Stage 2 Disinfectants and Disinfection
Byproducts Rule
Consecutive Systems Guidance Manual
Office of Water (4607M) EPA 815-R-09-017 March 2010 www.epa.gov/safewater
-------
Office of Water (4607M)
EPA815-R-09-017
March 2010
www.epa.gov/safewater
-------
Purpose:
The purpose of this guidance manual is solely to help consecutive systems understand
and meet the requirements of the Stage 2 Disinfectants and Disinfection Byproducts Rule
(DBPR). 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. Interested parties are free to raise questions and objections
to the guidance and the appropriateness of using it in a particular situation. The mention of trade
names or commercial products does not constitute endorsement or recommendation for use.
Authorship:
This manual was developed under the direction of EPA's Office of Water, and was
prepared by The Cadmus Group, Inc. and Malcolm Pirnie, Inc. Questions concerning this
document should be addressed to:
Thomas Grubbs
U.S. Environmental Protection Agency
Mail Code 4607M
1200 Pennsylvania Avenue NW
Washington, DC 20460
Tel: (202) 564-5262
Fax: (202) 564-3767
Email: grubbs.thomas@epa.gov
Acknowledgements:
Steve Lohman - Denver Water
James Parsons - Cobb County-Marietta Water Authority
Consecutive Systems Guidance Manual Hi March 2010
-------
CONTENTS
Exhibits vi
Acronyms vii
Glossary ix
1.0 Introduction 1-1
1.1 Purpose of this Manual 1-1
1.2 Manual Organization 1-2
2.0 Overview of Existing Regulatory Requirements for Consecutive Systems 2-1
2.1 Public Notification Rule 2-1
2.2 Consumer Confidence Report (CCR) Rule 2-2
2.3 Consecutive Systems Monitoring Requirements (40 CFR 141.29) 2-3
3.0 Stage 2 DBPR Requirements for Consecutive Systems 3-1
3.1 Disinfection Byproduct Maximum Contaminant Levels 3-1
3.2 Initial Distribution System Evaluation 3-2
3.3 Stage 2 (subpart V) Compliance Monitoring Requirements 3-4
3.3.1 Stage 2 DBPR Monitoring Plan 3-4
3.3.2 Stage 2 DBPR Compliance Monitoring 3-5
3.3.3 Reporting and Recordkeeping Requirements 3-8
3.4 Disinfectant Residual Monitoring 3-8
3.5 Operational Evaluations 3-9
3.6 Simultaneous Compliance 3-10
4.0 Compliance Options for Consecutive Systems 4-1
4.1 DBF Control in Consecutive Systems 4-1
4.2 Water Age Management 4-3
4.2.1 Pipe Looping 4-4
4.2.2 Managing Valves 4-4
4.2.3 Bypassing Oversized Pipes 4-4
4.2.4 Installing Dedicated Transmission Main 4-4
4.2.5 Improving Tank Mixing and Turnover 4-5
4.2.6 Eliminating Excess Storage and Tanks in Series 4-9
4.3 Reduction of Disinfectant Demand 4-10
4.3.1 Replacing or Cleaning and Lining Unlined Cast Iron Pipes 4-10
4.3.2 Distribution System Flushing 4-10
4.4 Chloramination 4-12
4.4.1 Water Quality Issues for Chloramines 4-12
4.4.2 Options for Chloramine Conversion 4-13
4.4.3 Cost, Handling, and Safety Issues 4-14
4.4.4 Public Education 4-15
5.0 Other Alternatives for Consecutive Systems 5-1
5.1 Improved Water Quality from the Wholesale System 5-1
5.2 Alternative Sources and Blending Strategies 5-3
Consecutive Systems Guidance Manual iv March 2010
-------
6.0 Communication Strategies for Consecutive and Wholesale Systems 6-1
6.1 Communication Strategies for Stage 2 DBPR Compliance Monitoring 6-1
6.2 Communication Strategies for Operational Evaluations 6-4
6.3 Agreements between Consecutive and Wholesale Systems 6-5
7.0 Developing Consecutive System Compliance Strategies 7-1
7.1 Data Acquisition 7-1
7.1.1 Monitoring Parameters 7-1
7.1.2 Monitoring Frequency 7-3
7.1.3 Monitoring Locations 7-3
7.2 Communication of Needs to the Wholesale System 7-6
8.0 Frequently Asked Questions 8-1
9.0 References 9-1
Appendices
Appendix A. Example of a Formal Agreement between Consecutive and Wholesale Systems
Consecutive Systems Guidance Manual v March 2010
-------
EXHIBITS
Exhibit 2.1 Tiers of Public Notice 2-2
Exhibit 3.1 DBF MCLs 3-1
Exhibit 3.2 Stage 2 DBPR Compliance Schedule for Wholesale and
Consecutive Systems 3-2
Exhibit 3.3 Stage 2 (subpart V) Routine Monitoring Requirements 3-6
Exhibit 4.1 Effect of Temperature Differential Between Inflow and Tank Bulk
Water on Mixing Characteristics 4-7
Exhibit 4.2 Effect of Inlet Pipe Orientation on Mixing Characteristics 4-9
Exhibit 6.1 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Consecutive System Receiving Water Directly from Wholesale System 6-2
Exhibit 6.2 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Consecutive System Receiving Water Through Another
Consecutive System 6-3
Exhibit 6.3 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Consecutive System Receiving Water from Wholesale System with No
Customers 6-3
Exhibit 6.4 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Approximate Water Age of Monitoring Locations is Known 6-4
Exhibit 6.5 Case Study of Formal Agreements between Consecutive and
Wholesale Systems 6-6
Exhibit 6.6 Case Study of Informal Agreements between Consecutive and
Wholesale Systems 6-7
Exhibit 7.1 DBF Formation from Wholesale to Consecutive System Example 7-4
Exhibit 7.2 Variation in DBF Formation with Chlorination and Chloramination 7-5
Consecutive Systems Guidance Manual
March 2010
-------
ACRONYMS
40CFR
AWWA
AwwaRF
BATs
CCR
CFD
CNBr
CNC1
CNX
CT
DBF
DBPR
DPD
EPA
IDSE
GAC
GWUDI
HAA
HAAS
HPC
IDSE
LCR
LRAA
LT2ESWTR
MCL
M-DBP
mg/L
mL
MRDL
N.d.
NDMA
NPDWR
NOM
NTNCWS
PAC
PWS
RAA
SCADA
SDWA
sss
SWTR
TCR
THM
TOC
TTHM
UV
Code of Federal Regulations, Title 40
American Water Works Association
American Water Works Association Research Foundation
Best available technologies
Consumer Confidence Report
Computational fluid dynamics
Cyanobromides
Cyanochlorides
Cyanohalides
Disinfectant residual concentration x contact time
Disinfection byproduct
Disinfectants and Disinfection Byproducts Rule
N, N-diethyl-p-phenylenediamine
United States Environmental Protection Agency
Initial Distribution System Evaluation
Granular activated carbon
Ground water under the direct influence of surface water
Haloacetic acid
The sum of five HAA species
Heterotrophic plate count
Initial distribution system evaluation
Lead and Copper Rule
Locational running annual average
Long Term 2 Enhanced Surface Water Treatment Rule
Maximum contaminant level
Microbial-disinfection byproducts
Milligrams per liter
Milliliter
Maximum residual disinfectant level
No date (for publication)
N-nitrosodimethylamine
National Primary Drinking Water Regulation
Natural organic matter
Nontransient noncommunity water system
Powdered activated carbon
Public water system
Running annual average
Supervisory control and data acquisition
Safe Drinking Water Act
System specific study
Surface Water Treatment Rule
Total Coliform Rule
Trihalomethane
Total organic carbon
Total trihalomethanes
Ultraviolet
Consecutive Systems Guidance Manual
March 2010
-------
VSS Very small system
WTP Water treatment plant
Consecutive Systems Guidance Manual viii March 2010
-------
GLOSSARY
Best available technology (BAT): the best technology, treatment techniques, or other means
which the Administrator finds, after examination for efficacy under field conditions and not
solely under laboratory conditions, are available (taking cost into consideration). For the
purposes of setting MCLs for synthetic organic chemicals, any BAT must be at least as effective
as granular activated carbon. (40 CFR 141.2)
Booster disinfection: the practice of adding disinfectant in the distribution system to maintain
disinfectant residual concentration throughout the distribution system.
Combined distribution system: the interconnected distribution system consisting of the
distribution systems of wholesale systems and of the consecutive systems that receive some or all
of their finished water from those wholesale system(s). (40 CFR 141.2)
Community water system: a public water system that serves at least 15 service connections used
by year-round residents or regularly serves at least 25 year-round residents. (40 CFR 141.2)
Consecutive system: a public water system that buys or otherwise receives some or all of its
finished water from one or more wholesale systems. Delivery may be through a direct
connection or through the distribution system of one or more consecutive systems. (40 CFR
141.2)
Disinfectant: any oxidant, including but not limited to chlorine, chlorine dioxide, chloramines,
and ozone added to water in any part of the treatment or distribution process, that is intended to
kill or inactivate pathogenic microorganisms. (40 CFR 141.2)
Disinfectant residual concentration: the concentration of disinfectant that is maintained in a
distribution system. Disinfectant could be free chlorine (the sum of the concentrations of
hypochlorous acid and hypochlorite acid) or combined chlorine (chloramines). It is used in the
Surface Water Treatment Rule as a measure for determining CT.
Disinfection: a process that inactivates pathogenic organisms in water by chemical oxidants or
equivalent agents. (40 CFR 141.2)
Disinfection byproduct (DBF): compound formed from the reaction of a disinfectant with
organic and inorganic compounds in the source or treated water during the disinfection process.
Dual sample set: a set of two samples collected at the same time and same location, with one
sample analyzed for TTHM and the other sample analyzed for HAAS. Dual sample sets are
collected for the purposes of conducting an IDSE under subpart U of 40 CFR 141.2 and
determining compliance with the TTHM and HAAS MCLs under subpart V of 40 CFR 141.2.
Finished water: water that is introduced into the distribution system of a public water system and
is intended for distribution and consumption without further treatment, except that treatment
necessary to maintain water quality in the distribution system (e.g., booster disinfection, addition
of corrosion control chemicals). (40 CFR 141.2)
Consecutive Systems Guidance Manual ix March 2010
-------
Ground water under the direct influence of surface water (GWUDI): any water beneath the
surface of the ground with (1) significant occurrence of insects or other macroorganisms, algae,
or large-diameter pathogens such as Giardia lamblia, or (2) significant and relatively rapid shifts
in water characteristics such as turbidity, temperature, conductivity, or pH that closely correlate
to climatological or surface water conditions. Direct influence must be determined for individual
sources in accordance with criteria established by the State. The State determination of direct
influence may be based on site-specific measurements of water quality and/or documentation of
well construction characteristics and geology with field evaluation. (40 CFR 141.2)
Haloacetic acid(HAA): one of the family of organic compounds named as a derivative of acetic
acid, wherein one to three hydrogen atoms in the methyl group in acetic acid are each substituted
by a halogen atom (e.g., chlorine and bromine) in the molecular structure.
Haloacetic acids (five) (HAAS): the sum of the concentrations in milligrams per liter of the
haloacetic acid compounds (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid,
monobromoacetic acid, and dibromoacetic acid), rounded to two significant figures after
addition. (40 CFR 141.2)
Heterotrophicplate count (HPC): a procedure for estimating the number of heterotrophic
bacteria in water, measured as the number of colony forming units per 100 mL.
Locational running annual average (LRAA): the average of sample analytical results for
samples taken at a particular monitoring location during the previous four calendar quarters. (40
CFR 141.2)
Maximum contaminant level (MCL): the maximum permissable level of a contaminant in water
that is delivered to any user of a public water system. (40 CFR 141.2)
Mixing zone: an area in the distribution system where water flowing from two or more different
sources blend.
Monitoring site: the location where samples are collected.
Nitrification: a two-step process in which nitrifying bacteria convert ammonia to nitrite and then
convert nitrite to nitrate. Nitrification can occur in water distribution systems in which naturally
occurring ammonia is present, or in systems that add ammonia to the water as part of the
chloramine disinfection process.
Noncommunity water system: a public water system that is not a community water system.
(40 CFR 141.2)
Nontransient noncommunity water system (NTNCWS): a public water system that is not a
community water system and that regularly serves at least twenty-five of the same persons over
six months per year. (40 CFR 141.2)
Public water system (PWS): a system for the provision to the public of piped water for human
consumption, if such system has at least fifteen service connections or regularly serves an
average of at least twenty-five individuals daily at least 60 days out of the year. Such term
includes (1) any collection, treatment, storage, and distribution facilities under control of the
Consecutive Systems Guidance Manual x March 2010
-------
operator of such system and used primarily in connection with such system, and (2) any
collection or pretreatment storage facilities not under such control that are used primarily in
connection with such system. A public water system is either a community water system or a
noncommunity water system. (40 CFR 141.2)
Residence time: the time period lasting from when the water is treated to the time when it reaches
a particular point in the distribution system. Also referred to as water age.
Running annual average: the average of monthly or quarterly averages of all analytical results of
samples taken throughout the distribution system, as averaged over the preceding four quarters.
Secondary disinfection: The process whereby a disinfectant (typically chlorine or chloramine) is
added to finished water in order to maintain a disinfection residual in the distribution system.
Also referred to as "residual disinfection."
State: the agency of the State or Tribal government that 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 Act, the term State means the
Regional Administrator, U.S. Environmental Protection Agency. (40 CFR 141.2)
Surface water: all water that is open to the atmosphere and subject to surface runoff. (40 CFR
141.2)
Total chlorine residual: the sum of combined chlorine (chloramine) and free available chlorine
residual.
Total trihalomethanes (TTHM): the sum of the concentration in milligrams per liter of the
trihalomethane compounds (trichloromethane [chloroform], dibromochloromethane,
bromodichloromethane, and tribromomethane [bromoform]), rounded to two significant figures.
40 CFR 141.2. Note: Some publications may use "THM4" instead of "TTHM."
Tracer study: a procedure for estimating hydraulic properties of the distribution system, such as
residence time. Where more than one water source feeds the distribution system, tracer studies
can be used to determine the zone of influence of each source.
Trihalomethane (TFDVI): one of the family of organic compounds named as derivatives of
methane, wherein three of the four hydrogen atoms in methane are each substituted by a halogen
atom in the molecular structure. (40 CFR 141.2)
Water distribution system model: a computer program that can simulate the hydraulic, and in
some cases, water quality behavior of water in a distribution system.
Wholesale system: a public water system that treats source water as necessary to produce finished
water and then sells or otherwise delivers finished water to another public water system.
Delivery may be through a direct connection or through the distribution system of one or more
consecutive systems. (40 CFR 141.2)
Consecutive Systems Guidance Manual xi March 2010
-------
1.0 Introduction
1.1 Purpose of this Manual
The intent of this manual is to help consecutive systems understand and meet the
requirements of the Stage 2 Disinfectants and Disinfection Byproducts Rule (DBPR). The Stage
2 DBPR defines a consecutive system as a public water system (PWS) that receives some or all
of its finished water from one or more wholesale systems. Delivery may be through a direct
connection or through the distribution system of one or more consecutive systems. Consecutive
systems that use a disinfectant other than ultraviolet (UV) light or that deliver water from
another system that has been treated with a disinfectant other than UV light are subject to the
Stage 2 DBPR.
Most Safe Drinking Water Act (SOWA) regulations promulgated to date have not
specifically addressed consecutive system requirements. Under the provisions of 40 CFR
141.29, a State may, with concurrence of the United States Environmental Protection Agency
(EPA), have modified monitoring requirements for a consecutive system to the extent that the
interconnection of a wholesale and a consecutive system justifies treating them as a single
system for monitoring purposes. Therefore, a consecutive system may not have been required by
the State to conduct monitoring for certain contaminants if the wholesale system has already
monitored for those contaminants.
The Stage 2 DBPR does not change 40 CFR 141.29, so a State may still modify
monitoring requirements (but not compliance determinations), with EPA's concurrence, for
consecutive systems as described above. However, absent EPA concurrence with a modification
under 40 CFR 141.29, State flexibility to allow a consecutive system to modify its own
distribution system monitoring for disinfection byproducts (DBF), depending on factors such as
the size of the consecutive system's distribution system, the amount of distribution system
storage, and the quality of the source water, is available under 40 CFR 142.16(m).
The Stage 2 DBPR may present certain challenges for consecutive systems. For
example, a consecutive system may receive water that has been disinfected and already contains
elevated levels of DBF. A consecutive system usually has no treatment facilities to control
DBFs already present in the water from the wholesale system, and limited ability to control the
continued formation of DBF in its own distribution system. For this reason, EPA has established
Best Available Technologies (BATs) specifically for consecutive systems in the Stage 2 DBPR.
EPA is aware of the difficulty in implementing consecutive system regulations because
the relationships between wholesale and consecutive systems are complex and varied. EPA is
also aware that there are a variety of State approaches to addressing regulatory requirements for
consecutive systems. The Stage 2 DBPR presents an opportunity for consecutive systems to
better define roles and responsibilities through discussions with their wholesaler and the State.
Some States have taken a very active role in establishing relationships between wholesale and
consecutive systems.
As discussed later in this document, some of the deadlines imposed by the Stage 2 DBPR
(deadlines related to the Initial Distribution System Evaluation (IDSE)) fall within six months of
Consecutive Systems Guidance Manual 1-1 March 2010
-------
rule promulgation. Although EPA has already provided guidance for consecutive systems to
comply with IDSE requirements, all consecutive systems, including those not previously
required to comply with the Stage 1 DBPR, are encouraged to contact their wholesaler and their
State to confirm their responsibilities for Stage 2 maximum contaminant level (MCL)
compliance. EPA has also provided other guidance, where appropriate, to assist PWSs and
States in implementing the Stage 2 DBPR.
1.2 Manual Organization
This guidance manual is organized as follows:
• Chapter 1 - Introduction: Explains the purpose of this manual.
• Chapter 2 - Overview of Existing Regulatory Requirements for Consecutive Systems:
Provides an overview of the provisions of existing regulations that apply to
consecutive systems.
• Chapter 3 - Stage 2 DBPR Requirements for Consecutive Systems: Provides an
overview of the Stage 2 DBPR requirements that apply to consecutive systems.
• Chapter 4 - Compliance Options for Consecutive Systems: Discusses BATs
identified by EPA for consecutive systems to decrease DBF formation in their
systems.
• Chapter 5 - Other Alternatives for Consecutive Systems: Discusses alternatives other
than BATs for consecutive systems to reduce DBF formation in their systems.
• Chapter 6 - Communication Strategies for Consecutive and Wholesale Systems:
Describes communication strategies for consecutive systems needing to coordinate
with wholesale systems to meet Stage 2 DBPR requirements.
• Chapter 7 - Developing Consecutive System Compliance Strategies: Suggests
approaches for consecutive systems to characterize DBF formation in their system
and how to coordinate with the wholesaler on control strategies.
• Chapter 8 - Frequently Asked Questions: Provides answers to questions frequently
asked by systems and States.
• Chapter 9 - References: Provides a bibliographic list of references cited in this
manual.
• Appendix A - Example of Formal Agreement between Consecutive and Wholesale
Systems: Provides an example of a formal agreement between consecutive and
wholesale systems that meets the requirements of the State of Colorado. Other States
may have specific requirements that must be met in preparing these agreements.
Consecutive Systems Guidance Manual 1-2 March 2010
-------
This guidance manual is intended to address consecutive system-specific issues and
contains many references to rules other than the Stage 2 DBPR that may apply to consecutive
systems. References to appropriate guidance manuals are provided throughout this document.
Copies of these manuals can be obtained by:
• Contacting the appropriate State office.
• Calling the Safe Drinking Water Hotline at 1 -800-426-4791.
• Downloading from EPA's Web site at http://www.epa.gov/safewater.
• Calling the National Service Center for Environmental Publications at 1-800-490-
9198 or visiting their Web site at http://www.epa.gov/nscep/.
Consecutive Systems Guidance Manual 1-3 March 2010
-------
2.0 Overview of Existing Regulatory Requirements for Consecutive Systems
There are several existing drinking water regulations that contain general provisions that
consecutive systems must meet for any rule (including Stage 2 DBPR). This chapter reviews the
following regulations that address consecutive system requirements:
• Public Notification Rule
• Consumer Confidence Report (CCR) Rule
• Consecutive System Monitoring Requirements Under 40 CFR 141.29
In addition, other drinking water rules (e.g., Lead and Copper Rule, Ground Water Rule)
have specific consecutive system requirements unrelated to the Stage 2 DBPR.
2.1 Public Notification Rule
The Public Notification Rule requires the owner or operator of any PWS to notify its
customers any time it incurs a violation of a national primary drinking water regulation
(NPDWR) and in other specific situations. The type of notification required varies depending on
the violation. Exhibit 2.1 shows the tier of notification required for certain types of violations or
situations as well as the notification frequency and method for each tier.
PWSs that sell or provide water to another public water system must give public notice to
its own customers as well as the owner or operator of the consecutive system (40 CFR
141.201(c)(l)). The consecutive system is then responsible for providing public notice to its
own customers. If the violation occurs in a portion of the distribution system that is physically
or hydraulically isolated from other parts of the distribution system, the State may allow the
system to limit public notification only to customers in that area of the distribution system. This
could occur in a consecutive system if the system receives water from more than one wholesale
system or has multiple entry points from a single wholesale system. However, the system must
receive permission from the State in writing to limit distribution of the public notice (40 CFR
Consecutive Systems Guidance Manual 2-1 March 2010
-------
Exhibit 2.1 Tiers of Public Notice
Tier
Types of Situations
When Notice is Required
Examples of Appropriate
Notification Methods1
NPDWR violations and
situations with significant
potential to have serious
adverse effects on human
health as a result of short-
term exposure.
As soon as practical but no
later than 24 hours after the
system learns of violation.
Consult with State as soon
as practical but no later than
24 hours after learning of
the violation to determine
additional public notification
requirements.
Broadcast media
Posting in conspicuous
location
Hand delivery
Other method approved by
State
All other NPDWR
violations and situations
with potential to have
serious adverse effects on
human health.
As soon as practical but no
later than 30 days after the
system learns of violation.
Repeat notice required
every 3 months or as
determined by State for as
long as violation or situation
persists.
Mail or other direct delivery
Newspaper notice
Posting in public places
Posting on the Internet
Delivery to community
organizations
All other NPDWR
violations and situations
not included in Tier 1 and
Tier 2.
No later than 1 year after
system learns of violation.
Repeat notice required
annually.
Mail or other direct delivery
Newspaper notice
Posting in public places
Posting on the Internet
Delivery to community
organizations
Inclusion in consumer
confidence report
Note that some notification methods are only available to certain types of systems.
For more information on Public Notification Rule requirements, refer to:
• Public Notification Handbook (USEPA, 2000a)
• The Public Notification Rule: A Quick Reference Guide (USEPA, 2000b)
2.2 Consumer Confidence Report (CCR) Rule
The CCR Rule requires community water systems to provide an annual report to their
customers that provides information on the quality of the water delivered by the system and any
risks from exposure to contaminants detected in the water. The report must be distributed by
July 1 of each year and must contain data collected during or prior to the previous calendar year.
Consecutive systems should include information about all purchased water in their CCRs, in
addition to information on their own total coliform and lead and copper monitoring. Wholesale
systems are required to deliver the applicable water quality information to consecutive systems
no later than April 1 of each year or by a date mutually agreed upon and included in a contract
between the consecutive and wholesale system (40 CFR 141.152(d)).
Consecutive Systems Guidance Manual
2-2
March 2010
-------
For more information on CCR requirements refer to:
• Preparing Your Consumer Confidence Report: Revised Guidance for Water Suppliers
(USEPA, 2005)
• Consumer Confidence Report Rule: A Quick Reference Guide (USEPA, 2004b)
2.3 Consecutive Systems Monitoring Requirements (40 CFR 141.29)
The provisions for consecutive systems under 40 CFR 141.29 allow the State to modify
the monitoring requirements for combined distribution systems. When justified, the State may
treat the combined distribution system as a single system for monitoring purposes. Such systems
must follow a monitoring schedule specified by the State and concurred with by the
Administrator of the EPA. States may not modify compliance requirements.
Consecutive Systems Guidance Manual 2-3 March 2010
-------
3.0 Stage 2 DBPR Requirements for Consecutive Systems
Many consecutive systems deliver water that has been treated with a disinfectant other
than UV light and which may therefore contain DBFs. Prior to promulgation of the Stage 2
DBPR, monitoring of consecutive systems for DBFs was not specifically addressed by the Safe
Drinking Water Act (SOWA) regulations. The intent of the Stage 2 DPBR with respect to
consecutive systems is to present an effective approach for identifying and resolving DBF
problems, keeping in mind that relationships between wholesale systems and consecutive
systems are often complex and varied. Depending upon the specific nature of these
relationships, States have some flexibility in their approach to the implementation of the Stage 2
DBPR requirements. Consecutive systems are encouraged to contact their wholesale systems
and their States as soon as possible after rule promulgation to discuss applicable requirements
and responsibilities.
This chapter describes the requirements of the Stage 2 DBPR that apply to consecutive
systems. The following rule requirements are discussed:
• Disinfection Byproduct MCLs;
• IDSEs;
• Stage 2 (subpart V) Compliance Monitoring Requirements;
• Disinfectant Residual Monitoring; and
• Operational Evaluations.
3.1 Disinfection Byproduct Maximum Contaminant Levels
The MCLs for total trihalomethanes (TTHM), haloacetic acid (five) (HAAS), bromate,
and chlorite have not changed from the Stage 1 DBPR; however, the method of calculating
compliance for TTHM and HAAS has changed from a running annual average in Stage 1 to a
locational running annual average in Stage 2. For more information on Stage 2 DBPR
compliance calculations, refer to Section 3.4. The MCLs for DBFs are shown in Exhibit 3.1.
The dates for complying with the Stage 2 DBPR MCLs for TTHM and HAAS are shown in
Exhibit 3.2.
Exhibit 3.1 DBF MCLs
Disinfection Byproduct
Bromate
Chlorite
TTHM
HAAS
MCL (mg/L)
0.010
1.0
0.080
0.060
Consecutive Systems Guidance Manual
3-1
March 2010
-------
Exhibit 3.2 Stage 2 DBPR Compliance Schedule for Wholesale and Consecutive
Systems
Population Served by the Largest
System in the Combined
Distribution System1
> 100,000 people
50,000 - 99,999 people
10,000-49,999 people
< 10,000 people
Date for Compliance with Stage 2 DBPR (subpart V)
Monitoring Requirements2
April 1,201 2
October 1,201 2
October 1,201 3
October 1 , 2013 if no Cryptosporidium monitoring is required
under LT2ESWTR
OR
October 1 , 2014 if Cryptosporidium monitoring is required under
LT2ESWTR
1A combined distribution system consists of the distribution systems of wholesale systems and of the consecutive
systems that receive some or all of their finished water from those wholesale system(s) (40 CFR 141.2).
2 If you are required to conduct quarterly monitoring, you must begin monitoring in the first full calendar quarter that
includes the compliance date in Exhibit 3.2. If you are required to conduct monitoring at a frequency that is less than
quarterly, you must begin monitoring in the calendar month recommended in the IDSE report (40 CFR 141.601 or
141.602) or the calendar month identified in the subpart V monitoring plan (141.622) no later than 12 months after the
date listed in Exhibit 3.2. The State may grant up to an additional 24 months for compliance if you require capital
improvements to comply with an MCL.
3.2 Initial Distribution System Evaluation
This section briefly summarizes the Stage 2 DBPR IDSE requirements. For more
information on Stage 2 IDSE requirements, refer to the Initial Distribution System Evaluation
(IDSE) Guidance Manual for the Final Stage 2 Disinfectants and Disinfection Byproducts Rule
(USEPA, 2006a). A separate guide has also been developed to briefly summarize the
requirements for systems serving fewer than 10,000 people (USEPA, 2006b).
Community water systems of any size and nontransient, noncommunity water systems
(NTNCWS) serving at least 10,000 people are subject to the IDSE requirements if they use a
primary or residual disinfectant other than UV light or deliver water that has been treated with a
primary or residual disinfectant other than UV light. The purpose of the IDSE requirements is to
help systems select representative high TTHM and HAAS compliance monitoring locations.
These sites are then used for compliance monitoring under the Stage 2 DBPR.
There are four options available for systems to meet IDSE requirements, depending on
their historical sampling data, size, and preference:
• Receive a Very Small System (VSS) Waiver. Systems serving fewer than 500
people with DBF sample results may be eligible for a waiver from the State. Systems
receiving the waiver have no further IDSE requirements.
Consecutive Systems Guidance Manual
3-1
March 2010
-------
Receive 40/30 certification. A
system has no further IDSE
requirements if the system can
certify to the State that all TTHM
and HAAS compliance data are
less than or equal to 0.040 mg/L
for TTHM and less than or equal
to 0.030 mg/L for HAAS during
a specified two year period. In
addition, the system must not
have had any TTHM or HAAS
monitoring violations during the
same period.
Conduct a System Specific
Study (SSS). A system may
conduct an IDSE study based on
existing monitoring results or a
hydraulic model instead of
conducting IDSE standard
monitoring. A system's model
or existing monitoring results
must meet specific criteria to be
used in an SSS.
Compliance Schedule for the IDSE
The State sent a letter to each system
with a determination of the system's IDSE
schedule based on system characteristics. The
compliance schedule for consecutive and
wholesale systems was based on the population
of the largest system in the combined
distribution system. For purposes of complying
with the IDSE schedule, the State may have
determined that the combined distribution
system does not include certain consecutive
systems based on factors such as receiving
water from a wholesale system only on an
emergency basis or receiving only a small
percentage and small volume of water from a
wholesale system. The State may also have
determined that the combined distribution
system does not include certain wholesale
systems based on factors such as delivering
water to a consecutive system only on an
emergency basis or delivering only a small
percentage and small volume of water to a
consecutive system.
Conduct Standard Monitoring
IDSE standard monitoring entails one year of distribution system monitoring. The
sampling frequency and minimum number of sample locations required depend on
system characteristics such as size, source water type, and whether the system is part
of a combined distribution system.
A combined distribution system consists of
the distribution systems of wholesale systems
and of the consecutive systems that receive
some or all of their finished water from those
wholesale system(s) (40 CFR 141.2). For
example, if a Town purchases water from a
City to supplement its own groundwater
supplies, the combined distribution system
includes the City's and the Town's distribution
systems.
Town System
City Syste
Consecutive systems that do not apply a
chemical disinfectant were not specifically
addressed by Stage 1 DBPR requirements.
Therefore, these systems may not have historical
TTHM and HAAS data unless the wholesale
system collected samples within the consecutive
system. In the absence of historic TTHM and
HAAS data, systems must either conduct
standard monitoring or an SSS to comply with
the IDSE requirements. Consecutive systems
should consider obtaining Stage 1 data from the
wholesaler to assist in IDSE site selection if no
historical data exists.
Consecutive Systems Guidance Manual
3-3
March 2010
-------
3.3 Stage 2 (subpart V) Compliance Monitoring Requirements
This section provides a brief summary of the Stage 2 (subpart V) compliance monitoring
requirements. For more information on Stage 2 DBPR monitoring, reporting, and recordkeeping
requirements, refer to:
• Stage 2 DBPR Operational Evaluation Guidance Manual (USEP A, 2008)
• Initial Distribution System Evaluation Guidance Manual for the Final Stage 2
Disinfectants and Disinfection Byproducts Rule (USEP A, 2006)
• Complying with the Stage 2 Disinfectant and Disinfection Byproducts Rule: Small
Entity Compliance Guide (USEPA, 2007c).
A system is subject to the Stage 2 (subpart V) requirements if it is a community water
system or a NTNCWS and it uses a primary or residual disinfectant other than UV light or
delivers water that has been treated with a primary or residual disinfectant other than UV light.
Therefore, consecutive systems that do not apply a disinfectant but purchase water that has been
treated with a disinfectant must comply with these requirements. In addition, these consecutive
systems must now comply with the Stage 1 DBPR analytical, monitoring, and maximum residual
disinfectant level (MRDL) requirements for chlorine and chloramines. The chlorine and
chloramine requirements are discussed further in Section 3.4.
The MCLs for TTHM and HAAS have not changed from the Stage 1 DBPR. However,
the method of calculating compliance has changed. Stage 2 DBPR compliance determination is
based on locational running annual averages (LRAAs) of TTHM and HAAS concentrations.
Compliance must be met at each monitoring location, instead of using the system-wide running
annual average (RAA) required under the Stage 1 DBPR.
3.3.1 Stage 2 DBPR Monitoring Plan
Systems must develop a monitoring plan to be used for Stage 2 monitoring and
compliance determination (40 CFR 141.622). The monitoring plan must include:
• Monitoring locations;
• Monitoring dates;
• Compliance calculation procedures; and
• Monitoring plans for any other systems in the combined distribution system if the
State has reduced monitoring requirements.
Note that systems will recommend Stage 2 DBPR compliance monitoring locations and
dates as part of their IDSE report.
Systems using surface water, ground water under the direct influence of surface water
(GWUDI), or purchased surface water and serving more than 3,300 people must submit a copy
Consecutive Systems Guidance Manual 3-4 March 2010
-------
of the monitoring plan to the State prior to the date they are scheduled to collect their first Stage
2 DBPR compliance samples. All systems must keep the plan on file for State and public
review. A system that has been granted a VSS waiver must comply by updating its Stage 1
monitoring plan or creating a new monitoring plan.
Systems should make modifications to their monitoring plan as needed to reflect changes
in treatment, distribution system operations and layout (including new service areas), or other
factors that may affect TTHM or HAAS formation. The State may also require modifications to
the monitoring plan.
3.3.2 Stage 2 DBPR Compliance Monitoring
Routine Monitoring
The Stage 2 DBPR routine monitoring requirements are shown in Exhibit 3.3. Systems
must comply with Stage 2 DBPR monitoring requirements by the deadlines shown in Exhibit 3.2
according to their Stage 2 DBPR monitoring plan. Consecutive and wholesale systems must
determine their compliance schedules based on the population of the largest system in the
combined distribution system.
Modified Monitoring for Combined Distribution Systems
In addition to modifying monitoring under 40 CFR 141.29 on a case-by-case basis with
EPA concurrence each time (see Section 2.3), the State is allowed to modify the Stage 2 DBPR
monitoring requirements of wholesale and consecutive systems on a case-by-case basis (40 CFR
142.16(m)) without EPA concurrence each time. These modifications would allow the State to
account for complex combined distribution systems, such as the following cases (USEPA,
2007b):
• Neighboring systems that buy and sell to each other regularly throughout the year;
• Situations where water passes through multiple consecutive systems before it reaches the
user; and
• A large group of interconnected systems.
The modified monitoring program must not undermine public health protection (USEPA,
2007b). The State may reduce the number of monitoring sites required for individual wholesale
and consecutive systems if the reduced number adequately represents DBF levels throughout the
individual system's distribution system. The combined distribution system must have at least the
minimum number of Stage 2 DBPR monitoring sites and monitoring frequency shown in Exhibit
3.3 based on the source water type and total population of the combined distribution system. In
addition, each consecutive or wholesale system must have at least one compliance monitoring
location.
Systems should note that regulatory requirements present the minimum acceptable
monitoring program. Monitoring above and beyond regulatory requirements is advised if the
system has adequate resources. The additional monitoring data can help the system to be
Consecutive Systems Guidance Manual 3-5 March 2010
-------
proactive in identifying areas of the distribution system with potentially high DBF levels, and to
optimize operating practices to minimize DBF levels.
There is a primacy requirement for States to decide how they will handle monitoring in
consecutive systems. States can satisfy this special primacy condition regarding consecutive
system monitoring by including a copy of the procedure they will use for addressing consecutive
systems outside the provisions of 40 CFR 141.29, as provided for in 40 CFR 142.16(m).
Alternatively, States can simply attest that they will not address consecutive system monitoring
outside of 40 CFR 141.29 (including EPA concurrence).
Consecutive systems are responsible for ensuring that required monitoring is completed
and the system is in compliance. Each consecutive system must base compliance on samples
collected within its distribution system. The consecutive system may conduct the monitoring
itself or arrange for the monitoring to be done by the wholesale system or another outside party.
Whatever approach it chooses, the consecutive system must document its monitoring strategy as
part of its DBF monitoring plan.
Exhibit 3.3 Stage 2 (subpart V) Routine Monitoring Requirements
Source
Water Type
subpart H
Ground
Water
Population Size
Category
<500
500 - 3,300
3,301 -9,999
10,000-49,999
50,000-249,999
250,000-999,999
1,000,000-4,999,999
> 5, 000, 000
<500
500 - 9,999
10,000-99,999
100,000-499,999
> 500,000
Monitoring
Frequency 1
per year
per quarter
per quarter
per quarter
per quarter
per quarter
per quarter
per quarter
per year
per year
per quarter
per quarter
per quarter
Number of Distribution System
Monitoring Sites
22
22
2
4
8
12
16
20
22
2
4
6
8
Source: 40 CFR 40 CFR 141.621 (a)
1 All systems must take at least one dual sample set during the month of highest DBP concentrations. Systems on
quarterly monitoring (except for subpart H systems serving 500-3,300 people) must take dual sample sets every 90
days.
2 A system is required to take individual TTHM and HAAS samples (instead of a dual sample set) at the locations with
the highest TTHM and HAAS concentrations, respectively. Only one location with a dual sample set per monitoring
period is needed if highest TTHM and HAAS concentrations occur at the same location.
Consecutive Systems Guidance Manual
3-6
March 2010
-------
Reduced Monitoring
Systems may reduce the number or frequency of samples taken if all of the following
occur:
• The LRAA is less than or equal to 0.040 mg/L for TTHM and 0.030 mg/L for HAAS
at each monitoring location.
• Only data collected under the Stage 2 DBPR (or under Stage 1 DBPR if you monitor
at the same locations for Stage 2) may be used to qualify for reduced monitoring.
• The source water annual average total organic carbon (TOC) level, before any
treatment, is less than or equal to 4.0 mg/L at each treatment plant treating surface
water or GWUDI based on monitoring conducted under the Stage 1 DBPR.
Consecutive systems should contact the wholesaler system to see if data are available.
See 40 CFR 141.623 for specific reduced monitoring provisions for different categories
of systems.
Systems that were on reduced TTHM and HAAS monitoring under the Stage 1 DBPR
may remain on reduced monitoring under the Stage 2 DBPR if all of the above criteria are met
and the system qualified for 40/30 certification or received a VSS waiver.
Systems may remain on reduced monitoring for as long as the following occur:
• For systems on quarterly monitoring: the LRAA is less than or equal to 0.040 mg/L
for TTHM and 0.030 mg/L for HAAS at each monitoring location
• For systems on annual or less frequent monitoring: each TTHM sample is less than
or equal to 0.060 mg/L and each HAAS sample is less than or equal to 0.045 mg/L.
• For systems using surface water or GWUDI: the source water annual average TOC
level, before any treatment, is less than or equal to 4.0 mg/L at each treatment plant
treating surface water or GWUDI based on monitoring conducted under the Stage 1
DBPR.
However, States may require systems to return to routine monitoring at their discretion.
For example, if a system makes significant changes to its treatment or distribution system, or if a
system changes monitoring locations, the State may require the system to return to routine
monitoring.
Increased Monitoring
Systems that are required to monitor at a particular location yearly or less frequently
under routine or reduced monitoring must begin increased monitoring at all locations if a TTHM
sample is greater than 0.080 mg/L or an HAAS sample is greater than 0.060 mg/L at any
location. Increased monitoring consists of dual sample sets once per quarter at each monitoring
location. The system may return to routine monitoring after it conducts increased monitoring for
at least four consecutive quarters and the LRAA for every monitoring location is less than or
Consecutive Systems Guidance Manual 3-7 March 2010
-------
equal to 0.060 mg/L for TTHM and 0.045 mg/L for HAAS. Systems that were on increased
monitoring under the Stage 1 DBPR must remain on increased monitoring under the Stage 2
DBPR until the criteria for returning to routine monitoring are met.
3.3.3 Reporting and Recordkeeping Requirements
Systems must report the results of Stage 2 (subpart V) TTHM and HAAS monitoring to
the State within 10 days of the end of any quarter in which monitoring is required. Systems
conducting quarterly monitoring must calculate the LRAAs for TTHM and HAAS by averaging
the data from the most recent four quarters of monitoring. For systems that conduct monitoring
yearly or less frequently, each sample is considered the LRAA for that monitoring location.
However, if any single sample has a TTHM or HAAS concentration greater than the MCL, the
system does not incur a violation immediately. Instead, the system must begin increased
monitoring.
Systems that are seeking to remain on reduced monitoring must also submit the results of
source water TOC monitoring for each surface water or GWUDI source. Note that source water
samples must be taken prior to treatment and would probably have to be taken by the wholesaler.
Systems must retain all monitoring results for ten years.
3.4 Disinfectant Residual Monitoring
Consecutive systems that do not add a chemical disinfectant to the water may not have
previously monitored to determine compliance with the MRDLs for chlorine and chloramines.
The Stage 2 DBPR (40 CFR 141.624) now specifically requires consecutive systems that deliver
water that has been treated with a disinfectant other than UV light to comply with the following
requirements for chlorine and chloramines:
• Analytical requirements in 40 CFR 141.131(c). This section lists approved methods
for chlorine and chloramine residual monitoring. The rule allows systems to use N,
N-diethyl-p-phenylenediamine (DPD) kits, among other methods, for measuring these
residuals. Only a party approved by EPA or the State may measure the residual
disinfectant concentration for compliance.
• Monitoring requirements in 40 CFR 141.132(c)(l). Systems must measure the
residual disinfectant concentration at the same time and location as total coliforms are
sampled. Reduced monitoring of disinfectant residuals is not allowed.
• Compliance requirements in 40 CFR 141.133(c)(l). Systems must determine MRDL
compliance using a running annual average (RAA), computed quarterly, of monthly
averages of residual disinfectant samples collected for compliance. If the RAA
exceeds the MRDL, the system is in violation of the MRDL and must report to the
State and notify the public. Systems that switch between chlorine and chloramines
must calculate compliance using results of both chlorine and chloramine residual
monitoring together. The MRDL for chlorine is 4.0 mg/L and the MRDL for
chloramines is 4.0 mg/L (40 CFR 141.65).
Consecutive Systems Guidance Manual 3-8 March 2010
-------
• Reporting requirements in 40 CFR 141.134(c). Systems must report the results of
chlorine and chloramine monitoring to the State by the tenth day of the month
following the end of each quarter. Systems must report the number of samples taken
during each month of the last quarter, the monthly average for samples taken in each
of the last twelve months, the average of all monthly averages for the last twelve
months, and whether the MRDL was exceeded. The State may instead choose to
perform the calculations and determine compliance for the system.
Systems must comply with these requirements beginning April 1, 2009, unless required
to do so earlier by the State. Also, the state may modify monitoring provisions under 40 CFR
141.29 (with EPA concurrence).
For more information on Stage 1 DBPR requirements, refer to:
• The Stage 1 Disinfectants and Disinfection Byproducts Rule: What Does it Mean to
you? (USEPA, 2001)
• Alternative Disinfectants and Oxidants Guidance Manual (USEPA, 1999a)
3.5 Operational Evaluations
The Stage 2 Microbial-Disinfection Byproducts (M-DBP) Agreement in Principle
acknowledges that DBF peaks will sometimes occur, even when systems are in full compliance
with the enforceable MCL. The operational evaluation requirements of the Stage 2 DBPR help
systems to identify and reduce these peaks. The rule establishes operational evaluation levels of
0.080 mg/L for TTHM and 0.060 mg/L for HAAS. A system exceeds the operational evaluation
level at any monitoring location where one of the following occurs:
• The two previous quarters' TTHM results plus twice the current quarter's TTHM
result, divided by four, exceeds 0.080 mg/L, or
• The two previous quarters' HAAS results plus twice the current quarter's HAAS
result, divided by four, exceeds 0.060 mg/L.
A system that exceeds the operational evaluation level must conduct an operational
evaluation and submit a written report of the evaluation to the State no later than 90 days after
being notified of the analytical result that caused it to exceed the operational evaluation level.
The operational evaluation must include an examination of system treatment and distribution
operational practices. However, the system may request that the State allow it to limit the scope
of the operational evaluation if it is able to identify the cause of the operational evaluation level
exceedance to the State's satisfaction. The operational evaluation must also include steps that
could be considered to minimize the possibility of future operational evaluation level
exceedances. Also, see Chapter 6 (section 6.2) for additional information about consecutive
system operational evaluations and the possible need for the coordination with the wholesale
system.
An operational evaluation level exceedance is not a violation of the Stage 2 DBPR.
However, failure to conduct an operational evaluation and submit the report to the State in the
Consecutive Systems Guidance Manual 3-9 March 2010
-------
required time frame is a violation and requires Tier 3 public notice (as required by the Public
Notification Rule).
For more information on operational evaluations refer to EPA's Stage 2 DBPR
Operational Evaluation Guidance Manual (USEPA, 2008).
3.6 Simultaneous Compliance
Systems may encounter compliance issues with the Long Term 2 Enhanced Surface
Water Treatment Rule (LT2ESWTR) when making changes to comply with the Stage 2 DBPR,
and vice versa. In addition to the challenges of complying with the suite of M-DBP rules
simultaneously, water system operators must also ensure that changes in treatment do not
adversely affect compliance with other drinking water regulations, such as the Lead and Copper
Rule (LCR) and Total Coliform Rule (TCR). Guidance on how to address these potential
conflicts can be found in EPA's Simultaneous Compliance Guidance Manual (USEPA, 2007a).
Consecutive Systems Guidance Manual 3-10 March 2010
-------
4.0 Compliance Options for Consecutive Systems
Consecutive systems purchase finished water from wholesale systems and may have
limited control over the quality of water entering the distribution system. Many purchasing
agreements specify the quantity of water available to a consecutive system from a wholesale
system, but may not include specific water quality requirements. When water quality is
included, purchasing agreements may stipulate only that water quality at the consecutive system
entry point will meet all State and Federal regulations. However, because DBF concentrations
can increase, sometimes significantly, from the consecutive system entry point through the
distribution system, consecutive systems may at times have difficulty meeting the Stage 2 DBPR
MCLs for TTHM and HAAS. As a result, there will be instances in which it is necessary for
consecutive systems to implement treatment and/or operational changes to comply with the Stage
2 DBPR.
This chapter discusses the treatment and operational alternatives most likely to be
available to consecutive systems to control DBF levels in treated water and comply with Stage 2
DBPR. This chapter includes the following sections:
4.1 DBF Control in Consecutive Systems
4.2 Water Age Management
4.3 Reduction of Disinfectant Demand
4.4 Chloramination
In addition, Chapters 5 and 6 provide information on approaches that may also help in
maintaining compliance, either by themselves or as part of a plan that includes multiple
approaches.
4.1 DBF Control in Consecutive Systems
Depending on the wholesale system-consecutive system physical arrangement and
hydraulic characteristics, DBF concentrations may be higher in the consecutive system than in
the wholesale system. This is particularly true when consecutive systems receive water through
a distribution grid rather than dedicated transmission mains. In such cases, the water entering the
purchasing system may already be several days old. Increased water age generally results in
increased distribution system DBF concentrations. Under the Stage 2 DBPR, wholesale systems
are not required to make treatment or operational modifications necessary to reduce DBF
concentrations in their consecutive systems as long as the wholesale system meets the MCLs
within its own distribution system. In such cases it may be necessary for the consecutive system
to implement treatment or operational changes to reduce distribution system DBF concentrations
and comply with the Stage 2 DBPR.
Consecutive Systems Guidance Manual 4-1 March 2010
-------
The treatment or operational changes considered and ultimately implemented by a
consecutive system to reduce DBF concentrations depend on the factor(s) causing the high DBF
levels. The factors that most significantly impact DBF formation are:
• Disinfectant type and dose. The type and dose of a disinfectant has a significant
impact on DBF formation. Chlorine is the most common primary disinfectant used in
water treatment, but it reacts with natural organic matter (NOM) to form chlorinated
DBFs such as trihalomethanes (THMs) and haloacetic acids (HAAs). Some of the
alternative primary disinfectants to chlorine are chlorine dioxide, ozone, and UV
light. While these alternative disinfectants can help to reduce levels of regulated and
unregulated chlorinated DBFs, they form other types of byproducts. Secondary
disinfectants used to maintain a residual in the distribution system include chlorine
and chloramines.
• Inorganic DBF precursor concentrations. Bromide reacts with chlorine to form
hypobromous acid, which is more aggressive in forming DBFs than chlorine
(hypochlorous acid). Bromide cannot be cost-effectively removed at this time.
• Organic DBF precursor concentration. NOM reacts with disinfectants to form DBFs.
Treatment processes that may help to reduce levels of organic DBF precursors
include enhanced coagulation, powdered activated carbon (PAC), granular activated
carbon (GAC), ozone and biological filtration, and nanofiltration.
• pH. DBF formation is affected by the pH of the water. Chiorination at higher pH
forms a higher amount of THMs, while the opposite is true for HAAs. Water at a
higher pH may also require a higher chlorine dose to maintain a consistent level of
microbial inactivation before entering the distribution system to comply with the
Surface Water Treatment Rule (SWTR). However, changes to pH to control DBFs
should be carefully considered to prevent a decrease in corrosion control
effectiveness in the distribution system and to avoid possible lead and copper
corrosion problems.
• Temperature. Seasonal variations in water temperature during treatment and in the
distribution system can have an effect on the reaction rate. Higher temperatures
increase reaction rates between DBF precursors and disinfectants to produce higher
levels of DBFs.
• Water age. The contact time between disinfectants and DBF precursors has a
significant effect on DBF formation. As the reaction time with the disinfectant
increases, so does DBF formation. However, biodegradation may actually reduce
HAAS levels if adequate disinfectant residuals are not maintained.
These factors are discussed in greater detail in the Stage 2 DBPR Initial Distribution
System Evaluation (IDSE) Guidance Manual (USEPA, 2006), Operational Evaluation Guidance
Manual (USEPA, 2008), and Stage 2 M-DBP Simultaneous Compliance Guidance Manual
(USEPA, 2007).
Among the major factors identified above, the removal of DBF precursors and pH
adjustment are typically achieved at the treatment plant of the wholesale system. Controlling the
Consecutive Systems Guidance Manual 4-2 March 2010
-------
water temperature is not a practical option for DBF control. Accordingly, the Stage 2 DBPR
identifies two BATs for consecutive systems to reduce DBF formation:
• For systems serving fewer than 10,000 people: hydraulic flow and storage
management to control and reduce water age.
• For systems serving at least 10,000 people: chloramination with hydraulic flow and
storage management.
These options are discussed further in sections 4.2 and 4.3.
Consecutive systems should consult their purchasing agreement with their wholesaler
before making modifications to reduce distribution system DBF concentrations. Purchasing
agreements may prevent the consecutive system from adding treatment chemicals or making
other system modifications. If so, the consecutive system may need to renegotiate its purchasing
agreement to add ammonia to convert free chlorine to chloramines. Purchasing agreements may
also assign responsibility for such modifications to the wholesaler.
4.2 Water Age Management
Water age is a significant factor in DBF formation. As water travels through the
distribution system, chlorine continues to react with NOM to form DBFs. The longer the travel
time or water age, the more likely it is that water quality will degrade and exhibit higher TTHM
and HAAS concentrations, reduced levels of residual chlorine, reduced effectiveness of chlorine
residual through formation of organochlorine compounds, increased microbial activity,
nitrification, and/or taste and odor problems. Where high water age is considered to be a
contributing factor to elevated DBF concentrations, consecutive systems might consider adoption
of operational practices to reduce water age in finished water storage facilities and distribution
system piping.
Some of the methods to reduce water age by hydraulic flow and storage management
include:
• Pipe looping,
• Managing valves,
• Bypassing oversized pipes,
• Installing dedicated transmission main,
• Improving tank mixing and turnover, and
• Eliminating excess storage and tanks in series.
These methods to reduce water age are discussed below. Additional information about
reducing water age in a distribution system can be found in the Operational Evaluation
Guidance Manual (USEPA, 2008).
Consecutive Systems Guidance Manual 4-3 March 2010
-------
4.2.1 Pipe Looping
The highest DBF concentrations in a distribution system are most often observed at dead-
ends (although this may not be true for HAAs because of biodegradation). Water at dead-ends is
often stagnant and therefore provides long contact times for DBF formation. Excessive
hydraulic residence time at dead ends can be reduced with pipe looping, which involves
constructing new pipe sections to make appropriate hydraulic connections among existing pipes.
Pipe looping may not always eliminate water age problems. For example, if two distribution
pipes with low demand are looped together and there is insufficient demand to cause water to
circulate, then an even larger hydraulic dead-end may result. This may create an even larger area
in the system that is subject to water quality problems resulting from high water age, such as
high DBF concentrations. Therefore, the specific hydraulic response of a system to looping
should be assessed to make sure that looping does not negatively impact the residence time of
other parts of the system. Further information on pipe looping can be found in the book
Comprehensive Water Distribution Systems Analysis Handbook published by AWWA (Boulos et
al., 2006).
4.2.2 Managing Valves
Intentional or unintentional closed valves in a distribution system may create stagnant
water leading to high DBF levels in those locations. The presence of unintentional closed valves
could be due to some valves being inadvertently turned in the wrong direction or being broken.
These valves may remain undetected due to poor record keeping or because the valve boxes are
buried or paved-over. A comprehensive valve inventory and maintenance program can help
systems locate valves, determine their status, and find improperly positioned and broken valves.
4.2.3 Bypassing Oversized Pipes
In portions of a distribution system where pipes are oversized, the water velocity is lower
and therefore hydraulic residence times are longer than necessary, causing high DBF levels.
Areas of a distribution system that have been abandoned or have experienced negative demand
growth over many years may contain oversized pipes, causing excessive hydraulic residence
time. Where appropriate, the pipe sizes in these areas can be reduced or sections of pipes can be
valved off if they are no longer needed to reduce the residence time of water. However, the
effect of bypassing or valving oversized pipes on downstream areas should be evaluated to make
sure that such modifications will not cause hydraulic constrictions for the downstream areas.
4.2.4 Installing Dedicated Transmission Main
When water travels through low demand areas and finished water storage facilities in a
distribution system before reaching a consecutive system, the water at the entry point to the
consecutive system may have high DBF levels due to high water age. In such cases, the
installation of a dedicated transmission main to supply water to the consecutive system can be
Consecutive Systems Guidance Manual 4-4 March 2010
-------
considered to reduce water age but its effects on water age in the wholesale system should be
estimated.
4.2.5 Improving Tank Mixing and Turnover
Excessive hydraulic residence time in distribution storage tanks results in high water age,
which can cause high DBF levels in the tank and at downstream locations in the distribution
system. The average hydraulic residence time in a tank can be estimated by the following
equation:
Theoretical average hydraulic residence time = [Vmax/(Vmax - Vmin)]/N
where Vm;n = average minimum daily volume
Vmax = average maximum daily volume
N = number of drain/fill cycles per day
(Units for Vmax and Vm;n must be consistent)
It is important to recognize that the above equation provides information about the
average amount of time spent by water inside a tank. In poorly mixed storage tanks, water age
may actually be much higher (or lower) than the average hydraulic residence time in some
portions of the tank. The Vmax and Vm;n values are numbers that are averaged from data collected
over several days or weeks to represent the typical operational characteristics of the tank. If tank
operations are changed from one season to another, then the Vmax and Vm;n values may be
different during different seasons. Typically, the average hydraulic residence time for a storage
tank should not exceed 5 days (Kirmeyer et al., 1999). However, some systems may need much
lower hydraulic residence times due to site-specific water quality constraints.
The average hydraulic residence time in a storage tank can be reduced by increasing the
volume turnover. The volume turnover can be increased by increasing the volume of water that
flows in and out of a tank during a given fill/drain cycle (the drawdown), or by increasing the
number of fill/drain cycles per day. When possible, the recommended approach is to increase
the drawdown between fill cycles. Increasing the number of fill/drain cycles is only effective
when 1) the tank is well-mixed at the end of each fill cycle and 2) the drawdown between each
fill/drain cycle is equal to the original drawdown. Increasing turnover by either of these
strategies may be limited by system hydraulic (pressure) constraints. It may be necessary to
adjust tank water level controls or the control settings for altitude valves to increase turnover.
Improving storage tank mixing characteristics can reduce average water age and
minimize stagnant zones in the tank. These stagnant zones often have higher water age and thus
tend to have higher DBF concentrations. Several tools can be employed to predict water mixing
characteristics of a tank:
• Desktop evaluations of hydraulic residence time, fill time, and inlet momentum.
• Computational fluid dynamic (CFD) modeling.
• Temperature measurements.
Consecutive Systems Guidance Manual 4-5 March 2010
-------
• Disinfectant residual measurements.
The mixing predictions from desktop evaluations, CFD modeling, temperature
measurements, and disinfectant residual measurements can be used to identify a storage tank
with inadequate mixing and, therefore, a potential for high DBF formation in some regions in the
tank. A method to estimate hydraulic residence time in a tank was presented previously in this
section. Fill time and inlet momentum can be estimated from operational records and
supervisory control and data acquisition (SCADA) data. Generally, longer fill times and greater
inlet momentum result in better tank mixing. The minimum acceptable hydraulic residence time
and inlet momentum is tank- and situation- specific, and depends on a number of system factors,
including water quality, tank geometry, inflow rate, and inlet/outlet pipe configuration.
CFD modeling provides a qualitative description of mixing characteristics by providing
visual images of mixing inside a tank. It can be used to determine the effects of fill time and
inlet momentum on mixing characteristics.
Poor mixing conditions can cause thermal stratification in a tank. Thermal stratification
in turn can exacerbate the poor mixing condition. Depending on the location and orientation of
the inlet pipe and tank geometry, the water entering a tank from buried pipes may be cooler than
the bulk water in the tank during the summer or warmer than the bulk water in the tank during
the winter. In a tank with poor mixing characteristics, colder, denser water remains in the lower
portion of the tank, whereas the warmer, less dense water has a tendency to rise to the top of the
tank. Water temperature profiles can be used to determine the existence of thermal stratification
inside a tank. The temperature profiles can be obtained from the collection of continuous water
temperature measurements at various locations in the tank over the course of several days.
Temperature differences as low as 1°C between the top and bottom of a tank may indicate a
thermally stratified tank with poor mixing.
Exhibit 4.1 shows cross-section views of water mixing characteristics observed in a
standpipe tank under slightly different temperature conditions. In this test, a solution containing
a one milligram per liter concentration of dye was added to water flowing into the tank. The dye
concentrations in the tank were then monitored for a one-hour period. The left-hand profile
shows the tank with a bulk water temperature 1° C warmer than the temperature of incoming
water. Note that the incoming, colder water remains in the lower portion of the tank. This water
will be the first to exit as demand draws water from the tank. The right-hand profile shows
much improved mixing when the inflow water and the tank water were at the same temperature.
Consecutive Systems Guidance Manual 4-6 March 2010
-------
Exhibit 4.1 Effect of Temperature Differential Between Inflow and Tank Bulk
Water on Mixing Characteristics
36" vertical inlet
1 mg/L tracer after 60 mins
Tank temp 1 C > Inlet Temp
Isothermal condition (20 C)
Source: Mahmood et al., 2005
Disinfectant residual measurements, collected either as grab samples or from continuous
online monitoring at various locations in the tank, can also be used to evaluate mixing and
identify water quality stratification. Residual levels in thermally stratified portions of the tank
representing older water will be less than residual levels in well mixed portions of the tank. In
one study, researchers observed an average difference of 0.4 mg/L between the chlorine residual
at the bottom of a standpipe compared to the top of the same standpipe based on samples
collected at different residence times (Mahmood et al., 2005). Authors note that differences in
chlorine residuals were consistent with differences in temperature (i.e., higher temperature
tracked with the lower residual readings).
Additional information about the use of desktop evaluations, CFD modeling, temperature
measurements, and disinfectant residual measurements to evaluate water mixing characteristics
in storage tanks, and operational and/or physical modifications to improve mixing characteristics
is presented in Water Quality Modeling of Distribution System Storage Facilities (Grayman et
al., 2000) and Evaluation of Water Mixing Characteristics in Distribution System Storage Tanks
(Mahmood et al., 2005).
Once the water mixing characteristics of a storage tank have been evaluated, appropriate
operational and/or physical modifications can then be recommended to improve water mixing in
the tank. The mixing characteristics can be improved by operational changes, which include
filling a tank for a longer time period and increasing inlet momentum. If operational changes are
not possible, then the mixing characteristics can also be improved by design modifications, such
as changing the location, orientation, and/or diameter of inlet/outlet pipes.
Inlet momentum (defined as velocity x flow rate) is a key factor for mixing water in a
storage tank. As the inlet momentum increases, the mixing characteristics in the tank improve.
The inlet momentum can be increased by increasing the flow rate (which also has the desirable
Consecutive Systems Guidance Manual
4-7
March 2010
-------
effect of increasing the velocity) through installation of booster pumps near the tank, or other
means. However, increasing the flow rate may not be practical due to the limitations of system
hydraulics. For example, distribution system pressure may not be adequate to achieve desirable
increases in flow rates, or a pump may not be available at the tank location to increase the
pumping rate into the tanks. In such cases, the inlet velocity can be increased by reducing the
inlet diameter.
The location and orientation of the inlet pipe relative to the tank walls can have a
significant impact on mixing characteristics. The optimum inlet pipe location and orientation to
obtain good mixing in a tank depends on a number of site-specific factors including tank
geometry, inflow rate, and temperature differences between the inflow and the bulk water in the
tank. As water enters a tank through an inlet pipe, a jet is formed and the water present in the
tank is drawn into the jet. This forms circulation patterns that result in mixing. The path of the
jet must be long enough to allow the mixing process to develop, and therefore should not be
pointed directly towards nearby impediments such as a wall or deflector. For example, in a tall,
narrow tank, a horizontal inlet pipe at the bottom of the tank is likely to cause the water jet to hit
the vertical wall of the tank, resulting in loss of inlet momentum and poor mixing near the top
portion of the tank. In general, outlet pipes are located near the bottom of tank, and relocating
the inlet pipe near the top of tank may improve mixing characteristics. However, the system
hydraulics should be evaluated to ensure there would be adequate pressure to allow the tank to
fill to the desired level. Inlet pipes located near the bottom of a tank can be angled upwards, or
multiple inlet pipes can be used to improve mixing conditions in a tank. Exhibit 4.2 shows
predicted mixing characteristics in tanks with two different inlet pipe orientations based upon the
results of CFD modeling. The left-hand profile shows limited mixing in a tank with a horizontal
inlet. The right-hand profile shows much improved mixing in a tank with a vertical inlet.
In water treatment plant basins, where contact time is required for disinfection and there
is generally simultaneous inflow and outflow, internal baffles are sometimes placed inside the
basins to encourage plug flow conditions. Since, chlorine contact time is usually not an issue in
distribution system tanks and reservoirs, baffles should generally be avoided. Baffles encourage
plug flow conditions and can result in poor mixing zones (dead zones) and greater variability in
DBF levels since dead zones within baffled tanks can have higher water age and therefore higher
DBF concentrations. Baffled tanks are likely to experience more significant disinfectant residual
decay than tanks with mixed flow conditions. There may be special circumstances, such as
separate inlet and outlet pipes in close proximity to each other, under which a baffle wall may be
desirable to force water into other parts of the tank. However, because of the wide variations in
tank geometry and inlet/outlet piping configurations for storage tanks, the use of baffles should
be carefully evaluated for each specific situation to determine if baffles have any beneficial
impact. Tracer testing, CFD modeling, and disinfectant residual monitoring are useful tools to
determine the effects of baffles, and to optimize the location, and orientation of the inlet/outlet
pipes.
Consecutive Systems Guidance Manual 4-8 March 2010
-------
Exhibit 4.2 Effect of Inlet Pipe Orientation on Mixing Characteristics
Isothermal condition (20 C)
1 rrgfL tracer after 30 rrins
Cone
0.8
0.6
0.4
0.2
0.1
0.01
36" horizontal inlet
36' vertical inlet
Source: Mahmood et al., 2005
4.2.6 Eliminating Excess Storage and Tanks in Series
Historically, distribution system storage tanks have generally been built to provide
adequate pressures, fire flows, and to meet peak demands. Tanks are also often designed to
accommodate future growth and long-term water system needs. Therefore, some distribution
system storage tanks may be oversized. Storage tanks may also be hydraulically isolated from
the distribution system due to high system pressures, low system demands, or inadequate tank
height. Oversized tanks and/or tanks that are hydraulically locked out (due to system pressure
being higher than the maximum water level in the tank most of the time) may not have adequate
volume turnover, resulting in high water age and high DBF formation potential. When events
such as main breaks, fire flows, or other unexpected peak demand conditions occur in a system,
water from these tanks may be drawn into the distribution system. Areas receiving water from
these tanks may have higher than normal DBF levels.
There are limited options to improve mixing characteristics and reduce water age for a
tank that is oversized or hydraulically isolated under normal system operating conditions. It may
be possible to increase volume turnover in a tank that is hydraulically isolated if the operational
hydraulic grade in the vicinity of that tank can be lowered. This may be accomplished by
valving off pipe sections during certain hours so that water demand in the vicinity of the tank is
supplied primarily by the tank rather than from other parts of the distribution system. More
water can be forced in and out of an oversized tank on a daily basis by installing pumps,
adjusting pumping schedules (if pumps already exist), or adjusting the control settings for
altitude valves. However these modifications may not be feasible due to system hydraulic
Consecutive Systems Guidance Manual
4-9
March 2010
-------
limitations. In such cases, decommissioning of the tank can be considered. If a consecutive
system has such a tank, and the wholesale system has another tank in the vicinity with adequate
storage, then the consecutive system may be able to decommission its tank. However,
coordination with the wholesale system is necessary to ensure that when the consecutive
system's tank is decommissioned, the wholesale system's tank has adequate hydraulic capacity
(both storage and piping) for equalization storage, fire flow, or emergency conditions such as
main breaks. Refer to Chapter 6 for additional information about communicating with the
wholesale system.
Tanks in series can also lead to high DBF levels in areas downstream of the tanks if there
is inadequate mixing and volume turnover in the tanks. If the mixing and volume turnover issues
cannot be addressed, consideration should be given to whether water can be re-routed to the
distribution system pipe network directly rather than through other tank(s). Re-routing the water
flow involves adjusting valve positions in the pipe network and pumping set points and
schedules. A system operational analysis (generally using a hydraulic model) will allow the
system to determine the pressure and flow impacts caused by re-routing the water flow. Since
elimination of tanks in series may reduce the volume turnover in these tanks due to associated
changes in frequency and magnitude of the drain/fill cycles, the system should evaluate these
impacts.
4.3 Reduction of Disinfectant Demand
Aging pipes such as unlined cast iron pipes exert high disinfectant demand because of the
presence of corrosion byproducts, biofilms, and sediment deposits. Consecutive systems can
reduce localized chlorine decay and thus reduce the overall disinfectant demand by replacing or
cleaning and lining pipes, and/or by conducting periodic flushing. Consecutive systems may see
improved results if they coordinate their efforts with their wholesale systems. See Chapter 6 for
more information.
4.3.1 Replacing or Cleaning and Lining Unlined Cast Iron Pipes
Pipe replacement may be the preferred option for reducing disinfectant demand if a
pipeline has structural problems or if there is a need to increase hydraulic capacity with a larger
diameter pipe. If a pipeline is structurally sound, then pipe cleaning is a less expensive option.
For unlined cast iron pipes, pipe lining may also be necessary to achieve a permanent
improvement and prevent a recurrence of the disinfectant demand problem. The AWWA
Standard, Rehabilitation of Water Mains (M28), 2nd Ed. (AWWA, 2001), provides information
and guidance on cleaning and lining technologies.
4.3.2 Distribution System Flushing
Periodic flushing can be an effective tool to control TTHM and HAAS peaks to remove
pipe sediments and biofilms, thereby reducing disinfectant demand. There are several
approaches to conduct distribution system flushing depending on system configuration and water
quality goals. The AwwARF report, Guidance Manual for Maintaining Distribution System
Water Quality (Kirmeyer et al., 2000) provides detailed information on various flushing
Consecutive Systems Guidance Manual 4-10 March 2010
-------
approaches. Regardless of the flushing method implemented, utilities should use water quality
data to identify periods when DBFs have historically been high. However, utilities cannot
simply flush in the area where DBF samples are collected prior to sampling dates for the
purposes of reducing DBF compliance monitoring results. This practice is not allowed because
such intermittent flushing is not considered normal operation.
Conventional flushing is considered routine distribution system maintenance and is
conducted by opening hydrants without directing the flow through the distribution system with
isolation valves. Fire hydrants are usually opened and allowed to run until the water clears.
While utilities often move through the system sequentially when practicing conventional
flushing, this should not be confused with directional flushing. The velocities used for
conventional flushing may be inadequate (less than 5 feet/second) for removing sediment,
corrosion byproducts, and other debris that can contribute to high DBF levels. It is also possible
to draw poor quality water from other areas into the areas being flushed. Additional information
on flushing practices and selection of flushing velocities can be found in the AwwaRF report,
Establishing Site-Specific Flushing Velocities (Friedman et al., 2003).
Directional flushing involves the flushing of water in one direction through systematic
operation of distribution system valves. Utilities practicing directional flushing typically begin
at a source of high quality water (e.g., a large transmission main) and systematically move
through the system opening hydrants and manipulating system valves to assure water moves in
only one direction through the system. Because water travels toward a hydrant in a single
direction, higher flushing velocities can be achieved. A properly designed and implemented
directional flushing program can achieve water velocities higher than 5 feet/second to scour the
pipe. In addition to increasing water flow in the selected main, directional flushing can reduce
the impact of other factors contributing to the formation of high DBF concentrations including
the accumulation of sediments and the build-up of corrosion byproducts. (Joseph and Pimblett,
2000)
"Blow-offs" can be used to eliminate dead-ends and stagnant water zones that have high
water age and therefore contribute to high DBF levels. Blow-offs can operate in an automatic
intermittent mode or continuous mode to remove old water from dead-end or stagnant zones and
pull fresher water into these locations from other areas. The velocities for a blow-off are
generally insufficient (< 2.5 feet/second) to remove sediments or biofilm. Blow-offs can be used
on a seasonal basis when DBF peaks are more likely to occur, such as during high water
temperature periods. The need for and appropriate locations for blow-offs can be determined
from distribution system flow models or distribution system historical records. Low disinfectant
residuals, high DBF concentrations, high heterotrophic plate counts (HPCs), coliform-positive
samples, or nuisance bacteria are often associated with high water age locations.
Whenever flushing is used, it may be necessary to dechlorinate or dechloraminate
flushing water to prevent adverse impacts on nearby streams. Both chlorine and chloramines can
have negative impacts on aquatic environments. Depending on where flushed water is
discharged, it may end up in nearby streams or other bodies of water. In such cases, a
dechlorinating agent (e.g., sodium bisulfite or sodium thiosulfate) can be used to prevent fish
kills or other adverse effects. Consult your State or local regulatory agency to determine if it is
necessary to dechlorinate or dechloraminate flushing discharges. Also consider discharging the
flushed water to the sewer system.
Consecutive Systems Guidance Manual 4-11 March 2010
-------
4.4 Chloramination
As identified in Section 4.1, the disinfectant type can be a significant factor in DBF
formation. Where the use of free chlorine is considered to be a contributing factor to elevated
DBF concentrations, consecutive systems might consider switching to chloramines for secondary
disinfection. THM and HAA formation is generally significantly lower for chloramines than for
free chlorine. However, consecutive systems should consider the following issues before
switching from free chlorine to chloramines:
• Water quality issues for chloramines such as the formation of other currently
unregulated DBFs, nitrification, corrosion, and taste and odor issues.
• Whether to switch all or only a portion of the distribution system to chloramines.
• Cost, handling, and safety issues.
These issues are discussed further in the following sections. Additional information on
chloramination can be found in EPA's Simultaneous Compliance Guidance Manual for the Long
Term 2 and Stage 2 DBF Rules (USEPA, 2007a)
4.4.1 Water Quality Issues for Chloramines
Chloramines are an effective secondary disinfectant because they are generally less
reactive than free chlorine causing them to be more persistent in the distribution system, and they
are able to better penetrate biofilms than chlorine. This greater persistence allows some utilities
(e.g., large systems in warm water climates) otherwise unable to maintain a disinfectant residual
using free chlorine to maintain a residual in the distribution system. In addition, the
concentrations of TTHM and HAAS usually decrease when switching from free chlorine to
chloramines. Chloramines can react with organic precursor material to form THMs, but the
reaction rates are very slow compared to free chlorine. Chloramines are highly effective at
reducing THM formation levels in the distribution system and the reduction in THM levels is
generally 40 to 80 percent compared to free chlorine. Chloramines also produce lower levels of
HAAs than free chlorine, but may not be effective in controlling all types of HAAs. Some
brominated HAAs are formed with chloramines. Chloramines generally produce lower levels of
total chlorinated byproducts than free chlorine.
Potential operational and simultaneous compliance issues when using chloramines
(which may be greater in a complex combined distribution system) include the following:
• Nitrification,
• Increased corrosion and metal release if corrosion control is not evaluated and
modified as necessary,
• Taste and odor issues,
• Weaker disinfectant,
Consecutive Systems Guidance Manual 4-12 March 2010
-------
• Blending issues - chloraminated and chlorinated waters,
• Issues with ozonation and GAC filtration, and
• Issues for dialysis patients, fish owners and industrial customers.
The reader is referred to EPA's Simultaneous Compliance Guidance Manual for the Long
Term 2 and Stage 2 DBF Rules (USEPA, 2007a) for more detailed information on these issues.
4.4.2 Options for Chloramine Conversion
When the wholesaler uses free chlorine for secondary disinfection and the consecutive
system switches to chloramines for secondary disinfection of the water it provides, the
consecutive system has two options for managing its water with disinfectants:
• Option 1: Convert part of the consecutive system's distribution system to chloramine
and physically separate that area from the wholesaler's and other areas of the
consecutive system's distribution systems.
• Option 2: Convert the consecutive system's entire distribution system to chloramine
and physically separate the system from the wholesaler's system.
Option 1
The first option may be considered if the consecutive system only needs to reduce high
DBF levels in specific areas. Depending on the hydraulic characteristics of the distribution
system, it may be feasible to isolate the chlorinated water from the chloraminated water in the
same way that different pressure zones are isolated. The separation of the waters in the
distribution system can be an inexpensive solution if it only involves closing a few existing
valves or if it requires the installation of only a few new valves. If the chloraminated portion of
the distribution system is connected to the chlorinated portion of the system with only a few
major pipes, rather than a maze of small mains, then the physical separation of the waters may be
an attractive solution.
Caution should be exercised when considering conversion of only a portion of the system
to chloramines. The physical separation of areas of the distribution system may reduce the
reliability of the water supply to some service areas. The separation could lead to reduced
fire-flow capacity and reduced pressure in some areas. The dynamics of water flow may also
change to prevent adequate turnover in storage tanks. Flow reversal might also occur and could
lead to water quality problems.
Option 2
The second option is more appropriate if the consecutive system desires reduction of
DBF levels throughout its distribution system. Depending on the wholesale system-consecutive
system interconnections, converting the entire distribution system to chloramines might
minimize the hydraulic separation issues. It may also prevent potential water quality problems
that would have resulted had the chlorinated and chloraminated water blended in the consecutive
Consecutive Systems Guidance Manual 4-13 March 2010
-------
distribution system due to valve failure between pressure zones. Conversion of the entire
distribution system from free chlorine to chloramines will require larger or additional ammonia
and chlorine storage and feed systems. The ammonia feed system would have to be installed at
the point-of-entry to the consecutive system such that the chlorine is converted to chloramines
prior to entering the distribution system. Systems should consider installing backflow prevention
devices or other control features at the interconnections between the wholesaler and consecutive
systems to ensure that chloraminated water from the consecutive system does not backflow into
the wholesaler's system and mix with the wholesaler's chlorinated water. Finally, systems must
account for and address simultaneous compliance issues.
Prior to conversion of all or a portion of the consecutive system to chloramines, the
consecutive system should contact the State to determine what additional permitting, operational,
or other requirements apply. Many States require review and approval of treatment changes
through their permitting process. While many consecutive systems may not employ certified
water treatment plant operators, the addition of chemical feed facilities may constitute treatment
and the State may require the system to employ full- or part-time certified water treatment plant
operators.
4.4.3 Cost, Handling, and Safety Issues
Conversion of chlorinated water to chloraminated water requires the addition of
ammonia. Ammonia can be added in the form of anhydrous ammonia, aqueous ammonia, or
ammonium sulfate. Each system should determine the most appropriate type of chemical to use
by evaluating factors such as chemical cost, safety, storage requirements, and ease of handling.
Ammonia costs in the United States vary considerably. Anhydrous ammonia is generally the
least expensive option, followed by aqueous ammonia, and then ammonium sulfate.
Considerations related to the use of these chemicals are discussed in Optimizing Chloramine
Treatment., First and Second Editions (Kirmeyer et al., 1993 and 2004).
The chemical feed systems for chlorine and ammonia must be capable of injecting the
prescribed chemical doses into the water. Accurate feed control is necessary to ensure that a
consistent desired chlorine to ammonia ratio (generally in the range of 4.5:1 to 5:1) is
maintained. Immediate adjustments to chlorine or ammonia feed rates are necessary in response
to changes in flow rates or other variables. These adjustments can be made automatically with
feedback systems such as flow pacing or compound loop control. In a flow pacing system, the
dose depends on the flow rate, which can be measured by a flow meter. This type of feed control
can work if the chlorine residual entering the consecutive system is consistent. When both the
flow rate and the chlorine residual vary, a compound loop control system is used to adjust the
chemical doses based on the flow rate and the chlorine residual. In this case, a flow meter
measures the flow rate and a chlorine analyzer measures the chlorine residual, and both signals
are sent to a controller. The controller integrates the two signals and sends a signal to adjust the
chemical doses. Many variations of the compound loop control system are available
commercially.
Consecutive Systems Guidance Manual 4-14 March 2010
-------
4.4.4 Public Education
Before converting from free chlorine to chloramines as the secondary disinfectant,
customer concerns should be addressed through public education and notification. Customer
concerns generally fall into one of two categories:
• Human health concerns. Chloramines are toxic when not removed prior to using
water in the kidney dialysis process. Each hospital and dialysis treatment center
should be advised before a conversion is made so they can provide adequate testing
and treatment.
• Miscellaneous household concerns. Chloramines (and chlorine) are generally toxic to
fish, so homeowners, pet stores, and related businesses should be contacted.
Each PWS should prepare a public education plan prior to a conversion to chloramines.
Public education information, including examples of public education materials, can be obtained
from A Guide for the Implementation and Use of Chloramines (Harms and Owen, 2004). PWSs
may also want to add relevant language to their CCRs to keep customers advised of the presence
of chloramines in their drinking water. Also, EPA has information about chloramine use on its
website at www.epa.gov/safewater.
Consecutive Systems Guidance Manual 4-15 March 2010
-------
5.0 Other Alternatives for Consecutive Systems
Treatment and operational options for consecutive systems to reduce DBF levels are
presented in Chapter 4. This chapter presents some of the other alternatives available for
consecutive systems to reduce distribution system DBFs and achieve compliance with the
requirements of the Stage 2 DBPR. The alternatives discussed in this chapter are (1) improving
water quality from a wholesale system by methods such as treatment changes, reducing hydraulic
residence time, and booster disinfection; and (2) finding alternative sources of water with higher
quality and blending with wholesaler's water either at the treatment plant or in the distribution
system. This chapter is divided as follows:
5.1 Improved Water Quality from the Wholesale System
5.2 Alternative Sources and Blending Strategies
5.1 Improved Water Quality from the Wholesale System
The finished water leaving a wholesale system's treatment plant can spend a considerable
amount of time in the distribution system pipes before reaching a consecutive system. High
hydraulic residence time combined with a sufficient disinfectant dose to maintain adequate
disinfectant residual throughout the distribution systems can lead to high DBF formation in the
consecutive system. For a consecutive system that uses free chlorine for secondary disinfection,
the increase in DBF concentrations in the distribution system may be significant. If a
consecutive system is unable to effectively reduce DBFs in its system because of the levels in the
purchased water, the consecutive system should consider discussing control strategies with the
wholesale system. Refer to Chapter 6 for additional information about communicating with the
wholesale system.
Some DBF control strategies that a wholesale system can implement include:
• Achieving better DBF precursor removal at the treatment plant by optimizing
coagulation and/or clarification processes, or by adding a new treatment step such as
GAC filtration or nanofiltration.
• Moving the point of primary disinfectant addition downstream after removal of more
DBF precursors.
• Using an alternative primary disinfectant (e.g., ozone, chlorine dioxide) and/or
secondary disinfectant.
• Reducing disinfectant demand.
• Reducing disinfectant dose.
• Reducing the hydraulic residence time between the wholesale system's treatment
plant and the consecutive system.
Consecutive Systems Guidance Manual 5-1 March 2010
-------
Chapter 4 discusses options to reduce water age in greater detail. More information on
these DBF control strategies can also be found in the following sources:
• Stage 2 DBPR Operational Evaluation Guidance Manual (USEPA, 2008)
• Enhanced Coagulation and Enhanced Precipitative Softening Guidance Manual
(USEPA, 1999b)
• Simultaneous Compliance Guidance Manual for the Long Term 2 and Stage 2 DBF
Rules (USEPA, 2007a)
If it is not feasible for the wholesale system to implement some of the DBF control
strategies identified above, then the use of booster disinfection systems can help reduce DBF
levels. Booster disinfection systems could be installed in areas within the wholesale or
consecutive system where it is difficult to maintain disinfectant residuals, thereby allowing the
wholesale system to reduce the disinfectant residual leaving the treatment plant. Optimizing the
location and operation of booster disinfection facilities in the distribution system is important to
obtain desired results. The results from hydraulic models, disinfectant residual data, disinfectant
decay data, and other water quality data are used to determine appropriate booster disinfection
locations.
The advantages of using booster disinfection facilities include:
• Increasing the disinfectant residual only in areas that require it without increasing the
disinfectant residual in other parts of the system beyond acceptable levels.
• Maintaining a more consistent disinfectant residual throughout the distribution
system.
• Reducing the disinfectant dose and DBF formation at the treatment plant and prior to
the point of booster disinfectant addition.
The disadvantages of using booster disinfection facilities include:
• Difficulty in controlling the required disinfectant dose at multiple booster stations due
to the dynamic nature of chlorine demand in the system.
• Regulatory concern with the degradation byproducts if hypochlorite is used or safety
issues if chlorine gas is used.
• Booster operation in chloraminated distribution systems can be challenging.
For a chlorinated system, the primary controlling factor for chlorine dose is the difference
between the measured and desired free chlorine residual. For the chlorine and ammonia dose in
a chloraminated system, there are additional controlling factors besides the difference between
the measured and desired total chlorine residual, such as excess free ammonia in the system due
to chloramine decay. It is important to note that while booster disinfection can lead to lower
DBF concentrations entering the consecutive system, it may do little to reduce DBF
Consecutive Systems Guidance Manual 5-2 March 2010
-------
concentrations at the extremities of the distribution system, particularly where water age is
excessive.
5.2 Alternative Sources and Blending Strategies
A consecutive system may consider the use of an alternative water source with higher
quality for reducing high DBF levels in the system. If high DBF levels in a consecutive system
are due to the wholesaler's use of a surface water supply, then the consecutive system can
consider using a new groundwater source or increase the use of an existing groundwater source
(if available) to supplement the surface water supply from the wholesaler. Groundwater tends to
have lower TOC concentrations than surface water and is also less subject to rapid fluctuations in
TOC levels that may occur with surface water during periods of heavy runoff. Lower TOC
levels can significantly reduce DBF formation at the treatment plant, and for systems that use
free chlorine for secondary disinfection, the DBF reduction may also be significant in the
distribution system. During the summer, groundwater has lower temperatures than surface
water. If a disinfectant is added at the treatment plant shortly after groundwater is withdrawn
from the ground, then lower temperatures can reduce DBF formation at the treatment plant.
Increasing groundwater use or finding new groundwater sources may be difficult because
excessive groundwater withdrawal can reduce the groundwater table below desirable levels.
This may result in degraded groundwater quality and may affect stream flow levels. Sustainable
use of groundwater as an alternative source requires careful planning to allow adequate time for
groundwater recharge.
Another option for a consecutive system to reduce high DBF levels is to obtain an
alternative water source by purchasing water from another adjacent utility if the utility can offer
higher quality water. This option may be economically feasible if the water supply from the
other utility is in close proximity to the consecutive system. Generally, when the availability of
higher quality water is limited, the consecutive system may deliver the higher quality water only
to parts of the distribution system that have high DBF levels. Interconnections between the two
systems, and new pipelines, valves, and pumps may be required to deliver the higher quality
water to the desired areas.
When two or more alternative water sources are mixed, the final characteristics of the
blended water depends on the water quality characteristics of the individual sources and the
blending ratios. For DBF control, the primary water quality characteristics of concern are the
types and concentrations of disinfectants and DBF precursor concentrations (such as TOC)
present in each source. In many cases, blending may minimize the formation of high DBF
levels, but other water quality problems may actually increase. Therefore, other water quality
characteristics such as corrosion potential, pH, taste, loss of disinfectant residual, and hardness
also need to be considered. Examples of water quality problems due to improper blending ratios
of alternative sources include:
• Loss of disinfectant residual when blending chlorinated and chloraminated water;
• Increases in taste and odor;
Consecutive Systems Guidance Manual 5-3 March 2010
-------
• Increased corrosivity or increased calcium carbonate precipitation due to changes in
pH, alkalinity, and hardness;
• Iron and manganese precipitation due to water in a reduced state (groundwater)
mixing with water in a higher oxidized state (surface water); and
• Continual changes in chemical reactions between pipe walls and blended water due to
intermittent flow reversals when the mixing zone of alternative water sources moves
in relation to variable water demands in the system.
Systems considering blending or making changes to their blending ratios should consider
first performing a blending analysis to determine the effects of blending the different water
sources. Blending analyses can be performed with hydraulic models, water quality models, or
bench scale tests. Hydraulic modeling can be used to predict the areas of the system primarily
supplied by each source and the areas where mixing of two or more sources takes place. Mixing
zones and the relative contribution of each source at a given location can be predicted. The
changes in the locations of mixing zones due to varying water demands can also be predicted.
Water quality modeling can be used to predict water age, disinfectant residual, and DBF levels.
Even if changes in water quality can be predicted from water quality models and spreadsheets,
water quality monitoring is necessary to verify the effects of blending.
It is generally easier to blend alternative sources before they enter the distribution system,
especially if the blended water can be treated to the desired quality. However, if a wholesale
system's treatment plant is far from the alternative water source, and the high DBF areas of a
consecutive system are in close proximity to the alternative source, then it may be more feasible
to introduce the alternative source to the affected part of the system directly through
interconnections.
If water quality problems arise when water is blended in the distribution system, systems
may consider physical or hydraulic separation of the different waters in the distribution system
using valves and additional piping. The physical separation of portions of a distribution system
may reduce water supply reliability, fire-flow capacity, and pressure in some areas. Detailed
distribution system studies are helpful to determine the impacts of physical separation.
Consecutive Systems Guidance Manual 5-4 March 2010
-------
6.0 Communication Strategies for Consecutive and Wholesale Systems
Consecutive systems and wholesale/consecutive system interactions and contractual
relationships can be complex. To improve compliance with the requirements of the Stage 2
DBPR, consecutive systems can utilize effective communication strategies with the wholesale
system. It is important to establish a communication process for the consecutive systems to be
aware of water quality and operational issues in the wholesale systems. Communication
approaches could include:
• Dedicated phone lines with afterhours forwarding or recorded message capacity;
• Web-based information pages and message posting;
• Pager and cell phone message transmission;
• E-mail notification; and
• Laboratory notification to both the consecutive and wholesale system.
For information on communication strategies for IDSEs, refer to Appendix A of the Stage 2
DBPR Initial Distribution System Evaluation Guidance Manual (USEPA, 2006).
This chapter is organized as follows:
6.1 Communication Strategies for Stage 2 DBPR Compliance Monitoring
6.2 Communication Strategies for Operational Evaluations
6.3 Agreements Between Consecutive and Wholesale Systems
6.1 Communication Strategies for Stage 2 DBPR Compliance Monitoring
This section provides possible communication strategies for consecutive and wholesale
systems related to Stage 2 DBPR compliance monitoring. Stage 2 DBPR compliance monitoring
requirements for consecutive systems vary by source water type and system size. Chapter 3
discusses Stage 2 DBPR compliance monitoring requirements in greater detail.
Before beginning Stage 2 DBPR compliance monitoring, each system must prepare a
subpart V monitoring plan. Consecutive and wholesale systems should work together to
coordinate their Stage 2 DBPR compliance monitoring schedules and should provide copies of
their final subpart V monitoring plans to one another. It is not necessary for each consecutive
system in a combined distribution system to provide copies of their monitoring plans to each
other, but each consecutive system should provide a copy to the wholesale system, and each
consecutive system should request a copy of the wholesale system's monitoring plan. Where a
consecutive system receives water through another consecutive system, the second consecutive
system should request a copy of both the first consecutive system's and the wholesale system's
monitoring plan.
Consecutive Systems Guidance Manual 6-1 March 2010
-------
Although not required by the Stage 2 DBPR, coordination of compliance monitoring will
allow both the wholesale and consecutive system to better understand DBF formation across the
combined distribution system and help to formulate an appropriate compliance strategy, when
necessary. Similarly, coordinating sampling schedules will better enable wholesale and
consecutive systems to identify changes in source, treatment, or operation that impact DBF
formation in the distribution system. More specifically, coordination of Stage 2 DBPR
compliance monitoring schedules will help consecutive and wholesale systems conduct
operational evaluations, when required. Recommended communication strategies for operational
evaluations are discussed in greater detail in Section 6.2.
To coordinate Stage 2 DBPR compliance monitoring for the wholesale and consecutive
systems, their sampling schedules should account for the approximate system water age. For
example, if it takes three or four days for water to pass through the consecutive system, the
consecutive system might consider sampling three or four days after the wholesale system.
When one consecutive system receives water through another consecutive system, the second
system should account for the approximate water age in the first system when scheduling
monitoring. Exhibits 6.1 and 6.2 show these concepts graphically. Exhibit 6.3 shows an
example where a consecutive system receives water from a wholesale system transmission main
with a known approximate water age. If approximate water ages at individual sample locations
are known more precisely, the consecutive system may schedule monitoring at those locations
based on individual location water ages. An example of this approach is provided in Exhibit 6.4.
Again, the Stage 2 DBPR does not require wholesale and consecutive systems to coordinate
monitoring schedules, and it does not require that monitoring schedules account for water age
differences between wholesale and consecutive systems. In fact, in complex distribution systems
and systems with limited understanding of hydraulic patterns and water age, such an approach
can be difficult to implement. Also, this monitoring approach presented in Exhibit 6.4 may
result in higher sampling costs since the consecutive system would be sampling on multiple
days.
Exhibit 6.1 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Consecutive System Receiving Water Directly from Wholesale System
Wholesale System
Monitoring Date
Consecutive System
Monitoring Date
1
Day 1
Day 2
Day 3
' i
Day 4
Day 5
Day 6
V
Typical Consecutive System
Water Age
Note: WTP = water treatment plant.
Consecutive Systems Guidance Manual
6-2
March 2010
-------
Exhibit 6.2 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Consecutive System Receiving Water Through Another Consecutive System
Wholesale System Consecutive System 1 Consecutive System 2
Monitoring Date Monitoring Date Monitoring Date
1
1
Day 2
Day 3
Day 4
' i
Day 5
Day 6
' \
Day 7
Day 8
Y
Typical Consecutive
System 1 Water Age
Y
Typical Consecutive
System 2 Water Age
Note: WTP = water treatment plant.
Exhibit 6.3 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Consecutive System Receiving Water from Wholesale System with No Customers
Consecu
Monito
i
^^^^^H Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
^ ^^ J
"V V
Typical Water Age in Wholesale TyPical Consecutive
System Transmission Main sVstem Water A9e
:ive System
ring Date
r
Day 8
Note: WTP = water treatment plant.
Consecutive Systems Guidance Manual
6-3
March 2010
-------
Exhibit 6.4 Coordinating Stage 2 DBPR Compliance Monitoring Schedules -
Approximate Water Age of Monitoring Locations is Known
ConsecuBveS
Average Residai
Wholesale System
Monitoring Data
1 f
^9 Daxf Day 2
Day 3 Day 4
F stern Monitors
ce Time Locations
Con secutive System MOT
High HAAS Location*
C
Day 5 Day 6 Day?
liters
"onswojirve System Monitora
Hnjh rn-JM Locations
Day 8 Day 9
V J
Y
Awige Rea
-------
resulting in values of 0.065, 0.07, 0.095 and 0.095 mg/L (operational evaluation value = 0.081
mg/L), would result in an exceedance of the TTHM OEL at this location. The Stage 2 DBPR
Operational Evaluation Guidance Manual (USEPA, 2008) provides much greater detail
regarding identification of an operational evaluation level exceedance and conducting an
operational evaluation.
For consecutive systems, conducting an operational evaluation requires communication
with the wholesale provider. Where water is received through another consecutive system,
communication between consecutive systems may also be necessary. The wholesale system is
most likely to have data regarding source and finished water TOC, disinfectant residual, pH,
temperature, and other water quality parameters that impact distribution system DBF
concentrations. Further, a comparison of wholesale and consecutive system DBF concentrations
may help to identify the cause of the operational evaluation level exceedance. For example, if
finished water quality was normal and wholesale system DBF concentrations were in their
expected range, the cause of the operational evaluation level exceedance might be attributed to
distribution system operations in the consecutive system (e.g., reduced demand contributing to
higher water age).
The need for communication between consecutive and wholesale systems when
conducting an operational evaluation also underscores the value of coordinating Stage 2 DBPR
compliance monitoring schedules. While finished water quality (e.g., TOC, temperature, etc.)
may help to identify the cause of an operational evaluation level exceedance, a comparison of
consecutive and wholesale system DBF concentrations may also be helpful in terms of how DBF
levels change as water moves further from the treated water source.
6.3 Agreements between Consecutive and Wholesale Systems
Agreements between consecutive and wholesale systems, both formal and informal, can
significantly improve coordination between consecutive and wholesale systems. These
agreements establish lines of communication and assign responsibility for water quality in each
of the systems. Such agreements can help to create cooperative, working relationships where no
prior relationship exists. Where prior relationships exist, such agreements can clarify or enhance
existing relationships. In either case, the agreement represents a commitment to protect public
health by both the consecutive and wholesale system. When developing agreements, discussions
between wholesale and consecutive systems may include evaluations of storage needs (including
firefighting) and where that storage is located to ensure operational reliability while controlling
water age, evaluation of different compliance and operational approaches (including who does
what and how costs are divided), and other issues of joint interest (such as research or pilot
studies). As necessary, systems should involve the State.
Exhibits 6.5 and 6.6 provide case studies of formal and informal agreements,
respectively.
Consecutive Systems Guidance Manual 6-5 March 2010
-------
Exhibit 6.5 Case Study of A Formal Agreement between Consecutive and
Wholesale Systems
Denver Water Department in Colorado serves more than 1 million customers in the City
of Denver, Denver County, and surrounding suburban areas. This includes nearly 80 water
service contracts with consecutive systems. The Denver system is very complex. In some cases,
water passes from one consecutive system to another. In other cases, water may pass through a
consecutive system and return to Denver's distribution system.
Under the Colorado Department of Public Health and Environment provisions for
integrated systems, Denver Water has executed formal agreements with each of these
consecutive systems. Under these agreements, Denver Water assumes responsibility for all
regulatory compliance monitoring and sample analysis. However, the consecutive system is
responsible for maintaining compliance with regulatory requirements. These requirements
dictate that the consecutive systems essentially operate in the same manner as Denver Water,
including flushing, storage tank cleaning, backflow prevention, and utilization of certified
operators.
Sources: Lohman, Steve. (303) 628-6000, Manager of Water Quality at Denver Water
Department. 2007. Phone conversation with Chris Hill, Associate, Malcolm Pirnie, Inc. (813)
242-7204.
Consecutive Systems Guidance Manual 6-6 March 2010
-------
Exhibit 6.6 Case Study of Informal Agreements between Consecutive and
Wholesale Systems
The Cobb County-Marietta Water Authority (the Authority) provides water to 13
consecutive systems in northwestern metropolitan Atlanta, Georgia. These systems include
municipal and county water systems, as well as one industrial and one institutional customer. Of
these customers, nine are sole-source customers buying their water only from the Authority. The
Authority provides water service to its consecutive systems under long-term service contracts up
to 50 years in length. These contracts stipulate that the Authority will provide the customer with
water at mutually agreeable locations (connections). The contracts include no mention of water
quality.
The Authority has no retail customers of its own, and has no contractual obligation other
than to "provide water" to its consecutive systems. The contracts also make no mention of sales
volume.
The Georgia Environmental Protection Division (EPD) has worked with the Authority
and its sole source customers to address water quality on a rule-by-rule basis. The Total
Coliform Rule is addressed by each consecutive system individually. The Lead and Copper Rule
is administered to the Authority and its sole source customers as a single entity. Under this
approach, if one system violates an MCL, then every consecutive system must respond as
directed by EPD. A consecutive system can unilaterally withdraw from this arrangement, but
must then conduct the monitoring and reporting to EPD individually. The Authority staff meets
regularly with its consecutive systems to discuss and address water quality and regulatory issues,
and all parties are involved in a cooperative working relationship.
For the Stage 1 DBPR, the Authority and its sole-source customers are considered by the
Georgia EPD as a combined distribution system. EPD worked with the Authority to develop the
combined system DBF monitoring plan. Under this arrangement, the Authority has
responsibility for all DBF monitoring in the combined sole-source distribution system.
In preparation for the IDSE required under the Stage 2 DBPR, the Authority and its
sole-source customers jointly conducted a fluoride tracer study to determine the areas of oldest
water in the system. The information gathered under this study was used individually by the
consecutive systems to develop their IDSE monitoring plans.
Source: Parsons, James. (770) 426-8788, Director of Engineering, Cobb County-Marietta Water
Authority. 2005. June 9, 2005.
Consecutive Systems Guidance Manual 6-7 March 2010
-------
Exhibit 6.5 is an example of how Denver has applied a program developed by the State.
The Colorado Department of Public Health and Environment (the Department) has established
requirements for integrated systems - which consider the consecutive and wholesale systems as a
single regulated entity (5 Colorado Code of Regulations 1003-1). The Department requires that
the wholesale and consecutive systems included in the integrated system execute a "...contract,
memorandum of agreement, or other enforceable mechanism." The application for consideration
as an integrated system includes the following:
• A contact person, address, and phone number for each participating system, and each
regulatory requirement for which an integrated system is being created.
• The number of persons served by the wholesale and each consecutive system and
whether the consecutive system is providing further disinfection.
• A map showing the supply system and each consecutive system including the relevant
elements of the distribution system such as meters, piping, pump stations, storage
tanks, and finished water reservoirs.
• A sampling plan for each regulatory provision covered by the integrated system (e.g.,
DBFs or disinfectant residual monitoring). The sampling plan shall meet all of the
requirements of the respective provision and shall also identify the responsibilities of
each party, including that each individual system is responsible for maintaining
compliance with MCLs and other regulatory requirements.
• A copy of each agreement between the consecutive and wholesale systems, including
a common set of operations and maintenance standards that the wholesale system has
established for each regulatory requirement for which an integrated system is being
created.
• A statement that clearly assigns legal responsibility to one of the participating
systems for compliance with each individual regulatory provision in the integrated
system. Under Stage 2, each system determines compliance based on samples taken
in its own distribution system.
An example of a formal agreement meeting the requirements of the State of Colorado is
provided in Appendix A. Other States may have specific requirements that must be met in
preparing these agreements. Water systems should contact their State to determine how specific
requirements apply to wholesale and consecutive systems.
Regularly scheduled communication between consecutive and wholesale systems can be
an effective tool for managing water quality. Regular meetings between a consecutive system
and its wholesale provider may be an appropriate forum to discuss and address water quality
concerns with the frequency determined by parties. Where multiple consecutive systems
purchase water from a wholesale system, meetings that involve all of the consecutive systems in
the combined distribution system may be useful. Systems that are part of more complex
combined distribution systems will generally need to make a greater effort to ensure effective
communication among multiple wholesale and consecutive systems, as will combined
distribution systems containing non-utility systems such as homeowners associations.
Consecutive Systems Guidance Manual 6-8 March 2010
-------
7.0 Developing Consecutive System Compliance Strategies
The Stage 2 DBPR specifically requires consecutive systems to comply with the same
MCLs for DBFs as wholesale systems and extends the disinfectant residual and MRDL
requirements of the Stage 1 DBPR to consecutive systems. Chapter 3 discusses these
requirements and their impacts on consecutive systems in greater detail. This chapter discusses a
methodology that can be employed by consecutive systems to develop a compliance strategy to
meet these requirements. It discusses the use of water quality monitoring data to identify
potential compliance issues and develop, in concert with the wholesale system, effective
compliance strategies. This chapter is organized into the following sections:
7.1 Data Acquisition
7.2 Communication of Needs to the Wholesale System
7.1 Data Acquisition
As part of normal system operations or as required by drinking water regulations,
consecutive systems should routinely monitor distribution system water quality. Parameters such
as DBF concentrations (TTHM and HAAS), pH, temperature, disinfectant residual (free chlorine,
total chlorine, or chloramine),TOC and microbiological parameters (total and fecal coliform,
HPC), can be used to characterize distribution system water quality and can be extremely useful
in developing a compliance strategy. A historical record of water quality data combined with
new data can be particularly useful in isolating and identifying DBF-related issues in the
distribution system. The remainder of this section discusses: 1) what parameters a consecutive
system might find useful in developing a compliance strategy; 2) when to monitor; and 3) where
to monitor. The importance of these routine water quality parameters and their relation to overall
DBF formation are further discussed below. In addition, systems should consider whether
changes could lead to simultaneous compliance issues.
7.1.1 Monitoring Parameters
TTHMandHAAS
Non-compliance operational monitoring of TTHM and HAAS throughout the consecutive
system after the IDSE may be a useful tool in determining if continuing compliance with the
Stage 2 DBPR will be a concern. TTHM and HAAS monitoring also help to determine the
requirements necessary to achieve and maintain compliance. A comparison of DBF
concentrations entering the system to concentrations throughout the distribution system will help
to determine if the DBF concentrations entering the consecutive system are too high to achieve
compliance with the Stage 2 DBPR, or if the consecutive system is able to employ some strategy
to achieve compliance. High DBF locations may need further monitoring and evaluation
because they likely correspond with longer residence time, lower disinfectant residuals, and
higher bioactivity. Some of the strategies a consecutive system can implement to control DBF
levels in the distribution system include water age management, using alternative disinfectants
such as chloramine, managing the chlorine dosages effectively to avoid under- or over-dosing,
Consecutive Systems Guidance Manual 7-1 March 2010
-------
blending with sources that have low DBF precursor levels, and/or purchasing water from a
different wholesaler. These strategies are discussed in more detail in Chapters 4 and 5. In
evaluating these strategies, systems should consider simultaneous compliance issues.
pH and Temperature
Water quality parameters such as pH and temperature can be used to identify seasonal
trends and irregularities in distribution system water quality. Seasonal variations in water
temperature can affect DBF formation in the distribution system. For instance, higher
temperatures increase the reaction rate of DBF formation. Therefore, warmer water temperatures
result in higher levels of TTHM and HAAS unless better removal of precursors is achieved
during treatment, alternative disinfection is practiced, or other DBP-minimizing strategies are
implemented. Changes in pH can lead to different DBF levels and mixes and can also affect
coagulation and disinfection conditions.
Disinfectant Residual Data
Disinfectant residual data should be routinely gathered and monitored throughout the
distribution system. A measurable disinfectant residual should be maintained throughout the
distribution system, as required by the SWTR, to provide adequate protection against the
possible entry of pathogens or untreated water, and to maintain the microbial water quality
achieved by primary disinfection.
A low disinfectant residual at consecutive system entry points may indicate increased
water age in the wholesale system. However, accumulation of sediments in a pipe, corrosion
conditions, biofilm growth, pipe materials, and the pipe lining in either system can also
contribute to disinfectant demand. Comparing historical data for a particular site may be helpful
in isolating the contributing factors. Strategies to minimize water age are discussed in greater
detail in Chapter 4.
Conversely, excessive disinfectant residual concentrations at the consecutive system
entry point may also contribute to higher DBF concentrations. In some instances, a high residual
entering the system may be necessary for the consecutive system to maintain a residual at the
ends of the system, or may be the result of the wholesale system needing to maintain a residual at
the end of their own system. Strategies to minimize the disinfectant residual dose, such as
optimizing the use of enhanced coagulation (to further reduce DBF precursor concentrations and
disinfectant demand) by the wholesale system at its water treatment plant, moderation of chlorine
residual levels through strategic placement of booster chlorination stations, chloramination, or
water age management may help to reduce DBF concentrations in the distribution system.
Microbial Data
Microbial data, such as total and fecal coliforms or HPCs, may be useful in identifying
potential DBF compliance strategies. Low disinfectant residual and increased microbial activity
are most likely to occur at locations with high water age. In such cases, increased disinfectant
doses might be considered necessary to maintain the residual and reduce microbiological
activity. However, increasing the dose may also lead to higher DBF concentrations.
Consequently, a strategy to reduce water age may be more appropriate to prevent increased
formation of DBFs. Chapter 4 discusses operational strategies to reduce system water age.
Consecutive Systems Guidance Manual 7-2 March 2010
-------
7.1.2 Monitoring Frequency
Consecutive systems should consider collecting routine non-compliance samples for the
various parameters discussed above at a regular frequency to better understand DBF formation in
the distribution system, in addition to compliance monitoring. To the extent possible,
consecutive systems may want to coordinate their monitoring schedule with the wholesale
system to provide the most complete analysis of DBF formation. Coordination of sampling
schedules allows for more accurate interpretation of data, as it is possible to see the change in
water as it moves from one system to the next over the same time period. Coordination of
monitoring with the wholesale system is discussed in greater detail in Chapter 6.
Collecting samples at regular frequencies helps identify short and long term DBF trends,
including seasonal impacts of water quality on distribution system DBF concentrations.
Requirements for many parameters, such as disinfectant residual and DBF concentrations, are
established by the Stage 2 DBPR. Chapter 3 provides a more thorough discussion of consecutive
system monitoring requirements.
7.1.3 Monitoring Locations
Samples should be collected throughout the consecutive system distribution system,
taking into account the population served and hydraulic profile. Sample locations should include
locations such as the master meter connection, middle of the distribution system, and near the
ends or other areas of the distribution system where the highest water age and DBF levels are
expected. Monitoring at many of these locations is already required by the Stage 2 DBPR. If
additional sites could be incorporated for monitoring, sampling locations should be spread
throughout the distribution system. Samples collected from only one location or region within
the distribution system may skew the DBF, disinfectant residual, or microbial data.
Understanding how DBF formation varies across the entire system is critical to developing an
effective DBF control strategy. Thus, it is important to collect and use data that represent the
entire distribution system.
Exhibits 7.1 and 7.2 provide case studies characterizing the differences in wholesale and
consecutive system DBF formation. These examples show how TTHM, HAAS and disinfectant
residual concentrations are impacted by differences in disinfection practices from the wholesale
system to the consecutive system.
Consecutive Systems Guidance Manual 7-3 March 2010
-------
Exhibit 7.1 DBF Formation from Wholesale to Consecutive System Example
/^ ^^
f System A \
Vv WTP )
25/22/1.0
TTHM/HAA5/CL Residuals
32/25/0.8
System B
System A Distribution
40/30/1.0
50/27/0.5
Note: WTP = water treatment plant; THMs = trihalomethanes; HAAs = haloacetic acids; CI2 = chlorine.
In Exhibit 7.1, System A is a wholesale system that provides drinking water to more than
100,000 people. Water is treated using an advanced filtration process followed by disinfection
using chlorine. The finished water then travels through large transmission lines from the water
treatment plant to the distribution system. Finished water is distributed to three consecutive
systems. System A supplies water to System B and System C, and System C supplies water to
System D.
Exhibit 7.1 illustrates the complex nature of wholesale and consecutive system
relationships. This figure shows average TTHM and HAAS concentrations, and chlorine
residuals in the wholesale and consecutive systems. Only wholesale system A and consecutive
system B practice booster chlorination to maintain chlorine residuals at acceptable levels.
Consecutive systems C and D are smaller systems and do not practice booster chlorination. The
chlorine residual in System A's distribution system averages about 1.0 mg/L. An equal or lower
chlorine residual is observed in the consecutive systems.
The DBF formation as the water travels from the treatment plant to the distribution
systems is also depicted in Exhibit 7.1. Within System A's distribution system, a 40 percent
increase in TTHM and a 25 percent increase in HAAS occurs because it is a large system with
booster chlorination systems at various locations. Although consecutive system B receives water
directly from the same treatment plant and practices booster chlorination, DBF formation is
lower than that of System A because it is a smaller system with lower overall water age. The
average TTHM level in consecutive system C is 25 percent higher than System A because of a
long transmission main between the two cities. Also, the use of booster chlorination by System
A causes TTHM levels to be fairly high in System C. The increase in TTHM levels from
consecutive system C to system D is minimal because these are both small systems with low
Consecutive Systems Guidance Manual
7-4
March 2010
-------
water age in close proximity to one another. However, the TTHM levels in the consecutive
systems are still fairly high because of the impact of System A. A small decrease in HAAS
concentration is noted in the consecutive systems due to biodegradation of some HAAS species
in the distribution system.
Exhibit 7.2 Variation in DBF Formation with Chlorination and Chloramination
70.0
^
|> 60.0
V)
2 50.0
c 40.0
fl
a
I 30-°
O)
20.0
(A
6 10.0
Q
0.0
DTTHM
DHAA5
DCI2 orNH2CI
CityX
CSofCityX
CityY
CS of City Y
Note: CS = Consecutive System; TTHM = total trihalomethane; HAAS = sum of five HAA species; CI2 = chlorine;
NH2CI = chloramines.
Exhibit 7.2 compares DBF formation in City X (chlorinated system) and City Y
(chloraminated system) which are both large wholesalers. City X uses free chlorine for
secondary disinfection. City Y uses chloramine for secondary disinfection and also practices
booster disinfection. Exhibit 7.2 shows the increase in DBF concentrations from the wholesale
to the consecutive system. As would be expected, the overall TTHM and HAAS concentrations
are significantly higher in City X. However, the percentage increases in TTHM and HAAS
concentrations are greater in the chloraminated system (City Y) than in the chlorinated system
(City X). This reflects the fact that while chloramines may result in lower DBF concentrations,
significant growth can still occur in the wholesale or consecutive system's distribution system.
Monitoring can be an effective tool to identify these relationships in your system. It is worth
noting that these results are site/system-specific and may not be typical of results seen in other
systems.
Consecutive Systems Guidance Manual 1-5 March 2010
-------
7.2 Communication of Needs to the Wholesale System
Consecutive systems should meet with the wholesale system to discuss options and
develop a mutually agreed-upon compliance strategy if possible. In developing the strategy,
systems should consider a variety of options, including those identified in Chapters 4, 5, and 6.
The strategy should clearly lay out responsibilities, including how costs will be apportioned.
Chapter 6 discusses communication strategies and agreements between consecutive and
wholesale systems in greater detail.
Consecutive Systems Guidance Manual 7-6 March 2010
-------
8.0 Frequently Asked Questions
Can I be both a consecutive system and a wholesale system?
Yes. If you sell water and you purchase water, you are both a wholesale system and a
consecutive system.
I buy all of my water. Do I follow the requirements for subpart H systems or ground water
systems?
If you purchase all of your water and any of it is surface water or GWUDI, you must follow the
requirements for subpart H systems. If you purchase all of your water and it is all ground water,
you should follow the requirements for ground water systems.
What if my wholesaler only serves groundwater?
If your system does not have any surface water or GWUDI sources and your wholesaler serves
only ground water, you should follow the requirements for ground water systems for Stage 2
compliance.
What if I purchase water but I also have my own sources?
If your system purchases water, it is considered a consecutive system even if your system has its
own sources. Your compliance schedule is based on the population of the largest system in the
combined distribution system. However, for purposes of the compliance schedule, the State may
determine that the combined distribution system does not include certain consecutive or
wholesale systems if water is purchased or sold only on an emergency basis or if only a small
percentage and small volume of water is purchased or sold by a system. While your compliance
schedule is based on the population of the largest system, your monitoring requirements are
based on your own retail population.
I have my own ground water wells and buy waterfront a subpart H system Do I follow the
requirements for subpart H systems or ground water systems?
If you purchase any surface water or GWUDI, you must follow the requirements for subpart H
systems.
Consecutive Systems Guidance Manual 8-1 March 2010
-------
What if I buy waterfront more than one wholesale system?
If you buy water from more than one wholesale system, you are considered to be part of a
combined distribution system that includes all of your wholesalers, all other systems served by
your wholesalers, and any systems to which you sell water. If your system is part of a combined
distribution system, your compliance schedule is based on the population of the largest system in
the combined distribution system. However, for purposes of the compliance schedule, the State
may determine that the combined distribution system does not include certain consecutive or
wholesale systems if water is purchased or sold only on an emergency basis or if only a small
percentage and small volume of water is purchased or sold by a system. While your compliance
schedule is based on the population of the largest system, your monitoring requirements are
based on your own retail population.
My system has only undisinfected groundwater sources. I only buy disinfected water in July
and August or when my supplies can't meet demand. Do I still have to comply with the Stage
2 DBF Rule?
Yes, your system is subject to the Stage 2 DBPR, but Stage 2 DBPR monitoring is only required
during the period when you are buying water. You should contact your State to confirm
monitoring requirements.
Why didn't EPA just use 40 CFR 141.29 for consecutive system monitoring requirements?
The Stage 2 M-DBP Federal Advisory Committee Agreement in Principle that was signed in
September 2000 recommended that the monitoring provisions of the Stage 2 DBPR provide
protection for customers in consecutive systems that is equivalent to that provided in wholesale
systems. EPA concurred with this recommendation and followed this principle in development
of the Stage 2 DBPR.
EPA believes that providing equivalent public health protection in consecutive systems by
assigning appropriate compliance monitoring locations throughout the combined distribution
system requires case-by-case modification of appropriate monitoring. These modifications
should be based on factors such as the amount and percentage of finished water provided;
whether finished water is provided seasonally, intermittently, or full-time; and improved DBF
occurrence information. In order to provide systems and States with improved DBF occurrence
information, the Stage 2 DBPR requires consecutive systems to address IDSE requirements.
Since the IDSE provides improved DBF occurrence information, States may consider
modifications to Stage 2 compliance monitoring requirements for consecutive systems on a case-
by-case basis as allowed by 40 CFR 141.29 or under the special primacy condition at 40 CFR
142.16(m) by taking all these factors into consideration. Note that 40 CFR 141.29 requires case-
by-case approval by EPA, but the Stage 2 rule has a special primacy condition that does not
require case-by-case approval by EPA. In making these case-by-case determinations, the State
can use its system-specific knowledge, along with the IDSE results, to develop an appropriate
monitoring plan for each system within the combined distribution system.
Consecutive Systems Guidance Manual 8-2 March 2010
-------
What are the minimum monitoring requirements for combined distribution systems if the
State modifies monitoring?
For combined distribution systems for which the State modifies monitoring requirements, the
minimum number of Stage 2 DBPR monitoring sites and monitoring frequency is based on the
total population of the combined distribution system. In addition, each consecutive and
wholesale system must have at least one compliance monitoring location. Also, each wholesale
or consecutive system must conduct its own IDSE. The schedule for your IDSE was based on
the population of the largest system in the combined distribution system. The rest of your IDSE
requirements were based on your individual system's population. You cannot conduct one IDSE
for the entire combined distribution system based on the combined service population. However,
an IDSE coordinated among systems in a combined distribution system, with each system
monitoring based on its retail population and submitting its own IDSE report, may result in
improved information (but requires a high level of coordination).
Why can't my consecutive system forego DBF monitoring and base my compliance status on
my wholesaler's compliance status?
Your consecutive system may not base your compliance status on your wholesaler's compliance
status because DBFs will continue to form in your consecutive system and may be significantly
higher than in your wholesaler's system. Therefore, DBF levels in your consecutive system may
exceed the MCL even though your wholesaler is in compliance. Conversely, your DBF levels
may be lower than the wholesale system's DBF levels and you should not be in violation if the
wholesale system exceeds the MCL. EPA believes that distribution systems and DBF formation
are too complex to base compliance determinations on another system's compliance monitoring
results.
Do I have to monitor at the same time as my wholesale system?
You are not required to monitor at the same time as your wholesaler. However, you may wish to
coordinate your monitoring schedule with your wholesaler to better understand DBF formation
in your combined distribution system. See Chapter 6 of this guidance manual for details.
If my wholesaler has a TTHM or HAAS violation, is my consecutive system in violation?
Your consecutive system is only in violation if TTHM or HAAS levels in your distribution
system exceed the MCL. However, your State may require additional follow-up monitoring or
public notification if your wholesaler has a TTHM or HAAS violation. If you receive water
from the area of your wholesaler's system where the TTHM or HAAS violation occurred, you
may also detect TTHM or HAAS levels above the MCL in your consecutive system.
Consecutive Systems Guidance Manual 8-3 March 2010
-------
If the lab with whom I have a contract does not collect DBF samples, am I in violation? What
if my contract is with my wholesale system?
Even if you have a contract with your laboratory or your wholesale system, you retain
responsibility for the collection of DBF samples. If your laboratory or wholesale system fails to
collect your DBF samples, your system incurs a monitoring violation.
Can I use my wholesale system's system-specific study or DBF data instead of monitoring my
own system?
Each wholesale and consecutive system must conduct its own IDSE. The schedule for your
IDSE must be based on the population of the largest system in the combined distribution system.
The rest of your IDSE requirements must be based on your individual system's population. You
cannot conduct one IDSE for the entire combined distribution system based on the combined
service population. However, an IDSE coordinated among systems in a combined distribution
system, with each system monitoring based on its retail population and submitting its own IDSE
report, may result in improved information (but requires a high level of coordination). The
individual IDSE reports may include analyses supporting a broader understanding of combined
distribution system hydraulics, DBF formation, etc. that leads to recommendations for more
effective compliance monitoring.
What if my wholesaler will not conduct the monitoring in my consecutive system?
As a public water system, you are responsible for ensuring that your monitoring is conducted. If
your wholesaler does not conduct monitoring in your consecutive system and you do not have a
contract with a laboratory to conduct monitoring in your system, you are responsible for
collecting all of your compliance samples in your system, ensuring that the samples are analyzed
in a certified laboratory, and reporting results to the State.
How do consecutive systems qualify for reduced monitoring?
There are no differences in how consecutive and non-consecutive systems qualify for reduced
monitoring. Consecutive systems qualify for reduced monitoring if the LRAA is less than or
equal to 0.040 mg/L for TTHM and less than or equal to 0.030 mg/L for HAAS at all compliance
monitoring locations. In addition, before any treatment, the source water average annual TOC
level must be less than or equal to 4.0 mg/L at each treatment plant treating surface water or
GWUDI, based on monitoring conducted under the Stage 1 DBPR. Consecutive systems will
need to obtain source water TOC monitoring results from all surface water and GWUDI sources
used by their wholesaler(s) in addition to their own sources to qualify. In addition, the State may
modify monitoring requirements using either 40 CFR 141.29 or the special primacy condition in
40CFR142.16(m).
Consecutive Systems Guidance Manual 8-4 March 2010
-------
How is compliance determined for a consecutive system?
A consecutive system's compliance is based on the LRAA calculated using the sample results
collected only in that system's distribution system. However, the State may require the
consecutive system to give public notice if the wholesaler has a violation, even if the consecutive
system does not incur a violation.
If my consecutive system is in danger of exceeding the TTHM or HAAS MCLs, who is
responsible for making changes to ensure compliance with the MCLs?
Even though some agreements between wholesale and consecutive systems may indicate that the
wholesale system is responsible for making changes, you are ultimately responsible for
providing water that meets the MCLs within your consecutive system. You should consider
discussing treatment changes with your wholesaler to reduce DBF levels prior to your entry
point. See Chapter 5 for more information. However, if your wholesaler is in compliance with
the MCLs, your wholesaler is not required by the Stage 2 DBPR to make any treatment changes
to meet the MCLs in your consecutive system. Therefore, you should also consider changes to
your distribution system to reduce DBF levels. See Chapter 4 for more information. If you are
still unable to meet the MCLs, you should consider an alternate source of water or blending
sources. See Chapter 5 for more information.
What if my wholesaler will not be making treatment changes to meet the Stage 2 DBPR?
If your system is in danger of exceeding the MCLs for TTHM or HAAS and your wholesaler
will not be making treatment changes to meet the Stage 2 DBPR, you should consider making
distribution system changes to reduce DBF levels. Refer to Chapter 4 for more information. If
you are still unable to meet the MCLs, you should consider alternate sources of water or
blending sources. See Chapter 5 for more information.
Consecutive Systems Guidance Manual 8-5 March 2010
-------
9.0 References
American Water Works Association (AWWA). 2005a. Fundamentals and Control of
Nitrification in Drinking Water Distribution Systems. Denver: AWWA.
AWWA. 2005b. Managing Change and Unintended Consequences: Lead and Copper Rule
Corrosion Control Treatment. Denver: AWWA.
AWWA. 2001. The AWWA Standard, Rehabilitation of Water Mains (M28), 2nd Ed. Denver:
AWWA.
Boulos, P.P., K. E. Lansey, B.W. Karney. 2006. Comprehensive Water Distribution Systems
Analysis Handbook. Denver: AWWA.
Chowdhury, Z.K., C.P. Hill, MJ. Sclimenti, S.W. Krasner, R.S. Summers, C. Valenti, and J.G.
Uber. 2009. Evaluation of Disinfection Practices for DBF and Precursor Occurrence in
Distribution Systems. Denver: AwwaRF.
Friedman, M.J., K. Martel, A. Hill, D. Holt, S. Smith, T. Ta, C. Sherwin, D. Hiltebrand, P.
Pommerenk, Z. Hinedi, and A. Camper. 2003. Establishing Site-Specific Flushing Velocities.
Denver: AwwaRF.
Grayman, W. M., L. A. Rossman, C. Arnold, R. A. Deininger, C. Smith, J. F. Smith, and R.
Schnipke. 2000. Water Quality Modeling of Distribution System Storage Facilities. Denver:
AwwaRF.
Harms, L. L., and C. Owen. 2004. A Guide for the Implementation and Use of Chlor amines.
Denver: AwwaRF.
Harrington, G. W., D. R. Noguera, C. C. Bone, A. I. Kandou, P. S. Oldenburg, J. M. Regan, and
D. V. Hoven. 2003. Ammonia From Chlor amine Decay: Effects on Distribution System
Nitrification. Denver: AwwaRF.
Joseph, S. and J. G. Pimblett. 2000. Flushed with Success - Unidirectional Flushing Program is
Clean Sweep. AWWA Opflaw, Vol.26, No. 1.
Kirmeyer, G.J., G.W. Foust, G.L. Pierson, JJ. Simmler, M.W. LeChevallier. 1993. Optimizing
Chloramine Treatment. First Edition. Denver: AwwaRF and AWWA.
Kirmeyer, G.J., M. Friedman, J. Clement, A. Sandvig, P.F. Noran, K.D. Martel, D. Smith, M.
LeChevallier, C. Volk, E. Antoun, D. Hiltebrand, J. Dykesen, and R. Gushing. 2000. Guidance
Manual for Maintaining Distribution System Water Quality. AwwaRF Report 90798. Project
#357. Denver: AwwaRF.
Kirmeyer, G.J., L. Kirby, B.M. Murphy, P.F. Noran, K. Martel, T.W. Lund, J.L. Anderson, and R.
Medhurst. 1999. Maintaining and Operating Finished Water Storage Facilities to Prevent Water
Quality Deterioration. Denver: AwwaRF and AWWA.
Consecutive Systems Guidance Manual 9-1 March 2010
-------
Kirmeyer G., Martel K., Thompson G., Radder L., Klement W., LeChevallier M., Baribeau H.,
Flores A. 2004. Optimizing Chloramine Treatment, Second Edition. Denver: AwwaRF.
Mahmood, F., Pimblett J. G., Grace N. O., and Grayman W. M. 2005. Evaluation of Water
Mixing Characteristics in Distribution System Storage Tanks. JournalAWWA, 97:3:74-88.
USEPA. 2008. Stage 2 Disinfectants and Disinfection Byproducts Rule Operational Evaluation
Guidance Manual. EPA 815-R-08-018. Available at: http://www.epa.gov/nscep/.
USEPA. 2007a. Simultaneous Compliance Guidance Manual for the Long Term 2 and Stage 2
DBF Rules. EPA 815-R-07-017. Available at: http://www.epa.gov/nscep/.
USEPA. 2007b. The Stage 2 Disinfectants and Disinfection Byproducts Rule Implementation
Guidance. EPA 816-R-07-007. Available at: http://www.epa.gov/nscep/.
USEPA. 2007c. Complying with the Stage 2 Disinfectant and Disinfection Byproducts Rule:
Small Entity Compliance Guide. EPA 815-R-07-014. Available at: http://www.epa.gov/nscep/.
USEPA. 2007d. Consecutive System Guide for the Ground Water Rule. EPA 815-R-07-020.
Available at: http://www.epa.gov/nscep/.
USEPA. 2006a. Initial Distribution System Evaluation Guidance Manual for the Final Stage 2
Disinfectants and Disinfection Byproducts Rule. EPA 815-B-06-002. Available at:
http ://www. epa. gov/nscep/.
USEPA. 2006b. Initial Distribution System Evaluation Guide for Systems Serving Fewer than
10,000 People for the Final Stage 2 Disinfectants and Disinfection Byproducts Rule. EPA 815-
B-06-001. Available at: http://www.epa.gov/nscep/.
USEPA. 2005. Preparing Your Consumer Confidence Report: Revised Guidance for Water
Suppliers. EPA 816-R-05-002. Available at: http://www.epa.gov/nscep/.
USEPA. 2004a. Code of Federal Regulations, Title 40 Section 141.2, Definitions.
USEPA. 2004b. Consumer Confidence Report Rule: A Quick Reference Guide. EPA 816-F-02-
026. Available at: http://www.epa.gov/nscep/.
USEPA. 2001. The Stage 1 Disinfectants and Disinfection Byproducts Rule: What Does it Mean
toyou? EPA 816-R-01-014. Available at: http://www.epa.gov/nscep/.
USEPA. 2000a. Public Notification Handbook. EPA 816R-00-010. Washington, D.C.: USEPA.
USEPA. 2000b. The Public Notification Rule: A Quick Reference Guide. EPA
816-F-00-023. Available at: http://www.epa.gov/nscep/.
USEPA. 1999a. Alternative Disinfectants and Oxidants Guidance Manual. Office of Water.
EPA 815-R-99-014. Available at: http://www.epa.gov/nscep/.
Consecutive Systems Guidance Manual 9-2 March 2010
-------
USEPA. 1999b. Enhanced Coagulation and Enhanced Precipitative Softening Guidance
Manual. EPA 815-R-99-012. Available at: http://www.epa.gov/nscep/.
Consecutive Systems Guidance Manual 9-3 March 2010
-------
Appendix A
Example of Formal Agreement between Consecutive and Wholesale Systems
[NOTE: Stage 2 DBPR or other rules may contain requirements that will result in a need to
modify or update existing agreements]
-------
-------
Date:
To the Denver Board of Water Commissioners:
The Board of (hereafter Distributor)
requests to be included in Denver Water's Integrated System under the Colorado
Primary Drinking Water Regulations (CPDWR). This Board acknowledges that it is
legally and enforceably obligated to comply with Denver Water's Operating Rules and
Engineering Standards through its distributor agreement with Denver Water. It further
acknowledges that such rules and standards include the standard operating procedures
adopted by the reference in Chapter 12 of the Engineering Standards.
Distributor's contact person:
Address:
Phone:
No. of people served:
The responsibilities of the parties are set forth as follows:
Denver Water is responsible for:
( ) all monitoring and MCL requirements related to microbiological
contaminants (Article 3, CDPWR)
( ) all monitoring, reporting and MCL requirements related to
disinfection byproducts (Art. 5 CPDWR) unless a distributor adds
disinfectant in the distribution system
( ) all tap monitoring, reporting, corrosion control and public education
requirements of the lead and copper rule (Art. 7, CDPWR)
( ) all collection, reporting and compliance with residual disinfectant
requirements (Art. 9, CPDWR)
( ) all public notification requirements (Art. 10, CPDWR)
( ) all requirements for annual consumer confidence report (Art. 13,
CPDWR)
( ) cleaning of treated water storage facilities (additional charge
required)
( ) cross-connection control program (Art. 12, CPDWR)
A-l
-------
Distributor is responsible for all other requirements for consecutive systems enumerated
by Article 1.6 of the CPDWR, specifically including but not limited to:
( ) distribution system operator certification
( ) hydrant inspection program
( ) valve inspection program
( ) lead service line replacement requirements (Art. 7, CPDWR)
( ) operation of treated water storage (check if distributor has
treated water storage)
( ) water quality customer complaints, communication and initial
response
( ) leak repair and main disinfection
( ) distribution system discharges
( ) maintenance of treated water storage (cleaning can be
contracted to Denver Water if checked above)
( ) Instead of having Denver Water responsible, the Distributor prefers
to be responsible for its own cross-connection control program,
including all reporting, record-keeping and enforcement of
hazardous cross-connection requirements and backflow prevention
(Art. 12, CPDWR) (if checked, cross out and initial the last
responsibility under Denver Water)
Distributor further certifies that it (does/does not) provide further disinfection to the water
it receives from Denver Water.
ATTEST:
[NAME OF DISTRIBUTOR]
By By
Title
Address
ACCEPTED BY DENVER WATER:
A-2
-------
Date:
Date:_
Manager of Water Quality
A-3
------- |