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Page i Assessing the TMDL Approach to Water Quality Management Committee to Assess the Scientific Basis of the Total Maximum Daily Load Approach to Water Pollution Reduction Water Science and Technology Board Division on Earth and Life Studies National Research Council NATIONAL ACADEMY PRESS Washington, D.C.
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Page ii 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 competencies and with regard for appropriate balance. Support for this project was provided by the U.S. Environmental Protection Agency under Cooperative Agreement No. X-82880401. International Standard Book Number 0-309-07579-3 Assessing the TMDL Approach to Water Quality Management is available from the National Academy Press , 2101 Constitution Avenue, N.W. , Washington, D.C. 20418 ; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet < http://www.nap.edu >. Copyright 2001 by the National Academy of Sciences . All rights reserved. Printed in the United States of America .
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Page iii THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine 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. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievement of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chair and vice chair, respectively, of the National Research Council.
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Page v COMMITTEE TO ASSESS THE SCIENTIFIC BASIS OF THE TOTAL MAXIMUM DAILY LOAD APPROACH TO WATER POLLUTION REDUCTION KENNETH H. RECKHOW, Chair, Duke University, Durham, North Carolina ANTHONY S. DONIGIAN, JR., AQUA TERRA Consultants, Mountain View, California JAMES R. KARR, University of Washington, Seattle JAN MANDRUP-POULSEN, Florida Department of Environmental Protection, Tallahassee H. STEPHEN McDONALD, Carollo Engineers, Walnut Creek, California VLADIMIR NOVOTNY, Marquette University, Milwaukee, Wisconsin RICHARD A. SMITH, U.S. Geological Survey, Reston, Virginia CHRIS O. YODER, Ohio Environmental Protection Agency, Groveport NRC Staff LEONARD SHABMAN, Visiting Scholar, Virginia Polytechnic Institute and State University LAURA J. EHLERS, Study Director M. JEANNE AQUILINO, Administrative Associate
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Page vi WATER SCIENCE AND TECHNOLOGY BOARD HENRY J. VAUX, JR., Chair, Division of Agriculture and Natural Resources, University of California, Oakland RICHARD G. LUTHY, Vice Chair, Stanford University, California RICHELLE M. ALLEN-KING, Washington State University, Pullman GREGORY B. BAECHER, University of Maryland, College Park JOHN BRISCOE, The World Bank, Washington, D.C. EFI FOUFOULA-GEORGIOU, University of Minnesota, Minneapolis STEVEN P. GLOSS, University of Wyoming, Laramie WILLIAM A. JURY, University of California, Riverside GARY S. LOGSDON, Black & Veatch, Cincinnati, Ohio DIANE M. MCKNIGHT, University of Colorado, Boulder 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, George Washington University, Washington, D.C. RUTHERFORD H. PLATT, University of Massachusetts, Amherst JOAN B. ROSE, University of South Florida, St. Petersburg JERALD L. SCHNOOR, University of Iowa, Iowa City R. RHODES TRUSSELL, Montgomery Watson, Pasadena, California Staff STEPHEN D. PARKER, Director LAURA J. EHLERS, Senior Staff Officer JEFFREY W. JACOBS, Senior Staff Officer MARK C. GIBSON, Staff Officer WILLIAM S. LOGAN, Staff Officer M. JEANNE AQUILINO, Administrative Associate PATRICIA A. JONES KERSHAW, Staff Associate ANITA A. HALL, Administrative Assistant ELLEN A. DE GUZMAN, Senior Project Assistant ANIKE L. JOHNSON, Project Assistant NORA BRANDON, Project Assistant RHONDA BITTERLI, Editor
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Page vii Preface The Total Maximum Daily Load (TMDL) program, initiated in the 1972 Clean Water Act, recently emerged as a foundation for the nation's efforts to meet state water quality standards. A “TMDL” refers to the “total maximum daily load” of a pollutant that achieves compliance with a water quality standard; the “TMDL process” refers to the plan to develop and implement the TMDL. Failure to meet water quality standards is a major concern nationwide; it is estimated that about 21,000 river segments, lakes, and estuaries have been identified by states as being in violation of one or more standards. To address this problem, the U. S. Environmental Protection Agency (EPA) proposed an ambitious timetable for states to develop TMDL plans that will result in attainment of water quality standards. Given the reduction in pollutant loading from point sources such as sewage treatment plants over the last 30 years, the successful implementation of most TMDLs will require controlling non-point source pollution. These two features, the ambitious timetable and nonpoint source controls, are probably the two most controversial of many issues that have been raised by those who have questioned the TMDL program. Behind and intertwined with these basic policy issues are important questions concerning the adequacy of the science in support of TMDLs. In the last year, the TMDL program has become one of the most discussed and debated environmental programs in the nation, primarily because of the drafting of final rules for the program. These rules follow several years of intense activity, including the formation of a Federal Advisory Committee devoted to this topic. In October 2000, Congress suspended EPA's implementation of these rules until further information could be gathered on several aspects of the program. In particular, Congress requested that the National Research Council (NRC) examine the
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Page viii scientific basis of the TMDL program. In recognition of the urgent need to address water quality standard violations, Congress established an aggressive schedule for completion of the study that allowed only four months from start to finish—unprecedented for most NRC studies. The eight-member committee, constituted in January 2001, immediately conducted its first meeting. This three-day meeting included two days devoted to public comments and a third day focused on internal committee discussions. The ensuing three months was a period of intense activity filled with correspondence, writing, and two additional committee meetings. The difficult challenges facing EPA and the states in the implementation of the TMDL program were immediately apparent to the committee. Because the committee faced a congressionally mandated deadline, a number of issues important to some stakeholders were not addressed comprehensively. These include bed sediment issues, atmospheric deposition, translating narrative standards into numeric criteria, and a full review of existing water quality models. Nonetheless, the committee found that substantial improvements can be made in a number of areas to strengthen the scientific basis of the TMDL program. Also of importance, the committee identified several policy issues that are restricting the use of the best science in the TMDL program. We urge Congress, EPA, and the states to give thoughtful attention to the recommendations made throughout this report so that resources can be more efficiently used to improve water quality. We greatly appreciate the assistance of Don Brady and Françoise Brasier of the EPA Office of Water for their assistance in initiating the study and organizing the first committee meeting. We are also grateful to those who spoke with and educated our committee, including congressional staff, EPA scientists, state representatives, and the many individuals and organizations that submitted comments to the committee. The committee recognizes the vital role of Water Science and Technology Board (WSTB) director Stephen Parker in making this study possible. The extremely short time period for this study created an enormous challenge for NRC study director Laura Ehlers, who was able to juggle her many responsibilities to keep us focused and provide invaluable assistance in crafting the text. Finally, it is fair to say that this study owes most thanks to Leonard Shabman (Virginia Polytechnic Institute and State University) who was working in the WSTB office as a visiting scholar during the study. Dr. Shabman's insight was invaluable; he added immensely to committee discussion and correspondence, and he
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Page ix played a key role in drafting the text and developing the recommendations. More formally, the report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC's Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the authors and the NRC in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The reviews and draft manuscripts remain confidential to protect the integrity of the deliberative process. We thank the following individuals for their participation in the review of this report: Richard A. Conway, consultant; Paul L. Freedman, Limno-Tech, Inc.; Donald R. F. Harleman, Massachusetts Institute of Technology (retired); Robert M. Hirsch, U.S. Geological Survey; Judith L. Meyer, University of Georgia; Larry A. Roesner, Colorado State University; Robert V. Thomann, Manhattan University (retired); and Robert C. Ward, Colorado State University. Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Frank H. Stillinger, Princeton University, and D. Peter Loucks, Cornell University. Appointed by the NRC, they were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the NRC. KENNETH H. RECKHOW Chair
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Page xi Contents EXECUTIVE SUMMARY, 1 TMDL Program Goals, 3 Changes to the TMDL Process, 4 Use of Science in the TMDL Program, 7 Final Thoughts, 11 1 INTRODUCTION, 12 The Return to Ambient-Based Water Quality Management, 12 National Research Council Study, 16 Current TMDL Process and Report Organization, 18 References, 21 2 CONCEPTUAL FOUNDATIONS FOR WATER QUALITY MANAGEMENT, 22 Ambient Water Quality Standards, 22 Decision Uncertainty, 28 Conclusions and Recommendations, 30 References, 31 3 WATERBODY ASSESSMENT: LISTING AND DELISTING, 32 Adequate Ambient Monitoring and Assessment, 33 Defining All Waters, 42 Desirable Criteria, 44 Listing and Delisting in a Data-Limited Environment, 50 Data Evaluation for the Listing and Delisting Process, 56 Use of Models in the Listing Process, 61 References, 63
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Page xii 4 MODELING TO SUPPORT THE TMDL PROCESS, 68 Model Selection Criteria, 69 Uncertainty Analysis in Water Quality Models, 73 Models for Biotic Response: A Critical Gap, 77 Additional Model Selection Issues, 80 References, 86 5 ADAPTIVE IMPLEMENTATION FOR IMPAIRED WATERS, 89 Science and the TMDL Process, 89 Review of Water Quality Standards, 90 Adaptive Implementation Described, 94 TMDL Implementation Challenges, 97 References, 102 APPENDIXES A List of Guest Presentations at the First Committee Meeting, 103 B Biographies of the Committee Members and NRC Staff, 105