[Federal Register: November 8, 2006 (Volume 71, Number 216)]
[Rules and Regulations]
[Page 65573-65660]
[DOCID:fr08no06-15]

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Part II

Environmental Protection Agency

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40 CFR Parts 9, 141, and 142

 National Primary Drinking Water Regulations: Ground Water Rule; Final
Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9, 141 and 142

[EPA-HQ-OW-2002-0061; FRL-8231-9]
RIN 2040-AA97

National Primary Drinking Water Regulations: Ground Water Rule

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency is promulgating a National
Primary Drinking Water Regulation, the Ground Water Rule, to provide
for increased protection against microbial pathogens in public water
systems that use ground water sources. This final rule is in accordance
with the Safe Drinking Water Act as amended, which requires the
Environmental Protection Agency to promulgate National Primary Drinking
Water Regulations requiring disinfection as a treatment technique for
all public water systems, including surface water systems and, as
necessary, ground water systems.
    The Ground Water Rule establishes a risk-targeted approach to
target ground water systems that are susceptible to fecal
contamination, instead of requiring disinfection for all ground water
systems. The occurrence of fecal indicators in a drinking water supply
is an indication of the potential presence of microbial pathogens that
may pose a threat to public health. This rule requires ground water
systems that are at risk of fecal contamination to take corrective
action to reduce cases of illnesses and deaths due to exposure to
microbial pathogens.

DATES: This final rule is effective on January 8, 2007. The
incorporation by reference of certain publications listed in this rule
is approved by the Director of the Federal Register as of January 8,
2007. For judicial review purposes, this final rule is promulgated as
of 1 p.m. Eastern time on November 22, 2006, as provided in 40 Code of
Federal Regulations (CFR) 23.7. The compliance date, unless otherwise
noted, for the rule requirements is December 1, 2009.

ADDRESSES: The Environmental Protection Agency (EPA) has established a
docket for this action under Docket ID No. EPA-HQ-OW-2002-0061. All
documents in the docket are listed on the http://www.regulations.gov

Web site. Although listed in the index, some information is not
publicly available, e.g., CBI or other information whose disclosure is
restricted by statute. Certain other material, such as copyrighted
material, is not placed on the Internet and will be publicly available
only in hard copy form. Publicly available docket materials are
available either electronically through http://www.regulations.gov or

in hard copy at the Water Docket.

    Note: The EPA Docket Center suffered damage due to flooding
during the last week of June 2006. The Docket Center is continuing
to operate. However, during the cleanup, there will be temporary
changes to Docket Center telephone numbers, addresses, and hours of
operation for people who wish to visit the Public Reading Room to
view documents. Consult EPA's Federal Register notice at 71 FR 54815
(September 19, 2006) or the EPA Web site at http://www.epa.gov/epahome/dockets.htm
 for current information on docket status,

locations and telephone numbers.

FOR FURTHER INFORMATION CONTACT: Crystal Rodgers, Standards and Risk
Management Division, Office of Ground Water and Drinking Water (MC-
4607M), Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460; telephone number:<PHONE_NUMBER>; e-mail address:
<EMAIL_ADDRESS>For general information, contact the Safe

Drinking Water Hotline, telephone number:<PHONE_NUMBER>. The Safe
Drinking Water Hotline is open Monday through Friday, excluding legal
holidays, from 10 a.m. to 4 p.m. Eastern time.

SUPPLEMENTARY INFORMATION:

I. General Information

    Entities potentially regulated by the Ground Water Rule (GWR) are
public water systems (PWSs) using ground water as a drinking water
source. Regulated categories and entities include the following:

------------------------------------------------------------------------
                                               Examples of  regulated
                 Category                             entities
------------------------------------------------------------------------
Industry..................................  Public ground water systems.
State, Local, Tribal or Federal             Public ground water systems.
 Governments.
------------------------------------------------------------------------

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action. This table lists the types of entities that EPA is now aware
could potentially be regulated by this action. Other types of entities
not listed in the table could also be regulated. To determine whether
your facility is regulated by this action, you should carefully examine
the applicability criteria found in Sec.  141.400 of this rule. If you
have questions regarding the applicability of this action to a
particular entity, consult the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.

Abbreviations Used in This Document

AIDS Acquired Immune Deficiency Syndrome
AGI Acute Gastrointestinal Illness
AWWA American Water Works Association
ASDWA Association of State Drinking Water Administrators
AWWARF American Water Works Association Research Foundation
AWWSCo American Water Works Service Company
BGLB Brilliant green lactose bile broth
BGM Buffalo Green Monkey
BMPs Best Management Practices
CAFO Concentrated Animal Feeding Operation
CBI Confidential Business Information
CCR Consumer Confidence Report
CDBG Community Development Block Grant
CDC Centers for Disease Control and Prevention
CFR Code of Federal Regulation
COI Cost of Illness
CT The Residual Concentration of Disinfectant (mg/L) Multiplied by
the Contact Time (in minutes)
CWS Community Water System
CWSS Community Water System Survey
DBPs Disinfection Byproducts
DWSRF Drinking Water State Revolving Fund
EA Economic Analysis
EPA United States Environmental Protection Agency
FR Federal Register
GAO United States Government Accountability Office
GI Gastrointestinal
GWUDI Ground Water Under the Direct Influence of Surface Water
GWR Ground Water Rule
GWS Ground Water System
HAV Hepatitis A Virus
HRRCA Health Risk Reduction and Cost Analysis
HSA Hydrogeologic Sensitivity Assessment
ICR Information Collection Request
IESWTR Interim Enhanced Surface Water Treatment Rule
IRFA Initial Regulatory Flexibility Analysis
LTB Lauryl tryptose broth
m Meters
mL Milliliters
MCL Maximum Contaminant Level
mg/L Milligrams per Liter
MPNIU Most Probable Number of Infectious Units
MRDL Maximum Residual Disinfectant Level
MWCO Molecular Weight Cut-Off
NCWS Non-Community Water System
NDWAC National Drinking Water Advisory Council
NF Nanofiltration
NODA Notice of Data Availability
NTNCWS Non-Transient Non-Community Water System
NTTAA National Technology Transfer and Advancement Act of 1995
NPDWR National Primary Drinking Water Regulation
O&M Operation and Maintenance

OMB Office of Management and Budget
P-A Presence-absence
PCR Polymerase Chain Reaction
PNR Public Notification Rule
PWS Public Water System
RFA Regulatory Flexibility Act
RIA Regulatory Impact Analysis
RO Reverse Osmosis
RT-PCR Reverse Transcriptase--Polymerase Chain Reaction
SAB Science Advisory Board
SBREFA Small Business Regulatory Enforcement Fairness Act
SD Standard Deviation
SDWA Safe Drinking Water Act
SDWIS Safe Drinking Water Information System
SEFA Small Entity Flexibility Analysis
Stage 2 DBPR Stage 2 Disinfectants and Disinfection Byproducts Rule
SWAP Source Water Assessment Program
SWTR Surface Water Treatment Rule
TCR Total Coliform Rule
TNCWS Transient Non-Community Water System
UIC Underground Injection Control
UMRA Unfunded Mandates Reform Act
US United States
USGS United States Geological Survey
UV Ultraviolet Radiation
VSL Value of Statistical Life
WHO World Health Organization
WTP Willingness To Pay

Table of Contents

I. General Information
II. Summary
    A. Why Is EPA Promulgating the GWR?
    B. What Does the GWR Require?
    1. Sanitary Surveys
    2. Source Water Monitoring
    3. Treatment Technique Requirements
    4. Compliance Monitoring
    C. How Has the Final Rule Changed From What EPA Proposed?
    D. Does This Regulation Apply to My Water System?
III. Background
    A. What Is the Statutory Authority for the GWR?
    B. What Is the Regulatory History of the GWR and How Were
Stakeholders Involved?
    C. What Public Health Concerns Does the GWR Address?
    1. Introduction
    2. Waterborne Disease Outbreaks in Ground Water Systems
    3. Microbial Contamination in Public Ground Water Systems
    4. Potential Risk Implications From Occurrence Data
IV. Discussion of GWR Requirements
    A. Sanitary Surveys
    1. What Are the Requirements of This Rule?
    2. What Is EPA's Rationale for the GWR Sanitary Survey
Requirements?
    3. What Were the Key Issues Raised by Commenters on the Proposed
GWR Sanitary Survey Requirements?
    B. Source Water Monitoring
    1. What Are the Requirements of This Rule?
    2. What Is EPA's Rationale for the GWR Source Water Monitoring
Requirements?
    3. What Were the Key Issues Raised by Commenters on the Proposed
GWR Source Water Monitoring Requirements?
    C. Corrective Action Treatment Techniques for Systems With
Significant Deficiencies or Source Water Fecal Contamination
    1. What Are the Requirements of This Rule?
    2. What Is EPA's Rationale for the GWR Treatment Technique
Requirements?
    3. What Were the Key Issues Raised by Commenters on the Proposed
GWR Treatment Technique Requirements?
    D. Providing Notification and Information to the Public
    1. What Are the Requirements of This Rule?
    2. What Is EPA's Rationale for the Public Notice Requirements?
    3. What Were the Key Issues Raised by Commenters on the Proposed
GWR Public Notification Requirements?
    E. What Are the Reporting and Recordkeeping Requirements for
Systems?
    1. Reporting Requirements
    2. Recordkeeping Requirements
    3. What Were the Key Issues Raised by Commenters on the Proposed
GWR Reporting and Recordkeeping Requirements for Systems?
    F. What Are the Special Primacy, Reporting, and Recordkeeping
Requirements for States?
    1. Primacy Requirements
    2. Reporting Requirements
    3. Recordkeeping Requirements
    4. What Were the Key Issues Raised by Commenters on the Proposed
GWR Special Primacy, Reporting, and Recordkeeping Requirements for
States?
    G. Variances and Exemptions
    1. Variances
    2. Exemptions
V. Explanation of Extent of GWR
    A. Mixed Systems
    B. Cross-Connection Control
VI. Implementation
VII. Economic Analysis (Health Risk Reduction and Cost Analysis)
    A. How Has the Final Rule Alternative Changed From the Proposed
Rule Alternative?
    B. Analyses That Support This Rule
    1. Occurrence Analysis
    2. Risk Analyses
    C. What Are the Benefits of the GWR?
    1. Calculation of Baseline Health Risk
    2. Calculation of Avoided Illnesses and Deaths
    3. Derivation of Quantified Benefits
    4. Nonquantifiable Benefits
    5. How Have the Benefits Changed Since the Proposal?
    D. What Are the Costs of the GWR?
    1. Summary of Quantified Costs
    2. Derivation of Quantified Costs
    3. Nonquantifiable Costs
    4. How Have the Costs Changed Since the Proposal?
    E. What Is the Potential Impact of the GWR on Households?
    F. What Are the Incremental Costs and Benefits of the GWR?
    G. Are There Any Benefits From Simultaneous Reduction of Co-
Occurring Contaminants?
    H. Is There Any Increase in Risk From Other Contaminants?
    I. What Are the Effects of the Contaminant on the General
Population and Groups Within the General Population That Are
Identified as Likely To Be at Greater Risk of Adverse Health
Effects?
    1. Risk of Acute Viral Illness to Children and Pregnant Women
    2. Risk of Viral Illness to the Elderly and Immunocompromised
    J. What Are the Uncertainties in the Risk, Benefit, and Cost
Estimates for the GWR?
    1. The Baseline Numbers of Ground Water Systems, Populations
Served, and Associated Disinfection Practice
    2. The Numbers of Wells Designated as More Versus Less
Vulnerable
    3. The Baseline Occurrence of Viruses and E. coli in Ground
Water Wells
    4. For the Sanitary Survey Provisions, the Percentage of Systems
Identified as Having Significant Deficiencies, the Percentage of
These Deficiencies That Are Corrected, and State Costs for
Conducting Surveys
    5. The Predicted Rates at Which Virally Contaminated (and Non-
Contaminated) Wells Will Be Required To Take Action After Finding E.
coli Ground Water Sources
    6. The Infectivity of Echovirus and Rotavirus Used to Represent
Viruses That Occur in Ground Water
    7. The Costs of Illnesses Due to Ingestion of Contaminated
Ground Water
    8. The Costs of Taking Action After Finding E. coli in Ground
Water Sources
    9. Nonquantifiable Benefits
    10. Optional Assessment Source Water Monitoring
    11. Corrective Actions and Significant Deficiencies
    12. Uncertainty Summary
    K. What Is the Benefit/Cost Determination for the GWR?
    L. What Were Some of the Major Comments Received on the Economic
Analysis and What Are EPA's Responses?
    1. Costs
    2. Benefits
    3. Risk Management
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    1. Energy Supply
    2. Energy Distribution
    3. Energy Use

    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act
    L. Analysis of the Likely Effect of Compliance With the GWR on
the Technical, Financial, and Managerial Capacity of Public Water
Systems
IX. Consultation With Science Advisory Board, National Drinking
Water Advisory Council, and the Secretary of Health and Human
Services; and Peer Review
X. References

II. Summary

    This section includes a discussion of the purpose of the Ground
Water Rule (GWR) and a summary of the GWR requirements.

A. Why Is EPA Promulgating the GWR?

    EPA is promulgating the GWR to provide for increased protection
against microbial pathogens, specifically viral and bacterial
pathogens, in public water systems (PWSs) that use ground water
sources. EPA is particularly concerned about ground water systems
(GWSs) that are susceptible to fecal contamination because these
systems may be at risk of supplying water that contains harmful
microbial pathogens. Viral pathogens found in GWSs may include enteric
viruses such as Echovirus, Coxsackie viruses, Hepatitis A and E,
Rotavirus and Noroviruses (i.e., Norwalk-like viruses) and enteric
bacterial pathogens such as Escherichia coli (most E. coli is harmless
but a few species are pathogenic, including E. coli O157:H7),
Salmonella species, Shigella species, and Vibrio cholerae. Ingestion of
these pathogens can cause gastroenteritis or, in certain cases, serious
illnesses such as meningitis, hepatitis, or myocarditis. Health
implications in sensitive subpopulations (e.g., children, elderly,
immuno-compromised) may be severe (e.g., hemolytic uremic syndrome) and
may cause death.
    One goal of the GWR is to identify and target GWSs that are
susceptible to fecal contamination because such contamination is the
likely source of viral and bacterial pathogens in drinking water
supplies. Ground water is fecally contaminated when fecal indicators
(e.g., E. coli, enterococci, or coliphage) are present. While fecal
indicators typically are not harmful when ingested, their presence
demonstrates that there is a pathway for pathogenic viruses and
bacteria to enter ground water sources. Another key objective of the
rule is to protect public health by requiring these higher risk GWSs to
monitor and, when necessary, take corrective action. Corrective action
can include correcting all significant deficiencies; providing an
alternate source of water; eliminating the source of contamination; or
providing treatment that reliably achieves at least 99.99 percent (4-
log) treatment of viruses (using inactivation, removal, or a State-
approved combination of 4-log virus inactivation and removal) for each
contaminated ground water source. Each of these corrective actions is
intended to remove all or nearly all fecal contamination, including
both viral and bacterial pathogens. This rule implements section
1412(b)(8) of the 1996 Safe Drinking Water Act (SDWA) Amendments to
promulgate a rule requiring GWSs to disinfect ``as necessary.'' The
risk-targeted approach in this rule is a critical distinction from the
approach outlined in the 1986 SDWA, which would have required all PWSs
using surface water or ground water to disinfect. Because there are so
many GWSs (approximately 147,000) in the United States, such a
requirement would have been a great challenge for systems and States to
implement.
    This rule is necessary to protect public health because current
regulatory provisions for GWSs (for example, sanitary survey
requirements in the Total Coliform Rule (TCR) (54 FR 27544, June 29,
1989) (USEPA, 1989a)) do not adequately address fecal contamination at
the ground water source. In fact, no Federal regulation exists that
requires either monitoring of ground water sources or corrective action
upon finding fecal contamination or identifying a significant
deficiency during a sanitary survey. In addition, the U.S. Government
Accountability Office (GAO) 1993 report (USGAO, 1993) found that many
sanitary surveys did not evaluate one or more of the components that
EPA recommended be evaluated, and that efforts to ensure correction
were often limited. Also, GAO found that follow-up on major problems
was often lacking. Moreover, the report found that problems associated
with system infrastructure identified during sanitary surveys
frequently remain uncorrected. The GWR provides much needed public
health protection by requiring systems that do not treat their ground
water sources to monitor their ground water source and to take
corrective actions when fecal contamination or a significant deficiency
is found.
    In addition, EPA has evaluated data on outbreaks and the occurrence
of waterborne viral and bacterial pathogens and indicators of fecal
contamination in ground water supplying PWS wells. These data indicate
that there is a subset of GWSs that are susceptible to fecal
contamination; therefore, EPA believes that risk management strategies
are needed to protect public health. Specifically, the Centers for
Disease Control and Prevention (CDC) reports that between 1991 (the
year in which the TCR became effective) and 2000, GWSs were associated
with 68 waterborne disease outbreaks that caused 10,926 illnesses
(Moore et al. (1993); Kramer et al. (1996); Levy et al. (1998); Barwick
et al. (2000); and Lee et al. (2002)). These outbreaks accounted for 51
percent of all waterborne disease outbreaks in the United States during
that time period. The major deficiencies identified by the CDC report
as the likely cause of the outbreaks were source water contamination
and inadequate treatment (or treatment failures); see Section III.C.2
for a summary of these outbreak data. Studies of viral and bacterial
pathogens and/or fecal indicator occurrence in ground waters that
supply PWSs show that dozens of the public ground water wells sampled
had fecal indicator or viral presence in their wells. See Section
III.C.3 of this preamble for a summary of occurrence studies. Based on
these outbreak and occurrence data, along with concern about lack of
monitoring and follow-up actions for GWSs, EPA has concluded that GWSs
need to implement targeted, risk management strategies to protect
public health from bacterial and viral pathogens in fecally
contaminated ground water sources.
    To provide a flexible, risk-targeted approach to achieve public
health protection, this rule builds on existing State programs--some
that emphasize the importance of disinfection and others that emphasize
assessments and technical assistance--to identify and target
susceptible GWSs. In addition, the GWR establishes treatment technique
requirements, which provide public GWSs with multiple options to
correct source water fecal contamination and significant deficiencies
that present a public health risk. Furthermore, this rule establishes
compliance monitoring requirements to ensure that treatment
effectiveness is maintained.

B. What Does the GWR Require?

    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 public GWSs. A central objective of the GWR is to identify the
subset of ground water sources that are at higher risk of fecal
contamination among the large number

of existing GWSs (approximately 147,000), and then further target those
systems that must take corrective action to protect public health. This
risk-targeting strategy includes the following:
     Regular GWS sanitary surveys to check for significant
deficiencies in eight key operational areas;
     A flexible program for identifying higher risk systems
through existing TCR monitoring and State determinations; and
     Ground water source monitoring to detect fecal
contamination at targeted GWSs that do not provide 4-log treatment of
viruses.
    Measures to protect public health include the following:
     Treatment technique requirements to address sanitary
survey significant deficiencies and fecal contamination in ground
water; and
     Compliance monitoring to ensure that 4-log treatment of
viruses is maintained where it is used to comply with this rule.
    To meet the treatment technique requirements of this rule, GWSs
with a significant deficiency or evidence of source water fecal
contamination, following consultation with their primacy agency (herein
referred to as ``the State''), must implement one or more of the
following corrective action options: Correct all significant
deficiencies; provide an alternate source of water; eliminate the
source of contamination; or provide treatment that reliably achieves at
least 99.99 percent (4-log) treatment of viruses (using inactivation,
removal, or a State-approved combination of 4-log virus inactivation
and removal) for each ground water source. Each of these corrective
actions is intended to remove all or nearly all fecal contamination,
including both viral and bacterial pathogens. In addition, the GWS must
inform its customers of any uncorrected significant deficiencies or
fecal indicator-positive ground water source samples.
    The following sections provide more detailed information on the
provisions of the GWR.
1. Sanitary Surveys
    Sanitary surveys are an important tool for identifying potential
vulnerabilities to fecal contamination at GWSs. The final GWR includes
Federal sanitary survey requirements for all GWSs for the first time.
This rule requires States, as a condition for primacy, to perform
regular comprehensive sanitary surveys of the following eight critical
components to the extent that they apply to the individual water system
being surveyed: (1) Source; (2) treatment; (3) distribution system; (4)
finished water storage; (5) pumps, pump facilities, and controls; (6)
monitoring, reporting, and data verification; (7) system management and
operation; and (8) operator compliance with State requirements. This
rule includes conditions of primacy in 40 CFR part 142 under which
States will have until December 31, 2012 to complete the initial
sanitary survey cycle for community water systems (CWSs), except those
that meet performance criteria, and until December 31, 2014 to complete
the initial sanitary survey cycle for all non-community water system
(NCWSs) and CWSs that meet performance criteria (refer to Section
IV.A.1 for crtieria). Following the initial sanitary survey cycle,
States must conduct these surveys every three years for CWSs (defined
in Sec.  141.2), and every five years for all NCWSs and CWSs that meet
certain performance criteria as discussed in Section IV.A.1.
    If a significant deficiency is identified as a result of a sanitary
survey, the system must take corrective action. If the system does not
complete corrective action within 120 days of receiving notification
from the State, or is not in compliance with a State-approved
corrective action plan and schedule, the system will be in violation of
the treatment technique requirements of this rule.
    The final GWR sanitary survey provision provides comprehensive and
effective public health protection by specifying the scope and
frequency of sanitary surveys and by requiring corrective action for
systems with significant deficiencies.
2. Source Water Monitoring
    This rule requires triggered source water monitoring and provides
States with the option to require assessment source water monitoring.
Source water monitoring is an effective tool to target at-risk systems
that must take corrective action to protect public health. Indications
of risk may come from total coliform monitoring, hydrogeologic
sensitivity analyses, or other system-specific data and information.
    In this rule, a GWS with a distribution system TCR sample that
tests positive for total coliform is required to conduct triggered
source water monitoring to evaluate whether the total coliform presence
in the distribution system is due to fecal contamination in the ground
water source. A GWS that does not provide at least 4-log treatment of
viruses must conduct triggered source water monitoring upon being
notified that a TCR sample is total coliform-positive. Within 24 hours
of receiving the total coliform-positive notice, the system must
collect at least one ground water sample from each ground water source
(unless the GWS has an approved triggered source water monitoring plan
that specifies the applicable source for collecting source samples).
The GWS must test the ground water source sample(s) for the presence of
one of three State-specified fecal indicators (E. coli, enterococci, or
coliphage). If the source sample is fecal indicator-positive, this rule
requires the GWS to notify the State and the public. Unless directed by
the State to take immediate corrective action, the GWS must collect and
test five additional source water samples for the presence of the same
State-specified fecal indicator within 24 hours. If any one of the five
additional source water samples tests positive for the State-specified
fecal indicator (E. coli, enterococci, or coliphage), this rule
requires the GWS to notify the State and the public and comply with the
treatment technique requirements, which require the system to take one
of four corrective actions discussed in the following section. The
compliance date of the triggered source water monitoring requirement is
December 1, 2009.
    As a complement to the triggered source water monitoring provision,
States have the option of requiring GWSs to conduct assessment source
water monitoring. This flexible provision gives States the opportunity
to target higher risk GWSs for additional source water monitoring and
evaluation. The State may require a GWS to conduct assessment source
water monitoring as needed. EPA recommends that States use
Hydrogeologic Sensitivity Assessments (HSAs) and TCR/triggered source
water monitoring results, along with other information to identify
higher risk systems for assessment source water monitoring. For
assessment source water monitoring, EPA recommends that GWSs take 12
monthly samples and test them for one of the GWR indicators (E. coli,
enterococci, or coliphage). Corrective action for systems performing
assessment source water monitoring is determined by the State.
3. Treatment Technique Requirements
    This rule requires a GWS to comply with the treatment technique
requirements if a significant deficiency is identified during a
sanitary survey. Also, the rule requires a GWS to comply with the
treatment technique requirements if one of the five additional ground
water source samples (or at State discretion, the initial source

sample) has tested positive for fecal contamination (i.e., the sample
is positive for one of the three fecal indicators and is not
invalidated by the State). The treatment technique requires that a GWS
implement at least one of the following corrective actions: correct all
significant deficiencies; provide an alternate source of water;
eliminate the source of contamination; or provide treatment that
reliably achieves at least 4-log treatment of viruses. Furthermore, the
GWS must inform the public served by the water system of any
uncorrected significant deficiencies and/or fecal contamination in the
ground water source. The compliance date of the treatment technique
requirements is December 1, 2009.
4. Compliance Monitoring
    Compliance monitoring requirements are the final defense against
viral and bacterial pathogens provided by this rule. All GWSs that
provide at least 4-log treatment of viruses using chemical
disinfection, membrane filtration, or a State-approved alternative
treatment technology must conduct compliance monitoring to demonstrate
treatment effectiveness. The compliance date of the compliance
monitoring requirement is December 1, 2009.

C. How Has the Final Rule Changed From What EPA Proposed?

    The primary elements of the proposed GWR were sanitary surveys,
triggered monitoring, HSAs, routine monitoring, corrective action, and
compliance monitoring. EPA received numerous comments on the proposed
GWR and has carefully considered those comments in developing the final
GWR. This consideration has led to a number of changes that the Agency
believes will result in a more flexible, more targeted, more protective
final GWR.
    Most of the changes are minor and are discussed throughout this
preamble in the pertinent sections. The most significant change from
the proposed rule to the final rule is to the routine monitoring
provision. The proposed routine monitoring provision would have
required GWSs in sensitive aquifers, as defined by a State performed
HSA, to collect monthly source water samples.
    EPA received many negative comments on the HSA provision. Some
States said that the proposed GWR did not allow sufficient time to
conduct the HSA prior to the start of routine monitoring, which would
result in GWSs in non-sensitive aquifers being required to monitor.
Others stated that they would not do the HSA; rather, they would
require all GWSs to conduct routine monitoring. In addition, EPA
received comments that the routine monitoring provision was too
burdensome.
    If the HSA provision would not be implemented in many States to
target the routine monitoring to systems in sensitive aquifers that are
most at risk, then the Agency agrees with the commenters that the
routine monitoring provision would be overly burdensome. This is
because some systems, located in non-sensitive aquifers, would be
conducting routine monitoring unnecessarily. Moreover, EPA now believes
that it is more difficult to capture contamination than estimated in
the proposal, which further highlights the importance of correctly
identifying systems for which source water monitoring would be prudent.
Furthermore, commenters strongly supported revision of the GWR proposal
to maximize State flexibility and discretion in making system-specific
decisions.
    Given the importance of correctly targeting systems for source
water monitoring, in conjunction with the State's desire for enough
flexibility to ensure sensible decisions on a case-by-case basis, EPA
decided to redesign the source water monitoring provision. Accordingly,
the final rule does not include a national requirement for HSAs and
routine monitoring for systems in sensitive aquifers. Rather, EPA
concludes that the States are in the best position to assess which
systems would most benefit from a source water monitoring program. The
final provision is similar to routine monitoring but is now optional
for States and has been renamed assessment source water monitoring.
States argued in their comments that the information available to them
from other programs such as source water assessments, wellhead
protection plans, and historical data would be important factors to
consider when determining the need for source water monitoring. Because
States are best able to identify higher risk systems, the final GWR
provides States with the option to require GWSs to perform assessment
source water monitoring. The Agency finds the comments received on the
proposal to be persuasive and to support the approach in the final GWR.
    The purpose of the optional assessment source water monitoring
requirement is to allow States to target such monitoring to GWSs that
the State believes are at higher risk for fecal contamination. States
specifically requested this flexibility and discretion in their
comments to EPA. The flexibility of this provision provides many
benefits. First, it gives States the ability to make case-by-case
determinations of the need for source water monitoring. Given the
variety of aquifer and well conditions across the United States and
even within each State, State programs make more sense than a
nationally-directed program. Second, the optional assessment source
water monitoring requirement allows States to require assessment source
water monitoring as needed. System conditions change over time and the
ability of States to target this requirement to a specific system and
time period will reduce burden and be critical to protecting public
health by allowing States to focus attention on problem systems. The
lack of time constraints will also allow States to prioritize
susceptibility assessments and further target those systems most in
need.
    EPA recommends that States use HSAs as one tool to identify high
risk systems for assessment source water monitoring. HSAs can be an
effective screening tool to identify sensitive hydrogeologic settings
that transmit water, and any pathogens in that water, quickly from the
surface to the aquifer. States have other information available to them
to target high risk systems, such as source water assessments, wellhead
protection plans, and historical monitoring data. Data on past
indications of source water fecal contamination, particularly from TCR
monitoring, in combination with GWR triggered source water monitoring
results, can be another important tool.

D. Does This Regulation Apply to My Water System?

    The requirements in this final rule apply to all PWSs (CWSs and
NCWSs) that use ground water sources, in whole or in part (including
consecutive systems that receive finished ground water from another
PWS), except that they do not apply to PWSs that combine all of their
ground water with surface water or ground water under the direct
influence of surface water (GWUDI) prior to treatment under the Surface
Water Treatment Rule (SWTR) (54 FR 27486, June 29, 1989) (USEPA,
1989b). The GWR ensures that the same level of public health protection
is provided to persons served solely by GWSs as to those served by
mixed systems supplied by both ground water and surface water sources.
See Section V.A of this preamble for more information on mixed systems.

III. Background

    This section includes a discussion of the statutory requirements,
regulatory

history, stakeholder involvement, and the public health concerns that
this rule addresses.

A. What Is the Statutory Authority for the GWR?

    Section 1412(b)(8) of the SDWA, as amended on August 6, 1996,
requires EPA to promulgate National Primary Drinking Water Regulations
(NPDWRs) requiring disinfection as a treatment technique for all PWSs,
including surface water systems and, as necessary, GWSs. In addition,
section 1412(b)(8) requires EPA to promulgate criteria as part of the
regulations for determining whether disinfection should be required as
a treatment technique for any PWS served by ground water. In contrast,
the 1986 Amendments to the SDWA directed EPA to promulgate regulations
requiring disinfection at all PWSs using either surface water or ground
water. The SWTR implemented that requirement for surface water systems,
but when Congress amended the SDWA again in 1996, EPA had not
promulgated regulations requiring disinfection for PWSs that use ground
water. In the legislative history of the 1996 Amendments to the SDWA,
Congress identified several reasons for the delay, including the
recognition that not all GWSs are at risk of contamination, as well as
the high cost of across-the-board disinfection. This rule implements
section 1412(b)(8) of the SDWA, as amended, by establishing a
regulatory framework for determining which GWSs are susceptible to
fecal contamination and requiring those systems to implement corrective
action options, only one of which is to provide 4-log treatment of
viruses (e.g., disinfection).
    Section 1413(a)(1) of the SDWA allows EPA to grant a State primary
enforcement responsibility (``primacy'') for NPDWRs when EPA has
determined that the State has adopted regulations that are no less
stringent than EPA's. To obtain primacy for this rule, States must
adopt comparable regulations within two years of EPA's promulgation of
the final rule, unless EPA grants the State a two-year extension. State
primacy requires, among other things, adequate enforcement (including
monitoring and inspections) authority and reporting requirement. EPA
must approve or deny State primacy applications within 90 days of
submission to EPA (SDWA section 1413(b)(2)). In some cases, a State
submitting revisions to adopt an NPDWR has primacy enforcement
authority for the new regulation while EPA's decision on the revision
is pending (SDWA section 1413(c)). Section 1445 of the SDWA authorizes
the Administrator to establish monitoring, recordkeeping, and reporting
regulations to assist the Administrator in determining compliance with
the SDWA and in advising the public of the risks of unregulated
contaminants. Section 1450 of the SDWA authorizes the Administrator to
prescribe such regulations as are necessary or appropriate to carry out
his or her functions under the Act.

B. What Is the Regulatory History of the GWR and How Were Stakeholders
Involved?

    EPA has devoted a tremendous effort to engage stakeholders in the
development of the GWR. EPA began developing the GWR in 1987 to address
potential fecal contamination of GWSs by requiring across-the-board
disinfection, as directed by the 1986 Amendments to the SDWA. A
preliminary public meeting on issues related to GWSs was held in 1990
(55 FR 21093, May 22, 1990) (USEPA, 1990). By 1992, EPA had developed a
draft proposed rule that would have required disinfection for all GWSs
(57 FR 33960, July 31, 1992) (USEPA, 1992). The draft proposed rule
incorporated stakeholder input and was made available for stakeholder
review. While some stakeholders supported the increased public health
protection for people drinking ground water, most stakeholders were
concerned that the rule was crafted such that all GWSs were assumed to
be contaminated until monitoring proved otherwise and that disinfection
waivers would be difficult to obtain.
    Throughout the early and mid-1990s, EPA conducted technical
discussions with ad hoc working groups during more than 50 conference
calls, with participation of EPA Headquarters, EPA Regional offices,
States, local governments, academicians, and trade associations. In
1996, Congress amended the SDWA and required EPA, under section
1412(b)(8), to develop regulations requiring disinfection as a
treatment technique for GWSs ``as necessary.'' As discussed previously,
this Amendment to the SDWA called for a different regulatory framework
to address fecal contamination in GWSs. In light of this statutory
change in direction, EPA determined that further stakeholder
involvement would be crucial to establishing an effective approach for
regulating fecal contamination in PWSs that use ground water sources.
    Technical meetings were held in Irvine, California in July 1996
(USEPA, 1996), and in Austin, Texas in March 1997 (USEPA, 1997a). These
technical discussions focused primarily on establishing a reasonable
means for determining if a ground water source was vulnerable to fecal
contamination. EPA evaluated the possibility of developing a
vulnerability assessment tool that would consider hydrogeologic
information and sources of fecal contamination.
    In addition, EPA held a series of stakeholder meetings (in
Portland, OR; Madison, WI; Dallas, TX; Lincoln, NE; and Washington, DC)
designed to engage all stakeholders in developing a risk-based
regulatory framework. The purpose of these meetings was to review
available information on risk and to discuss methods to identify GWSs
that are susceptible to fecal contamination, and therefore, should be
required to take corrective actions. EPA also held three early
involvement meetings with State representatives (in Portland, OR;
Chicago, IL; and Washington, DC) and received valuable input from small
system operators as part of an Agency outreach initiative under the
Small Business Regulatory Enforcement Fairness Act. Over the course of
these stakeholder meetings, the participants evaluated a continuum of
regulatory approaches. The meetings fostered EPA's understanding of how
State strategies fit together as a part of a national strategy. Taken
together, the meetings were crucial in guiding the Agency's development
of regulatory components for the GWR proposal.
    On February 3, 1999, EPA distributed a preliminary draft preamble
using the approach developed during the stakeholder meetings. Eighty
individual comment letters were received from representatives of State
and local governments, trade associations, academic institutions,
individual PWSs, and other Federal agencies. EPA considered all of the
comments received from this informal process as the Agency revised the
draft proposal.
    The proposed GWR was published in the Federal Register in 2000 (65
FR 30194, May 10, 2000) (USEPA, 2000a). The comment period closed on
August 9, 2000, and EPA received comments from over 250 individuals,
corporations, organizations, PWSs, States and Tribes, industry and
trade associations, and environmental groups. EPA has carefully
considered all of these comments in developing this final rule.
Comments received on the proposed rule, along with EPA's responses, are
compiled in the Public Comment and Response Document for the Final
Ground Water Rule (USEPA, 2006c).
    EPA published a Notice of Data Availability (NODA) in the Federal
Register in 2006 (71 FR 15105, March

27, 2006) (USEPA, 2006e). The purpose of the NODA was to present
additional studies that the Agency was considering in conducting its
economic analysis for the final rule. The comment period closed on
April 26, 2006. EPA received 14 sets of comments from individuals,
trade associations, State and local governments, an organization, and a
university. Comments received on the NODA, along with EPA's responses,
are also compiled in the Public Comment and Response Document for the
Final Ground Water Rule (USEPA, 2006c).

C. What Public Health Concerns Does the GWR Address?

    This section explains the public health concerns associated with
fecal contamination in GWSs by summarizing information on how ground
water sources could become fecally contaminated, the causes of ground
water outbreaks, and the health effects of consuming contaminated
water.
1. Introduction
    EPA estimates that approximately 114 million people consume
drinking water from PWSs that use ground water sources (Table III-1).
These PWSs (total of about 147,000) distribute disinfected or
undisinfected ground water to their customers. Approximately 18 percent
(20 million) of people served by PWSs that use ground water sources
receive undisinfected water, while over 60 percent (70 million) receive
either undisinfected water or water treated to less than 4-log
inactivation or removal of viruses.
    Over 100 million people receive ground water from community water
systems (CWSs) (Table III-1), while about 14 million people receive
ground water from non-community water systems (NCWSs); non-transient
non-community water systems (NTNCWSs) serve ground water to about five
million people and transient non-community water systems (TNCWSs) serve
ground water to about nine million people. Table III-1 shows that, of
the number of people receiving water from CWSs, NTNCWSs, and TNCWSs,
approximately 9.3 million (9.2 percent), 3.6 million (71 percent), and
7.2 million, (83 percent), respectively, receive water that is not
disinfected at all. The Table also shows that 56.8 million people
served by CWSs, 4.7 million people served by NTNCWSs, and 8.6 million
people served by TNCWSs receive water that is either undisinfected or
treated to less than 4-log.

                             Table III-1.--Population Served by Ground Water Systems
                                                   [Millions]
----------------------------------------------------------------------------------------------------------------
                                                                                Population served
                                                                                ground water that
                                                     Total population    Population served        is either
                                                     served by ground     untreated ground     undisinfected or
                                                      water systems            water           treated to less
                                                                                than 4-log
----------------------------------------------------------------------------------------------------------------
CWSs.............................................                100.4                  9.3                 56.8
NTNCWSs..........................................                  5.1                  3.6                  4.7
TNCWSs...........................................                  8.7                  7.2                 8.6
----------------------------------------------------------------------------------------------------------------
Source: Exhibit 4.4 of the GWR EA (USEPA, 2006d).

    As discussed previously in Section II.A, the CDC identified source
water contamination and inadequate treatment as the major causes for
ground water-related outbreaks between 1991 and 2000. Untreated or
inadequately treated ground water may contain viral and bacterial
pathogens. Therefore, undisinfected ground water or water treated to
less than 4-log may pose a public health risk to consumers.
    Waterborne disease attributable to viral and bacterial pathogens is
a significant public health problem. EPA's Science Advisory Board cited
drinking water contamination, particularly contamination by pathogenic
microorganisms, as one of the most important environmental risks
(USEPA/SAB, 1990). The CDC reports significant numbers of recent
waterborne disease outbreaks and cases of illness associated with
ground waters (Moore et al. (1993); Kramer et al. (1996); Levy et al.
(1998); Barwick et al. (2000); Lee et al. (2002)).
    Most waterborne pathogens, including viral and bacterial pathogens,
cause gastrointestinal (GI) illness with diarrhea, abdominal
discomfort, nausea, vomiting, and other symptoms. The effects of a
waterborne disease are usually acute, resulting from a single exposure.
Most GI illnesses are generally of short duration and result in mild
illness, but some can result in severe illness and even death. For
example, during a recent ground water outbreak in New York, a healthy
three-year old child died from hemolytic uremic syndrome (kidney
failure) (New York State Department of Health, 2000). Waterborne
pathogens also cause other serious disorders such as hepatitis,
Legionnaires Disease, myocarditis, paralysis, acute hemorrhagic
conjunctivitis, meningitis, and reactive arthritis. Waterborne
pathogens have also been associated with diabetes, encephalitis, and
other diseases (Lederberg, 1992).
    Sensitive populations are at greater risk from waterborne disease
from viral and bacterial pathogens than the general population. These
sensitive subpopulations include children (especially the very young);
the elderly; the malnourished; pregnant women; chronically ill patients
(e.g., those with diabetes or cystic fibrosis); and a broad category of
those with compromised immune systems, such as AIDS patients, those
with autoimmune disorders (e.g., rheumatoid arthritis, lupus
erythematosus, and multiple sclerosis), organ transplant recipients,
and those receiving chemotherapy (Rose, 1997). Sensitive subpopulations
(or those with compromised immune systems) represent almost 20 percent
of the population in the United States (Gerba et al., 1996). The
severity and duration of illness is often greater in sensitive
subpopulations than in healthy individuals, and may occasionally result
in death.
    When humans are exposed to and infected by an enteric pathogen,
such as a bacterium or virus, the pathogen becomes capable of
reproducing in the gastrointestinal tract. As a result, healthy humans
shed pathogens in their feces for a period ranging from days to weeks.
This shedding of pathogens often occurs in the absence of any signs of
clinical illness. Regardless of whether a pathogen causes clinical
illness in the person who sheds it in his or her feces, the pathogen
being shed may infect other people directly (by person-to-person
spread, contact with contaminated surfaces, etc.), which is referred to
as secondary spread.

Waterborne pathogens thus may infect people via a variety of routes.
    Fecal contamination of drinking water is a primary cause of
waterborne disease (Szewzyk et al., 2000). Viral and bacterial
pathogens associated with fecal contamination can reach ground water
via pathways in the subsurface and near surface. First, fecal
contamination from, for example, improper storage or management of
manure, runoff from land-applied manure, leaking sewer lines, or failed
septic systems can reach the ground water source by traveling--
sometimes great distances--through the subsurface (especially through
transmissive materials such as karst, gravel, or fractured bedrock).
Twenty-five million households in the United States use conventional
onsite wastewater treatment systems, according to the 1990 Census.
These systems include septic systems and leach fields. A national
estimate of failure rates of these systems is not available; however, a
National Small Flows Clearinghouse survey reports that in 1993 alone,
90,632 failures were reported (USEPA, 1997b). The volume of septic tank
waste alone that is released into the subsurface has been estimated at
one trillion gallons per year (Canter and Knox, 1984). This
contamination may eventually reach the intake zone of a drinking water
well.
    Second, fecal contamination from the surface may enter a drinking
water well along the casing or through cracks in the sanitary seal if
it is not properly constructed, protected, or maintained. In addition
to source contamination, fecal contamination may also enter the
distribution system when cross-connection controls fail or when
negative pressure in a leaking pipe allows contaminant infiltration. A
subset of GWSs is susceptible to contamination by one or more of these
routes.
2. Waterborne Disease Outbreaks in Ground Water Systems
    The Centers for Disease Control and Prevention (CDC) reports that
between 1991 (the year in which implementation of the TCR began) and
2000, GWSs (both CWSs and NCWSs) were associated with 68 outbreaks that
caused 10,926 illnesses (Table III-2). These account for 51 percent of
all waterborne disease outbreaks in the United States during that
period. The outbreak data illustrate that the major deficiency in GWSs
was source water contamination. Contaminated source water was the cause
of 79 percent of the outbreaks in GWSs (63 percent of CWS outbreaks and
86 percent of NCWS outbreaks), shown as untreated ground water and
treatment deficiencies in Table III-2. Consumers of undisinfected water
are especially vulnerable to source water contamination. Approximately
70 percent of GWSs provide either untreated ground water or provide
treatment of less than 4-log virus inactivation or removal as discussed
in the GWR EA (USEPA, 2006d).
    Of the 68 outbreaks in GWSs, 14 (21 percent) were associated with
specific bacterial pathogens (see Table III-3). The fecal bacterial
pathogen Shigella caused more reported outbreaks (five, seven percent)
than any other bacterial agent. Identified viral pathogens were
associated with four (six percent) reported outbreaks. Etiologic agents
were not identified in 39 (57 percent) outbreaks; however, EPA suspects
that many of these outbreaks were caused by viruses given that it is
generally more difficult to analyze for viral pathogens than bacterial
pathogens. EPA regulates for protozoa, including Giardia and
Cryptosporidium, under the SWTRs, which also cover GWUDI systems. For
the most part, the outbreaks associated with protozoa that occurred in
GWSs were later determined by the State to be GWUDI systems.

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    Large outbreaks are rarely associated with GWSs because most GWSs
are small. In addition, the number of identified and reported outbreaks
in the CDC database is believed to substantially understate the actual
incidence of waterborne disease outbreaks and cases of illness (Craun
and Calderon, 1996; National Research Council, 1997). This
underestimation is due to a number of factors. Many people experiencing
gastrointestinal illness do not seek medical attention. Where medical
attention is provided, testing to identify the pathogenic agent is
often not done and even if it is, the pathogenic agent may not be
identified through correct testing (e.g., when a sample is tested for a
limited number of pathogens). Physicians often lack sufficient
information to attribute gastrointestinal illness to any specific
origin, such as drinking water, and few

States have an active outbreak surveillance program. Furthermore, the
outbreak reporting system in the U.S. is paper-based and voluntary.
Consequently, waterborne disease outbreaks are often not recognized in
a community or, if recognized, are not traced to a drinking water
source even though it may be the cause of the outbreak. Although it
occurred in a community served by a surface water source, the 1993
Cryptosporidium outbreak in Milwaukee, Wisconsin is an example of how
difficult it is to recognize a drinking waterborne disease outbreak. In
one study of this large outbreak, only six percent sought health care
and only six percent of those health care cases were tested for
parasites (with only four percent of those cases specifically tested
for Cryptosporidium) (Juranek, 1997). Thus, over 99 percent of
estimated cases of illness went undiagnosed in this outbreak. In
addition to epidemic illness, an unknown but probably significant
portion of waterborne disease is endemic (i.e., isolated cases not
associated with an outbreak) and is even more difficult to recognize.
    Collectively, the data indicate that outbreaks in GWSs are a
problem and that source water contamination and inadequate treatment
(or treatment failures) are responsible for the great majority of
outbreaks.
3. Microbial Contamination in Public Ground Water Systems
    The extent to which viral and bacterial pathogens occur in public
ground water supplies influences the risk of exposure to populations
consuming ground water from PWSs. Such risks of exposure pertain to
populations using both undisinfected and disinfected water supplies.
For undisinfected supplies, pathogens in the water are an immediate
risk, since no treatment barrier exists prior to consumption. For
disinfected supplies, if disinfection is inadequate or if treatment
plant upsets occur, pathogens can reach consumers. These exposure risks
were discussed in Section III.C.2 from an outbreak perspective. This
section will discuss data on the occurrence of waterborne viral
pathogens and indicators of fecal contamination in ground water
supplying PWS wells.
    a. Occurrence studies and data. For this rule, EPA examined the
occurrence of viral pathogens and some fecal indicators. EPA reviewed
data from 24 studies on pathogen and fecal indicator occurrence in
ground water wells that supply PWSs. This total includes 16 studies
described in the proposal, seven studies that became available since
proposal as described in the NODA (USEPA, 2006e), and one study that
was provided to EPA in comment as a result of the NODA. Each study was
conducted independently and with a different objective and scope. The
Occurrence and Monitoring Document for the Final Ground Water Rule
(USEPA, 2006b) provides a detailed discussion of each examined
occurrence study. The available data show a wide range of enterovirus
and fecal indicator occurrence in water drawn from wells across the
U.S. EPA selected 15 studies to estimate national viral and fecal
indicator occurrence in ground water. To arrive at the conclusion that
these 15 studies provide the best possible representation of ground
water contamination at a national level, EPA evaluated all available
studies (24 studies) that were applicable to the risk assessment
analyses (USEPA, 2006d). See Section VII.B.1 of this preamble for a
discussion of study selection.
    Enterovirus cell culture data from the 15 studies were used to
estimate the baseline risk related to virus occurrence in ground water.
EPA believes that enterovirus cell culture measurements provide the
best available basis for estimating pathogenic viral occurrence since
they capture viruses that are infectious. However, because the cell
culture procedure only captures a portion of all viruses that may
actually occur in well water due to assay limitations, use of this
method may underestimate viral occurrence.
    EPA used data on the indicator E. coli from these same studies to
inform estimates of fecal contamination occurrence. Indicator data are
important because illness can result from consuming ground water with
fecal contamination in the absence of identified viruses. For example,
some viruses such as infectious norovirus are not recoverable, other
viruses such as enteroviruses have variable and limited recovery, and a
variety of bacteria of fecal origin can cause disease. EPA chose to use
E. coli data instead of other fecal indicator data for this analysis.
This choice was driven by EPA's assessment that E. coli will be the
most likely fecal indicator used when PWSs implement the GWR, because
E. coli is frequently used to fulfill follow-up monitoring requirements
under the TCR. Therefore national estimates of E. coli occurrence can
be used to inform potential cost implications for implementing the GWR.
EPA recognizes that any indicator organism, including E. coli, may or
may not co-occur with pathogens and that co-occurrence could be
intermittent. E. coli is an imperfect indicator of viral occurrence.
Some wells with E. coli have no viral occurrence. Some wells with viral
occurrence have no E. coli.
    b. Estimates of national occurrence of viral and fecal indicator
contamination. This section discusses national occurrence of viral and
fecal indicator (E. coli) contamination, which includes estimates of
viral concentrations in contaminated wells and estimates of the
probability that a well may have detectable viral and/or fecal
indicator contamination. For purposes of this analysis, EPA uses the
term ``sometime contamination'' as contamination that occurs at one or
more points in time. Because fecal contamination is intermittent,
viruses and E. coli will only be present at detectable levels some
fraction of the time in a contaminated well. These fractions will vary
from well to well. Some wells may be frequently contaminated but others
may only be contaminated for a small fraction of time.
    EPA analyzed the 15 studies for data to inform the concentration
analysis. Among the 15 studies used for the national occurrence
analysis, 12 provided data on occurrence of enterovirus cell culture
and 11 provided data on occurrence of E. coli. Among the 12 data sets
with enterovirus cell culture measurement, three included viral
concentration data. Concentration measurements in the three surveys
ranged from 0.09 to 212 enteric virus infectious units (plaque forming
units) per 100 liters. Although the measurement methods were often not
capable of detecting viruses at concentrations below 0.2 units per 100
liters, it is likely that viruses also occur at levels below the
detection limit.
    Data from each of the 15 studies were combined into one complete
data set to determine the probabilities of sometime well contamination
for viral (indicated by enterovirus cell culture) or fecal indicator
(indicated by E. coli) contamination. The results of this effort led
naturally to a combined analysis, which models occurrence and co-
occurrence of viruses and E. coli. EPA's analysis also considers
uncertainty and variability about these estimates. The model serves as
the basis of EPA's national quantitative occurrence estimates. See the
Occurrence and Monitoring Document for the Final Ground Water Rule for
more information (USEPA, 2006b).
    Overall, the analysis indicates a public health concern in that
approximately 26 percent of the wells sometimes have fecal
contamination (indicated by E. coli) and approximately 27 percent of
the wells sometimes have

viral contamination. Due to the intermittent nature of fecal
contamination, some of these wells are only contaminated for a small
fraction of time. On average, wells with sometime virus occurrence have
detectable concentrations about 11 percent of the time, and wells with
sometime E. coli occurrence have detectable concentrations about 14
percent of the time. The remainder of the time, the well's water is
essentially virus free (assuming that concentration is zero when not
detected by measurement methods like those used in the occurrence
studies). Compared to the analysis in the proposal, the number of wells
with fecal contamination is greater but the frequency at which
contamination occurs in each well is less.
    In summary, EPA's occurrence analysis shows that fecal
contamination is intermittent and that some individuals are at risk
because pathogens and/or fecal indicators occur at PWSs that use ground
water as a source of drinking water. The next section discusses this
risk.
4. Potential Risk Implications From Occurrence Data
    As discussed previously, to assess the public health risk
associated with drinking ground water, EPA evaluated information and
conducted analyses on (1) Health effects data from a range of
pathogens, (2) waterborne disease outbreak data, and (3) occurrence
data from ground water studies and surveys. As a result of this
evaluation and analysis, EPA concludes that the potential risk to
public health posed by a subset of PWSs with contaminated ground water
sources is significant enough to warrant regulation.
    When a PWS uses contaminated source water, its customers are at
risk of infection and illness. Their risk depends on a number of
factors including whether the system provides at least 4-log treatment
of viruses, the frequency at which the well is contaminated, the level
of contamination (i.e., concentration), and the infectivity of the
pathogens that are present.
    To develop risk estimates from viral exposure, EPA considered two
types of viruses, Type A (represented by data available on rotavirus)
and Type B (represented by data available on enterovirus or echovirus),
which are used to estimate risk from exposure to viral-contaminated
wells. These two virus types have different infection morbidity and
disease severity characteristics. Type A viruses are considered to be
highly infectious but cause primarily mild illness, while Type B
viruses are considered much less infectious but may cause more severe
illnesses.
    The infectivity of a virus relates the probability of infection to
a given amount, or dose, of virus consumed. Together with infectivity,
morbidity (risk of illness given infection) and mortality (risk of
premature death given an illness) are used to predict the disease
burden associated with a particular virus level in drinking water. As
discussed in the previous section, a typical contaminated well may have
detectable virus concentrations 11 percent of the time. The remainder
of the time, the well's water is essentially virus free (assuming that
concentration is zero when not detected by measurement methods like
those used in the occurrence studies). EPA has viral concentration data
from the three studies as discussed in Section III.C.3.b of this
preamble. Virus concentration data combined with viral exposure data
can be used to predict infection rates given viral dose-response
information. Figure III-1 indicates the annual risk of infection from
exposure to rotavirus, assuming one liter of water consumed per day,
based on a range of possible mean annual source water concentrations
and different levels of treatment. For example, if an untreated ground
water source had a mean annual source water concentration of 0.1
viruses per 100 L (e.g., a source water concentration of one virus per
100 L, 10 percent of the time), people consuming one liter of this
water per day would have approximately a seven percent probability of
being infected in the course of the year (90 percent confidence
interval of three percent to 13 percent). The risk of infection
implications from exposure to echovirus are 10 to 100 times less than
those from rotavirus, assuming the same levels of exposure. However,
illness resulting from infection of echovirus may be more severe than
illness resulting from infection by rotavirus.
    It is important to recognize that EPA's quantitative risk analysis
is limited by the data available, specifically data on rotavirus and
echovirus. Other pathogenic viruses also cause disease and may be more
or less infectious than those modeled. Pathogens may cause chronic and
acute illnesses in addition to those considered in the quantitative
risk analysis. Furthermore, EPA's quantitative risk analysis does not
consider bacterial illness and deaths resulting from contaminated
drinking water due to limited data. Taken together, these limitations
imply an underestimate of the actual illnesses and deaths that result
from exposure to contaminated ground water when only these sources of
uncertainty are considered. The GWR national risk implications from
exposure to pathogenic viruses and bacteria are discussed in Section
VII of this preamble and more fully discussed in the GWR EA (USEPA,
2006d).
    Even at the levels EPA is able to quantify, the risk analysis
supports the conclusion that a substantial number of people served by
GWSs are at risk of exposure to waterborne pathogens. EPA's occurrence
analysis (USEPA, 2006b) demonstrates that some wells have high viral
occurrence while others have lower occurrence, and thus lower risk. For
public health protection, it is most important to target those wells
with higher occurrence. In addition, the occurrence analysis
demonstrates that contamination is intermittent. Because of the
intermittent nature of contamination, an ongoing monitoring program is
critical to effectively target higher risk systems.
    The intent of the GWR is to reduce risk by targeting susceptible
systems for corrective action. The corrective action options are:
Correct all significant deficiencies; provide an alternate source of
water; eliminate the source of contamination; or provide treatment that
reliably achieves at least 4-log treatment of viruses. As illustrated
in Figure III-1, treatment will provide large improvements in public
health. Thus, the final GWR components of sanitary surveys, source
water monitoring, and corrective action are each critical steps to
improving public health in communities served by undisinfected (or
inadequately disinfected) GWSs.
    Implementation of this rule is expected to result in approximately
42,000 avoided viral illnesses and one avoided death annually. The
analysis is uncertain and these estimates could be an over-or under-
estimate of actual illnesses and deaths. The nonquantified benefits are
those that the Agency was unable to quantify due to data limitations,
which include decreased incidence of other acute viral disease
endpoints, decreased incidence of chronic viral illness sequelae,
decreased incidence of bacterial illness and death, decreased incidence
of waterborne disease outbreaks and epidemic illness, and decreased
illness through minimizing treatment and distribution system failures.
The nonquantified benefits associated with this rule are significant
and are discussed in detail in Section 5.4 of the GWR EA (USEPA,
2006d).

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IV. Discussion of GWR Requirements

    This section describes the rule requirements and rationale for each
component of the risk-targeted strategy of this rule. A summary of, and
responses to, key comments on the proposed rule are also provided.

A. Sanitary Surveys

    EPA believes that comprehensive, periodic sanitary surveys and the
identification and correction of significant deficiencies are
indispensable for ensuring the long-term safety of drinking water
supplies. They are an important tool for identifying potential
vulnerabilities to fecal contamination at GWSs. The final GWR includes
Federal requirements for sanitary surveys of all GWSs for the first
time.
    This rule provides the States with flexibility to prioritize and
carry out the sanitary survey process, while ensuring that the survey
is an effective, preventive tool for GWSs. The sanitary survey
provision in this rule builds on existing State sanitary survey
programs established under the 1989 TCR and the Interim Enhanced
Surface Water Treatment Rule (IESWTR) (63 FR 69477, December 16, 1998)
(USEPA, 1998b) and gives States the authority to define both
outstanding performance and significant deficiencies. At the same time,
the GWR's sanitary survey requirements for minimum frequencies, scope,
documentation, and mandatory corrective action strengthen existing
sanitary survey programs and address many of the concerns associated
with current sanitary survey programs as identified by the GAO (USGAO,
1993).

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1. What Are the Requirements of This Rule?
    This rule requires States to perform sanitary surveys for all GWSs.
Ground water systems must provide the State with any pertinent,
existing information that will enable the State to perform the sanitary
survey. This rule goes beyond the existing definition of sanitary
survey at Sec.  141.2, explicitly references the use and relevance of
source water assessments required under the 1996 SDWA Amendments, and
specifies in more detail the scope of a sanitary survey. Specifically,
this rule requires that States evaluate eight components as part of the
sanitary survey to the extent that they apply to an individual system:
(1) Source; (2) treatment; (3) distribution system; (4) finished water
storage; (5) pumps, pump facilities, and controls; (6) monitoring,
reporting, and data verification; (7) system management and operation;
and (8) operator compliance with State requirements. This rule outlines
the eight minimum elements using broad categories and recognizes that
certain elements may not be present in a particular system depending on
its size or complexity.
    This rule requires States to conduct sanitary surveys of ground
water CWSs every three years (every five years for CWSs that meet
performance criteria as described in the following paragraph) and of
ground water NCWSs every five years. States are required to complete
the initial sanitary survey cycle by December 31, 2012 for CWSs, except
those that meet performance criteria, and December 31, 2014 for all
NCWSs and CWSs that meet performance criteria. States may conduct more
frequent sanitary survey cycles for any GWS as appropriate.
    This rule allows individual components of a sanitary survey to be
conducted according to a phased review process (e.g., as part of
ongoing State assessment programs). While all

applicable components need not be evaluated at the same time, they must
be evaluated within the required three-or five-year frequency interval.
Also, this rule allows the three-year CWS schedule to be extended to a
five-year frequency if the system meets certain criteria (referred to
in this preamble as ``performance criteria''). These performance
criteria are:
     Provides 4-log treatment of viruses (using inactivation,
removal, or a State-approved combination of 4-log virus inactivation
and removal) before or at the first customer for all its ground water
sources, or
     Has an outstanding performance record (as defined by the
State) documented in previous sanitary surveys, and has no history of
total coliform MCL or monitoring violations under the TCR since the
last sanitary survey.
    Finally, this rule requires that GWSs correct any significant
deficiencies identified in sanitary surveys. Significant deficiencies,
as determined by the State, include, but are not limited to, defects in
design, operation, or maintenance, or a failure or malfunction of the
sources, treatment, storage, or distribution system that the State
determines to be causing, or have the potential for causing, the
introduction of contamination into the water delivered to consumers.
    Significant deficiencies may include, but are not limited to, the
following:
    Source
     Well near a source of fecal contamination (e.g., failing
septic systems or a leaking sewer line).
     Well in a flood zone.
     Improperly constructed well (e.g., improper surface or
subsurface seal).
     Spring boxes that are poorly constructed and/or subject to
flooding.
    Treatment
     Inadequate application of treatment chemicals (e.g.,
disinfection contact time is inadequate).
     Lack of redundant mechanical components where disinfection
is required.
     Unprotected cross-connections with treatment chemical
systems.
     Inadequate treatment process monitoring.
    Distribution System
     Negative pressures that could result in the entrance of
contaminants.
     Inadequate disinfectant residual monitoring, when
required.
     Unprotected cross-connections.
    Finished Water Storage
     Inadequate internal cleaning and maintenance of storage
tanks.
     Lack of proper screening of overflow pipes, drains, or
vents.
     Storage tank roofs or covers need repair (e.g., holes or
hatch of improper construction).
    Pumps, Pump Facilities, and Controls
     Inadequate pump capacity.
     Inadequate maintenance.
     Inadequate/inoperable control system.
    Monitoring, Reporting, and Data Verification
     Failure to properly monitor water quality.
     Failure to meet reporting requirements.
     Inadequate recordkeeping.
    System Management and Operation
     Failure to meet water supply demands/interruptions to
service (e.g., unreliable water source or lack of auxiliary power).
     Lack of approved emergency response plan.
     Inadequate follow-up to deficiencies noted in previous
assessment/survey.
    Operator Compliance with State Requirements
     Operator is not certified as required by the State.
     Lack of operator training.
    The State must provide the GWS with written notification, which
describes any significant deficiencies found, no later than 30 days
after the State identifies the significant deficiency. The notice may
be sent to the PWS, or it may be provided on-site either at the time
the sanitary survey is conducted or the significant deficiency is
identified. The State may specify appropriate follow-up corrective
action steps in the notice or may notify the GWS of appropriate
corrective actions during the consultation period. After receiving the
written notification, the GWS has 30 days to consult with the State
regarding corrective actions. However, the State may prescribe
corrective actions and completion dates, including immediate and/or
interim corrective actions, in lieu of the consultation process. Under
this rule, a GWS must complete corrective action or be in compliance
with a State-approved corrective action plan and schedule within 120
days of receiving written notice from the State, as described in
Section IV.C of this preamble. Failure to do so will result in a
treatment technique violation. This rule requires systems to notify
customers of uncorrected significant deficiencies. When a significant
deficiency is identified at a PWS that uses both ground water and
surface water sources, the GWR treatment technique requirements apply
except in cases where the State determines that the significant
deficiency is in a portion of the distribution system that is served by
surface water (or ground water under the direct influence of surface
water).
2. What Is EPA's Rationale for the GWR Sanitary Survey Requirements?
    As discussed in the proposed GWR, sanitary surveys enable States
(and systems) to provide a comprehensive and accurate review of the
components of water systems, to assess the operating conditions and
adequacy of the water system, and to determine if past recommendations
have been implemented effectively. A GWS has the responsibility of
providing the information necessary to conduct a sanitary survey to the
State upon request to enable a comprehensive assessment of the system.
The purpose of the sanitary survey is to evaluate and document the
capabilities of the water system's sources, treatment, storage,
distribution network, operation and maintenance, and overall management
to ensure the provision of safe water. In addition, sanitary surveys
provide an opportunity for PWS inspectors to visit the water system and
educate operators about proper monitoring and sampling procedures and
to provide technical assistance.
    Historically, sanitary surveys have been conducted by State
drinking water programs as preventative tools for identifying water
system deficiencies before contamination occurs. In 1976, EPA
regulations required, as a condition of primacy, that States develop a
systematic program for conducting sanitary surveys, but EPA did not
define the scope of sanitary surveys or specify minimum criteria at
that time. In 1989, the TCR included a provision requiring sanitary
surveys for systems collecting fewer than five TCR samples per month
(systems serving fewer than 4,100 people). For those systems, sanitary
surveys are required under the TCR once every five years for CWSs and
NCWSs (but once every 10 years for NCWSs that use protected or
disinfected ground water). However, the TCR did not establish what must
be evaluated in a sanitary survey or specifically address significant
deficiencies.
    Consequently, a number of concerns have been raised regarding post-
TCR sanitary survey practices. For example, the GAO investigated
sanitary survey practices in 1993 and found that many surveys did not
evaluate one or more of the major components and operations that EPA
requires be evaluated under the final GWR and that efforts to ensure
that deficiencies were corrected were often limited (USGAO, 1993). A
review of State regulations found that many States do not specifically
require systems to correct deficiencies. These

factors, coupled with information on contaminant occurrence and
analysis of microbial waterborne disease outbreak data, indicated that
public health protection can be strengthened by requiring regular
sanitary surveys, specifying the scope of surveys, and requiring
corrective action of significant deficiencies.
    In 1995, EPA and the States (through the Association of State
Drinking Water Administrators) issued a joint guidance on sanitary
surveys entitled EPA/State Joint Guidance on Sanitary Surveys (USEPA/
ASDWA, 1995). Recognizing the essential role of sanitary surveys and
the need to define the broad areas that all sanitary surveys should
cover, the guidance recommended eight elements for a comprehensive
sanitary survey. The guidance also recommended the development of
assessment criteria, proper documentation of results, and thorough
follow-up, tracking, and enforcement after the survey. The IESWTR,
(USEPA, 1998b), requires States to address the same eight elements in
sanitary surveys conducted at surface water systems and at GWUDI
systems. The GWR incorporates the same eight elements into the sanitary
survey requirements for GWSs to be consistent with, and as
comprehensive as, the IESWTR. Based on consultation with the States and
EPA regions, EPA believes that the majority of States today include the
eight elements in their sanitary survey programs for both surface water
and GWSs.
    In addition to requiring these eight elements, the GWR requires the
State to conduct sanitary surveys no less frequently than every three
years for CWSs and every five years for NCWSs. This rule provides the
State with the flexibility to reduce the frequency for CWSs to every
five years for systems that meet performance criteria (refer to Section
IV.A.1 for criteria). These frequencies are consistent with the
recommendations for surface water systems made by the Microbial/
Disinfection Byproducts Federal Advisory Committee, which included
various stakeholders representing a wide range of sectors in the
drinking water community. Given this, EPA believes that the same three-
and five-year interval for conducting sanitary surveys is appropriate
for GWSs. The GWR requires the first sanitary survey cycle to be
completed by December 31, 2012 for CWSs, except those that meet
performance criteria, and December 31, 2014 for all NCWSs and CWSs that
meet performance criteria. See Section VI of this preamble for
explanation of initial sanitary survey completion dates.
    As noted earlier, this regulation attempts to build on existing
State public health programs to the extent possible. Consequently, the
GWR allows individual elements of a sanitary survey to be conducted on
a phased review schedule as part of ongoing State assessment programs
within the established three-or five-year frequency interval. This
allows States to more efficiently use existing assessment schedules and
maximize the effective allocation of staff resources and expertise
across a State in conjunction with other priorities. EPA believes that
the frequency of sanitary surveys and the required eight sanitary
survey elements in this rule ensure greater public health protection
while providing adequate flexibility for States and systems to
effectively implement the requirements. The GWR requires the initial
sanitary surveys to be completed six years after rule promulgation for
CWSs and eight years after rule promulgation for NCWSs. The six to
eight year time frame for initial sanitary surveys is based on several
considerations. First, States need time to adopt the rule and obtain
primacy (two to four years allowed by the SDWA at 1413(a)(1)). In
addition, systems are given three years to comply with drinking water
regulations by the SDWA at (1412(b)(10)). Finally, States need three to
five years to complete the first cycle of sanitary surveys because
there are many GWSs and States have limited resources.
    A key finding of the GAO report was that deficiencies identified in
one sanitary survey were often found still uncorrected at the next
sanitary survey. For example, in a four-State sample of 200 sanitary
surveys, GAO found approximately 60 percent of the surveys cited
deficiencies that were also cited in previous surveys. While the report
indicated that smaller systems (serving 3,300 or fewer people) were in
the greatest need of improvement, GAO found that, regardless of system
size, previously identified deficiencies frequently went uncorrected.
GAO found that some States lacked the authority to ensure that water
system owners and operators correct documented deficiencies. Additional
causes for uncorrected deficiencies included a lack of documentation or
ineffective tracking of survey results. The Agency believes that a
sanitary survey is an effective tool for identifying significant
deficiencies. Once identified, it is also essential that such
deficiencies be corrected in a timely manner. A study of the
effectiveness of a range of best management practices shows that
follow-up and correction of sanitary survey deficiencies were
correlated with lower levels of total coliform, fecal coliform, and E.
coli (ASDWA, 1998). Thus, this rule requires that systems coordinate
with the State within 30 days of being notified of the significant
deficiency and that the systems correct the significant deficiency (or
be on an enforceable State-prescribed schedule) within 120 days of
being notified of the significant deficiency. See Section IV.C for
details on corrective action time frames.
3. What Were the Key Issues Raised by Commenters on the Proposed GWR
Sanitary Survey Requirements?
    The majority of commenters on the GWR proposal were supportive of a
sanitary survey requirement for all GWSs. Most commenters supported the
proposed frequencies of three years for CWSs and five years for NCWSs.
Several commenters noted that some States conduct surveys at more
frequent intervals than required in this rule. However, a few
commenters suggested extending the frequency interval for CWSs, because
they believed that CWSs would be less likely to have significant
deficiencies.
    The Agency believes that frequent, comprehensive sanitary surveys
are an important proactive public health measure and that the minimum
frequencies of sanitary surveys under this rule balance public health
protection with State implementation issues. This rule requirement is
consistent with the frequency required for surface water systems under
the IESWTR. The GWR provides flexibility in allowing States to perform
more frequent sanitary surveys or to reduce the frequency for CWSs to
five years if the CWS meets performance criteria (Section IV.A.1).
States also have the flexibility to phase-in the evaluation of sanitary
survey elements within the required frequency interval. The Agency
believes that a frequency of three years for CWSs and five years for
NCWSs, combined with flexibility on both timing and implementation,
appropriately considers limited resource issues while advancing public
health protection.
    EPA specifically requested comments on ``grandfathering'' sanitary
surveys conducted under the TCR to satisfy the initial sanitary survey
requirements of the GWR. The majority of comments favored allowing the
use of sanitary surveys conducted under the TCR or existing State
programs to meet the initial sanitary survey requirements of the GWR.
These comments were largely based on an interest in reducing State

implementation burden and allowing States to transition their existing
sanitary survey programs into programs and schedules that meet the
requirements of the GWR.
    Because of the time frames laid out in the GWR for initial and
repeat sanitary surveys, grandfathering sanitary surveys is not
practicable. States must complete their initial CWS sanitary surveys
six years after rule promulgation for CWSs and eight years for NCWSs.
The deadline for completing the first round of sanitary surveys is
longer than the minimum required sanitary survey frequency, so
grandfathering would not result in a burden reduction for the State.
For example, if a State were to grandfather a CWS sanitary survey from
2005, they would be required to complete a second sanitary survey by
2008 and a third by 2011, whereas a State that completed their first
sanitary survey in 2009 would not be required to complete their second
sanitary survey until 2012. As described in Section IV.A.2, the six to
eight year time frame for initial sanitary surveys is based on several
considerations. First, States need time to adopt the rule and obtain
primacy (two to four years allowed under the SDWA at 1413(a)(1)). In
addition, systems are given three years to comply with drinking water
regulations by the SDWA at (1412(b)(10)). Finally, States need three to
five years to complete the first cycle of sanitary surveys because
there are many GWSs and States have limited resources.
    EPA believes that it is important to reduce State implementation
burden and that information from existing sanitary surveys and other
sources is an important resource. Thus, this rule allows States to
reduce the frequency of sanitary surveys for CWSs that meet performance
criteria (Section IV.A.1) at any time subsequent to the effective date
of this rule from every three to every five years. This allows States
to reduce the implementation burden of sanitary surveys based on
information collected under the TCR and existing sanitary survey
programs while still ensuring a minimum sanitary survey frequency of
five years for both CWSs and NCWSs. Since a significant proportion of
GWSs are small NCWSs and the GAO report found the greatest need for
improvement in smaller systems, EPA believes that a reduction in
frequency for NCWSs would not advance public health protection. EPA
notes that surveys or elements of sanitary surveys conducted under the
TCR or as part of site assessment or other State programs may be used
to meet the GWR requirements if they meet the criteria specified in the
GWR (i.e., if the minimum eight elements specified in the GWR are
addressed at the specified GWR frequency).
    EPA received a number of comments on the 30-day time frame that
States have to notify a system when a significant deficiency is
identified in the sanitary survey. Some commenters noted that this
requirement is consistent with current procedures; notice of
significant deficiencies is often provided to a system much sooner.
However, other commenters were concerned that this requirement placed
an unnecessary deadline on the State and that current State policies
and practices adequately address timely notification of systems with
significant deficiencies.
    The Agency believes that timely notification of significant
deficiencies is essential to the timely correction of those
deficiencies and to the safety of drinking water. EPA believes
requiring a 30-day maximum notification period in all States is
reasonable, given the potential public health risk of significant
deficiencies, and ensures equitable protection of public health across
the nation.
    EPA also received comments on what constitutes a significant
deficiency under the GWR. EPA proposed defining significant
deficiencies as a defect in design, operation, or maintenance, or a
failure or malfunction of the sources, treatment, storage, or
distribution system that the State determines to be causing, or has the
potential for causing, the introduction of contamination into the water
delivered to consumers. Several commenters urged EPA to go beyond that
definition and require States to specify a minimum list of significant
deficiencies under each of the applicable eight sanitary survey
components set out in the EPA/State Joint Guidance on Sanitary Surveys.
EPA also received comments regarding specific examples of significant
deficiencies in each applicable component. Section IV.A.1 of this
preamble includes specific examples of some significant deficiencies
provided by commenters.
    The Agency believes that to provide adequate public health
protection, States must identify and require correction of all
significant deficiencies. Also, EPA recognizes the importance for the
State to include additional case-specific deficiencies. This rule
states that significant deficiencies ``include, but are not limited to,
defects in design, operation, or maintenance, or a failure or
malfunction of the sources, treatment, storage, or distribution system
that the State determines to be causing, or has the potential for
causing, the introduction of contamination into the water delivered to
consumers.'' The GWR requires each State, in its primacy application,
to define and describe at least one specific significant deficiency in
each of the eight sanitary survey elements. This enables States to work
within their existing programs to define significant deficiencies as
part of their primacy application and to define and describe
significant deficiencies that may be unique to system size, type,
location, or State requirements. EPA also recognizes that some systems
may not have all eight components; for example, some TNCWSs may not
have storage or require certified operators.
    EPA requested comment on having public involvement and/or meetings
for certain PWSs to discuss the results of sanitary surveys and
specifically what approaches might be practical and not overly
burdensome to involve the public in working with water systems to
address the results of sanitary surveys. Some commenters suggested
publishing the results in the system's Consumer Confidence Report (CCR)
or reviewing the results at a public meeting. Others supported
notifying the public that the results were available and how those
results could be obtained. Some commenters noted that significant
deficiencies would be corrected rapidly and that involving or informing
the public after the correction might not be useful. One commenter
suggested posting the results of surveys in a public place for non-
community systems.
    EPA believes that adequate opportunities exist for customers to
obtain information on the complete sanitary survey of their water
supplier. Results of sanitary surveys and notification from the State
to the water supplier of significant deficiencies would be available to
the public upon request from the State or the water supplier. However,
EPA also believes that the public served by the water system should be
made aware of significant deficiencies found in sanitary surveys that
remain uncorrected and be fully informed as to how and when those
deficiencies will be corrected. This rule requires systems to notify
customers of such significant deficiencies including the date and
nature of the significant deficiency, the schedule for correction, any
interim measures taken, and the progress to date. The State may require
the system to notify customers of corrected significant deficiencies.
This requirement is described further in Section IV.D of this preamble.
    EPA received comments suggesting that the sanitary survey
provisions of

the TCR are sufficient to address viral and bacterial pathogens in GWSs
and there is no need for sanitary surveys under the GWR. While EPA
believes the TCR was a significant step forward for public health
protection in 1989, the TCR does not require systems to correct
significant deficiencies or require a minimum frequency of sanitary
surveys for all systems. Thus, the GWR sanitary survey requirement
better addresses the potential public health consequences of
uncorrected significant deficiencies.

B. Source Water Monitoring

    This rule requires ground water source monitoring as an essential
element in its risk-targeted approach for identifying those GWSs with
source water fecal contamination that need corrective action. Systems
targeted for source water monitoring are those with an indication that
they may be at risk for fecal contamination. Indicators of risk may
come from total coliform monitoring, hydrogeologic sensitivity
analyses, or other system-specific data and information. This rule
requires triggered source water monitoring and provides States with the
option to require assessment source water monitoring. Source water
monitoring is not required for any GWS that is already providing at
least 4-log treatment of viruses.
    A GWS with a distribution system TCR sample that tests positive for
total coliform is required to conduct triggered source water monitoring
to evaluate whether the total coliform presence in the distribution
system is due to fecal contamination in the ground water source.
Triggered source water monitoring provides a critical ongoing
evaluation of GWSs.
    As a complement to the triggered source water monitoring provision,
the GWR gives States the flexibility to require more comprehensive
assessment source water monitoring on a case-by-case basis. The purpose
of this optional assessment source water monitoring requirement is to
target source water monitoring to systems that the State determines are
at higher risk for fecal contamination. States are in the best position
to assess which systems are at risk and would most benefit from source
water monitoring.
    EPA believes that source water monitoring targeted at higher risk
systems, namely triggered source water monitoring, in conjunction with
optional assessment source water monitoring, will be effective in
identifying systems with source water fecal contamination. With
implementation of the follow-up corrective action requirements outlined
in Section IV.C, these requirements will provide meaningful
opportunities to reduce public health risk for a substantial number of
people served by GWSs.

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1. What Are the Requirements of This Rule?
    a. Triggered source water monitoring. A GWS must conduct triggered
source water monitoring within 24 hours of receiving notification that
a routine sample collected in accordance with Sec.  141.21(a) (TCR) is
total coliform-positive. A GWS must collect at least one ground water
source sample from each ground water source (e.g., a well or spring) in
use at the time the total coliform-positive sample was collected.
Triggered source water monitoring is required unless: (1) The system
provides at least 4-log treatment of viruses (using inactivation,
removal, or a State-approved combination of 4-log virus inactivation
and removal) before or at the first customer for each ground water
source; (2) the system is notified that a positive sample collected in
accordance with Sec.  141.21(a) (TCR) has been invalidated under Sec.
141.21(c); or (3) the cause of the total coliform-positive collected
under Sec.  141.21(a) directly relates to the distribution system as
determined by the system according to State criteria or as determined
by the State. The State may extend the 24-hour limit on a case-by-case
basis if the State determines that 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.
    Systems are not required to conduct triggered source water
monitoring if, according to State criteria or a State determination,
the cause of the total coliform-positive sample collected under Sec.
141.21(a) directly relates to the distribution system. If the GWS makes
the decision according to State criteria, the GWS must document the
decision in writing; if the decision is made by the State, the State
must document the decision in writing. In the primacy application, the
State must include criteria that will be used to determine that the
cause of a total coliform-positive sample collected under Sec.
141.21(a) is directly related to the distribution system.
    If the State approves the use of E. coli as a fecal indicator for
triggered source water monitoring, GWSs serving 1,000 people or fewer
may use a TCR repeat sample collected from a ground water source to
simultaneously meet the requirements of Sec.  141.21(b) and satisfy the
GWR's triggered source water monitoring requirements for that ground
water source only.
    If approved by the State, systems with more than one ground water
source may conduct triggered source water monitoring at a
representative ground water source or sources. The State may require
systems with more than one ground water source to submit for approval a
triggered source water monitoring plan that the system will use for
representative sampling. A triggered source water monitoring plan must
identify ground water sources that are representative of each
monitoring site in the system's TCR sample siting plan.
    If any initial triggered source water sample is fecal indicator-
positive, the system must collect five additional source water samples
within 24 hours at that site, unless the State requires immediate
corrective action to address contamination at that site. The samples
must be tested for the same fecal indicator for which the initial
source water sample tested positive.
    Ground water systems that purchase or sell finished drinking water
(referred to as consecutive or wholesale systems, respectively) must
comply with triggered source water monitoring provisions for their own
sources.
    Consecutive and wholesale systems must also comply with other
triggered source water monitoring requirements. A consecutive GWS that
has a total coliform-positive sample collected under Sec.  141.21(a)
(TCR) must notify the wholesale system(s) within 24 hours of being
notified of the total coliform-positive sample. If a wholesale GWS
receives notice from a consecutive system it serves that a sample
collected under Sec.  141.21(a) (TCR) is total coliform-positive, the
wholesale GWS must conduct triggered source water monitoring. If the
sample is fecal indicator-positive, in addition to notifying its own
customers, the wholesale GWS must notify all consecutive systems served
by that ground water source. The consecutive system is responsible for
providing any required public notice to the persons it serves.
    b. Assessment source water monitoring. The GWR provides States with
the option to require systems to conduct assessment source water
monitoring at any time and require systems to take corrective action.
See Section IV.B.2.b for EPA's recommendations of when assessment
source water monitoring may be appropriate and how to structure the
monitoring program. If the State chooses to use HSAs to determine the
appropriateness of assessment source water monitoring, then systems
must comply with State requests for information.
    c. Source water microbial indicators and analytical methods. A
system that collects a source water sample to comply with this rule
must analyze the sample for one of the three fecal indicators (E. coli,
enterococci, or coliphage). Under this rule, GWSs must use one of seven
specified analytical methods for E. coli, one of three methods
specified for enterococci, or one of two methods specified for
coliphage. The system is required to test at least a 100 mL sample
volume for one of the three fecal indicators (E. coli, enterococci, or
coliphage). All analyses must be conducted by a laboratory certified by
the State or EPA.
    d. Invalidation of a fecal indicator-positive ground water source
sample. This rule allows systems to obtain written State invalidation
of a fecal indicator-positive ground water source sample under either
of the following conditions: (1) The system provides the State with
written notice from the laboratory that improper sample analysis
occurred; or (2) the State determines and documents in writing that
there is substantial evidence that a fecal indicator-positive ground
water source sample is due to a circumstance that does not reflect
source water quality. If the State invalidates a fecal indicator-
positive ground water source sample, the system must collect another
ground water source sample within 24 hours of being notified of the
invalidation by the State and have it analyzed for the same fecal
indicator. The State may extend the 24-hour limit on a case-by-case
basis if it determines that the system cannot collect the ground water
source water sample within 24 hours due to circumstances beyond the
system's control. In the case of an extension, the State must specify
how much time the system has to collect the sample.
2. What Is EPA's Rationale for the GWR Source Water Monitoring
Requirements?
    a. Triggered source water monitoring.
    i. Overall basis for provision. The GWR builds on the public health
protection provided by the TCR by requiring systems to collect a ground
water source sample when a TCR distribution system sample is total
coliform-positive. Because a total coliform-positive sample in the
distribution system may be caused by either a distribution system
problem or source water contamination, the GWR triggered source water
monitoring provision is necessary to distinguish between these two
possible sources of fecal contamination. Thus, using the total coliform
indicator is an efficient way to target higher risk systems where
source water monitoring is warranted to investigate potential fecal

contamination. EPA believes that the GWR triggered source water
monitoring provisions provide an effective means for improving public
health protection.
    Total coliform monitoring in the distribution system is already
required under the TCR. Thus, total coliform monitoring provides a no-
cost screening for potential fecal contamination and pathogen
occurrence at the source. Total coliform is a sensitive indicator for
the presence of potential fecal contamination. In the occurrence
studies evaluated for the GWR, wells that were monitored with high
frequency for enterovirus and total coliforms detected both enterovirus
and total coliform in their source water (i.e., Lieberman et al., 2002;
Karim et al., 2004; Wisconsin Department of Health, 2000). Total
coliform presence in source water can also be an indicator of recent
surface and near surface water inflow to ground water, and pathogens
originate at or near the surface.
    Triggered source water monitoring provides an ongoing evaluation of
fecal contamination in the source water of all GWSs. Because well
conditions and sources of fecal contamination can change over time, EPA
believes that the ongoing continuous assessment provided by triggered
source water monitoring is important.
    EPA believes that the triggered source water monitoring
requirements of the GWR will effectively target higher risk GWSs. EPA's
analysis indicates that the triggered source water monitoring
provisions will identify nearly 40 percent of those wells with fecal
contamination in their source water (See Chapter 6 of USEPA, 2006d). In
addition, the wells with the highest frequencies of fecal contamination
occurrence (which EPA believes are the highest risk wells from a public
health perspective) will likely be captured first and wells with less
frequent fecal contamination will be identified over time (USEPA,
2006d).
    ii. Reduced burden for small systems. Under the final GWR, a GWS
serving 1,000 people or fewer may use a TCR repeat sample to
simultaneously meet requirements of the TCR and the GWR. Under the TCR,
when a total coliform sample at a small system (serving 1,000 people or
fewer) is positive, the TCR requires the system to collect four repeat
samples (one upstream and proximate to the initial total coliform-
positive, one at the same location, one downstream and proximate to the
original total coliform-positive, and one at another unspecified
location). If the State approves the use of E. coli as a fecal
indicator for ground water source monitoring, the GWR allows these
small systems to meet the repeat monitoring requirements of Sec.
141.21(b) (TCR) by collecting their unspecified fourth repeat sample at
the ground water source, thereby satisfying the GWR's triggered source
water monitoring requirements for that ground water source at the same
time. The purpose of this provision is to mitigate the triggered fecal
indicator source water monitoring burden for small systems and to
improve upon the diagnostic value of repeat sampling under the TCR.
    The TCR repeat sample can be used for satisfying both the TCR
repeat sample requirement and the initial source water fecal indicator
under the GWR because the TCR methods and requirements provide the
information necessary for complying with the GWR. If the repeat sample
is negative for total coliform bacteria, then it is also negative for
E. coli bacteria, and no further testing under the GWR is required.
Under the TCR, if a repeat sample is positive for total coliform
bacteria, the sample must then be further analyzed for the presence of
either E. coli or fecal coliforms. If the sample is analyzed for E.
coli, that will satisfy the GWR triggered monitoring requirements.
    Total coliform bacteria are a group of bacteria that include E.
coli. The methods approved for the analysis of the water samples taken
under the TCR can be found at Sec.  141.21. Most of these methods are
also approved for E. coli monitoring under the GWR (see Table IV-1 and
Sec.  141.402(c)). The analytical methods approved for use under the
TCR listed in Table IV-1 may all be used for both total coliform
detection, and most can be used for subsequent E. coli detection under
the GWR. Two of the methods approved under the TCR (and listed with an
asterix in Table IV-1) can be used for total coliform detection only.
In these two techniques (one of which is multiple tube fermentation and
the other of which is membrane filtration using m-Endo medium), total
coliforms are first cultured and confirmed. The laboratory analyst
could then proceed to further analyze the total coliform-positive
culture for either fecal coliforms or E. coli by simply choosing which
subsequent medium to inoculate. Testing for fecal coliforms requires
EC-Broth while testing for E. coli requires use of EC-MUG broth. These
two broths are similar, and require the same incubation temperatures
and conditions. The only difference between the two media is the
addition of the substrate 4-methylumbelliferone-[beta]-D-glucuronide
(MUG) to EC Broth, which is added to detect E. coli. Thus, if the State
has approved E. coli as the fecal indicator for the GWR, the E. coli
sample analyzed under the TCR will meet the GWR source water sample
requirements. For the TCR repeat sample, a PWS must collect a 100 mL
water sample and analyze it for total coliform bacteria, and further
analyze it for a fecal indicator if it is total coliform-positive. This
means that small systems (serving 1,000 people or fewer) have no
additional sampling burden or costs from the GWR triggered source water
monitoring requirement for an initial source water sample.

  Table IV-1.--Methods Approved for Detection of Total Coliforms Under the TCR and for the Detection of E. coli
                  Under the GWR (See Sec.   141.402(c) for Details Regarding These Methods) **
----------------------------------------------------------------------------------------------------------------
                                                                            Total
          Method technology type                      Method              coliforms      E. coli       TCR/GWR
                                                                          detected      detected      approval
----------------------------------------------------------------------------------------------------------------
Multiple tube fermentation...............  (LTB/P-A [rarr] BGLB)*.....            X   ............            X
                                           EC-MUG.....................  ............            X             X
                                           NA-MUG.....................  ............            X             X
Enzyme Substrate.........................  Colilert/Colilert-18.......            X             X             X
                                           Colisure...................            X             X             X
                                           E* Colite Test.............            X             X             X
Membrane filtration......................  (m-Endo[rarr]LTB/BGLB)*....            X   ............            X
                                           EC-MUG.....................  ............            X             X
                                           MI Agar....................            X             X             X

                                           m-ColiBlue 24 Test.........            X             X            X
----------------------------------------------------------------------------------------------------------------
* Methods in parentheses detect total coliforms but not E. coli; if a total coliform sample is determined by
  this method in the source water sample, the analyst can choose the appropriate inoculation medium to analyze
  for E. coli.
** If a total coliform sample is determined negative, no further testing under the GWR is required. If it is
  positive, the analyst can choose the appropriate E. coli method.

    iii. Provision for total coliform-positive result directly related
to the distribution system. EPA recognizes that some systems may have a
known problem in their distribution system that causes total coliform-
positive results. In cases when the cause of a total coliform-positive
result collected under Sec.  141.21(a) is directly related to the
distribution system according to State criteria or a State
determination, systems are not required to collect ground water source
samples to investigate potential fecal contamination in the source
water. A State must include in its primacy application the criteria it
will use to determine whether the cause of a total coliform-positive
sample collected under Sec.  141.21(a) is directly related to the
distribution system. Systems will use these criteria to determine if
the cause of a total coliform-positive sample is directly related to
the distribution system. If the sample meets the criteria, the system
is not required to do triggered source water monitoring. The State
needs to determine these criteria as part of their primacy package so
that GWSs that collect a total coliform-positive sample can decide
whether they need to collect a source water sample(s) within the
required 24 hour timeframe. The system must document this determination
to the State within 30 days so the State can ensure that the criteria
are used correctly and that no potential public health risk from source
water contamination has been overlooked. For issues not covered by the
pre-determined criteria, the State can also make a determination that
the cause of the total coliform-positive sample directly relates to the
distribution system.
    iv. Basis for additional fecal indicator sampling following
triggered source water monitoring. Numerous public comments on the
proposal expressed concern that a corrective action should not be
required based on one source water indicator-positive sample, as EPA
proposed for triggered source water monitoring. The rationale for the
proposal was that the likelihood of a false positive result occurring
in both the distribution system sample and the fecal indicator source
water sample would be small, and therefore it would be likely that the
source water positive result was caused by true contamination.
    EPA has re-evaluated the use of repeat samples under the triggered
source water monitoring provisions. Given that total coliform-positives
in the distribution system can result from either distribution system
or source water causes, a total coliform-positive in the distribution
system does not necessarily predict fecal contamination of the source
water. The possibility of false positives at the source and the
associated potential for unnecessary follow-up corrective actions, even
if relatively infrequent, prompted EPA to revise the final rule
triggered source water monitoring provisions to require five additional
samples following the initial positive sample before requiring
corrective action (if one or more additional sample is positive),
unless the State determines that immediate corrective action is
necessary. In addition, the potential cost implications for a
corrective action could be substantial, especially for small systems.
    EPA believes that in most cases these five additional samples
should capture the fecal contamination event since the samples are
taken within 24 hours. Discrete contamination releases, such as fecal
septage, together with discrete precipitation events, become dispersed
by hydrogeological processes over time. As a result, shorter duration
events at the original contamination source may become longer duration
(i.e., days or weeks) but more diluted events at the well. Thus, if an
initial fecal indicator-positive is detected at the well, that
occurrence should be detectable again with additional samples within 24
hours. Nevertheless, since the nature and source of contamination and
the subsurface condition vary from site to site, prompt resampling
within 24 hours is needed to capture events that may not be dispersed
over time. Prompt resampling is particularly important in cases where
the initial sampling event transpires at the tail-end of the well
contamination event.
    b. Assessment source water monitoring. As a complement to the
triggered source water monitoring provision, States have the option of
requiring systems to conduct assessment source water monitoring. This
flexible provision gives States the opportunity to target higher risk
systems for additional source water monitoring and require corrective
action, if necessary. EPA decided not to include requirements for
assessment source water monitoring in the GWR for the reasons given in
Section II.C of the preamble. Rather, EPA decided to give States
flexibility to require assessment source water monitoring on a case-by-
case basis. The purpose for this optional source water monitoring
provision is to target systems that the States believe are at high risk
from fecal contamination for a thorough evaluation of source water
quality. Also, this allows lower risk GWSs to avoid unnecessary
sampling (as determined by States).
    While EPA believes that triggered source water monitoring will
capture many high risk systems, EPA also recognizes that the triggered
source water monitoring provisions have limitations. Triggered source
water monitoring under the TCR may not be timely (soon enough) or
frequent enough to identify systems with intermittent fecal
contamination. Also, coliforms are not a good indicator in certain
aquifers in which viruses travel faster and further than bacteria. EPA
believes that assessment source water monitoring can be an important
complement to triggered source water monitoring because assessment
source water monitoring provides a thorough examination of the source
water at those systems that States deem to be at potentially high risk
from fecal contamination. The flexibility of this requirement allows
States to require assessment source water monitoring when and where it
is needed most. Source water quality can change over time, so it is
important for States to be

able to use assessment source water monitoring at any point in time.
State programs work closely with PWSs on a daily basis and are thus
knowledgeable about system specific conditions and issues. Therefore,
EPA believes that the States are in the best position to assess for
which systems the thorough evaluation of source water quality provided
by assessment source water monitoring is most appropriate. EPA believes
that assessment source water monitoring programs within the States'
discretion will be important to identify fecally contaminated systems
for which corrective action is necessary to protect public health. EPA
expects that States may use assessment source water monitoring for
high-risk systems that are potentially susceptible to fecal
contamination, especially where contamination is often present but
intermittent enough to be missed by triggered source water monitoring.
    i. EPA's recommendations for targeting systems for assessment
source water monitoring. Information on a system's potential
susceptibility to fecal contamination is available to the States from
many sources. For example, HSAs, source water assessments, wellhead
protection plans, past microbial monitoring data particularly triggered
source water monitoring results and frequency, and sanitary survey
findings are available to States. In addition to these sources of
information, EPA recommends that States consider the following risk
factors in targeting susceptible systems for assessment source water
monitoring: (1) High population density combined with on-site
wastewater treatment systems, particularly those in aquifers with
restricted geographic extent, such as barrier island sand aquifers; (2)
aquifers in which viruses may travel faster and further than bacteria
(e.g. alluvial or coastal plain sand aquifers); (3) shallow unconfined
aquifers; (4) aquifers with thin or absent soil cover; (5) wells
previously identified as having been fecally contaminated; and (6)
sensitive aquifers. These factors are described in more detail below.
    Some localities may be at high risk because they serve large,
sometimes seasonal, populations in areas without centralized sewage
treatment and their aquifers are of restricted geographic extent, such
as barrier island sand aquifers and Great Lakes island karst limestone
aquifers. In these locations, the large population using septic tanks
can overload the subsurface attenuation capability. Outbreaks have
occurred in such resort communities (e.g., South Bass Island, OH, Ohio
EPA, 2005, CDC, 2005; Drummond Island, MI, Ground Water Education in
Michigan, 1992; Chippewa County Health Department, unpublished report,
1992) due to overloaded septic tanks.
    Viruses travel faster and further than bacteria in some aquifers.
In barrier island sand aquifers, traditional bacterial fecal indicator
organisms such as total coliform and E. coli may not be mobile or
sufficiently long-lived in the subsurface so as to adequately indicate
the hazard from longer-lived and more mobile viral pathogens. Thus, a
system could have fecal contamination and yet not be triggered for
source water monitoring by TCR monitoring results. In such cases,
assessment source water monitoring using coliphage would be the best
means for identifying fecal contaminants because coliphage is a viral
fecal indicator and thus is more likely to reach the well than
bacterial indicators such as E. coli and enterococci.
    Shallow, unconfined aquifers are high risk because the vertical
flow path to the aquifer is short and unrestricted by barriers.
Pathogens originate at or near the surface and may be more likely to
contaminate well water when the travel time for infiltrating
precipitation is short and unhindered.
    Wells previously identified as having been fecally contaminated
should be considered high risk because such fecal contamination can
reoccur. For example, wells in this category may include wells
associated with a previous acute TCR violation related to the source or
those wells that had an initial fecal indicator-positive triggered
source water sample but had five negative additional samples
(especially wells with highly variable source water such as those in
sensitive aquifers). Wells with highly variable source water may be
subject to occasional short-lived contamination events. Thus it is
possible to have a true fecal indicator-positive sample followed by
true fecal indicator-negative samples. Exposures during intermittent
contamination events can be significant, so it is important to identify
such high-risk systems. This is best accomplished through a thorough
source water evaluation program such as assessment source water
monitoring.
    Sensitive aquifers (e.g., karst, fractured bedrock, or gravel) can
have fast (kilometers per day) and direct ground water flow through
large interconnected openings (void spaces) during which very little
pathogen attenuation may occur (either by natural inactivation or
attachment) between a fecal source of contamination and the well.
Consequently, sensitive aquifers are efficient at transmitting
pathogens, if present, from surface and near-surface sources to PWS
wells. Ground water flow in non-sensitive aquifers (such as a sand
aquifer) tends to be very slow (feet per day), takes a very indirect
path around a very large number of sand grains, and provides more
opportunities for pathogen die-off and attachment. The faster flow
travel time within a sensitive, as opposed to a non-sensitive, aquifer
enables a much larger contaminant plume from potential fecal
contamination events (e.g., failing septic systems or a leaking sewer
line).
    When ground water flow is fast and direct as in sensitive aquifers,
contamination can be short and intermittent and difficult to capture.