs may be required. Other elements of the monitoring program may include periodic monitoring of appropriate indicators for the MNA parameters. At most affected properties, long-term monitoring of geochemical indicator parameters (such as dissolved oxygen, methane, etc.) is not needed if organic contamination parameters are measured. The long-term monitoring program should

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focus on trends in the organic parameter concentrations, rather than continued monitoring of geochemical conditions. Within these programs the monitoring results should be evaluated as they become available to verify the effectiveness of the MNA. Monitoring results typically would be submitted to the responsible state agency in accordance with the set schedule to document the remedial progress. Key Reference Documents MNA as a remediation technology has been of interest to the regulatory and regulated community. As a result, there are numerous resources that can be accessed to learn about natural attenuation and its implementation for remediation. The references provided here include a listing of guidance documents, as well as other selected natural attenuation resources including textbooks and models. The resources listed below are provided for informational reference purposes. References Anderson, M.P. and W.W. Woessner. 1992. Applied Groundwater Modeling: Simulation of Flow and Advective Transport. Academic Press, NY. Aronson, D. and Howard, P., 1997. Anaerobic Biodegration of Organic Chemicals in Groundwater: A Summary of Field and Laboratory Studies (SRC TR-97-0223F), Environmental Science Center, Syracuse Research Corporation, 6225 Running Ridge Road, North Syracuse, NY. ASTM, 2001, Standard Guide for Remediation of Ground Water by Natural Attenuation at Petroleum Release Sites ASTM Committee E-50 ASTM E 1943-98 American Society of Testing and Materials, West Conshohocken,PA Battelle, 1996. Draft Evaluation of Funnel-and-Gate Pilot Study at Moffett Federal Airfield with Groundwater Modeling. Prepared for the U.S. Department of Defense, Environmental Security Technology Certification Program and Naval Facilities Engineering Services Center, Port Hueneme, CA. September 11. Battelle, 1997. Design/Test Plan: Permeable Barrier Demonstration at Area 5, Dover AFB. Prepared for Air Force Research Laboratory, Tyndall AFB. November 14. Brigham Young University. 1996. Brady, P. V. , and Borns, D.J., 1997. Natural Attenuation of Metals and Radionuclides: Report from a Workshop held by Sandia National Laboratories - SAND97-2727. Sandia National Laboratories. Buscheck, T. and C. M. Alcantar, 1995. Regression Techniques and Analytical Solutions to Demonstrate Intrinsic Bioremediation. In: Intrinsic Bioremediation, R.E. Hinchee, J.T.Wilson, and D.C. Downey (eds). Battelle Press, Columbus, OH. Cohen, R.M. and J.W. Mercer, 1993. DNAPL Site Evaluation. C.K. Smoley (ed.), CRC Press, Boca Raton, FL. Domenico, P.A., 1987. An Analytic Model Multidimensional

MONITORED NATURAL ATTENUATION

Transport of a Decaying Contaminant Species, J. Hydrol., v. 91, p. 49-58. Everhart, D. 1996. Theoretical Foundations of GROWFLOW. ARA-TR-96-5286-3. Prepared by Applied Research Associates, Inc. for U.S. Air Force, Tyndall Air Force Base. April. GMS: Department of Defense Groundwater Modeling System, Version 2.0. Environmental Simulations, Inc. 1996. Groundwater Vistas. Government Accounting Office, 2000. The Reality behind the Rhetoric: The Failures of EPA’s Brownfields Initiative. Committee on Commerce, U.S. House of Representatives. (Available on the Internet at com-notes.house.gov/brown/ brown.htm) Guiguer, N., J. Molson, E.O. Frind and T. Franz. 1992. FLONET—Equipotential and Streamlines Simulation Package. Waterloo Hydrogeologic Software and the Waterloo Center for Groundwater Research, Waterloo, Ontario. Gupta, N. and T.C. Fox. 1999. Hydrogeologic Modeling for Permeable Reactive Barriers. Journal of Hazardous Materials, 68: 19-39. Harbaugh, A.W., 1990. A Computer Program for Calculating Subregional Water Budgets Using Results from the U.S. Geological Survey Modular Three-Dimensional Finite-Difference Ground-Water Flow Model. United States Geological Survey Open-File Report 90-392. Hatfield, K., 1996. Funnel-and-Gate Design Model. ARA-TR96-5286-4. Prepared by Applied Research Associates, Inc. for U.S. Air Force, Tyndall Air Force Base. April. Heron, G., T.H. Christensen, T. Heron and T.H. Larson, 2000. Thermally Enhanced Remediation of DNAPL Sites: The Competition between Downward Mobilization and Upward Volatilization. In: Treating Dense Nonaqueous-Phase Liquids (DNAPLs): Remediation of Chlorinated and Recalcitrant Compounds. Battelle Press, Columbus, Ohio. Hsieh, P.A. and J.R. Freckleton. 1993. Documentation of a Computer Program to Simulate Horizontal-Flow Barriers Using the U.S. Geological Survey Modular Three-Dimensional Finite-Difference Ground-Water Flow Model. United States Geological Survey Open-File Report 92-477. Interstate Technology and Regulatory Council (ITRC), 2000. DNAPLs: Review of Emerging Characterization and Remediation Technologies. ITRC/DNAPLs-1. Interstate Technology and Regulatory Council (ITRC), 2001. Technical and Regulatory Guidance: In Situ Chemical Oxidation. ITRC/ISCO-1. Kipp, Jr., K.L., 1987. HST3D: A Computer Code for Simulation of Heat and Solute Transport in Three-Dimensional GroundWater Flow Systems. WRI 86-4095. United States Geological Survey, Denver, CO. Koenigsberg, S.S., C.A. Sandefur, and K. Lapus, 2001. Proceedings from In Situ and On-Site Bioremediation, The Sixth International Symposium, 2001. Battelle Press, Columbus, OH. Kram, M.L., A.A., Keller, J. Rossabi and L.G. Everett, 2001. DNAPL characterization methods and approaches, Part I: Performance comparisons. Ground Water Monitoring & Remediation, 21, no. 4: pp. 109–123. McDonald, M.G. and A.W. Harbaugh, 1988. A Modular Three-

Dimensional Finite-Difference Ground-Water Flow Model: Techniques of Water-Resources Investigations of the United States Geological Survey. Book 6. Modeling, Version 2.0. Geraghty & Miller, Inc., Reston, VA. National Research Council, 1994. Alternatives for Ground Water Cleanup. National Academy Press, Washington, D.C. Natural Resources, Illinois State Water Survey, Bulletin 65. Naymik, T.G. and N.J. Gantos, 1995. Solute Transport Code Verification Report for RWLK3D, Internal Draft Battelle Memorial Institute, Columbus, OH. Pankow, J.F. and Cherry, J.A., Eds. 1996. Dense Chlorinated Solvents and Other DNAPLs in Ground Water. Waterloo Press, Portland, Oregon. Pollock, D.W., 1989. Documentation of Computer Programs to Compute and Display Pathlines Using Results from the U.S. Geological Survey Modular Three-Dimensional Finite-Difference Ground-Water Flow Model. United States Geological Survey Open-File Report 89-381. Prickett, T.A., T.G. Naymik and C.G. Lounquist. 1981. A "Random Walk" Solute Transport Model for Selected Groundwater Quality Evaluations. Illinois Department of Energy. Rifai, H.S., C.J. Newell, J.R.Gonzales, S. Dendrou, L.Kennedy, and J. Wilson, 2001. BIOPLUME III Natural Attenuation Decision Support System, EPA/600/R-98/010, www.epa.gov /ada/csmos/models.html. Rao, P.C. S J.W. Jawitz, C.G. Enfield, R.W. Falta, M.D. Annable and A.L. Wood, 2001. Technology Integration for Contaminated Site Remediation: Cleanup Goals & Performance Criteria. Proceedings from Groundwater Quality 2001, The Third International Conference, 2001. Rossabi, J., B.B. Looney, C.A. Eddy-Dilek, B.D. Riha and D.G. Jackson, 2000. DNAPL Site Characterization: The Evolving Conceptual Model and Toolbox Approach. WSRC-MS2000-00183. Rumbaugh, J.O., III., 1993. ModelCad386: Computer-Aided Design Software for Groundwater. Schnarr, M., C. Traux, G. Farquhar, E. Hood, T. Gonullu, and B. Stickney, 1998. Laboratory and controlled field experiments using potassium permanganate to remediate TCE and PCE DNAPLs in porous media. J. Contaminant Hydrology 29:205–224. Schwille, F., 1988. Dense Chlorinated Solvents in Porous and Fractured Media: Model Experiments. Translated from the German by J.F. Pankow, Lewis Publishers, Boca Raton, FL. ShiFaze, S., 1996. 3D Numerical Modeling of Ground-Water Flow in the Vicinity of Funnel-and-Gate Systems. ARA-TR96-5286-1. Prepared by Applied Research Associates, Inc. for U.S. Air Force, Tyndall Air Force Base. April. Stegemeier, G.L. and H.J. Vinegar, 2001. Thermal Conduction Heating for In Situ Thermal Desorption of Soils. In: Hazardous and Radioactive Waste Treatment Technologies Handbook. CRC Press, Boca Raton, FL. TNRCC , 2001. document RG-366/TRRP-26 TNRCC, 2001. guidance document. Toxicity Factors and Chemical/Physical Properties (RG-366/TRRP-19 Therrien, R. 1992. Three-Dimensional Analysis of Variably-Saturated Flow and Solute Transport in Discretely-Fractured Porous Media. Ph.D. thesis, Dept. of Earth Science, Univer-

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MONITORED NATURAL ATTENUATION sity of Waterloo, Ontario, Canada. Therrien, R. and E. Sudicky, 1995. Three-Dimensional Analysis of Variably-Saturated Flow and Solute Transport in Discretely-Fractured Porous Media., Jour. of Contaminant Hydrology, 23: 1-44. Thomas, A.O., D.M. Drury, G. Norris, S.F. O’Hannesin and J.L. Vogan. 1995. The In Situ Treatment of Trichloroethene-Contaminated Groundwater Using a Reactive Barrier-Result of Laboratory Feasibility Studies and Preliminary Design Considerations. In Brink, Bosman and Arendt (Eds.), Contaminated Soil ’95, pp. 1083-1091. Kluwer Academic Publishers. U.S. Environmental Protection Agency (EPA), 1993. Guidance for Evaluating Technical Impracticability of Groundwater Restoration. OSWER Directive 9234.2-25. U.S. EPA, 1994. DNAPL Site Characterization. OSWER Publication 9355.4-16FS. U.S. EPA, 1995. Superfund Ground Water RODs: Implementing Change This Fiscal Year. OSWER Memorandum 9335.503P, EPA/540-F-99-005. U.S. EPA, 1996. Presumptive Response Strategy and Ex-Situ Treatment Technologies for Contaminated Groundwater at CERCLA Sites. OSWER Directive 9283.1-12. U.S. EPA, 1997. Rules of Thumb for Superfund Remedy Selection. OSWER Directive 9355.0-69. U.S. EPA, 1997a. Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites. OSWER Directive 9200.4-17, December 1, 1997 Interium Final. U.S. EPA, 1998. Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water. Office of Research and Development. EPA/600/R 98/128. U.S. EPA, 1999a. Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action and Underground Storage Tank Sites. OSWER Directive 9200.4-17P. U.S. EPA, 1999b. A Guidebook of Financial Tools: Tools for Financing Brownfields Redevelopment. Environmental Finance Program, Section 9. U.S. EPA, 1999c. Cost and Performance Summary Report: SixPhase Heating at a Former Manufacturing Facility, Skokie, Illinois. OSWER, Technology Innovation Office. U.S. EPA, 1999d. Groundwater Cleanup: Overview of Operating Experience at 28 Sites. OSWER, Technology Innovation Office. EPA 542-R-99-006. U.S. Department of Energy (DOE), 2000a. Electrical Resistance Tomography for Subsurface Imaging. Innovative Technology Summary Report, DOE/EM-0538. U.S. Department of Energy (DOE), 2000b. Tomographic Site Characterization Using CPT, ERT, and GPR. Innovative Technology Summary Report, DOE/EM-0517. van der Heijde, P.K.M. and O.A. Elnawawy. 1993. Compilation of Groundwater Models. EPA/600/2-93/118. U.S. EPA’s R.S. Kerr Environmental Research Laboratory, Ada, OK. Vogan, J.L., J.K. Seaberg, B.G. Gnabasik and S. O’Hannesin. 1994. Evaluation of in Situ Groundwater Remediation by Metal Enhanced Reductive Dehalogenation Laboratory Column Studies and Ground-Water Flow Modeling, 87th Annual Meeting and Exhibition of the Air and Waste Association, Cincinnati, OH, June 19-24.

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Wang, H.F. and M.P. Anderson, 1982. Introduction to Groundwater Modeling: Finite Difference and Finite Element Methods. W.H. Freeman and Company, NY. Waterloo Hydrogeologic, Inc. 1999a. FLOWPATH II for Windows 95/NT. Waterloo Hydrogeologic, Inc. 1999b. Visual MODFLOW User’s Manual. Zheng, C. 1989. PATH3D. S.S. Papadopulos and Assoc., Rockville, MD.

APPENDIX A1 GLOSSARY

APPENDIX A1

GLOSSARY OF TECHNICAL TERMS

A1-1

APPENDIX A1 GLOSSARY

GLOSSARY OF TECHNICAL TERMS Absorption: The process by which one substance is taken into and included within another substance, as the absorption of water by soil or nutrients by plants. (2) Acidity, total: The total acidity in a soil or clay, usually an estimated by a buffered salt determination of (cation exchange minus exchangeable bases) = total acidity. (1) Adsorption: The increased concentration of molecules or ions at a surface, including exchangeable cations and anions on soil particles. (2)

Alkylated aromatics: The class of ringed aromatic compounds containing one or more aliphatic side chains. Alkynes: The group of unsaturated hydrocarbons with a triple carbon-carbon bond having the general formula CH2.-2 Anabolism: The process whereby energy is used to build organic compounds such as enzymes and nucleic acids that are necessary for life functions. In essence, energy is derived from catabolism, stored in high-energy intermediate compounds such as adenosine triphosphate (ATP), guanosine. Anaerobe: Organisms that do not require oxygen to live.

Aerobe: Bacteria that use oxygen as an electron acceptor.

Anaerobic: In the absence of oxygen.

Aggregation: The act of soil particles cohering so as to behave mechanically as a unit. (2)

Analyte: The element, ion or compound that an analysis seeks to identify; the element of interest.

Air permeability: Permeability of soil with respect to air. Measured in darcys or units of centimeters per second. An important parameter in the design of soil-gas surveys.

Anisotropic mass: A mass having different properties in different directions at any given point. (5)

Air-dry: (a) The state of dryness (of a soil) at equilibrium with the moisture content in the surrounding atmosphere. The actual moisture content will depend upon the relative humidity and the temperature of the surrounding atmosphere. (b) To allow to reach equilibrium in moisture content with the surrounding atmosphere. (1) Aliphatic: Of or pertaining to a broad category of carbon compounds distinguished by a straight or branched, open chain arrangement of the constituent carbon atoms. The carboncarbon bonds may be either saturated or unsaturated. Alkanes, alkenes and alkynes are aliphatic hydrocarbons. Aliquot: A measured portion of a sample taken for analysis. One or more aliquots make up a sample. Alkaline soil: Any soil having a pH > 7.0. (1) Alkanes: Aliphatic hydrocarbons having the general formula CH2n-12. Alkanes can be straight chains, branched chains or ring structures. Also referred to as paraffins. Alkenes: The group of unsaturated hydrocarbons having the general formula CnH2n and characterized by being highly chemically reactive. Also referred to as olefins.

A1-2

Annular space; annulus: The space between two concentric tubes or casings or between the casing and the borehole wall. This would include the space(s) between multiple strings of tubing/ casings in a borehole installed either concentrically or multi-cased adjacent to each other. (9) Anthropogenic: Man-made. Aquiclude: A body of relatively impermeable soil or rock that is capable of absorbing water slowly but does not transmit it rapidly enough to supply a well or spring. Aquifer: A geologic formation, group of formations or part of a formation that is saturated and is capable of providing a significant quantity of water. (9) Aquitard: A lithologic unit that impedes ground-water movement and does not yield water freely to wells or springs but that may transmit appreciable water to or from adjacent aquifers. Where sufficiently thick, may act as a ground-water storage zone. Synonymous with confining unit. (9) Aquitard: A geologic formation that may contain ground water but is not capable of transmitting significant quantities of ground water under normal hydraulic gradients. In some situations aquitards may function as confining beds.

APPENDIX A1 GLOSSARY

Area of attainment: The area over which cleanup levels will be achieved in the ground water. It encompasses the area outside the boundary of any waste remaining in place and up to the boundary of the contaminant plume. Usually, the boundary of the waste is defined by the source control remedy. Note: This area is independent of property boundaries or potential receptors; it is the plume area to which the ground water must be returned to beneficial use during the implementation of a remedy.

ASTM Type V (Portland): A construction cement that is a high sulfate resistant formulation. Used when there is severe sulfate action from soils and ground water. (9)

Aromatic: Organic compounds that are unsaturated and contain at least one six-carbon benzene ring.

Autotrophs: Microorganisms that materials from carbon dioxide.

Assessment investigation: The study of a particular area or region for defining the appropriateness of the area for waste disposal.

Available water: The portion of water in a soil that can be readily absorbed by plant roots. Considered by most workers to be water held in the soil against a pressure of up to approximately 15 bars. (1)

Assessment monitoring: Investigative monitoring that is initiated after the presence of a contaminant has been detected in ground water above a relevant criterion at one or more locations. The objective of the program is to determine if there is a statistical exceedance of a standard or criteria at a potential area of concern (PAOC) or at the ground water discharging to surface water interface and/or to quantify the rate and extent of migration of constituents detected in ground water above applicable criteria. Assessment monitoring: An investigative monitoring program that is initiated after the presence of a contaminant in ground water has been detected. The objective of this program is to determine the concentration of constituents that have contaminated the ground water and to quantify the rate and extent of migration of these constituents. (9) ASTM cement types: Portland cements meeting the requirements of ASTM C 150 (Standard Specifications for Portland Cement). Cement types have slightly different formulations depending on use. ASTM Type I (Portland): A general-purpose construction cement with no special properties. ASTM Type III (Portland high early strength): A construction cement that produces a high early strength. This cement reduces the curing time required when used in cold environments and produces a higher heat of hydration than ASTM Type 1. ASTM Type Il (Portland): A construction cement that is moderately resistant to sulfates and generates a lower heat of hydration at a slower rate than ASTM Type 1. ASTM Type IV (Portland): A construction cement that produces a low heat of hydration (lower than ASTM Types I and II) and develops strength at a slower rate.

Auger: A tool for drilling/boring into unconsolidated earth materials (soil) consisting of a spiral blade wound around a central stem or shaft that is hollow (hollowstem auger). Augers commonly are available in flights (sections) that are connected together to advance the depth of the borehole. synthesize

organic

Average: Arithmetic mean. Azeotrope: A mixture with a fixed boiling point that cannot be further separated by fractional distillation. Azeotropic distillation: A technique that uses the ability of selected organic compounds to form binary azeotropes with water to facilitate the separation of the compounds from complex mixtures. Bailer: A hollow tubular receptacle used to facilitate withdrawal of fluid from a well or borehole. (9) Ballast: Materials used to provide stability to a buoyant object (such as casing within a borehole filled with water). (9) Bar: A unit of pressure equal to one million dynes per square centimeter. (1) Barrel sampler: Open-ended steel tube used to collect soil samples. The sampler has a sharpened end, or shoe, that is pushed or driven into the ground. A soil core is collected inside of the sampler. Baseline: A surveyed condition which serves as a reference point to which later surveys are coordinated or correlated. Base-saturation percentage: The extent to which the adsorption complex of a soil is saturated with exchangeable cations other than hydrogen. It is expressed as a percentage of the total cation exchange capacity. (1) Batch: A group of samples prepared at the same time in the same location using the same method. Bearing capacity: Ability of a material to support a load normal to the surface. (6)

A1-3

APPENDIX A1 GLOSSARY

Bedrock: The more or less continuous body of rock that underlies the overburden soils. (7)

Bulk specific gravity: The ratio of the bulk density of a soil to the mass of unit volume of water. (1)

Bentonite clay: An altered deposit of volcanic ash usually consisting of sodium montmorillonite clay. (9)

Bulk volume: The volume, including the solids and the pores, of an arbitrary soil mass. (1)

Bentonite: A colloidal clay, largely made up of the mineral sodium montmorillonite, a hydrated aluminum silicate. Because of its ability to expand when moist, bentonite is commonly used to provide a tight seal around a well casing. Biodegradation: A process by which microbial organisms transform or alter (through metabolic or enzymatic action) the structure of chemicals introduced into the environinent. Bladder pumps: Also known as squeeze pumps, bladder pumps operate by the compression of a flexible bladder housed inside the pump. Water enters the bladder through a check valve. Once the bladder is filled, it is squeezed by compressed air that has been injected into the housing surrounding the bladder. Water cycles through the bladder in evenly spaced pulses. Blank: See Method blank. Blow-in: The inflow of ground water and unconsolidated material into a borehole or casing caused by differential hydraulic heads; that is, caused by the presence of a greater hydraulic head outside of a borehole/casing than inside. (9) Borehole: A circular open or uncased subsurface hole created by drilling. (9) Borehole: Hole made with boring (drilling) equipment. Also used in reference to hole made by DP equipment, but DP hole and probe hole are preferred terms in the latter case. Borehole log: The record of geologic units penetrated, drilling progress, depth, water level, sample recovery, volumes and types of materials used and other significant facts regarding the drilling of an exploratory borehole or well. (9) Bridge: An obstruction within the annulus that may prevent circulation or proper emplacement of annular materials. (9) Bulk density, soil: The mass of dry soil per unit bulk volume. The bulk volume is determined before drying to constant weight at 105 degrees Centigrade. (1)

A1-4

Calibration standards: A series of known standard solutions used by the analyst for calibration of the instrument (e.g., preparation of the analytical curve). Calibration: The establishment of an analytical curve based on the absorbance, emission intensity or other measured characteristic of known standards. Used to define the linearity and dynamic range of the response of the analytical equipment to the target compounds. California bearing ratio: The ratio of: (1) the force per unit area required to penetrate a soil mass with a 3 square inch (8 cm) circular piston (approximately 1.95 inch [51 mm] diameter) at the rate of 0.05 inches (1.3 mm)/minute, to (2) the force required for corresponding penetration of a standard material. The ratio is usually determined at 0.1 inch (12.7 mm). Corps of Engineers procedures require determination of the ratio at 0.1 inch and 0.2 inch (5.1 mm). Capable fault: A fault defined by the Nuclear Regulatory Commission as one that is capable of near future movement; in general, a fault on which there has been movement within the last 35,000 years. The definition was developed for use in the siting of nuclear power plants. Capillary attraction: The movement of a liquid over or retention by a solid surface due to the interaction of adhesive and cohesive forces. (1) Capillary conductivity: (obsolete) See Soil water hydraulic conductivity. Capillary fringe: A zone just above the water table (zero gauge pressure) that remains almost saturated. (The extent and degree of definition of the capillary fringe depend upon the sizedistribution of pores). (1) The zone of a porous medium above the water table within which the porous medium is saturated by water under pressure that is less than atmospheric pressure. Capillary migration (capillary flow): The movement of water by capillary action. (5) Capillary potential: The amount of work that must be done per unit of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water, identical in composition to the

APPENDIX A1 GLOSSARY

soil water, from a pool at the elevation and the external gas pressure of the point under consideration, to the soil water. Cased DP system: A rod system consisting of inner rods and outer drive casing. Also referred to as dual-tube DP systems. The soil sampling barrel is attached to inner rods. The inner rods and outer casing are typically driven simultaneously. The sampling tool is then withdrawn, emptied and reinserted, while the outer drive casing is left in the ground to keep the hole open. Minimizes sloughing and contamination of soil samples. Casing, protective: A section of larger diameter pipe that is placed over the upper end of a smaller diameter monitoring well riser or casing to provide structural protection to the well and restrict unauthorized access into the well. (9) Casing, surface: Pipe used to stabilize a borehole near the surface during the drilling of a borehole that may be left in place or removed once drilling is completed. (9) Casing: Pipe finished in sections, with either threaded connections or bevelled edges to be field welded, which is installed temporarily or permanently to counteract caving, to advance the borehole and/or to isolate the zone being monitored. (9) Catabolism: The process whereby energy is extracted from organic compounds by breaking them down into their component parts. Cation exchange: The interchange between a cation and solution and another cation on the surface of any surface-active material such as clay colloid or organic colloid. Cation-exchange capacity (CEQ): The sum total of exchangeable cations that a soil can absorb. Expressed in milliequivalents per 100 grams or per gram of soil (or of other exchangers such as clay). (1) Caving; sloughing: The inflow of unconsolidated material into a borehole which occurs when the borehole walls lose their cohesive strength. (9) Cement; Portland cement: Commonly known as Portland cement. A mixture that consists of calcareous, argillaceous or other silica-alumina- and iron-oxidebearing materials manufactured and formulated to produce various types which are defined in ASTM C 150. Portland cement is also considered a hydraulic cement because it must be mixed with water to form a cement-water paste that has the ability to harden and develop strength even if cured under water (see ASTM Cement Types). (9)

Centralizer: A device that assists in the centering of a casing or riser within a borehole or another casing. (9) Channels: Voids that are significantly larger than packing voids. They are generally cylindrical shaped and smooth walled, have regular conformation and have relatively uniform cross-sectional size and shape. (4) Check-valve tubing pump: A water sampling tool consisting of plastic tubing with a check valve attached to the bottom. Also referred to as a Waterrae pump. Oscillation of the tubing moves water up through it. The check valve prevents water from draining out of the tubing when it is withdrawn from the well. In this way, the tubing acts like a long, skinny bailer. Circulation: Applies to the fluid rotary drilling method; drilling fluid movement from the mud pit, through the pump, hose and swivel, drill pipe, annular space in the hole, and returning to the mud pit. (9) Clay: (a) A soil separate consisting of particles > 0.002 mm in equivalent diameter; (b) a textural class. (1) Clay films: Coating of clay on the surfaces of soil peds and mineral grains and in soil pores. (Also called clay skins, clay flows, illuviation cutans, argillans, or tonhautchen.) Clay mineral: Naturally occurring inorganic crystalline material found in soils and other earthy deposits, the particles being clay sized; that is, >0.002 mm in diameter. (1) Clod: A compact, coherent mass of soil ranging in size from 5 to 100 mm to as much as 20 to 25 cm that is produced artificially usually by the activity of humans by plowing, digging, etc., especially when these operations are performed on soils that are either too wet or too dry for normal tillage operations. Coarse fragments: Rock or mineral particles >2.0 mm in diameter. (1) Coarse texture: The texture exhibited by sand, loamy sands and sandy loams except very fine sandy loams. (1) Coefficient of variation: Sample standard deviation divided by the mean. Cofactor: A small molecule required for the function of an enzyme. Cohesionless soil: A soil that when unconfined has little or no strength when air-dried and that has little or no cohesion when submerged. (S) Cohesive soil: A soil that when unconfined has considerable strength when air-dried and that has significant cohesion when submerged. (5)

A1-5

APPENDIX A1 GLOSSARY

Colloidal particles: Particles that are so small that the surface activity has an appreciable influence on the properties of the particle. (1)

written or illustrated visualization of geologic/ hydrogeologic/environmental conditions of a particular area.

Cometabolism: The process in which a compound is fortuitously degraded by an enzyme or cofactor produced during microbial metabolism of another compound.

Conductance (specific): A measure of the ability of the water to conduct an electric current at 77° F (25° C). It is related to the total concentration of ionizable solids in the water. It is inversely proportional to electrical resistance. (9)

Compaction: The densification of a soil by means of mechanical manipulation. (5) Compaction curve (Proctor curve; moisture-density curve): The curve showing the relationship between the dry unit weight (density) and the water content of a soil for a given compactive effort. (5) Compaction test (moisture-density test): A laboratory compacting procedure whereby a soil at a known water content is placed in a specified manner into a mold of given dimensions, subjected to a compactive effort of controlled magnitude and the resulting unit weight is determined. The procedure is repeated for various water contents sufficient to establish a relation between water content and unit weight. (5) Compliance Monitoring: As specified under 40 CFR 264.99, Compliance Monitoring is instituted when hazardous constituents have been detected above a relevant criterion at the compliance point during RCRA detection monitoring. Groundwater samples are collected at the compliance point, facility property boundary and upgradient monitoring wells for analysis of hazardous constituents to determine if they are leaving the regulated unit at statistically significant concentrations. Composite underground storage tank: A fiberglass coated steel tank. Compressibility: Property of a soil or rock pertaining to its susceptibility to decrease in volume when subjected to load. (5) Compression curve: See Pressure-void ratio curve. Compressive strength (unconfined or uniaxial compressive strength): The load per unit area at which an unconfined cylindrical specimen of soil or rock will fail in a simple compression test. Commonly the failure load is the maximum that the specimen can withstand in the test. (5) Conceptual model: A written description or illustrated picture of the geologic, hydrogeologic, or environmental conditions of a particular area; a

A1-6

Conductivity: A coefficient of proportionality describing the rate at which a fluid (water or gas) can move through a permeable medium. Conductivity is a function of both the intrinsic permeability of the porous medium and the kinematic viscosity of the fluid which flows through it. Conductivity probe: A DP tool that measures the electrical conductivity of the soil to define lithology. Conductivity, hydraulic: See Soil water. Cone penetrometer testing (CPT): A DP system used to measure lithology based on the penetration resistance of the soil. Sensors are mounted in the tip (cone) of the DP rods to measure tip resistance and side-wall friction. Electrical signals are carried to digital processing equipment at the ground surface, where plots of soil type vs. depth are recorded. It defines the type of soil based on calibration curves, not site-specific conditions. Therefore, CPT data require on-site calibration/ correlation with actual soil cores. Cone: Downhole sensor used with CPT. At a minimum, consists of load cells to measure tip resistance and side-wall friction. Confining layer: A geologic formation characterized by low permeability that inhibits the flow of water (see also Aquitard). Confining unit: A term that is synonymous with aquiclude, aquitard, and aquifuge; defined as a body of relatively low permeable material stratigraphically adjacent to one or more aquifers. (9) Consistency: (a) The resistance of a material to deformation or rupture. (b) The degree of cohesion or adhesion of the soil mass. (1) Consolidation: The gradual reduction in volume of a soil mass resulting from an increase in compressive stress. (a) Initial consolidation (initial compression): A comparatively sudden reduction in volume of a soil mass under an

APPENDIX A1 GLOSSARY

applied load due principally to expulsion and compression of gas in the soil voids preceding primary consolidation. (b) Primary consolidation (primary compression) (primary time effect): The reduction in volume of a soil mass caused by the application of a sustained load to the mass and due principally to a squeezing out of water from the void spaces of the mass and accompanied by a transfer of the load from the soil water to the soil solids. (c) Secondary consolidation (secondary compression) (secondary time effect): The reduction in volume of a soil mass caused by the application of a sustained load to the mass and due principally to the adjustment of the internal structure of the soil mass after most of the load has been transferred from the soil water to the soil solids. (5) Consolidation test: A test in which the specimen is laterally confined in a ring and is compressed between porous plates. (5) Consolidation time curve (time curve; consolidation curve; theoretical time curve): A curve that shows the relation between: (1) the degree of consolidation, and (2) the elapsed time after the application of a given increment of load. (5) Constituent: An essential part or component of a system or group (e.g., an ingredient of a chemical mixture). For instance, benzene is one constituent of gasoline.

Creep: Slow mass movement of soil and soil material down relatively steep slopes primarily under the influence of gravity, but facilitated by saturation with water and by alternate freezing and thawing. (1) Cross-contamination: The movement of contaminants from one depth to another due to invasive subsurface activities. Cross-reactivity: The potential for constituents that are not the target compound to be detected as the target compound by an analytical method. Crust: A surface layer on soils, ranging in thickness from a few millimeters to perhaps as much as an inch, that is much more compact, hard, and brittle when dry than the material immediately beneath it. (1) Cutan: A modification of the texture, structure, or fabric at natural surfaces in soil materials due to concentration of particular soil constituents or in situ modification of the plasma; cutans can be composed of any of the component substances of the soil material. (4) Cuttings: The spoils created from conventional drilling with hollow-stem auger or rotary drilling equipment. Cuttings are not generated with DP equipment.

Constituent(s) of concern: Specific chemicals that are identified for evaluation in the site assessment process.

d-10: The diameter of a soil particle (usually in millimeters) at which 10% by weight of the particles of a particular sample are finer. Synonymous with the effective size or effective grain size. (9)

Contaminant: An undesirable substance not normally present or an unusually high concentration of a naturally occurring substance in water or soil. (9)

d-60: The diameter of a soil particle (usually in millimeters) at which 60% by weight of the particles of a particular sample are finer. (9)

Conventional site assessment: A site assessment in which the majority of sample analysis and interpretation of data is completed off-site. The process typically requires multiple mobilizations in order to ftilly determine the extent of contamination.

Darcy’s law: (a) A law describing the rate of flow of water through porous media. (named for Henry Darcy of Paris who formulated it in 1856 from extensive work on the flow of water through sand filter beds).

Corrective Action Monitoring: Under RCRA, Corrective Action Monitoring is instituted when hazardous constituents from a RCRA regulated unit have been detected at statistically significant concentrations between the compliance point and the downgradient facility property boundary as specified under 40 CFR 264.100. Corrective action monitoring is conducted throughout a corrective action program that is implemented to address ground-water contamination. At non-RCRA sites, corrective action monitoring is conducted throughout the active period of corrective action to determine the progress of remediation and to identify statistically significant trends in ground-water contaminant concentrations.

Daughter product: A compound that results directly from the biodegradation of another. For example cis-1,2dichloroethene (cis-1,2-DCE) is commonly a daughter product of trichloroethylene (TCE). Deadmen: Anchors drilled or cemented into the ground to provide additional reactive mass to DP sampling rigs. The rigs are able to pull against the anchors, thus increasing the force that can be applied to the DP rods. Deflocculate: (a) To separate the individual components of compound particles by chemical and/or physical means. (b) To cause the particles of the disperse phase of a colloidal system to become suspended in the dispersion medium. (1)

A1-7

APPENDIX A1 GLOSSARY

Deformation: A change in the shape or size of a solid body. (7)

determine if there is a statistically significant exceedance.

Degradation: The breakdown of substances by biological action. (2)

Differential water capacity: The absolute value of the rate of change of water content with soil water pressure. The water capacity at a given water content will depend on the particular desorption or adsorption curve employed. Distinction should be made between volumetric and specific water capacity.

Degree of consolidation (percent consolidation): The ratio, expressed as a percentage of: (a) the amount of consolidation at a given time within a soil mass, to (b) the total amount of consolidation obtainable under a given stress condition. (5) Degree of saturation: The extent or degree to which the voids in rock contain fluid (water, gas, or oil). Usually expressed in percent related to total void or pore space. (7) Dehydrohalogenation: Elimination of a hydrogen ion and a halide ion resulting in the formation of an alkene. Dense nonaqueous phase liquid (DNAPL): A nonaqueous phase liquid (NAPL) with a specific gravity greater than 1.0. Because the specific gravity of water is equal to 1.0, DNAPLs sink through the water column until they encounter a confining layer. DNAPLs flow along the surface of the confining layer and can migrate in directions contrary to the hydraulic gradient because DNAPLs are found at the bottom of aquifers (rather than floating on the water table) typical Deposit: Material left in a new position by a natural transporting agent such as water, wind, ice, or gravity, or by the activity of humans. (1) Depression curve: Record of profile of water table as a result of pumping. (6) Detection limit (DL): The true concentration at which there is a specified level of confidence (e.g., 99% confidence) that the hypothsis of zero concentration will be correctly rejected. Detection Monitoring: A program of monitoring for the express purpose of determining whether or not there has been a release of a contaminant to ground water. Under RCRA, Detection Monitoring involves collection of ground-water samples from compliance point and upgradient monitoring wells on a semiannual basis for analysis of hazardous constituents of concern, as specified under 40 CFR 264.98. Results are evaluated to determine if there is a statistically significant exceedance of the ground-water protection criterion and/or background. At nonRCRA sites, monitoring is conducted in a similar manner and results are compared to criteria to

A1-8

Diffusion: The process whereby molecules move from a region of higher concentration to a region of lower concentration as a result of Brownian motion. Dihaloelimination: Reductive elimination of two halide substituents resulting in formation of an alkene. Direct methods: Methods (e.g., boreholes and monitoring wells) that entail the excavation or drilling, collection, observation, and analysis of geologic materials and water samples. Direct push: A growing family of tools used for performing subsurface investigations by driving, pushing, and/or vibrating small-diameter hollow steel rods into the ground. Also known as direct drive, drive point, or push technology. Direct push sampling: Ground-water sampling conducted with a device that is temporarily pushed into the ground with a hydraulic system or with a hammer. After ground-water sample collection, the device is removed from the ground. Examples include Geoprobe®, Hydropunch® direct push, and environmental soil probe. Discontinuity: (a) Boundary between major layers of the Earth that have different seismic velocities. (b) Interruption of the homogeneity of a rock mass (e.g. joints, faults, etc.). (5) Disperse: (a) To break up compound particles, such as aggregates, into the individual component particles. (b) To distribute or suspend fine particles, such as clay, in or throughout a dispersion medium, such as water. (1) Dispersivity: A property that quantifies mechanical dispersion in a medium. Disposal: The discharge, deposit, injection, dumping, spilling, leaking, or placing of any solid waste or hazardous waste into or on any land or water so that such solid waste or hazardous waste or any constituent thereof may enter the environment or be emitted into the air or discharged into any waters, including ground waters.

APPENDIX A1 GLOSSARY

Dissolution: The process where soluble organic components from DNAPLs dissolves in groundwater or infiltration and forms a ground-water contaminant plume. The duration of remediation measures (either clean-up or containment) is determined by (1) the rate of the dissolution process that can be achieved in the field, and (2) the mass of soluble components in the residual DNAPL trapped in the aquifer. (10) Disturbed samples: Soil samples obtained in a manner that destroys the original orientation and some of the physical properties of the naturally disposed material. (6) DNAPL: A dense nonaqueous phase liquid. Also known as free product or a sinking plume (sinker). (10) DNAPL entry location: The area where DNAPL has entered the subsurface. (10) DNAPL site: A site where DNAPL has been released and is now present in the subsurface as an immiscible phase. (10) DNAPL zone: The portion of a site affected by freephase or residual DNAPL in the subsurface (either the vadose zone or saturated zone). The DNAPL zone has organics in the vapor phase (unsaturated zone), dissolved phase (both unsaturated and saturated zone), and DNAPL phase (both unsaturated and saturated zone). (10) Downgradient: It the direction (potentiometric) head.

of

decreasing

static

Downhole geophysics: Techniques that use a sensing device that is lowered into a borehole for the purpose of characterizing geologic formations and their associated fluids. The results can be interpreted to determine lithology, resistivity, bulk density, porosity, permeability, and moisture content and to define the source, movement, and physical/ chemical characteristics of ground water. physical and/or chemical properties of the earth (e.g., electromagnetic conductivity, electrical resistivity, specific conductance, geophysical logging, aerial photography). DP hole: A hole in the ground made with direct push equipment. DP rod: Small-diameter hollow steel rod that is pushed, driven, or vibrated into the ground in order to investigate and sample the subsurface. DP rods used with CPT rigs may be referred to as cone rods; DP rods used with other DP systems may be referred to as probe rods. Drawdown curve: The trace of the top surface of the water table in an aquifer or of the free water surface, when a new or changed means of extraction of water takes place. (6)

Drill cuttings: Fragments or particles of soil or rock with or without free water, created by the drilling process. (9) Drilling fluids: Fluid used to lubricate the bit and convey drill cuttings to the surface with rotary drilling equipment. Usually composed of a bentonite slurry, muddy water, or air. Can become contaminated, leading to crosscontamination, and may require special disposal. Not used with DP methods. Drive cap: A steel cap that is attached to the top of the sequence of DP rods. Percussion hammers pound on the drive head, rather than the DP rods, to prevent damaging the threads on the rod connections. Drive casing: Heavy-duty steel casing that is driven along with the sampling tool with cased DP systems. The drive casing keeps the hole open between sampling runs, and is not removed until the last sample has been collected. Drive head: See Drive cap. Drive shoe: The sharp, beveled end of a DP soil sampling tool. The shoe is beveled out so the soil core is cut cleanly. The beveled surface of the shoe forces soil to the outside of the sampler, where it is pushed into the formation. Drive-point profiler: An exposed ground-water DP system used to collect multiple depth-discrete ground-water samples. Ports in the tip of the probe connect to an internal stainless steel or Teflon tube that extends to the ground surface. Samples are collected via suction or air-lift methods. Deionized water is pumped down through the ports to prevent plugging while driving the tool to the next sampling depth. Dry-weight percentage: The ratio of the weight of any constituent (of a soil) to the oven-dry weight of the soil. See Oven-dry soil. (1) Dual tube DP system: See Cased DP system. Ductility: The condition in which material can sustain permanent deformation without losing its ability to resist load. (7) Duplicate: A second aliquot of a sample that is treated the same as the original sample in order to determine the precision of the analytical method. Duripan: A mineral soil horizon that is cemented by silica, usually opal or microcrystalline forms of silica, to the point that air-dry fragments will not slake in water or HCl. A duripan may also have accessory cement such as iron oxide or calcium carbonate. (1) Effective porosity: The percentage of void volume that contributes to percolation; roughly equivalent to the specific yield.

A1-9

APPENDIX A1 GLOSSARY

Effective solubility: The actual aqueous solubility of an organic constituent in ground water that is in chemical equilibrium with a mixed DNAPL (a DNAPL containing several organic constituents). The effective solubility of a particular organic chemical can be estimated by multiplying its mole fraction in the DNAPL mixture by its pure phase solubility. (10) Elastic limit: Point on stress-strain curve at which transition from elastic to inelastic behavior takes place. (7) Electrical conductivity: A measure of a substance’s ability to transmit an electrical current. Units are typically expressed in millimhos/meter when geophysical measurements are made. Electrical resistivity: A measure of the ability of a substance to inhibit the transmission of an electrical current. Units are typically expressed in ohms/meter when geophysical measurements are made. Electrical resistivity is the reciprocal of electrical conductivity. Electrical resistivity geophysical methods: Methods of measuring subsurface conditions through the use of an electrical current that is applied to the ground through a set of electrodes. Another set of electrodes is then used to measure the resulting voltage. The greater the distance between electrodes, the deeper the investigation. Electromagnetic geophysical methods: Methods of measuring subsurface conductivities by lowfrequency electromagnetic induction. A transmitter coil radiates an electromagnetic field which induces eddy currents in the subsurface. The eddy currents, in turn, induce a secondary electromagnetic field. The secondary field is then intercepted by a receiver coil. The voltage measured in the receiver coil is related to the subsurface conductivity. Electron acceptor: A compound capable of accepting electrons during oxidation-reduction reactions. Electron acceptors are compounds that are relatively oxidized and include oxygen, nitrate, iron (III), manganese (IV), sulfate, carbon dioxide, or in some cases the chlorinated aliphatic hydrocarbons such as perchloroethylene (PCE), TCE, DCE, and vinyl chloride. Electron donor: A compound capable of supplying (giving up) electrons during oxidation-reduction reactions. Microorganisms obtain energy by transferring electrons from electron donors such as organic compounds (or sometimes reduced inorganic compounds such as sulfide) to an

A1-10

electron acceptor. Electron donors are compounds that are relatively reduced and include fuel hydrocarbons and native organic carbon. Electrophile: A reactive species that accepts an electron pair. Elimination: Reaction where two groups such as chlorine and hydrogen are lost from adjacent carbon atoms and a double bond is formed in their place. Enzyme: Any of numerous proteins or conjugated proteins produced by living organisms and functioning as biochemical catalysts. Eolian: Pertaining to material transported and deposited by the wind. Includes earth materials ranging from dune sands to silt loess deposits. (3) Ephemeral: A stream or portion of a stream that flows only in direct response to precipitation. It receives little or no water from springs and no long-continued supply from melting snow or other sources. Its channel is at all times above the water table. The term may be arbitrarily restricted to streams that do not flow continuously for periods of 1 month. Epoxidation: A reaction wherein an oxygen molecule is inserted in a carbon-carbon double bond and an epoxide is formed. Equivalent diameter: In sedimentation analysis, the diameter assigned to a non-spherical particle, numerically equal to the diameter of a spherical particle of the same density and velocity of fall. (1) Erode: To wear away or remove the land surface by wind, water, or other agents. (1) Evaporation: The process by which a liquid enters the vapor (gas) phase. Evapotranspiration: The combined loss of water from a given area, and during a specified period of time, by evaporation from the soil surface and by transpiration from plants. (1) Expedited site assessment: A process for collecting and evaluating site information in a single mobilization. Parameters assessed include site geology/hydrogeology, nature, and distribution of the chemicals of concern, source areas, potential exposure pathways, and points of exposure. An ESA employs rapid sampling techniques, field analysis and hydrogeological evaluation, and field

APPENDIX A1 GLOSSARY

decision making to provide a comprehensive "snapshot" of subsurface conditions.

Field blank: Any sample submitted from the field identified as a blank.

Expendable tip: A disposable steel or aluminum tip that attaches to the end of DP rods. The tip seals the DP rods or sampling tool while it is driven through the soil. Once the desired sampling depth has been reached, the rods are pulled back, exposing the target interval.

Field capacity (field moisture capacity): (obsolete in technical work) The percentage of water remaining in a soil 2 or 3 days after having been saturated and after free drainage has practically ceased. (The percentage may be expressed on the basis of weight or volume.) See also Moisture tension. (1)

Fabric (soils): The physical constitution of a soil material as expressed by the spatial arrangement of the solid particles and associated voids. Fabric is the element of structure that deals with arrangement. (4) Facultative anaerobes: microorganisms that use (and prefer) oxygen when it is available but can also use alternate electron acceptors such as nitrate under anaerobic conditions when necessary. Failure (in rocks): Exceeding the maximum strength of the rock or exceeding the stress or strain requirement of a specific design. (7) False negative: A negative result when the concentration of the target constituent is above the detection limit of the analytical method. False-negative rate: The rate at which the statistical procedure does not indicate contamination when contamination is present. False positive: A positive result when the concentration of the target constituent is below the detection limit of the analytical method. False-positive rate: The rate at which the statistical procedure indates contamination when contamination is not present. Fatal flaws: Any site or near-site condition that could render a proposed facility unlicensable, which could significantly impact the cost/profit ratio of operation or which might later lead to noncompliance with performance objectives of the operating permit. Fault: A fracture or fracture zone along which there has been displacement of the two sides relative to one another parallel to the fracture. Fermentation: Microbial metabolism in which a particular compound is used both as an electron donor and an electron acceptor resulting in the production of oxidized and reduced daughter products. Field analytical methods: Methods or techniques that measure physical properties or chemical presences in soils, soil-gas, and ground water immediately.

Field manager: An individual who is on site and is responsible for directing field activities and decision making during the site assessment. The field manager should be familiar with the purpose of the site assessment, pertinent existing data, and the data collection and analysis program, The field manager is the principle investigator, developing and refining the conceptual model of site conditions. This individual should have the necessary experience and background to perform the required site characterization activities, to accurately interpret the results, and to direct the investigation. Fill: Man-made deposits of natural soils or rock products and waste materials. (5) Film water: A layer of water surrounding soil particles and varying in thickness from 1 or 2 to perhaps 100 or more molecular layers. Usually considered as that water remaining after drainage has occurred because it is not distinguishable in saturated soils. (1) Fine texture: Consisting of or containing large quantities of the fine fractions, particularly of silt and clay. (Includes all clay loams and clays; that is, clay loams, sandy clay loam, silty clay loam, sandy clay, silty clay, and clay textural classes. Sometimes subdivided into clayey texture and moderately fine texture.) See soil texture. (1) Firm: A term describing the consistency of a moist soil that offers distinctly noticeable resistance to crushing but can be crushed with moderate pressure between the thumb and forefinger. See Consistency. (1) Fissure flow: Flow of water through joints and larger voids. (5) Flow curve: The locus of points obtained from a standard liquid limit test and plotted on a graph representing water content as ordinate on an arithmetic scale and the number of blows as abscissa on a logarithmic scale. (5) Flow line: The path that a particle of water follows in its course of seepage under laminar flow conditions. (5) Flow path: Represents the area between two flow lines along which ground water can flow. (9) Flow tubes: Area between two adjacent flow lines.

A1-11

APPENDIX A1 GLOSSARY

Flownet: A graphical representation of flow lines and equipotential (piezometric) lines used in the study of seepage phenomena. (5)

Geohydrology: Science of the occurrence, distribution, and movement of water below the surface of the Earth. (6)

Fluorescence: The emission of electromagnetic radiation (e.g., visible light) by a substance during exposure to external electromagnetic radiation (e.g., x-rays).

Geomorphology: The description of currently exposed surfaces of the crust of the Earth, seeks to interpret these surfaces in terms of natural processes (chiefly erosion) which lead or have led to their formation. (6)

Flush joint or flush coupled: Casing or riser with ends threaded such that a consistent inside and outside diameter is maintained across the threaded joints or couplings. (9) Fracture: A break in a rock formation due to structural stresses. Faults, shears, joints, and planes of fracture cleaveage are all types of fractures, Includes joints and faults. (5) Fragipan: A natural subsurface horizon with high bulk density relative to the solum above, seemingly cemented when dry, but when moist showing a moderate to weak brittleness. The layer is low in organic matter, mottled, and slowly or very slowly permeable to water and usually shows occasional or frequent bleached cracks forming polygons. It can be found in profiles of either cultivated or virgin soils but not in calcareous material. (1) Free product: A petroleum hydrocarbon in the liquid (free or nonaqueous) phase (see also Nonaqueous phase liquid (NAPL). Free water (gravitational water; ground water; phreatic water): Water that is free to move through a soil or rock mass under the influence of gravity. (5) Free-phase DNAPL: Immiscible liquid exiting in the subsurface with a positive pressure such that it can flow into a well. If not trapped in a pool, free phase DNAPL will flow vertically through an aquifer or laterally down sloping fine-grained stratigraphic units. Also called mobile DNAPL or continuous phase DNAPL. (10) Friable: A consistency term pertaining to the ease of crumbling of soils. See also Consistency. (1) Friction reducer: A wide section of the DP cone or probe designed to enlarge a boring so that the DP rods above the friction reducer do not inhibit the advancement of the probe. Expendable friction reducers can be used for grouting on advance. Gas pressure potential: This potential component is to be considered only when external gas pressure differs from atmospheric pressure as, for example, in a pressure membrane apparatus.

A1-12

Geophysical borehole geophysics.

logging:

See

Downhole

Geophysics: The study of all the gross physical properties of the Earth and its parts, particularly associated with the detection of the nature and shape of unseen subsurface rock bodies by measurement of such properties and property contrasts. Small scale applied geophysics is now a major aid in geological reconnaissance. (6) Geotechnical: Pertaining to geotechnics, which is the application of scientific methods to problems in engineering geology. (6) Glacial drift: Rock debris that has been transported by glaciers and deposited, whether directly from the ice or from the meltwater. The debris may or may not be heterogeneous. (1) Glacial geology: The study of the direct effects of the formation and flow under gravity of large ice masses on the Earth’s surface. Glaciology is concerned with the physics of ice masses. (6) Glacial outwash: Stratified sand and gravel produced by glaciers and carried, sorted, and deposited by water that originated mainly from the melting of glacial ice. Outwash deposits may occur in the form of valley fills (valley trains and/or outwash terraces) or as widespread outwash plains. (3) Glacial till: Unsorted and unstratified glacial drift, generally unconsolidated, deposited directly by a glacier without subsequent reworking by water from the glacier and consisting of a heterogeneous mixture of clay, silt, sand, gravel, and boulders varying widely in size and shape. (3) Glaciofluvial deposits: Material moved by glacier. Glaciolacustrine deposits: Material ranging from fine clay to sand derived from glaciers and deposited in glacial lakes by water originating mainly from the melting of glacial ice. Many are bedded or laminated with varves. (3)

APPENDIX A1 GLOSSARY

Gleying: Formation of gray or green material in soil when stagnation of water results in exclusion of air and reduction of iron. (6) Gradation (grain-size distribution; texture): The proportions by mass of a soil or fragmented rock distributed in specified particle-size ranges. (5) Grading: A well-graded sediment containing some particles of all sizes in the range concerned. Distinguish from well sorted, which describes a sediment with grains of one size. (6) Grain-size analysis (mechanical analysis) (particle size analysis): The process of determining grainsize distribution. (5) Granule: A natural soil aggregate or ped that is relatively nonporous. See soil structure and soil structure types. (1) Gravel: Round or semirounded particles of rock that will pass a 3-in. (76.2 mm) sieve and be retained on a No. 4 (4.75 mm) U.S. standard sieve. (5) Gravel pack: Common nomenclature for the preferred terminology, primary filter of a well (see Primary filter pack). (9) Gravitational potential: The amount of work that must be done per unit quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water, identical in composition to the soil water, from a pool at a specified elevation and at atmospheric pressure to a similar pool at the elevation of the point under consideration (see Soil water). Greenfield development: A new disposal facility on an area previously not developed for this purpose. Ground-penetrating radar: A geophysical method that uses high frequency electromagnetic waves to obtain subsurface information. The waves are radiated into the subsurface by an emitting antenna. When a wave strikes a suitable object, a portion of the wave is reflected back to the receiving antenna. Ground water: The portion of the total precipitation which at any particular time is either passing through or standing in the soil and the underlying strata and is free to move under the influence of gravity. (1) The water contained in the pore spaces of saturated geologic media. Ground-water level: The level below which the rock and subsoil, to unknown depths, are saturated. (7) Ground-water regime (ground water): Water below the land surface in a zone of saturation.

Grout: A low-permeability material placed in the annulus between the well casing or riser pipe and the borehole wall (i.e., in a single cased monitoring well), or between the riser and casing (i.e., in a multi-cased monitoring well), to maintain the alignment of the casing and riser and to prevent movement of ground water or surface water within the annular space. (9) Cement and/or bentonite slurry used to seal DP holes and other exploratory borings. It is also used to seal the annular space around well casings to prevent infiltration of water or short-circuiting of vapor flow. Grout shoe: A plug fabricated of relatively inert materials that is positioned within the lowermost section of a permanent casing and fitted with a passageway, often with a flow check device, through which grout is injected under pressure to fill the annular space. After the grout has set, the grout shoe is usually drilled out. (9) Hardpan: A hardened soil layer in the lower A or B horizon caused by cementation of soil particles with organic matter or with materials such as silica, sesquioxides, or calcium carbonate. The hardness does not change appreciably with changes in moisture content and pieces of the hard layer do not slake in water. (1) Head: The energy, either kinetic or potential, possessed by each unit weight of a liquid, expressed as the vertical height through which a unit weight would have to fall to release the average energy possessed. It is used in various compound terms such as pressure head, velocity head, and loss of head. (2) Head (static): The height above a standard datum of the surface of a column of water (or other liquid) that can be supported by the static pressure at a given point. The static head is the sum of the elevation head and the pressure head. (9) Head (total): The sum of three components at a point: (1) elevation head, he, which is equal to the elevation of the point above a datum; (2) pressure head, hp, which is the height of a column of static water that can be supported by the static pressure at the point; and (3) velocity head, hv, which is the height the kinetic energy of the liquid is capable of lifting the liquid. (9) Headspace: The vapor/air mixture trapped above a solid or liquid in a sealed vessel. Heave: Upward movement of soil caused by expansion or displacement resulting from phenomena such as moisture absorption, removal of overburden, driving of piles, frost action, and loading of an adjacent area. (5) Henry’s law: The relationship between the partial pressure of a compound and the equilibrium concentration in the liquid through a proportionality constant.

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APPENDIX A1 GLOSSARY

Henry’s law constant: The ratio of the concentration of a compound in air (or vapor) to the concentration of the compound in water under equilibrium conditions. Henry’s law constants are temperature dependent. Heterogeneity: Having different properties at different points. (7) Heterogeneous: Varying in structure or composition at different locations in space. Heterotroph: Organism that uses organic carbon as an external energy source and as a carbon source. Holding time: The maximum amount of time a sample may be stored before analysis. Hollow-stem auger drilling: A conventional drilling method that uses rotating augers to penetrate the soil. As the augers are rotated, soil cuttings are conveyed to the ground surface via spiral flights. Hollow-stem augers allow the rig operator to advance DP tools inside of the augers. Holocene: An epoch of the Quarternary period, from the end of the Pleistocene, approximately 10,000 years ago, to the present time; also, the corresponding series of rocks and deposits. When the Quarternary is designated as an era, the Holocene is considered to be a period. Homogeneous: Uniform in structure or composition at all locations in space. Homogeneous mass: A mass that exhibits essentially the same physical properties at every point throughout the mass. (5) Horizon: See Soil horizon. Hydration: The physical binding of water molecules to ions, molecules, particles, or other matter. (2) Hydraulic conductivity: A coefficient of proportionality describing the rate at which water can move through a permeable medium. Hydraulic conductivity is a function of both the intrinsic permeability of the porous medium and the kinematic viscosity of the water which flows through it. In older documents, hydraulic conductivity is referred to as the coefficient of permeability. Hydraulic conductivity: The volume of water at the existing kinematic viscosity and density that will move in unit time under unit gradient through a unit area measured at right angles to the direction of flow. The proportionality factor in Darcy’s law

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as applied to the viscous flow of water in soil, i.e., the flux of water per unit gradient of hydraulic potential. For the purpose of solving the partial differential equation of the non-steady-state flow in unsaturated soil it is often convenient to introduce a variable termed the soil water diffusivity. (9) Hydraulic gradient: The change in total potentiometric (or piezometric) head between two points divided by the horizontal distance separating the two points. The loss of hydraulic head per unit distance of flow. (5) Hydraulic head: The elevation with respect to a specified reference level at which water stands in a piezometer connected to the point in question in the soil. Its definition can be extended to soil above the water table if the piezometer is replaced by a tensiometer. The hydraulic head in systems under atmospheric pressure may be identified with a potential expressed in terms of the height of a water column. More specifically it can be identified with the sum of gravitational and capillary potentials, and may be termed the hydraulic potential. Hydrocarbon: Chemical compounds composed only of carbon and hydrogen. Hydrogenolysis: A reductive reaction in which a carbon-halogen bond is broken, and hydrogen replaces the halogen substituent. Hydrogeology: The study of the natural (and artificial) distribution of water in rocks and its relationship to those rocks. Inasmuch as the atmosphere is a continuation of the hydrosphere and is in physical and chemical balance with it, there is a close connection with meteorology. (6) Hydrologic unit: Geologic strata that can be distinguished on the basis of capacity to yield and transmit fluids. Aquifers and confining units are types of hydrologic units. Boundaries of a hydrologic unit may not necessarily correspond either laterally or vertically to lithostratigraphic formations. (9) Hydrophilic: Having an affinity for water (waterloving), or capable of dissolving in water; soluble or miscible in water. Hydrophobic: Tending not to combine with water, or incapable of dissolving in water; insoluble or immiscible in water (water-fearing). A property exhibited by nonpolar organic compounds, including the petroleum hydrocarbons.

APPENDIX A1 GLOSSARY

Hydrostatic pressure: A state of stress in which all the principal stresses are equal (and there is no shear stress). (7) Hydroxylation: Addition of a hydroxyl group to a chlorinated aliphatic hydrocarbon. Hygroscopic water: Water adsorbed by a dry soil from an atmosphere of high relative humidity; water remaining in the soil after air-drying or water held by the soil when it is in equilibrium with an atmosphere of a specified relative humidity at a specified temperature, usually 98% of relative humidity at 25 degrees Centigrade. (1) Igneous rock: Rock formed from the cooling and solidification of magma and that has not been changed appreciably since its formation. (1) Immobilization: The conversion of an element from the inorganic to the organic form in microbial tissues or in plant tissues. (1) Immunoassay: A test for a constituent or class of constituents based on the antibody/antigen reaction. Impervious: Resistant to penetration by fluids or by roots. (1) in situ: In its original place; unmoved; unexcavated; remaining in the subsurface. Infiltration: The downward entry of water into the soil. Influenced by genetic and environmental factors of parent material, climate (including moisture and temperature effects), macro- and microorganisms, and topography, all acting over a period of time and producing a product, soil, that differs from the material from which it is derived in many physical, chemical, biological, and morphological proper ties and characteristics. (1) Infiltration rate: A soil characteristic determining or describing the maximum rate at which water can enter the soil under specified conditions, including the presence of an excess of water. (1) The rate at which a soil under specified conditions can absorb falling rain or melting snow; expressed in depth of water per unit time (cm/sec; in/hr). Infrared radiation: Electromagnetic radiation with wave lengths greater than visible light but less than microwave radiation. inner barrel: Internal sample barrel seated inside of a cased DP systems. Injection: Introduction of the analytical sample into the instrument excitation system for the purpose of measuring absorbance, emission, or concentration of an analyte.

Inner barrel: Internal sample barrel seated inside of a cased DP systems. Integral sampling: A technique of core drilling which provides knowledge of the original orientation of the samples recovered. (6) Intergrade: A soil that possesses moderately well-developed distinguishing characteristics of two or more genetically related soil Great Groups. (1) Intermittent: (1) Stream which flows but part of the time, as after a rainstorm, during wet weather, or during but part of the year. (2) Stream flows only at certain times when it receives water from springs (spring fed) or from some surface source (surface fed) such as melting snow in mountainous areas. Internal friction (shear resistance): The portion of the shearing strength of a soil or rock that is usually considered to be due to the interlocking of the soil or rock grains and the resistance to sliding between the grains. (5) Intrinsic permeability: A measure of the relative ease with which a permeable medium can transmit a fluid (liquid or gas). Intrinsic permeability is a property only of the medium and is independent of the nature of the fluid. Ion exchange: A chemical process involving reversible interchange of ions between a liquid and a solid but no radical change in structure of the solid. (2) Ionization potential: The energy required to ionize a particular molecule. Isochrome: A curve showing the distribution of the excess hydrostatic pressure at a given time during a process of consolidation. (5) Isoconcentration: More than one sample point exhibiting the same analyte. Isocontours: A line drawn on a map to indicate equal concentrations of a solute in ground water. Isograms: A general term proposed by Galton (1889, p. 651) for any line on a map or chart connecting points having an equal numerical value of some physical quantity (such as temperature, pressure, or rainfall); an isopleth. Isomorphous substitution: The replacement of one atom by another of similar size in a crystal lattice without disrupting or changing the crystal structure of the mineral. (1) Isopleth: A general term for any map showing the areal distribution of some variable quantity in terms of lines

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APPENDIX A1 GLOSSARY

of equal or constant value; e.g., an isopach map. The line or area represented by an isoconcentration. Isotropic: Having the same properties in all directions. (6) Jetting: When applied as a drilling method, water is forced down through the drill rods or casing and out through the end aperture. The jetting water then transports the generated cuttings to the ground surface in the annulus of the drill rods or casing and the borehole. The term jetting may also refer to a development technique (see Well screen jetting). (9)

Laser-induced fluorescence: A method for measuring the relative amount of soil and/or groundwater contamination with an in situ sensor. Laser light is transmitted to the sensor, where it fluoresces in proportion to the concentration of petroleum hydrocarbons adjacent to the sensor. Leach: To cause water or other liquid to percolate through soil. (2) Light

nonaqueous phase liquid (LNAPL): A nonaqueous phase liquid (NAPL) with a specific gravity less than 1.0. Because the specific gravity of water is equal to 1.0, LNAPLs float on top of the water table. Most of the common petroleum hydrocarbon fuels and lubricating oils are LNAPLs.

Joint: A break of geological origin in the continuity of a body of rock occurring either singly or more frequently in a set or system, but not attended by a visible movement parallel to the surface of discontinuity. (7)

Line of seepage (seepage line; phreatic line): The upper free water surface of the zone of seepage. (5)

Kame: A moundlike hill of ice-contact glacial drift, composed chiefly of stratified sand and gravel. (3)

Linear range: The concentration range over which the analytical curve remains linear.

Karst: A type of topography that is characterized by closed depressions or sink holes and is dependent upon underground solution and the diversion of surface waters to underground routes. It is formed over limestone, dolomite, gypsum and other soluble rocks as a result of differential solution of these materials and associated processes of subsurface drainage, cave formation, subsidence, and collapse. (3)

Liners: Tubes lining DP soil sampling tools. Used to collect soil cores for chemical and/or lithologic analysis. Commonly made of stainless steel, brass, or plastic.

Kinematic viscosity: The ratio of dynamic viscosity to mass density. Kinematic viscosity is a measure of a fluid's resistance to gravity flow — the lower the kinematic viscosity, the easier and faster the fluid will flow. Laminar flow (streamline flow; viscous flow): Flow in which the head loss proportional to the first power of the velocity. Landform: Any physical, recognizable form or feature of the Earth’s surface, having a characteristic shape, and produced by natural causes. (3) Landscape: All the natural features, such as fields, hills, forests, and water that distinguish one part of the Earth’s surface from another part; usually that portion of land or territory which the eye can comprehend in a single view, including all of its natural characteristics. The distinct association of landforms, especially as modified by geologic forces, that can be seen in a single view. (3)

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Liquefaction: Act or process of liquefying or of rendering or becoming liquid; reduction to a liquid state. (2) Liquid limit: The minimum percentage (by weight) of moisture at which a small sample of soil will barely flow under a standard treatment. Synonymous with upper plastic limit. See Plastic limit. (1) Liquidity index (water-plasticity ratio; relative water content): The ratio, expressed as a percentage, of (1) the natural water content of a soil minus its plastic limit, to (2) its plasticity index. (5) Lithologic: Pertaining to the physical character of a rock. (3) Lithology: Mineralogy, grain size, texture, and other physical properties of granular soil, sediment, or rock. Lithotroph: Organism that uses inorganic carbon such as carbon dioxide or bicarbonate as a carbon source and an external source of energy. Loading: The time rate at which material is applied to a treatment device involving length, area, volume or other design factor. (1)

APPENDIX A1 GLOSSARY

Loess: Material transported and deposited by wind and consisting of predominantly silt-sized particles. (1) Lognormal distribution: A frequency distribution whose logarithm follows a normal distribution. Loss of circulation: The loss of drilling fluid into strata to the extent that circulation does not return to the surface. (9) Lower confidence limit (LCL): An estimate of the lower bound for the true concentration(or other parameter) with specified level of confidence (e.g., 95%). Taken together with the upper confidence limits, forms a confidence interval for the estimate with confidence level that accounts for both tail areas (e.g., 90%). Lower detection limit: The smallest signal above background noise that an instrument can reliably detect. Lower explosive limit (LEL): The concentration of a gas below which the concentration of vapors is insufficient to support an explosion. LELs for most organics are generally 1 to 5% by volume. Lower prediction limit (LPL): A statistical estimate of the minimum concentration that will provide a lower bound for the next series of k measurements from that distribution, or the mean of m new measurements for each of k sampling locations, with specified level of confidence (e.g., 95%).

Matric potential: See Potential, soil water. Matrix spike: Aliquot of a matrix (water or soil) fortified (spiked) with known quantities of specific compounds and subjected to the entire analytical procedure in order to indicate the appropriateness of the method for the matrix by measuring recovery. Matrix spike duplicate: A second aliquot of the same matrix as the matrix spike that is spiked in order to determine the precision of the method. Mechanical analysis: (obsolete) See Particle-size analysis and Particle-size distribution. Mechanical dispersion: A physical process of mixing along a flow path in an aquifer resulting from differences in path length and flow velocity. This is in contrast to mixing due to diffusion. Mesh: One of the openings or spaces in a screen. The value of the mesh is usually given as the number of openings per linear inch. This gives no recognition to the diameter of the wire and thus mesh number does not always have a definite relation to the size of the hole. (2) Metabolic byproduct: A product of the reaction between an electron donor and an electron acceptor. Metabolic byproducts include volatile fatty acids, daughter products of chlorinated aliphatic hydrocarbons, methane, and chloride.

Lysimeter: A device for measuring percolation. Macropores: Soil pores that are secondary soil features such as root holes or desiccation cracks. They can create significant conduits for vertical migration of NAPL, dissolved contaminants, or vapor-phase contaminants. Magnetic geophysical methods: Methods of determining subsurface conditions by measuring the Earth’s total magnetic field at a particular location. Because buried ferrous materials distort the magnetic field, a magnetic anomaly is created and their location can be approximated. Magnetic geophysical methods: Methods of determining subsurface conditions by measuring the earth's total magnetic field at a particular location. Because buried ferrous materials distort the magnetic field, a magnetic anomaly is created and their location can be approximated. Manometer: An instrument for measuring pressure. It usually consists of a U-shaped tube containing a liquid, the surface of which in one end of the tube moves proportionally with changes in pressure on the liquid in the other end. Also, a tube type of differential pressure gauge. (2)

Metal detection geophysical methods: Methods designed to specifically locate metal in the subsurface through electromagnetic induction (see electromagnetic geophysical methods). When the subsurface current is measured at a specific level, the presence of metal is indicated with a meter reading or with a sound, or with both. Metamorphic rock: Rock derived from preexisting rocks but that differ from them in physical, chemical, and mineralogical properties as a result of natural geological processes, principally heat and pressure, originating in the Earth. The preexisting rocks may have been igneous, sedimentary, or another form of metamorphic rock. (1) Method blank: An analytical control consisting of all reagents, internal standards, and surrogate standards, that is carried through the entire analytical procedure. The method blank is used to define the level of laboratory background and reagent contamination. Microorganisms: Microscopic organisms including bacteria, protozoans, yeast, ftmgi, mold, viruses, and algae. Microorganisms obtain energy by transferring electrons from electron donors such as organic compounds (or sometimes reduced inorganic compounds such as sulfide) to an electron acceptor.

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APPENDIX A1 GLOSSARY

Mobilization: The movement of equipment and personnel to the site, conducted during a continuous time frame to prepare for, collect, and evaluate site assessment data.

Multiport systems: A single hole device in which points are installed that are capable of sampling or measuring at multiple levels within a formation or series of formations.

Modulus of elasticity (modulus of deformation): The ratio of stress to strain for a mineral under given loading condition; numerically equal to the slope of the tangent or the secant of a stress-strain curve.

Neat cement: A mixture of Portland cement (ASTM 150) and water. (9)

Moisture content (water content): The ratio, expressed as a percentage, of: (a) the weight of water in a given soil mass, to (b) the weight of solid particles. Moisture content: The amount of water lost from a soil upon drying to a constant weight, expressed as the weight per unit weight of dry soil or as the volume of water per unit bulk volume of the soil. For a fully saturated medium, moisture content equals the porosity. Moisture-retention curve: A graph showing the soil moisture percentage (by weight or by volume) versus applied tension (or pressure). Points on the graph are usually obtained by increasing (or decreasing) the applied tension or pressure over a specified range. (1) Molecular weight: The amount of mass in one mole of molecules of a substance as determined by summing the masses of the individual atoms which make up the molecule. Monoaromatic: Aromatic hydrocarbons containing a single benzene ring. Monoaromatic: Aromatic hydrocarbons containing a single benzene ring. Monooxygenase: A microbial enzyme that catalyzes reactions in which one atom of the oxygen molecule is incorporated into a product and the other atom appears in water. Morphology: See Soil morphology. Mud pit: Usually a shallow, rectangular, open, portable container with baffles into which drilling fluid and cuttings are discharged from a borehole and that serves as a reservoir and settling tank during recirculation of the drilling fluids. Under some circumstances, an excavated pit with a lining material may be used. (9) Multi-cased well: A well constructed by using successively smaller diameter casings with depth. (9)

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Negative pressure: A pressure less than the local atmospheric pressure at a given point. (3) Nonaqueous phase liquid (NAPL): Contaminants that remain as the original bulk liquid in the subsurface (see also Free product). Nonparametric: A term referring to a statistical technique in which the distribution of the constituent in the population is unknown and is not restricted to be of a specified form. Nonparametric prediction limit: The largest (or second largest) of n background samples. The confidence level associated with the nonparametric prediction limit is a function of n, m and k. Nonsealed DP tools: Sampling tools that are not sealed as they are advanced through the soil. Examples of these tools are barrel samplers and split-barrel samplers. Can yield erroneous chemical results because samples collected with these devices can be a composite of samples from different horizons. Can result in cross-contamination of samples. Normal distribution: A frequency distribution whose plot is a continuous, infinite, bell-shaped curve that is symmetrical about its arithmetic mean, mode and median (which are numerically equivalent). The normal distribution has two parameters, the mean and variance. Normally consolidated soil deposit: A soil deposit that has never been subjected to an effective pressure greater than the existing overburden pressure. (5) Nuclear logging: A downhole geophysical logging method that uses naturally occurring or induced radiation to define lithology, ground-water conditions, or contaminant distributions. Nucleophile: A chemical reagent that reacts by forming covalent bonds with electronegative atoms and compounds. N-value: The number of blows required to drive the sampler of the standard penetration test its last 12 in. (300 mm.).

APPENDIX A1 GLOSSARY

Obligate aerobe: Microorganisms that can use only oxygen as an electron acceptor. Thus, the presence of molecular oxygen is a requirement for these microbes. Obligate anaerobes: Microorganisms that grow only in the absence of oxygen; the presence of molecular oxygen either inhibits growth or kills the organism. For example, methanogens are very sensitive to oxygen and can live only under strictly anaerobic conditions. Sulfate reducers, on the other hand, can tolerate exposure to oxygen, but cannot grow in its presence. Observation well: Typically, a small diameter well used to measure changes in hydraulic heads, usually in response to a nearby pumping well. (9) Oil air filter: A filter or series of filters placed in the air flow line from an air compressor to reduce the oil content of the air. (9) Olefins: See Alkenes. Oil trap: A device used to remove oil from the compressed air discharged from an air compressor. (9) Optimum moisture content (optimum water content): The water content at which a soil can be compacted to a maximum dry unit weight by a given compactive effort. Organophyllic: A substance that combines with organic compounds. Osmotic potential: The amount of work that must be done per unit quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water from a pool of pure water, at a specified elevation and at atmospheric pressure, to a pool of water identical in composition to the soil water (at the point under consideration), but in all other respects being identical to the reference pool. Osmotic pressure: The pressure to which a pool of water, identical in composition to the soil water, must be subjected in order to be in equilibrium, through a semipermeable membrane, with a pool of pure water (semipermeable means permeable only to water). May be identified with the osmotic potential defined above.

Oven-dry soil: Soil that has been dried at 105 degrees Centigrade until it reaches constant weight. (1) Overburden: The loose soil, sand, silt, or clay that overlies bedrock. (7) Overburden load: The load on a horizontal surface underground due to the column of material located vertically above it. (7) Overconsolidated soil deposit: A soil deposit that has been subjected to an effective pressure greater than the present overburden pressure. (5) Oxidation-reduction (redox): A chemical reaction consisting of two halfreactions; an oxidation reaction in which a substance loses or donates electrons, and a reduction reaction in which a substance gains or accepts electrons. Redox reactions are always coupled because free electrons cannot exist in solution and electrons must be conserved. Oxidation-reduction potential: The potential required to transfer electrons from the oxidant to the reductant and used as a qualitative measure of the state of oxidation in wastewater treatment systems. (2) Packer: A transient or dedicated device placed in a well that isolates or seals a portion of the well, well annulus, or borehole at a specific level. (9) An inflatable gland, or balloon, that is used to create a temporary seal in borehole, probe hole, well, or drive casing. Made of rubber or non-reactive materials like Vitong. Paraffins: See Alkanes. Parametric: A term referring to a statistical technique in which the distribution of the constituent in the population is assumed to be known. Parent material: The unconsolidated and more or less chemically weathered mineral or organic matter from which the solum of soil is developed by pedogenic processes. (1) Particle density: The mass per unit volume of the soil particles. In technical work, usually expressed as grams per cubic centimeter. See Bulk density, soil. (1)

Outer drive casing: Same as drive casing. Outlier: A measurement that is statistically inconsistent with the distribution of other measurements from which it was drawn. Outwash plain: An extensive lowland area forming the surface of a body of coarse textured, glaciofluvial material. An outwash plain is commonly smooth; where pitted, due to melt-out of incorporated ice masses, it is generally low in relief. (3)

Particle size: The effective diameter of a particle measured by sedimentation, sieving, or micrometric methods. (1) Particle-size analysis: Determination of the various amounts of the different separates in a soil sample, will usually be sedimentation, sieving, micrometry, or combinations of these methods. (1)

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APPENDIX A1 GLOSSARY

Particle-size distribution: The amounts of the various soil separates in a soil sample, usually expressed as weight percentages. (1) Ped: An individual natural soil aggregate consisting of a cluster of primary particles, and separated from adjoining peds by surfaces of weakness which are recognizable as natural voids or by the occurrence of cutans. (4) Pedologic: One of the disciplines of soil science, the study of soil morphology, genesis, and classification. It is sometimes used as a synonym of soil science. Pedology: (a) The description of those parts of the present Earth surface which have become weathered or otherwise modified in situ by solar energy and by the effects of organisms to form a soil which is of primary importance to man in agriculture. (6) The science of soils, that is, the study of the origin, classification, description and use of natural soil bodies. (4) Pedon: A three-dimensional body of soil with lateral dimensions large enough to permit the study of horizon shapes and relations. Its area ranges from 1 to 10 square meters. Penetrability: The ease with which a probe can be pushed into the soil (may be expressed in units of distance, speed, force, or work depending on the type of penetrometer used). (1) Penetration resistance (standard penetration resistance; proctor penetration resistance): (1) A number of blows of a hammer of specified weight falling a given distance required to produce a given penetration into soil of a pile, casing, or sampling tube. (2) Unit load required to maintain constant rate of penetration into soil of a probe or instrument. (3) Unit load required to produce a specified penetration into soil at a specified rate of a probe or instrument. For a Proctor needle, the specified penetration is 2.5 in. (63.5 mm) and the rate is 0.5 in. (12.7mm)/s. (5) Penetration resistance curve (Proctor penetration curve): The curve showing the relationship between: (a) the penetration resistance, and (b) the water content. (5) Percent compaction: The ratio, expressed as a percentage, of: (a) dry unit weight of a soil, to (b) maximum unit weight obtained in a laboratory Compaction test. (5) Percent saturation (degree of saturation): The ratio, expressed as a percentage, of: (a) the volume of

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water in a given soil or rock mass, to (b) the total volume of intergranular space (voids). (5) Perched aquifer: A lens of saturated soil above the main water table that forms on top of an isolated geologic layer of low permeability. Perched water table: A water table usually of limited area maintained above the normal free water elevation by the pressure of an intervening relatively impervious confining stratum. (5) Percolation: The flow or trickling of a liquid downward through a contact or filtering medium. The liquid may or may not fill the pores Percussion hammer: A hydraulic or pneumatic hammer, much like a jackhammer, that is used to pound DP rods into the ground. Commonly used in the construction industry to break concrete. Perennial: Streams that flow throughout the year and from source to mouth. Performance evaluation well: A ground-water monitoring well placed to monitor the effectiveness of the chosen remedial action. Peristaltic pump: A type of suction-lift pump that creates a vacuum by turning a rotating head against flexible tubing. Generally limited to approximately 25 feet of lift. Permanent strain: The strain remaining in a solid with respect to its initial condition after the application and removal of stress greater than the yield stress (commonly also called residual strain). (7) Permeability: Also referred to as intrinsic permeability. It is a qualitative description of the relative case with which rock, soil, or sediment will transmit a fluid (i.e., liquid or gas). Often used as a synonym for hydraulic conductivity or coefficient of permeability; however, unlike hydraulic conductivity, permeability is not a function of the kinematic viscosity of the fluid that flows through it. Permeability, soil: (1) The ease with which gases, liquids, or plant roots penetrate or pass through a bulk mass of soil or a layer of soil. Because different soil horizons vary in permeability, the particular horizon under question should be designated. (2) The property of a porous medium itself that relates to the ease with which gases, liquids, or other substances can pass through it. Previously, frequently considered the k in Darcy's law. See Darcy’s law and Soil water. (1)

APPENDIX A1 GLOSSARY

Petroleum: Crude oil or any fraction thereof that is liquid at standard conditions of temperature and pressure (600° F at 14.7 psia). The term includes petroleum based substances comprised of a complex blend of hydrocarbons derived from crude oil through the process of separation, conversion, upgrading, and finishing, such as motor fuels, jet oils, lubricants, petroleum solvents, and used oils. pH: A measure of the acidity of a solution. pH is equal to the negative logarithm of the concentration of hydrogen ions in a solution. A pH of 7 is neutral. Values less than 7 are acidic, and values greater than 7 are basic. pH, soil: The negative logarithm of the hydrogen-ion activity of a soil. The degree of acidity (or alkalinity) of a soil as determined by means of a glass, quinhydrone, or other suitable electrode or indicator at a specified moisture content or soilwater ratio, and expressed in terms of the pH scale. (1) Phase I Environmental Site Assessment: Non-intrusive investigation that identifies PAOCs which may require further investigation in subsequent phases of work. Phase II Environmental Site Assessment (ESA): Intrusive survey to confirm or deny existence of a release into the environment at a PAOC at levels which may adversely impact public health or the environment. Physical properties (of soil): Those characteristics, processes, or reactions of a soil caused by physical forces and which can be described by, or expressed in, physical terms or equations. Sometimes confused with and difficult to separate from chemical properties; hence, the terms physical-chemical or physiochemical. Examples of physical properties are bulk density, water-holding capacity, hydraulic conductivity, porosity, pore- size distribution, etc. (1) Piezocone: A type of CPT cone that incorporates a pressure transducer to measure hydrostatic pressure. Piezometer: A nonpumping well, generally of small diameter, which is used to measure the elevation of the water table or potentiometric surface. A piezometer generally has a short well screen; the water level within the casing is considered to be representative of the potentiometric surface at that particular depth in the aquifer. Piezometric head: Hydrostatic pressure in an aquifer, relative to a common datum, such as mean sea level. The piezometric head in an unconfined aquifer is the water table. The piezometric head in a confined aquifer occurs above the top of the aquifer. Piezometer nest: A set of two or more piezometers set in close proximity to one another but screened at different

depths. This allows for determination of vertical flow gradients or differences in water chemistry with depth. Piezometric surface: (1) The surface at which water will stand in a series of piezometers. (5) (2) An imaginary surface that everywhere coincides with the static level of the water in the aquifer. (7) An outdated term for potentiometric surface. Piping: An underground flow of water with a sufficient pressure gradient to cause scour along Piston sampler: Sealed soil sampling tool that uses an internal piston to seal the tool while it is pushed or driven to the target zone. A tube with an internal piston used for obtaining relatively undisturbed samples from cohesive soils. (6) Plane of weakness: Surface or narrow zone with a (shear or tensile) strength lower than that of the surrounding material. (7) Plane stress (strain): A state of stress (strain) in a solid body in which all stress (strain) components normal to a certain plane are zero. (7) Plastic equilibrium: State of stress within a soil or rock mass or a portion thereof, which has been deformed to such an extent that its ultimate shearing resistance is mobilized. (5) Plastic flow (plastic deformation): The deformation of a plastic material beyond the point of recovery, accompanied by continuing deformation with no further increase in stress. Plastic limit: (1) The water content corresponding to an arbitrary limit between the plastic and the semisolid states of consistency of a soil. (2) Water content at which a soil will just begin to crumble when rolled into a thread approximately 1/8 in. (3.2 mm) in diameter. (5) Plasticity: The property of a soil or rock which allows it to be deformed beyond the point of recovery without cracking or appreciable volume change. (5) Plasticity range: The range of moisture weight percentage within which a small sample of soil exhibits plastic properties. (1) Plume: The zone of contamination containing organics in the dissolved phase. The plume usually will originate from the DNAPL zone and extend downgradient for some distance depending on site hydrogeologic and chemical conditions. To avoid confusion, the term DNAPL plume should not be used to describe a DNAPL pool; plume should be used to refer only to dissolved-phase organics. (10)

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APPENDIX A1 GLOSSARY

Polyaromatic hydrocarbon (PAH): Aromatic hydrocarbons containing more than one fused benzene ring. Polynuclear aromatic hydrocarbon (PNA): Synonymous with polyaromatic hydrocarbon. Pool and lens: A zone of free-phase DNAPL at the bottom of an aquifer. A lens is a pool that rests on a hydraulic conductivity contrast. Pore-size distribution: The volume of the various sizes of pores in a soil. Expressed as percentages of the bulk volume (soil plus pore space). (1) Porosity: The ratio, usually expressed as a percentage, of: (a) the volume of voids of a given soil or rock mass, to (b) the total volume of the soil or rock mass. (5); (c) the volume fraction of a rock or unconsolidated sediment not occupied by solid material but usually occupied by liquids, vapor, and/or air. Potential area of concern: Areas with a documented release or likely presence of a hazardous substance that could pose an unacceptable risk to human health or the environment.

a characteristic shape when plotted on semilog paper with pressure on the log scale. The various parts of the curve and extensions to the parts have been designated as recompression, compression, virgin compression, expansion, rebound, and other descriptive names by various authorities. (5) Primary filter pack: A clean silica sand or sand and gravel mixture of selected grain size and gradation that is installed in the annular space between the borehole wall and the well screen, extending an appropriate distance above the Primary state of stress: The stress in a geological formation before it is disturbed by manmade works. (7) Principal stress (strain): The stress (strain) normal to one of three mutually perpendicular planes on which the shear stresses (strains) at a point in a body are zero. (7 Probe hole: Synonym for DP hole (the hole resulting from advancement of DP tools). Profile, soil: A vertical section of the soil through all its horizons and extending into the parent material. (1)

Potential, soil water: See Soil water. Potentiometric surface: An imaginary surface representing the static head of ground water. The water table is a particular potentiometric surface. Note: Where the head varies with depth in the aquifer, a potentiometric surface is meaningful only if it describes the static head along a particular specified surface or stratum in that aquifer. More than one potentiometric surface is required to describe the distribution of head in this case. (9) The surface to which water in an aquifer will rise by hydrostatic pressure. Preconsolidation pressure (prestress): The greatest effective pressure to which a soil has been subjected. (5)

Protocol: Describes the exact procedures to be followed with respect to sample receipt and handling, analytical methods, data reporting and deliverables, and document control. PTFE tape: Joint sealing tape composed of polytetrafluoroethylene. (9) Puddled soil: A soil in which structure has been mechanically destroyed, which allows the soil to run together when saturated with water. A soil that has been puddled occurs in a massive nonstructural state. (2)

Pressure gradient: A pressure differential in a given medium (e.g., water, air) which tends to induce movement from areas of higher pressure to areas of lower pressure.

Purge and trap (device): Analytical technique (device) used to isolate volatile (purgeable) organics by stripping the compounds from water or soil with a stream of inert gas, trapping the compounds on an adsorbent such as a porous polymer trap, and thermally desorbing the trapped compounds into the gas chromatographic column.

Pressure surface: The level of the water surface in an (imaginary) vertical well connecting with an aquifer. (5)

Purging: Removing stagnant air or water from sampling zone or sampling equipment prior to collecting the sample.

Pressure-void ratio curve (compression curve): A curve representing the relationship between effective pressure and void ratio of a soil as obtained from a consolidation test. The curve has

Pyroclastic: Pertaining to fragmental materials produced by usually explosive, aerial ejection of clastic particles from a volcanic vent. (3)

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APPENDIX A1 GLOSSARY

Quality assurance: Documentation designed to ensure that proper sampling and/or analysis protocol are being followed. Quality control: The implementation of protocols designed to ensure that the final sampling or analytical results are reliable. Quantification limit: (QL): A lower limit on the concentration at which quantitative determinations of an analyte’s concentration in the sample can be reliably made during routine laboratory operating conditions.

Residual shrinkage: The decrease in the bulk volume of soil in addition to that caused by the loss of water. (1) Residual stress: Stress remaining in a solid under zero external stress after some process that causes the dimensions of the various parts of the solid to be incompatible under zero stress; for example, (a) deformation under the action of external stress when some parts of the body suffer permanent strain or (b) heating or cooling of a body in which the thermal expansion coefficient is not uniform throughout the body. (5)

Reaction, soil: The degree of acidity or alkalinity of a soil, usually expressed as a pH value. Descriptive terms commonly associated with certain ranges in pH are extremely acid, less than 4.5; very strongly acid, 4.5 to 6.0; slightly acid, 6.1 to 6.5; neutral, 6.6 to 7.3; slightly alkaline, 7.4 to 7.8; moderately alkaline, 7.9 to 8.4; strongly alkaline 8.5 to 9.0; and very strongly alkaline, greater than 9.1.0)

Retainers: Plastic or steel retaining caps that prevent soil cores from falling out of sample barrel when they are withdrawn from the ground. Also referred to as soil catchers.

Recharge: Natural or artificial replenishment of an aquifer.

Retentivity profile, soil: A graph showing the retaining capacity of a soil as a function of depth. The retaining capacity may be for water, for water at any given tension, for cations, or for any other substances held by soils. (1)

Re-entry grouting: A grouting method that requires re-entering the probe hole with special DP rods or tremie pipe for grouting. In some circumstances, the DP rods used for grouting may not go down the same hole as the hole created by the DP sampling tool. Generally inferior to retraction grouting.

Retention time: In chromatography, the time between when a sample is injected and the time the chromatographic peak is recorded.

Regolith: All unconsolidated earth materials above the solid bedrock. (3)

Retractable tip: A steel tip that is connected to the DP rods so that it can be detached at a designated depth while still being removed when the DP rods are withdrawn. The tip is connected to the tip holder with a small-diameter steel rod.

Relative consistency: Ratio of (a) the liquid minus the natural water content, to (b) the plasticity index. (5)

Riser: The pipe extending from the well screen to or above the ground surface. (9)

Remolded soil: Soil that has had its natural structure modified by manipulation. (5)

Rotary drilling: A conventional drilling method that uses water- or air-based fluids to cool the drill bit and remove drill cuttings from the borehole.

Residual: Immiscible phase liquid held in the pore spaces or fractures by capillary forces (negative pressure on DNAPL). Residual will remain trapped within the pore of the porous media unless the viscous forces (caused by the dynamic force of water against the DNAPL) are greater than the capillary forces holding the DNAPL in the pore. At most sites the hydraulic gradient required to mobilize all of the residual trapped in an aquifer is usually much greater than can be produced by wells or trenchers. (10) Residual saturation: The fraction of available pore space containing residual DNAPLs, or the saturation level where free-phase DNAPL becomes residual DNAPL. In the vadose zone, residual saturation range up to 20% of total pore volume while in the saturated zone residual saturations range up to 50% of total pore volume. (10)

Rotohammers: A hand-held, high-frequency impact hammer used to advance small-diameter DP rods. Sample: A portion of material to be analyzed that is contained in single or multiple containers. Sand: (1) A soil particle between 0.05 and 2.0 mm in diameter. (2) Any one of five soil separates, namely: very coarse sand, coarse sand, medium sand, fine sand, and very fine sand. See soil separates. (3) A soil textural class. See Soil texture. (1) Saprolite: A soft, earthy, clay-rich, thoroughly decomposed rock formed in place by chemical weathering of igneous or metamorphic rocks. Forms in humid, tropical, or subtropical climates.

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APPENDIX A1 GLOSSARY

Saturated zone: The zone in which all the voids in the rock or soil are filled with water at a pressure that is greater than atmospheric. The water table is the top of the saturated zone in an unconfined aquifer.

Semiquantitative: Numeric values which only approximate the true concentration of the analytes. Provides an order of magnitude of concentrations (e.g., 10s, 100s, 1000s).

Saturation: A condition reached by a material, whether it be in solid, gaseous, or liquid state, that holds another material within itself in a given state in an amount such that no more of such material can be held within it in the same state. The material is then said to be saturated on in a condition of saturation. (2)

Semivolatile organic compounds: A general term for organic compounds that volatilize relatively slowly at standard temperature (20°C) and pressure (1 atm).

Scope of work: A written description of site assessment work to be performed within an investigation.

Shear failure (failure by rupture): Failure in which movement cause by shearing stresses in a soil or rock mass is of sufficient magnitude to destroy or seriously endanger a structure. (1) General shear failure: Failure in which the ultimate strength of the soil or rock is mobilized along the entire potential surface of sliding before the structure supported by the soil or rock is impaired by excessive movement. (2) Local shear failure: Failure in which the ultimate shearing strength of the soil or rock is mobilized only locally along the potential surface of sliding at the time the structure supported by the soil or rock is impaired by excessive movement. (5)

Sealed DP tools: Soil, groundwater, and soil-gas sampling tools that are sealed while they are pushed to the target depth. Secondary filter pack: A clean, uniformly graded sand that is placed in the annulus between the primary filter pack and the over-lying seal or between the seal and overlying grout backfill or both, to prevent movement of seal or grout, or both, into the primary filter pack. (9) Secondary porosity: The porosity developed in a rock after its deposition or emplacement, through such processes as solution or fracturing. Sediment sump: A blank extension beneath the well screen used to collect fine-grained material from the filter pack and adjacent strata. The term is synonymous with rat trap or tail pipe. (9) Sedimentation: The process of subsidence and deposition of suspended matter carried by water, wastewater, or other liquids, by gravity. It is usually accomplished by reducing the velocity of moving water or air. Seepage (percolation): The slow movement of gravitational water through the soil or rock. (5) Seepage force: The force transmitted to the soil or rock grains by seepage. (5)

Sensitivity: Ratio of disturbed to undisturbed shear strength of a soil. (6)

Shear force: A force directed parallel to the surface element across which it acts. (7) Shear plane: A plane along which failure of material occurs by shearing. (7) Shear strain: The change in shape, expressed by the relative change of the right angles at the corner of what was in the undeformed state an infinitesimally small rectangle or cube. (7) Shear strength: A measure of the shear or gel properties of a drilling fluid or grout; also, the maximum resistance of a soil or rock to shearing stresses. (9) Shear stress: Stress directed parallel to the surface element across which it acts. (7) Shoe: See Drive shoe.

Seismic reflection: A method of determining subsurface conditions by creating acoustic waves and measuring the travel time as they reflect off of materials of different composition. Seismic refraction: A method of determining subsurface conditions by creating acoustic waves and measuring their travel times to the surface as they interface with two materials having different acoustic velocities.

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Short circuiting: As it applies to soil gas surveys, the entry of ambient air into the extraction well without first passing through the contaminated zone. Short circuiting may occur through utility trenches, incoherent well or surface seals, or layers of high permeability geologic materials.

APPENDIX A1 GLOSSARY

Shrinkage limit: The maximum water content at which a reduction in water content will not cause a decrease in volume of the soil mass. (5) Silt: A soil separate consisting of particles between 0.005 and 0.002 mm in equivalent diameter. Single-cased well: A monitoring well constructed with a riser but without an exterior casing. (9) Single-rod DP system: A DP rod system that uses a single sequence of rods to advance the sampling tool or sensor. Site assessment: A formal means of exploring and characterizing a proposed waste management facility or location so that all physical factors are identified and so quantified as to serve as the basis of an environmentally sound design and operational plan. Site characterization and analysis penetrometer system (SCAPS): An in situ sensor that uses laser-induced fluorescence to determine the relative amounts of polyaromatic hydrocarbons in the subsurface. The sensor is mounted in the cone of CPT equipment. Developed by the U.S. military.

(a) those with worm-type bits, unenclosed; (b) those with worm-type bits enclosed in a hollow cylinder; and (c) those with a hollow cylinder with a cutting edge at the lower end. (1) Soil catchers: Flexible attachments on the bottom of soil sampling tools that allow soil to enter the sampler but inhibit soil from falling out while the sampler is being retrieved. Also referred to as soil retainers. Soil fabric: The physical constitution of a soil material as expressed by the spatial arrangement of the solid particles and associated voids. (4) Soil horizon: A layer of soil or soil material approximately parallel to the land surface and differing from adjacent genetically related layers in physical, chemical, and biological properties or characteristics such as color, structure, texture, consistency, kinds and numbers of organisms present, degree of acidity or alkalinity, etc. (1) Soil mechanics: The science dealing with all phenomena that affect the action of soil in a capacity in any way associated with engineering. (8)

Skeleton grains: The individual grains larger than colloidal size (> 0.002 mm) of a soil material; they consist of mineral grains originally present in the parent material and resistant siliceous and organic bodies. (4)

Soil mineral: (1) Any mineral that occurs as a part of or in the soil. (2) A natural inorganic compound with definite physical, chemical, and crystalline properties (within the limits of isomorphism) that occurs in the soil. (1)

Slam bar: A hand-held weight used to pound DP rods into the ground. Originally designed for steel fence posts.

Soil moisture: The water contained in the pore spaces in the unsaturated zone; Water contained in the soil. (1)

Slickensides: Polished and grooved surfaces produced by one mass sliding past another. (1)

Soil-moisture tension: See moisture tension (or pressure).

Slough: Soil that falls into a probe hole after a sampling tool or in situ sensor has been withdrawn. S-matrix: The material (plasma and/or skeleton grains and associated voids) within the simplest (primary) peds, or composing apedal soil materials that does not occur as pedalogical features other than plasma separations; it may be absent in some soil materials, for example those that consist entirely of pedological features. (4) Soil: (1) The unconsolidated mineral material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants. (2) The unconsolidated mineral matter on the surface of the Earth that has been subjected to weathering. Soil air: The soil atmosphere; the gaseous phase of the soil, being that volume not occupied by solid or liquid. (1) Soil auger: A tool for boring into the soil and withdrawing a small sample for field or laboratory observation. Soil augers may be classified into several types as follows:

Soil morphology: (1) The physical constitution, particularly the structural properties, of the soil profile as exhibited by the kinds, thickness, and arrangement of the horizons in the profile, and by the texture, structure, consistency, and the porosity of each horizon. (2) The structural characteristics of the soil or any of its parts. (1) Soil physics: The organized body of knowledge concerned with the physical characteristics of soil and with the methods employed in their determinations. (5) Soil piping or tunneling: Accelerated erosion that results in subterranean voids and tunnels. (1) Soil science: That science dealing with soils as a natural resource on the surface of the Earth including soil formation, classification, and mapping, and physical, chemical, biological, and fertility properties of soil per se and these properties in relation to their management. (1) Soil separates: Mineral particles, < 2.0 mm in equivalent diameter, ranging between specified size limits. The

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APPENDIX A1 GLOSSARY

names and size limits of separates recognized in the U.S.D.A. system are: very coarse sand, 2.0 to 1.0 mm; coarse sand, 1.0 to 0.5 mm; medium sand, 0.5 to 0.25 mm; fine sand, 0.25 to 0.10 mm; very fine sand, 0.10 to 0.05 mm; silt, 0.05 to 0.002 mm; and clay, < 0.002 mm. The U.S.C.S. particle and size ranges are as follows: coarse sand, 2.0 to 4.76 mm; medium sand, 0.42 to 2.0 mm; fine sand, 0.074 to 0.42 mm; fines (silt and clay), < 0.074 mm. (Note: U.S.C.S. silt and clay designations are determined by response of the soil to manipulation at various water contents rather than by measurement of size.) Soil

series: The basic unit of U.S.D.A. soil classification; a subdivision of a family and consisting of soils which are essentially alike in all major profile characteristics except the texture of the A horizon. (1)

Soil solution: The aqueous liquid phase of the soil and its solutes. (1) Soil structure: The combination or arrangement of primary soil particles into secondary particles, units, or peds. These secondary units may be, but usually are not, arranged in the profile in such a manner as to give a distinctive, characteristic pattern. The secondary units are characterized and classified on the basis of size, shape, and degree of distinctness into classes, types, and grades, respectively. (1) Soil suction: A measure of the force of water retentior in unsaturated soil. Soil suction is equal to a force per unit area that must be exceeded by an externally applied suction to initiate water flow from the soil. Soil suction is expressed in standard pressure terms. (2)

permeable wall with the soil water. May be identified with the capillary potential defined above. Solid waste disposal facilities: A facility or part of a facility at which solid waste is intentionally placed into or on any land or water, and at which waste will remain after closure. Solubility: The amount of mass of a compound that will dissolve in a unit volume of solution. Solvolysis: A reaction in which the solvent serves as the nucleophile. Sorption: A general term used to encompass the processes of absorption, adsorption, ion exchange, and chemisorption. Sounding: A general term indicating the recording of vertical measurements. Commonly used to describe vertical measurements collected with geophysical methods and cone penetrometer testing. Source area(s): The location(s) of liquid hydrocarbons or the zone(s) of highest soil or ground-water concentrations, or both, of the chemical(s) of concern. Sparge or sparging: Injection of air below the water table to strip dissolved volatile organic compounds and/or oxygenate the groundwater to facilitate aerobic biodegradation of organic compounds.

Soil water: A general term emphasizing the physical rather than the chemical properties and behavior of the soil solution.

Specific gravity: The dimensionless ratio of the density of a substance with respect to the density of water. The specific gravity of water is equal to 1.0 by definition. Most petroleum products have a specific gravity less than 1.0, generally between 0.6 and 0.9. As such, they will float on water; these are also referred to as LNAPLs, or light nonaqueous phase liquids. Substances with a specific gravity greater than 1.0 will sink through water-; these are referred to as DNAPLs, or dense nonaqueous phase liquids.

Soil water diffusivity: The hydraulic conductivity divided by the differential water capacity (care being taken to be consistent with units), or the flux of water per unit gradient of moisture content in the absence of other force fields.

Specific gravity (of solids): Ratio of: (a) the weight in air of a given volume of solids at a stated temperature, to (b) the weight in air of an equal volume of distilled water at a stated temperature. (1)

Soil water pressure: The pressure (positive or negative), relative to the external gas pressure or the soil water, to which a solution identical ir composition to the soil water must be subjected in order to be in equilibrium through a porous

Specific retention: Ratio of volume of suspended water to volume of associated voids. (6)

Soil texture: The relative proportion of the various soil separates in a soil as described by the classes of soil texture. (1)

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Specific surface: The surface area per unit of volume of soil particles. (5)

APPENDIX A1 GLOSSARY

Specific yield: Ratio of voids not occupied by suspended water to the total volume of the associated area. (6) Split-barrel sampler: A nonsealed soil sampling tool that is split longitudinally. The split barrel allows easy removal of soil cores. Some split-barrel samplers can hold stainless steel liners, which facilitate preservation of samples for chemical analysis (the steel liners minimize the loss of volatile organic compounds). Also known as a split-spoon sampler. Stability: The condition of a structure or a mass of material when it is able to support the applied stress for a long time without suffering any significant deformation or movement that is not reversed by the release of stress. (7) Standard analysis: An analytical detennination made with known quantities of target compounds; used to determine response factors. Standard penetration test (SPT): The most commonly used in situ test to measure in relative terms the resistance of soil to deformation by shearing. (6) Static water level: The elevation of the top of a column of water in a monitoring well or piezometer that is not influenced by pumping or conditions related to well installation, hydrologic testing, or nearby pumpage. (9) Stereograms: A graphic diagram on a plane surface, giving a three-dimensional representation, such as projecting a set of angular relations (e.g., a block diagram of geologic structure, or a stereographic projection of a crystal). Storativity: The volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head. It is equal to the product of specific storage and aquifer thickness. In an unconfined aquifer, the storativity is equivalent to the specific yield. Also called storage coefficient. Strain (linear or normal): The change in length per unit of length in a given direction. (5) Stratification: Layering or bedding of geologic materials (e.g., rock, sediments). Stratified: Arranged in strata, or layers. The term refers to geologic material. Layers in soils that result from the processes of soil formation are called horizons; those inherited from the parent material are called strata. (3) Stratigraphy: The formation, composition, and sequence of sediments, whether consolidated or unconsolidated.

Stress: The force per unit area acting within the soil mass. Structure: One of the larger features of a rock mass, such as bedding, foliation, jointing, cleavage, or brecciation; also the sum total of such features as contrasted with texture. Also, in a broader sense, it refers to the structural features of an area such as anticlines or synclines. (7) See also Soil structure. Subsidence: The downward displacement of the overburden (rock or soil, or both) lying above an underground excavation or adjoining a surface excavation. Also the sinking of a part of the Earth’s crust. (7) Subsoil: In general concept, that part of the soil below the depth of plowing. (2) Summation curve, particle size: A curve showing the accumulative percentage by weight of particles within increasing (or decreasing) size limits as a function of diameter; the percent by weight of each size fraction is plotted accumulatively on the ordinate as a function of the total range of diameter represented in the sample plotted on the abscissa. (1) Swelling pressure: Pressure exerted by confined swelling clays when moisture content is increased. (6) Surface sealing: The orientation and packing of dispersed soil particles in the immediate surface Tamper: A heavy cylindrical metal section of tubing that is operated on a wire rope or cable. It slips over the riser and fits inside the casing or borehole annulus. It is generally used to tamp annular sealants or filter pack materials into place and prevent bridging. (9) Target: In detection monitoring programs, the ground-water flow path from a particular area or facility into which monitoring wells will be screened. The target monitoring zone should be a stratum (strata) in which there is a reasonable expectation that a vertically placed well will intercept migrating contaminants. Target monitoring zone: The ground-water flow path from a particular area or facility into which monitoring wells will be screened. The target monitoring zone should be a stratum (strata) in which there is a reasonable expectation that a vertically placed well will intercept migrating contaminants. (9) Tedlar® bags: Gas-tight bags constructed of non-reactive material (Tedlar) for the collection and transport of gas/ vapor samples. Tensile strength (unconfined or uniaxial tensile strength): The load per unit area at which an unconfined

Strength: Maximum stress which a material can resist without failing for any given type of loading. (7)

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APPENDIX A1 GLOSSARY

cylindrical specimen will fail in a simple tension (pull) test. (5) Tensiometer: A device for measuring the negative pressure (or tension) of water in soil in situ; a porous, permeable ceramic cup connected through a tube to a manometer or vacuum gauge.

extract must be passed through silica gel to remove the non-petroleum fraction of the hydrocarbons. The comparable SW-846 method is 8440 which uses perchlorethane (PCE) as an IR solvent instead of Freon-113.

Tension, soil water: The expression, in positive terms, of the negative hydraulic pressure of soil water. (2)

Transmissivity: The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of an aquifer under a unit hydraulic gradient. It equals the hydraulic conductivity multiplied by the aquifer thickness.

Test pit: A shallow excavation made to characterize the subsurface. (9)

Transpiration: Water loss from leaves and other plant organs to the atmosphere. (6)

Thin-walled tube samplers: A thin-walled non-sealed soil sampling tool used to collect undisturbed soil samples. Used in unconsolidated fine sands, silt, and clay. Larger diameter thin-walled tube samplers are referred to as Shelby tubes.

Tremie pipe: A flexible or rigid pipe used to convey grout to the bottom of a boring or probe hole.

Time series: A series of statistical data collected at regular intervals of time; a frequency distribution in which the independent variable is time. Total petroleum hydrocarbons (TPH): A measure of the concentration or mass of petroleum hydrocarbon constituents present in a given amount of soil or water. The term “total” is a misnomer; few, if any, of the procedures for quantifying hydrocarbons are capable of measuring all fractions of petroleum hydrocarbons present in the sample. Volatile hydrocarbons are usually lost in the process and not quantified, and some non-petroleum hydrocarbons are sometimes included in the analysis. Total pressure: The pressure (positive or negative), relative to the external gas pressure on the soil water, to which a pool of pure water must be subjected in order to be in equilibrium through a semipermeable membrane with the soil water. Total pressure is thus equal to the sum of soil water pressure and osmotic pressure. Total pressure may also be derived from the measurement of the partial pressure of the water vapor in equilibrium with the soil water. May be identified with the total potential defined above when gravitational and external gas pressure potentials can be neglected. Total recoverable petroleum hydrocarbons (TRPH): A U.S. EPA method (418.1) for measuring petroleum hydrocarbons in samples of soil or water. Hydrocarbons are extracted from the sample using a chlorofluorocarbon solvent (typically Freon-113) and quantified by infrared spectrophotometry. The method specifies that the

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Triaxial compression: Compression caused by the application of normal stresses in three perpendicular directions. (7) Triaxial shear test (triaxial compression test): A test in which a cylindrical specimen of soil or rock encased in an impervious membrane is subjected to a confining pressure and then loaded axially to failure. (5) Tuff: Volcanic ash usually more or less stratified and in various states of consolidation. (1) Ultimate bearing capacity: The average load per unit of area required to produce failure by rupture of a supporting soil or rock mass. (5) Ultraviolet radiation: Electromagnetic radiation with wave lengths less than visible light but greater than x-rays. Unconfined aquifer: An aquifer in which there are no confining beds between the capillary fringe and land surface, and where the top of the saturated zone (the water table) is at atmospheric pressure. Unconsolidated-undrained test (quick test): A soil test in which the water content of the test specimen remains practically unchanged during the application of the confining pressure and the additional axial (or shearing) force. (5) Undisturbed sample: A soil sample that has been obtained by methods in which every precaution has been taken to minimize disturbance to the sample. (5) Uniaxial (unconfined) compression: Compression caused by the application of normal stress in a single direction. (7)

APPENDIX A1 GLOSSARY

Uniformity coefficient: The size ratio of the 60% finer (d-60) grain size to the 10% (d-10) finer grain size of a sample of granular material (refer to ASTM Standard Test Method D 2487). (9) Uniformly graded: A quantitative definition of the particle size distribution of a soil which consists of the majority of particles being of the same approximate diameter. A granular material is considered uniformly graded when the uniformity coefficient is less than about 5 (refer to ASTM Standard Test Method D 2487). Analogous with the geologic term well sorted. (9) Unsaturated flow: The movement of water in a soil that is not filled to capacity with water. (1) Unsaturated zone: The zone between land surface and the capillary fringe within which the moisture content is less than saturation and pressure is less than atmospheric. Soil pore spaces also typically contain air or other gases. The capillary fringe is not included in the unsaturated zone.

contain air or other gases. The capillary fringe is included in the vadose zone. Vane shear test: An in-place shear test in which a rod with thin radial vanes at the end is forced into the soil and the resistance to rotation of the rod is determined. (5) Vapor pressure: (1) The pressure exerted by a vapor in a confined space. It is a function of the temperature. (2) The partial pressure of water vapor in the atmosphere. (c) Partial pressure of any liquid. (3) Also, the force per unit area exerted by a vapor in an equilibrium state with its pure solid, liquid, or solution at a given temperature. Vapor pressure is a measure of a substance’s propensity to evaporate. Vapor pressure increases exponentially with an increase in temperature. (2) Vented cap: A cap with a small hole that is installed on top of the riser. (9)

Upgradient: The direction of increasing static (potentiometric) head.

Vibratory head: An assembly made of hydraulically operated vibrators that clamp onto DP rods. High-frequency vibration helps advance DP rods in fine-grained soil. Usually accompanied by simultaneously applying pressure to the DP rods.

Uplift: The hydrostatic force of water exerted on or underneath a structure, tending to cause a displacement of the structure. (7)

Viscosity: The cohesive force existing between particles of a fluid which causes the fluid to offer resistance to a relative sliding motion between particles. (2)

Upper confidence limit: (UCL) An estimate of the upper bound for the true concentration (or other parameters) with specified level of confidence (e.g., 96%), Taken together with the lower confidence limit, it forms a confidence interval for the estimate with confidence level that accounts for both tail areas (e.g., 90%).

Void ratio: The ratio of: (a) the volume of void space, to (b) the volume of solid particles in a given soil mass.

Upper detection limit: The largest concentration that an instrument can reliably detect. Upper prediction limit: (UPL) A statistical estimate of the maximum concentration that will not be exceeded by the next series of k measurements from that distribution, or the mean of m new measurements for each of k sampling locations, with specified level of confidence (e.g., 95%) based on a sample of n background measurements. Uppermost aquifer: The geologic formation nearest the natural ground surface that is an aquifer, as well as lower aquifers that are hydraulically interconnected with this aquifer within the facility's property boundary. Vadose zone: The zone between land surface and the water table within which the moisture content is less than saturation (except in the capillary fringe) and pressure is less than atmospheric. Soil pore spaces also typically

Voids: Entities interconnected with each other through voids of dissimilar size and shape, through narrow necks, or through intersection with voids of similar size and shape. (4) Volatilization: The process of transfer of a chemical from the aqueous or liquid phase to the gas phase. Solubility, molecular weight, and vapor pressure of the liquid and the nature of the gas-liquid interface affect the rate of volatilization. Volumetric shrinkage (volumetric change): The decrease in volume, expressed as a percentage of the soil mass when dried, of a soil mass when the water content is reduced from a given percentage to the shrinkage limit. (5) Washout nozzle: A tubular extension with a check valve utilized at the end of a string of casing through which water can be injected to displace drilling fluids and cuttings from the annular space of a borehole. (9) Water content: The amount of water lost from the soil upon drying to a constant weight at 105 degrees Centigrade; expressed either as the weight of water per unit weight of dry soil or as the volume of water per unit bulk

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APPENDIX A1 GLOSSARY

volume of soil. The relationships between water content and soil water pressure can be referred to as the soil moisture characteristic curve. Depending upon whether the curve is determined with decreasing or increasing water content one may designate it as a desorption or adsorption curve, respectively. Water in soil is subject to several force fields originating from: the presence of the soil solid phase; the dissolved salts; the action of external gas pressure; and, the gravitational field. These effects may be quantitatively expressed by assigning an individual component potential to each. The sum of these potentials is designated the total potential of soil water and may be identified with the partial specific Gibb’s free energy of the soil water relative to free pure water at the same temperature. It should be noted that soil water is understood to be the equilibrium solution in the soil; pure water refers to the chemically pure compound. (1) Water table: The ground-water surface in an unconfined aquifer at which the pressure is equal to that of the atmosphere; the surface between the zone of saturation and the zone of aeration. (9). The upper surface of ground water or that level below which the soil is saturated with water; locus of points in soil water at which the hydraulic pressure is equal to atmospheric pressure. (1) Water-cement ratio: The amount of mixing water in gallons used per sack of cement. (9)

Well screen: A filtering device used to retain the primary or natural filter pack; usually a cylindrical pipe with openings of a uniform width, orientation, and spacing. (9) Well screen jetting (hydraulic jetting): When jetting is used for development, a jetting tool with nozzles and a high pressure pump is used to force water outwardly through the screen, the filter pack, and sometimes into the adjacent geologic unit. (9) Yield stress: The stress beyond which the induced deformation is not fully annulled after complete destressing. (7) Zero air: Atmospheric air that has been purified to contains less than 0. 1 ppm total hydrocarbons. Zero air voids curve (saturation curve): The curve showing the zero air voids unit weight as a function of water content. (1) Zone of aeration: That part of the ground in which the voids are not continuously saturated. (1) Zone of saturation: A hydrologic zone in which all the interstices between particles of geologic material or all of the joints, fractures, or solution channels in a consolidated rock unit are filled with water under pressure greater than that of the atmosphere. (9) SOURCES

Water-holding capacity: The smallest value to which the water content of a soil or rock can be reduced by gravity drainage. (5) Water-retention curve: See Moisture-retention curve. Weathering: All physical and chemical changes produced in rocks, at or near the Earth’s surface, by atmospheric agents. (1) The process during which a complex compound is reduced to its simpler component parts, transported via physical processes, or biodegraded over time. Weep hole: A small diameter hole (usually 1/4 in.) drilled into the protective casing above the ground surface to allow drainage from excess water traped between the outer protective casing and riser. Well completion diagram: A record that illustrates the details of a well installation. (9)

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(1) Soil Science Society of America. 1975. Glossary of Soil Science Terms. Madison, Wisconsin. 35 pp. (2) Small Scale Waste Management Project (SSWMP). 1978. Management of Small Waste Flows. EPA 600/2-78-173, U.S. Environmental Protection Agency, Cincinnati, Ohio. 764 pp. (3) Soil Conservation Service. 1977. Glossary of Selected Geologic and Geomorphic Terms. Western Technical Service Center, Portland, Oregon. 24 pp. (4) Brewer, R. 1976. Fabric and Mineral Analysis of Soils. R.E. Krieger Publishing Co., Huntington, New York. 482 pp. (5) ASTM Committee D-18. 1979. Tentative Definitions of Terms and Symbols Relating to Soil Mechanics, ASTM D 653-42T. Annual Book of ASTM Standards, Part 19, Amer. Soc. for Testing and Materials, Philadelphia, Pennsylvania. (6) Institution of Civil Engineers. 1976. Manual of Applied Geology for Engineers. Institution of Civil Engineers, London. 378 pp.

APPENDIX A1 GLOSSARY

(7) International Society for Rock Mechanics. 1972. Final Document on Terminology, English Version. Comm. on Terminology, Symbols and Graphic Representation. 19 pp. (8) Taylor, Donald W. 1948. Soil Mechanics. John Wiley and Sons, Inc. 700 pp. (9) ASTM Committee D-18. 1990. D5092 Annual Book of ASTM Standards, Part 19, Amer. Soc. for Testing and Materials, Philadelphia, Pennsylvania. (10) Nonaqueous Phase Liquids, 1991. EPA Groundwater Issue paper EPA/540/4-91-002.

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APPENDIX B1-KEY ELEMENTS

APPENDIX B1

KEY ELEMENTS FOR THE DEVELOPMENT OF PHASE I HYDROGEOLOGICAL INVESTIGATION REQUEST FOR PROPOSAL

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APPENDIX B1-KEY ELEMENTS

PURPOSE: The purpose of this document is to highlight the key elements to be included in a Phase I Hydrogeologic Investigation Request for Proposal (RFP). The goal of the Phase I investigation would be to define the field work necessary for completion of a ground-water monitoring system. SCOPE: The following list itemizes the recommended contents of an RFP for a standard Phase I Hydrogeologic Investigation leading toward development of a ground-water monitoring system. The more extensive Phase I study for remedial investigations of greenfield siting is not addressed in the scope of this document. INTRODUCTION: An actual RFP must reflect site-specific details. For instance, a greenfield study would include a search for all items on the list. Where a facility already exists, the list must be modified to exclude existing information from the scope of work. In this case, the RFP would include (1) a summary of existing and reviewed data in the introduction and (2) a task to verify any existing data that cannot be substantiated by the current documentation. Where previous geotechnical and/or hydrogeological investigations have been conducted, it is recommended that these studies be reviewed prior to developing the RFP. These documents can direct the scope of further investigations and enhance or supplement available site information. KEY ELEMENTS: The following list presents the key components of a Phase I RFP. In the actual preparation of an RFP, it may not be necessary to include the rationale for an objective or task. However, the consultant and the WMNA/EMD project manager should state in a clear and concise manner the reasons for each component of the RFP. •

OPENING STATEMENT Invite a firm to develop a proposal to do the work specified in the scope of work to follow. The opening statement should provide details on the following items: a. b. c. d.

•

Introductory paragraph Summary of the RFP tasks Deadline dates and submittal locations Client staff responsible for the work

INTRODUCTION a. b. c.

Describe site location and physical features Summarize known geology/hydrogeology Summarize existing wells, borings, piezometers, test pits, etc.

Rationale: To provide the potential firm with a general idea of the physical setting and known site characteristics significant to understanding the scope of work. •

SCOPE OF WORK a.

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Project Objectives

APPENDIX B1-KEY ELEMENTS

Provide project objectives prior to describing tasks. The following statements are the primary objectives of a Phase I study: 1. Develop an understanding of the regional and site-specific geology and hydrogeology as understood by the existing literature. 2. Determine if and how the potential for leachate migration from the site might impact ground water. 3. Develop a preliminary conceptual model of the hydrogeological system. 4. Determine the scope of work for a Phase II study. Rationale: Project objectives provide direction for the individual tasks itemized in the scope of work. b.

Project Tasks

List project tasks in logical order. The following discussions present the primary Phase I tasks: Task 1: Literature Review –– Conduct a detailed literature review of regional and site-specific (if any) geology, hydrogeology and surface water hydrology. Key data to recover, if available include: Land Use –– Topographic maps, air photos Climatology –– Ten-year average annual temperature and precipitation and seasonal variations; landfill water balance Surface Water Hydrology –– Drainage patterns, runoff volumes, delineation of the 100-year flood plain Geology –– Soils maps, geologic maps, stratigraphic column Hydrogeology –– Area boring/coring logs, cross-sections or regional stratigraphic columns illustrating hydrostratigraphic units, isopach of uppermost aquifer and significant confining units, regional averages and previously defined site-specific values for hydraulic conductivity, transmissivity, storage coefficient or specific yield, thickness of uppermost aquifer and confining unit(s), gradient, flow direction, recharge source, general water quality (i.e., background), surface-water/ground-water interrelationships Rationale: The literature review for the above listed data will (1) identify potential hydrogeologic complexities and contingencies that may require further analysis in later phased investigations and (2) provide the basis for the development of the field work in a Phase II investigation. Task 2: Conduct a site reconnaissance to identify significant surface characteristics, structural features, surface drainage, erosional conditions and vegetation. Rationale: This information is basic to an evaluation of the site-specific geology, hydrogeology and surface water hydrology. Task 3: Conduct a well inventory of all wells within a one-half-mile radius of the site. The inventory should include the following data if they exist: well locations, owner’s name, total depth, aquifer tapped, depth of water, pumping rates and water quality. Conduct an integrity check of existing site piezometers and monitoring wells. This check should include water level measurements. Rationale: This data are used to assess the potential impact of leachate migration and to determine adequacy of existing monitoring wells and/or piezometers.

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APPENDIX B1-KEY ELEMENTS

Task 4: Assimilate data recovered in Tasks 1 to 3 to develop the following items (if not already available): (1) site or regional topographic map; (2) description of the depositional history of the area; (3) delineation of uppermost aquifer and significant confining units in cross-sections or fence diagrams (as necessary); (4) estimates of flow paths, gradients and potential directions; and (5) description of water quality and water levels. Rationale: These tools are used to define a conceptual model of the hydrogeologic regime. Task 5: Develop a preliminary conceptual model of the hydrogeologic regime. Rationale: A conceptual model is a picture or description of the physical system that the geohydrologist forms in his/her mind. Developing such a picture is essential to fully understanding potential ground-water flow paths and, hence, determine appropriate locations for exploratory boreholes, piezometers and monitoring wells. The key to developing a conceptual model is to incorporate the essential features of the physical system under study. With this constraint, the conceptualization is tailored to an appropriate level of detail or sophistication for the problem under study (i.e., detection versus assessment or RI). Task 6: Prepare a clear, comprehensive report. The Phase I report is to include the purpose of the investigation (objectives), the scope (tasks), summary of results, conclusions, recommendations and the data in appendices. This report should not exceed 30 pages in length. Task 7: Prepare the scope of work for the Phase II investigation* using the preliminary conceptual model and data developed in this Phase I study as an appendix to the Phase I report. Rationale: The technical comprehensiveness and adequacy of the existing information recovered in the Phase I determines the need for or the extent of a Phase II study.

*In cases where the hydrogeology is relatively noncomplex, a monitoring system can be designed solely on the basis of the Phase I investigative results.

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

APPENDIX B2

EXAMPLE OF A 2003 STATEMENT OF WORK FOR A REMEDIAL INVESTIGATION AND FEASIBILITY STUDY WHERE RISK ASSESSMENT IS AN IMPORTANT PART OF THE EVALUATION FOR AN INDUSTRIAL SITE

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

STATEMENT OF WORK FOR A REMEDIAL INVESTIGATION AND FEASIBILITY STUDY AT THE EXAMPLE INDUSTRIAL SITE

PURPOSE:

The purpose of this Statement of Work (SOW) is to set forth requirements for the preparation of an initial report and Work Plan evaluating and proposing interim actions at the Example Industrial Park Site (“the Site”) for water supply alternatives and for the preparation of a streamlined Remedial Investigation (RI) and Feasibility Study (FS). The RI shall evaluate the nature and extent of contamination at and from the Site, which includes source area control and ground-water assessment and shall assess the risk from this contamination on human health and the environment. The FS shall evaluate alternatives for addressing the impact to human health and the environment from the contamination at the Site and nearby areas. The RI and FS Reports shall be conducted, at a minimum, consistent with the “Guidance for Conducting Remedial investigations and Feasibility Studies Under CERCLA” (U.S. EPA, Office of Emergency and Remedial Response, October, 1988) and any other guidance that U.S. EPA uses to conduct an RI/FS, as well as any additional requirements in the Administrative Order on Consent (AOC). All documents or deliverables required as part of this SOW shall be submitted to U.S. EPA, with a copy to the Illinois Environmental Protection Agency (Illinois EPA), for review and approval by U.S. EPA, in consultation with Illinois EPA. The PRPs shall furnish all personnel, materials and services necessary for or incidental to, performing the RI/FS at the Site, except as otherwise specified herein.

At the completion of the RI/FS, U.S. EPA, in consultation with Illinois EPA, will be responsible for the selection of a Site remedy or remedies and will document this remedy selection in a Record of Decision (ROD). The remedial actions selected by U.S. EPA will meet the cleanup standards specified in CERCLA Section 12 1. That is, the selected remedial actions will be protective of human health and the environment, will be in compliance with or include a waiver of, applicable or relevant and appropriate requirements of other laws, will be cost effective, will use permanent solutions and alternative treatment technologies or resource recovery technologies to the maximum extent practicable and will address the statutory preference for treatment as a principal element. The final RI and FS Reports as adopted by U.S. EPA will, with the administrative record, form the basis for the selection of the Site remedies and will provide the information necessary to support the development of the record of decision (ROD).

As specified in CERCLA Section 104(a)(1), as amended by SARA, U.S. EPA will provide oversight of the PRPs' activities throughout the RI/FS, including all field sampling activities. The PRPs will support U.S. EPA’s initiation and conduct of activities related to the implementation of oversight activities.

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

SCOPE:

The tasks to be completed as part of this RI/FS are:

Task 1: Evaluating and Proposing Interim. Actions Task 2: R1/FS Work Plan Task 3: Additional Site-Specific Plans Task 4: Treatability Studies Task 5: Monthly Progress Reports

TASK 1: EVALUATING AND PROPOSING INTERIM ACTIONS

The PRPs shall prepare and submit a report to U.S. EPA and Illinois EPA evaluating and proposing water supply alternatives. The report shall also outline efforts associated with the abandonment of groundwater wells and simultaneously conducting a residential vapor intrusion study. The PRPs shall also submit a residential vapor intrusion study proposal that should include modeling using ASTM model 1739-95, soil gas sampling and indoor air sampling. Upon approval of the interim actions report, the PRPs shall prepare and submit a Work Plan detailing the activities associated with providing alternative water supply, abandonment of ground-water wells and conducting a residential vapor intrusion study.

TASK 2: RIMS WORK PLAN

The PRPs shall prepare and submit a RI/FS Work Plan within 120 calendar days from the effective date of the AOC. The PRPs shall use information from the existing information/documents, appropriate U.S. EPA guidance and technical direction provided by the U.S. EPA Remedial Project Manager (RPM) as the basis for preparing the RI/FS Work Plan. If U.S. EPA disapproves of or requires revisions to the RI/FS Work Plan, in whole or in part, the PRPs shall amend and submit to U.S. EPA a revised Work Plan which is responsive to the directions in all U.S. EPA comments, within 21 days of receiving U.S. EPA’s comments. The RI/FS work must be coordinated and properly sequenced with the U.S. EPA. The PRPs shall submit duplicate copies of the Work Plan to the U.S. EPA RPM and the Illinois Project Manager.

The RI/FS Work Plan shall include a comprehensive description of project tasks, the procedures to accomplish them, project documentation and project schedule. PRPs shall use their quality assurance/quality control (QA/QQ) systems and procedures to assure that the work plan and other deliverables are of professional quality requiring only minor revisions. Specifically, the Work Plan shall include the following elements:

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

Identification of RI/FS project elements and the associated tasking including review of site documentation; previous field sampling and analysis activities, data gap description and treatability study activities. Output of this task will be a detailed work breakdown structure of the RI/FS project.

The PRPs's technical approach to each task to be performed, including a detailed description of each task; the assumptions used; any information to be produced during and at the conclusion of each task; and a description of the work products that will be submitted to U.S. EPA. Information shall be presented in a sequence consistent with the SOW.

A schedule with specific dates for completion of each required activity and submission of each deliverable required by the SOW. This schedule shall also include information regarding timing, initiation and completion of all critical path milestones for each activity and deliverable and the expected review time for the U.S. EPA.

A list of key personnel providing support on the work assignment.

2.1 Health and Safety Plan. Prepare a site-specific HASP that specifies employee training, protective equipment, medical surveillance requirements, standard operating procedures and a contingency plan in accordance with 40 CFR 300.150 of the NCP and 29 CFR 1910.1201(1) and (1)(2) and U.S. EPA’s OSHA Manual. A task-specific HASP must also be prepared to address health and safety requirements for site visits.

2.2 Quality Assurance and Sampling. The PRPs shall prepare a Quality Assurance Project Plan (QAPP) in accordance with EPA QA/R-5 (latest draft or revision). The QAPP shall describe the project objectives and organization, functional activities and quality assurance/quality control (QA/QC) protocols that shall be used to achieve the desired Data Quality Objectives (DQOs). The DQOs shall, at a minimum, reflect use of analytical methods for identifying contamination and addressing contamination consistent with the levels for remedial action objectives identified in the National Contingency Plan. The QAPP developed for the RI/FS should be referenced or adapted whenever possible when preparing the QAPP for the RI/FS. The PRPs shall also prepare a Field Sampling Plan (FSP) that defines the sampling and data collection methods that shall be used for the project. The FSP shall include sampling objectives; sample locations and frequency; sampling equipment and procedures; sample handling and analysis; and a breakdown of samples to be analyzed through the Contract Laboratory Program (CLP) and through other sources, as well as the justification for those decisions. The FSP shall consider the use of all existing data and shall justify the need for additional data whenever existing data will meet the same objective. The FSP shall be written so that a field sampling team unfamiliar with the site would be able to gather the samples and field information required. The PRPs shall document any required changes to the FSP in a memorandum to the RPM.

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

2.3. Report. The RI Report will be developed in three primary phases: the Phase I Technical Memorandum, the Phase II Technical Memorandum and the Risk Assessment Report.

2.3.1 Phase I Technical Memorandum. PRPs shall submit to U.S. EPA for approval (with a copy to Illinois EPA) a Phase I Technical Memorandum. The first phase of investigation will be carried out to characterize the physical and chemical aspects of contaminated ground water and of soil and sediment contaminant source areas. The investigation of these source areas will involve obtaining data related to: characteristics (e.g., type, quantity, chemical and physical properties and concentrations) of on-site soils and sediments.

This information will be obtained from a combination of existing site information, field inspections and site sampling activities. The source characterization will culminate in the preparation and submittal of a Technical Memorandum for the Phase I investigation activities. This Technical Memorandum will summarize the findings of the source characterization and may be used to refine the scope of the Phase II investigation activities outlined below.

The PRPs shall complete site characterization within 21 days of U.S. EPA's approval or modification of the Work Plan and sampling and analysis plans. PRPs shall provide U.S. EPA with analytical data within 21 days of each sampling activity, in a electronic format (i.e., computer disk) showing the location, medium and results. Within 7 days of completion of field activities, PRPs shall notify U.S. EPA in writing.

2.3.2 Phase II Technical Memorandum. PRPs shall submit to U.S. EPA for approval (with a copy to IEPA) a Phase II Technical Memorandum. The second phase of investigation will consist of a migration pathway assessment. The potential migration pathways at the site consist of groundwater. The migration pathway assessment will culminate in the preparation and submittal of a Phase II Technical Memorandum describing the findings of the Phase II investigations.

2.3.3 Risk Assessment Reports. The Risk Assessment will determine whether site contaminants pose a current of potential risk to human health and the environment in the absence of any remedial action. The PRPs shall address the contaminant identification, exposure assessment, toxicity assessment and risk characterization. The Risk Assessment will be used to determine whether remediation is necessary at the site, provide justification for performing remedial action and determine what exposure pathways need to be remediated.

2.3.3.1 Human Health Risk Assessment Report. The human health risk assessment shall focus on actual and potential risks to persons coming into contact with on-site contaminants as well as risks to the nearby residential and industrial worker populations from exposure to contaminated soils, sediments, surface water, air and ingestion of contaminated organisms in nearby, impacted ecosystems. Central tendency

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

and reasonable maximum estimates of exposure shall be defined for current land use conditions and reasonable future land use conditions. The risk assessment shall use data from the Site and nearby areas to identify the contaminants of concern (COC), provide an estimate of how and to what extent human receptors might be exposed to these contaminants and provide an assessment of the health effects associated with these contaminants. The evaluation shall project the potential risk of health problems occurring if no cleanup action is taken at the Site and/or nearby areas and establish target action levels for COCs (carcinogenic and non-carcinogenic).

The risk evaluation shall be conducted in accordance with U.S. EPA guidance including, at a minimum: “Risk Assessment Guidance for Superfund (RAGS), Volume I - Human Health Evaluation Manual (Part A),” “Interim Final (EPA-540-1-89-002),” OSWER Directive 9285.7-OIA; December 1, 1989; and “Risk Assessment Guidance for Superfund (RAGS), Volume I ~ Human Health Evaluation Manual (Part D, Standardized Planning, Reporting and Review of Superfund Risk Assessments),” Interim, (EPA 540-R-97-033), OSWER 9285.7-01D, January, 1998.

The human health risk assessment shall also include the following elements: •

• • • • • •

Hazard Identification (sources). The PRPs shall review available information on the hazardous substances present at the Site and nearby areas and identify the major COCs. COCs should be selected based on their detected concentrations and intrinsic toxicological properties. Conceptual Site Model and Exposure/Pathway Analysis. Characterization of Site and Potential Receptors. Exposure Assessment. PRPs shall develop central tendency and reasonable maximum estimates of exposure for current and potential land use conditions. at and near the Site. Toxicity Assessment Risk Characterization. Identification of Limitations/Uncertainties.

2.3.3.2 Ecological Risk Assessment Report. The ecological risk assessment shall be conducted in accordance with U.S. EPA guidance including, at a minimum: "Ecological Risk Assessment Guidance for Superfund, Process for Designing and Conducting Ecological Risk Assessments," (EPA-540-R-97006, June 1997), OSWER Directive 9285.7-25. The ecological risk assessment shall describe the data collection activities conducted as part of Task I (B)(vi) as well as the following information: • • • •

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Hazard Identification (sources). The PRPs shall review available information on the hazardous substances present at and adjacent to the Site and identify the major COCs. Dose-Response Assessment. COCs should be selected based on their intrinsic toxicological properties. Preparation of Conceptual Exposure/Pathway Analysis. Characterization of Site and Potential Receptors.

EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

•

•

•

•

•

2.4

Selection of Chemicals, Indicator Species and End Points. In preparing the assessment, the PRPs shall select representative chemicals, indicator species (species that are especially sensitive to environmental contaminants) and end points on which to concentrate. Exposure Assessment. The exposure assessment will identify the magnitude of actual exposures, the frequency and duration of these exposures and the routes by which receptors are exposed. The exposure assessment shall include an evaluation of the likelihood of such exposures occurring and shall provide the basis for the development of acceptable exposure levels. Toxicity Assessment/Ecological Effects Assessment. The toxicity and ecological effects assessment will address the types of adverse environmental effects associated with chemical exposures, the relationships between magnitude of exposures and adverse effects and the related uncertainties for contaminant toxicity (e.g., weight of evidence for adverse effects). Risk Characterization. During risk characterization, chemical-specific toxicity information, combined with quantitative and qualitative information from the exposure assessment, shall be compared to measured levels of contaminant exposure levels and the levels predicted through environmental fate and transport modeling. These comparisons shall determine whether concentrations of contaminants at or near the Site are affecting or could potentially affect the environment. Dentification of Limitations/Uncertainties. The PRPs shall identify critical assumptions (e.g., background concentrations and conditions) and uncertainties in the report.

FS Report. Within 60 calendar days after written approval of the RI report or upon such alternative time as requested by PRPs and approved by U.S. EPA, the PRPs shall submit to U.S. EPA for approval (with a copy to IEPA) a draft FS Report consisting of a detailed analysis of alternatives and cost-effectiveness analysis in accordance with NCP 300.68(h)(3)(1)(2). The FS report shall contain (1) a summary of alternative remedial actions in accordance with Chapter 3, NCP 300.68(h)(3)(1)(2)(A); (2) Cost Analysis in accordance with Chapter 7, NCP 300.68(h)(3)(1)(1)(B); (3) Institutional analysis in accordance with Chapter 4, NCP 300.68(h)(3)(1)(2)(C); (4) Public-health analysis in accordance with Chapter 5, NCP 300.68(h)(3)(I)(2)(D); (5) Environmental analysis in accordance with Chapter 6, NCP 300.68(h)(3)(I)(2)(E). The FS Report will be developed in three primary phases: the Remedial Alternatives Technical Memorandum, the Remedial Alternatives Evaluation and the draft FS Report.

2.4.1 Remedial Alternatives Technical Memorandum. PRPs shall submit to U.S. EPA for approval (with a copy to IEPA) a Remedial Alternatives Technical Memorandum. The Remedial Alternatives Technical Memorandum shall develop an appropriate range of waste management options that will be evaluated through the development and screening of alternatives. PRPs shall identify remedial action objectives, summarize the development and screening of remedial alternatives and include an alternatives array document.

2.4.2 Remedial Alternatives Evaluation. PRPs shall submit to U.S. EPA for approval (with a copy to IEPA) a Remedial Alternatives Evaluation. The preliminary list of alternatives to address soil, sediments surface water, ground water and air contamination at the Site and nearby areas shall consist of, but is not limited to, treatment technologies (i.e., thermal methods), removal and off-site treatment/disposal, removal and on-site disposal and in-place containment for soils, sediments and wastes.

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

Based on the analysis of the nature and extent of contamination and on the cleanup objectives developed in the previous sections, a limited number of alternatives appropriate for addressing the remedial action objectives shall be identified and assessed. The limited number of alternatives identified shall be a result of a preliminary screening and evaluation of the larger set of remedial alternatives initially identified. The limited number of alternatives shall include a “no-action alternative.” Whenever practicable, the treatment over conventional containment or land disposal approaches.

The use of presumptive remedy guidance, if appropriate and applicable to any of the disposal areas of the Site, may also provide an immediate focus to the identification and analysis of alternatives. This guidance includes, but is not limited to: “Implementing Presumptive Remedies” (EPA 540-R-97-029, October 1997). Presumptive remedies involve the use of remedial technologies that have been consistently selected at similar sites or for similar contamination.

The limited number of alternatives selected for detailed analysis, including any identified presumptive remedies, shall be described with enough detail so that the entire treatment process can be understood. Technologies that may apply to the media or source of contamination shall be listed in the RI/FS Report.

TASK 3: ADDITIONAL SITE-SPECIFIC PLANS

3.1 Develop Site Management Plan. After the U.S. EPA approval of the RI/FS Work Plan, the PRPs shall prepare a Site Management Plan (SMP) 30 days after RI/FS Work Plan approval that provides U.S. EPA with a written understanding of how access, security, contingency procedures, management responsibilities and waste disposal are to be handled.

3.1.1 Develop Pollution Control and Mitigation Plan. PRPs shall prepare a Pollution Control and Mitigation Plan that outlines the contaminants or pollutants are not released off-site during theprocess, procedures, and safeguards that will be used to ensure implementation of the RI.

3.1.2 Develop Transportation and Disposal Plan (Waste Management Plan). PRPs shall prepare a Transportation and Disposal Plan that outlines how wastes that are encountered during the RI will be managed and disposed of. The PRPs shall specify the procedures that will be followed when wastes will be transported off-site for storage, treatment, and/or disposal.

3.1.3 Data Management Plan. PRPs shall prepare a Data Management Plan that outlines the procedures for storing, handling, accessing, and securing data collected during the RI.

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

3.1.4 Develop Other Plan(s). PRPs shall develop other plans, as necessary, to implement the RA.

TASK 4: TREATABILITY STUDIES

Technologies that may be suitable to the Site should be identified as early as possible to determine whether there is a need to conduct treatability studies to better estimate costs and performance capabilities. At present, it is unknown whether a bench test or pilot study will be conducted. However, should a bench test or pilot study be determined as necessary, the PRPs shall submit a testing plan identifying the types and goals of the study. The treatability study shall determine the suitability of remedial technologies to site conditions and problems.

The three levels of treatability studies are laboratory screening, bench-scale testing, and pilot scale testing. The laboratory screening is used to establish the validity of a technology to treat waste and is normally conducted during the FS. Bench-scale testing is used to identify the performance of the technology specific to a type of waste for an operable unit. Often bench-scale tests are conducted during the FS. Pilot-scale testing is used to provide quantitative performance, cost, and design information for remediation and is typically performed during RI/FS (see the Fact Sheet, Guide for Conducting Treatability Studies Under CERCLA, November, 1993).

During treatability studies, PRPs shall provide U.S. EPA with the following deliverables:

4.1 Identification of Candidate Technologies Memorandum. This memorandum shall be submitted within 30 days after completion of field investigations. If U.S. EPA disapproves of or requires revisions to the technical memorandum identifying candidate technologies, in whole or in part, PRPs shall amend and submit to U.S. EPA a revised technical memorandum identifying candidate technologies which is responsive to the directions in all U.S. EPA comments, within 21 days of receiving U.S. EPA's comments.

4.2 Treatability Testing Statement of Work If U.S. EPA determines that treatability testing is required, within 30 days thereafter (or as specified by U.S. EPA), PRPs shall submit a Treatability Testing Statement of Work.

4.3 Treatability Testing Work Plan. Within 30 days of submission of the Treatability Testing Statement of Work, PRPs shall submit a Treatability Testing Work Plan, including a schedule. If U.S. EPA disapproves of or requires revisions to the Treatability Testing Work Plan, in whole or in part, PRPs shall amend and submit to U.S. EPA a revised Treatability Testing Work Plan which is responsive to the directions in all U.S. EPA comments, within 21 days of receiving U.S. EPA’s comments.

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

4.4 Treatability Study Sampling and Analysis Plan. Within 30 days of the identification of the need for a separate or revised QAPP or FSP, PRPs shall submit are Treatability Study Sampling and Analysis Plan. If U.S. EPA disapproves of or requires revisions to the Treatability Study Sampling and Analysis Plan, in whole or in part, PRPs shall amend and submit to U.S. EPA a revised Treatability Study Sampling and Analysis Plan which is responsive to the directions in all U.S. EPA comments, within 21 days of receiving U.S. EPA's comments.

4.5 Treatability Study Site Health and Safety Plan. Within 30 days of the identification of the need for a revised health and safety plan, PRPs shall submit a treatability study site health and safety plan.

4.6 Treatability Study Evaluation Report. Within 30 days of completion of any treatability testing, PRPs shall submit a Treatability Study Evaluation Report as provided in the Statement of Work and Work Plan. If U.S. EPA disapproves of or requires revisions to the Treatability Study Evaluation Report, in whole or in part, PRPs shall amend and submit to U.S. EPA a revised Treatability Study Evaluation Report which is responsive to the directions in all U.S. EPA comments, within 21 days of receiving U.S. EPA's comments.

TASK 5: MONTHLY PROGRESS REPORTS

The PRPs shall submit monthly written progress reports to U.S. EPA and Illinois EPA concerning actions undertaken pursuant to the AOC and this SOW, beginning 30 calendar days after the effective date of the AOC, until termination of the AOC, unless otherwise directed in writing by the RPM. These reports shall describe all significant developments during the preceding period, including the work performed and problems encountered, analytical data received during the reporting period, and developments anticipated during the next reporting period, including a schedule of work to be performed, anticipated problems, and actual or planned resolutions of past or anticipated problems.

Summary of Major Submittals for the Remedial Investigation/Feasibility (RI/FS) Study Example Industrial Site Illinois

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

DELIVERABLE

COPIES

SUBMITTAL DATE

Interim Actions Report

3

60 days after effective date of AOC

Residential Vapor Intrusion

3

60 days after effective date of AOC

3

30 days after approval of Interim Actions

Draft RI/FS Work Plan

3

120 days after effective date of AOC

Final RI/FS Work Plan

3

21 days after EPA comments

Health & Safety Plan

3

within 120 days after effective date of AOC

Field Sampling Plan

3

within 120 days after effective date of AOC

Quality Assurance & Analysis

3

within 120 days after effective date of AOC

3

45 days after approval of Risk Assessment

Phase I Tech. Memo

3

30 days after RI/FS Work Plan approval

Phase II Tech. Memo

3

60 days after RI/FS Work Plan approval

Human Health Risk Assessment

3

90 days after RI/FS Work Plan approval

3

90 days after RI/FS Work Plan approval

Feasibility Study Report

3

60 days after completion of RI

Remedial Alternatives Tech.

3

30 days after completion of field

Study Interim Action Work Plan Report

Plan Remedial Investigation (RI) Report

Report Ecological Risk Assessment Report

Memo

investigations

Remedial Alternatives Evaluation

3

30 days After approval of RA Tech Memo

Site Management Plan

3

30 days after approval of RI/FS Work Plan

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EXAMPLE RI/FS STATEMENT OF WORK-APPENDIX B2

Summary of Major Submittals for the Remedial Investigation/Feasibility (RI/FS) Study Example Industrial Park Illinois

DELIVERABLE Pollution control and Mitigation

COPIES

SUBMITTAL, DATE

3

30 days after approval of RI/FS Work Plan

Transportation and Disposal Plan-

3

30 days after approval of RI/FS Work Plan

Data Management Plan

3

30 days after approval of RI/FS Work Plan

Identification of Candidate

3

30 days after completion of field

Plan

Technologies Memorandum Treatability Testing Statement of

investigations 3

Work Treatability Testing Work Plan

30 days after completion of field investigations

3

30 days after approval of Treatability Testing Statement of Work

Treatability Study Sampling and

3

Analysis Plan Treatability Study Site Health

investigations 3

and Safety Plan Treatability Study Evaluation

B2-12

30 days after completion of field investigations

3

Report Monthly Progress Reports

30 days after completion of field

30 days after completion of field investigations

3

In accordance with the AOC

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

APPENDIX B3 MODEL STATEMENT OF WORK

PHASES I AND II

HYDROGEOLOGIC INVESTIGATION

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

MODEL STATEMENT OF WORK PHASES I AND II HYDROGEOLOGIC INVESTIGATION TABLE OF CONTENTS

1.0 1.1

INTRODUCTION PROJECT DESCRIPTION

2.0 2.1 2.2 2.3

PHASE I – DESK STUDY LITERATURE REVIEW – TASK 1 AIR PHOTO COVERAGE SURFACE WATER 2.3.1 2.3.2

2.4 2.5

100-Year Flood Zones Wetlands, Stream Flow and Runoff

CLIMATIC DATA GROUND WATER 2.5.1 2.5.2

Geology/Hydrogeology Well Inventory

2.6 2.7 2.8 2.9 2.10

SOILS AND VEGETATIVE COVER BASIC DATA CHECKLIST ENVIRONMENTAL REVIEW SITE VISIT – TASK 2 PHASE I REPORT PREPARATION – TASK 3

3.0 3.1 3.2 3.3 3.4

PHASE II – SUBSURFACE HYDROGEOLOGICAL INVESTIGATION INTRODUCTION GEOLOGICAL MAPPING – TASK 2-1 GEOPHYSICAL SURVEY – TASK 2-2 FIELD DRILLING PROGRAM – TASK 2-3 3.4.1 3.4.2 3.4.3 3.4.4

3.5 3.6 3.7 3.8

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Logging Test Holes Laboratory Tests – Task 2-4 Installation of Monitoring Wells and Piezometers – Task 2-5 Performance Tests – Task 2-6

FIELD ECOLOGICAL SURVEY – TASK 2-7 HISTORY AND ARCHAEOLOGY – TASK 2-8 PHASE II REPORT – TASK 2-9 REPORT PRESENTATION

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

MODEL STATEMENT OF WORK PHASES I AND II HYDROGEOLOGIC INVESTIGATION

1.0 INTRODUCTION The CLIENT is interested in receiving proposals for conducting preliminary engineering for the expansion of a solid waste landfill. Work will consist of two projects: (1) completion of a hydrogeologic investigation and (2) conceptual design of the sanitary landfill. This Request for Proposal (RFP) details the Scope of Work required to be addressed in the consultant’s proposal for the hydrogeologic investigation. 1.1 PROJECT DESCRIPTION [EMD Engineer fill in Site Description.]

GENERAL PHYSICAL FEATURES [General Physical Features.]

GENERAL GEOLOGY [General Geology, if known.]

HYDROGEOLOGY [General Hydrogeology, if known.]

The policy of THE CLIENT is to gather sufficient information to assess site hydrogeologic conditions, identify potential leachate pathways and select appropriate placement of monitoring wells capable of defining the landfill’s potential impact on the uppermost aquifer. This identification of ground-water pathways and the successful placement of monitoring wells in these pathways represent the main goal of a site hydrogeologic analysis.

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

A CLIENT’S hydrogeologic analysis is composed of a series of phases. This RFP for hydrogeologic investigations is similar to a performance specification where deliverables are well known and scheduled throughout the various phases of the study. The Phase I activities are primarily desk-based; summarizing literature, reports and raw data into a literature whole with a maximum length of 30 to 40 pages of main text. Supporting documentation should be placed in appendices.

2.0 PHASE I – DESK STUDY 2.1 LITERATURE REVIEW – TASK 1 Reviewing published literature and THE CLIENT data is always required in Phase I project execution. This review may put limits on the extent, depth and location of required borings and monitoring wells; define the type and number of soil and water quality analyses; and identify potential hydrogeologic complexities and contingencies that may require further analysis in later investigations. The latter may include the presence of faults, multiple and preexisting land uses, potential for reversing ground-water gradients, likelihood of variable background water quality and uncertain stratigraphy. THE CLIENT would expect that the literature will be sufficiently reviewed so that important information about the site will not go unnoticed. An important source of site information, in addition to appropriate state and federal agencies, is the THE CLIENT files of boring logs, engineering reports and drawings. It is expected that the consultant will avail himself of pertinent site data from our District Engineering files. 2.2 AIR PHOTO COVERAGE Photographs are available either as contact prints or enlargements at scales ranging from 1:20,000 to 1:4,000. Where the photographs have been taken with sufficient overlap, they may be used with a stereoscope to obtain a three-dimensional view of the terrain. We expect air photos to be obtained in stereo coverage for at least one date and preferably for numbers of dates, for a site that has numerous air photo flight dates. Two copies of the stereoscopic coverage photos should be submitted to THE CLIENT for distribution to District and Corporate CLIENT staff. 2.3 SURFACE WATER The surface-water hydrology baseline study will describe drainage systems, flow characteristics, water quality of streams and water bodies and aid in determining ground-water/surface-water relationships at the site. This information will document the baseline conditions and form the basis of assessing environmental impacts. 2.3.1 100-Year Flood Zones THE CLIENT’s policy is to avoid disposing of solid waste in areas subjected to flooding. State regulations require documentation that the proposed site will be above the 100-year flood zone. These data may be obtained by review of the most recent U.S. Geological Survey, Army Corps of Engineers or the Federal Insurance Administration 100-Year Frequency Floodplain Map for the area (if available). The consultant should prepare a site plan utilizing THE CLIENT’s most recent aerial topography to delineate areas subject to flooding during 100-year flood events. 2.3.2 Wetlands, Stream Flow and Runoff One of THE CLIENT’s most important environmental policies is the prevention of surface water pollution. This policy is directed at protection of wetlands and control of runoff from waste disposal areas into surface water bodies.

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

Consultants, therefore, must include on base maps locations of wetlands and all surface water found in the area of the proposed site within a one-half mile radius of the site’s boundary. As part of the available data assessment, stream and river flows — where monitored by state and federal agencies — should be documented in this report. The final goal of this section is to define, under state regulations, if the landfill is: a. b.

Located on a flood plain; and Located within 300 feet of any classified body of water.

2.4 CLIMATIC DATA In ground-water investigations, records of precipitation, temperatures, wind movement, evaporation and humidity may be essential or useful supplemental data. Climatic data are used primarily for estimating the seasonal variations and amounts of precipitation which may be available for ground-water recharge. The consultant should present precipitation (10-year average) and other pertinent climatological data, as required, to complete surface runoff calculations and landfill water budgets. 2.5 GROUND WATER THE CLIENT’s greatest environmental consideration in landfill siting is the regional and site-specific hydrogeology. The consultant must fully document that the landfill is sited in a manner which protects ground-water quality. The primary purposes of the ground-water study (existing data review) in Phase I is the following: •

Define and quantify, to the extent practical, the overall ground-water flow systems (occurrence, recharge, discharge, direction and rate of movement) at the site areas and the vicinity;

•

Define the present ground-water quality in the areas of concern;

•

Determine the maximum high ground-water table elevation; and

•

Evaluate the importance of the ground-water resource which might be affected by the operation of a landfill facility.

2.5.1 Geology/Hydrogeology This Phase I task requires that all available data are reviewed and assimilated into a report that describes the known regional geology and hydrogeology for the site area. Sections on regional geology and hydrogeology should contain all pertinent information on federal, state and university studies of the geology and hydrogeology for the site area. Maps should support the text with appropriate regional cross-sections. This Phase I review should set the stage for Phase II field tasks. The location and logs of existing test pits, borings or local water well logs should be included for supplemental information. Particular attention should be paid to primary sand and gravel recharge areas of significant ground water aquifers. 2.5.2 Well Inventory The locations of all wells (differentiated between public water, domestic, industrial and other) and springs should be shown on a base map with a scale of 1 inch = 500 feet within 2,000 feet of the property boundaries.

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

Supporting information on the proximity and withdrawal rates of users and the availability of alternative drinking water supplies must be included in the review documentation. The well inventory should include such available data as: location, owner, surface elevation, aquifer tapped, water quality, well depth, casing size and depth, depth to water, estimated rate of pumpage or use and date of inventory. 2.6 SOILS AND VEGETATIVE COVER Soil maps and reports are not usually as readily available as topographic and geologic maps and vary more widely with respect to the quantity and quality of the information they contain. Soil maps and reports supply information on soil characteristics and surface gradients which influence runoff and infiltration. The consultant should contact appropriate data sources and present a plan documenting site soil characteristics based upon readily available data. 2.7 BASIC DATA CHECKLIST The consultant should compile and present normally available data in published and unpublished reports and records as an aid in planning the data to be obtained by field investigations and tests. The following data list is suggested given the extent of existing readily available data. THE CLIENT requests that the consultant present the following noted data in the Phase I report. If additional data are obtained, the consultant should include it as appropriate. Phase I Basic Data Checklist A.

Maps, Cross-Sections and Fence Diagrams 1. 2. 3.

Planimetric Topographic Geologic (a) Structure (b) Stratigraphy (c) Lithology

4.

Hydrologic (a) (b) (c) (d) (e)

5. 6. 7. B.

Vegetative cover Soils Aerial photographs

Data on Wells, Observation Holes and Springs 1. 2. 3. 4. 5.

B3-6

Location of wells, observation holes and springs Ground water table and piezometric contours Depth to water Quality of water Recharge, discharge and contributing areas

Location, depth, diameter, types of well and logs Static and pumping water level, hydrographs, yield, specific capacity, quality of water Present and projected ground-water development and use Corrosion, incrustation, well interference and similar operation and maintenance problems Location, type, geologic setting and hydrographs of springs

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

6. 7. C.

Aquifer Data 1. 2. 3. 4. 5. 6. 7. 8.

D.

Type, such as unconfined, artesian or perched Thickness, depths and formational designation Boundaries Transmissivity, storativity and permeability Specific retention Discharge and recharge Ground and surface water relationships Aquifer models

Climatic Data 1. 2. 3. 4.

E.

Observation well networks Water sampling sites

Precipitation Temperature Evapotranspiration Wind velocities, directions and intensities

Surface Water 1. 2. 3. 4. 5.

Use Quality Runoff distribution, reservoir capacities, inflow and outflow data Return flows, section gain or loss Recording stations

2.8 ENVIRONMENTAL REVIEW The Federal Regulations contain a criterion that required solid waste facilities or management practices to not harm or threaten any plants, fish or wildlife in danger of extinction. In general, states have developed location standards which would prevent the siting of landfills in areas which would cause or contribute to the endangerment of threatened species. THE CLIENT thoroughly investigates proposed sites for potential endangered species or practices which may result in the destruction or adverse modification of the critical habitat of endangered or threatened species identified in 50 CFR Part 17. The consultant must assess if the proposed facility will impact endangered species. This review of available data must be performed by a Certified Ecologist. This environmental review section may be subcontracted to an experienced ecologist. The Phase I botanical work should include a review of air photos to survey botanical zones. Many states also require mapping of archaeological and historic sites as part of the overall permit application. THE CLIENT also promotes the protection of archaeological and historic sites. We, therefore, require the mapping of archaeological and historic sites within 2,000 feet of the perimeter of the facility. The Phase I environmental review is based on document ranges of endangered or threatened species supplemented by a field visit. Archaeological and historic sites are also reviewed by literature surveys, review of air photos and a site visit. Detailed site data will be generated within the Phase II field investigation scope of work.

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

2.9 SITE VISIT – TASK 2 The consultant should plan to visit the site to gain a thorough understanding of current site conditions. Terminology, units, abbreviations, balance and emphasis in the final report. The draft and final report should be read thoroughly by the Project Manager and Senior Hydrogeologist assigned to the project. The consultant should have, upon the conclusion of the Phase I investigation, an understanding of the site’s basic geologic and hydrogeologic environment. This information must be used to formulate a specific Phase II investigation to fully assess the proposed site’s hydrogeological conditions.

3.0 PHASE II – SUBSURFACE HYDROGEOLOGIC INVESTIGATION 3.1 INTRODUCTION Subsurface hydrogeologic investigations must be of sufficient intensity to determine the conditions that may influence the design and the construction of both the landfill and the ground water monitoring system. The extent of geologic investigation required for a particular site depends on: (1) complexity of the site conditions, (2) size of the landfill construction and (3) potential damage if there is functional failure in the liner. Detailed geotechnical/hydrogeologic exploration and location of the monitoring system would typically consist of four tasks: (1) determining and interpreting subsurface conditions, (2) taking samples for soil and rock tests, (3) installing the monitoring wells and (4) preparation of a final report detailing all findings. 3.2 GEOLOGICAL MAPPING – TASK 2-1 Conduct a geologic mapping program on the surfical material present at the site. If sufficiently detailed maps are available for the assessment, this task may not be required under the Phase II scope. The primary purpose of the mapping is to aid in monitoring well locations. The maps are expected to be extended on the basis of the later drilling program. 3.3 GEOPHYSICAL SURVEY – TASK 2-2 Geophysics can often be employed during the hydrogeological investigation to solve specific problems or merely to provide information cheaply and rapidly. On the basis of geophysical surveys, depth to bedrock, water tables and anomalous geologic conditions can be assessed for later drilling. Seismic velocities can also be used for later ripability analyses. THE CLIENT expects that geophysical seismic refraction methods will assist in selection of locations for geotechnical borings. The seismic survey should tie into existing borings for control of depth and for correlation of lithologies with velocities. The estimated seismic survey lengths should be costed on the basis of [ ] feet. All geophysical work should be performed and interpreted by adequately trained geophysicists. 3.4 FIELD DRILLING PROGRAM – TASK 2-3 During Phase II, test holes must be put down and logged in the landfill’s foundation and potential borrow areas. Selection of drilling locations must be based on geophysical interpretation and results of Phase I studies. These test holes must be deep enough to penetrate all pertinent materials. The number and spacing of test holes must be adequate for correlation in both longitudinal and transverse directions for complete interpretation of any condition that may influence the local permeabilities. Geologic structural features, such as faults, folds and joints, must be obtained

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

during drilling and sufficient information is required on soils to classify them and to determine their location, thickness and extent. Test holes can be put down by drilling or by excavating pits or trenches in areas of shallow soils. The data gathered during this drilling program are analyzed on the site and behavior characteristics and engineering significance of the materials and conditions are evaluated. From this analysis and evaluation, the geologist and the engineer determine what materials are to be sampled and what laboratory analyses are needed. The necessary samples are obtained by using appropriate sampling procedures. Any additional or special in-place field tests should be completed at this time. Because we believe weathered and fractured bedrock may represent a major hydraulic component of ground-water flow, holes should be advanced at least into unweathered bedrock. These holes should be diamond cored with at least an NX-sized core barrel. For estimating costs, provide footage costs for coring and estimate feet of coring per hole. Unconsolidated materials should be sampled every 5 feet and at changes in materials to obtain a clear picture of the lithology of the overburden. 3.4.1 Logging Test Holes Logging is the recording of data concerning the materials and conditions in individual test holes. It is imperative that logging be accurate to provide a true picture of subsurface conditions. It is equally imperative that recorded data be concise and complete and be presented in descriptive terms that are readily understood and evaluated in the field, laboratory and design office. The basic element of logging is a geologic description of the material between specified depths or evaluations. This description includes such items as name, texture, structure, color, mineral content, moisture content, relative permeability, age and origin. To this must be added any information that indicates the engineering properties of the material. Examples are gradation, plasticity and the unified soil classification symbol determined by field identification. In addition, the results of any field test, such as the standard penetration test, must be recorded along with the specific vertical interval that was tested. After a hole is logged, it should be plotted graphically to scale and properly located both vertically and horizontally on the applicable cross-section or profile. Correlation and interpretation of these graphic logs indicate the need for any additional test holes and their location and permit the plotting of stratigraphy and structure and the development of complete geologic profiles. Analysis of the geologic profile frequently gives more information on the origin of the deposits. It should be noted that driller’s logs will not be acceptable to THE CLIENT. THE CLIENT expects that a professional geologist or soils engineer will be present at the drill rig at all times that drilling is underway for logging and supervising drilling operations. All logging should be completed on THE CLIENT Field Assessment Forms. Copies of these forms can be obtained at Regional and District CLIENT’S offices. 3.4.2 Laboratory Tests – Task 2-4 Laboratory tests of soils collected during the field drilling task defines four basic properties of soils and their suitability for use on landfill sites. These soil characteristics can be summarized as: 1. 2. 3. 4.

Strength Compressability Permeability Chemistry

The following laboratory tests are designed to provide information on the quantity and physical characteristics of both borrow and landfill cut areas. Guidelines for the numbers of tests are given below; however, good engineering judgment must apply to adequately describe the quality and quantity of the individual soils located on the property. The investigations will generally consist of (1) drilling and sampling soil borings or excavating shallow test pits, (2) obtaining bulk samples of representative soils and (3) evaluating these samples for use as borrow material.

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APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

Soil samples will be evaluated by performing the following laboratory tests: A.

Particle-size analysis of soils (ASTM D422-63).

B.

Liquid and plastic limits (ASTM D4318-83).

C.

Classification of soils for engineering purposes (ASTM D2487-69).

D.

Moisture/density relationship utilizing five compaction points (standard proctor) to determine the maximum dry density and ultimate moisture content (ASTM D698-78).

E.

Organic content by the burn-off method (ASTM D6341-79).

F.

Permeability at 90% of standard proctor density within 12 percentage points of optimum moisture content. A falling head test method using back pressure should be done in general accordance with Corps of Engineers’ Manual EM 1110-2-1906, “Laboratory Soils Testing,” Appendix VII.7.

G.

Strength test: Test for unconsolidated, undrained strength of cohesive soils in triaxial compression (ASTM D2850-70) or in general in accordance with Appendix X of the Corps of Engineers’ Manual EM 1110-2-1906 for noncohesive soils.

H.

Consolidation tests: Test for one-dimensional consolidation properties of soils (ASTM D2435-70).

I.

Cation Exchange Capacity Tests. The U.S. EPA tests methods 9080 and 9081 were adopted from standard methods for soil analysis used by the American Society of Agronomy (Chapman, H.D., Cation Exchange Capacity in C.A. Black [ed.] Methods of Soil Analysis, American Society of Agronomy, Madison, WI, Part 2 [1965]).

J.

Soil pH: By electrometric method reference in (I) above.

The particle-size, liquid and plastic limit tests should be costed at three per boring. Care must be taken to select particle-size test samples for those zones being selected for piezometer monitoring. The classification of soils for engineering purposes must be made initially during drilling and reviewed during laboratory testing to confirm the classification. Moisture density tests should be made at the rate of one per each material type found during drilling, with more tests performed on suitable liner material. Estimate ten tests total for moisture density. Both organic content and permeability tests should be run for each material type, unless sound engineering judgment suggests that additional tests are required. For purposes of this proposal, estimate ten tests for organic content and laboratory permeability. Consolidation tests should also be made for each material type. Cation exchange tests, which determine the potential capacity of the soil to exchange cations with leachate, should be run on every different material found at the proposed site. Soil pH tests should be run in the laboratory program for each material found at the site. 3.4.3 Installation of Monitoring Wells and Piezometers – Task 2-5 The estimated borings required in this program provide an opportunity to assess the hydrogeologic environment to: 1. 2. 3. 4. 5. 6.

Define in-place permeability of each geologic unit. Assess the directions of ground water flow. Calculate the rates or velocity of flow and estimated flux. Determine the maximum high ground water table elevation and aquifer types. Define ground water recharge and discharge areas. Determine background water quality.

In order to convert the soil borings into reliable monitoring wells and piezometers, the consultant must construct and document these installations according to THE CLIENT’s specifications. Deviations from these specifications

B3-10

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

without written approval from THE CLIENT will require the consultant to reinstall the installation at their expense. Professional field control of installation of monitoring wells and piezometers cannot be overemphasized. THE CLIENT’s general plan for installation of wells and piezometers would require that soil borings near the edge of the landfill that would not be covered by landfilling operations would be 2 inch PVC. Installation must be according to the THE CLIENT specifications in Appendix A. These monitoring wells should be completed in the uppermost aquifer. The uppermost aquifer would be the first continuous permeable zone under the base of the proposed landfill which could supply economic quantities of water to wells or springs off-site. Because the site has several potential upgradient areas, one or two monitoring wells should be located in the upgradient directions and two to three monitoring wells sited in the downgradient directions. The actual location and depth of wells for this ground-water monitoring must be based on two major factors: 1. 2.

The direction of ground-water flow; and The first or “uppermost” aquifer depth.

The wells to be installed under this monitoring phase must be designed to intercept potential landfill leachate downgradient of the waste area in the first continuous saturated and permeable zone adjacent to the waste disposal area. All the technical work to be performed in this Phase II effort must be directed toward this goal. The final performance assessment of the consultant and peer review will be directed toward determining if the consultant has met this goal. The second type of ground-water assessment installation is 3/4-inch PVC piezometers. The borings not selected for 2-inch monitoring well installations should be completed as small diameter piezometers where only water levels will be taken. The construction of these 3/4-inch PVC piezometers should be according to the THE CLIENT’s specification for monitoring well installation with a number of acceptable modifications: 1.

The piezometers should be of 3/4-inch PVC with machine cut slots to obtain the open screened area. The screened length should be based on drilling observations of permeable zones and should adequately monitor pressure heads within individual zones.

2.

The location or depth of the piezometers can be varied from the uppermost aquifer zone. Good engineering judgment should be used to obtain the required hydraulic data to reach the six goals previously listed in this section. The consultant should select adequate numbers of piezometers to assess permeability, flow directions, ground-water velocity, water levels and vertical and horizontal gradients for the geologic materials located on site. This may include both consolidated and unconsolidated materials for primary and secondary porosity.

3.

Gravel or filter sand packing of the screens, construction details, bentonite seals, grouting, protective casings and surveying should be equivalent to the THE CLIENT’s specifications for monitoring wells.

4.

Small-diameter piezometers can be constructed in central areas where landfilling may destroy the piezometer at some point during the life of the facility.

3.4.4 Performance Tests – Task 2-6 THE CLIENT requires that all piezometers and monitoring wells be tested for permeability through appropriate hydrogeologic methods. The field permeability testing of geologic materials through variable head or constant head techniques represents a relatively quick method that will establish defensible field permeability for each of the geologic materials present on site. THE CLIENT expects the consultant to be fully conversant with these techniques and adequately document the performance of the test. These tests can be performed quickly; however, early time data must be taken to establish reliable values for permeability for each monitoring well and piezometer.

B3-11

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

3.5 FIELD ECOLOGY SURVEY – TASK 2-7 (if required) The purpose of conducting a summer ecological survey is to take advantage of the season to obtain information that will be used to address the issue of threatened and endangered plant and animal species. The summer biological field survey should consist of three field activities: • • •

Botanical survey to refine previous air-photo-based map surveys Early morning bird surveys Small mammal trapping.

A vegetation map should be produced based on an examination of aerial photographs of the site (obtained during Phase I). All areas in which vegetation types could not be readily identified from aerial photographs will be checked in the field. In addition, all mapped boundaries between adjacent vegetation types will be reviewed in the field for accuracy. Known or potential habitat for sensitive plant species should be identified during the survey. Bird surveys should be conducted for 2 to 4 hours on two mornings. In order to observe a high proportion of the species occurring at the site, these surveys will be conducted primarily in the vicinity of springs, drainages (including ephemeral and intermittent streams), rocky hillsides and areas of woodland. All birds seen and heard should be identified as to species and, whenever possible, to sex. A minimum of 25 Sherman live traps should be set on two nights to determine the occurrence of small mammals. In order to detect a high proportion of species present at the site, traps should be placed primarily in the vicinity of springs, drainages, rocky hillsides and areas of woodland. All small mammals should be identified as to species, sex, and, whenever possible, age. In addition, all wildlife species observed during these three field activities must be recorded. As with the previous Phase I activity, only Certified Ecologists are acceptable for performing this work. 3.6 HISTORY AND ARCHAEOLOGY – TASK 2-8 (if required) A professional archaeologist should be retained to document the cultural importance of the area. A regional overview of the area has been developed in Phase I based primarily on literature review. In addition, a Phase II reconnaissance survey should be conducted to confirm the presence or absence of significant historical or achaeological sites on the site. The reconnaissance survey includes the deployment of multiple transects involving systematic examination of samples of subsurface conditions at 15 meter intervals. Standard survey procedures also include visual examination of all disturbed earth areas such as road cuts, farmers’ fields, spoil from rodent burrows, etc. These procedures are necessary in heavily forested areas with heavy groundcover conditions. These procedures should result in the field check of known or suspected locations of archaeological and historical remains. They may also result in the discovery of previously unknown remains. The precise location of these new sites, together with maps which indicate areas which failed to produce evidence of remains, will be prepared. All recovered archaeological and historical debris should be washed, marked and cataloged and will be deposited in the appropriate museum of anthropology. 3.7 PHASE II REPORT – TASK 2-9 “Introduction” should include the background, contract and proposal citation and objectives of the assessment. Abbreviations for the client and facility to be used throughout the report should be included in this section.

B3-12

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

“Setting” should include regional and local descriptions of geographic matters, such as climate, rainfall, flooding, runoff and drainage, attitude, land use and agricultural soils, surface geology, topography and other pertinent factors. “Facility Description” should locate the site on a regional map (first figure), describe the site features, land use, land surface elevations, local drainage patterns and slopes. “Regional Hydrogeology and Ground-water Quality’’ should include a discussion of the major aquifers, their usage, stratigraphy, ground-water conditions –– gradient directions and magnitudes, elevation of the ground-water surface. An indication of regional ground-water quality and related issues should be included. “Site Hydrogeology and Ground-Water Quality” should provide locations of borings and piezometers (second figure) and include discussions of the site stratigraphy, subsurface profiles (additional figures) and shallowest water-bearing soils. Shallow ground-water conditions –– gradient directions and magnitude, elevation of water table or piezometric surface –– should be covered in detail. This section should also include a description of local ground-water quality, with significant anomalies and frequencies and seasonal fluctuations noted. “Assessment” should combine the hydraulic analysis of the site hydrogeology and the analysis of the site’s soils and geology. A reasonable picture of the potential for contaminant migration from the waste facility from seepage and horizontal or vertical movement through and off the site should be produced. Imminent and potential ground-water quality risks to the public must be identified. “Recommendations” should refine the quality of the hydraulic and water quality analysis and evaluate the synthesis of hydrogeologic and geologic analysis and work towards statistical significance if needed. Recommendations should be presented in a natural and supportive way so that the client is logically drawn toward them. The consultant must answer the following requirements: a.

Determine the availability, quality and quantity of on-site soil for cover material;

b.

Evaluate the influence that geologic factors would have on the ease of excavation and potential for ground water and surface water pollution;

c.

Determine the maximum high ground-water table elevation and ground-water flow patterns;

d.

Determine background water quality of ground water at the site and of surface water at the most likely discharge area; and

e.

Evaluate the importance of the ground-water resource which might be affected by the operation of a landfill facility.

“Figures” should include a vicinity map, site plan with boring and monitoring well locations, two subsurface profiles (N–S and E–W) and a local geohydrologic column at a minimum. The site plan should show the location of the gradient. If ground-water anomalies are clearly present, additional figures may highlight this through anomaly maps which overextend the size of anomalies because of sparse and distant control points. “References’’ should include all cited literature, the consultant’s and client’s files, conversations with agency personnel and client reports. Confidential reports completed for other clients with nearby facilities should not be explicitly cited. “Appendices” should include any available field exploration and soil laboratory testing, ground-water monitoring network, ground-water sampling and analysis plans and analyses of ground-water samples. Specific tables, such as logs of borings, summary of ground-water level measurements, well completion data, soil laboratory tests, field water

B3-13

APPENDIX B3 EXAMPLE HYDROGEOLOGY STUDY

quality analyses, laboratory water quality analyses and chain of custody records, are appropriate. Personnel involved and procedures utilized in the various phases of the project should be identified. Examples include notations such as “water levels were measured with a steel tape by...;” “elevations were determined with a topographic survey by...;” “field measurements were made with a conductivity meter, pH meter and thermometer by...;” etc. Data should be reported to significant figures. Basic data collected during the investigation must be provided so that THE CLIENT can perform an independent assessment of the information generated by the investigation. The draft and final reports should be thoroughly reviewed for technical accuracy and editorial consistency. Reports should be checked for numerical, citation and typographical errors as well as tone, consistency, emphasis and logic. A poorly written report will erode credibility, diminish future opportunities and cause later expense and embarrassment. 3.8 REPORT PRESENTATION THE CLIENT should be given five copies of the draft final report to review. THE CLIENT may correct any facilityrelated or procedural errors that the consultant has made; hence, this draft must be as clear and accurate as possible. It is generally more vivid and consequently more effective, for the consultant to review the report in the physical presence of the client.

B3-14

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

APPENDIX C1 RCRA SUBTITLE D CHEMICAL PARAMETERS

C1-1

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

RCRA SUBTITLE D (SOLID WASTE Rule)

On August 30, 1988, U.S. EPA proposed a series of regulations for municipal solid waste landfills under Subtitle D of RCRA. Schedule E, Part 258, of the proposed ruling covers ground-water monitoring and corrective action. U.S. EPA is establishing minimum requirements in these areas and delegating further authority to the individual states. There is a maximum five-year phase-in period associated with this ruling. U.S. EPA has delegated authority to the State and is expecting the States to establish specific criteria on: • • • •

number and location of monitoring wells sampling frequency statistical determination of contamination individual compound ground-water trigger levels

U.S. EPA’s minimum requirements for ground-water monitoring at Subtitle D facilities consist of a two-phase program. Each facility must monitor, at a minimum semi-annually, the Phase I list of parameters. The Phase I list of parameters consists of 15 ground-water quality indicators (conventionals), 9 metals and 46 volatile organics.

A statistical change from background on two or more Phase I ground-water quality parameters or one or more Phase I metal or volatile organic parameters may force the owner/operator into Phase II sampling. The Phase II (RCRA SUBTITLE D-Appendix II) list of parameters contains 245 organic and inorganic parameters, many of them not considered to be prevalent at solid waste facilities. SUBTITLE D PHASE I PARAMETERS (l) Ammonia (as N) (2) Bicarbonate (HC02) (3) Calcium (4) Chloride (S) Iron (6) Magnesium (7) Manganese, dissolved (8) Nitrate (as N) (9) Potassium (10) Sodium (11) Sulfate (S04) (12) Chemical Oxygen Demand (COD) (13) Total Dissolved Solids (TDS) (14) Total Organic Carbon (TOC) (15) pH (16) Arsenic (17) Barium (18) Cadmium (19) Chromium (20) Cyanide (21) Lead (22) Mercury (23) Selenium (24) Silver (25) The volatile organic compounds (VOCs) listed in RCRA SUBTITLE D-Appendix I.

Volatile Organic Constituents for Groundwater Monitoring Appendix I - SW-846 Method 8240

Acetone, Acrolein, Acrylonitrile, Benzene, Bromochloromethane, Bromodichloromethane, cis-1,3-Dichloropropene, Trans-1,3-Dichloropropene, 1,4-Difluorobenzene, Ethanol, Ethylbenzene, Ethyl methacrylate, 4 Bromofluorobenzene, Bromoform, Bromomethane, 2-Butanone, (Methyl ethyl ketone), Carbon disulfide, Carbon Tetrachloride, Chlorobenzen,e Chlorodibromomethane, Chloroethane, 2-Chloroethyl, Vinyl ether, Chloroform, Dichloroethane, 2 Hexanone, Iodomethane, Methylene chloride, 4-Methyl-2-pentanone, 1,1-Dichloroethane, trans-1,2-Dichloroethane, Styrene, 1,1,2,2-Tetrachloroethane, Toluene, 1,1,1-Trichloroethane, 1,1,2-Trichloroethane, Trichloroethene, Trichlorofluoromethane, 1,2,3-Trichloropropane, Vinyl acetate, Vinyl Chloride, Xylene.

C1-2

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

Subtitle D - Phase II Parameters

SYSTEMATIC NAME Acenaphthylene Acenaphthylene, 1,2-dihydroAcetamide, N-(4-ethoxphenyl)-H Acetamide, N-9H-fluoren-2-yl Acetic acid ethenyl ester Acetic acid (2,4,5-trichloro-phenoxy)Acetic acid(2,4-dichloro-phenoxy)Acetronitrite Aluminum Anthracene Antimony Aroclor 1016 Aroclor 1221 Aroclor 1232 Aroclor 1242 Aroclor 1248 Aroclor 1254 Aroclor 1260 Arsenic Barium Benz[a]anthracene,7,12,-dimethyl Benz[a]aceanthrylene,1,2-dihydo-3-methyl Benz[e]acephenanthrylene Benzamide,3,5-dichloror-N(1,1-dimethyl-2-propynl)Benz[a]anthracene Benzenamine Benzenamine, 2-methyl-5-nitro Benzenamine, 2-nitro Benzenamine, 3-nitro Benzenamine, 4-chloro Benzenamine, 4-nitroBenzenamine, 4,4'-methylene bis-[2-chloro Benzenamine, N-nitroso-N-phenyl Benzenamine, N-phenylBenzenamine, N,N-dimethy-4-(phenylazo)Benzene Benzene, l-bromo-4-phenoxyBenzene, l-chloro-4-phenoxyBenzene, l-methyl-2,4-dinitro Benzene, 1,1'-(2,2,2-trichloroethylidene)bis[4-chloroBenzene, 1,1'-(2,2,2-trichloroethylidene)bis[4-methoxy Benzene, 1,1'-(2,2-dichloroethylidene)bis[4-chloroBenzene 1,1'-(2,2-dichloroethenylidene)bis[4-chloro-

CAS RN

COMMON NAME

206-96-B 83-32-9 62-44-2 53-96-3 106-05-4 93-76-5 94-75-7 75-05-8 7429-90-5 120-12-7 7440-36-0 12674 ~ 2 11104-26-2 11141-16-5 53468-21-9 12672-29-6 11097-69-1 11096-82-5 7440-38-2 7440-39-3 57-97-6 56-49-5 205-99-2 23950-58-5

Acenaphthalene Acenaphthene Phenacetin 2-Acetylaminofluorene Vinyl acetate 2,4,5-T 2,4-Dichlorophenoxy-acetic acid Acetonitrile Aluminum (total) Anthracene Antimony (total) Aroclor 1016 Aroclor 1221 Aroclor 1232 Aroclor 1242 Aroclor 1248 Aroclor 1254 Aroclor 1260 Arsenic (total) Barium (total) 7,12-Dimethylbenz[a]antracen 3-Methylcholanthrene Benzo[b]fluoranthene Benzo[b]fluoranthene

56-55-3 62-53-3 99-55-8 88-74-4 99-09-2 106-47-8 100-01-6 101-14-4 86-30-8 122-39-4 60 -11-7 71-43-2 101-55-3 7005-72-3 121-14-2 50-29-3

Benx[a]anthracene Aniline 5-Nitro-o-toluidine 2-Nitroaniline 3-Nitroaniline p-Chloroaniline p-nitroaniline 4,4'-Methylenehis(2-chloroaniline N-Nitrosodi phenylmamine Diphenylamine p-Dimethylamino-azobenzene Benzene 4-Bromophenyl phenyl ether 4-Chlorophenyl phenyl ether 2,4-Dinitrotoluene DDT

72-43-5

Methoxychlor

72-54-8

DDD

72-55-9

DDE

C1-3

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

Benzene 1,2-dichloroBenzene 1,2,4-trichloroBenzene 1,2,4,5-tetrachloroBenzene 1,3-DichloroBenzene 1,4-dichloroBenzene 1,4-dinitroBenzene, 2-methyl-1,3-dinitroBenzene, chloro Benzene, dimethylBenzene, ethenylBenzene, ethylBenzene, hexachloroBenzene, methyl Benzene, nitroBenzene, pentachloroBenzene, pentachloronitroBenzeneacetic acid, 4-chloro_-(4-chlorophenyl)-_-hydroxy-, ethyl ester 1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester 1,2-Benzenedicarboxylic acid, butyl phenylmethyl ester 1,2-Benzenedicarboxylic acid, dibutyl ester 1,2-Benzenedicarboxylic acid, diethyl ester 1,2-Benzenedicarboxylic acid, dimethyl ester 1,2-Benzenedicarhoxylic acid, dioctyl ester 1,3-Benzenediol Benzenethanamine, _,_-dimethyl-

95-50-1 120-82-1 95-94-3 541-73-1 106-46-7 100-25-4 606-20-2 108-90-7 1330-20-7 100-42-5 100-41-4 118-74-1 106-88-3 96-95-3 606-93-5 82-68-8 510-15-6

o-Dichlorobenzene 1,2,4-trichlorobenzene 1,2,4,5-Tetrachloro-benzene m-Dichlorobenzene p-Dichlorobenzene meta-Dinitrobenzene 2,6-Dinitrotoluene Chlorobenzene Xylene (total) Styrene Ethyl benzene Hexachlorobenzene Toluene Nitrobenzene Pentachlorobenzene Pentachloronitro benzene Chlorobenzilate

117-81-7

bis(2-ethylhexyl) phthalate

85-68-7

Butyl benzyl phthalate

84-74-2 84-66-2 131-1-3 117-84-0 106-46-3 122-09-8

Benzenemethanol Benzenethiol 1,3-Benodioxole, 5 - propenyl)1,3-Benzodioxole, 5-(2-propenyl)Benzo[k]fluoranthene Benzoic acid Benzo[rst]pentaphene Benzo[ghi]perylene Benzo[a]pyrene Beryllium 1,1'-Biphen[yi]4,4'-diamine, 3,3'-dichlorol,l'-Biphen[yi]-4,4'-diamine, 3,3'-dimethoxyl,l'-Biphen[yi]-4,4'-diamine, 3,3'-dimethyl l,l'-Biphenyl[-4-amine 1, l'-Biphenyl[-4-4-amine 1,3-Butadiene, 1,1,2,3,4,4-hexachloro1,3-Butadiene, 2-chlorol-Butanamine, N-butyl-N-nitroso2-Butanone 2-Butene, 1,4-dichloro-,(E)Cadmium Calcium Carbon disulfide Chromium Chrysene

100-51-8 106-98-5 120-58-1 94-59-7 207-08-9 65-85-0 189-55-9 191-24-2 50-32-8 7440-41-7 91-94-1 119-90-4 119-93-7 92-67-1 92-87-5 87-68-3 126-99-8 924-16-3 78-93-3 110-57-6 7440-43-9 7440-70-2 75-15-0 7740-47-3 218-01-9

Di-n-butyl phthalate Diethyl phthalate Dimethyl phthalate Di-n-octyl phthalate Resorcinol _,_-Dimethylphenethylamine Benzyl alcohol Benzenethiol Isosafrole Safrole Benzo[k]fluoranthene Benzoic acid Dibenzo[a,l]pyrene Benzo(ghi)perylene Benzo[a]pyrene Beryllium (total) 3,3'-Dichlorobenzidine 3,3'-Dimethoxybenzidine 3,3'-Dimethylbenzidine 4-Aminobiphenyl Benzidine Hexachorobutadiene 2-Chloro-1,3-butylamine N-Nitrosodi-n-butylamine Methyl ethyl ketone trans-1,4-Dichloro-2-butene Cadmium (total) Calcium (total) Carbon disulfide Chromium (total) Chrysene

C1-4

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

Cobalt Copper Cyanide 2,5-Cyclohexadiene-1,4 dione Cyclohexane, 1,2,3,4,5,6hexachloro-(la,2a,3B,4a,5B,6B)Cyclohexane, 1,2,3,4,5,6hexachloro-(la,2B,3a,4B,5a,6B)Cyclohexane, 1,2,3,4,5,6hexachloro-(la,2a,3a,4B,5a,6B)Cyclohexane, 1,2,3,4,5,6hexachloro-(la,2a,3B,4a,5a,6B)2-Cyclohexen-l-one,3,5,5-trimethyl 1,3-Cyclopentadiene, 1,2,3,4,5,5-hexachloroDibenz[a,h]anthracene Dibenzo[b,e][1,4]dioxin, 2,3,7,8-tetrachloro dioxin, hexachlorodibenzo

7440-48-4 7440-50-8 57-12-5 106-51-4 319-84-6

Cobalt (total) Copper (total) Cyanide p-Benzoquinone _-BHC

319-85-7

`-BHC

319-86-8

b-BHC

58-89-9

a-BHC

78-59-1 77-47-4 53-70-3 1746-01-6

Dibenzo[b,def]chrysene Dibenzofuran

189-64-0 132-64-9

2,7:3,6-Dimethanonaphth[2,3-b]oxirene, 3,4,5,6,9,9-hexachlorola,2,2a,3,6,6a,7,7a-octahydro, laa,2B,2aa,3B,6B,6aa,7B,7aa)2,7:3,6-Dimethanonaphth[2,3-b]oxirene, 3,4,5,6,9,9-hexachlorola,2,2a,3,6,6a,7,7a-octahydro, laa,2B,2aB,3a,6a,6aB,7B,7aa)1,4:5,8-Dimethanonaphthalene, 1,2,3,4, 10, 10-hexachloro1,4,4a,5,8,8a-hexahydro1aa,4a,4aB,5a,8a,8aB)1,4:5,8-Dimethanonaphthalene, 1,2,3,4,10,10-hexachloro1,4,4a,5,8,8a-hexahydro-, laa,4a,4aB,5B,8B,8aB)1,4-Dioxane Ethanamine, N-ethyl-N-nitroso Ethanamine, N-methyl-N-nitrosoEthane, l,l-dichloroEthane, l,l'-[methylenebis(oxy)]bis[2-chloroEthane, 1,1'-oxy bis[2-chloroEthane, l,l'-trichloroEthane, 1,1,1,2-tetrachloroEthane, 1,1,2-trichloroEthane, 1,1,2,2-tetrachloroEthane, 1,2-dibromoEthane, 1,2-dichloroEthane, chloro-

60-57-1

Isophorone Hexachlorocyclopent-adlene Dibenz[a]anthracene 2,3,7,8-Tetrachlorodibenzo-p p-dioxin, pentachlorodibenzo-p-dioxins; tetra-chlorodibenzop-dioxins Dibenzo[a,h]pyrene Dibenzofuran, hexachlorodibenzofurans pentachlorodibenzo-furans; tetrachlorodidenzofurans Dieldrin

72-20-8

Endrin

309-00-2

Aldrin

465-73-6

Isodrine

123-91-1 55-18-5 10595-95-6 75-34-3 111-91-1 44-4 71-55-6 630-20-6 79-00-5 79-34-5 106-93-4 107-06-2 75-00-3

1,4-Dioxane N-Nitrosodiethylamine N-Nitrosomethyl ethylame l,l-Dichloroethane bis(2-chloroethoxy)methane bis(2-chloroethyl)ether l,l,l-Trichloroethane 1,1,1,2-Tetrachloroethane 1,1,2-Trichloroethane 1,1,2,2-Tetrachloroethane 1,2-Dibromoethane 1,2-Dichloroethane Chloroethane

C1-5

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

Ethane, hexachloroEthane, pentachloro1,2-Ethanediamine, N,N-dimethylN'-'2-pyridinyl-N'-(2-thienylmethyl)Ethanone, l-phenylEthene, (2-chloroethoxy)Ethene, l,l-dichloroEthene, 1,2-dichloro-(E)Ethene, chloroEthene, tetrachloroEthene, trichloroFluoranthene Fluoride 9H-Fluorene 2-Hexanone Hydrazine, 1,2-diphenylIndeno[1,2,3-cd]pyrene Iron Lead Magnesium Manganese Mercury Methanamine, N-methyl-N-nitroso Methane, bromoMethane, bromodichloroMethane, chloroMethane, dibromoMethane, dibromochloroMethane, dichloroMethane, dichlorodifluoroMethane, iodoMethane, tetrachloroMethane, tribromoMethane, trichloroMethane, trichlorofluoroMethanesulfonic acid, methyl ester Methanethiol, trichloro4,7-Methano-lH-indene1,2,4,5,6,7,8,8-octachloro2,3,3a,4,7,7a-hexahydro4,7-Methano-lH-indene1,4,5,6,7,8,8-heptachloro3a,4,7,7a-tetrahydro2,5-Methano-2H-indeno[1,2-b] oxirene, 2,3,4,5,6,7,7heptachloro-la,lb,5,5a,6,6ahexahydro-,( laa, lbB,2a,5a,5aB,6B,6aa) 6,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10hexachloro- 1,5,5a,6,9,9ahexahyrdo-,3-oxide(3a,5aB,6a,9a,9aB) 6,9-Methano-2,4,3-benzo-dioxathiepin, 6,7,8,9,10,10-hexachloro, 1,5,5a,6,9,9a-hexahydro-,

C1-6

67-72-1 76-01-7 91-80-5

Hexachloroethane Pentachloroethane Methapyrilene

98-86-2 110-75-8 75-35-4 156-60-5 75-01-4 127-18-4 79-01-6 206-44-0 12984-48-8 86-73-7 501-78-6 122-66-7 193-39-5 7439-89-6 7439-92-1 7439-94-4 7439-96-5 7439-97-6 62-75-9 74-83-9 75-27-4 74-87-3 74-95-3 124-48-1 74-09-2 75-71-8 74-88-4 56-23-5 75-25-2 67-66-3 75-69-4 66-27-3 75-70-7 57-74-9

Acetophenone 2-Chloroethyl vinyl ether l,l-Dichloroethylene trans-1,2-Dichloro ethene Vinyl chloride Tetrachloroethene Trichloroethene Fluoranthene Fluoride Fluorene 2-Hexanone 1,2-Diphenylhydrazine Indeno(1,2,3-cd)pyrene Iron (total) Lead (total) Magnesium (total) Manganese (total) Mercury (total) N-Nitrosodimethylamine Bromomethane Bromodichloromethane Chloromethane Dibromomethane Chlorodibromomethane Dichloromethane Dichlorodifluoro methane Iodomethane Carbon tetrachloride Tribromomethane Chloroform Trichloromonofluoro methan Methyl methane sulfonate Trichloromethanethiol Chlordane

76-44-8

Heptachlor

1024-57-3

Heptachlor epoxide

959-96-8

Endosulfan I

33213-65-9

Endosulfan II

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

3-oxide, (3a,5aa,6B,9B,9aa) 1,3,4-Methano-2H-cyclobutal[cd]pentalen-2-one, 1, la,3,3a,4,5,5,5a,5b"6decachloro-octahydro1,2,4-Methanocyclopental[cd] pentalene-5carboxaldehyde, 2,2a,3,3,4,7-hexachlorodecahydro-,( la,2B,2aB,4B,4aB,SB,6aB,6aB,7R) Morpholine, 4-nitrosol-Naphthalenamine 2-Naphthalenamine Naphthalene Naphthalene, 2-chloroNaphthalene, 2-methyl1,4-Naphthalenedione Naphtho[1,2,3,4-def]chrysene Nickel Osmium Oxirane 2-Pentanone, 4-methylPhenanthrene Phenol Phenol,2 ~ methylpropyl)-4,6-dinitro Phenol, 2-chloroPhenol, 2-methylPhenol, 2-methyl-4,6-dinitroPhenol, 2-nitroPhenol,2,2'-methylene bis[3,4,6-trichloroPhenol, 2,3,4,6-tetrachloroPhenol,2,4-dichloroPhenol, 2,4-dimethylPhenol, 2,4-dinitroPhenol, 2,4,5-trichloroPhenol, 2,4,6-trichloroPhenol, 2,6-dichloroPhenol, 4-chloro-3-methyl Phenol, 4-methyl Phenol, 4-nitroPhenol, pentachloroPhosphorodithioic acid, O,O-diethyl S-[(ethylthio) methyl] ester Phosphorodithioic acid, O,O-diethyl Phosphorothioic acid, 0-[4-[(dimethylamino) sulfonyl)]phenyl] O,O-di-methyl ester Phosphorothioic acid, O,O-diethyl 0(4-nitrophenyl) ester Phosphorothioic acid, O,O-diethyl O-pyrazinyl ester Phosphorothioic acid, O,O-dimethyl 0-(4-nitrophenyl) ester Piperidine, l-nitroso Potassium l-Propanamine, N-nitroso-N-propylPropane, 1,2-dibromo-3-chloro

143-50-0

Kepone

7421-93-4

Endrin aldehyde

59-89-2 134-32-7 91-59-8 91-20-3 91-58-7 91-57-6 130-15-4 192-65-4 7440-02-0 7440-04-2 75-21-8 108-10-1 85-01-8 108-95-2 88-85-7 95-57-8 95-48-7 534-52-1 88-75-5 70-30-4 58-90-2 120-83-2 105-67-9 51-28-5 95-95-4 88-06-2 87-65-0 59-50-7 106-44-5 100-02-7 87-86-5 298-02-2

N-Nitrosomorpholine l-Naphthylamine 2-Naphthylamine Naphthalene 2-Chloronaphthalene 2-Methylnaphthalene 1,4-Naphthoquinone Dibenzo[a,e]pyrene Nickel (total) Osmium (total) Ethylene oxide 4-Methyl-2-pentanone Phenanthrene Phenol 2-sec-Butyl-4,6-dinitro-pheno 2-Chlorophenol ortho-Cresol 4,6-Dinitro-o-cresol 2-Nitrophenol Hexachlorophene 2,3,4,6-Tetrachloro phenol 2,4-Dichlorophenol 2,4-Dimethylphenol 2,4-Dinitrophenol 2,4,5-Trichlorophenol 2,4,6-Trichlorophenol 2,6-Dichlorophenol p-Chloro-m-cresol para-Cresol 4-Nitrophenol Pentachlorophenol Phorate

298-04-4 52-85-7

Disulfoton S-[2-(ethylthio)ethyl] ester Famphur

56-38-2

Parathion

297-97-2 296-00-0

O,O-Diethyl 0,2-pyrazinyl phosphorothioate Methyl parathion

100-75-4 7440-09-7 621-64-7 96-12-8

N-Nitrosopiperidine Potassium (total) Di-n-propylnitrosamine 1,2-Dibromo-3-chloro-propan,

C1-7

APPENDIX C1 RCRA SUBTITLE D PARAMETERS

Propane, 1,2-dichloroPropane, 12,3-tri chloroPropane, 2,2'-oxy bis[1-chloroPropanedinitrile Propanenitrile Propanenitrile, 3-chloroPropanoic acid, 2-(2,4,5-trichlorophenoxyl)l-Propanol, 2,3-dibromo-phosphate (3:1)

78-87-5 96-18-4 106-60-1 109-77-3 107-12-0 542-76-7 93-72-1 126-72-7

l-Propanol, 2-methyl2-Propanone 2-Propenal l-Propene, 1,1,2,3,3,3-hexachlorol-Propene, 1,3-dichloro-,(E)l-Propene, 1,3-dichloro-,(Z)l-Propene, 1,3-chloro2-Propenenitrile, 2-methyl2-Propenenitrile 2-Propenoic acid, 2-methyl-,ethyl ester 2-Propenoic acid, 2-methyl-,methyl ester 2-Propen-l-ol 2-Propyn- l-ol Pyrene Pyridine Pyridine, 2-methylPyridine, l-nitroso Selenium Silver Sodium Sulfide Sulfurous acid, 2-chloroethyl 2-[4-(1, l-dimethylethyl) phenoxy)-l-methy-lethyl ester Thallium Thiodiphosphoric acid ([H0)2 P(S)]20), tetraethyl ester Tin Toxaphene Vanadium Zinc

78-83-1 67-64-1 107-02-8 1888-71-7 10061-02-6 10061-01-5 107-05-1 126-98-7 107-13-1 97-63-2 80-62-6 107-18-6 107-19-7 129-00-0 110-86-1 109-06-8 930-55-2 7782-49-2 7440-22-4 7440-23-5 18496-25-8 140-57-8

C1-8

7440-28-0 3689-24-5 7440-31-2 8001-35-2 7440-62-2 7440-66-6

1,2-Dichloropropane 1,2,3-Trichloropropane bis(2-Chloroisopropyl)ether Malononitrile Ethyl cyanide 3-Chloropropionitrile Silvex tris(2,3-Dibromopropyl) phosphate Isolcutyl alcohol Acetone Acrolein Hexachloropropene trans-1,3-Dichloropropene cis-1,3-Dichloropropene 3-Chloropropene Methacrylonitrile Acrylonitrile Ethyl Methacrylate Methyl methacrylate Allyl alcohol 2-Propynol Pyrene Pyridine 2-Picoline N-Nitrosopyrrolidine Selenium (total) Silver (total) Sodium (total) Sulfide Aramite

Thallium (total) Tetraethyldithiopyrophosphate Tin (total) Toxaphene Vanadium (total) Zinc (total)

APPENDIX C2 RISK TABLES

APPENDIX C2 RISK CALCULATION TABLES Source: Region III EPA

C2-1

EPA Region III RBC Table 4/2/2002

1 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

ACETALDEHYDE ACETOCHLOR ACETONE

CAS 34256821 67641

ACETONITRILE

75058 98862

ACRYLAMIDE ACRYLONITRILE ALACHLOR ALAR ALDICARB ALDICARB SULFONE ALDRIN ALUMINUM

107028 79061 107131 15972608

4-AMINOPYRIDINE AMMONIA ANTIMONY ANTIMONY PENTOXIDE

RfDi

1596845

mg/kg/d

1/mg/kg/d

mg/kg/d 2.57E-03 I

ug/l

ug/m3 1.6E+00 C

8.1E-01 C

7.3E+02 N

7.3E+01 N

Industrial

Residential

DAF 1

mg/kg

mg/kg

mg/kg

mg/kg

2.7E+01 N

4.1E+04 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

1.2E-01

1.2E+02 N

6.2E+01 N

2.9E-02

5.8E-01 N

4.2E-02 N

2.1E-02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

1.1E-05

2.2E-04 N

2.00E-02 H

5.70E-06 I

y

4.2E-02 N

2.1E-02 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

1.0E-05

2.0E-04 N

1.5E-02 C

1.4E-03 C

7.0E-04 C

1.3E+00 C

1.4E-01 C

3.7E-06

7.4E-05 C

y

3.7E-02 C

2.6E-02 C

5.8E-03 C

1.1E+01 C

1.2E+00 C

7.4E-06

1.5E-04 C

8.4E-01 C

7.8E-02 C

3.9E-02 C

7.2E+01 C

8.0E+00 C

3.5E-04

7.0E-03 C

2.00E-04 I

4.50E+00 I

4.50E+00 I

1.00E-03 H

5.40E-01 I

1.00E-02 I

8.00E-02 H

5.70E-04 I

2.40E-01 I

5.5E+03 N

1.50E-01 I

5.5E+02 N

2.0E+02 N

3.1E+05 N

1.2E+04 N

116063

1.00E-03 I

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

1.0E-02

2.1E-01 N

1.00E-03 I

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

7.5E-03

1.5E-01 N

3.8E-04

7.7E-03 C

309002 7429905

3.00E-05 I

1.70E+01 I

1.70E+01 I 1.00E-03 E

1.00E+00 E 6.00E-05 E

504245

7440360 1314609

7440382

y

2.86E-02 I 7.00E-03 E

5.70E-03 I

2.90E-04 I

4.00E-04 I 5.00E-04 H

3.00E-04 I

5.70E-05 I 1.51E+01 I

1.50E+00 I

9.00E-03 I

1912249

3.50E-02 I

2.20E-01 H 1.10E-01 I

1.10E-01 I

103333

1.9E-04 C

3.4E-01 C

3.8E-02 C

1.4E+03 N

2.0E+06 N

7.8E+04 N

2.2E-01 N

8.1E-02 N

1.2E+02 N

4.7E+00 N

2.7E-02 N

4.1E+01 N

1.6E+00 N

2.1E+02 N

1.0E+02 N

1.2E+01 C

1.1E+00 N

5.5E-01 C

1.0E+03 C

1.1E+02 C

1.5E+01 N

1.5E+00 N

5.4E-01 N

8.2E+02 N

3.1E+01 N

1.40E-04 A

7.3E-02 N

1.8E+01 N

1.8E+00 N

1.5E+01 N

1.5E+00 N

5.4E-01 N

8.2E+02 N

3.1E+01 N

1.5E+01 N

2.1E-01 N

5.4E-01 N

8.2E+02 N

3.1E+01 N

4.5E-02 C y

1.40E-05 I

7784421 76578148

3.7E-04 C 3.7E+00 N

2.2E+00 N 7.3E-01 N

2.00E-05 H

7664417 62533

3.9E-03 C 3.7E+04 N

4.1E-04 C

6.8E-01 N

1.0E+03 N

7.0E+02 N

3.0E-01 C

2.8E-02 C

1.4E-02 C

2.6E+01 C

2.9E+00 C

4.4E-04

6.1E-01 C

5.7E-02 C

2.9E-02 C

5.2E+01 C

5.8E+00 C

1.8E-03

3.5E-02 C

2.6E+03 N

5.1E-01 N

9.5E+01 N

1.4E+05 N

5.5E+03 N

1.1E+02

2.1E+03 N

1.5E+02 N

1.5E+01 N

5.4E+00 N

8.2E+03 N

3.1E+02 N

9.0E-05

1.8E-03 C

2.50E-02 I 3.00E-02 I

1.1E+03 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

1.00E-01 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

y

3.2E-01 C

2.2E-01 C

5.7E-02 C

1.0E+02 C

1.2E+01 C

y

6.1E-02 N

3.7E-02 N

1.4E-02 N

2.0E+01 N

7.8E-01 N

BENZIDINE BENZOIC ACID BENZYL ALCOHOL BENZYL CHLORIDE BERYLLIUM BIPHENYL

2.9E-04 C

2.7E-05 C

1.5E+05 N

1.5E+04 N

5.4E+03 N

8.2E+06 N

3.1E+05 N

3.00E-01 H

1.1E+04 N

1.1E+03 N

4.1E+02 N

6.1E+05 N

2.3E+04 N

2.00E-03 I

92524

5.00E-02 I

111444 542881

BIS(2-ETHYLHEXYL)PHTHALATE

117817

BROMOFORM BROMOMETHANE BROMOPHOS 1,3-BUTADIENE

5.7E-06 I

2.00E-02 I 9.00E-02 I

75274

2.00E-02 I

74839

1.40E-03 I

4.4E+00

8.8E+01 N

6.2E-02 C

3.7E-02 C

1.9E-02 C

3.4E+01 C

3.8E+00 C

1.9E-05

3.7E-04 C

7.3E+01 N

7.5E-04 C

2.7E+00 N

4.1E+03 N

1.6E+02 N

5.8E+01

1.2E+03 N

3.0E+02 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

4.8E+00

9.6E+01 N

1.10E+00 I

y

9.6E-03 C

5.7E-03 C

2.9E-03 C

5.2E+00 C

5.8E-01 C

2.2E-06

4.4E-05 C

7.00E-02 H

3.50E-02 H

y

2.6E-01 C

1.8E-01 C

4.5E-02 C

8.2E+01 C

9.1E+00 C

8.4E-05

1.7E-03 C

2.20E+02 I

y

4.8E-05 C

2.8E-05 C

1.4E-05 C

2.6E-02 C

2.9E-03 C

9.7E-09

1.9E-07 C

1.40E-02 I

1.40E-02 E

4.8E+00 C

4.5E-01 C

2.3E-01 C

4.1E+02 C

4.6E+01 C

1.4E+02

2.9E+03 C

5.4E-05

1.1E-03 C

3.3E+03 N

2.1E+01 N

1.2E+02 N

1.8E+05 N

7.0E+03 N

y

1.7E-01 C

1.0E-01 C

5.1E-02 C

9.2E+01 C

1.0E+01 C

y

1.1E-01 C

5.7E-02 C

8.5E+00 C

1.6E+00 C

4.0E-01 C

7.2E+02 C

8.5E+00 N

5.1E+00 N

1.9E+00 N

1.8E+02 N

1.8E+01 N

6.8E+00 N

7.0E-03 C

3.5E-03 C

5.70E-03 H 6.20E-02 I 8.6E-04 I

2.00E-02 I

2.8E-03 C

2.20E+02 I

593602 75252

8.40E+00 I y

1.10E+00 I 4.00E-02 I

7440428

2104963

y

0.17 I

100447 7440417

108601

2.30E+02 I

2.5E-02 C

2.0E+03 N

3.00E-03 I

2.30E+02 I

1.4E-05 C

5.1E+04 N

4.00E+00 I

BIS(CHLOROMETHYL)ETHER BORON

3.4E+01 N

65850

BIS(2-CHLOROISOPROPYL)ETHER

BROMODICHLOROMETHANE

2.90E-02 I

9.1E+01 N

92875 100516

BIS(2-CHLOROETHYL)ETHER

BROMOETHENE

9.1E+02 N

1.70E-03 E

8.8E-03 C

4.3E-01 C

1.8E+04 N

100527

5.5E-02 I

2.6E-02 C

3.8E+00 C

1.2E+01 N

68359375

1.00E-05 H

1.3E-03

2.1E-03 C

5.1E-02 N

25057890

3.00E-03 E

1.3E+01 N

3.3E+01 N

BAYTHROID

71432

1.4E-01 C

6.6E-01

1.0E-01 N

BENTAZON

108985

6.8E-03

3.3E+02 N

4.00E-03 I

BENZENETHIOL

!

3.9E+01 N

7.00E-02 I

BENZENE

2.5E+00 N

6.1E+02 N

114261

BENZALDEHYDE

7.7E-03 C

y

7440393

BARIUM

mg/kg

1.6E+03 N

y

4.00E-04 H

BAYGON

DAF 20 3.8E-04

y

4.00E-04 H

ATRAZINE

y

Soil, for groundwater migration

Soil Fish

1.7E-02 I

1332816

AZOBENZENE

VOC

air

5.70E-06 W

1.00E-01 I

1309644

ARSINE

7.7E-03 I

Ambient

water

1.00E-01 I

ANTIMONY TETROXIDE ARSENIC

1/mg/kg/d

2E-02 I

ANTIMONY TRIOXIDE

ASSURE

CSFi

1646884

AMINODINITROTOLUENES

ANILINE

CSFo

75070

ACETOPHENONE ACROLEIN

RfDo

Tap

1.10E-01 H 3.90E-03 I

7.90E-03 I

y

1.40E-03 I

5.00E-03 H 1.80E+00 H

106990

y

5.4E-05

1.1E-03 C

8.1E+01 C

3.3E-03

6.7E-02 C

2.9E+03 N

1.1E+02 N

2.1E-03

4.1E-02 N

1.0E+04 N

3.9E+02 N 3.9E-06

7.8E-05 C

1-BUTANOL

71363

1.00E-01 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

7.8E-01

1.6E+01 N

BUTYLBENZYLPHTHALATE

85687

2.00E-01 I

7.3E+03 N

7.3E+02 N

2.7E+02 N

4.1E+05 N

1.6E+04 N

8.4E+02

1.7E+04 N

2.7E+01 N

BUTYLATE N-BUTYLBENZENE SEC-BUTYLBENZENE TERT-BUTYLBENZENE

2008415 104518

y

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

2.4E+02 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

2.4E+02 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

5.7E-05 E

6.30E+00 I

1.8E+01 N

9.9E-04 C

6.8E-01 N

1.0E+03 N

3.9E+01 N

1.4E+00

7440439

1.00E-03 I

5.7E-05 E

6.30E+00 I

3.7E+01 N

9.9E-04 C

1.4E+00 N

2.0E+03 N

7.8E+01 N

2.7E+00

5.5E+01 N

105602

5.00E-01 I

1.8E+04 N

1.8E+03 N

6.8E+02 N

1.0E+06 N

3.9E+04 N

63252

1.00E-01 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

1.5E+00

3.0E+01 N

1.0E+03 N

7.3E+02 N

4.00E-02 E

98066

4.00E-02 E

7440439

CADMIUM-FOOD CAPROLACTAM

y

1.8E+03 N 2.4E+02 N

5.00E-04 I

135988

CADMIUM-WATER

CARBARYL

5.00E-02 I 4.00E-02 E

y

75150

1.00E-01 I

1.4E+02 N

2.0E+05 N

7.8E+03 N

9.5E-01

1.9E+01 N

56235

7.00E-04 I

1.6E-01 C

1.2E-01 C

2.4E-02 C

4.4E+01 C

4.9E+00 C

1.1E-04

2.1E-03 C

55285148

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

CHLORAL HYDRATE

302170

1.00E-01 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

CHLORANIL

118752

4.6E-02

9.2E-01 C

CARBON DISULFIDE CARBON TETRACHLORIDE CARBOSULFAN

CHLORDANE

57749

y

2.00E-01 I 1.30E-01 I

5.71E-04 E

5.30E-02 I

4.00E-01 H 5.00E-04 I

3.5E-01 I

2.00E-04 I

3.5E-01 I

y

1.7E-01 C

1.6E-02 C

7.9E-03 C

1.4E+01 C

1.6E+00 C

1.9E-01 C

1.8E-02 C

9.0E-03 C

1.6E+01 C

1.8E+00 C

APPENDIX C2 RISK TABLES

C2-2

Chemical

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

EPA Region III RBC Table 4/2/2002

2 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

Chemical CHLORINE CHLORINE DIOXIDE

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

CAS

RfDo

CSFo

RfDi

CSFi

mg/kg/d

1/mg/kg/d

mg/kg/d

1/mg/kg/d

7782505

1.00E-01 I

10049044

3.00E-02 I

VOC

5.7E-05 E 5.70E-05 I

Soil, for groundwater migration

Soil

Tap

Ambient

water

air

Fish

Industrial

Residential

DAF 1

DAF 20

ug/l

ug/m3

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

y

4.2E-01 N

2.1E-01 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

y

4.2E-01 N

2.1E-01 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

2.00E-03 H

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

4-CHLOROANILINE

106478

4.00E-03 I

1.5E+02 N

1.5E+01 N

5.4E+00 N

8.2E+03 N

3.1E+02 N

4.8E-02

9.7E-01 N

CHLOROBENZENE

108907

2.00E-02 I

y

1.1E+02 N

6.2E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

4.0E-02

8.0E-01 N

1.2E-02 C

2.1E+01 C

2.4E+00 C

1.3E-03

2.7E-02 C

7.3E+03 N

7.3E+02 N

2.7E+02 N

4.1E+05 N

1.6E+04 N

y

1.4E+01 N

7.3E+00 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

6.0E-03

1.2E-01 N

y

2.4E+03 N

1.5E+03 N

5.4E+02 N

8.2E+05 N

3.1E+04 N

1.0E+00

2.0E+01 N

1.1E+00 C

2.0E+03 C

2.2E+02 C

9.6E-04

1.9E-02 C

1.4E+01 N

2.0E+04 N

7.8E+02 N

4.5E-05

9.1E-04 C

CHLOROACETIC ACID

CHLOROBENZILATE

79118

510156

2.00E-02 I

74113

2.00E-01 H

2-CHLORO-1,3-BUTADIENE

126998

2.00E-02 A

1-CHLOROBUTANE

109693

4.00E-01 H

P-CHLOROBENZOIC ACID

75683 75456 75003

4.00E-01 E

**CHLOROFORM

67663

1.00E-02 I

74873

4-CHLORO-2-METHYLANILINE

95692

BETA-CHLORONAPHTHALENE

91587

2.70E-01 H

2.70E-01 H 2.00E-03 H

2.90E-03 E

2.3E-02 C

1.0E+05 N

5.1E+04 N

1.40E+01 I

y

1.0E+05 N

5.1E+04 N

2.90E+00 I

y

3.6E+00 C

2.2E+00 C

y

1.5E-01 C

8.6E-05 E 1.30E-02 H

2.5E-01 C

y

1.40E+01 I

1-CHLORO-1,1-DIFLUOROETHANE CHLORODIFLUOROMETHANE CHLOROETHANE CHLOROMETHANE

1.7E-02 E

2.6E-02 I

8.10E-02 I 3.5E-03 E

7.7E-02 C 1.8E+00 C

!

2.4E-01 C

4.4E+02 C

4.9E+01 C

y

2.1E+00 C 1.2E-01 C

1.1E-02 C

5.4E-03 C

9.9E+00 C

1.1E+00 C

y

4.9E+02 N

2.9E+02 N

1.1E+02 N

1.6E+05 N

6.3E+03 N 2.6E+01 C

5.80E-01 H 8.00E-02 I

!

O-CHLORONITROBENZENE

88733

2.50E-02 H

y

4.2E-01 C

2.5E-01 C

1.3E-01 C

2.3E+02 C

P-CHLORONITROBENZENE

100005

1.80E-02 H

y

5.9E-01 C

3.5E-01 C

1.8E-01 C

3.2E+02 C

3.5E+01 C

y

3.0E+01 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

y

2.1E+02 N

1.1E+02 N

y

1.2E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

2-CHLOROPHENOL

95578

2-CHLOROPROPANE

75296

O-CHLOROTOLUENE

95498

5.00E-03 I 2.90E-02 H 2.00E-02 I

7.0E+01

1.4E+03 N

7.0E+01

1.4E+03 N

5.2E-04

1.0E-02 C

1.6E+00

3.2E+01 N

6.6E-02

1.3E+00 N

6.5E-02

1.3E+00 N

3.00E-03 I

1.1E+02 N

1.1E+01 N

4.1E+00 N

6.1E+03 N

2.3E+02 N

3.2E+00

6.3E+01 N

1.00E-02 H

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

CHROMIUM III

16065831

1.50E+00 I

5.5E+04 N

5.5E+03 N

2.0E+03 N

3.1E+06 N

1.2E+05 N

9.9E+07

2.0E+09 N

CHROMIUM VI

18540299

3.00E-03 I

2.1E+00

4.2E+01 N

1.1E+04 N

CHLORPYRIFOS CHLORPYRIFOS-METHYL

**COBALT

2921882 5598130

7440484

COKE OVEN EMISSIONS (COAL TAR)

8007452

COPPER

7440508

CROTONALDEHYDE CUMENE CYANIDE (FREE)

57125

4.10E+01 H

5.7E-06 E

1.1E+02 N

1.5E-04 C

4.1E+00 N

6.1E+03 N

2.3E+02 N

7.3E+02 N

2.1E-02 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

2.8E-03 C

2.2 I 1.5E+03 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

5.3E+02

y

5.6E-03 C

3.3E-03 C

1.7E-03 C

3.0E+00 C

3.4E-01 C

1.5E-05

3.1E-04 C

y

6.6E+02 N

4.0E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

3.2E+00

6.4E+01 N

1.6E+03 N

7.4E+00

1.5E+02 N

2.6E-05

5.3E-04 C

1.1E-01

2.2E+00 N

3.1E+01

6.2E+02 N

4.00E-02 H 1.90E+00 H

123739 98828

3.00E-05 I

2.00E-02 E

1.10E-01 I

1.00E-01 I

7.3E+02 N

2.00E-02 I

7.3E+01 N

2.7E+01 N

4.1E+04 N

CALCIUM CYANIDE

592018

4E-02 I

1.5E+03 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

COPPER CYANIDE

544923

5.00E-03 I

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

CYANAZINE

21725462

CYANOGEN

460195

4.00E-02 I

CYANOGEN BROMIDE

506683

9.00E-02 I

CYANOGEN CHLORIDE

506774

5.00E-02 I

74908

2.00E-02 I

151508

5.00E-02 I

HYDROGEN CYANIDE POTASSIUM CYANIDE

2.00E-03 H

8.0E-02 C

7.5E-03 C

3.8E-03 C

6.8E+00 C

7.6E-01 C

y

2.4E+02 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

y

6.2E+00 N

3.1E+00 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

8.40E-01 H

3.3E+03 N 8.60E-04 I

3.3E+02 N

7.3E+03 N

7.0E+03 N

POTASSIUM SILVER CYANIDE

506616

2.00E-01 I

4.1E+05 N

1.6E+04 N

SILVER CYANIDE

506649

1.00E-01 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

143339

4.00E-02 I

1.5E+03 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

1.8E+03 N

5.00E-02 E

1.8E+02 N

2.7E+02 N

1.8E+05 N

SODIUM CYANIDE THIOCYANATE

7.3E+02 N

1.2E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

557211

5.00E-02 I

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

1.1E+02

2.3E+03 N

108941

5.00E+00 I

1.8E+05 N

1.8E+04 N

6.8E+03 N

1.0E+07 N

3.9E+05 N

6.1E+01

1.2E+03 N

CYHALOTHRIN/KARATE

68085858

5.00E-03 I

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

CYPERMETHRIN

52315078

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

1861321

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

3.00E-02 I

3.5E-01

7.1E+00 N

DACTHAL DALAPON

75990

1.1E+03 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

DDD

72548

2.40E-01 I

2.8E-01 C

2.6E-02 C

1.3E-02 C

2.4E+01 C

2.7E+00 C

5.6E-01

1.1E+01 C

DDE

72559

3.40E-01 I

2.0E-01 C

1.8E-02 C

9.3E-03 C

1.7E+01 C

1.9E+00 C

1.8E+00

3.5E+01 C

9.3E-03 C

1.7E+01 C

DDT

50293

5.00E-04 I

DIAZINON

333415

9.00E-04 H

DIBENZOFURAN

132649

4.00E-03 E

1,4-DIBROMOBENZENE

106376

1.00E-02 I

DIBROMOCHLOROMETHANE

124481

2.00E-02 I

1,2-DIBROMO-3-CHLOROPROPANE

96128

1,2-DIBROMOETHANE

106934

DIBUTYLPHTHALATE

84742

1.00E-01 I

1918009

3.00E-02 I

95501

9.00E-02 I

DICAMBA

C2-3

1,2-DICHLOROBENZENE 1,3-DICHLOROBENZENE

541731

3.00E-02 E

1,4-DICHLOROBENZENE

106467

3.00E-02 E

3,3'-DICHLOROBENZIDINE

91941

1,4-DICHLORO-2-BUTENE

764410

2.0E-01 C

3.40E-01 I

3.40E-01 I

y

1.9E+00 C

5.8E-02

3.3E+01 N

3.3E+00 N

1.2E+00 N

1.8E+03 N

7.0E+01 N

2.1E-02

4.3E-01 N

2.4E+01 N

1.5E+01 N

1.8E-02 C

5.4E+00 N

8.2E+03 N

3.1E+02 N

3.8E-01

7.7E+00 N

1.2E+00 C

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

7.5E-02 C

8.3E-04 C

y

1.3E-01 C

3.8E-02 C

6.8E+01 C

7.6E+00 C

4.1E-05

1.40E+00 H

5.70E-05 I

2.40E-03 H

y

4.7E-02 C

2.1E-01 N

2.3E-03 C

4.1E+00 C

4.6E-01 C

4.4E-05

8.50E+01 I

5.70E-05 H

7.60E-01 I

y

7.5E-04 C

8.2E-03 C

3.7E-05 C

6.7E-02 C

7.5E-03 C

4.3E-07

8.5E-06 C

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

2.5E+02

5.0E+03 N

8.40E-02 I

4.00E-02 H 2.40E-02 H

2.29E-01 I

2.2E-02 E

8.7E-04 C

1.1E+03 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

2.2E-01

4.5E+00 N

y

2.7E+02 N

1.5E+02 N

1.2E+02 N

1.8E+05 N

7.0E+03 N

2.3E-01

4.6E+00 N

y

1.8E+02 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

1.5E-01

2.9E+00 N

y

4.7E-01 C

2.8E-01 C

1.3E-01 C

2.4E+02 C

2.7E+01 C

3.6E-04

7.1E-03 C

1.5E-01 C

1.4E-02 C

7.0E-03 C

1.3E+01 C

1.4E+00 C

2.5E-04

4.9E-03 C

1.3E-03 C

6.7E-04 C

4.50E-01 I 9.30E+00 H

!

y

4.0E-07

8.0E-06 C

DICHLORODIFLUOROMETHANE

75718

2.00E-01 I

5.00E-02 A

y

3.5E+02 N

1.8E+02 N

2.7E+02 N

4.1E+05 N

1.6E+04 N

5.5E-01

1.1E+01 N

1,1-DICHLOROETHANE

75343

1.00E-01 H

1.40E-01 A

y

8.0E+02 N

5.1E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

2.3E-01

4.5E+00 N

APPENDIX C2 RISK TABLES

ZINC CYANIDE CYCLOHEXANONE

EPA Region III RBC Table 4/2/2002

3 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

RfDo

CSFo

mg/kg/d

CAS

1,2-DICHLOROETHANE

107062

1,1-DICHLOROETHENE

75354

RfDi

1/mg/kg/d

3.00E-02 E

9.10E-02 I

9.00E-03 I

6.00E-01 I

CSFi

mg/kg/d 1.40E-03 E

water

1/mg/kg/d

VOC

Fish

air

ug/l

Soil, for groundwater migration

Soil

Ambient mg/kg

ug/m3

Industrial

Residential

DAF 1

mg/kg

mg/kg

mg/kg

DAF 20 mg/kg

9.10E-02 I

y

1.2E-01 C

6.9E-02 C

3.5E-02 C

6.3E+01 C

7.0E+00 C

5.2E-05

1.0E-03 C

1.75E-01 I

y

4.4E-02 C

3.6E-02 C

5.3E-03 C

9.5E+00 C

1.1E+00 C

1.8E-05

3.6E-04 C

CIS-1,2-DICHLOROETHENE

156592

1.00E-02 H

y

6.1E+01 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

1.7E-02

3.5E-01 N

TRANS-1,2-DICHLOROETHENE

156605

2.00E-02 I

y

1.2E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

4.1E-02

8.2E-01 N

TOTAL 1,2-DICHLOROETHENE

540590

9.00E-03 H

y

5.5E+01 N

3.3E+01 N

1.2E+01 N

1.8E+04 N

7.0E+02 N

1.9E-02

3.7E-01 N

2,4-DICHLOROPHENOL

120832

3.00E-03 I

1.1E+02 N

1.1E+01 N

4.1E+00 N

6.1E+03 N

2.3E+02 N

6.0E-02

1.2E+00 N

94757

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

4.5E-01

9.0E+00 N

2.9E+02 N

2.9E+01 N

1.1E+01 N

1.6E+04 N

6.3E+02 N 1.0E-04

2.1E-03 C

1.6E-04

3.1E-03 C

2,4-D 4-(2,4-DICHLOROPHENOXY)BUTYRIC ACID 1,2-DICHLOROPROPANE 2,3-DICHLOROPROPANOL 1,3-DICHLOROPROPENE DICHLORVOS DICOFOL

94826

8E-03 I 6.80E-02 H

78875 616239

3.00E-03 I

542756

3.00E-02 I

62737

5E-04 I

77736

DIELDRIN

60571

1.00E-01 I

5.71E-03 I

0.29 I

1.43E-04 I

84662 112345

DIETHYLENE GLYCOL, MONOETHYL ETHER

111900

DI(2-ETHYLHEXYL)ADIPATE DIETHYLSTILBESTROL 1,1-DIFLUOROETHANE DIISOPROPYL METHYLPHOSPHONATE (DIMP)

103231

5.00E-05 I

y 1.60E+01 I

1.60E+01 I

9.2E-02 C

4.6E-02 C

8.4E+01 C

9.4E+00 C

1.1E+01 N

4.1E+00 N

6.1E+03 N

2.3E+02 N

4.4E-01 C

6.3E-01 C

3.2E-02 C

5.7E+01 C

6.4E+00 C

2.3E-01 C

2.2E-02 C

1.1E-02 C

2.0E+01 C

2.2E+00 C

5.5E-05

1.1E-03 C

1.5E-01 C

1.4E-02 C

7.2E-03 C

1.3E+01 C

1.5E+00 C

9.3E-04

1.9E-02 C

4.4E-01 N

2.2E-01 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

3.9E-04 C

2.0E-04 C

3.6E-01 C

4.0E-02 C

1.1E-04

2.2E-03 C

2.3E+01

4.5E+02 N

8.5E-06

1.7E-04 N

3.4E-01

6.7E+00 N

1.8E-03

3.7E-02 N

4.2E-03 C

5.1E+00 N 2.9E+04 N

8.00E-01 I

1445756 119904 124403

6.00E-01 I

1.20E-03 I 4.70E+03 H

95681

N,N-DIMETHYLANILINE

121697

1.10E+01 I

y

5.70E-06 W

y

8.00E-02 I 1.40E-02 H 5.80E-01 H

21436964

2,4-DIMETHYLANILINE

1.6E+06 N

6.3E+04 N

7.3E+03 N

2.9E+03 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

5.6E+01 C

5.2E+00 C

2.6E+00 C

4.8E+03 C

5.3E+02 C

2.1E+01 N

8.00E-02 I

75376

3,3'-DIMETHOXYBENZIDINE

1.1E+03 N

7.3E+04 N

5.70E-03 H 2.00E+00 H

56531 43222486

DIMETHYLAMINE 2,4-DIMETHYLANILINE HYDROCHLORIDE

y

1.6E-01 C 1.1E+02 N

1.40E-03 I

DIETHYLENE GLYCOL, MONOBUTYL ETHER

DIFENZOQUAT (AVENGE)

1.00E-02 I

6.00E-05 A

3E-02 H

DIESEL EMISSIONS DIETHYLPHTHALATE

y

4.4E-01 W

115322

DICYCLOPENTADIENE

1.14E-03 I

7.50E-01 H 2.00E-03 I

1.4E-05 C

1.3E-06 C

6.7E-07 C

1.2E-03 C

1.4E-04 C

2.9E+03 N

2.9E+02 N

1.1E+02 N

1.6E+05 N

6.3E+03 N

8.0E+04 N

4.0E+04 N

2.9E+03 N

2.9E+02 N

1.1E+02 N

1.6E+05 N

6.3E+03 N

4.8E+00 C

4.5E-01 C

2.3E-01 C

4.1E+02 C

4.6E+01 C

4.2E-02 N

2.1E-02 N

1.2E-01 C

1.1E-02 C

5.4E-03 C

9.9E+00 C

1.1E+00 C

8.9E-02 C

8.3E-03 C

4.2E-03 C

7.6E+00 C

8.5E-01 C

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

6.8E-04 C

3.4E-04 C

6.2E-01 C

6.9E-02 C

1,1-DIMETHYLHYDRAZINE

57147

2.60E+00 W

3.50E+00 W

2.6E-02 C

1.8E-03 C

1.2E-03 C

2.2E+00 C

2.5E-01 C

1,2-DIMETHYLHYDRAZINE

540738

3.70E+01 W

3.70E+01 W

1.8E-03 C

1.7E-04 C

8.5E-05 C

1.5E-01 C

1.7E-02 C

2,4-DIMETHYLPHENOL

105679

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

3,3'-DIMETHYLBENZIDINE

7.3E-03 C

9.20E+00 H

119937

2.00E-02 I

2,6-DIMETHYLPHENOL

576261

6.00E-04 I

2.2E+01 N

2.2E+00 N

8.1E-01 N

1.2E+03 N

4.7E+01 N

3,4-DIMETHYLPHENOL

95658

1.00E-03 I

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

DIMETHYLPHTHALATE

131113

1.00E+01 W

3.7E+05 N

3.7E+04 N

1.4E+04 N

2.0E+07 N

7.8E+05 N

1,2-DINITROBENZENE

528290

4.00E-04 H

1.5E+01 N

1.5E+00 N

5.4E-01 N

8.2E+02 N

3.1E+01 N

1,3-DINITROBENZENE

99650

1.00E-04 I

3.7E+00 N

3.7E-01 N

1.4E-01 N

2.0E+02 N

7.8E+00 N

1,4-DINITROBENZENE

100254

4.00E-04 H

1.5E+01 N

1.5E+00 N

5.4E-01 N

8.2E+02 N

3.1E+01 N

4,6-DINITRO-O-CYCLOHEXYL PHENOL

131895

2.00E-03 I

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

4,6-DINITRO-2-METHYLPHENOL

534521

2,4-DINITROPHENOL

51285

1.00E-03 E

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

2.00E-03 I

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

9.8E-02 C

6.80E-01 I

DINITROTOLUENE MIX

9.2E-03 C

4.6E-03 C

8.4E+00 C

9.4E-01 C

2,4-DINITROTOLUENE

121142

2.00E-03 I

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

2.9E-02

5.7E-01 N

2,6-DINITROTOLUENE

606202

1.00E-03 H

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

1.2E-02

2.5E-01 N

DINOSEB

88857

DIOCTYLPHTHALATE

117840

1,4-DIOXANE

123911

DIPHENYLAMINE

122394

1.00E-03 I 2.00E-02 H 1.10E-02 I 2.50E-02 I

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

8.7E-03

1.7E-01 N

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

1.2E+05

2.4E+06 N

6.1E+00 C

5.7E-01 C

2.9E-01 C

5.2E+02 C

5.8E+01 C

1.3E-03

2.6E-02 C

9.1E+02 N

9.1E+01 N

3.4E+01 N

5.1E+04 N

2.0E+03 N

1.3E+00

2.5E+01 N

8.4E-02 C

7.8E-03 C

3.9E-03 C

7.2E+00 C

8.0E-01 C

1.3E-04

2.5E-03 C

85007

2.20E-03 I

8.0E+01 N

8.0E+00 N

3.0E+00 N

4.5E+03 N

1.7E+02 N

1.7E-02

3.3E-01 N

DISULFOTON

298044

4.00E-05 I

1.5E+00 N

1.5E-01 N

5.4E-02 N

8.2E+01 N

3.1E+00 N

3.2E-03

6.4E-02 N

1,4-DITHIANE

505293

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

DIURON

330541

2.00E-03 I

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

5.8E-02

1.2E+00 N

ENDOSULFAN

115297

6.00E-03 I

2.2E+02 N

2.2E+01 N

8.1E+00 N

1.2E+04 N

4.7E+02 N

9.8E-01

2.0E+01 N

2.7E-01

5.4E+00 N

1,2-DIPHENYLHYDRAZINE DIQUAT

ENDRIN

72208

8.00E-01 I

8.00E-01 I

122667

3.00E-04 I

EPICHLOROHYDRIN

106898

2.00E-03 H

ETHION

563122

5.00E-04 I

2-ETHOXYETHANOL

110805

ETHYL ACETATE

141786

9.00E-01 I

**ETHYLBENZENE

100414

1.00E-01 I

ETHYLENE DIAMINE

107153

2.00E-02 H

ETHYLENE GLYCOL

107211

2.00E+00 I

ETHYLENE GLYCOL, MONOBUTYL ETHER

111762

5.00E-01 I

9.90E-03 I

2.90E-01 I

ETHYLENE THIOUREA

96457

8.00E-05 I

ETHYL ETHER

60297

2.00E-01 I

y

1.1E+01 N

1.1E+00 N

4.1E-01 N

2.0E+00 N

1.0E+00 N

3.2E-01 C

1.8E+01 N

1.8E+00 N

6.8E-01 N

1.0E+03 N

2.1E+02 N

5.4E+02 N

1.5E+04 N 3.85E-03 E

3.50E-01 H

6.1E+02 N !

5.8E+02 C

2.3E+01 N !

6.5E+01 C

!

4.2E-04

8.4E-03 N

3.9E+01 N

3.2E-01

6.4E+00 N

8.2E+05 N

3.1E+04 N

3.3E+00

6.5E+01 N

y

5.5E+03 N

3.3E+03 N

1.2E+03 N

1.8E+06 N

7.0E+04 N

1.7E+00

3.5E+01 N

y

3.3E+00 C

1.6E+00 C

1.4E+02 N

2.0E+05 N

7.8E+03 N

1.8E-03

3.6E-02 C

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N 1.5E+01

3.0E+02 N

4.8E-06

9.5E-05 C

4.2E-01

8.5E+00 N

3.70E+00 I 1.00E+00 H

75218

4.20E-03 I

5.70E-02 I

4.00E-01 H

ETHYLENE OXIDE

2.86E-04 I

y

7.3E+04 N

7.3E+03 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

1.8E+04 N

1.4E+04 N

6.8E+02 N

1.0E+06 N

3.9E+04 N

2.3E-02 C

1.8E-02 C

3.2E-03 C

5.7E+00 C

6.4E-01 C

6.1E-01 C

1.1E-01 H y

1.2E+03 N

!

5.7E-02 C 7.3E+02 N

!

2.9E-02 C 2.7E+02 N

!

5.2E+01 C 4.1E+05 N

!

5.8E+00 C 1.6E+04 N

!

APPENDIX C2 RISK TABLES

C2-4

Tap Chemical

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

EPA Region III RBC Table 4/2/2002

4 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

Tap Chemical ETHYL METHACRYLATE FENAMIPHOS FLUOMETURON FLUORINE FOMESAFEN FONOFOS FORMALDEHYDE FORMIC ACID FURAN

CAS

HEXABROMOBENZENE

CSFi 1/mg/kg/d

VOC

air

Fish

Industrial

Residential

DAF 1

ug/m3

mg/kg

mg/kg

mg/kg

mg/kg

DAF 20 mg/kg

3.3E+02 N

1.2E+02 N

1.8E+05 N

7.0E+03 N

1.0E+00

2.1E+01 N

9.1E-01 N

3.4E-01 N

5.1E+02 N

2.0E+01 N

7.8E-03

1.6E-01 N

2164172

1.30E-02 I

4.7E+02 N

4.7E+01 N

1.8E+01 N

2.7E+04 N

1.0E+03 N

7782414

9.00E-02 H

2.2E+03 N

6.00E-02 I 1.90E-01 I

72178020 944229

2.00E-03 I

50000

2.00E-01 I

64186

2.00E+00 H

110009

y

water ug/l 9.1E+00 N

98011

HEPTACHLOR EPOXIDE

RfDi mg/kg/d

5.5E+02 N

FURFURAL

HEPTACHLOR

CSFo 1/mg/kg/d

2.50E-04 I

97632

67458

GLYPHOSATE

RfDo mg/kg/d

Soil, for groundwater migration

Soil

Ambient

22224926

FURAZOLIDONE GLYCIDALDEHYDE

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

4.50E-02 I y

1.00E-03 I 3.80E+00 H

2.2E+02 N

8.1E+01 N

1.2E+05 N

4.7E+03 N

3.5E-01 C

3.3E-02 C

1.7E-02 C

3.0E+01 C

3.4E+00 C

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

1.8E-01

3.5E+00 N

7.3E+03 N

1.4E-01 C

2.7E+02 N

4.1E+05 N

1.6E+04 N

1.5E+00

3.0E+01 N

7.3E+04 N

7.3E+03 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

6.1E+00 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

1.8E-02 C

1.6E-03 C

8.3E-04 C

1.5E+00 C

1.7E-01 C

4.1E+00 N

6.1E+03 N

2.3E+02 N

3.00E-03 I

1.00E-02 A

1.1E+02 N

3.7E+01 N

2.90E-04 H

1.5E+01 N

1.1E+00 N

5.4E-01 N

8.2E+02 N

3.1E+01 N

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

765344

4.00E-04 I

1071836

1.00E-01 I

1.5E-03

3.0E-02 N

2.3E-02

4.6E-01 N

7.8E+03 N

2.6E+01

5.3E+02 N

76448

5.00E-04 I

4.50E+00 I

4.50E+00 I

1.5E-02 C

1.4E-03 C

7.0E-04 C

1.3E+00 C

1.4E-01 C

4.2E-02

8.4E-01 C

1024573

1.30E-05 I

9.10E+00 I

9.10E+00 I

7.4E-03 C

6.9E-04 C

3.5E-04 C

6.3E-01 C

7.0E-02 C

1.2E-03

2.5E-02 C

87821

2.00E-03 I

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

1.60E+00 I

4.2E-02 C

7.80E-02 I

7.80E-02 I

8.6E-01 C

ALPHA-HCH

319846

6.30E+00 I

6.30E+00 I

1.1E-02 C

9.9E-04 C

5.0E-04 C

9.1E-01 C

1.0E-01 C

4.5E-05

8.9E-04 C

BETA-HCH

319857

1.80E+00 I

1.80E+00 I

3.7E-02 C

3.5E-03 C

1.8E-03 C

3.2E+00 C

3.5E-01 C

1.6E-04

3.1E-03 C

HEXACHLOROBENZENE HEXACHLOROBUTADIENE

GAMMA-HCH (LINDANE) TECHNICAL HCH

118741 87683

58899

8.00E-04 I 2.00E-04 H

3.00E-04 I

77474

HEXACHLORODIBENZODIOXIN MIX

19408743

HEXACHLOROETHANE

67721

1.00E-03 I

HEXACHLOROPHENE

70304

3.00E-04 I

1,6-HEXAMETHYLENE DIISOCYANATE

6.00E-02 H 4.00E-02 E

HEXAZINONE

51235042

3.30E-02 I

2691410

5.00E-02 I

HMX HYDROGEN CHLORIDE HYDROGEN SULFIDE HYDROQUINONE **IRON

7783064

4.9E-01 C

3.2E+00 C

3.5E-01 C

1.2E+04 N

4.7E+02 N

1.1E-05 C 4.8E+00 C

1.4E-06 C !

4.5E-01 C

5.1E-07 C !

2.3E-01 C

9.2E-04 C !

4.1E+02 C

!

2.6E-03

5.2E-02 C

9.2E-02

1.8E+00 C

2.2E-04

4.3E-03 C

8.8E+01

1.8E+03 N

1.0E-04 C !

4.6E+01 C

1.8E-02

3.6E-01 C

4.1E-01 N

6.1E+02 N

2.3E+01 N

1.0E+02

2.0E+03 N

2.1E+02 N

8.1E+01 N

1.2E+05 N

4.7E+03 N

6.9E-01

1.4E+01 N

5.1E+00 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

1.1E+01 N

1.1E+00 N

3.5E+02 N 1.5E+03 N

!

1.1E-02 N y

5.71E-02 I 1.4E-03 E

1.70E+01 I

1.2E+03 N

1.2E+02 N

4.5E+01 N

6.7E+04 N

2.6E+03 N

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

2.2E-02 C

3.7E-04 C

1.1E-03 C

1.9E+00 C

2.1E-01 C

4.1E+00 N

6.1E+03 N

2.3E+02 N

2.1E+01 N 1.1E+02 N

2.85E-04 I

1.0E+00 N

123319

4.00E-02 H

1.5E+03 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.00E-01 E

1.1E+04 N

1.1E+03 N

4.1E+02 N

6.1E+05 N

2.3E+04 N

1.8E+03 N

1.1E+03 N

4.1E+02 N

6.1E+05 N

2.3E+04 N

5.9E-01

1.2E+01 N

7.0E+01 C

6.6E+00 C

3.3E+00 C

6.0E+03 C

6.7E+02 C

2.1E-02

4.1E-01 C

5.5E+02 N

5.5E+01 N

2.0E+01 N

3.1E+04 N

1.2E+03 N 4.6E-05

9.2E-04 N

3.00E-01 I

ISOPHORONE

78591

2.00E-01 I

ISOPROPALIN

33820530

1.50E-02 I

ISOPROPYL METHYL PHOSPHONIC ACID

4.4E+00 C

8.2E+00 C

7439896 78831

TETRAETHYLLEAD

4.0E-01 C !

1.8E-03 C

5.70E-03 I

ISOBUTANOL

LITHIUM

2.4E-03 C

7.3E+01 C

8.1E+00 N

1.40E-02 I

3.00E-03 I

3.6E+00 C !

3.5E-03 C

4.55E+03 I

7647010

4.8E-03 C

4.0E-02 C

2.1E-01 N

1.40E-02 I

3.00E+00 I

302012

2.0E-03 C !

3.7E-02 C

2.90E-06 I

110543 591786

8.0E-02 C

2.2E+02 N

6.20E+03 I

822060

HEXANE 2-HEXANONE

HYDRAZINE

1.80E+00 I 5.7E-05 I

6.00E-03 I

3.9E-03 C !

5.2E-02 C

1.30E+00 H 1.80E+00 I

608731

HEXACHLOROCYCLOPENTADIENE

1.60E+00 I

y 9.50E-04 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

3.1E+03 N

7.8E+03 N

1832548

1.00E-01 I

78002

1.00E-07 I

3.7E-03 N

3.7E-04 N

1.4E-04 N

2.0E-01 N

7.8E-03 N

2.00E-02 E

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

7439932

7.3E+01 N

4.0E-01

8.1E+00 N

1.00E-01 I

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

7439965

2.00E-02 I

1.43E-05 I

7.3E+02 N

5.2E-02 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

4.8E+01

9.5E+02 N

MANGANESE-FOOD

7439965

1.40E-01 I

1.43E-05 I

5.1E+03 N

5.2E-02 N

1.9E+02 N

2.9E+05 N

1.1E+04 N

3.3E+02

6.7E+03 N

3.3E+00 N

3.3E-01 N

1.2E-01 N

1.8E+02 N

7.0E+00 N

1.1E+03 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

1.1E+01 N

1.1E+00 N

4.1E-01 N

6.1E+02 N

2.3E+01 N

MALATHION MALEIC ANHYDRIDE

MEPHOSFOLAN

121755

950107

2.00E-02 I

9.00E-05 H

24307264

3.00E-02 I

MERCURIC CHLORIDE

7487947

3.00E-04 I

MERCURY (INORGANIC)

743 9976

MEPIQUAT CHLORIDE

METHYLMERCURY METHACRYLONITRILE METHANOL METHIDATHION

7.8E+00 N 7.8E+00 N

2.1E-04

4.2E-03 N

6.8E+02 N

1.0E+06 N

3.9E+04 N

3.8E+00

7.5E+01 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

5.00E-01 I

1.8E+04 N

1.8E+03 N

1.00E-03 I

3.7E+01 N

3.7E+00 N

96333

2-METHYLANILINE

95534

4-(2-METHYL-4-CHLOROPHENOXY) BUTYRIC ACID

94815

2-METHYL-4-CHLOROPHENOXYACETIC ACID (MCPA)

2.0E+02 N 2.0E+02 N

67561

5.00E-03 I

C2-5

2-(2-METHYL-4-CHLOROPHENOXY)PROPIONIC ACID (MCPP)

1.4E-01 N 1.4E-01 N

950378

1.00E+00 H

METHYLCYCLOHEXANE

3.7E-01 N 7.3E-01 N

1.00E-04 I

72435

METHYL ACRYLATE

3.7E+00 N

1.00E-04 I

126987

79209

3.00E-02 A

5.00E-04 I 1.00E-03 I

74953

1.00E-02 A

METHYLENE CHLORIDE

75092

6.00E-02 I

7.50E-03 I

7.00E-04 H

1.30E-01 H

101144 101611 101688

6.8E+00 N

1.0E+04 N

3.9E+02 N

1.5E+01

3.1E+02 N

3.7E+03 N

1.4E+03 N

2.0E+06 N

7.8E+04 N

1.2E+00

2.5E+01 N

y

1.8E+02 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

y

8.60E-01 H

METHYLENE BROMIDE 4,4'-METHYLENE BIS(2-CHLOROANILINE)

1.8E+01 N

6.1E+03 N

2.40E-01 H

94746

4,4'-METHYLENE BIS(N,N'-DIMETHYL)ANILINE

1.8E+02 N y

1.00E-02 I

93652

4,4'-METHYLENEDIPHENYL ISOCYANATE

y

2.00E-04 A

108872

8.60E-01 H

1.65E-03 I 1.30E-01 H

4.60E-02 I 1.7E-04 I

1.6E+03 N

1.0E+00 N

22967926

METHOXYCHLOR

4.1E+04 N

3.1E-01 N

8.60E-05 I

METHYL ACETATE

2.7E+01 N

2.3E+03 N

5.0E-01

1.0E+01 N

2.8E-01 C

2.6E-02 C

1.3E-02 C

2.4E+01 C

2.7E+00 C

2.8E-04

5.7E-03 C

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

1.8E+01 N

1.8E+00 N

6.8E-01 N

1.0E+03 N

3.9E+01 N

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

6.3E+03 N

3.1E+03 N

y

6.1E+01 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

1.5E-02

3.0E-01 N

y

4.1E+00 C

3.8E+00 C

4.2E-01 C

7.6E+02 C

8.5E+01 C

9.5E-04

1.9E-02 C

5.2E-01 C

4.8E-02 C

2.4E-02 C

4.4E+01 C

4.9E+00 C

1.5E+00 C

1.4E-01 C

6.9E-02 C

1.2E+02 C

1.4E+01 C

6.2E-01 N

APPENDIX C2 RISK TABLES

7.3E+02 N

108316

MANGANESE-NONFOOD

EPA Region III RBC Table 4/2/2002

5 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

RfDo mg/kg/d

CAS

METHYL ETHYL KETONE (2-BUTANONE)

78933

METHYL HYDRAZINE

60344

METHYL ISOBUTYL KETONE (4-METHYL-2-PENTANONE) METHYL METHACRYLATE 2-METHYL-5-NITROANILINE METHYL PARATHION 2-METHYLPHENOL 3-METHYLPHENOL 4-METHYLPHENOL METHYLSTYRENE MIX ALPHA-METHYLSTYRENE **METHYL TERT-BUTYL ETHER METOLACHLOR (DUAL) MIREX MOLYBDENUM MONOCHLORAMINE NALED

108101 80626

CSFo

RfDi

1/mg/kg/d

mg/kg/d

CSFi

mg/kg

Industrial

Residential

DAF 1

mg/kg

mg/kg

mg/kg

1.0E+03 N

8.1E+02 N

1.2E+06 N

4.7E+04 N

6.1E-02 C

5.7E-03 C

2.9E-03 C

5.2E+00 C

5.8E-01 C

1.4E+02 N

7.3E+01 N

1.1E+02 N

1.6E+05 N

6.3E+03 N

6.5E-02

1.3E+00 N

y

1.4E+03 N

7.3E+02 N

1.9E+03 N

2.9E+06 N

1.1E+05 N

3.2E-01

6.5E+00 N

4.3E-03

8.5E-02 N

2.0E+00 C

1.9E-01 C

9.6E-02 C

1.7E+02 C

1.9E+01 C

2.50E-04 I

9.1E+00 N

9.1E-01 N

3.4E-01 N

5.1E+02 N

2.0E+01 N

95487

5.00E-02 I

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

3.30E-02 H

1.8E+03 N

5.00E-02 I

106445

5.00E-03 H

25013154

6.00E-03 A

98839

7.00E-02 A

1.00E-02 A 4.00E-03 O

1634044

8.57E-01 I

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

y

5.5E+01 N

3.7E+01 N

8.1E+00 N

1.2E+04 N

4.7E+02 N

5.1E-02

1.0E+00 N

y

4.3E+02 N

2.6E+02 N

9.5E+01 N

1.4E+05 N

5.5E+03 N

4.0E-01

7.9E+00 N

y

2.6E+00 C

1.6E+00 C

7.9E-01 C

1.4E+03 C

1.6E+02 C

5.9E-04

1.2E-02 C

1.2E-03

2.3E-02 N

8.7E-02

1.7E+00 N

51218452

1.50E-01 I

5.5E+03 N

5.5E+02 N

2.0E+02 N

3.1E+05 N

1.2E+04 N

2385855

2.00E-04 I

7.3E+00 N

7.3E-01 N

2.7E-01 N

4.1E+02 N

1.6E+01 N

7439987

5E-03 I

10599903

1E-01 I

300765

2E-03 I

7440020

2.00E-02 I

1.00E-01 H

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

7.3E+01 N

7.3E+00 N

2.7E+00 N

4.1E+03 N

1.6E+02 N

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

7.5E-03 C

8.4E-01 I 1.60E+00 I

10102439

1.00E-01 W

NITRITE

14797650

1.00E-01 I

88744

NITROBENZENE

98953

5.00E-04 I

NITROFURANTOIN

67209

7.00E-02 H

4-NITROPHENOL

100027

5.8E+03 N

2.2E+03 N

3.3E+06 N

1.3E+05 N

6.1E+02 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E+03 N

y

3.5E+00 N

2.2E+00 N

6.8E-01 N

1.0E+03 N

3.9E+01 N

2.6E+03 N

2.6E+02 N

9.5E+01 N

1.4E+05 N

5.5E+03 N

2.1E-01 N

6.00E-04 A 1.50E+00 H

59870 55630

5.8E+04 N y 5.70E-05 H

2-NITROANILINE

10102440

7.9E+00 N

y

99558

NITROGLYCERIN

mg/kg

2.00E-01 I

298000 108394

DAF 20 4.0E-01

2.00E-02 A

14797558

2-NITROPROPANE

ug/m3 1.9E+03 N

8.00E-02 H

NITRATE

NITROGEN DIOXIDE

Fish

air

ug/l

1.40E+00 I

NITRIC OXIDE

NITROFURAZONE

VOC y

1.10E+00 W

NICKEL REFINERY DUST NICKEL

water

1/mg/kg/d

2.86E-01 I

6.00E-01 I

Soil, for groundwater migration

Soil

Ambient

y

1.00E+00 W 1.4E-02 E 8.00E-03 E 5.70E-03 I

79469

N-NITROSO-DI-N-BUTYLAMINE

924163

5.40E+00 I

N-NITROSODIETHANOLAMINE

1116547

2.80E+00 I

N-NITROSODIETHYLAMINE

55185

1.50E+02 I

N-NITROSODIMETHYLAMINE

62759

5.10E+01 I

9.40E+00 H

y

5.60E+00 I

y

4.5E-02 C

4.2E-03 C

2.1E-03 C

3.8E+00 C

4.3E-01 C

6.1E+03 N

3.7E+03 N

1.4E+03 N

2.0E+06 N

7.8E+04 N

4.8E+00 C

4.5E-01 C

2.3E-01 C

4.1E+02 C

4.6E+01 C

2.9E+02 N

2.9E+01 N

1.1E+01 N

1.6E+04 N

6.3E+02 N

1.3E-03 C

6.7E-04 C

3.2E-07

6.4E-06 C

1.4E-06

2.7E-05 C

1.9E-03 C

1.1E-03 C

5.8E-04 C

1.1E+00 C

1.2E-01 C

2.4E-02 C

2.2E-03 C

1.1E-03 C

2.0E+00 C

2.3E-01 C

1.50E+02 I

4.5E-04 C

4.2E-05 C

2.1E-05 C

3.8E-02 C

4.3E-03 C

1.1E-07

2.3E-06 C

5.10E+01 I

1.3E-03 C

1.2E-04 C

6.2E-05 C

1.1E-01 C

1.3E-02 C

2.8E-07

5.7E-06 C

4.90E-03 I

1.4E+01 C

1.3E+00 C

6.4E-01 C

1.2E+03 C

1.3E+02 C

3.8E-02

7.6E-01 C

N-NITROSODIPROPYLAMINE

621647

7.00E+00 I

9.6E-03 C

8.9E-04 C

4.5E-04 C

8.2E-01 C

9.1E-02 C

2.4E-06

4.7E-05 C

N-NITROSO-N-ETHYLUREA

759739

1.40E+02 H

4.8E-04 C

4.5E-05 C

2.3E-05 C

4.1E-02 C

4.6E-03 C

1.9E-01

3.8E+00 N

N-NITROSODIPHENYLAMINE

N-NITROSO-N-METHYLETHYLAMINE N-NITROSOPYRROLIDINE

86306

3.0E-03 C

2.20E+01 I

10595956 2.00E-02 E

O-NITROTOLUENE

88722

1.00E-02 H

P-NITROTOLUENE

99990

1.00E-02 H

2.8E-04 C

1.4E-04 C

2.6E-01 C

2.9E-02 C

3.2E-02 C

3.0E-03 C

1.5E-03 C

2.7E+00 C

3.0E-01 C

1.2E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

y

6.1E+01 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

y

6.1E+01 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

2.6E+01 N

2.6E+00 N

9.5E-01 N

1.4E+03 N

2.10E+00 I

2.10E+00 I

930552 99081

M-NITROTOLUENE

y

5.5E+01 N

NUSTAR

85509199

7.00E-04 I

ORYZALIN

19044883

5.00E-02 I

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

OXADIAZON

19666309

5.00E-03 I

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

OXAMYL

23135220

2.50E-02 I

9.1E+02 N

9.1E+01 N

3.4E+01 N

5.1E+04 N

2.0E+03 N

OXYFLUORFEN

42874033

3.00E-03 I

1.1E+02 N

1.1E+01 N

4.1E+00 N

6.1E+03 N

2.3E+02 N

PARAQUAT DICHLORIDE PARATHION PENTACHLOROBENZENE PENTACHLORONITROBENZENE PENTACHLOROPHENOL PERMETHRIN

191 0425 56382 608935

1.6E+02 N

1.6E+01 N

6.1E+00 N

9.2E+03 N

3.5E+02 N

6.00E-03 H

2.2E+02 N

2.2E+01 N

8.1E+00 N

1.2E+04 N

4.7E+02 N

5.0E-01

1.0E+01 N

8.00E-04 I

2.9E+01 N

2.9E+00 N

1.1E+00 N

1.6E+03 N

6.3E+01 N

1.0E+00

2.0E+01 N

4.50E-03 I

3.00E-03 I

2.60E-01 H

87865

3.00E-02 I

1.20E-01 I

52645531

5.00E-02 I

82688

1.2E-02 C

2.2E+01 C

2.5E+00 C

4.1E-03

8.2E-02 C

5.6E-01 C

5.2E-02 C

2.6E-02 C

4.8E+01 C

5.3E+00 C

1.8E+03 N

2.6E-01 C

1.8E+02 N

2.4E-02 C

6.8E+01 N

1.0E+05 N

3.9E+03 N

1.2E+02

2.4E+03 N

PHENOL

108952

6.00E-01 I

2.2E+04 N

2.2E+03 N

8.1E+02 N

1.2E+06 N

4.7E+04 N

6.7E+00

1.3E+02 N

M-PHENYLENEDIAMINE

108452

6.00E-03 I

2.2E+02 N

2.2E+01 N

8.1E+00 N

1.2E+04 N

4.7E+02 N

4.9E-02

9.8E-01 N

O-PHENYLENEDIAMINE

95545

1.4E+00 C

1.3E-01 C

6.7E-02 C

1.2E+02 C

1.4E+01 C

6.9E+03 N

6.9E+02 N

2.6E+02 N

3.5E+01 C

3.3E+00 C

1.7E+00 C

3.0E+03 C

3.4E+02 C

1.1E+01 N

3.1E-01 N

4.1E-01 N

6.1E+02 N

2.3E+01 N

2.6E+01

5.2E+02 N

P-PHENYLENEDIAMINE 2-PHENYLPHENOL

106503 7803512

PHOSPHORIC ACID

7664382

PHOSPHORUS (WHITE)

7723140

PHTHALIC ANHYDRIDE

100210 85449

1.90E-03 H

12674112 11104282

3.9E+05 N

1.5E+04 N

1.1E+01 N

2.90E-03 I 2.00E-05 I

7.3E-01 N

7.3E-02 N

1.00E+00 H

3.7E+04 N

3.7E+03 N

1.4E+03 N

2.0E+06 N

7.8E+04 N

7.3E+04 N

1.3E+02 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

7.5E-03 C

7.0E-04 C

3.5E-04 C

6.4E-01 C

7.2E-02 C

3.43E-02 H

2.00E+00 I 8.90E+00 H

2.00E+00 I

3.3E-02 C

7.00E-02 I

7.00E-02 I

9.6E-01 C

2.00E+00 I

2.00E+00 I

3.3E-02 C

2.00E+00 I

1336363

AROCLOR-1016 AROCLOR-1221

8.60E-05 I

3.00E-04 I

7.00E-06 H

POLYBROMINATED BIPHENYLS POLYCHLORINATED BIPHENYLS

1.90E-01 H

90437

PHOSPHINE

P-PHTHALIC ACID

4.70E-02 H

7.00E-05 I

2.7E-02 N

3.1E-03 C !

8.9E-02 C 3.1E-03 C

4.1E+01 N

1.6E-03 C !

4.5E-02 C 1.6E-03 C

1.6E+00 N

2.9E+00 C !

8.2E+01 C 2.9E+00 C

!

!

3.2E-01 C

2.1E-02

4.1E-01 C

5.5E+00 N

2.1E-01

4.2E+00 C

3.2E-01 C

APPENDIX C2 RISK TABLES

C2-6

Tap Chemical

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

EPA Region III RBC Table 4/2/2002

6 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

Chemical

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

CAS

RfDo

CSFo

RfDi

CSFi

mg/kg/d

1/mg/kg/d

mg/kg/d

1/mg/kg/d

VOC

Soil, for groundwater migration

Soil

Tap

Ambient

water

air

Fish

Industrial

Residential

DAF 1

DAF 20

ug/l

ug/m3

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

AROCLOR-1232

11141165

2.00E+00 I

2.00E+00 I

3.3E-02 C

3.1E-03 C

1.6E-03 C

2.9E+00 C

3.2E-01 C

AROCLOR-1242

53469219

2.00E+00 I

2.00E+00 I

3.3E-02 C

3.1E-03 C

1.6E-03 C

2.9E+00 C

3.2E-01 C

AROCLOR-1248

12672296

2.00E+00 I

2.00E+00 I

3.3E-02 C

3.1E-03 C

1.6E-03 C

2.9E+00 C

3.2E-01 C

AROCLOR-1254

11097691

2.00E+00 I

2.00E+00 I

3.3E-02 C

3.1E-03 C

1.6E-03 C

2.9E+00 C

3.2E-01 C

AROCLOR-1260

11096825

2.00E+00 I

2.00E+00 I

3.3E-02 C

3.1E-03 C

1.6E-03 C

2.9E+00 C

3.2E-01 C

POLYCHLORINATED TERPHENYLS

61788338

2.00E-05 I

!

5.4E-02

1.1E+00 C

1.5E-02 C

1.4E-03 C

7.0E-04 C

1.3E+00 C

1.4E-01 C

83329

6.00E-02 I

y

3.7E+02 N

2.2E+02 N

8.1E+01 N

1.2E+05 N

4.7E+03 N

5.2E+00

1.0E+02 N

120127

3.00E-01 I

y

1.8E+03 N

1.1E+03 N

4.1E+02 N

6.1E+05 N

2.3E+04 N

2.3E+01

4.7E+02 N

4.50E+00 E

POLYNUCLEAR AROMATIC HYDROCARBONS: ACENAPHTHENE ANTHRACENE

56553

7.30E-01 E

9.2E-02 C

8.6E-03 C

4.3E-03 C

7.8E+00 C

8.7E-01 C

7.3E-02

BENZO[B]FLUORANTHENE

205992

7.30E-01 E

9.2E-02 C

8.6E-03 C

4.3E-03 C

7.8E+00 C

8.7E-01 C

2.3E-01

4.5E+00 C

BENZO[K]FLUORANTHENE

207089

7.30E-02 E

9.2E-01 C

8.6E-02 C

4.3E-02 C

7.8E+01 C

8.7E+00 C

2.3E+00

4.5E+01 C

BENZ[A]ANTHRACENE

BENZO[A]PYRENE CARBAZOLE CHRYSENE DIBENZ[A,H]ANTHRACENE DIBENZOFURAN FLUORANTHENE FLUORENE INDENO[1,2,3-C,D]PYRENE 2-METHYLNAPHTHALENE

50328

7.30E+00 I

4.3E-04 C

7.8E-01 C

8.7E-02 C

86748

2.00E-02 H

3.3E+00 C

3.1E-01 C

1.6E-01 C

2.9E+02 C

3.2E+01 C

2.3E-02

4.7E-01 C

218019

7.30E-03 E

9.2E+00 C

8.6E-01 C

4.3E-01 C

7.8E+02 C

8.7E+01 C

7.3E+00

1.5E+02 C

4.00E-03 E

206440

4.00E-02 I

86737

4.00E-02 I

91576

2.00E-02 E

9.2E-03 C

8.6E-04 C

4.3E-04 C

7.8E-01 C

8.7E-02 C

7.0E-02

1.4E+00 C

1.5E+01 N

5.4E+00 N

8.2E+03 N

3.1E+02 N

3.8E-01

7.7E+00 N

1.5E+03 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

3.1E+02

6.3E+03 N

y

2.4E+02 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

6.8E+00

1.4E+02 N

9.2E-02 C

8.6E-03 C

4.3E-03 C

7.8E+00 C

8.7E-01 C

6.4E-01

1.3E+01 C

y

1.2E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

1.1E+00

2.2E+01 N

9.00E-04 I

y

6.5E+00 N

3.3E+00 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

7.7E-03

1.5E-01 N

y

1.8E+02 N

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

3.4E+01

6.8E+02 N

5.5E+02 N

5.5E+01 N

2.0E+01 N

3.1E+04 N

1.2E+03 N 3.1E+02 N

1.4E+00

2.8E+01 N

91203

2.00E-02 I

129000

3.00E-02 I

1610180

1.50E-02 I

PROMETRYN

7287196

4.00E-03 I

1.5E+02 N

1.5E+01 N

5.4E+00 N

8.2E+03 N

PROPACHLOR

1918167

1.30E-02 I

4.7E+02 N

4.7E+01 N

1.8E+01 N

2.7E+04 N

1.0E+03 N

709988

5.00E-03 I

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

2312358

2.00E-02 I

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

2.4E+02 N

1.5E+02 N

5.4E+01 N

8.2E+04 N

3.1E+03 N

7.3E+05 N

7.3E+04 N

2.7E+04 N

4.1E+07 N

1.6E+06 N

NAPHTHALENE PYRENE PROMETON

PROPANIL PROPARGITE N-PROPYLBENZENE PROPYLENE GLYCOL

103651

4.00E-02 E

57556

2.00E+01 H

52125538

7.00E-01 H

y

2.6E+04 N

2.6E+03 N

9.5E+02 N

1.4E+06 N

5.5E+04 N

2.6E+04 N

2.1E+03 N

9.5E+02 N

1.4E+06 N

5.5E+04 N

PURSUIT

81335775

2.50E-01 I

9.1E+03 N

9.1E+02 N

3.4E+02 N

5.1E+05 N

2.0E+04 N

PYRIDINE

110861

1.00E-03 I

3.7E+01 N

3.7E+00 N

1.4E+00 N

2.0E+03 N

7.8E+01 N

PROPYLENE GLYCOL, MONOETHYL ETHER PROPYLENE GLYCOL, MONOMETHYL ETHER

**QUINOLINE RDX RESMETHRIN RONNEL ROTENONE

107982

3.00E-03 I 3.00E-02 I

83794

2.2E-02 C

3.00E+00 I

91225 121824 10453868 299843

5.70E-01 I

7.00E-01 H

3.7E-01 C

2.4E+01 N

7.30E-01 E

193395

2.0E-03 C

y

7.30E+00 E

53703 132649

9.2E-03 C

3.10E+00 E

1.9E-02

1.5E+00 C

1.10E-01 I

1.1E-03 C

1.9E+00 C

6.1E-01 C

5.7E-02 C

2.9E-02 C

5.2E+01 C

5.8E+00 C

1.1E+03 N

1.1E+02 N

2.1E-03 C

4.1E+01 N

6.1E+04 N

2.3E+03 N

2.1E-01 C

5.00E-02 H

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

4.00E-03 I

1.5E+02 N

1.5E+01 N

5.4E+00 N

8.2E+03 N

3.1E+02 N

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

SELENIUM

7782492

5.00E-03 I

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

9.5E-01

1.9E+01 N

SILVER

7440224

5.00E-03 I

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

1.6E+00

3.1E+01 N

4.8E+01 C

5.3E+00 C

1.7E-04

3.3E-03 C

1.5E+04 N

SELENIOUS ACID

SIMAZINE SODIUM AZIDE SODIUM DIETHYLDITHIOCARBAMATE STRONTIUM, STABLE STYRENE 2,3,7,8-TETRACHLORODIBENZODIOXIN 1,2,4,5-TETRACHLOROBENZENE 1,1,1,2-TETRACHLOROETHANE 1,1,2,2-TETRACHLOROETHANE **TETRACHLOROETHENE 2,3,4,6-TETRACHLOROPHENOL P,A,A,A-TETRACHLOROTOLUENE 1,1,1,2-TETRAFLUOROETHANE

5.00E-03 I

1.20E-01 H

5.6E-01 C

5.2E-02 C

2.6E-02 C

1.5E+02 N

1.5E+01 N

5.4E+00 N

8.2E+03 N

3.1E+02 N

2.5E-01 C

2.3E-02 C

1.2E-02 C

2.1E+01 C

2.4E+00 C

2.2E+04 N

2.2E+03 N

8.1E+02 N

1.2E+06 N

4.7E+04 N

7.7E+02

1.1E+01 N

1.1E+00 N

4.1E-01 N

6.1E+02 N

2.3E+01 N

8.3E-03

1.7E-01 N

1.0E+03 N

2.7E+02 N

4.1E+05 N

1.6E+04 N

2.9E+00

5.7E+01 N

122349

5.00E-03 I

26628228

4.00E-03 I

148185

3.00E-02 I

7440246

6.00E-01 I

57249

3.00E-04 I

100425

2.00E-01 I

1.6E+03 N

2.70E-01 H

y

2.86E-01 I 1.50E+05 H

1.50E+05 H

95943

3.00E-04 I

630206

3.00E-02 I

2.60E-02 I

2.60E-02 I

y

6.00E-02 E

2.00E-01 I

2.00E-01 I

y

1.00E-02 E

y

1746016

79345 127184

1.00E-02 I

58902

3.00E-02 I

5.2E-02 E

1.4E-01 E

2.00E+01 H

5216251

y

2.29E+01 I

811972

4.2E-08 C 1.1E+00 N

4.1E-01 N

6.1E+02 N

2.3E+01 N

3.3E-02

6.6E-01 N

4.1E-01 C

2.4E-01 C

1.2E-01 C

2.2E+02 C

2.5E+01 C

2.0E-04

4.0E-03 C

5.3E-02 C

3.1E-02 C

2.1E-08 C

3.8E-05 C

4.3E-06 C

1.6E-02 C

2.9E+01 C

3.2E+00 C

3.4E-05

6.8E-04 C

6.3E-01 C

6.1E-02 C

1.1E+02 C

1.2E+01 C

1.4E-03

2.9E-02 C

1.1E+02 N

4.1E+01 N

6.1E+04 N

2.3E+03 N

3.3E-03 C

3.1E-04 C

1.6E-04 C

2.9E-01 C

3.2E-02 C

1.7E+05 N

8.4E+04 N

1.8E-01

3.6E+00 N

109999

2.00E-01 E

8.8E+00 C

9.2E-01 C

4.2E-01 C

7.5E+02 C

8.4E+01 C

479458

1.00E-02 H

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

THALLIC OXIDE

1314325

7.00E-05 W

2.6E+00 N

2.6E-01 N

9.5E-02 N

1.4E+02 N

5.5E+00 N

THALLIUM

7440280

7.00E-05 O

2.6E+00 N

2.6E-01 N

9.5E-02 N

1.4E+02 N

5.5E+00 N

9.00E-05 I

3.3E+00 N

3.3E-01 N

1.2E-01 N

1.8E+02 N

7.0E+00 N

THALLIUM ACETATE

C2-7

THALLIUM CARBONATE THALLIUM CHLORIDE THALLIUM NITRATE THALLIUM SULFATE (2:1) THIOBENCARB TIN

563688 6533739

8.00E-05 I

2.9E+00 N

2.9E-01 N

1.1E-01 N

1.6E+02 N

6.3E+00 N

7791120

8.00E-05 I

2.9E+00 N

2.9E-01 N

1.1E-01 N

1.6E+02 N

6.3E+00 N

10102451

9.00E-05 I

3.3E+00 N

3.3E-01 N

1.2E-01 N

1.8E+02 N

7.0E+00 N

7446186

8.00E-05 I

1.1E-01 N

1.6E+02 N

6.3E+00 N

28249776

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

6.00E-01 H

2.2E+04 N

2.2E+03 N

8.1E+02 N

1.2E+06 N

4.7E+04 N

7440315

8.6E-06 C

6.3E-01 C

TETRAHYDROFURAN

8.6E-02 E

4.3E-07

1.1E+03 N

TETRYL

7.6E-03 E

6.8E-03 E

4.5E-07 C 1.1E+01 N

2.9E+00 N

2.9E-01 N

APPENDIX C2 RISK TABLES

STRYCHNINE

7783008

7 Basis: C = Carcinogenic effects N = Noncarcinogenic effects ! = RBC at HI of 0.1 < RBC-c

Sources: I = IRIS H = HEAST A = HEAST Alternate W = Withdrawn from IRIS or HEAST

Chemical TITANIUM TITANIUM DIOXIDE TOLUENE TOLUENE-2,4-DIAMINE

CAS

RfDo

CSFo

RfDi

CSFi

mg/kg/d

1/mg/kg/d

mg/kg/d

1/mg/kg/d

air

Fish

Industrial

Residential

DAF 1

DAF 20

ug/l

ug/m3

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

4.00E+00 E

8.60E-03 E

1.5E+05 N

3.1E+01 N

5.4E+03 N

8.2E+06 N

3.1E+05 N

4.00E+00 E

8.60E-03 E

1.5E+05 N

3.1E+01 N

5.4E+03 N

8.2E+06 N

3.1E+05 N

7.5E+02 N

4.2E+02 N

2.7E+02 N

4.1E+05 N

1.6E+04 N

2.1E-02 C

2.0E-03 C

9.9E-04 C

1.8E+00 C

2.0E-01 C

108883

3.20E+00 H

95705

6.00E-01 H

823405

2.00E-01 H

TOXAPHENE

8001352 615543 56359

2,4,6-TRICHLOROANILINE

634935

1,2,4-TRICHLOROBENZENE

120821

y

1.14E-01 I

2.00E-01 I

95807

106490

TRIBUTYLTIN OXIDE

Ambient

water

7440326

TOLUENE-2,6-DIAMINE

1,2,4-TRIBROMOBENZENE

VOC

Soil, for groundwater migration

Soil

Tap

13463677

P-TOLUIDINE

TOLUENE-2,5-DIAMINE

Region III SSLs

Risk-based concentrations

E = EPA-NCEA provisional value O = other

1.90E-01 H 1.10E+00 I

1.10E+00 I 5.00E-03 I

8.8E+00 N

2.2E+04 N

2.2E+03 N

8.1E+02 N

1.2E+06 N

4.7E+04 N

7.3E+03 N

7.3E+02 N

2.7E+02 N

4.1E+05 N

1.6E+04 N

3.5E-01 C

3.3E-02 C

1.7E-02 C

3.0E+01 C

3.4E+00 C

3.0E-04

5.9E-03 C

6.1E-02 C

5.7E-03 C

2.9E-03 C

5.2E+00 C

5.8E-01 C

3.1E-02

6.3E-01 C

1.8E+02 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

1.1E+01 N

3.00E-04 I

4.4E-01

1.1E+00 N

4.1E-01 N

6.1E+02 N

2.3E+01 N

2.0E+00 C

1.8E-01 C

9.3E-02 C

1.7E+02 C

1.9E+01 C

1.00E-02 I

5.70E-02 H

y

1.9E+02 N

2.1E+02 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

3.8E-01

7.5E+00 N

6.30E-01 E

y

3.2E+03 N

2.3E+03 N

3.8E+02 N

5.7E+05 N

2.2E+04 N

3.0E+00

6.0E+01 N

3.40E-02 H

1,1,1-TRICHLOROETHANE

71556

2.80E-01 E

1,1,2-TRICHLOROETHANE

79005

4.00E-03 I

5.70E-02 I

**TRICHLOROETHENE

79016

3.00E-04 E

4.00E-01 E

TRICHLOROFLUOROMETHANE

75694

3.00E-01 I 1.00E-01 I

1.00E-02 E

5.60E-02 I

y

1.9E-01 C

1.1E-01 C

5.5E-02 C

1.0E+02 C

1.1E+01 C

3.9E-05

4.00E-01 E

y

2.6E-02 C

1.6E-02 C

7.9E-03 C

1.4E+01 C

1.6E+00 C

1.3E-05

2.6E-04 C

y

1.3E+03 N

7.3E+02 N

4.1E+02 N

6.1E+05 N

2.3E+04 N

1.1E+00

2.3E+01 N

2.00E-01 A

3.7E+03 N

3.7E+02 N

1.4E+02 N

2.0E+05 N

7.8E-04 C

7.8E+03 N

2,4,5-TRICHLOROPHENOL

95954

2,4,6-TRICHLOROPHENOL

88062

6.1E+00 C

6.3E-01 C

2.9E-01 C

5.2E+02 C

5.8E+01 C

2,4,5-T

93765

1.00E-02 I

3.7E+02 N

3.7E+01 N

1.4E+01 N

2.0E+04 N

7.8E+02 N

9.8E-02

2.0E+00 N

2-(2,4,5-TRICHLOROPHENOXY)PROPIONIC ACID

93721

8.00E-03 I

2.9E+02 N

2.9E+01 N

1.1E+01 N

1.6E+04 N

6.3E+02 N

1.1E+00

2.1E+01 N 2.5E-01 N

1.00E-02 I

1.10E-02 I

y

3.0E+01 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

1.2E-02

1.4E-03 E

y

5.3E-03 C

3.1E-03 C

1.6E-03 C

2.9E+00 C

3.2E-01 C

1.8E-06

y

3.0E+01 N

1.8E+01 N

6.8E+00 N

1.0E+04 N

3.9E+02 N

1.2E-02

2.5E-01 N

8.60E+00 H

y

5.9E+04 N

3.1E+04 N

4.1E+04 N

6.1E+07 N

2.3E+06 N

1.2E+02

2.3E+03 N

2.6E+02

5.1E+03 N

1,1,2-TRICHLOROPROPANE

598776

5.00E-03 I

1,2,3-TRICHLOROPROPANE

96184

6.00E-03 I

1,2,3-TRICHLOROPROPENE

96195

5.00E-03 H

1,1,2-TRICHLORO-1,2,2-TRIFLUOROETHANE

76131

3.00E+01 I

1,2,4-TRIMETHYLBENZENE

95636

5.00E-02 E

1.70E-03 E

y

1.2E+01 N

6.2E+00 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

1,3,5-TRIMETHYLBENZENE

108678

5.00E-02 E

1.70E-03 E

y

1.2E+01 N

6.2E+00 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

TRIMETHYL PHOSPHATE

512561

1,3,5-TRINITROBENZENE

99354

3.00E-02 I

2,4,6-TRINITROTOLUENE

118967

5.00E-04 I

7440611

3.00E-03 I

URANIUM (SOLUBLE SALTS; from IRIS)

2.00E+00 E

3.70E-02 H

1.8E+00 C

3.00E-02 I

2.2E+00 C

1.7E-01 C

1.1E+03 N 1.1E+02 N

2.1E-01 C 1.1E+01 N

1.5E+02 C

4.1E+01 N !

1.1E-01 C 4.1E+00 N

1.7E+01 C

6.1E+04 N !

1.9E+02 C 6.1E+03 N

2.1E+01 C

7.3E-01 N

2.7E-01 N

7440622

7.00E-03 H

2.6E+02 N

2.6E+01 N

9.5E+00 N

1.4E+04 N

5.5E+02 N

1314621

9.00E-03 I

3.3E+02 N

3.3E+01 N

1.2E+01 N

1.8E+04 N

7.0E+02 N

2.00E-04 E

!

2.3E+02 N

VANADIUM

7440611

4.1E+02 N

2.3E+03 N !

VANADIUM PENTOXIDE

URANIUM (SOLUBLE SALTS; provisional)

7.3E+00 N

8.5E-02 C

1.1E+02 N !

3.6E-05 C

1.6E+01 N

VANADIUM SULFATE

16785812

2.00E-02 H

7.3E+02 N

7.3E+01 N

2.7E+01 N

4.1E+04 N

1.6E+03 N

VINCLOZOLIN

50471448

2.50E-02 I

9.1E+02 N

9.1E+01 N

3.4E+01 N

5.1E+04 N

2.0E+03 N

1.4E+03 N

2.0E+06 N

7.8E+04 N

8.7E-02

1.7E+00 N

9.0E-02 C

1.7E-05

3.3E-04 C

4.4E-03 C

7.9E+00 C

y

4.1E+02 N

2.1E+02 N

VINYL CHLORIDE inc earlylife(see cover memos)

75014

3.00E-03 I

1.40E+00 I

2.8E-02 I

3.00E-02 I

y

1.5E-02 C

7.2E-02 C

VINYL CHLORIDE: adult (see cover memos)

75014

3.00E-03 I

7.20E-01 I

2.8E-02 I

1.5E-02 I

y

VINYL ACETATE

108054

5.71E-02 I

1.00E+00 H

1.1E+01 N

1.1E+00 N

6.1E+02 N

2.3E+01 N

2.2E-02

4.4E-01 N

M-XYLENE

108383

2.00E+00 H

y

1.2E+04 N

7.3E+03 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

1.3E+01

2.5E+02 N

O-XYLENE

95476

2.00E+00 H

y

1.2E+04 N

7.3E+03 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

1.1E+01

2.3E+02 N

1330207

2.00E+00 I

y

1.2E+04 N

7.3E+03 N

2.7E+03 N

4.1E+06 N

1.6E+05 N

8.5E+00

1.7E+02 N

ZINC

7440666

3.00E-01 I

1.1E+04 N

1.1E+03 N

4.1E+02 N

6.1E+05 N

2.3E+04 N

6.8E+02

1.4E+04 N

ZINC PHOSPHIDE

1314847

3E-04 I

1.1E+01 N

1.1E+00 N

4.1E-01 N

6.1E+02 N

2.3E+01 N

12122677

5E-02 I

1.8E+03 N

1.8E+02 N

6.8E+01 N

1.0E+05 N

3.9E+03 N

WARFARIN

P-XYLENE XYLENES

ZINEB

81812

3.00E-04 I

4.1E-01 N

y

106423

APPENDIX C2 RISK TABLES

C2-8 EPA Region III RBC Table 4/2/2002

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX C3

RCRA GROUND WATER APPENDIX IX PARAMETER LISTS

C3-1

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

The Appendix VIII groups of chemicals were intended to be a comprehensive list of chemicals that could exist in hazardous waste, were considered to be a health hazard and should therefore be regulated. Chemicals were listed in Appendix VIII as they would exist in a pure state, as opposed to the forms they would be expected to take after being dispersed in the environment. No attempt was made to examine factors such as amount of production or environmental fate.

Therefore, Appendix VIII contains both prevalent, mobile and toxic chemicals that present major risks in ground water at hazardous waste sites, as well as chemicals which do not present such risks because of factors such as low prevalence or instability in water.

Furthermore, the Appendix VIII list of chemicals has a variety of analytical problems associated with it including ambiguous listings, compound categories, constituents unstable in water, unavailable reference standards, lack of standardized test methods and technical problems.

In response to these problems U.S. EPA promulgated on July 9, 1987 a final ruling replacing the use of the Appendix VIII list of chemicals with a new list, Appendix IX. In summary, the Appendix IX list contains those chemicals from the Appendix VIII list that are amenable to SW846 analytical techniques plus 17 additional compounds routinely analyzed under the Superfund program. Appendix IX contains 233 compounds. The Appendix IX list also contains practical quantitation limits (PQLs) for each constituent using the suggested method. PQLs are the lowest concentrations of the analyte in ground water which can be accurately determined using the indicated method under routine laboratory operating conditions. In many cases the PQL is based on a general estimate for the method not on experimentation. The PQLs are NOT part of the regulation.

C3-2

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX

COMPOUND NAME Acenaphthene

CAS RN 83-32-9

Acenaphthylene

208-96-8

Acetone Acetophenone Acetonitrile; Methyl cyanide 2-Acetylaminofluorene; 2 AAF Acrolein

67-64-1 98-86-2 75-05-8 53-96-3 107-02-8

Acrylonitrile

107-13-1

Aldrin

309-00-2

Allyl chloride

107-05-1

4-Aminobiphenyl Aniline Anthracene

92-67-1 62-53-3 120-12-7

Antimony

(Total)

Aramite Arsenic

140-57-8 (Total)

Barium

(Total)

Benzene

71-43-2

Benzo[a]anthracene; Benzanthracene

56-55-3

Benzo[b]fluoranthene

205-99-2

Benzo[k]fluoranthene

207-08-9

Benzo[gh]perylene

191-24-2

Benzo[a]pyrene

50-32-8

Benzyl alcohol Beryllium

100-51-6 (Total)

alpha BHC

319-84-6

Suggested Methods 8100 8270 8100 8270 8240 8270 8015 8270 8030 8240 8030 8240 8080 8270 8010 8240 8270 8270 8100 8270 6010 7040 7041 8270 6010 7060 7061 6010 7080 8020 8240 8100 8270 8100 8270 8100 8270 8100 8270 8100 8270 8270 6010 7090 7091 8080 8250

PQL μg/L (μ 200 10 200 10 100 10 100 10 5 5 5 5 0.05 10 5 100 10 10 200 10 300 2000 30 10 500 10 20 20 1000 2 5 200 10 200 10 200 10 200 10 200 10 20 3 50 2 0.05 10

C3-3

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.) COMPOUND NAME ` BHC b BHC

CAS RN 319-85-7 8250 319-86-8

a BHC; Lindane

58-89-9

bis(2-chloroethoxy)methane bis(2-chloroethyl)ether bis(2-chloro- l-methyl)ether,2,2'Di-chlorodiisopropyl ether

111-91-1 111-44-4 108-60-1

bis(2-ethylhexyl)phthalate

117-81-7

Bromodichloromethane

75-27-4

Bromoform; Tribromomethane

75-25-2

4-Bromophenyl phenyl ether Butyl benzyl phthalate; Benzyl butyl phthalate

101-55-3 85-68-7

Cadmium

(Total)

Carbon disulfide Carbon tetrachloride

75-15-0 56-23-5

Chlordane

57-74-9

p-Chloroaniline Chlorobenzene

106-47-8 108-90-7

Chlorobenzilate p-Chloro-m-cresol

510-15-6 59-50-7

Chloroethane; Ethyl chloride

75-00-3

Chloroform

67-66-3

2-Chloronaphthalene

91-58-7

2-Chlorophenol

95-57-8

4-Chlorophenyl phenyl ether Chloroprene

7005-72-3 126-99-8

Chromium

(Total)

C3-4

Suggested Methods 8080 40 8080 8250 8080 8250 8270 8270 8010 8270 8060 8270 8010 8240 8010 8240 8270 8060 8270 6010 7130 7131 8240 8010 8240 8080 8250 8270 8010 8020 8240 8270 8040 8270 8010 8240 8010 8240 8120 8270 8040 8270 8270 8010 8240 6010 7190 7191

PQL μg/L (μ 0.05 0.1 30 0.05 10 10 10 100 10 20 10 5 2 5 10 5 10 40 50 5 5 0.1 10 20 2 2 5 10 5 20 5 10 0.5 5 10 10 5 10 10 50 5 70 500 10

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.)

COMPOUND NAME Chrysene

CAS RN 218-01-9

Cobalt

(Total)

Copper

(Total)

m-Cresol o-Cresol p-Cresol Cyanide 2,4-D,2,4,-Dichlorophenoxyacetic acid 4,4'-DDD

108-39-4 95-48-7 106-44-5 57-12-5 94-75-7 72-54-8

4,4'-DDE

72-55-9

4,4'-DDT

50-29-3

Diallate Dibenz[a,h]anthracene

2303-16-4 53-70-3

Dibenzofuran Dibromochloromethane; Chlorodibromomethane

132-64-9 124-48-1

1,2-Dibromo-d-chloropropane,DBCP

96-12-8

1,2-Dibromoethane; Ethylene dibromide

106-93-4

Di-n-butyl phthalate

84-74-2

o-Dichlorobenzene

95-50-1

m-Dichlorobenzene

541-73-1

p-Dichlorobenzene

106-46-7

3,3' Dichlorobenzidine trans-1,4-Dichloro-2-butene Dichlorodifluoromethane

91-94-1 110-57-6 75-71-8

Suggested Methods 8100 8270 6010 7200 7201 601060 7210 8270 8270 8270 9010 8150 8080 8270 8080 8270 8080 8270 8270 8100 8270 8270 8010 8240 8010 8240 8270 8010 8240 8060 8270 8010 8020 8120 8270 8010 8020 8120 8270 8010 8020 8120 8270 8270 8240 8010 8240

PQL μg/L (μ 200 10 70 500 10 200 10 10 10 40 10 0.1 10 0.05 10 0.1 10 10 200 10 10 5 100 5 10 10 5 5 10 2 5 10 10 5 5 10 10 2 5 15 10 20 5 10 5

C3-5

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.)

COMPOUND NAME

CAS RN

l,l-Dichloroethane

75-34-3

1,2-Dichloroethane; Ethylene dichloride

107-06-2

l,l-Dichloroethylene; Vinylidene chloride

75-35-4

trans-1,2-Dichloroethylene

156-60-5

2,4-Dichlorophenol

120-83-2

2,6-Dichlorophenol 1,2-Dichloropropane

87-65-0 78-87-5

cis-1,3-Dichloropropene

10061-01-5

trans-1,3-Dichloropropene

10061-02-6

Dieldrin

60-57-1

Diethyl phthalate

84-66-2

O,O-Diethyl O-2-pyrazinyl phosphorothioate-Thionazin Dimethoate p-(Dimethylamino)azobenzene 7/12-Dimethylbenz[a]anthracene 3,3'-Dimethylbenzidine _,_-Dimethylphenethylamine(2) 2,4-Dimethylphenol

297-97-2 60-51-5 60 ~ 7 57-97-6 119-93-7 122-09-8 105-67-9

Dimethyl phthalate

131 ~ 3

m-Dinitrobenzene 4,6-Dinitro-o-cresol

99-65-0 534-52-1

2,4-Dinitrophenol

51-28-5

2,6-Dinitroluene 2,4-Dinitrotoluene

606-20-2 121-14-2

Dinoseb; DNBP, 2-sec-Butyl-4,6-dinitro phenol

88-85-7

Di-n-octyl phthalate

117-84-0

1,4-Dioxane Diphenylamine Disulfoton

123-91-1 122-39-4 298-04-4

C3-6

Suggested Methods 8010 8240 8010 8240 8010 8240 8010 8240 8040 8270 8270 8010 8240 8010 8240 8010 8240 8080 8270 8060 8270 8270 8270 8270 8270 8270 8270 8040 8270 8060 8270 8270 8040 8270 8040 8270 8090 8090 8270 8150 8270 8060 8270 8015 8270 8140

PQL μg/L (μ

5 0.5 5 5 5 5 10 10 0.5 5 20 5 5 5 0.05 10 5 10 10 10 10 10 10 10 5 10 5 10 10 150 50 150 50 0.1 0.2 10 10 30 10 150 10 2

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.)

COMPOUND NAME

CAS RN

Endosulfan I

959-98-9

Endosulfan II Endosulfan sulfate

33213-65-9 1031-07-8

Endrin

72-20-8

Endrin aldehyde

7421-93-4

Ethylbenzene

100-41-4

Ethyl methacrylate

97-63-2

Ethyl methanesulfonate Famphur Fluoranthene

62-50-0 52-85-7 206-44-0

Fluorene

86-73-7

Heptachlor

76-44-8

Heptachlor epoxide

1024-57-3

Hexachlorobenzene

118-74-1

Hexachlorobutadiene

87-68-3

Hexachlorocyclopentadiene

77-47-4

Hexachloroethane

67-72-1

Hexachlorophene Hexachloropropene 2-Hexanone Indeno(1,2,3-cd)pyrene

70-30-4 1888-71-7 591-78-6 193-39-5

Isobutyl alcohol Isodrin Isophorone

78-83-1 465-73-6 78-59-1

Isosafrole Kepone Lead

120-58-1 143-50-0 (Total)

Mercury

(Total)

Suggested Methods 8270 8080 8250 8080 8080 8270 8080 8250 8080 8270 8020 8240 8015 8240 8270 8270 8270 8100 8270 8100 8270 8080 8270 8080 8270 8120 8270 8120 8270 8120 8270 8120 8270 8270 8270 8240 8100 8270 8015 8270 8090 8270 8270 8270 6010 7420 7421 7470

PQL μg/L (μ 10 0.1 10 0.05 0.5 10 0.1 10 0.2 10 2 5 10 5 10 10 10 200 10 200 10 0.05 10 10 0 10 5 10 5 10 0 10 10 10 50 200 10 50 10 60 10 10 10 40 1000 10 2

C3-7

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.)

COMPOUND NAME Methacrylonitrile

CAS RN 126-98-7

Methapyrilene (1) Methoxychlor

91-80-5 72-43-5

Methyl bromide; Bromomethane

74-83-9

Methyl chloride; Chloromethane

74-87-3

3-Methylcholanthrene Methylene bromide; Dibromomethane

56-49-5 74-95-3

Methylene chloride; Dichloromethane

75-09-2

Methyl ethyl ketone; MEK

78-93-3

Methyl iodide; Iodomethane

74-88-4

Methyl methacrylate

80-62-6

Methyl methanesulfonate 2-Methylnaphthalene Methyl parathion; Parathion methyl

66-27-3 91-57-6 298-00-0

4-Methyl-2-pentanone, Methyl isobutyl ketone

108-10-1

Naphthalene

91-20-3

1,4-Naphthoquinone l-Naphthylamine 2-Naphthylamine Nickel

130-15-4 134-32-7 91-59-8 (Total)

o-Nitroaniline m-Nitroaniline p-Nitroaniline Nitrobenzene

88-74-4 99-09-2 100-01-6 98-95-3

o-Nitrophenol

88-75-5

p-Nitrophenol

100-02-7

4-Nitroquinoline l-oxide (1) N-Nitrosodi-n-butylamine N-Nitrosodiethylamine N-Nitrosodimethylamine N-Nitrosodiphenylamine

56-57-5 924-16-3 55-18-5 62-75-9 86-30-6

C3-8

Suggested Methods 8015 8240 8270 8080 8270 8101 8240 8010 8240 8270 8010 8240 8010 8240 8015 8240 8010 8240 8015 8240 8270 8270 8140 8270 8015 8240 8100 8270 8270 8270 8270 6010 7520 8270 8270 8090 8270 8040 8270 8040 8270 8270 8270 8270 8270 8270

PQL μg/L (μ 5 5 10 2 10 20 10 10 10 5 5 5 5 10 100 40 5 2 5 10 10 0.5 10 5 50 200 10 10 10 10 50 40 50 50 50 40 10 5 10 10 50 10 10 10 10 10

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.)

COMPOUND NAME N-Nitrosodipropylamine; Di-n-propyl-nitrosamine N-Nitrosomethylethylamine N-Nitrosomorpholine N-Nitrosopiperidine N-Nitrosopyrrolidine (1) 5-Nitro-o-toluidine Parathion Polychlorinated biphenyls; PCBs (3)

CAS RN 621-64-7 10595-95-6 59-89-2 100-75-4 930-55-2 99-55-8 56-38-2

Polychlorinated dibenzo-p-dioxins (4) PCDDs Polychlorinated dibenzofurans; PCDFs (5) Pentachlorobenzene Pentachloroethane (2)

608-93-5 76-01-7

Pentachloronitrobenzene Pentachlorophenol

82-68-8 87-86-5

Phenacetin Phenanthrone

62-44-2 85-01-8

Phenol

108-95-2

p-Phenylenediamine Phorate

106-50-3 298-02-2

2-Picoline

109-06-8

Pronamide Propionitrile; Ethyl cyanide

23950-58-5 107-12-0

Pyrene

129-00-0

Pyridine (6)

110-86-1

Safrole Selenium

94-59-7 (Total)

Silver

(Total)

Silvex, 2,4,5-TP Styrene

93-72-1 100-42-5

Suggested Methods 8270 8270 8270 8270 8270 8270 8270 8080 8250 8280 8280 8270 8240 8270 8270 8040 8270 8270 8100 8270 8040 8270 8270 8140 8270 8240 8270 8270 8015 8240 8100 8270 8240 8270 8270 6010 7740 774 1 6010 7760 8150 8020 8240

PQL μg/L (μ 10 10 10 10 10 10 10 50 100 0.01 0.01 10 5 10 10 5 50 10 200 10 10 10 2 10 5 10 10 60 5 200 10 5 10 10 750 20 20 70 100 2 5

C3-9

APPENDIX C3 RCRA APPENDIX IX PARAMETERS

APPENDIX IX (Cont.)

COMPOUND NAME Sulfide 2,4-T; 2,4,5-Trichlorophenoxyacetic acid 2,3,7,8-TCDD; 2,3,7,8-Tetrachloro-dibenzo-p-dioxin 1,2,4,5-Tetrachlorobenzene 1,1,1,2-Tetrachloroethane

CAS RN 18496-25-8 93-76-5 1746-01-6 95-94-3 630-20-6

1,1,2,2-Tetrachloroethane

79-34-5

Tetrachloroethylene; Perchloroethylene; Tetrachloroethene

127-18-4

2,3,4,6-Tetrachlorophenol Tetraethyl dithiopyrophosphate; Sulfotepp (2) Thallium

58-90-2 3689-24-5 (Total)

Tin Toluene

(Total)

o-Toluidine Toxaphene

95-53-4 8001-35-2

1,2,4-Trichlorobenzene l,l,l-Trichloroethane; Methylchloroform 1,1,2-Trichloroethane

120-82-1 71-55-6 79-00-5

Trichloroethylene; Trichloroethene

79-01-6

Trichlorofluoromethane

75-69-4

2,4,5-Trichlorophenol 2,4,6-Trichlorophenol

95-95-4 88-06-2

1,2,3-Trichloropropane

96-18-4

O,O,O-Triethyl phosphorothioate (2) sym-Trinitrobenzene (1) Vanadium

126-68-1 99-35-4 (Total)

Vinyl acetate Vinyl chloride

108-05-4 75-01-4

Xylene (total)

1330-20-7

Zinc

(Total)

C3-10

Suggested Methods 9030 8150 8280 8270 8010 8240 8010 8240

PQL μg/L (μ 10000 2 0.005 10 5 5 0,5 5

8010 8240 8270 8270 6010 7840 7841 7870 108-88-3 8240 8270 8080 8250 8270 8240 8010 8240 8010 8240 8010 8240 8270 8040 8270 8010 8240 8270 8270 6010 7910 7911 8240 8010 8240 8020 8240 6010 7950

0.5 5 10 10 400 1000 10 8000 80202 5 10 2 10 10 5 0 5 5 10 5 10 5 10 10 5 10 10 80 2000 40 5 2 10 5 5 20 50

WATER QUALITY STANDARDS APPENDIX C4

APPENDIX C4 SAFE DRINKING WATER ACT PARAMETER LISTS

C4-1

WATER QUALITY STANDARDS APPENDIX C4

The Safe Drinking Water Act (SDWA) of 1974 is the basis for the comprehensive regulation of drinking water. Two major regulatory programs are contained in the Act, one related to public water supplies and the other to underground well injections. The SDWA regulates both primary and secondary drinking water contaminants. In 1986 Congress passed major amendments to the SDWA as a result of the growing public concern over contamination of public drinking water supplies and a lack of adequate federal standards. The amendments ask EPA to set enforceable standards for contaminants in drinking water based upon the level of removal that can be achieved using the best available technology to treat contaminated water.

Chemical MCL (μg/L) Benzene ............................................. 5.0 Carbon tetrachloride .......................... 5.0 1,2-Dichloroethane ............................ 5.0 Trichloroethylene............................... 5.0 p-Dichlorobenzene............................. 75.0 1, l-Dichloroethylene ......................... 7.0 1,1, l-Trichloroethane ........................ 200.0 Vinyl chloride .................................... 2.0 p-Dichlorobenzene............................. 75.0 (MCLG) Monitoring requirements for the above list of chemicals varies from quarterly to once per five years based on whether VOCs have been detected in the initial sampling and the vulnerability of the system. Initial monitoring was to be accomplished January 1, 1988, January 1, 1989 or January 1, 1991 depending on the system size (population served). On July 8, 1987 when U.S. EPA finalized MCLs on the eight VOCs described above, they also requested each source to monitor, one time only, for 51 unregulated contaminants. The purpose of this monitoring effort was to gather information on detectibility of VOCs for potential regulation in the future. Since 1987 the Agency has revised the Drinking Water Standards and Health Advisories tables periodically by U.S. EPA’s Office of Water on an as needed basis. The Summer 2002 edition of the tables as presented below has retained the content and format changes introduced in the Summer 2000 edition and has added the Chemical Abstracts Service Registry Numbers (CAS RN) for the chemical contaminants. The following changes should be kept in mind when using the Tables: The Reference dose (RfD) values have been updated by the agency to reflect the values in the US EPA’s Integrated Risk Information System (IRIS) and the drinking water equivalent level (DWEL) has been calculated accordingly. Thus, both the RfD and DWEL will differ from the values in the Health Advisory document if the IRIS RfD is more recent than the Health Advisory value. The RfD values from IRIS that differ from the values in the Health Advisory documents are given in BOLD type. For unregulated chemicals with a new IRIS RfD, the lifetime Health Advisory was calculated from the DWEL using the relative source contribution value published in the Health Advisory. For regulated chemicals, where the revised lifetime value differed from the maximum contaminant level goal (MCLG), no lifetime value was provided in the following Tables. For regulated chemicals, the cancer group designation and 10-4 cancer risk reflect the status at the time of regulation. For unregulated chemicals, the cancer group designation and 10-4 cancer risk reflect the values currently on IRIS. New cancer group designations and 10-4 cancer risk values are given in BOLD type. Several pesticides listed in IRIS have been re-evaluated by the Office of Pesticide Programs (OPP) resulting in an RfD other than that in IRIS. For these pesticides, the IRIS value is listed in the Table and the newer OPP value is given in a footnote. In some cases there is a Health Advisory value for a contaminant but there is no reference to a Health Advisory document. These Health Advisory values can be found in the Drinking Water Criteria Document for the contaminant. With a few exceptions, the Health Advisory values have been rounded to one significant figure. These figures are current to late 2002; however, you should obtain the most recent Drinking Water Standards and Health Advisories tables from the Water Science home page at http://www.epa.gov/waterscience. The tables are accessed under the Health Advisories heading.

C4-2

Drinking Water Standards and Health Advisories Page 1

Summer 2002 Health Advisories

Standards 10-kg Child

Chemicals

CASRN Number

Status Reg.

83-32-9 62476-59-9 79-06-1 107-13-1 15972-60-8 116-06-3 1646-88-4 1646-87-3 309-00-2 834-12-8 7773-06-0 120-12-7 1912-24-9 114-26-1 25057-89-0 56-55-3 71-43-2 50-32-8 205-99-2 191-24-2 207-08-9 39638-32-9 314-40-9 108-86-1

-

MCLG (mg/L)

MCL (mg/L)

Status HA Document

Oneday (mg/L)

Ten-day (mg/L)

2 1.5 0.1 0.01 0.01 0.01 0.0003 9 20 0.04 0.3 0.2 4 5 4

2 0.3 0.1 0.01 0.01 0.01 0.0003 9 20 0.04 0.3 0.2 4 5 4

RfD (mg/kg/ day)

DWEL (mg/L)

Lifetime (mg/L)

0.06 0.01 0.0002 0.01 0.001 0.001 0.001 0.00003 0.009 0.2 0.3 0.035 0.004 0.03 0.04 0.1 -

2 0.4 0.007 0.4 0.04 0.04 0.04 0.001 0.3 8 10 1 0.1 1 1 5 -

0.06 2 -

mg/L at 10-4 Cancer Risk

Cancer Group

ORGANICS

1

2 3 4 5

C4-3

6

F F F4 F4 F4 F F F -

zero zero 0.001 0.001 0.001 0.003 zero zero -

TT1 0.002 0.003 0.003 0.004 0.003 0.005 0.0002 -

F ’88 F ‘87 F ‘88 F ‘95 F ‘95 F ‘95 F ‘92 F ‘88 F ‘88 F ‘88 F ‘88 F ‘99 F ’87 F ‘89 F ‘88 D ‘86

0.003 0.2 0.3 0.09 -

0.1 0.0008 0.006 0.042 0.0002 0.1 0.0005 -

B2 B2 B1 B2 D D D B2 D D D C C E B2 A B2 B2 D B2 D C D

When acrylamide is used in drinking water systems, the combination (or product) of dose and monomer level shall not exceed that equivalent to a polyacrylamide polymer containing 0.05% monomer dosed at 1 mg/L. Determined not to be carcinogenic at low doses by OPP. The MCL value for any combination of two or more of these three chemicals should not exceed 0.007 mg/L because of similar mode of action. Administrative stay of the effective date. PAH = Polycyclic aromatic hydrocarbon. Under review.

WATER QUALITY STANDARDS APPENDIX C4

Acenaphthene Acifluorfen (sodium) Acrylamide Acrylonitrile Alachlor Aldicarb3 Aldicarb sulfone3 Aldicarb sulfoxide3 Aldrin Ametryn Ammonium sulfamate Anthracene (PAH) 5 Atrazine 6 Baygon Bentazon Benz[a]anthracene (PAH) Benzene Benzo[a]pyrene (PAH) Benzo[b]fluoranthene (PAH) Benzo[g,h,i]perylene (PAH) Benzo[k]fluoranthene (PAH) bis-2-Chloroisopropyl ether Bromacil Bromobenzene

Page 2

Summer 2002 Health Advisories

Standards 10-kg Child

Chemicals

CASRN Number

Status Reg.

MCLG (mg/L)

MCL (mg/L) -

Bromochloromethane Bromodichloromethane1 (THM) Bromoform (THM) Bromomethane Butyl benzyl phthalate (PAE)3 Butylate Carbaryl Carbofuran1 Carbon tetrachloride Carboxin Chloramben Chlordane Chloroform (THM) Chloromethane Chlorophenol (2-) Chlorothalonil Chlorotoluene oChlorotoluene pChlorpyrifos5 Chrysene (PAH)

74-97-5 75-27-4

F

zero

75-25-2 74-83-9 85-68-7 2008-41-5 63-25-2 1563-66-2 56-23-5 5234-68-4 133-90-4 57-74-9 67-66-3 74-87-3 95-57-8 1897-45-6 95-49-8 106-43-4 2921-88-2 218-01-9

F F F F F -

zero 0.04 zero zero zero -

Cyanazine

21725-46-2

-

1

-

0.082 0.082

Status HA Document F ‘89 D ‘93

Oneday (mg/L)

50 6

Ten-day (mg/L)

RfD (mg/kg/ day)

DWEL (mg/L)

Lifetime (mg/L)

mg/L at 10-4 Cancer Risk

Cancer Group

1 6

0.01 0.02

0.5 0.7

0.09 -

0.06

D B2

0.01 0.4 0.7 0.04 0.7 0.1 0.03 0.04 0.1 0.1 0.02 -

0.4 0.03 0.01 0.15 -

B2 D C D D E B2 D D B2 B24 D D B2 D D D B2

0.04 0.005 0.002 0.081 -

D ‘93 D ‘89 F ‘89 F ‘88 F ‘87 F ‘87 F ‘88 F ‘88 F ‘87 D ‘93 F ‘89 D ‘94 F ‘88 F ‘89 F ‘89 F ‘92 -

5 0.1 2 1 0.05 4 1 3 0.06 4 9 0.5 0.2 2 2 0.03 -

2 0.1 2 1 0.05 0.2 1 3 0.06 4 0.4 0.5 0.2 2 2 0.03 -

0.02 0.001 0.2 0.05 0.1 0.005 0.0007 0.1 0.015 0.0005 0.01 0.004 0.005 0.015 0.02 0.02 0.003 -

0.7 0.05 7 2 4 0.2 0.03 4 0.5 0.02 0.4 0.1 0.2 0.5 0.7 0.7 0.1 -

-

D ‘96

0.1

0.1

0.002

0.07

0.001

-

Under review. 1998 Final Rule for Disinfectants and Disinfection By-products: The total for trihalomethanes is 0.08 mg/L. 3 PAE = phthalate acid ester. 4 By the 1999 Draft Guidelines for Carcinogen Risk Assessment, chloroform is likely to be carcinogenic to humans by all routes of exposure under high-dose conditions that lead to cytotoxicity and regenerative hyperplasia in susceptible tissues. Chloroform is not likely to be carcinogenic to humans by all routes of exposures at a dose level that does not cause cytotoxicity and cell regeneration 5 New OPP RfD = 0.0003 mg/kg/day. 2

WATER QUALITY STANDARDS APPENDIX C4

C4-4

Drinking Water Standards and Health Advisories

Drinking Water Standards and Health Advisories Page 3

Summer 2002 Standards

Health Advisories 10-kg Child

Chemicals Cyanogen chloride1 2,4-D (2,4dichlorophenoxyacetic acid) DCPA (Dacthal) Dalapon (sodium salt) Di(2-ethylhexyl)adipate

1 2 3 4

C4-5

5

Status Reg.

MCLG (mg/L)

MCL (mg/L)

506-77-4 94-75-7

F

0.07

0.07

F ‘87

1861-32-1 75-99-0 103-23-1

F F

0.2 0.4

0.2 0.4

F ‘88 F ‘89 -

117-81-7

F

zero

0.006

333-41-5 124-48-1

F

0.06

0.082

96-12-8

F

zero

84-74-2 1918-00-9 76-43-6 95-50-1 541-73-1 106-46-7 75-71-8 107-06-2 75-35-4 156-59-2 156-60-5 75-09-2 120-83-2 78-87-5 542-75-6 60-57-1 84-66-2

F F F F F F F F F -

zero 0.6 0.075 zero 0.007 0.07 0.1 zero zero -

Oneday (mg/L) 0.05 1

Ten-day (mg/L) 0.05 0.3

RfD (mg/kg/ day)

DWEL (mg/L)

Lifetime (mg/L)

mg/L at 10-4 Cancer Risk

Cancer Group

0.05 0.01

2 0.4

0.07

-

D D

0.07 0.2 0.4

3

D D C

80 3 20

80 3 20

0.01 0.03 0.6

0.4 0.9 20

-

-

0.02

0.7

-

0.3

B2

F ‘88 D ‘93

0.02 6

0.02 6

0.00009 0.02

0.003 0.7

0.0006 0.06

0.04

E C

0.0002

F ’87

0.2

0.05

-

-

-

0.003

B2

0.063 0.6 0.075 0.005 0.007 0.07 0.1 0.005 0.005 -

F ‘88 D ‘95 F ‘87 F ‘87 F ‘87 F ’89 F ‘87 F ‘87 F ‘90 F ‘87 D ‘93 D ‘94 F ’87 F ‘88 F ‘88 -

0.2 0.6 0.6 0.075 1 0.006 0.07 0.1 0.02 -

-

D D B2 D D C D B2 C D D B2 E B2 B2 B2 D

-

0.3 5 9 9 11 40 0.7 2 4 20 10 0.03 0.03 0.0005 -

0.3 5 9 9 11 40 0.7 1 1 1 2 0.03 0.09 0.03 0.0005 -

Under review. 1998 Final Rule for Disinfectants and Disinfection By-products: The total for trihalomethanes is 0.08 mg/L. 1998 Final Rule for Disinfectants and Disinfection By-products: The total for five haloacetic acids is 0.06 mg/L. A quantitative risk estimate has not been determined. The values for m-dichlorobenzene are based on data for o-dichlorobenzene.

0.1 0.03 0.004 0.09 0.09 0.1 0.2 0.009 0.01 0.02 0.06 0.003 0.03 0.00005 0.8

4 1 0.1 3 3 4 5 0.3 0.4 0.7 2 0.1 1 0.002 30

-

-4 0.04 0.006 0.5 0.06 0.04 0.0002 -

WATER QUALITY STANDARDS APPENDIX C4

Di(2-ethylhexyl)phthalate (PAE) Diazinon Dibromochloromethane1 (THM) Dibromochloropropane (DBCP) Dibutyl phthalate (PAE) Dicamba Dichloroacetic acid1 Dichlorobenzene oDichlorobenzene m- 5 Dichlorobenzene pDichlorodifluoromethane Dichloroethane (1,2-) Dichloroethylene (1,1-) Dichloroethylene (cis-1,2-) Dichloroethylene (trans-1,2-) Dichloromethane Dichlorophenol (2,4-) Dichloropropane (1,2-) Dichloropropene (1,3-) Dieldrin Diethyl phthalate (PAE)

CASRN Number

Status HA Document

Page 4

Summer 2002 Health Advisories

Standards 10-kg Child

Chemicals Diisopropyl methylphosphonate Dimethrin Dimethyl methylphosphonate Dimethyl phthalate (PAE) Dinitrobenzene (1,3-) Dinitrotoluene (2,4-) Dinitrotoluene (2,6-) Dinitrotoluene (2,6 & 2,4) 1 Dinoseb Dioxane pDiphenamid Diquat Disulfoton Dithiane (1,4-) Diuron Endothall Endrin Epichlorohydrin Ethylbenzene Ethylene dibromide (EDB)5 Ethylene glycol Ethylene Thiourea (ETU) Fenamiphos 1 2 3 4

5

CASRN Number

Status Reg.

MCLG (mg/L)

MCL (mg/L)

Status HA Document

Oneday (mg/L)

Ten-day (mg/L)

RfD (mg/kg/ day)

DWEL (mg/L)

Lifetime (mg/L)

mg/L at 10-4 Cancer Risk

Cancer Group

1445-75-6

-

-

-

F ‘89

8

8

0.08

3

0.6

-

D

70-38-2 756-79-6

-

-

-

F ‘88 F ‘92

10 2

10 2

0.3 0.2

10 7

2 0.1

0.7

D C

131-11-3 99-65-0 121-14-2 606-20-2 88-85-7 123-91-1 957-51-7 85-00-7 298-04-4 505-29-3 330-54-1 145-73-3 72-20-8 106-89-8 100-41-4 106-93-4 107-21-1

F F F F F F F -

F ‘91 F ‘92 F ‘92 F ‘92 F ‘88 F ‘87 F ‘88 F ‘88 F ‘92 F ‘88 F ‘88 F ‘87 F ‘87 F ‘87 F ‘87 F ‘87

0.04 0.50 0.40 0.3 4 0.3 0.01 0.4 1 0.8 0.02 0.1 30 0.008 20

0.04 0.50 0.40 0.3 0.4 0.3 0.01 0.4 1 0.8 0.005 0.1 3 0.008 6

0.0001 0.002 0.001 0.001 0.03 0.0022 0.00004 0.01 0.0023 0.02 0.0003 0.002 0.1 2

0.005 0.1 0.04 0.04 1 0.07 0.001 0.4 0.07 0.7 0.01 0.07 3 70

0.001 0.007 0.2 0.0003 0.08 0.01 0.1 0.002 0.7 14

0.005 0.005 0.005 0.3 0.3 0.00004 -

D D B2 B2 B2 D B2 D D E D D D D B2 D B2 D

96-45-7 22224-92-6

-

F ‘88 F ‘88

0.3 0.009

0.3 0.009

0.00008 0.00025

0.003 0.009

0.002

0.02 -

B2 D

0.007 0.02 0.1 0.002 zero 0.7 zero -

0.007 0.02 0.1 0.002 TT4 0.7 0.00005 -

Technical grade. New OPP RfD = 0.005 mg/kg/day New OPP RfD = 0.003 mg/kg/day. When epichlorohydrin is used in drinking water systems, the combination (or product) of dose and monomer level shall not exceed that equivalent to an epichlorohydrinbased polymer containing 0.01% monomer dosed at 20 mg/L. 1,2-dibromoethane.

WATER QUALITY STANDARDS APPENDIX C4

C4-6

Drinking Water Standards and Health Advisories

Drinking Water Standards and Health Advisories Page 5

Summer 2002 Standards

Health Advisories 10-kg Child

Chemicals

1

Status Reg.

2164-17-2 86-73-7 944-22-9 50-00-0 1071-83-6 76-44-8 1024-57-3 118-74-1 87-68-3 77-47-4 67-72-1 110-54-3 51235-04-2 2691-41-0 193-39-5

F F F F F -

78-59-1 1832-54-8

-

98-82-8 58-89-9 121-75-5 123-33-1 94-74-6 16752-77-5 72-43-5 78-93-3 298-00-0

F F -

Cancer Group

MCL (mg/L)

0.7 zero zero zero 0.05 -

0.7 0.0004 0.0002 0.001 0.05 -

F ‘88 F ‘88 D ‘93 F ‘88 F ‘87 F ‘87 F ‘87 D ‘98 F ‘91 F ‘87 F ‘96 F ‘88 -

2 0.02 10 20 0.01 0.01 0.05 0.3 5 10 3 5 -

2 0.02 5 20 0.01 0.05 0.3 5 4 2 5 -

0.01 0.04 0.002 0.2 0.12 0.0005 0.00001 0.0008 0.00024 0.006 0.001 0.055 0.05 -

0.5 1 0.07 7 4 0.02 0.0004 0.03 0.007 0.2 0.04 2 2 -

0.09 0.01 1 0.7 0.001 0.001 0.4 0.4 -

0.0008 0.0004 0.002 0.05 0.3 -

D D D B11 D B2 B2 B2 C E C D D D B2

-

-

F ‘92 F ‘92

15 30

15 30

0.2 0.1

7 4

0.1 0.7

4 -

C D

0.0002 0.04 -

0.0002 0.04 -

D ‘87 F ‘87 F ‘92 F ‘88 F ‘88 F ‘88 F ‘87 F ‘87 F ‘88

11 1 0.2 10 0.1 0.3 0.05 75 0.3

11 1 0.2 10 0.1 0.3 0.05 7.5 0.3

0.1 0.0003 0.02 0.5 0.00059 0.025 0.005 0.6 0.00025

0.0002 0.1 4 0.004 0.2 0.04 4 0.002

-

D C D D D E D D D

Carcinogenicity based on inhalation exposure. New OPP RfD = 2 mg/kg/day. 3 Under review. 4 Draft Ambient Water Quality Criteria for the protection of human health (EPA 822-R-98-004) 5 The Health Advisory is based on a new OPP RfD rather than the IRIS RfD. 6 HMX = octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. 7 Lindane = γ − hexachlorocyclohexane. 8 MCPA = 4(chloro-2-methoxyphenoxy)acetic acid. 9 New OPP RfD = 0.0015 mg/kg/day. 2

DWEL (mg/L)

mg/L at 10-4 Cancer Risk

MCLG (mg/L)

Oneday (mg/L)

Ten-day (mg/L)

RfD (mg/kg/ day)

4 0.01 0.8 20 0.02 0.9 0.2 20 0.009

C4-7

WATER QUALITY STANDARDS APPENDIX C4

Fluometuron Fluorene (PAH) Fonofos Formaldehyde Glyphosate Heptachlor Heptachlor epoxide Hexachlorobenzene Hexachlorobutadiene3 Hexachlorocyclopentadiene Hexachloroethane Hexane (n-) Hexazinone HMX6 Indeno[1,2,3,-c,d]pyrene (PAH) Isophorone Isopropyl methylphosphonate Isopropylbenzene (cumene) Lindane 7 Malathion Maleic hydrazide MCPA 8 Methomyl Methoxychlor Methyl ethyl ketone Methyl parathion

CAS Number

Lifetime (mg/L)

Status HA Standards

Page 6

Summer 2002 Standards

Health Advisories 10-kg Child

Chemicals Metolachlor Metribuzin Monochloroacetic acid3 Monochlorobenzene Naphthalene Nitrocellulose5 Nitroguanidine Nitrophenol pOxamyl (Vydate) Paraquat Pentachlorophenol Phenanthrene (PAH) Phenol Picloram Polychlorinated biphenyls (PCBs) Prometon Pronamide Propachlor Propazine Propham Pyrene (PAH) RDX8 Simazine Styrene 2,4,5-T (Trichlorophenoxyacetic acid)

1 2 3 4 5 6 7 8

DWEL (mg/L)

Lifetime (mg/L)

mg/L at 10-4 Cancer Risk

MCLG (mg/L)

MCL (mg/L)

Status HA Document

F F F F F F

0.1 0.2 zero 0.5 zero

0.064 0.1 0.2 0.001 0.5 0.0005

F ‘88 F ‘88 F ‘87 F ‘90 F ‘88 F ‘90 F ‘92 F ‘87 F ‘88 F ‘87 D ‘92 F ‘88 D ‘93

2 5 4 0.5 10 0.8 0.2 0.1 1 6 20 -

2 5 4 0.5 10 0.8 0.2 0.1 0.3 6 20 -

0.151 0.0252 0.02 0.02 0.1 0.008 0.0256 0.0045 0.03 0.6 0.077 -

5 0.9 0.7 0.7 4 0.3 0.9 0.2 1 20 2 -

0.1 0.2 0.1 0.1 0.7 0.06 0.2 0.03 4 0.5 -

0.03 0.01

F F -

0.004 0.1 -

0.004 0.1 -

F ‘88 F ‘88 F ‘88 F ‘88 F ‘88 F ‘88 F ‘88 F ‘87 F ‘88

0.2 0.8 0.5 1 5 0.1 0.5 20 0.8

0.2 0.8 0.5 1 5 0.1 0.5 2 0.8

0.015 0.075 0.01 0.02 0.02 0.03 0.003 0.005 0.2 0.01

0.5 3 0.5 0.7 0.6 0.1 0.2 7 0.4

0.1 0.05 0.09 0.01 0.1 0.002 0.004 0.1 0.07

0.03 -

CASRN Number

Status Reg.

51218-45-2 21087-64-9 79-11-8 108-90-7 91-20-3 9004-70-0 556-88-7 100-02-7 23135-22-0 1910-42-5 87-86-5 85-01-8 108-95-2 1918-02-1 1336-36-3 1610-18-0 23950-58-5 1918-16-7 139-40-2 122-42-9 129-00-0 121-82-4 122-34-9 100-42-5 93-76-5

Oneday (mg/L)

Ten-day (mg/L)

RfD (mg/kg/ day)

New OPP RfD = 0.1 mg/kg/day. New OPP RfD = 0.013 mg/kg/day. Under review. 1998 Final Rule for Disinfectants and Disinfection By-products: the total for five haloacetic acids is 0.06mg/L. The Health Advisory Document for nitrobenzene does not include HA values and describes this compounds as relatively nontoxic. New OPP RfD = 0.001 mg/kg/day. New OPP RfD = 0.2 mg/kg/day. RDX = hexahydro -1,3,5-trinitro-1,3,5-triazine.

Cancer Group C D D C D D E C B2 D D D B2 D C D C D D C C C D

WATER QUALITY STANDARDS APPENDIX C4

C4-8

Drinking Water Standards and Health Advisories

Drinking Water Standards and Health Advisories Page 7

Summer 2002 Standards

Health Advisories 10-kg Child

Chemicals

CASRN Number

Status Reg.

MCLG (mg/L)

MCL (mg/L)

Status HA Document

Oneday (mg/L)

Ten-day (mg/L)

1746-01-6

F

zero

3E-08

F ’87

1E-06

1E-07

Tebuthiuron Terbacil Terbufos Tetrachloroethane (1,1,1,2-) Tetrachloroethane (1,1,2,2-) Tetrachloroethylene Trichlorofluoromethane Toluene Toxaphene 2,4,5-TP (Silvex) Trichloroacetic acid1 Trichlorobenzene (1,2,4-) Trichlorobenzene (1,3,5-) Trichloroethane (1,1,1-) Trichloroethane (1,1,2-) Trichloroethylene 1 Trichlorophenol (2,4,6-) Trichloropropane (1,2,3-) Trifluralin Trimethylbenzene (1,2,4-) Trimethylbenzene (1,3,5-) Trinitroglycerol Trinitrotoluene (2,4,6-) Vinyl chloride Xylenes

34014-18-1 5902-51-2 13071-79-9 630-20-6 79-34-5 127-18-4 75-69-4 108-88-3 8001-35-2 93-72-1 76-03-9 120-82-1 108-70-3 71-55-6 79-00-5 79-01-6 88-06-2 96-18-4 1582-09-8 95-63-6 108-67-8 55-63-0 118-96-7 75-01-4 1330-20-7

F F F F F F F F F F F

zero 1 zero 0.05 0.3 0.07 0.2 0.003 zero zero 10

0.005 1 0.003 0.05 0.062 0.07 0.2 0.005 0.005 0.002 10

F ‘88 F ‘88 F ‘88 F ‘89 F ‘89 F ‘87 F ‘89 D ‘93 F ‘96 F ‘88 D ‘96 F ‘89 F ‘89 F ‘87 F ‘89 F ‘87 D ‘94 F ‘89 F ‘90 D ‘87 D ‘87 F ‘87 F ‘89 F ‘87 D ‘93

3 0.3 0.005 2 0.04 2 7 20 0.004 0.2 4 0.1 0.6 100 0.6 0.03 0.6 0.08 10 0.005 0.02 3 40

3 0.3 0.005 2 0.04 2 7 2 0.004 0.2 4 0.1 0.6 40 0.4 0.03 0.6 0.08 0.005 0.02 3 40

1 2 3

Under review. 1998 Final Rule for Disinfectants and Disinfection By-products: The total for five haloacetic acids is 0.06 mg/L. New OPP RfD = 0.024 mg/kg/day.

1E-09 0.07 0.01 0.0001 0.03 0.00005 0.01 0.3 0.2 0.0004 0.008 0.1 0.01 0.006 0.035 0.004 0.007 0.0003 0.006 0.00753 0.0005 0.003 2

DWEL (mg/L) 4E-08 2 0.4 0.005 1 0.002 0.5 10 7 0.01 0.3 4.0 0.4 0.2 1 0.1 0.2 0.01 0.2 0.3 0.02 0.1 70

Lifetime (mg/L) 0.5 0.09 0.0009 0.07 0.0003 0.01 2 1 0.05 0.3 0.07 0.04 0.2 0.003 0.04 0.005 0.005 0.002 10

mg/L at 10-4 Cancer Risk 2E-08 0.1 0.02 0.003 0.06 0.3 0.3 0.5 0.2 0.1 0.002 -

Cancer Group B2 D E D C C D D B2 D C D D D C B2 B2 C D D C A D

C4-9

WATER QUALITY STANDARDS APPENDIX C4

2,3,7,8-TCDD (Dioxin)

RfD (mg/kg/ day)

Page 8

Summer 2002 Standards

Health Advisories 10-kg Child

Chemicals

Lifetime (mg/L)

mg/L at 10-4 Cancer Risk

700-MFL

Status Reg.

MCLG (mg/L)

MCL (mg/L)

Status HA Document

7664-41-7 7440-36-0 7440-38-2 1332-21-4

F F F

0.006 zero 7 MFL1

0.006 0.01 7 MFL

D ‘92 F ‘92 D ‘95 -

0.01 -

0.01 -

0.0004 0.0003 -

0.01 0.01 -

30 0.006 -

7440-39-3 7440-41-7 7440-42-8 7789-38-0 7440-43-9 10599-90-3 7782-50-5 10049-04-4 7758-19-2 7440-47-3 7440-50-8 143-33-9 7681-49-4 7439-92-1 7439-96-5 7487-94-7 7439-98-7 7440-02-0

F F F F F F F F F F F F F F F

2 0.004 zero 0.005 45 45 0.85 0.8 0.1 1.3 0.2 4 zero 0.002 -

2 0.004 0.01 0.005 45 45 0.85 1 0.1 TT7 0.2 4 TT7 0.002 -

D ‘93 F ‘92 D ‘92 D ‘98 F ’87 D ‘95 D ‘95 D ‘98 D ‘98 F ‘87 D ‘98 F ‘87 F ‘87 D ‘93 F ‘95

0.7 30 4 0.2 0.04 1 3 0.84 0.84 1 0.2 0.002 0.08 1

0.7 30 0.9 0.04 1 3 0.84 0.84 1 0.2 0.002 0.08 1

0.07 0.002 0.09 0.004 0.0005 0.1 0.1 0.03 0.03 0.0036 0.028 0.069 0.1410 0.0003 0.005 0.02

2 0.07 3 0.14 0.02 3.5 5 1 1 0.1 0.8 0.01 0.2 0.7

2 0.6

CASRN Number

Oneday (mg/L)

Ten-day (mg/L)

RfD (mg/kg/ day)

DWEL (mg/L)

Cancer Group

INORGANICS Ammonia Antimony Arsenic Asbestos (fibers/l >10μm length) Barium Beryllium Boron3 Bromate Cadmium Chloramine4 Chlorine Chlorine dioxide Chlorite Chromium (total) Copper (at tap) Cyanide3 Fluoride Lead (at tap) Manganese Mercury (inorganic) Molybdenum Nickel 1

0.005 3.0 4 0.8 0.8 0.2 0.002 0.04 0.1

0.005 -

MFL = million fibers per liter. Carcinogenicity based on inhalation exposure. 3 Under review. 4 Monochloramine; measured as free chlorine. 5 1998 Final Rule for Disinfectants and Disinfection By-products: MRDLG=Maximum Residual Disinfection Level Goal; and MRDL=Maximum Residual Disinfection Level. 6 IRIS value for chromium VI. 7 Copper action level 1.3 mg/L; lead action level 0.015 mg/L. 8 This RfD is for hydrogen cyanide. 9 Based on dental fluorosis in children, a cosmetic effect. MCLG based on skeletal fluorosis. 10 Dietary manganese. 2

D D A A2 D D B2 D D D D D D D B2 D D D -

WATER QUALITY STANDARDS APPENDIX C4

C4-10

Drinking Water Standards and Health Advisories

Drinking Water Standards and Health Advisories Page 9

Summer 2002 Health Advisories

Standards 10-kg Child

CASRN Number

Status Reg.

MCLG (mg/L)

MCL (mg/L)

14797-55-8 14797-65-0

F F F F F -

10 1 10 0.05 0.0005 -

10 1 10 0.05 0.002 -

Beta particle and photon activity (formerly man-made radionuclides)

F

zero

Gross alpha particle activity

F

zero

Chemicals Nitrate (as N) Nitrite (as N) Nitrate + Nitrite (both as N) Selenium Silver Strontium Thallium White phosphorous Zinc

7782-49-2 7440-22-4 7440-24-6 7440-28-0 7723-14-0 7440-66-6

Status HA Document D ‘93 D ‘93 D ‘93 F ‘92 D ‘93 F ‘92 F ‘90 D ‘93

Oneday (mg/L) 101 11 0.2 25 0.007 6

Ten-day (mg/L)

RfD (mg/kg/ day)

DWEL (mg/L)

Lifetime (mg/L)

101 11 0.2 25 0.007 6

1.6 0.16 0.005 0.0052 0.6 0.00007 0.00002 0.3

0.2 0.2 20 0.002 0.0005 10

0.05 0.1 4 0.0005 0.0001 2

mg/L at 10-4 Cancer Risk -

Cancer Group D D D D D

-

RADIONUCLIDES

7440-14-4 10043-92-2

F P

zero zero

Uranium

7440-61-1

F

zero

1 2 3 4

These values are calculated for a 4-kg infant and are protective for all age groups. Based on a cosmetic effect. AMCL = Alternative Maximum Contaminant Level Soluble uranium salts.

-

-

-

-

-

-

4 mrem/yr

A

-

-

-

-

-

-

15 pCi/L

A

-

-

-

-

-

-

150 pCi/L

A A

-

-

-

0.0034

0.1

-

-

A

C4-11

WATER QUALITY STANDARDS APPENDIX C4

Combined Radium 226 & 228 Radon

4 mrem/ yr 15 pCi/L 5 pCi/L 300 pCi/L AMCL3 4000 pCi/L 30 μg/L

Page 10

Summer 2002 Chemicals

CAS Number

Status

SDWR

Aluminum

7429-90-5

F

0.05 to 0.2 mg/L

Chloride

7647-14-5

F

250 mg/L

Color

NA

F

15 color units

Copper

7440-50-8

F

1.0 mg/L

Corrosivity

NA

F

non-corrosive

Fluoride

7681-49-4

F

2.0 mg/L

Foaming agents

NA

F

0.5 mg/L

Iron

7439-89-6

F

0.3 mg/L

Manganese

7439-96-5

F

0.05 mg/L

Odor

NA

F

3 threshold odor numbers

pH

NA

F

6.5 – 8.5

Silver

7440-22-4

F

0.1 mg/L

Sulfate

7757-82-6

F

250 mg/L

Total dissolved solids (TDS)

NA

F

500 mg/L

Zinc

7440-66-6

F

5 mg/L

WATER QUALITY STANDARDS APPENDIX C4

C4-12

Secondary Drinking Water Regulations

Microbiology Page 11

Summer 2002 Status HA Document

MCLG

MCL

Treatment Technique

Cryptosporidium

F

F 01

-

TT

Systems that filter must remove 99% of Cryptosporidium

Giardia lamblia

F

F 98

-

TT

99.9% killed/inactivated

Legionella

F1

F 98

zero

TT

No limit; EPA believes that if Giardia and viruses are inactivated, Legionella will also be controlled

Heterotrophic Plate Count (HPC)

F1

-

NA

TT

No more than 500 bacterial colonies per milliliter.

Total Coliforms

F

-

zero

5%

No more than 5.0% samples total coliform-positive in a month. Every sample that has total coliforms must be analyzed for fecal coliforms; no fecal coliforms are allowed.

Turbidity

F

-

NA

TT

At no time can turbidity go above 5 NTU (nephelometric turbidity units)

Viruses

F1

-

zero

TT

99.99% killed/inactivated

Final for systems using surface water; also being considered for regulation under groundwater disinfection rule.

C4-13

WATER QUALITY STANDARDS APPENDIX C4

1

Status Reg.

Page 12

Summer 2002 Chemicals

Status

Health-based Value

Taste Threshold

Ammonia

D ‘92

Not Available

30 mg/L

Methyl tertiary butyl ether (MtBE)

F ‘98

Not Available

40 μg/L

Sodium

D ‘02

20 mg/L (for individuals on a 500 mg/day restricted sodium diet).

30-60 mg/L

Sulfate

D ‘02

500 mg/L

250 mg/L

Odor Threshold

20 μg/L

Taste Threshold: Concentration at which the majority of consumers do not notice an adverse taste in drinking water; it is recognized that some sensitive individuals may detect a chemical at levels below this threshold. Odor Threshold: Concentration at which the majority of consumers do not notice an adverse odor in drinking water; it is recognized that some sensitive individuals may detect a chemical at levels below this threshold.

WATER QUALITY STANDARDS APPENDIX C4

C4-14

Drinking Water Advisory Table

WATER QUALITY STANDARDS APPENDIX C4

DEFINITIONS The U.S. EPA provided the following definitions for terms used in the previous tables; they are not to be considered all-encompassing and should not be construed to be official definitions. Action Level: The concentration of a contaminant which, if exceeded, triggers treatment or other requirements which a water system must follow. For lead or copper it is the level which, if exceeded in over 10% of the homes tested, triggers treatment. Cancer Group: A qualitative weight-of-evidence judgement as to the likelihood that a chemical may be a carcinogen for humans. Each chemical is placed into one of the following five categories: • • • • • • •

A B

Human carcinogen Probable human carcinogen: B1 indicates limited human evidence B2 indicates sufficient evidence in animals and inadequate or no evidence in humans C Possible human carcinogen D Not classifiable as to human carcinogenicity E Evidence of noncarcinogenicity for humans

This categorization is based on EPA’s 1986 Guidelines for Carcinogen Risk Assessment. The Proposed Guidelines for Carcinogen Risk Assessment which were published in 1996, when final, will replace the 1986 cancer guidelines. 10-4 Cancer Risk: The concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 10,000. Drinking Water Advisory: A nonregulatory concentration of a contaminant in water that is likely to be without adverse effects on both health and aesthetics. DWEL: Drinking Water Equivalent Level. A lifetime exposure concentration protective of adverse, non-cancer health effects, that assumes all of the exposure to a contaminant is from drinking water. HA: Health Advisory. An estimate of acceptable drinking water levels for a chemical substance based on health effects information; a Health Advisory is not a legally enforceable Federal standard, but serves as technical guidance to assist Federal, State and local officials. One-Day HA: The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to one day of exposure. The One-Day HA is normally designed to protect a 10-kg child consuming 1 liter of water per day. Ten-Day HA: The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to ten days of exposure. The Ten-Day HA is also normally designed to protect a 10-kg child consuming 1 liter of water per day. Lifetime HA: The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for a lifetime of exposure. The Lifetime HA is based on exposure of a 70-kg adult consuming 2 liters of water per day. The Lifetime HA for Group C carcinogens includes an adjustment for possible carcinogenicity. LED10: Lower Limit on Effective Dose10. The 95% lower confidence limit of the dose of a chemical needed to produce an adverse effect in 10% of those exposed to the chemical, relative to the control. MCLG: Maximum Contaminant Level Goal. A non-enforceable health goal which is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. MCL: Maximum Contaminant Level. The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLG as feasible using the best available analytical and treatment technologies and taking cost into consideration. MCLs are enforceable standards. RfD: Reference Dose. An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. SDWR: Secondary Drinking Water Regulations. Non-enforceable federal guidelines regarding cosmetic effects (such as tooth or skin discoloration) or aesthetic effects (such as taste, odor or color) of drinking water. TT: Treatment Technique. A required process intended to reduce the level of a contaminant in drinking water. ABBREVIATIONS D = Draft F = Final NA = Not Applicable NOAEL = No-Observed-Adverse-Effect Level OPP = Office of Pesticide Programs P = Proposed Reg = Regulation TT = Treatment Technique

C4-15

APPENDIX C5 CERLA PARAMETER LISTS

APPENDIX C5 CERCLA CHEMICAL PARAMETER LISTS

C5-1

APPENDIX C5 CERLA PARAMETER LISTS

CERCLA CHEMICAL PARAMETER LISTS

In 1980 Congress passed the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) commonly known as Superfund. This law provided broad federal authority to respond directly to releases or threatened releases of hazardous substances that may endanger public health or welfare of the environment. The law provides the EPA with the authority to respond directly or to compel potentially responsible parties (PRPs) to respond through litigation and negotiations. Under the 1980 law, a trust fund was established, financed through a special tax on the chemical and petroleum industries. This trust fund, known as the Superfund, was used to finance site remediation when no viable PRPs are found or when PRPs fail to take necessary response actions. In 1986 CERCLA was increased and amended. The major goals of the amendments, known as The Superfund Amendments Second Reauthorization Act (SARA), were a faster pace of clean-up, more public participation and more rigid and clearly defined clean-up standards, with an emphasis on achieving remedies that permanently and significantly reduce the mobility, toxicity or volume of wastes. There are two types of reporting requirements under Superfund: spill reporting and facility notification requirements. The first reporting requirement under CERCLA 103(a) relates to actual releases (including spills) of hazardous substances; the second, under CERCLA 103(c), relates to facilities where hazardous wastes have been disposed of and where such releases might potentially occur. Separate reporting requirements were created under Title III of SARA, known as the Emergency Planning and Community Right-to-Know Act of 1986, requiring you to provide (1) immediate notice for accidental releases of hazardous substances and extremely hazardous substances; (2) information to local emergency planning committees for the development of emergency plans; and (3) Material Safety Data Sheets, emergency and hazardous chemical inventory forms and toxic chemical release forms. A. Contract Laboratory Program The EPA's Contract Laboratory Program (CLP) was established in 1980 to support EPA enforcement activities under CERCLA. The analytical results generated under the CLP are used to help determine the severity of site contamination and whether a site should be placed on the National Priority List. The National Priority List designates the nation's worst known sites contaminated with hazardous substances. Only sites included on this list are eligible for long-term remedial action under the Superfund project. CLP protocol is generally used for all PRP-funded Remedial Investigation/Feasibility Studies (RI/FS).

C5-2

APPENDIX C5 CERLA PARAMETER LISTS

ORGANIC CLIP TARGET COMPOUND LIST

Volatile Organics CAS Number 74-87-3 74-83-9 75-01-4 75-00-3 75-09-2 67-64-1 75-15-0 75-35-4 75-34-3 540-59-0 67-66-3 107-06-2 78-93-3 71-55-6 56-23-5 108-05-4 75-27-4 79-34-5 78-87-5 10061-02-6 79-01-6 124-48-1 79-00-5 71-43-2 10061-01-5 75-25-2 108-10-1 591-78-6 127-18-4 108-88-3 108-90-7 100-41-4 100-42-5 1330-20-7

Compound Chloromethane Bromomethane Vinyl Chloride Chloroethane Methylene chloride Acetone Carbon disulfide 1,1-Dichloroethene 1,1-Dichloroethane 1,2-Dichloroethene (total) Chloroform 1,2-Dichloroethane 2-Butanone 1,1,1-Trichloroethane Carbon tetrachloride Vinyl acetate Bromodichloromethane 1,1,2,2-Tetrachloroethane 1,2-Dichloropropane trans-1,3-Dichloropropene Trichloroethene Dibromochloromethane 1,1,2-Trichloroethane Benzene cis-1,3-Dichloropropene Bromoform 4-Methyl-2-pentanone 2-Hexanone Tetrachloroethene Toluene Chlorobenzene Ethylbenzene Styrene Xylene (total)

Contract Required Quantitation Limits* Low Soil/ Water Sediment (b) (μg/L) (μg/kg) 10 10 10 10 10 10 10 10 10 5 5 5 5 5 5 10 5 5 10 5 5 5 5 5 5 5 5 5 5 10 10 5 5 5 5 5 5

10 5 5 5 5 5 5 10 5 5 10 5 5 5 5 5 5 5 5 5 5 10 10 5 5 5 5 5 5

(a) Medium Water Contract Required Quantitation Limits (CRQL) for Volatile TCL Compounds are 125 times the individual Low Soil/Sediment CRQL. * Specific quantitation limits are highly matrix dependent. The quantitation limits listed herein are provided for guidance and may not always be achievable. Quantitation limits listed for soil/sediment are based on wet weight. The quantitation limits calculated by the laboratory for soil/ sediment, calculated on dry weight basis as required by the contract, will be higher.

C5-3

APPENDIX C5 CERLA PARAMETER LISTS

Semi-Volatile Compounds:

CAS Number 108-95-2 111-44-4 95-57-8 541-73-1 106-46-7 100-51-6 95-50-1 95-48-7 108-60-1 106-44-5 621-64-7 67-72-1 98-95-3 78-59-1 88-75-5 105-67-9 65-85-0 111-91-1 120-83-2 120-82-1 91-20-3 106-47-8 87-68-3 59-50-7 91-57-6 77-47-4 88-06-2 95-95-4 91-58-7 88-74-4 131 ~ 3 208-96-8 606-20-2 99-09-2 83-32-9 51-28-5 100-02-7 132-64-9 121-14-2 84-66-2 7005-72-3 86-73-7 100-01-6 534-52-1

C5-4

Compound Phenol bis(2-Chloroethyl)ether 2-Chlorophenol 1,3-Dichlorobenzene 1,4-Dichlorobenzene Benzyl alcohol 1,2-Dichlorobenzene 2-Methylphenol bis(2-chloroisopropyl)ether 4-Methylphenol N-Nitroso-di-n-propylamine Hexachloroethane Nitrobenzene Isophorone 2-Nitrophenol 2,4-Dimethylphenol Benzoic acid bis(2-Chloroethoxy)methane 2,4-Dichlorophenol 1,2,4-Trichlorobenzene Naphthalene 4-Chloroaniline Hexachlorobutadiene 4-Chloro-3-methylphenol 2-Methylnaphthalene Hexachlorocyclopentadiene 2,4,6-Trichlorophenol 2,4,5-Trichlorophenol 2-Chloronaphthalene 2-Nitroaniline Dirnethylphthalate Acenaphthylene 2,6-Dinitrotoluene 3-Nitroaniline Acenaphthene 2,4-Dinitrophenol 4-Nitrophenol Dibenzofuran 2,4-Dinitrotoluene Diethylphthalate 4-Chlorophenyl-phenyl ether Fluorene 4-Nitroaniline 4,6-Dinitro-2-methylphenol

Contract Required Quantitation Limits* Low Soil/ Water Sediment (b) (μg/ L) (μg/kg) 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 50 1600 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 10 330 50 1600 10 330 50 1600 10 330 10 330 10 330 50 1600 10 330 50 1600 50 1600 10 330 10 330 10 330 10 330 10 330 50 1600 50 1600

APPENDIX C5 CERLA PARAMETER LISTS

86-30-6 101-55-3 118-74-1 87-86-5 85-01-8 120-12-7 84-74-2 206-44-0 129-00-0 85-68-7 91-94-1 56-55-3 218-01-9 117-81-7 117-84-0 205-99-2 207-08-9 50-32-8 193-39-5 53-70-3 191-24-2 (a)

(a)

4-Bromophenyl-phenylether Hexachlorobenzene Pentachlorophenol Phenanthrene Anthracene Di-n-butylphthalate Fluoranthene Pyrene Butylbenzylphthalate 3,3'-Dichlorobenzidine Benzo(a)anthracene Chrysene bis(2-Ethylhexyl)phthalate Di-n-octylphthalate Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Indeno(1,2,3-cd)pyrene Dibenz(a,h)anthracene Benzo(g,h,i)perylene

10 10 10 50 10 10 10 10 10 10 20 10 10 10 10 10 10 10 10 10 10

330 330 330 1600 330 330 330 330 330 330 660 330 330 330 330 330 330 330 330 330 330

Cannot be separated from Diphenylamine

(b) Medium

Soil/Sediment Contract Required Quantitation Limits (CRQL) for Semi-Volatile TCL Compounds are 60 times the individual Low Soil/Sediment CRQL. Specific quantitation limits are highly matrix dependent. The quantitation limits listed herein are provided for guidance and may not always be achievable. Quantitation limits listed for soil/sediment are based on wet weight. The quantitation limits calculated by the laboratory for soil/ sediment, calculated on dry weight basis as required by the contract, will be higher. The 1985 Contract List also included the following compound: 92-87-5

Benzidine

80 μg/L

2600 μg/kg

The use of gel permeation clean-up (GPQ is strongly recommended for the preparation of soil/sediments under the TCL/Routine Analytical Services (RAS) protocols. It should be noted that the use of GPC increases the CRQL by a factor of two (2). Combination of base neutral and acid extracts for water samples increase the CRQLs by a factor of two (2).

C5-5

APPENDIX C5 CERLA PARAMETER LISTS

Semi-Volatile Compounds:

319-84-6 319-85-7 319-86-8 58-89-9 76-44-8 309-00-2 1024-57-3 959-98-8 60-57-1 72-55-9 72-20-8 33213-65-9 72-54-8 1031-07-8 50-29-3 72-43-5 53494-70-5 5103-71-9 5103-74-2 8001-35-2 12674-2 11104-28-2 11141-16-5 53469-21-9 12672-29-6 11097-69-1 11096-82-5

_-BHC `-BHC b-BHC a-BHC (lindane) Heptachlor Aldrin Heptachlor epoxide Endosulfan 1 Dieldrin 4,4'-DDE Endrin Endosulfan 11 4,4'-DDD Endosulfan sulfate 4,4'-DDT Methoxychlor Endrin ketone _-chlordane a-chlordane Toxaphene Aroclor-1016 Aroclor-1221 Aroclor-1232 Aroclor-1242 Aroclor-1248 Aroclor-1254 Aroclor-1260

Contract Required Quantitation Limits* Low Soil/ Water Sediment (b) (μg/L (μg/kg) 0.05 8.0 0.05 8.0 0.05 8.0 0.05 8.0 0.05 8.0 0.05 8.0 0.05 8.0 0.05 8.0 0.10 16.0 0.10 16.0 0.10 16.0 0.10 16.0 0.10 16.0 0.10 16.0 0.10 16.0 0.5 80.0 0.10 16.0 0.5 80.0 0.5 80.0 1.0 160.0 0.5 80.0 0.5 80.0 0.5 80.0 0.5 80.0 0.5 80.0 1.0 160.0 1.0 160.0

(c) Medium Soil/Sediment Contract Required Quantitation Limits (CRQL) for Pesticide/PCB TCL compounds are 15 times the individual Low Soil/Sediment CRQL. Specific quantitation limits are highly matrix dependent. The quantitation. limits listed herein are provided for guidance and may not always be achievable. Quantitation limits listed for soil/sediment are based on wet weight. The quantitation limits calculated by the laboratory for soil/sediment, calculated on dry weight basis as required by the contract, will be higher.

C5-6

APPENDIX C5 CERLA PARAMETER LISTS

Metals

CAS Number

Compound

7429-90-5 7440-36-0 7440-38-2 7440-39-3 7440-41-7 7440-43-9 7440-70-2 7440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-95-4 7439-96-5 7439-97-6 7440-02-0 7440-09-7 7782-49-2 7440-22-4 7440-23-5 7440-28-0 7440-62-2 7440-66-6

Aluminum Antimony Arsenic Barium Beryllium Cadmium Calcium Chromium Cobalt Copper Iron Lead Magnesium Manganese Mercury Nickel Potassium Selenium Silver Sodium Thallium. Vanadium Zinc

Contract Required Quantitation Limits* Low Soil/ Water Sediment (b) (μg/L) (μg/kg) 200 60 10 200 5 5 5000 10 50 25 100 5 5000 15 0.2 40 5000 5 10 5000 10 50 20

200 60 10 200 5 5 5000 10 50 25 100 5 5000 15 0 40 5000 5 10 5000 10 50 20

25

500

Conventionals 57-12-5

Cyanide

B. Hazardous Substances Priority List A requirement of SARA is that EPA and the Agency for Toxic Substances and Disease Registry (ATSDR) prepare a list of hazardous substances which are most often found at facilities on the CERCLA National Priorities List and which the agencies determine are posing the most significant potential threat to human health. The first priority list of 100 substances was published on April 17,1987. The second list was published October 20,1988.

C5-7

APPENDIX C5 CERLA PARAMETER LISTS

LIST OF FIRST 100 HAZARDOUS SUBSTANCES Priority Group 1 CAS Number 50-32-8 53-70-3 56-55-3 57-12-5 60-57-1, 309-00-2 67-66-3 71-43-2 75-01-4 75-09-2 76-44-8,1024-57-3 79-01-6 86-30-6 106-46-7 117-81-7 127-18-4 205-99-2 218-01-9 1746-01-6 7439-92-1 7440-02-0 7440-38-2 7440-41-7 7440-43-9 7440-47-3 11096-82-5, 11097-69-1, 12672-29-6, 53469-21-9, 11141-16-5, 11104,28-2, 12674-11-2

Substance Name Benzo(a)pyrene Dibenzo(a,h)anthracene Benzo(a)anthracene Cyanide Dieldrin/aldrin Chloroform Benzene Vinyl chloride Methylene chloride Heptachlor/heptachlor epoxide Trichloroethylene N-Nitrosodiphenylamine 1,4-Dichlorobenzene bis(2-ethylhexyl)phthalate Tetrachloroethylene Benzo(b)fluoranthene Chrysene 2,3,7,8-Tetrachlorodibenzo-p-dioxin Lead Nickel Arsenic Beryllium Cadmium Chromium PCBs-Aroclor 1260, 1254, 1248, 1242,1232, 1221,1016,

Priority Group 2 56-23-5 57-74-9 62-75-9 72-55-9, 50-29-3, 72-54-8 75-00-3 75-27-4 75-35-4 78-59-1 78-87-5 79-00-5 79-43-5 87-86-5 91-94-1 92-87-5 107-06-2 108-88-3 108-95-2

C5-8

Carbon tetrachloride Chlordane N-Nitrosodimethylamine 4,4'-DDE, DDT, DDD Chloroethane Bromodichloromethane 1,1-Dichloroethane Isophorone 1,2-Dichloropropene 1,1,2-Trichloroethane 1,1,2,2-Tetrachloroethane Pentachlorophenol 3,3'-Dichlorobenzidine Benzidine 1,2-Dichloroethane Toluene Phenol

APPENDIX C5 CERLA PARAMETER LISTS

111-44-4 121-14-2 319-64-6,58-89-9, 319-65-7, 319-86-8, 542-86-1 621-64-7 7439-97-6 7440-66-6 7782-49-2

bis(2-Chloroethyl) ether 2,4-Dinitrotoluene BHC-alpha, gamma, beta, delta bis(chloromethyl) ether N-Nitrosodi-n-propylamine Mercury Zinc Selenium

Priority Group 3 71-55-6 74-87-3 75-21-8 75-25-2 75-34-3 84-74-2 88-06-2 91-20-3 100-41-4 107-02-8 107-13-1 108-90-7 118-74-1 122-66-7 124-48-1 156-60-5 193-39-5 606-20-2 1330-2-07 7621-93-4,72-20-8 7440-22-4 7440-50-8 7664-41-7 8001-35-2

1,1,1-Trichloroethane Chloromethane Oxirane Bromoform 1,1-Dichloroethane Di-n-butyl phthalate 2,4,6-Trichlorophenol Naphthalene Ethylbenzene Acrolein Acrylonitrile Chlorobenzene Hexachlorobenzene 1,2-Dinitrotoluene Chlorodibromomethane 1,2-trans-Dichloroethene Indeno(1,2,3-cd)pyrene 2,6-Dinitrotoluene Total xylenes Endrin aldehyde/endrin Silver Copper Ammonia Toxaphene Priority Group 4

51-28-5 59-50-7 62-53-3 65-85-0 67-72-1 74-83-9 75-15-0 75-69-4 75-71-8 78-93-3 84-66-2 85-01-8 87-68-3 95-48-7 95-50-1 105-67-9

2,4-Dinitrophenol p-Chloro-m-cresol Aniline Benzoic acid 1-Hexachloroethane Bromethane Carbon disulfide Fluorotrichloromethane Dichlorodifluoromethane 2-Butanone Diethyl phthalate Phenanthrene Hexachlorobutadiene 2-Methylphenol 1,2-Dichlorobenzene 2,4-Dimethylphenol

C5-9

APPENDIX C5 CERLA PARAMETER LISTS

108-10-1 120-82-1 120-83-2 123-91-1 131-3 206-44-0 534-52-1 541-73-1 7440-28-0

4-Methyl-2-pentanone 1,2,4-Trichlorobenzene 2,4-Dichlorophenol 1,4-Dioxane Dirnethyl. phthalate Fluoranthene 4,6-Dinitro-2-methylphenol 1,3-Dichlorobenzene Thallium

LIST OF SECOND 100 HAZARDOUS SUBSTANCES

Priority Group 1 CAS No. 51-75-2 77-47-4 100-42-5 108-05-4 115-29-7 118-96-7 120-12-7 129-00-0 302-01-2 591-78-6 1332-21-4 1517-48-3 7439-96-5 7440-14-4 7440-29-1 7440-31-5 7440-36-0 7440-39-3 7440-42-6 7440-48-4 7440-61-1 8001-58-9 10043-92-2 10061-02-6 16984-48-8

Substance Name Mechlorethamine Hexachlorocyclopentadiene Styrene Vinyl acetate Endosulfan (_, `, sulfate) 2,4,6-Trinitrotoluene Anthracene Pyrene Hydrazine 2-Hexanone Asbestos Plutonium Manganese Radium and compounds Thorium and compounds Tin Antimony Barium and compounds Boron and compounds Cobalt and compounds Uranium and compounds Cresote Radon and compounds trans-1,3-Dichloropropene Fluorides/fluorine/hydrogen fluoride Priority Group 2

50-00-0 56-38-2 67-64-1 75-44-5 83-32-9 86-73-7 91-57-6 96-18-4

C5-10

Chlorodibenzodioxins Formaldehyde Parathion (DNTP) Acetone Phosgene Acenaphthene Fluorene 2-Methylnaphthalene 1,2,3-Trichloropropane

APPENDIX C5 CERLA PARAMETER LISTS

100-02-7 106-47-8 106-93-4 110-75-8 117-84-0 132-64-9 156-59-2 191-24-2 207-08-9 208-96-6 298-04-4 505-60-2 1912-24-9 7440-62-2 7446-09-5 14797-55-8

4-Nitrophenol 4-Chloroaniline 1,2-Dibromoethane 2-Chloroethyl vinyl ether Di-n-octyl phthalate Dibenzofuran cis-1,2-Dichloroethylene Benzo(g,h,i)perylene Benzo(k) fluoranthene Acenaphthylene Disulfoton Mustard gas Atrazine Vanadium Sulfur Dioxide Nitrates/nitr Priority Group 3

63-25-2 68-12-2 72-43-5 74-97-5 75-45-6 85-68-7 88-74-4 88-75-5 93-72-1 93-76-5 94-75-7 95-57-8 95-95-4 96-12-8 100-51-6 101-14-4 109-66-0 110-54-3 121-82-4 540-59-0 2385-85-5 7783-06-4 26471-62-5

Polybrominated-biphenyls Chlorodibenzofurans Sevin (Carbaryl) Dimethyl formamide (DMF) Methoxychlor Bromochloromethane Chlorodifluoromethane Butylbenzyl phthalate o-Nitroaniline 2-Nitrophenol 2,4,5-TP acid (Silvex) 2,4,5-T 2,4-D, salts and esters 2-Chlorophenol 2,4,5-Trichlorophenol Dibromochloropropene Benzyl alcohol 4,4'-Methylene-bis-(2-chloraniline) n-Pentane Hexane RDX (Cyclonite) 1,2-Dichloroethylene Mirex Hydrogen sulfide Toluene diisocyanite Priority Group 4

67-56-1 76-13-1 80-62-6 99-09-2 99-35-4 101-55-3 106-44-5

Methanol 1,1 2-Trichloro-1,2,2-trifluoroethane Methyl methacrylate m-Nitroaniline 1,3,5-Trinitrobenzene I-Bromo-4-phenyoxy benzene 4-Methylphenol

C5-11

APPENDIX C5 CERLA PARAMETER LISTS

107-21-1 108-94-1 109-99-9 111-65-9 111-91-1 121-75-5 140-57-8 142-82-5 479-45-8 608-93-5 1319-77-3 7005-72-3 7439-98-7 7440-24-6 7664-93-9 10028-17-8 10061-01-5 25154-55-6

C5-12

Ethylene glycol Cyclohexanone Tetrahydrofuran Octane bis(2-Chloroethoxy)methane Malathion Aramite Heptane Trinitrophenylmethylnitramine Pentachlorobenzene Cresols 4-Chlorophenyl phenyl ether Molybdenum Strontium Sulfuric acid Tritium cis-1,3-Dichloropropene Nitrophenol

EXAMPLE PRODUCTION WELL SPECIFICATION APPENDIX D1

APPENDIX D1

SPECIFICATIONS FOR CONSTRUCTING A FIRE PROTECTION WELL

D1-1

APPENDIX D1: EXAMPLE PRODUCTION WELL SPECIFICATION

GENERAL CONDITIONS The term “Owner” shall mean either the Owner or the Owner’s Representative.

Section 1: Scope of Work The work to be performed here under includes the furnishing of all labor, material, transportation, tools, supplies, plant, equipment and appurtenances, unless hereinafter specifically excepted, necessary for the complete and satisfactory construction, disinfecting and testing of one (l) reverse rotary drilled gravel envelope well as herein specified.

Section 2: Contractor’s Qualifications The Contractor shall have been engaged in the business of constructing reverse rotary-drilled gravel-envelope wells of diameter, depth and capacity similar to the proposed well for a period of at least three (3) years. The Contractor shall submit a list of three or more well owners for whom the Contractor has drilled similar wells. The list shall include the owner’s name and address, the casing diameter and depth, the well’s maximum capacity and the well’s specific capacity. The Contractor shall also submit a list of his last 3 major jobs.

Section 3: Competent Workmen The Contractor shall employ only competent workmen for the execution of his work and all such work shall be performed under the direct supervision of an experienced well driller satisfactory to the Owner. The Contractor shall list the position and experience of all drilling personnel to work on this contract.

Section 4: Permits, Certificates, Laws and Ordinances The Contractor shall, at his own expense, procure all permits, certificates and licenses required of him by law for the execution of his work. He shall comply with all federal, state or local laws ordinances or rules and regulations relating to the performance of the work. The Owner has obtained the proper State Appropriation Well Permits.

Section 5: Location The well to be hereunder is to be located in the NW 1/4 of the SE 1/4 of Section 30, T27N, R22W, in ________ County, _________ This locality is about _____ miles north of the town of ________ near State Highway ___.

Section 6: Local Conditions Information regarding subsurface conditions is given on the attached log and is intended to assist the Contractor in preparing his bid. However, the Owner does not guarantee its accuracy, nor that it is necessarily indicative of conditions to be encountered in drilling the well to be constructed hereunder and the Contractor shall satisfy himself regarding all local conditions affecting his work by personal investigation and neither the information contained in this section nor that derived from maps or plans or from the Owner or his agents or employees shall act to relieve the Contractor from any responsibility hereunder or from fulfilling any and all of the terms and requirements of his contract.

D1-2

EXAMPLE PRODUCTION WELL SPECIFICATION APPENDIX D1

Section 7: Boundaries of Work The Owner shall provide land or rights-of-way for the work specified in this contract and make suitable provisions for ingress and egress and the Contractor shall not enter on or occupy with personnel, tools, equipment or material, nor shall the Contractor discharge water either directly or indirectly to or on any ground outside the property of the Owner without the written consent of the Owner of such ground. Other contractors and employees or agents of the Owner may for all necessary purposes enter upon the work and premises used by the Contractor and the Contractor shall conduct his work so as not to impede unnecessarily any work being done by others on or adjacent to the site.

Section 8: Protection of the Site Excepting as otherwise provided herein, the Contractor shall protect all structures, walks, pipelines, trees, shrubbery, lawns/ etc., during the progress of his work; shall remove from the site all cuttings, drillings, debris and unused materials; and shall, upon completion of the work, restore the site as nearly as possible to its original condition, including the replacement, at the contractor’s expense, of any facility or landscaping which has been damaged beyond restoration to its original condition or destroyed. Water pumped from the well shall be conducted to a place where it will be possible to dispose of the water without damage to property or the creation of a nuisance. It shall be assumed that the Contractor has inspected the site. Section 9: Capping the Well 1. At all times during the progress of the work, the Contractor shall use all reasonable measures to prevent either tampering with the well or the entrance of foreign matter into it. The Contractor shall be responsible for any objectionable material that may fall into the well and its consequences until the completion and acceptance of the work by the Owner. 2. After testing the well, the Contractor shall furnish and install a cap on the well. The cap shall consist of 1/4inch steel plate cut to the OD of the casing and tack-welded to cover the top of the well. A 1 inch-diameter threaded nipple and pipe cap shall be attached by threads or welding to a matching hole drilled in the center of the cap.

Section 10: Standby Times Measurements of standby time will be made only for inactive periods resulting from the Contractor being notified by written communication to cease operations during normal working hours. Idle time required for maintenance of equipment or caused by failure of equipment shall not be measured for standby time. Standby time will be paid for a maximum of 8 hours per day, regardless of Contractor’s actual work schedule. Standby time will not be paid for time on Saturdays, Sundays or national holidays on which work is not customarily performed unless the Contractor had previously agreed to work on such days. Payment for standby time will be made at the unit price per hour quoted in Bid Item 9. Section 11: Abandoned Hole If the well fails to conform to specifications and because of Contractor’s fault he is unable to correct the condition at his own expense or negotiate a mutually acceptable cost reduction for specification deviations, it shall be considered an abandoned hole and Contractor shall immediately start a new well at a nearby location designated by the owner. The abandoned hole shall be treated as follows: 1. Contractor may salvage as much casing and screen from the initial well as possible and use in a new well if it is not damaged. 2. Salvage material shall remain the property of Contractor.

D1-3

APPENDIX D1: EXAMPLE PRODUCTION WELL SPECIFICATION

3. The initial hole shall be filled with clayey material to within 15 feet of the land surface and then a 10-footlong concrete plug should be formed in the hole. 4. Casing remaining in the hole shall be cut off at least 5 feet below ground surface. The remaining 5 feet of hole shall be filled with native top soil. 5. No payment will be made for work done on an abandoned hole or for salvaging materials and sealing the hole. If the well fails to conform to the Owner’s needs and the Contractor has faithfully fulfilled his obligations under this contract, the Owner may direct the Contractor to abandon the hole. In this event, negotiations between the two parties for salvage and sealing the hole will determine payment.

Section 12: Subcontractors None of this work may be sublet without the written consent of the Owner. If any part is sublet the subcontractor shall be considered as an employee of the Contractor.

Section 13: Records The Contractor shall keep records providing the following information: 1. A log of the formation drilled from surface to total depth showing each change in formation. 2. The final well log shall show: diameter, wall thickness, depths and quantities of casings and screens installed; details of reducing sections; type, aperture size and pattern of perforations; borehole diameters; cemented sections; gradation of gravel envelope; quantity of gravel initially installed; quantity of gravel added during development operations; quantity of material removed during development operations; and all other pertinent details. 3. A record of drilling fluid properties at 4-hour intervals. The record shall show weight, funnel viscosity, 30-minute water loss, cake thickness and sand content. 4. Development and test records shall be maintained on an hourly basis, showing production rate, static water level, pumping level, drawdown, production of sand and all other pertinent information concerning method of development. These records shall be provided to the Owner upon demand at any time during or at the completion of the well drilling. Two copies of the Water Well Driller’s Report submitted to the State of ________ upon completion of the well shall be provided to the Owner as well within 1 week of completion.

Section 14: Arbitration Any dispute regarding performance of work, quality of workmanship or materials and interpretation of the intent and content of these specifications shall immediately be brought to the attention of all parties concerned. If disputes cannot be resolved through arbitration between Contractor and Owner, a mutually acceptable third party shall be appointed to resolve said differences.

D1-4

EXAMPLE PRODUCTION WELL SPECIFICATION APPENDIX D1

REFERENCE LOGS

Owner: Location:

Contractor: Date

Northern States Power NE 1/4 of SW 1/4, Sec. 30, T27N, R22W, Dakota County, Minnesota, 1200 feet west of well proposed herein Keyes Well Drilling Company Completed: September, 2000 Well Log Depth (ft) 0-55 55-75 75-215 215-335 335-380 380-390 390-435 435-450 450-480

Owner: Location:

Contractor: Date Completed: December, 2001

Material Drift, undifferentiated. Sand & Gravel, yellow-brown, silty. Sand, Brown to tan, clean to silty, very fine to medium. Sand, tan, fine with some gravel. Sand, tan, fine to coarse, poorly sorted Gravel, tan, very fine. Sand, tan to brown, clean to silty. Sand to gravel, tan, clean. Jordan Sandstone, medium ss, well sorted, well rounded & frosted grains, quartzose, very clean.

Northern States Power NW 1/4 of SE 1/4, Sec. 30, T27N, R22W, about 50 feet west of well proposed herein, Dakota County, Minnesota Layne-Minnesota Company

Depth (ft) 0- 8 8-248 248-358 358-358 ft 6 in. 358ft 6 in.-373 373-382 382-398 398-403

Material Red sandy clay, gravel. Red sand and small gravel cemented seams Gray firm sand. Cemented sand Soft gray-black clay Gray sandy clay Gray clay, rock seams Lime rock, harder

D1-5

APPENDIX D1: EXAMPLE PRODUCTION WELL SPECIFICATION

SPECIFICATIONS

1. DRILLING: A 24-inch hole shall be drilled to an estimated depth of 360 feet more or less, as determined by the Owner. A pilot bore or test hole, if used, shall be of such diameter as selected by the Contractor, but shall be of such size and depth as to adequately determine the character of the underground formation. Samples of the subsurface formations shall be obtained every 10 feet and preserved in sample bags for inspection by the Owner. The drilling shall be done with a first-class, high-speed, reverse rotary drilling unit, subject to the approval of the Owner. No unnecessary delays nor work stoppages due to negligence or willful mis-operation of the Contractor will be tolerated and the Contractor shall be held responsible and payment withheld for damage done to the well due to such negligence or mis-operation. The equipment shall be of the proper type and shall be in good condition so that the work performed can be done without any interruption arising from defective or improper equipment; however, the Contractor shall not be held liable for stoppage or delays due to mechanical failures beyond his control. Water for drilling and developing purposes shall be agreed upon between the Contractor and the Owner prior to drilling. It is expected that a nearly continuous 25-gpm water supply would be available from a well approximately 50 feet from the well proposed herein. If, at the completion of developing and test pumping, the well yield is insufficient for its intended use, the Owner may require the well to be deepened to about 480 feet and through the Jordan sandstone using a cable tool churn drilling rig. A cable tool rig is the preferred drilling method below about 360 feet to avoid invading the glacial outwash aquifer with clay particles. Approximately 60 feet of 12-inch ID casing shall be installed in this hole with at least a 3-foot overlap into the 16-inch O.D. casing. The annulus between the 16-inch OD casing and the 12-inch ID casing shall be plugged with a swaged lead seal. The 10-inch diameter open-hole portion of the deepened well tapping the Jordan sandstone shall be developed by the appropriate means. If the open hole is enlarged through blasting with explosives, care must be taken to avoid damaging the well screens in the glacial outwash aquifer. Only small quantities of explosives may be used at any one time and only with the approval of the Owner. A graphical description of the casing and well design is shown on Plate 1 attached to the Specifications. 2. CASING: The casing shall be only new standard pipe (Schedule 40) Class A, electric-welded, single-wall casing, complying with the requirements of ASTM Standard Specifications A 283-Grade B, with any subsequent amendments thereto or ASTM A-242-55 (Grade 2 Kaisaloy or equivalent). The surface water shut-off casing, if any, shall be at the Contractor’s discretion. The well casing shall consist of 16-inch outside diameter pipe casing. The casing shall have an inside diameter of 15.250 inches, a wall thickness of 0.375 inches and shall weight 62.58 pounds per lineal foot. The string of casing shall be about 300 feet in total length. All well screens put into the casing string shall be Stainless Steel 304 Johnson or its equivalent or better. The slot size of the screens will be determined by the Owner. Intermediate joints in screen sections shall be made by welding of a material and type recommended by the well screen manufacturer. The well screens shall be about 60 feet in total length. The bottom of the 16-inch OD tail pipe below the lowest well screen shall be plugged with 2-feet of Portland cement. Cement will be used for the bottom of the 16-inch OD casing so that the well can be drilled deeper if necessary.

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EXAMPLE PRODUCTION WELL SPECIFICATION APPENDIX D1

If any auxiliary casing is used in the bottom of the well it shall be 12-inch ID pipe with an outside diameter of 12.750 inches, a wall thickness of at least 0.375 inches and a weight of at least 49.56 pounds per lineal foot. If used, an estimated 60 feet of 12-inch ID casing would be installed from about 357 to about 417 feet. 3. GRAVEL: The gravel for the gravel envelope shall be clean, rounded, water-washed quartz or granitic gravel, free from silt, clay and other deleterious material. Crushed or granular rock will not be permitted. Gravels shall be as near uniform sizes as possible and shall consist of a uniform size to be determined by the Owner. Sufficient gravel shall be furnished for initial graveling of the well and such additional’ gravel as the well may take during development activities. The gravel shall be installed after l2 hours advance notification to the Owner and shall be approved by the Owner prior to installation. 4. MUD: Drilling fluids are expected to consist of water. However, if a higher viscosity fluid is needed, only a timedegradable drilling mud such as Revert (manufactured by Johnson) plus any additives normally used with Revert shall be permitted in the well. 5. LOG AND RECORD: After the hole has been drilled to the desired depth, the Owner, at his option, may request an electric log of the entire well from the ground surface to the bottom. The contractor shall be paid for his idle time, if during normal working hours, in accordance to Bid Item 9 Standby time. 6. PLUMBNESS: The completed well shall be straight and plumb. Plumbness of the hole is of primary importance. To assure plumbness, drill collars of sufficient size and length are required. The alignment of the completed well shall not deviate more than 6 inches per 100 feet of depth. The Contractor may use any appropriate means, upon the approval of the Owner, to correct any misalignment. Failure or inability of a Contractor to properly plumb the well shall be sufficient cause of its rejection. 7. PLACING OF WELL CASING: After the hole has been drilled no less than 24 inches in diameter to a depth of 360 feet, the well casing shall then be installed. The bottom of the casing shall be held slightly above the bottom of the reamed hole by suspending the casing from the ground surface until the gravel has been placed. 8. CENTRALIZERS: The casing shall be so centered that the completed string will be plumb and true. The casing shall be fitted with proper centering brackets, installed at locations as directed by the Owner, but spaced not over 50 feet apart. 9. PLACING OF GRAVEL: After the well casing has been installed and centered, water shall be introduced into the circulating drilling fluid to properly thin the fluids without endangering the wall structure. The annular space shall then be carefully and completely packed with gravel. The gravels may be pumped to the bottom through one or two columns of 2- or 2 1/2-inch pipe or tubing. Whether pumped or dumped, a constant check must be made to determine the actual position of the gravel. A careful record and computation must be made and furnished as to the amount of gravel introduced into the annulus of the well to compare it with the total amount required to properly gravel the well. Fluid circulation shall be continuous with the placing of the gravel by pumping from the inside of the well casing. The method of placement of the gravel shall be approved by the Owner. 10. PROTECTIVE GROUTING: The Contractor shall be required for public health safety to place a cement grout of an approved mixture in the annular space between the well casing and the drilled hole. The Contractor shall place all cement grout in accordance to the State Laws governing such practices as adapted July 15, 19__ and he shall include in his bid price the cost of such work. If local conditions are not sufficiently known prior to drilling operations to specify necessary depth and grouting, the required work may be determined in the field by the Owner and such work shall be considered an extra, payment for which shall be at price agreed to by the Contractor and the Owner in writing before such operation is begun. 11. SWABBING AND JET DEVELOPMENT OF THE WELL: Upon completion of the setting of the well casing and the graveling, the well shall be swabbed at the Contractor’s option. Development by jetting the screen and gravel pack as later described is mandatory.

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APPENDIX D1: EXAMPLE PRODUCTION WELL SPECIFICATION

The swab used should have a diameter not less than 1/8 inch smaller than the diameter of pipe to be swabbed. This work should be done by operating a suction swabber immediately after completion of initial graveling. Swabbing should continue opposite the perforated section of the well casing until as much as possible of the drilling fluids, silt and fine sand has been removed and as long as the gravel continues to move in the peripheral area around the well casing. All material drawn into the well shall be removed often enough to prevent cementing of this material into lower formations. A careful record must be kept and furnished to the Owner as to the quantity and character of material removed from the well as a result of swabbing operations. If, in the Contractor’s opinion, due to some cause over which he has no control, the structural stability of the well is endangered, he may discontinue swabbing, of that particular section of the well casing where danger is imminent. The Contractor shall develop the well by using a hydraulic jet nozzle to break up bridges in the gravel pack at the slots in the screen. During such an operation, circulation will be maintained by pumping at least 30% more water from the well than that being jetted into the well. The pressure of the jet shall not be less than 150 nor more than 200 psi or as directed by the Owner. The tip of the jet nozzle shall be centralized so as not to be more than 2 inches from the well screen. No less than 100 gpm nor more than 200 gpm shall be jetted to the screens through no more than 2 jet nozzles rotating at about 1 rpm. During development there shall be available up to a 2-inch stream of water which shall be applied to the top of the gravel pack in whatever quantities required. The water is to furnish additional weight to facilitate movement of the gravel. Application of the water may be discontinued, if in the opinion of the Owner, the hole is endangered. Application of the water shall be through a tremie pipe to within a few feet of the gravel pack. Payment for development of the open-hole portion of the well in the Jordan sandstone (if drilled) shall be at the same rate as Item 8, Bid Items. Any additional supplier and materials shall be at a negotiated price between the Contractor and the Owner. 12. SWAGING: A rigid 15-foot long tapered swage having a diameter 1/2-inch less than the internal diameter of the casing must pass freely from the top to the bottom of the casing. The taper shall not be more than 2 feet from either end of the swage. 13. DEVELOPING AND TESTING: After completely swabbing, jet developing and sand pumping the well, the Contractor shall furnish and install a test pump with a capacity of 1500 gpm at a head of 300 feet to provide for testing and developing the well. The pump should be driven by a diesel or automotive-type engine or an electric motor in good condition and of sufficient horsepower to adequately deliver power required for the development of the well. The discharge pipe should be not less than 10 inchs ID and should be equipped with a sharp-edged orifice plate not less than 8 inches ID A gate valve should be installed in the discharge piping close to the pump. Pumping shall be started at a low rate of flow. The rate of production shall be gradually increased, depending upon the turbidity of the water and surged until the desired production from the well is obtained. The well should be developed until it produces no more sand that the amount specified by the Owner. The sand production shall be measured by a device such as the centrifugal sand sampler described in the AWWA Journal of February, 1954. Turbidity shall be less than 10 on the silica scale described in Standard Methods of Water Analysis. No deviation from this stipulation will be allowed except upon approval of the Owner. In no case will sand be allowed to exceed 5 parts per million of water. If in the opinion of the Owner after pumping for 48 hours additional development is necessary, the Contractor shall perform this work at his expense for a reasonable period of time.

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EXAMPLE PRODUCTION WELL SPECIFICATION APPENDIX D1

The Owner must be notified 72 hours in advance when the Contractor intends to start development. Because of certain conditions, over which the Owner has no control, all development work should be carried out in daylight hours only as far as practical. Upon completion of the test and development described above, to the satisfaction of the Owner, the Contractor shall remove the test pump and clean the well to the bottom. After the well has been initially pumped in this manner, no further work shall be done on the well for a period of not less than 12 hours or as determined by the Owner. The test pumping shall be performed for a minimum of 48 hours and shall be directed by the Owner. Pumping may be continued for a period of up to 10 days if determined to be necessary by the Owner. The Contractor shall be paid for the non-operating time the test pump is installed in the well if authorized in writing by the Owner according to Bid Item 12A. After installation of the permanent well pump, the well pump and all appurtenances will be chlorinated in accordance with the Minnesota State Board of Health specifications. 14. PUMP INSTALLATION AND WELL COMPLETION: The Contractor shall furnish and install a vertical line shaft turbine pump and related appurtenances as shown in Plate 2 and described below. The final design of the pumping equipment will be made after completing and analyzing the aquifer test. The following preliminary design is a guide and represents the probable maximum pumping equipment; 1. The pump shall be a oil-lubricated vertical line shaft turbine capable of pumping 1500 gpm with a total head (pumping lift plus line pressure) of 600 feet; equivalent to Tait 12BCH. 2. The bottom of the pump bowls shall be at a depth of about 260 feet below ground surface. 3. The multiple-stage pump bowl assembly shall not be less than 11 7/8-inch OD and not more than 13 7/8inch OD. 4. The tail pipe shall be 10 feet of 10-inch ID pipe (wall thickness not less than 0.25 inch). 5. The line shaft bearings and bowl bearings shall be bronze. 6. The line shaft shall be not less than 1-15/16 inch in diameter; and shall be of No. C1045 chrome plated, turned; and polished steel to about 130 feet below the motor, the remainder of the shaft shall be No. 416 stainless steel or better; all couplings shall be of the appropriate material and shall be enclosed in a 3inch ID schedule 80 oil tube. 7. The column shall be 10-inch ID with flange fittings (300 psi). 8. The discharge head shall be close-grain cast iron (minimum 30,000 pounds) and have a 10-inch ID discharge flange (300 psi);Tait 1012HA or equivalent. 9. The electric motor shall be 300 hp, 3-phase, 60-cycle, 460-volt, 1770 RPM non-reversible, Nema enclosure, shielded, hollow shaft, equivalent to General Electric or better. 10. The pump base shall be 3 feet square by 6 feet high of which 4 feet shall be below grade and consist of structurally reinforced concrete as specified and shown in Plates 3 and 4.

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APPENDIX D1: EXAMPLE PRODUCTION WELL SPECIFICATION

15. APPURTENANCES: The Contractor shall furnish the following appurtenances on the discharge line: 1.

A pressure gauge having a dial not less than 3 inches in diameter shall be connected near the discharge head by 1/4-inch cock with level handle and appropriate fittings. The gauge shall be graduated in pounds per square inch to at least 300 psi.

2.

A 2-inch or larger automatic air release valve is required to vent air from the column and discharge head upon starting the pump and also to serve to admit air to the column to dissipate the vacuum when the pump is stopped. This valve shall be located at the highest point in the discharge line between the pump and the discharge check valve. The air release valve shall be Consolidated Valve Co. No. 1541H or its equivalent.

3.

A 6-inch ID relief valve shall be mounted vertically on a 10 × 10 × 6-inch reducing tee. The relief valve discharge shall be to an 8-inch ID line to outside the pumphouse. Pressure relief valve shall have a 6inch inlet and outlet flange plates, with the outlet flange on the side of the vertically mounted valve. The inlet flange shall be rated not less than 250 psi and the side outlet flange can be rated to 125 psi. The relief pressure valve shall be manually adjustable with a side wheel. The pressure relief valve shall be Kunkle No. 218 or its equivalent. The pressure relief valve shall be set at 175 psi.

4.

Check valve shall be 10-inch ID and rated not less than 175 psi (non-shock). The check valve shall be Crane Ferrosteel Clearway Swing Check No. 375 or its equivalent.

5.

Gate valve shall be rated not less than 175 psi (non-shock) and shall be a 10-inch I.D. Crane Ferrosteel Gate Valve No. 467 or its equivalent.

6.

The 10-inch I.D. tee shall be a 10 times 10 yimes 6-inch reducing tee rated for not less than 175 psi.

7.

All flange fittings shall be of standard design and shall be joined using appropriate gaskets and bolt and nut fasteners as recommended by the manufacturers.

8.

The relief valve discharge line shall consist of a 6-inch ID 125 psi long-radius 90° elbow with a flange at one end and the other end plain, a plain-end long-radius 90° elbow and two pieces of standard 6-inch ID pipe in the appropriate lengths the total not to exceed 15 feet; the components shall be welded together as one unit.

Payment for the above discharge line appurtenances shall be according to Bid Item 14. The Contractor is not responsible for furnishing nor constructing starter or electric controls.

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EXAMPLE PRODUCTION WELL SPECIFICATION APPENDIX D1

BID ITEMS

1. MOBILIZATION:

Furnish all equipment, personnel, etc. Lump Sum_________________

2. ROTARY DRILLING:

No less than 24-inch diameter hole in accordance with attached specifications to an estimated depth of 360 feet. Price/Foot _________________

3. CABLE TOOL DRILLING: (At Owner’s Option)

A. No less than 12-3/4-inch diameter hole to accommodate the casing in Item 5. Total estimated quantity of drilling: 57 feet. Price/Foot_________________ B. No less than 10-inch diameter hole. Total estimated quantity of drilling: 63 feet. Price/Foot_________________

4. PIPE:

Furnish and install 16-inch OD standard pipe casing in accordance with attached specifications. Total estimated quantity: 300 feet. Price/Foot_________________

5. PIPE:

Furnish and install 12-inch ID standard pipe casing and a swaged lead seal all in accordance with attached Specifications. Total estimated quantity: 60 feet. (At Owner’s option.) Price/Foot_________________

6. SCREEN:

Furnish and install 16-inch OD pipe-size stainless steel #304 (U. O. P. Johnson or equivalent) well screens in slot sizes determined by the Owner in accordance with attached specifications. Total estimated quantity: 60 feet. Price/Foot__________________

7. GRAVEL PACK:

Install gravel pack at sizes and in a quantity as determined by the Owner and in accordance with attached specifications. Price/Yard_________________

8. DEVELOPMENT:

Develop the test well by jetting and swabbing in accordance with attached specifications. Price/Hour_____________

9. STANDBY TIME:

For the Contractor’s time after being notified by written communication to cease operations during normal working hours. Under such conditions, standby time will be in effect, all in accordance with attached Specifications. Price/Hour __________________

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APPENDIX D1: EXAMPLE PRODUCTION WELL SPECIFICATION

10. GROUTING:

Install concrete grout in annulus between the wall of the hole and the casing in accordance with attached specifications and in compliance with Minnesota State Law of July 15, 1974, concerning such practices. Price/Cubic Yard______________

11. TEST PUMP:

Furnish, install and remove a line-shaft turbine pump in accordance to the attached specifications. This item includes prime mover, discharge piping, gate valve and orifice in accordance with attached specifications. Lump Sum__________________

12. TEST PUMP RENTAL:

Test pump rental of the equipment in Item 11, in accordance with attached specifications. A. Non-operating time Price/Day_________________ B. Operating time with Contractor’s personnel Price/Day_________________ C. Operating time without Contractor’s personnel Price/Day__________________

13. PUMP BASE:

Construct steel-reinforced concrete pump base in accordance with attached specifications. Lump Sum_________________

14. PUMP:

Furnishing and installing vertical line-shaft turbine pump, motor in accordance with attached specifications. Lump Sum_________________

15. APPURTENANCES:

Furnishing and installing discharge line appurtenances in accordance with the attached specifications. Lump Sum_________________

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

APPENDIX D2 EXAMPLE SPECIFICATIONS FOR CONSTRUCTING A GROUND-WATER SUPPLY SYSTEM TECHNICAL SPECIFICATIONS

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

1. DRAWINGS The drawings accompanying and referred to in these specifications are as follows: Drawing 1 Drawing 2 Drawing 3 Drawing 4

Location Plan Exploration and Production Borehole Construction Diagram Details of Borehole Headworks Details of Jetting Tool

2. LOCAL CONDITIONS The areas are not normally subject to extreme flooding except in the main stream channels, though flash floods can occur and, after rain, access to and between bore sites could be difficult. Under dry conditions, existing access tracks are adequate for most vehicles, and tracks will be cleared for access to new borehole locations. Accommodation and messing facilities are not available at the Facility and the Contractor shall supply his own camp and messing facilities. Temporary camps or caravans may be established in the area of operation on written approval from the Client. The Contractor shall be totally responsible for his own supply of food. _______ is served by a large supermarket from which perishables can be purchased. Water is available in town, the Contractor will supply his own method of carting water.

3. CLIMATE The area is normally dry with the temperature ranging from -5° to 40°C.

4. GEOLOGICAL INFORMATION From the numerous bores now constructed within the area the following geological log illustrates the expected formations to be encountered: 0 - 10 meters 10 - 100 meters 100 - 200 meters 200 - 250 meters

Kalahari Formation: sands, silcretes and calcretes Basalt: weathered to fresh Sandstone with minor siltstones: may be fractured Mudstone, silt stones: may be hydrating, minor sandstones

All levels are relative to ground level. The depths indicated above are approximate only and the Engineer accepts no responsibility as to the accuracy of the values indicated.

5. MATERIALS 5.1 Materials Supplied by the Contractor The Contractor shall supply and deliver on site, in new and undamaged condition, all materials necessary to complete the Contract without interruption. The materials used shall be paid for at the rates tendered by the Contractor in the Schedule of Quantities and Rates.

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

5.2 203-mm ID nominal (3-mm wall thickness) steel surface casing: The casing shall be plain ended or slip socket, BS43 (SABS 719) or equivalent. 5.3 168-mm ID nominal (3-mm and 4-mm wall thickness) steel plain casing: This casing shall be plain ended or slip socket, BS43 (SABS 719) or equivalent. 5.4 168-mm I.D nominal (3mm and 4mm wall thickness) slotted steel casing: This casing shall be plain ended or slip socket, BS43 (SABS 719) or equivalent. It shall be pre-slotted prior to arrival on site. Slots must be 2-mm width and the casing characterized by a minimum open area of 3% per meter length. 5.5 Other Materials All other items required in the construction of the bore shall be constructed in a manner approved by the Engineer or the Technical Supervisor and SABS code of practices. Because of the nature of the exploration program extra materials may have to be mobilized to the site during the Contract.

6. BOREHOLE CONSTRUCTION 6.1 Depth The bottom depth of the bore and all other significant depths involved in the design of the bore shall be determined by the Engineer or the Technical Supervisor on site from the cutting samples collected by the Contractor from his strata log and by electrical and gamma ray logging carried out by the Technical Supervisor. It is intended that drilling shall be completed when a 6-m sump has been drilled or at some lesser depth as specified by the Engineer or Technical Supervisor. 6.2 Techniques The Contractor may use any drilling techniques he feels applicable to achieve the depth and diameter required, providing that the techniques used are those specified in his Tender or are approved by the Engineer or Technical Supervisor and that they do not permit formation collapse/or hole erosion or involve the use of lost circulation agents, sawdust, or any form of plugging that may ultimately affect the production capacity of the water bearing strata intersected. The Contractor will set the surface casing l m below the depth of intersection of basalt or as directed by the Engineer or the Technical Supervisor on site. The Technical Supervisor must be present during the placing of the casings in boreholes. The Contractor should note that sloughing and/or fractured formations may be intersected and the use of special techniques may be required. The Contractor will be expected to provide coring capabilities at a diameter of 75 mm or greater. Core length requirements are a minimum 300 mm and core sampling will be as directed. It is anticipated that a minimum of 5 samples will be required over the sections of sandstones intersected per borehole. Cores should be collected using rotary airfoam or air-flush techniques and coring will be paid on an hourly worktime basis as indicated in Item 12a of the Schedules of Rates.

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

6.3 Drilling Media The Contractor may use any form of drilling media which he feels is applicable to achieve the depth and diameter required, providing that the media used are those specified in his Tender or are otherwise approved by the Engineer or Technical Supervisor and that they do not permit formation collapse, cause hole erosion or involve the use of native clay, oil, salt or any lost circulation agent, sawdust, cement or any form of plugging that could affect the production capacity of the water bearing strata intersected. The Contractor should note that sloughing and/or fractured formations may be intersected and the use of special media may be required. Low solids, degradable drilling mud may be used where applicable. Where permission is given for the use of Bentonitic muds, they shall be fully hydrated prior to use. The conditions of the bentonitic drilling mud shall be maintained as follows: Mud weights:

At all times other than in flowing artesian conditions less than 1,08 kg/L

Viscosity:

Greater than 35 seconds Marsh Funnel where applicable with a maximum of 42 seconds

Filter cake:

Less than 2 mm where practicable with a maximum of 3 mm

Fluid loss:

Less than 5 cc where practicable with a maximum of 8 cc

Sand content:

Less than 2% where practicable with a maximum of 5%

The conditions of degradable mud shall be maintained as follows: Mud weight:

At all times other than in flowing artesian conditions, less than 1.08kg/L

Viscosity:

Where practicable less than 42 seconds Marsh Funnel reading

Sand Content:

Less than 2, with a maximum of 5%

pH:

According to manufacturer’s specification

Measurements of the mud conditions shall be collected every 1 hour or as directed by the Engineer or Technical Supervisor and shall be recorded on the report sheet. Steps should be taken to treat immediately any excessive variation of the preferred value listed. Two steel tanks with a minimum capacity of 9 cubic meters (approximately 2000 gallons) shall be used in which to mix and hold all drilling fluid. These tanks should be at least twice as long as they are wide and be fitted with V serrated baffle plates. The flow channel from the bore head to the mud tanks shall be of sufficient length and capacity to allow flocculation and settling of clays and tailings from the drilling fluid. The mud tanks and flow channel shall at all times be kept clean of flocculated and settled material.

7. SAMPLING Representative samples of the strata intersected shall be collected by the Contractor every 2 m by whatever method is standard for the drilling technique in use and approved by the Engineer or Technical Supervisor. The Contractor will

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

take every possible precaution to guard against sample contamination due to poor circulation, hole erosion or caving. The sample should be bagged, labeled with the bore number and depth increment, and stored in a position where they will not be contaminated by site conditions or drilling operations. The Contractor shall supply stable sample bags and labels as required. During mud drilling, lag time shall be accurately calculated and timed so that the sample collected relates to the depth at which it was cut. Water samples shall be collected from each bore on the completion of development or at other intervals as directed by the Engineer or Technical Supervisor in containers which will be supplied by the Engineer. Each water sample bottle should be marked with the well number, depth, and date in nonsoluble ink.

8. DRILLING AND CONSTRUCTION OF BORES Bores shall be drilled through the surface formation to an anticipated maximum depth of 10 m at a diameter of 254 mm. The pre-collar will be completed to a depth of 1 or 2 m into bedrock. On completion of the surface drilling, surface casing shall be set and grouted in position using quick setting cement slurry (1.5 Kg/L). Subsequent to the cement setting, drilling shall proceed at a diameter which will permit the insertion of exploration and production casing types to a depth as directed by the Engineer or Technical Supervisor. On completion of drilling, geophysical logging will be carried out and well development commenced thereafter. Subsequently, the casing string shall be lowered into position and left in tension. Subsequent to the casing string being positioned in the hole, aquifer development shall proceed as directed by the Engineer or Technical Supervisor.

9. DIMENSIONS OF BOREHOLES • Surface casing 203 mm (8 inches) diameter • Production casing to total depth below the surface 168 mm (6-5/8 inch) in diameter

10. YIELD MONITORING When air drilling or air developing, a 90° V-notch flow measurement device shall be permanently set up in an approved manner, level and vertical, in the drain line so that continuous monitoring of air lift yields can be obtained. Average yields shall be read and noted every 2 m of penetration and recorded in the driller’s log. Care shall be taken to ensure that no floating debris impedes the flow of water over the V. The weir shall at all times be kept clear of a buildup of silt.

11. SETTING CASING IN POSITION All casing strings shall be lowered into position under tension. Any casing string that requires its upper end to be terminated below ground level shall be set in position by being attached to drilling rods by means of a j latch, left-hand backoff thread, or other approved connections and lowered into position. If a casing string is required to have the upper end terminated below ground level and left in tension, it shall be set in position and suspended by use of a set of tapered support rings. Under no circumstances will it be permitted to drop casing into position.

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

12. PLUMBNESS AND ALIGNMENT All boreholes shall be drilled and cased straight and vertical and all casings and liners shall be set round, plumb and true to line. The Engineer or Technical Supervisor shall have the right to reject any or all drilling or casing which fails to meet this specification and all work and casing rejected will be replaced at the Contractor’s expense. Any delays encountered in running casing considered to be due to poor hole alignment shall be at the Contractor’s expense.

13. REQUIREMENTS TO TEST To demonstrate the compliance of the work with this requirement, the Contractor shall furnish all labor, tools and equipment and shall make the tests described herein in the manner prescribed by and to the satisfaction of the Engineer or Technical Supervisor. Tests for plumbness and alignment must be made after complete construction of the well and before its acceptance.

14. DESCRIPTION OF TEST Alignment shall be tested by lowering into the well to a depth as directed by the Engineer or Technical Supervisor a section of (dummy) pipe 3 m in length. The outer diameter of the dummy shall not be more than 10 mm smaller than the diameter of that part of the casing being tested. The dummy shall be suspended on a wire cable and lowered at a maximum rate of 10 m/min. The Contractor shall be responsible for bringing his own pre-constructed dummy onto site. The Engineer or Technical Supervisor, at his discretion, may carry out additional plumbness and alignment tests using specialized equipment to ensure compliance with this clause.

15. REQUIREMENTS FOR PLUMBNESS AND ALIGNMENT Should the dummy fail to move freely throughout the length of the casing or hole to the required depth or should the well vary from the vertical in excess of 30% of the smallest inside diameter of that part of the well being tested per 30-m depth or beyond limitations of this or any other test performed by the Engineer or Technical Supervisor, the plumbness and alignment of the well shall be corrected by the Contractor at his own expense. Should the Contractor fail to correct such faulty alignment of plumbness, the Engineer or Technical Supervisor may refuse to accept the well and no payment shall be made for same.

16. PROTECTION During the Contract period when work is not in progress, the bores shall be kept capped in such a manner as to prevent the entrance of foreign material. The Contractor shall remove any foreign matter at his own expense. On completion of each bore, the Contractor shall complete the borehole as shown on Drawing 3.

17. EXPERTISE The Contractor under this contract is considered to be an expert water well driller and is expected to organize and carry out the work specified hereunder in an expert manner. Drilling problems encountered will be overcome entirely within the framework of the specification and schedule of quantities and rates and no claim for extra payment will be entertained for problems foreshadowed in the specification or due to limitations placed by this specification.

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

18. ABANDONMENT The Engineer or Technical Supervisor shall have the right, at any time during the progress of the work, to order the abandonment of a borehole. The Contractor thereupon shall withdraw the casing and screens, if applicable and salvage or attempt to salvage all such materials as the Engineer or Technical Supervisor may direct and/or up until he revokes such direction and shall fill or leave the bore to the satisfaction of the Engineer or Technical Supervisor. Payment shall be made for such abandoned bores at the rate of drilling and other rates as are appropriate or as detailed in this specification. 19. LOST BOREHOLE Should accident to the plant, behavior of the ground, jamming of the tools or casing or any other cause prevent the satisfactory completion of the works, the borehole shall be deemed to be lost and no payment shall be made for that bore nor for any materials not recovered there from nor for any time lost. Any material provided by the Client which is not recovered from the lost bore in good condition may be at the Contractor’s expense and may be deducted from the Contractor’s payment. In the event of a lost bore, the Contractor shall construct a bore adjacent to the lost bore or at a site indicated by the Engineer or Technical Supervisor. The option of declaring any bore lost shall rest with the Contractor subject to direction from the Engineer, If the Engineer or Technical Supervisor directs that a replacement bore be re-drilled at a site more than 60 m distant, the Contractor shall be paid in full for the move and 10% of the value of the drilling of the lost bore. If the Engineer or Technical Supervisor directs that the lost bore be re-drilled close to the lost bore and the Contractor is concerned regarding the possible loss of air or other media the Contractor shall back fill the lost bore with approved material. The top 10 m of the hole shall be cement grouted to provide a complete seal. All work and material shall be at the Contractor’s expense. 20. DEVELOPMENT The water bore on the completion of drilling shall be developed to a maximum yield of water, free of suspended materials. Development will be carried out using water jetting, air surging and back washing, air lift pumping, isolated air pumping and surging, valve surging, simultaneous airlift/high pressure jetting, polyphosphate treatment and such other standard techniques as may be directed by the Engineer or Technical Supervisor. Any nonstandard techniques such as acidizing will be paid for at the development rate, though time spent in making up specialized equipment which holds up progress of rig operation will be paid for under standby rates in the schedule of quantities and rates. Any borehole which is found by the Engineer or Technical Supervisor to be characterized by an excess of 10% sidewall degradation of permeability following completion of 8 hours of airlift development, will be redeveloped for a period of 4 hours by the Contractor. Should further hydraulic testing show that the bore is still characterized by an unacceptable level of formation degradation, then the Contractor will undertake further remedial action at his own expense. Should the performance of the borehole prove unsatisfactory after this period of remedial action, the bore will be declared lost by the Engineer on site. Payment for the borehole will be negotiable and dependent on the final degree of degradation and the bore’s utilization potential. The Contractor should note that it is anticipated that simultaneous airlift/high-pressure jetting technique will need to be employed in the development of the bores. The Contractor will be required to bring a jetting tool as outlined in Drawing 4 onto site.

D2-7

APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

21. PUMP TESTING All pumping tests will be carried out by the Engineer or Technical Supervisor.

22. TESTS FOR ACCEPTABILITY The Contractor shall submit each exploration and production borehole for the Engineer or Technical Supervisor acceptance test. Boreholes shall only be accepted after passing the following tests and being finally completed: (a) A multiple-stage discharge test with each stage lasting 60 minutes. (b) Passing all plumbness and alignment tests and any photographic/video tests deemed necessary. The Contractor shall submit each borehole for the Engineer’s or Technical Supervisor’s acceptance test and shall give him at least 12 hours notice of such test. In order not to unduly delay payment for completed boreholes which have not undergone all tests the Engineer or Technical Supervisor may issue a provisional acceptance. If, however, the bore does not pass any test remaining after the provisional acceptance a Final Acceptance will not be issued and the bore will be deemed not to be acceptable and therefore not due for payment. Any moneys which may have been paid on provisional acceptance shall be deducted from the Contractor’s succeeding invoices and final payment. 23. REPORTS The Contractor shall provide the following reports to the Engineer or Technical Supervisor: NAME

DESCRIPTION

SUPPLIED

Strata Log

An accurate record of strata passed through and the depths at which the strata intersected, also progressive measured air lifted yields when drilling with air or air developing

DAILY

Penetration Log

An accurate record of the penetration rates achieved in minutes per 2 m through the various strata, broken down to not more than 2-m increments together with weight applied at the bit, type and grade of bit.

DAILY

Drilling Media Log

An accurate record of the components and quantities used in or injected into the drilling media, including for drilling muds, viscosity, weight, sand content, water loss, filter cake,

DAILY

D2-8

APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

pH and temperature: the Contractor will carry out all of the above tests each hour and as directed at random by the Engineer or Technical Supervisor

Construction Log

An accurate record of all casing, slotted casing, and screen length positions run into the borehole

No completion of construction

Time Log

An accurate record of time spent on all phases of drilling

Daily and a summary of completion of construction to Engineer of Technical Supervisor for signature

24 . PAYMENTS 24.1 Drilling The rates of drilling are based on depth measurement, diameter and penetration rate and are to cover all the costs involved in drilling, including mud mixing, carting of water, injection of mixes, bit sharpening, conditioning of the drilling fluid and cleaning the hole of all bridging, obstructions and backfill ready for geophysical logging, tripping in and out of the hole, and all other such works as are associated with the works and are not covered under other allowable payments. 24.2 Supply and Install Casing This rate is to cover the supply and installation of bore casing into exploration or production bores. It does not cover the running or pulling of casing in bores declared lost or in which the casing cannot be set in position due to misalignment or other operational problems. No claim for extra payment will be entertained by reason of remoteness, wharfage, insurance etc. or by reason of omission in calculating the tender rate. 24.3 Standby Time This time rate is to cover only those items when the rig and crew are waiting on geophysical logging or decisions by the Engineer or Technical Supervisor. 24.4 Work Time The work time rate is to cover time spent using the rig to carry out any directive by the Engineer or Technical Supervisor for nonstandard work not included in the specification. It does not include mud or cement mixing time. 24.5 Bore Development The bore development time rate is to cover all the time spent on bore development, except where included under other time rates. Contractors will note that time rates do not allow for the manufacture of standard development tools on site. All bore development is subject to the approval of the Engineer or Technical Supervisor.

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APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

24.6 Vacation of Project This item is to cover the removal of all plant, equipment and personnel permanently from the project and the restoration of the drilling sites to a level and tidy state. 24.7 Supply and Delivery of Materials on Site The above rate is to cover purchase cost, transport to and delivery and safe storage on site of all materials required for drilling, construction, development and use in the bores and shall be measured and invoiced for each bore. Bulk payment for materials will not be made and all materials remain the property of the Contractor until they are accepted as part of a completed bore by the Engineer Technical Supervisor. 24.8 Moving Borehole Sites This item of payment is to cover the movement of the rig and ancillary equipment from one bore site to the next. The Contractor shall note that sites are expected to be located within 3 km of each other but may be up to 10 km apart. 25. TIME FOR COMPLETION The drilling is to be completed by the Contractor as detailed in the contract program, unless otherwise agreed to in writing by the Engineer. The Contractor must mount two 12-hour shifts for 6 days per week until the works are complete. 26. SHUT DOWN Notwithstanding any other time-rate clause in the specification and the General Conditions of Contract, the Engineer reserves the right to shut down the Contractor’s operations without notice, if, in the Engineer’s or Technical Supervisor’s opinion, the Contractor is failing to carry out the work in accordance with this specification. In this event, the Engineer shall not be liable for payment, but a site conference shall be called immediately between the Contractor’s Senior Representative and the Engineer to discuss and resolve this problem. 27. SUPERVISION OF WORKS The Contractor shall have a skilled senior tool pusher on site at all times to give technical instructions to the drilling crew, manage and organize the Contract and to liaison with the Engineer or Technical Supervisor. 28. SAFETY STANDARDS All safety standards normal to the Engineer or which are required by site regulations shall be adhered to.

D2-10

APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

SCHEDULE 1 OF QUANTITIES AND RATES FOR EXPLORATION AND PRODUCTION DRILLING

1.

ITEM DESCRIPTION Establishment

ESTIMATE MEASURE 1

RATE Item

2.

Move and Setup between Bores

5

No.

3.

Drill 254-mm Air Hammer or Air Rotary

60

m

4.

Supply and Install 203-mm ID Steel Precollar

62

m

Cement Grout Steel Precollar to Include Waiting Time for Setting of Accelerated Cement

6

No.

6.

Drill 200-mm Air Hammer

1500

m

7.

Supply 168-mm ID Plain Steel Casing to Site (3-mm wall thickness)

700

m

Supply 168-mm ID Slotted Steel Casing to Site (3-mm wall thickness)

800

m

9.

Install 168-mm ID Plain Steel Casing

700

m

10.

Install 168-mm ID Slotted Steel Casing

800

m

11.

Supply and Install Plain 168-mm ID. Steel Casing

700

m

Supply and Install Slotted 168-mm ID Steel Casing

800

m

13.

Bore Development

72

Hr

14.

Completion of Bore Headworks

6

No

15.

Standby Time Awaiting Logging, etc.

24

Hr

16.

Work Time as Directed

50

Hr

16a.

Work Time Involved with Coring

100

Hr

17.

Vacating of Site

1

Item

18.

Supply of Materials 14.1 Polyphosphate

Rate

Kg

5.

8.

12.

TOTAL FOR EXPLORATION BORES C/F to Form of Tender Page

D2-11

APPENDIX D2- ALTERNATIVE EXAMPLE PRODUCTION WELL SPECIFICATIONS

SCHEDULE 2 OF QUANTITIES AND RATES FOR EXPLORATION AND PRODUCTION DRILLING ITEM DESCRIPTION 1. Establishment

ESTIMATE MEASURE 1

RATE Item

2. Move and Setup between Bores

23

No.

3.

Drill 254-mm Air Hammer or Air Rotary

240

m

4.

Supply and Install 203-mm ID Steel Precollar

252

m

5. Cement Grout Steel Precollar to Include Waiting Time for Setting of Accelerated Cement

24

No.

6. Drill 200-mm Air Hammer

6000

m

7. Supply 168-mm ID Plain Steel Casing to Site (4-mm wall thickness)

2000

m

Supply 168-mm ID Slotted Steel Casing to Site (4-mm wall thickness)

4000

m

Install 168-mm ID. Plain Steel Casing

2000

m

10. Install 168-mm ID. Slotted Steel Casing

4000

m

11. Supply and Install Plain 168-mm ID Steel Casing

2000

m

12. Supply and Install Slotted 168-mm ID Slotted Steel Casing

4000

m

13. Borehole Development

288

Hr

14. Completion of Bore Headworks

24

No

15. Standby Time Awaiting Logging Engineers Instructions.

100

Hr

16. Work Time as Directed 16c. Work Time Involved with Coring

100 360

Hr Hr

17. Vacating of Site

1

Item

18. Supply of Materials 14.1 Polyphosphate

Rate Only

Kg

8.

9.

TOTAL FOR EXPLORATION AND PRODUCTION BORES C/F to Form of Tender Page...

D2-12

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATIONS

D3-1

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

TABLE OF CONTENTS

PART I

INTRODUCTION

D/3–2

PART II

GENERAL CONDITIONS

D/3–2

Definitions

D/3–2

TECHNICAL PROVISIONS

D/3–8

General Decontamination of Equipment and Materials Drilling Procedures and Steel Casing Installation Sampling of Formations, Water and Materials Well Construction Materials Well Screen, Riser and Sampler Installation Well Development and Acceptance

D/3–8 D/3–11 D/3–13 D/3-17 D/3–18 D/3–21 D/3–23

Section 2.1 PART III Section 3.1 Section 3.2 Section 3.3 Section 3.4 Section 3.5 Section 3.6 Section 3.7

D3-2

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

PART I – INTRODUCTION Drilling and well construction services are generally subcontracted by the Consultant of Record, on behalf of Owner, in accordance with prevailing Master Agreements. Therefore, the only contractual issue this specification addresses is the method of subcontractor selection and reimbursement for drilling and well installation services. Because the consultant of record is ultimately responsible for adherence to this well specification and the quality of the work products and deliverables, the selection of a qualified drilling firm is the Consultant's responsibility. Owner does reserve the right to request documentation of the selected or proposed drilling firm's qualifications and experience and to reject the subcontracting of drilling firms which Owner deems to be unqualified. Such rejections will constitute the basis for renegotiation of that portion of the contract pertaining to drilling and well installation. Owner expects the consultant to procure cost-effective drilling and well installation services through the competitive bidding process. Owner reserves the right of prior approval to review and make recommendations to the Consultant prior to the Consultant's awarding of the drilling subcontract. Drilling and well construction services performed at Owner’s facilities should be performed on principally a footage and materials basis in accordance with a previously submitted and accepted schedule of fees. An example of a fee schedule that would be provided in a bid package is shown on Table A–l. All drilling activities should be reimbursed on a per-foot basis. The basic drilling footage rate must include, but is not limited to, any sample and testing protocols which are specified as part of the scope of work, estimated drilling depths, estimated number of borings, decontamination of drilling tools between individual borings and the cost of any basic safety monitoring equipment or personal protection clothing that is required by the drilling firm or its insurance carrier. Separate footage rates should be provided for different drilling methods or equipment requirements. Footage surcharge fees should be provided for work performed in adverse weather conditions, in Level A, B, or C personal protective attire or for deep borings. Mobilization/demobilization, on-site moves and setups and well construction (including development) should be reimbursed on a per-event basis. All well construction materials and expendable items (i.e., drill bits, auger baskets, core boxes, etc.) should be reimbursed on a unit cost basis. Authorized standby is the only item that will be reimbursed on an hourly basis. To facilitate subcontractor conformance with this reimbursement method, Owner recommends that the consultant provide the bidding firms with a formatted fee schedule, such as that shown in Table A–1, complete with the estimated units. The estimated drilling depths and number of borings should also be provided. PART II – GENERAL CONDITIONS SECTION 2.1 – DEFINITIONS 2.1–01

Agreement The contract between the Owner and Contractor including supplements and change orders issued by the Owner's Representative.

2.1–02

Annular Space The space between two concentric tubes or casings or between the casing and the well hole.

2.1–03

Aquifer A geologic formation, group of formations or part of a formation that is saturated and contributes a significant quantity of water to wells or springs.

2.1–04

Artesian A condition in an aquifer where the groundwater is confined under pressure.

D3-3

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

2.1–05

ASTM The American Society for Testing and Materials provides guidelines and standards for material testing. The address is 1916 Race Street, Philadelphia, PA 19103.

2.1–06

Bailer A tabular hollow receptacle with a check valve used to facilitate withdrawal of fluid from a well or borehole.

2.1–07

Bentonite A highly plastic absorptive, colloidal natural clay composed largely of sodium montmorillonite and which is sold commercially in dry powder or pelletized form.

2.1–08

Bid The offer or proposal of the bidder submitted on the prescribed form setting forth the prices for the work to be performed.

2.1–09

Bidder Any person, firm or corporation invited to submit a bid for the work.

2.1–10

Blow Out The inflow of groundwater and soil into the well hole or casing caused by a differential pressure head greater outside the well hole or casing than inside, generally due to a lower water level inside the well hole than that of the surrounding potentiometric level.

2.1–11

Casing Tubular steel, finished in sections with either threaded connections or bevelled edges to be field welded, which is installed to counteract caving of the drilled hole.

2.1–12

Casing, Flush Joint Casing with squared threaded ends such that a fixed inside and outside diameter is maintained across joints.

2.1–13

Casing, Protective Anodized aluminum pipe with aluminum locking lid with provisions for a heavy duty padlock installed at 3 feet above ground surface to protect the PVC well from damage.

2.1–14

Casing, Surface A single section of clean black steel pipe used to stabilize the well hole near the surface during the initial drilling of the hole.

2.1–15

Cement Portland Cement Type 1 meeting ASTM C 150 furnished in 94-lb bags.

2.1–16

Cement Float Shoe A plug or packer constructed of inert materials within the lowermost section of permanent casing fitted with a passageway through which grout is injected under pressure to fill the annular space. After the grout has hardened, the cement float shoe is drilled out.

2.1–17

Centering Disk A flat, perforated disk constructed of PVC which slides over the riser and/or well screen and fits inside the temporary casing or hollow-stem auger to center the riser within the casing.

D3-4

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

2.1–18

Centralizer See Centering Disk.

2.1–19

Change Order A written order to the Contractor signed by the Owner's Representative authorizing an addition, deletion or revision in the work or an adjustment in the Contract price or the contract time issued after execution of the agreement.

2.1–20

Conductivity See Specific Conductance.

2.1–21

Cone of Depression The zone influenced by withdrawal of water from an aquifer by some artificial or natural means such as a pumped well, leak or spring.

2.1–22

Confined Aquifer Groundwater under pressure significantly greater than atmospheric pressure; the upper limit of the aquifer being the bottom of a zone of distinctly lower hydraulic conductivity than that of the material in which the confined water occurs.

2.1–23

Contractor The person, firm or corporation with whom the Owner has executed the agreement.

2.1–24

Cuttings The fragments, particles or slurry of soil or rock created during the drilling of the well hole.

2.1–25

DCDMA The Diamond Core Drill Manufacturer's Association.

2.1–26

Drawdown The difference in elevation between the static water level and the surface of the cone of depression at the time of development.

2.1–27

Drawings Refer to the attached for drawing of single- and multi-cased wells.

2.1–28

Drilling Fluid A water based fluid used in the drilling operation to wash cuttings from the hole, to clean and cool the bit, to reduce friction between the drill stem and sides of the hole and to seal the sides of the hole to prevent loss of drilling fluids. NOTE: COMMERCIAL DRILLING FLUIDS WITH ADDITIVES ARE NOT TO BE USED.

2.1–29

Drive Shoe A forged steel collar with a cutting edge fastened onto the bottom of the casing to shear off irregularities in the hole as the casing advances and to protect the lower edge of the casing as it is driven.

2.1–30

d–15 The theoretical diameter of the soil particle in millimeters at which 15% of the particles are finer and 85% are coarser.

2.1–31

d–85 The theoretical diameter of the soil particle in millimeters at which 85% of the particles are finer and 15% are coarser.

D3-5

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

2.1–32

Engineer An individual with a degree in civil engineering and having experience in the installation of monitoring wells who is employed by the consultant.

2.1–33

Filter A clean sand of selected grain size and gradation which is installed in the annular space between the well pipe and the wall of the casing or well hole above the gravel pack and below the bentonite seal.

2.1–34

Geologist An individual with formal training in the science of geology.

2.1–35

Gravel Pack A gravel or coarse sand installed between the well screen and the well hole extending 5 feet above the top of the well screen.

2.1–36

Groundwater Naturally occurring water encountered below the ground surface.

2.1–37

Grout A mixture of cement, bentonite, lime and water which is used to form a seal between the borehole and well casing.

2.1–38

Hazardous Waste A hazardous waste as defined by the Resource Conservation Recovery Act (RCRA) in 40 CFR 261.3.

2.1–39

Homogeneous The property of a material to be essentially uniform in its characteristics of composition, texture, appearance, etc.

2.1–40

Hydraulic Gradient The change in static head per unit of distance in a given direction. If not specified, the direction of flow generally is understood to be that of the maximum rate of decrease in head.

2.1–41

Jetting Water is forced down through the drill rods or well by means of the pressure pump and out through holes in the bit or well screen. This water, being under pressure, creates a quick condition and allows the well or drill rods to sink into the soil or cuttings.

2.1–42

Leachate Contaminated water resulting from the passage of rain, surface water or groundwater through waste.

2.1–43

Lower Zone A readily defined soil strata consisting of a predominate soil type different from the zone(s) above it.

2.1–44

Measuring Tape An electronic water level indicator which utilizes the water as a conductor to indicate submergence of a point containing an energized probe and a neutral wire separated by a short distance.

2.1–45

Mud Pan A metal tub into which the drilling fluid and cuttings are discharged and which serves as a reservoir and settling tank during recirculation of the drilling fluids.

D3-6

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

2.1–46

Oil Trap A filter and separator used to remove oil from the compressed air flowing out of the storage tank.

2.1–47

Owner The legal Owner of the facility for which the work is being performed.

2.1–48

Owner's Representative The authorized representative of the Owner who is assigned to the project and who has the authority to bind the Owner to an agreement.

2.1–49

Packer A device temporarily placed in a well which plugs or seals a portion of the well at a specific level.

2.1–50

Perched Groundwater Groundwater in a saturated zone of relatively limited horizontal extent which is separated from the main body of groundwater by an unsaturated zone or thick zone of low permeability.

2.1–51

Permeability A measure of the relative ease with which a porous medium can transmit a liquid under a potential gradient. It is a property of the medium that is dependent upon the shape and size of the pores. The rate at which water flows through a soil deposit in response to a differential in hydraulic pressure.

2.1–52

pH The intensity of acidic or alkaline condition of a solution; the symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram–atoms per liter.

2.1–53

Potentiometric Level The level in or above a confined or unconfined aquifer at which the pressure is atmospheric. This level is determined at a location by the static water level in a monitoring well screened in the aquifer.

2.1–54

Reaming The process of enlarging the well hole to remove geologic material from the sides of the well hole.

2.1–55

Revert (R) An organic polymer drilling fluid additive of high viscosity manufactured by the Johnson Well Screen Company. NOT TO BE USED PER Owner SPECIFICATIONS.

2.1–56

Riser The pipe extending from the well screen to above the ground surface.

2.1–57

Seal Tamper A heavy cylindrical metal section of tubing which is secured to a cable that slips over the riser and fits inside the casing or well hole which is used to tamp the bentonite pellets, gravel pack or filter.

2.1–58

Specifications The instructions to bidders, the general conditions, the special conditions and the technical provisions.

2.1–59

Specific Conductance The potential for electrical conductivity of a water sample at 25°C as expressed in micro–ohms per centimeter.

D3-7

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

2.1–60

Standby Authorized periods of shutdown whereby drilling and well installation stop by orders of the Owner’s Representative.

2.1–61

Static Water Level The vertical elevation of the top of a column of water in a monitoring well which is no longer influenced by effects of installation, pumping or other temporary conditions.

2.1–62

Stick–up The vertical length of the portion of the protective casing which protrudes above the ground surface.

2.1–63

Subcontractor An individual, firm or corporation employed by the Contractor or any other subcontractor for the performance of a part of the work at the site, other than employees of the Contractor.

2.1–64

Transmissivity The rate at which water of prevailing kinematic viscosity is transmitted through a unit width of an aquifer under a unit hydraulic gradient.

2.1–65

Tremie Pipe A pressurized pipe or tube used to transport the flow of grout from the surface into the annular space beginning at the bottom of the annular space and proceeding upwards. (NOTE: HORIZONTAL OR SIDE DISCHARGE IS REQUIRED.)

2.1–66

Uniformly Graded A particle size distribution of a soil which consists of the majority of particles being of the same appropriate diameter.

2.1–67

Upper Zone A soil strata consisting of a dominant soil type different from the zone immediately below it.

2.1–68

Utilities Service lines or equipment located above, upon or below the ground surface used for conveyance of electricity, natural gas, petroleum, communications, storm water, waste water, potable water, etc.

2.1–69

Washout Nozzle A device utilized at the end of a string of casing equipped with a check valve through which clear water or grout can be injected to wash out drilling fluids and cuttings from the annular space.

2.1–70

Water Cement Ratio The proportion of the weight of mixing water in pounds to weight of cement in pounds.

2.1–71

Water Table The surface in an unconfined aquifer at which the pressure is atmospheric. This level is determined at a location by the static water level in a monitoring well screened in the aquifer.

2.1–72

Well Hole The open subsurface hole created by conventional drilling methods.

2.1–73

Well Protector See Casing, Protective.

D3-8

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

PROTECTIVE COVER WITH LOCKING CAP

6 in. (152 mm) CLEARANCE FOR SAMPLER

WELL IDENTIFICATION LABELED INSIDE AND OUTSIDE THE CAP VENTED CAP

TOP OF RISER 3 ft. (1.0 m) ABOVE GRADE

WASHED PEA GRAVEL OR COARSE SAND MIXTURE PROTECTIVE CASING

SLOPE BENTONITE/SOIL MIXTURE OR 4in (101mm) THICK CONCRETE PAD AWAY FROM CASING

1/4 in. (6.3 MM) WEEP HOLE AT 6 in. ABOVE GROUND LEVEL

SLOPE GROUT AWAY FROM CASING OR RISER TO PREVENT INFILTRATION, BUT DO NOT CREATE A MUSHROOM FOR GROUT WHICH WILL BE SUBJECT TO FROST HEAVE

3 ft. - 5 ft. (1.0 to 1.5 m) EXTENDED PROTECTIVE CASING DEPTH TO BELOW FROST LINE

NEAT CEMENT GROUT DRY BENTONITE

MINIMUM 2 in. (50 mm) ID RISER WITH FLUSH THREADED CONNECTIONS GROUT LENGTH VARIES

CENTRALIZERS AS NECESSARY

6 in. - 1 ft. (152 mm to 304 mm) FINAL SECONDARY FILTER PACK

BOREHOLE WALL 3 ft. - 5 ft. (1.0 to 1.5 m) BENTONITE SEAL

1 ft. - 2 ft. (303 mm to 608 mm) FIRST SECONDARY FILTER PACK WHERE CONDITIONS WARRANT EXTEND PRIMARY FILTER PACK 20% OF SCREEN LENGTH OR 2 ft. (608mm) ABOVE SLOTTED WELL SCREEN, UNLESS CONDITIONS WARRANT LESS

CENTRALIZERS AS NECESSARY

WELL SCREEN LENGTH VARIES

PLUG

SEDIMENT SUMP (AS APPROPRIATE)

Monitoring Well Design -- Single -Cased Well Figure D/3-1 Single-Well Casing Design D3-9

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

2.1–74

Well Screen Commercially manufactured pipe or cylindrical tubing with slits of a uniform width orientation and spacing.

2.1–75

Zone of Saturation The zone below the water table or below the top of a confined aquifer in which all interstices are filled with groundwater.

PART III – TECHNICAL PROVISIONS

SECTION 3.1 – GENERAL 3.1–01

Well Locations and Dimensions A.

General. General well locations are provided on the Permit or in the Scope of Work. Prior to drilling, the Contractor and the Consultant of Record should establish the exact location of each well by conventional field inspection methods, giving consideration to the requirements established by the Local, State and Federal Agency permit requirements so as to avoid utility interference and to provide useful data and an accessible well. Subsequent to well construction, the exact location and elevation at each well should be established by conventional survey methods.

B.

Surveying. The Contractor should determine: 1.

Horizontal coordinates of wells to an accuracy of ±l.0 foot, relative to the facility grid.

2.

Ground elevation at well to an accuracy of ±0.0l foot MSL.

3.

Elevation of top of well casing and top of protective casing to an accuracy of ±0.01 foot.

C.

Controls. A benchmark and horizontal control of the facility property will be provided by the Owner. All surveying will commence at the provided control and will traverse to the well and back to the control using standard closure procedures. A copy of the field notes should be furnished to the Owner.

D.

Water. The source of water to be used, if any, will be identified by the Owner's Representative. The Contractor should locate the source of water by survey. If the source is a well, include the log for the well with the monitoring well logs. If the well log is unavailable, do not use that source. The source of water must be analyzed by the Owner before it may be used.

E.

Depth of Well and Screen Placement 1. Determine the elevation of the top and bottom of the well screen referenced to ±0.l foot MSL. 2. Determine the bottom of the drilled hole referenced to ±0.l foot, MSL. 3. The dimensions of the casing, riser and well screen should be reported in inches.

D3-10

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

4. All elevation data should be shown on the well log. 3.1–02

3.1–03

Permits and Utility Clearances A.

Licensure. The Contractor should be legally qualified and, if necessary, licensed to install wells in the state or county in which wells are being installed.

B.

Utilities. The Contractor should ascertain that well construction does not interfere with overhead and underground utilities. Do not proceed until utilities are cleared. If a field tile or other feature is encountered, stop and notify the Owner's Representative for instruction as to whether to abandon the hole or modify the well casing.

C.

Permits. Where permits are required by the State to install wells at a particular site or location, the Owner's Representative or Contractor should obtain all permits required. The Contractor should also be responsible for compliance with all conditions of the permit during installation of the wells.

D.

Conflicts. All work should be done in accordance with applicable Federal and State regulations; however, if a conflict between these specifications and other regulations exists, the Contractor should request clarification from the Owner's Representative.

Documentation A.

General. This section covers the record keeping procedures and documentation required for the acceptance of a well by the Owner's Representative. Owner has developed standard forms for borehole logging and documenting well construction details. Additional forms summarizing daily drilling and well construction activity are also available from Owner District offices. These forms should be utilized by the Contractor. Submission of nonstandard documentation or Contractor's forms in lieu of the Owner standard forms will result in rejection of the forms by the Owner's Representative. Copies of these forms are provided in Appendix D, along with detailed instructions and completed examples.

B.

Surveying. The surveyed location and elevation data on the well as specified in Section 3.1–01 should be presented on the log of the well hole. Coordinates and MSL elevation references should be utilized unless other instructions are given by the Owner's Representative.

C.

Well Hole Logging. A geotechnical engineer or geologist should be present during the well drilling, construction and development operations to represent the Contractor and to document the field work. The engineer/geologist should direct the sampling, log the well hole, document on-site testing activities and results and maintain daily records of the Contractor’s activities. A typed boring log should be developed from the field log and the laboratory test results (see Appendix D for standard boring logs). A daily drilling summary should also be prepared using Owner standard forms and submitted to the Owner's Representative.

D.

Well Construction Record. The Contractor should develop an as-built drawing of the well showing the elevations of the ground, the static water level, top of riser, top and bottom of gravel pack, top of seal, length of permanent steel casings, strata, etc. The diameter and thickness of the casing and riser, the well screen slot size and any other pertinent information

D3-11

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

should be presented on the Owner standard forms presented in Appendix D. The format of the sketch should be ink on mylar or comparable.

3.1–04

E.

Well Recovery Graph. A well recovery graph should be presented on the well construction record. If recovery is instantaneous, it should be noted on the record. A tabulation of recovery test readings should be furnished. The interval of readings will vary depending on the aquifer characteristics and the Engineer should establish the pattern of readings that is appropriate (refer to Appendix D).

F.

Number and Disposition of Copies. Four copies of the typed well boring log and the well construction record should be furnished to the Owner's Representative (refer to Appendix D).

G.

Examples. Example boring logs, well construction records and well recovery graphs are attached (Appendix D).

Measurement for Payment A.

General. This section describes the methods to be used to determine the quantities and units of work completed and for which payment will be made by the Owner to the Contractor for all work and materials required to construct the wells.

B.

Mobilization. Mobilization includes all work preparatory to arriving at the site including the purchase and delivery of materials; clearing utilities; surveying the well locations; transporting the drill rig, tools, engineer and operators to the site; and the removal of all unused materials, all equipment and personnel from the site. Removal of trees and construction of temporary roads is not included in mobilization. This cost is based on time and materials in accordance with the fee schedule. If the work is terminated by the Owner's Representative for failure of the Contractor to adhere to the specifications or because the method of well drilling proposed by the Contractor proves infeasible, then the Contractor should be paid only for a prorated portion of the amount bid for mobilization. The prorated amount to be paid for mobilization should be based on the percentage of wells completed and accepted by the Owner's Representative, except that the minimum payment for mobilization in the event the contract is terminated before the Contractor begins drilling in which event no payment should be made. No other materials including wells which are abandoned, incomplete or which are not accepted by the Owner's Representative will be paid.

C.

Monitoring Wells. Monitoring wells which are drilled, fitted with a well screen and well pipe and developed in accordance with these specifications and accepted by the Owner's Representative should be paid for at the unit price bid for monitoring wells, measured from ground surface to the bottom of the well screen, which payment should be the total compensation for all work and materials. No other payment will be made and all other work including documentation, well development and field and laboratory soils testing should be considered incidental to the unit price established for monitoring wells. Any special laboratory soil testing work should be a separate unit price.

SECTION 3.2 – DECONTAMINATION OF EQUIPMENT AND MATERIALS 3.2–01

General This section covers the decontamination of equipment, tools and materials utilized in the well construction.

D3-12

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

3.2–02

Condition of Drill Rig and Equipment The condition of the equipment should be such that contamination is not created. Leaking seals, hoses, pumps or tanks containing oils and fluids other than water should not be permitted.

3.2–03

3.2–04

Procedures To Be Used for Cleaning Equipment A.

All cleaning is to be performed on site.

B.

Remove all drill rods, augers, samplers and other equipment except that in the tool boxes of the rig which will not be utilized in the operations. Color code or lock the tool boxes as a precaution to prevent contaminated tools from being used.

C.

Steam clean the drill rig utilizing water only from the source designated by the Owner's Representative or another approved source. Sample the water used in the process and retain the sample for 90 days after well completion. Record the name, model and serial number of the steam cleaning unit.

D.

Lay drill rods, augers, casing, samplers, pipe wrenches, etc., on horses or other supports and clean until all visible signs of grease, oil, mud, etc., are removed. Use brushes as required.

E.

Do not use greasy gloves when handling tools after cleaning. Surgeons’ gloves or new clean cotton work gloves should be used.

F.

Do not use new painted bits and tools which will leave paint chips in the hole.

G.

Clean water tanks, pumps, mud pans, and hoses, including hoses and tanks used to transfer water from the source to the drill rig tank (e.g., pickup truck water tanks).

H.

Fittings on the drilling equipment may be greased and fluids may be added to the equipment with care before cleaning. Precautions should be taken to prevent contamination of the well with oil and grease. Lubricants should not be used on the drilling and sampling tools or fittings thereto.

Decontamination of Materials A.

Use only new materials that have been certified by the manufacturer (refer to 3.5–01). Only bagged cement, powdered bentonite in bags or bentonite pellets in well protectors should be used.

B.

Use PVC pipe for risers and well screens which has cured and is free of plasticizers. Oil should not be used during the factory threading operations.

C.

Factory cleaned PVC pipe should be supplied. Workers should use clean cotton gloves when handling riser and well screen.

D.

Steam clean the protective well casing and any casing pipe that was not cleaned and properly sealed by the manufacturer.

E.

Water used in drilling and grouting operations is to be obtained only from the source designated by the Owner’s Representative.

D3-13

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3 PROTECTIVE COVER WITH LOCKING CAP

6 in. (152 mm) CLEARANCE FOR SAMPLER

WELL IDENTIFICATION LABELED INSIDE AND OUTSIDE THE CAP VENTED CAP

TOP OF RISER 3 ft. (1.0 m) ABOVE GRADE

WASHED PEA GRAVEL OR COARSE SAND MIXTURE PROTECTIVE CASING

SLOPE BENTONITE/SOIL MIXTURE OR 4 in (101mm) THICK CONCRETE PAD AWAY FROM CASING

1/4 in. (6.3 mm) WEEP HOLE AT 6 in. ABOVE GROUND LEVEL

SLOPE GROUT AWAY FROM CASING OR RISER TO PREVENT INFILTRATION, BUT DO NOT CREATE A MUSHROOM FOR GROUT WHICH WILL BE SUBJECT TO FROST HEAVE STEEL CASING INSTALLED AND STABILIZED AT A MINIMUM 2 ft (608 mm) INTO CONFINING LAYER

3 ft. - 5 ft. (1.0 to 1.5 m) EXTENDED PROTECTIVE CASING DEPTH TO BELOW FROST LINE

NEAT CEMENT GROUT DRY BENTONITE

MINIMUM 2 in. (50 mm) ID RISER WITH FLUSH THREADED CONNECTIONS GROUT LENGTH VARIES

CENTRALIZERS AS NECESSARY

6 in. - 1 ft. (152 mm to 304 mm) FINAL SECONDARY FILTER PACK

BOREHOLE WALL 3 ft. - 5 ft. (1.0 to 1.5 m) BENTONITE SEAL

1 ft. - 2 ft. (303 mm to 608 mm) FIRST SECONDARY FILTER PACK WHERE CONDITIONS WARRANT EXTEND PRIMARY FILTER PACK 20% OF SCREEN LENGTH OR 2 ft. (608mm) ABOVE SLOTTED WELL SCREEN, UNLESS CONDITIONS WARRANT LESS.

CENTRALIZERS AS NECESSARY

WELL SCREEN LENGTH VARIES

PLUG

SEDIMENT SUMP (AS APPROPRIATE)

Monitoring Well Design -- Multi-Cased Well Figure D/3-2 Multi-well Casing Design

D3-14

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

3.2–05

Decontamination of Well Development Tools A.

All pumps used in well development should be steam cleaned with the water specified in Section 3.2-04E. Pumps which leak or otherwise may cause contamination will not be used. Electrical tape should not be used to band pumps. Bands should be stainless steel or plastic ties.

B.

Only compressors equipped with operable oil traps and a filter should be utilized. The oil trap and filter should be of a design approved by the Owner's Representative.

C.

Nitrogen gas, if utilized, should be regulated before it enters the well. The source of the nitrogen should be identified in the report.

SECTION 3.3 – DRILLING PROCEDURES AND STEEL CASING INSTALLATION 3.3–01

General This section covers creating a stable, open, vertical well hole for installation of the well screen and riser. The method listed on the Bid Form should be utilized except if the method indicated is unsuccessful, in which case the Contractor should notify the Owner's Representative and the Contractor should stop work. If the method proposed by the Contractor is unsuccessful, the Owner's Representative may terminate the contract, in which case the Contractor should abandon the hole. The Contractor will be paid only for the prorated mobilization. Abandoned holes should be grouted by the Contractor in accordance with Section 3.3–10 and this should be incidental to mobilization. Following contract termination, the Owner's Representative may negotiate a new contract with the Contractor or other Bidders to construct the wells.

3.3–02

Prohibited Methods Addition of drilling fluids containing chemical additives or organic matter during the drilling of the well hole such as Bariod® (East mud) or Revert® is prohibited. Mixing of water or cuttings from upper zones with lower zones is prohibited and any drilling method which has the potential to cause such mixing should not be utilized.

3.3–03

Preferred Drilling Procedures Whenever feasible, the Contractor is encouraged to utilize drilling procedures which do not require the introduction of water or liquid drilling fluids into the well hole. In general, the following drilling methods are listed in decreasing order: (1) drilling with hollow-stem augers is the most preferable method; (2) air rotary drilling with an oil filter/trap; (3) cable tool methods and other percussion tool drilling methods may be attempted in hard, consolidated formations; (4) reverse-circulation drilling fluid is preferable to wet rotary drilling; and (5) wet rotary drilling with clear water only and insertion of temporary flush joint casing, subject to approval of the Owner's Representative, with particular consideration being given to the procedures used to prevent mixing of upper zones with lower zones.

3.3–04

Double-Cased Wells As shown on the drawings or where conditions warrant, the use of permanent steel casing installed to prevent mixing of upper zones with lower zones is encouraged. Conceivably, several permanent casings may be required. Installation of permanent steel casing should be completed prior to drilling into a lower zone. A cement float shoe should be utilized when grouting the annular space between the well bore and the permanent steel casing except when the casing is driven and a tight seal is created between the well bore and the steel casing. When a steel

D3-15

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

casing is installed in a predrilled hole and then driven, the driven length of permanent casing should be at least 3 feet. An alternate procedure to the use of a cement shoe and always when permanent steel casing is inserted in a predrilled hole and driven below the bottom of the predrilled hole, should be to fill the predrilled hole with grout via a tremie pipe, insert the casing and drive it while the grout is still plastic. The grout inside the casing may be washed or drilled out, except that during the period between 1.5 hours and 48 hours after mixing of the grout the casing should not be disturbed. 3.3–05

Hollow-Stem Auger Drilling Where a monitoring well screen is to be constructed in a saturated, permeable zone of soil under low or no artesian pressure overlain by a continuous zone of low permeability soils free of saturated interbedded zones of permeable soils, hollow stem augers may be utilized to drill and stabilize the well hole. The inside diameter of the hollow stem auger should be at least 1.33 times the outside diameter of the well screen and riser. Only hollow stem augers with watertight joints should be utilized. When “blow out” occurs, the hollow-stem auger should be filled with water from the approved source and a three inch diameter split spoon sampler or other decontaminated tool driven into the “blow out” to carefully clean the hole. A roller bit or jetting should not be used to clean the hole.

3.3–06

Rotary Drilling with Clear Water and Temporary Flush Joint Steel Casing A.

General. This technique utilizes temporary steel flush joint casing to stabilize the well hole, rotary drilling to cut and pulverize the formation and clear water as a medium to cool the bit and wash the cuttings from the well hole. This technique requires a large source of clear water; a drill rod with a large inside diameter, a high-capacity, high-pressure pump; and a drill with high torque and weight. This drilling technique is encouraged where the depth of the well hole exceeds the depth to which hollow-stem augers are adaptable and where sandy, bouldery or gravelly soils or weathered bedrock must be penetrated and temporarily cased to create an open well hole.

B.

Tools to be Utilized 1. Only flush joint steel casing with an inside diameter at least 1.33 times the outside diameter of the screen and riser should be utilized. 2. The roller bit or drag bit should create a well hole no more than 3/8 inch smaller than the inside diameter of the casing. Preferably, these bits should be of the side discharge design. 3.

The drill rod should have a minimum inside diameter of 1.375 inches.

4. The water swivel should have a minimum inside diameter of 1.25 inches. The pump hose should have a minimum inside diameter of 1.50 inches. 5. A settling tank and screens may be used if the pump creates an uphole velocity of 100 to 150 ft/min. Note that the velocity will depend on the inside diameter of the casing and the outside diameter of the drill rod, as well as the pump capacity.

D3-16

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

C.

3.3–07

Procedure. The well hole should be drilled and the casing driven in increments of 5 feet maximum. The addition of bentonite should not be permitted. Blow out should be counteracted by maintaining the casing full of water at all times. Bentonite powder may be added at the surface to the outside of the casing to lubricate the outside of the casing and facilitate removal. The rotation speed and rate of bit feed should be such that the formation being drilled is ground to medium to fine sand-sized particles. The size of particles removed is related to the uphole velocity.

Air Rotary Methods A.

General. This technique utilizes temporary and/or permanent steel casing, rotary drilling and compressed air as a medium to remove cuttings from the hole. The technique is only useful in hard formations where the rotary bit is not subject to plugging. The system requires a large air compressor, a large inside diameter drill pipe, a conventional water swivel and large diameter hoses. The use of this method is encouraged when drilling at least 20 feet of medium to hard bedrock and coring is not required. This technique is especially useful where loss of water would be a problem if the hole was drilled wet rotary.

B.

Tools to be Utilized 1. Steel casing should be set to create an open stable well hole down to the top of bedrock or the hard strata to be drilled by the air rotary method. 2. The compressor should deliver a minimum of 400 cfm and sufficient pressure to create up hole velocities of at least 3 ft/sec. The compressor should be equipped with filters to trap oil and other foreign materials from entering the well hole. 3. The drill rod should have a minimum inside diameter of 1.375 inches. 4. The water swivel and hose should have a minimum inside diameter of 1.25 inches.

C.

3.3–08

Procedure. The rotation speed and drill advance rate should be low enough that cuttings are blown out of the well hole and do not clog the casing.

Cable Tool and Percussion Principles of Operation A cable tool rig uses a heavy, solid steel, chisel-type drill bit suspended on a steel cable which, when raised and dropped, chisels or pounds a hole through the soil and rock. When drilling through the unsaturated zone, some water may be added to the hole (refer to Section 3.1–01D for source of water). The cuttings are suspended in the water and then bailed out periodically. When soft caving formations are encountered, it is necessary to drive casing as the hole is advanced to prevent collapse of the hole. Often the drilling can be only a few feet below the bottom of the casing. Because the drill bit is covered through the casing, the hole created by the bit is smaller than the casing. Therefore, the casing (with a sharp, hardened casing shoe on the bottom) must be driven into the hole. The shoe, in fact, cuts a slightly larger hole than the drill bit. This tight-fitting drive shoe should not, however, be relied upon to form a seal from overlying water-bearing zones.

3.3–09

Reverse Circulation The common reverse circulation rig is a water or mud rotary rig with a large diameter drill pipe and which circulates the drilling water down the annulus and up the inside of the drill pipe

D3-17

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

(reverse flow direction from a direct mud rotary). This type of rig is used for the construction of large-capacity production water wells and is not suited for small, water quality sampling. These techniques may be utilized subject to approval of the Owner's Representative. 3.3–10

Grouting Abandoned Well Holes A.

General. The purpose of properly abandoning a well hole is to prevent the hole from acting as a channel for contamination or vertical movement of water. The abandonment must be done in a manner that will not impair original water quality of the aquifer. All well-abandoning procedures should be in accordance with state and local regulations.

B.

Procedures. All cased wells in unconsolidated and consolidated formations should be completely overdrilled 1.5 times larger than the original boring. The well hole should be grouted completely using a pressured tremie pipe (side discharge) method and a grout mixture as specified in Section 3.5–05.

SECTION 3.4 – SAMPLING OF FORMATIONS, WATER and MATERIALS 3.4–01

General This section covers sampling the soil, bedrock, and ground water. Geologic samples are required to determine the strata thickness and type and to provide the information necessary to develop a log of the well hole. Material samples are required to evaluate specification compliance.

3.4–02

D3-18

Sampling Interval and Type A.

Continuous soil sampling is preferred, particularly in cohesive and semicohesive soils. At a minimum, soil should be sampled at regular intervals not exceeding 5 feet except that a minimum of two samples should be taken in any strata in which a monitoring well screen is to be set. Sampling should be performed in accordance with ASTM D 1586 or 1587. Place ASTM D 1586 samples in 8-ounce Paragon jars and seal. Exposed portions of samples taken in accordance with ASTM D 1587 should be sealed with nonshrinking wax.

B.

Continuously core the zone of bedrock in which well screen is to be set, NX size or larger. At least 80% of the core run should be recovered except when the RQD is less than 25%, in which case 60% core recovery is acceptable. Core should be placed in commercial plastic, cardboard or shop-made wooden core boxes and properly identified with core loss blocks provided.

C.

Roller bit and percussion drilling cuttings should be logged at 3-ft intervals and sampled at 10ft intervals, place samples in jars and label if coring is specifically omitted by the Owner's Representative.

D.

When drilling through old refuse or under other unusual conditions, sampling requirements will be at the Owner's Representative's discretion.

E.

Water quality samples should be placed in bottles provided by the Owner.

F.

A sample of the gravel pack should be placed in two 8-ounce Paragon jars, labeled and retained by the Contractor for 6 months.

G.

A sample of the filter should be placed in two 8-ounce Paragon jars, labeled and retained by the Contractor for 6 months.

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

H.

3.4–03

A sample of the plastic grout from each grouting operation on each well should be placed in an 8-ounce Paragon jar, labeled and retained by the Contractor.

Testing and Storing of Samples A.

Cohesive samples should be tested for moisture content and Atterburg limits.

B.

If applicable, granular soil samples from the strata in which the well screen is set should be tested for particle size distribution, ASTM D 422.

C.

The core, after placement in the core box and marking, should be photographed and color prints furnished with the report.

D.

All soil or rock samples should be stored at the site until final site closure. The consultants may remove these samples to an off-site location for detailed inspection and analysis, but all samples must be returned to the Owner Site Manager. Inasmuch as these samples constitute the primary means of documenting the site subsurface conditions, they should be treated in the same manner as a permit document. The Site Manager will, therefore, be responsible for the storage and maintenance of these samples.

E.

Other testing such as consolidation, permeability and soil water characteristics should be performed at the Owner's Representative's request only.

F.

Water quality samples should be stored for 180 days by the Contractor.

SECTION 3.5 – WELL CONSTRUCTION MATERIALS 3.5–01

General This section stipulates the well construction materials including well screen, riser pipe, well protector, gravel pack, grout mix and water. All materials used in construction should be free of chemicals, paint, coatings, etc., that could leach. All materials should be decontaminated in accordance with Section 3.2–04.

3.5–02

Well Screen Continuously slotted PVC plastic well screen should be utilized, unless directed otherwise by the Owner's Representative. The diameter of the well screen should be as shown on the drawing. Well screen should be furnished in 5-ft long sections or longer. The bottom plug should be threaded and should withstand all installation and well development pressures without becoming dislodged or damaged. Unless instructed otherwise, typical screen slots size is 0.010 inch on all well screens.

3.5–03

Riser Pipe The riser pipe should consist of PVC pipe meeting ASTM D 1785 with flush joint threads. Schedule 40 or 80 pipe, as designated on the drawing, should be utilized. The interval between joints should be 5 to 20 ft. “Triloc” Monitoring Well Pipe® with Teflon® taped joints and without O rings should be permitted in lieu of Schedule 40 PVC pipe. A.

Threads are to be in accordance with DCDMA standards, or by independent tests the manufacturer should demonstrate equivalency of the threaded joint to crushing.

D3-19

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

3.5–04

3.5–05

D3-20

B.

All joints should be Teflon taped.

C.

Glued joints of any type should not be permitted.

D.

Rivet joints should not be permitted.

E.

The slot (screen) size should be determined relative to the formation and gravel pack in which the screen is to be set. The Contractor should make the screen selection based on field sieves.

F.

The length of the screen should be as shown on the drawings. A minimum length of 5 ft should be provided.

Permanent Steel Casing For Permanently Double-Cased Wells A.

The diameter of the casings in multicased wells should be selected so that a 2-in. annular space is maintained between the casing and the borehole.

B.

The minimum wall thickness of steel casing should be 0.125 inches.

C.

The ends of sections of casing should be threaded or beveled for welding.

D.

All casing is to be new black pipe free of interior coatings.

Grout Mix A.

Cement. Cement should be Portland cement® Type I in conformance with ASTM C 150. The cement should be delivered to the job site in 94-lb sacks. The use of Hi Early® Type III cement and other quick setting cements is prohibited unless authorized by the Owner's Representative.

B.

Water. Water should be obtained from the source designated by the Owner's Representative.

C.

Hydrated Lime. Hydrated lime should be ASTM C 207, Type S, furnished in sacks. Hydrated lime should not contain air entrainment additives.

D.

Bentonite. Bentonite should be powdered sodium bentonite furnished in sacks without additives.

E.

Proportions. Cement should be mixed with water in the proportions of 5 to 6 gallons of water per sack of cement. Hydrated lime may be substituted for cement up to 10% by volume. Between two and four pounds of bentonite powder should be added to the mix for each sack of cement used.

F.

Mixing. The grout should be thoroughly mixed with a paddle-type mechanical mixer or by circulating the mix through a pump until all lumps are removed. Grout that is lumpy should be rejected.

G.

Grouting Lines. All hoses, tubes, pipes, water swivels, drill rods or other passageways through which the grout will be pumped should have an inside diameter of at least 0.50 inches.

H.

Grouting Procedure. Grout should be injected under pressure to displace water and cuttings from the level immediately above the seal placed above the screened zone up to the top of the

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

well hole. Grout injection should be deflected to the sides and continued until clean grout flows out the top of the well hole.

3.5–06

I.

Grouting of Multicased Wells. For wells that penetrate multiple aquifers, Owner requires the installation of multiple or telescoping casing utilizing special grouting and construction techniques. Owner requires that a minimum 2 in. annular space be maintained between telescopic reductions (i.e., a 2-inch diameter screen will require first setting a 6.5-in. diameter casing in an ll-in. diameter boring). After the outer boring has penetrated not less than 2 ft of the first targeted aquitard, an outer casing is lowered to the bottom of the boring. A tremie line is then installed through an inflatable packer and this entire assembly is lowered through the casing to within 3 feet of the bottom of the casing. After the packer is inflated, grout is injected through the tremie line until the entire annular space between the casing is filled and the grout returns to the surface. The casing string may have to be lifted 1 to 2 inches off the bottom of the boring to facilitate the even distribution of grout in the annular space. The grout should be allowed to cure for not less than 48 hours before drilling through the grout plug at the bottom of the casing and advancing the borehole through the next aquifer. This step is repeated for each separate aquifer unit. Upon reaching the final target depth, the inner casing and screen is set through the outer casing. Subsequent to the placement of the gravel, filter packs and bentonite seal, the remaining annular space is grouted in the same manner as described in Section 3.5–05H.

J.

Grouting Set Time. The well should not be disturbed for at least 48 hours after grouting to allow the grout to set up and gain sufficient strength.

K.

Samples Required. 02H.

Samples of grout should be taken in accordance with Section 3.4–

Gravel Pack Gravel pack is the material placed in the annular space around the well screen.

3.5–07

A.

Gradation. Gravel pack should be uniformly graded sand or gravel comprised of hard durable particles washed and screened with a particle size at least four times the d-15 size (15% of the soil is finer than the d-15) of the formation and no more than four times the d-85 size of the formation soil.

B.

Purity and Decontamination. If necessary or directed by the Owner's Representative, the gravel pack should be decontaminated in accordance with Section 3.2-04.

C.

Samples. Samples of gravel pack should be retained by the Contractor for 6 months in accordance with Section 3.4-02F.

Filter Pack The filter is the layer of material placed in the annular space between the gravel pack and the bentonite seal.

3.5–08

A.

Gradation. The filter should be uniformly graded fine sand with 100% by weight passing the No. 30 sieve and less than 2% by weight passing the 200 sieve.

B.

Samples. Samples of filter should be obtained in accordance with Section 3.4-02G.

Bentonite Pellets or Chips for Seals Bentonite pellets are a commercial product consisting of compressed bentonite balls and sand.

D3-21

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

A.

Composition. The Bentonite pellets should be from a commercial source free of contaminants.

B.

Size. The diameter of the pellets should be less than one half the width of the annular space into which they are to be placed.

Bentonite chips are a coarse grade Wyoming bentonite consisting of a natural sodium base bentonite. A.

Composition. The pebble-size chips of bentonite should be natural, unaltered mineral with no contaminants or added chemicals.

B.

Size. The diameter of the chips should be less than one half the width of the annular space into which they are to be used.

SECTION 3.6 – WELL SCREEN, RISER and SAMPLER INSTALLATION 3.6–01

General This section covers the placement of the well screen, gravel pack, seals and annular grout in a well hole. The specifications relative to drilling and temporary stabilization of the well hole are covered in other sections. This section includes removal of the temporary casing and placement of the permanent well protector and sampling system.

3.6–02

D3-22

A.

Stable Borehole. A stable borehole should be constructed prior to attempting to install the well screen. If the borehole tends to cave or ”blow out,” the Contractor should take steps to stabilize the well hole before attempting installation of the well screen. Boreholes which are not plumb or are partially obstructed should be corrected prior to attempting the installations described herein. Jetting or driving the well screen should not be permitted.

B.

Sequence. The sequence of operations described herein should be adhered to unless a specific agreement is made with the Owner's Representative.

Assembly of Well Screen and Riser A.

Handling. The well screen including the bottom plug and/or wash out nozzle approved by the Owner's Representative should be decontaminated as described in Section 3.2–03 immediately prior to assembly. The workmen should take precautions to assure that grease, oil or other contaminants do not contact the well screen. The workmen handling the well screen should wear a new pair of cotton or surgical gloves while handling the well screen. To prevent kinking of the threads, no more than 15-ft of screen or riser pipe should be assembled above ground.

B.

Teflon Taped Joints. The male threaded part of each joint should be wrapped with Teflon® tape. Joints should be tightened by hand; however, if necessary, decontaminated pipe or chain wrenches may be utilized. The well screen and riser will be inserted into a well hole which is at least partially filled with water.

C.

Ballasting the Riser. The well screen and riser should be ballasted to counteract the tendency to float in the borehole by continuously filling the string of riser pipe with water from the approved source. Preferably water should not be added, but the riser should be slowly pushed into the water in the borehole with the aid of the hydraulic ram and held in place with chains as additional sections of riser are added to the string.

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

3.6–03

Setting the Well Screen The well screen should be lowered to the predetermined level and held in position by suspending the string of riser pipe or, if the string tends to float, by manipulating the hydraulic ram. On deep holes where the weight of the string of riser pipe is significantly more than the flotation force, care should be taken to keep the riser pipe plumb. The riser should extend above grade at least 3 ft. The riser should be trimmed to the proper length after the grout is in place. If the plumbness of the riser is especially critical or the well is extremely deep, a 10-ft pipe section at 0.90 times the inside diameter of the casing should be lowered down the inside of the riser to verify that the riser is not kinked.

3.6–04

3.6–05

Placement of the Gravel Pack A.

Volume of Gravel Pack. The volume of gravel pack required to fill the annular space between the well screen and the well hole should be computed and carefully measured out. The gravel pack should typically extend 5 feet above the uppermost row of slots in the well screen or to 5 ft above the top of the granular zone being monitored, except where limited separation between aquifers occurs.

B.

Centering the Well Screen. The well screen should be centered in the well hole and temporary casing by pouring in approximately 10% of the gravel pack then placing a centering disk over the riser and tamping the disk into place with the seal tamper. The remaining gravel pack should be placed in increments with centering disks as required to assure that the well screen is centered. The level of each layer of gravel pack filter and seal should be verified and recorded.

C.

Withdrawal of the Temporary Casing/Augers. While holding the riser pipe with the drill rig, the temporary casing or hollow stem augers should be carefully withdrawn such that the lowermost point on the casing is exactly at the top of the gravel-packed portion of the well hole. This may be accomplished in increments; however, after each increment, a centering disk and the seal tamper should be inserted and slid down to ascertain that the gravel pack has not bridged and raised during casing withdrawal operation. If necessary, the gravel pack should be tamped back into place with the centering disk. Check the level of the gravel pack relative to the well screen. Additional gravel may have to be added after auger withdrawal.

Placement of the Filter A volume of filter sand that will extend a distance of 2 ft up the annular space from the top of the gravel pack should be carefully measured out. The filter should be poured into the annular space through a clean, flush threaded, 1-in. PVC pipe lowered to within 3 feet of the placement interval. If the level of water in the well hole extends above the gravel pack, the seal tamper or a jetting tube should be used to stir up the filter and prevent the segregation of the filter as it settles in the water in the well. The bottom of the temporary casing should be raised to a level at least 5 but no more than 10 ft above the gravel pack. Where conditions warrant, the filter may be eliminated. The Contractor should evaluate the need for the filter considering the gradation of the gravel pack, the hydraulic head and the potential for grout intrusion into the gravel pack.

3.6–06

Placement of the Seal A volume of bentonite pellets to create a seal three to 5 feet long should be measured out and carefully poured into the annular space. If the bentonite seal is being constructed above the water level in the well hole, exactly 5 gallons of water should be poured into the annular space. The seal tamper should be lowered down and utilized to tamp the pellets into a cohesive mass

D3-23

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

of clay. Alternatively, a heavy bentonite slurry may be carefully tremied into the annular space to form the required seal. 3.6–07

3.6–08

Grouting the Annular Space – Single Cased Wells A.

Volume of Grout. The volume of grout required to completely fill the annular space between the seal and the ground surface should be prepared in the proportions specified in Section 3.5– 05. The volume should include a quantity to compensate for losses. The end of the tremie pipe should be equipped with a deflection plate or side discharge to prevent displacement of the filter and gravel pack materials.

B.

Injection Procedures. The grout should be injected via a tremie pipe (side discharges), the opening for which is temporarily set immediately above the seal. The grout should be pumped into the tremie pipe continuously until it flows out at the surface.

C.

Casing Removal. The temporary casing/auger should be removed immediately and in advance of the time when the grout begins to set. Casing removal and injection may proceed concurrently provided the top of the column of grout is maintained at least 20 ft above the bottom of the casing and provided injection is not interrupted. If casing removal does not commence until grout injection is completed, then additional grout should be periodically poured into the annular space so as to maintain a continuous column of grout up to the ground surface.

D.

Grout Setting and Curing. The riser pipe should not be disturbed until 48 hours after grouting is completed except for water level measurements made using an electronic water level indicator. Trimming of the riser pipe may be completed while the grout is plastic or at least 48 hours after the hole is grouted. Trimming should not be attempted during the interim period. Precautions should be taken to prevent pipe cuttings from entering the riser.

Well Protector Anodized aluminum well protector, as shown on the drawing, should be set in the neat cement. The well protector should be positioned and maintained in a plumb position. A 6-in. clearance between the top of the riser and the well protector should be maintained for the sampler. This can best be accomplished by placing a 6.0-in. piece of trimmed or notched 6-in. wood stock between the well riser and the cap. Grout which has overflowed the well hole should be carefully removed so as to prevent the formation of horizontal projections (mushrooming) which may be subject to frost heave. A 1/4-in. diameter hole should be drilled in the well protector 6 inches above the ground surface to permit water to drain out of the annular space. Dry bentonite pellets should be placed in the annular space below ground level. Coarse sand and pea gravel should be placed in the annular space above the dry bentonite pellets and hole to prevent insects from entering through the drill hole.

3.6–09

Installation of the Sampler The sampler is to be installed in accordance with the manufacturer's instructions after completion of well development.

SECTION 3.7 – WELL DEVELOPMENT AND ACCEPTANCE 3.7–01

General This section covers the purging and development of a newly constructed well, the measurement of the well characteristics and the initial sampling and on-site water quality testing. Also described is the acceptance criteria for a completed well.

D3-24

APPENDIX D3 EXAMPLE MONITORING WELL SPECIFICATION

3.7–02

3.7–03

Pumps for Well Development A.

General. All wells should be pumped or evacuated using filtered compressed air or nitrogen to produce representative formation water. This section describes the approved pumps and appurtenant works to be utilized in development of monitoring wells. All pumps and other devices used in well development should be decontaminated as specified in Section 3.2–05.

B.

Submersible Pumps. Submersible pumps should include electric motor-powered centrifugal or positive displacement type pumps which are operated under submergence. If a submersible pump is utilized for well development, it should be of a type and capacity such that it can pump water from the well continuously for a period of at least 15 min. without shutting off. Back pressure or other methods may be utilized to accomplish the desired rate of pumping. The pump should be capable of being turned on and off instantaneously to create surges in the well. The pump should be fitted with a check valve.

C.

Bladder Pumps. A bladder or diaphragm pump is a type of pump that operates under the cycling of compressed air. The compressed air cycling inflates and deflates a diaphragm which creates a pumping action. Bladder pumps approved for well development should be capable of pumping at least 1 gpm continuously when installed in the well.

D.

Jet Pumps. A jet pump utilizes the Venturi principle to create subatmospheric pressure which allows a suction pump to be utilized below a depth at which suction alone would not normally lift the water. Jet pumps approved for well development should be capable of pumping at least 3 gpm continuously when installed in the well.

E.

Suction Pumps. Suction pumps should not be utilized in wells the depth of which exceeds 20 ft. Suction pumps used to develop wells less than 25 ft deep should be capable of pumping at least 5 gpm continuously without pumping the well dry in less than 5 minutes.

F.

Bailers. Bailers should not be utilized for well development except after an approved submersible, bladder, jet or suction pump has been installed in the well or compressed air or bottled nitrogen has been used and the rate of well recovery is so slow that these methods are ineffective.

G.

Compressed Air. Compressed air supplied by an engine-driven compressor equipped with an approved oil trap and filter may be utilized provided the source of compressed air is capable of evacuating 50% of the column of water from the well once every minute.

H.

Bottled Nitrogen. Bottled nitrogen may be utilized provided a regulator is employed and the system is capable of evacuating 50% of the column water from the well once every minute.

Periods of Well Development A.

General. Well development should be continued until representative formation water free of the effects of well construction is obtained. Representative formation water should be assumed to have been obtained when pH, temperature and conductivity readings are stable and the water is clean and the minimum periods of development specified herein have been completed. Testing of pH, temperature and conductivity should be performed by the Contractor; however, the Owner may perform the testing or direct others to perform the testing which should not relieve the Contractor of his responsibility to develop the well until acceptance.

D3-25

EXAMPLE MONITORING WELL SPECIFICATION APPENDIX D3

B.

Period of Development. The minimum period of well development should be in accordance with the following guidelines depending on the well development procedure selected: 1. Pumping with a Submersible Pump. 4 hours. 2. Pumping with a Bladder Pump. 8 hours. 3. Pumping with a Jet Pump. 4 hours. 4. Pumping with a Suction Pump. 4 hours. 5. Compressed Air. 4 hours cycling at 2-min intervals. 6. Bottled Nitrogen. 4 hours cycling at 2- min intervals. 7. Bailers. 8 hours continuously alternating two men. This method to be used only if all other methods prove infeasible.

3.7–04

Well Recovery Test A well recovery test should be performed immediately after development by the Contractor. Readings should be taken at 1-min intervals until the well has recovered to its static water level.

3.7–05

Well Acceptance A well will be accepted by the Owner’s Representative when development has been completed in accordance with these specifications and the documentation required under Section 3.1-03 is furnished to the Owner’s Representative. Once a well has been approved, the Contractor should be relieved of any further responsibility for the performance, maintenance or testing of that well.

D3-26

Index A AASHTO T-206 169 ABEM Fotobor 161 Acoustics 141 Active soil-gas sampling 743 Aerial photograph as in mapping geology 95 Aerial photography 137 Air-entry permeameter 259, 260 Alkalinity 594 Alternate concentration limit (ACL) 682 Alternative Superfund methods 700 Ambient air monitoring 760 Ambient air temperature 126 Ambient quality of ground water 132 Ambient sound 142 Angle drilling 342 Anisotropic conditions 630 Anomaly maps gravity 104 Anthropogenic 797 Aquatic ecology 134 Aquicludes 457 Aquifer boundaries 457 Aquifer characteristics 501, 706 Aquifer hydraulic properties 711 Aquifer properties 252 Aquifer pump test procedures 274 Aquitard 457 Aquitards 706 Assessment monitoring 607 Assessment monitoring program 682 Assessment monitoring programs 677 ASTM 5092-90 614 ASTM D-1586 STP test 169 ASTM standard E1527 65 ASTM visual–manual procedure 175 Attenuation action levels 941 Attenuation clean-up action levels 940 Attenuation monitoring points 942 Auger bucket 155 continuous-flight 157 helical 155 hollow stem 155 solid stem 155 Auger drilling 155 Average linear velocity 472

B Background 864 Background concentrations of ground water 132 Backhoe trenching 95 Backhoe trial pits 154

Barometric efficiency 237 Barometric efficiency determinations 238 Base map 24, 85, 87 Bedrock stratigraphy 29 Blind wells 784 Block samples 167. 178, 349 Blunders 860 Borehole common in situ tests 191 Borehole geophysical logs 190 Borehole geophysical methods 352 Borehole geophysics caliper 191 deviation survey 191 natural gamma 191 resistivity 191 spontaneous potential 191 temperature 191 Borehole geophysics setup 358 Borehole hydraulic conductivity test 267 Borehole logging techniques 421 Borehole permeameter 256 Borehole plan 152 Boring plan 148 Borings rational 153 Boundaries constant-head 539 impermeable 539 unconfined aquifer boundaries 539 Boundaries and recharge 708 Brunauer-Emmett-Teller (BET) adsorption 736 BS 1377 1975 STP Tests 196 Bulk density 470

C Calculation of intakes 778 Caliper logs 358 Capillary fringe 81 Capillary potential 652 Captions, titles and headings 894 Carbon-13 592 Categories of sites requiring remediation 697 CCTV 363 CCTV example fracture sets 363 CCTV probe 356 Cement bond log 57 CERCLA 3 Channel deposits 565, 636 Chemical finger print 712 Chemical intakes 778 Chemicals of potential concern (COCs) 774 Chlorinated solvents 903 Classification of soil USC 169 Clean Water Act 39 Clean-up technologies 695

Climatic data 39 Climatology 125 Cochran’s approximation to the Behrans-Fisher (CABF) T-test 679 Codisposal environmental pathways 759 Codisposal sites 758 Coefficient of proportionality 307, 309 Coefficient of retardation 472 Cohesive soils 170 Common aquifer matrix materials 470 Common patterns of chlorated solvents 909 Compaction permeameter 308 Comparisons of remedial programs 678 Complex geologic settings 434 Compliance audit 58 Composite conceptual models 524 Composite geophysical logs 362 Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) 677 Computer flow model 937 Concentration vs. distance plots 927 Concentration vs. time rate 932 Conceptual flow NAPL sites 762 Conceptual model preliminary 45 Conceptual models 495 aquifer characteristics 500 boundaries 501 building process 506 conceptual “cartoons” 507 conceptualization process 499 consolidated bedrock 514 consolidated channel deposits 516 constructing piezometric maps 504 fence diagram 497 flow characteristics 501 geologic information used 497 geologic units 505 oblique flow 520 Phase I 496 potential pathways 501 prediction 495 process 495 recharge/discharge zones 501 regional geologic maps 496 remedial process 524 site characterization 495 stratigraphic zones 497 structure contour maps 497 topographic information 502 topographic maps 496 transmissivity 501 unconsolidated deposits 511 unified conceptual/flow model 496 vadose zone 528 Conceptual models of greenfields 54 Conceptual recharging conditions 628 Conceptual site model 909 Conceptualization process 497

I-1

FRACTURED ROCK ASSESSMENTS

Cone penetrometer pest 197 Cone penetrometer test uses and limitations 210 Cone penetrometer testing 221 Confidence limits 868 Confined aquifer piezometer nest 622 Confined ground water system 610 Confining layers 451 Confining unit 458 Consolidation cells (consolidometers) 309 Consolidation permeameter 308 Constant-head tests 267 Contaminant mobility characteristics 715 Contaminant sources 716 Continuous wells 785 Contour maps 438 bedrock topography 444 computer contouring 444 construction principles 438 interpretative contouring 442 mechanical contouring technique 442 structure contours 442 Contouring of data 438 Contract check-off list 898 Contract laboratory program (CLP) 717 Control of runoff 38 Cooper-Jacob drawdown curve 389 Core photography 182 preservation time 182 recovery 189 Core drilling 342 Core indenter 343 Core sample labeling 349 Core storage box design 351 Cored boreholes 181 Cores broken zone 189 fracture frequency 189 logging 183 preservation 182 RQD 188 Coring optimum core recovery 181 Corrective action program 687 Corrective measures implementation 682 Corrective measures study (CMS) 681 Cover letters 876 Criteria for landfill siting 49 Cross-sectional stratigraphic data 504 Cross-sections 444 aquifer boundaries 451 borehole data 448 borehole logs 445 completion 450 computer generated 453 edited borehole data 447 errors in logging 445 faults 447 hydrogeologic properties 451 lithological boundaries 447 location map 451 map inspection 448 plausibility 448 reasonable extrapolation 448

I-2

schematic site stratigraphy 450 sequence of work 445 stratigraphic boundaries 447 surfical data 447 topographical profiles 447 unconformities 447 vertical and horizontal scales 444 Crust-imposed, steady flux 261

D Darcy's coefficient of hydraulic conductivity 307 Darcy's coefficient of permeability 532 Darcy’s law 532 Data analysis and interpretation 429 Data collection tiers 913 Data quality objectives 718 Data quality objectives 73 Data set normalization 926 Data types 432 Daughter products 924 Decommissioning 244 Degradation of common chlorinated solvents 908 Dense nonaqueous liquids 762 Dense nonaqueous phase liquid 219 Depth to ground water maps 460 Design criteria surface water 128 Design fracture sets 340, 341 Detection monitoring 607, 616 Deuterium 593 Diamicts 174 Diamond core drilling 181 Dipping geologic structures 566 Direct push (DP) technology 197 Discharge areas 459 Discharge zones 708 Discharging sand layers 626 Discontinuous sand units 624 Discrete zone (Dz) approach 382 Distance attenuation rate constant 931 Distribution of head 707 DNAPL conceptual model 772 cone penetrometer 770 exploratory borings 768 ground-water analyses 767 major factors 764 measuring DNAPL’s levels 771 residual determination 769 sampling 771 site characterization 766 soil-gas surveys 772 well level measurements 770 DNAPL in soil cores 763 DNAPL organic parameters 763 Double ring infiltrometer 258 Double-reciprocal Langmuir 735 Double-tube method 259 Down-hole TV cameras 56 DP Systems cased systems 200 conductivity probes 211

cone end bearing resistance 208 cone penetrometer testing 205 CPTU soil classification 208 diaphragm type pressure transducer 208 dual-tube 200 Dutch cone sampling 210 electrical cone penetrometers 209 equipment 219 equipment recommendations 219 exposed-screen samplers 203 friction ratio 209 friction sleeve resistance 208 fuel fluorescence detector 213 fuel fluorescence detectors 213 generated pore pressure 209 in situ analysis 212 laser-induced fluorescence (LIF 213 lithologic description 202 mechanical cone penetrometers 205 MIP’s example 215 nonsealed soil samplers 201 nuclear logging tools 211 penetrometer 207 piezocone 207 pore pressure dissipations 209 pore pressure ratio 209 pore-pressure dissipation tests 207 recommendations 200 sampling tools 201 sealed soil (piston) samplers 202 sealed-screened samplers 204 sealing direct push holes 219 semi-permeable membranes (MIPs 213 single-rod systems 200 soil samplers 201 stratification of contaminants 217 three-channel cone 206 Waterloo profile sampling device 217 DP systems rods 200 DP technologies depth useable 198 Drag-down water quality 603 Driller’s logs 183 Drilling air foam 160 core drilling 159 flushing medium 159 open hole 159 rotary-vibratory (sonic) 161 Drilling fluid 159 Drive samples 169 Drive sampling 167 Drive-point profiler 203 Dry cleaners 69 Dual-porosity systems 323

E Earth Manual U.S.B.R. 175, 399 Earthwork engineer 5 Eastman-Whipstock tool 161 Ecological risk assessment 779 Ecological surveys 134 Ecologically sensitive areas 134

FRACTURED ROCK ASSESSMENTS

Edited final boring-Logs 436 Effective porosity 313, 469, 470 common Soils 316 fine-grained sediments 314 Elevation survey 243 EM-31 113, 341 EM-34-3 depth penetration 114 EM ground conductivity meters 64 Enforcement steps in the Superfund process 692 Environmental data levels of 9 Environmental site assessments 58 Equipotentials 529 Evaluate sources 859 Evaporation 126 Evapotranspiration 126 Evidence of contamination 720 Excavation 139, 140 Existing quality of ground water 130 Expedited site characterization 9 Exploratory excavations 139 Exposure pathway analysis 916 Exposure pathways 777 Exposure point concentrations 778

F Facies codes 172 facility disposal practices 75 False-color infrared 29 Fatal flaws 54 Fate and transport modeling 717 Fate and transport models 940 Fault active 137 capable 137 Faults 327 age determination 141 exploratory trenching 138 geophysical methods 138 reports 141 surface geologic reconnaissance 138 Field borehole log information 180 Field hydraulic conductivity 254 Field hydraulic conductivity tests 267 Field-screening procedures 717 Figures and plates 895 Final conceptual geologic model 496 Final report content 890 Financial status spreadsheet 888 First generational data 9 Flat gradient 617 Flat horizontal gradients 465 Flood hazard boundary maps 39 Floridan aquifer 601 Flow diagram monitoring system design 615 Flow in layered deposits 631 Flow meter logs 362 Flow meters 360 Flow modeling codes 936 Flow rate calculations 471 field determination 471

Flowmeter use 360 Flowmeters 356 Flownet construction steps 540 dipping heterogeneous rock 566 phase ii investigations 572 stream discharge zone 569 subsurface spatial variability 570 Flownet analysis 529 Flownet construction 505, 532 Flownets applicability of Darcy’s law 537 area flownets 559 boundary conditions 539 common problems 537 conceptual models 536 consolidated rock 564 construction 540 darcy’s law 532 deflections 530 discharging to streams 569 downward ground-water flow 531 drawing 541 dye traces 530 equipotential lines 529 equipotentials 535 examples 545 flow lines 529 flow path 533 flownet refraction 543 free surface/water table 559 fundamental rules 540 heterogeneous isotropic 547 heterogeneous, anisotropic 552 heterogeneous, isotropic systems 543 homogeneous anisotropic 551 homogeneous isotropic flow system 542 homogeneous, anisotropic 550 homogeneous, isotopic systems 538 Hubbert’s model 530 linked conceptual hydrogeologic model 554 mass balance calculations 555 method of analysis 554 modified area flownet analysis 561 piezometer head relationships 539 reflection of flow 531 sand tank constructions 530 seepage boundaries 535 seepage face conditions 558 seepage solutions 532 stream tubes 535 symbols 563 three layers 549 three layers with downward flow 549 transformations 550 variable Materials 544 Vertical Flow Examples 536 very low gradients 532 FLUTe system 414 Formation drawdown response 57 Fracture filling 339 Fracture lineaments 421 Fracture surface form 348 Fractured rock

aquifer characteristics 328 assessment monitoring techniques 336 assessment monitoring wells 419 barometric pressure 379 Borehole Logging 334 borehole pressure tests 399 Boulton solution 387 Boulton Solution Type Curves 388 clusters of joints 374 color photographs 349 comparisons 330 complex responses to recharge 379 conceptual models 331, 332, 417 conceptual understanding 325 construction of monitoring wells 422 continuum approach 333 Cooper and Jacob semi-log method 395 Cooper-Jacob solutions 386 core drilling 342 core scribing 343 data analysis 416 design fracture sets 340 determination of applicable monitoring points 420 discrete approach 333 discrete fracture approach 416 discrete zone (DZ) approach 382 distribution of hydraulic conductivity 333 downhole geophysical 353 downhole techniques 352 drawdown relationships 390 earth tides 379 edited logs 349 EM 16R 341 EM 34 341 equal area projection 371 equatorial stereonet 371 exact borehole locations 342 example borehole log 347 field log 348 fitting a distribution 375 fixed interval length approach 382 flow directions 380 flow systems 417 format for field logs 348 friction loss 400 geologic mapping 336 geological discontinuities 339 geophysics 340 gradient analysis 417 high-permeability zones 422 homogeneity 330 hydraulic barriers 394 hydraulic Conductivity 328 inferring hydraulic properties 381 information Typically Recorded 346 isotropy 328 key Parameters 338 labeling of samples 349 Lambert equal area nets 371 linear flow conditions 417 local reconnaissance methods 336 major discontinuities 339 mapping 337 natural outcrops 337 mass averaging approach 382, 383

I-3

FRACTURED ROCK ASSESSMENTS

microfractures 326 meridional stereonet 371 monitoring wells 421 multiple completion piezometers 417 multiple-method approach 419 natural fractures 348 natural fractures recognization 327 near-field hydraulic parameters 390 nonintrusive data 331 open interval 422 orientation 369 oriented core 342 Phase I 330 Phase IIs 336 placement of monitoring wells 421 polar stereonet 370 porous-media-equivalent aquifers 378 potentiometric-surface maps 377 pumping test curves 386 pumping test responses 334 radial flow assumptions 384 radial flow condition 418 rates of ground-water flow 380 recharge 330 scale of fracture 324 scope of field investigations 326 seasonal fluctuations 379 significant dewatering 396 single-hole methods 381 skin effects 391 slickensides 327 slug tests 334 soil-bedrock interface 421 spacing of discontinuities 376 specific capacity 396 spherical flow 418 split triple tube 343 stereographic nets 370 stereographic projection 370 storage coefficient 395 storage of core samples 349 systematic orientations 370 temporal changes in hydraulic head 378 transmissivity of specific zones 380 trenches 338 type of porosity 328 U.S.B.R. Method E-18 398 Use of tracer tests 380 variations in hydraulic head 335 variations in water chemistry 334 vertical component of flow 378 Walton solution type curves 387 Water-Table Configuration 333 well bore storage 391, 392 well loss 396 well yield 394 Fractures and piezometer response 577 Fracture-set mapping 338 Frequency of sampling 167

G General monitoring procedure 796

I-4

General procedure site investigations 13 General steps in the Superfund process 690 Generic scopes of work 781 Geochemical analysis 859 Geochemical characterization 591 Geochemical evaluations 584, 589 Geochemical footprints plot 930 Geochemical indicators 919 Geochemistry / modeling 925 Geologic columns 436 Geologic conceptualization 496 Geologic framework 612 Geologic history 434 Geologic logs 153, 708 Geologic mapping 145 area procedure 94 examples 91 Geologic structural control 636 Geologic structural maps 437 Geologic structure 34 Geological cross-sections 573 Geological survey 145 Geophysical gravity surveys 104 Geophysical logging 363 Geophysical logging techniques 353 Geophysical logs 356 Geophysical methods buried waste 122 depth to ground water 123 detection of LNAPLS 124 electromagnetic 112 geology & hydrogeology 123 gravitational maps 102 induced polarization 116 refraction 105 reflection 105 resistivity 114 resistivity profiling 116 Geophysical survey organic detection 121 planning 101 Geophysical technique field applications 117 Geophysical techniques 98, 354 downhole 119 for hydrogeologic investigations 97 Geophysics acoustic televiewer 354 Acoustic-televiewer 366 azimuth rose diagrams 368 bedrock topography 119 borehole cameras 354 caliper geophysical tool 365 caliper logs 363, 364 detection of inorganics 120 electrical sounding 115 electromagnetic induction 113 EM resistivity methods 113 flow meter surveys 365 ground penetrating radar 125 histograms of depth/permeability 368 leachate plumes 118 lineation directions 367 magnetometry 109, 123 metal detectors 108, 123

natural gamma logs 363 orientation diagrams 367 orientation of discontinuities 369 program goals 100 sonic log 356 spontaneous potential logs 363 structural domains 368 Geostatistics 723 Geotechnical borings 150 Geotechnical drilling 153 Glacial geologic model 508 Glauconitic sands 573 GPR depth of penetration 112 Grab samples of ground water 64 Gradient control 619 Gradient controlled sites 619 Gravimetric moisture content 261 Gravity geoid/reference spheroid 104 Ground penetrating radar 64, 107 Ground-water flow directions 459 Ground-water flow discharges 707 Ground-water flow rates 471 Ground-water level maps 459 Ground-water surface 377 Ground-water surface contour map 459 Ground-water-elevation contour maps 459 Grout alkaline pH interferences 858 Grouting during advancement 221 Gypsum crust method 264 Gypsum crust-cube method 260

H Hardness classification for rocks 343 Hazardous substances lists (HSL) 783 Heat-Pulse Flowmeter 361 Henry’s law constant 742 High-toxicity, low-volume sites 762 Historic air photo analysis 76 Historic land use air photo analysis 61 Historical comparison reports 857 Historical use information 65 Hollow stem 157 Holocene 138 Holocene faulting 51, 137 Holocene faults 141 air photos 137 Horizontal wells 784 Hot spot 721 Human exposure assessment 776 Human health and the environment risk factors 681 Hvorslev 90% calculations 64 Hydraulic conductivity 307, 706 aquifer pumping test 273 constant-head test 268 falling head tests 270 full scale pumping test 273 individual pumping wells 272 pretest analysis 274 rising head tests 270 single borehole test 267

FRACTURED ROCK ASSESSMENTS

single-well tests 270 slug tests 269 variable head test 269 Hydraulic conductivity (K) 466 Hydraulic conductivity conversions 402 hydraulic conductivity testing single-borehole 265 Hydraulic conductivity-depth diagrams 368 Hydraulic connection 57 Hydraulic gradient (dH/dL) 468 Hydraulic gradient (I) 467 Hydraulic gradient calculation 468 Hydraulic gradients in Maps 461 Hydraulic grain size analysis 310 Hydraulic head 81 Hydraulic head and gradient 467 Hydraulically upgradient 611 Hydrogeologic information 710 Hydrologic fluctuations 463 Hydrostatic time lag 230

I Identification of contaminants 711 In situ geotechnical tests 251 Index map 25 Industrial history 59 Infiltration rate precipitation 127 Infiltrometer methods 257 Initial conceptual model 45 Initial screening process 906 Innovative characterization technologies 14 In situ borehole field methods pictograph 192 In situ field methods 193 In situ measurements stress 194 In situ shear tests 195 In situ tests primary advantages 191 Instantaneous profile 261 Interim remedial measures 17 Intrinsic remediation 12, 902 Investigative techniques 82 Isopleth maps 926 Isotope evaluations 584, 589 Isotopic groundwater study 593 ITRC 14

K Karst unstable areas 53

L Laboratory classification tests 167 Laboratory hydraulic conductivity 309 Laboratory hydraulic properties of rocks 317 Laboratory tests 297 Land use 41 Landfill gas 760 Landfill siting 48 Langmuir equilibrium adsorption 735

Laplace equations 532 Large volume/low toxicity (LV/LT) 697 Laser-induced fluorescence (LIF) 213 Law of universal gravitation 103 Layered deposits 632 Leachate 758 Leachate data 591 Leachate generation 758 Legget 148 Linear velocity 471 Lines of evidence 904 Lithological description 96 Lithology 433 Local flow cells 620 Locations for monitoring wells 607 Log field log 183 Losing stream condition 617 Losing stream target monitoring 618 Loss prevention wording 898 Low hydraulic conductivity environments 635 Lower confidence limit (LCL) 864

M Magnetometers 109 Mapping approaches traverse 94 Marbut system 89 Matric potential 652 Matrix hydraulic conductivity 572 Maximum concentration limits (MCLs) 682 Maximum contaminant limits (MCLs) 3 Meteorological 125 Method SW-846 856 Microcosm 939 Micro-gravity surveys 104 Migration pathways 590 Minimal borings 145 MIPs DP systems 213 MODFLOW 936, 939 Moisture content 261 Molecular Bioassay Studies 939 Monitored natural attenuation 901, 903, 908, 923 Monitoring programs complex ground water flow conditions 645 density consideration 651 evenly distributed flow pathway 643 fractured rock 641 gradient and lithology control 645 gradient controlled 646 Karst rock localized flow 644 localized flow pathways 642 perched ground water 637 simple gradient control 645 structural control 638 vadose zone 650 Monitoring system evaluation of 55 Monitoring system design criteria 673 Monitoring system design summary 613

Multilevel installations 225 Multiple ground water surfaces 576 Multiple plumes 911 Multiple point sources (MPS) 697 Multiple-port casing installation 226 Municipal ground-water facilities 41

N National Contingency Plan 72 National Contingency Plan (NCP) 689 National Flood Insurance Program 38 National Priority List 73 National Weather Bureau, 39 Natural assimilation 902 Natural attenuation 868, 903, 917 Natural attenuation pathways for inorganics 920 Natural ground-water quality 797 Natural inter-aquifer interferences 857 Natural isotopes 591 Natural spatial variability 797 Neutron logs 57 Neutron moderation 654 Nonaqueous phase liquids (NAPLs) 677 Noncohesive soil 170, 178 Nondetects 840 Nondischarging sand lenses 625 Nonleaky artesian formula (Theis) 398 Nonsealed samplers 202 Numerical ratio of maps 26

O Oblique flow conceptual model 522 Observational method 698 Oriented core section 344 Orphan shares 689 Other lines of evidence 904 Oxygen-18 593

P Packer permeability tests 297, 383, 398 Packer testing calibration of pressure tests 410 column pressure 400 common problems 400 constant pressure injection test 406 data requirements 403 friction loss 400 friction loss estimates 403 gauge pressure 399 low hydraulic conductivity bedrock 404 low K constant rate injection test 409 low K downhole testing system 406 low K pressure-pulse test 410 net Pressure 399 preliminary setup 401 steps recommended 401 surface equipment 404 Packer tests 296, 421 Pajari mechanical single-shot surveying instru-

I-5

FRACTURED ROCK ASSESSMENTS

ment 161 Partition coefficient 739 Passive soil-gas sampling 743, 747 Passive soil-gas surveys costs 749 Pedelogy 90 Penetration rates 162 Perched ground water 637 Perched water zones 457 Perched water tables 457 Performance monitoring 716 Permeability 307 correlations using mean grain diameter 311 Fair and Hatch 312 Hazen relationship 312 Kozeny equation 311 Masch and Denny method 313 Navier-Stokes equation 311 semi-empirical correlations 311 theoretical correlations 311 Permeability correlations 310 Phase I 19 Phase I preliminary investigations 19 Phase I reports for assessment monitoring 76 Phase II characterizations 80 descriptions of wells 79 Phase II work components 99 piezometer multiple 225 Piezometer classifications 227 Piezometer completion 232 Piezometer installation methods 232 Piezometer nest 225 Piezometer placement decisions 223 Piezometer response rates 230 Piezometers 223, 576 annular sealants 233 closed tube hydraulics 228 common problems 233 electrical-resistance-type 228 FLUTe internal liner system 414 FLUTe system 415 hydraulic response 231 individual 225 limitations of depth 231 mechanical diaphragm 228 multilevel piezometer 411 performance Tests 235 pneumatic 235 rehabilitation methods 235 response characteristics 231 slow recovery 231 solist Waterloo multiport system 413 stand pipe installation 228 type A 228 type B 228 type C 228 type D 228 vibrating wire strain gauge 228 Westbay Instruments 413 Piezometers Piezometric surfaces 459 Piston samplers 202

I-6

Piteau roughness categories 342 Plume delineation method 782 Plume Status 922 Pneumatic slug testing 221 Point sources (PT) 697 Poor well construction 858 Porosity 468 Post-remediation monitoring 716 Potentiometric gradients 711 Potentiometric surface 460, 503, 512 Potentiometric surface maps 460, 464 Precipitation 125 Predefined work, health & safety and QA Plans 781 Preliminary investigation 20 Pressure cell apparatus 307 Pressure meter dilatometer 196 Menard type 196 self-boring type 196 Presumptive remedy 16 Primary line of evidence 904 Principles of quality assurance 884 Procedure for statistical sampling 862 Professional liability 897 Progress report format 887 Progress Reports 887 Project organization chart 881 Property acquisitions 63 assessments for 59 Property transaction 59 Proposal check-off list 898 Proposal manpower spreadsheet 883 Proposal organization chart 882 Proposal rebillables spreadsheet 884 Proposal schedule 880 Proposal transmittal letter 878 Proposals 875 Proton procession magnetometers 110 Published soil survey 36 Pump test analysis of test results 289 analysis procedures 485 analytical techniques 480 aquifer radial anisotropy 490 assessment of confining units 282 barometric pressure changes 287 Boulton 485 data ploting method 486 defining well construction data 276 design 277 discharge-control 280 discharging ground water 279 distance-drawdown analysis 489 existing well information 276 fully penetrating condition 489 general design 276 hydraulic properties 277 large-scale pump testing 481 length of test 288 Mandel-Cryer effect 290 measurement equipment 280 monitoring discharge rate 288 Neuman analysis 485 Noordbbergum effect 290 observation wells 280

partial penetration 489 plotting data 289 potential yield 284 pretest conceptual mode 283 pretest monitoring 286 pretest water levels 287 recovery test 481 steady-state or equilibrium methods 472 test procedures 287 transient or nonequilibrium methods 472 type curve selection 484 water level measurements 278 well functions 483 Pump test precautions 289 Pumping off-site 463 Pygmy current meter 128

Q Qualifications 881, 886 Quality assurance 882 Quantitative uncertainty analysis 16

R Radioactive isotopes 593, 594 Radius map report 65 Ralph B. Peck 7 Random errors 860 Rate calculations 929 Ratio method 294 RCRA detection monitoring program 683 RCRA facility investigation 680 RCRA RFI 74 RCRA Subtitle C 679 RCRA Subtitle D 609 Re 220 Real estate transactions assessments 64 Reasonable maximum exposure (RME) 777 Reasonable time frame 923 Reasonableness of remediation time frame 921 REC findings 67 Recharge 502 Recharge areas 459 Recharge of perched water 511 Record of decision (ROD) 73, 695, 698 Records of decisions (RODs) 761 Reductive dehalogenation 902 Re-entry grouting 220, 221 References cited 895 Reflection seismic surveys 107 Refraction seismic methods 106 Regional base map 24, 26 Regional conceptualizations 8 Regional setting 434 Regulatory compliance documentation 24 Regulatory concepts 608 Remedial investigations (Rls) 780 Remediation time frame calculation 935 Report writing 887 Reporting Water quality data 861 Representative elementary volume 332 Requests for proposals 875 Required scales 434

FRACTURED ROCK ASSESSMENTS

Resample well 859 Residual soils fissures 170 Resource Conservation and Recovery Act (RCRA) 677 Retraction grouting 221 RI/FS 19 Ribbon NAPL sampler 14 Richard’s principle 653 Risk 717 Risk assessment 16, 717, 773 Risk assessments 779 Risk characterization 779 Rock index property 188 pore-size distribution 317 Rock quality designation 153, 188, 189 Rock units (stratigraphy) 434 ROST™ DP systems 213 Rotary drilling 159 Rotary sampling 167 Rotosonic drilling 161

S Sample 805 Sampling 165 handling and labelling 181 thin-wall 169 Thin-walled stationary piston 169 Sampling procedure for site assessments 167 Sanborn 65 Sanborne insurance atlas 59 Sanitary landfill siting of 48 Saturated zone 457 SCAPS DP systems 213 Schedule chart 876 Schematic site stratigraphy 437 Scope statements 876 Sealing holes 220 Seasonal variations 463 Secondary line of evidence 904 Seismic impact zone 51 Seismic surveys 105 Selection of ground-water monitoring locations 709 Selection of remedy 687 Semipermeable membrane sensor (MIPs) 213 Sen’s nonparametric trend tes 869 Sen’s test 867 Setbacks for landfills 51 Shallow permeable zones 622 Shallow reflection 107 Shapiro-Wilk test 868, 869 Side gradient 797 Single-ring infiltrometer 258 Site 4, 495 Site assessment categories of 21 fractured rock 323

Site geologic maps 91 Site geologic survey 91 Site geological map procedure 91 Site investigations categories 4 Site rankings 53 Site stratigraphy 436 Slug test analysis of field data 292 single-well test 291 Slug tests 473 Bouwer–Rice method 475 Cooper–Bredehoeft–Papadopulos method 477 critically damped 480 DP slug test data 478 falling head 476 Ferris–Knowles method 473 Hvorslev method 473 overdamped 480 pneumatic data results 479 underdamped 480 Slug tests 222 Soil active soil-gas sampling 744 adsorption coefficient 733 adsorption isotherms 733 adsorptive effect 732 air permeabilities 743 alternative soil sampling design 723 ancillary soil parameters 727 background concentrations 754 background reference values 754 background soil concentration 749 batch method adsorption 732 bulk density 194 cation exchange capacity (cec) 728 characteristic 726 color 170 column method adsorption 732 consistency 170 contaminant properties 730 density 194 desorption of contaminants 733 dominant sorbant process 731 engineering characteristics 731 geostatistics 724 grid pattern 723 hydraulic pressure cells 195 mass transport 730 moisture condition 170 neutron probe technique 194 organic carbon content 728 partition coefficient 739 reaction characteristics 730 regression estimation method 737 sample design 722 simple random sampling 722 soil-screening 725 sorption determinations 732 sorption mechanisms 731 stratified random sampling 722 structure 170 structure activity relationships 740 transport 728

Soil Conservation Service 36 Soil density relationships 304 Soil properties 90 Soil psychrometers 654 Soil samples ASTM D2487-69 300 bulk density 302 cation exchange capacity 306 classification of soils for engineering purposes 300 consolidation tests 305 estimating strength 304 grain size distribution 302 index tests 301 labels 181 laboratory permeability 307 liquid limit 301 mechanical index properties 298 moisture content 300 particle size analysis (ASTM D422) 300 preserved 181 relative density 300 representative samples 298 sampling criteria 306 shear strength 304 specific gravity 303 triaxial compression test 305 typical plasticity characteristics 303 water content 301 Soil sampling 721 common methods 168 direct methods 169 Soil sampling designs 719 Soil sampling objectives 719 Soil series 89 Soil shear test ASTM D-2573 195 BS 1377-1975 195 Soil suction 652 Soil test pressure meter 195 Soil vapor hydraulic conductivity 653 Soil/water distribution coefficient (Kd) 736 Soil-gas sampling 203 Soil-gas surveys 741, 746 Soils residual 172 slickensided 170, 172 surveys 88 Sole source 133 Solid waste management units (SWMUs) 681 Sonic drill rig advantages 163 Source identification 717 Source lifetime models 940 Sources of variability 797 Spatial variability of the water quality 429 Specific yield 469 Spill delineation 717 SPT sampler 178 St. Francis Dam 6 Stable isotopes 591 Standard penetration test 165, 169 Standard penetration test (SPT) 183, 196 Standpipe piezometers 232 State archaeologist 137

I-7

FRACTURED ROCK ASSESSMENTS

State registries of historic sites 41 Statistical approaches for assessment monitoring 862 Steep gradient 619 Stereo pairs of air photos 29 Stereoscopic aerial photos 85 Stiff diagrams 591 Stratigraphic borings 148 deep 150 Stratigraphic column 29 Stratigraphic names 433 Stratigraphic units 465 Streamlined approach 760 Streamlining site characterization 758 Stress testing 472 Structural effects on ground-water flow 566 Structural elements 433 Structural geology 434 Subsurface exploratory work general guidance 147 Subtitle D assessment monitoring 684 Subtitle D corrective action program 685 Superfund 69 Superfund Amendments and Reauthorization Act, (SARA) 689 Superfund regulations 677 Surface examination 145 Surface geophysical surveys 341 Surface runoff 126 Surface water quality 133 Surface water hydrology 127 Surfical geology 37 mapping 90 Surrounding land uses 133 Surveys archaeological sites 136 SUTI 656 Systematic errors 860

T Table of contents 876 Target monitoring zone 614 Target monitoring zones 622 Taylor Instabilities 653 Technical enforcement guidance document 609, 679 TEGD 679 Tensiometer 652 Terrestrial ecology 134 Terzaghi 5 Tests for evaluating normality 720 Three-layer flow model 634 Tidal effects 236 Tidal processes 464 Time domain reflectometry 653 Toolbox approach 13 Topographic maps 24, 85 Topographic maps features 25

I-8

scales 24 Total suspended solids (TSS) 128 Toxicity assessment 775 Toxicity information 779 Traditional RI methodology 699 Transport computer model 938 Traverse geologic mapping 94 Trench logs 95 Trenches 154 Trial pit 154 Triaxial cells 308 Trilineal diagrams 593 Tritium 593 Two-layer flow mode 633 Types of aquifers 457 Typical siting study 53 Typical stratigraphic sequence 437

U U.S. Forest Service 41 U.S. Soil Service 90 Unconfined aquifer piezometer nest 622 Unconfined ground water system 610 Unconfined/confined flownets 621 Unconformities 436 Unified Soil Classification System 37, 174, 175, 661 United Soil Classification (USC) description 169 Unsaturated hydraulic conductivity 256 Unstable area 51 Upper prediction limit (UPL) 865 Uppermost aquifer 457, 611, 614 USGS quadrangle 26 UST regulations 69

V Vadose zone 80, 81 Vadose zone detection monitoring 653 Vadose zone equipment 654 Vadose zone monitoring 653 Vadose-zone hydraulic conductivity 260 Vane shear test 195 Vapor pressure 742 Variable head methods 267 Verification of Release 859 Vertical components of flow 461 Vertical distribution of hydraulic head 411 Vertical flow 581 Vertical fluid movement 357 Vertical leakage 564 Vibratory drilling 161

W Water FLUTe installation 415 Water level trends 582, 586 Water quality

analytical laboratories 800, 802 background 798, 805 box plots 812 chemical parameters 798 confidence limits 828 contour maps 808 criteria 799 data inquiries 802 data normality 823 environmental indicators 798 exceedance 856 histogram of leachate data 816 histograms 812 independence of data 822 indicator parameters 798 instrument detection limits 803 laboratory selection 799 laboratory selection process 800 low levels of organics 805 method detection limits (MDLs) 803 natural variability 806 nonparametric approach 841 nonparametric statistical tests 823 normal probability plots 817 outliers 807 out-of-control incident 803 parameter list 799 prediction intervals 828 prediction limits 828 QA reports 803 quality assurance project plan 800 reporting 806 resampling 848 sample dilution 805 significant digits 806 statistical hypothesis testing 822 statistical methodology 824 Tabular summaries 815 tests of central tendency 827 tests of trend 827 time series comparisons 813 time-series formats 809 tolerance limits 828 trilinear diagram 818 trilinear diagrams 818 types of statistical tests 826 units of measure 807 Water quality analyses 795 Water–bearing potentials 433 Water-level accuracy 239 Water-level fluctuations 243 Water-level measurements 235 Well census 34, 76 Well construction details 55 Well deviation 241, 358 Well functions and type curves 483 Well inventory 56 Well loss solutions 397 Westbay Instruments 226 Wetlands 38 Wetlands protection 51 Withdrawal rates of ground water 130