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Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
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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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

THE NATIONAL ACADEMIES PRESS

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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.

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Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
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Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
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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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

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:

Page viii Cite
Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
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  1. —As background and based on available information, identification of trends relevant to the deterioration of drinking water in water supply distribution systems.

  2. —Identification and prioritization of issues of greatest concern for distribution systems based on review of published material.

  3. —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.

  4. —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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×
Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
×

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

Suggested Citation:"Front Matter." National Research Council. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks. Washington, DC: The National Academies Press. doi: 10.17226/11728.
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Protecting and maintaining water distributions systems is crucial to ensuring high quality drinking water. Distribution systems -- consisting of pipes, pumps, valves, storage tanks, reservoirs, meters, fittings, and other hydraulic appurtenances -- carry drinking water from a centralized treatment plant or well supplies to consumers’ taps. Spanning almost 1 million miles in the United States, distribution systems represent the vast majority of physical infrastructure for water supplies, and thus constitute the primary management challenge from both an operational and public health standpoint. Recent data on waterborne disease outbreaks suggest that distribution systems remain a source of contamination that has yet to be fully addressed. This report evaluates approaches for risk characterization and recent data, and it identifies a variety of strategies that could be considered to reduce the risks posed by water-quality deteriorating events in distribution systems. Particular attention is given to backflow events via cross connections, the potential for contamination of the distribution system during construction and repair activities, maintenance of storage facilities, and the role of premise plumbing in public health risk. The report also identifies advances in detection, monitoring and modeling, analytical methods, and research and development opportunities that will enable the water supply industry to further reduce risks associated with drinking water distribution systems.

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