DRINKING WATER DISTRIBUTION SYSTEMS

ASSESSING AND REDUCING RISKS

Committee on Public Water Supply Distribution Systems: Assessing and Reducing Risks

Water Science and Technology Board

Division on Earth and Life Studies

NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES

THE NATIONAL ACADEMIES PRESS

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Drinking Water Distribution Systems: Assessing and Reducing Risks DRINKING WATER DISTRIBUTION SYSTEMS ASSESSING AND REDUCING RISKS Committee on Public Water Supply Distribution Systems: Assessing and Reducing Risks Water Science and Technology Board Division on Earth and Life Studies NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES THE NATIONAL ACADEMIES PRESS Washington, D.C. www.nap.edu

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Drinking Water Distribution Systems: Assessing and Reducing Risks THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. Washington, DC 20001 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 EPA Contract No. 68-C-03-081. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. International Standard Book Number-10 0-309-10306-1 (Book) International Standard Book Number-13 978-0-309-10306-0 (Book) International Standard Book Number-10 0-309-66432-2 (PDF) International Standard Book Number-13 978-0-309-66432-5 (PDF) Drinking Water Distribution Systems: Assessing and Reducing Risks is available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Illustration on the book cover is designed by Alight Tsai, MWH Soft. Copyright 2006 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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Drinking Water Distribution Systems: Assessing and Reducing Risks THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine 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. Ralph J. Cicerone 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. Wm. 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. Harvey V. Fineberg 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. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice-chair, respectively, of the National Research Council. www.national-academies.org

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Drinking Water Distribution Systems: Assessing and Reducing Risks COMMITTEE ON PUBLIC WATER SUPPLY DISTRIBUTION SYSTEMS: ASSESSING AND REDUCING RISKS VERNON L. SNOEYINK, Chair, University of Illinois, Urbana-Champaign CHARLES N. HAAS, Vice-Chair, Drexel University, Philadelphia, Pennsylvania PAUL F. BOULOS, MWH Soft, Broomfield, Colorado GARY A. BURLINGAME, Philadelphia Water Department, Philadelphia, Pennsylvania ANNE K. CAMPER, Montana State University, Bozeman ROBERT N. CLARK, Environmental Engineering and Public Health Consultant, Cincinnati, Ohio MARC A. EDWARDS, Virginia Polytechnic and State University, Blacksburg MARK W. LECHEVALLIER, American Water, Voorhees, New Jersey L. D. MCMULLEN, Des Moines Water Works, Des Moines, Iowa CHRISTINE L. MOE, Emory University, Atlanta, Georgia EVA C. NIEMINSKI, Utah Department of Environmental Quality, Salt Lake City CHARLOTTE D. SMITH, Charlotte Smith and Associates, Inc., Orinda, California DAVID P. SPATH, California Department of Health Services (Retired), Sacramento RICHARD L. VALENTINE, University of Iowa, Iowa City National Research Council Staff LAURA J. EHLERS, Study Director ELLEN A. DE GUZMAN, Research Associate

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Drinking Water Distribution Systems: Assessing and Reducing Risks WATER SCIENCE AND TECHNOLOGY BOARD R. RHODES TRUSSELL, Chair, Trussell Technologies, Inc., Pasadena, California MARY JO BAEDECKER, U.S. Geological Survey (Retired), Vienna, Virginia JOAN G. EHRENFELD, Rutgers University, New Brunswick, New Jersey DARA ENTEKHABI, Massachusetts Institute of Technology, Cambridge GERALD E. GALLOWAY, Titan Corporation, Reston, Virginia SIMON GONZALES, National Autonomous University of Mexico, Mexico CHARLES N. HAAS, Drexel University, Philadelphia, Pennsylvania KIMBERLY L. JONES, Howard University, Washington, DC KAI N. LEE, Williams College, Williamstown, Massachusetts JAMES K. MITCHELL, Virginia Polytechnic Institute and State University, Blacksburg CHRISTINE L. MOE, Emory University, Atlanta, Georgia ROBERT PERCIASEPE, National Audubon Society, New York, New York LEONARD SHABMAN, Resources for the Future, Washington, DC HAME M. WATT, Independent Consultant, Washington, DC CLAIRE WELTY, University of Maryland, Baltimore County JAMES L. WESCOAT, JR., University of Illinois, Urbana-Champaign GARRET P. WESTERHOFF, Malcolm Pirnie, Inc., White Plains, New York Staff STEPHEN D. PARKER, Director LAUREN E. ALEXANDER, Senior Staff Officer LAURA J. EHLERS, Senior Staff Officer JEFFREY W. JACOBS, Senior Staff Officer STEPHANIE E. JOHNSON, Senior Staff Officer WILLIAM S. LOGAN, Senior Staff Officer M. JEANNE AQUILINO, Financial and Administrative Associate ANITA A. HALL, Senior Program Associate ELLEN A. DE GUZMAN, Research Associate JULIE VANO, Research Associate DOROTHY K. WEIR, Research Associate MICHAEL J. STOEVER, Project Assistant

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Drinking Water Distribution Systems: Assessing and Reducing Risks Preface The distribution system is a critical component of every drinking water utility. Its primary function is to provide the required water quantity and quality at a suitable pressure, and failure to do so is a serious system deficiency. Water quality may degrade during distribution because of the way water is treated or not treated before it is distributed, chemical and biological reactions that take place in the water during distribution, reactions between the water and distribution system materials, and contamination from external sources that occurs because of main breaks, leaks coupled with hydraulic transients, and improperly maintained storage facilities, among other things. Furthermore, special problems are posed by the utility’s need to maintain suitable water quality at the consumers tap, and the quality changes that occur in consumers’ plumbing, which is not owned or controlled by the utility. The primary driving force for managing and regulating distribution systems is protecting the health of the consumer, which becomes more difficult as our nation’s distribution systems age and become more vulnerable to main breaks and leaks. Certainly factors that cause water of poor aesthetic quality to be delivered to the tap, or that increase the cost of delivering water, are also important. Possibly because they are underground and out of sight, it is easy to delay investments in distribution systems when budgets are considered. Rather than wait for further deterioration, however, there is an urgent need for new science that will enable cost-effective treatment for distribution, and design, construction, and management of the distribution system for protection of public health and minimization of water quality degradation. This report was undertaken at the request of the U.S. Environmental Protection Agency (EPA) and was prepared by the Water Science and Technology Board (WSTB) of the National Research Council (NRC). The committee formed by the WSTB conducted a study of water quality issues associated with public water supply distribution systems and their potential risks to consumers. Although the report focused on public systems that serve at least 25 people, much that is said in the report is also applicable to private, individual distribution systems. The study considered regulations and non-regulatory approaches to controlling quality; the health effects of distribution system contamination; physical, hydraulic, and water quality integrity; and premise plumbing issues. Important events that constitute health risks, such as cross connections and backflow, pressure transients, nitrification and microbial growth, permeation and leaching, repair and replacement of water mains, aging infrastructure, corrosion control, and contamination in premise plumbing, were examined. The activities of the Committee included the following tasks:

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Drinking Water Distribution Systems: Assessing and Reducing Risks —As background and based on available information, identification of trends relevant to the deterioration of drinking water in water supply distribution systems. —Identification and prioritization of issues of greatest concern for distribution systems based on review of published material. —Focusing on the highest priority issues as revealed by task #2, (a) evaluation of different approaches to characterization of public health risks posed by water-quality deteriorating events or conditions that may occur in public water supply distribution systems; and (b) identification and evaluation of the effectiveness of relevant existing codes and regulations and identification of general actions, strategies, performance measures, and policies that could be considered by water utilities and other stakeholders to reduce the risks posed by water-quality deteriorating events or conditions. Case studies were identified and recommendations were presented in their context. —Identification of advances in detection, monitoring and modeling, analytical methods, information needs and technologies, research and development opportunities, and communication strategies that will enable the water supply industry and other stakeholders to further reduce risks associated with public water supply distribution systems. The Committee prepared an interim report entitled “Public Water Supply Distribution Systems: Assessing and Reducing Risks, First Report” in March 2005 that dealt with the first two tasks listed above; the interim report has been incorporated into this report in order to make this report a complete compilation of Committee’s activities. The third and fourth tasks constitute the subject matter of the present report; an explanation of where individual issues are discussed in the report can be found at the end of Chapter 1. The EPA is in the process of considering changes to the Total Coliform Rule (TCR), which is one of the existing rules governing water quality in distributions systems. This report does not include a comprehensive evaluation of the science behind the TCR, a critique of that science, or specific suggestions on how to change the Rule. However, the Committee believes that this report should be considered when developing changes to the Rule, in order to determine whether the revised Rule could better encompass distribution system integrity. When preparing the report the committee made a series of assumptions that affected the outcome of the report. First, it was assumed that both treated and distributed water has to meet U.S. water quality standards. Second, water distribution will almost certainly be accomplished with the existing infrastructure in which the nation has invested billions of dollars and which is continuously being expanded. Thus, the report focuses on how to best use

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Drinking Water Distribution Systems: Assessing and Reducing Risks traditionally designed distribution systems in which potable water is distributed for all uses. These assumptions led the Committee to devote only a small section of the report to non-traditional distribution system design (such as dual distribution systems), investigation of which was not in the Committee’s charge. The Committee believes that alternative methods of distributing water, including dual distribution systems, point-of-use and point-of-entry treatment systems, and community-based treatment systems need more research and evaluation to determine their effectiveness and applicability, both in the United States and elsewhere in the world. The Committee did not consider lead and copper corrosion because this subject is part of the Lead and Copper Rule and for this reason was intentionally excluded from the committee’s charge by the study sponsor. Corrosion in distribution systems, in general, has very important impacts on water quality in distribution systems, and the committee believes that state-of-the-art internal and external corrosion control procedures should be made available to the industry, perhaps in the form of a manual of practice. Finally, at the request of EPA, the committee did not consider issues surrounding the security of the nation’s distribution systems, including potential threats and monitoring needed for security purposes. In developing this report, the Committee benefited greatly from the advice and input of EPA representatives, including Ephraim King, Yu-Ting Guilaran, Elin Betanzo, and Kenneth Rotert and from presentations by Russ Chaney, IAPMO; Barry Fields, CDC; Johnnie Johannesen, Matt Velardes, and Chris Kinner, Irvine Ranch Water District; Laura Jacobsen, Las Vegas Valley Water District; Dan Kroll, HACH HST; Kathy Martel, Economic and Engineering Services; Pankaj Parehk, LA Department of Water and Power; Paul Schwartz, USC Foundation for Cross-Connection Control and Hydraulic Research; and Walter J. Weber, Jr., University of Michigan. We also thank all those who took time to share with us their perspectives and wisdom about the various issues affecting the water resources research enterprise. The Committee was ably served by the staff of the Water Science and Technology Board and its director, Stephen Parker. Study director Laura Ehlers kept the Committee on task and on time, provided her own valuable insights which have improved the report immeasurably, and did a superb job of organizing and editing the report. Ellen de Guzman provided the Committee with all manner of support in a timely and cheerful way. This report would not have been possible without the help of these people. This report has been reviewed in draft form 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 institution in making its 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 review comments and draft manuscript

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Drinking Water Distribution Systems: Assessing and Reducing Risks remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: Gunther F. Craun, Gunther F. Craun and Associates; Stephen Estes-Smargiassi, Massachusetts Water Resources Authority; Timothy Ford, Montana State University; Jerome B. Gilbert, J. Gilbert, Inc.; Gregory J. Kirmeyer, HDR; Michael J. McGuire, McGuire Environmental Consultants, Inc.; Danny D. Reible, University of Texas; Philip C. Singer, University of North Carolina; and James Uber, University of Cincinnati. Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions and recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by Edward Bouwer, Johns Hopkins University. Appointed by the National Research Council, he was 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 institution. Vernon Snoeyink, Committee Chair

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Drinking Water Distribution Systems: Assessing and Reducing Risks Contents     SUMMARY,   1 1   INTRODUCTION,   15      Introduction to Water Distribution Systems,   17      Distribution System Integrity,   39      Impetus for the Study and Report Roadmap,   40      References,   43 2   REGULATIONS, NON-REGULATORY APPROACHES, AND THEIR LIMITATIONS,   47      Regulatory Environment,   47      Limitations of Regulatory Programs,   70      Voluntary and Non-regulatory Programs that Influence Distribution System Integrity,   73      Conclusions and Recommendations,   82      References,   83 3   PUBLIC HEALTH RISK FROM DISTRIBUTION SYSTEM CONTAMINATION,   87      Introduction to Risk,   87      Evidence from Pathogen Occurrence Measurements,   92      Evidence from Outbreak Data,   103      Epidemiology Studies,   112      Risks from Legionella,   125      Conclusions and Recommendations,   130      References,   132 4   PHYSICAL INTEGRITY,   142      Factors Causing Loss of Physical Integrity,   144      Consequences of a Loss in Physical Integrity,   154      Detecting Loss of Physical Integrity,   162      Maintaining Physical Integrity,   170      Recovering Physical Integrity,   180      Conclusions and Recommendations,   186      References,   187

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Drinking Water Distribution Systems: Assessing and Reducing Risks 5   HYDRAULIC INTEGRITY,   192      Factors Causing Loss of Hydraulic Integrity,   194      Consequences of a Loss in Hydraulic Integrity,   198      Detecting Loss of Hydraulic Integrity,   203      Maintaining Hydraulic Integrity,   206      Recovering Hydraulic Integrity,   212      Conclusions and Recommendations,   216      References,   218 6   WATER QUALITY INTEGRITY,   221      Factors Causing Loss of Water Quality Integrity and their Consequences,   221      Detecting Loss of Water Quality Integrity,   237      Maintaining Water Quality Integrity,   247      Recovering Water Quality Integrity,   252      Conclusions and Recommendations,   256      References,   258 7   INTEGRATING APPROACHES TO REDUCING RISK FROM DISTRIBUTION SYSTEMS,   269      Monitoring,   273      Distribution System Modeling,   290      Data Integration,   298      Feasibility of Adopting G200 for Small Systems,   303      How to Provide Incentives to Adopt G200,   304      Conclusions and Recommendations,   308      References,   310 8   ALTERNATIVES FOR PREMISE PLUMBING,   316      Key Characteristics of Premise Plumbing,   316      Gaps in Research and Monitoring,   323      Why Home Treatment Devices Are Not Always the Answer,   326      Policy Alternatives,   328      Conclusions and Recommendations,   334      References,   336     ACRONYMS,   341     APPENDIXES          APPENDIX A  Public Water Supply Distribution Systems: Assessing and Reducing Risks, First Report,   345      APPENDIX B  Committee Biographical Information,   386