Office of Water (4607M) EPA 815-R-07-020 July 2007 www.epa.gov/safewater 

Consecutive System Guide 

for the Ground Water Rule 
 
Consecutive System Guide i July 2007 

for the Ground Water Rule 

Purpose 

The purpose of this guidance manual is solely to provide technical information for water 

systems and states to assist them in complying with Ground Water Rule (GWR). The statutory 

provisions and EPA regulations described in this document contain legally binding 

requirements. This guidance is not a substitute for applicable legal requirements, nor is it a 

regulation itself. Thus, it does not impose legally-binding requirements on any party, including 

EPA, States, or the regulated community. While EPA has made every effort to ensure the 

accuracy of the discussion in this guidance, the obligations of the regulated community are 

determined by statutes, regulations, or other legally binding requirements. In the event of a 

conflict between the discussion in this document and any statute or regulation, this document 

would not be controlling. 

Interested parties are free to raise questions and objections to the guidance and the 

appropriateness of using it in a particular situation. 

Although this manual describes suggestions for complying with GWR requirements, the 

guidance presented here may not be appropriate for all situations, and alternative approaches 

may provide satisfactory performance. 

Authorship 

This manual was prepared by EPA’s Office of Water. Questions concerning this 

document should be addressed to: 

 

Michael Finn 

U.S.EPA Office of Ground Water and Drinking Water 

Standards and Risk Management Division 

1200 Pennsylvania Ave, N.W. 4607M 

Washington D.C. 20460-0001 

finn.michael@epa.gov

202-564-5261 

202-564-3767(facsimile) 

Acknowledgements 

American Water Works Association 

Association of Metropolitan Water Agencies 

Association of State Drinking Water Administrators 

Eugene Leung – California Department of Public Health 
Consecutive System Guide ii July 2007 

for the Ground Water Rule 

CONTENTS 

1. Introduction....................................................................................................................................1-1 

1.1 General requirements of the GWR ............................................................................................1-1 

2. GWR Requirements for Consecutive and Wholesale Ground Water Systems .............................2-1 

2.1 Is triggered source water monitoring always required?.............................................................2-2 

2.2 What if you believe a fecal indicator-positive source water sample is due to a lab error or other 

cause rather than source water contamination? ........................................................................2-2 

2.3 What does the GWR require for a consecutive system that has a TC-positive routine sample 

collected under TCR in its distribution system?.......................................................................2-3 

2.4 What does the GWR require for wholesale systems that are notified that its consecutive system 

has a TC-positive routine sample collected under TCR in the consecutive system distribution 

system? .....................................................................................................................................2-3 

2.5 What are the GWR triggered source water monitoring requirements for a consecutive system 

with its own ground water sources? .........................................................................................2-3 

2.6 What are the GWR triggered source water monitoring requirements for a consecutive system 

with more than one connection to a wholesale system (or connections to more than one 

wholesale system)?...................................................................................................................2-5 

2.7 What are the GWR triggered source water monitoring requirements for a wholesale system 

with multiple wells? .................................................................................................................2-6 

2.8 What steps can a wholesale system take to facilitate meeting the requirements for triggered 

source water monitoring under the GWR?...............................................................................2-7 

2.9 What steps can a consecutive system take to facilitate meeting the GWR notification 

requirements for TC-positive samples collected under TCR? .................................................2-8 

2.10 What if a consecutive system is supplied with ground water by another consecutive system? 2-8 

3. GWR Consecutive System Examples............................................................................................3-1 

3.1 Example 1 ..................................................................................................................................3-1 

3.2 Example 2 ..................................................................................................................................3-3 

3.3 Example 3 ..................................................................................................................................3-5 

4. Example: Triggered Source Water Monitoring Plan....................................................................4-1 

5. Glossary .........................................................................................................................................5-1 
Consecutive System Guide iii July 2007 

for the Ground Water Rule 

 

Abbreviations 

GWR Ground Water Rule (40 CFR Part 141 Subpart S) 

SDWA Safe Drinking Water Act 

TCR Total Coliform Rule (40 CFR Part 141 Subpart C) 

LCR Lead and Copper Rule (40 CFR Part 141 Subpart I) 

TC Total Coliform 

For more information, contact EPA's Safe Drinking Water Hotline, 1 (800) 426-4791, or see the 

Office of Ground Water and Drinking Water web page at http://www.epa.gov/safewater. 

 

This guidance manual is available electronically at 

http://www.epa.gov/safewater/disinfection/gwr/compliancehelp.html. To order a paper copy of 

guidance manuals, you may contact the US EPA Water Resource Center at 202-566 -1729 or by mail 

at: 

 

US Environmental Protection Agency 

Water Resource Center (RC-4100) 

1200 Pennsylvania Ave NW 

Washington DC 20460 

E-mail: center.water-resource@epa.gov

Other Guidance Manuals 

EPA has developed other guidance manuals to aid EPA, State agencies, and you in 

implementing the GWR and other rules and to help to ensure consistent implementation. 

Consider the Source: A Pocket Guide to Protecting Your Source: Drinking Water Pocket 

Guide #3 - An electronic version is available at http://www.epa.gov/safewater/sourcewater. 

Public Notification Handbook (EPA 816- R- 00-010) - An electronic version is available at 

http://www.epa.gov/safewater/publicnotification/compliancehelp.html. 

Preparing Your Drinking Water Consumer Confidence Report (CCR), Revised Guidance 

for Water Suppliers EPA 816-R-002, April 2005. This document provides information to 

assist drinking water systems with preparing and distributing CCRs. An electronic version is 

available at http://www.epa.gov/safewater/ccr/compliancehelp.html. 

Consumer Confidence Report Rule: A Quick Reference Guide (EPA 816-F-02-026), 

November 2002 - A condensed guide that provides a brief overview of the Consumer 

Confidence Report Rule. An electronic version is available at 

http://www.epa.gov/safewater/ccr/compliancehelp.html. 

Surface Water Treatment Rule Guidance Manual - The Appendices also include CT tables 

for the inactivation of Giardia and viruses for chlorine, chlorine dioxide and ozone. 
Consecutive System Guide iv July 2007 

for the Ground Water Rule 

EPA is also developing a series of guidance documents to help public water systems implement 

requirements associated with the GWR. Electronic versions of the guidance documents are, or will be, 

available on the GWR Compliance Help page at 

http://www.epa.gov/safewater/disinfection/gwr/compliancehelp.html.

Complying with the Ground Water Rule: Small Entity Compliance Guide (EPA 815-R07-018) - This guide is designed for owners and operators of public water systems serving 

10,000 or fewer persons that are required to comply with the Ground Water Rule. 

Ground Water Rule Corrective Action Guidance Manual - This manual provides 

information for ground water systems that must provide corrective action as a result of 

significant deficiencies or fecally-contaminated source water. The guidance includes technical 

information on selecting appropriate disinfection technologies to enable primacy agencies and 

PWSs to select the treatment most appropriate for a given system. It also provides technical 

information to States and systems on eliminating sources of contamination, utilizing alternate 

sources, and correcting significant deficiencies for situations in which disinfection is not the 

selected corrective action. 

Sanitary Survey Guidance Manual for Ground Water Systems - This guidance provides 

information to assist States and other primacy programs in conducting sanitary surveys of 

ground water systems. 

Ground Water Rule Source Water Monitoring Methods Guidance Manual (EPA 815-R01-019) - This manual provides guidance on triggered and optional assessment source water 

monitoring issues such as: selection of fecal indicators, sample collection and shipping, source 

water monitoring methods, laboratory quality assurance (QA) and quality control (QC), and 

evaluation of fecal indicator data. This manual also provides an overview of GWR 

requirements and includes frequently asked questions regarding source water monitoring. 

Ground Water Rule Source Assessment Guidance - This manual provides information on 

procedures for identifying ground water sources at risk for contamination. Risk factors are 

discussed with emphasis on identifying readily available factors suitable for office, rather than 

field determination of risk at an individual PWS well. The guidance also lists sources of 

information for making determinations and includes field methods for determining the presence 

of a hydrogeologic barrier. 
Consecutive System Guide 1-1 July 2007 

for the Ground Water Rule 

1. Introduction 

 This guide describes the regulatory requirements of the Ground Water Rule (GWR) as it 

applies to wholesale systems that supply ground water and to the consecutive water systems that 

receive and distribute that ground water supply. 

The GWR applies to all public water systems that use ground water unless the system combines 

all of its ground water with surface water prior to treatment under 40 CFR 141 Subpart H 

(Filtration and Disinfection). 

A wholesale system is a public water system that supplies finished water to one or more other 

public water systems. 

A consecutive system is a public water system that buys or otherwise receives some or all of its 

finished water from a wholesale system. 

 This document is intended to provide guidance to wholesale and consecutive ground water 

systems and States in employing source water monitoring to identify fecal contamination of ground 

water sources, one of the risk-based components of the GWR 

 

Consecutive systems, and wholesale/consecutive system interactions and contractual 

relationships, can be complex. There are a variety of State approaches to addressing regulatory 

requirements for consecutive systems since most previous regulations under the SDWA did not 

specifically address consecutive systems. 

 In the development of the GWR, the Stage 2 Disinfectants and Disinfection Byproducts Rule 

and the Long Term 2 Enhanced Surface Water Treatment Rule under the SDWA, EPA has explicitly 

addressed the applicability of these regulations to consecutive systems. EPA is providing guidance to 

assist public water systems and States in implementing these regulations addressing consecutive 

systems. 

1.1 General requirements of the GWR 

 The requirements of the GWR (40 CFR Subpart S) constitute national primary drinking water 

regulations. The GWR was published in the Federal Register on November 8, 2006 (71 Federal 

Register 65574). A copy of the rule language can be found on EPA’s website at 

http://www.epa.gov/safewater/disinfection/gwr/regulation.html. 
Consecutive System Guide 1-2 July 2007 

for the Ground Water Rule 

The following are general GWR requirements applicable to wholesale and consecutive ground 

water systems: 

(a) Provide requested existing information to the State to aid the State in performing a 

sanitary survey of your system. 

(b) Correct any significant deficiencies identified by the State in your system within a 

required timeframe. 

(c) A consecutive system is required to report TC-positive routine sample collected under 

TCR to the wholesale supplier(s) within 24 hours of being notified of the TC-positive 

sample, unless the consecutive system or wholesale system(s) provide(s) 4-log (99.99 

percent) treatment of viruses (by inactivation, removal or a combination of inactivation 

or removal) for the wholesale ground water source(s). 

(d) Wholesale systems and consecutive systems with their own ground water sources 

must perform triggered microbial monitoring of ground water source(s) after a TCpositive routine sample collected under TCR if they do not provide 4-log (99.99 

percent) treatment of viruses (by inactivation, removal or a combination of inactivation 

or removal) for the source. 

(e) A wholesale system is required to notify the consecutive system(s) of a fecal indicatorpositive ground water source sample within 24 hours of being notified of the fecal 

indicator-positive sample. 

(f) Correct fecal contamination of your ground water source(s) within a required 

timeframe. 

(g) If required by your State, provide existing information to the State to aid the State in 

performing a hydrogeologic sensitivity assessment for your source(s). 

(h) Wholesale systems and consecutive systems with their own ground water sources 

must perform assessment microbial monitoring of ground water source(s) if required 

by the State. 

(i) If required by the State, monitor any treatment process used to provide 4-log (99.99 

percent) treatment of viruses (by inactivation, removal or a combination of inactivation 

or removal) of viruses for your source(s), and 

(j) Keep records and report to the State for certain requirements listed in (a)-(i) above. 

 The requirements specific to wholesale and consecutive systems are discussed in greater detail 

in the next section. 
Consecutive System Guide 2-1 July 2007 

for the Ground Water Rule 

2. GWR Requirements for Consecutive and Wholesale Ground Water Systems 

Exhibit 2.1 describes some of the specific responsibilities of consecutive and wholesale ground 

water systems under the GWR. 

 

Exhibit 2.1 GWR Requirements for Wholesale and Consecutive Systems 

(Yes=Required, No=Not Required) 

Ground Water Rule Requirement Wholesale 

System

Consecutive 

System -100% of 

supply 

purchased

Consecutive system - 

purchased and own 

supply

Provide the State with information it requests to complete the 

sanitary survey. 

Correct any significant deficiencies identified by the State within 

a required timeframe. 

Notify your wholesale supplier within 24 hours of being notified 

by your laboratory of a TC-positive routine sample collected 

under TCR in your distribution system if you or your wholesale 

supplier do not provide 4-log treatment of viruses for your 

ground water supply. 

Triggered1 source water monitoring of your own sources2

 if you 

do not provide 4-log treatment of viruses for those sources 

Triggered1

 source water monitoring of your source(s)2 if you are 

notified of TC-positive routine sample collected under TCR by a 

consecutive system you serve and if you or the consecutive 

system do not provide a 4-log treatment of viruses for your 

sources. 

Notify consecutive systems you serve within 24 hours if a ground 

water source sample is fecal indicator-positive. 

Corrective action and/or treatment of your ground water sources, 

if required, after a fecal indicator-positive source water sample. 

If directed by the State, provide the State with information it 

requests to complete the hydrogeologic sensitivity assessment for 

your water system. 

If directed by the State, conduct assessment source water 

monitoring of your ground water sources. 

Monitor treatment processes in accordance with GWR and State 

requirements. 

Reporting, record keeping and public notification requirements of 

the GWR. 

Yes 

Yes 

No 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

No 

No 

No 

No 

No 

No 

Yes 

Yes 

Yes 

Yes 

Yes 

Yes 

No 

No 

Yes 

Yes 

Yes 

Yes 

Yes 

1 Triggered source monitoring consists of collecting a sample from your ground water sources(s) after a TC-positive 

routine sample collected under TCR and analyzing the sample for a fecal indicator approved by the State.

2 All sources do not have to be monitored under triggered monitoring if a “triggered source water monitoring plan” has 

been developed and approved by the State. 
Consecutive System Guide 2-2 July 2007 

for the Ground Water Rule 

2.1 Is triggered source water monitoring always required? 

A wholesale system or a consecutive system with its own ground water source(s) that has 

evidence that the TC-positive routine sample collected under TCR is due to a distribution system 

deficiency in the wholesale or consecutive 

system distribution system, rather than 

source water contamination, may apply to 

the State for an exception to the triggered 

source water monitoring requirements on a 

case-by-case basis. 

• The State is then required to make a 

determination that the total coliformpositive sample is caused by a distribution system deficiency in the wholesale or consecutive 

distribution system. 

• If the State decides to grant an exception to the triggered source water monitoring 

requirements, then the State must document the decision in writing. 

• You should have information that demonstrates the distribution problem that caused the 

positive sample available for the State when you make your request for an exception. 

The State may also establish criteria for distribution system conditions that will cause total 

coliform-positive samples. If the total coliform-positive sample was collected in the wholesale or 

consecutive distribution system under conditions that meet those State-specified criteria, you are not 

required to conduct triggered source water monitoring. You must notify the State within 30 days of the 

total coliform-positive sample that met State criteria for an exception to the triggered monitoring 

requirements of the GWR. You should become familiar with your State’s criteria for exceptions to 

triggered monitoring. 

2.2 What if you believe a fecal indicator-positive source water sample is due to a lab error or 

other cause rather than source water contamination? 

 

The State may invalidate a fecal indicator-positive source sample if the laboratory establishes 

that improper sample analysis occurred or if the State has substantial grounds to believe that a sample 

result is due to circumstances that do not reflect source water quality. 

 

• If the State invalidates a fecal indicator-positive sample, then the GWR requires that the State 

document the decision in writing. 

• You should have information from the laboratory about the analysis or information that 

demonstrates the fecal indicator-positive does not reflect source water quality available for the 

State to review when you make your request to invalidate. 

• If the State invalidates a fecal indicator-positive source water sample, the GWR requires that 

the system must collect another source water sample and have it analyzed for the same fecal 

indicator within 24 hours of being notified of the invalidation. 

If the wholesale system or consecutive 

system provides 4-log treatment of 

viruses for a ground water source and 

conducts compliance monitoring, triggered 

source water monitoring for that source is 

not required. 
Consecutive System Guide 2-3 July 2007 

for the Ground Water Rule 

2.3 What does the GWR require for a consecutive system that has a TC-positive routine 

sample collected under TCR in its distribution system? 

 

The GWR requires that a consecutive system that serves ground water from a wholesale system 

that has not received 4-log treatment for viruses do the following after it is notified of a TC-positive 

routine sample collected under TCR in the consecutive system’s distribution system: 

• Notify the wholesale system(s) of the TC-positive routine sample collected under TCR within 

24 hours. 

• Conduct public notification if a source water sample from a source that serves the consecutive 

system is fecal indicator-positive. 

2.4 What does the GWR require for wholesale systems that are notified that its consecutive 

system has a TC-positive routine sample collected under TCR in the consecutive system 

distribution system? 

 

The GWR requires that a wholesale system that supplies ground water that has not received 4-

log treatment for viruses do the following when it is notified that its consecutive system has a TCpositive routine sample collected under TCR in the consecutive system’s distribution system: 

• Collect a sample from the wholesale system’s ground water source(s) and analyze the sample 

for a fecal indicator; 

• If a source water sample is fecal indicator-positive, notify all consecutive systems served by the 

source (and conduct public notification if the source also serves the wholesale system’s 

consumers); 

• Complete corrective action if required by the State after the initial fecal indicator-positive 

sample; and 

• Complete corrective action if any of the five additional samples collected after the initial fecalindicator positive is also fecal indicator-positive. 

2.5 What are the GWR triggered source water monitoring requirements for a consecutive 

system with its own ground water sources? 

 One of the main elements of the GWR is to identify contaminated ground water sources 

through sampling and correct them as needed. If a consecutive system that has its own source(s) of 

ground water has a TC-positive routine sample collected under TCR in its distribution system and does 

not know which source is the cause, it must sample its source(s) and must notify its wholesale supplier 

as required by the GWR. 
Consecutive System Guide 2-4 July 2007 

for the Ground Water Rule 

 However, if the consecutive system can identify portions of its system that are served by only 

one source, monitoring of all the sources may not be necessary. Consecutive systems with their own 

sources should review their distribution system and available water quality data to determine if certain 

parts of its system are served by a particular source. Information that could help identify areas served 

by a particular source includes: 

• Distribution system maps with pressure zones, isolation valves, storage tanks, sources, flow 

meters, and any other significant facilities identified, 

• Normally closed valves between service areas or pressure zones, 

• Water quality information that identifies a particular source (alkalinity, pH, disinfectant 

residual, fluoride, Lead and Copper Rule parameters etc.), and/or 

• Distribution system models (proprietary software , EPANET). These tools need to be properly 

calibrated and verified for valid results to be obtained in a specific distribution system. 

 If sufficient information is available, it may be possible to associate a routine TCR monitoring 

site with a particular source. In the event of a TC-positive routine sample collected under TCR at such 

a site, the system and the State can be confident that the correct source is being sampled. 

 A triggered source water monitoring plan can help ensure the correct source is sampled without 

collecting unnecessary samples. Under the GWR, States may require a triggered source water 

monitoring plan to be submitted for systems with more than one ground water source. Even if your 

State does not require you to submit a triggered source water monitoring plan, you may wish to 

develop one anyway and discuss it with your State. You may also want to develop a monitoring plan if 

you rotate the wells you use on a regular basis or if you only use a well during certain times of the 

year. For example, a triggered source water monitoring plan for a system with seasonal sources could 

include both a summer and winter monitoring plan. The GWR requires that a triggered source water 

sample be collected within 24 hours of being notified of a TC-positive routine sample collected under 

TCR. A triggered source water monitoring plan can help you make a decision about where to collect a 

sample more rapidly. 

If directed by the State, systems must submit for State approval a triggered source 

water monitoring plan that identifies one or more ground water sources that are 

representative of each monitoring site in the system’s sample siting plan under 

141.21(a) (commonly known as the Total Coliform Rule) and that the system intends to 

use to meet the triggered monitoring requirements of the Ground Water Rule 

(§141.402). 
Consecutive System Guide 2-5 July 2007 

for the Ground Water Rule 

2.6 What are the GWR triggered source water monitoring requirements for a consecutive 

system with more than one connection to a wholesale system (or connections to more than 

one wholesale system)? 

A consecutive system with multiple connections to a wholesale system or with connections to 

more than one wholesale system may not know which connection is responsible for a TC-positive 

routine sample collected under TCR in its distribution system. If the system does not know which 

connection could be the cause and has more than one wholesale supplier, it must notify all its 

wholesale suppliers as required by the GWR. However, if the consecutive system can identify portions 

of its system that are served by a particular connection, monitoring of all the wholesale sources may 

not be necessary. 

Wholesale systems that serve through multiple connections should review their distribution 

system and available water quality data to determine if certain consecutive systems or certain 

connections are served by a particular source. As in the previous discussion, water quality data, 

pressure zone and valve maps, and modeling can be useful in determining if a particular consecutive 

system connection is served by particular source. This would also apply to wholesale systems that 

serve consecutive systems served by more than one wholesale system. If there is sufficient information 

to demonstrate that a particular sample location in a consecutive system is served by a particular 

wholesale supply, then the required triggered source water monitoring may not have to be completed 

for all sources. 

For wholesale systems with multiple consecutive systems and consecutive systems with 

multiple wholesale suppliers, the decision about where to collect a source water sample may not be 

straightforward. As discussed previously, a triggered source water monitoring plan can help ensure the 

correct source is sampled without collecting unnecessary samples. States may require a triggered 

source water monitoring plan to be submitted for consecutive systems. Even if your State does not 

require you to submit a triggered source water monitoring plan, you may wish to develop one and have 

it reviewed by your State. 

• A triggered source water monitoring plan is particularly useful for wholesale systems with 

multiple consecutive systems and multiple sources and for consecutive systems with their own 

sources, multiple wholesale suppliers, or multiple connections to a wholesale supplier. 

• Wholesale and consecutive systems may also want to develop a triggered source water 

monitoring plan if they rotate the wells used on a regular basis or only use a well during certain 

times of the year. 
Consecutive System Guide 2-6 July 2007 

for the Ground Water Rule 

2.7 What are the GWR triggered source water monitoring requirements for a wholesale 

system with multiple wells? 

Most wholesale ground water systems will have more than one well. The wells may not draw 

from the same aquifer or certain wells may not serve certain parts of the system or customers. Once the 

wholesale system is notified of a TC-positive routine sample collected under TCR by one of its 

consecutive systems it must decide (within 24 hours) where to collect the required source water 

samples and then collect the sample. 

 

• If you are a wholesale system with more than one ground water source and you cannot identify 

which wells serve the consecutive system, or identify a well or wells representative of the 

ground water you supplied, you must sample all your sources. 

• A representative well (or wells) should represent all your ground water sources that have the 

potential to serve the area that had the total-coliform positive sample. Use of a representative 

well (or wells) requires State approval. 

• If a well (or wells) only serves some of the consecutive system(s) or portions of the wholesale 

distribution system and you provide this information to the State in a triggered source water 

monitoring plan, you may be able to sample only the source(s) that serves the system, or 

portions of the system, with a TC-positive routine sample collected under TCR. 

The GWR requires that each source in use be sampled within 24 hours of being 

notified of a TC-positive routine sample collected under TCR. However, a Stateapproved triggered source water monitoring plan can reduce the number of sources that 

need to be sampled by identifying the specific source(s) serving the site of the TCpositive routine sample collected under TCR. 

With a triggered source water monitoring plan approved by the State, the system and the 

State can have confidence that the correct source is being sampled after a TC-positive 

routine sample collected under TCR without collecting a sample from every source in the 

system. Part 4 of this guidance document describes the recommended minimum 

elements of a triggered source water monitoring plan 

A triggered source water monitoring plan can help ensure that the source(s) that serve(s) the TCR 

sample site is sampled without collecting samples from every source. States may require a triggered 

source water monitoring plan to be submitted for systems with more than one ground water source. 

The triggered source water monitoring plan can identify representative sources, or areas served by 

different sources for likely distribution system scenarios, as well as sources used only seasonally or 

on a rotating schedule so that the appropriate sources are sampled. Even if your State does not 

require you to submit a triggered source water monitoring plan, you may wish to develop one anyway 

and discuss it with your State. Part 4 of this guidance document describes the recommended 

minimum elements of a triggered source water monitoring plan. 
Consecutive System Guide 2-7 July 2007 

for the Ground Water Rule 

2.8 What steps can a wholesale system take to facilitate meeting the requirements for 

triggered source water monitoring under the GWR? 

Under the GWR, a wholesale system is responsible for collecting a source water sample from 

each source in use after being notified of a TC-positive routine sample collected under TCR in its own 

or any of its consecutive systems’ distribution system(s) unless it is has a State-approved triggered 

source water monitoring plan that permits more focused source monitoring. Information about and 

communication with the consecutive systems is needed to meet the GWR requirements 

Steps a wholesale system can take to facilitate notification of TC-positive routine samples 

collected under TCR in the consecutive systems it serves include: 

 

• Identify all consecutive systems subject to TCR and to GWR triggered source water monitoring 

under the GWR. 

• Identify all connection(s) to those consecutive systems. Include information about the source 

and status (active, standby, abandoned etc.) of each connection. Identify who has the ability to 

alter the status of the connection and the date the status was last confirmed, if applicable. 

• Identify those consecutive systems with their own ground water sources and those supplied by 

another wholesale water system. 

• Identify a contact (and alternates and after hours contacts) for each consecutive system, keep a 

record of contact phone numbers, and develop a procedure to keep the contact list up to date 

and accurate. 

• Provide training and/or outreach materials on the requirements for notification by consecutive 

systems to their wholesale suppliers and the need for timely notification to the wholesaler of 

TC-positive routine samples collected under TCR in the consecutive system(s) distribution 

system(s). 

• Identify any consecutive systems that are non-community water systems. These systems may 

not have full time staff and may have special needs for communication and training and 

outreach. Timely notification of the wholesale system is an important element of the triggered 

monitoring requirements of the GWR. The wholesale system may need to make special efforts 

and arrangements for non-community consecutive systems. 

• Identify the local laboratories used by the consecutive systems and contacts in those 

laboratories. With cooperation of the consecutive systems and the laboratory, develop a 

response plan for notification of any TC-positive routine samples collected under TCR from 

either the wholesale system or the consecutive system. 

• Identify staff contacts within the wholesale systems for consecutive system communication and 

liaison functions. 

• Develop a documentation process for all communications. 
Consecutive System Guide 2-8 July 2007 

for the Ground Water Rule 

2.9 What steps can a consecutive system take to facilitate meeting the GWR notification 

requirements for TC-positive samples collected under TCR? 

It is important to establish a communication process for the consecutive systems to notify the 

wholesale system of TC-positive routine samples collected under TCR and be aware of water quality 

and operational issues in the wholesale systems. Communication processes could include: 

• Written communication and notification procedures. Non-community water systems without 

full-time staff may need to make special arrangements to ensure timely notification from the 

laboratory and timely notification of and communication with the wholesale system. 

• Dedicated phone lines with after hours forwarding or recorded message capacity. 

• Web-based information pages and message posting. 

• Pager, cell phone, and wireless message transmission. 

• E-mail notification. 

• Laboratory notification of both the consecutive and wholesale system for a TC-positive routine 

sample collected under TCR. 

2.10 What if a consecutive system is supplied with ground water by another consecutive 

system? 

The GWR requires that a wholesale system collect and analyze at least one source water 

sample if the wholesale system (or the consecutive system) does not provide 4-log virus treatment of 

the ground water supplied to the consecutive system and a TC-positive routine sample collected under 

TCR occurs in the consecutive system. 

 

In some systems, the wholesale supply may pass through one or more consecutive systems 

before reaching its final consecutive connection. In these cases, a triggered source water monitoring 

plan and reliable communications and notification processes are important to ensure that both the 

consecutive system and the wholesale system meet their responsibilities under the GWR. Triggered 

source water monitoring plans can be prepared for the combined wholesale/consecutive distribution 

system or on a system-by-system basis. 

Source water monitoring plans for wholesale systems should identify the consecutive systems 

served and, if applicable, the sources serving each consecutive system. Source water monitoring plans 

for consecutive systems should identify the wholesale supply or suppliers for the points of entry. 

Source water monitoring plans for combined wholesale/consecutive should include all the information 

describe previously for individual wholesale or consecutive systems. Sections 2.8 and 2.9 describe 

important elements of communication and notification between wholesale and consecutive systems. 

Part 4 of this guidance document describes the recommended minimum elements of a triggered source 

water monitoring plan. 
Consecutive System Guide 3-1 July 2007 

for the Ground Water Rule 

3. GWR Consecutive System Examples 

3.1 Example 1 

Figure 3.1 – First Valley Water District System 

– The First Valley Water District purchases ground water from the Big Mountain Water District 

in addition to having one well. 

– The First Valley supply is delivered through valved connections from Big Mountain’s Cross 

County Pipeline. 

– First Valley Water District also has its own well that is used routinely. 

– Pressure in the Big Mountain supply is only adequate to serve the low zone of the system. 

– Some mixing of the Big Mountain supply and First Valley’s own supply occurs between the 

low and the high zone (Mixed Zone). 

– The Big Mountain supply can only reach the high zone when the Walnut Grove Pump Station 

is operated to move water between zones and this occurs only when the Alder Grove Well is 

W- 1

High Zone

Mixed Zone

Low Zone

P-2

S-1

P-1

T-1

T-2

T-3

T-4

T-5

T-6

Key

S-1 Source #1- Purchased Water from Big Mountain Water Dist.

P-1 Pump Station #1- Walnut Grove Pump Station

(operational only if W-1 is out of service)

W-1 Well #1- Alder Grove Well 

P-2 Pump Station #2 – Alder Grove Well Pump Station

T-1 TCR Sampling Site #1

T-2 TCR Sampling Site #2

T-3 TCR Sampling Site #3

T-4 TCR Sampling Site #4

T-5 TCR Sampling Site #5

T-6 TCR Sampling Site #6

W- 1

High Zone

Mixed Zone

Low Zone

P-2

S-1

P-1

T-1

T-2

T-3

T-4

T-5

T-6

Key

S-1 Source #1- Purchased Water from Big Mountain Water Dist.

P-1 Pump Station #1- Walnut Grove Pump Station

(operational only if W-1 is out of service)

W-1 Well #1- Alder Grove Well 

P-2 Pump Station #2 – Alder Grove Well Pump Station

T-1 TCR Sampling Site #1

T-2 TCR Sampling Site #2

T-3 TCR Sampling Site #3

T-4 TCR Sampling Site #4

T-5 TCR Sampling Site #5

T-6 TCR Sampling Site #6
Consecutive System Guide 3-2 July 2007 

for the Ground Water Rule 

out of service or in an emergency (fire, major leak). 

Based on the hydraulics of the First Valley system: 

– A TC-positive routine sample collected under TCR in the low zone (TCR sites 1 and 2) triggers 

source water sampling in the Big Mountain Water District’s sources. 

– A TC-positive routine sample collected under TCR in the high zone (TCR sites 5 and 6) 

triggers a source water sample from the Alder Grove Well. This is true as long as the Walnut 

Grove Pump Station was not operating at the time of the TC-positive routine sample collected 

under TCR. 

– The mixed zone contains water from both sources. Since a single source cannot be identified 

for this zone, triggered source water samples must be collected from both the Big Mountain 

source(s) and the Alder Grove Well after a TC-positive routine sample collected under TCR in 

the mixed zone (TCR sites 3 and 4). 

 In this example, system hydraulics and operation allow for some of the routine TCR monitoring 

sites to be identified as supplied by only one of the First Valley District’s sources. The GWR requires 

that source water samples be collected no more than 24 hours after being notified of a TC-positive 

routine sample collected under TCR, or for a wholesale system, no more than 24 hours after being 

notified by their consecutive system of TC-positive routine sample collected under TCR in the 

consecutive system’s distribution system. To meet these requirements, it important that samples be 

properly identified and that system personnel are aware of the correct response to a TC-positive routine 

sample collected under TCR at a particular sample location. Also, the State would have to approve 

representative sampling or a triggered source water monitoring plan. 
Consecutive System Guide 3-3 July 2007 

for the Ground Water Rule 

3.2 Example 2 

Figure 3.2 – Second Valley Water District System 

The Second Valley Water District purchases its entire supply from the Big Mesa Water District 

and the Third Valley Water District. 

– Second Valley has three pressure zones in its system. 

– Two zones are served by connection to Big Mesa; the third zone is served by a connection to a 

Third Valley Water District pipeline. 

– The Big Mesa Water District adds chlorine to its ground water supply but does not provide a 4-

log inactivation of viruses. 

– The Third Valley Water District adds chloramine to its supply. 

– The Third Valley supply is a mix of surface water and ground water depending on the time of 

year and Third Valley provides a 4-log virus inactivation for its ground water supply. 

P-1

Pressure Zone 1

Pressure Zone 2

Pressure Zone 3

Key

S-1 Source #1 - Purchased Water from Big Mesa Water District

S-2 Source #2 – Purchased Water from Third Valley Water District 

P-1 Pump Station (normally isolated)

Note: Figures not drawn to scale

S-1

S-2

P-1

Pressure Zone 1

Pressure Zone 2

Pressure Zone 3

Key

S-1 Source #1 - Purchased Water from Big Mesa Water District

S-2 Source #2 – Purchased Water from Third Valley Water District 

P-1 Pump Station (normally isolated)

Note: Figures not drawn to scale

S-1

S-2
Consecutive System Guide 3-4 July 2007 

for the Ground Water Rule 

– The three zones are interconnected but the Second Valley operators keeps the connections 

between the zones at valves and pump stations closed to prevent mixing and the taste and odor 

complaints that often happen when the two supplies mix. 

In this example, there are multiple wholesale sources, however the two sources do not mix 

under normal conditions. If a TC-positive routine sample collected under TCR occurred in the Second 

Valley system: 

– A source water sample from the Big Mesa sources would be required for a TC-positive routine 

sample collected under TCR in the two zones served by the Big Mesa supply. 

– No source water sample would be required for TC-positive routine sample collected under TCR 

that occurred in the zone served by the Third Valley supply since Third Valley provides a 4-log 

virus inactivation for its sources. 
Consecutive System Guide 3-5 July 2007 

for the Ground Water Rule 

3.3 Example 3 

Figure 3.3 – Fourth Valley Water District System 

The Fourth Valley Water District purchases its entire supply from the Big Gulch Water District 

and the Last Valley Water District. Fourth Valley has three pressure zones in its system. One zone is 

served by the connection to Big Gulch the other two zones are served by connections to the Last 

Valley Water District transmission pipeline. 

– The Big Gulch Water District adds chlorine to its wholesale ground water supply but does not 

provide a 4-log inactivation of viruses. 

– The Last Valley Water District supply is a mix of surface water and ground water. 

– The Last Valley Water District also adds chlorine to its supply but does not provide a 4-log 

inactivation of viruses for its ground water sources. 

S-1

Pressure Zone 1

Pressure Zone 2

Pressure Zone 3

Key

S-1 Source #1 - Purchased Water from Big Gulch Water District

S-2 Source #2 - Purchased Water from Last Valley Water District

Note: Figures not drawn to scale

S-2

S-1

Pressure Zone 1

Pressure Zone 2

Pressure Zone 3

Key

S-1 Source #1 - Purchased Water from Big Gulch Water District

S-2 Source #2 - Purchased Water from Last Valley Water District

Note: Figures not drawn to scale

S-2
Consecutive System Guide 3-6 July 2007 

for the Ground Water Rule 

– The Last Valley Water District surface water supply has a low alkalinity and the Last Valley 

District adjusts the pH to protect its pipelines and meet the water quality parameters set by the 

State under the Lead and Copper Rule. 

– As Fourth Valley has conducted its Lead and Copper Rule water quality parameters tap 

sampling it has identified the parts of its service area that receive the Last Valley supply. That 

information has been put on a distribution system map along with the locations of the routine 

TCR monitoring sites. 

 

 This example is more complicated than the first two because Fourth Valley has two wholesale 

supplies with both surface and ground water sources and multiple pressure zones. For large wholesale 

systems with multiple customers and multiple sources, deciding where to collect the required source 

water samples could be even more complicated. 

 In this example, Fourth Valley has information it collected for the Lead and Copper Rule that 

could allow it to identify the wholesale supply at any of its routine TCR monitoring sites and reduce 

the number of source water samples that must be collected. The water quality information combined 

with a triggered source water monitoring plan would allow the Fourth Valley system to quickly 

identify the source and notify the correct wholesale supplier. 
Consecutive System Guide 4-1 July 2007 

for the Ground Water Rule 

4. Example: Triggered Source Water Monitoring Plan 

 

A triggered source water monitoring plan can help ensure that the source(s) that serve the TCR 

sample site is sampled without collecting samples from every source. States may require a triggered 

source water monitoring plan to be submitted for systems with more than one ground water source. 

The triggered source water monitoring plan can identify representative sources, or areas served by 

different sources for likely distribution system scenarios, as well as sources used only seasonally or on 

a rotating schedule so that the appropriate sources are sampled. For example, a triggered source water 

monitoring plan for a system with seasonal sources could include both a summer and a winter 

monitoring plan. Even if your State does not require you to submit a triggered source water monitoring 

plan, you may wish to develop one anyway and discuss it with your State. 

A triggered source water monitoring plan is particularly useful for wholesale systems with 

multiple consecutive systems and multiple sources and for consecutive systems with their own 

sources, multiple wholesale suppliers, or multiple connections to a wholesale supplier. A triggered 

source water monitoring plan should include the following minimum elements: 

1) Map or schematic of the system with sources and/or points of entry and TCR compliance 

monitoring locations identified. Your distribution system map or schematic should not 

contain information that poses a security risk to your system. EPA recommends that you 

submit either a distribution system schematic with no landmarks or addresses or a City map 

without locations of pipes indicated. 

2) Identify the source type for each source/point of entry (e.g., seasonal, emergency, ground 

water, surface water etc.). 

3) Identify the source(s) serving each TCR compliance monitoring location and the basis for the 

determination (e.g., system hydraulics, operation, water quality data, etc.). 

4) For wholesale systems, the consecutive systems served and, if applicable, the sources serving 

each consecutive system. 

5) For consecutive systems, the wholesale supply or suppliers for the points of entry. 

6) Identify any representative ground water source(s) that will be used to satisfy the triggered 

monitoring requirements of the GWR and the basis for the selection (e.g. 

geologic/hydrogeologic information, well construction data, water quality data, sanitary 

surveys, Source Water Assessments, etc.). 

7) Any changes or variations expected in the monitoring plan (e.g., use of seasonal sources, 

rotating sources, etc.). 

Exhibit 4-1 is an example triggered source water monitoring plan. The plan is for the First 

Valley Water system described in Section 3.1 and illustrated in Figure 3.1. 
Consecutive System Guide 4-2 July 2007 

for the Ground Water Rule 

Exhibit 4.1 Triggered Source Water Monitoring Plan – First Valley Water System 

(See Section 3.1 and Figure 3-1) 

Routine TCR site Served by Source sample at/by Comments/Instructions 

#1 Turnout Valve lot Big Mountain Big Mountain WD Contact Big Mountain 

WD Water Quality 

Section 

#2 Redwood Park Big Mountain Big Mountain WD Day phone: 

Fax: 

After hours: 

#3 Old Town Both Big Mountain WD 

First Valley WD 

(Alder Grove Well 

sample tap) 

Contact Big Mountain 

WD Water Quality 

Section. 

Contact lab for sample 

pick up. 

Day phone: 

Fax: 

After hours : 

# 4 Walnut Grove 

PS 

Both Big Mountain WD 

First Valley WD 

(Alder Grove Well 

sample tap) 

Sample bottles at corp 

yard -label as SOURCE 

and follow chain of 

custody 

# 5 Freshwater 

School 

Alder Grove Well First Valley WD 

(Alder Grove Well 

sample tap) 

Contact lab for sample 

pick up. 

# 6 Corporation 

Yard 

Alder Grove Well First Valley (Alder 

Grove Well sample 

tap) 

Sample bottles at corp 

yard -label as SOURCE 

and follow chain of 

custody 
Consecutive System Guide 5-1 July 2007 

for the Ground Water Rule 

5. Glossary 

Consecutive system - A public water system that buys or otherwise receives some or all of its finished 

water from a wholesale system.

Fecal Indicator – Microorganisms (i.e., bacteria and viruses) that are closely associated with fecal 

contamination and indicate that a source of water may be fecally-contaminated. For the GWR, fecal 

indicators are E.Coli, enterococci, or coliphage, as specified by the State. 

Sanitary survey – A “sanitary survey”, as conducted by the State, includes, but is not limited to, an 

onsite review of the water source (identifying sources of contamination by using results of source 

water assessments or other relevant information, where available), facilities, equipment, operation, 

maintenance, and monitoring compliance of a public water system to evaluate the adequacy of the 

system, its sources and operations and the distribution of safe drinking water. 

Significant deficiency – A “significant deficiency” includes, but is not limited to, a defect in design, 

operation, or maintenance, or a failure or malfunction of the sources, treatment, storage, or distribution 

system that the State determines to be causing, or has the potential for causing, the introduction of 

contamination into the water delivered to consumers. 

State – Refers to the agency of the State or Tribal government which has jurisdiction over public water 

systems. During any period when a State or Tribal government does not have primary enforcement 

responsibility pursuant to Section 1413 of the Safe Drinking Water Act, the term ‘State’ means the 

Regional Administrator of the U.S. Environmental Protection Agency. 

Source sample – A sample collected at the source of water for the public water system before 

treatment or, if no treatment is provided, before the distribution system (i.e., at the wellhead) 

Subpart H system – A public water system serving surface water or ground water under the influence 

of surface water. These systems are subject to the filtration and disinfection requirements of 40 CFR 

Subpart H.

Total Coliforms – A group of closely related bacteria that are generally harmless. They are natural 

and common inhabitants of the soil and ambient waters (such as lakes and rivers). 

Treatment technique violation – Violation of a treatment technique established in lieu of a Maximum 

Contaminant Level. For the GWR, this includes failure to provide corrective action for fecal 

contamination of ground water source and failure to correct significant deficiencies. Treatment 

technique violations require the system to provide public notification and systems in violation of 

treatment technique requirements are subject to enforcement actions by the State and EPA. 

Triggered Monitoring – For the GWR, ground water source samples collected after a routine TCpositive routine sample collected under TCR and analyzed for a fecal indicator. Triggered monitoring 

consists of collection of source water samples and analysis of those samples for a fecal indicator 

specified by the State. For systems collecting one routine TCR sample or fewer each month, one of the 
Consecutive System Guide 5-2 July 2007 

for the Ground Water Rule 

four repeat samples required under the TCR may be collected from the ground water source to satisfy 

the triggered ground water source monitoring requirements of the GWR. The GWR is not applicable to 

any source determined by the State to be ground water under the direct influence of surface water 

(GWUDI). 

Well- For the purposes of the GWR, the term “well” includes springs, spring boxes, vertical and 

horizontal wells, infiltration galleries and any other method of delivering ground water. 

Wholesale system – A wholesale system is a public water system that treats source water as necessary 

to produce finished water and then delivers some or all of that finished water to another public water 

system. Delivery may be through a direct connection or through the distribution system.