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
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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
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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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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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1 Additional Information
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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
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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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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
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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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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
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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.
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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.
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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.
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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:
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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.
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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.
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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.
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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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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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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.
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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.
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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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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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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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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
Triggered and Representative Source
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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
Ground Water Rule A-9 Public Review Draft
Triggered and Representative Source
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Ground Water Rule A-10 Public Review Draft
Triggered and Representative Source
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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
Ground Water Rule A-11 Public Review Draft
Triggered and Representative Source
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Ground Water Rule A-12 Public Review Draft
Triggered and Representative Source
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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
Ground Water Rule
Triggered and Representative Source
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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
Ground Water Rule
Triggered and Representative Source
Water Monitoring Guidance Manual
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Public Review Draft
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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.
Ground Water Rule
Triggered and Representative Source
Water Monitoring Guidance Manual
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Public Review Draft
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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.
Ground Water Rule A-16 Public Review Draft
Triggered and Representative Source
Water Monitoring Guidance Manual
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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
Ground Water Rule A-17 Public Review Draft
Triggered and Representative Source
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Ground Water Rule A-18 Public Review Draft
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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
Ground Water Rule A-19 Public Review Draft
Triggered and Representative Source
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Ground Water Rule A-20 Public Review Draft
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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
Ground Water Rule
Triggered and Representative Source
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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 >•
Ground Water Rule
Triggered and Representative Source
Water Monitoring Guidance Manual
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Public Review Draft
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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.
Ground Water Rule
Triggered and Representative Source
Water Monitoring Guidance Manual
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Public Review Draft
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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.
Ground Water Rule A-24 Public Review Draft
Triggered and Representative Source
Water Monitoring Guidance Manual
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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
Ground Water Rule
Triggered and Representative Source
Water Monitoring Guidance Manual
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Public Review Draft
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Ground Water Rule A-26 Public Review Draft
Triggered and Representative Source
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1 APPENDIX B
2 Example Triggered Source Water Monitoring Plan (Template)
Ground Water Rule B-l Public Review Draft
Triggered and Representative Source
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Ground Water Rule B-2 Public Review Draft
Triggered and Representative Source
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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
Ground Water Rule B-3 Public Review Draft
Triggered and Representative Source
Water Monitoring Guidance Manual
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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
Ground Water Rule B-4 Public Review Draft
Triggered and Representative Source
Water Monitoring Guidance Manual
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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
Triggered and Representative Source
Water Monitoring Guidance Manual
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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
Triggered and Representative Source
Water Monitoring Guidance Manual
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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
Ground Water Rule B-7 Public Review Draft
Triggered and Representative Source
Water Monitoring Guidance Manual
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1
2
Ground Water Rule B-8 Public Review Draft
Triggered and Representative Source
Water Monitoring Guidance Manual
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