PUBLIC WATER SUPPLY DISTRIBUTION SYSTEMS: ASSESSING AND REDUCING RISKS

FIRST REPORT

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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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report PUBLIC WATER SUPPLY DISTRIBUTION SYSTEMS: ASSESSING AND REDUCING RISKS FIRST REPORT 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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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report 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 Contact 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. Additional copies of this report are 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. International Standard Book Number 0-309-09628-6 Copyright 2005 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.

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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report 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. 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. 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. Bruce M. Alberts and Dr. Wm. A. Wulf are chair and vice-chair, respectively, of the National Research Council. www.national-academies.org

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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report 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, Shaw Environmental and Infrastructure, Inc., Cincinnati, Ohio Marc A. Edwards, Virginia Polytechnic and State University, Blacksburg Mark W. LeChevallier, American Water Corporation, 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, Sacramento Gary A. Toranzos, University of Puerto Rico, San Juan 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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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report WATER SCIENCE AND TECHNOLOGY BOARD R. RHODES TRUSSELL, Chair, Trussell Technologies, Inc., Pasadena, California MARY JO BAEDECKER, U.S. Geological Survey (Retired), Vienna, Virginia GREGORY B. BAECHER, University of Maryland, College Park JOAN G. EHRENFELD, Rutgers University, New Brunswick, New Jersey DARA ENTEKHABI, Massachusetts Institute of Technology, Cambridge, Massachusetts GERALD E. GALLOWAY, Titan Corporation, Reston, Virginia PETER GLEICK, Pacific Institute for Studies in Development, Environment, and Security, Oakland, California CHARLES N. HAAS, Drexel University, Philadelphia, Pennsylvania KAI N. LEE, Williams College, Williamstown, Massachusetts CHRISTINE L. MOE, Emory University, Atlanta, Georgia ROBERT PERCIASEPE, National Audubon Society, New York, New York JERALD L. SCHNOOR, University of Iowa, Iowa City LEONARD SHABMAN, Resources for the Future, Washington, DC KARL K. TUREKIAN, Yale University, New Haven, Connecticut HAME M. WATT, Independent Consultant, Washington, DC CLAIRE WELTY, University of Maryland, Baltimore County JAMES L. WESCOAT, JR., University of Illinois, Urbana-Champaign Staff STEPHEN D. PARKER, Director LAURA J. EHLERS, Senior Staff Officer JEFFREY W. JACOBS, Senior Staff Officer WILLIAM S. LOGAN, Senior Staff Officer LAUREN E. ALEXANDER, Staff Officer STEPHANIE E. JOHNSON, Staff Officer M. JEANNE AQUILINO, Financial and Administrative Associate ELLEN A. DE GUZMAN, Research Associate PATRICIA JONES KERSHAW, Study/Research Associate ANITA A. HALL, Administrative Assistant DOROTHY K. WEIR, Senior Project Assistant

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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report 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 suitable pressure, and failure to do so is a serious system deficiency. Water quality may degrade during water 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, improperly maintained storage facilities, and other factors. 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, but 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. Our nation’s distribution systems are aging and becoming more vulnerable to main breaks and leaks, possibly because they are underground and out of sight, and thus it is easy to delay distribution system investment when budgets are considered. There is an urgent need for new research 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 study of the Water Science and Technology Board of the National Research Council (NRC) was undertaken at the request of the U.S. Environmental Protection Agency (EPA). The purpose of this report is to: Identify trends relevant to the deterioration of drinking water quality in water supply distribution systems, using available information, and Identify and prioritize issues of greatest concern for distribution systems based on review of published material. This first report was requested by the EPA, as it considers revisions to the Total Coliform Rule in 2005. It will be followed in about 18 months by a more comprehensive final report that evaluates different approaches to characterization of public health risks posed by water-quality deteriorating events, identifies and evaluates the effectiveness of relevant existing codes and regulations, and identifies 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. Advances in detection, monitoring and modeling, analytical methods, information needs

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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report 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 will also be addressed. This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with the 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 of 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: Gunther F. Craun, Craun and Associates, Virginia; Jerry Ongerth, East Bay Municipal Utility District, California; Jerald L. Schnoor, The University of Iowa, Iowa; R. Rhodes Trussell, Trussell Technologies, Inc., Califonia; and Jack Wang, Louisville Water Company, Kentucky. 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 Edward Bouwer of the Johns Hopkins University. Appointed by the NRC, 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. Vernon Snoeyink, Chair

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Public Water Supply Distribution Systems: Assessing and Reducing Risks - First Report Contents 1   INTRODUCTION   1 2   TRENDS RELEVANT TO THE DETERIORATION OF DRINKING WATER IN DISTRIBUTION SYSTEMS   4      Distribution Pipe Age and Replacement Rates   4      Waterborne Disease Outbreaks   6      Changes in the United States Population   7      Use of Bottled Water and Household Water Treatment Devices   8 3   HIGHEST PRIORITY ISSUES   10      Cross Connections and Backflow   11      New and Repaired Water Mains   12      Finished Water Storage   14      Additional Issues of Concern   15 4   MEDIUM PRIORITY ISSUES   19      Biofilm Growth   19      Loss of Residual via Water Age and Nitrification   20      Low Pressure Transients and Intrusion   22 5   LOWER PRIORITY ISSUES   24      Other Effects of Water Age   25      Other Effects of Nitrification   25      Permeation   26      Leaching   27      Additional Issues of Concern   28 6   SUMMARY   30     REFERENCES   35 APPENDIX A   Committee Biographical Information   43

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