E' Ground Water Rule Factsheet:
Monitoring Requirements
WHAT is THE GROUND WATER RULE?
The U.S. Environmental Protection Agency (EPA) published the Ground Water Rule (GWR) on November
8, 2006. One goal of the GWR is to provide increased protection against microbial pathogens,
specifically bacterial and viral pathogens, in public water systems (PWSs) that use ground water.
Instead of requiring disinfection for all ground water sources, the GWR establishes a risk-targeted
approach to identifying ground water sources that are susceptible to fecal contamination. The GWR
requires systems with ground water sources at risk of microbial contamination to take corrective action
to protect consumers from harmful bacteria and viruses. Monitoring is a key element of this risk-
targeted approach.
There are two types of monitoring required by the GWR:
• Source Water Monitoring: Triggered source water monitoring is used to determine if fecal
contamination is present in the ground water source. Triggered source water monitoring is
required for any GWS that has a positive total coliform result under the Total Coliform Rule
(TCR) routine sampling and does not provide and monitor for 4-log treatment of viruses.
Alternatively, states may require GWSs with sources that seem susceptible to fecal
contamination to conduct assessment source water monitoring.
• Compliance Monitoring: Systems that notify the state that they provide and monitor for 4-log
treatment of viruses are required to conduct compliance monitoring.
WHAT ARE THE SOURCE WATER MONITORING REQUIREMENTS? _
Some ground water systems (GWSs) will be required to conduct triggered source water monitoring or
assessment source water monitoring of a fecal indicator (e.g., E. coli, enterococci, or coliphage) to
detect microbial contamination in the source.
Triggered Source Water Monitoring
Within 24 hours of being notified of a positive total coliform result under routine TCR monitoring, a
GWS must collect at least one ground water source sample from each source in use when the positive
total coliform result under the TCR was collected. These samples are triggered source water samples.
If a triggered source water sample is positive for a fecal indicator, the state will require the system to
take corrective action or take five additional samples from the same source within 24 hours of
notification of the fecal indicator-positive result and analyze the additional samples for a fecal
indicator. If any one of the five additional samples is fecal indicator-positive, the system must take
corrective action.
Triggered Source Water Monitoring Exceptions
A state may waive the triggered source water monitoring requirement if the state determines and
documents, in writing, that the total coliform-positive routine sample is the result of a documented
distribution system deficiency.
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In addition, states may develop criteria for distribution system conditions that cause total coliform-
positive samples. A GWS can document to the state that it met the state criteria within 30 days of the
total coliform-positive sample and be exempt from collecting the triggered source water sample(s).
GWSs providing at least 99.99 percent (4-log) treatment of
viruses (using inactivation, removal, or a state-approved
combination of inactivation and removal) of all of their
ground water can notify the state of this treatment and would
not be required to conduct triggered source water
monitoring. Those systems are, however, required to conduct
compliance monitoring to show they are providing consistent
and sufficient treatment. Compliance monitoring
requirements depend on the system's size and the type of
treatment it is using. Compliance monitoring requirements
are discussed below.
GWSs serving fewer than 1,000 people that have a total coliform-positive result under the TCR may use
the triggered source water monitoring sample collected from the ground water source to meet both the
triggered source water monitoring requirement of the GWR as well as part of the repeat sampling
requirement of the TCR (if the state approves the use of E. coli as a fecal indicator for source water
monitoring).
A consecutive system with a positive routine total coliform result under the TCR must notify its
wholesale system(s) within 24 hours of being notified of the positive sample.
A wholesale system that receives notice from a consecutive system
of a positive total coliform result under routine monitoring of the
TCR must collect a triggered source water sample from its ground
water source(s) and analyze the source water sample(s) for a fecal
indicator within 24 hours of being notified by the consecutive
system. If the triggered source water sample is positive for the
fecal indicator, the wholesale system must notify all consecutive
systems served by that source within 24 hours of the positive
sample result. The wholesale system and any consecutive systems
served by the fecal indicator-positive source must all notify their
consumers within 24 hours of learning of the result. If the state
does not require corrective action for this fecal indicator-positive
sample, the wholesale system must collect five additional source
water samples from the same source within 24 hours of receiving
notification of the fecal indicator-positive sample.
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States may require GWSs with sources that seem susceptible to fecal
contamination to conduct assessment source water monitoring. States
may require assessment source water monitoring at any time, on a
case-by-case basis. Based on the results of the assessment source
water monitoring, systems may have to take corrective action.
Assessment source water monitoring requirements are in addition to
triggered source water monitoring requirements. A system may,
however, use a triggered source water sample to meet part of the
assessment source water monitoring requirement.
E. CO/7
Enterococci
Coliphage
9223 B
EPA Method 1604
9221 F
9222 G
9230B
9230C
EPA Method 1600
EPA Method 1601
EPA Method 1602
GWSs that begin service from a new source after November 30, 2009, may be required by their state to
conduct assessment source water monitoring. The state may require the system to begin assessment
source water monitoring before the new source provides water to the public.
for All
Triggered, additional, and assessment source water monitoring samples must be collected prior to
treatment or at a state-approved location.
All source water samples must be at least 100 ml for all fecal indicator analytical methods.
ARE THE
Compliance monitoring requirements apply to systems that provide 4-
log treatment of viruses and are not subject to triggered source water
monitoring requirements. These systems must:
* Notify the state that they provide 4-log treatment of viruses.
* Conduct compliance monitoring rather than triggered source
water monitoring.
« Systems with existing ground water sources must notify the
state in writing by December 1, 2009, that they provide at
least 4-log treatment of viruses for the sources.
« Systems with ground water sources placed into service after November 30, 2009, must notify
the state in writing that they provide at least 4-log treatment of viruses of those sources and
begin compliance monitoring within 30 days of placing the source in service or conduct
triggered source water monitoring.
After November 30, 2009, GWSs that begin providing at least 4-log treatment of viruses must notify the
state and conduct compliance monitoring to avoid being required to conduct triggered source water
monitoring. Systems that provide 4-log treatment should check with their state regulators to see if they
need to satisfy any additional state compliance monitoring requirements (e.g. Stage 1 Disinfectants and
Disinfection Byproducts Rule (DBPR)) beyond the requirements listed below.
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Disinfecting GWSs serving <_ 3,300
Disinfecting GWSs serving > 3,300
Residual disinfectant concentration (must
meet state minimum)
Daily or continuous1'2
Continuous only1'3
State-
approved
location (s)
GWSs using membrane filtration
Membrane filtration process effectiveness
Consult state for specific information
GWSs using state-approved
alternative treatment
Alternative treatment effectiveness
1. Provisions available for equipment failure.
2. If any daily grab sample is less than the minimum disinfectant residual concentration, the system must take follow-up samples every 4 hours
until the residual meets or exceeds the minimum.
3. System must record the lowest residual disinfectant concentration each day water from the ground water source is served to the public.
ARE THE
Individual states may have earlier compliance requirement dates.
Source Water Monitoring
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The following guidance materials for states and PWSs have been released or will be released in 2008:
- This guide provides a description of the GWR and
includes critical deadlines and requirements.
- Including factsheets on GWR general requirements, monitoring
requirements, and Public Notice, Consumer Confidence Reports, and Special Notices.
- This guidance
provides states, tribes, and other primacy agencies with a brief review of the sanitary survey regulatory
provisions, give examples of what may constitute a significant deficiency, and provide a checklist of
elements that should be evaluated during the course of a sanitary survey inspection.
- This guidance
provides states, tribes, and other primacy agencies with a brief review of hydrogeologic sensitivity
assessments, an overview of the characteristics of a sensitive aquifer, information about how source
water assessments may be used, and information about how to determine if a sensitive aquifer has a
hydrogeologic barrier.
- This guidance provides GWSs, states, tribes, and other primacy agencies with a brief review of
the source water monitoring provisions. Primacy agencies may select fecal indicators (e.g., E. coli,
enterococci, coliphage) that systems would be required to test for in the ground water source sample.
The source water monitoring guidance manual provides criteria to assist primacy agencies in their
determination of which fecal indicator(s) may be most appropriate.
- This guidance will provide states, tribes,
other primacy agencies and GWSs with an overview of the treatment technique requirements of the
GWR. The guidance manual will provide assistance with determining the information that should be
included in a system's corrective action plan.
- This guidance
describes the regulatory requirements of the GWR that apply to wholesale GWSs and the consecutive
systems that receive and distribute that ground water supply.
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- This document is
intended to be an official compliance guide to the GWR for small PWSs, as required by the Small
Business Regulatory Enforcement Fairness Act of 1996. This guide contains a general introduction and
background for the GWR, describes the specific requirements of the GWR and provides information on
how to comply with those requirements.
For additional information, please contact the Safe Drinking Water Hotline at 1-800-426-4791, or
visit
Office of Water (4606M) EPA 816-F-08-025 June 2008
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