M/DBP Stakeholder
Meeting: Ground Water Disinfection Rule
EXECUTIVE SUMMARY
December 18-19, 1997
EPA held a Ground Water Disinfection Rule (GWDR) stakeholders meeting
on December 18-19, 1997 in Washington, D.C. The purpose of the meeting
was to engage stakeholders in analysis of data, solicit further data from
stakeholders, discuss EPA's next steps for rule development and stakeholder
involvement, and to identify additional parties who may be interested
in participating in future meetings.
Background
EPA has the responsibility to develop a ground water rule which not only
specifies the appropriate use of disinfection but, just as important,
addresses other components of ground water systems to assure public health
protection. Section 1412(b)(1)(A) of the Safe Drinking Water Act requires
EPA to establish National Primary Drinking Water Regulations for contaminants
that may have an adverse public health effect and that present a meaningful
opportunity for health risk reduction. This general provision is supplemented
with an additional requirement under Section 1412(b)(8) that EPA also
develop regulations specifying the use of disinfectants for ground water
systems as necessary. To meet these requirements EPA is working with stakeholders
to develop a GWDR proposal by March 1999, and a final rule by November
2000.
Summary
Six technical issues presented and discussed at the meeting are summarized
below.
Ground Water Microbial Occurrence Studies. EPA is analyzing
15 recent studies which have focused on the occurrence of viral/bacteriological
pathogens or fecal contamination indicators found in ground water.
Human enterovirus data are available from more than 600 samples representing
491 wells. Thirty-six wells were positive using cell culture methods,
representing 7% of the wells. Total coliform bacteria were found in 23%,
fecal coliform bacteria or E.coli were found in 24%, and enterococci
were found in 22% of the wells tested. These represent studies of large
community wells to private wells. Male-specific coliphage were found in
13% and somatic coliphage in 14% of wells tested, representing primarily
community wells. Human viruses detected by PCR were found in 38% of wells
tested, representing primarily community wells.
With respect to fecal contamination, the interpretation of these studies
is that a substantial number of groundwater sources show evidence of fecal
contamination. A central issue with regard to this data is the degree
to which it is representative of public wells in general.
State Ground Water Management Practices. EPA recognizes
that State management practices can contribute significantly to the reduction
of waterborne illness, however, the variability in these practices is
high. The GWDR is likely to be more effectively implemented and enforced
if the new regulatory scheme is based upon what successful States and
utilities are already doing. To the extent possible, EPA intends to strengthen
what is in place, not replace it.
Both disinfection and Best Management Practices (BMPs) shows high state-to-state
variability. Forty-nine State drinking water programs require disinfection
of some sort, but when and where disinfection is required varies considerably.
Approximately 55% of community water systems, 28% of nontransient noncommunity
water systems, and 17% of transient noncommunity systems disinfect.
Proper well construction is one of the most widespread required State
practices. Forty-eight States require that water systems be constructed
according to State codes. Forty-seven States have minimum setback distances
for microbial contaminants in their well codes but the distance varies
from 0-200 feet for sewer lines and 0-500 feet for septic tanks and pit
privies. Twenty-four States always and five States sometimes use hydrogeological
criteria in well construction codes. Requirements for casing and grouting
depths are often dependent on the aquifer used and overlying materials.
The specific requirements within each State code vary considerably.
All States except one conduct sanitary surveys. However, based on a nationwide
questionnaire and a review of 200 sanitary surveys conducted in four States,
the U.S. General Accounting Office (GAO) found that sanitary surveys were
often deficient in how they are conducted, documented, and/or interpreted.
Sanitary survey requirements and corrective actions were inconsistent
among States. GAO also found that regardless of systems' size, deficiencies
previously disclosed frequently went uncorrected. The most common deficiency
cited by States was inadequate cross-connection programs.
Evaluating Best Management Practices for Public Ground Water
Systems. A wide range of BMPs are required by State laws and
implemented in different fashions. In developing the GWDR, an important
question is which of these practices are most efficient and which should
be considered as regulatory components. Two studies have been completed
to analyze the relative effectiveness of BMPs using coliform bacteria
as an indicator of contamination.
EPA Study of State BMPs - Six State required BMPs were analyzed:
disinfection, hydrogeological criteria in well construction, minimum setback
distances, flushing of distribution systems, wellhead monitoring, and
a State wellhead protection program. Of these 6 practices, only disinfection
and hydrogeological construction criteria showed a significant statistical
relationship to lower statewide TCR violation rates.
For example, the ten States with the highest percentage of community
water systems with disinfection treatment in place were compared to the
ten States with the lowest percentage of systems with disinfection treatment.
The highest disinfecting States had an average TCR violation rate of 16%
over the four year period, versus 33% for the ten States with the lowest
disinfection rates.
Association of State Drinking Water Administrators (ASDWA) Analysis
of Community Water System BMPs - The purpose of the ASDWA study was
to test the hypothesis that there is a correlation between a low incidence
of coliform bacteria detection (total, fecal or E. coli) at the
tap and the use of BMPs. Information was collected for community water
systems only.
It was found that greater percentages of larger systems, than smaller
systems implement BMPs and systems without coliform detections (total,
fecal or E. coli) are more likely to implement BMPs than systems
with coliform detections. Information was collected for community water
systems only. BMPs with the strongest correlation to fewer total coliform
detections were correction of deficiencies identified by the sanitary
survey and operator certification. This varies depending on system size.
Maintaining a disinfectant residual, operator training, and correcting
deficiencies identified by the State were found to be associated with
significant reductions of total coliform. Treatment for purposes other
than disinfection, (e.g., iron removal) and operator training were found
to be associated with significant reductions of fecal coliform or E.
coli detections.
Ground Water Baseline Profile. The GWDR proposal is
likely to affect a large number of public ground water systems throughout
the United States. There will be both benefits and costs for each possible
regulatory component of the proposal which EPA must consider.
Particular attention will be paid to small water systems which may be
impacted by the rule. For purposes of drinking water regulations, EPA
is defining small as those public water supply systems that serve 10,000
or fewer people. EPA is focusing its efforts on collecting information
on the existing conditions of small systems so the proposed rule can take
into account the resources of these systems as well as what steps are
necessary to assure high quality drinking water and protection of public
health.
There are over 158,000 public ground water systems.The majority of ground
water systems serve non-community; 60% (94,400) are transient non-community
systems and 12% (19,600) are non-transient non-community. Community water
systems make up the remaining 28% (44,000). Almost 89 million people are
served by community ground water systems and 20 million people are served
by non-community ground water systems.
Ninety-nine percent (157,000) of ground water systems serve fewer than
10,000 people. Ninety-seven percent (154,000) serve 3,300 or fewer people.
However, systems serving more than 10,000, serve 55% (over 60 million)
of all people who get their drinking water from public ground water systems.
The largest numbers of ground water systems are in the States of Wisconsin,
Michigan, Pennsylvania, New York and Minnesota. These five States account
for over 50,000 ground water systems, one third of the total number in
the U.S.
Thirty-six percent of systems are publicly operated, 35% are privately
owned and operated by private entities whose primary business is providing
drinking water, and 29% of community ground water systems are ancillary
water systems which are operated by entities whose primary business is
not providing drinking water, but do so to support their primary business
(e.g., mobile home park operators).
The mean revenue for community ground water systems serving less than
3,300 people is over $68,000 per year and the mean annual expenses for
these systems is over $49,000 per year, however, these mean dollar figures
are significantly influenced by the large number of systems serving less
than 500. When isolated from the smallest systems, community ground water
systems serving between 1,001 and 3,300 have mean revenue of over $186,000
and mean expenses of $167,000 per year. Community systems serving between
3,300 and 10,000 people have mean revenues of $570,000 and mean expenses
of $517,000 per year. Systems with service populations between 10,000
and 50,000 have mean revenues of 2.2 million dollars and mean expenses
of over 1.9 million dollars per year.
Small community ground water systems, those serving less than 10,000,
typically have between one to three operators, one or two of which have
been certified by the State. Larger systems have more operators. Ground
water systems serving more than 100,000 people have an average of seventeen
operators, thirteen of which have been State certified.
Vulnerability Assessment Techniques. Approximately 158,000
PWSs rely on ground water as their source for drinking water supplies.
Given this large number of systems, an essential task in developing a
proposed ground water rule is how to prioritize wells for further action
or analysis.
An assessment of the vulnerability of a PWS well or wellfield is an attempt
to answer the question, "How likely is a source water at the well to have
fecal contamination?" Varying levels of resources and data are available
to assess vulnerability. Given the varying availability of site-specific
information in different situations, the three approaches presented below
are not universally applicable to all ground water systems yet there may
be more than one approach that can yield a satisfactory result.
The vulnerability assessment approach uses existing information to evaluate
a well's vulnerability to fecal contamination. The information is summarized
on a "checklist." Decision trees are used to evaluate the information,
leading to a vulnerability rating of either "high" or "low." If there
is insufficient information to make a determination, the vulnerability
is "unknown." The technique is useful, technically sound, simple to use,
and builds on existing information, however, it may require information
that is not readily available to all systems or wells and requires some
expertise in hydrogeology to conduct the assessments.
The vulnerability components approach uses general criteria (nine) to
determine whether PWS wells are vulnerable to fecal contamination (i.e.,
significant sanitary survey deficiencies have been identified, source
water protection programs are not in place, state setback distances are
not observed, the well does not have a history of stable nitrate concentrations,
etc.) PWS wells are identified as vulnerable if any of the criteria are
met.
The vulnerability screening approach is a statistically based technique
that is intended to be simple, inexpensive and will be used to discriminate
low-risk wells from high-risk wells based on a few simple physical parameters.
This approach is potentially applicable to wells in all regions.
Monitoring Methods and Indicators Data. Monitoring plays
an important role both in detecting fecal contamination in source waters,
as well as in assessing best management practices and disinfection practices.
EPA is focusing on indicators of fecal contamination rather than on individual
pathogens as a screening tool to identify vulnerable or at-risk wells.
Under this approach, if a well is fecally contaminated, the system will
be required to take corrective action.
EPA is focusing on E. coli, enterococci, and male-specific coliphage
as the candidate indicators. In evaluating the utility of microbial indicators
of fecally contaminated ground water, EPA is considering factors such
as method cost, feasibility, performance, and availability, as well as
occurrence data on the groundwater surveys currently being conducted.
Currently, all groundwater systems must comply with the Total Coliform
Rule (TCR). Under TCR, total coliform samples are tested at the tap. This
means that, for an untreated groundwater supply, the system cannot easily
determine whether the presence of a total coliform-positive (or E.
coli-positive) sample represents a contaminated source water or a
problem in the distribution system. Another issue is the low monitoring
frequency required under the TCR for small systems. For example, community
water systems serving 1,000 people or fewer only need to monitor once
per month or less; a similar size non-community water system needs to
monitor only once per quarter or less.
Next Steps
EPA will continue to evaluate occurrence data as it becomes available
and work with stakeholders to develop an estimate of national occurrence
and risk. EPA seeks additional human pathogen and indicator data.
EPA will continue to work with stakeholders to evaluate the BMP approach
as a regulatory framework. Further analyses of the EPA and ASDWA data
and additional BMP information may be necessary. EPA welcomes comments
on the draft BMP studies and ideas for further data analysis.
EPA will continue to work with stakeholders to evaluate the draft vulnerability
assessment techniques and develop a technique which effectively prioritizes
wells for further action or analysis. EPA welcomes comments on the draft
techniques.
EPA will continue to work with stakeholders to further evaluate the applicability
of microbial indicators of fecal contamination. In particular, EPA will
evaluate research on somatic and male-specific coliphage and low volume
sample collection for the detection of viruses by polymerase chain reaction.
In order to complete the baseline profile, EPA will evaluate any additional
information that stakeholders can provide about ground water systems.
In particular, EPA seeks information that will help to identify the types
of entities which operate non-community systems and data on the finances,
existing level of treatment, and staffing for these systems. Additionally,
information describing the communities served by non-community systems
would help our analysis.
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