National Primary Drinking Water Regulations: Ground Water Rule, 65574-65660 [06-8763]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 71, Number 216 (Wednesday, November 8, 2006)]
[Rules and Regulations]
[Pages 65574-65660]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-8763]



[[Page 65573]]

-----------------------------------------------------------------------

Part II





Environmental Protection Agency





-----------------------------------------------------------------------



40 CFR Parts 9, 141, and 142



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

Federal Register / Vol. 71, No. 216 / Wednesday, November 8, 2006 / 
Rules and Regulations

[[Page 65574]]


-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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 https://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 https://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 https://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: (202) 564-5275; e-mail address: 
rodgers.crystal@epa.gov. For general information, contact the Safe 
Drinking Water Hotline, telephone number: (800) 426-4791. 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

[[Page 65575]]

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

[[Page 65576]]

    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

[[Page 65577]]

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

[[Page 65578]]

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

[[Page 65579]]

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

[[Page 65580]]

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.

[[Page 65581]]

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.

BILLING CODE 6560-50-P

[[Page 65582]]

[GRAPHIC] [TIFF OMITTED] TR08NO06.000

BILLING CODE 6560-50-C

    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

[[Page 65583]]

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

[[Page 65584]]

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 wate