4
        United States
        Environmental Protection
        Agency
 5  GROUND WATER RULE
 6  TRIGGERED AND REPRESENTATIVE SOURCE
 7  WATER MONITORING GUIDANCE MANUAL (DRAFT)
 9
10  December 2008
11  Public Review Draft
12
13  EPA815-D-08-004

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 1                                       DISCLAIMER
 2
 O
 4    The statutory provisions and U.S. Environmental Protection Agency (EPA) regulations described
 5    in this document contain legally binding requirements. This guidance is not a substitute for
 6    applicable legal requirements, nor is it a regulation itself. Thus, it does not impose legally-
 7    binding requirements on any party, including EPA, states, or the regulated community. While
 8    EPA has made every effort to ensure the accuracy of the discussion in this guidance, the
 9    obligations of the regulated community are determined by statutes, regulations, or other legally
10    binding requirements. In the event of a conflict between the discussion in this document and any
11    statute or regulation, the statute and regulation, not this document, would be controlling.
12
13    Interested parties are free to raise questions and objections to the guidance and the
14    appropriateness of using it in a particular situation.
15
16    Although this manual describes suggestions for complying with Ground Water Rule (GWR)
17    requirements, the guidance presented here may not be appropriate for all situations,  and
18    alternative approaches may provide satisfactory performance.
19
20    Mention of trade names or commercial products does not constitute an EPA endorsement or
21    recommendation for use.
22
23    Comments on this document should be addressed to:
24
25    Jeremy Bauer
26    U.S. EPA
27    2218B, EPA East: MC-4607M
28    1201 Constitution Ave, N.W.
29    Washington, DC 20460-0001
30    bauer.jeremy@epa.gov
31    202-564-2775
32    202-564-3767 (facsimile)
33
34
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 1                                         CONTENTS
 2
 O
 4    Exhibits	iii
 5    Acronyms	iv
 6
 7    1. Introduction	1
 8      1.1 Purpose of this Document	2
 9      1.2 Data Needed to Support Representative Monitoring Decisions	2
10      1.3 Organization of this Guidance Manual	3
11
12    2. Ground Water Rule Requirements	1
13      2.1 Sanitary Surveys	3
14      2.2 Source Water Monitoring	3
15        2.2.1 Triggered source water monitoring	3
16        2.2.2 Additional source water monitoring	4
17        2.2.3 Assessment source water monitoring	4
18      2.3 Corrective Action	4
19      2.4 Compliance Monitoring	5
20
21    3. Representative Source Water Monitoring	1
22      3.1 Wells Representing Coliform Monitoring Locations in the Distribution System	2
23      3.2 Wells Representing Other Wells	3
24      3.3 Triggered Source Water Monitoring Plan	3
25
26    4. Wells Representing Coliform Monitoring Locations in the Distribution System	1
27      4.1 Linking Sources to TCR Sites	1
28      4.2 Tools	2
29        4.2.1 Distribution system maps	2
30        4.2.2 Coliform sample siting plan	4
31        4.2.3 Operations records	5
32        4.2.4 Distribution system hydraulic models	5
33        4.2.5 Distribution system tracer studies	6
34        4.2.6 Customer complaint records	6
35        4.2.7 Water quality parameters	7
36      4.3 Criteria to Include in the Plan	7
37
38    5. Wells Representing other Wells	1
39      5.1 Physical Properties	1
40        5.1.1 Well proximity to  other wells	1
41        5.1.2 Well construction	2
42        5.1.3 Water chemistry	4
43          5.1.3.1    Total Dissolved Solids	5
44          5.1.3.2   Nitrates	5
45      5.2 Hydrogeological Representativeness	6
46        5.2.1 Aquifer type and driller's logs	6
47        5.2.2 Additional data	9

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 1           5.2.2.1    Hydrogeologic data sources	9
 2        5.3.2 Capture zone models	16
 3
 4    6.      Approval of Representative Wells	1
 5      6.1   Reviewing the Proposal	1
 6        6.1.1 Technical considerations when reviewing proposals for representative monitoring	1
 7        6.1.2 Ensuring the proposal is complete	2
 8           6.1.2.1    Wells representing coliform monitoring locations in the distribution system... 3
 9           6.1.2.2    Wells representing other wells	4
10      6.2  Notifying the System and Recordkeeping Associated with a Representative Monitoring
11      Decision	5
12
13    Appendix A:  Examples of Three Triggered Source Water Monitoring Plans	A-l
14    Appendix B:  Example Triggered Source Water Monitoring Plan (Template)	B-l
15
16
17
18
19
20
21
22
23
24
25
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 1                                         EXHIBITS
 2
 O
 4   Exhibit 2.1: Summary of GWR Requirements	2-2
 5   Exhibit 3.1: Simplified Representative Monitoring Scenarios	3-2
 6   Exhibit 4.1: Example Distribution System Map	4-4
 7   Exhibit 4.2: Total Coliform Sample Site Locations	4-5
 8   Exhibit 4.3: Example Triggered Source Water Map and Table	4-9
 9   Exhibit 5.1: Potentially Good Candidates for Representative Sampling	5-3
10   Exhibit 5.2: Inappropriate Candidates for Representative Sampling	5-3
11   Exhibit 5.3: Wells in Close Proximity Not Representative Due to Fractured Bedrock	5-4
12   Exhibit 5.4: Wells Screened in aKarst Aquifer Overlain by a Continuous Layer	5-8
13   Exhibit 5.5: Wells Screened in a Karst Aquifer Overlain by a Discontinuous Layer	5-8
14   Exhibit 5.6: Strike and Dip	5-12
15   Exhibit 5.7: The Importance of Map Scale for Determining Aquifer Type	5-14
16
17
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1
2
                                        ACRONYMS
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
AWWA
AWWARF
ASTM
CDC
CCR
CFR
CT

CWS
OEMs
DLGs
DMA
EPA
EROS
ESICs
FR
GPS
GWR
GWS
GWUDI
HSA
HPC
LCR
NAPP
NCGMP
NCWS
NRC
NRCS
PWS
QA
QC
RASA
SDWA
Stage 1 DBPR
Stage 2 DBPR
SWAP
TC
TCR
TDS
USDA
USGS
UV
WHPAs
WHPP

American Water Works Association
American Water Works Association Research Foundation
American Society of Testing Materials
Centers for Disease Control and Prevention
Consumer Confidence Report
Code of Federal Regulations
The Residual Concentration of Disinfectant (mg/L) Multiplied by the
Contact Time (in minutes)
Community Water System
Digital Elevation Models
Digital Line Graphs
Defense Mapping Agency
United States Environmental Protection Agency
Earth Resources Observation Systems
Earth Science Information Centers
Federal Register
Global Positioning System
Ground Water Rule (40 CFR Part 141 Subpart S)
Ground Water System
Ground Water Under the Direct Influence of Surface Water
Hydrogeologic Sensitivity Assessment
Heterotrophic Plate Count
Lead and Copper Rule (40 CFR Part 141 Subpart I)
National Aerial Photography Program
National Cooperative Geologic Mapping Program
Non-Community Water System
National Research Council
National Resources Conservation Service
Public Water System
Quality Assurance
Quality Control
Regional Aquifer-System Analysis
Safe Drinking Water Act
Stage 1 Disinfectants and Disinfection Byproducts Rule
Stage 2 Disinfectants and Disinfection Byproducts Rule
Source Water Assessment Program
Total Coliform
Total Coliform Rule (40 CFR Part 141 Subpart C)
Total Dissolved Solids
United States Department of Agriculture
United States Geological Survey
Ultraviolet
Wellhead Protection Areas
Wellhead Protection Program

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                                                     IV
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 1                                  Additional Information
 2
 O
 4   For more information, contact EPA's Safe Drinking Water Hotline at 1-800-426-4791, or see the
 5   Office of Ground Water and Drinking Water Web page at http://www.epa.gov/safewater.
 6
 7   This guidance manual is available electronically at:
 8          http://www.epa.gov/safewater/disinfection/gwr/compliancehelp.html.
 9
10   To order a paper copy of guidance manuals, you may contact the US EPA Water Resource
11   Center at 202-566-1729 or by mail at:
12
13          US Environmental Protection Agency
14          Water Resource Center (RC-4100)
15          1200 Pennsylvania Ave NW
16          Washington, DC 20460
17          E-mail: center.water-resource@epa.gov
18
19   Guidance Manuals and Materials for the Ground Water Rule
20
21   EPA is developing a series of guidance documents to help public water systems implement
22   requirements associated with the Ground Water Rule. Electronic versions of the guidance
23   documents are, or will be, available on the Ground Water Rule Compliance Help page at
24   http://www.epa.gov/safewater/disinfection/gwr/compliancehelp.html.
25
26          Complying with the Ground Water Rule: Small Entity Compliance Guide (EPA
27          815-R-07-018) - This guide is designed for owners and operators of public water systems
28          serving 10,000 or  fewer persons that are required to comply with the Ground Water Rule.
29
30          Ground Water Rule Corrective Actions Guidance Manual (EPA 815-R-08-011) -
31          This manual provides information for ground water systems that must provide corrective
32          action as a result of significant deficiencies or fecally-contaminated source water. The
33          guidance includes technical information on selecting  appropriate disinfection
34          technologies to enable primacy agencies and public water systems to select the treatment
35          most appropriate for a given system.  It also provides technical information to states and
36          systems on eliminating sources of contamination, utilizing  alternate sources, and
37          correcting significant deficiencies for situations in which disinfection is not the selected
3 8          corrective acti on.
39
40          Sanitary Survey Guidance Manual for Ground Water Systems (EPA 815-R-08-015)
41          - This guidance provides information to assist states and other primacy programs in
42          conducting sanitary surveys of ground water systems.
43
44          Ground Water Rule Source Water Monitoring Methods Guidance Manual (EPA
45          815-R-07-019) - This manual provides guidance on triggered and optional assessment
46          source water monitoring issues such as: selection of fecal indicators, sample collection
47          and shipping, source water monitoring methods, laboratory quality assurance (QA) and
48          quality control (QC),  and evaluation of fecal indicator data. This  manual also provides an
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 1          overview of Ground Water Rule requirements and includes frequently asked questions
 2          regarding source water monitoring.
 3
 4          Ground Water Rule Source Assessment Guidance (EPA 815-R-07-023) - This
 5          manual provides information on procedures for identifying ground water sources at risk
 6          for fecal contamination. Risk factors are discussed with emphasis on identifying readily
 7          available factors suitable for desk-top rather than field evaluation of individual public
 8          water system wells.  The guidance also lists sources of information for making a risk
 9          determination, and includes field methods for determining the presence of a
10          hydrogeologic barrier.
11
12          Consecutive System Guide for the Ground Water Rule (EPA 815-R-07-020) - This
13          guidance describes the regulatory requirements of the Ground Water Rule that apply to
14          wholesale ground  water systems and their consecutive systems.
15
16    Other Guidance Manuals and Materials
17
18    EPA has developed other guidance manuals to aid EPA, state agencies, and water systems in
19    implementing the Ground Water Rule and other rules, and to help to ensure consistent
20    implementation.
21
22          Consider the Source: A Pocket Guide to Protecting Your Drinking Water Pocket
23          Guide #3 (EPA 816-K-02-002) - An electronic version is available at
24          http://www.epa.gov/safewater/sourcewater.
25
26          Revised Public Notification Handbook (EPA 816-R-07-003) - An electronic version is
27          available at http://www.epa.gov/safewater/publicnotification/compliancehelp.html.
28
29          Preparing Your Drinking Water Consumer Confidence Report (CCR), Revised
30          Guidance for Water Suppliers (EPA 816-R-002) - This document provides
31          information to assist drinking water  systems with preparing and distributing Consumer
32          Confidence Reports.  An electronic version is available at
33          http://www.epa.gov/safewater/ccr/compliancehelp.html.
34
35          Consumer Confidence Report Rule: A Quick Reference Guide (EPA 816-F-02-026)
36          - A condensed guide that provides a brief overview of the Consumer Confidence Report
37          Rule. An electronic version is available at
38          http://www.epa.gov/safewater/ccr/compliancehelp.html.
39
40          Surface Water Treatment Rule Guidance Manual - The Appendices include CT
41          tables for the inactivation of Giardia and viruses for chlorine, chlorine dioxide and
42          ozone. An electronic version is available at
43          http://www.epa.gov/safewater/mdbp/guidsws.pdf
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 1                                        1. Introduction
 2
 O
 4          EPA developed the Ground Water Rule (GWR) to provide for increased public health
 5    protection for consumers of water from public water systems that use ground water.  A key
 6    element of the GWR is to identify public ground water sources that are susceptible to fecal
 7    contamination. The GWR also ensures that these systems take corrective action to eliminate the
 8    source of contamination or to remove or inactivate pathogens in the drinking water they provide
 9    to the public.  Fecal contamination is a broad term that refers to microbial contaminants from
10    human or animal feces. It is a likely source of viral and bacterial  pathogens in drinking water.
11    These microbial pathogens are a significant threat to public health because they can cause serious
12    illness and even death when consumed.
13
14          Fecal contamination may be introduced into finished ground water via inadequately
15    treated or inadequately protected source water or from problems in the distribution system.
16    Common sources of ground water contamination include septic systems, leaking sewer pipes,
17    landfills, sewage lagoons, storm water runoff, and improperly abandoned wells. Microbial
18    contamination in an aquifer can be localized or may be transported as water moves through the
19    aquifer.
20
21          The GWR requires ground water systems (GWSs) that either inadequately treat to control
22    viral pathogens (i.e., less than  4-log removal, inactivation, or state-approved combination of
23    these) or that do not perform compliance monitoring of treatment to sample their source water
24    for the presence of a fecal indicator when total coliform bacteria are detected in the distribution
25    system. This monitoring requirement is triggered by the results of routine coliform sampling
26    performed for compliance with the Total Coliform Rule (TCR). The triggered monitoring
27    requirement is designed to allow systems and states to identify and to correct public health risks
28    from fecal contamination  found at the source. Additionally, assessment source water monitoring
29    may be required for specific systems at the state's discretion. Assessment source water
30    monitoring is routine monitoring of the system's specified ground water source(s) for a fecal
31    indicator at the frequency and  duration determined by the state.
32
33          If approved by the state, systems with more than one ground water source may conduct
34    triggered  source water monitoring at a representative ground water source or sources. The state
35    may require systems with more than one ground water source to submit for approval a triggered
36    source water monitoring plan that the system will use for representative sampling. A triggered
37    source water monitoring plan must identify ground water sources that are representative of each
38    monitoring site in the system's TCR sample siting plan. EPA believes that this alternative can be
39    as protective of public health as monitoring all wellheads, provided that the chosen wells are
40    truly representative of all wellheads. In addition, for situations where a particular  sample site is
41    inaccessible, the  state may identify an alternate sampling site that is representative of the water
42    quality of the ground water at the inaccessible sample site.
43
44          Representative source water monitoring  for the GWR, also called representative
45    monitoring, falls within one of two categories:
46
47
48   	
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 1
 2
 3           1. Wells representing coliform monitoring locations in the distribution system.  This
 4           relates to situations in which a system has more than one source but not all sources are
 5           hydraulically able to provide water to each total coliform sample collection site in the
 6           distribution system.  In this case, if approved by the state, only those sources that
 7           hydraulically represent (or provide water to) a specific total coliform sample site would
 8           need to be sampled under the triggered monitoring provision of GWR if a routine sample
 9           from that site were total coliform-positive.
10
11           2. Wells representing other wells.  This relates to situations in which a system has
12           multiple sources and some are so similar (e.g., physically and hydrogeologically) that a
13           reasonable case could be made that one source may be representative of another or of
14           others with regard to the risk of fecal contamination.  In this case, one or more of the
15           sources would be sampled to indicate the source water quality of all of the representative
16           sources. If approved by the state, representative sources based  on physical and
17           hydrogeological properties could be used for triggered monitoring and for assessment
18           source water monitoring.
19
20    1.1    Purpose of this Document
21
22           The purpose of this guidance manual is to provide GWSs and states with
23    recommendations and  examples of the types of information, data, and tools that might be used to
24    demonstrate the appropriateness of representative source water monitoring.  Because every
25    system has unique well locations, distribution system hydraulics, and aquifer hydrogeologic
26    characteristics, a decision of whether representative monitoring adequately protects public health
27    should be made on a case-by-case basis by the state or primacy agency.
28
29           Although some GWSs may have a wealth of information on which to base representative
30    monitoring requests, many, if not most,  GWSs likely have little data but might still be able to
31    make a good case for representative monitoring. This guidance is designed to show the various
32    ways that systems, working with their primacy agency, might use the information at their
33    disposal to demonstrate whether representative monitoring is an appropriate option.
34
35    1.2    Data Needed to Support Representative Monitoring Decisions
36
37           The type and amount of evidence systems will utilize to make their case for
38    representative monitoring is likely to vary depending on the characteristics of the specific
39    system.  For example,  a large system with multiple, interconnected pressure zones might utilize a
40    complicated distribution system model to identify sources that are hydraulically representative of
41    each routine total coliform  sample site.  In contrast, a less complex system might be able to make
42    the same point with a simple map of the distribution system, which includes locations of the
43    system's wells, critical valves, and pressure zones.  Similarly, existing  information on each
44    well's zone of influence, construction details, source water chemistry, and aquifer characteristics
45    may provide sufficient information to support evaluation of source physical and hydrogeological
46    representativeness.
47

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 1          As discussed in Chapter 3, the suggested steps for identifying representative sources
 2    begins by initially grouping those that appear similar to each other using the most readily
 3    available information.  The grouped wells are then compared using sequentially more complex
 4    information. The overall recommended process is one of elimination - removing wells from
 5    consideration that would not be representative of other wells with regard to the risk of fecal
 6    contamination. It is recommended that water system operators work deliberately through the
 7    suggestions addressed  in this guidance, gather any information at their disposal, and exercise and
 8    document their conclusions based on their best professional judgment.
 9
10          Ultimately, each state will decide  if the specifics of a particular system warrant
11    representative monitoring and  should give approval for representative monitoring accordingly.
12    The GWR has granted states flexibility on representative monitoring in that it is not an all-or-
13    nothing approval process. For systems that are interested in sampling at representative well(s),
14    state approval of representative monitoring is required before it can be applied by a system;
15    therefore, a GWS must conduct triggered monitoring at each source prior to state approval.
16
17    1.3    Organization of this Guidance Manual
18
19          The remaining  six chapters and the two appendices of this guidance manual are organized
20    as follows:
21
22         Chapter 2 - Ground Water Rule Requirements: Provides a brief overview of the
23          GWR and how source water monitoring fits into the other regulatory requirements.
24
25         Chapter 3 - Representative Source Water Monitoring: Provides an overview of the
26          different types  of representative monitoring applicable to the GWR. The types include
27          wells representing coliform monitoring locations in the distribution system and wells
28          representing other wells. This chapter also describes the critical elements of a triggered
29          source water monitoring plan, which some states may require from systems in order to
30          qualify for representative source water monitoring.  The chapter also includes a general
31          outline of steps that may be followed to determine whether representative monitoring is
32          appropriate for a GWS. Details of the outlined steps are discussed in subsequent
33          chapters.
34
35         Chapter 4 - Wells Representing Coliform Monitoring Locations in the Distribution
36          System: Examines what information on distribution system hydraulics may be useful and
37          how it may be applied when considering whether some but not all sources are
38          representative of specific routine total coliform sampling sites.
39
40         Chapter 5 - Wells Representing Other Wells: Discusses various source water
41          chemistry, well construction details, and hydrogeological data useful when considering
42          whether a source is representative of the fecal contamination health risk of multiple
43          sources.  This chapter is applicable to both triggered source water monitoring and
44          assessment source water monitoring.
45
46         Chapter 6 - Approval of Representative Wells: Examines information a state might
47          consider when  deciding whether to approve representative monitoring.

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 2         Appendix A - Examples of Three Triggered Source Water Monitoring Plans:
 3          Presents three example case studies of hypothetical systems pursuing representative
 4          monitoring.
 5
 6         Appendix B - Example Triggered Source Water Monitoring Plan (Template):
 7          Provides a blank template to help water systems develop a Triggered Source Water
 8          Monitoring Plan.
 9
10
11
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 1                           2. Ground Water Rule Requirements
 2
 O
 4          EPA published the Ground Water Rule (GWR) in the Federal Register on November 8,
 5    2006 (Federal Register Volume 71, Number 216, 65574) and a rule correction on November 21,
 6    2006 (Federal Register Volume 71, Number 224, 67427). Copies of the Federal Register are
 7    available at:
 8
 9         http://www.epa.gov/fedrgstr/EPA-WATER/2006/November/Dav-08/w8763.pdf
10         http://www.epa.gov/fedrgstr/EPA-WATER/2006/November/Dav-21/w8763.pdf
11
12          The GWR addresses source water fecal  contamination in systems that use wells or other
13    ground water sources. The rule applies to all public water systems (PWSs) including community
14    and non-community systems regardless of size that:
15
16         Rely entirely on one or more ground water sources;

17         Are consecutive systems that receive finished ground water; or

18         Mix surface and ground water, where ground water is added directly to the distribution
19          system and provided to consumers without treatment equivalent to the treatment required
20          for surface water.
21
22          The GWR does not apply to PWSs that combine all of their ground water with surface
23    water before treatment. The GWR also does not apply to systems using ground water sources
24    that have been determined by the state to be ground water under the direct influence of surface
25    water (GWUDI). A GWUDI source refers to any water beneath the surface of the ground with
26    significant occurrence of insects or other macroorganisms, algae, or large-diameter pathogens
27    such  as Giardia lamblia or Cryptosporidium, or significant and relatively rapid shifts in water
28    characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to
29    climatological or surface water conditions (40 CFR 141.2).  Direct influence must be determined
30    for individual  sources in accordance with criteria established by the State. These sources are
31    subj ect to the treatment requirements of surface water systems.
32
33          For the purposes of this document, the term "ground water system" (or GWS) will be
34    used  to refer to a system to which the GWR applies.  Key provisions of the GWR include:
35
36         Periodic on-site reviews and inspections of GWSs addressing eight specific sanitary
37          survey elements to evaluate the system for the presence of significant deficiencies.
38         Source water monitoring either through triggered monitoring or state-directed assessment
39          monitoring to test for the presence of one of three fecal indicators (E. coli, enterococci, or
40          coliphage).

41         Requirements to correct significant deficiencies and eliminate or treat for fecal
42          contamination through specified actions.

43         Compliance monitoring to ensure that treatment technologies, installed to treat drinking
44          water,  reliably achieve at least 99.99 percent (4-log) inactivation or removal of viruses.
45
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1
2
3
4
5
           GWSs must comply, unless otherwise noted, with the GWR beginning December 1,
2009.  The flow chart provided in Exhibit 2.1  includes a summary  of the GWR requirements.

                                Exhibit 2.1: Summary of GWR Requirements
1

Conduct routine sampling
underthe Tata! Coliforrn Rule
(TCR)
                                                        Initial and periodic sanitary surveys performed by the State
                                                       * Community water systems (CWSs) every 3-5 years
                                                         Non-community water systems (NCWSs) every 5 years
                                                          Consult State within 30 days of notification regarding
                                                              appropriate corrective action, if necessary
                                                        Implement State approved or specified corrective actions
                                                                       Options include

                                                        Eliminate source of contamination
                                                        Correct significant deficiency
                                                        Provide an alternate water source
                                                        Provide treatment to achieve 4-log reduction of viruses
                                                                  Complete or be in accordance
                                                                  with State-specified corrective
                                                                  action within 120 days of initial
                                                                  notification of contamination or
                                                                     significant deficiency
                                                                                    M*.
                                                                 ' Continue State-re quired GWR
                                                                  compliance sanitary surveys,
                                                                   triggered monitoring, TCR
                                                                       compliance, and
                                                                    assessment monitoring

1
Alternative
Treatment
1
Monitor the
alternative
treatment
process in
accordance
with State-
specified
requirements




*
Che mi ca 1
Disinfection
1

f~ ^
Serving
3,300
people
Monitor
residual
disinfectant
daify via grab
sample at
peak flow

Serving
>3,3QO
people
Continuously
monitor
residual
disinfectant


1
Membrane
Filtration
|
Monitorthe
filtration
process in
accordance
with State -
specified
requirements
                                                                        (1)The GWR applies to all public water systems (PWSs) that use ground
                                                                           water, except public water systems that combine all of their ground water
                                                                           with surface water or with ground water under the direct influence of surface
                                                                           water prior to treatment.

                                                                        (2) Treatment using inactivation, removal, or State-approved combination to
                                                                           achieve a 4-log reduction of viruses before or at the first customer Compliance
                                                                           monitoring required

                                                                        (3) If the State determines that the distribution system is deficient or causes total
                                                                           coliform-positive samples, the system may be exempted from triggered source
                                                                           water monitoring

                                                                        (4) The State must provide the GWS with written notice describing any significant
                                                                           deficiencies within 30 days of identifying the significant deficiency
       Ground Water Rule
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 1    2.1    Sanitary Surveys
 2
 3          Under the GWR, states are required to conduct regular comprehensive sanitary surveys.
 4    GWSs must provide, at the state's request, any existing information that would allow the state to
 5    perform a sanitary survey.  If a significant deficiency is identified, either during a sanitary survey
 6    or at any other time, the GWS is required to take corrective action. Failure to complete the
 7    required corrective action will result in a treatment technique violation. "Significant
 8    deficiencies" include, but are not limited to, defects in  design, operation, or maintenance, or a
 9    failure or malfunction of the sources, treatment, storage, or distribution system that the state
10    determines to be causing, or have the potential for causing, the introduction of contamination
11    into the water delivered to consumers.
12
13          The sanitary surveys must be conducted, at a minimum, every three years for community
14    GWSs and every five years for noncommunity GWSs and must include a review of eight critical
15    elements, as applicable to the system. The eight elements are:
16
17         Source (protection,  physical components, and condition)
18         Treatment
19         Distribution System
20         Finished Water Storage
21         Pumps, Pump Facilities, and Controls
22         Monitoring, Reporting, and Data Verification
23         Water System Management and Operations
24         Operator Compliance with State Requirements
25
26          The state may reduce the frequency of sanitary  surveys for community GWSs to at least
27    once every five years if the community GWS has an outstanding performance record as
28    determined by the state, or the community GWS is providing 4-1 og treatment of viruses and
29    conducting compliance monitoring of the treatment system under the GWR.
30
31    2.2    Source Water Monitoring
32
33          The GWR has three general categories of ground water source microbial monitoring
34    requirements: 1) triggered source  water monitoring, 2) additional source water sampling, and 3)
35    assessment source water monitoring. GWSs conducting source water monitoring under the
36    GWR must collect and analyze at least 100 mL of source water for one of three fecal indicators
37    (E. co//', enterococci, or coliphage) using one of the analytical methods specified in the GWR.
38
39    2.2.1  Triggered source water monitoring
40
41          Any GWS that does not provide at least 4-log treatment of viruses before or at the first
42    customer or does not conduct compliance monitoring of the treatment system as specified by
43    GWR must comply with the triggered source water monitoring requirement.  When a GWS is
44    notified  of a total coliform-positive routine sample, the GWS must collect at  least one sample
45    from each ground water source in use at the time the total coliform-positive routine sample was
46    collected, unless the system has approval from the state to do otherwise. If approved by the
47    state, systems with more than one ground water source may conduct triggered source water

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 1    monitoring at a representative ground water source or sources.  The state may require systems
 2    with more than one ground water source to submit for approval a triggered source water
 3    monitoring plan that the system will use for representative sampling. When it is required by the
 4    state, a triggered source water monitoring plan must identify ground water sources that are
 5    representative of each monitoring site in the system's TCR sample siting plan.
 6
 7          Each triggered source water sample must be analyzed for the presence of an approved
 8    fecal indicator.  If a triggered source water sample is fecal indicator-positive, the GWS must
 9    either take corrective action, as directed by the state, or, if corrective action is not required and
10    the sample is not invalided by the state, the GWS must collect five additional  source water
11    samples.
12
13    2.2.2  Additional source water monitoring
14
15          If the state does  not require corrective action in response to a fecal indicator-positive
16    triggered source water sample, the GWS must collect five additional source water samples from
17    each fecal indicator-positive source within 24 hours of being notified of the fecal indicator-
18    positive result. All five of the additional samples must be analyzed for the presence of a fecal
19    indicator.  If any of the five additional source water samples is fecal indicator-positive, the GWS
20    must take corrective action.
21
22    2.2.3  Assessment source water monitoring
23
24          As a  complement to the triggered source water monitoring provision, states may require
25    GWSs to conduct  assessment source water monitoring, as needed.  The purpose of optional
26    assessment monitoring is to allow states to target monitoring of GWSs that the state believes are
27    at higher risk for fecal contamination. As discussed in the preamble of the GWR, EPA
28    recommends that states  require systems that are conducting  assessment source water monitoring
29    to collect a total of 12 ground water source samples that represent each month the system
30    provides ground water to the public.  However, the state determines the requirements for
31    assessment source water monitoring, including the number of samples and their sampling
32    interval and whether one or more wells within the GWS could be sampled to physically and
33    hydrogeologically represent multiple wells.
34
35    2.3    Corrective Action
36
37          GWSs must take corrective action if any one of the three situations applies:
38
39         A significant deficiency is identified,

40         A triggered source sample has tested positive for a fecal indicator and corrective action is
41          required by the state, or

42         At least one of the five additional source water samples collected in response to a fecal
43          indicator-positive triggered sample has also tested positive for a fecal indicator.
44
45          If corrective action is required, the GWS  must consult with the state regarding the
46    necessary action or implement at least one of the following, as directed by the state:
47
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 1          Correct all significant deficiencies
 2          Provide an alternate source of water

 3          Eliminate the source(s) of contamination

 4          Provide treatment that reliably achieves at least 4-log treatment of viruses at or before the
 5           first customer (using inactivation, removal, or a state-approved combination of 4-log
 6           virus inactivation and removal) and conduct compliance monitoring.
 7
 8    2.4     Compliance Monitoring
 9
10           Compliance monitoring for the GWR refers to monitoring the effectiveness or reliability
11    of the treatment system installed to ensure 4-log removal or inactivation, or a combination of
12    removal and inactivation, of viruses. Only wells that provide 4-log treatment of viruses and that
13    perform compliance monitoring are excluded from the triggered source water monitoring
14    requirements of GWR.
15
16           To not be subject to triggered source water monitoring, by December 1, 2009, a GWS
17    must notify the state that it provides at least 4-log treatment of viruses before or at the first
18    customer.  The GWS must then begin compliance monitoring by December  1,  2009.  In addition,
19    any GWS that is required to provide 4-log treatment of viruses as a corrective action must also
20    conduct compliance monitoring to ensure that the 4-log treatment is functioning properly.
21
22           One of the compliance monitoring requirements is that GWSs that use chemical
23    disinfection and that serve more than 3,300 people must continuously monitor  their disinfectant
24    residual concentration.  GWSs must maintain the minimum disinfectant residual concentration
25    determined by the state.  GWSs that use chemical disinfection and serve 3,300 people or fewer
26    must take daily grab samples for disinfectant residual concentration or meet the continuous
27    monitoring requirements. If any daily grab sample measurement falls below the minimum state-
28    required residual disinfectant concentration,  the GWS must take follow-up samples every 4
29    hours until the residual is restored to the required level.
30
31           GWSs using membrane filtration for 4-log treatment of viruses must monitor the
32    membrane filtration process according to state-specified monitoring requirements and must
33    operate the membrane filtration according to all state-specified compliance requirements.
34
35           GWSs may use alternative treatment technologies (e.g., ultraviolet radiation [UV])
36    approved by the state, if the alternative treatment technology, alone or in combination (e.g.,
37    membrane filtration with UV) can reliably provide at least 4-log treatment of viruses. GWSs
38    must monitor the alternative treatment according to state-specified monitoring  requirements and
39    must operate the alternative treatment according to compliance requirements established by the
40    state.
41
42
43
44
45
46

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 1                       3. Representative Source Water Monitoring
 2
 O
 4           The GWR establishes a risk-targeted approach to identify and address ground water
 5    sources that are susceptible to fecal contamination. A key provision of the GWR is monitoring
 6    sources of ground water systems providing less than 4-log treatment of viruses to determine if
 7    they are fecally contaminated, as indicated by the presence of fecal indicator organisms.
 8
 9           Systems that provide 4-log treatment of viruses and the related compliance monitoring
10    are not subject to the source water monitoring requirements of the GWR. However, ground
11    water sources of systems that do not provide 4-log treatment of viruses must be monitored for
12    fecal indicators if triggered by a TCR-related total coliform-positive routine sample in the
13    distribution system.  For triggered monitoring, a GWS must collect, within 24 hours of
14    notification of the total coliform-positive sample, at least one sample from each ground water
15    source in use at the time the total coliform-positive routine sample was collected under the TCR,
16    unless the system has approval from the state to conduct triggered source water monitoring at a
17    representative ground water source or sources.
18
19           The state may require systems with more than one ground water source to submit for
20    approval a triggered source water monitoring plan that the system will use for representative
21    sampling.  A triggered source water monitoring plan must identify ground water sources that are
22    representative of each monitoring site in the system's TCR sample siting plan. EPA believes that
23    this alternative can be as protective of public health as monitoring all wellheads, provided that
24    the chosen wells are truly representative of all wellheads.  In addition, for situations where a
25    particular sample site is inaccessible, the state may identify an alternate sampling site that is
26    representative of the water quality of the ground water at the inaccessible sample site. When
27    considering representative sampling, EPA encourages water systems to consult the state or
28    primacy agency early to determine if representative sampling is applicable for the system and the
29    level of efforts and information that may be needed to ensure equivalent public health protection
30    as monitoring all sources or wellheads.
31
32           In addition, a GWS may be directed by the state to conduct assessment source water
33    monitoring of ground water sources that are at risk for fecal contamination.  The GWR allows
34    representative monitoring if a state requires a system to perform  assessment source water
35    monitoring and gives the GWS approval to use representative monitoring.
36
37           This chapter  describes the two types of representative monitoring and presents the basic
38    elements that GWSs should present to States when requesting permission to conduct
39    representative monitoring. The first type of representative monitoring is based on the distribution
40    system's water flow characteristics or hydraulics and is  discussed in section 3.1 and in Chapter 4.
41    This is  applicable to triggered source water monitoring.  The second type is based on the
42    systems' sources and their physical and hydrogeologic similarity. This type of representative
43    monitoring is discussed in more detail in section 3.2 and in Chapter 5, and applies to triggered
44    monitoring and assessment source water monitoring.  In all cases, representative source water
45    monitoring must be approved by the state before it is implemented, and  a written plan may be
46    required to be submitted for state approval.  Section 3.3 briefly addresses these plans; example
47    plans and templates are included in Appendix A and B,  respectively.
48   	
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3.1    Wells Representing Coliform Monitoring Locations in the Distribution System

       A system may be able to use system hydraulics to demonstrate that a given source does
not supply water to a section of the distribution system in which a specific TCR routine sample
site is located to show that it could not contribute water to the site and would not be
"representative" of that site.  The state has the discretion to determine whether to require the
system to take source water samples at such a site.

       GWSs that have hydraulically separate or distinct zones in their distribution system can
request state approval of representative triggered monitoring based on an identification of which
sources supply each section of the distribution system, and therefore which source(s) could
potentially contribute water to each TCR routine sample site. If the system can demonstrate that
the water at a TCR sampling site can only come from a subset of its sources, state-approved
representative monitoring would limit triggered sampling to only those sources that could have
been the source of the contamination.

       Exhibit 3.1 depicts a simple illustration of representative monitoring scenarios. In this
example, Well 1 feeds Pressure Zone  1 (the shaded area to the left), and Wells 2 and 3 feed
Pressure Zone 2 (the shaded area to the right). Total Coliform (TC) sample site X is located in
Pressure Zone 1; TC sample site Y is located in an area that is a mix of Pressure Zones 1 and 2;
and TC sample site Z is located in Pressure Zone 2.
            Exhibit 3.1: Simplified Representative Monitoring Scenarios
       This system may propose that a positive total coliform result at TC sample site Z would
only require triggered source water sampling at Wells 2 and 3, and not at Well 1 because Well 1
is hydraulically separate from TC sample site Z. Also, a positive total coliform result at TC
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 1    sample site X, would only require representative triggered monitoring at Well 1.  However, it
 2    might be more difficult to determine the source of a positive total coliform sample near the
 3    margins of the pressure zones, such as TC sample site Y.  In such a case, the triggered source
 4    water monitoring plan, if required, should specify that the system will sample all three wells in
 5    response to a positive result at site Y, unless the system is able to demonstrate to the state that
 6    wells 2 and 3 are representative of one another based on physical and hydrogeological properties,
 7    in which case the state may determine and approve sampling only one of them, as described in
 8    section 3.2.
 9
10    3.2    Wells Representing Other Wells
11
12           This type of representative monitoring is based on the assumption that if multiple
13    sources feed a given TCR sample site, and they are similar enough (e.g., construction, well
14    completion, water chemistry, etc.), the state may allow the system to sample one or more sources
15    to represent multiple wells.  This type of representative monitoring applies to both triggered and
16    assessment source water monitoring.
17
18          For the system shown in Exhibit 3.1, the GWS may provide information indicating that
19    Wells 2  and 3 are located geographically near each other, have similar well construction, and are
20    drilled to the same depth and in the same aquifer to demonstrate that they are physically and
21    hydrogeologically similar.  In addition, the system may provide a general chemical (non-
22    regulated constituents) screening analysis from each well demonstrating that they are also
23    chemically similar. Based on these characteristics, the system may make a case to the state that
24    these two wells are representative of each other, and if the state approves and if source sampling
25    is triggered or assessment monitoring is required, the system would be able to use a sample at
26    one well to represent both wells.
27
28    3.3    Triggered Source Water Monitoring Plan
29
30          The GWR does not require every GWS that proposes to conduct representative triggered
31    source water monitoring to complete or submit a triggered source water monitoring plan. The
32    state may require that a plan be developed and submitted for approval. However, even if the state
33    does not require that the  GWS prepare a plan, the GWS may wish to develop one and include the
34    plan in its  operations manual. A written triggered source water monitoring plan may be helpful to
35    GWSs for any of the following reasons:
36
37         If a GWS is part of a network of wholesale and consecutive  systems, and the triggered
38          source water monitoring plan would provide direction as to whom should be notified and
39          who should collect fecal  indicator source water samples under different total coliform-
40          positive scenarios.

41         If the operation of the GWS is divided so that the distribution system is operated and
42          maintained by different staff than the sources and their related treatment.

43         If sample collection for the GWS is conducted by staff other than the operators (e.g., a
44          commercial laboratory) and a written plan would help the GWS  and laboratory staff
45          ensure that the proper locations are sampled.
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 1         If the GWS has enough staff that a written, accessible sampling plan will prevent in-
 2          house communication errors and the chance of inadequate or inaccurate sampling.
 O
 4          A triggered source water monitoring plan helps to ensure that the correct source(s) is
 5    sampled without collecting unnecessary samples. The purpose of the triggered source water
 6    monitoring plan is for the GWS to have a step-by-step plan in place that identifies which sources
 7    must be  sampled in response to a total coliform-positive sample at any given TCR site. It is
 8    important that the plan be readily available to water system personnel responsible for sample
 9    collection, since triggered source water samples must be collected within 24 hours of learning of
10    the TCR routine sample result.
11
12          A triggered source water monitoring plan should include the following minimum
13    elements:
14       1. Map or schematic of the system with sources and/or points of entry and TCR sample
15          siting plan monitoring locations identified.  The distribution system map or schematic
16          should not contain information that poses a security risk to the system. EPA recommends
17          that the schematic include either a distribution system schematic with no landmarks or
18          addresses or a city map without locations of pipes indicated.
19       2. The source type and level of treatment provided for each source/point of entry and
20          whether it is seasonal, emergency, ground water, surface water, a wholesale supply, etc.
21       3. The source(s) serving each TCR routine monitoring location and the basis for the
22          determination (e.g., system hydraulics, operation, water quality data, etc.)
23       4. Any representativeness among sources based on the physical and hydrogeological
24          properties of sources and the basis for the determination (e.g., well construction, water
25          chemistry, aquifer type, well log, etc.)
26       5. For wholesale systems, the consecutive systems served and, if applicable, the sources
27          serving each consecutive system.
28       6. Any changes or variations expected in the monitoring plan such as the use of seasonal
29          sources, rotating sources, etc.
30
31          The triggered source water monitoring plan can be a stand-alone, independent document
32    or the system may incorporate it as part of its TCR sample siting plan. Doing so may be useful
33    because  of the direct relationship that exists between TCR and GWR. In addition, many systems
34    might need to create a multi-scenario monitoring plan to reflect the variety of ways in which
35    their systems are operated throughout the year. For example, a GWS that uses a well field only
36    during certain months to meet high demand may need to have one monitoring plan for those
37    months and another monitoring plan for the others.  However, where there is uncertainty of
38    which wells are in use, a conservative approach should be used in which all potential sources are
39    included.
40
41          Appendix A provides three examples of triggered source water monitoring plans for
42    hypothetical systems. These examples vary in complexity and information used to justify the
43    plan. Appendix B provides a blank template for the example plans used in Appendix A. This
44    template is only a suggested format; each state agency may develop their own source water
45    monitoring plan requirements.

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 1       4. Wells Representing Coliform Monitoring Locations in the Distribution
 2                                            System
 o
 4
 5           Some wells may be representative of certain coliform monitoring locations in the
 6    distribution system based on system hydraulics. In such cases, ground water source(s) are
 7    capable of providing water to specific TCR routine sample sites based on the hydraulics of the
 8    distribution system.  Triggered monitoring requires that samples be collected from each ground
 9    water source following a total coliform-positive routine TCR sample unless the system has
10    approval from the state to conduct triggered source water monitoring at a representative ground
11    water source or sources.
12
13           Identifying sources  that could not have provided water to specific sites is a recommended
14    first step in  determining whether reducing the number of source water samples that must be
15    collected is  appropriate for the GWS. The distribution system should be analyzed from  a
16    hydraulic perspective. This chapter outlines step-by-step procedures and tools that can be used
17    to evaluate system hydraulics and provides guidance on determining whether a source is
18    hydraulically connected to  a particular TCR sampling site.
19
20    4.1    Linking Sources to TCR Sites
21
22           System design and operational practices impact the direction and velocity of flow in the
23    distribution system.  The water's hydraulic path is affected by source entry point locations, pump
24    station operations, finished water storage tank locations, valve settings,  elevations throughout the
25    system, consumer demand, and operational settings of all tanks and pumps.  Systems will
26    typically be knowledgeable of their distribution system configuration and will generally have a
27    good understanding of water movement in their system. However, for the purposes of
28    representative sampling,  it  is important to definitively determine which ground water source or
29    sources could provide water to each routine total coliform sample site and which sources could
30    not have provided water.
31
32           Those sources that could not have provided water to a sampling site  may be excluded
33    from being a representative location for triggered monitoring, if approved by the state.  All other
34    sources that could provide water to the  coliform sample site are thereby linked to that site. In
35    some instances, water flow from one zone to another is possible but generally unlikely during
36    normal operating conditions.  To ensure that the appropriate sources are sampled if monitoring is
37    triggered, systems should eliminate only those sources that clearly cannot provide water to the
38    coliform sampling site.
39
40           Simple  water systems with uncomplicated distribution systems will likely be straight-
41    forward to evaluate, while those that are more hydraulically complicated will likely require more
42    advanced analysis of water movement,  especially in  cases with very extensive delineation of
43    hydraulic zones and separation of sources from zones.  In either case, when  considering
44    representative sampling,  EPA encourages water systems to consult the state or primacy agency
45    early to determine if representative sampling is applicable for the system and the level of efforts
46    and information that may be needed to ensure equivalent public health protection as monitoring
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 1    all sources or wellheads. The following is a general step-by step process for linking sources to
 2    TCR routine sample collection sites:
 3
 4       1.  Map what is already known.  Water systems should work with the state or primacy
 5           agency to determine the amount of effort to invest in additional studies of their
 6           distribution systems and sources.  The various maps of system water quality, pressure
 7           zones, etc. that are applicable are discussed in section 4.2.1.
 8       2.  Superimpose the routine sample collection sites for the TCR-related sample siting plan on
 9           the distribution system map.  For many systems, this step will have already been
10           completed as part of developing the initial sample siting plan. Coliform sample siting
11           plans are discussed in section 4.2.2.
12       3.  Review operations records.  Historical operations records, such as well pumping
13           compared to tank levels and controls, may provide insight into water flow patterns under
14           typical  operating conditions.  See section 4.2.3.
15       4.  Apply information from a hydraulic model, if available.  The modeled results may be
16           useful when gathering data to make a case for representative source water monitoring.
17           See section 4.2.4 for more on hydraulic models.
18       5.  Review water quality parameter data. Distribution system water quality parameter data
19           may be helpful if the system's water sources are of differing water quality. This
20           information may help to identify sources that serve specific coliform sample sites and is
21           discussed in section 4.2.5.
22
23    4.2    Tools
24
25           Ground water systems will have a wide variety of tools available to evaluate the
26    distribution system to determine which sources contribute to each TCR site. In some instances,
27    states may determine that information from simply locating sources, entry points, and TCR sites
28    on the distribution system map is adequate. In other cases, states may require that additional
29    information from hydraulic models or tracer studies be used to confirm whether sections  of the
30    distribution system are hydraulically separated.
31
32    4.2.1   Distribution system maps
33
34           The most critical tool available to begin analyzing how water moves in a water system
35    and identifying hydraulically separated pressure zones is a distribution system map.
36
37           Many distribution systems have distinct zones that allow water movement to be managed.
38    Zones can be created and managed to maintain a constant range of pressures in a distribution
39    system with different elevations. Valves, pumps, and storage facilities all  provide ways for a
40    distribution system to maintain different zones and, as a result, reliable water system pressure.
41
42           Control valves, such as pressure reducing valves and gate valves, are used to regulate
43    flow or pressure in a distribution system. Locations of valves and how they are operated will
44    influence whether water in different parts of the distribution system mixes significantly. Valves
45    that are improperly maintained and exercised may leak and not serve as reliable tools for
46    isolating different zones. Valve condition, therefore,  should also be considered.
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 1
 2           Pumps are often used in distribution systems to boost water to higher elevations or
 3    increase pressure. Another way to satisfy the need for adequate capacity and pressure is to use
 4    standpipes, elevated tanks, and large storage reservoirs. Knowing the locations, specifications,
 5    and condition of the valves, booster pumps, and storage facilities that comprise the distribution
 6    system is important for personnel who are trying to characterize its water movement.
 7
 8           A system map may be as simple as a schematic or a street map  or may be quite detailed
 9    and based on as-built drawings and system surveys.  The distribution system map or schematic
10    should not contain information that poses a security risk to the system.  EPA recommends that
11    the schematic include either a distribution system schematic with no landmarks or addresses or a
12    city map without locations of pipes indicated.  The following locations should be indicated on
13    the map or included with the map:
14
15          All water source entry points including any interties (i.e., interconnections) with other
16           water systems.

17          Treatment facilities and the extent of treatment provided.
18          All routine total coliform sampling sites with  an identifying number.

19          Storage tanks / reservoirs.

20          Pressure regulation facilities (reducing stations).

21          Other infrastructure that may affect pressure and/or flow in the distribution system.

22          Booster pump stations.

23          Pressure zone boundaries.
24          Transmission mains.

25          Critical valves (those valves whose function is vital to the successful operation of the
26           system or whose failure can lead to serious consequences [Dorf, 2005]).
27
28           The system map should reflect operational changes that have altered the hydraulic zones
29    linked to each TCR site.  It may be helpful to prepare a summary table listing each source and
30    the pressure zone(s) it serves.
31
32           Exhibit 4.1 illustrates a simple multi-pressure zone distribution system map. Assume that
33    all pressure zones are hydraulically separated as demonstrated by evidence presented by the
34    system (e.g., significant differences of elevations among pressure zones, presence of closed
35    valves among zones, other supporting data, etc.) and  source sampling has been triggered by a
36    total coliform positive result in Zone 1.  Representative monitoring based on system hydraulics
37    could specify that only the wells in Zone 1 must be sampled (because wells in Zones 2 and 3 do
38    not contribute to Zone 1 and are therefore not representative of Zone 1).
39
40           Chapter 5 explains how the case for representative monitoring can be further developed
41    to include wells representing other wells. For example, consider a system that is required by the
42    state to develop a triggered source water monitoring plan to qualify for representative source
43    water monitoring. If the system presents supporting information, and the state agrees, that two or

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more of the wells in pressure Zone 1 are representative of each other, then the triggered source
water monitoring plan could specify that fewer than all 4 wells would need to be sampled. In
this case, the water quality of the sampled wells would be representative of that of the unsampled
wells. However, if the wells in pressure Zone 1 are not shown to be similar enough based on
their physical and hydrogeological properties then all of the wells in pressure Zone 1  would need
to be sampled.
                    Exhibit 4.1: Example Distribution System Map
      Key
      well
      pressure zone boundary
      pipes
4.2.2   Coliform sample siting plan

       Each ground water system should have a coliform sample siting plan as required by 40
CFR 141.21(a). The purpose of this sample siting plan is to identify sites throughout the
distribution system that are representative of the water quality of the entire distribution system.
An analysis of which sources feed each section of the distribution system may have been
completed in developing the coliform sample siting plan since it is necessary to identify
sampling sites that are hydraulically upstream and downstream from the routine total coliform
monitoring sites. If available, this analysis could be useful during the development of the
triggered source water monitoring plan.
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1
2
3
4
5
6
       The coliform sample siting plan typically includes a map and an address list of routine,
upstream, and downstream sample sites with descriptions of tap locations.  Sample information
is listed in Exhibit 4.2.

                  Exhibit 4.2: Total Coliform Sample Site Locations

Site ID
1H-1
1H-18
1H-2
1H-3
Primary Location
Name
FH#9,
1617 U St. NW
Bread for the City,
1525 7th St. NW
FH#16,
101 8 13th St. NW
FH#1,
2225 M St. NW
Tap location
Bathroom in
Officer's room
Hose bib
Bathroom sink
Kitchen sink
Upstream Location
Name
V Best Supermarket
1507UStNW
Dollar Plus Savings
Store
1541 7th St. NW
Stoney's Beef and
Beer 1 307 L St NW
Federal Market 1215
23rd St NW
Downstream
Location
Name
Keren Restaurant
1780 Florida Ave NW
Kennedy Recreation
Center
1401 7th St. NW
Roy Rogers
1275KStNW
Medical Society of
DC2215MStNW
           Another resource may be historical operations records such as tank levels and pumping
     data and interviews with system operators. For example, a review of well pump status (whether
     the well pump is operating) and tank level data (whether the tank is filling) for the same time
     period can indicate which area is served by each well, after taking consumer demand in to
     consideration.  System operators will generally understand which sources serve which parts of
     the distribution system based on their experience with pump controls and related telemetry.
     When operations records and operator experience indicate that the areas served by ground water
     sources are not clearly delineated, additional information is likely required to determine whether
     hydraulically representative monitoring is feasible.

     4.2.4  Distribution system hydraulic models

           Hydraulic modeling can be used to determine the flow path from one point to another in a
     distribution system.  For example, it can be used to determine the upstream hydraulic path from
     the routine total coliform sampling site to the source(s) of supply. In order to give accurate
     results, the hydraulic model should meet these criteria (Martel et al. 2005):

          The model is calibrated.

          Demand patterns are accurately detailed.

          The model is regularly updated to reflect changes in the hydraulic configuration of the
           system.

          The model provides more than a "skeleton" view of the  distribution system.
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 1           Some utilities have used hydraulic models to meet the requirements of the Stage 2
 2    Disinfection Byproducts Rule (Stage 2 DBPR) Initial Distribution System Evaluation.  In this
 3    evaluation, the hydraulic model estimates water age throughout the distribution system. Systems
 4    may be able to utilize the work completed for Stage 2 DBPR to confirm which source or sources
 5    contribute to a routine total coliform sampling site.
 6
 7           Hydraulic modeling may not available to most small groundwater systems, but it may not
 8    be necessary for some ground water systems with simplistic distribution systems. However,
 9    some systems (such as very complex systems with numerous pressure zones) may need the
10    information from a hydraulic model in order to justify representative monitoring to their state.
11
12    4.2.5  Distribution system tracer studies
13
14           A tracer study may help a system to better understand the paths and destinations that
15    water takes from a source  to various points throughout the system and the proportion of that
16    water taking a particular path.  These studies involve adding a chemical such as fluoride or
17    chlorine to the distribution system at one point, and measuring the chemical concentration at
18    downstream points to estimate the travel time between the two points. After the tracer is added,
19    the operator will sample in the distribution system to determine how levels of the tracer appear
20    and then diminish over time, providing an indication of the water's age and the area served by
21    the source. If the system already adds fluoride to the water, it is possible for the tracer study to
22    be conducted by stopping  the fluoride feed in one source at a time and measuring the decreasing
23    fluoride concentration at downstream points.
24
25           For the purposes of a triggered source water monitoring plan,  one recommended
26    approach is to add the tracer at one source and not at others, with monitoring throughout the
27    distribution system to identify areas where the tracer appears. Tracer studies should be done
28    with some care, however,  to consider consumer demand, finished water storage influences, and
29    other source water pumping, so that a valid assessment of the area served by the investigated
30    source can be made with confidence.
31
32    4.2.6  Customer complaint records
33
34           Customer complaints records sometimes function as a sentinel for water utility personnel.
35    These records can reveal water quality issues overlooked by sampling and other barriers that are
36    in place to protect public health. The TCR white papers (available at
37    http://www.epa.gov/OGWDW/disinfection/tcr/regulation_revisions.html) include several
38    examples in which water quality issues correlate with customer complaints.  Customer
39    complaints may supplement other tools mentioned above to help the states or primacy agency to
40    determine if representative monitoring sampling is appropriate for a system. For instance, if the
41    utility is receiving the same types of customer complaints from two areas, this may be an
42    indication that the areas may be connected or are receiving water from the same contaminated
43    source. In this case, the system should utilize other tools to investigate the problem and confirm
44    whether the areas are actually hydraulically  separated.
45
46           Customer complaint records may also be helpful in  identifying areas in which different
47    sources are mixing.  If the distribution system is fed by multiple sources with varying water
48    quality, the release of biofilms, scales, or sediments may occur where different sources blend.
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 1    For example, the City of Tulsa, Oklahoma, found that the majority of positive coliform samples
 2    that were detected over a two year period occurred at the interface between two treated waters in
 3    the distribution system (Kirmeyer et al. 2000). Customers in this area of blended water
 4    complained of red or brownish water that may have been caused by loosening or dissolution of
 5    scale material due to changing water quality.  In such areas where mixing occurs, water is
 6    coming from more than one source. This should be considered when determining which wells to
 7    sample when triggered source water monitoring is required.
 8
 9    4.2.7  Water quality parameters
10
11          Water quality varies with each source of supply. The source water may or may not
12    contain dissolved minerals, dissolved gases, organic matter, or combinations of these impurities
13    that can be used to distinguish one source from another, or to link the source to a particular
14    routine total coliform sample site.  For example, ground water from wells tends to contain more
15    dissolved minerals than either lake or river water since the groundwater seeps through minerals
16    in the earth.
17
18          If available, the following water quality parameters may be used to help to characterize a
19    ground water source and link it to coliform sites if the same parameters are also monitored at the
20    sample collection sites:
21
22         Total hardness as calcium carbonate
23         Alkalinity as calcium carbonate
24         Conductivity
25         Chlorides
26         Fluoride
27         Nitrates
28         Phosphate
29         Sulfate
30         pH
31         Total dissolved solids
32         Aesthetic quality of water
33         Water temperature
34
35          If the system is unsure whether a source feeds a certain area of the distribution system,
36    and they have a well or well field with water quality characteristics that are unique to that site,
37    they may conduct monitoring in the distribution system to determine where in the distribution
38    system those same characteristics are found. For instance, if a system has one set of wells with
39    relatively high sulfate levels and the other sources have low levels, sulfate sampling in the
40    distribution system may help clarify whether that source contributes water to that part of the
41    distribution system.
42
43    4.3    Criteria to Include in the Plan
44
45          This section  discusses criteria that may be included in a triggered source water
46    monitoring plan.  As discussed previously, the state may require systems with more than one
47    ground water source to submit for approval a triggered source water monitoring plan that the
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 1    system will use for representative sampling. If a plan is not required, the system may still wish
 2    to consider the same criteria described here in determining whether representative monitoring is
 3    appropriate.  In either case, EPA encourages water systems to consult the state or primacy
 4    agency early to determine if representative sampling is applicable for the system and the level of
 5    efforts and information that may be needed to ensure equivalent public health protection as
 6    monitoring all sources or wellheads.
 7
 8           Once the system has pulled together the tools available to help determine which sources
 9    feed each routine total coliform  sampling site, the next step is to begin to prepare the triggered
10    source water monitoring plan. The system should start by reviewing the system map to identify
11    any areas of the distribution system that are clearly and defensibly hydraulically separated.
12
13           The plan should include  a distribution system map that identifies all sources, critical
14    infrastructure such as tanks and  pump stations, delineation of pressure zones, identification of
15    system elevations, and all routine total coliform sampling sites. The plan should also provide a
16    discussion of how the link from  each source to each site was determined.
17
18           When determining which sources do not require sampling after a total coliform-positive
19    sample, the system should take a conservative approach.  For example, sources should only be
20    excluded if there is very little or no likelihood that water from that well can contribute to the mix
21    of water at the sample location.
22
23           The example in Exhibit 4.3 provides a simple schematic of a distribution system along
24    with a table identifying each routine total coliform sampling site and identifying sources that can
25    supply water to each site. In this example, the South Pressure Zone is at a lower elevation than
26    both the West Pressure Zone and the North Pressure Zone, and the West Pressure Zone is at a
27    lower elevation than the North Pressure Zone. Using their understanding of hydraulics, the
28    operators reasoned that water flows from the North Pressure Zone to both the West and South
29    Pressure Zones and that water flows from the West Pressure Zone to the South Pressure Zone.
30    This assertion can be further supported by conducting tracer studies. The case for hydraulic
31    separation is strengthened if (1)  a tracer is introduced into the South Pressure Zone, and it is not
32    detected in either the West Pressure Zone or the North Pressure Zone and (2) a tracer is
33    introduced into the West Pressure Zone, and it is not detected in the North Pressure Zone.
34
35           The next section of this manual will build on this example by discussing criteria for
36    identifying whether wells are representative of each other based on physical and hydrogeological
37    properties.
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1
2
Exhibit 4.3: Example Triggered Source Water Map and Table
             West Side Well
3
4

                     West Pressure Zone

                               Diehl Well



                  Storage tank
                                                        _ Main Well

                                                        I I Main Well
                                                           South Pressure Zone
                                             South AveWell 1
                                            South Ave Well 2
5
TCR Site
1
2
3
4
Pressure Zone
South
North Central
West Side
West Side
Contributing Wells
South Ave Well 1
South Ave Well 2
Diehl Drive Well
Main Well 1
Main Well 2
Main Well 3
West Side Well
Main Well 1
Main Well 2
Main Well 3
Main Well 1
Main Well 2
Main Well 3
West Side Well
Main Well 1
Main Well 2
Main Well 3
West Side Well
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 1   References
 2
 3   Dorf, Richard C. 2005.  The Engineering Handbook. Boca Raton, Florida. CRC Press.
 4
 5   Iowa Department of Natural Resources. Groundwater Basics Occurrence, Movement, and
 6   Quality. Available at:
 7   www.igsb.uiowa.edu/GWBASICS/Chapters/Groundwater%20Basics%20Occurrence%20Move
 8   ment%20and%20Qualitv.pdf
 9
10   Kirmeyer, G., M. Friedman, J. Clement, A. Sandvig, P. Noran, K. Martel, D. Smith, M.
11   LeChevallier, C. Volk, E. Antoun, D. Hiltebrand, J. Dyksen, and R. Gushing. 2000. Guidance
12   Manual for Maintaining Distribution System Water Quality: CD-ROM. AWWA Research
13   Foundation. Denver, CO.
14
15   Martel et al. 2005. Data Integration for Water Quality Management. Denver, Colo.: AwwaRF.
16
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 1                             5. Wells Representing other Wells
 2
 O
 4           A public water system may request that one or more wells be considered representative of
 5    multiple wells' risk for fecal contamination based on physical and hydrogeological evidence.  If
 6    approved by the state, the system may not need to sample all of the wells that serve a TCR site
 7    when triggered source water monitoring is required. This representativeness based on physical
 8    and hydrogeological properties may also reduce the source water monitoring burden that applies
 9    to assessment source water monitoring directed by the state.  When considering representative
10    sampling, EPA encourages water systems  to consult the state or primacy agency early to
11    determine if representative sampling is applicable for the system and the level of efforts and
12    information that may be needed to ensure  equivalent public health protection  as monitoring all
13    sources or wellheads.
14
15           Wells that are determined to be representative of each other based on physical and
16    hydrogeological properties should have similar well construction, draw water from the same
17    hydrogeological setting, and have the same vulnerability to fecal contamination. It is important
18    to emphasize that even wells that appear nearly identical in location, construction, and water
19    chemistry (their physical representativeness), and that tap the same aquifer (their
20    hydrogeological representativeness), may  have different vulnerabilities to fecal  contamination
21    based on their distance to source(s) of fecal contaminants and the wells' recharge zones. Any
22    one of these  items may provide information that indicates wells under evaluation are not
23    representative of each  other.  The state or primacy agency may determine that wells are not
24    representative of each  other based on any one of these criteria.
25
26           This  chapter discusses the information that systems could use to determine whether wells
27    are representative of other wells, and presents a decision-making approach that removes from
28    further consideration sources that do not meet any one of these suggested criteria.
29
30           Total coliform  monitoring data and heterotrophic plate count bacteria  (HPC) data are not
31    included as information useful to decision makers of representative monitoring programs since
32    an absence of these microbes is generally expected for ground water sources.  Wells with a
33    history of total coliform organisms or elevated HPC levels should be monitored for fecal
34    indicator organisms. In addition, an absence of total coliforms  should not be interpreted to mean
35    a fecal  indicator would also be absent. A viral pathogen may be present even though bacterial
36    indicators are not detected. Coliphage may be used as the fecal indicator for the source water
37    with viral pathogens.
38
39    5.1     Physical Properties
40
41           To begin to inform whether wells have the same risk for fecal contamination, physical
42    properties of the wells should be evaluated. Physical similarities described in this chapter
43    address the proximity of the wells, their construction, and the water chemistry of the wells.
44
45    5.1.1   Well  proximity to other wells
46
47           Because fecal contamination in an  aquifer can be localized, a relatively easy aspect for a
48    system to consider would be the physical proximity of the wells.  Although any representative
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 1    scheme will be at the discretion of the state and based on the professional judgment of state and
 2    system personnel, a general rule of thumb is that the farther the geographical/physical distance
 3    between two sources, the less likely that one source can represent the fecal contamination risk or
 4    water quality at the other.  The consideration of well separation distances are system and source-
 5    specific.
 6
 7           Some systems may have supply wells located intermittently throughout a community.
 8    Wells spaced intermittently throughout a community are unlikely to be good candidates for
 9    representative sampling if there are great distances between them. The assumption that wells
10    that are relatively distant from one another are not representative of one another may generally
11    be true for shallow wells or hard rock wells common in the Eastern U.S. However, this may not
12    be true for the large, deep wells commonly found in the Western U.S.
13
14           Systems having well fields or clusters of wells are likely to have wells located relatively
15    close to one another.  These wells may be excellent candidates for representative sampling if
16    they are able to meet the other physical and hydrogeological criteria.
17
18    5.1.2   Well construction
19
20           Well construction information is vital to the process of designating representative wells.
21    Well construction refers to many aspects including the drilling method, depth of the well,
22    grouting depth, the screened interval, and the condition of the sanitary well seal. Differences in
23    these physical characteristics of a well would render some wells more susceptible to
24    contamination than others, particularly if contaminants could enter the well through means other
25    than via the aquifer. Poorly constructed wells have higher probability or risk to contaminate.
26    For example, surface runoff may enter the well down the casing of a poorly constructed well.
27    Representative sampling would be inappropriate for wells with different construction.
28
29           Drillers' logs provide important information not only on the location of the well, geologic
30    descriptions that aid in determining the aquifer type from which the well draws water, and the
31    depths  of screened intervals, but also information on the casing and grouting, which can help
32    states and systems evaluate well integrity. If drillers' logs are not available for each of the wells,
33    it will be difficult for primacy agencies to approve representative sampling for those wells.
34
35           The importance of considering information from drillers' logs on the depths of screened
36    intervals is demonstrated in Exhibits 5.1 and 5.2, below, which show a cluster of three wells at
37    an airport that are very close to each other at the surface. In Exhibit 5.1, the wells are likely to be
38    good candidates for representative sampling because the wells are similarly constructed and
39    screened at the same depth. Drillers' logs would be the primary way of identifying the problem
40    in Exhibit 5.2, where although the wells are close at the surface, they are drawing water from
41    different depths in the aquifer, and, in the case of one well, from  a different aquifer altogether.
42    Such wells would not be good candidates for representative sampling.
43
44           States may require information in addition to well location, construction, and drillers'
45    logs to approve representative sampling.
46
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          Exhibit 5.1: Potentially Good Candidates for Representative Sampling
2
3
4
5
6
7
                                                            Sand
                                                            Clay
                                                            Gravel
                                       50 Feet
Exhibit 5.2: Inappropriate Candidates for Representative Sampling
                                                            Sand
                                                            Clay
                                                            Gravel
                                       50 Feet
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 1    5.1.3  Water chemistry
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
       Source water chemistry data can be an excellent tool in providing evidence that two or
more wells are or are not representative of each other. Water chemistry comparisons may be as
simple as evaluating basic chemical screens that capture total dissolved solids, hardness, and
sodium, or may include more elaborate monitoring data information. Wells located close to each
other, even those that are screened at the same depths, but that have significantly different source
water chemistries, may be drawing water from different subsurface sources, given that
subsurface hydrogeology may be very complex.

       In fractured bedrock, for example (one of the most complex of subsurface environments),
two subsurface fractures that are very close to each other (even only feet or inches away from
each other) may be hydraulically disconnected, with each fracture containing water from one of
two near-surface sources that are very far apart near the surface (see Exhibit 5.3). In this case,
two wells that are near to each other and screened at the same depth (but, unbeknownst to the
system, drawing water from the two hydraulically disparate fractures), could have remarkably
different source water chemistries and vulnerability to fecal contamination, and thus could  not be
considered representative of each other.

     Exhibit 5.3: Wells in Close Proximity Not Representative Due to  Fractured
                                        Bedrock
       Two particular types of source water chemistry data are discussed below.  A state or
system may have one, all, or some of these indicators on which to base a decision about
representativeness. Additional types of source water chemistry data may be available to assist in
determining if wells are representative of each other. Significant differences in TDS or nitrate
levels among wells suggest that wells are not representative of each other.  The state may
determine that because all wells have certain levels and types of TDS or nitrates (whether those
levels are similar or dissimilar among wells) that all wells should be sampled under the triggered
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 1    source water monitoring requirement of GWR because the State may determine that the TDS and
 2    nitrates in the wells are tied to pathways or potential sources of fecal contamination.
 3
 4          Because considering multiple chemical indicators (as opposed to one) provides a greater
 5    degree of confidence regarding a decision about wells being representative of each other, states
 6    may require additional information during the approval process.
 7
 8    5.1.3.1 Total Dissolved Solids
 9
10          Total Dissolved Solids (TDS) is a measure of the amount of solid material that has been
11    dissolved in water. TDS can include carbonate, bicarbonate, chloride, sulfate, phosphate, nitrate,
12    calcium, magnesium, sodium, organic ions, and other ions.
13
14          Sources of TDS in ground water include the solid material of the aquifer itself and non-
15    point source pollutants such as road salt, lawn fertilizer, and septic system effluent. Much of the
16    TDS found in ground water samples may also be used to indicate proximity to a surface water
17    source. This may be important if fecal contamination in the surface water could reach the
18    ground water source.
19
20          Wells with significantly dissimilar TDS contents should not be treated as representative
21    of each other. However, caution should be applied in using similar TDS data to determine
22    whether wells are representative of each other. Water samples with  similar TDS values may in
23    some cases have different major ion contents that happen to add up to similar TDS values (in
24    which case the wells from which the samples were taken would not be representative of each
25    other). Whether this possibility is likely would depend on aquifer type, distance between wells,
26    etc.
27
28    5.1.3.2 Nitrates
29
30          Because excessive levels of nitrate in drinking water have caused serious illness and
31    sometimes death, it is a regulated contaminant for all public water systems and is commonly
32    monitored at the source water entry point to the distribution system.  Nitrate is also fairly easy to
33    test for.  Thus, nitrate data may be  one piece of evidence in  an investigation of whether two or
34    more wells should be considered representative of one another, particularly if wells have
3 5    comparable and low levels of nitrate.
36
37          Nitrate is derived from nitrogen, which is present in fertilizers and animal manure.
38    Airborne nitrogen compounds from automobile and industrial emissions can also contribute to
39    nitrate in ground water. (In general, nitrogen is converted to nitrate in natural waters.) In
40    residential areas, lawn fertilizers, septic systems, and pets are common sources of nitrates,
41    whereas in agricultural areas nitrates are even more common due to frequent application of
42    fertilizers. Nitrates generally persist in ground water for decades (USGS,  1988).
43
44          In many rural areas in the U.S. in which wastewater is treated through individual on-site
45    septic systems, elevated nitrate levels can be used as an indicator of possible wastewater
46    influence. If two or more wells have elevated levels of nitrate, this may be an indication that
47    wastewater has contaminated the aquifer and pathogens may be present. Because pathogens tend
48    to be less uniformly distributed in an aquifer than nitrates, elevated nitrates in two or more wells
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 1    is not a good reason to consider the wells representative of each other. Thus, except in those
 2    cases where fertilizer or other background concentrations of nitrate are the cause of the elevated
 3    concentrations in samples, elevated nitrates in samples from wells indicates a need for more
 4    sampling of the aquifer, not less.  In summary, if the source of the nitrate is wastewater or animal
 5    manure, it would not be prudent to rely on representative monitoring to eliminate one or more of
 6    the high nitrate wells from sampling for fecal indicators.
 7
 8          Nitrate is often in the form of ammonium nitrate when found in drinking water.
 9    Comparisons of ammonia data between two wells may be a better indicator of whether the wells
10    are representative of one another than comparisons of total nitrate concentrations. This is
11    because ammonia converts to nitrate after a short time, so the presence of ammonia indicates a
12    recent influx of ammonia. Nitrates, being longer-lived and also attributable to a variety of
13    sources, are commonly found in many wells.  Thus, when available, ammonia data is preferred to
14    nitrate data for determining  representativeness.
15
16    5.2    Hydrogeological Representativeness
17
18          The following sections discuss desktop sources and types of hydrogeologic information
19    that is available for helping  to make decisions on the representativeness of wells.  These sources
20    can provide information on  aquifer type as well as confining layer information. Other factors,
21    such as heterogeneity and anisotropy (directional dependence) of the aquifer from which the well
22    produces water, may affect the capture zones of individual wells such that wells within a well
23    cluster are not very representative of one another. Thus, it is important to use a weight-of-
24    evidence approach to determining which wells are good candidates for representative sampling.
25
26          States and systems should make use of all  available data, including well location, depth
27    of the screened intervals, well construction, aquifer properties, water chemistry data, etc. The
28    additional information on more complex hydrogeological analyses provided in section 5.2.2 may
29    not be useful or necessary for most systems but is provided here to accommodate those that will
30    find it beneficial.
31
32    5.2.1 Aquifer type and driller's  logs
33
34          Data on aquifer type can be useful when determining if two or more wells can be
35    considered representative of one another. States should consider the information along with the
36    hydrogeology of the site as a whole, including the type of confining layer overlying the aquifer
37    in question.
38
39          For example, two wells screened in a karst aquifer overlain by a continuous  confining
40    layer (Exhibit 5.4) are more likely to be representative of each other than two wells screened in a
41    karst aquifer overlain by a discontinuous confining layer (Exhibit 5.5). This is the case even if in
42    both scenarios  the two wells are fairly close to each other, both in horizontal distance and in the
43    vertical separation of the screened interval of each well.  This is because the discontinuous
44    confining layer may not be providing the same level of protection to all wells because it is
45    discontinuous.  A continuous barrier protects all wells equally while a discontinuous layer may
46    allow contamination to enter one well more easily than another.
47

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 1           When wells draw water from fractured bedrock aquifers, it is difficult to determine the
 2    direction of ground water flow and vulnerability to sources of contamination. It is also very
 3    likely that nearby wells (both drawing from fractured bedrock aquifers) are producing water of
 4    markedly different quality, or at least markedly  different vulnerability to contamination. Thus,
 5    wells in fractured bedrock aquifers are among the worst candidates for representative sampling,
 6    and only in rare cases where systems have fairly detailed knowledge of subsurface conditions
 7    should representative sampling be considered in fractured bedrock aquifers.
 8
 9
10
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2
      Exhibit 5.4: Wells Screened in a Karst Aquifer Overlain by a Continuous Layer
3
4
                                                                          Sand
                                                                          Clay

                                                                          Limestone
Exhibit 5.5: Wells Screened in a Karst Aquifer Overlain by a Discontinuous Layer
                                                                         Sand
                                                                         Clay
                                                                         Limestone
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 1          Drillers' logs are often a good way of identifying aquifer type. A driller's log typically
 2    records changes in lithology with depth, although local terminology may be used and may need
 3    deciphering. For example, in much of the United States the term "artesian well" is used by
 4    drillers as a lay term to indicate a producing bedrock well. This contrasts  with the
 5    hydrogeologist's definition - a confined aquifer where the water in a well  rises above the top of
 6    the aquifer, sometimes flowing to the land surface. Another example is the use of the term
 7    "hardpan"  by drillers to describe what may be a dense glacial till, a cemented soil, or a hard clay.
 8    A driller's  log may also include information on the drilling method employed, which may give
 9    clues to the type of materials the  drillers encountered.
10
11    5.2.2  Additional data
12
13          This section discusses in detail a wide spectrum of data that states  may consider useful.
14    Some information may not be readily available to systems.  Before expending significant
15    resources to gather additional data, systems should consult with the state or primacy agency and
16    consider the trade-offs for investing so heavily in a pursuit of representative monitoring because
17    they may not need to conduct significant amounts of triggered monitoring. On the other hand,
18    some systems may have one or more of these helpful pieces of information available that can aid
19    them with their representative monitoring analysis and justification.
20
21    5.2.2.1 Hydrogeologic data sources
22
23          A number of EPA publications provide detailed discussions of hydrogeologic data
24    sources.  An EPA workgroup was convened in 1993 to develop a guidance document on ground
25    water resource assessment. The guidance describes sources of hydrogeologic data and how this
26    data may be used to evaluate aquifer sensitivity (USEPA 1993a). EPA also published the
27    Ground Water Information Systems Roadmap, A Directory of EPA Systems Containing Ground
28    Water Data (USEPA 1994a). Another reference that summarizes hydrogeologic data sources is
29    an EPA Handbook entitled Ground Water and Wellhead Protection (USEPA 1994b).
30
31    State and Federal Hydrogeologic Investigations
32
33          These data sources are electronic or hard copy reports or data produced through previous
34    desktop analyses or field investigations. Such information may have been generated to meet the
35    requirements of Source Water Assessment Plans (SWAPs), or through water quality  or water
36    supply investigations initiated at  the local, state,  or federal level.  Existing data for a given PWS
37    well may be used. For example,  if an existing report or appropriate scale  map indicates whether
38    two wells are screened in a particular aquifer, then that information can be used to help
39    determine if the wells should be considered representative of each other.  Generally,  spatial  data
40    at the scale of 1:100,000 or larger (e.g., 1:24,000) are sufficiently detailed for most purposes
41    [Note: large scale maps provide detailed information of small geographic  areas.]
42
43    Wellhead Protection and Source Water Assessment Studies
44
45          The Safe Drinking Water Act (SOWA), as amended in  1986, created the Wellhead
46    Protection  Program (WHPP). Each state is required to adopt a program to protect wellhead areas
47    within its jurisdiction from contaminants that may have adverse health effects and to submit the
48    program plan to the EPA Administrator. Currently, 49 states and two territories have WFtPPs in
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 1    place. In their WHPPs, states address all program elements including how to delineate wellhead
 2    protection areas (WHPAs) and how to identify and inventory all potential sources of
 3    contamination.
 4
 5           Section 1453 of the 1996 SDWA Amendments required all states to establish SWAPs
 6    and to submit plans to EPA for approval by February 6, 1999. These SWAPs address both
 7    surface water and ground water protection, and their SWAP plans detail how states will: (1)
 8    delineate source water protection areas; (2) inventory significant contaminants in these areas; and
 9    (3) determine the susceptibility of each public water supply to contamination.  States may use
10    any available information to carry out the SWAP, including data generated through the WHPP.
11    After plan approval, the states must have completed  susceptibility determinations for all PWSs
12    by November 6, 2001, unless the state was granted an 18-month extension until May 6, 2003.
13
14           EPA encourages states and systems to build upon previous SWAP or WHPP efforts to
15    help determine if two or more wells are representative of one another. A review of selected,
16    approved state SWAP plans across EPA regions indicates that many states intend to evaluate
17    hydrogeologic information that may enable them to determine a PWS well's aquifer type. Data
18    in approved SWAP plans may include the aquifer types in which PWS plans are screened as well
19    as information on the continuity  of confining layers (e.g., WIDNR 1999). Other approaches to
20    fulfilling SWAP requirements are also likely to result in data that will be useful for determining
21    representativeness of wells.  Case studies # 2 and # 4, presented in sections 3.2.2 and 3.3.2,
22    respectively, of the Ground Water Rule Source Assessment Guidance Manual (available at
23    http://www.epa.gov/safewater/disinfection/gwr/pdfs/guide_gwr_sourcewaterassessments.pdf)
24    illustrate just two ways in which data can be extracted from SWAP investigations.
25
26    State Geologic Survey, VSGS, and Other Hydrogeologic Investigations
27
28           Many state geologic  surveys or agencies of natural resources have significant experience
29    studying local and regional aquifer systems and investigating ground water quality and quantity
30    issues.  Although many of these  studies may have directly supported, or continue to support,
31    SWAP or WHPP work, many more studies have been conducted independent of these efforts.  In
32    addition to state geologic surveys, the United States  Geological Survey (USGS) has district
33    offices that perform similar work in each state, sometimes in  cooperation with state agencies.
34    Universities, local governments, and non-governmental organizations also conduct pertinent
35    hydrogeologic research.
36
37    Hydrogeologic and Geologic Maps
38
39           Hydrogeologic or aquifer maps generally show the location, spatial extent, and depth of
40    aquifers in a region. Such maps  typically include information on aquifer type as well.
41    Hydrogeologic maps will  often be the most direct means to evaluating aquifer type and presence
42    of continuity of confining layers.
43
44           Geologic maps may depict a region's surficial geology, which would include the
45    locations and extent of distinct unconsolidated deposits and bedrock units exposed at the earth's
46    surface, or, alternatively, the bedrock geology of an area. Surficial geologic maps are available
47    for many areas from the USGS and often include a key to interpret the results of various test
48    holes shown on the map. Using  geologic maps is a less direct means to identifying aquifer type
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 1    than using hydrogeologic maps, but by using analytical techniques such as projection (described
 2    below) and using information such as well depth, these data can help determine aquifer type.
 3
 4           The availability of hydrogeologic maps at an appropriate scale varies among states and
 5    among regions.  The following sources may be useful to states and systems in obtaining
 6    appropriate maps for use in determining representativeness of wells. As part of its Regional
 7    Aquifer-System Analysis (RASA) program, the USGS produced a large variety of hydrogeologic
 8    maps at various scales.  Some of these maps are at scales that may be useful for determining
 9    representativeness. The RASA program completed studies of 25 major U.S. aquifer systems in
10    1995.  The Ground Water Atlas of the United States was developed as part of the RASA
11    program, and provides small-scale (i.e., less detailed coverage of large geographic areas)
12    hydrogeologic data for the country both as a printed atlas and as a digital dataset (available on
13    the Internet (accessed 6/30/08) at: http://pubs.usgs.gov/ha/ha730/).  The printed atlas has 13
14    individual chapters that cover specific U.S. regions.  The Ground Water Atlas data, however, are
15    compiled at scales that may not be suitable for evaluating representativeness of wells at PWSs
16    (e.g., at the relatively small 1:5,000,000 and 1:2,500,000 scales).
17
18           In areas where hydrogeologic maps are not available, it is possible to use a geologic map
19    along with the projection method to determine the aquifer type for a well of a given depth.
20    Projection is a structural  geologic technique which can be used to determine aquifer depth, or the
21    depth of any local geologic unit at a well, using the strike and dip of the aquifer as measured at
22    nearby outcrops. Typically, bedding (layering)  can be described in terms of its strike and dip.
23    Bedding also occurs but may be indistinct in some sedimentary rocks, in metamorphic rocks
24    called metasediments, and in some igneous rocks such as volcanic flows (e.g., basalts). Outcrop
25    mapping  of the bedrock is shown on many geologic maps with the values of the strike and dip of
26    the bedding.  The strike is the compass direction or azimuth of the line formed by  the intersection
27    of the bed with its horizontal (planar) surface. The dip is the angle in degrees between the
28    bedding and  a horizontal surface, measured at right angle to the strike (see Exhibit 5.6). If the
29    bedrock is a known aquifer, the depth to that aquifer can be determined by projecting the dip
30    over the distance to the well location. Using simple trigonometry, the depth to the aquifer is then
31    equal to the tangent of the angle multiplied by the distance.  This method can be used in areas of
32    simple geology.
33
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                              Exhibit 5.6: Strike and Dip
                                               North
                           Plane View
                              Surface
                         Cross Section
       More detailed hydrogeologic and geologic maps are available from a variety of public
and private entities.  The USGS, as well as state geologic surveys or natural resources agencies,
are the most prolific sources. However, coverage is highly variable from state to state. The
National Research Council (NRC) estimated in 1988 that less than 20 percent of the United
States has been geologically mapped at a scale of 1:24,000 or larger (NRC 1993). In response to
this situation, Congress enacted the National Geologic Mapping Act of 1992. This act
established the National Cooperative Geologic Mapping Program (NCGMP) to implement
expanded geologic mapping efforts through a consortium of geologic mappers.  As part of this
program, the USGS conducts federal mapping projects through its FEDMAP program;
STATEMAP, run by state geological surveys, is a matching-funds grant program; and
universities participate in another matching-funds program - EDMAP. The USGS coordinates
the NCGMP, which has a long term goal of producing 1:24,000 scale geologic maps for high
priority areas of the states, and national coverage at the 1:100,000 scale.

       The NCGMP also maintains an exceptionally useful database for locating existing
geologic maps produced by a wide variety of entities. The database includes mapping currently
in progress through the consortium and is searchable by location, scale, and other parameters.
The database, as well as general information on the program, is available on the Internet at
http://ngmdb.usgs.gov/.  A geologic map index is also available for many  states showing
boundaries for compiled map projects and references.
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 1    Topographic Data
 2
 3          Well coordinates, depth to the screened interval of a well, and topographic maps
 4    (described below) can be used to determine whether particular wells are drawing water from a
 5    given aquifer. Imprecise plotting of a well's location could lead to an erroneous assessment of
 6    the aquifer type from which the well is drawing water (and thus possibly an incorrect evaluation
 7    of whether the well is representative of a nearby well).  Accurate determinations of well
 8    locations are critical for determining representativeness using a desktop analysis; thus, it is
 9    important to use large scale topographic maps (e.g.,  1:24,000 topographic quadrangles) for
10    plotting the well's location (see Exhibit 5.4). In the  absence of a detailed topographic map (e.g.,
11    1:24,000), a base map of comparable scale is needed to accurately locate the well. Such a map
12    might be available from the local community (e.g., Assessor's Office, Engineering Department,
13    Department of Public Works, Water Board, Board of Health, Planning Board, and Conservation
14    Commission) or from state, federal, or regional  natural resource agencies and planning
15    departments.
16
17          Accurate well coordinates may be sought first from the PWS's records.  Well registration
18    information collected by federal, state, and local regulatory programs also usually include
19    coordinates, or they may be available from the well drilling company records.  If necessary, well
20    coordinates can also be obtained in the field using Global Positioning System (GPS) technology.
21
22          Exhibit 5.7 below shows the importance of map scale for determining aquifer type.  In
23    Exhibit 5.7, X indicates the location of a well with known areal coordinates and depth.  Use of
24    the larger scale map, Map A, allows for more precise plotting of the well's location, while use of
25    the smaller scale map, Map B, introduces much more error into the  plotting of the well's
26    location.  The cross-section shows a correct identification, based on Map B, of the well's aquifer
27    as gravel and an incorrect identification, based on Map A, of the well's aquifer as sand.  The
28    exhibit shows how the error introduced by imprecise plotting translates into erroneous
29    determination of aquifer type.
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
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      Exhibit 5.7: The Importance of Map Scale for Determining Aquifer Type

                                Lake Wobegone
                        Map A                    MapB
                1:250,000                 1:25,000
                                                                     Sand
                                                                    Clay
                                                                   o Gravel
                                                                   D Bedrock
       Topography can be represented in two dimensions with contours, continuous lines that
join points of equal value (equal elevation in this case). The contour interval, which is the
change in elevation between each successive contour line (e.g., 20 feet), is chosen depending
upon the scale of the map and the topographic relief.  The USGS and the Defense Mapping
Agency (DMA) have produced most of the topographic maps for the United States (NRC 1993).
The USGS produces maps at a variety of scales, but the most common scales for topographic
maps are 1:24,000/1:25,000,  1:100,000, and 1:250,000. The 1:250,000 scale maps are available
for the entire United States.  The much more detailed topographic quadrangles (1:24,000 or
1:25,000) are available for most of the country.  Index maps for each state showing available
topographic  maps are provided by the USGS without charge. Each 1:24,000 topographic map
covers approximately 58 square miles, where 1 inch corresponds to 2,000 feet.

       Digital topographic data for the United States are also available from the USGS as Digital
Line Graphs (DLGs) and Digital Elevation Models (OEMs). DLGs are vector data files that
represent linear and areal features commonly found on topographic maps, including contour
lines.  OEMs are data files that store point elevations  spaced at regular intervals in  a matrix.
Detailed OEMs have  10- and 30- meter resolutions. Because national coverage is incomplete for
both DLGs and OEMs, and state-wide coverage varies considerably by state, the remainder of
this section will focus on paper topographic quadrangles.
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 1    Stereoscopic Aerial Photography
 2
 3          Aerial photographs taken with approximately 30 percent overlap allow three dimensional
 4    imaging of land surface features with the aid of stereoscopes. In regions with limited geologic or
 5    topographic data, stereoscopic air photos may help locate wells. In most cases, however, such
 6    photos will be most useful for determining aquifer types when used in conjunction with other
 7    data sources.  For example, if low resolution geologic maps or well log data indicate that a given
 8    PWS well may be screened in a karst aquifer, stereoscopic air photos could be used to determine
 9    the presence or absence of sinkholes or other characteristic karst landform features.  Aerial
10    photographs are available from several entities within the USD A and from the USGS.
11
12          The NRCS and the Forest Service, both under the USD A, have extensive U.S. coverage
13    at scales appropriate for hydrogeologic sensitivity assessments. As noted above, the NRCS uses
14    high resolution aerial photography to compile their county level soil surveys at scales ranging
15    from 1:12,000 to 1:63,360. The USDA Aerial Photography Field Office, Farm Service Agency
16    acts as the clearinghouse for all USDA aerial imagery, archiving over 10,000,000  images dating
17    to 1955. USDA aerial photo coverage, availability, and ordering information are available
18    through their Website at: http://www.apfo.usda.gov/.
19
20          The USGS National Mapping Division administers the National Aerial Photography
21    Program (NAPP). The NAPP coordinates the collection of cloud-free coverage of the
22    conterminous United States and Hawaii at a uniform scale (approximately 1:40,000) about every
23    five years. NAPP photographs are available in black-and-white, and in many cases, color
24    infrared.  The imagery is available from the USGS's Earth Resources Observation Systems
25    (EROS) data center (http://edc.usgs.gov/) or Earth Science Information Centers (ESICs;
26    http://edc.usgs.gov/guides/napp.html).  NAPP photos are also available from the USDA Aerial
27    Photography Field Office, Farm Service Agency (see link above).
28
29          Well registration information and well logs collected by local,  state, and federal
30    regulatory programs may  be very useful for determining aquifer type.  Well registrations usually
31    indicate well locations, which is information necessary to determine if wells may be considered
32    representative of one another. A sufficiently detailed driller's log for a PWS well could itself, or
33    in combination with other data sources, adequately characterize the subsurface stratigraphy and
34    aquifer type.  For example, based upon a regional bedrock geology map that is of moderately low
35    resolution (e.g., 1:700,000),  a state may identify that two PWS wells are located in an area
36    underlain primarily by limestone. The state may review the driller's logs (if available) to
37    confirm that, in fact, the wells are screened in the same limestone aquifer.  Certain states such as
38    New Jersey and New Hampshire require drillers to file a log for each well with the appropriate
39    state agency, such as a water well board or the state Environmental Protection Agency.
40
41          Additional desktop sources include consultant reports and database searches for property
42    site assessments conducted by private search companies. These searches of federal, state, and
43    local agency databases are conducted as part of due diligence investigations for property site
44    assessments and are usually  in accordance with the standards of the American Society of Testing
45    Materials (ASTM).  These database searches include a description of the bedrock  and surficial
46    geology, a well inventory, and usually air photo coverage for the area in question. The well
47    inventory summarizes well locations, construction, soil and bedrock type, water quality, and
48    other pertinent data.
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 1   5.3.2  Capture zone models
 2
 3          EPA's Source Water Assessment Guidance Manual (USEPA, 2008) provides a detailed
 4   discussion of capture zone models that are very appropriate for helping to determine whether two
 5   or more wells can be considered as possibly representative of one another. Many systems
 6   conduct such modeling as part of their wellhead protection efforts. Models in use include
 7   WHPA and WHAEM.  Systems and states are encouraged to make full use of information that
 8   may be easily available and appropriate in determining representativeness. In cases where
 9   capture zone modeling has already been conducted, the results of such modeling likely fall in this
10   category.  Where resources permit, EPA recommends that states or systems conduct capture zone
11   modeling for the express purpose of determining whether two or more wells are drawing water
12   from the same areas of the same aquifer, and thus can be considered representative of one
13   another.
14
15
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 1   References
 2
 3   Barlow, Paul. 1995. Particle Tracking Analysis of Contributing Areas of Public-Supply Wells in
 4          Simple and Complex Flow Systems, Cape Cod, Massachusetts. United States Geological
 5          Survey Water-Supply Paper 2434.
 6
 7   NRC. 1993. Ground Water Vulnerability Assessment: Predicting Relative Contamination
 8          Potential under Conditions of Uncertainty. Washington, D.C.: National Academy Press.
 9          204 pp.
10
11   USGS. 1988.  A national look at nitrate contamination of ground water, By Bernard T. Nolan,
12          Barbara  C. Ruddy, Kerie J. Hitt, and Dennis R. Helsel. Available on the Internet at
13          http://water.usgs.gov/nawqa/wcp/.
14
15   USEPA, 2008. Ground Water Rule Source Assessment Guidance Manual., Office of Water, EPA,
16          EPA document 815-R-07-023.
17
18   USEPA. 1993 a. Ground Water Resource Assessment. Office of Water, EPA. EPA Report 813/R-
19          93-003 166 pp and 4 appendices.
20
21   USEPA. 1994a. Ground Water Information Systems Roadmap, A Directory of EPA Systems
22          Containing Ground Water Data. EPA Report 813 -B -94-001.
23
24   USEPA. 1994b. Handbook, Ground Water and Wellhead Protection. EPA Report 625/R-94/001.
25          269 pp.
26
27   Wisconsin Department of Natural Resources (WIDNR). 1999. Wisconsin's Source Water
28          Assessment Program Plan. Available on the Internet at:
29          http://www.dnr.state.wi.us/org/water/dwg/gw/SWP.HTM. Accessed August 20. 2008,
30          last updated November 18, 2004.
31
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 1                          6.     Approval of Representative Wells
 2
 O
 4           The GWR includes flexibility for representative source water monitoring to reduce the
 5    burden of sampling ground water sources. Ultimately, each state will decide if the specifics of a
 6    particular system warrant representative monitoring and whether a written triggered source water
 7    monitoring plan will be required. As noted in section 1.2 of this manual, the GWR has granted
 8    states flexibility on representative monitoring in that it is not an all-or-nothing approval process.
 9    That is, not all systems need to participate, and not all sources in a given system warrant
10    representative monitoring.
11
12           The GWR is clear in requiring state approval of all representative monitoring - whether it
13    is requested for triggered monitoring or as part of a state-mandated assessment source water
14    monitoring program.  The GWR is also specific in requiring that representative monitoring be
15    approved before it can be applied by a system; therefore, a GWS cannot conduct monitoring only
16    at representative sources without prior state approval. When considering representative
17    sampling, EPA encourages water systems to consult the state or  primacy agency  early to
18    determine if representative sampling is applicable for the system and the level of efforts and
19    information that may be needed to ensure equivalent public health protection as monitoring all
20    sources or wellheads.
21
22           This chapter describes the information EPA recommends states require and/or review
23    prior to approving representative monitoring of ground water wells. All of these items have been
24    discussed previously in this manual; this information is presented here to serve as a checklist of
25    the elements EPA considers essential to making an informed decision.
26
27    6.1     Reviewing the Proposal
28
29           States are responsible for reviewing requests from water  systems to conduct
30    representative source water monitoring. Water utilities are encouraged to submit the highest
31    quality data available to support their case for conducting representative monitoring.  EPA
32    believes that representative source water monitoring can be as protective of public health as
33    monitoring all wellheads, provided that the chosen wells are truly representative  of all wellheads.
34
35           As they review requests from utilities, states should consider the goal of not
36    compromising public health protection by approving representative monitoring when it is not
37    appropriate. This section discusses what information states should consider requesting from
38    systems, and provides guidance on how to evaluate a system's request for representative
39    monitoring.
40
41    6.1.1   Technical considerations when reviewing proposals for representative monitoring
42
43           There are two general reasons a system will propose conducting representative
44    monitoring: 1) to sample certain wells that represent certain TCR sampling sites in the
45    distribution system (and not sample other wells that do not provide water to  the particular TCR
46    sampling site; or 2) to sample one or more wells that represent multiple wells. States may allow
47    a ground water system to address either or both of these circumstances in their proposal to

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 1    conduct representative monitoring.  Some criteria that states may use during a technical review
 2    of both these categories of representative monitoring are provided below.
 3
 4
 5
 6    6.1.2  Ensuring the proposal is complete
 7
 8           The first step in a state's review process should be to ensure the proposal provided by the
 9    system has considered all of the  information needed for a complete review. Depending on the
10    nature of the system's request, different materials will be submitted.  These may include a
11    written plan (if required by the state), which should include:
12
13           For approving one or more representative wells serving a TCR sampling site:
14
15          Map or schematic of the  system. The distribution system map or schematic should not
16           contain information that poses a security risk to the system, but should include the
17           following:
18              o  Pressure zone boundaries in the distribution system.
19              o  TCR routine  monitoring locations, distinctly labeled.
20              o  Entry points of all sources, distinctly labeled, with the contributing sources clearly
21                 identified.
22              o  Entry points and status of any interconnections to other systems.
23              o  Storage tanks / reservoirs.
24              o  Pressure regulation facilities (reducing stations).
25              o  Other infrastructure that may affect pressure and/or flow in the distribution
26                 system.
27              o  Booster pump stations.
28              o  Critical valves.

29          The source type and level of treatment provided for each source/point of entry such as
30           whether it is seasonal, emergency, ground water, surface water, a wholesale supply, etc.

31          The source(s) serving each TCR compliance monitoring location and the basis for the
32           determination such as system hydraulics, operation, water quality data, etc.
33           For approving one or more representative wells at the source:

34          Physically and hydrogeologically representative ground water sources that will be used to
35           satisfy the triggered monitoring requirements or state required assessment or additional
36           monitoring requirements of the GWR and the basis for the selection.

37          Any changes or variations expected in the triggered source water monitoring plan such as
38           the use of seasonal sources, rotating sources, etc.
39
40           The triggered source water monitoring plan can be a stand-alone, independent document
41    or it can incorporate the TCR sample siting plan. In addition, many systems might need to create

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 1    a multi-scenario triggered source water monitoring plan to reflect the variety of ways their
 2    system is operated over the year. The system should not only submit the appropriate supporting
 3    study results and other information, but should also include a narrative explaining how the
 4    information supports the system's case for representative monitoring.
 5
 6    6.1.2.1 Wells representing coliform monitoring locations in the distribution system
 7
 8           Groundwater systems have a wide variety of tools available for evaluating the
 9    distribution system and determining which sources contribute to each TCR site.  Simple water
10    systems with uncomplicated distribution systems should be straightforward to evaluate. For
11    some systems, locating sources, entry points, pressure zones, and TCR sites on the distribution
12    system map may suffice.  Systems that are more hydraulically complex will require a more
13    advanced analysis of water movement. Hydraulic models or tracer studies help to inform
14    whether sections of the distribution system are hydraulically separated.  To provide maximum
15    public health protection, states should take a conservative approach when considering reducing
16    the number of sources that have to be sampled when source sampling is triggered.  Sources
17    should only be excluded hydraulically from triggered source water monitoring if there is very
18    little or no likelihood that water from that well can be the source of the total coliform-positive
19    sample in the distribution system.
20
21           Some questions to consider when reviewing a system's request to conduct representative
22    monitoring include:
23
24          Does the system identify each TCR sampling site as well as each source / entry point into
25           the distribution system?

26          Does the system make a convincing case that areas of the distribution system are
27           consistently hydraulically disconnected due to elevation, pressure gradients, tank
28           locations, or through valving?

29          Do historical operating records of the system's wells and distribution system
30           convincingly support the system's proposal for representative monitoring?

31          Is water flow possible from one zone to another but generally unlikely during normal
32           operating conditions? If so, is this enough to justify representative monitoring?
33          Do all sources of information available, including water quality data, convincingly match
34           certain wells to certain sampling sites in the distribution system? Does the water quality
35           differ enough among the various distribution system locations to distinguish the sources
36           of water?

37          If a distribution system hydraulic model is used:
38              o  Is the model calibrated?
39              o  Are demand patterns accurately detailed?
40              o  Does the model characterize the current hydraulic configuration of the distribution
41                 system?
42              o  Does the model provide a sufficiently detailed view of the distribution system?
43

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 1    6.1.2.2 Wells representing other wells
 2
 3           Determining whether one or more wells are representative of the risk of fecal
 4    contamination of multiple wells should be based on a single-elimination approach.  That is, if a
 5    ground water source fails to meet any one of several details, it would be eliminated from further
 6    consideration of representative monitoring.
 7
 8           Helpful data or information used to determine if wells should be considered
 9    representative of one another includes proximity to other wells, well construction, water
10    chemistry, the aquifer type tapped by the well and the overall hydrogeology of the site.  Example
11    sources of information that might be submitted include:
12
13          Well locations plotted using GPS or other means to denote proximity to other wells.
14          Well construction details for each well, including depth, grouting, sanitary seal, and
15           screened interval.
16          Water chemistry analysis results demonstrating differences among wells or
17           vulnerabilities of wells to contamination.

18          Aquifer information and other hydrogeologic studies, as appropriate. Hydrogeologic
19           studies may include:
20              o  Wellhead protection or source water assessment studies (may inform location and
21                 proximity to potential sources of contamination).
22              o  State Geologic Survey, USGS, and other hydrogeologic investigations.
23              o  Hydrogeologic and geologic maps.
24              o  Topographic data.
25              o  Stereoscopic aerial photography.
26              o  Capture zone models.
27
28           An important consideration when evaluating whether a system can conduct representative
29    monitoring is the sanitary condition of the wells themselves. Wells being considered for
30    representative monitoring should be structurally sound (e.g., raised casing, sanitary seal) and
31    similar in design to one another. The state should be careful not to approve representative
32    monitoring resulting in a well not being sampled that is in  poor sanitary condition.  If such a
33    situation were approved, the well that was in poor sanitary condition and not sampled could be a
34    source of fecal contamination that would not be identified  under triggered source water
35    monitoring.
36
37           While source water chemistry data can be an excellent tool for identifying wells  that are
38    representative of each other, states should ensure that water chemistry results submitted are
39    representative of the wells under all operating conditions.  Results submitted for TDS, chloride,
40    nitrate, or other  chemical parameters should be accompanied by a narrative explaining why the
41    data should be considered representative of the wells under all conditions, and how the water
42    chemistry data collected reflects the spectra of flows and seasonal variability that may impact
43    each well's water quality.
44   	
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 1           Submittals to the state of hydrogeologic studies should provide information on aquifer
 2    type as well as confining layer information.  Systems should include in their submittals a
 3    narrative that interprets the findings of any submitted hydrogeologic studies in the context of the
 4    wells being addressed by the proposed representative monitoring.
 5
 6           Some questions to consider when evaluating a proposal to monitor wells that represent a
 7    multiple wells are:
 8
 9          Is each well's structure and condition sufficiently characterized?  Are the structural
10           conditions of the wells being grouped similar?

11          Did the system provide third party information about the structure and condition of its
12           wells (e.g., driller's log or well completion report) to support the characterization of the
13           wells?
14          Are flows from the wells being addressed similar to one another?

15          If a hydrogeologic study is included, does it provide information on the  aquifer type and
16           the confining layer?

17          If water quality data are included and integral to defining the representative monitoring
18           locations, do the data characterize all wells in use under the full ranges of seasonal and
19           flow conditions?

20          If multiple wells are determined  to be representative of each other, how  many wells will
21           be sampled? Will the sampled wells be alternated?
22
23    6.2     Notifying the System and Recordkeeping Associated with a Representative
24           Monitoring Decision
25
26           GWSs should confirm with their state or primacy Agency that they have approval before
27    implementing representative source water monitoring.  If the state approves representative
28    monitoring for a system but does not require the system to prepare a written triggered source
29    water monitoring plan, the state may want to include in the written record of its decision the
30    conditions of the approved representative monitoring.
31
32           As part of the National Primary Drinking Water Regulations for Implementation, states
33    are required to keep records of approvals of triggered source water monitoring plans (40
34    CFR142.14(d)(17)(vi)). These records include all supporting  information and an explanation of
35    the technical basis of each decision.  This recordkeeping requirement of states is another reason
36    that may compel  states to require systems to submit written triggered source water monitoring
37    plans.
38
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10
11
12
13
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18
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 1   APPENDIX A

 2   Examples of Three Triggered Source Water Monitoring Plans
 O
 4         Example 1 - Demonstrates hydraulic representation of ground water sources in a system
 5          with two pressure zones
 6
 7         Example 2 - Demonstrates hydrogeologic representation of ground water sources in a
 8          system with one pressure zone
 9
10         Example 3 - Demonstrates a combination of hydraulic and hydrogeologic representation
11          of ground water sources in a system with three pressure zones
12
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1    EXAMPLE 1

2    Triggered Source Water Monitoring Plan for Our Town Water System
O

4    Hydraulic representation of ground water sources in a system with two pressure zones.
5
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i    A. System Information
2    (Enter the following information about the water system.)
     Water System Name:
                           Our Town Water System
     PWSID #:
                                AA7654321
     County or District:

     Ground Water
     Sources:
                           Clark County
                           Source Name
                       WeUl
    Source ID Number
WL002
   Well Depth
200ft
                            Well 2
                                                                         800ft
                            2 hydropneumatic tanks - each 100 gallons
                            None
                            None
                            One
Storage:
Treatment:
Booster Stations:
Pressure Reducing
Stations:
Pressure Zones:       There are 2 pressure zones. Well I serves the western pressure
                       zone (zone I). Well 2 can serve both pressure zones (zones I or 2).
TCR sample sites:     We have two TCR sites. One site is in the western zone (zone I) and the
                       other is in eastern zone (zone 2). (See map attached).
     Population and Connections by Pressure Zone
         Pressure Zone 1  Western
                                                          Population
                              Connections
                                                      750
                            302
         Pressure Zone 2 - Eastern
                                                      1,085
                            452
         Total Population and Connections Served
                                                                         754
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1
2
3
4
B. Map of the Water System
(Provide a map either below or attached that shows the location of the sources, pressure zones,
distribution system, storage tanks, and TCR sites.)

                             Two Pressure Zone Water System
                      Western Zone (1)
     Well!

                             Storage Tank

                             TCR Monitoring Site
                                                                                        U
                                                                                  Well 2
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1
2
3
4
C. Wells Representative of Each TCR Site
(Provide the following information on the system's TCR sites and how it was determined
which source provides the water to that site.)
     Tools used to identify wells
     that contribute to TCR sites
     Distribution system maps:
     Coliform Monitoring Plan:


     Distribution system hydraulic
     models:
     Water quality parameters:
     Other:
                                  Explanation of how tool was used for identification

                                  Our system has two pressure zones. The western zone is at a lower
                                  elevation and is generally fed by Well I although during high demand, it
                                  is also fed by Well 2. The eastern zone is higher and is fed by well 2 only.
                                  Our plan identifies primary TCR sampling sites as well as upstream and
                                  downstream sites that are sampled in the event of a TC+ sample.
                                  Not used.

                                  Not used.
                                  Under normal operating conditions Well I is sufficient to serve the western
                                  pressure zone (zone I), and Well 2 serves the eastern zone (zone 2).
                                  However, during the high demand experienced during summer months
                                  (May through September), Well I does not have enough capacity to meet
                                  the demand in Zone I.  When pressures in zone I drop to 35psi, water is
                                  fed from the eastern zone into the western zone through a pressure
                                  reducing valve located at a valve vault near the intersection of Main and
                                  Elm Streets.
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i   D. Wells Representative of Each Other
2   (Provide information about sources and justification for representativeness.)
    Are there ground water sources in your system that can be    JVo
    representative of each other:
    If Yes, list sources and provide justification:
    Ground water sources:
    Justification:
     Ground Water Rule                           A-8                          Public Review Draft
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i    E. Representative Triggered Monitoring Plan
2    (Complete the following information to indicate the ground water sources to be sampled based
3    on a routine total coliform positive sample taken at a TCR site. Attach additional sheets if
4    necessary.)
     TCR Site    Zone       Sources       Contributing    Representative      Seasonal
                          Contributing      Sources          Source to      Considerations
                           to this TCR    Representative       Sample
                               Site        of Each Other     (Triggered)
                                                                             Well 2 only serves
                                                                            this site during high
                                                                              demand (when
                                                                            pressures drop below
                                                                              35psi).  This is
                                                                              typically in the
                                                                              months of May
                                                                            through September
                 Western
        1        (Zone 1)      Wells 1 & 2	Wells 1 & 2

                 Eastern
        2        (Zone 2)        Well 2                             Well 2             n/a
5
6
7
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1    EXAMPLE 2

2    Triggered Source Water Monitoring Plan for Lakeview Water System
O

4    Hydrogeologic representation of ground water sources in a system with one pressure zone.
5
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i   A. System Information
2   (Enter the following information about the water system.)
    Water System Name:
    PWSID #:
    Lakeview Water System
                               AA3434343
    County or District:


    Ground Water
    Sources:
     Storage:

     Treatment:

     Booster Stations:

     Pressure Reducing
     Stations:
     Pressure Zones:

     TCR sample sites:
    Trout County
    Source Name
WeUl
    Source ID Number
WL002
   Well Depth
250ft
                           Well 2
                                                250ft
2 hydropneumatic tanks - each 100 gallons
None
None
None
There is a single pressure zone.
There is one site.
    Population and Connections by Pressure Zone
        Single Pressure Zone
                                 Population
                             Connections
                              511
                          204
4
5
6
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1
2
3
4
5
B. Map of the Water System
(Provide a map either below or attached that shows the location of the sources, transmission
mains and primary distribution mains, pressure zones, distribution system, storage tanks, TCR
sites and a scale.)

                       Single Pressure Zone Water System
    Well 1
    Well 2
                                     Storage Tank
                                 X j TCR Monitoring Site
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i    C. Wells Representative of Each TCR Site
2    (Provide the following information on the system's TCR sites and how it was determined
3    which source provides the water to that site.)
     Tools used to identify wells that  Explanation of how tool was used for identification
     contribute to TCR sites
    Distribution system maps:
     Coliform Monitoring Plan:
    Distribution system hydraulic
    models:
    Water quality parameters:

    Other:
Both wells serve the entire distribution system.
We have 1 TCR site. Both wells contribute
                                    to this site.
Not used.
Not used.
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i    D. Wells Representative of Each Other
2    (Provide information about sources and justification for representativeness.)
     Are there ground water sources in your system that can be    Yes
     representative of each other:
     If Yes, list sources and provide justification:
     Ground water sources:        Wells 1 and 2
     Justification:
         The town is served by a small well field of 2 wells, both within a 2 acre site at the west side of town. The
         attached well logs show that all wells were completed in the same aquifer and drilled to approximately 250
         feet.  In 2007 our engineering consultant prepared a wellhead protection plan (also attached) which shows that
         the wells all have a common recharge area which is free of any obvious sources of nearby fecal contamination.

         We feel that each of these wells are representative of the water quality drawn from this site, and are therefore
         appropriate for representative monitoring. If source monitoring is triggered by a TCR positive sample, we
         propose to sample onfy 1 of the 2 sources for E. coli.
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i   E. Representative Triggered Monitoring Plan
2   (Complete the following information to indicate the ground water sources to be sampled based
3   on a routine total coliform positive sample taken at a TCR site. Attach additional sheets if
4   necessary.)
    TCR Site   Zone      Sources      Contributing    Representative      Seasonal
                         Contributing      Sources          Source to     Considerations
                          to this TCR   Representative      Sample
                             Site        of Each Other    (Triggered)
        1         1        Wells 1&2       Wells 1&2         Well lor 2            n/a
5
6
1
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1    EXAMPLE 3

2    Triggered Source Water Monitoring Plan for Hydropolis Water System
O

4    Combination of hydraulic and hydrogeologic representation of ground water sources in a system
5    with three pressure zones.
6
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1
2
A. System  Information
(Enter the following information about the water system.)
Water System Name:      Hydropolis Water System
     PWSID #:

     County or District:

     Ground Water
     Sources:
     Storage:



     Treatment:

     Booster Stations:

     Pressure Reducing
     Stations:
     Pressure Zones:
     TCR sample sites:
                            AA1234567
                            Beaverhead County
                            Source Name
                        WettX
Source ID Number
   Well Depth
200ft
                             WellY
                                                                            200ft
                             WellZ
                                               WL004
                         350ft
                             Well A
                                               WL005
                         150ft
                             WellB
                                               WL006
                         800ft
                        2 ground level storage tanks - each 50,000 gallons. The Blueberry Tank is located in
                        the Blueberry Hills zone (zone 2). The Eill Tank is located in the Eydropolis zone (zone
                        None
                        None
                        None
                        There are 3 pressure zones. Wells X, If, and Zpump to the Blueberry Tank in zone 2
                        (Blueberry Hills zone). Well Z is a seasonal well that operates in the summer months
                        only. Wells A and B pump to the Hydropolis Tank in zone 3 (Hydropolis zone). Zone
                        1 (Montgomery zone) is fed by all of the wells.
                        We have four TCR sites. One site is in the Blueberry Hill zone, one site is in Montgomery
                        zone, and two sites are in the Hydropolis zone. (See map attached).
     Population and Connections by Pressure Zone
         Pressure Zone I - Montgomery Estates
                                                            Population
                            Connections
                                                        980
                         412
         Pressure Zone 2 - Blueberry Hills
                                                        1,200
                         542
         Pressure Zone 3 - Hydropolis
                                                        1,525
                         784
         Total Population and Connections Served
                                                        3,705
                         1,73}
3
4
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1
2
3
4
5
B. Map of the Water System
(Provide a map either below or attached that shows the location of the sources, pressure zones,
distribution system, storage tanks, and TCR sites.)


                              Multi Pressure Zone Water System
                     Zone 1
         Storage Tank

6     TCR Monitoring Site
       Well 1
       Well 2	>
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i    C. Wells Representative of Each TCR Site
2    (Provide the following information on the system's TCR sites and how it was determined
3    which source provides the water to that site.)
     Tools used to identify wells       Explanation of how tool was used for identification
     that contribute to TCR sites
     Distribution system maps:
     Coliform Monitoring Plan:
     Distribution system hydraulic
     models:
     Water quality parameters:
     Other:
Zone 1 (Montgomery) is at an elevation of 2000 ft, Zone 2 (Blueberry) is
at an elevation of 2500 ft, and Zone 3 (Hydropolis)  is at
an elevation of 2700 ft.	
Our plan identifies the wells that serve each zone and each TCR site. We
made this determination based on our map and a hydraulic model
prepared for us by our consultant.
The hydraulic model indicates that Wells I, If, and Zfeed the Blueberry
Hills zone.  Similarly, Wells A and B, located at the eastern end of town,
feed  the Hydropolis zone.  The lower elevation Montgomery Estates zone is
fed by both sets of wells. The model also shows that Hydropolis zone and
the Blueberry Hills zone are not hydraulically connected.
          J                 J        J
Not used.
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i    D. Wells Representative of Each Other
2    (Provide information about sources and justification for representativeness.)
     Are there ground water sources in your system that can be     Yes
     representative of each other:
     If Yes, list sources and provide justification:
     Ground water sources:         Wells I and Y
4
5
6
     Justification:
         The Western well field includes Wells I, Y, and Z.  Well Z is our oldest well. It was drilled in 1968 and is onfy
         40 feet deep.  This well is only used when required by very high demand.  Wells I and Y were drilled in 2004
         and 2007.  They are approximately 400 feet apart, and each is drilled past the perched aquifer at 40 feet and
         into the deeper more confined aquifer at 130 feet.  The logs show a common lithologyfor each of these wells,
         and a comparison of water chemistry shows similar TtiS levels and no detects on nitrate or nitrite. In addition,
         the recharge areas for these two wells overlap considerably, and neither has a potential source of
         contamination unique to that well.

         We believe that Wells I and Y are similar enough both physically and chemically that they can be considered
         representative of each other. Well Z however is not representative of the other wells at this site and should be
         sampled if it is in use when a TCR sample is total coliform positive in the Blueberry Hills or Montgomery zones.
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1
2
3
4
5
6
7
E. Representative Triggered Monitoring Plan
(Complete the following information to indicate the ground water sources to be sampled based
on a routine total coliform positive sample taken at a TCR site.  Attach additional sheets if
necessary.)
TCR Site    Zone       Sources      Contributing    Representative
                     Contributing      Sources         Source to
                      to this TCR   Representative      Sample
                         Site       of Each Other     (Triggered)
                                                                     Well Z  operational
                                                                      from May through
          Montgomery                                                     September
                                                                             Seasonal
                                                                          Considerations
1
2
3
4
(lone I) Wells X, Y,& Z Wells X&Y
Blueberry Wells X J, Z,
Hills
(Zone 2) A,&B Wells X&Y
Hydropolis
(Zone 3) Wells A &B
Hydropolis
(Zone 3) Wells A &B
Wells X or Y, Z
Well Z  operational
Wells XorY,Z from May through
September
A,&B
Wells A &B

Wells A &B





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1    APPENDIX B

2    Example Triggered Source Water Monitoring Plan (Template)
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i   A. System Information
2   (Enter the following information about the water system.)
    Water System Name:
3
4
5
    PWSID #:

    County or District:
    Ground Water           Source Name        Source ID Number        Well Depth
    Sources:
    Storage:

    Treatment:

    Booster Stations:

    Pressure Reducing
    Stations:
    Pressure Zones:

    TCR sample sites:
    Population and Connections by Pressure Zone          Population       Connections
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i   B. Identification of Which Wells Contribute to Each TCR Site
2   (Provide the following information on the system's TCR sites and how it was determined
3   which source provides the water to that site.)
    Tools used to identify wells      Explanation of how tool was used for identification
    that contribute to TCR sites

    Distribution system maps:
    Coliform Monitoring Plan:

    Distribution system hydraulic
    models:
    Water quality parameters:

    Other:
4
5
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i    C. Map of the Water System
2    (Provide a map either below or attached that shows the location of the sources, pressure zones,
3    distribution system, storage tanks, and TCR sites.)
4
5
6
     Ground Water Rule                            B-5                           Public Review Draft
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i   D. Representative Ground Water Sources
2   (Provide information about sources and justification for representativeness.)
    Are there ground water sources in your system that can be
    representative of each other:
    If Yes, list sources and provide justification:
    Ground water sources:
    Justification:
     Ground Water Rule                          B-6                          Public Review Draft
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i   E. Representative Triggered Monitoring Plan
2   (Complete the following information to indicate the ground water sources to be sampled based
3   on a routine total coliform positive sample taken at a TCR site. Attach additional sheets if
4   necessary.)
    TCR Site   Zone       Sources      Contributing    Representative      Seasonal
                         Contributing      Sources         Source to      Considerations
                          to this TCR    Representative       Sample
                             Site       of Each Other     (Triggered)
5
6
7
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1
2
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