NATIONAL ACADEMY PRESS
2101 Constitution Avenue, N.W. Washington, DC 20418
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.
Support for this project was provided by the American Petroleum Institute under contract no. 97-0000-1957, the Chemical Manufacturers’ Association, Chevron, the Lawrence Livermore National Laboratory, the National Mining Association, the Nuclear Regulatory Commission under contract no. NRC-04-97-068, the U.S. Army under contract no. DACA31-97-P-1191, the U.S. Department of Energy under contract no. DE-FC01-94EW54069, the U.S. Environmental Protection Agency under contract no. R-826445-01-0, the U.S. Geological Survey under contract no. 1434-HQ-97-AG-01775, and the U.S. Navy under contract no. N62467-97-M-1009.
Library of Congress Cataloging-in-Publication Data
Natural attenuation for groundwater remediation / Committee on Intrinsic Remediation, Water Science and Technology Board [and] Board on Radioactive Waste Management, Commission on Geosciences, Environment, and Resources.
p. cm.
Includes bibliographical references and index.
ISBN 0-309-06932-7 (casebound)
1. Hazardous wastes—Natural attenuation—Evaluation. 2. In situ bioremediation—Evaluation. 3. Hazardous waste site remediation—Evaluation. 4. Groundwater—Purification. I. National Research Council (U.S.). Committee on Intrinsic Remediation.
TD1060 .N37 2000
628.1′68—dc21 00-008896
Natural Attenuation for Groundwater Remediation is available from the
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THE NATIONAL ACADEMIES
National Academy of Sciences
National Academy of Engineering
Institute of Medicine
National Research Council
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences.
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COMMITTEE ON INTRINSIC REMEDIATION
BRUCE E. RITTMANN, Chair,
Northwestern University, Evanston, Illinois
MICHAEL J. BARDEN,
Geoscience Resources Ltd., Albuquerque, New Mexico
BARBARA A. BEKINS,
U.S. Geological Survey, Menlo Park, California
DAVID E. ELLIS,
DuPont Specialty Chemicals, Wilmington, Delaware
MARY K. FIRESTONE,
University of California, Berkeley (through June 1998)
STEPHEN LESTER,
Center for Health, Environment, and Justice, Falls Church, Virginia
DEREK LOVLEY,
University of Massachusetts, Amherst
RICHARD G. LUTHY,
Stanford University, Stanford, California
DOUGLAS M. MACKAY,
University of Waterloo, Ontario, Canada
EUGENE MADSEN,
Cornell University, Ithaca, New York
PERRY L. MCCARTY,
Stanford University, Stanford, California
EILEEN POETER,
Colorado School of Mines, Golden
ROBERT SCOFIELD,
ENVIRON Corporation, Emeryville, California
ARTHUR W. WARRICK,
University of Arizona, Tucson
JOHN T. WILSON,
U.S. Environmental Protection Agency, Ada, Oklahoma
JOHN ZACHARA,
Pacific Northwest National Laboratories, Richland, Washington
Staff
JACQUELINE A. MACDONALD, Study Director
ELLEN A. DE GUZMAN, Senior Project Assistant
KIMBERLY SWARTZ, Project Assistant (through June 1999)
WATER SCIENCE AND TECHNOLOGY BOARD
HENRY J. VAUX, Jr., Chair,
Division of Agriculture and Natural Resources, University of California, Oakland
CAROL A. JOHNSTON, Vice-Chair,
University of Minnesota, Duluth
RICHELLE M. ALLEN-KING,
Washington State University, Pullman
GREGORY B. BAECHER,
University of Maryland, College Park
JOHN S. BOYER,
University of Delaware, Lewes
JOHN BRISCOE,
The World Bank, Washington, D.C.
DENISE D. FORT,
University of New Mexico, Albuquerque
STEVEN P. GLOSS,
University of Wyoming, Laramie
EVILLE GORHAM,
University of Minnesota, St. Paul (through January 2000)
WILLIAM A. JURY,
University of California, Riverside
GARY S. LOGSDON,
Black & Veatch, Cincinnati, Ohio
RICHARD G. LUTHY,
Stanford University, Stanford, California
JOHN W. MORRIS,
J. W. Morris Ltd., Arlington, Virginia
PHILIP A. PALMER, (Retired)
E. I. du Pont de Nemours & Co., Wilmington, Delaware
REBECCA T. PARKIN,
The George Washington University, Washington, D.C.
JOAN B. ROSE,
University of South Florida, St. Petersburg
R. RHODES TRUSSELL,
Montgomery Watson, Pasadena, California
ERIC F. WOOD,
Princeton University, Princeton, New Jersey
Staff
STEPHEN D. PARKER, Director
LAURA J. EHLERS, Senior Staff Officer
CHRIS ELFRING, Senior Staff Officer
JEFFREY W. JACOBS, Senior Staff Officer
WILLIAM S. LOGAN, Staff Officer
MARK C. GIBSON, Staff Officer
M. JEANNE AQUILINO, Administrative Associate
PATRICIA A. JONES, Study/Research Associate
ANITA A. HALL, Administrative Assistant
ELLEN A. DE GUZMAN, Senior Project Assistant
ANIKE L. JOHNSON, Project Assistant
BOARD ON RADIOACTIVE WASTE MANAGEMENT
JOHN F. AHEARNE, Chair,
Sigma Xi, The Scientific Research Society, and Duke University, Research Triangle Park, North Carolina
CHARLES MCCOMBIE, Vice-Chair, Consultant,
Gipf-Oberfrick, Switzerland
ROBERT M. BERNERO, Consultant,
Gaithersburg, Maryland
ROBERT J. BUDNITZ,
Future Resources Associates, Inc., Berkeley, California
GREGORY CHOPPIN,
Florida State University, Tallahassee
JAMES H. JOHNSON, JR.,
Howard University, Washington, D.C.
ROGER E. KASPERSON,
Clark University, Worcester, Massachusetts
JAMES O. LECKIE,
Stanford University, Stanford, California
JANE C. S. LONG,
University of Nevada, Reno
ALEXANDER MACLACHLAN,
E.I. du Pont de Nemours & Company (retired), Olney, Maryland
WILLIAM A. MILLS,
Oak Ridge Associated Universities (retired), Olney, Maryland
MARTIN J. STEINDLER,
Argonne National Laboratory (retired), Argonne, Illinois
ATSUYUKI SUZUKI,
University of Tokyo, Japan
JOHN J. TAYLOR,
Electric Power Research Institute, Palo Alto, California
VICTORIA J. TSCHINKEL,
Landers and Parsons, Tallahassee, Florida
MARY LOU ZOBACK,
U.S. Geological Survey, Menlo Park, California
Staff
KEVIN D. CROWLEY, Director
ROBERT S. ANDREWS, Senior Staff Officer
JOHN R. WILEY, Senior Staff Officer
BARBARA PASTINA, Staff Officer
SUSAN B. MOCKLER, Research Associate
TONI GREENLEAF, Administrative Associate
ANGELA R. TAYLOR, Senior Project Assistant
LATRICIA C. BAILEY, Project Assistant
LAURA D. LLANOS, Project Assistant
COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES
GEORGE M. HORNBERGER, Chair,
University of Virginia, Charlottesville
RICHARD A. CONWAY,
Union Carbide Corporation (retired), South Charleston, West Virginia
LYNN GOLDMAN,
Johns Hopkins School of Hygiene and Public Health, Baltimore, Maryland
THOMAS E. GRAEDEL,
Yale University, New Haven, Connecticut
THOMAS J. GRAFF,
Environmental Defense Fund, Oakland, California
EUGENIA KALNAY,
University of Maryland, College Park
DEBRA KNOPMAN,
Progressive Policy Institute, Washington, D.C.
BRAD MOONEY,
J. Brad Mooney Associates, Ltd., Arlington, Virginia
HUGH C. MORRIS,
El Dorado Gold Corporation, Vancouver, British Columbia
H. RONALD PULLIAM,
University of Georgia, Athens
MILTON RUSSELL,
Joint Institute for Energy and Environment and University of Tennessee (emeritus), Knoxville
ROBERT J. SERAFIN,
National Center for Atmospheric Research, Boulder, Colorado
ANDREW R. SOLOW,
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
E-AN ZEN,
University of Maryland, College Park
MARY LOU ZOBACK,
U.S. Geological Survey, Menlo Park, California
Staff
ROBERT M. HAMILTON, Executive Director
GREGORY H. SYMMES, Associate Executive Director
JEANETTE SPOON, Administrative and Financial Officer
SANDI FITZPATRICK, Administrative Associate
Preface
In 1992, when I chaired the National Research Council’s Committee on In Situ Bioremediation, the committee addressed whether or not microorganisms could clean up contamination of soil and groundwater. The committee’s 1993 report, In Situ Bioremediation: When Does It Work?, concluded that microorganisms are capable of destroying common groundwater contaminants. The report concluded that in situ bioremediation is scientifically valid and technically feasible. The report also stressed that possible biodegradation reactions must be documented clearly with several lines of evidence from the field.
One of the important distinctions made in the 1993 report is between engineered bioremediation and intrinsic bioremediation. Engineered bioremediation uses engineered technologies to enhance microbiological activity and increase the rate of biodegradation. Examples include sparging the subsurface with air to supply oxygen and adding nutrients to stimulate microbial growth. On the other hand, intrinsic remediation relies only on the natural supply rates of substances such as oxygen and nutrients that promote contaminant biodegradation. When these supply rates are sufficient, the intrinsic biodegradation capacity of the microorganisms at the site can prevent migration of the contaminants in groundwater and eventually lead to a site cleanup.
At the time the Committee on In Situ Bioremediation was deliberating, in situ bioremediation was carried out almost exclusively by engineered approaches. Soon after In Situ Bioremediation: When Does It Work? was published, the pendulum began to swing towards intrinsic bio-
remediation, which was accepted as a final cleanup remedy at more and more sites. Another important change was taking place in parallel. The term intrinsic bioremediation was slowly being superseded by natural attenuation, an approach having a much broader definition. Besides biodegradation, natural attenuation includes natural physical processes that can immobilize contaminants and natural chemical reactions that can destroy contaminants. It also includes dilution, dispersion, volatilization, adsorption, and other processes that do not destroy or immobilize the contaminants.
By 1998, many regulators were happy to “close the books” on sites by accepting a natural attenuation remedy. Responsible parties were relieved to have an approach that seemed to save them money and headaches. The types of sites and contaminants for which natural attenuation was being considered were growing steadily: petroleum hydrocarbons, chlorinated solvents, heavy metals, radionuclides, and more. Clearly the pendulum had swung toward using natural, in situ processes.
However, not everyone was so pleased with the rapidly expanding acceptance of natural attenuation as a remedy. Members of communities living near contaminated sites suspected that natural attenuation really meant “do nothing” and “walk away.” Scientists and engineers expert in bioremediation were concerned that natural attenuation was being accepted whether or not it was documented—or even likely—at a site. Perhaps the pendulum had swung too far.
The National Research Council (NRC) formed the committee that prepared this report—the Committee on Intrinsic Remediation—in 1997 in order to establish a proper basis for selecting remedies that rely on natural attenuation processes. The committee was charged with the following tasks:
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assess current knowledge about the natural subsurface processes that play critical roles in intrinsic remediation;
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outline what intrinsic remediation can and cannot achieve;
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assess risks associated with leaving contaminants in place;
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identify the measurements, observations, and monitoring needed when intrinsic remediation is chosen instead of engineered remediation; and
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evaluate the adequacy of existing protocols for determining whether intrinsic remediation is an appropriate strategy for contaminant management.
This report summarizes the findings of the committee, which was made up of 14 experts in the technical and decision-making aspects of natural attenuation. Committee members brought to the table state-of-
the-art expertise in environmental microbiology, geochemistry, environmental engineering, hydrogeology, soil science, and risk assessment. Academia, industry, government, and community-based institutions were represented. The committee also interviewed a wide range of community activists, researchers, regulators, practitioners, and protocol developers.
The findings presented in this report represent the unanimous consensus of the committee. Despite coming from disparate backgrounds and interest groups, all of the committee members agreed with the message that this report delivers. Clearly, the concept that natural attenuation processes can, under the proper conditions, cause the destruction or transformation of contaminants in the environment is valid. However, natural attenuation should never be a default choice. The cause-and-effect link between a decrease in contaminant concentration and the process or processes causing it must be documented before natural attenuation is accepted as a remedy. These processes must continue to occur for as long as is necessary to protect human health and the environment. Furthermore, affected communities need to be part of the decision to accept natural attenuation.
Chapter 1 outlines the factors that led the National Research Council to form this committee. Chapter 2 details why community groups have an especially strong stake in decisions involving natural attenuation, and it provides guidance on how community groups can be involved effectively. Chapter 3 reviews the scientific foundation for natural attenuation and summarizes the likelihood that natural attenuation will work for the major classes of contaminants. Chapter 4 describes the steps needed to evaluate whether or not natural attenuation is protecting human health and the environment for a given site; it stresses that many types of information must be integrated to assess natural attenuation potential and provides guidance on the relative level of effort needed to gather and interpret information. Finally, Chapter 5 provides a critical review of the protocols published as of the end of 1998 and offers guidance on topics that protocols developed in the future should address.
I want to thank the organizations that sponsored this project for having confidence in the National Research Council process and our committee. In particular, thanks are due to Ken Lovelace and Rich Steimle at the Environmental Protection Agency; Ira May at the Army Environmental Center; Cliff Casey at the Naval Facilities Engineering Command, Southern Division; Herb Buxton and Frank Chapelle of the U.S. Geological Survey; Steve Golian of the Department of Energy; Tom Nicholson and Ralph Cady of the Nuclear Regulatory Commission; Bruce Bauman of the American Petroleum Institute; David Mentall of the Chemical Manufacturers’ Association; Katie Sweeney of the National Mining Association; K. C. Bishop and Tim Buscheck of Chevron USA, Inc.; and David Rice and
Ellen Raber of Lawrence Livermore National Laboratory. The organizations that these individuals represent provided not only the financial support that made this study possible, but also valuable background information.
I sincerely thank each committee member for his or her unique contributions and for being fully invested in the common goal. Being the chair of such a hard-working committee—a true team—has been a most satisfying experience. Finally, I thank our study director, Jacqueline MacDonald, who made the committee’s work go smoothly and who really helped us figure out what “we meant to say,” whether or not we actually had said it.
This report has been reviewed, in accordance with NRC procedures, by individuals chosen for their expertise and broad perspectives on natural attenuation issues. This independent review provided candid and critical comments that assisted the authors and the NRC in making the published report as sound as possible and ensured that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The content of the review comments and the draft manuscript remain confidential to protect the integrity of the deliberative process. The committee wishes to thank the following individuals for their participation in the review of this report and their many instructive comments:
Charles Andrews, S. S. Papadopulous and Associates
Michael Aitken, University of North Carolina
Isabelle Cozzarelli, U.S. Geological Survey
Paul Hadley, California Department of Toxic Substances Control
Michael Kavanaugh, Malcolm Pirnie, Inc.
Debra Knopman, Progressive Policy Institute
Rebecca Parkin, The George Washington University Medical Center
Leonard Siegel, Pacific Studies Center
Donald Sparks, University of Delaware
Susan Wiltshire, J. K. Associates
While the individuals listed above have provided constructive comments and suggestions, it must be emphasized that responsibility for the final content of this report rests entirely with the authoring committee and the institution.
BRUCE E. RITTMANN
Chair