United States
Environmental Protection
Agency
Office of Water (4601M)
Office of Ground Water and Drinking Water
Total Coliform Rule Issue Paper
A Review of Distribution System Monitoring
Strategies under the Total Coliform Rule
January 2007
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PREPARED FOR:
U.S. Environmental Protection Agency
Office of Ground Water and Drinking Water
Standards and Risk Management Division
1200 Pennsylvania Ave., NW
Washington DC 20004
PREPARED BY:
American Water Works Association
Background and Disclaimer
The USEPA is revising the Total Coliform Rule (TCR) and is considering new possible
distribution system requirements as part of these revisions. As part of this process, the
USEPA is publishing a series of issue papers to present available information on topics
relevant to possible TCR revisions. This paper was developed as part of that effort.
The objectives of the issue papers are to review the available data, information and
research regarding the potential public health risks associated with the distribution
system issues, and where relevant identify areas in which additional research may be
warranted. The issue papers will serve as background material for EPA, expert and
stakeholder discussions. The papers only present available information and do not
represent Agency policy. Some of the papers were prepared by parties outside of EPA;
EPA does not endorse those papers, but is providing them for information and review.
Additional Information
The paper is available at the TCR web site at:
http://www.epa.gov/safewater/disinfection/tcr/requlation revisions.html
Questions or comments regarding this paper may be directed to TCR@epa.gov.
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Table of Contents
Table of Contents
Overview
Nature and Purpose of the Paper
Regulatory Objectives of the TCR
Monitoring Strategies
Sampling Plan Design
Sample Location
Sampling Protocols
Information Gaps
1.0 Introduction
1.1 Summary of TCR Technical Requirements
1.2 Regulatory Objectives of the TCR
1.2.1 Monitoring Frequency
1.2.2 Sampling Sites
1.2.3 Repeat Samples
1.2.4 Research Needs
2.0 Overview of Monitoring Strategies
2.1 Distribution System Microbial Monitoring Objectives
2.2 Sampling Plan Design
2.3 Understanding the Underlying Population: Coliform Occurrence, Transport, and Persistence in
Distribution Systems
2.3.1 Coliform Occurrence in Distribution Systems
2.3.2 Coliform Transport within Distribution Systems
2.3.3 Coliform Persistence in Distribution Systems
2.3.4 Alternative Monitoring Parameters for Biofilms
3.0 TCR Objectives and Sampling Design Issues
3.1 Linkage of TCR Monitoring Objectives to Other Strategy Components
3.1.1 Process Control Objective
3.1.2 System Characterization Objective
3.1.3 Contamination Detection Obj ective
3.2 Number and Frequency of Samples
3.2.1 Sampling In Consecutive Systems
3.3 Sampling Locations
3.3.1 Survey Findings on Sampling Locations
3.3.2 Alternative Sample Location Considerations
3.3.3 Sample Timing
3.3.4 Number of Samples per Site
3.4 Repeat Sampling Monitoring Strategies
4.0 Appropriateness of TCR Analytical Designs and Statistical Methods
4.1 TCR Parameters: Correlation between TCR and Waterborne Disease
4. 2 TCR Sampling Protocols
4.2.1 Sample Collection Logistics
4.2.3 Dedicated Sample Taps
4.2.4 Sample Volume
4.2.4 Sample Handling
4.3 TCR Methods
4.4 Statistical Methods Used In Coliform Rule Development and Compliance Evaluations
4.4.1 Frequency Distribution of Total Coliforms
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4.4.2 Presence/Absence vs Density 38
4.4.3 Limitations of Analytical Methods in Screening for Rare Events 39
5.0 Alternative Distribution System Monitoring Strategies 39
5.1 AwwaRF Guidance Manual: Developing a Bacterial Sampling Plan 41
5.2 Statistically-Based Network Design 41
5.3 Use of Hydraulic Models to Aid in Monitoring Site Selection 42
5.4. Approaching the Distribution System as a Process 43
5.5 Sampling for Rare Events (Inverse Sampling) 43
5.6 Sampling at the Worst Case Areas 43
5.7 Statistical Process Control Theory 44
5.8 Tiered Response Action Approach 44
5.9 Use of Alternative Process Control and System Characterization Tools 45
6.0 Summary of Findings and Research Needs 45
6.1 Ongoing Research 45
6.2 Research Gaps 47
7.0 References 48
Appendix A. Partial Excerpt of Section 141 of the Code of Federal Regulations Pertinent to the Total Coliform
Rule Monitoring Requirements 54
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A Review of Distribution System Monitoring
Strategies Under the Total Coliform Rule
Overview
Nature and Purpose of the Paper
This document summarizes existing information, literature, and research on distribution system
compliance monitoring strategies for the Total Coliform Rule (TCR). The TCR requires all Public
Water Systems (PWSs) to monitor for the presence of total coliforms and fecal coliforms or E.
coli in the distribution system as an indicator of effectiveness of treatment and the vulnerability
of a system to fecal contamination (54 Federal Register 27544, June 29,1989). The focus of this
white paper is on the design of coliform monitoring strategies (monitoring objectives, sampling
plan design, analytical design, and statistical methods).
Separate white papers address the usefulness of total coliform as an indicator parameter, the
TCR compliance history of water systems, and the potential applicability of Hazard Analysis
Critical Control Point methodology in monitoring and controlling indicator organisms or
pathogens in drinking water.
Regulatory Objectives of the TCR
The specific regulatory objectives of the 1989 TCR are fundamental to understanding the origins
of water system monitoring practice under the TCR and to assess the effectiveness of existing
monitoring strategies in meeting the regulatory objectives. The preamble to the proposed TCR
describes the purpose of monitoring total coliforms: to evaluate the effectiveness of treatment,
to determine the integrity of the distribution system, and to signal the possible presence of fecal
contamination (USEPA, 1987). To meet these objectives the monitoring program must consider
the three potential sources of microorganisms in distribution systems:
1. Microorganisms that pass through treatment,
2. Microorganisms that enter the system from the outside via means other than the
treatment process (distribution system intrusion/contamination) or
3. Microorganisms multiplying within the distribution system, either in the bulk fluid
or associated with deposits or biofilms.
This in turn requires understanding the importance of these pathways for coliform entry.
Monitoring Strategies
To evaluate TCR monitoring strategies, individual consideration of the components of the
strategy is useful. Monitoring strategies consist of monitoring objectives linked to appropriate
sampling designs, analytical designs, and statistical methods. Thus, more specific TCR
monitoring objectives might be restated as follows:
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1. Process Control: Monitor the effectiveness of the treatment process by determining
whether coliforms are present in water entering the distribution system.
2. Characterizing System Reliability: Characterize the integrity of the distribution
system by determining whether total coliforms, ubiquitous in the environment, are
finding pathways to enter the distribution system or are persisting within the
system (e.g., within biofilms or stagnant zones of storage tanks).
3. Contaminant Detection and Investigation: Detect fecal contamination (by
analyzing for the presence of fecal coliforms or E. coli wherever total coliforms are
found); use repeat sample information to aid in investigation and control of
problem.
Sampling Plan Design
The dispersion of coliforms bears discussion because of its potential effect on the design of
monitoring strategies and its implications for the sample volume and repeat sampling
requirements of the existing TCR. Pipes and Christian demonstrated that coliforms were not
randomly or uniformly dispersed in these water distribution systems. They showed that
coliform count data could be fitted to either the truncated lognormal or the negative binomial
distribution. Other researchers reported similar findings. Pipes and Christian also found that
the variance of the counts was much greater than the mean.
Pipes and Christian summarized the challenge of TCR sampling plan design as follows:
"It would be impossible to assure the microbial safety of every drop of water provided
by a water system. For a 1 MGD system, there are 37,800,000 potential 100 mL
samples per day or 1.34xlOEE9 samples per month. The fraction of water that is tested
for total coliforms is extremely small."
Allen, Clancy, and Rice (2001) argued for increased emphasis on monitoring indicator
parameters for process control purposes, compared to direct pathogen monitoring, as a more
appropriate means of protecting public health.
Speight and DiGiano (2004) utilized modeling and statistical techniques to assess the adequacy
of distribution system sampling, and numerous other researchers have applied modeling tools
to the task of developing monitoring plans.
Sample Location
The TCR specifies the total number of samples per month, but as noted above, the actual sample
plan is determined by the utility and approved by the state. Consequently, sampling strategies
vary nationally with respect to specific sample site requirements, the placement of sample sites,
and the frequency of sampling at any one site.
Narasimhan (2003) surveyed current state policies regarding TCR sample collection and
location selection. Narasimham found variation from state-to-state in the types of sites used for
sampling. For example, with regard to sampling of storage facilities, the authors found that
sampling practices range from collecting samples at each tank to no samples being taken in the
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vicinity of tanks. Also, sample plans including consumer taps, dedicated sampling stations, and
combinations of the two are acceptable depending on the individual state and circumstances.
The sampling protocol also varies among the states. Some states require systems to have
exactly the same number of sampling locations as their required number of samples, and to
collect one sample per month from each site. Other systems must identify a large pool of
sample sites and rotate among the sites either randomly or based on a fixed schedule. Other
systems identified fewer sites than the number of required samples and collect samples more
frequently than once per month from the identified sites.
Each of these sampling strategies has advantages and disadvantages. Fixed sampling points
provide more uniform information and a more reliable history of water quality. The second
approach includes gathering observations at more (and presumably more geographically
diverse) sites within the distribution system over time. However, each individual site is visited
very infrequently; so the likelihood of capturing coliform positives due to site-specific factors
may be reduced. Approaches that reduce the number of sample locations offers a greater ability
to evaluate trends in water quality at each site, since data are collected more frequently at each
site. Also, systems with a more limited number of sites may be able to better to reduce false
positive and false negative samples by achieving better control of the environment at that
sample location.
Also, by specifying (or excluding) particular sample locations, such as in water storage
reservoirs, the primacy agency is biasing the TCR sample. Wong et al. (2005) demonstrates that
sampling for total chlorine, free chlorine, nitrate, free ammonia, HPC, pH, and temperature can
be very useful for managing reservoirs and as a component of a nitrification plan. Wong's use
of reservoir monitoring to proactively manage nitrification illustrates that reservoirs are more
likely to be sample sites with high HPC levels. Such an intentional bias can be effective, but it
must be coordinated with the remainder of the monitoring strategy, including the interpretation
and actions taken based on the observed results.
Sampling Protocols
Burlingame (1998) made recommendations for improved sampling practices to ensure that
representative samples are collected, including sampling apparatus design, installation, and
maintenance and flushing practices to discourage coliform growth in sampling lines. Dufresne
et al. (1997) and Burlingame (1998) identified criteria for accepting or rejecting individual
sampling stations for TCR compliance based on the potential for cross contamination. Studies
by Ball et al. and Gueco, among others, showed improvements in TCR compliance after a
system converted a large number of its sampling sites to dedicated sampling stations (Ball et al.
1999; Gueco, 1999).
Information Gaps
1. Tools are available to assist drinking water utilities and states to develop effective
TCR monitoring strategies. The AwwaRF report, Developing a Bacterial Sampling
Plan, is one document that provides a rational guideline for utilities of all sizes to
design effective bacterial sampling plans (Narasimhan and Brereton, 2004). The
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manual lays out a six-step approach to develop a distribution system bacterial
sampling plan.
2. To determine how to use available tools to improve monitoring will require a clear
understanding of the TCR monitoring objectives. Monitoring strategies can then
be evaluated against those objectives and the practical realities of monitoring for
rare events.
3. The statistics of monitoring rare events is critical to understanding the number of
samples and allocation of samples for TCR sampling:
¦ Hrudey and Rizak (2004) demonstrated that false-positive rates are quite
high when monitoring rare events This has implications for the monitoring
plan, analytical method performance requirements, and the actions
required based on observed positives.
¦ Pipes (1988) demonstrated that stratified, random sampling could be
applied to water distribution systems but more recent research bears
consideration and may lead to an alternative monitoring design.
4. Employing dedicated sampling stations or other means to reduce environmental
contamination associated with the sample tap can substantially reduce noise
observed in TCR monitoring.
5. There are significant opportunities for research that would refine the issues
described in this report:
¦ What are the relative contributions and absolute concentrations of
infectious pathogens in tap water resulting from treatment plant pass-
through, loss of integrity in the distribution system piping, biofilm
development, backflow events, and on-premise plumbing? Which specific
pathogens are occurring as a result of each of these potential sources? How
effectively does the monitoring strategy identify the conditions when these
pathogens are likely to be introduced to finished drinking water?
¦ What factors are the most significant determinants of coliform occurrence
distribution in public water system distribution systems? What practical
indicators can be used to identify when individual public water systems
should target particular determining factors to improve distribution system
management?
¦ Recognizing that the TCR's total coliform-E. coli-chlorine residual
monitoring strategy is imperfect, could a more effective and efficient
monitoring strategy be developed using another suite of indicators?
¦ Can analytical methods for coliform bacteria, particularly E. coli, be
improved to facilitate the current monitoring strategy by improving
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holding times, reducing susceptibility to elevated temperatures during
holding times, or increasing sample volume?
¦ Are there implementation training strategies that consistently achieve
reductions in monitoring and reporting violations by systems?
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A Review of Distribution System Monitoring
Strategies Under the Total Coliform Rule
1.0 Introduction
This document summarizes existing information, literature, and research on distribution system
compliance monitoring strategies for the Total Coliform Rule (TCR). The TCR requires all public
water systems (PWSs) to monitor for the presence of total coliforms and fecal coliforms or
Escherichia coli in the distribution system as an indicator of the effectiveness of treatment and the
vulnerability of a system to fecal contamination (54 Federal Register 27544, June 29,1989). The
focus of this white paper is on the design of coliform monitoring strategies (monitoring
objectives, sampling plan design, analytical design, and statistical methods).
This white paper does not address coliform monitoring for security purposes. Separate white
papers address the usefulness of total coliform as an indicator parameter, the TCR compliance
history of water systems, and the potential applicability of risk management methodologies,
such as the Hazard Analysis Critical Control Point (HACCP) methodology, in monitoring and
controlling indicator organisms or pathogens in drinking water. It is expected that some
overlapping themes may emerge between this white paper and the other documents.
This white paper is organized as follows:
Section 1. Introduction
Section 2. Overview of Monitoring Strategies
Section 3 TCR Objectives and Sampling Design Issues
Section 4. Appropriateness of TCR Analytical Designs and Statistical Methods
Section 5. Alternative Distribution System Monitoring Strategies
Section 6. Summary of Findings and Research Needs
Section 7. References
1.1 Summary of TCR Technical Requirements
Several aspects of the current TCR that will be discussed in this document are summarized in
Table 1. Information in the table is presented for discussion purposes only and is not intended
to be used for compliance decisions. Some information has been omitted for brevity. A
complete copy of the codified rule is included in Appendix A.
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Table 1. Summary of Existing TCR Requirements Addressed in this Document
Sampling Plan
Systems must collect routine total coliform samples at sites that are
representative of water throughout the distribution system according to a
written sample siting plan. These plans are subject to state review and
revision.
Number and
Frequency of
Samples
The TCR requires systems to monitor for total conforms at a frequency
determined by the number of people served, ranging from 1 sample per
month for systems serving fewer than 1,000 persons to 480 samples per
month for systems serving over 3,960,000 persons.
The system must collect samples at regular time intervals throughout the
month, except that a system that uses only ground water (except ground
water under the direct influence of surface water (GWUDI)), and serves 4,900
persons or fewer, may collect all required samples on a single day if they are
taken from different sites.
Analytical Method,
Sample Volume
The TCR considers the presence or absence of coliform bacteria in a sample
rather than the bacterial density in a sample, using an approved method. The
minimum sample size is 100 mL.
Repeat Samples
If any sample is total coliform-positive, the system must: test the positive
culture for the presence of either fecal conforms or E. coli; take one set of
three or four repeat samples within 24 hours; and take at least five routine
samples the next month of operation.
The system must collect at least one repeat sample from the sampling tap
where the original total coliform-positive sample was taken, and at least one
repeat sample at a tap within five service connections upstream and at least
one repeat sample at a tap within five service connections downstream of the
original sampling site.
If one or more repeat samples are total coliform-positive, the system must
collect an additional set of repeat samples within 24 hours. The system must
repeat this process until either total conforms are not detected in one
complete set of repeat samples or the system determines that the MCL for
total conforms has been exceeded and notifies the state. Results of all routine
and repeat samples not invalidated by the state must be included in
determining compliance with the MCL for total conforms.
Use of Repeat and
Special Purpose
Samples in
Calculation of MCL
Special purpose samples, such as those taken to determine whether
disinfection practices are sufficient following pipe placement, replacement, or
repair, are not used in the MCL compliance calculation.
Unfiltered Surface
Water and GWUDI
Systems
Unfiltered surface water and GWUDI systems must collect at least 1 sample
near the first service connection each day the turbidity level of the source
water exceeds 1 NTU. This sample must be analyzed for the presence of total
conforms. Sample results from this coliform monitoring must be included in
determining compliance with the MCL for total conforms.
Small Protected
Groundwater
Systems
Protected groundwater systems serving fewer than 1,000 people may reduce
their sampling frequency under certain circumstances, with state approval.
Non-Community
Systems
Monitoring frequencies may be reduced under specific circumstances that
apply to certain non-community systems.
Sanitary Surveys
PWSs serving fewer than 4,100 persons must undergo a sanitary survey at
least every 5 years (every 10 years for a noncommunity system using only
protected and disinfected groundwater). The state must review the results
and determine if the existing monitoring frequency is adequate.
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1.2 Regulatory Objectives of the TCR
The specific regulatory objectives of the 1989 TCR are fundamental to understanding the origins
of water system monitoring practice under the TCR and to assess the effectiveness of existing
monitoring strategies in meeting the regulatory objectives. For decades, U.S. public health
personnel have relied on enteric bacterial indicator microorganisms (predominantly
"coliforms") as the primary means to detect the possible presence of microbial contamination of
drinking water from human waste (National Research Council, 2004; US EPA, 1987). The 1989
TCR evolved from the coliform monitoring provisions of the 1975 National Interim Primary
Drinking Water Regulations and its predecessor regulation, the U.S. Public Health Service's
1962 Federal Drinking Water Standards, which was in turn based upon federal drinking water
standards established in 1914 (Clark et al. 2004). The TCR was proposed in 1987 and finalized
in 1989.
According to the preamble to the proposed TCR, total coliforms are monitored to evaluate the
effectiveness of treatment, to determine the integrity of the distribution system, and to signal
the possible presence of fecal contamination (USEPA, 1987). Bacterial monitoring contributes
to meeting these objectives but, as required by the TCR, is not adequate to assure that they are
met. The effectiveness of treatment is determined by frequent or continuous measurement of
turbidity and the disinfectant residual in the treated water. The stability of the treatment
process is very important and there is a need for real time evaluation of its effectiveness.
Compliance with the TCR is only one of several programs that a water utility needs to assure
microbiological safety of the water.
The proposed rule put forth the concept of a monthly MCL to warn of acute health risk and a
long-term MCL to characterize the consistency of the quality of the drinking water over a 12-
month period or longer. The primary purpose of the long-term MCL was to ensure the
reliability of the water system over time and water quality throughout the distribution system.
EPA defined "reasonably safe" water for purposes of the long-term MCL as demonstrating 95
percent confidence that the fraction of water with coliforms present is less than 10 percent,
noting that this definition was consistent with the recommendations of a 1981 workshop
sponsored by EPA's Office of Drinking Water in conjunction with the American Society for
Microbiology. EPA considered that acute contamination would be indicated by several
coliform-positive samples closely spaced in time, and, therefore, proposed a limit of coliform-
positive samples per month of five percent.
The final TCR modified the acute and long-term MCL as presented in the proposed rule. Under
the current regulation, an acute MCL violation is one in which fecal coliforms or E. coli are
present in either initial or repeat samples or both. The long-term concept evolved into the total
coliform MCL: no more than 5.0 percent of the monthly samples may be coliform positive (for
systems analyzing at least 40 samples per month) or no more than one sample per month may
be total coliform-positive (for systems analyzing fewer than 40 samples per month). No
statistical justification was made for the presumed "safe" water concept of having 95%
confidence that less than 10% of the water is contaminated with coliform bacteria. In addition,
no scientific reason has been described for evaluating water quality at time intervals of calendar
months.
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Specific monitoring provisions for the final 1989 TCR were developed following a public
comment process. It is clear from the transcript of one professional discussion (recorded in
1988) that many of the issues that might be considered in revision of the 1989 TCR were actively
considered during the discussions leading up to the 1989 rule (Celdreich, 1988). Three topics
discussed during the TCR development are integrally related to the current discussion of the
objectives of TCR monitoring plans and are discussed in greater detail: monitoring frequency,
sampling sites, and repeat samples.
1.2.1 Monitoring Frequency
The final TCR established public water service population as the basis for setting monitoring
frequency. Alternative approaches considered in the proposed TCR are summarized in Table
2.
Table 2. Monitoring Frequency Considerations
Proposed Criterion for
Monitoring Frequency
Considerations
Population served
As the population served increases, so does size and
complexity of system and the potential for distribution network
contamination by back-siphonage and cross connections.
Also, the larger the population served, the greater the number
of persons at risk when water treatment is defective.
Number of service
connections (excluding fire
hydrants)
Large populations of multi-family residences or workplace sites
are not reflected in the number of service connections.
Total length of the
distribution pipe network
Increased length of pipe network reflects increased risk of
contamination from residential and commercial service
connections and by ground disturbance in the area of
construction projects. Where local topography requires long
distribution lines to reach small clusters of homes, this
approach is misleading.
Volume of water provided
(e.g., by different pressure
zones of a system)
Public water systems know, with some accuracy, the water
demand of different zones of the distribution system. A
significant portion of water demand may relate to industrial use
and lawn watering, rather than to drinking water consumption.
Upon establishing population as the criterion for monitoring frequency, EPA had to determine
what number of samples would be required to be collected by different population categories.
The numbers used in the interim regulations (also population-based) were based on the 1962
regulations, which were founded upon an unpublished study of sampling practices in New
York state that reflected what was financially and technically attainable at that time. This
monitoring frequency was only slightly modified for the final 1989 TCR to simplify the number
of population categories (52 Federal Register 42224, 54 Federal Register 27544). Table 3 shows
the required monitoring frequency for the TCR.
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The number of samples that small systems would be required to collect was the subject of
various studies from which EPA concluded that most samples, even in a contaminated system,
will be coliform-free, due to the uneven dispersion of coliforms, and therefore, a larger number
of samples is necessary to detect contamination (52 Federal Register 42224; Pipes and Christian,
1982; Christian and Pipes, 1983; Pipes, 1983). Thus EPA proposed that small systems serving a
population of 3,300 or fewer persons collect a minimum of five samples per month.
EPA restructured the monitoring approach in the final TCR in response to comments expressing
concern about the monitoring burden. The final rule focuses on evaluating the severity and
extent of any contamination problem by requiring increased repeat monitoring when a positive
coliform is detected, while placing less emphasis on collecting many routine samples. This
modification allows certain systems to collect fewer than five samples per month.
1.2.2 Sampling Sites
The interim regulations suggested, but did not specify, sampling throughout the water
distribution system. EPA proposed to refine the interim regulatory requirement that "samples
are to be taken at points representative of conditions within the distribution system" by
"requiring systems to collect samples from at least three times the number of sites every year as
the number of monthly samples required or the total number of service connections." In
addition, EPA recommended, but did not require, that systems select new sampling sites every
year. The intent of these provisions was to insure that the system would eventually collect
samples from all major sections of the distribution system (54 Federal Register 27544). The
rationale for this proposal was work by Pipes and Christian in 1982 that found that differences
in the frequency of coliform occurrences could be substantial in different parts of a distribution
system. The study also found that the variability did not increase with distance from the water
source. EPA concluded that all parts of the system should be sampled eventually.
However, EPA dropped the proposed sampling location requirements after encountering
significant opposition. Some commenters recommended that EPA allow all, or at least some,
sampling sites, to be fixed to afford utilities the opportunity to maintain long-term records to
detect trends at specific sites. Others were concerned that the proposed strategy would force
systems to use private homes, with possible problems of access, especially for repeat samples
(54 Federal Register 27544). EPA ultimately deci:ed to require systems to use a sample-siting
plan acceptable to the state (May 6,1988, notice).
"Each system must develop and monitor according to a written sample siting plan,
which is subject to state review and revision. The state must develop and implement a
process which ensures the adequacy of the sample siting plan for each PWS in the
state, including periodic review of each system's plan. For the vast majority of
systems, EPA expects the state will conduct this periodic review as part of the periodic
sanitary survey. The siting plan should ensure that the system will eventually detect
contamination in any portion of the distribution system if it is present. While
reviewing the siting plan, the state should also review the sample collection timing
patterns for each system to determine whether the system should collect samples on a
regular basis throughout the month, or whether it is acceptable to collect some or all
required samples at the same time" (54 Federal Register 27544).
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Table 3. Total Coliform Sampling Requirements,
According to Population Served
Population served
Minimum number of
routine samples per month
25 to 1,000
1
1,001 to 2,500
2
2,501 to 3,300
3
3,301 to 4,100
4
4,101 to 4,900
5
4,901 to 5,800
6
5,801 to 6,700
7
6,701 to 7,600
8
7,601 to 8,500
9
8,501 to 12,900
10
12,901 to 17,200
15
17,201 to 21,500
20
21,501 to 25,000
25
25,001 to 33,000
30
33,001 to 41,000
40
41,001 to 50,000
50
50,001 to 59,000
60
59,001 to 70,000
70
70,001 to 83,000
80
83,001 to 96,000
90
96,001 to 130,000
100
130,001 to 220,000
120
220,001 to 320,000
150
320,001 to 450,000
180
450,001 to 600,000
210
600,001 to 780,000
240
780,001 to 970,000
270
970,001 to 1,230,000
300
1,230,001 to 1,520,000
330
1,520,001 to 1,850,000
360
1,850,001 to 2,270,000
390
2,270,001 to 3,020,000
420
3,020,001 to 3,960,000
450
3,960,001 or more
480
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1.2.3 Repeat Samples
EPA proposed collection of five repeat samples for every coliform-positive sample in its 1987
proposed rule, and that this set of samples be collected at the same service connection as the
coliform-positive sample, except that some of the repeat samples may be taken at the next
service connection "above or below". Furthermore, a system would be required to collect
repeat samples at these locations until a set of five samples was coliform-negative or until an
MCL was exceeded. In the final TCR, EPA reiterated that its intent in requiring collection of
repeat samples was to encourage the investigation of the extent of coliform contamination and
to determine if the degree of contamination jeopardizes the safety of the water, rather than to
confirm a total-coliform-positive initial sample, which, it noted, cannot be done because
coliforms are not distributed uniformly in the distribution system—the absence of total
coliforms in a follow-up sample does not imply that coliforms were not present in the water
represented by the initial sample.
In the final TCR, the repeat sampling requirements were modified to require only three repeat
samples for larger systems collecting more than one routine sample per month: one at the same
tap as the original coliform-positive sample, one at a tap within five service connections
upstream and one at a tap within five service connections downstream of the original sampling
site. Systems collecting only one sample or fewer per month would be required to collect four
repeat samples and would be required to collect at least five routine samples the following
month.
The primary rationale behind the minimum repeat sample requirements seems to have been to
provide data to more immediately evaluate the safety of the water, based on EPA's statistical
definition of "reasonably safe" referenced in the proposed TCR (95 percent confidence that the
fraction of water with coliforms present is less than 10 percent). The upstream/downstream
provision was intended to provide the system information as to whether the contamination is a
non-distribution-system problem.
1.2.4 Research Needs
Research questions that have emerged concerning the objectives of the TCR may be
summarized as follows:
¦ Why are there generally a large number of monitoring violations associated with
the TCR, compared to other primary drinking water regulations? Does the large
number of monitoring violations reflect that the rule is effective in protecting
consumers from microbial risks (e.g., TCR monitoring minimizes the risk of
consumers drinking water that is actually contaminated)? Does it imply an
unnecessarily high water utility risk (e.g., water that is actually of acceptable
quality is being deemed unacceptable)?
¦ What are the current operational objectives of coliform monitoring in the
distribution system? Have these objectives differed from the three historical
purposes of coliform monitoring?
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What evidence exists to measure the effectiveness of the strategies used by water
systems in meeting the TCR's implied objectives?
¦ How well do the monitoring strategies employed by water systems support the
TCR objectives? That is, how well do the sites and frequencies established in
sample siting plans, the sampling practices used by systems, and the analytical
tests used in TCR compliance support the TCR objectives?
¦ How effective has the upstream/ downstream follow-up sampling provision been
in aiding in the assessment of coliform occurrences?
¦ With regard to monitoring total coliforms for purposes of process control, are
typical monitoring programs structured to collect data frequently enough and at
appropriate locations so that the coliform data can be used for immediate process-
related decision making? If not, what is the appropriate structure of such a
sampling program and how would it be implemented?
¦ With regard to monitoring total coliforms for purposes of system characterization,
should sampling sites be chosen on the basis of system characteristics that are
associated with intrusion, permeation, main breaks, disinfectant decay, etc., (such
as pipe age, pipe materials, or low flow conditions)?
2.0 Overview of Monitoring Strategies
To evaluate TCR monitoring strategies, it is useful to consider, individually, several
components that, taken together, constitute the strategies. Monitoring strategies consist of
monitoring objectives linked to appropriate sampling designs, analytical designs, and decision
rules. These components are depicted in Figure 1. The USEPA's Guidance for the Data Quality
Objectives Process describes a systematic approach that integrates these components using a 7-
step process as summarized in Table 4 (USEPA, 1994).
Figure 1. Monitoring Strategy Components
Sampling Plan Design
- Number of samples
- Frequency of sampling
- Locations of sampling stations
Monitoring
Objectives
>
Analytical Design
- Parameters
- Sampling protocols
- Analytical methods
Decision Rules
Source: EPA Guidance for the Data Quality Objectives Process
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Table 4. Summary of the Data Quality Objectives Process (USEPA, 1994)
1
State the Problem
Concisely describe the problem to be studied. Review prior
studies and existing information to gain a sufficient
understanding to define the problem.
2
Identify the Decision
Identify what questions the study will attempt to resolve, and
what actions may result.
3
Identify Inputs to the
Decision
Identify the information that needs to be obtained and the
measurements that need to be taken to resolve the decision
statement.
4
Define the Study Boundaries
Specify the time periods and spatial area to which decisions
will apply. Determine when and where data should be
collected.
5
Develop a Decision Rule
Define the statistical parameter of interest, specify the action
level, and integrate the previous DQO outputs into a single
statement that describes the logical basis for choosing among
alternative actions.
6
Specify Tolerable Limits on
Decision Errors
Define the decision makers' tolerable decision error rates
based on a consideration of the consequences of making an
incorrect decision.
7
Optimize the Design
Evaluate information from the previous steps and generate
alternative data collection designs. Choose the most resource-
effective design that meets all DQOs.
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In developing the TCR, EPA assumed a goal for reasonably safe water quality of 95 percent
confidence that coliforms were present in less than 10 percent of the water. Assuming that this
definition of reasonably safe water continues to be acceptable, the TCR monitoring strategies
should test whether water meets this goal. Maintaining Distribution System Water Quality
(A WW A, 1986), provided a straightforward description of the ideal strategy: "Establishing
representative sampling points ensures that sampling results give an accurate indication of the
bacteriological quality of the water supplied throughout the distribution system. Results of
system sampling should show if there are quality changes in all or parts of the system and may
point to the source of the problem." In practice, however, defining "representative sampling
points" with regard to TCR monitoring is difficult for a number of reasons, which are discussed
in subsequent sections of this white paper. Monitoring objectives and sampling plan design are
discussed further in Sections 2 and 3, and analytical designs and decision rules are discussed in
Section 4.
2.1 Distribution System Microbial Monitoring Objectives
AwwaRF's Guidance Manual for Distribution System Monitoring states that the critical first step in
developing a monitoring strategy is to identify the objective of monitoring (Kirmeyer, et al.,
2002). The authors suggested several possible objectives of distribution system monitoring,
including regulations-driven monitoring aimed at rule compliance; public health protection;
operations monitoring to optimize distribution system operations; maintenance-driven
monitoring aimed at planning and conducting maintenance; monitoring to support capital
improvements; and customer-related monitoring. The TCR "regulatory-driven" monitoring
strategy takes place in the context of public water system operations. Examples of questions
posed within the operations context are listed in Table 5.
Table 5. Operations Monitoring Objectives and Questions
Monitoring Objective
Example Question
Operations
What is the optimal operation of
configurations to maintain water quality?
Maintenance-driven
Can monitoring anticipate and/or predict the
onset of water quality deterioration?
Support for capital improvements
Do we need to replace the piping system?
Customer-related
What data can be collected to anticipate or
prevent customer complaints?
The sampling plan design for these other monitoring needs may or may not align with the
regulatory monitoring scheme, but to the extent to which the monitoring strategy meets
multiple needs, then the more effective it will be for the public water system to implement.
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Pipes and Christian (EPA R-805-637) stated that the objective of microbiological monitoring of a
water distribution system is to provide a quantitative measure of the reliability of multiple
barriers against the transmission of waterborne disease, rather than to assure the safety of the
water. They clearly distinguished safety from reliability, noting that it is impractical to test any
significant fraction of the water from a distribution system that will be consumed by humans to
achieve the reasonable assurance of safety afforded by the absence of coliform bacteria in the
samples.
Kirmeyer et al. (2002) suggested monitoring for coliforms to meet various objectives, including:
baseline monitoring, management of water age, monitoring reservoir ingress and
contamination, managing new construction and pipe replacement, and as part of flushing
programs. For each of these purposes, the authors propose the type of monitoring sites (e.g.,
reservoir outlets, dead ends, or sites throughout the system) that should be selected.
Havelaar (1994) recommended including frequent monitoring of total coliforms and other
parameters at critical control points to prevent system contamination from cross connections
and storage facilities when applying the HACCP risk assessment approach to distribution
systems.
EPA has stated that total coliforms are monitored under the TCR to evaluate the effectiveness of
treatment, to determine the integrity of the distribution system, and to signal the possible
presence of fecal contamination (USEPA, 1987). Thus, more specific TCR monitoring objectives
might be restated as follows:
¦ Process Control: Monitor the effectiveness of the treatment process by determining
whether coliforms are present in water entering the distribution system.
¦ Characterizing System Reliability: Characterize the integrity of the distribution
system by determining whether total coliforms, ubiquitous in the environment, are
finding pathways to enter the distribution system or are persisting within the
system (e.g., within biofilms or stagnant zones of storage tanks).
¦ Contaminant Detection and Investigation: Detect fecal contamination (by analyzing
for the presence of fecal coliforms or E. coli wherever total coliforms are found); use
repeat sample information to aid in investigation and control of problems.
Kirmeyer et al. (2002) described four organizational categories that are also important to the
data collection strategy. Those categories are:
1. Management, for which the key data uses are overall administration and financing
of the water system.
2. Maintenance, which needs information associated with the sanitary conditions of
the system related to maintenance, repair, and cleaning.
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3. Operations, which is primarily concerned with the hydraulic operation of the
system, but is also responsible for identifying and responding to complaints,
contamination, and factors that affect ongoing regulatory compliance.
4. Engineering, which requires data to plan for the future of the organization, both
with respect to capital and operational decisions; frequently this function
encompasses research on water quality impacts.
Recently, the engineering organizational category has had to address concerns regarding
identifying analytical tools, sampling strategies, and algorithms to diagnosis distribution
system security breaches. At present it remains a separate, parallel monitoring consideration.
Developing a contaminant warning system to identify deliberate contamination of distribution
systems faces a number of implementation hurdles. These challenges are reflected in the report
of an expert workgroup on contaminant warning systems that was organized by AWWA in
2005 (Roberson and Morley, 2005):
1. Lack of a clear objective for contaminant warning system design and operation.
2. Inadequate information to determine, where to most effectively place monitoring
locations.
3. Absence of demonstrated monitoring technologies.
4. Inadequate information and tools supporting integration of indicator data into
actionable information.
5. Uncertainty as to what constitutes an "alarm" condition.
6. Absence of guidance or practice as to what action a public water system should
take, when alarm conditions are reached.
Roberson and Morley (2005) reported that addressing these needs and demonstrating
effective implementation of a contaminant warning system complete with response
protocols was necessary prior to significant public water system investment in these types
of systems.
The remainder of this report focuses exclusively on the "regulatory-driven" monitoring
associated with the TCR, with a particular focus on the objectives articulated previously
for the TCR specifically.
2.2 Sampling Plan Design
After monitoring objectives have been established, the next component of a monitoring strategy
is the design of a sampling plan.
The sampling plan consists of the number of samples to be collected and frequency of sample
collection, along with the sampling locations. According to Kish (1995), "sample design has two
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aspects: a selection process, the rules and operations by which some members of the population
are included in the sample; and an estimation process (or estimator) for computing the sample
statistics, which are sample estimates of population values." The selection process requires
applying a clear understanding of the underlying population to establish a spatial and temporal
sampling plan; it also involves determining the scale of the decision-making (the smallest
subpopulations for which decisions will be made) (EPA, 1994). Applied to the TCR, the
selection process consists of the rules and operations that water systems and states use to
establish TCR sampling locations, sample event timing, and sampling frequency.
A methodology for establishing a sampling plan utilizing statistically based random selection of
sample sites has been presented by Speight, et al., and Speight and DiGiano (2004). Their
approach divided the distribution system along spatial lines based on pipe material, pipe
diameter, and distance from the treatment plant, but other spatial variables could be used.
Analysis of the statistically selected sites was based on a synthetic data set of predicted chlorine
residual produced with a free chlorine model of the distribution system (EPANET). Results of
the analysis showed that with a random sample site approach, the estimate of error can be
calculated. Also, they found no "wrong" sample designs, only designs that were more or less
efficient at predicting the proportion of samples with low chlorine residual. Since chlorine acts
differently in the distribution system than total coliform, use of a similar approach for TCR
sample site selection would require additional investigation.
Crumbling (2002) noted that, historically, environmental sampling programs have focused on
quality control of the analytical methods employed in sampling, with relatively little attention
devoted to improving the quality of the sampling plan itself by eliminating sampling design
biases. She argued that analytical quality is insufficient to ensure sound science, because it
ignores the repercussions of multifaceted issues collectively referred to as "representativeness"
in sampling programs. Crumbling stated that sampling uncertainty now accounts for the
majority of all the data uncertainty and recommended that it be managed by increasing the
sampling density and/ or by targeting sample collection designs to yield the most valuable
information, such as collecting more information at boundaries between "clean" and "dirty"
areas and less at obviously "clean" or "dirty" areas.
Simcox (1998) described three sources of bias that are a major cause of inaccurate
characterization of water quality in stream sampling networks, which also apply to distribution
system sampling networks: design, analytical, and statistical bias. Design bias refers to bias
associated with sampling design, which prescribes the location and frequency of sampling.
Analytical bias refers to bias associated with the sampling protocols, field equipment, and
analytical methodologies. Statistical bias can occur, for example, if an assumption that all
samples consist of random, independent, identically distributed measurements from a common
underlying population is faulty.
When design bias is present, the sampled and target population do not match. Sources of
design bias include spatial design (i.e., location of sampling), temporal design (sampling
frequency/times), and scale effects (Simcox, 1998). An example of spatial design bias might be
if samples were collected only from water mains near the points of entry that represented the
shortest travel times; they would not necessarily be representative of the entire distribution
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system (the underlying population). Likewise, temporal bias could be introduced if certain
sample sites were sampled in summer and a different set of sample sites sampled during the
winter.
Olstadt et al. (2005) demonstrated that there is significant bias introduced through the selection
of one approved analytical method vs another; testing 13 different analytical systems Olstadt
illustrated almost half of the total coliform tests were susceptible to Aeromonas spp., while the
reminder were not. Similarly, some approved test systems failed to provide positive
observations for Citrobacter, Enterobacter, E. coli, Klebsiella, and Serratia, while others responded
positively to some or all of these species of coliform bacteria. Olstadt also illustrated that
detection of both total coliform and E. coli varied as a function of the test water matrix; potential
confounders were high levels of heterotrophic bacteria, inadequate media buffering for low pH
waters, and incomplete suppression of Aeromonas spp. Consequently, with multiple test systems
approved for TCR compliance monitoring, observed results are biased based on the selected
analytical method.
Eliminating all bias is quite difficult, if not impossible, so the objective of developing a sampling
plan is to first understand the effects of bias on subsequent observations and then to control
significant sources of bias that would be problematic in achieving the monitoring objectives,
given all the relevant constraints, including practicality and costs.
2.3 Understanding the Underlying Population: Coliform Occurrence,
Transport, and Persistence in Distribution Systems
Effective monitoring for coliforms requires knowledge of coliform occurrence and behavior in
distribution systems. An understanding of coliform occurrence, transport, and persistence in
distribution systems is essential to evaluate the effectiveness of various monitoring strategies in
meeting the TCR objectives. The occurrence and behavior of coliforms in distribution systems is
integrally linked to the monitoring objectives; for example, sampling close to the point-of-entry
is reasonable to determine if the treatment process has been compromised. Assumptions
about the occurrence distribution of the coliform population are used in the statistical basis for
the existing coliform rule, and thus should be reconfirmed in the context of an improved
understanding of coliform occurrence and behavior.
2.3.1 Coliform Occurrence in Distribution Systems
There are thought to be three primary sources for microorganisms occurring in distribution
systems: 1) microorganisms pass through treatment barriers; 2) microorganisms enter the
system from the outside via means other than the treatment process (distribution system
intrusion/contamination) or 3) microorganisms multiply within the distribution system, either
in the bulk fluid or associated with deposits or biofilms (Besner, Gauthier, Servais, and Camper,
2002). EPA (2002b) summarized literature and reported the following pathogen entry routes:
¦ Treatment breakthrough
¦ Leaking pipes, valves, joints, and seals
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¦ Cross-connections and backflow
¦ Finished water storage vessels
¦ Improper treatment of materials, equipment, or personnel before entry
¦ Inadequate distribution system security
Understanding the occurrence patterns for these events and the relative importance of these
pathways for coliform entry into distribution systems could help water systems make decisions
about the best locations and techniques to sample to achieve the ultimate goal of protecting
public health.
2.3.2 Coliform Transport within Distribution Systems
The TCR does not specify what parts of the distribution system should be sampled (e.g., low-
flow areas or within storage facilities). Once coliform bacteria exist in the distribution system,
they may be further dispersed or aggregated, but relatively little is known about the fate and
transport of coliform bacteria within distribution systems and whether their origin influences
their subsequent behavior.
Some researchers, using mathematical modeling (Lu, Pratim, and Clark, 1995) and bench
experiments (Sethi, 1996), demonstrated how microbial organisms may be transported and
attached preferentially to certain areas of a distribution system operating under typical
hydrodynamic and physical conditions. Therefore, they concluded that coliform bacteria may
be more prevalent in some parts of a system than another (e.g., near pipe expansions or
multiple bends and tees, in the vicinity of unused service lines, or in portions of the network
where laminar flow conditions prevail). Herson et al. (1991) demonstrated that coliform and
indigenous noncoliform organisms are able to accumulate on surfaces, resulting in dramatic
differences in microbial numbers between the bulk water phase and surfaces and suggesting a
need for alternative techniques for the bacterial monitoring of surfaces other than traditional
bulk water phase sampling.
A perception may exist that bacterial contaminants, like soluble chemical contaminants, would
disperse uniformly in distribution systems. The dispersion of coliforms bears discussion
because of its potential effect on the design of monitoring strategies and its implications for the
sample volume and repeat sampling requirements of the existing TCR. McCoy and Olson
(1986) reported that the existence of significant numbers of bacterial aggregates in a distribution
system sampling study was an important factor that contributed to a substantial
underestimation of total cell concentration by colony forming unit assays. Christian and Pipe's
(1983) work on coliform occurrence in nine small Pennsylvania community water systems
showed that coliform count data could be fitted to either the truncated lognormal or the
negative binomial distribution. This finding demonstrated that coliforms were not randomly or
uniformly dispersed in these water distribution systems. The researchers also found that the
variance of the counts was much greater than the mean.
Other researchers reported similar findings:
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" [Coliform occurrences are] not necessarily uniformly distributed in the network nor
in any one location. The coliforms may also be clumped. Springfield, Illinois tried
several sampling mechanisms during some of their outbreaks. On one occasion, they
collected duplicate samples from the same site; and analyzed them both; one had
coliforms too numerous to count and the other had no coliforms. Continuous
sampling from a flowing tap revealed serial samples to be sometimes positive and
sometimes negative...the probability of actually detecting positive coliforms is
probably very, very low because they are not always homogeneously mixed" (Jones,
cited in Geldreich, 1988).
In addition to the uncertainties associated with coliform dispersion, there are other questions
about coliform transport.
"Coliforms that slough off biofilms on corroded iron mains during flow reversals
might travel as particulates through the system, settling out and resuspending as flow
changes occur. Coliforms that break through treatment might be unattached and
smaller in grouping size or cluster, and might stay suspended in the water. Do clumps
of cells break apart or do single cells clump together? " (Burlingame, 2003).
2.3.3 Coliform Persistence in Distribution Systems
Besner et al. (2002) reviewed literature documenting the ability of coliform bacteria to survive
and even grow in pilot distribution studies of drinking water biofilms, identifying water
temperature, disinfectant concentration and type, nutrients, sediment buildup, and pipe
corrosion as factors influencing the persistence of heterotrophic bacteria and biofilms.
Grayman, et al. (2004) studied and modeled the mixing and aging of water quality within
distribution system storage facilities and found areas of long residence times that depress
disinfectant residuals and can promote bacterial regrowth, and areas of uneven mixing that can
result in zones of older water.
Baribeau et al. (2005) illustrated in bench-scale studies that environmental microorganism
strains (E. coli was one of the microorganisms tested) were no more resistant than laboratory
strains to chlorine. She also found that particulate shielding of microorganisms from
disinfection did not consistently interfere with either chlorine or chloramine disinfection.
2.3.4 Alternative Monitoring Parameters for Biofilms
Feliers et al. (2005) demonstrated that biofilm density and species composition in test
distribution systems were highly site specific. Feliers et al. noted the single parameter,
disinfectant residual, was consistently predictive of biofilm occurrence. While variability was
significant in the dataset the there was a consistent trend to lower biofilm levels as disinfectant
residuals increased from approximately 0.005 to 1.00 mg/L free chlorine. A decrease of 2-3 log
colony forming units was observed with an increase in disinfectant residual from 0.005 to 0.10
mg/L. This observation suggests that the presence of a chlorine residual could be used as an
indicator that biofilm levels are under control. Similar findings for total coliform and E. coli
indicators were not located. Observations by Feliers et al. were consistent with the review
paper prepared by Friedman et al. (2005), as well as in surveys of full-scale distribution system
episodes and pilot-scale testing by Baribeau et al. (2005). Similarly Spencer et al. (2005) found
21
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heterotrophic plate counts (HPCs) decreasing with change from free chlorine to chloramines.
Spencer's work confirms summary information provided by Friedman et al. (2005) that both
free chlorine and total chlorine residuals (with respect to chloramines) can provide control of
biofilm development. Chlorine residual monitoring is already a component of the SWTR
monitoring requirements for public water systems that treat surface water or groundwater
under the influence of surface water. Chlorine residual monitoring is generally coordinated
with TCR sampling by testing for chlorine residual on each TCR sample. Thus each TCR
sample typically provides paired results of total coliform and chlorine residual.
3.0 TCR Objectives and Sampling Design Issues
Total coliform monitoring strategies predate the TCR, with total coliform monitoring beginning
at the turn of the century. By 1915 the U.S. Public Health Service standards already included a
coliform standard. Consequently, there is a long history of coliform testing practice in drinking
water systems (AWWA, 2005). The current monitoring strategies were first developed under
the current rule requirements in 1989. Since those initial plans were developed, they have been
reviewed in the context of numerous sanitary surveys (sanitary surveys occur at an interval of 3
- 5 years in most states where larger systems are evaluated more frequently). Also, over the
intervening 17 years, individual systems and states have had the opportunity to adjust the
monitoring strategy to most effectively capture the data targeted in the rule. Figure 2 reflects
the overall planning paradigm that has been in place over this period in the absence of specific
federal rulemakings. The amount of change that has taken place over this period is state and
system specific. The authors could not locate sufficient information to characterize the amount
of change that has occurred. Specific states (e.g., California, Ohio, Texas, Utah) have noted that
considerable effort has been expended to assure that current monitoring plans are appropriately
constructed.
3.1 Linkage of TCR Monitoring Objectives to Other Strategy
Components
The TCR refers to three monitoring objectives — a process control objective (treatment
performance), a system characterization objective (distribution system integrity), and a
contamination detection objective (warning of potential fecal contamination). The ideal
sampling design for meeting each objective may be different. For example, monitoring
disinfectant residual levels at the TCR monitoring sites may be an example of a disconnected
monitoring objective and sampling plan design. Full characterization of the disinfectant
residual may be better accomplished through an alternative sampling program as suggested by
Speight and DiGiano (2004), rather than at sites selected for TCR monitoring. When the linkage
between monitoring objectives and sampling plan design is not explicitly defined, or when
multiple objectives exist, the sampling plan design may not achieve the intended monitoring
purpose(s).
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Figure 2. Water Quality Monitoring Program Development
Planning
Design
Implementation
Refine Data
Collection
NO
YES
Identify End-Users
Utility Decision Making
Identify PWS Resources
Manage and Analyze Data
Summarize Historical Data
Conduct Baseline Monitoring
Identify Monitoring Plan Objectives
Develop Baseline Data Collection Plan
Determine Costs and System Resources
Are further water quality evaluations necessary?
Develop Data Analysis and Data Management Plans
Source: Adapted from Kirmeyer et al., 2002
3.1.1 Process Control Objective
Concentrating finite resources on monitoring for process control purposes may be worthwhile
from the public health perspective. Crumbling (2002) recommended sampling more densely at
higher value locations to monitor for process control purposes and suggested concentrating
samples frequently at specific sites such as point-of-entry or selected tank effluents. Allen,
Clancy, and Rice (2001) argued for increased emphasis on monitoring indicator parameters for
process control purposes, compared to direct pathogen monitoring, as a more appropriate
means of protecting public health.
3.1.2 System Characterization Objective
Characterizing the system by identifying opportunities for microorganisms to enter the system
or to flourish and grow within the system is another objective of the TCR monitoring. The
literature generally recognizes that microorganisms can be introduced into the distribution
23
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either through passage through the treatment facility or by introduction to the distribution
system through improper maintenance techniques, cross-connections, and distribution system
pressure failures. A developing body of research focuses on the potential for pressure
transients, which result from abrupt changes in water velocity, to introduce contaminants
(LeChevallier, et al. 2002). LeChevallier et al. discussed the potential for environmental water
contaminated with fecal indicators to enter a water distribution system during pressure
transients via leaks or air relief vents. It is not clear from the available research to what degree
this phenomenon affects distribution system integrity (e.g., how likely infectious pathogens are
to reach the consumer via this route).
Microorganisms, including coliforms, pathogens and opportunistic pathogens, have
demonstrated their ability to survive in biofilms; frequent coliform-positive results may indicate
the presence of significant biofilm. Unlined cast iron pipes, particularly older pipes, are
especially prone to biofilms (Clement, Camper, and Sandvig, 2002). Some other types of pipe
and appurtenance materials are especially prone to biofilm development. A system can
address biofilm development in the monitoring plan by placing compliance monitoring samples
in portions of the distribution prone to biofilm development based on pipe material, flow
regime, or frequent nitrification episodes. However, none of the available information indicates
that such measures are being applied to any considerable degree either through state policies or
individual utility actions.
3.1.3 Contamination Detection Objective
Contaminants may enter the distribution system at virtually any point through accident or
intentional malevolent act. Depending on the contaminant, some degree of protection against
microbial contaminants may be provided by maintenance of a disinfectant residual. However,
such protection is a function of water quality, disinfectant type and concentration, and contact
time. The role of the disinfectant residual is described in detail in a separate white paper.
Detection of contaminants may be best focused at points of particular vulnerability. A recently
completed AwwaRF project (Murphy, et al, 2005) assessed vulnerable points of distribution
systems from the perspective of terrorism and intentional contamination. Accessible finished
water storage facilities are an obvious point of vulnerability. Low-pressure areas may be
another point as they are vulnerable to accidental contamination through backflow.
For the more specific goal of detecting fecal contamination, unanswered questions include:
¦ What is the relative importance of various mechanisms for fecal coliform entry into
distribution systems (e.g., intrusion through small holes or breaks in pipes during
pressure transients vs. cross connections vs. intrusion via the point of entry)?
¦ How valuable are repeat monitoring results in investigating and resolving cases of
fecal contamination?
Pipes and Christian (1982) wrote:
"It would be impossible to assure the microbial safety of every drop of water provided
by a water system. For a 1 MGD system, there are 37, 800,000 potential 100 mL
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samples per day or 1.34 billion samples per month. The fraction of water that is tested
for total coliforms is extremely small."
The success of contaminant detection depends on having adequate knowledge of the fate and
transport of the contaminant in the distribution system and on the efficacy of the monitoring
program.
3.2 Number and Frequency of Samples
The TCR specifies the minimum number of samples and the frequency of sample collection on
the basis of population served and other system characteristics such as status as a non-transient-
non- community or protected groundwater system. The TCR requires that samples be collected
at regular times throughout the month except for certain small groundwater systems that may
collect all samples in one day. The TCR currently bases the number of required samples on
population. Alternatively, the required sampling could be based on some other measure, such
as the water production rate, the size (geographic extent) of distribution system, or the volume
of distribution system (diameter and length of pipe, volume of storage), or a statistically-
derived number based on desired level of confidence. The population-based approach
recognizes that smaller systems may have limited resources available for monitoring.
The objectives of the monitoring strategy are important to establishing an appropriate sampling
frequency. If the goal of the sampling is to detect every instance of fecal contamination, then
sufficient sampling is key. When a system is not collecting samples frequently enough, or is
collecting insufficient numbers of samples overall, then incidents of fecal contamination may
not be detected in a timely fashion, even if the sampling locations are geographically and
hydraulically representative.
Christian and Pipes (1983) found that the occurrence of coliform bacteria in distribution system
samples is adequately represented by either a negative binomial or lognormal distribution.
Their work showed that coliforms are not randomly dispersed in a typical water distribution
system. Dempsey and Pipes (1986) then used this information to demonstrate how the number
of samples collected would affect the frequency of coliform-positive samples. Dempsey and
Pipes' mathematical modeling showed that the number of samples used to determine
compliance with a frequency-of-occurrence (presence/ absence) MCL has a profound effect on
the stringency of the rule. They concluded that 60 samples a year would be necessary to make a
statistically valid judgment whether less than 10% of a system's water contains coliforms with
95% confidence. This modeling was completed subsequent to the initial regulatory
development discussion that small systems would not be overburdened by taking 60 samples a
year utilizing presence/ absence testing. Small systems were accustomed to taking one sample a
month that was then analyzed in five aliquots, resulting in five analyses a month or 60 a year.
In an evaluation of the statistical basis for compliance decision rules in the 1989 TCR, Borup
(1992) found:
¦ Water with acceptable quality may be found to be in violation of the MCL a significant
fraction of the time.
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¦ Water with unacceptable quality may be found to meet standards, particularly when fewer
than 30 samples are taken. Localized integrity breaches are unlikely to result in TCR
violations.
¦ Large numbers of samples would be required to minimize the two concerns listed above. For
example, to ensure with 90% confidence that less than 10% of the water contains coliforms,
90 samples would be required.
¦ Repeat samples provide little information except in situations where very few original
samples are collected.
¦ TCR decision rules are based on a a set of assumptions that are not often present in water
systems, especially during contamination events.
Like Borup, Hamilton (1994) calculated sample sizes (number of samples to be collected) based
on the probability of getting false positives or negatives. Speight and DiGiano (2004) calculated
an upper bound for sample size when considering chlorine residual decay in distribution
systems and were able to generate a range of sample sizes based on different values of
confidence level and margin of error, shown in Table 6, where P is the estimate of the overall
proportion of samples with below-target chlorine residual concentration.
Table 6. Maximum number of samples from distribution system required to achieve a given
margin of error and confidence level, estimated P=0.2
Confidence
Margin of Error on P
level (%)
0.01
0.02
0.03
0.04
0.05
80
2,146
622
285
162
104
85
2,584
774
357
204
131
90
3,161
991
462
264
171
95
4,031
1,359
645
372
241
97.5
4,767
1,716
830
482
313
Source: Speight and DiGiano, 2004.
Applying Speight and DiGiano's (2004) methodology to TCR sampling would require some
consideration of the difference between the persistence of chlorine residual in a distribution
system and the theoretical distribution of total coliforms in the distribution system.
Anecdotal information suggests that states have used different approaches in implementing the
sampling frequency requirements. Some systems regularly collect samples until they have
reached the minimum number of required samples, unless at that number they would exceed
the MCL for total coliforms. In that case, the system may continue sampling in an attempt to
"dilute" the number of coliform-positive samples to below 5 percent or until time runs out at
the end of the month. However, some proponents argue that this practice improves knowledge
of water quality in the distribution system by increasing the total number of samples collected
beyond the minimum.
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3.2.1 Sampling In Consecutive Systems
Some separate water systems are connected so that one of the systems receives water through a
wholesale purchase from the supplying water utility. The system purchasing water is
considered a consecutive system. Such transfers of water can introduce both spatial and
managerial separation between the water treatment plant and the consecutive system's TCR
sampling sites. This issue is managed by states on a site-by-site basis under 40 CFR 141.29. This
section gives primacy agents the option to consider suppliers and consecutive systems as single
systems for the purposes of monitoring under any of the drinking water regulations. Therefore,
a primacy agent has the authority to consider a supplier and a consecutive system as a single
system, or as separate systems, for purposes of compliance with the monitoring requirements of
the SWTR and TCR (EPA, 1999). This authority allows states with EPA concurrence to reduce
the overall number of samples taken within individual public water systems based on the
overall consecutive system sample plan. This approach is consistent with the underlying
random sample strategy for TCR sampling and the population-based sample requirements; it is
also consistent with the more recent Stage 2 Disinfectants and Disinfection Byproducts Rule
(Stage 2 DBPR) compliance-monitoring framework that is also population-based and also
allows consolidation of sampling plans across consecutive systems (40 CFR 141.29).
3.3 Sampling Locations
For clarity, the discussion of sampling locations will distinguish between two types: general
sampling locations and specific sampling sites (typically, a customer's tap, a hose bib, a
hydrant, etc.).
3.3.1 Survey Findings on Sampling Locations
Under the TCR, a public water system must submit sampling plans to the primacy agency for
review and approval. This review is in lieu of prescriptive requirements defining the
monitoring plan. Narasimhan et al. (2003) in an AwwaRF project report Sample Collection
Procedures and Locations for Bacterial Compliance Monitoring, surveyed and assessed current state
policies regarding TCR sample collection and location selection in California, Washington,
Arizona, Michigan, Maine, Alabama, and West Virginia. "Generally, utilities developed
sampling plans independently with limited regulatory guidance, and plans are approved and
reviewed periodically by primacy agencies. " The authors concluded that, in practice, there is
no national uniformity in the approaches to select TCR sample locations. Case-by-case
determinations are typically made to select specific locations rather than through an
overarching state guidance or policy document that would address considerations like the
impacts of treatment processes, water quality, pipe materials and booster chlorination facilities.
The authors reported that, in general, spatial distribution of sampling locations is based on a
visual observation of a system's map.
In addition to variations in sampling location selection, Narasimhan et al. (2003) found
variability within the types of sites used for sampling. For example, with regard to sampling of
storage facilities, the authors found that sampling practices ranged from collecting samples at
each tank to no samples taken in the vicinity of tanks. Similarly, some utilities use a
combination of consumer taps and dedicated sampling stations, or strictly one or the other.
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The report cited a 1985 survey (which pre-dates the TCR) of 1,796 utilities, undertaken by an
A WW A committee on Bacterial Sampling Frequency in Distribution Systems, which also
demonstrated wide variations in the types of sites selected by utilities (fire hydrants, storage
tanks, pumping stations, commercial buildings, public buildings, and private residences). The
same survey responders showed 36 percent of utilities using only fixed locations, 16 percent
using only variable locations, and 47 percent using fixed and variable locations. Utilities
responding to the survey considered area representation, convenience, centrality, and
representation of peripheral areas in their selection of sampling locations.
The TCR requires that systems collect routine total coliform samples at sites that are
"representative of water throughout the distribution system" but offers no guidance as to what
constitutes "representative." Narasimhan et al. (2004) stated that TCR sample siting plans
"have usually been developed based on a visual examination of the distribution system and the
convenience of sampling locations." Visual location selection (viewing a system map and
selecting sites according to a superimposed grid) may fail to account for parameters that may
affect monitoring results, such as variability in typical water demand and flow reversals.
3.3.2 Alternative Sample Location Considerations
Kirmeyer et al. (2002) identified common issues in distribution system monitoring program
designs, and suggested potential monitoring stations based on sampling objectives:
¦ At various points in the system reflecting different water ages
¦ At locations where water mixes or there is an interface between multiple sources
¦ At storage facilities
¦ At locations reflecting different water main materials and conditions
¦ At locations where supplemental (booster) disinfection is applied (if any), and
¦ At locations of critical facilities (e.g., hospitals)
Depending on the specific monitoring objectives, researchers target sampling designs to yield
information necessary to answer pertinent questions. For example, a system experiencing
nitrification may develop a sampling design that includes intensive sampling at locations where
disinfectant residual is expected to be low to determine the role of disinfectant decay in
nitrification.
The locations of interest in TCR monitoring would depend on the specific objective(s) being
considered. For example, locations of critical facilities, such as hospitals and child-care centers,
may be of particular interest in contaminant detection strategies, whereas distribution zones
known to be susceptible to breaks or leaks may be of particular interest in characterizing
distribution system integrity. Many utilities calculate percent leakage on a regular basis.
Higher leakage rates may indicate a system is more susceptible to intrusion and that the system
practices a lower level of overall maintenance.
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3.3.3 Sample Timing
The TCR requires public water systems to collect samples at regular time intervals throughout
the month, with one exception. Public water systems that only use ground water under the
direct influence of surface water and serve 4,900 persons or fewer, may collect all required
samples on a single day if they are taken from different sites. Consequently, sampling in
community water systems is not only distributed spatially, but also temporally over the
monthly monitoring period.
Guistino (2003) suggested that diurnal variations in distribution pumping schedules and
biological and chemical activity may play a role in obtaining a representative grab sample from
the distribution system. For example, Guistino noted that the logistics of sampling, sample
shipping, and laboratory scheduling tend to encourage a monitoring schedule that occurs early
in the day, when water demand is typically high, which may affect observed values. However,
for water systems that do most pumping at night and in the early morning, an early sampling
schedule may unintentionally bias results toward higher water quality. Sampling that occurs
later in the day when all pumping stops would reflect a higher proportion of water from
storage in higher [pressure] zones, which is often more susceptible to quality degradation based
on longer water age, chlorine residual loss, and increased heterotrophic plate count bacteria.
Note that as online chlorine analyzers gain in sue, diurnal and weekly variations within a
distribution system can be better understood. In drafting a sampling plan, the utility must
balance representative sampling with logistical challenges and resource constraints reflected in
a compliance sampling plan, such as:
1. Limitations imposed by the sample method holding times (e.g., time to collect the
samples and get the sample to the laboratory for processing),
2. Available certified laboratory capacity,
3. Personnel safety, and
4. Available staff time.
Guistino (2003) proposed procedures for sampling from distribution system reservoirs based on
timing of pumping (e.g., for common inlet-outlets, no sooner than one hour after pumping is
terminated) and provided guidance on sampling from reservoir hatches, mixers, and dedicated
sample lines at reservoirs in order to characterize water quality within individual storage
facilities. AWWA's Committee on Bacteriological Sampling Frequency in Distribution Systems
(1985) found that sampling is generally arranged by time of day, time of week, and time of
month.
3.3.4 Number of Samples per Site
The TCR requires that each compliance sample be collected based on a plan approved by the
state; it does not specify that sampling occurs from a discrete location. Similarly the TCR
specifies the total number of samples per month; it does not specify the total number of sites a
system must use. Consequently, state approved plans reflect state-specific and, in some
instances, system-specific approaches. Plans may be framed in one of the following ways:
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• A utility may identify exactly the same number of sampling locations as their
required number of samples, and collect one sample per month from each site.
• A large pool of sample sites, might be identified with the utility rotating among
these sites either randomly or based on a regular routine.
• A utility may identify fewer sites than the number of required samples, collecting
samples more frequently than once per month from these sites.
Each of these approaches is based on a different interpretation of the TCR's monitoring
requirements. As a result, one system that is collecting 210 samples per month may collect them
from 210 discrete sites, and may rotate them such that the next month none of the original sites
are revisited. Another system serving the same population size, also collecting 210 samples per
month, may have a total of 50 discrete sites that are visited about 4 times per month, every
month. Each of these sampling strategies has advantages and disadvantages.
The advantages of the first approach include gathering observations at more (and presumably
more geographically diverse) sites within the distribution system over time. However, each
individual site is visited very infrequently; consequently, the likelihood of the sampling at a
given site coinciding with a coliform occurrence may be extremely low unless an individual site
is subject to specific conditions that increase the number of coliforms at that location or has a
chronic water contamination problem. The second approach offers a greater ability to evaluate
trends in water quality at each site, since data are collected more frequently at each site. Also,
systems with a more limited number of sites may be able to better to reduce false positive and
false negative samples by achieving better control of the environment at the tap (improved
quality control in sampling).
Fixed sampling points provide more uniform information and a more reliable history of water
quality, whereas random sampling from different locations is useful when the total number of
samples is limited or to provide coverage of all areas when the system is complicated
(Narasimhan et al. 2004). Depending on system size, it is often naive to consider that,by
sampling at different sites, the likelihood of detecting an acute, short-term contamination event
will be significantly increased.
3.4 Repeat Sampling Monitoring Strategies
Pipes and Christian (1982) and Christian and Pipes (1983) showed that the distribution of
coliforms in the distribution system is not uniform. Therefore, repeat samples cannot always be
used to determine the validity of a total coliform-positive sample. Collecting more samples
(erroneously titled "repeat" samples) allows a utility to get a better measure of the frequency of
coliform bacteria in the system. The final TCR prohibits invalidating a total coliform-positive
sample because subsequent samples taken at the same tap and/ or nearby taps/ service
connections are total coliform-negative. However, EPA believes that if any repeat sample is total
coliform-positive at the same tap as the original total coliform-positive sample, but all repeat
samples at nearby service connections are total coliform-negative, this is a strong indication of a
domestic or other non-distribution system plumbing problem. Therefore, in this case, the final
rule allows the state to invalidate the original total coliform-positive sample. When the state
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determines that a coliform-positive result is a domestic or other non-distribution system
plumbing problem rather than a distribution system problem, EPA recommends that the state
instruct the system to inform all consumers at the affected location of the problem and to advise
them to boil their drinking water until the problem is corrected.
As noted in Table 1, the existing TCR requirement is to collect at least one repeat sample from
the sampling tap where the original total coliform-positive sample was taken, and at least one
repeat sample at a tap within five service connections upstream and at least one repeat sample
at a tap within five service connections downstream of the original sampling site within 24
hours. If one or more repeat samples in the set is total coliform-positive, the public water
system must collect an additional set of repeat samples within 24 hours. The system must repeat
this process until either total coliforms are not detected in one complete set of repeat samples or
the system determines that the MCL for total coliforms has been exceeded and notifies the state.
EPA wrote that, conceptually, if coliforms are present in repeat samples at the original tap and
also in either (or both) of the upstream and downstream repeat samples, then this occurrence
may be taken as evidence that the coliforms may be associated with water under the public
water system's control, as opposed to representing only the water within the customer's
premises. In contrast, if repeat sampling indicates the absence of total coliforms at upstream
and downstream sites, then the source of the contamination may be within the customer's
premises (e.g., the building's internal plumbing). Another purpose of repeat sampling is to
rule out tap contamination, which happens in non-sterile, general use taps and unsanitary tap
environments (Burlingame and O'Donnell, 1993).
The requirement that water systems be able to collect repeat samples within five service
connections upstream and downstream of the original sampling site places a constraint on some
water systems in selecting their routine sampling locations. Some systems prefer to use
commercial or government buildings for all compliance sampling, including upstream and
downstream sites, because of the potential need to gain access to the site on very short notice to
meet the 24-hour requirement of the rule. Finding sites with three commercial establishments
within 10 or 12 service connections along the same main poses an obstacle in many residential
neighborhoods.
The TCR requires a public water system to obtain a repeat sample within 24 hours if a positive
total coliform sample or a positive E. coli or fecal coliform result is obtained. Similar concerns
exist about locating sampling locations with accessible alternative sites within five service
connections due to the requirement to collect a repeat sample within 24 hours . The state may
extend the 24-hour limit on a case-by-case basis if the system has a logistical problem in
collecting the repeat samples within 24 hours that is beyond its control. In the case of an
extension, the state must specify how much time the system has to collect the repeat samples.
4.0 Appropriateness of TCR Analytical Designs and Statistical
Methods
The analytical design, which includes the parameters monitored, the sample collection
protocols used, and the analytical methods employed, is the third component of a monitoring
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strategy after establishing objectives and designing a sampling plan. The statistical methods
used to describe the monitoring data and the statistical methods and assumptions upon which
inferences and decisions are based are the final element of the overall monitoring strategy.
4.1 TCR Parameters: Correlation between TCR and Waterborne Disease
The parameters measured under the TCR include total coliforms, fecal coliforms or E. coli, and
indirectly, under the auspices of the Surface Water Treatment Rule, disinfectant residual or
heterotrophic plate count bacteria. In a well-designed monitoring program, the parameters
monitored must have relevance for the specific monitoring objective.
Borup (1992) stated that one of the major reasons for the change in TCR monitoring strategy
from density to presence-absence in 1989 was that no quantitative relationship between
coliform density and pathogen density or between coliform density and the potential for
outbreak of waterborne disease had been found to provide a measurable likelihood of the
potential for risk as would occur in setting an MCL. Therefore, it was not possible to determine
the risk associated with a particular coliform density, and thus a rational MCL could not be
established based on coliform densities. However, during at least one investigation of an
individual distribution system-related waterborne disease outbreak, investigators found
evidence of high levels of total coliforms in the water systems' compliance samples prior to the
outbreak (Clark et al. 1996).
Nwachuku, Craun, and Calderon (2002) conducted a retrospective epidemiological study
evaluating the utility of TCR compliance as an indicator of outbreak vulnerability and
concluded that TCR compliance monitoring is not able to identify those water systems that are
generally vulnerable to a waterborne outbreak but is predictive of bacterial outbreaks. In
comparing TCR violations for water systems that had and had not reported an outbreak during
1991-1998, they found that few systems experiencing outbreaks (22 percent of the community
water systems studied) had violated the TCR MCL in the 12-month period preceding the
outbreak. They also found no significant differences in the frequency of "outbreak" and
"nonoutbreak" systems' TCR MCL and monitoring violations.
Although their findings generally confirmed that coliforms were frequently found when
samples were collected during a time of suspected contamination, Nwachuku et al. (2002) found
that routine coliform monitoring was inadequate to predict waterborne outbreaks. The lack of
association between total coliform-positive incidents and waterborne disease outbreaks
reported by Nwachuku et al. may indicate a problem with the data available to document
outbreaks, the indicator parameter itself (which the authors noted, since routine TCR violations
were associated with bacterial outbreaks in the study, but not with all types of waterborne
disease outbreaks, such as those associated with protozoa), or it may indicate a problem with
using TCR monitoring data to support epidemiological analyses, or it may indicate inherent
biases in the monitoring strategies employed by water systems.
For example, investigators evaluating the waterborne disease outbreak in Cabool, Missouri, in
early 1990 concluded that the TCR compliance monitoring program focused on sites near the
center of town, but speculated that routine TCR compliance monitoring may have revealed the
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contaminating event if sampling locations had included areas near dead ends or slow flow areas
(Geldreich et al, 1992).
Allen, Clancy, and Rice (2000) questioned the value of pathogen monitoring of environmental
samples for the purpose of public health protection (e.g., contaminant detection monitoring)
and instead urged the use of process control measures to protect public health.
"Today the concept persists among regulatory agencies, public health organizations, and
the drinking water community worldwide that public health can only be ensured by
pathogen monitoring. ... [However], ensuring pathogen-free drinking water may depend
on treatment processes and operational practices that result in optimal removal or
inactivation of pathogens. Decades of research and field experience have confirmed that
well-operated, well-maintained, and well-monitored treatment processes can reliably
remove and inactivate pathogens."(Allen, et al. 2000)
These researchers propose that pathogen monitoring be replaced by alternative strategies such
as optimizing treatment and maintaining water quality throughout storage and distribution
because "past experience and data have shown that pathogen monitoring does not and cannot
confirm the absolute presence or absence of infectious microorganisms in drinking water."
A separate white paper addresses the appropriateness of total coliform and E. coli as indicators.
4. 2 TCR Sampling Protocols
4.2.1 Sample Collection Logistics
Selecting general, representative locations for sampling is just one step in establishing a sample
siting plan. Systems must also select the specific sampling sites in terms of the building and
tap. Several researchers have identified common logistical considerations in selecting specific
sampling sites for TCR compliance monitoring:
1. Systems must secure permission from site owners or occupants to collect samples.
2. Sites must be safe for water system staff to enter.
3. Taps must be accessible by water system staff; accessible taps located within 5
service connections upstream and downstream must be available in case repeat
sampling is required.
4. Systems must manage travel times for efficient sampling, minimizing sample
holding times, and conforming to work-day schedules.
5. Sources of potential cross contamination must be minimized.
Kirmeyer et al. (2002) summarized the key advantages and disadvantages of six typical
sample collection strategies (see Table 7). This table is not specific to coliform monitoring
but it is inclusive of considerations pertinent to coliform monitoring.
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Table 7. Comparison of Distribution System Sample Collection Strategies
State
Advantages
Disadvantages
Kitchen Tap
Ease of sample collection.
Contamination potential, accessibility to
residential sites may be difficult.
Hose Bib
Accessiblity; ease of sample collection.
Contamination potential; possible access
issue.
Fire Hydrant
Accessibility.
Contamination potential; may not represent
typical distribution system conditions.
Dedicated
Sample
Station
Clean, reliable, accessible sampling
point. Direct connection to distribution
system; ease of sample collection;
lockable; tamper-resistant.
Site Security; cost; maintenance; disposal of
flushing water.
On-line
Analyzer
Continuous, real-time data; potential
operational cost savings; improved
process control; ease of sample
collection.
Analyzers not available for all parameters
(i.e., DBPs, bacteria, taste and odor);
instrument maintenance required; water
disposal; chemical storage and use may be
difficult; increased data volume to be
reviewed.
Finished
Water Storage
Facilities
Key location for many monitoring
objectives.
Accessibility; may not represent typical
distribution system conditions; difficult to
collect sample representative of entire
contents.
Source: Kirmeyer et al. 2002.
4.2.2 Contamination of Compliance Samples from External Sources
Burlingame and O'Donnell (1993) proposed the concept of "noise" to describe coliform-positive
samples in which the organisms originate from external sources other than the distribution
system or the water supplied to a customer's service, such as coliform bacteria present in the
interior plumbing of a customer's facility. They documented case studies where coliform
contamination originated from faucets, building plumbing, and flooded meter pits and
recommended measures to control this noise. Burlingame and Choi (1998) recommended
practices for improved sampling practices to ensure that representative samples are collected,
including sampling apparatus design, installation, and maintenance and flushing practices to
discourage coliform growth in sampling lines. Dufresne et al. (1997) and Burlingame and Choi
(1998) identified criteria for accepting or rejecting individual sampling stations for TCR
compliance based on the potential for environmental contamination.
4.2.3 Dedicated Sample Taps
Studies by Ball et al. (1993) and Gueco (1999), among others, showed improvements in TCR
compliance after a system converted a large number of its sampling sites to dedicated sampling
stations. The City of Philadelphia found that the use of dedicated samplers improved the
usefulness of the total coliform indicator by providing higher-quality data that was
representative of distribution system water quality and was free of "noise" (Burlingame and
O'Donnell, 1993). The water systems attributed the improvements to more carefully controlled
sampling environments with fewer opportunities for environmental cross contamination.
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Critics have suggested that systems perhaps install dedicated sample taps in portions of the
distribution system where they are unlikely to find coliform bacteria.
Burlingame (2004) proposed a conceptual framework for considering the applicability of
dedicated sampling sites (Figure 3). Because noise can be controlled more effectively at
dedicated sites, and because control points such as the point of entry, pump stations, and
storage facilities (the entry and transmission level) have the potential to affect the greatest
number of customers, such sites are especially suitable for dedicated sampling sites.
Conversely, it is much more difficult to control the sampling environment, and thus the noise,
at homes and buildings —the service level. This concept illustrates that it may be much more
feasible to reliably achieve the TCR objective of process control compared to the objective of
contaminant detection at the service level because of the problem of noise.
Figure 3. Conceptual Framework for the Applicability of Dedicated Sampling Sites
Entry Points
Pump Stations
Storage Facilities
Dedicated
Samplers
Application of
Dedicated
Sampling
Sites
Level of
"Noise"
Interfering
with
Coliform
Monitoring
Entry Level
I
Transmission
Level
Service Level
Homes & Buildings
Control over Sampling vs Background Noise
Source: Burlingame, 2004.
4.2.4 Sample Volume
Dempsey and Pipes (1986) demonstrated mathematically the effect of minimum required
volume on the probability of compliance, showing that larger sample volumes were more
sensitive to detection of coliforms. For example, analyzing varying volumes (25 mL, 50 mL, 100
mL, or 200 mL) of the same theoretical sample containing lognormal-distributed coliforms
would yield a determination of approximately 4, 7,10, or 13 % total coliforms, respectively.
Haas (1993) showed the importance of the assumption regarding the underlying distribution of
the microorganisms in determining whether it is better to use a large number of small volume
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samples or a small number of large volume samples. For data that follow a Poisson
distribution, there is no difference. For data that follow a negative binomial distribution, there
is a difference, and the answer depends on whether the dispersion parameter, k, varies with
sample volume or is independent of sample volume, which he notes can only be determined
experimentally.
Research performed by the Honolulu Board of Water Supply to assess the vulnerability of
groundwater sources to fecal contamination specifically considered the effect of sample volume
on method sensitivity for detecting total coliform, fecal coliform, E. coli, and fecal streptococci
bacteria (Fujioka et al. 2001). The authors concluded that, "if the standard (100-mL) volume of
groundwater samples was tested, 3 of 79 water samples (4%) were positive for total coliform.
By increasing the sample volume assayed to 1000 mL, 7 of 79 water samples (9%) were
determined to be positive for total coliform.. .By increasing the volume of sample to be tested
from 100 to 1,000 mL, the sensitivity for the detection of total coliform bacteria increased by a
factor of two or three." Pryor et al. (2005) illustrated a similar pattern of increased likelihood of
positive total coliform sample recovery by increasing sample volume from 100 mL to 2 liters;
using an experimental method, detections increased in chlorinated water, though less so than
when testing unchlorinated water. In one study, researchers used a composite sampler to
improve the detection of coliform bacteria in finished water (Pipes and Minnigh, 1990).
4.2.4 Sample Handling
Pipes and Christian (1982) found that the density of coliforms collected from a distribution
system can change within twenty-four hours. However, in a study to determine whether
holding time and storage conditions had an effect on E. coli densities in surface water, Pope, et
al. (2003) reported that most surface water E. coli samples analyzed by commonly used methods
beyond 8 hours after sample collection can generate E. coli data comparable to those generated
within 8 hours of sample collection, if samples are held below 10°C and are not allowed to
freeze.
4.3 TCR Methods
Coliforms include several genera of bacteria belonging to the family Enterobacteriaceae. The
historical definition of this group is based on its ability to ferment lactose as used in the test
method. The issue of coliform occurrence is complicated by the fact that new methods, with
different analytical techniques (media, plating techniques, and incubation methods) produce
different results. Thus, the definition of a coliform has changed over time.
EPA has approved a variety of methods for TCR compliance, including methods for total
coliforms, fecal coliforms, and E. coli. These methods include presence-absence, membrane
filter, and multiple tube fermentation techniques. (The presence-absence analytical technique is
distinct from the reporting of presence or absence of coliforms in lieu of coliform densities). All
three analytical methods use cultivation, on either classical lactose-based media or defined-
substrate media, to detect and confirm the presence of total coliforms.
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In approving analytical methods for TCR monitoring, U.S. EPA evaluated the effectiveness of
these methods (64 Federal Register 67454) and indicated that appreciable false positive rates
may be experienced with the routine practice of some TCR methods (see Table 8).
Table 8. False Positive Rates Reported for Commercial Coliform/E. coli Tests
Method
Total Coliforms
E. coli
E*Colite
16.0%
7.2%
m-ColiBlue24
26.8%
2.5%
The agency noted in that rulemaking that:
"... the different methods may not be testing for exactly the same set of organisms,
and this situation clouds the meaning of the term "false-positive." Second, the
Agency believes that public health would not be jeopardized with the higher false-
positive rates because any false-positive result would err on the side of safety.
Third, the Agency notes that a single total coliform-positive sample does not result
in an MCL violation. Thus the adverse consequence of a "false-positive" for the
system is mitigated." (64 FR 67454).
Burlingame (2004) reported that use of an approved TCR method resulted in false-positive total
coliform results caused by the presence of Gram-positive cocci, such as Staphylococcus spp. He
concluded that a standardized confirmation and identification step is needed before final TCR
reporting occurs. The approved methods for coliforms do not adequately address the
confirmation of a positive test results.
EPA's December, 1999 notice indicated that the Agency was open to approving analytical
methods with equal or even higher false positive rates. This example of how the current list of
approved methods introduces substantial uncertainty into the reported level of positive
samples illustrates that the effectiveness of the TCR Monitoring Strategy is closely linked to the
analytical methods employed. The strengths and limitations of the approved TCR methods are
important to understanding the variability in the observed TCR data and the appropriate
thresholds for action. There is a separate white paper on the TCR indicators and the associated
analytical methods; readers should refer to that paper for more information on the analytical
method performance. Also, an AwwaRF research study is currently underway to address the
4.4 Statistical Methods Used In Coliform Rule Development and
Compliance Evaluations
4.4.1 Frequency Distribution of Total Coliforms
As discussed in Sections 2.3 and 3.2, research on the frequency of occurrence of coliforms was
conducted prior to the promulgation of the 1989 TCR. Borup (1992) noted that the TCR was
developed on the basis of the assumption that results from presence-absence testing can be
described by the negative binomial distribution. However, he pointed out that one of the
underlying assumptions for applying the binomial distribution is that the probability of
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obtaining a positive coliform result is the same for each sample (e.g., that the fraction of positive
samples is the same at every point in the distribution system over the total time period of
sampling). This condition is likely to fail under circumstances that the rule should be designed
to identify (e.g., when system integrity is breached, allowing external contamination to enter.)
Borup also found problems with the statistical basis of the TCR. He found that water of
acceptable quality (95% confidence that less than 10% of the water passing through a
distribution system would contain coliforms) may be found to be in violation of the standard a
significant portion of the time and that water of unacceptable quality may be found to meet
standards, particularly when small numbers of samples are taken.
Hamilton (1994) evaluated the statistical basis for the 1989 TCR and found the regulation
potentially allows a higher chance of coliform-contaminated water to be present in a system
than intended. He calculated a false pass rate of less than 1% and a false fail rate between 40%
and 50% for the TCR when large numbers of samples are taken (>200), and a higher false pass
rate for systems collecting small numbers of samples. Hamilton agreed with Borup's findings
that use of the binomial distribution may be problematic because it ignores inherent
uncertainties (e.g., in sampling mechanisms, storage, transport, analysis) and suggested that the
error rates would be even higher if these uncertainties were considered.
4.4.2 Presence/Absence vs Density
The 1989 TCR adopted a presence-absence monitoring strategy that replaced a density
approach. According to the EPA, the advantages of the presence-absence strategy include:
¦ The presence or absence of coliforms is easy to determine, eliminating some of the
uncertainty of the estimation-of-density techniques
¦ Sample transit times are less critical, because a decrease in coliform density seldom
results in complete die-out of coliform organisms
¦ The data truncation errors associated with very high and very low densities
measured by the multiple-tube fermentation techniques are eliminated.
USEPA identified the following disadvantages:
¦ High coliform levels that may occasionally act as important signals of water quality
problems are not distinguished by the presence-absence test.
¦ People accustomed to the density approach may have trouble adjusting to the new
approach.
Borup (1992) evaluated the effect of this change in strategy from a statistical perspective and
suggested that, for a distribution system whose integrity has been compromised, the MCL
would be far less likely to be violated when water quality is impaired in a localized section of
the distribution system under the presence-absence strategy than under the density strategy
and that systems would therefore have less incentive to investigate and remediate such
problems. However, the 1989 TCR added a requirement for repeat sampling to provide
incentive to investigate problems.
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4.4.3 Limitations of Analytical Methods in Screening for Rare Events
Hrudey and Rizak (2004) proposed a statistical framework for evaluating rare contamination
events, demonstrating that, "as the hazard for which the search is being conducted becomes
more rare, false positives can be expected to exceed true-positives unless a test offers a false-
positive rate approaching the frequency of the hazard." They illustrated the situation using a
hypothetical analytical method with only a 3 percent false positive rate, showing that it would
need to have a hazard frequency of at least one in 33, or 3 percent, to have a 50-50 chance of any
positive being correct. Since total coliforms apparently occur in compliant public water systems
at rates sometimes far below 5 percent, this concept may be a useful tool for evaluating the
acceptability of total coliform analytical methods.
The following two tables (Tables 9 and 10) illustrate the occurrence of total coliforms based on
regulatory monitoring compilations from 14 states and 6 example public water systems.
Table 9. Total Coliform Occurrence in Example States
State
Number of
Years of Data
Collected
Number of Total
Coliform Samples
Collected
Percent of
Positive Total
Coliform Samples
MO
6
467,896
0.05%
IL
6
680,738
0.40%
PA
6
878,849
0.53%
OH
6
692,051
0.66%
FL
2
537,495
0.74%
AZ
5
328,298
1.76%
IA
6
303,110
1.96%
NH
6
74,993
2.18%
WA
6
671,118
2.69%
NE
6
157,165
3.42%
IN
6
437,006
3.64%
NC
6
436,338
4.07%
VA
6
227,474
4.41%
MD
6
311,925
4.70%
Source: Rosen et al. 2006.
5.0 Alternative Distribution System Monitoring Strategies
In evaluating monitoring strategies under the TCR, it may be useful to consider alternative
distribution system monitoring strategies described in the literature and in recent international
forums. These concepts include fully developed sampling plan strategies as well as ideas that
may be applicable in a restructured TCR as triggers for action, for example, or as follow-up
actions. The following concepts are discussed in this section:
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Table 10. Total Coliform Occurrence at Example Utilities
PWS
Number of
Years of
Data
Collected
Number of
Total Coliform
Samples
Collected
Percent of
Positive Total
Coliform
Samples
Maximum
Monthly
Percent
Positive Total
Coliform
Samples
Number of
Positive E.
coli Samples
Virginia PWS serving >
100,000
9
24,351
0.12%
1.25%
1
Pennsylvania PWS
serving > 100,000
5
28,599
0.15%
nc*
2
Florida PWS (1) serving
>100,000
6
28,624
0.22%
nc*
11
Florida PWS (2) serving
>100,000
2
17,003
0.27%
nc*
6
Florida PWS (3) serving
>100,000
8
22,444
0.78%
6.18%
3
Private Utility (multi-
State)
8
12,882
2.39%
2.18%
6
Note: * NC equals "not calculated"
Source: Rosen et al. 2006.
¦ AwwaRF Guidance Manual: Developing a Bacterial Sampling Plan
¦ Statistically-Based Sampling Network Design
¦ Use of Hydraulic Models to Aid in Monitoring Station Selection
¦ Hazard Analysis Control Evaluation Process
¦ Sampling for Rare Events (Inverse Sampling)
¦ Sampling at Worst Case Areas
¦ Statistical Process Control Theory
¦ Tiered Response Action Approach
¦ Use of Alternative Process Control and System Characterization Tools
An AwwaRF project, "Methodologies for assessing and improving water quality sampling
programs in drinking water distribution system/' which has not yet reported its findings, may
shed light on additional strategies.
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5.1 AwwaRF Guidance Manual: Developing a Bacterial Sampling Plan
The AwwaRF Guidance Manual Developing a Bacterial Sampling Plan provided rational
guidelines for utilities of all sizes to design effective bacterial sampling plans (Narasimhan and
B re re ton, 2004). The manual lays out a six-step approach to develop a distribution system
bacterial sampling plan. The approach begins by allocating the required number of TCR
compliance samples among sectors, the number of which are dictated by population served,
ranging from one sector for small systems to six sectors for systems serving upwards of 3.9
million persons. The recommended number of sectors is based on logistical considerations (10-
20 samples that can be collected per day by one sampler within a sector). Spatial sectors are
defined using political boundaries, pressure zones, influence zones of water sources, pressure
zones, and so forth. Next, the total number of required samples is divided among each sector on
the basis of population. The approach presumes collection of the number of samples specified
in the TCR unless the system cannot be adequately characterized by that number of samples.
Critical factors that influence bacterial monitoring results are considered next, and the number
of samples may be adjusted above the minimum requirements of the TCR to adequately
characterize water quality. Critical factors include source variation, disinfectant level, pressure
zones, pipe material or age, demand variation, land use variation, dead ends, sensitive
populations, reservoirs or storage tanks, and other considerations such as nitrification history.
Once sites are selected, then the specific taps are selected; the taps are chosen considering
accessibility, hydraulic conditions, and other factors that could influence bacterial results by
representing building or site contamination as opposed to system water quality in the local area.
5.2 Statistically-Based Network Design
Bahadur et al. (2003) stated that the best sampling design "will be based on an objective
approach, dependent on a number of factors, including the desired statistical power and level of
confidence in the final decision and the variability of the environmental attribute of interest."
Although Pipes (1988) suggested that stratified, random sampling could be applied to water
distribution systems, application of statistical approaches to network sampling designs has been
limited until recently.
Speight, Kalsbeek, and DiGiano(2004) proposed a methodology for randomization and
stratification to allow a distribution system sampling plan to identify optimal locations and
sample collection frequencies to meet specific data goals. For example, for a sample siting plan
to be representative spatially, the utility's service area could be divided into strata representing
various categories of radial distance to the treatment plant. For representative sample collection
timing, "peak" and "non-peak" strata could be defined. The total number of samples required
for a specific confidence level and margin of error would be allocated among the various strata.
The advantages of this approach in providing statistically valid samples at a defined level of
confidence would need to be balanced with practical considerations regarding sample size
(Speight et al, 2004).
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5.3 Use of Hydraulic Models to Aid in Monitoring Site Selection
Various researchers have considered the use of hydraulic modeling to aid in selecting
monitoring sites within distribution systems or to test the effectiveness of a particular
monitoring plan if a metric for the plan's effectiveness can be established. In addition, several
recent research projects have sought to determine optimal monitoring strategies through the use
of hydraulic modeling or network analysis. The impetus for this work has been the concern
about purposeful contamination of distribution systems and where monitors should be located
to best observe the contamination. A major issue is whether the monitoring objectives
associated with monitoring for security purposes are similar to the monitoring objectives
associated with the TCR. Most of the security-related modeling approaches assume a single
point of contaminant introduction, which may or may not be applicable for TCR monitoring.
Lee, Deininger, and Clark (1991) attempted to systemize and optimize monitoring station
selection using a mathematical model in conjunction with a hydraulic model and assuming that
downstream water quality could be used to infer upstream water quality. By considering the
routes that water could theoretically travel (the pathways) from the point-of-entry to each node
of the model, along with each node's contribution to downstream water demand, they could
determine the theoretical "coverage" that a given arrangement of sampling stations would
provide in characterizing water quality systemwide. This technique may be able to represent
more of the distribution system with fewer samples. One limitation is that the technique may
be biased toward monitoring for coliform bacteria that enter the distribution system via the
treatment plant or source water (Narasimhan et al. 2003) rather than other routes within the
system.
Berry, Fleischer, Hart, and Phillips (2003) used hydraulic modeling with an integer
programming approach to optimize sensor placement in municipal water networks to minimize
the fraction of the population at risk. They noted other objectives could be minimizing the
volume of water consumed before detection or minimizing the time before detection, for
example. Ostfeld and Salomons (2003) used a genetic algorithm approach with EPANET to
optimize the layout of a detection system for introduced contaminants, considering the
unsteady hydraulics, dilution effects, and decay properties of the water quality constituents.
Their methodology locates a set of monitoring stations intended to capture the maximum
volume of contaminant exposure to the public at a concentration higher than a minimum
hazard level. Bhadur, Samules, Grayman, Amstutz, and Pickus (2003) used a combination of
hydraulic modeling with extended period simulation using PipelineNet and GIS to select nodes
for monitoring in case of contaminant intrusion. The PipelineNet system converts hydraulic and
water quality parameter modeling output files into ArcView shapefiles, which are displayed in
ArcView along with GIS layers depicting the distribution system and other infrastructure.
Despite the potential usefulness of hydraulic modeling tools, developing, calibrating, and
maintaining a valid distribution system hydraulic model is a very costly endeavor — one that
remains beyond the reach of many water systems.
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5.4. Approaching the Distribution System as a Process
One of the primary objectives of the TCR is to serve as a process control reliability check in the
multiple-barrier approach. Coliform sampling provides a quality control check on the overall
treatment, transmission, and distribution process when it focuses on sampling locations that are
reflective of overall or average conditions or that are identified as critical process control points.
As noted previously, a separate white paper is addressing the identification of critical control
points for water distribution systems. Critical control point monitoring using multiple
parameters has its origins in Hazard Analysis and Critical Control Point (HACCP). Currently,
Australia employs HACCP as the overall framework for assuring drinking water quality from
catchment to tap. The HACCP model is also being considered in Canada as the provinces
continue to respond to the Walkerton outbreak.
In the international arena, the World Health Organization (WHO) adapted the HACCP concept
to drinking water. WHO is currently advising both industrialized and developing countries to
consider the use of "Water Safety Plans" as a management framework for public drinking water
systems. In May, 2004 EPA recommended that the HACCP approach be considered in the
revision of the TCR.
5.5 Sampling for Rare Events (Inverse Sampling)
Coliform occurrences in TCR compliance sampling programs are generally rare events —
occurring in fewer than 5 percent of samples collected by compliant water systems.
Occurrences of E. coli or fecal coliforms are even less frequent. Water utilities may be able to
draw upon the experience of other disciplines for monitoring strategies aimed at sampling for
rare events. For example, it may be possible to adapt some of the methodologies used in the
public health area for syndromic surveillance. Statistical methods such as aberration detection
algorithms are frequently used by epidemiologists to assist them in identifying and
characterizing disease outbreaks by rapidly assessing changes in frequencies and rates of
different health outcomes and for the characterization of unusual trends or clusters
(Hutwagner, Thompson, Seeman, and Treadwell, 2003). Applying such surveillance
methodologies to coliform occurrence data might also promote a better understanding of the
link between waterborne outbreaks and coliform occurrence. To use such tools would likely
involve confirming the underlying distribution of coliform data in water systems; developing or
adapting an applicable methodology; addressing the question of whether coliform events are
indeed random, independent variables (if required by the algorithm); and considering the role
of distribution system hydraulics.
5.6 Sampling at the Worst Case Areas
It is possible to conceive of a monitoring strategy that would attempt to maximize the number
of positive samples by sampling intensively in areas that are most likely to harbor them. This
approach is premised on the assumption that finding and preventing contamination at these
locations is an efficient and effective means of ensuring that contamination does not occur
throughout the entire distribution system. For example, this monitoring strategy might focus
43
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on sampling in areas of low flow, at dead ends, at stagnant areas within storage facilities, in
corroded cast iron pipes, and in areas where low disinfectant residuals occur frequently. Such
a strategy would presume that we can identify areas that are susceptible to coliforms and might
involve restructuring the compliance system to reward systems for seeking out and finding
coliforms and remedying any problem areas.
5.7 Statistical Process Control Theory
It may be possible to apply statistical process control concepts, such as control charts, to
develop a sampling plan design to capture either data excursions of significance or gradual
water quality deterioration, such as a gradual increase in background levels of total coliforms or
other parameters of significance. This approach may be particularly applicable for the process
control objective of monitoring at the points of entry or at storage facilities. It may also be
applicable for characterizing areas that are particularly susceptible to biofilm growth. The
number of samples needed for this sampling framework is most likely beyond the capabilities
of manual grab sampling and analysis. However, rapid advances in on-line monitoring and
automation in the drinking water arena are occurring, and the growing opportunities for real-
time decision-making tools to aid in public health protection should be considered.
5.8 Tiered Response Action Approach
Total-coliform-positive results could trigger tiered investigations and response actions. It is
reported (DWI, 2000, cited in Health Canada, 2004) that "the Drinking Water Inspectorate of
England and Wales has included in its regulations a mandatory value of zero coliforms per 100
mL in water leaving treatment works, a mandatory value of zero coliforms per 100 mL in 95%
of samples for water in service reservoirs, and a non-mandatory value of zero coliforms per 100
mL at the consumer's tap. In these regulations, non-mandatory values do not need to be met,
but exceedances need to be investigated and actions taken only if they represent a health risk."
A few examples of such investigations and actions include the following:
¦ Determine coliform density. Some researchers (Borup, 1992) predicted that the
change from considering coliform densities to a presence/absence-based MCL
would result in the loss of valuable information on localized problems in portions of
the distribution system. Therefore, it may be useful to require systems to analyze
coliform density under some circumstances.
¦ Sample more intensively near the areas where coliforms are found.
¦ Undertake a unidirectional flushing program to remove accumulated sediments and
biomass.
¦ Use mapping tools to graphically display locations of coliform occurrences and
potential influences, such as distribution system maintenance activities, areas of low
pressure or low water demand, etc.
44
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¦ Employ microbial source tracking to determine whether fecal contamination
originates with human or animal sources. According to the National Research
Council (2004), there are several promising microbial source tracking techniques in
development.
¦ Undertake a comprehensive cross connection control program.
Many more possible activities could be envisioned for better investigating and resolving
coliform occurrences.
5.9 Use of Alternative Process Control and System Characterization Tools
Total coliform is monitored, in part, as a process control and system characterization tool—to
evaluate the effectiveness of the treatment process in inactivating bacteria and to determine
whether bacteria are finding post-treatment routes into the distribution system. Reasoner (1990)
proposed using heterotrophic plate counts (HPC) for several similar objectives, including
monitoring the efficiency of the water treatment process, assessing the integrity of the
distribution system (e.g., assessing changes in finished-water quality during distribution and
storage), and confirming that high HPC levels were not interfering with coliform/E. coli
measurements. Given that coliform occurrences are relatively rare, whereas HPC occurrences
are more widespread, there may be advantages in monitoring HPC rather than total coliforms
for process control and system characterization, from a statistical perspective. However,
monitoring for HPC would not provide the warning of potential fecal contamination that
monitoring for total coliforms provides.
6.0 Summary of Findings and Research Needs
6.1 Ongoing Research
The following seven ongoing research projects were identified through a review of AwwaRF
and DRINK databases. Ongoing research projects that relate directly to TCR monitoring
strategies are included. Projects more closely related to other TCR white papers were not
included in this listing:
¦ Assessing and Improving Water Quality Sampling Programs in Drinking Water
Distribution Systems AwwaRF #3017, Malcolm Pirnie, Inc. This project is to
identify distribution-system-sampling needs and develop methods and tools to help
utilities evaluate sampling plans and improve them to achieve multiple goals.
Results are due August 2007.
¦ Testing and Evaluation of Currently-Used Water Monitoring Technologies for their
Ability to Meaningfully Respond to Changes in Drinking Water Quality. EPA-
National Homeland Security Research Center. This project involves controlled tests
to evaluate currently used water monitoring technologies and their ability to
respond to changes in drinking water quality due to the introduction of various
contaminants. The research conducted will support large and small treatment water
45
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utilities with particular emphasis on distribution systems. All test and evaluation
research will be conducted under controlled conditions using technologies currently
located at the Water Awareness Technology Evaluation Research and Security
(WATERS) Center located at EPA's Test & Evaluation (T&E) Facility in Cincinnati,
OH. Preliminary results were reported in 2005 but further testing is planned (EPA,
2005).
Identification of Heterotrophic Bacteria That Colonize Chloraminated Drinking
Water Distribution Systems, AwwaRF #3088, Univerisity of Wisconsin at Madison.
This project's goal is identifying and quantifying the heterotrophic bacteria that
colonize chloraminated drinking water distribution systems. It anticipates
determining whether bench- and pilot-scale chloraminated systems are adequate
models to study the type of bacteria that colonize full-scale systems. It will also
formulate mechanisms and hypotheses for the role of these bacteria as the critical
microbial group in nitrification of chloraminated distribution systems. Results are
due April 2008.
Strategy to Manage and Respond to Total Coliforms and E. coli in the Distribution
System, AwwaRF #3116, HDR/EES. The purpose of the project is to develop a
practical guide to help utilities manage microbial water quality and develop
response strategies to total coliforms and E. coli events in the distribution system.
Will also include the application of available microbial source tracking tool(s) for the
determination of contamination source(s) in the distribution system. The results of
this project bear on determining under which conditions upstream and downstream
sampling are important to the monitoring strategy. Results are due January, 2009.
Development of Performance Criteria and Measurement Parameters for On-Line
Monitoring Instrumentation, AwwaRF #2978, Sandia National Laboratories. This
project will develop performance criteria for existing on-line monitoring
instrumentation. It will determine surrogates for evaluating and testing the
performance of a select group of on-line instruments for possible detection of
chemical or biological contaminants in the distribution system. While this project is
focused on security related distribution system monitoring, the information
collected will be relevant to the TCR monitoring strategy discussion. Results are
due April 2008.
Data Processing and Analysis for Online Distribution System Monitoring, AwwaRF
#3035, Commonwealth Scientific and Industrial Research Organization (CSIRO),
Australia. The aim of this project is to examine data processing methods that can
distinguish normal variability from patterns related to specific contamination
events. Will develop a general data processing approach to assist water quality
managers and water system operators to detect abnormal patterns in online
monitoring data. This project bears on the integration of chlorine residual or other
parameters for which there are on-line monitoring devices for the TCR monitoring
framework. Results are due August, 2007.
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¦ Cross-Connection and Backflow Vulnerability: Monitoring and Detection, AwwaRF
#3022, American Water. This project is intended to determine the most effective
technologies available, as well as recommended placement, to prevent, monitor and
rapidly detect contamination in the distribution system related to cross-connection
and backflow events. Results are due January 2009.
6.2 Research Gaps
The fundamental problem in designing a total coliform monitoring program is the lack of
understanding of the processes that must be monitored. As a result, some of the research
needs pertain to understanding coliform behavior and causal factors. Other research
needs pertain more directly to addressing different objectives in monitoring under
different system-specific conditions. At present, research gaps include:
1. A clear and specific definition of the objectives of the TCR and/ or other
monitoring program, including metrics for each objective. A comprehensive
evaluation of how to develop an optimal water quality sampling and monitoring
network that is not single purpose, but meets the public water system's need for
monitoring to assure operational control, regulatory compliance, customer
acceptance, and other purposes.
2. A good understanding of the behavior, fate and transport of microbial
contaminants entering the distribution system by different pathways, including a
systematic assessment of the role of biofilms in total coliform and E. coli occurrence
in distributed water; a systematic assessment of the frequency of events that are
likely to introduce microbial contaminants into the distribution system; and the
factors most significant in determining the frequency and amount of microbial
contamination introduced to distributed water.
3. An understanding of the effect of system-specific variables such as disinfectant
type or system configuration on microbial contaminant behavior.
4. A systematic evaluation of response strategies following an observation of elevated
total coliform or E. coli levels in the distribution system.
5. An understanding of the extent to which chlorine-resistance is developing in target
species and impacts of such resistance (if it exists) on analytical method
performance.
6. An understanding of the connection between flow, chlorine residual, and coliform
bacteria occurrence in a distribution system and integrating this understanding
into monitoring development approaches utilizing modeling tools.
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53
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Appendix A.
A Partial Excerpt of Section 141 of the Code of Federal
Regulations Pertinent to the Total Coliform Rule Monitoring
Requirements
A-l
-------
Environmental Protection Agency
§141.21
in this section apply to filtered sys-
tems until June 29, 1993. The require-
ments in this section apply to
unfiltered systems that the State has
determined, in writing pursuant to
§1412(b)(7)(C)(iii), must install filtra-
tion, until June 29, 1993, or until filtra-
tion is installed, whichever is later.
(a) One turbidity unit (TU), as deter-
mined by a monthly average pursuant
to §141.22, except that five or fewer tur-
bidity units may be allowed if the sup-
plier of water can demonstrate to the
State that the higher turbidity does
not do any of the following:
(1) Interfere with disinfection;
(2) Prevent maintenance of an effec-
tive disinfectant agent throughout the
distribution system; or
(3) Interfere with microbiological de-
terminations.
(b) Five turbidity units based on an
average for two consecutive days pur-
suant to §141.22.
[40 FR 59570, Dec. 24, 1975]
§141.15 Maximum contaminant levels
for radium-226, radium-228, and
gross alpha particle radioactivity in
community water systems.
The following are the maximum con-
taminant levels for radium-226, ra-
dium-228, and gross alpha particle ra-
dioactivity:
(a) Combined radium-226 and radium-
228—5 pCi/1.
(b) Gross alpha particle activity (in-
cluding radium-226 but excluding radon
and uranium)—15 pCi/1.
[41 FR 28404, July 9, 1976]
Effective Date Note: At 65 FR 76745, Dec.
7, 2000, §141.15 was removed, effective Dec. 8,
2003.
§141.16 Maximum contaminant levels
for beta particle and photon radio-
activity from man-made radio-
nuclides in community water sys-
tems.
(a) The average annual concentration
of beta particle and photon radioac-
tivity from man-made radionuclides in
drinking water shall not produce an
annual dose equivalent to the total
body or any internal organ greater
than 4 millirem/year.
(b) Except for the radionuclides list-
ed in Table A, the concentration of
man-made radionuclides causing 4
mrem total body or organ dose equiva-
lents shall be calculated on the basis of
a 2 liter per day drinking water intake
using the 168 hour data listed in "Max-
imum Permissible Body Burdens and Max-
imum Permissible Concentration of Radio-
nuclides in Air or Water for Occupational
Exposure," NBS Handbook 69 as amend-
ed August 1963, U.S. Department of
Commerce. If two or more radio-
nuclides are present, the sum of their
annual dose equivalent to the total
body or to any organ shall not exceed 4
millirem/year.
Table A—Average Annual Concentrations
Assumed to Produce a Total Body or
Organ Dose of 4 mrem/yr
Radionuclide
Tritium
Strontium-90 .
Critical organ
Total body
Bone marrow .
pCi per
liter
[41 FR 28404, July 9, 1976]
Effective Date Note: At 65 FR 76745, Dec.
7, 2000, §141.16 was removed, effective Dec. 8,
2003.
Subpart C—Monitoring and
Analytical Requirements
§141.21 Coliform sampling.
(a) Routine monitoring. (1) Public
water systems must collect total coli-
form samples at sites which are rep-
resentative of water throughout the
distribution system according to a
written sample siting plan. These plans
are subject to State review and revi-
sion.
(2) The monitoring frequency for
total coliforms for community water
systems is based on the population
served by the system, as follows:
Total Coliform Monitoring Frequency for
Community Water Systems
Population served
25 to 1,0001 ..
1,001 to 2,500
2,501 to 3,300
3,301 to 4,100
4,101 to 4,900
4,901 to 5,800
5,801 to 6,700
6,701 to 7,600
Minimum
number
of sam-
ples per
month
345
-------
§141.21
40 CFR Ch. I (7-1-02 Edition)
Total Coliform Monitoring Frequency for
Community Water Systems—Continued
Minimum
number
Population served
of sam-
ples per
month
7,601 to 8,500
9
8,501 to 12,900
10
12,901 to 17,200
15
17,201 to 21,500
20
21,501 to 25,000
25
25,001 to 33,000
30
33,001 to 41,000
40
41,001 to 50,000
50
50,001 to 59,000
60
59,001 to 70,000
70
70,001 to 83,000
80
83,001 to 96,000
90
96,001 to 130,000
100
130,001 to 220,000
120
220,001 to 320,000
150
320,001 to 450,000
180
450,001 to 600,000
210
600,001 to 780,000
240
780,001 to 970,000
270
970,001 to 1,230,000
300
1,230,001 to 1,520,000
330
1,520,001 to 1,850,000
360
1,850,001 to 2,270,000
390
2,270,001 to 3,020,000
420
3,020,001 to 3,960,000
450
3,960,001 or more
480
11ncludes public water systems which have at least 15
service connections, but serve fewer than 25 persons.
If a community water system serving
25 to 1,000 persons has no history of
total coliform contamination in its
current configuration and a sanitary
survey conducted in the past five years
shows that the system is supplied sole-
ly by a protected groundwater source
and is free of sanitary defects, the
State may reduce the monitoring fre-
quency specified above, except that in
no case may the State reduce the mon-
itoring frequency to less than one sam-
ple per quarter. The State must ap-
prove the reduced monitoring fre-
quency in writing.
(3) The monitoring frequency for
total coliforms for non-community
water systems is as follows:
(i) A non-community water system
using only ground water (except
ground water under the direct influ-
ence of surface water, as defined in
§141.2) and serving 1,000 persons or
fewer must monitor each calendar
quarter that the system provides water
to the public, except that the State
may reduce this monitoring frequency,
in writing, if a sanitary survey shows
that the system is free of sanitary de-
fects. Beginning June 29, 1994, the
State cannot reduce the monitoring
frequency for a non-community water
system using only ground water (ex-
cept ground water under the direct in-
fluence of surface water, as defined in
§141.2) and serving 1,000 persons or
fewer to less than once/year.
(ii) A non-community water system
using only ground water (except
ground water under the direct influ-
ence of surface water, as defined in
§141.2) and serving more than 1,000 per-
sons during any month must monitor
at the same frequency as a like-sized
community water system, as specified
in paragraph (a)(2) of this section, ex-
cept the State may reduce this moni-
toring frequency, in writing, for any
month the system serves 1,000 persons
or fewer. The State cannot reduce the
monitoring frequency to less than
once/year. For systems using ground
water under the direct influence of sur-
face water, paragraph (a)(3)(iv) of this
section applies.
(iii) A non-community water system
using surface water, in total or in part,
must monitor at the same frequency as
a like-sized community water system,
as specified in paragraph (a)(2) of this
section, regardless of the number of
persons it serves.
(iv) A non-community water system
using ground water under the direct
influence of surface water, as defined
in §141.2, must monitor at the same
frequency as a like-sized community
water system, as specified in paragraph
(a)(2) of this section. The system must
begin monitoring at this frequency be-
ginning six months after the State de-
termines that the ground water is
under the direct influence of surface
water.
(4) The public water system must col-
lect samples at regular time intervals
throughout the month, except that a
system which uses only ground water
(except ground water under the direct
influence of surface water, as defined
in §141.2), and serves 4,900 persons or
fewer, may collect all required samples
on a single day if they are taken from
different sites.
(5) A public water system that uses
surface water or ground water under
the direct influence of surface water, as
defined in §141.2, and does not practice
filtration in compliance with Subpart
346
-------
Environmental Protection Agency
§141.21
H must collect at least one sample near
the first service connection each day
the turbidity level of the source water,
measured as specified In § 141.74(b)(2),
exceeds 1 NTU. This sample must be
analyzed for the presence of total coil-
forms. When one or more turbidity
measurements In any day exceed 1
NTU, the system must collect this coil-
form sample within 24 hours of the first
exceedance, unless the State deter-
mines that the system, for logistical
reasons outside the system's control,
cannot have the sample analyzed with-
in 30 hours of collection. Sample re-
sults from this collform monitoring
must be Included In determining com-
pliance with the MCL for total coil-
forms In §141.63.
(6) Special purpose samples, such as
those taken to determine whether dis-
infection practices are sufficient fol-
lowing pipe placement, replacement, or
repair, shall not be used to determine
compliance with the MCL for total
collforms In §141.63. Repeat samples
taken pursuant to paragraph (b) of this
section are not considered special pur-
pose samples, and must be used to de-
termine compliance with the MCL for
total collforms In §141.63.
(b) Repeat monitoring. (1) If a routine
sample Is total collform-posltlve, the
public water system must collect a set
of repeat samples within 24 hours of
being notified of the positive result. A
system which collects more than one
routine sample/month must collect no
fewer than three repeat samples for
each total collform-posltlve sample
found. A system which collects one
routine sample/month or fewer must
collect no fewer than four repeat sam-
ples for each total collform-posltlve
sample found. The State may extend
the 24-hour limit on a case-by-case
basis If the system has a logistical
problem In collecting the repeat sam-
ples within 24 hours that Is beyond Its
control. In the case of an extension,
the State must specify how much time
the system has to collect the repeat
samples.
(2) The system must collect at least
one repeat sample from the sampling
tap where the original total collform-
posltlve sample was taken, and at least
one repeat sample at a tap within five
service connections upstream and at
least one repeat sample at a tap within
five service connections downstream of
the original sampling site. If a total
collform-posltlve sample Is at the end
of the distribution system, or one away
from the end of the distribution sys-
tem, the State may waive the require-
ment to collect at least one repeat
sample upstream or downstream of the
original sampling site.
(3) The system must collect all re-
peat samples on the same day, except
that the State may allow a system
with a single service connection to col-
lect the required set of repeat samples
over a four-day period or to collect a
larger volume repeat sample(s) In one
or more sample containers of any size,
as long as the total volume collected Is
at least 400 ml (300 ml for systems
which collect more than one routine
sample/month).
(4) If one or more repeat samples In
the set Is total collform-posltlve, the
public water system must collect an
additional set of repeat samples In the
manner specified In paragraphs (b) (1)-
(3) of this section. The additional sam-
ples must be collected within 24 hours
of being notified of the positive result,
unless the State extends the limit as
provided In paragraph (b)(1) of this sec-
tion. The system must repeat this
process until either total collforms are
not detected In one complete set of re-
peat samples or the system determines
that the MCL for total collforms In
§141.63 has been exceeded and notifies
the State.
(5) If a system collecting fewer than
five routine samples/month has one or
more total collform-posltlve samples
and the State does not Invalidate the
sample(s) under paragraph (c) of this
section, It must collect at least five
routine samples during the next month
the system provides water to the pub-
lic, except that the State may waive
this requirement If the conditions of
paragraph (b)(5) (1) or (11) of this sec-
tion are met. The State cannot waive
the requirement for a system to collect
repeat samples In paragraphs (b) (l)-(4)
of this section.
(1) The State may waive the require-
ment to collect five routine samples
the next month the system provides
water to the public If the State, or an
agent approved by the State, performs
347
-------
§141.21
40 CFR Ch. I (7-1-02 Edition)
a site visit before the end of the next
month the system provides water to
the public. Although a sanitary survey
need not be performed, the site visit
must be sufficiently detailed to allow
the State to determine whether addi-
tional monitoring' and/or any correc-
tive action is needed. The State cannot
approve an employee of the system to
perform this site visit, even if the em-
ployee is an agent approved by the
State to perform sanitary surveys.
(ii) The State may waive the require-
ment to collect five routine samples
the next month the system provides
water to the public if the State has de-
termined why the sample was total
coliform-positive and establishes that
the system has corrected the problem
or will correct the problem before the
end of the next month the system
serves water to the public. In this case,
the State must document this decision
to waive the following month's addi-
tional monitoring requirement in writ-
ing, have it approved and signed by the
supervisor of the State official who
recommends such a decision, and make
this document available to the EPA
and public. The written documentation
must describe the specific cause of the
total coliform-positive sample and
what action the system has taken and/
or will take to correct this problem.
The State cannot waive the require-
ment to collect five routine samples
the next month the system provides
water to the public solely on the
grounds that all repeat samples are
total coliform-negative. Under this
paragraph, a system must still take at
least one routine sample before the end
of the next month it serves water to
the public and use it to determine com-
pliance with the MCL for total con-
forms in §141.63, unless the State has
determined that the system has cor-
rected the contamination problem be-
fore the system took the set of repeat
samples required in paragraphs (b) (1)-
(4) of this section, and all repeat sam-
ples were total coliform-negative.
(6) After a system collects a routine
sample and before it learns the results
of the analysis of that sample, if it col-
lects another routine sample(s) from
within five adjacent service connec-
tions of the initial sample, and the ini-
tial sample, after analysis, is found to
contain total coliforms, then the sys-
tem may count the subsequent sam-
ple(s) as a repeat sample instead of as
a routine sample.
(7) Results of all routine and repeat
samples not invalidated by the State
must be included in determining com-
pliance with the MCL for total coli-
forms in §141.63.
(c) Invalidation of total coliform sam-
ples. A total coliform-positive sample
invalidated under this paragraph (c)
does not count towards meeting the
minimum monitoring requirements of
this section.
(1) The State may invalidate a total
coliform-positive sample only if the
conditions of paragraph (c)(1) (i), (ii),
or (iii) of this section are met.
(i) The laboratory establishes that
improper sample analysis caused the
total coliform-positive result.
(ii) The State, on the basis of the re-
sults of repeat samples collected as re-
quired by paragraphs (b) (1) through (4)
of this section, determines that the
total coliform-positive sample resulted
from a domestic or other non-distribu-
tion system plumbing problem. The
State cannot invalidate a sample on
the basis of repeat sample results un-
less all repeat sample(s) collected at
the same tap as the original total coli-
form-positive sample are also total
coliform-positive, and all repeat sam-
ples collected within five service con-
nections of the original tap are total
coliform-negative (e.g., a State cannot
invalidate a total coliform-positive
sample on the basis of repeat samples if
all the repeat samples are total coli-
form-negative, or if the public water
system has only one service connec-
tion).
(iii) The State has substantial
grounds to believe that a total coli-
form-positive result is due to a cir-
cumstance or condition which does not
reflect water quality in the distribu-
tion system. In this case, the system
must still collect all repeat samples re-
quired under paragraphs (b) (l)-(4) of
this section, and use them to deter-
mine compliance with the MCL for
total coliforms in §141.63. To invalidate
a total coliform-positive sample under
this paragraph, the decision with the
rationale for the decision must be doc-
umented in writing, and approved and
348
-------
Environmental Protection Agency
signed by the supervisor of the State
official who recommended the decision.
The State must make this document
available to EPA and the public. The
written documentation must state the
specific cause of the total coliform-
positive sample, and what action the
system has taken, or will take, to cor-
rect this problem. The State may not
invalidate a total coliform-positive
sample solely on the grounds that all
repeat samples are total coliform-nega-
tive.
(2) A laboratory must invalidate a
total coliform sample (unless total
coliforms are detected) if the sample
produces a turbid culture in the ab-
sence of gas production using an ana-
lytical method where gas formation is
examined (e.g., the Multiple-Tube Fer-
mentation Technique), produces a
turbid culture in the absence of an acid
reaction in the Presence-Absence (P-A)
Coliform Test, or exhibits confluent
growth or produces colonies too numer-
ous to count with an analytical method
using a membrane filter (e.g., Mem-
brane Filter Technique). If a labora-
tory invalidates a sample because of
such interference, the system must col-
lect another sample from the same lo-
cation as the original sample within 24
hours of being notified of the inter-
ference problem, and have it analyzed
for the presence of total coliforms. The
system must continue to re-sample
within 24 hours and have the samples
analyzed until it obtains a valid result.
The State may waive the 24-hour time
limit on a case-by-case basis.
(d) Sanitary surveys. (l)(i) Public
water systems which do not collect five
or more routine samples/month must
undergo an initial sanitary survey by
June 29, 1994, for community public
water systems and June 29, 1999, for
non-community water systems. There-
after, systems must undergo another
sanitary survey every five years, ex-
cept that non-community water sys-
tems using only protected and dis-
infected ground water, as defined by
the State, must undergo subsequent
sanitary surveys at least every ten
years after the initial sanitary survey.
The State must review the results of
each sanitary survey to determine
whether the existing monitoring fre-
quency is adequate and what additional
§141.21
measures, if any, the system needs to
undertake to improve drinking water
quality.
(ii) In conducting a sanitary survey
of a system using ground water in a
State having an EPA-approved well-
head protection program under section
1428 of the Safe Drinking Water Act,
information on sources of contamina-
tion within the delineated wellhead
protection area that was collected in
the course of developing and imple-
menting the program should be consid-
ered instead of collecting new informa-
tion, if the information was collected
since the last time the system was sub-
ject to a sanitary survey.
(2) Sanitary surveys must be per-
formed by the State or an agent ap-
proved by the State. The system is re-
sponsible for ensuring the survey takes
place.
(e) Fecal coliforms/Escherichia coli (E.
coli) testing. (1) If any routine or repeat
sample is total coliform-positive, the
system must analyze that total coli-
form-positive culture medium to deter-
mine if fecal coliforms are present, ex-
cept that the system may test for E.
coli in lieu of fecal coliforms. If fecal
coliforms or E. coli are present, the sys-
tem must notify the State by the end
of the day when the system is notified
of the test result, unless the system is
notified of the result after the State of-
fice is closed, in which case the system
must notify the State before the end of
the next business day.
(2) The State has the discretion to
allow a public water system, on a case-
by-case basis, to forgo fecal coliform or
E. coli testing on a total coliform-posi-
tive sample if that system assumes
that the total coliform-positive sample
is fecal coliform-positive or E. coli-posi-
tive. Accordingly, the system must no-
tify the State as specified in paragraph
(e)(1) of this section and the provisions
of §141.63(b) apply.
(f) Analytical methodology. (1) The
standard sample volume required for
total coliform analysis, regardless of
analytical method used, is 100 ml.
(2) Public water systems need only
determine the presence or absence of
total coliforms; a determination of
total coliform density is not required.
349
-------
§141.21
40 CFR Ch. I (7-1-02 Edition)
(3) Public water systems must con- ance with one of the analytical meth-
duct total coliform analyses in accord- ods in the following table.
Organism
Methodology12
Citation1
Total Coli-
Total Coliform Fermentation Tech-
9221 A, B
forms2.
nique3-4-5.
Total Coliform
9222
Membrane Filter
A, B, C
Technique6
Presence-Absence
9221
(P-A) Coliform Test5'7
ONPG-MUG Test8
9223
Colisure Test9
E*Colite® Test10
m-ColiBlue24® Test11
The procedures shall be done in accordance with the documents listed below. The incorporation by reference of the following
documents listed in footnotes 1, 6, 8, 9, 10 and 11 was approved by the Director of the Federal Register in accordance with 5
U.S.C. 552(a) and 1 CFR Part 51. Copies of the documents may be obtained from the sources listed below. Information regard-
ing obtaining these documents can be obtained from the Safe Drinking Water Hotline at 800-426-4791. Documents may be in-
spected at EPA's Drinking Water Docket, 1200 Pennsylvania Ave., NW., Washington, DC 20460 (Telephone: 202-260-3027); or
at the Office of Federal Register, 800 North Capitol Street, NW, Suite 700, Washington, D.C. 20408.
I Methods 9221 A, B; 9222 A, B, C; 9221 D and 9223 are contained in Standard Methods for the Examination of Water and
Wastewater, 18th edition (1992) and 19th edition (1995) American Public Health Association, 1015 Fifteenth Street NW, Wash-
ington, D.C. 20005; either edition may be used.
2The time from sample collection to initiation of analysis may not exceed 30 hours. Systems are encouraged but not required
to hold samples below 10 °C during transit.
3 Lactose broth, as commercially available, may be used in lieu of lauryl tryptose broth, if the system conducts at least 25 par-
allel tests between this medium and lauryl tryptose broth using the water normally tested, and this comparison demonstrates that
the false-positive rate and false-negative rate for total coliform, using lactose broth, is less than 10 percent.
4 If inverted tubes are used to detect gas production, the media should cover these tubes at least one-half to two-thirds after
the sample is added.
5 No requirement exists to run the completed phase on 10 percent of all total coliform-positive confirmed tubes.
6 Ml agar also may be used. Preparation and use of Ml agar is set forth in the article, "New medium for the simultaneous de-
tection of total coliform and Escherichia coii in water" by Brenner, K.P., et al., 1993, Appl. Environ. Microbiol. 59:3534-3544.
Also available from the Office of Water Resource Center (RC-4100), 401 M. Street SW, Washington, DC 20460, EPA/600/J-99/
225.
7 Six-times formulation strength may be used if the medium is filter-sterilized rather than autoclaved.
8The ONPG-MUG Test is also known as the Autoanalysis Colilert System.
9A description of the Colisure Test, Feb 28, 1994, may be obtained from IDEXX Laboratories, Inc., One IDEXX Drive,
Westbrook, Maine 04092. The Colisure Test may be read after an incubation time of 24 hours.
10 A description of the E*Colite® Test, "Presence/Absence for Coliforms and E. Coii in Water," Dec 21, 1997, is available from
Charm Sciences, Inc., 36 Franklin Street, Maiden, MA 02148-4120.
II A description of the m-ColiBlue24® test, Aug 17, 1999, is available from the Hach Company, 100 Dayton Avenue, Ames, IA
50010.
12 EPA strongly recommends that laboratories evaluate the false-positive and negative rates for the method(s) they use for
monitoring total coliforms. EPA also encourages laboratories to establish false-positive and false-negative rates within their own
laboratory and sample matrix (drinking water or source water) with the intent that if the method they choose has an unacceptable
false-positive or negative rate, another method can be used. The Agency suggests that laboratories perform these studies on a
minimum of 5% of all total coliform-positive samples, except for those methods where verification/confirmation is already re-
quired, e.g., the M-Endo and LES Endo Membrane Filter Tests, Standard Total Coliform Fermentation Technique, and Presence-
Absence Coliform Test. Methods for establishing false-positive and negative-rates may be based on lactose fermentation, the
rapid test for (3-galactosidase and cytochrome oxidase, multi-test identification systems, or equivalent confirmation tests. False-
positive and false-negative information is often available in published studies and/or from the manufacturer(s).
(4) [Reserved]
(5) Public water systems must con-
duct fecal coliform analysis in accord-
ance with the following procedure.
When the MTF Technique or Presence-
Absence (PA) Coliform Test is used to
test for total coliforms, shake the lac-
tose-positive presumptive tube or P-A
vigorously and transfer the growth
with a sterile 3-mm loop or sterile ap-
plicator stick into brilliant green lac-
tose bile broth and EC medium to de-
termine the presence of total and fecal
coliforms, respectively. For EPA-ap-
proved analytical methods which use a
membrane filter, transfer the total
coliform-positive culture by one of the
following methods: remove the mem-
brane containing the total coliform
colonies from the substrate with a ster-
ile forceps and carefully curl and insert
the membrane into a tube of EC me-
dium (the laboratory may first remove
a small portion of selected colonies for
verification), swab the entire mem-
brane filter surface with a sterile cot-
ton swab and transfer the inoculum to
EC medium (do not leave the cotton
swab in the EC medium), or inoculate
individual total coliform-positive colo-
nies into EC Medium. Gently shake the
350
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Environmental Protection Agency
§141.21
inoculated tubes of EC medium to in-
sure adequate mixing and incubate in a
waterbath at 44.5 ± 0.2 °C for 24 ± 2
hours. Gas production of any amount
in the inner fermentation tube of the
EC medium indicates a positive fecal
coliform test. The preparation of EC
medium is described in Method 9221E
(paragraph la) in Standard Methods for
the Examination of Water and Waste-
water, 18th edition, 1992 and in the 19th
edition, 1995; either edition may be
used. Public water systems need only
determine the presence or absence of
fecal coliforms; a determination of
fecal coliform density is not required.
(6) Public water systems must con-
duct analysis of Escherichia coli in ac-
cordance with one of the following ana-
lytical methods:
(i) EC medium supplemented with 50
Hg/ml of 4-methylumbelliferyl-beta-D-
glucuronide (MUG) (final concentra-
tion). EC medium is described in Meth-
od 9221 E as referenced in paragraph
(f)(5) of this section. MUG may be
added to EC medium before
autoclaving. EC medium supplemented
with 50 |ig/ml of MUG is commercially
available. At least 10 ml of EC medium
supplemented with MUG must be used.
The inner inverted fermentation tube
may be omitted. The procedure for
transferring a total coliform-positive
culture to EC medium supplemented
with MUG shall be as specified in para-
graph (f)(5) of this section for transfer-
ring a total coliform-positive culture
to EC medium. Observe fluorescence
with an ultraviolet light (366 nm) in
the dark after incubating tube at 44.5 ±
0.2 °C for 24 ± 2 hours; or
(ii) Nutrient agar supplemented with
100 |ig/ml 4-methylumbelliferyl-beta-D-
glucuronide (MUG) (final concentra-
tion). Nutrient Agar is described in
Method 9221 B (paragraph 3) in Stand-
ard Methods for the Examination of
Water and Wastewater, 18th edition, 1992
and in the 19th edition, 1995; either edi-
tion may be used. This test is used to
determine if a total coliform-positive
sample, as determined by the Mem-
brane Filter Technique or any other
method in which a membrane filter is
used, contains E. coli. Transfer the
membrane filter containing a total
coliform colony(ies) to nutrient agar
supplemented with 100 |ig/ml (final con-
centration) of MUG. After incubating
the agar plate at 35 °C for 4 hours, ob-
serve the colony(ies) under ultraviolet
light (366 nm) in the dark for fluores-
cence. If fluorescence is visible, E. coli
are present.
(iii) Minimal Medium ONPG-MUG
(MMO-MUG) Test, as set forth in the
article "National Field Evaluation of a
Defined Substrate Method for the Si-
multaneous Detection of Total Coli-
forms and Escherichia coli from Drink-
ing Water: Comparison with Presence-
Absence Techniques" (Edberg et al.),
Applied and Environmental Microbi-
ology, Volume 55, pp. 1003-1008, April
1989. (Note: The Autoanalysis Colilert
System is an MMO-MUG test). If the
MMO-MUG test is total coliform-posi-
tive after a 24-hour incubation, test the
medium for fluorescence with a 366-nm
ultraviolet light (preferably with a 6-
watt lamp) in the dark. If fluorescence
is observed, the sample is E. coli-posi-
tive. If fluorescence is questionable
(cannot be definitively read) after 24
hours incubation, incubate the culture
for an additional four hours (but not to
exceed 28 hours total), and again test
the medium for fluorescence. The
MMO-MUG Test with hepes buffer in
lieu of phosphate buffer is the only ap-
proved formulation for the detection of
E. coli.
(iv) The Colisure Test. A description
of the Colisure Test may be obtained
from the Millipore Corporation, Tech-
nical Services Department, 80 Ashby
Road, Bedford, MA 01730.
(v) The membrane filter method with
MI agar, a description of which is cited
in footnote 6 to the table in paragraph
(f)(3) of this section.
(vi) E*Colite® Test, a description of
which is cited in footnote 10 to the
table at paragraph (f)(3) of this section.
(vii) m-ColiBlue24® Test, a descrip-
tion of which is cited in footnote 11 to
the table in paragraph (f)(3) of this sec-
tion.
(7) As an option to paragraph
(f)(6)(iii) of this section, a system with
a total coliform-positive, MUG-nega-
tive, MMO-MUG test may further ana-
lyze the culture for the presence of E.
coli by transferring a 0.1 ml, 28-hour
MMO-MUG culture to EC Medium +
MUG with a pi pet. The formulation and
incubation conditions of EC Medium +
351
-------
§141.22
40 CFR Ch. I (7-1-02 Edition)
MUG, and observation of the results
are described in paragraph (f)(6)(i) of
this section.
(8) The following materials are incor-
porated by reference in this section
with the approval of the Director of the
Federal Register in accordance with 5
U.S.C. 552(a) and 1 CFR part 51. Copies
of the analytical methods cited in
Standard Methods for the Examination
of Water and Wastewater (18th and 19th
editions) may be obtained from the
American Public Health Association et
al.; 1015 Fifteenth Street NW., Wash-
ington, DC 20005. Copies of the methods
set forth in Microbiological Methods for
Monitoring the Environment, Water and
Wastes may be obtained from ORD Pub-
lications, U.S. EPA, 26 W. Martin Lu-
ther King Drive, Cincinnati, Ohio 45268.
Copies of the MMO-MUG Test as set
forth in the article "National Field
Evaluation of a Defined Substrate
Method for the Simultaneous Enu-
meration of Total Coliforms and Esch-
erichia coli from Drinking Water: Com-
parison with the Standard Multiple
Tube Fermentation Method" (Edberg et
al.) may be obtained from the Amer-
ican Water Works Association Re-
search Foundation, 6666 West Quincy
Avenue, Denver, CO 80235. A descrip-
tion of the Colisure Test may be ob-
tained from the Millipore Corp., Tech-
nical Services Department, 80 Ashby
Road, Bedford, MA 01730. Copies may be
inspected at EPA's Drinking Water
Docket; 401 M St., SW.; Washington,
DC 20460, or at the Office of the Federal
Register; 800 North Capitol Street,
NW., suite 700, Washington, DC.
(g) Response to violation. (1) A public
water system which has exceeded the
MCL for total coliforms in §141.63 must
report the violation to the State no
later than the end of the next business
day after it learns of the violation, and
notify the public in accordance with
subpart Q.
(2) A public water system which has
failed to comply with a coliform moni-
toring requirement, including the sani-
tary survey requirement, must report
the monitoring violation to the State
within ten days after the system dis-
covers the violation, and notify the
public in accordance with subpart Q.
[54 FR 27562, June 29, 1989, as amended at 54
FR 30001, July 17, 1989; 55 FR 25064, June 19,
1990; 56 FR 642, Jan. 8, 1991; 57 FR 1852, Jan.
15, 1992; 57 FR 24747, June 10, 1992; 59 FR
62466, Dec. 5, 1994; 60 FR 34085, June 29, 1995;
64 FR 67461, Dec. 1, 1999; 65 FR 26022, May 4,
2000]
§141.22 Turbidity sampling and ana-
lytical requirements.
The requirements in this section
apply to unfiltered systems until De-
cember 30, 1991, unless the State has
determined prior to that date, in writ-
ing pursuant to section 1412(b)(7)(iii),
that filtration is required. The require-
ments in this section apply to filtered
systems until June 29, 1993. The re-
quirements in this section apply to
unfiltered systems that the State has
determined, in writing pursuant to sec-
tion 1412(b)(7)(C)(iii), must install fil-
tration, until June 29, 1993, or until fil-
tration is installed, whichever is later.
(a) Samples shall be taken by sup-
pliers of water for both community and
non-community water systems at a
representative entry point(s) to the
water distribution system at least once
per day, for the purposes of making
turbidity measurements to determine
compliance with §141.13. If the State
determines that a reduced sampling
frequency in a non-community will not
pose a risk to public health, it can re-
duce the required sampling frequency.
The option of reducing the turbidity
frequency shall be permitted only in
those public water systems that prac-
tice disinfection and which maintain
an active residual disinfectant in the
distribution system, and in those cases
where the State has indicated in writ-
ing that no unreasonable risk to health
existed under the circumstances of this
option. Turbidity measurements shall
be made as directed in § 141.74(a)(1).
(b) If the result of a turbidity anal-
ysis indicates that the maximum al-
lowable limit has been exceeded, the
sampling and measurement shall be
confirmed by resampling as soon as
practicable and preferably within one
hour. If the repeat sample confirms
that the maximum allowable limit has
been exceeded, the supplier of water
352
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Break in Sequence
Environmental Protection Agency
(16) Polychlorlnated blphenyls
(PCBs)
(17) Tetrachloroethylene
(18) Toxaphene
(19) Benzo[a]pyrene
(20) Dlchloromethane (methylene
chloride)
(21) Di(2-ethylhexyl)phthalate
(22) Hexachlorobenzene
(23) 2,3,7,8-TCDD (Dloxln)
(b) MCLGs for the following contami-
nants are as Indicated:
§141.54
Contaminant
(1) 1,1-Dichloroethylene
(2) 1,1,1-Trichloroethane
(3) para-Dichlorobenzene
(4) Aldicarb
(5) Aldicarb sulfoxide
(6) Aldicarb sulfone
(7) Atrazine
(8) Carbofuran
(9) o-Dichlorobenzene
(10) cis-1,2-Dichloroethylene
(11) trans-1,2-Dichloroethylene .
(12) 2,4-D
(13) Ethylbenzene
(14) Lindane
(15) Methoxychlor
(16) Monochlorobenzene
(17) Styrene
(18) Toluene
(19) 2,4,5-TP
(20) Xylenes (total)
(21) Dalapon
(22) Di(2-ethylhexyl)adipate
(23) Dinoseb
(24) Diquat
(25) Endothall
(26) Endrin
(27) Glyphosate
(28) Hexachlorocyclopentadiene
(29) Oxamyl (Vydate)
(30) Picloram
(31) Simazine
(32) 1,2,4-Trichlorobenzene
(33) 1,1,2-Trichloroethane
MCLG in
mg/l
Contaminant
MCLG (mg/l)
Antimony
0.006
Arsenic
zero1
Asbestos
7 Million fibers/liter
(longer than 10 |im).
Barium
2
Beryllium
.004
Cadmium
0.005
Contaminant
MCLG (mg/l)
Chromium
0.1
Copper
1.3
Cyanide (as free Cyanide)
.2
Fluoride
4.0
Lead
zero
Mercury
0.002
Nitrate
10 (as Nitrogen).
Nitrite
1 (as Nitrogen).
Total Nitrate+Nitrite
10 (as Nitrogen).
Selenium
0.05
Thallium
.0005
0.007
0.20
0.075
0.001
0.001
0.001
0.003
0.04
0.6
0.07
0.1
0.07
0.7
0.0002
0.04
0.1
0.1
1
0.05
10
0.2
.4
.007
.02
.1
.002
.7
.05
.2
.5
.004
.07
.003
1This value for arsenic is effective January 23, 2006. Until
then, there is no MCLG.
[50 FR 47155, Nov. 14, 1985, as amended at 52
FR 20674, June 2, 1987; 56 FR 3593, Jan. 30,
1991; 56 FR 26548, June 7, 1991; 56 FR 30280,
July 1, 1991; 57 FR 31846, July 17, 1992; 60 FR
33932, June 29, 1995; 66 FR 7063, Jan. 22, 2001]
§141.52 Maximum contaminant level
goals for microbiological contami-
nants.
MCLGs for the following' contami-
nants are as indicated:
Contaminant
(1) Giardia lamblia
(2) Viruses
(3) Legionella
(4) Total coliforms (including fecal coliforms
and Escherichia coli).
(5) Cryptosporidium
zero
zero
zero
zero.
[54 FR 27527, 27566, June 29, 1989; 55 FR 25064,
June 19, 1990; 63 FR 69515, Dec. 16, 1998]
§141.53 Maximum contaminant level
goals for disinfection byproducts.
MCLGs for the following disinfection
byproducts are as Indicated:
Disinfection byproduct
[50 FR 46901, Nov. 13, 1985, as amended at 52
FR 20674, June 2, 1987; 52 FR 25716, July 8,
1987; 56 FR 3592, Jan. 30, 1991; 56 FR 30280,
July 1, 1991; 57 FR 31846, July 17, 1992]
§141.51 Maximum contaminant level
goals for inorganic contaminants.
(a) [Reserved]
(b) MCLGs for the following contami-
nants are as Indicated:
Bromodichloromethane
Bromoform
Bromate
Dichloroacetic acid
Trichloroacetic acid
Chlorite
Dibromochloromethane
MCLG
(mg/L)
Zero
Zero
Zero
Zero
0.3
0.8
0.06
[63 FR 69465, Dec. 16, 1998,
FR 34405, May 30, 2000]
as amended at 65
§141.54 Maximum residual disinfect-
ant level goals for disinfectants.
MRDLGs for disinfectants are as fol-
lows:
Disinfectant residual
MRDLG(mg/L)
4 (as Cl2).
4 (as Cl2).
Chloramines
425
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Break in Sequence
Environmental Protection Agency
§141.63
BAT FOR INORGANIC COMPOUNDS
LISTED IN SECTION 141.62(B)
Small System Compliance Technologies
(SSCTs)1 for Arsenic2—Continued
Chemical Name
Asbestos ..
Barium
Beryllium ..
Cadmium .
Chromium
Cyanide ....
Mercury ....
Nickel
Nitrate
Nitrite
Selenium ..
Thallium ...
BAT (s)
2.3.8
5,6,7,9
1,2,5,6,7
2,5,6,7
2,5,6 2,7
5,7,10
21,4,61,71
5,6,7
5.7.9
5,7
1,23,6,7,9
1,5
Small system compliance
Affordable for listed small
technology
system categories3
Activated Alumina (central-
All size categories.
ized).
Activated Alumina (Point-of-
All size categories.
Use)4.
Coagulation/Filtration5
501-3,300, 3,301-10,000.
Coagulation-assisted Micro-
501-3,300, 3,301-10,000.
filtration.
Electrodialysis reversal6
501-3,300, 3,301-10,000.
Enhanced coagulation/filtra-
All size categories
tion.
Enhanced lime softening
All size categories.
(pH> 10.5).
Ion Exchange
All size categories.
Lime Softening5
501-3,300, 3,301-10,000.
Small system compliance
Affordable for listed small
technology
system categories3
Oxidation/Filtration 7
All size categories.
Reverse Osmosis (central-
501-3,300, 3,301-10,000.
ized) 6.
Reverse Osmosis (Point-of-
All size categories.
Use)4.
1 BAT only if influent Hg concentrations <10|ig/1.
2 BAT for Chromium III only.
3 BAT for Selenium IV only.
4BATs for Arsenic V. Pre-oxidation may be required to con-
vert Arsenic III to Arsenic V.
5To obtain high removals, iron to arsenic ratio must be at
least 20:1.
Key to BATS in Table
l=Activated Alumina
2 = Coagulation/Filtration (not BAT for sys-
tems < 500 service connections)
2=Coagulation/Filtration
3=Direct and Diatomite Filtration
4=Granular Activated Carbon
5=Ion Exchange
6 = Lime Softening (not BAT for systems <
500 service connections)
7=Reverse Osmosis
8=Corrosion Control
9=Electrodialysis
10= Chlorine
ll=Ultraviolet
12 = Oxidation/Filtration
(d) The Administrator, pursuant to
section 1412 of the Act, hereby identi-
fies in the following1 table the afford-
able technology, treatment technique,
or other means available to systems
serving 10,000 persons or fewer for
achieving compliance with the max-
imum contaminant level for arsenic:
Small System Compliance Technologies
(SSCTs)1 for Arsenic2
1 Section 1412(b)(4)(E)(ii) of SDWA specifies that SSCTs
must be affordable and technically feasible for small systems.
2SSCTs for Arsenic V. Pre-oxidation may be required to
convert Arsenic III to Arsenic V.
3The Act (ibid.) specifies three categories of small systems:
(i) those serving 25 or more, but fewer than 501, (ii) those
serving more than 500, but fewer than 3,301, and (iii) those
serving more than 3,300, but fewer than 10,001.
4When POU or POE devices are used for compliance, pro-
grams to ensure proper long-term operation, maintenance,
and monitoring must be provided by the water system to en-
sure adequate performance.
5 Unlikely to be installed solely for arsenic removal. May re-
quire pH adjustment to optimal range if high removals are
needed.
technologies reject a large volume of water—may not be
appropriate for areas where water quantity may be an issue.
'To obtain high removals, iron to arsenic ratio must be at
least 20:1.
[56 FR 3594, Jan. 30, 1991, as amended at 56
FR 30280, July 1, 1991; 57 FR 31847, July 17,
1992; 59 FR 34325, July 1, 1994; 60 FR 33932,
June 29, 1995; 66 FR 7063, Jan. 22, 2001]
§141.63 Maximum contaminant levels
(MCLs) for microbiological contami-
nants.
(a) The MCL is based on the presence
or absence of total coliforms in a sam-
ple, rather than coliform density.
(1) For a system which collects at
least 40 samples per month, if no more
than 5.0 percent of the samples col-
lected during a month are total coli-
form-positive, the system is in compli-
ance with the MCL for total coliforms.
(2) For a system which collects fewer
than 40 samples/month, if no more than
one sample collected during a month is
total coliform-positive, the system is
in compliance with the MCL for total
coliforms.
(b) Any fecal coliform-positive repeat
sample or E. coK-positive repeat sam-
ple, or any total coliform-positive re-
peat sample following a fecal coliform-
positive or E. coH-positive routine sam-
ple constitutes a violation of the MCL
for total coliforms. For purposes of the
public notification requirements in
subpart Q, this is a violation that may
pose an acute risk to health.
(c) A public water system must deter-
mine compliance with the MCL for
total coliforms in paragraphs (a) and
(b) of this section for each month in
429
-------
§141.64
40 CFR Ch. I (7-1-02 Edition)
which it is required to monitor for
total coliforms.
(d) The Administrator, pursuant to
section 1412 of the Act, hereby identi-
fies the following' as the best tech-
nology, treatment techniques, or other
means available for achieving compli-
ance with the maximum contaminant
level for total coliforms in paragraphs
(a) and (b) of this section:
(1) Protection of wells from contami-
nation by coliforms by appropriate
placement and construction;
(2) Maintenance of a disinfectant re-
sidual throughout the distribution sys-
tem;
(3) Proper maintenance of the dis-
tribution system including appropriate
pipe replacement and repair proce-
dures, main flushing programs, proper
operation and maintenance of storage
tanks and reservoirs, and continual
maintenance of positive water pressure
in all parts of the distribution system;
(4) Filtration and/or disinfection of
surface water, as described in subpart
H, or disinfection of ground water
using strong oxidants such as chlorine,
chlorine dioxide, or ozone; and
(5) For systems using ground water,
compliance with the requirements of
an EPA-approved State Wellhead Pro-
tection Program developed and imple-
mented under section 1428 of the
SDWA.
[54 FR 27566, June 29, 1989; 55 FR 25064, June
19, 1990, as amended at 65 FR 26022, May 4,
2000]
§141.64 Maximum contaminant levels
for disinfection byproducts.
(a) The maximum contaminant levels
(MCLs) for disinfection byproducts are
as follows:
Disinfection byproduct
Total trihalomethanes (TTHM)
Haloacetic acids (five) (HAA5)
Bromate
Chlorite
MCL
(mg/L)
with this section beginning January 1,
2004.
(2) A system that is installing GAC
or membrane technology to comply
with this section may apply to the
State for an extension of up to 24
months past the dates in paragraphs
(b)(1) of this section, but not beyond
December 31, 2003. In granting the ex-
tension, States must set a schedule for
compliance and may specify any in-
terim measures that the system must
take. Failure to meet the schedule or
interim treatment requirements con-
stitutes a violation of a National Pri-
mary Drinking Water Regulation.
(c) The Administrator, pursuant to
Section 1412 of the Act, hereby identi-
fies the following as the best tech-
nology, treatment techniques, or other
means available for achieving compli-
ance with the maximum contaminant
levels for disinfection byproducts iden-
tified in paragraph (a) of this section:
Disinfection
byproduct
HAA5
Bromate
Chlorite ..
Best available technology
Enhanced coagulation or enhanced softening
or GAC10, with chlorine as the primary and
residual disinfectant
Enhanced coagulation or enhanced softening
or GAC10, with chlorine as the primary and
residual disinfectant.
Control of ozone treatment process to reduce
production of bromate.
Control of treatment processes to reduce dis-
infectant demand and control of disinfection
treatment processes to reduce disinfectant
levels.
[63 FR 69465, Dec. 16,
FR 3776, Jan. 16, 2001]
1998, as amended at 66
§141.65 Maximum residual disinfect-
ant levels.
(a) Maximum residual disinfectant
levels (MRDLs) are as follows:
0.080
0.060
0.010
1.0
Disinfectant residual
MRDL (mg/L)
4.0 (as Cl2).
4.0 (as Cl2).
0.8 (as CI02).
(b) Compliance dates. (1) CW£s and
NTNCWSs. Subpart H systems serving1
10,000 or more persons must comply
with this section beginning1 January 1,
2002. Subpart H systems serving fewer
than 10,000 persons and systems using
only ground water not under the direct
influence of surface water must comply
(b) Compliance dates. (1) CW£s and
NTNCWSs. Subpart H systems serving
10,000 or more persons must comply
with this section beginning January 1,
2002. Subpart H systems serving fewer
than 10,000 persons and systems using
only ground water not under the direct
influence of surface water must comply
430
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Break in Sequence
Environmental Protection Agency
at least 10,000 people must meet the re-
quirements for other filtration tech-
nologies In § 141.173(b). Beginning Janu-
ary 14, 2005, systems serving fewer than
10,000 people must meet the require-
ments for other filtration technologies
In §141.550 through 141.553.
[54 FR 27527, June 29, 1989, as amended at 63
FR 69516, Dec. 16, 1998; 66 FR 3776, Jan. 16,
2001; 67 FR 1836, Jan. 14, 2002]
§141.74 Analytical and monitoring re-
quirements.
(a) Analytical requirements. Only the
analytical method(s) specified In this
paragraph, or otherwise approved by
EPA, may be used to demonstrate com-
pliance with §§141.71, 141.72 and 141.73.
Measurements for pH, turbidity, tem-
perature and residual disinfectant con-
centrations must be conducted by a
person approved by the State. Measure-
ment for total collforms, fecal coil-
forms and HPC must be conducted by a
laboratory certified by the State or
EPA to do such analysis. Until labora-
tory certification criteria are devel-
oped for the analysis of fecal collforms
and HPC, any laboratory certified for
total collforms analysis by the State or
EPA Is deemed certified for fecal coll-
forms and HPC analysis. The following
procedures shall be conducted In ac-
cordance with the publications listed
In the following section. This Incorpo-
ration by reference was approved by
the Director of the Federal Register In
accordance with 5 U.S.C. 552(a) and 1
CFR part 51. Copies of the methods
published In Standard Methods for the
Examination of Water and Wastewater
may be obtained from the American
Public Health Association et al., 1015
Fifteenth Street, NW., Washington, DC
20005; copies of the Minimal Medium
ONPG-MUG Method as set forth In the
article "National Field Evaluation of a
Defined Substrate Method for the Si-
multaneous Enumeration of Total Coll-
forms and Esherichia coli from Drinking
Water: Comparison with the Standard
Multiple Tube Fermentation Method"
(Edberg et al.), Applied and Environ-
mental Microbiology, Volume 54, pp.
1595-1601, June 1988 (as amended under
Erratum, Applied and Environmental
Microbiology, Volume 54, p. 3197, De-
cember, 1988), may be obtained from
the American Water Works Association
§141.74
Research Foundation, 6666 West Qulncy
Avenue, Denver, Colorado, 80235; and
copies of the Indigo Method as set forth
In the article "Determination of Ozone
In Water by the Indigo Method" (Bader
and Holgne), may be obtained from
Ozone Science & Engineering,
Pergamon Press Ltd., Falrvlew Park,
Elmsford, New York 10523. Copies may
be Inspected at the U.S. Environmental
Protection Agency, Room EB15, 401 M
St., SW., Washington, DC 20460 or at
the Office of the Federal Register, 800
North Capitol Street, NW., suite 700,
Washington, DC.
(1) Public water systems must con-
duct analysis of pH and temperature In
accordance with one of the methods
listed at §141.23(k)(l). Public water sys-
tems must conduct analysis of total
collforms, fecal collforms,
heterotrophic bacteria, and turbidity
In accordance with one of the following
analytical methods and by using ana-
lytical test procedures contained In
Technical Notes on Drinking Water Meth-
ods, EPA-600/R-94-173, October 1994,
which Is available at NTIS PB95-104766.
Organism
Methodology
Citation1
Total Coliform2
Total Coliform Fer-
9221 A, B, C
mentation Tech-
nique3'4'5.
Total Coliform
9222 A, B, C
Membrane Filter
Technique6.
ONPG-MUG
9223
Test7.
Fecal Coliforms2 ...
Fecal Coliform
9221 E
Procedure8.
Fecal Coliform Fil-
9222 D
ter Procedure.
Heterotrophic bac-
Pour Plate Method
9215 B
teria2.
Turbidity
Nephelometric
2130 B
Method.
Nephelometric
180.1 9
Method.
Great Lakes In-
Method 210
struments.
The procedures shall be done in accordance with the docu-
ments listed below. The incorporation by reference of the fol-
lowing documents listed in footnotes 1, 6, 7, 9 and 10 was ap-
proved by the Director of the Federal Register in accordance
with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the docu-
ments may be obtained from the sources listed below. Infor-
mation regarding obtaining these documents can be obtained
from the Safe Drinking Water Hotline at 800-426-4791. Doc-
uments may be inspected at EPA's Drinking Water Docket,
1200 Pennsylvania Ave., NW., Washington, DC 20460 (Tele-
phone: 202-260-3027); or at the Office of the Federal Reg-
ister, 800 North Capitol Street, NW, Suite 700, Washington,
D.C. 20408.
1 Except where noted, all methods refer to Standard Meth-
ods for the Examination of Water and Wastewater, 18th edi-
tion, 1992 and 19th edition, 1995, American Public Health As-
sociation, 1015 Fifteenth Street NW, Washington, D.C. 20005;
either edition may be used.
439
-------
§141.74
40 CFR Ch. I (7-1-02 Edition)
2The time from sample collection to initiation of analysis
may not exceed 8 hours. Systems must hold samples below
10°C during transit.
3 Lactose broth, as commercially available, may be used in
lieu of lauryl tryptose broth, if the system conducts at least 25
parallel tests between this medium and lauryl tryptose broth
using the water normally tested, and this comparison dem-
onstrates that the false-positive rate and false-negative rate
for total coliform, using lactose broth, is less than 10 percent.
4 Media should cover inverted tubes at least one-half to two-
thirds after the sample is added.
5 No requirement exists to run the completed phase on 10
percent of all total coliform-positive confirmed tubes.
6 Ml agar also may be used. Preparation and use of Ml
agar is set forth in the article, "New medium for the simulta-
neous detection of total coliform and Escherichia coli in water"
by Brenner, K.P., et al., 1993, Appl. Environ. Microbiol.
59:3534-3544. Also available from the Office of Water Re-
source Center (RC-4100), 1200 Pennsylvania Ave., NW.,
Washington, DC 20460, EPA 600/J-99/225.
7The ONPG-MUG Test is also known as the Autoanalysis
Colilert System.
8A-1 Broth may be held up to three months in a tightly
closed screw cap tube at 4 °C.
9"Methods for the Determination of Inorganic Substances in
Environmental Samples", EPA/600/R-93/100, August 1993.
Available at NTIS, PB94-121811.
10GLI Method 2, "Turbidity", November 2, 1992, Great
Lakes Instruments, Inc., 8855 North 55th Street, Milwaukee,
Wisconsin 53223.
(2) Public water systems must meas-
ure residual disinfectant concentra-
tions with one of the analytical meth-
ods in the following table. The methods
are contained in both the 18th and 19th
editions of Standard Methods for the Ex-
amination of Water and Wastewater, 1992
and 1995; either edition may be used.
Other analytical test procedures are
contained in Technical Notes on Drink-
ing Water Methods, EPA-600/R-94-173,
October 1994, which is available at
NTIS PB95-104766. If approved by the
State, residual disinfectant concentra-
tions for free chlorine and combined
chlorine also may be measured by
using DPD colorimetric test kits. Free
and total chlorine residuals may be
measured continuously by adapting a
specified chlorine residual method for
use with a continuous monitoring in-
strument provided the chemistry, accu-
racy, and precision remain same. In-
struments used for continuous moni-
toring must be calibrated with a grab
sample measurement at least every
five days, or with a protocol approved
by the State.
Residual
Methodology
Methods
Free Chlo-
Amperometric Titration
4500-CI D
rine.
DPD Ferrous
4500-CI F
Titri metric.
DPD Colorimetric
4500-CI G
Syringaldazine
4500-CI H
(FACTS).
Total Chlo-
Amperometric Titration
4500-CI D
rine.
Residual
Methodology
Methods
Amperometric Titration
4500-CI E
(low level measure-
ment).
DPD Ferrous
4500-CI F
Titri metric.
DPD Colorimetric
4500-CI G
lodometric Electrode ...
4500-CI I
Chlorine Di-
Amperometric Titration
4500-CI02 C
oxide.
DPD Method
4500-CI02 D
Amperometric Titration
4500-CI02 E
Ozone
Indigo Method
4500-03 B
(b) Monitoring requirements for systems
that do not provide filtration. A public
water system that uses a surface water
source and does not provide filtration
treatment must begin monitoring, as
specified in this paragraph (b), begin-
ning December 31, 1990, unless the
State has determined that filtration is
required in writing pursuant to
§1412(b)(7)(C)(iii), in which case the
State may specify alternative moni-
toring requirements, as appropriate,
until filtration is in place. A public
water system that uses a ground water
source under the direct influence of
surface water and does not provide fil-
tration treatment must begin moni-
toring as specified in this paragraph (b)
beginning December 31, 1990, or 6
months after the State determines that
the ground water source is under the
direct influence of surface water,
whichever is later, unless the State has
determined that filtration is required
in writing pursuant to
§1412(b)(7)(C)(iii), in which case the
State may specify alternative moni-
toring requirements, as appropriate,
until filtration is in place.
(1) Fecal coliform or total coliform
density measurements as required by
§ 141.71(a)(1) must be performed on rep-
resentative source water samples im-
mediately prior to the first or only
point of disinfectant application. The
system must sample for fecal or total
coliforms at the following minimum
frequency each week the system serves
water to the public:
System size (persons served)
£500
501 to 3,300
3,301 to 10,000
10,001 to 25,000
>25,000
1 Must be taken on separate days.
Samples/
week1
440
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Environmental Protection Agency
§141.74
Also, one fecal or total coliform den-
sity measurement must be made every
day the system serves water to the
public and the turbidity of the source
water exceeds 1 NTU (these samples
count towards the weekly coliform
sampling' requirement) unless the State
determines that the system, for
logistical reasons outside the system's
control, cannot have the sample ana-
lyzed within 30 hours of collection.
(2) Turbidity measurements as re-
quired by § 141.71(a)(2) must be per-
formed on representative grab samples
of source water Immediately prior to
the first or only point of disinfectant
application every four hours (or more
frequently) that the system serves
water to the public. A public water sys-
tem may substitute continuous tur-
bidity monitoring for grab sample
monitoring If It validates the contin-
uous measurement for accuracy on a
regular basis using a protocol approved
by the State.
(3) The total Inactlvatlon ratio for
each day that the system Is In oper-
ation must be determined based on the
CT99.9 values In tables 1.1-1.6, 2.1, and
3.1 of this section, as appropriate. The
parameters necessary to determine the
total Inactlvatlon ratio must be mon-
itored as follows:
(I) The temperature of the disinfected
water must be measured at least once
per day at each residual disinfectant
concentration sampling point.
(II) If the system uses chlorine, the
pH of the disinfected water must be
measured at least once per day at each
chlorine residual disinfectant con-
centration sampling point.
(III) The disinfectant contact tlme(s)
("T") must be determined for each day
during peak hourly flow.
(Iv) The residual disinfectant con-
centrations) ("C") of the water before
or at the first customer must be meas-
ured each day during peak hourly flow.
(v) If a system uses a disinfectant
other than chlorine, the system may
demonstrate to the State, through the
use of a State-approved protocol for on-
site disinfection challenge studies or
other Information satisfactory to the
State, that CT99.9 values other than
those specified In tables 2.1 and 3.1 In
this section other operational param-
eters are adequate to demonstrate that
the system Is achieving the minimum
Inactlvatlon rates required by
§ 141.72(a)(1).
Table 1.1— CT Values (CT99.9) for 99.9 Per-
cent INACTIVATION OF GlARDIA LAMBLIA
Cysts by Free Chlorine at 0.5 °C or
Lower1
Resid-
ual
(mg/l)
pH
£6.0
6.5
7.0
7.5
8.0
8.5
0
01
VII
T
O
VII
137
163
195
237
277
329
390
0.6
141
168
200
239
286
342
407
0.8
145
172
205
246
295
354
422
1.0
148
176
210
253
304
365
437
1.2
152
180
215
259
313
376
451
1.4
155
184
221
266
321
387
464
1.6
157
189
226
273
329
397
477
1.8
162
193
231
279
338
407
489
2.0
165
197
236
286
346
417
500
2.2
169
201
242
297
353
426
511
2.4
172
205
247
298
361
435
522
2.6
175
209
252
304
368
444
533
2.8
178
213
257
310
375
452
543
3.0
181
217
261
316
382
460
552
1 These CT values achieve greater than a 99.99 percent in-
activation of viruses. CT values between the indicated pH val-
ues may be determined by linear interpolation. CT values be-
tween the indicated temperatures of different tables may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature and at the high-
er pH.
Table 1.2—CT Values (CT 99.9) for 99.9
Percent Inactivation of Giardia Lamblia
Cysts by Free Chlorine at 5.0 °C1
Free
resid-
pH
ual
(mg/l)
£6.0
6.5
7.0
7.5
8.0
8.5
0
01
VII
T
O
VII
97
117
139
166
198
236
279
0.6 ..
100
120
143
171
204
244
291
0.8 ..
103
122
146
175
210
252
301
1.0 ..
105
125
149
179
216
260
312
1.2 ..
107
127
152
183
221
267
320
1.4 ..
109
130
155
187
227
274
329
1.6 ..
111
132
158
192
232
281
337
1.8 ..
114
135
162
196
238
287
345
2.0 ..
116
138
165
200
243
294
353
2.2 ..
118
140
169
204
248
300
361
2.4 ..
120
143
172
209
253
306
368
2.6 ..
122
146
175
213
258
312
375
2.8 ..
124
148
178
217
263
318
382
3.0 ..
126
151
182
221
268
324
389
1 These CT values achieve greater than a 99.99 percent in-
activation of viruses. CT values between the indicated pH val-
ues may be determined by linear interpolation. CT values be-
tween the indicated temperatures of different tables may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature, and at the
higher pH.
441
-------
§141.74
40 CFR Ch. I (7-1-02 Edition)
Table 1.3—CT Values (CT 99.9) for 99.9
Percent Inactivation of Giardia Lamblia
Cysts by Free Chlorine at 10.0 °C1
Free
pH
resid-
ual
(mg/l)
£6.0
6.5
7.0
7.5
8.0
8.5
0
01
VII
T
O
VII
73
88
104
125
149
177
209
0.6 ..
75
90
107
128
153
183
218
0.8 ..
78
92
110
131
158
189
226
1.0 ..
79
94
112
134
162
195
234
1.2 ..
80
95
114
137
166
200
240
1.4 ..
82
98
116
140
170
206
247
1.6 ..
83
99
119
144
174
211
253
1.8 ..
86
101
122
147
179
215
259
2.0 ..
87
104
124
150
182
221
265
2.2 ..
89
105
127
153
186
225
271
2.4 ..
90
107
129
157
190
230
276
2.6 ..
92
110
131
160
194
234
281
2.8 ..
93
111
134
163
197
239
287
3.0 ..
95
113
137
166
201
243
292
1 These CT values achieve greater than a 99.99 percent in-
activation of viruses. CT values between the indicated pH val-
ues may be determined by linear interpolation. CT values be-
tween the indicated temperatures of different tables may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature, and at the
higher pH.
Table 1.4—CT Values (CT 99.9) for 99.9
Percent Inactivation of Giardia Lamblia
Cysts by Free Chlorine at 15.0 °C1
Free
pH
resid-
ual
(mg/l)
£6.0
6.5
7.0
7.5
8.0
8.5
£9.0
T
O
VII
49
59
70
83
99
118
140
0.6 ..
50
60
72
86
102
122
146
0.8 ..
52
61
73
88
105
126
151
1.0 ..
53
63
75
90
108
130
156
1.2 ..
54
64
76
92
111
134
160
1.4 ..
1.6 ..
55
56
65
66
78
79
94
96
114
116
137
141
165
169
1.8 ..
57
68
81
98
119
144
173
2.0 ..
58
69
83
100
122
147
177
2.2 ..
59
70
85
102
124
150
181
2.4 ..
60
72
86
105
127
153
184
2.6 ..
61
73
88
107
129
156
188
2.8 ..
62
74
89
109
132
159
191
3.0 ..
63
76
91
111
134
162
195
1 These CT values achieve greater than a 99.99 percent in-
activation of viruses. CT values between the indicated pH val-
ues may be determined by linear interpolation. CT values be-
tween the indicated temperatures of different tables may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature, and at the
higher pH.
Table 1.5—CT Values (CT99.9) for 99.9 Per-
cent Inactivation of Giardia Lamblia
Cysts by Free Chlorine at 20°C1
Free
pH
resid-
ual
(mg/l)
£ 6.0
6.5
7.0
7.5
8.0
8.5
0
01
VII
T
O
VII
36
44
52
62
74
89
105
0.6
38
45
54
64
77
92
109
0.8
39
46
55
66
79
95
113
1.0
39
47
56
67
81
98
117
1.2
40
48
57
69
83
100
120
1.4
41
49
58
70
85
103
123
1.6
42
50
59
72
87
105
126
1.8
43
51
61
74
89
108
129
2.0
44
52
62
75
91
110
132
2.2
44
53
63
77
93
113
135
2.4
45
54
65
78
95
115
138
2.6
46
55
66
80
97
117
141
2.8
47
56
67
81
99
119
143
3.0
47
57
68
83
101
122
146
1 These CT values achieve greater than a 99.99 percent in-
activation of viruses. CT values between the indicated pH val-
ues may be determined by linear interpolation. CT values be-
tween the indicated temperatures of different tables may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature, and at the
higher pH.
Table 1.6—CT Values (CT99.9) for 99.9 Per-
cent Inactivation of Giardia Lamblia
Cysts by Free Chlorine at 25°C1 and
Higher
Free
pH
resid-
ual
(mg/l)
£ 6.0
6.5
7.0
7.5
8.0
8.5
0
01
VII
T
O
VII
24
29
35
42
50
59
70
0.6
25
30
36
43
51
61
73
0.8
26
31
37
44
53
63
75
1.0
26
31
37
45
54
65
78
1.2
27
32
38
46
55
67
80
1.4
27
33
39
47
57
69
82
1.6
28
33
40
48
58
70
84
1.8
29
34
41
49
60
72
86
2.0
29
35
41
50
61
74
88
2.2
30
35
42
51
62
75
90
2.4
30
36
43
52
63
77
92
2.6
31
37
44
53
65
78
94
2.8
31
37
45
54
66
80
96
3.0
32
38
46
55
67
81
97
1 These CT values achieve greater than a 99.99 percent in-
activation of viruses. CT values between the indicated pH val-
ues may be determined by linear interpolation. CT values be-
tween the indicated temperatures of different tables may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature, and at the
higher pH.
Table 2.1—CT Values (CT99.9) for 99.9 Percent Inactivation of Giardia Lamblia Cysts by
Chlorine Dioxide and Ozone1
Temperature
< 1 °C
5°C
10°C
15°C
20 °C
£ 25 °C
63
26
1.9
23
19
15
11
2.9
1.4
0.95
0.72
0.48
1 These CT values achieve greater than 99.99 percent inactivation of viruses. CT values between the indicated temperatures
may be determined by linear interpolation. If no interpolation is used, use the CT99.9 value at the lower temperature for deter-
mining CT99.9 values between indicated temperatures.
442
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Environmental Protection Agency
§141.74
Table 3.1— CT Values (CT 99.9) for 99.9
Percent Inactivation of Giardia Lamblia
Cysts By Chloramines1
Temperature
< 1 °C
cn
d
O
0
cn
d
20 °C
25 °C
3,800
2,200
1,850
1,500
1,100
750
1 These values are for pH values of 6 to 9. These CT val-
ues may be assumed to achieve greater than 99.99 percent
inactivation of viruses only if chlorine is added and mixed in
the water prior to the addition of ammonia. If this condition is
not met, the system must demonstrate, based on on-site stud-
ies or other information, as approved by the State, that the
system is achieving at least 99.99 percent inactivation of vi-
ruses. CT values between the indicated temperatures may be
determined by linear interpolation. If no interpolation is used,
use the CT99.9 value at the lower temperature for determining
CT99.9 values between indicated temperatures.
(4) The total inactivation ratio must
be calculated as follows:
(i) If the system uses only one point
of disinfectant application, the system
may determine the total inactivation
ratio based on either of the following'
two methods:
(A) One inactivation ratio (CTcalc/
CT99.9) is determined before or at the
first customer during peak hourly flow
and if the CTcalc/CT99.9 s 1.0, the 99.9
percent Giardia lamblia inactivation re-
quirement has been achieved; or
(B) Successive CTcalc/CTgg.g values,
representing sequential inactivation
ratios, are determined between the
point of disinfectant application and a
point before or at the first customer
during peak hourly flow. Under this al-
ternative, the following method must
be used to calculate the total inactiva-
tion ratio:
(1)
(2)
(3)
Determine for each sequence.
CT
99.9
CTcalc
Add the — values together
if I
CTq,
f CTcalc^
(CTcalc)
CTq,
CT999 ^
> 1.0, the 99.9 percent Giardia
lamblia inactivation requirement has
been achieved.
(ii) If the system uses more than one
point of disinfectant application before
or at the first customer, the system
must determine the CT value of each
disinfection sequence immediately
prior to the next point of disinfectant
application during peak hourly flow.
The CTcalc/CT99.9 value of each se-
quence and
v CTcalc
may be calculated by solving the fol-
lowing equation:
Percent inactivation = 100 -
100
10z
where z=3x^
f CTcalc^
CTqq q
CT99 9
must be calculated using the method
in paragraph (b)(4)(i)(B) of this section
to determine if the system is in com-
pliance with § 142.72(a).
(iii) Although not required, the total
percent inactivation for a system with
one or more points of residual dis-
infectant concentration monitoring
(5) The residual disinfectant con-
centration of the water entering the
distribution system must be monitored
continuously, and the lowest value
must be recorded each day, except that
if there is a failure in the continuous
monitoring equipment, grab sampling
every 4 hours may be conducted in lieu
of continuous monitoring, but for no
more than 5 working days following
the failure of the equipment, and sys-
tems serving 3,300 or fewer persons may
take grab samples in lieu of providing
continuous monitoring on an ongoing
443
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§141.74
40 CFR Ch. I (7-1-02 Edition)
basis at the frequencies prescribed
below:
System size by population
<500
501 to 1,000 ...
1,001 to 2,500
2,501 to 3,300
Samples/
day1
1 The day's samples cannot be taken at the same time. The
sampling intervals are subject to State review and approval.
If at any time the residual disinfectant
concentration falls below 0.2 mg/1 in a
system using grab sampling in lieu of
continuous monitoring, the system
must take a grab sample every 4 hours
until the residual concentration is
equal to or greater than 0.2 mg/1.
(6)(i) The residual disinfectant con-
centration must be measured at least
at the same points in the distribution
system and at the same time as total
coliforms are sampled, as specified in
§141.21, except that the State may
allow a public water system which uses
both a surface water source or a ground
water source under direct influence of
surface water, and a ground water
source, to take disinfectant residual
samples at points other than the total
coliform sampling points if the State
determines that such points are more
representative of treated (disinfected)
water quality within the distribution
system. Heterotrophic bacteria, meas-
ured as heterotrophic plate count
(HPC) as specified in paragraph (a)(3) of
this section, may be measured in lieu
of residual disinfectant concentration.
(ii) If the State determines, based on
site-specific considerations, that a sys-
tem has no means for having a sample
transported and analyzed for HPC by a
certified laboratory under the requisite
time and temperature conditions speci-
fied by paragraph (a)(3) of this section
and that the system is providing ade-
quate disinfection in the distribution
system, the requirements of paragraph
(b)(6)(i) of this section do not apply to
that system.
(c) Monitoring requirements for systems
using filtration treatment. A public water
system that uses a surface water
source or a ground water source under
the influence of surface water and pro-
vides filtration treatment must mon-
itor in accordance with this paragraph
(c) beginning June 29, 1993, or when fil-
tration is installed, whichever is later.
(1) Turbidity measurements as re-
quired by §141.73 must be performed on
representative samples of the system's
filtered water every four hours (or
more frequently) that the system
serves water to the public. A public
water system may substitute contin-
uous turbidity monitoring for grab
sample monitoring if it validates the
continuous measurement for accuracy
on a regular basis using a protocol ap-
proved by the State. For any systems
using slow sand filtration or filtration
treatment other than conventional
treatment, direct filtration, or diato-
maceous earth filtration, the State
may reduce the sampling frequency to
once per day if it determines that less
frequent monitoring is sufficient to in-
dicate effective filtration performance.
For systems serving 500 or fewer per-
sons, the State may reduce the tur-
bidity sampling frequency to once per
day, regardless of the type of filtration
treatment used, if the State deter-
mines that less frequent monitoring is
sufficient to indicate effective filtra-
tion performance.
(2) The residual disinfectant con-
centration of the water entering the
distribution system must be monitored
continuously, and the lowest value
must be recorded each day, except that
if there is a failure in the continuous
monitoring equipment, grab sampling
every 4 hours may be conducted in lieu
of continuous monitoring, but for no
more than 5 working days following
the failure of the equipment, and sys-
tems serving 3,300 or fewer persons may
take grab samples in lieu of providing
continuous monitoring on an ongoing
basis at the frequencies each day pre-
scribed below:
System size by population
±500
501 to 1,000 ...
1,001 to 2,500
2,501 to 3,300
Samples/
day1
1 The day's samples cannot be taken at the same time. The
sampling intervals are subject to State review and approval.
If at any time the residual disinfectant
concentration falls below 0.2 mg/1 in a
system using grab sampling in lieu of
continuous monitoring, the system
must take a grab sample every 4 hours
444
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Environmental Protection Agency
until the residual disinfectant con-
centration is equal to or greater than
0.2 mg/1.
(3)(i) The residual disinfectant con-
centration must be measured at least
at the same points in the distribution
system and at the same time as total
coliforms are sampled, as specified in
§141.21, except that the State may
allow a public water system which uses
both a surface water source or a ground
water source under direct influence of
surface water, and a ground water
source to take disinfectant residual
samples at points other than the total
coliform sampling points if the State
determines that such points are more
representative of treated (disinfected)
water quality within the distribution
system. Heterotrophic bacteria, meas-
ured as heterotrophic plate count
(HPC) as specified in paragraph (a)(3) of
this section, may be measured in lieu
of residual disinfectant concentration.
(ii) If the State determines, based on
site-specific considerations, that a sys-
tem has no means for having a sample
transported and analyzed for HPC by a
certified laboratory under the requisite
time and temperature conditions speci-
fied by paragraph (a)(3) of this section
and that the system is providing ade-
quate disinfection in the distribution
system, the requirements of paragraph
(c)(3)(i) of this section do not apply to
that system.
[54 FR 27527, June 29, 1989, as amended at 59
FR 62470, Dec. 5, 1994 ; 60 FR 34086, June 29,
1995; 64 FR 67465, Dec. 1, 1999]
§141.75 Reporting and recordkeeping
requirements.
(a) A public water system that uses a
surface water source and does not pro-
vide filtration treatment must report
monthly to the State the information
specified in this paragraph (a) begin-
ning December 31, 1990, unless the
State has determined that filtration is
required in writing pursuant to section
1412(b)(7)(C)(iii), in which case the
State may specify alternative report-
ing requirements, as appropriate, until
filtration is in place. A public water
system that uses a ground water source
under the direct influence of surface
water and does not provide filtration
treatment must report monthly to the
State the information specified in this
§141.75
paragraph (a) beginning December 31,
1990, or 6 months after the State deter-
mines that the ground water source is
under the direct influence of surface
water, whichever is later, unless the
State has determined that filtration is
required in writing pursuant to
§1412(b)(7)(C)(iii), in which case the
State may specify alternative report-
ing requirements, as appropriate, until
filtration is in place.
(1) Source water quality information
must be reported to the State within 10
days after the end of each month the
system serves water to the public. In-
formation that must be reported in-
cludes:
(i) The cumulative number of months
for which results are reported.
(ii) The number of fecal and/or total
coliform samples, whichever are ana-
lyzed during the month (if a system
monitors for both, only fecal coliforms
must be reported), the dates of sample
collection, and the dates when the tur-
bidity level exceeded 1 NTU.
(iii) The number of samples during
the month that had equal to or less
than 20/100 ml fecal coliforms and/or
equal to or less than 100/100 ml total
coliforms, whichever are analyzed.
(iv) The cumulative number of fecal
or total coliform samples, whichever
are analyzed, during the previous six
months the system served water to the
public.
(v) The cumulative number of sam-
ples that had equal to or less than 20/
100 ml fecal coliforms or equal to or
less than 100/100 ml total coliforms,
whichever are analyzed, during the pre-
vious six months the system served
water to the public.
(vi) The percentage of samples that
had equal to or less than 20/100 ml fecal
coliforms or equal to or less than 100/
100 ml total coliforms, whichever are
analyzed, during the previous six
months the system served water to the
public.
(vii) The maximum turbidity level
measured during the month, the date(s)
of occurrence for any measurement(s)
which exceeded 5 NTU, and the date(s)
the occurrence(s) was reported to the
State.
(viii) For the first 12 months of rec-
ordkeeping, the dates and cumulative
445
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§141.75
40 CFR Ch. I (7-1-02 Edition)
number of events during which the tur-
bidity exceeded 5 NTU, and after one
year of recordkeeping for turbidity
measurements, the dates and cumu-
lative number of events during which
the turbidity exceeded 5 NTU in the
previous 12 months the system served
water to the public.
(ix) For the first 120 months of rec-
ordkeeping, the dates and cumulative
number of events during which the tur-
bidity exceeded 5 NTU, and after 10
years of recordkeeping for turbidity
measurements, the dates and cumu-
lative number of events during which
the turbidity exceeded 5 NTU in the
previous 120 months the system served
water to the public.
(2) Disinfection information specified
in § 141.74(b) must be reported to the
State within 10 days after the end of
each month the system serves water to
the public. Information that must be
reported includes:
(i) For each day, the lowest measure-
ment of residual disinfectant con-
centration in mg/1 in water entering
the distribution system.
(ii) The date and duration of each pe-
riod when the residual disinfectant
concentration in water entering the
distribution system fell below 0.2 mg/1
and when the State was notified of the
occurrence.
(iii) The daily residual disinfectant
concentration(s) (in mg/1) and dis-
infectant contact time(s) (in minutes)
used for calculating the CT value(s).
(iv) If chlorine is used, the daily
measurement(s) of pH of disinfected
water following each point of chlorine
disinfection.
(v) The daily measurement(s) of
water temperature in °C following each
point of disinfection.
(vi) The daily CTcalc and CTcalc/
CT99.9 values for each disinfectant
measurement or sequence and the sum
of all CTcalc/CT99.9 values ((CTcalc/
CT99.9)) before or at the first customer.
(vii) The daily determination of
whether disinfection achieves adequate
Giardia cyst and virus inactivation,
i.e., whether (CTcalc/CT99.9) is at least
1.0 or, where disinfectants other than
chlorine are used, other indicator con-
ditions that the State determines are
appropriate, are met.
(viii) The following information on
the samples taken in the distribution
system in conjunction with total coli-
form monitoring pursuant to §141.72:
(A) Number of instances where the
residual disinfectant concentration is
measured;
(B) Number of instances where the
residual disinfectant concentration is
not measured but heterotrophic bac-
teria plate count (HPC) is measured;
(C) Number of instances where the re-
sidual disinfectant concentration is
measured but not detected and no HPC
is measured;
(D) Number of instances where the
residual disinfectant concentration is
detected and where HPC is >500/ml;
(E) Number of instances where the
residual disinfectant concentration is
not measured and HPC is >500/ml;
(F) For the current and previous
month the system served water to the
public, the value of "V" in the fol-
lowing formula:
a + b
where:
a=the value in paragraph (a)(2)(viii)(A) of
this section,
b=the value in paragraph (a)(2)(viii)(B) of
this section,
c=the value in paragraph (a)(2)(viii)(C) of
this section,
d=the value in paragraph (a)(2)(viii)(D) of
this section, and
e=the value in paragraph (a)(2)(viii)(E) of
this section.
(G) If the State determines, based on
site-specific considerations, that a sys-
tem has no means for having a sample
transported and analyzed for HPC by a
certified laboratory under the requisite
time and temperature conditions speci-
fied by § 141.74(a)(3) and that the sys-
tem is providing adequate disinfection
in the distribution system, the require-
ments of paragraph (a)(2)(viii) (A)-(F)
of this section do not apply to that sys-
tem.
(ix) A system need not report the
data listed in paragraphs (a)(2) (i), and
(iii)-(vi) of this section if all data listed
in paragraphs (a)(2) (i)-(viii) of this sec-
tion remain on file at the system, and
the State determines that:
(A) The system has submitted to the
State all the information required by
446
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Environmental Protection Agency
§141.75
paragraphs (a)(2) (i)-(viii) of this sec-
tion for at least 12 months; and
(B) The State has determined that
the system is not required to provide
filtration treatment.
(3) No later than ten days after the
end of each Federal fiscal year (Sep-
tember 30), each system must provide
to the State a report which summa-
rizes its compliance with all watershed
control program requirements specified
in §141.71(b)(2).
(4) No later than ten days after the
end of each Federal fiscal year (Sep-
tember 30), each system must provide
to the State a report on the on-site in-
spection conducted during that year
pursuant to § 141.71(b)(3), unless the on-
site inspection was conducted by the
State. If the inspection was conducted
by the State, the State must provide a
copy of its report to the public water
system.
(5)(i) Each system, upon discovering
that a waterborne disease outbreak po-
tentially attributable to that water
system has occurred, must report that
occurrence to the State as soon as pos-
sible, but no later than by the end of
the next business day.
(ii) If at any time the turbidity ex-
ceeds 5 NTU, the system must consult
with the primacy agency as soon as
practical, but no later than 24 hours
after the exceedance is known, in ac-
cordance with the public notification
requirements under § 141.203(b)(3).
(iii) If at any time the residual falls
below 0.2 mg/1 in the water entering the
distribution system, the system must
notify the State as soon as possible,
but no later than by the end of the next
business day. The system also must no-
tify the State by the end of the next
business day whether or not the resid-
ual was restored to at least 0.2 mg/1
within 4 hours.
(b) A public water system that uses a
surface water source or a ground water
source under the direct influence of
surface water and provides filtration
treatment must report monthly to the
State the information specified in this
paragraph (b) beginning June 29, 1993,
or when filtration is installed, which-
ever is later.
(1) Turbidity measurements as re-
quired by § 141.74(c)(1) must be reported
within 10 days after the end of each
month the system serves water to the
public. Information that must be re-
ported includes:
(1) The total number of filtered water
turbidity measurements taken during
the month.
(ii) The number and percentage of fil-
tered water turbidity measurements
taken during the month which are less
than or equal to the turbidity limits
specified in §141.73 for the filtration
technology being used.
(iii) The date and value of any tur-
bidity measurements taken during the
month which exceed 5 NTU.
(2) Disinfection information specified
in § 141.74(c) must be reported to the
State within 10 days after the end of
each month the system serves water to
the public. Information that must be
reported includes:
(i) For each day, the lowest measure-
ment of residual disinfectant con-
centration in mg/1 in water entering
the distribution system.
(ii) The date and duration of each pe-
riod when the residual disinfectant
concentration in water entering the
distribution system fell below 0.2 mg/1
and when the State was notified of the
occurrence.
(iii) The following information on the
samples taken in the distribution sys-
tem in conjunction with total coliform
monitoring pursuant to §141.72:
(A) Number of instances where the
residual disinfectant concentration is
measured;
(B) Number of instances where the
residual disinfectant concentration is
not measured but heterotrophic bac-
teria plate count (HPC) is measured;
(C) Number of instances where the re-
sidual disinfectant concentration is
measured but not detected and no HPC
is measured;
(D) Number of instances where no re-
sidual disinfectant concentration is de-
tected and where HPC is >500/ml;
(E) Number of instances where the
residual disinfectant concentration is
not measured and HPC is >500/ml;
(F) For the current and previous
month the system serves water to the
public, the value of "V" in the fol-
lowing formula:
a + b
447
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§141.76
40 CFR Ch. I (7-1-02 Edition)
where:
a=the value in paragraph (b)(2)(iii)(A) of this
section,
b=the value in paragraph (b)(2)(iii)(B) of this
section,
c=the value in paragraph (b)(2)(iii)(C) of this
section,
d=the value in paragraph (b)(2)(iii)(D) of this
section, and
e=the value in paragraph (b)(2)(iii)(E) of this
section.
(G) If the State determines, based on
site-specific considerations, that a sys-
tem has no means for having a sample
transported and analyzed for HPC by a
certified laboratory within the req-
uisite time and temperature conditions
specified by § 141.74(a)(3) and that the
system is providing adequate disinfec-
tion in the distribution system, the re-
quirements of paragraph (b)(2)(iii) (A)-
(F) of this section do not apply.
(iv) A system need not report the
data listed in paragraph (b)(2)(i) of this
section if all data listed in paragraphs
(b)(2) (i)-(iii) of this section remain on
file at the system and the State deter-
mines that the system has submitted
all the information required by para-
graphs (b)(2) (i)-(iii) of this section for
at least 12 months.
(3)(i) Each system, upon discovering
that a waterborne disease outbreak po-
tentially attributable to that water
system has occurred, must report that
occurrence to the State as soon as pos-
sible, but no later than by the end of
the next business day.
(ii) If at any time the turbidity ex-
ceeds 5 NTU, the system must consult
with the primacy agency as soon as
practical, but no later than 24 hours
after the exceedance is known, in ac-
cordance with the public notification
requirements under § 141.203(b)(3).
(iii) If at any time the residual falls
below 0.2 mg/1 in the water entering the
distribution system, the system must
notify the State as soon as possible,
but no later than by the end of the next
business day. The system also must no-
tify the State by the end of the next
business day whether or not the resid-
ual was restored to at least 0.2 mg/1
within 4 hours.
[54 FR 27527, June 29, 1989, as amended at 65
FR 26022, May 4, 2000]
§141.76 Recycle provisions.
(a) Applicability. All subpart H sys-
tems that employ conventional filtra-
tion or direct filtration treatment and
that recycle spent filter backwash
water, thickener supernatant, or liq-
uids from dewatering processes must
meet the requirements in paragraphs
(b) through (d) of this section.
(b) Reporting. A system must notify
the State in writing by Decemeber 8,
2003, if the system recycles spent filter
backwash water, thickener super-
natant, or liquids from dewatering
processes. This notification must in-
clude, at a minimum, the information
specified in paragraphs (b)(1) and (2) of
this section.
(1) A plant schematic showing the or-
igin of all flows which are recycled (in-
cluding, but not limited to, spent filter
backwash water, thickener super-
natant, and liquids from dewatering
processes), the hydraulic conveyance
used to transport them, and the loca-
tion where they are re-introduced back
into the treatment plant.
(2) Typical recycle flow in gallons per
minute (gpm), the highest observed
plant flow experienced in the previous
year (gpm), design flow for the treat-
ment plant (gpm), and State-approved
operating capacity for the plant where
the State has made such determina-
tions.
(c) Treatment technique requirement.
Any system that recycles spent filter
backwash water, thickener super-
natant, or liquids from dewatering
processes must return these flows
through the processes of a system's ex-
isting conventional or direct filtration
system as defined in §141.2 or at an al-
ternate location approved by the State
by June 8, 2004. If capital improve-
ments are required to modify the recy-
cle location to meet this requirement,
all capital improvements must be com-
pleted no later than June 8, 2006.
(d) Recordkeeping. The system must
collect and retain on file recycle flow
information specified in paragraphs
(d)(1) through (6) of this section for re-
view and evaluation by the State be-
ginning June 8, 2004.
(1) Copy of the recycle notification
and information submitted to the
State under paragraph (b) of this sec-
tion.
448
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Break in sequence
§141.201
filter number, the turbidity measure-
ment, and the date(s) on which the ex-
ceedance occurred. In addition, the sys-
tem must arrange for the conduct of a
comprehensive performance evaluation
by the State or a third party approved
by the State no later than 30 days fol-
lowing the exceedance and have the
evaluation completed and submitted to
the State no later than 90 days fol-
lowing the exceedance.
(c) Additional reporting requirements.
(1) If at any time the turbidity exceeds
1 NTU in representative samples of fil-
tered water in a system using conven-
tional filtration treatment or direct
filtration, the system must inform the
State as soon as possible, but no later
than the end of the next business day.
(2) If at any time the turbidity in
representative samples of filtered
water exceeds the maximum level set
by the State under § 141.173(b) for filtra-
tion technologies other than conven-
tional filtration treatment, direct fil-
tration, slow sand filtration, or diato-
maceous earth filtration, the system
must inform the State as soon as pos-
sible, but no later than the end of the
next business day.
[63 FR 69516, Dec. 16, 1998, as amended at 66
FR 3779, Jan. 16, 2001]
Subpart Q—Public Notification of
Drinking Water Violations
Source: 65 FR 26035, May 4, 2000, unless
otherwise noted.
§141.201 General public notification
requirements.
Public water systems in States with
primacy for the public water system
supervision (PWSS) program must
comply with the requirements in this
subpart no later than May 6, 2002 or on
the date the State-adopted rule be-
comes effective, whichever comes first.
Public water systems in jurisdictions
where EPA directly implements the
PWSS program must comply with the
requirements in this subpart on Octo-
ber 31, 2000. Prior to these dates, public
water systems must continue to com-
ply with the public notice require-
ments in §141.32 of this part. The term
"primacy agency" is used in this sub-
part to refer to either EPA or the State
40 CFR Ch. I (7-1-02 Edition)
or the Tribe in cases where EPA, the
State, or the Tribe exercises primary
enforcement responsibility for this sub-
part.
(a) Who must give public notice? Each
owner or operator of a public water
system (community water systems,
non-transient non-community water
systems, and transient non-community
water systems) must give notice for all
violations of national primary drink-
ing water regulations (NPDWR) and for
other situations, as listed in Table 1.
The term "NPDWR violations" is used
in this subpart to include violations of
the maximum contaminant level
(MCL), maximum residual disinfection
level (MRDL), treatment technique
(TT), monitoring requirements, and
testing procedures in this part 141. Ap-
pendix A to this subpart identifies the
tier assignment for each specific viola-
tion or situation requiring a public no-
tice.
Table 1 to §141.201—Violation Cat-
egories and Other Situations Requiring
a Public Notice
(1) NPDWR violations:
(i) Failure to comply with an applicable
maximum contaminant level (MCL) or
maximum residual disinfectant level
(MRDL).
(ii) Failure to comply with a prescribed
treatment technique (TT).
(iii) Failure to perform water quality mon-
itoring, as required by the drinking
water regulations.
(iv) Failure to comply with testing proce-
dures as prescribed by a drinking
water regulation.
(2) Variance and exemptions under sections
1415 and 1416 of SDWA:
(i) Operation under a variance or an ex-
emption.
(ii) Failure to comply with the require-
ments of any schedule that has been
set under a variance or exemption.
(3) Special public notices:
(i) Occurrence of a waterborne disease
outbreak or other waterborne emer-
gency.
(ii) Exceedance of the nitrate MCL by
non-community water systems
(NCWS), where granted permission by
the primacy agency under 141.11(d) of
this part.
526
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Environmental Protection Agency
§141.202
Table 1 to §141.201—Violation Cat-
egories and Other Situations Requiring
a Public Notice—Continued
(iii) Exceedance of the secondary max-
imum contaminant level (SMCL) for
fluoride.
(iv) Availability of unregulated contami-
nant monitoring data.
(v) Other violations and situations deter-
mined by the primacy agency to re-
quire a public notice under this sub-
part, not already listed in Appendix A.
(b) What type of public notice is re-
quired for each violation or situation?
Public notice requirements are divided
into three tiers, to take into account
the seriousness of the violation or situ-
ation and of any potential adverse
health effects that may be involved.
The public notice requirements for
each violation or situation listed in
Table 1 of this section are determined
by the tier to which it is assigned.
Table 2 of this section provides the def-
inition of each tier. Appendix A of this
part identifies the tier assignment for
each specific violation or situation.
Table 2 to § 141.201 .—Definition of Public
Notice Tiers
(1) Tier 1 public notice—required for NPDWR
violations and situations with significant po-
tential to have serious adverse effects on
human health as a result of short-term ex-
posure.
(2) Tier 2 public notice—required for all other
NPDWR violations and situations with po-
tential to have serious adverse effects on
human health.
(3) Tier 3 public notice—required for all other
NPDWR violations and situations not in-
cluded in Tier 1 and Tier 2.
(c) Who must be notified?
(1) Each public water system must
provide public notice to persons served
by the water system, in accordance
with this subpart. Public water sys-
tems that sell or otherwise provide
drinking water to other public water
systems (i.e., to consecutive systems)
are required to give public notice to
the owner or operator of the consecu-
tive system; the consecutive system is
responsible for providing public notice
to the persons it serves.
(2) If a public water system has a vio-
lation in a portion of the distribution
system that is physically or hydrau-
lically isolated from other parts of the
distribution system, the primacy agen-
cy may allow the system to limit dis-
tribution of the public notice to only
persons served by that portion of the
system which is out of compliance.
Permission by the primacy agency for
limiting distribution of the notice
must be granted in writing.
(3) A copy of the notice must also be
sent to the primacy agency, in accord-
ance with the requirements under
§ 141.31(d).
§141.202 Tier 1 Public Notice—Form,
manner, and frequency of notice.
(a) Which violations or situations re-
quire a Tier 1 public notice? Table 1 of
this section lists the violation cat-
egories and other situations requiring
a Tier 1 public notice. Appendix A to
this subpart identifies the tier assign-
ment for each specific violation or sit-
uation.
Table 1 to §141.202.—Violation Cat-
egories and Other Situations Requiring
a Tier 1 Public Notice
(1) Violation of the MCL for total conforms
when fecal coliform or E. coli are present
in the water distribution system (as speci-
fied in § 141.63(b)), or when the water sys-
tem fails to test for fecal coliforms or E.
coli when any repeat sample tests positive
for coliform (as specified in § 141.21 (e));
(2) Violation of the MCL for nitrate, nitrite, or
total nitrate and nitrite, as defined in
§ 141.62, or when the water system fails to
take a confirmation sample within 24 hours
of the system's receipt of the first sample
showing an exceedance of the nitrate or
nitrite MCL, as specified in § 141.23(f)(2);
(3) Exceedance of the nitrate MCL by non-
community water systems, where permitted
to exceed the MCL by the primacy agency
under §141.11(d), as required under
§141.209;
527
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§141.203
40 CFR Ch. I (7-1-02 Edition)
Table 1 to §141.202—Violation Cat-
egories and Other Situations Requiring
a Tier 1 Public Notice—Continued
(4) Violation of the MRDL for chlorine diox-
ide, as defined in §141.65(a), when one or
more samples taken in the distribution sys-
tem the day following an exceedance of
the MRDL at the entrance of the distribu-
tion system exceed the MRDL, or when
the water system does not take the re-
quired samples in the distribution system,
as specified in § 141.133(c)(2)(i);
(5) Violation of the turbidity MCL under
§ 141.13(b), where the primacy agency de-
termines after consultation that a Tier 1 no-
tice is required or where consultation does
not take place within 24 hours after the
system learns of the violation;
(6) Violation of the Surface Water Treatment
Rule (SWTR), Interim Enhanced Surface
Water Treatment Rule (IESWTR) or Long
Term 1 Enhanced Surface Water Treat-
ment Rule (LT1ESWTR) treatment tech-
nique requirement resulting from a single
exceedance of the maximum allowable tur-
bidity limit (as identified in Appendix A),
where the primacy agency determines after
consultation that a Tier 1 notice is required
or where consultation does not take place
within 24 hours after the system learns of
the violation;
(7) Occurrence of a waterborne disease out-
break, as defined in §141.2, or other wa-
terborne emergency (such as a failure or
significant interruption in key water treat-
ment processes, a natural disaster that dis-
rupts the water supply or distribution sys-
tem, or a chemical spill or unexpected
loading of possible pathogens into the
source water that significantly increases
the potential for drinking water contamina-
tion);
(8) Other violations or situations with signifi-
cant potential to have serious adverse ef-
fects on human health as a result of short-
term exposure, as determined by the pri-
macy agency either in its regulations or on
a case-by-case basis.
(b) When is the Tier 1 public notice to
be provided? What additional steps are
required? Public water systems must:
(1) Provide a public notice as soon as
practical but no later than 24 hours
after the system learns of the viola-
tion;
(2) Initiate consultation with the pri-
macy agency as soon as practical, but
no later than 24 hours after the public
water system learns of the violation or
situation, to determine additional pub-
lic notice requirements; and
(3) Comply with any additional public
notification requirements (including'
any repeat notices or direction on the
duration of the posted notices) that are
established as a result of the consulta-
tion with the primacy agency. Such re-
quirements may include the timing,
form, manner, frequency, and content
of repeat notices (if any) and other ac-
tions designed to reach all persons
served.
(c) What is the form and manner of the
public notice? Public water systems
must provide the notice within 24
hours in a form and manner reasonably
calculated to reach all persons served.
The form and manner used by the pub-
lic water system are to fit the specific
situation, but must be designed to
reach residential, transient, and non-
transient users of the water system. In
order to reach all persons served, water
systems are to use, at a minimum, one
or more of the following forms of deliv-
ery:
(1) Appropriate broadcast media
(such as radio and television);
(2) Posting of the notice in con-
spicuous locations throughout the area
served by the water system;
(3) Hand delivery of the notice to per-
sons served by the water system; or
(4) Another delivery method approved
in writing by the primacy agency.
[65 FR 26035, May 4, 2000, as amended at 67
FR 1836, Jan. 14, 2002]
§141.203 Tier 2 Public Notice—Form,
manner, and frequency of notice.
(a) Which violations or situations re-
quire a Tier 2 public notice? Table 1 of
this section lists the violation cat-
egories and other situations requiring
a Tier 2 public notice. Appendix A to
this subpart identifies the tier assign-
ment for each specific violation or sit-
uation.
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Environmental Protection Agency
Table 1 to §141.203—Violation Cat-
egories and Other Situations Requiring
a Tier 2 Public Notice
(1) All violations of the MCL, MRDL, and
treatment technique requirements, except
where a Tier 1 notice is required under
§141.202(a) or where the primacy agency
determines that a Tier 1 notice is required;
(2) Violations of the monitoring and testing
procedure requirements, where the pri-
macy agency determines that a Tier 2 rath-
er than a Tier 3 public notice is required,
taking into account potential health impacts
and persistence of the violation; and
(3) Failure to comply with the terms and con-
ditions of any variance or exemption in
place.
(b) When is the Tier 2 public notice to
be provided?
(1) Public water systems must pro-
vide the public notice as soon as prac-
tical, but no later than 30 days after
the system learns of the violation. If
the public notice is posted, the notice
must remain in place for as long as the
violation or situation persists, but in
no case for less than seven days, even if
the violation or situation is resolved.
The primacy agency may, in appro-
priate circumstances, allow additional
time for the initial notice of up to
three months from the date the system
learns of the violation. It is not appro-
priate for the primacy agency to grant
an extension to the 30-day deadline for
any unresolved violation or to allow
across-the-board extensions by rule or
policy for other violations or situa-
tions requiring a Tier 2 public notice.
Extensions granted by the primacy
agency must be in writing.
(2) The public water system must re-
peat the notice every three months as
long as the violation or situation per-
sists, unless the primacy agency deter-
mines that appropriate circumstances
warrant a different repeat notice fre-
quency. In no circumstance may the
repeat notice be given less frequently
than once per year. It is not appro-
priate for the primacy agency to allow
less frequent repeat notice for an MCL
violation under the Total Coliform
Rule or a treatment technique viola-
tion under the Surface Water Treat-
ment Rule or Interim Enhanced Sur-
face Water Treatment Rule. It is also
§141.203
not appropriate for the primacy agency
to allow through its rules or policies
across-the-board reductions in the re-
peat notice frequency for other ongoing
violations requiring a Tier 2 repeat no-
tice. Primacy agency determinations
allowing repeat notices to be given less
frequently than once every three
months must be in writing.
(3) For the turbidity violations speci-
fied in this paragraph, public water
systems must consult with the primacy
agency as soon as practical but no
later than 24 hours after the public
water system learns of the violation, to
determine whether a Tier 1 public no-
tice under § 141.202(a) is required to pro-
tect public health. When consultation
does not take place within the 24-hour
period, the water system must dis-
tribute a Tier 1 notice of the violation
within the next 24 hours {i.e., no later
than 48 hours after the system learns of
the violation), following the require-
ments under § 141.202(b) and (c). Con-
sultation with the primacy agency is
required for:
(i) Violation of the turbidity MCL
under § 141.13(b); or
(ii) Violation of the SWTR, IESWTR
or LT1ESWTR treatment technique re-
quirement resulting from a single ex-
ceedance of the maximum allowable
turbidity limit.
(c) What is the form and manner of the
Tier 2 public notice? Public water sys-
tems must provide the initial public
notice and any repeat notices in a form
and manner that is reasonably cal-
culated to reach persons served in the
required time period. The form and
manner of the public notice may vary
based on the specific situation and type
of water system, but it must at a min-
imum meet the following require-
ments:
(1) Unless directed otherwise by the
primacy agency in writing, community
water systems must provide notice by:
(i) Mail or other direct delivery to
each customer receiving a bill and to
other service connections to which
water is delivered by the public water
system; and
(ii) Any other method reasonably cal-
culated to reach other persons regu-
larly served by the system, if they
would not normally be reached by the
notice required in paragraph (c)(l)(i) of
529
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§141.204
40 CFR Ch. I (7-1-02 Edition)
this section. Such persons may include
those who do not pay water bills or do
not have service connection addresses
(e.g., house renters, apartment dwell-
ers, university students, nursing home
patients, prison inmates, etc.). Other
methods may include: Publication in a
local newspaper; delivery of multiple
copies for distribution by customers
that provide their drinking water to
others (e.g., apartment building owners
or large private employers); posting in
public places served by the system or
on the Internet; or delivery to commu-
nity organizations.
(2) Unless directed otherwise by the
primacy agency in writing, non-com-
munity water systems must provide
notice by:
(i) Posting the notice in conspicuous
locations throughout the distribution
system frequented by persons served by
the system, or by mail or direct deliv-
ery to each customer and service con-
nection (where known); and
(ii) Any other method reasonably cal-
culated to reach other persons served
by the system if they would not nor-
mally be reached by the notice re-
quired in paragraph (c)(2)(i) of this sec-
tion. Such persons may include those
served who may not see a posted notice
because the posted notice is not in a lo-
cation they routinely pass by. Other
methods may include: Publication in a
local newspaper or newsletter distrib-
uted to customers; use of E-mail to no-
tify employees or students; or, delivery
of multiple copies in central locations
(e.g., community centers).
[65 FR 26035, May 4, 2000, as amended at 67
FR 1836, Jan. 14, 2002]
§141.204 Tier 3 Public Notice—Form,
manner, and frequency of notice.
(a) Which violations or situations re-
quire a Tier 3 public notice? Table 1 of
this section lists the violation cat-
egories and other situations requiring
a Tier 3 public notice. Appendix A to
this subpart identifies the tier assign-
ment for each specific violation or sit-
uation.
Table 1 to §141.204—Violation Cat-
egories and Other Situations Requiring
a Tier 3 Public Notice
(1) Monitoring violations under 40 CFR part
141, except where a Tier 1 notice is re-
quired under § 141.202(a) or where the pri-
macy agency determines that a Tier 2 no-
tice is required;
(2) Failure to comply with a testing procedure
established in 40 CFR part 141, except
where a Tier 1 notice is required under
§141.202(a)) or where the primacy agency
determines that a Tier 2 notice is required;
(3) Operation under a variance granted under
Section 1415 or an exemption granted
under Section 1416 of the Safe Drinking
Water Act;
(4) Availability of unregulated contaminant
monitoring results, as required under
§141.207; and
(5) Exceedance of the fluoride secondary
maximum contaminant level (SMCL), as
required under § 141.208.
(b) When is the Tier 3 public notice to
be provided?
(1) Public water systems must pro-
vide the public notice not later than
one year after the public water system
learns of the violation or situation or
begins operating under a variance or
exemption. Following the initial no-
tice, the public water system must re-
peat the notice annually for as long as
the violation, variance, exemption, or
other situation persists. If the public
notice is posted, the notice must re-
main in place for as long as the viola-
tion, variance, exemption, or other sit-
uation persists, but in no case less than
seven days (even if the violation or sit-
uation is resolved).
(2) Instead of individual Tier 3 public
notices, a public water system may use
an annual report detailing all viola-
tions and situations that occurred dur-
ing the previous twelve months, as
long as the timing requirements of
paragraph (b)(1) of this section are met.
(c) What is the form and manner of the
Tier 3 public notice? Public water sys-
tems must provide the initial notice
and any repeat notices in a form and
manner that is reasonably calculated
to reach persons served in the required
time period. The form and manner of
530
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