United States
Environmental Protection
Agency
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Ground Water Rule Triggered and
Representative Monitoring: A Quick
Reference Guide
Overview of the Rule
Title
Purpose
General
Description
Utilities
Covered
Ground Water Rule (GWR) 71 FR 65574, November 8, 2006, Vol. 71, No. 216
Correction 71 FR 67427, November 21, 2006, Vol. 71, No. 224
Reduce the risk of illness caused by microbial contamination in public ground
water systems (GWSs).
The GWR establishes a risk-targeted approach to identify GWSs susceptible
to fecal contamination and requires corrective action to correct significant
deficiencies and source water fecal contamination in all public GWSs.
The GWR applies to all public water systems (PWSs) that use ground water,
including consecutive systems, except that it does not apply to PWSs that
combine all of their ground water with surface water or with ground water
under the direct influence of surface water prior to treatment.
Purpose of Triggered Source Water Monitoring
The purpose of triggered source water monitoring is to evaluate whether the presence of
total coliform in the distribution system is due to fecal contamination in the ground water
source.
This type of source water monitoring is triggered by routine total coliform monitoring
required by the Total Coliform Rule (TCR) (40 CFR 141.21).
• Since TCR monitoring is conducted regularly, triggered source water monitoring can
occur at any time and thus provides an ongoing evaluation of ground water sources.
Triggered Source Water Monitoring Requirements
Systems Required to Conduct Triggered Source Water Monitoring
GWSs are
subject to
triggered source
water monitoring
if they:
^- Do not provide, and conduct compliance monitoring for, at least 4-log
treatment of viruses (through inactivation and/or removal).
• This includes systems that decide to discontinue 4-log treatment.
>• Do not purchase 100% of their water (and therefore have a source at
which to sample).
Situations Leading to Triggered Source Water Monitoring
GWSs must
conduct
triggered source
water monitoring
when:
>• The system is notified of a total coliform-positive sample collected in
compliance with the TCR unless:
• The total coliform sample is invalidated by the State.
• The State allows an exception to the GWR triggered source water
monitoring requirements.
OR
>• The system is a wholesale system and is notified by one of its
consecutive systems that the consecutive system had a total coliform-
positive sample during TCR monitoring.
Collecting and Analyzing Triggered Source Water Monitoring Samples
When triggered
source water
monitoring is
required, GWSs
must:
>• Collect at least one ground water source sample from each source in
use at the time the total coliform-positive sample was collected.
• Samples must be collected within 24 hours of being notified of the
total coliform-positive sample (unless the 24-hour limit is extended
by the State).
• Sample must be taken before treatment or at a State-approved
location after treatment (see the diagram on the next page).
>• Ensure all samples are analyzed for the presence of a fecal indicator
(e.g., E. co//, enterococci, or coliphage) using an approved GWR
method.
^ If a fecal indicator-positive source sample is invalidated by the State,
the GWS must collect another source water sample within 24 hours
of being notified by the State of the sample invalidation using an
approved method. See the "Analytical Methods Approved for the
Ground Water Rule" at http://www.epa.gov/safewater/methods/
analyticalmethods.html.
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^- The diagram below represents an appropriate sampling location for triggered source water monitoring. GWSs
a sample tap at each source that enables triggered source water monitoring.
Treatment p^
^f \
V
,uu^Jl L^ Distribution
.g, | System 1
^^^^ ^ /////
Ground ^L
Water ^
Source SAMPLING LOCATION
should have
Additional Sampling
>• If the initial triggered source water sample is fecal indicator-postive, and the State does not require corrective action in
response, GWSs must conduct additional source water monitoring.
• GWSs must collect five additional source water samples (from the source(s) that contained the original fecal indicator-
positive samples) within 24 hours of being notified of the fecal indicator-positive sample.
• The additional samples must be tested for a fecal indicator using an approved GWR method.
^- If any one of the five additional samples is fecal indicator-positive, the system must take corrective action.
^- If any additional sample is found to be fecal indicator-positive but is subsequently invalidated by the State, the GWS must
resample for the same fecal indicator within 24 hours of being notified of the invalidation.
Note: If the GWS is a wholesale system, it must notify all consecutive systems served by a source of any fecal indicator-
positive samples from that source within 24 hours of being notified of the sample result.
Sampling at Representative Sources and Triggered Source Water Monitoring Plans
Representative Source Sampling
>• If a GWS has multiple sources, the State may allow the GWS to conduct representative source sampling.
>• Representative source water sampling allows systems to collect samples from the sources that represent (serve) the TCR
monitoring site rather than from all sources. These representative ground water sources must be approved by the State.
>• Systems must still:
• Sample within 24 hours of total coliform-positive sample.
• Analyze using an approved GWR method.
Triggered Source Water Monitoring Plan
If the State allows representative site sampling, the State may require the GWS to submit a triggered source water
monitoring plan for approval before the GWS starts conducting representative source sampling.
• A triggered source water monitoring plan may include:
• A map of the water system (including location of ground water sources, location of pressure zones, and location of
storage facilities),
• A written explanation of how the GWS knows which source feeds which section of the distribution system, and
• Seasonal or intermittent ground water sources and when they are used.
• Regardless of whether or not the State requires a plan to be submitted, all representative source sampling locations
must be approved by the State.
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The diagram below provides an example of a system schematic that could be used to determine representative sources
and develop a triggered source water monitoring plan, based on where in the distribution system the total coliform-
positive sample is found. If approved by the State, the system could sample sources 1 and 2 after a total coliform-positive
at Site 1 since Site 1 is in the zone served by those sources. A total coliform-positive at Site 2 would require source
sampling from all sources since this area is served by all sources.
Variations in Requirements Based on System Size
GWSs Serving Fewer than 1,000 Persons
GWSs that serve fewer than 1,000 persons may be able to meet TCR repeat monitoring requirements and GWR triggered
source water monitoring requirements together if the State allows:
• Repeat TCR monitoring at the source
AND
• E co// to be used as a fecal indicator under the GWR.
If the State allows this situation, then the GWS can use a TCR repeat sample collected at the source to meet the triggered
source water monitoring requirement of the GWR. The fourth TCR repeat sample is collected at the source. Upstream and
downstream samples and a sample at the TCR site are still needed to meet TCR requirements.
Labs must use an approved GWR method to test for E co//.
Note: If the TCR repeat sample collected at the source is TCR-positive but E co// is not found, the GWR does not require
further action but the system is in violation of the TCR MCL.
Consecutive Systems and Wholesale Systems
Consecutive
Systems
^- Consecutive systems that purchase 100% of their water (and therefore do not have a source from which to
sample) must:
• Notify their wholesale system within 24 hours of receiving notice of a total coliform-positive sample
taken under the TCR.
• Upon hearing from the wholesale system of a fecal indicator-positive source water sample (either initial
triggered samples or additional samples), notify the public within 24 hours.
>• Consecutive systems that purchase only some of their water must:
• Notify their wholesale system within 24 hours of receiving notice of a total coliform-positive sample
taken under the TCR.
• Collect GWR triggered source water monitoring samples and additional samples as required.
• Upon receipt of notification from the laboratory about a fecal indicator-positive source water sample at
the system's source(s) take corrective action, if required, and notify the public within 24 hours.
• Upon receipt of notification from the wholesale system of a fecal indicator-positive sample (either initial
triggered samples or additional samples) at the wholesale system's source(s), notify the public within 24
hours.
Wholesale
Systems
Wholesale systems that are notified by a consecutive system of a total coliform-positive sample must:
• Within 24 hours of being notified, collect at least one ground water source sample from each source in
use (unless representative sampling is allowed) when the total coliform-positive sample was collected.
• Notify the public and ALL consecutive systems served by the source within 24 hours of learning that a
source water sample is fecal-indicator positive.
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Invalidation of Fecal Indicator-Positive Samples
>• The State can invalidate a fecal indicator-positive triggered source water sample if:
• The system provides the State with written notice from the laboratory that improper sample analysis occurred or
• The State determines there is substantial evidence that the sample does not reflect source water quality.
• The State must document in writing there is substantial evidence that the fecal indicator-positive ground water
source sample is not related to source water quality.
^- If any sample is found to be fecal indicator-positive and is subsequently invalidated by the State, the GWS must resample
for the same indicator within 24 hours of being notified of the invalidation.
Exceptions to the Triggered Source Water Monitoring Requirements
Extension of the 24-hour collection limit
>• The State may extend the 24-hour limit for collecting source water samples on a case-by-case basis if the State
determines the system cannot collect the ground water source water sample within 24 hours due to circumstances
beyond its control.
>• In the case of an extension, the State must specify how much time the system has to collect the sample.
Total Coliform-Positive Sample Is The Result of Distribution System Conditions
A GWS is not required to conduct triggered source water monitoring under one of the following circumstances:
• The State determines and documents in writing that the total coliform-positive TCR sample is caused by a distribution
system deficiency.
• The GWS determines the total coliform-positive TCR sample was collected at a location that meets State criteria for
distribution conditions that will cause total coliform-positive samples and notifies the State within 30 days.
Notification Requirements
If a GWS receives notice of a fecal
indicator-positive source water sample
collected under the GWR, the system must:
If a GWS fails to conduct required triggered
or additional monitoring, the system must:
Wholesale and consecutive systems are
subject to:
>• Consult with the State within 24 hours.
>• Notify the public within 24 hours.
• Tier 1 Public Notification.
>• If the system is a community GWS, they must provide Special Notice of the
fecal indicator-positive sample in their CCR.
>• Notify the public within 12 months.
• Tier 3 Public Notification.
>• Community GWSs may be able to use their CCR.
>• The same notification requirements outlined above, in addition to the
requirements to notify the wholesale or consecutive systems.
Critical Deadlines for Triggered Source Water Monitoring for Drinking Water Systems
November 30, 2009
New ground water sources put in place after this date must conduct triggered source water monitoring
if the GWS does not provide 4-log virus treatment and conduct compliance monitoring and the GWS is
notified that a sample collected for the TCR is total coliform-positive.
December 1, 2009
GWSs must conduct triggered source water monitoring if the GWS does not provide 4-log virus
treatment and conduct compliance monitoring and the GWS is notified that a sample collected for the
TCR is total coliform-positive.
Office of Water (4606)
EPA815-F-08-004
www.epa.gov/safewater
July 2008
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