UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C. 20460

OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD

March 19, 2010

EPA-SAB-10-004

The Honorable Lisa P. Jackson

Administrator U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, N.W. Washington, DC 20460

Subject: Review of EPA’s Supporting Analysis for Revisions of the Total Coliform Rule

Dear Administrator Jackson:

The Total Coliform Rule (TCR) was published in 1989 and became effective in 1990. The TCR requires routine sampling by all public water systems (PWSs) to monitor for the presence of total coliforms in th e distribution system. The monito ring of total coliforms is used as an indicator of the adequacy of water treatment and the integr ity of the distribution system. The TCR is mandated by law to be reviewed ev ery six years as part of the existing drinking water regulations requiring revisions to impr ove/maintain public health protection. In preparation for the TCR revisions, EPA assemble d a committee of stakeholders that met over several months to address the TCR objectives and enhance the approach for protecting public health. As a result of these efforts, an Ag reement in Principal (AIP) which takes a more proactive approach to identifyi ng and fixing problems was developed. The TCR revisions are intended to improve the effec tiveness of monitori ng requirements by balancing public health gains from proactive find-and-fix requirements with reduced sampling requirements. Under the revised TCR, TC-positive sampling results would prompt an assessment to identify sanitary defects instead of having a Maximum Contamin ant Level Goal/Maximum Contaminant Level (MCLG/MCL) for TC.

In response to a request from EPA’s Office of Water, the Science Advisory Board (SAB) convened the Drinking Water Committee with add itional experts from the Board to conduct a review of EPA's proposed revision of the To tal Coliform Rule (rTCR) . The SAB committee during their deliberations examined the supporti ng analysis, AIP and draft chapters of the proposed rTCR. Specifically the SAB was asked to comment on:

(1) the statistical analysis of the monitoring data which were used to estimate the positive result rates for total coliform (TC) and E. coli (EC) samples and predict the underlying baseline;(2) the list of corrective actions as describe d by the EPA that PWSs will implement and the percentage of systems that will implement certain types of corrective actions; (3) the methodology and assumptions used to estima te the net regulatory impacts of the current TCR (with and without the effects of other EPA water regulations) as compared to the recommendations contained in the Agreement in Principle (AIP) or the Alternative Analysis (AA) which has more frequent routine m onitoring requirements than the AIP; and (4) the use of the reduction in E. coli- and TC-positive sample results and acute violations as an

indicator of benefits.

In general, the Committee was impressed by the work the Agency undertook. The Agency obviously did a great deal of work and put a significant amount of thought into making use of the limited amount of data. The Ag ency’s engagement with stakeholders and development of the AIP which addr esses goals for improvement and research needs was laudable. The Committee, however, also found that there were several areas that can be enhanced; therefore, in their report, th ey provide a number of recommenda tions that are aimed at making the rTCR more transparent and improve the scientif ic basis for the proposed revisions. While a more detailed description of th e technical recommendations is cont ained in the body of the report, the key points and recommendations are highlighted below.

In response to the first charge question, the Committee found that while the Agency’s statistical analysis of the T CR data from monitoring samples used to estimate the underlying baseline of TC- and EC- positive result rates was reasonable, it would benefit from some refinements and further explanati on. The Committee suggests that some of the key issues should be further explored through sensitivity analyses. In addition to the Agency’s current analysis, these sensitivity analyses would provide a more robust basis for predicting and describing TCand EC- positive result rates.

In response to the second charge questi on, the Committee found the types of corrective actions that systems would implement was r easonable as described by the Agency. The Committee recommends that the Agency explain how this list of corrective actions was compiled. The Agency, through its discussion with state representatives, has estimated that only 10% of the small systems are able to find the cause of TC- or EC- positive samples and as a result will take

corrective action. The Committee believes that the rTCR should id eally be revised and designed, so that a larger percentage of small systems would take corrective actions that result in long-term benefits. Since systems may take corrective ac tions without knowing the exact cause, such as implementation of a flushing program, the Committ ee recommends that the sensitivity analysis use a wider range of implementa tion of corrective actions up to around 50%, especially after a more rigorous examination of the system. Conversely, the Committee questions whether the benefits of flushing will result in reduced risks for multiple years as used in the model, since PWSs may take actions to correct sanitary defect s, yet still continue to have TC-positive results for a period of time.

In response to the third charge question, the Committee believes that a more robust database than the current six-ye ar data, that was specifically a nd voluntarily obtained and used in the impact analysis by the Agency, is required to address the long list of assumptions. The Committee recommends that the impact analysis and discussion should include identifying and

iisummarizing all the variables with known modeling distributions. It should also be noted that until more data are available, the Agency’s model may be used to establish a reference baseline, but should not be used as a predictive tool. The Committee also noted that an increased risk of

waterborne disease outbreaks ma y occur as a result of the propos ed reduced monitoring strategy and therefore, the anticipated savings in the a nnual national costs for the detection assays may not be very significant. Furthermore, once a PW S is placed in the reduced monitoring regimen, it is highly unlikely, unless the sanitary defect is egregious, that the system will be triggered into more frequent sampling. The Committee is concerned that TC- or EC- positive sample results will not be detected in a timely fashion by a quarterly or annual sampling plan. Overall, the AA with its more frequent monitoring requirement s appears to address public health protection sooner in time than the AIP proposed implementation.

In responding to the forth charge questi on, the Committee felt that because of the difficulties in linking TC- and EC- positive results to adverse human health outcomes, it is equally difficult to determine whether measurable h ealth-related benefits c ould be attributable to the reductions in monitoring violations (pos itive results). TC monitoring results are not effective

sole endpoints for measuring benefits. The Agency’s proposal of using TC as part of an overall treatment technique evaluation where sanitary de fects are identified and corrected as result of TC-positive sampling results instead of having an MC LG/MCL for TC, is seen as a positive step

forward. The Committee recommends that other i ndicators should also be considered since TC is not an adequate measure of health risk. While E.coli is viewed as a more appropriate measure of risk of enteric disease, it does not capture the health risks from other pathogens, such as Legionella , for example. Other measures, includi ng structural and hydraulic integrity of distribution systems, have been recently consid ered in a report by the National Research Council and may provide valuable supplemental informati on on health risk associ ated with distributed

water.

The SAB appreciates the opportunity to provide EPA w ith advice on this important subject. We look forward to r eceiving the Agency’s response.

Sincerely,

/Signed/ /Signed/

Dr. Deborah L. Swackhamer, Chair Dr. Joan Rose, Chair EPA Science Advisory Board SAB Drinking Water Committee

iiiNOTICE

This report has been written as part of the ac tivities of the EPA Science Advisory Board, a public advisory committee providing extramural scientific information and advice to the Administrator and other officials of the Environmental Protection Agency. The Board is structured to provide balanced, expert assessment of scientific matters related to problems facing the Agency. This report has not been reviewed for approval by the Agency and, hence, the contents of this report do not necessarily represent the views and policies of the Environmental Protection Agency, nor of other agencies in the Executive Branch of the Federal government, nor does mention of trade names or commercial products constitute a recommendation for use. Reports of the EPA Science Advisory Board are posted on the EPA Web site at: http://www.epa.gov/sab

.

iv

### U.S. Environmental Protection Agency Science Advisory Board Drinking Water Committee Augmented for the R eview of EPA's Supporting Analysis for Revi sions of the Total Coliform Rule

CHAIR

Dr. Joan B. Rose , Professor and Homer Nowlin Chair for Water Research, Department of Fisheries and Wildlife, Michigan St ate University, East Lansing, MI

MEMBERS

Dr. Mark Borchardt* , Director, Public Health Microb iology Laboratory, National Farm Medicine Center, Marshfield Clinic Research Foundation, Marshfield, WI

Dr. John (Jack) Colford , Professor, Division of Public Health, Biology & Epidemiology, School of Public Health, Universi ty of California, Berkeley, CA

Dr. Penelope Fenner-Crisp , Independent Consultant, North Garden, VA

Dr. Joseph R. Landolph, Jr. , Associate Professor, Molecu lar Microbiology and Immunology and Pathology, Keck School of Medicine and As sociate Professor of Molecular Pharmacology and Pharmaceutical Science, School of Phar macy, and Member, USC/Norris Comprehensive Cancer Center, University of Southe rn California, Los Angeles, CA

Dr. Desmond F. Lawler , Bob R. Dorsey Professor of E ngineering, Department of Civil, Architectural and Environmental Engineer ing, University of Texas, Austin, TX

Dr. Christine Moe , Eugene J. Gangarosa Professor of Safe Water and Sanitation, Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, GA

Dr. Christine Owen , Water Quality Assurance Officer, Tampa Bay Water, Clearwater, FL

Dr. Richard Sakaji , Manager, Planning and Analysis fo r Water Quality, East Bay Municipal Utility District, Oakland, CA

Dr. Gary Sayler , Beaman Distinguished Professo r of Microbiology, and Ecology and Evolutionary Biology, Director of the Joint Inst itute for Biological Sciences and Director of the Center for Environmental Biotechnology, Oa k Ridge National Laboratory, University of

Tennessee

Dr. Gina Solomon , Senior Scientist, Health and E nvironment Program, Natural Resources Defense Council, San Francisco, CA

vMs. Susan Teefy , Principle Engineer, Water Quality and Treatment Solutions, Inc., Canoga Park,

CA

Dr. Lauren Zeise , Chief, Reproductive and Cancer Hazard Assessment Branch, Office of Environmental Health Hazard Assessment, Ca lifornia Environmental Protection Agency, Oakland, CA

* provided written comments but did not attend the face-to-face meeting

SCIENCE ADVISORY BOARD STAFF

Dr. Sue Shallal , Designated Federal Officer, 1200 Pe nnsylvania Avenue, Washington, DC, Phone: 202-343-9977, Fax: 202-233-0643, (shallal.suhair@epa.gov)

vi

### U.S. Environmental Protection Agency Science Advisory Board

CHAIR

Dr. Deborah L. Swackhamer , Professor and Charles M. Denny, Jr., Chair in Science, Technology and Public Policy and Co-Director of the Water Resources Center, Hubert H. Humphrey Institute of Public Affairs, University of Minnesota, St. Paul, MN

SAB MEMBERS

Dr. David T. Allen , Professor, Department of Chemical Engineering, University of Texas, Austin, TX

Dr. Claudia Benitez-Nelson , Associate Professor, Department of Earth and Ocean Sciences and Marine Science Program, University of South Carolina, Columbia, SC

Dr. Timothy Buckley , Associate Professor and Chair, Division of Environmental Health Sciences, College of Public Health, Th e Ohio State University, Columbus, OH

Dr. Thomas Burke , Professor, Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD

Dr. Deborah Cory-Slechta , Professor, Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, NY

Dr. Terry Daniel , Professor of Psychology and Natural Resources, Department of Psychology, School of Natural Resources, University of Arizona, Tucson, AZ

Dr. George Daston , Victor Mills Society Research Fe llow, Product Safety and Regulatory Affairs, Procter & Gamble, Cincinnati, OH

Dr. Costel Denson , Managing Member, Costech Technologies, LLC, Newark, DE

Dr. Otto C. Doering III , Professor, Department of Agricu ltural Economics, Purdue University, W. Lafayette, IN

Dr. David A. Dzombak , Walter J. Blenko Sr. Professor , Department of Civil and Environmental Engineering, College of Engin eering, Carnegie Mellon University, Pittsburgh,

PA

Dr. T. Taylor Eighmy , Vice President for Research, Office of the Vice President for Research, Texas Tech University, Lubbock, TX

Dr. Elaine Faustman , Professor, Department of Environmental and Occupational Health Sciences, School of Public Hea lth and Community Medicine, Univ ersity of Washington, Seattle,

WA

viiDr. John P. Giesy , Professor and Canada Research Chair, Veterinary Biomedical Sciences and Toxicology Centre, University of Saskat chewan, Saskatoon, Saskatchewan, Canada

Dr. Jeffrey Griffiths , Associate Professor, Department of Public Health and Community Medicine, School of Medicine, Tufts University, Boston, MA

Dr. James K. Hammitt , Professor, Center for Risk Anal ysis, Harvard University, Boston, MA

Dr. Rogene Henderson , Senior Scientist Emeritus, Lovelace Respiratory Research Institute, Albuquerque, NM

Dr. Bernd Kahn , Professor Emeritus and Associate Dire ctor, Environmental Radiation Center, School of Mechanical Engineering, Geor gia Institute of Technology, Atlanta, GA

Dr. Agnes Kane , Professor and Chair, Department of Pathology and La boratory Medicine, Brown University, Providence, RI

Dr. Nancy K. Kim , Senior Executive, New York Stat e Department of Health, Troy, NY

Dr. Catherine Kling , Professor, Department of Economics, Iowa State University, Ames, IA

Dr. Kai Lee , Program Officer, Conservation and Scie nce Program, David & Lucile Packard Foundation, Los Altos, CA

Dr. Cecil Lue-Hing , President, Cecil Lue-Hing & Assoc. Inc., Burr Ridge, IL

Dr. Floyd Malveaux , Executive Director, Merck Childhood Asthma Network, Inc., Washington,

DC

Dr. Lee D. McMullen , Water Resources Practice Leader, Snyder & Associates, Inc., Ankeny,

IA

Dr. Judith L. Meyer , Distinguished Research Professo r Emeritus, Odum School of Ecology, University of Georgia, Lopez Island, WA

Dr. Jana Milford , Professor, Department of Mechanical Engineering, University of Colorado, Boulder, CO

Dr. Christine Moe , Eugene J. Gangarosa Professor, Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, GA

Dr. Eileen Murphy , Manager, Division of Water S upply, New Jersey Department of Environmental Protection, Trenton, NJ

viiiDr. Duncan Patten , Research Professor , Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT

Dr. Stephen Polasky , Fesler-Lampert Professor of Ecological/Environmental Economics, Department of Applied Economics, Univ ersity of Minnesota, St. Paul, MN

Dr. Stephen M. Roberts , Professor, Department of Physiol ogical Sciences, Dir ector, Center for Environmental and Human Toxicology, Univer sity of Florida, Gainesville, FL

Dr. Amanda Rodewald , Associate Professor, School of E nvironment and Natural Resources, The Ohio State University, Columbus, OH

Dr. Joan B. Rose , Professor and Homer Nowlin Chair for Water Research, Department of Fisheries and Wildlife, Michigan St ate University, East Lansing, MI

Dr. Jonathan M. Samet , Professor and Flora L. Thornton Chair, Department of Preventive Medicine, University of Southern California, Los Angeles, CA

Dr. James Sanders , Director and Professor, Skidaway Institute of Oceanography, Savannah,

GA

Dr. Jerald Schnoor , Allen S. Henry Chair Professor, De partment of Civil and Environmental Engineering, Co-Director, Center for Global a nd Regional Environmental Research, University of Iowa, Iowa City, IA

Dr. Kathleen Segerson , Professor, Department of Economics , University of Connecticut, Storrs,

CT

Dr. V. Kerry Smith , W.P. Carey Professor of Economics , Department of Economics , W.P Carey School of Business , Arizona State University, Tempe, AZ

Dr. Herman Taylor , Professor, School of Medicine, University of Mississippi Medical Center, Jackson, MS

Dr. Barton H. (Buzz) Thompson, Jr. , Robert E. Paradise Professor of Natural Resources Law at the Stanford Law School and Perry L. McCarty Director, Woods Institut e for the Environment, Stanford University, Stanford, CA

Dr. Paige Tolbert , Associate Professor, Department of Environmental and Occupational Health, Rollins School of Public Health, Emory University, Atlanta, GA

Dr. Thomas S. Wallsten , Professor and Chair, Department of Psychology, University of Maryland, College Park, MD

Dr. Robert Watts , Professor of Mechanical Engineering Emeritus, Tulane University, Annapolis, MD

ixSCIENCE ADVISORY BOARD STAFF

Mr. Thomas Miller , Designated Federal Officer, 1200 Pennsylvania Avenue, NW 1400F, Washington, DC

xACRONYMS

AA Alternative Analysis

AIP Agreement in Principle

CWS Community Water System

DWC Drinking Water Committee

EA Economic Assessment

EC Escherichia coli (E. Coli)

EPA Environmental Protection Agency

GW Ground Water

GWDR Ground Water Disinfection Rule

HPC Heterotrophic Plate Count

MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

PCR Polymerase Chain Reaction

PWS Public Water System

rTCR revised Total Coliform Rule

SAB Science Advisory Board

SDWIS/FED Safe Drinking Water Info rmation System /Federal Version

SW Surface Water

SWTR Surface Water Treatment Rule

TC Total Coliform

TCR Total Coliform Rule

TCRDSAC Total Coliform Rule / Dist ribution System Advisory Committee

TT Treatment Technique

TWG Technical Working Group

UA Uncertainty Analysis

xixii TABLE OF CONTENTS

EXECUTIVE SUMMARY ............................................................................................................ 1

BACKGROUND ON THE REVISI ONS TO THE TOTAL COLIFORM RULE (TCR) ............. 4 CHARGE QUESTIONS TO THE COMMITTEE......................................................................... 5

RESPONSE TO THE CHARGE.................................................................................................... 6 DWC’s Overall Critique of Revisions to the Total Coliform Rule (TCR)................................. 6 Charge Question 1....................................................................................................................... 8 Assumptions to Justify and Explain........................................................................................ 9 Explaining and Disentangling Un certainty and Variability.................................................. 10 Criterion for Significance a nd Combining Data Sets ........................................................... 11 Charge Question 2..................................................................................................................... 11 Analysis of Percentage of System s Implementing Corrective Action.................................. 13 Charge Question 3..................................................................................................................... 15 Safe Drinking Water Information System /Feder al Version and 6-year Review Databases 16

Corrective Actions ............................................................................................................. ... 18 Alternatives and Suggestions................................................................................................ 20 Charge Question 4..................................................................................................................... 22 TC as an appropriate endpoint .............................................................................................. 22 Reductions in acute violations as appropr iate endpoints for informing benefits.................. 23 Added value of the proposed revisions................................................................................. 23 Other analyses or endpoints that might be considered.......................................................... 24

### EXECUTIVE SUMMARY

EPA’s Office of Water (OW) requested that the Science Advisory Board (SAB) Drinking Water Committee (DWC) review its draft supporti ng analysis in preparation for revising the Total Coliform Rule (TCR). The Total Coliform Ru le (TCR) was established in 1989 and is one of the primary national regulations governing th e microbiological quality of treated drinking

water in the US. The Total Coliform Rule addr esses the monitoring of coliform bacteria and

E.coli , and is an important element in the pr otection against water borne diseases via demonstration of appropriate di sinfection and groundwater protecti on. As the Agency embarks on revising the TCR, it has expended a great amount of time and effort to include stakeholder inputs, setting up mee tings with state regulators, wa ter utilities, local governments, environmental advocates, public health profession als, consumer advocates, Indian tribes, and others through a FACA process. As a result of these discussions, an Agreement in Principle (AIP) was developed that is being used as the foundation for the proposed Revised Total Coliform Rule (rTCR). This has included a proposed new, more proactive approach for identifying sanitary defects and incorrect monitoring practices.

The DWC of the EPA Science Advisory Boar d met in June 2009 to deliberate on four charge questions raised by OW to address the draft supporting analysis. These questions focused on: (1) the underlying statistical analysis of the TCR monitoring data used to inform the prediction of the underlying ba seline total coliform and E. coli occurrence and violation rates, (2) the characterization of the types of corrective actions that systems will implement and the percentages of systems that will implement cer tain corrective actions, (3) the methodology and assumptions used to predict the net impacts in total coliform-positive (TC+) samples, E. coli

positive (EC+) samples, acute violations, assessments, and corrective actions between the current TCR (with and without the effects of the Ground Water Rule), the AIP, and the Alternative Analysis, and (4) the use of reduction in E. coli and TC occurrence and acute violations as endpoints for informing benefits.

The text of the complete rTCR was not available to the Committee, and the focus was on the supporting analyses and drafts of key chapte rs. The members relied on and examined the text of the AIP and several of the rTCR Chapters for their evaluation and to address the charge questions. This Executive Summary highlights the outcome of the Committee’s deliberations

and the recommendations.

1. The Underlying Statistical Analysis

The Committee commends the Agency for all the work and analyses undertaken. The Agency performed a partial sensitivity analysis wh ich increases confidence in the assessment. There was only a limited amount of data from the Safe Drinking Water Information System – Federal Version (SDWIS/FED) and in the six-year review databases used in the Economic Analysis that was deemed useful for the rTCR an alyses and the Agency did a good deal of work and put a significant amount of thought and effort into addressing those segments of the database that would be useful. The work of the Agency toward engagement with stakeholders and

1development of the Agreement in Principle whic h addresses goals for improvement and research

needs was laudable.

The Committee found that the Agency’s statis tical analysis of the TCR monitoring data used to inform the prediction of th e underlying baseline total coliform and E. coli occurrence and violation rates is reasonable but would benefit from some refinements and further explanation. The Agency is commended for the development and application of a statistical approach to a large, complex dataset, thereby enabling the anal ysis of a difficult and diverse problem. The Committee had considered recommending variou s improvements on the analytical work done, but noted that the proposed changes were unlikel y to show a substantially different result and would involve a significant effort over a prot racted period. Instead, the Committee suggested that some of the key issues (including seasona lity and systems within specific classes and the difference in their average characteristics regardin g positive TC rates) should be further explored through limited sensitivity analyses. The Commit tee believes that these additional analyses, together with the work already performed, will provide a sufficient basis for adequate predictions and descriptions of total coliform and E. coli occurrence and violation rates.

The Committee, after lengthy discussions with Agency representatives, concluded that while the analysis was well done, there was, how ever, insufficient background explanation of the assumptions and methods used. The Committee wa s unable to ascertain whether the analysis was reasonable solely by readi ng the materials provided. For exam ple, the Data Quality Report which was referenced through out the document wa s not available to the Committee. Several assumptions were not stated or were not clearly explained. The approach was not completely described, thus the analysis and critical assumptions are in need of further justification and this

needs to be included in the rTCR as it moves forward.

2. The Characterization of the Types of Corrective Actions

The Committee agreed that the Agency’s ch aracterization of the types of corrective actions that systems would impl ement was reasonable and complete. Corrective actions are closely aligned with the assessments that must follow positive TC/EC test results during routine system monitoring. The Committee recommends the Ag ency explain how it compiled this list of corrective actions, and where the information came from (i.e., from expert discussions in the Technical Workgroup of the TCRDSAC, and from information provided by utilities). In working with states, the Agency fo und that 10% or less of the utilities were able to find the cause

of the coliform or E.coli occurrence and as a result take co rrective actions. Thus, the Agency estimated that only 10% of the small systems will take corrective action which represents only a

modest benefit from the current rule. This is without the impact of the Ground Water Rule

. However, there are corrective actions that ma y be undertaken without knowing the exact cause, such as implementation of a flushing program. Therefore, the Committ ee recommends that the sensitivity analysis use a wider range of co rrective action implementation including corrective actions up to and including 50%, es pecially after a Level 2 assessm ent. Disinfection seemed to

be the main corrective action consider ed. If this is correct, then, th is fact should be stated, and if it is not, then the other corrective action opti ons, their costs, and the results of sensitivity analyses should be clearly desc ribed. The Committee also ques tioned whether the benefits of flushing would result in reduced risk s for as long as several years (as used in the model) unless a

2routine flushing program is implemented, if so- this should be clarified. Such assumptions should also have justification.

3. The Methodology and Assumptions Used to Predic t the Net Impacts as part of the Economic Analysis

The framework and methodology of the Economic An alysis (EA) appear to be consistent

with the USEPA Guidelines for Economic Anal ysis (2000). The US EPA guideline should be

referenced so that readers understand where th e framework for this EA originates and better understand the reasoning behind the rTCR EA stru cture. The Committee recommends that an analysis and discussion in the EA would be tter inform policy makers by identifying and summarizing all the variables with known distribu tions. Further, it should also be clearly noted that the EA model was developed as a reference baseline and should not be used as a predictive tool. Ultimately, the Agency will need a far more robust database than th e six-year data review database used in the EA to improve the reliability of the model. The number of assumptions can be reduced by enhancing the data collection process.

While a reduction in the annual national co sts is likely to result from the reduced monitoring strategy, it is unclear fr om the analysis whether this may be offset by an increased

risk of waterborne disease outbr eaks or endemic waterborne diseas e. The DWC is skeptical that the monitoring frequencies for small systems (< 1,000 people) will provide a change to the TCR that improves public health protection. The DWC is not generally s upportive of decreased monitoring. Overall, the Alterna tive Analysis (AA) appears to a ddress and protect public health sooner in time than the AIP proposed implementation.

4. The Use of Reduction in E. coli and TC Occurrence and Acute Violations as Appropriate Endpoints

The Committee found it difficult to identify spec ific measurable health-related benefits attributable to the suggested revisions which w ill be part of the Total Coliform Rule. From a public health standpoint, the Committee felt that measuring reductions in total coliforms (TC)

and E. coli (EC) occurrences are not effective sole endpoints for informing benefits because of the difficulties in linking these indicators to adverse human health outcomes. The Committee agrees with the Agency’s proposal to use TC as part of an overall treatment technique evaluaton and sees this as a positive step forward. In stead of having an MCLG /MCL for TC, TC-positive sampling results would trigger an assessment to identify sanitary defects. Implementation of appropriate corrective action is e xpected to decrease waterborne disease and occurrence of acute violations. However, several ot her indicators could be considere d, as TC, in itself, is not an adequate measure of health risk. While E.coli is viewed as more appropriate measure of risk of enteric disease, it does not capture the health risks from other pathogens (e.g., Legionella ). Other measures may provide valuable supplemental information on health risks from distributed water including structural and hydraulic integrity of dist ribution systems.

3

### BACKGROUND ON THE SUPPLEMENTS TO FUTURE REVISIONS OF THE TOTAL COLIFORM RULE (TCR)

The Total Coliform Rule (TCR), established in 1989, is one of the primary national regulations governing the microbiol ogical quality of treated drinki ng water in the US. As such, it is an important element for prot ecting against waterborne disease. Each standard is mandated by law to be reviewed and revised, if appropriate, every six years as part of the existing drinking water regulations requiring revisions to improve /maintain public health protection, including the TCR. As part of the review and in order to revise the TCR, the Agency and its advisory

committees conducted a substantia l amount of work, which include d the evaluation of available data and research on aspects of distribution system s that may create risk to public health. The Agency also began working with stakeholders to address controls for cross connections and requirements for backflow prevention in dist ribution systems, as these are known to be associated with significant risks, but in some cas es, may be out of the water system’s direct line of control. (C. Rodgers-Jenkins, USEPA, Offi ce of Water, SAB teleconference presentation, 5/20/09).

The Agency began the review of the 1989 TCR in 2003. Based on stakeholder comments, the Agency prepared a series of white pape rs on the TCR and dist ribution system issues 1 (2006). In July 2007, the Agency establ ished the Total Coliform Rule/D istribution System Advisory Committee (TCRDSAC). The TCRDSAC consisted of fifteen members representing the Agency and state regulators, water uti lities, local governments, enviro nmental advocates, public health professionals, consumer advocates, and Indian tr ibes. The Agency charged the TCRDSAC with two major tasks; 1) provide th e Agency with recommendations on how best to revise the TCR, and 2) develop information and research needs to improve the understanding of the risks posed by distribution system issues. TCRDSAC then fo rmed a technical work group (TWG) to provide data analysis and information to contribute to th e discussion of the Committee. An Agreement in Principle (AIP) was developed as a result of these discussions, and the AIP is being used as the foundation for the proposed Revised Total Colifor m rule (rTCR). TCRDSAC met thirteen times between 2007 and 2008. Each representative on the TCRDSAC agreed to support the proposed rTCR components that reflect th e elements of the AIP.

Highlights of TCRDSAC recommendations are: 1) There will no longer be an MCLG/MCL for total coliforms (TC); 2) TC- and E. coli (EC) positive sampling results will trigger investigation (assessment), leading water managers to find the problem and fix it; 3) Monitoring on a quarterly and annual basis ma y be allowed for some small ground water systems; 4) Distribution system research and inform ation collection will need to be a priority; 5)

There will be an overall shift in focus from monitoring results that lead to public notification to monitoring results that trigger an assessment and corrective action. Benefits from these recommendations will lead to a more proactive a pproach to public hea lth protection which can

be instituted which should reduce co nfusion associated with the actions needed for TC violations. The Agency stated that it was committed to proposing a rule (rTCR) consistent with TCRDSAC

1 See USEPA, Office of Water, Total Colform Rule (TCR) and Distribution System Issue Papers Overview at the following URL: http://www.epa.gov//safewat er/disinfection/tcr/pdfs/issuepaper_tcr_overview.pdf

4recommendations. The initial rule will be proposed in 2011. The final rule will be proposed in 2012, and compliance with the final rule is expected in 2015.

The Agency’s recommendations toward the rT CR are to use TC as part of an overall treatment technique, where there is no MCLG /MCL for TC, but where TC-positive sampling results would trigger an assessmen t to identify sanitary defects. A sanitary defect finding would then trigger corrective action. A treatment technique (TT) viol ation would be assessed if the investigation or corrective action was not comple ted. The Agency would retain an MCLG = 0

for E. coli and the current MCL associated with pres ence of TC/EC. The Agency would not use fecal coliforms as a water quality indicator in this Rule, and there would be public notification

for TT or acute MCL violations.

In the AIP, for systems serving ≤ 1,000 people, there would be new criteria for both increased and reduced monitoring, a transition fro m the existing monitoring frequency unless the primacy agency determines otherwise and a d ecrease in the number of additional routine monitoring and repeat monitoring samples. Fo r systems serving > 1,000 people, there are no changes in routine monitoring but a decrease in repeat samples and the elimination of additional routine monitoring for systems serving ≤ 4,100 people.

As a principle of the assessments, the goal is that the rTCR would pro-actively enhance public health by identifying sanitary defects and incorrect monitoring practices. In this new scenario, the public water system (PWS) is responsible for the investigation which should ensure barriers are in place and effective. Two levels of assessment would be created based on the severity of the trigger, Level 1 and Level 2. The systems would be required to correct all sanitary defects found in the assessments. A TT vi olation would consist of: 1) failure to perform a Level 1 or 2 assessment when triggered, 2) failure to correct all sanitary defects identified in the assessment, and 3) failure to correct sanitary defects according to an agreed upon schedule. Four types of violations that n eed public notification are: 1) an E. coli MCL violation (Tier 1); 2) a treatment technique violation (Tier 2); 3) a routine monitoring violation (Tier 3); and 4) a reporting violation (Tier 4).

It should be noted that the data analysis to support the revisions to the TCR are based on current and historical water qua lity data and practices in th e United States. The SAB DWC comments are tailored specifically to those water quality data and practices.



### CHARGE QUESTIONS TO THE COMMITTEE

The Agency requests that the SAB Drinking Wate r Committee review the materials provided and provide recommendations in the areas specified in the charge questions. As the Committee considers the specific charge questions that follo w, it is asked to consider whether the overall approach that the Agency has taken to assess the impacts of rTCR is appropriate, given the availability of the information, and, if it is not, whether there are alternatives that might be

considered.

51. Is the underlying statistical analys is of the TCR monitoring data used to inform the prediction of the underlying baseline total coliform and E. coli occurrence and violation rates reasonable? If not, what changes or refinements might be appropriate?

2. Is the characterization of the types of correc tive actions that systems will implement and the percentages of systems that will implement certa in corrective actions reasonable? If not, what else might be considered?

3. Are the methodology and assumptions used to predict the net impact s in total coliformpositive (TC+) samples, E. coli -positive (EC+) samples, acute violations, assessments, and

corrective actions between the current TCR (with and without the effects of the Ground Water Rule), the AIP, and the Alternative Anal ysis reasonable? If not, what alternatives might be considered?

4. Are reduction in E. coli and TC occurrence and acute viol ations appropriate endpoints for informing benefits? Do they appropriatel y capture the added value of the proposed revisions? If not, what other analyses or endpoints might be considered?

The following attachments were included to facilitate the SAB discussions:

• Draft Supporting Analyses

• Baseline Conditions (Chapter 4)

• Occurrence and Predictive Model (Chapter 5)

• Benefits Analysis (Chapter 6)

• Cost Analysis (Chapter 7)

• Draft Technology and Cost Document

• Agreement in Principle

• Background on Current TCR and Rule Revi sions Development (presentation)

• Comparison of Current TCR Requirements with the AIP and Alternative Analysis (table)



### RESPONSE TO THE CHARGE

DWC’s Overall Critique of the Supporting Materi al, Analyses and Draft Chapters toward the Revision of the Total Coliform Rule (TCR)

The DWC evaluated the five TCRDSAC recommendations and found them to be appropriate overall. First, the total coliform (T C) has little relationship to fecal pollution and public health risk, and thus it is appropriate that there is no longer an MCLG/MCL for total coliforms (TC). The second recommendation, that TC- and E. coli- positive sampling results will trigger investigation (assessment), is intended to lead water managers to find the problem and fix it. This should place an emphasis on inve stigating and correcting th e deficiencies, rather than on just reporting them. The third reco mmendation, that monitoring on a quarterly and annual basis may be allowed for some small gr ound water systems, is appropriate as long as these systems have demonstrated the ability to maintain microbiological water quality and groundwater protection, particular ly during the rainy seasons. The fourth recommendation, that distribution system research and information collecti on need to be a priorit y, is also appropriate. The fifth recommendation, of an overall shift in focus from monitoring information that only result in public notification to monitoring information that trigger an assessment and corrective

6action, is a significant advancement if it is prope rly executed. It places the emphasis where it should be, on corrective action. The DWC agrees that benefits from this more proactive approach to public health protection should re duce confusion associated with what follow-up actions are necessary and taken for TC viola tions. However the DWC notes that the EPA analysis appears to assume a low rate of correc tive actions (10% of TC detection events), which appears to contradict these stated goals.

The Agency’s recommendations of using TC as part of an overall treatment technique, where TC-positive sampling results would trigger an assessment to identify sanitary defects instead of having an MCLG/MCL for TC, is seen as a positive step forward in principle. The fact that a sanitary defect finding would trigger correctiv e action is also very good and appropriately places more emphasis on remedial action. The DWC agrees that a treatment technique (TT) violation should be assessed if an investigatio n or corrective action was not completed. The DWC also agrees that th e Agency should retain an MCLG = 0 for E. coli , as well as the current MCL-associ ated with the absence of TC /EC , and not use fecal coliforms as indicators of water quality in this Rule. Ther e should be public notifica tion for any TT or acute

MCL violations.

For systems serving ≤ 1,000 people, there are new crite ria for increased and reduced monitoring, a transition with existing monitoring frequenc y unless the primacy agency

determines otherwise and a decr ease in number of additional routine monitoring and repeat monitoring samples. For systems serving > 1,000 people, there are no changes in routine monitoring but a decrease in rep eat samples and elimination of additional routine monitoring for systems serving ≤ 4,100 people. The DWC is skeptical that the monitoring frequencies for small systems (< 1,000 people) will provide a change to the TCR that improves public health protection. The DWC is not gene rally supportive of decreased mon itoring. According to the Agency’s document, the highest percentage of T CR violations occurs in the smaller systems; hence, it appears as though small systems are more vulnerable and are more likely to experience a waterborne outbreak. Thus, this vulner ability may be better captured with improved comprehensive assessments. The problems in the sanitation of these small water systems, which do not have substantial capital and person nel to monitor their systems comprehensively, may be best controlled only through a required monitoring scheme.

The DWC agrees that in the scenario pr oposed for the rTCR, the PWS should be responsible for assessment, and this should strength en their capacity to ensure barriers are in place and effective. DWC also agrees that there should be two levels of assessment, based on the severity of the trigger, Le vel 1 and Level 2, and that the sy stems should correct all sanitary

defects found in the assessments. A TT violation would consist of failure to perform a Level 1 and/or 2 assessment when triggered, failure to correct all sanitary de fects identified in the assessment, and failure to correct sanitary def ects according to an agreed upon schedule. The public notification continues to be important an d should include not only a description of the violation but also the necessary follow-up remedial actions. This would assist in alleviating public concerns that the PWS is not attending to th e problems. The four t ypes of violations that need public notification are: 1) an E. coli MCL violation (Tier 1) wh ich may be of immediate public health concern; 2) a treatment technique violation (Tier 2); 3) routine monitoring violation

7(Tier 3); and 4) a reporting violation (Tier 4). DWC agrees with these re visions as they would apply to the future TCR.

It appears from the table pr ovided to the DWC, entitled, “Comparison of Current TCR Requirements with the AIP and Alternative An alysis,” that the PWS can still do its own assessment (left to the discretion of the primacy agency; but the person doing the assessment is required to have specific qualifications, unlike a Le vel 1 Assessment), even if the PWS’s lack of action results in frequent Level 1 triggers that then lead to a Level 2 assessment. This could result in a public health risk th at may be unaddressed in a timely fa shion If the issue is raised to a Level 2 Assessment. the primacy agency shoul d be deeply involved.). The Drinking Water Committee (DWC) generally agrees that the a ssessment concept will orient the PWS toward action and that this will likely improve the microbiological quality of the drinking water

delivered.

Charge Question 1. Is the underlying statisti cal analysis of the TCR monitoring data used to inform the prediction of the und erlying baseline total coliform and E. coli occurrence and violation rates reasonable? If not, what changes or refinements might be appropriate?

The statistical analysis of the TCR monitori ng data is reasonable, and the Agency is commended for its systematic and thoughtful analysis of such a large dataset. The documentation of the statistical analysis in a draft Chapter 5, however, should be improved, which will address transparency and clarity. The Committee recommends that Chapter 5 be

revised with details which allow the reader to understand better what was done, and all key assumptions should be clearly stated and justif ied. The Committee also suggests that further sensitivity analyses be undertaken.

The Agency did a good job analyzing a diffi cult and diverse problem. This involved developing and applying a statistica l approach to a large, complex dataset. Positive samples for different classes of water systems were characterized and used for prediction. Water systems within a class were allowed to vary in their characteristics. The approach was reasonable and appears well executed. A significant amount of t hought went into structuring the problem and the analysis.

The Committee had considered recommending various improvements on the analytical work done, but noted that the proposed changes we re unlikely to show a substantially different result and would involve a significant effort over a protracted period with little added benefit. Instead, the Committee suggests that some of the key issues be further explored through a limited sensitivity analyses. The Committee ultimately fi nds that these additional analyses, together with the work already performed (with a few refinements discussed below), will provide a basis for adequate descriptions of total coliform and E. coli occurrence and violation rates.

In making these findings, the Committee notes, however, that the explanation of the analysis is deficient. The Committee was unable to ascertain whether the analysis was reasonable solely by reading the materials prov ided, including the draft Chapter 5, where the analysis is laid out. Several assumptions are not stated or are not clearly explained. The

8approach is not completely described, and the analysis and critical assumptions need further justification.

The Committee was only able to understand what was done as a result of the discussion during the meeting. The Committee members had to ask a number of clarifying questions to understand the analyses performed. EPA staff explaine d what was done and why. After hearing these explanations, the Committee was satisfied that the analyses performed were reasonable and,

with a few minor refinements noted belo w, adequate and, in fact, commendable.

The Committee recommends that Chapter 5 be revised to describe the analysis in

sufficient detail so that the reader can understa nd the basics of what was done. Assumptions should be stated clearly and justified. The key as sumptions that affect the entire analysis should be stated early in the chapter and better justified. Implicit as sumptions should be stated and explained. The basic elements of the analysis should be clearly described. As the chapter currently stands, the read er is left to use his or her judgmen t as to whether the assumptions are justified and what was done.

The Committee does recognize that the analys is performed is complex and somewhat difficult to explain, and that it ma y take extra effort than may typically be the case to make the chapter clear and understandable. It may help to have a number of technically facile, non-expert readers review the revised chapter to see whet her they understand the analysis, whether they could explain it to someone else based on what was written, and whether they find the analysis including assumptions adequately justifie d. Specific comments, suggestions and recommendations are given below.

Suggestion 1. Assumptions to Justify and Explain

The Committee found that the assumptions in the statistical analys is were not clearly presented and/or justified. Some examples of assumptions and procedures are provided below that would benefit from better explanation. These are given only as examples, and we leave it to the Agency staff to work through the document to make sure that all major assumptions are clearly articulated and adequately explained. Again, the Committee is recommending that the key assumptions be presented earl y, and that other minor ones are ex plained as they occur in the description of the anal ysis and results.

• It is not clearly stated that a main goal of the model fitting exercise is to get a characteristic distribution of probability of positive hits for each water system class, and that the distribution is repres enting how systems within the class vary from one another in that probability.

• There needs to be an explanation of the basic model structure. Exhibit 5.2 appears to be an attempt at showing how different parameters in the beta distribut ion are related to one another for different systems within a water syst em class. The title is very general, and the exhibit has no legend. Subscripts are us ed to indicate the different water systems within the class; however, the s ubscripts are not used anywhere else in the chapter. What

9would be a difficult concept to convey even with full annotation is totally incomprehensible. The figure also needs a more explanatory title. If the figure is retained, it needs to be expl ained in a figure legend and in the text. The Committee also

recommends the addition of another illustra tion to show data inputs and model outputs, with full accompanying annotation and description.

• The reason for assuming that seasonality does not impact the analysis should be discussed and justified, perhaps th rough a sensitivity analysis.

• There is a hierarchy to the analysis that is left unexplained. Each water system class has its own characteristic beta distribution. Yet, alpha and beta in the figure and text are not subscripted. In the text, the probability para meters, number of samples (binomial “N”s), positive samples (binomial “K”s), all have no subscript. In the figure, for example, subscripts were left out of equations (such as on p 5-7). This made it unclear that they were relevant to each individual system. While the use of subscripts can be avoided, the underlying assumptions need to be clear, e.g., be clearer about the fa ct that independent analyses (probability distribu tions) of the routine and repeat samples were performed.

Suggestion 2. Explaining and Disent angling Uncertainty and Variability

The Committee noted that the discussion of un certainty and variability was unclear. At times, it appeared that the terms uncertainty and variability were being used interchangeably. Both uncertainty and variability are an issue in the analysis as illustrated in the following example. Within a given system classification, wa ter systems can vary cons iderably in terms of whether they will test positive and in terms of thei r violation rates because some of the causes for TC positives are not under the control of the PWS. For some classes of systems, there may be a large number of systems within the class and the certainty regarding how much they vary from one another and the difference in their average ch aracteristics may be high . For other classes, there may be far fewer observations which may contribute to less certainty. The Committee

found that the document needed to be clearer in how these issues were handled and suggests that Chapter 5 and the analysis address the issue through further sensitivity analysis and in graphical presentations.

Chapter 5 could, for example, include a figure plotting positive occurrence rates for some different prototypical classes of systems. This would provide th e reader a visual representation for how systems can differ within a class. Chap ter 5 could also provide plots of the maximum likelihood estimate for mean positive occurrence for a system class and display the uncertainty in that estimate. Agency staff has developed some plots like this that could be annotated and included with proper explanation in the document. Plots that disentan gle uncertainty from variability would be helpful. On the basis of the discussion with Agency staff, the Committee believes that these plots have been done and that the analysis is fine in this regard, but the presentation is somewhat lacking.

The Committee recognizes that there are data gaps and that assumptions based on best professional judgment were made. Therefore, the Committee is not recommending a full Monte

10Carlo analysis of uncertainty; ra ther, we suggest the issue be explored in a limited way in a sensitivity analysis. The analysis can be quali tative or semi-quantitativ e and should explain how uncertainty in the beta distribution for classe s, where uncertainties are relatively large, may affect the ultimate result. The Agency stated th at uncertainties are greate st for classes with few observations, and that this is due to the fact that the actua l number of systems in the class is small. However, while this may be a reasonable rationale, it might also be due to one or two outliers

that skew the distribution. The Committee suggests that some simple calculations should adequately illustrate that the ove rall result is robust and the rationale has been tested rather than

assumed.

Suggestion 3. Criterion for Significance and Combining Data Sets

The Committee believes that the criterion for testing significance and for deciding to combine or not combine different data sets should be more explicitly stated and perhaps more rigorously done, including a statistical power test. In a number of places, the chapter asserts that systems do not significantly differ in the probability that they will test positive for total coliform. That finding is used to justify combining data sets for different types of systems. Figure 5.3 is the only attempt to explain this combining, and bo th the figure itself and the explanation of for combining data sets are weak.

In the Agency’s analysis, the criterion fo r deciding whether there is a significant difference in probabilities is based solely on whether there is a difference in the mean probabilities of a positive test result for the two systems being compared. However, some system types can have the same mean, yet the system s may vary within that class. An analysis of

a class of non-disinfected water systems may, for example, include a large number of systems on a pristine water source in a cold climate, and at the same time also include a large number of systems with a not so pristine source. The vari ance for this class can have a wide frequency distribution, but the mean may be the same as th at for another class that is more homogeneous but relatively pristine. Violatio ns may be more common in the fi rst class than the second. Thus, in addition to the mean, the variance should also be considered. The beta distributions for these two classes will differ. Therefore, an alternat ive criterion for combining could be based on the hypothesis that both systems have the same beta distribution.

Charge Question 2. Is the characterization of the type s of corrective actions that systems will implement, and the percentages of systems that will implement certain corrective actions, reasonable? If not, what else might be considered?

To answer charge question 2, the Committee reviewed Chapter 5, Appendix D, and the supporting document Technology and Cost Document for the Revised Total Coliform Rule. The Committee agrees that the Agency’s characteriza tion of the types of co rrective actions that systems will implement is reasonable and extensive. The types of corrective actions can be ascertained from current practices. Corrective ac tions are closely aligne d with Level 1 and 2 assessments following positive TC/EC testing during routine system monitoring. Both assessments are intended to be part of a proactiv e approach to identify sa nitary defects that may

11put public health at risk, due to the potential exposure to and consumption of contaminated potable water. Such contamination can arise fr om source water and ineffective treatment (not a sanitary defect, but the lack of a barrier or ineffective barrier), any practice or event that results in intrusion into the distribution system, reservoirs such as biofilms, or stagnant and aged waters within the system itself (for example as a re sult of poor operation and maintenance practices).

The proposed rTCR clearly recognizes these i ssues and uses an a ssessment process to initiate analysis of system variables that tri gger corrective actions. Assessments are intended to aid in the following:

• Identifying inadequacies in sampling site s and protocols, sample processing and presumably appropriateness and QA/QC of the TC/EC analytical methodology.

• Identifying atypical events such as storm flows or construction breaks affecting or indicating impaired water quality.

• Identifying changes in distribution system maintenance and operation that may affect water quality.

• Identifying changes in source water quality and/ or treatment resulting in the potential for impaired water quality.

• Identifying inadequacies in the underl ying WQ monitoring data itself.

These assessment elements and corrective act ions are clearly identified in supporting documentation for the rTCR, specifically in the Technology and Cost Document for the Revised Total Coliform Rule . H o wever, they could be more clearly lis ted in Chapter 5, so the reader does not have to delve into supporting re ports to find the information.

Cost estimates principally for salary and wage s (including monitoring, reporting, and operations and analytical analysis) are also provided. The corrective actions are summarized as follows:

1) Flushing 2) Sampler Training 3) Replacement and Repair 4) Pressure Maintenance 5) Hydraulic Residence Time Maintenance 6) Storage Facility Maintenance 7) Booster Disinfection 8) Cross Connection and Backflow Prevention 9) On-line Monitoring and Control 10) General Security Measures 11) Standard Operation Procedure Training and Implementation

The Committee recommends that the Agen cy explain how it compiled this list of corrective actions and from where the information came (i.e., from expert discussions in the Technical Workgroup of the TCRDSAC, and from information provided by utilities). It is important for the Agency to acknowledge that this is not a definitive list of all actions that could be taken and that it is possible that even if all these actions were implemented in a system, that all total coliform positive observations may not be eliminated. Coliform-positive samples may

be the result of numerous fact ors in a water system, including cross connections, construction,

12sampling, etc. It is also noted that a Level 2 assessment mandates that a “certified” operator must respond to violations. Ce rtification is rather ill define d and is a responsibility of the individual State. The expertise of the “certified” operator will be very important in determining the efficacy of the investigations and the perc entage of systems taki ng corrective action after

Level 2 assessments.

The list of corrective actions appears somewhat dismissive of investments in analytical methods and monitoring, source water analysis, water quality databases and analysis resulting

from the Level 1 and 2 assessments. Real tim e microbial monitoring, ultimately capable of targeting specific pathogens of direct public hea lth significance, is on the horizon and real time residual chlorine monitoring is on ly a limited surrogate approach.

Suggestion 1. Analysis of Percentage of Systems Implementing Corrective Action

The percentages of systems that will implem ent corrective actions are un-knowable, so there is nothing the Agency or the DWC can do excep t to take a best guess. An estimate that is based on expert judgment is a reasonable approach to this situation. Two things need to be done when taking a best guess: (1) a careful justifi cation of what expert information sources were relied upon and (2) a sensitivity analysis. The Committee commends the Agency for doing the latter, which greatly increases confidence in th e assessment. However, the Agency could do a much clearer job justifying and explaining how it arrived at these numbers. Specifically, there should be some text explaining the tables in Appendix D, and there s hould be reference to Appendix D and the list of correct ive actions in Chapter 5. As the tables stand now, it appears that large surface water-community water system s (SW CWS) would do nothing in response to a TC positive; zero percent implementation is assigned for all Level 1 Corrective Actions for those system categories. Presumably, this is because large systems are assumed to already be doing assessments and corrective actions. The Agency should clearly document the logic for these assigned values.

Based primarily on the results of a limited survey of current TCR requirements, the Agency estimates that corrective actions will on average be implemented only 10% of the time (section 6.2.7 and associated footnot e 1 on page 6-8). It is surpri sing that such a relatively small percentage of systems are projected to take some kind of corrective action – at least by flushing their systems - after a Level 1 or Level 2 event. We expect that flushing would (and should) be a more common practice. Therefore, we think it would be justifiable for the Agency to use a greater than 10% likelihood of taking corrective action. In addition, after a Level 2 event, a serious assessment, done by a certif ied operator, should find some t ype of corrective action that can be taken in most small systems, especially if the menu of corrective actions includes a switch

to disinfection.

This entire discussion appears overly weighted on the influence of the ground water rule (GWR) and instituting disinfection processes for GW. Does implementation of disinfection in ground water (GW) systems bias the presumed 10% of corrective action? The sensitivity analysis uses a range of 5-20% for correctiv e action implementation. We suggest a broader range for analysis, including corrective actions up to around 50%, especially after a Level 2 assessment. In addition, if disinfection is the main corrective action, this shoul d be stated. If it is

13not, then the sensitivity analysis results should be clearly disc ussed for other corrective action

alternatives and the costs associated with them.

Assessment and corrective actions are well described. However, the discussion of corrective action appears to emphasize flushing in response to a TC/EC positive monitoring result. While offering immediate public hea lth protection, flushing alone may not provide solutions to the underlying problem causing the positive TC/EC monitoring result. Therefore, the Committee questions whether the benefits of flushing will result in decreased risks for several years, as the Agency currently estimates in the model. The Committee recognizes that from a utility perspective, flushing and disinfection is a cost effective solu tion, if the origins of the TC/EC cannot not be adequately documented, thus avoiding potential costly repair and replacement corrective actions that may not ultim ately be warranted. It makes sense to switch some proportion of GW systems to long-term disi nfection in the model, and thus change their attributed rates accordingl y after a positive finding.

Overall, the challenge laid down to the Ag ency by the TCRDSAC was to come up with a revised TCR that will foster continuous improve ment in the industry by encouraging assessments and corrective actions. It is discouraging to see that the Agency’s projections do not fully realize that vision. The rule should be designed so that a larger percentage of small systems would take corrective actions that result in long-term be nefits. The central estimate of 10%, although perhaps realistic, represents only a modest bene fit from the rule, although it may be better than

the status quo for small systems. It would be useful for the Agency to run the model with a significantly higher percentage of corrective actions (i.e., 50 %), to determine whether the benefits would increase substantially if the rule can be designed such as to achieve these higher

rates.

Suggestion 2. Alternative monitoring and measures

The AIP recognizes the evoluti on of analytical capabilities (section 3.2) for TC and EC. As part of Assessment and Corrective Action, best available methods are appropriate. As an active area of research, future relevant analytical methodologies should be embraced as they become available, and the rTCR should not be co nstrained to current be st available technology. It is important to note that wh ile various methods may report TC, not all the TC’s mean the same thing. There is an ongoing study comparing the me thods and the AIP contains a component that addresses it. The Committee also suggests that the Agency consider moving to alternative measures other than TC which they believe is not a reliable indicator from a public health perspective.

Monitoring needs are also identified. As part of research and information needs (4.2.c),

Tier 1 should include molecular microbial met hods, stable isotope ratio techniques, and mass spectroscopic analytical methods for source and contaminant identification which need to be developed to assist in focused corrective acti on, rather than corrective action in immediate response to a proposed rTCR mon itoring violation. Tier 2 needs emphasis on human and animal pathogen detection and real time monitoring.

14Charge Question 3. Are the methodology and assumptions used to predict the net impacts in total coliform positive (TC+) samples, E. coli -positive (EC+) samples, acute violations, assessments, and corrective acti ons between the current TCR (w ith and without the effects of the Ground Water Rule), the AIP, and the Alt ernative Analysis reasonable? If not, what alternatives might be considered?

The framework and methodology of the Economic An alysis (EA) appear to be consistent with a properly conducted EA based on the USEPA Guidelines for Economic Analysis (2000). The USEPA guideline should be referen ced so readers understand where the framework for this EA originates and be tter understand the reasoning behind the proposed revision to Total Coliform Rule (rTCR) EA structur e. Using this framework, the Agency should guide the reader through the EA clearly pointing out elements th at were completed, where assumptions were made, and where steps were omitted (along with justification for omitting them).

The Council for Regulatory Environmental Modeling notes in their November, 2003, guidelines, both an uncertainty analysis and a sensitivity analysis should be conducted on any model developed and used as a basis for a regulat ory decision. The term “uncertainty analysis” itself can lead to confusion, because an overall Uncertainty Analysis (UA) is composed of two separate components, sensitivity and uncertainty, one of which uses the same term as the overall analysis itself. Both components are necessary to complete the overall uncertainty analysis. The sensitivity analysis illustrates th e degree of impact that one variable has on the outcome when all other values are held constant ( possibly using a median or average value), such as the use of the lower and upper bound estimates used in the proposed rTCR EA.

Unlike the sensitivity analysis, the uncertainty analysis examines the inherent variability in the data and its subsequent impact on the distribution of the output. Some variability is inherent and a portion may be associated with the measurements used to characterize the population. The Agency should identify the sources of uncertainty and determine the level of confidence that should be placed in the final results.

In reviewing the EA guideline, it is apparent that one deficiency in the rTCR uncertainty analysis originates from the guideline itself a nd is not a deficiency introduced by the rTCR EA. While the EA guideline does admit the approach outlined may be different than what other disciplines consider a complete uncertainty analysis, the USEPA EA Guideline appears to discuss conducting an Uncertainty Analysis (UA) only. The Agency should identify that the UA is comprised of a single part, the sensitivity anal ysis. Since the Agency’s EA guideline is not a regulation or legislated requireme nt, its structure and content are not so rigid as to preclude interpretation and improvement, when and if the a pplication warrants it. In this case, the Agency should point out that the UA in the EA is only comprised of a sensitivity analysis, which does

not include an actual evaluation of uncertainty associated with the output. The analysis and discussion in the EA would better inform po licy makers by identifying and summarizing all the

variables with known distributi ons, and those without, to ai d risk managers with the interpretation of the results.

The EA also seems to assume that the variables for which there are no data will not have a significant impact on the overall uncertainty. Until the EA can better characterize the error

15associated with the output, one should be cautious about inferring too much from the results. Statements, such as the one beginning on line 23 pg 5-31 (and others similar to it), should be

made with consideration for the error or uncer tainty surrounding the out come, as the observed difference is probably not significant. The EA discusses some differences as if they are significant and other differences as if they are not, without a simultaneous discussion as to how the difference is judged to be significant in one case, but not in the other.

When evaluating the baseline condition, the admission that data are missing from 15 states, including states with la rge populations (California, Flor ida, and Pennsylvania), requires additional discussion on what impact this data gap might have on the final result. In addition, the number of states submitting TC and EC data in each tier (1 – 4) is not described. Again, there is no discussion of how the missing data may have biased the baseline estimate.

In addition, the Committee recommends that in regard to the effectiveness of the

corrective actions to reduce future TC- and EC- positive samples, the Agency should repeat the analysis with values for the percentage of co mmunities that will actual ly implement corrective

actions from 1% for the less effective corrective actions to 50% for the most effective. In addition, it is not clear that the reduced monito ring strategy offers significant savings in the annual national costs for the assays that are not o ffset by an increased risk of waterborne disease outbreaks. Overall, the Alternative Analysis (AA) appears to provide public health protection in a more timely fashion than the AIP .

The Drinking Water Committee (DWC) of th e Science Advisory Board (SAB), while providing comments on the methodology and assumptions used to predict th e net impacts of the proposed rTCR under the current TCR, AIP, and A lternative Analysis (AA), cannot provide an adequate assessment which could serve as a substitu te for an Uncertainty Analysis. In this EA, one can argue the Uncertainty Anal ysis is not complete, because of the undefined or ill-defined

distributions associated with ma ny of the input variables. Rega rdless, it appears that the EA represents the best possible analysis gi ven the paucity of available data.

Suggestion 1. The Safe Drinking Water Info rmation System (SDWIS)/Federal Version (FED) and 6-year Review Databases

The Total Coliform Rule is the drinking water rule that applies to all public water systems regardless of size, source or treatment. Utilities across the United States have invested billions of dollars in monitoring to meet th e requirements of this rule. Unfortunately, management for these data has been challenging. There was only a limited amount of data from the Safe Drinking Water Information System – Federal Version (SDWIS/FED) and six-year

review databases used in the EA deemed useful for the rTCR analyses. Given this limited data, there was still a good deal of work, along with a significant amount of thought and effort, expended on identifying those segmen ts of the database that would be useful. A large amount of data has been gathered and screened by the USEPA when the States voluntarily submitted electronic monitoring data refl ecting records from l998-2005.

In estimating the baseline in Chapter 4, ther e is one troubling assumption - basing the analysis solely on one year (2005) out of six year s of total coliform (TC) and enteric coliforms

16(EC) occurrence data. The Agency states, “Using only a single year of data was beneficial in that it [ sic ] simplified the analysis...” (page 4-6, line 36). This assumption completely ignores potentially large inter-annual differences in TC and EC occurrence. Such differences could be driven, for example, by inter-annual variability in precipitation pattern s, which the Agency acknowledges with the statem ent (line 39): “...changing envi ronmental factors may be important.” Even groundwater shows large year to year differences in the occurrence and quantity of human enteric viruses, as evidenced in studies of municipal wells 2 . The baseline occurrence rate could shift up or down depending on which year of data is analyzed. It may be possible to evaluate the importance of TC and EC inter-annual variability using data from the states that submitted complete 6 year datasets. It may also be possible to clarify this issue by expanding on the statement regarding the consis tency of the TC-positive rates in the years outside the year selected for this analysis.

Further, it should be noted that the EA model was developed to produce a reference

baseline and not to be used as a predictive tool. The EA us es the SDWIS/FED database of

violations as the reference for their model. Th e data for the model came from the six-year data review data set, which contained all sample re sults (with the stated limitations). The model output was compared to the SDWIS/FED data as the means of validating it. The violations in the SDWIS/FED database should reflect the sampling re sults in the six-year data review for those same periods of time, since the sampling result s determine PWS compliance. However, this

should not be considered a “validation” of the model as a predictive tool. A model should only be considered validated as a predictive tool if it can be shown that it acc urately forecasts events that have not yet taken place. Until additional data are available to confirm the model output, the

EA model should be considered for establishi ng a reference baseline only. The Agency will

need a database that is far more robust than the 1 year of data from th e six-year data review

database used in the EA to validate the model an d decrease the long list of assumptions used in the current EA (see comments in next section).

Given the scheduling of the revised total colif orm rule (rTCR), the assumptions used to fill the data gaps identified in the six-year review database should be considered adequate for this EA. However, they indicate a deficiency in the data collection system that should be rectified prior to implementation of the proposed rTCR. On page 4-7 one justifica tion includes the line “...single year data allows for a single database.” This statement implies that the databases were

of such different format and structure that the in formation in the database from the years prior to 2005 could not be combined into a single database . This points to a need to improve data management and collection practices. To address at least one of the items in Section 3.17 of the AIP, the Agency will need a database that is far more robust than the six-year data review

database used in the EA.

To assess the long-term effec tiveness of the proposed rTCR (Section 3.17 of the AIP), the

metrics will need to be established and the data collection systems put into place, before the rule is promulgated. This will allow data collected, under the current TCR, to be used as a reference

2 MA Borchardt, PD Bertz, SK Spencer, and DA. Battigelli, (2003) Incidence of Enteric Viruses in Groundwater from

Household Wells in Wisconsin. Applied and Environmental Microbiology , p. 1172-1180, Vol. 69, No. 2.

17baseline against which future regulatory actions a nd their impacts can be compared. Failure to do so will result in the need to employ simila rly weak assumptions in future regulatory

documents and evaluations.

Suggestion 2. Corrective Actions

Filling data gaps by making assumptions is sometimes necessary, especially when the

data needed are not available or have not been collected. Such is the case for the corrective

actions in Exhibit 7.16. These data have never been collected, so the table was populated using the professional judgment of the TCRDSAC Technical Workgroup (TWG). However, the Agency should recognize that current data system s are not set up to collect this information as the rTCR moves forward. Until the data systems ar e set up to collect this information, future EAs and regulation assessments will be limited in their usefulness as quantitative assessments upon which risk managers can and should base their policy decisions.

The biggest red flag (assumpti on) is the effectiveness of the corrective actions in reducing future TC- and EC-positive samples. The Agency should repeat the analysis with more extreme values for the percentage of communities that will actually impl ement corrective actions, e.g., 1% for the less effective corrective actions a nd 50% for the most effective. It is not clear how the current values in the analysis -10%, 5% , and 20% - were selected. The extreme values are justified, in our opinion, given the absence of any previous knowledge on how well these assessments will be performed or the true long-term effectiveness of the corrective actions.

The assumption that systems following a correctiv e action will be TC -free for a period of time should be reconsidered. As the EA implies, there are a number of causes for a TC-positive result. Each of the causes may or may not be linked to a corrective action. In addition, the causes should be viewed as independent events. Just because a corrective action has been taken and a sanitary defect corrected, does not mean the public water systems (PWS) will be free of TC-positive results for a period of time. Granted, some actions ma y result in long-term solutions, such as rebuilding a problematic sampling station or modifying sampling habits. However, given the reports on the aging infras tructure of our water distribution systems in the U. S. and the fact that distribution systems are continually being exposed to disruptive external conditions (plumbing activities, excavation, pipe replacemen t), assuming a system will be coliform-free for a period of time following a corrective action is a not a justifiable assumption. Assuming that a corrective action will result in TC and EC complia nce for three to five years assumes that once a sanitary defect is found and co rrected, a similar incursion won’t happen again for another three to five years. As there are a variety of events , separated by time and space, that could produce a TC or EC violation, there is no guarantee that one of these events would not produce a TC or EC violation immediately following reme dial action in an entirely diffe rent part of the system.

Each column or corrective action in Exhib it 7.16 represents an action triggered by an independent event. These actions are not dependent on each other. Thus, the corrective actions should not be pooled or linked. Th e causes listed in Exhibit 7.16 a ppear to be all inclusive as each line (for a given size system) seems to add to 100%. By summing to 100% for a given size

18category, it appears as though the corrective actions listed are the only ones that could mitigate a sanitary defect identified in a Leve l 1 or 2 triggered assessment.

The list of corrective actions focuses on actions associated with the distribution system to correct a TC or EC trigger. The list does not include remedial actions taken on other components of the multiple barriers (source a nd treatment) that may contribute to a TC or EC trigger. The

discussion of corrective actions should acknowledge changes or modifications made in the maintenance or operation of the treatment proce ss train, as the assessments may trigger changes

in or the addition of treatment . While it is assumed that the actions taken on the treatment barriers would be an appropriate response under the Groundwater Disinfec tion Rule (GWDR) or Surface Water Treatment Rule (SWTR), these ac tions may be triggered by monitoring in the distribution system under the rTCR and identified by the assessment. The linkage between the rules and the subsequent impact on the EA needs to be fully and clearly explained so the reader knows which impacts are being included and which ha ve been attributed to previous rules.

The rTCR allows for reduced monitoring, wh ich opens up a policy and technical issue regarding the adequacy of sampling. 1) The public water systems given more options to qualify for reduced monitoring are the small systems. Unfortunately, these are the very same systems most likely to have water sanitary quality probl ems. This is evident in Exhibit 4.10 where the public water systems (Community Water Syst ems + Non-transient, non-community water systems + Transient Non-Community Water Sy stems) serving a population size less than 1,000 are responsible for 90% (7,822/8,734) of the TCR violations! The DWC believes that these small water systems simply do not have the capital investment to provide the necessary monitoring and corrective actions to reduce this high level of viol ations. A possible solution is to encourage smaller water systems to combin e with larger systems which may reduce the number of TCR violations. 2) The TC and EC assays are the only routine, widely-available distribution system monitoring tool for assessi ng and ensuring the microbiological quality of drinking water delivered to the public. The TC and EC monitoring has its limitations, but why does that translate to requiring less rather than more monitoring? 3) The TC and EC assays are inexpensive. It is difficult to believe that a re duced monitoring strategy o ffers significant savings in the annual national costs for the assays that ar e not offset by an increa sed risk (and costs) of

waterborne disease outbreaks. 4) Experience with viral pathogens in groundw ater and distribution systems shows that occurrence is amazingly variable in space and time (Borchardt et al). Thus it may be there is no such thing as steady-state fecal contamination. Granted, TC and EC are not 100% correlated with virus occurrence, but the ba cterial indicators do provide some information, particularly if there is a positive test result. The only way to counter the variability and not miss an event is to perform more frequent sampling, not less. A quarterly or a nnual sampling plan is highly unlikely to detect a TC or EC event lasting only one week. Therefore, once a public water system is placed in this reduced monitoring regimen, it is highly unlikely, unless the sanitary defect is egregious, to be trigge red into more frequent sampling.

Delaying rule implementation to improve the da ta sets on which this EA is based would not be protective of public health. From the di scussion, it is clear that the Agency needs to improve the databases containing monitori ng and compliance information. Without improvements, future EAs will be hampered by th e issues discussed herein. As the TCRDS FAC

19recognized, it is important to characterize the impacts of promulgated rules by identifying, establishing, and collecting the necessary metrics to do so. The long list of assumptions needed to cover data gaps in the EA reinforces the need for better data collection.

It is understood the analytical and labor co sts listed represent national averages for routine sampling. However, a coliform-positive test will trigger additional sampling, assessments, or other actions that may not be accommodated within normal work schedules. As noted in the previous paragraph, other responsib ilities may force TCR activities, especially nonroutine activities, into overtime. Hence, some cost factor to account for these activities outside

of the normal labor rates should be considered. After all, one would hope that repeat sampling and assessment activities are not routine, but th at they are conducted by personnel trained and knowledgeable in these areas. (If assessments are conduced using outside contracts, the labor costs may actually be higher than the utility’s pa y scale, considering the level of expertise that might be required.). In additi on, the projected labor costs incl ude fringe benefits, but do not include overhead (an additional multiplier to cover ad ministrative activities, utilities, office space, etc.). Not including the state costs in the ratepaye r cost table could skew the underlying cost distribution. Those states (CA a nd AL) that operate their regulatory programs on a cost recovery basis will have their fees passe d along directly to the ratepaye r (in 2005, the labor cost for an hour of a state engineer’s time was $105). This raises a concern, because when the state costs and the utility costs (both of which are higher in CA than the national average) are combined, the cost to the CA ratepayer will be greater. If one considers the distribution of ratepayers, this will skew the ratepayer costs among the states, pushing the states with higher costs even further out (widening one end of the distribution).

The Drinking Water Committee believes the model output with respect to the relative impacts of the AIP and AA is satisfactory, given the limitations of the corrective actions input data. Since the frequency distributions for TC and EC monitoring results for the AIP and AA are the same, the only principle difference between the AIP and AA appears to be the initial monitoring requirements (AIP allows for a tran sitional period, while AA does not). Since the AA requires more initial monitoring, not allowi ng for a transition period, the impacts of the

rTCR under the AA will be observed sooner. Howe ver, the overall frequency of TC- or ECpositives remains essentially the same in both ca ses. From the standpoint of public health protection, the AA would be preferred becau se the endpoint improvements are achieved relatively sooner than the timeline in the AIP. In addition, getting such a program running at the small utility and state level woul d pose initial logistical and admi nistrative challenges. The net cost for the AA is slightly higher than the AIP, but given the absence of underlying distributions, the significance of the net difference is not known. In fact, given all the assumptions made, the

difference in the net cost between the AA and AIP is likely not significant, which an uncertainty analysis would probably verify.

Suggestion 3. Alternatives and Modifications

The following is a summary of some of th e changes that could be considered.

• Consider revisions to the Fede ral data collection system to ensure the data collected are adequate to establish a baseline from wh ich to measure the future rTCR impact.

20• Rerun the EA using more extreme values for the proportion of water systems that implement corrective actions, e. g., 1% and 50%.

• Revise the assumption that corrective actions will lead to extended periods of TC- and EC-negative results.

• Revise cost estimates to compensate for the overtime needed for repeat sampling and analyses in response to TC- or EC positiv es samples or the additional costs for contracting out an assessment.

• List, identify, and separate those actions and costs associated with TC- or EC- positives that would be mitigated by other rules, such as the surface water treatment rule or groundwater disinfection rule. This will more clearly identify those actions and impacts

associated with the different rules an d show how the rules are linked.

The Agency should continue its long-term res earch efforts to deve lop tests to identify specific disease-causing organisms, particularly pathogenic strains of E. coli and other pathogenic bacteria, to enable public water system s to eliminate these disease-causing organisms from their water systems. This would require a long-term research project(s) which should commence now with high priority. It is important to take advantage of the latest techniques in molecular biology, such as Polymerase Chain R eaction (PCR), which have exquisite sensitivity and specificity, to advance the problem of iden tification of pathogenic bacteria in the water systems. One could visualize firs t moving to pathogenic strains of E. coli by culture methods and biochemical methods, and later by PCR methodol ogy, which is very rapid and very specific. The PCR detection of pathogens fits within th e rubric of other recommendations made by the DWC to the EPA concerning the monitoring for, a nd the rapid detection of, pathogens. This is yet one more example of how moving along to th is form of monitoring would be helpful and protective of public health. The DWC recognizes that this form of monitoring acts to address multiple threats to public health, and has the potential to provide timely and specific information. This should be done carefully and with exte nsive validation of molecular biology methodology against classical culture and microbiology methodology to determ ine whether adoption of these methodologies would actually advance water sanita tion. In addition, the Agency still has to balance maintaining a broad bacterial screen vs. moving to screens for specific pathogenic organisms.

Those small and large water systems that fail to comply with corrective action requirements should perhaps be tasked with more frequent monitoring and reporting requirements to encourage them to rapidly become compliant with the proposed rTCR for long periods of time, at which point th e requirements could be relaxed.

Overall, the Drinking Water Committee (DWC) advises USEPA to move forward deliberately to ensure any changes made in ge nerating the rTCR actually result in a significant reduction in the frequency and severity of To tal Coliform observations in our drinking water systems. DWC recommends substantial caution in developing the rTCR. To date, most U. S. water systems are maintained well, hence, DW C recommends being very careful in adopting new changes to the TCR, unless there is a ve ry high probability they will improve water distribution system sanitation, i.e., The DWC recommends caution in making changes to the TCR, and incorporating only those changes that have a high probability of making water systems more sanitary as this is likely a means to lower frequencies of water-borne illnesses.

21The rTCR should be written to make it clear a nd easy to comply with for the convenience of the PWS. In addition, the DWC strongly recommends placing all information related to aspects of the rTCR on one website with links to supporting materials. The DWC believes that development of a similar book embodying all the ru les contained within the rTCR would be very valuable to the water quality community.

Charge Question 4. Are reductions in E. coli and TC occurrence and acute violations appropriate endpoints for informing benefits ? Do they appropriately capture the added value of the proposed revisions? If not, wh at other analyses or endpoints might be

considered?

The Committee struggled with its response to Charge Question 4 in trying to determine

whether there are measurable health-related benef its that could be attributable to the revised Total Coliform Rule (rTCR). If the goal of the Rule is to protect public health, the Committee feels that measuring reductions in total coliforms (TC) and E. coli (EC) occurrences are not

effective sole endpoints for informing benefits because of the difficulties (discussed below) in linking these indicators to human he alth outcomes. It is expected that there will be a decrease in

the number of acute violations with the assu mption that assessment, followed by corrective

action will decrease the occurrence. The Committee believes there is value in the TT-model. However, there are a number of other indicators that need to be considered, as TC is not an adequate measure of health risk. Even though E. coli is viewed as a more appropriate measure of risk of enteric illness, they do not capture the health risks from Legionella , for example Other measures, including structural and hydraulic integr ity, have been recently considered in a report by the National Research Council and may provide valuable supplemental information on health

risks of distributed water.

Suggestion 1. TC as an appropriate endpoint

With respect to the use of TC, the Committee notes the following:

• TC can be considered an indica tor of treatment efficacy at the point of treatment. To that end, it may be judicious to encourage utilitie s to sample for TC at plant effluent. However, there is no evidence (of which we ar e aware) to suggest th at the detection of TC in the distribution system indicates risk to human hea lth. The Committee recognizes that there are many reasons why TC could be detected in the distribution system, e.g. release from biofilms, intrusion, regrowth, improper sampling, nitrification, and crossconnections. Therefore, the significance of TC detection is difficult to interpret and depends in part on context (such as temperature, season and climate).

• For many systems, the number of samples that will be collected under the revised TCR is inadequate to measure statistically signifi cant reductions in TC and EC occurrence.

• There exist acknowledged probl ems with false negative and false positive results that further complicate the interpretation of results.

• These indicators are not used by most other industrialized co untries around the world as a measure of drinking water quality. We believe that they are used only by the US and Canada (and only under some circumstances).

22Despite these limitations, th e Committee recognizes that:

• The use of TC represents a tool that is already in place, relatively inexpensive, and familiar to users. Specifically, there is alr eady existing expertise and infrastructure with which to conduct these analyses in most water systems.

• The presence of TC is indicative of gro ss contamination, a breach in treatment or distribution system failure.

• The fact that there exist differences in occurrence between disinfected and nondisinfected water systems suggest s that, at some level, there is a correlation with water quality improvement.

With respect to E. coli , the Committee felt that it represents a more credible indicator of public health risk. The utility of E. coli testing, however, is limited by th e rarity of its detection. It is useful as a confirmatory, follow-up test, a nd the Committee felt it appropriate to retain it as an MCL. The Committee notes that the Agency ’s modeling does not predict much effect on E.

coli occurrence, potentially limiting its useful ness as an indicator of improvement.

Suggestion 2. Reductions in acute violations as appropriate endpoints for informing

benefits

It is expected that there will be a decreas e in the number of acute violations and associated Public Notifications following implem entation of the rTCR. This expectation is fueled by the assumption that many Level 1 and Level 2 assessments will be done, that corrective actions will be taken, and that EC- positive occurrences will decrease. Because information on the relationship between EC-positive occurrence rates and illness rates is not available, we have to assume that a reduction in acute violations will lead to reduction in waterborne illness, which is reasonable. Th is seems like a reasonable assumption but it is currently not supported by data. Further, in the years since the implementation of the original TCR, there has been a persistent level of acute violations among small water systems that has not changed substantially. Generally, these small wa ter systems lack sufficient resources to bring their systems into compliance. It is assumed th at the number of systems in this acute violation category will be reduced by the new emphasis in the revised rule on assessments and repairing defects. This is an appropriate and measurable endpoint.

Suggestion 3. Added value of the proposed revisions

The DWC agrees that there is value in moving from an MCL-model to a TT-model to

better address the nature of the issue. It is more logical to treat these microorganisms as indicators of the possible presence of pathogens and to require corrective action than to employ a fixed number (e.g. 5% of all samples) as a “bri ght line” indicator of a public health problem. There is value in having a regulation that is more rational and closely aligned with the nature of the contamination problems. This is discussed br iefly at the end of Chapter 6. Increasing the awareness and familiarity of the operators of sma ll water systems with their specific issues and

23focusing efforts on correcting deficiencies rather than meeting strict numerical targets is more likely to decrease overall risk to the communities served.

Suggestion 4. Other analyses or en dpoints that might be considered

Given the limitations of TC and EC as endpoi nts (as measures of health benefit), the Committee questioned whether there may be valu e in adding additional endpoints, even though these additional endpoints may also have limitations. The question raised was whether several endpoints, in combination, may be more effective than the use of single i ndicators. It was not our intention to suggest these additional endpoi nts as replacements for TC and EC. Several possible additional indicators were discussed.

First, the Committee considered measures of improvement in public health, such as

surveillance for waterborne dis ease outbreaks and/or measures of endemic gastrointestinal illnesses in communities. The Committee recogn ized that there are issues of sensitivity, timeliness and cost associated with any surveillance system. However, there may be circumstances when enhanced surveillance sy stems (such as monitoring nurse hotline calls, monitoring sales of anti-diarrheal medication, mo nitoring hospital emergency department visits for gastrointestinal illness) could be useful in areas where there is concern about water quality and/or vulnerable populations. For example, New York City used enhanced surveillance systems for gastrointestinal disease as pa rt of their strategy to protect public health while avoiding water filtration (see Watershed Management for Potable Water Supply: Assessing the New York City Strategy , National Research Council, 2000).

In addition to considering health endpoints, the Committee also considered indicators of health risk and asked the following questions an d looked to the NAS study for guidance. a) What

factors are “known” to be associat ed with health risk? b) What factors can be measured by small systems?; by large systems? A recent study by the National Research Council entitled Drinking Water Distribution Systems: Assessing and Reducing Risks (2006) suggested the following

measures as useful indicators of risk associ ated with drinking wate r distribution systems:

1. Measures of hydraulic integrity following the use of the indicators:

• Decreased frequency of pressure drops

• Areas of the distribution system with extreme water age 2. Measures of structural integrity and distribution system management

• Chlorine residual

• Heterotrophic Plate Count (HPC) bacteria

• Assessment of biofilms using snaking cameras

• Number of utilities with rou tine prophylactic flushing program

• Number of utilities with ac tive leak detection program

• Number of utilities with active cross-connection detection program

• Number of utilities with ac tive backflow prevention progr am (e.g. Increased number of utilities that adopt bett er management practices)

2425 Some combination of these measures may serve as helpful endpoints when trying to assess the impact of the revised TCR.

Finally, the Committee also discus sed concerns about health ri sks that are not adequately captured by these endpoints, in particular, risks due to Legionella that is associated with a significant number of waterborne disease outbr eaks each year (Surveillance for Waterborne

Disease and Outbreaks Associated with Drinki ng Water and Water not Intended for Drinking - United States, 2005–2006, MMWR

, September 12, 2008 / Vol. 57 / No.SS-9). Thus, some of these pathogen-specific measures may need to be monitored if they are not captured by the fecal endpoints.