April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 1

FINAL

PRIORITIES OF THE DISTRIBUTION SYSTEM

RESEARCH AND INFORMATION COLLECTION

PARTNERSHIP

April 2010
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 2

Disclaimer

This Priorities of the Distribution System Research and Information Collection Partnership 

document was jointly written by the U.S. Environmental Protection Agency (USEPA) and the 

Water Research Foundation (Foundation) under a Memorandum of Understanding signed on 

January 29, 2009 (Memorandum of Understanding, On the Total Coliform Rule/Distribution 

System Research and Information Collection Partnership). To the extent this document mentions 

or discusses statutory or regulatory authority, it does so for information purposes only. The 

document does not substitute for those statutes or regulations, and readers should consult the 

statutes or regulations themselves to learn what they require. The mention of trade names for 

commercial products does not represent or imply the approval or the endorsement of either the 

USEPA or the Foundation.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 3

Table of Contents

EXECUTIVE SUMMARY ........................................................................................................ 5

E.S. 1 Introduction ..................................................................................................................... 5

E.S. 2 The Research and Information Collection Partnership (RICP) and the RICP Steering 

Committee................................................................................................................................... 6

E.S. 3 Prioritization of Research and Information Collection Project Area Documents........... 6

1. Introduction........................................................................................................................... 10

1.1 The Total Coliform Rule / Distribution System Advisory Committee Agreement in 

Principle .................................................................................................................................... 10

1.1.1 Research and Information Collection Partnership ........................................................... 11

1.1.2 Steering Committee ......................................................................................................... 11

1.1.3 Communications Process................................................................................................. 12

1.2 Overview of Public Health Risks Associated with Drinking Water Distribution Systems 13

1.2.1 General Overview of Public Health Risks....................................................................... 13

1.2.2 Overview of the Seven Distribution System Issues Identified in the AIP....................... 14

2. Prioritization of Research and Information Collection Project Area Documents................. 20

2.1 Research and Information Collection Needs Analysis ....................................................... 20

2.2 Project Area Documents..................................................................................................... 22

2.2.1 Definition of a Successful Project................................................................................... 23

2.2.2 Prioritization Approach................................................................................................... 24

2.2.3 Final Review by Steering Committee ............................................................................. 26

2.2.4 Other Considerations Used in Steering Committee Decisions........................................ 26

2.2.5 List of SC adjustments with rationales ............................................................................ 27

3. Research and Information Collection Priorities.................................................................... 28

Appendix A – Steering Committee Members........................................................................... 81

Appendix B – Project Area Titles and Codes........................................................................... 84

Appendix C – Lower Priority Project Area Documents........................................................... 87

Appendix D – Scoring System Description and Initial Results.............................................. 167

Appendix E – First Generation Project Area Documents....................................................... 169
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 4

Acronyms

AIP: Agreement in Principle

AMWA: Association of Metropolitan Water Agencies

ANSI: American National Standards Institute

AWWA: American Water Works Association

BP: best practices

CC: cross connection project area

Con: contaminant accumulation project area

CWSS: Community Water System Survey

DBP: disinfection by-product

DS: distribution system

DWINS: Drinking Water Infrastructure Needs Survey

EPA: US Environmental Protection Agency

Hea: health effects project area

MAC: Mycobacterium avium Complex

MCL: Maximum Contaminant Level

Mon: monitoring project area

MOU: Memorandum of Understanding

NPDWR: National Primary Drinking Water Regulation

NRWA: National Rural Water Association

Pres: pressure project area

PWS: public water system

QMRA: quantitative microbial risk assessment

RFP: request for proposal

RIC: Research and Information Collection

RICP: Research and Information Collection Partnership

RisM: risk management project area

SC: Steering Committee

Stor: storage project area

Sur: survey project area

TCR: Total Coliform Rule

TCRDSAC: Total Coliform Rule / Distribution System Advisory Committee

WaterRF: Water Research Foundation

Definitions

Partners –EPA and WaterRF (signatories to the RICP memorandum of understanding)

Experts (or subject matter experts) – Technical consultants to the partners in each of the seven 

topic areas, as well as in organizing and compiling the project area documents

Steering Committee – Advisory group to the RICP 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 5

EXECUTIVE SUMMARY

Spanning almost one million miles in the United States, drinking water distribution systems 

represent the vast majority of physical infrastructure for drinking water supplies, and thus 

constitute a primary management challenge from both an operational and public health 

standpoint. Potential public health risks can occur if the operation and functioning of the 

distribution system is compromised. Therefore, ensuring the integrity and effective operation of 

distribution systems is critical for public health protection. While infrequently reported, 

waterborne disease outbreaks and other events of public health significance do occur as a result 

of compromised distribution systems (NRC, 2006). The purpose of this document is to 

summarize what research and information collection would be valuable in order to more fully 

evaluate the public health risks associated with water quality degradation in the distribution 

system.

E.S. 1 Introduction

During 2007 and 2008, the US Environmental Protection Agency (EPA) convened the Total 

Coliform Rule / Distribution System Advisory Committee (TCRDSAC). EPA charged the 

TCRDSAC to provide recommendations on: (1) revisions to the Total Coliform Rule (US EPA, 

1989a) and (2) what information about distribution systems is needed to better understand and 

address possible public health impacts from potential degradation of drinking water quality in 

distribution systems (US EPA, 2008). The TCRDSAC developed an Agreement in Principle 

(AIP) (US EPA, 2008) in September 2008. While most of the language in the AIP focuses on 

recommendations for changes to the Total Coliform Rule, the document also contains 

recommendations concerning distribution system water quality (Section 4 of the AIP). To 

address these needs, the AIP recommends the formation of a Research and Information 

Collection Partnership (RICP) to identify priorities for research and information collection. This 

document was developed as a result of these recommendations.

The AIP identifies seven technical topic areas, or issues, as the most relevant to protecting public 

health and maintaining the integrity of drinking water distribution systems and categorizes these 

topic areas into two tiers. The seven distribution system issues and their associated tiers are:

Tier One: ―The following issues have been associated with documented health outcomes. 

Some information is available to characterize the extent of these issues, although more 

national characterization of the occurrence and relationship between these issues is 

needed. Some best practices information is available.‖ (US EPA, 2008)

1. Cross connections and backflow of contaminated water

2. Contamination due to storage facility design, operation or maintenance

3. Contamination due to main installation, repair or rehabilitation practices

4. Contaminant intrusion due to pressure conditions and physical gaps in distribution 

system infrastructure
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 6

Tier Two: ―For the following issues, some evidence exists that they do occur in public 

drinking water systems and adverse public health impacts are suspected to be associated 

with these topics, although available information is more anecdotal in nature and 

additional research and information collection is necessary to better define public health 

risks. Little occurrence information is available to document or characterize these 

issues.‖ (US EPA, 2008)

5. Significance and control of biofilm and microbial growth

6. Nitrification issues that lead to public health effects

7. Accumulation and release of contaminants from distribution system scales and 

sediments

E.S. 2 The Research and Information Collection Partnership (RICP) and the RICP 

Steering Committee

In the AIP, TCRDSAC recommended that a RICP be formed to inform and support the drinking 

water community in developing future national risk management decisions pertaining to drinking 

water distribution systems. The current members, hereafter called partners, of the RICP are EPA 

and the Water Research Foundation (WaterRF). EPA and WaterRF signed a memorandum of 

understanding (MOU) in January 2009, which officially formed the RICP.

The AIP specifies that the RICP is to ―establish a science-driven, mutually-agreed-upon, 

strategically-focused, decision-relevant research and information collection agenda that 

encompasses short, medium, and long term research and information needs‖ (US EPA, 2008). 

The objective of the RICP is to stimulate distribution system research and information collection 

from all interested parties.

The AIP also specified that the RICP form a Steering Committee (SC). The role of the SC is to 

review and accept the products of the RICP. SC members were selected to provide a broad 

perspective on the relevant drinking water distribution system issues. The RICP SC contains 

nine members, including three members from EPA, three members from water utilities, one 

member representing a public health perspective, one representing an environmental advocate 

perspective, and one representing a state regulator perspective. In addition, at least one member 

also represents a small system perspective. 

This document describes the results of the deliberations of the partners, with input from a 

Steering Committee. The partners followed a systematic process, described later in this 

document, to identify high priority research and information collection project areas for the 

relevant AIP issues. These priorities, when completed, are expected to support future risk 

management decisions by the drinking water community.

E.S. 3 Prioritization of Research and Information Collection Project Area Documents

The partners used a five step process to identify high priority research and information collection 

project areas. The steps included: (1) conducting research and information collection (RIC) 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 7

needs analysis for each of the seven issue areas in the AIP, (2) compiling RIC needs identified in 

the needs analysis, (3) sorting and organizing the RIC needs into related project areas, (4) 

developing project area documents based on results of RIC needs analysis, and (5) prioritizing 

project area documents. The partners solicited comments from the SC throughout the process. 

The RIC needs analysis resulted in approximately 180 needs. After the partners compiled, sorted 

and organized the RIC needs, they developed 29 project area documents. The partners 

developed a scoring system to help evaluate which of the project areas should receive the highest 

priority and presented the initial score results to the SC. The criteria, or factors, that the scoring 

system takes into account are:

relevance to each of the seven issues described in the AIP, with higher priority given to 

project areas that address multiple issues

the extent to which the project area is expected to inform an understanding of the 

magnitude of public health risk

the extent to which the project area is expected to inform an understanding of the 

mitigation of public health risk

The project area documents are meant to serve as guides for the areas of research or information 

collection related to distribution system issues. The project area documents are generally 

intended to identify groupings of similar needs rather than individual, stand alone projects. It is 

possible that some of these documents may be more appropriate to divide into multiple projects 

to fully address the information needs described.

The results of the project area documents are intended to inform decisions regarding the need for 

possible development of guidance, best management practices, regulations, or additional 

research and/or information collection on distribution system issues. Stakeholders may also use 

this information for education and training. Out of the 29 project area documents, the SC 

accepted ten as high priority project area documents (see Table E.S. 1)
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 8

Table E.S. 1 Final Ten High Priority Project Area Documents (in alphabetical order)

Project 

Area 

Document 

Code1

Project Area Document 

Title

Goals

CC1 Best Practices to 

Minimize Risks 

Associated with Cross 

Connections and 

Backflow

Identify and characterize the best practices (BPs) 

(including design, operations and costs) for cross 

connections and backflow that can be used to 

mitigate potential contamination concerns. 

Con3 Contaminant Entry from 

Breaches in Storage 

Facilities 

To compile data to better understand and predict 

health risks associated with contaminant entry 

through structural breaches in storage facilities.

Con4 Estimation of 

Contaminated Water 

Volumes and Contaminant 

Concentrations Introduced 

Into Distribution Systems 

Due to Backflow Events 

from Unprotected CrossConnections Based on 

Model Predictions and 

Field and Pilot-Scale 

Experiments

To compile data to better predict health risks 

associated with entry of external contaminants into 

drinking water distribution systems through 

unprotected cross-connections.

Hea1 Quantitative Microbial 

Risk Assessment (QMRA) 

to Evaluate Exposure to 

Pathogens through 

Drinking Water 

Distribution Systems

To develop an adaptive tool that can be used to 

estimate relative risks of exposure to distribution 

system pathogens and the effectiveness of risk 

management strategies for preventing/controlling 

microbial risks. 

Hea2 Epidemiological Studies 

of Health Effects 

Associated with Low or 

Negative Pressure Events 

in Distribution Systems 

To obtain information on the incidence and 

severity of adverse health effects occurring among 

customers who are impacted by low or negative 

pressure events in water distribution systems. The 

information can inform estimates of both baseline 

risks and reduction in those risks from mitigation 

actions.

 

1 CC, cross connection; Con, contaminant accumulation; Hea, health effects; Pres, pressure; Stor, storage; Sur, 

surveys 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 9

Pres1 Survey of Distribution 

System Pressure 

Management Practices

To assess pressure management practices in water 

distribution systems to determine the prevalence of 

specific high risk distribution system attributes 

leading to low or negative pressures.

Pres2 Characterize Propagation 

of Pressure Events 

through Water 

Distribution Systems to 

Improve Pressure 

Management Approaches

Evaluate the propagation of pressure events 

through the distribution system and compare field 

data with surge model results for the same events. 

Evaluate pressure propagation events at a number 

of systems and investigate the impact and cost of 

changes intended to mitigate the number and 

extent of such events. 

Stor1 Best Practices for 

Minimizing Risks 

Associated with Storage 

Facilities.

Identify and characterize the best practices (BPs) 

for storage that can be used to mitigate potential 

contamination exposure concerns.

Sur1 Survey of Large Drinking 

Water Utility Distribution 

Systems

To identify characteristics of drinking water 

distribution and storage systems that serve > 

50,000 people.

Sur4 Targeted Surveys to 

Obtain Information on 

State and Local 

Regulations, Policies, 

Manufacturing Practices 

and Guidelines for 

Distribution Systems

To evaluate extent to which distribution system 

risk management and mitigation practices are 

implemented by states or through manufacturing, 

installation, or inspection programs.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 10

1. Introduction

1.1 The Total Coliform Rule / Distribution System Advisory Committee Agreement in 

Principle

During 2007 and 2008, the US Environmental Protection Agency (EPA) convened the Total 

Coliform Rule / Distribution System Advisory Committee (TCRDSAC) to provide 

recommendations on: (1) revisions to the Total Coliform Rule (US EPA, 1989a) and (2) what 

information about distribution systems is needed to better understand and address possible public 

health impacts from potential degradation of drinking water quality in distribution systems (US 

EPA, 2008). The TCRDSAC developed an Agreement in Principle (AIP) (US EPA, 2008) in 

September 2008. The AIP contains the recommendations of the TCRDSAC, which represent the 

consensus of the parties that are signatories to the document. While most of the language in the 

AIP focuses on recommendations for changes to the Total Coliform Rule, the document also 

contains recommendations concerning distribution system water quality (section 4 of the AIP). 

The TCRDSAC found that additional research and information collection is needed to inform 

potential additional national risk management decisions concerning distribution systems. To 

address these needs, the AIP recommends the formation of a Research and Information 

Collection Partnership (RICP) to identify priorities for research and information collection. 

Additionally, the AIP identifies seven technical topic areas, or issues, as the most relevant to 

protecting public health and maintaining the integrity of drinking water distribution systems.

The AIP categorizes the seven technical topic areas, or issues, into two tiers. The seven 

distribution system issues and their associated tiers are:

Tier One: ―The following issues have been associated with documented health outcomes. 

Some information is available to characterize the extent of these issues, although more 

national characterization of the occurrence and relationship between these issues is 

needed. Some best practices information is available.‖ (US EPA, 2008)

1. Cross connections and backflow of contaminated water

2. Contamination due to storage facility design, operation or maintenance

3. Contamination due to main installation, repair or rehabilitation practices

4. Contaminant intrusion due to pressure conditions and physical gaps in distribution 

system infrastructure

Tier Two: ―For the following issues, some evidence exists that they do occur in public 

drinking water systems and adverse public health impacts are suspected to be associated 

with these topics, although available information is more anecdotal in nature and 

additional research and information collection is necessary to better define public health 

risks. Little occurrence information is available to document or characterize these 

issues.‖ (US EPA, 2008)

5. Significance and control of biofilm and microbial growth

6. Nitrification issues that lead to public health effects
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 11

7. Accumulation and release of contaminants from distribution system scales and 

sediments

For more detailed information on the seven AIP issues and the TCRDSAC‘s recommended 

approach to identify research and information collection needs, see section 4.2 of the AIP (US 

EPA, 2008).

1.1.1 Research and Information Collection Partnership

In the AIP, the TCRDSAC recommended that a RICP be formed to inform and support the 

drinking water community in developing future national risk management decisions pertaining to 

drinking water distribution systems. The current members, hereafter called partners, of the RICP

are EPA and the Water Research Foundation (WaterRF). EPA and WaterRF signed a 

memorandum of understanding (MOU) in January 2009, which officially formed the RICP.

The AIP specifies that the RICP is to ―establish a science-driven, mutually-agreed-upon, 

strategically-focused, decision-relevant research and information collection agenda that 

encompasses short, medium, and long term research and information needs‖ (US EPA, 2008). 

The objective of the RICP is to stimulate distribution system research and information collection 

from all interested parties.

This document describes the results of the deliberations of the partners, with input from a 

Steering Committee. The partners followed a systematic process, described later in this 

document, to identify high priority research and information collection project areas for the 

relevant AIP issues. These priorities, when completed, are expected to support future risk 

management decisions by the drinking water community, such as possible development of 

guidance, best management practices, regulations, or additional research and/or information 

collection on distribution system issues. Stakeholders may also use this information for 

education and training.

1.1.2 Steering Committee

The TCRDSAC also recommended that the RICP form a Steering Committee (SC). The SC was 

selected to provide a broad perspective on the relevant drinking water distribution system issues. 

The RICP SC contains nine members, including three members from EPA, three members from 

water utilities, one member representing a public health perspective, one representing an 

environmental advocate perspective, and one representing a state regulator perspective. In 

addition, at least one member also represents a small system perspective. The members of the 

SC can be found in Appendix A.

As specified in the AIP, the SC developed and accepted operating principles which outline roles 

and responsibilities, decision making procedures, safeguards, and data and information 

management provisions. The operating principles establish that the SC is responsible for review 

and acceptance of the products of the RICP. The SC members agreed to avoid the actual or

appearance of gain or preference in their role with the SC. Non-governmental SC members 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 12

agreed to an ethics policy developed for the committee, while the federal government SC 

members agreed to adhere to the federal ethics regulations.

The SC met a total of seven times during development of this priorities document. Three 

meetings were face-to-face (April 2009, September 2009 and April 2010) and four were 

conference calls (June 2009, November 2009, February 2010 and March 2010). The partners 

estimate that the SC will typically meet once per year over the duration of the research and 

information collection agenda (priorities) depending upon need and partner resources. For more 

detailed information on the SC, see section 4.1 of the AIP (US EPA, 2008).

1.1.3 Communications Process

The AIP also specifies that the partners develop a process for communicating research and 

information collection. In response, the partners developed a communications process to: (1)

provide transparency to stakeholders and the public about the work of the Partnership; (2) inform 

and engage potential researchers about request for proposals (RFPs) and high priority on-going 

research; and (3) inform and engage potential participants and funders of information collection 

activities.

The partners expect to communicate the research and information collection activities by taking 

actions such as:

- Posting materials developed through the RICP to the partners‘ websites. This includes 

posting this document which includes research and information collection priorities, 

summaries of the SC meetings, and links to information about high priority research 

projects and RFPs sponsored by the partners, descriptions of high priority information 

collection sponsored by the partners, and results of completed high priority research and 

information collection projects sponsored by the partners.

- Disseminating fact sheets describing the activities of the RICP at conferences, 

symposia, and stakeholder meetings. 

- Distributing e-mail messages to stakeholders, drinking water utilities, the water research 

community, and others who express interest, to announce the release of the research and 

information collection priorities. E-mail messages may also be sent to announce RFPs

sponsored by the partners.

The specific form of the communication will vary depending upon the target audience. For 

instance, some fact sheets may target the general public, whereas much of the information related 

to RFPs will more specifically target the research community. The partners plan to collaborate 

with individuals and institutions engaged in research and information collection activities to 

leverage communication opportunities.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 13

1.2 Overview of Public Health Risks Associated with Drinking Water Distribution 

Systems

1.2.1 General Overview of Public Health Risks

Water distribution systems consist of an interconnected series of pipes, storage facilities, and 

components that convey drinking water and are also designed to meet fire protection needs for 

cities, homes, schools, hospitals, businesses, industries and other facilities. Public water systems 

depend on distribution systems to provide an uninterrupted supply of pressurized safe drinking 

water to all consumers. Distribution systems convey water from treatment facilities (or from the 

source in the absence of treatment) to the consumer. Spanning almost one million miles in the 

United States, drinking water distribution systems represent the vast majority of physical 

infrastructure for drinking water supplies, and thus constitute a primary management challenge 

from both an operational and public health standpoint. Storage facilities provide in-line storage 

of water and also can modulate pressure fluctuations and provide additional capacity to equalize 

flow and pressure, particularly during high water usage times and emergency situations. 

The sizes, materials, methods of construction, and age of drinking water distribution system

components vary depending on regional and community development patterns. As distribution 

systems age deterioration can occur due to corrosion, materials erosion, and external pressures 

that can lead to breaches in pipes and storage facilities, intrusion, and main breaks. In recent 

years, deteriorating water infrastructure in many parts of the US has resulted in frequent water 

main breaks, openings in storage tanks, pressure aberrations, and other situations that can pose 

intermittent or persistent health risks (US EPA, 2009 and ASCE, nd.). For example, main breaks 

cause flooding and potential pathways for contaminants to enter the distribution system or be 

mobilized from internal distribution system surfaces. Main breaks may also lead to low pressure 

situations in other parts of the distribution system that can result in backflow events or otherwise

affect the quality of water delivered to customers. Therefore, ensuring the integrity and effective 

operation of distribution systems is critical for public health protection. While infrequently

reported, waterborne disease outbreaks and other events of public health significance do occur as 

a result of compromised distribution systems (NRC, 2006). 

EPA has promulgated regulations that pertain to drinking water distribution systems. These are 

the Surface Water Treatment Rules (disinfectant residual and sanitary survey requirements) (US 

EPA, 1989b; US EPA, 1998a; US EPA, 2002b; US EPA, 2006a), the Stage 1 and 2 Disinfectants 

and Disinfection Byproducts Rules (DBPR) (monitoring for DBPs in the distribution system) 

(US EPA, 1998b; US EPA, 2006b), the Ground Water Rule (sanitary surveys) (US EPA, 2006c) 

and the Total Coliform Rule (monitoring for bacterial contamination in distribution systems) (US 

EPA, 1989a).

Public health issues may also be a result of premise plumbing issues. Premise plumbing is a 

term that describes the pipes, faucets, showerheads, hot and cold water tanks, and other 

appurtenances that convey water within buildings. It includes the plumbing portion of the 

potable water system that delivers drinking water from the service line into and through schools, 

hospitals, commercial and industrial facilities, office buildings, public and private housing and 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 14

other buildings before reaching consumers at tap outlets. It is connected to the public drinking 

water distribution system via the service line. Virtually every change in water quality associated 

with the public water system can also occur in premise plumbing, although there are additional 

concerns such as those related to water temperature and stagnation that can be exacerbated in 

premise plumbing. The characteristics of the water provided from the treatment plant, and its 

interactions within the distribution system, and the unique characteristics of premise plumbing 

all affect the public health risk of the drinking water at the tap and complicate the formulation of 

coherent strategies to minimize risk.

1.2.2 Overview of the Seven Distribution System Issues Identified in the AIP

When the operation and functioning of the distribution system is compromised, potential public 

health risks can occur. As discussed in Section 1.1, the AIP identifies the following seven 

drinking water distribution system areas that can potentially contribute to public health risks: 

Cross connections and backflow. A cross connection is any interconnection between a potable 

water supply and a non-potable source where it is possible for a contaminant to enter the 

drinking water supply. The presence of an unprotected cross connection represents a loss of 

physical integrity in a distribution system through which backflow of contaminants can occur

(NRC, 2006). Contaminant introduction through an unprotected cross connection occurs when 

the non-potable contaminant source is at a greater pressure than the potable water distribution 

system. Backflow can occur from either backsiphonage or backpressure. Backsiphonage occurs 

when contaminants from the non-potable source enter the drinking water supply due to low or 

negative distribution system pressure. Backpressure occurs when the non-potable source of a 

contaminant exceeds a positive pressure in the potable water distribution system.

External contaminant introduction diminishes the water quality of drinking water distribution 

systems. While there are cross connection control programs in place in many locales, many 

others lack such programs. There is evidence that inconsistent implementation of such control 

programs can result in public health risk (NRC, 2006).

Storage. Finished water storage facilities play a vital role in providing a safe, adequate, and 

reliable supply of water. Many types of customers, including schools, hospitals, nursing homes, 

factories, fire departments, and home owners all depend on a consistent, dependable supply of 

safe water. Failure to maintain the structural and sanitary integrity of storage facilities can lead 

directly to the loss of property, (e.g. due to fires), illness, and death. Finished water storage 

facilities are designed to provide equalization of demands during high water usage times, 

additional supply for fires, and emergency water supply in case of outages. The type, 

configuration and quantity of finished water storage tanks and reservoirs vary from system-tosystem depending on several factors, including local requirements and topography. The design 

and operation of storage facilities plays a key role in protecting public health. Contaminants can 

be present in storage facilities, either by introduction through openings or indirectly due to 

inadequate inactivation of pathogens brought on by increased disinfectant demand and microbial 

and chemical reactions that impact water quality (NRC, 2006). Variable water use patterns can 

trigger hydrodynamic fluctuations that may slough biofilms and solids that accumulate on tank
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 15

surfaces and suspend sediments present in the storage facilities, introducing contaminants into 

the bulk water. When storage facilities are located in areas prone to low water use rates, the 

water within the tank may stagnate. Long detention times (high water age) and variable 

temperatures in storage tanks also affect the rate and extent of disinfectant decay, microbial 

growth and die-off, and nitrification reactions (AWWA and EES, 2002). Because storage 

facilities contain large volumes of water and have the ability to affect a large number of 

consumers in a distribution system, undetected or unaddressed contamination events within 

storage facilities can result in public health risks.

Main breaks, repair, and installation. Construction, rehabilitation, and repair of water mains 

are common activities that occur in all water systems. Sanitary construction practices must be 

used during main repair and installation of new mains and other infrastructure to prevent the 

introduction of contaminants. Putting a new or repaired main into service requires vigilance. 

When distribution system pipes break, rapid response is needed to isolate the affected mains and 

restore service as quickly as possible. During the main repair and installation process, 

distribution systems may be vulnerable to potential entry of microbial or chemical contaminants 

from the surrounding environment (Pierson et al., 2001). Low pressure events during main 

repairs can trigger contamination from intrusion, backflow, and concurrent release of biofilms 

and sediments from storage facilities and pipes, all of which can result in decay of disinfectant 

residuals in systems that provide disinfection. These distribution system contamination events 

may result in degradation of water quality which may result in public health risks.

Intrusion/Pressure. Intrusion is defined as ―the flow of non-potable water into drinking water 

mains through leaks, cracks, submerged air valves, faulty seals, and other openings resulting 

from low or negative pressures. Transient pressure regimes are inevitable; all systems will, at 

some time, be started up, switched off, or undergo rapid flow changes such as those caused by 

hydrant flushing, and they will likely experience the effects of human errors, equipment 

breakdowns, earthquakes, or other risky disturbances.‖ (NRC, 2005, p. 22)

Positive pressure in water distribution systems mitigates infiltration of external contaminants that 

might be present in the soil or water outside the buried pipes (Kirmeyer et al., 2001). 

Maintenance of pressure is typically accomplished through a combination of pumping and 

elevated storage tanks. When pressure is not adequately maintained in a distribution system, 

several types of contamination events are possible. Depending on the system‘s operating 

conditions and other factors that could influence pressure fluctuations (e.g., main breaks, pump 

start up or shut down), pressure fluctuations can occur for various time intervals, on the order of 

seconds to minutes (Besner et al., 2007; Besner et al., 2010; Gullick et al., 2004; Gullick et al., 

2005) or possibly hours for extreme events such as major pipe breaks (The Tech 2005). Sudden 

changes in water usage, main breaks, valves opening and closing, and other service changes can 

also cause pressure changes. When the pressure inside the pipes is lower than the external 

pressure exerted by soil and groundwater conditions, intrusion of contaminated water through 

leaks or holes in the pipe can occur (Kirmeyer et al., 2001). Low or negative pressure can occur 

for several hours or longer, during events such as main breaks, major fires, and power outages. 

Because of the risk of drawing contaminants into the distribution system, low to negative 

pressure events may pose a potential public health risk.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 16

Biofilms. There is not one universally recognized definition for biofilms; however, common 

among the definitions is that a water distribution system biofilm is a complex mixture of 

microbes, organic and inorganic material accumulated amidst a microbially produced organic 

polymer matrix attached to the inner surface of the distribution system. Some organisms 

harbored within biofilms may be primary pathogens (i.e., those that cause disease in healthy 

individuals), while others may be opportunistic pathogens (i.e., those that cause disease in

susceptible individuals with underlying conditions that may facilitate infection). Biofilms allow

organisms, including some pathogens, to accumulate, grow and die-off (US EPA, 2002a). This 

cycle can release pathogens into the water delivered to consumers and is of potential public 

health concern. Drinking water systems are designed to produce safe water by controlling 

disease-causing organisms (pathogens), but water in distribution systems is not sterile. There are 

two general classes of pathogens, those that the water industry has focused on, which come from 

fecal contamination of waters, and pathogens that are native to aquatic environments, some of 

which may grow after drinking water treatment. Further, water contains harmless microbes that 

survive the treatment process or enter the distribution system through the pipe network. These 

naturally occurring microorganisms in water can colonize internal surfaces of pipes and storage 

facilities in growths known as biofilms. 

The extent of biofilm growth within a given distribution system depends on many factors, 

including water chemistry, system design, materials, operation, and maintenance practices. 

Sudden changes in water velocity due to pressure events or changes in water chemistry can 

slough biofilms from internal surfaces (US EPA, 2002a). Biofilm growth in storage facilities 

(and release of pathogens from biofilms in such tanks) is also an important public health risk 

consideration. The role of pressure changes in distribution systems on biofilm—including 

sloughing, transport, reattachment, colonization, and interactions between biofilm in distribution 

systems and premise plumbing—is poorly understood and needs further study to help inform 

public health risk assessment of biofilm/pathogen dynamics in drinking water distribution 

systems.

Nitrification. For water systems that contain sources of ammonium (e.g., either source water 

ammonum, or ammonium added to provide chloramine residuals), reactions can occur in

distribution and storage systems that convert ammonium to nitrate, most of which is further 

converted by different microorganisms to nitrite. Some water sources also contain dissolved 

nitrite and nitrate, particularly in water sources that are impacted by agricultural activities. 

Nitrification is undertaken by microbes that can survive and grow in biofilms (AWWA, 2006), 

some of which may be released back into drinking water and continue the process. The extent of 

nitrification varies from system-to-system depending on factors such as design, operation, and 

water quality. Secondary impacts from nitrification include decay of chloramine residual and

release of ammonium, and reduction in pH, which can aggravate metal release and corrosion

(AWWA and EES, 2002). National Primary Drinking Water Regulations (NPDWR) exist for 

nitrite and nitrate. The maximum contaminant levels (MCL) for nitrite and nitrate are (MCL=1 

mg/L) and (MCL=10 mg/L), respectively. However, the point of compliance is at the entry point

to the distribution system, not downstream where biofilm-related nitrification may occur. 

Therefore, limited information is available on the extent to which nitrification reactions impose 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 17

additional health risks and remove residual disinfectant in distribution systems at points further 

from the entry point to the distribution system.

Contaminant accumulation and release from scales and sediments. Inorganic contaminants, 

including minerals that vary in solubility (calcium, magnesium, iron, manganese), metals (lead, 

copper, vanadium, arsenic), and inorganic contaminants that are not completely removed in 

treatment, can precipitate onto internal surfaces within pipes and storage facilities and 

accumulate (US EPA, 2006d). When operational conditions, such as pressure events or high 

water demands, result in changes in water velocities or water quality conditions promote 

corrosion reactions, contaminants can be re-dissolved or re-suspended into the bulk water and 

may pose health risks (US EPA, 2006d). The surfaces of accumulated scales and sediments can 

also harbor biofilms and associated pathogens. Limited information is available on the extent to 

which these reactions occur, the potential public health risks they pose, and the effectiveness of 

risk management practices.

REFERENCES

ASCE. n.d. Report Card for America‘s Infrastructure. Available online: 

http://www.asce.org/reportcard/index.cfm?reaction=factsheet&page=6

AWWA. 2006. Fundamentals and Control of Nitrification in Chloraminated Drinking Water 

Distribution Systems (M56). AWWA, Denver, CO.

AWWA and EES. 2002. Nitrification. Available online at: 

http://www.epa.gov/ogwdw000/disinfection/tcr/pdfs/whitepaper_tcr_nitrification.pdf

(March, 2010).

AWWA and EES. 2002. Finished Water Storage Facilities. Available online at: 

http://www.epa.gov/ogwdw000/disinfection/tcr/pdfs/whitepaper_tcr_storage.pdf (March, 

2010).

Besner, M.C., Morissette, C., Lavoie, J. and Prévost, M. (2007). Pressure transients and water 

quality changes associated with various O&M activities. In Proc. of AWWA Distribution 

Research Symposium, Reno, NV.

Besner, M.C., Broseus, R., Lavoie, J., Di Giovanni, G., Payment, P. and Prévost, M. (2010). 

Pressure monitoring and characterization of external sources of contamination at the site 

of the Payment drinking water epidemiological studies. Environmental Science and 

Technology, 44. 269-277.

Gullick, R.W., LeChevallier, M.W., Svindland, R.C. & Friedman, M.J. 2004. Occurrence of 

Transient Low and Negative Pressures in Distribution Systems. Journal of the American 

Water Works Association 96: 11. 52-66.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 18

Gullick, R.W., LeChevallier, M.W., Case, J., Wood, D.J., Funk, J.E. & Friedman, M.J. 2005. 

Application of Pressure Monitoring and Modelling to Detect and Minimize Low Pressure

Events in Distribution Systems. Water Supply: Research and Technology-Aqua. 54: 2. 

65-81.

Kirmeyer G.J., M. Friedman, K. Martel, D, Howie, M. LeChevallier, M. Abbaszadegan, M. 

Karim, J. Funk, and J. Harbour. 2001. Pathogen Intrusion Into the Distribution System. 

AWWARF. Denver, Colorado, USA.

NRC. 2006. Drinking Water Distribution Systems: Assessing and Reducing Risks, National 

Academies Press, Washington, DC.

NRC. 2005. Public Water Supply Distribution Systems: Assessing and Reducing Risks -- First

Report, National Academies Press, Washington, DC.

Pierson, G., K. Martel, A. Hill, G. Burlingame, A. Godfree. 2001. Practices to Prevent 

Microbiological Contamination of Water Mains. AWWARF, Denver, Colorado, USA 

The Tech, 2005. Pipe break causes campus water outage. The Tech, Online Edition, Vol. 125, 

Issue 2 http://tech.mit.edu/V125/N2/2water.2n.html (Feb 4, 2005)

US EPA. 2009. Sustainable Infrastructure for Water and Waste Water. Available online: 

http://www.epa.gov/waterinfrastructure/ (February 18, 2010).

US EPA. 2008. US Environmental Protection Agency Total Coliform Rule/Distribution Federal 

Advisory Committee Agreement in Principle. Available online: 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf (March 2010).

US EPA. 2006a. National Primary Drinking Water Regulations: Long Term 2 Enhanced 

Surface Water Treatment Rule; Final Rule. 71 FR 654. (January 5, 2006). Available 

online in three parts: http://www.epa.gov/fedrgstr/EPA-WATER/2006/January/Day05/w04a.pdf, http://www.epa.gov/fedrgstr/EPA-WATER/2006/January/Day05/w04b.pdf, and http://www.epa.gov/fedrgstr/EPA-WATER/2006/January/Day05/w04c.pdf

US EPA. 2006b. National Primary Drinking Water Regulations: Stage 2 Disinfectants and 

Disinfection Byproducts Rule; Final Rule. 71 FR 388. (January 4, 2006). Available 

online: http://www.epa.gov/fedrgstr/EPA-WATER/2006/January/Day-04/w03.pdf

US EPA. 2006c. National Primary Drinking Water Regulations: Ground Water Rule; Final 

Rule. 71 FR 65574. (November 8, 2006). Available online: 

http://www.epa.gov/fedrgstr/EPA-WATER/2006/November/Day-08/w8763.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 19

US EPA. 2006d. Inorganic Contaminant Accumulation in Potable Water Distribution Systems. 

Available online: 

http://www.epa.gov/ogwdw000/disinfection/tcr/pdfs/issuepaper_tcr_inorganiccontaminan

taccumulation.pdf (March, 2010).

US EPA. 2002a. Health Risks from Microbial Growth and Biofilms in Drinking Water 

Distribution Systems. Available online:

http://www.epa.gov/ogwdw000/disinfection/tcr/pdfs/whitepaper_tcr_biofilms.pdf

(March, 2010).

US EPA. 2002b. National Primary Drinking Water Regulations: Long Term 1 Enhanced 

Surface Water Treatment Rule; Final Rule. 67 FR 1812. (January 14, 2002). Available 

online: http://www.epa.gov/fedrgstr/EPA-WATER/2002/January/Day-14/w409.pdf

US EPA. 1998a. National Primary Drinking Water Regulations: Interim Enhanced Surface 

Water Treatment Rule; Final Rule. 63 FR 69477. (December 16, 1998). Available 

online: http://www.epa.gov/safewater/mdbp/ieswtrfr.pdf

US EPA. 1998b. National Primary Drinking Water Regulations. Stage 1 Disinfectants and 

Disinfection Byproducts; Final Rule. 63 FR 69389. (December 16, 1998). Available 

online: http://www.epa.gov/safewater/mdbp/dbpfr.html

US EPA. 1989a. Drinking Water; National Primary Drinking Water Regulations: Total 

Coliforms (Including Fecal Coliforms and E. coli); Final Rule. 54 FR 27544. (June 29, 

1989). Available online: 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/fr_tcr_1989rule.pdf

US EPA. 1989b. National Primary Drinking Water Regulations: Filtration, Disinfection, 

Turbidity, Giardia lamblia, Viruses, Legionella, and Heterotrophic Bacteria; Final Rule. 

54 FR 27486. (June 29, 1989). 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 20

2. Prioritization of Research and Information Collection Project Area Documents

The partners used a five step process to identify high priority research and information collection 

project areas. The steps included: (1) conducting research and information collection (RIC) 

needs analysis for each of the seven issue areas in the AIP, (2) compiling RIC needs identified in 

the needs analysis, (3) sorting and organizing the RIC needs into related project areas, (4) 

developing project area documents based on results of RIC needs analysis, and (5) prioritizing

project area documents. The following subsections provide a description of these steps. The 

partners solicited comments from the SC throughout the process. 

2.1 Research and Information Collection Needs Analysis

The first step in developing the Research and Information Collection Priorities was to identify a 

comprehensive list of research and information collection needs for each of the seven AIP issues. 

The RIC needs analysis defined distribution system-related research and information collection 

needs relevant to protect public health; or to inform possible future guidance, regulatory, or best 

management practices decisions related to the distribution system issues. To identify needs, the 

partners assembled teams of subject matter experts to assist in the development of an analysis for 

each of the seven AIP issues.

 

The partners directed the experts to perform literature reviews to define the state of the science

for each issue by first defining a contamination event and then identifying potential public health 

risks in the context of distribution system vulnerabilities and risk management/interventions. 

The clear definition of the contamination event, including the specific vulnerability factors and 

failures of mitigation barriers, provides a way to begin to understand commonalities among 

different public health outcomes and ways to predict, diagnose, prevent, and manage the 

potential health risk. A contamination event can occur either when contaminants gain entry into 

distribution and storage systems from external pathways, or as a result of internal microbial or 

physical/chemical reactions. In each case, contamination events occur only when specific 

barriers within the distribution system fail. Figure 1 illustrates the range of conditions necessary 

for a contamination event to pose a public health risk. 

The experts used a systematic approach for each of the AIP issues to determine what relevant 

data, information, and models are currently available to aid in identifying potential public health 

risks. Data sources included monitoring and operations data, surveys, utility data, and research 

studies, publications and reports. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 21

Figure 1 - Illustration of the Components of a Contamination Event

As part of the research needs analysis, conceptual models were developed to qualitatively assess 

gaps in information to better enable an estimation of public health risk and evaluate the 

effectiveness of risk mitigation strategies. Through this process the partners gained further 

insights into the uncertainties associated with different input variables and the value of 

completing research and information collection priorities. 

Along with the consideration of individual contamination events, the experts also determined the 

types of research and information collection that would be most useful to estimate the potential 

national magnitude associated with the events. For several of the issues, the greatest gaps were 

not in the definition of the contamination event but rather in the estimation of the frequency and 

duration of such events in a given system, and by extension the national frequency of events that 

warrant public health concern. In addition, the experts explored available strategies for risk 

mitigation in order to be able to define which risk mitigation technologies, strategies and 

practices warranted more information in order to be more fully understood, especially with 

regard to the effectiveness of the risk mitigation.

The partners compiled the results of the experts‘ analyses and used this information to better 

assess the ―needs‖ or current gaps in understanding the factors that may affect distribution 

system water quality. There were approximately 180 needs identified. Following the RIC 

compilation step, the partners categorized all the needs as either research or information 

collection needs. As an outcome of their discussions, the partners defined research as generating

new data and information on a topic by conducting studies at the laboratory, bench, pilot, 

modeling, or full-system scales. Information collection was defined as obtaining existing data on 

a topic from water systems, equipment manufacturers, suppliers, or other related entities through 

surveys, data call-ins, or other similar means. The information should already be available and 

could be accumulated by surveying states, systems, or other entities. Information collection

requires clearly defined information which the owner would be willing to share. 

Exposure 

pathway

Presence of a 

contaminant

Failure to 

detect or 

mitigate

Public 

Health Risk
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 22

Subsequently, the partners sorted the needs from all seven topic areas and organized them into 

thematic project areas. The partners did not narrow down or eliminate the needs, but instead 

grouped them into project areas. Project areas include surveys to collect distribution systemrelated information, and specific projects focused on pressure and intrusion, public health 

assessment contaminant characterization, cross connections, storage, monitoring, and risk 

management. Table 1 defines the eight project areas.

Table 1. Project Areas (Code) and Definitions

Contaminant (Con): Identification or estimation of contaminants of concern as well as 

mechanism of entry and contaminant concentrations.

Cross Connection (CC): The SC felt that cross connections is a Tier One issue (as defined by 

the TCRDSAC) that is among the closest to final risk management decisions in terms of risk 

mitigation and management. Therefore, project areas focused on cross connections are

appropriate. 

Health Effects (Hea): Estimation of disease incidence and risk factor implications related to 

distribution systems.

Monitoring (Mon): Actual monitoring activity or development of monitoring techniques and 

strategy.

Pressure (Pres): Relates to ambient pressure and pressure events in the distribution system. 

Related to both pressure levels and consequences of ineffective pressure management.

Storage (Stor): The SC felt that storage is a Tier One issue (as defined by the TCRDSAC) 

that is among the closest to final decisions in terms of risk mitigation and management. 

Therefore, project areas focused on storage are appropriate.

Surveys (Sur): Efforts to collect information through a survey or questionnaire. The 

information should already be collected and could be accumulated by surveying states, 

systems, or other entities. It requires clearly defined information which the owner would be 

willing to share.

Risk Management (RisM): Improves understanding for directly evaluating risk mitigation 

options and effectiveness including: diagnostics and controls relevant to events in individual 

systems and nationally, and effectiveness of known risk mitigations and alternatives.

2.2 Project Area Documents

Once the categories of research and information collection needs were established, and the needs 

sorted into the project areas, the partners developed specific research or information collection

project area documents. The partners determined that several of the needs were related or 

redundant. Therefore, it would not be efficient or practical to design a specific project around 

each individual need. Instead, the partners determined that it would be more feasible to develop 

a set of project area documents that would adequately address all the needs identified. The 

partners consulted the team of experts for each project area to assist with this task. Each team 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 23

developed a set of project area documents that would encompass needs in that project area. This 

process, with input from the SC, yielded 29 different project area documents2in the eight project 

areas. The project area documents are meant to serve as guides for the areas of research or 

information collection related to distribution systems. The project area documents are generally 

intended to identify groupings of similar needs rather than individual, stand alone projects. 

2.2.1 Definition of a Successful Project

When a partner party decides to undertake a particular project stemming from the project area 

documents, it is expected that the partner or an outside party would create a more detailed project 

request for proposals based on such factors as technical feasibility, project methods, and funding 

levels. In the case of the partners, this may include a full request for proposal. However, other 

methods of accomplishing these project area documents may be more appropriate (such as for 

the survey projects). It is also possible that some of the project area documents may be more 

appropriate to divide into multiple projects to fully understand the information needs described. 

In addition, because all needs were grouped into project area documents, the goals and objectives 

of the documents may be met by only conducting a subset of the activities listed. It will be up to 

the partner or entity following up on the project to determine the most efficient way to meet the 

goals and objectives described in the project area document, considering what is learned from 

other projects or research and information collection conducted by the partners and other entities.

The project area documents are not intended to provide complete detail on how the project areas 

are to be executed. This means that they are not intended to be used directly as requests for 

proposals. 

Organizations that may conduct research or information collection have different funding levels, 

mechanisms, and prioritization approaches. These project area documents provide a starting 

point for developing specific project requests for proposals for research and information 

collection. Any organization with an interest in these topics will consider the priority project 

area documents in the context of their own processes for resource allocation.

While each of the project area documents is different and will require customized 

implementation steps based on the individual characteristics of the project areas, there are some 

aspects that all projects should contain in order to be considered successful. First and foremost, 

implemented projects should address the goals and objectives found in the project area 

documents. These goals and objectives were written specifically to address the research and 

information collection needs, which represent the information missing from the current 

understanding of each of the seven AIP issues to inform risk management decisions by the 

drinking water community.

As the projects are developed, it is suggested that the project sponsors invite an identification and 

evaluation of the potential impacts and existing risks on minority, low-income, tribal, and other 

vulnerable populations. This may involve an evaluation of the proximity of distribution system 

 

2

Twenty-seven out of the 29 project area documents were scored. See Section 2.3.3 for rationale.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 24

issues (e.g., cross-connection and backflow, storage breaches, main breaks) to these populations, 

the number of distribution systems that may be impacting these populations, the type and amount 

of contaminants that may be affecting them, and whether there are any distinct exposure 

pathways that specifically affect them versus the general population.

In addition, it is important for researchers or those responsible for information collection to 

disseminate ongoing work related to their projects and not simply the completed published work. 

Since much of the ongoing work related to these project needs may be conducted by the RICP 

partners, it will be necessary for the partners to share, and encourage researchers to disseminate 

results as soon as practicable. This is to ensure efficiency, enhance the speed of knowledge 

transfer, promote coordination, and minimize duplication among researchers. 

The results of the project area documents are intended to inform decisions regarding the need for 

possible development of guidance, best management practices, regulations, or additional 

research and/or information collection distribution system issues. Stakeholders may also use this 

information for education and training.

2.2.2 Prioritization Approach

The following subsections in this section describe the process that was used to set priorities 

among the project area documents. Out of the 29 project area documents, the SC accepted ten as 

high priority project area documents. Each project area document was assigned a project area 

document code. A table which lists each project area title and its identification code is found in 

Appendix B.

The partners worked with the SC to identify the high priority project area documents. Given 

limited overall resources and a lack of resources to complete work in all 29 project areas, it was 

vital to prioritize the project areas based on agreed-upon criteria. To aid in this prioritization, the 

partners developed a scoring system to help evaluate which of the project areas should receive 

the highest priority. The prioritization is helpful to assist funders and researchers to focus their 

efforts on the most important areas first. Focusing on the highest priority to fill the most 

important research and information needs is the strategy the partners believe will most likely 

yield a body of focused, decision relevant knowledge that may be applied to support risk 

management decisions.

The criteria, or factors, that the scoring system takes into account are:

relevance to each of the seven issues described in the AIP, with higher priority given to 

project areas that address multiple issues

the extent to which the project area is expected to inform an understanding of the

magnitude of public health risk

the extent to which the project area is expected to inform an understanding of the

mitigation of public health risk
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 25

In developing the scoring system, the partners sought input from the SC to ensure that the system 

would be a valuable tool for use by the SC and the RICP. The SC specifically recommended that 

the scoring system incorporate the AIP tiering structure for the seven issues in order to better 

reflect the recommendations in the AIP. The SC also noted that considerations for the timing of 

project area documents (when project would be complete) and dependencies (which projects 

areas could benefit from work in other project areas) are important. However, the SC felt that 

the three factors above should be the primary drivers of the scoring and ranking, while the 

dependencies and timing factors should be used primarily as a way to differentiate among project 

area documents that had very similar initial scores.

The partners completed the scoring for each of the project areas and compiled the scores using 

the scoring system. Figure 2 provides an overview of the process used to identify the ten high 

priority project area documents. A detailed description of the scoring process and criteria, as 

well as the final scores, can be found in Appendix D.

Figure 2 - Overview of Process to Identify the Ten High Priority Project Area Documents

Partners developed and 

Steering Committee 

accepted the scoring 

system.*

Partners used the scoring 

system to calculate initial 

scores based on criteria 

found in section 2.2.2**

Steering Committee 

provided feedback on

initial scores and used 

best professional 

judgment to make 

adjustments. 

* See Appendix D for a description of how 

the scoring system works.

** See Appendix D for initial scoring 

results.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 26

2.2.3 Final Review by Steering Committee

The partners presented initial scores (found in Appendix D) to the SC for review. The SC 

elected not to rank each project area document in order. Instead, the SC separated the list of 

project area documents into two groups. The first group was identified as the group of highest 

priority project area documents. The remaining project area documents were not considered to 

be the most critical at this time because they were not as decision relevant. The list of high 

priority project area documents is found in Table 2. The full descriptions of these project area 

documents are found in section 3. The remaining project area documents can be found in 

Appendix C of this document. 

2.2.4 Other Considerations Used in Steering Committee Decisions

In addition to the partner scores, the SC considered several other pieces of information when 

making their recommendations on the high priority project area descriptions. One main 

consideration for the SC was the sequence in which the project area documents would be 

addressed. In order to address these concerns, the SC used the results of a ―generational 

approach‖ analysis that the partners provided. 

In the generational approach, the partners evaluated all project area documents to determine 

which ones had a ―strict dependence‖ relationship with other project area documents. A ―strict 

dependence‖ relationship means that the results from a particular project area document are 

prerequisites for work to begin on another project area document. For example, if project area 

document B strictly depends on project area document A, then project area document A must be 

completed before work on project area document B begins. The generational approach also 

evaluated which projects had an ―informational‖ relationship. An ―informational‖ relationship 

means that while a project area document may not strictly require information from another 

project area document before proceeding, information learned in the first project area document 

is likely to be useful in carrying out research or information collection in the second project area 

document. For example, if project area document B is informed by project area document A, 

then it is possible to complete project area document B without waiting for the results of project 

area document A. However, the design and usefulness of the findings from project area 

document B will likely be maximized if work on project area document A is completed before 

work begins on project area document B. 

The partners used best professional judgment to establish the generational and informational 

relationships among project area documents based on the definitions above. The relationships 

among the project area documents are listed in the table in the ―Project Area Constraints and 

Timing‖ section of each project area document. Based on these tables, the partners produced a 

list of project area documents containing all possible projects that could begin first without the 

need for results from other project area documents. The project area documents on this list are 

project areas that do not strictly depend on other project areas and are not informed by other 

project areas. First generation project areas are those in which work could begin immediately 

and maximize the usefulness of the results by informing projects in later generations. The list of 

first generation of project area documents can be found in Appendix E. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 27

2.2.5 List of SC adjustments with rationales

The SC used the top ten ranked project area documents from the initial scoring described in 

Appendix D as a starting point for their discussion. Based on that initial list, the SC made 

adjustments using principles outlined in section 2.2.4. The SC noted that several of the project 

area documents which received high scores were dependent on, or at least informed by, several 

other project area documents. They believed that it would not make sense to place these project

area documents on the high priority list. Therefore, the SC removed project area documents

Sur2, Sur3, RisM1 and Pres3 from the high priority list based on this rationale.

Sur2/Sur3 – Sur2 is dependent on partial completion of Sur1. Sur3 is in turn dependent on Sur2. 

The SC recognized that Sur2 is envisioned to rely heavily on lessons learned from Sur1 and that 

certain elements of Sur2 may be refined based on findings in Sur1. Similarly, Sur3 relies on 

Sur2 since baseline data and survey design elements could be incorporated from Sur2. 

Therefore, the SC did not consider a designation of high priority for Sur2 and Sur3 to be

appropriate.

RisM1 – RisM1 is a project area that could be used to incorporate much of the information 

learned as part of the RICP process. It is either directly dependent on or could benefit from the 

completion of work in many different project area documents including Sur1, Sur2, Sur3, Sur4, 

Con2, Con3, Con4, RisM4.

Pres3 – Pres3, which develops strategies to monitor for pressure fluctuations, is dependent on

several different project area documents which examine the causes and frequencies of pressure 

fluctuations, including Sur1, Sur2, Pres1 and Pres2.

The SC also added project areas to the list of high priority items that were not originally found 

on the list of top ranked project area documents from the initial scoring. These project area 

documents were given high priority based on circumstances that were not reflected in the scoring 

system. The SC added project area documents CC1, Stor1, Con3 and Con4 to the set of high 

priorities. 

CC1 and Stor1 – The SC recognized both CC1 and Stor1 as high priority project area documents. 

The SC felt that Cross Connections and Storage are the two Tier One issues (as defined by the 

TCRDSAC) that are the closest to final risk management decisions. Both project area 

documents concern best practices for risk mitigation in those two specific areas. The SC 

recognized that while these two project areas did not receive a high score during the partner 

scoring process, this was due to the structure of the scoring mechanism. Project areas that 

address issues across several topic areas receive more points in the scoring system. Project area

documents such as CC1 and Stor1, which only address one topic area in a specific way, therefore 

did not receive high scores from the scoring system. Therefore, despite their relatively low

scores, the SC recognized that these two project areas were high priority based on the degree to 

which they will help address the Tier One topic areas in a specific way.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 28

Con3 and Con4 – Con3 and Con4 were also added to the list based on similar rationale to CC1 

and Stor1. The SC noted that these project areas also received low scores in the scoring process 

due to their focus on a specific topic area. In particular, the SC showed interest in Con3 and 

Con4 because they complement CC1 and Stor1 by informing the magnitude of risk from Cross 

Connections and Storage. Con3 concerns the incidence of risk factors associated with Storage 

contamination events and Con4 examines the incidence of risk factors associated with Cross 

Connections and backflow. The SC believed that the combination of CC1 and Con3, and Stor1 

and Con4, is expected to provide decision relevant information. Therefore, they included Con3 

and Con4 among the high priority project area documents. In particular, the SC recognized the 

results of Sur1, when combined with Con3 or Con4, should yield sufficient decision relevant 

information to support risk management decisions.

3. Research and Information Collection Priorities

As a result of their deliberations, the Steering Committee accepted a list of ten high priority 

project area documents. Table 2 provides a list of those documents as well as a summary of their 

goals.

Table 2. Final Ten High Priority Project Area Documents (in Alphabetical Order)

Project 

Area 

Document 

Code3

Project Area Document 

Title

Goals

CC1 Best Practices to Minimize 

Risks Associated with Cross 

Connections and Backflow

Identify and characterize the best practices (BPs) 

(including design, operations and costs) for cross 

connections and backflow that can be used to mitigate 

potential contamination concerns. 

Con3 Contaminant Entry from 

Breaches in Storage 

Facilities 

To compile data to better understand and predict health 

risks associated with contaminant entry through 

structural breaches in storage facilities.

Con4 Estimation of Contaminated 

Water Volumes and 

Contaminant Concentrations 

Introduced Into Distribution 

Systems Due to Backflow 

Events from Unprotected 

Cross-Connections Based on 

Model Predictions and Field 

and Pilot-Scale Experiments

To compile data to better predict health risks associated 

with entry of external contaminants into drinking water 

distribution systems through unprotected crossconnections.

 

3 CC, cross connection; Con, contaminant accumulation; Hea, health effects; Pres, pressure; Stor, storage; Sur, 

surveys
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 29

Hea1 Quantitative Microbial Risk 

Assessment (QMRA) to 

Evaluate Exposure to 

Pathogens through Drinking 

Water Distribution Systems

To develop an adaptive tool that can be used to 

estimate relative risks of exposure to distribution 

system pathogens and the effectiveness of risk 

management strategies for preventing/controlling 

microbial risks. 

Hea2 Epidemiological Studies of

Health Effects Associated 

with Low or Negative 

Pressure Events in 

Distribution Systems 

To obtain information on the incidence and severity of 

adverse health effects occurring among customers who 

are impacted by low or negative pressure events in 

water distribution systems. The information can 

inform estimates of both baseline risks and reduction in 

those risks from mitigation actions.

Pres1 Survey of Distribution 

System Pressure 

Management Practices

To assess pressure management practices in water 

distribution systems to determine the prevalence of 

specific high risk distribution system attributes leading 

to low or negative pressures.

Pres2 Characterize Propagation of 

Pressure Events through 

Water Distribution Systems 

to Improve Pressure 

Management Approaches

Evaluate the propagation of pressure events through the 

distribution system and compare field data with surge 

model results for the same events. Evaluate pressure 

propagation events at a number of systems and 

investigate the impact and cost of changes intended to 

mitigate the number and extent of such events. 

Stor1 Best Practices for 

Minimizing Risks 

Associated with Storage 

Facilities.

Identify and characterize the best practices (BPs) for 

storage that can be used to mitigate potential 

contamination exposure concerns.

Sur1 Survey of Large Drinking 

Water Utility Distribution 

Systems

To identify characteristics of drinking water 

distribution and storage systems that serve > 50,000 

people.

Sur4 Targeted Surveys to Obtain 

Information on State and 

Local Regulations, Policies, 

Manufacturing Practices and 

Guidelines for Distribution 

Systems

To evaluate extent to which distribution system risk 

management and mitigation practices are implemented 

by states or through manufacturing, installation, or 

inspection programs.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 30

The remainder of this section contains the complete text of these ten high priority project area 

documents.

______________________________________________________________________________

Project Area Document Code: CC1 

Project Area Title: Best Practices to Minimize Risks Associated with Cross Connections and 

Backflow

Goal(s): Identify and characterize the best practices (BPs) (including design, operations and 

costs) for cross connections and backflow that can be used to mitigate potential contamination 

concerns. Help industry personnel to:

1 Better diagnose potential problems

2 Better understand risk factors (e.g., failure of a barrier) associated with cross 

connections and backflow events

3. Provide operators with best practices to reduce those risks

4. Provide information on the cost effectiveness of BPs

Rationale:

The presence of an unprotected cross-connection represents potential distribution system (DS) 

vulnerability, through which backflow can occur. This situation can provide a conduit for 

chemical, microbial and/or radiological contaminants to enter the DS, particularly when the 

pressure in the potable source is lower than the pressure in the contaminant source. These lower 

pressures result from common events in DS, including valve and pump operations, power 

outages, main breaks, high demand, flushing, and even a rise in pressures from the contaminant 

source (e.g., a boiler). 

The extent and magnitude of health risks associated with backflows is site-specific and depends 

on the source of contamination (sewage, industrial discharges, etc.), the location of the backflow, 

the distribution system characteristics, and the effectiveness of prevention and inspection 

programs. The durations of consumers‘ exposures to the contaminants is highly variable and 

depends on water use practices, system hydraulics, the nature of the cross connection, an 

understanding by the system that a risk may exist and the ability of the system to find and 

remedy the problem. Given that limited monitoring occurs in DS, these events often escape 

detection. Frequently events are detected through customer complaints rather than routine 

monitoring. Even then, the event will often have passed by the time the utility investigates. As a 

result, undetected and uncorrected cross connections may result in recurring backflow 

occurrence, imposing unquantifiable health risks. 

Currently, there are no federal regulations that explicitly require drinking water systems to 

protect against or document cross connections and backflow events. Based on 2001 data, while 

every state has a requirement related to cross-connection control and/or backflow prevention, 

only 32 states require that public water systems implement a cross-connection and/or backflow 

prevention program (EPA, 2001). There are variations among the states in the extent of 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 31

implementation, enforcement, inspection, and oversight due to local situations including 

competing priorities, funding and resource limitations, political factors, and the lack of federal 

drivers or incentives. Developing metrics to quantify program effectiveness, along with 

aggregating information about required elements of state programs and their relative 

effectiveness, and compiling components of programs from exemplary utilities, industry groups, 

universities, and other practitioners can be used by states and utilities to implement improved 

practices.

Objectives: 

1. Compile existing materials that document BPs that are used by a range of different 

audiences (e.g., utility personnel, plumbers) to diagnose, prevent and mitigate backflow 

contamination risk factors, including cross connection hazard surveys, elements of 

effective cross-connection control programs and responses to contamination events. 

Information related to implementation costs and barriers to implementation will also be 

compiled.

2. Provide a single reference resource for industry personnel to evaluate cross connection 

and backflow related risk factors, and risk mitigation options (including costs and 

potential implementation obstacles). Risk factors are those factors which potentially 

contribute to the occurrence of backflow (e.g., unstable operating pressures).

3. Evaluate attributes of effective training programs provided to water utilities, plumbers, 

etc. and provide a resource from which training materials could be developed.

4. Determine key barriers to development, implementation and enforcement of crossconnection control and backflow prevention programs, and provide case study examples 

of how these barriers have been overcome.

5. Develop strategies to quantify and benchmark the effectiveness of BPs used by utility 

personnel, plumbers, etc. and document case studies of successful programs.

Suggested Approach:

Develop a “State-of-Knowledge” Synthesis of Existing Knowledge and Information Relative to 

Cross Connections and Backflow —Provide a comprehensive review and summary of key 

existing information and knowledge from literature, references, manuals, training materials, 

industry surveys, interviews and site visits, and existing cross connections and backflow 

materials.

Collect and summarize available information on potential risk factors 

Collect and summarize evidence of links between backflow events, contaminant exposure, 

health effects, and waterborne disease outbreaks. 

Compile relative costs of components of cross-connection control and back-flow 

prevention programs, diagnostic approaches, and mitigation measures.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 32

Develop a glossary with illustrations, definitions, etc., that can be used by the water 

industry and others to promote dialog and to more fully characterize cross connections and 

backflow. 

Provide easy-to-use examples and case studies of cross connections and backflow riskrelated regulations, standards, policies, certification programs, ordinances, key program 

elements, codes and best practices (assimilated from States/EPA, vendors, associations, 

inspectors, utility operators/managers, plumbing organizations) and provide comparative 

costs and constraints for adoption of risk evaluation, prevention and mitigation measures.

Provide case study examples of how some systems have overcome key barriers to 

development, implementation and enforcement of cross-connection control and backflow 

prevention programs.

Conduct follow-up as needed to gather, assemble and summarize key information and 

knowledge.

Assess the Effectiveness of Cross Connection Control and Backflow BPs –Incorporate key 

information useful for evaluating (1) potential backflow related risk factors and (2) backflow risk 

mitigation.

Develop tools for industry personnel and others to better evaluate backflow risk factors 

and risk mitigation, including costs.

Conduct expert review of BPs.

Strategies to Gauge Industry Application of BPs

Develop strategies and approaches to assess application, usefulness and effectiveness of 

BPs and to assimilate data from applications of project area results. 

Develop metrics and benchmarks of program effectiveness 

Results and Applications:

Information collected in this project area will help system operators better diagnose and correct 

problems related to cross connections and backflow. It will also help system operators to 

recognize and address potential risk factors (e.g., failure of a barrier) associated with cross 

connections and backflow and evaluate elements of effective cross-connection control and 

backflow prevention programs that help to mitigate risk factors. Information collected in this 

project area will identify opportunities for improving the effectiveness of BPs and will also 

evaluate barriers to implementation and mechanisms for improving adoption, implementation, 

and vigilance. 

The results of information collection in this project area will provide BPs for use by a wide range 

of stakeholders (e.g., utilities, states, industry, and plumbing organizations). It will provide tools 

to assist utility personnel in diagnosing backflow related problems, highlight effective BPs, and 

provide strategies for overcoming obstacles for managing backflow risks. Information collected 

in this project area will inform a national perspective on the use, costs and effectiveness of the 

BPs. Information collected in this project area will also elucidate social science factors that 

might be relevant to improving the consistency of cross-connection control and backflow 

prevention programs.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 33

Knowledge incorporated into the content and format of the BPs will facilitate more informative 

cross connection and backflow related surveys, sampling, and data analysis, and may also be 

useful in sanitary surveys required under the SWTRs and GWR. The results of information 

collection in this project area can also be used to assist with optimization of DS practices.

Decision Relevance:

How is information collection in this project area likely to inform evaluation of the magnitude 

of public health risk?

Information developed in this project area will include descriptions of cross connection and 

backflow contamination events where health impacts have occurred. These accounts will 

illustrate the severity and extent of outcomes that can result from cross connection and backflow 

events and will inform industry personnel and others of potential risks assisting in the selection 

of risk mitigation options. System level hazard assessments and cross connection and backflow 

risk evaluations will better inform utility personnel and others about the potential risks in their 

systems. The assimilation of data about the use of the BPs will yield more representative and 

useful cross connection and backflow related (performance and cost) information and knowledge

than is currently available nationally.

How is information collection in this project area likely to inform opportunities for mitigation 

and risk reduction?

The results of information collection in this project area would go beyond informing 

opportunities for mitigation and risk reduction by providing BPs to implement known, effective, 

mitigation and risk reduction strategies. Increased industry personnel understanding will support 

efforts to plan more effective system level hazard assessments and cross-connection control and 

backflow prevention programs. For systems with advanced programs, the information will help 

them evaluate their current practices. Cost and performance effectiveness of existing crossconnection control and backflow prevention strategies can be evaluated as well. Utilities, 

contractors, and regulators can use these evaluation and mitigation BPs to address crossconnection and backflow risks in the interim period while national surveys and studies are 

ongoing, and national risk management decisions are pending.

What types of distribution system decisions could be supported by information collection in 

this project area?

If future decisions regarding the need for regulation, guidance, policy statements, or other actions 

are to be taken, the materials developed in this project area could be used to support those 

decisions. Follow up on the results of the availability of BPs and improved surveys and research 

will provide a better understanding of the national status of cross connection and backflow 

related risks and the obstacles to implementation of risk mitigation measures. Additionally, 

many of the BPs that are expected to be captured from information collection in this project area 

will be evaluated in more detail (in terms of degree of implementation and effectiveness) as part 

of the other RIC priority project areas under consideration by the DS RICP. 

Project Area Constraints and Timing:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 34

This project area is a stand-alone project that can begin immediately, and could be completed 

within two years. It is not dependent on the completion of information collection in other project 

areas, nor is any other project area dependent on completion of information collection in this 

project area. However, the completion of this information collection project area may influence

several other project areas. See the table below for information on the project areas that build on 

CC1. 

Relationship to 

other RICP project

areas

Project

area 

document

code

RICP project area document 

title (under consideration by the 

DS RICP)

Information needs 

(what will be used in 

follow-on project

areas)

This project area 

depends on. . .

No other project areas NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project

area

Pres4 Toolkit for pressure management Cross connection 

control best practices 

developed in CC1 

may be considered for 

inclusion in pressure 

management toolkit.

Sur4 Targeted surveys to obtain 

information on state and local 

regulations, policies,

manufacturing practices and 

guidelines for distribution systems

Information on cross 

connection control 

practices from CC1 

could be compared 

with information 

collected in Sur4.

Factors that might influence the timing of completion of information collection in this project 

area include:

Familiarity with existing cross-connection control program publications.

Access to state databases and/or other information needed from states

Ability to obtain expert peer review and/or input regarding key elements for which 

additional understanding is needed.

A quick project area timeline would enhance the understanding of backflow risks and 

mitigation, needed in the interim when DS RIC efforts are beginning and regulatory 

decisions are pending. 

Relevance to the Agreement in Principle:

This project area is relevant to the cross-connection which is a Tier One priority area. 

Information collected in this project area will contribute towards fulfillment of the AIP objective 

of optimizing DS integrity by assembling BPs associated with cross-connection and backflow 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 35

prevention programs and providing the tools for utilities and states to evaluate existing programs. 

Information collection in this project area will also build upon the Cross Connection Control 

practices library outlined in section 3.17.a.

Key References:

ABPA (1999) American Backflow Prevention Association State Program Survey. 

www.abpa.org/originalsite/ABPA_Survey_Report.pdf

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf

EPA. (2001) Potential Contamination Due to Cross-Connections and Backflow and the 

Associated Health Risks. Distribution System White Paper. 

www.epa.gov/safewater/disinfection/tcr/pdfs/issuepaper_tcr_crossconnectionbackflow.pdf.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 36

Project Area Document Code: Con3

Project Area Title: Contaminant Entry from Breaches in Storage Facilities 

Goal: To compile data to better understand and predict health risks associated with contaminant 

entry through structural breaches in storage facilities.

Rationale: Research in this project area will provide data on the extent to which contaminants 

can gain entry into distribution systems from storage breaches (e.g. poorly sealed hatches, 

unprotected vents, tears in covers, or structural cracks or holes). Research in this project area 

will involve monitoring and source tracking to determine the relative magnitude of 

contamination that may result from storage breaches. Since water that is released from aboveground and underground storage facilities into distribution systems has the potential to introduce 

contamination to significant populations, it is important to understand the magnitude of this risk. 

In addition, the variability of storage operations necessitates well-designed sampling efforts that 

are coupled with hydraulic modeling. 

Storage facilities are uniquely vulnerable to contamination due to their often remote, elevated 

locations, unstaffed sites, the potential for long residence time (water age) and changes in 

temperature, disinfectant residuals, and other water quality parameters, and the challenges 

associated with regular programs for monitoring, inspecting and maintaining the structures. 

Animals, birds and insects can enter storage facilities through breaches and potentially introduce 

human/animal fecal pathogens (e.g. Salmonella, Campylobacter, E. coli). For example, in the 

1993 storage-related outbreak in Gideon, Missouri, operator flushing of the system to resolve 

taste and odor problems dispersed Salmonella-contaminated water from storage causing more 

than 600 illnesses and 9 deaths (Clark et. al. 1996). Storage contamination was also cited as a 

cause of a waterborne disease outbreak in Alamosa, Colorado in 2008. Opportunistic pathogens 

(Legionella, MAC) have also been observed to thrive in biofilms and amoebae, apparently 

shielded from disinfectants (Lau and Ashbolt 2009), making storage sediments possible locations 

for these opportunistic pathogens to grow if introduced through storage breaches. 

The knowledge goals of research in this project area are: (1) Understanding of factors 

contributing to or controlling contaminant entry through storage breaches; (2) Characterization 

of types and patterns of contaminants that may enter storage directly via breaches, and; (3) 

Understanding the fate of, and risk from, breach-related contaminants in storage upon release to 

the system. The overarching questions this project area will answer are: (1) Under what 

conditions and scenarios do storage breaches lead to entry of contaminants into storage facilities, 

and/or inoculation of distribution systems resulting from storage breaches? (2) What factors 

affect the types and quantities of contaminants that can enter/occur via storage breaches? (3) 

What is the expected fate or the behavior of storage-associated contaminants during storage and 

transport through the distribution system?

Objectives: 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 37

Enhance the understanding of effectiveness of various storage breach-related risk 

mitigation measures, costs, and implementation obstacles.

To characterize storage breach entry pathways, causes, sizes, convection mechanisms, 

durations, and frequencies of occurrence.

Measure contaminants in bulk and stored water, and sediments within storage facilities.

Estimate the extent to which pathogen accumulation, growth, or die-off occurs due to 

storage conditions or operations (e.g., fill/draw, mixing, stratification, disinfection 

effectiveness, entrapment in sediments or biofilms) to develop predictive models to 

estimate release from storage into the distribution system.

Suggested Approach:

Summarize scientific literature on environmental pathogen occurrence, survival rates, and 

disinfection susceptibility in storage tanks and underground finished water reservoirs. 

Identify potential pathogen sources of contaminants that might gain entry to storage 

facilities (mostly animals, birds, and insects). 

Delineate possible storage contamination scenarios and relative risks including animal 

access. 

Conduct observational studies of storage facilities to evaluate the potential for animal 

access.

Develop and implement plans to characterize and sample storage systems with a range of 

potential vulnerabilities to external contamination, including a range of influencing factors 

such as geographical and seasonal variability, storage facility design, etc. Plans should 

include systematic approaches for selecting representative sampling sites, the number of 

samples to be collected per site, and the total number of scenarios to be sampled to inform 

a national estimate of the magnitude of risk. 

Conduct targeted sampling and laboratory testing of storage conditions that impact 

pathogen viability (e.g. disinfectant type and concentration, stratification, temperature, 

biofilms, or solids accumulation) 

Estimate pathogen concentrations in different types of storage facilities and underground 

finished water reservoirs, and the extent to which accumulation, amplification or die-off 

occurs due to storage conditions or operations (e.g., fill/draw, mixing, stratification, 

disinfection effectiveness, entrapment in sediments or biofilms).

To the extent feasible research this project area should include a qualitative estimation of 

the effects of mixing on the dispersion of pathogens in the stored water.

Develop preliminary predictive models to estimate release from storage into distribution 

systems which encompass a range of storage configurations (e.g. range of cycling, mixing, 

and stratification, disinfectants). 

Results and Applications: Concentrations, types, and patterns of storage breach-related 

contaminants measured through research in this project area can be used as inputs into fate and 

transport models and risk models to estimate exposures/health risks from storage breach-related 

contamination events. Research in this project area will provide new insights on the types, 

quantities, patterns, and pathways of pathogens entering systems via various storage breach 

pathways. Understanding storage-related events gained through research in this project area will 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 38

provide insights about the magnitude of risks and opportunities for risk mitigation across a wide 

array of systems. Although not the direct intent of this project area, the results from research in 

this project area may also provide a measure of the effectiveness of best practices comparing 

vulnerable systems that implement versus those that do not implement best practices. 

Decision relevance:

How is research in this project area likely to inform the evaluation of the magnitude of public 

health risk?

Research in this project area is designed to characterize contaminants that gain entry to water 

distribution systems directly from storage breaches. It will provide key new insights about 

sources and occurrence patterns from animal and insect-borne pathogens introduced to storage, 

and which may be harbored or grown in storage and transported into and through systems.

How is research in this project area likely to inform opportunities for mitigation and risk

reduction?

The nature and occurrence of the pathogens will help develop a greater understanding of the 

potential risk mitigation options that systems may want to use to target these risks through the 

identification of specific types of breaches that may be present and the types of pathogens that 

can enter storage through these breaches. This understanding is critical to the selection and 

ongoing evaluation of appropriate risk mitigation measures relative to storage breaches.

What types of distribution system decisions could be supported by research in this project

area?

Research in this project area will provide information important in decisions regarding storage 

inspection or monitoring. Research results will be important for consideration in decisions

utilities may make related to storage inspections and monitoring, utility associations may make 

regarding the substance of storage guidance, and regulatory agencies may make about storagerelated requirements or guidance. 

Project Area Constraints and Timing: 

Research in this project area should be able to proceed based on information already available in 

existing industry surveys and other sources. 

Relationship to 

other RICP project

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project

areas or what will be 

used in follow-on 

project areas

This project area 

depends on. . .

No other project areas. N/A

Project areas that this 

project area builds on

None. N/A
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 39

Project areas that 

build on this project

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Identification of the 

mechanisms of 

storage contamination 

will inform the most 

appropriate best 

practices for 

controlling 

contamination.

RisM5 Develop next generation models 

for informing distribution system 

and storage water quality including 

episodic release/mobilization of 

chemical contaminants from 

accumulated solids and biofilm

Identification of 

potential storage 

contamination will 

inform the 

contaminants of 

concern and release 

mechanisms.

* While this project area could benefit from data and information generated under Sur1 and Sur2, this 

project area does not directly depend on or build on those project areas. Instead, this project area along 

with Sur1 and Sur2 will provide information on the occurrence of risk factors that must be present for 

storage related contamination of distribution systems to result.

What are the potential constraints to the implementation of this project area?

Cross-disciplinary knowledge and expertise is needed for study design, implementation and 

results interpretation—[e.g. natural environment (weather, wildlife), storage design & 

operations; microbiology of pathogens; disinfection alternatives and efficacy; mechanisms of 

sediment and biofilm formation, accumulation and release; storage sampling and monitoring 

techniques, etc.]; 

Technical expertise is required to properly select, apply, and evaluate ongoing effectiveness of 

various mitigation strategies;

Access to storage facilities is needed and participation of utilities;

Historical data on storage inspection and monitoring is needed for study design.

Relevance to the Agreement in Principle: 

Research in this project area helps address multiple issues identified as high priorities in Section 

4.2a of the AIP under headings of ―contamination due to storage facility design operations and 

maintenance,‖ ―significance and control of biofilm and microbial growth;‖ and ―accumulation 

and release of contaminants from DS scales and sediments.‖ For example, enhanced 

understanding of storage-breach-related pathogen occurrence, potential, and management options 

will aid understanding of storage impacts on pathogen occurrence in the system overall. This 

will, in turn, enhance the understanding of important storage design, operation, and maintenance 

practices. Research in this project area will also provide important knowledge/content to help 

address the TCRDSAC recommendation (in Section 3.17c of the AIP) that EPA, in cooperation 

with primacy agencies, develop minimum qualifications and a standardized training program for 

sanitary surveyors, and evaluate the need for certification.

Key References:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 40

Clark, RM, EE Geldreich, KR Fox, EW Rice, CH Johnson, JA Goodrich, JA Barnick, F 

Abdesaken, JE Hill, and FJ Angulo. (1996). A waterborne Salmonella typhimurium 

outbreak in Gideon, Missouri: results of a field investigation. Intl. J. Environ. Health Res.

6:187-193.

Lau, H.Y. and Ashbolt, N.J. (2009) . The Use of Acanthamoeba as a tool for understanding 

Legionella pathogenesis: Implications for drinking water. Journal of Applied 

Microbiology 106, 368-378.

National Research Council. (2006). Drinking Water Distribution Systems: Assessing and 

Reducing Risks, The National Academies Press, Washington D.C.

USEPA. (2002). Finished Water Storage Facilities. Washington D.C.: USEPA. Distribution 

System Issue Paper.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 41

Project Area Document Code: Con4

Project Area Title: Estimation of Contaminated Water Volumes and Contaminant 

Concentrations Introduced Into Distribution Systems Due to Backflow Events from Unprotected 

Cross-Connections Based on Model Predictions and Field and Pilot-Scale Experiments

Goal: To compile data to better predict health risks associated with entry of external 

contaminants into drinking water distribution systems through unprotected cross-connections.

Rationale:

Contamination of the distribution system through unprotected cross-connections has resulted in 

documented public health impacts. US EPA has compiled information describing 469 backflow 

incidents which occurred between 1971 and 2006. In 164 of these events (35 percent), 

contaminants reached the distribution system serving the public. Contaminated water was 

contained within the premise plumbing at the source for 185 events (39 percent). The 

contaminant entry point to the distribution system was undocumented or undetermined for the 

remaining 120 events.

While the mechanisms that can result in backflow (including backsiphonage and backpressure) 

are well understood, and the effectiveness of backflow prevention devices is well documented, 

limited data are available on the extent of the distribution system that can potentially become 

contaminated through unprotected cross-connections. A better understanding of the magnitude 

and duration of pressure events that cause contaminants to reach the distribution system under 

various flow, pressure, and piping configuration boundary conditions (e.g., causes of pressure 

events that may lead to reductions of possible public health significance) is needed. Additionally, 

statistically sound information is needed on the magnitude of contamination that can occur under 

various scenarios. This project area would inform the definition of the conditions under which 

contaminants are likely to enter the distribution system and potential exposure consequences, 

thereby providing quantitative information on potential public health risk.

Objectives: 

1. To determine the magnitude and duration of pressure reductions under which 

contaminated water could be introduced to the DS through unprotected crossconnections.

2. To estimate the potential frequency and volume of contamination that may be occurring 

nationwide through unprotected cross-connections. 

3. To estimate the contaminant concentration in the contaminant sources (if feasible).

Suggested Approach: 

Review utility records and existing literature to identify contaminants of concern, number 

of unprotected cross-connections per service connection, and available information (e.g., 

duration of pressure reductions) on contamination events reaching the distribution system 

versus those events for which contaminants were isolated within the premise. Research 

conducted in this project area should use the same definition of pressure reduction as that 

developed for Sur1. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 42

Review design standards and plumbing codes to estimate most typical lengths and sizes 

of service lines for various types of service connections. Compile information related to 

configuration, and causative factors (e.g., system operating pressure) for different types 

of services (i.e., residential, commercial, industrial).

Identify a minimum of three ―representative‖ physical configurations (e.g., representing 

the distance, pipe size, meter size, etc. for residential, commercial, industrial services) to 

be used in subsequent analyses.

Estimate contaminant concentrations in sources from which backflow contaminants 

originate.

Using existing models or by building a computer model calculate the magnitude and 

duration of pressure events needed to draw a contaminant through service plumbing and 

past the service connection into the distribution system for the three representative 

service types. Conduct sensitivity analyses regarding pipe diameter, flow rate, pipe 

length and configuration, pressure, number and location of contaminant sources at the 

service connection, etc. Both backsiphonage and backpressure events should be 

evaluated. It is assumed that both spreadsheet and hydraulic/surge models will be needed 

for this task.

Construct a pilot-scale system or field demonstration projects to test different

configurations of service connections, multiple types of cross-connections, plumbing 

configurations, pressure conditions, etc. Pilot-scale units were constructed and evaluated 

for intrusion investigations during transient pressure events as reported in Lee et al., 

(2009) and Friedman et al., (2004). 

o Phase 1 - demonstrate the range of magnitude and duration of pressure events 

needed to allow contaminants to reach the DS through an unprotected crossconnection for the given configuration. 

o Phase 2 - determine the range of contaminant volumes that could reach the DS as 

a function of pressure, flow rate, and other boundary conditions identified during 

modeling. Determine contaminant concentrations in sources.

Use modeling and pilot-scale or field results to extrapolate range of contaminant volumes 

and frequency of contamination at unprotected cross-connections within and across fullscale systems. 

Results and Applications: The project area results can be used as inputs to a fate and 

transport/risk model to estimate the potential exposure/health risk from backflow of 

contaminated water through unprotected cross-connections. The results can also be used to 

estimate the national potential for public health risk due to contamination through unprotected 

cross-connections by assessing the frequency with which the minimum pressure and durations 

allowing for contamination occur. For example, the results may indicate the ranges of pressure 

event magnitude and duration that are needed to draw contamination through varying lengths of 

residential and service line piping. If pressures are maintained above those boundary conditions, 

then it is very unlikely that contaminants from an unprotected cross-connection at residential, 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 43

commercial or industrial service connections could reach the distribution system. Ultimately 

completed research and analyses will look at information to clarify and update distribution 

system areas of concern. This evaluation may result in follow-up studies that can provide more 

detail on significant factors that may impact public health.

Decision relevance:

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk?

Research in this project area will provide the data needed to assess the likely frequency and 

magnitude of distribution system contamination events through unprotected cross-connections, 

under a variety of operating conditions. This can help determine the potential public health risks 

posed by these events, which will inform local and national risk management decisions.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

Research in this project area could be used to assess the need for risk management strategies in 

all or only vulnerable areas of distribution systems. It will help to identify conditions under 

which contamination is unlikely, thereby allowing for the best use and focus of risk management 

strategies. It will help the drinking water community (PWSs, States, EPA) determine whether 

and what type of policies should be implemented to reduce potential risks.

What types of distribution system decisions could be supported by this research in this project

area?

Research in this project area will provide information on the possible need to emphasize the 

application of cross-connection control and backflow prevention programs, through voluntary 

standards, local policies, municipal ordinances, plumbing standards, and State or Federal 

guidance or regulation. It will provide a technical basis for determining what the minimum 

pressures or optimal operating ranges needed to prevent contamination due to backflow through 

unprotected cross-connections.

Project Area Constraints and Timing:

Con 4 could be conducted on its own schedule, as funding is made available. The literature 

search and data compilation pieces are not necessarily dependent on other project areas; but, if 

Con 4 is conducted afterwards some project areas (e.g., Sur 2), duplication in efforts could 

theoretically be avoided. Similarly, the output of Con 4 will be useful as inputs to other project 

areas; however, it is not necessary to delay research and information collection in the other 

project areas until Con 4 is completed. 

Relationship to 

other RICP project

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 44

This project area 

depends on. . .

No other project areas. N/A

Project areas that this 

project area builds on

Sur1 Survey of Large Drinking Water 

Utility Distribution Systems

Baseline data, 

identification of 

additional information 

gaps, pool of potential 

participants.

Project areas that 

build on this project

area

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Identification of the 

potential for and 

mechanisms of 

contamination from 

cross connections and 

backflow will inform 

the most appropriate 

best practices for 

controlling 

contamination.

Pres4 Toolkit for pressure management Evaluation of 

different system 

configurations and 

sources of 

contamination will 

inform the most 

appropriate best 

practices for 

controlling 

contamination. 

* While this project area could benefit from data and information generated under Sur1, Sur2 and Pres2, 

this project area does not directly depend on or build on those project areas. Instead, this project area 

along with Sur1, Sur2 and Pres2 will provide information on the occurrence of risk factors that must be 

present for cross connection and backflow related contamination of distribution systems to result.

Factors that might influence the timing of completion of research in this project area include:

Willingness of utilities to provide information during the modeling and pilot phases and 

participate in monitoring for potential contamination events as pilot systems.

Ability of utility personnel to provide timely response to pressure events during the pilot 

phase in order to determine the potential volumes of contaminated water entering the 

system.

Ability of pilot utility personnel to accurately pinpoint the source of the contamination 

and obtain data on the contaminant concentrations from these sources.

Ability to construct a computer model that adequately simulates the ranges of physical 

and hydraulic conditions of interest
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 45

Ability to construct a pilot facility that adequately simulates the ranges of physical and 

hydraulic conditions of interest

Relevance to Agreement in Principle:

As stated in the Introduction section of the AIP, one of the major objectives of the TCRDSAC 

was to provide advice and recommendations on what data should be collected, research 

conducted, and/or risk management strategies evaluated to better inform distribution system 

contaminant occurrence and associated public health risks in distribution systems. This was 

intended to ―initiate a process for addressing cross connection control and backflow prevention 

requirements and consider additional distribution system requirements related to significant 

health risks‖.

As described in section 4.2c, cross-connection control and backflow are listed as Tier 1 topics. 

Con 4 specifically provides the inputs needed to assess potential public health impacts as well as 

fate and transport studies by providing the data needed for risk assessment modeling. Con 4 also 

provides the needed information for estimating the national potential for contamination of 

distribution systems through unprotected cross-connections.

Key References: 

Friedman, M., Radder, L., Harrison, S., Howie, D., Britton, M., Boyd, G., Wang, H., Gullick, R., 

LeChevallier, M., Wood, D. & Funk, J. 2004. Verification and Control of Pressure 

Transients and Intrusion in Distribution Systems. AWWARF, Denver, Colorado, USA.

Lee, Juneseok, V. K. Lohani, A. M. Dietrich, and G.V. Loganathan. 2009. Low Pressure 

Propagation at Service Lines. World Environmental and Water Resources Congress. 

Great Rivers ASCE.

Research and Information Collection Needs Analysis – Cross-Connection and Backflow. CC 

Deliverable 1. September, 2009.

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 46

Project Area Document Code: Hea1

 

Project Area Title: Quantitative Microbial Risk Assessment (QMRA) to Evaluate Exposure to 

Pathogens through Drinking Water Distribution Systems

Goal: To develop an adaptive tool that can be used to estimate relative risks of exposure to 

distribution system pathogens and the effectiveness of risk management strategies for 

preventing/controlling microbial risks. 

Rationale: Quantitative microbial risk assessment (QMRA) is a systematic approach for 

evaluating potential health consequences associated with distribution system vulnerabilities and 

the effectiveness of risk mitigation alternatives. The effectiveness of QMRA depends on the 

availability of data on microbial risks and system vulnerabilities. Research in this project area 

will involve designing QMRA models to integrate information from literature reviews, surveys, 

modeling, and other research activities. Research in this project area will be coordinated with 

other RICP activities to inform the need for guidance or policies to address different distribution 

system vulnerabilities. In addition, QMRA will be used to conduct sensitivity analyses to 

identify additional research and information collection needs. 

Objectives: 

Develop models that will enable quantification, as sufficient information becomes 

available. 

Depending on available and sufficient information, quantify magnitude of exposure to 

pathogens associated with distribution systems and identify sources of microbial 

contamination (bulk water, biofilms, cross-connection, infrastructure breaches or 

failures), fate and transport factors (growth, die-off, interactions with internal surfaces 

and biofilms), and potential public health concerns.

Apply QMRA to identify approaches to optimize monitoring and improve the ability to 

diagnose, prevent, and manage microbial risks.

Integrate QMRA into the design and implementation of pathogen-related studies to 

provide a common framework for interpreting data and evaluating the extent to which

management options are effective at reducing health risks associated with exposure to 

water from distribution systems.

Suggested Approach: 

This project area will proceed in two phases. Phase 1 - model development, and Phase 2 -

application of the model to inform risk management implications.

Phase 1 – Develop/refine existing models (e.g., models for intrusion, cross connection and 

backflow, storage facility breaches, etc.) to characterize potential pathogen exposure associated 

with individual distribution system contamination events. Use model to identify data needs that 

are most influential in reducing model uncertainties.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 47

Phase 2 – Using additional research and information collection to fill gaps, run QMRA models to 

inform robust risk mitigation decision making. Phase 2 may require iterative model runs to 

identify and fill data gaps.

Phases 1 and 2 will include the following steps with a goal towards iteratively reducing data and 

model uncertainty:

- Conduct statistical analyses of frequency and magnitude of contamination events for 

different types of distribution system vulnerabilities.

- Evaluate scenarios under which contamination events results in pathogen exposure 

through public water systems considering different scales and intensity of contamination 

events (general population and vulnerable sub-populations such as young children, 

pregnant women, home-bound elders).

- Apply dose-response models to translate estimates of pathogen densities in drinking 

water to estimates of disease, including consideration of variations in pathogen 

concentrations over time and secondary spread.

- Use QMRA to define drinking water system conditions necessary to avoid exceeding 

health based targets (such as a daily infection benchmark) at locations within distribution 

systems and storage, including the role of biofilms in modulating pathogen fate, 

transport, and virulence.

- Use research in this project area to evaluate microbial risks associated with alternative 

designs and management outcomes from a wide range of distribution system-related 

studies. 

- To the extent feasible research in this project area will provide a tool to examine the 

degree of risk reduction provided by the use of various distribution system risk 

management strategies. 

- Research in this project area includes: 1) development of computer-based tools for 

QMRA using a synthesis of any available data on distribution system pathogens; 2) 

collection of data from epidemiologic and research studies that inform exposures; and 3) 

implementation of QMRA modeling in conjunction with hydraulic models to evaluate 

fate and transport, monitoring alternatives, and the type of data needed to determine the 

degree to which management practices may be effective at reducing microbial and related 

chemical risks. 

- Provide documentation of the basis for parameter assumptions used in the sensitivity 

analyses.

Results and Applications:

Research in this project area will provide a basis for evaluating the relative importance of factors 

that impact microbial risks in distribution systems. The results of research in this project area 

will provide information on target parameter levels for the management of safe drinking water. 

Also, identification of potential premise plumbing issues may also be included to the extent to 

which they are influenced by distribution system factors and conditions.

Decision relevance:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 48

How is research in this project area likely to inform evaluation of the magnitude of health 

risk? 

Research in this project area will inform an evaluation of the magnitude of pathogen risks on an 

individual and across system basis for vulnerability factors associated with cross connection and 

backflow; storage; main construction and repair; pressure and intrusion; biofilm; nitrification; 

and contaminant accumulation.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction? T

he use of QMRA in conjunction with results from other research projects and surveys can inform 

the extent and effectiveness of risk reduction that may be available for different mitigation 

strategies in different DS topic areas and for specific vulnerability factors. 

What types of distribution system decisions could be supported by research in this project

area?

Research in this project area would inform the potential benefits that might be realized for 

various distribution system risk management strategies on the local, regional, state and national 

level. 

Project Area Constraints and Timing:

The quality and robustness of the final risk assessment in any topic area will be constrained by 

the quality and uncertainty of the input data and model constructed to use that data. The strength 

and limitations of the QMRA should be explicitly delineated to appropriately inform both 

research and information collection priorities and risk management decisions.

Research in this project area can begin without dependence on any other effort under 

consideration by the DS RICP. 

Relationship to 

other RICP project

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by the 

DS RICP)

Information needs 

(what will be used in 

follow-on project

areas)

This project area 

depends on. . .

No other project areas. NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project

area

None. NA

Relevance to Agreement in Principle: 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 49

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Health Effects and Risk to the Public

o Measure health consequences from exposure to contaminants

o Monitor for situations that pose a public health concern

o Measure and track the national significance of the described situations

Effectiveness of mitigation measures

o Characterize preventative measures or steps to minimize or prevent exposure

o Identify and implement remediation steps when contamination occurs

o Quantify the national significance of additional mitigation measures

Research in this project area that characterizes the health risks and distribution system risk 

factors is highly relevant to the Tier One priority topic areas, namely intrusion and cross 

connection/backflow. It is also highly relevant to the Tier One priority topic areas, storage and 

main construction/repair.

Key References: 

Medema G, Loret J-C, Stenström TA, Ashbolt N. 2006. Quantitative Microbial Risk Assessment 

in the Water Safety Plan. Final Report on the EU MicroRisk Project. Brussels: European 

Commission.

Mons MN, Van der Wielen JML, Blokker EJM, Sinclair ML, Hulshof KFAM, Dangendorf F, 

Hunter PR, Medema GJ. 2007. Estimation of the consumption of cold tap water for 

microbiological risk assessment: an overview of studies and statistical analysis of data. 

Journal of Water and Health 5: 151-170.

Storey MV, Ashbolt NJ. 2003. A risk model for enteric virus accumulation and release from 

recycled water distribution pipe biofilms. Water Science and Technology: Water Supply 3: 

93-100.

Van Lieverloo JHM, Blokker EJM, Medema G. 2007. Quantitative microbial risk assessment of 

distributed drinking water using faecal indicator incidence and concentrations. Journal of 

Water and Health 5: 131-149.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 50

Project Area Document Code: Hea2

Project Area Title: Epidemiological Studies of Health Effects Associated with Low or 

Negative Pressure Events in Distribution Systems 

Goal: To obtain information on the incidence and severity of adverse health effects occurring 

among customers who are impacted by low or negative pressure events in water distribution 

systems. The information can inform estimates of both baseline risks and reduction in those 

risks from mitigation actions.

Rationale: Several studies suggest linkage between low or negative pressure events and 

adverse human health effects, e.g. Nygard K et al. 2007, Hunter PR et al, 2005; Geldreich EE, 

1992. However, these studies did not fully characterize risks, or the potential for risk reductions 

among the population served by public water systems where these events occur. The primary 

purpose of this study is to assess whether low pressure events result in increased incidence of 

AGI and ARI among populations served by PWS in the U.S. and to provide the data to allow for 

a more thorough risk characterization associated with pressure events (e.g., such as those caused 

by main breaks).

Objectives: 

Identify rates of adverse health effects, including gastrointestinal illness, and other 

diseases occurring in customers consuming drinking water in periods following known 

low or negative pressure events. 

Develop estimates of risk measures (e.g., relative risks, odds ratios) to differentiate the 

potential for these adverse health effects between customers consuming water affected by 

low pressure events and those not affected.

Develop estimates of potential reduction in the risk associated with the most common 

pressure management strategies to reduce the system‘s vulnerability to intrusion events 

(e.g., the extent to which reductions in pressure events would reduce AGI and possible 

strategies for achieving this)

Suggested Approach: 

Research in this project area is expected to proceed in two sequential phases: Phase 1 – Develop 

the method and approach for the study, and Phase 2 – Implementation of full scale epidemiology 

studies.

Phase 1 - The first phase will be a scoping effort and the second will be one or more full scale 

epidemiology studies.

The scoping phase of the research will be aimed primarily at:

o Developing the method and approach for the full epidemiology study. This will 

include such aspects as developing system vulnerability and community eligibility 

criteria, identifying the specific health end-points to consider (e.g., whether to 

include respiratory illness in addition to gastroenteritis) and how to obtain 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 51

necessary information on those health outcomes from both affected and nonaffected water system customers 

o Developing power calculations that indicate the extent to which different survey 

designs can inform risk attributed to pressure events

o Identifying approaches to determine where and when major pressure events occur 

in the participating systems and how to best identify customers in both the 

exposed and unexposed areas 

o Determining the appropriate risk measures to use to characterize potential 

differences in the incidence of adverse health effects among the affected and nonaffected customers 

The scoping phase may also include some limited pilot study efforts in communities and 

their water systems to test and if necessary revise the initial method, and approach 

including data collection protocols, and system and community selection criteria.

During the scoping phase, efforts will also be made to identify and recruit public water 

systems to participate in the full epidemiology study.

Phase 2 – The second phase is implementation of the full scale study. It is anticipated that 

the full epidemiology study will be structured as a prospective, cohort study involving 

multiple (3 to 5) public water systems. Systems will be selected on the basis of known 

histories of low/negative pressure events, and other eligibility criteria, including the 

willingness of the utility management to collaborate and participate in the study. Each 

participating system will enroll for a period of one year and agree to follow the study 

protocol. 

For the participating systems, it is expected that it will be necessary to conduct a baseline 

assessment of the system‘s vulnerability to intrusion events and to develop a systemspecific data collection plan in line with the epidemiology study‘s methodology. It may 

also be necessary to install some pressure monitoring devices and conduct hydraulic 

modeling to characterize conditions in various sections of the participating systems that 

will be studied. It will be necessary to resolve the details of the baseline assessment and 

system monitoring with the individual utilities recruited to participate in the study. 

Data on system risk factors will be collected to provide information to assess distribution 

system associated mitigation practices. 

An approach to support data management will be needed.

Inclusion of a consumer risk communication plan needs to be seriously considered.

Results and Applications: 

The results from the epidemiology studies are characterizations of whether low pressure 

events are associated with increased incidence of adverse health events, including 

gastroenteritis (and potentially respiratory illness) in U.S. populations served by PWS. If 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 52

the study results find no significant risk attributable to pressure events, this finding will 

only indicate the absence of risk below a particular level which still might be a concern 

(only not detectable due to the power limitations of the study).

The application of these results is expected to contribute to an understanding of the 

potential health benefits from implementing the risk mitigation strategies either through 

technical guidance and/or regulations.

The results may provide a basis to assess benefits due to distribution system 

infrastructure upgrades that reduce leaks, pipe failures and pressure fluctuations, and to 

increased risk-targeted distribution system monitoring and component inspection and 

maintenance.

Decision Relevance: 

How is research in this project area likely to inform evaluation of the magnitude of health 

risk? 

Ideally, Research in this project area will provide quantitative estimates on the degree of risk 

attributed to low or negative pressure events occurring in the distribution system. 

How is research in this project area likely to inform opportunities for risk reduction? 

Depending upon whether positive point estimates are found with low or negative pressure events, 

research in this project area could also inform the extent to which risks due to low or negative 

pressure events might be reduced by implementation of various mitigation strategies.

What types of distribution system decisions could be supported by research in this project

area?

The results of this study will help inform the basis to determine whether the current risks and risk 

reduction potential regarding low or negative pressure events merit regulatory action, technical 

guidance, or both.

Project Area Constraints and Timing: 

Research in this project area can begin without dependence on any other effort. The full study 

phase depends upon the successful completion of the scoping phase, including a pilot and 

development of a data collection protocol that meets the study‘s data requirements. The scoping 

phase should be able to be completed in 1-2 years and the full scale study within another 1-2 

years. Potential constraints include gaining full cooperation of water system managers, to 

participate in the study for its full planned duration. 

Relationship to 

other RICP project

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by the 

DS RICP)

Information needs 

(what will be used in

follow-on project

areas)

This project area 

depends on. . .

No other projects. NA

Project areas that this None. NA
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 53

project area builds on

Project areas that 

build on this project

area

None. NA

* Although this project area is not dependent on the Pres2 project area, there would be 

advantages to the same utilities participating in Pres2 as this project area since the field 

monitoring data generated under Pres2 would be useful for this project area.

Relevance to the Agreement in Principle:

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Health Effects and Risk to the Public

o Measure health consequences from exposure to contaminants

o Monitor for situations that pose a public health concern

o Measure and track the national significance of the described situations

Effectiveness of mitigation measures

o Characterize preventative measures or steps to minimize or prevent exposure

o Identify and implement remediation steps when contamination occurs

o Quantify the national significance of additional mitigation measures

Research in this project area is highly relevant to the following Tier One priority topic areas of 

AIP: intrusion, cross connection/backflow, storage and main construction/repair.

Key References: 

Geldreich, E.E., Fox, K.R., Goodrich, J.A., Rice, E.W., Clark, R.M. & Swerdlow, D.L. 1992. 

Searching for a Water Supply Connection in the Cabool, Missouri Disease Outbreak of 

Escherichia coli OI57:H7. Water Research. 26 : 8. 1127-1137.

Hunter, P.R., Chalmers, R.M., Hughes, S. & Syed, Q. 2005. Self-Reported Diarrhea in a Control 

Group: a Strong Association with Reporting of Low-Pressure Events in Tap Water. 

Clinical Infectious Diseases. 40 : 4. e32-e34.

Nygard, K., Wahl, E., Krogh, T., Tveit, O.A., Bohleng, E., Tverdal, A. & Aavitsland, P. 2007. 

Breaks and Maintenance Work in the Water Distribution Systems and Gastrointestinal 

Illness: a Cohort Study. International of Journal Epidemiology. 36 : 4. 873-880.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 54

Project Area Document Code: Pres1

Project Area Title: Survey of Distribution System Pressure Management Practices

Goal: To assess pressure management practices in water distribution systems to determine the 

prevalence of specific high risk distribution system attributes leading to low or negative 

pressures.

Rationale: Low or negative pressures in water distribution systems can result in drinking water 

contamination through unprotected cross connections or intrusion of external contaminants. Low 

or negative pressure events are typically transient in nature, with durations of only seconds to 

minutes (Friedman, 2004; Gullick, 2004), although main breaks can result in prolonged negative 

pressures. A number of design and operational factors have been shown to lead to transient low 

and negative pressure events in distribution systems (Fleming, 2006). Design or operational 

conditions that may lead to low or negative pressure transients include:

Few floating storage facilities, especially for systems in locations with flat or moderately 

hilly terrain

Areas of the distribution system near no floating storage facilities

Operation at steady-state pressures less than 60 psi

Dead-end areas of the distribution system, especially those far away from floating storage 

facilities

Operation of equipment such as valves or fire hydrants that causes sudden flow changes

Pump operated with on/off cycles

Loss of power at pump stations

Lack of surge control equipment

Although there is evidence indicating the causes of pressure transients, the nationwide 

prevalence of these risk factors is largely unknown. Currently available distribution system 

inventories such as WaterSTATS from the American Water Works Association (AWWA) 

contain a variety of distribution system design attributes but do not capture the operational 

parameters and design details to fully assess the national risk of contamination due to low or 

negative pressure events. Furthermore, the development of a national understanding of 

distribution system pressure management provides an opportunity to evaluate the cost impacts 

associated with elimination of these risk factors through various available mitigation strategies. 

Objectives: 

1. Identify 400-600 utilities to participate in survey. Sur1may be used to identify the

sampling frame of utilities for such a survey

2. Generate a comprehensive information base characterizing the diversity of distribution 

system infrastructure and operation related to pressure and pressure management in the 

U.S.

3. Assess the prevalence of pressure-related distribution system attributes that may increase 

the risk of low or negative pressures. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 55

Suggested Approach: 

This research and information collection project area is intended to collect detailed design and 

operational information associated with distribution systems. It is intended to build on 

information collected in Sur 1 and Sur 2, so surveys in this project area should be designed to 

supplement the information in those survey areas, and not collect any of the same information. 

Approximately 400-600 utilities would be asked to compile pressure-related information from 

existing records and enter the information into electronic surveys. Follow-up will include 

specific written communications, telephone interviews, and site visits as necessary to confirm or 

expand on survey responses. Key information of interest includes:

- System size, service population, wholesale accounts, water sources, topography and 

demand patterns; number of pressure zones, overall system design and operational 

parameters

- Type and nature of surge protection infrastructure

- Number and type of storage facilities with design and operational parameters 

- Number of pump stations with design and operational criteria including pumped entry 

points

- Number of pressure control valves with design and operational criteria

- Number of pumps and pressure control valves with backup power 

- Frequency of power failures and percent of service connections affected

- Frequency of hydrant, valve and pump operation (automated and manual)

- Frequency of low pressure events tabulated from customer complaints and existing 

pressure recorders

- Numbers and types of main leaks and breaks

- Description of any efforts to optimize pressure management and a summary of the results

Results and Applications: 

Research conducted and information collected in this project area is expected to generate a 

dataset of pressure management infrastructure attributes and operational practices across all 

regions, system sizes, source waters, and topographies. Research collected and information 

collected in this project area will indicate the prevalence of known risk factors leading to low or 

negative pressures and generate an understanding of the level of effort associated with driving 

the drinking water industry toward optimized pressure management.

Decision relevance:

How will research conducted and information collected in this project area inform the 

evaluation of the magnitude of public health risk? 

Information collected will identify how low and negative pressure events impact distribution 

contamination events (e.g., cross-connection, intrusion). The results from this project area may 

be used to identify the frequency and degree of potential distribution system contamination 

resulting from low and negative pressure events. The results combined with other project results 

(e.g., Con3, Hea1) will support the estimation of the risk level of detrimental health outcomes 

due to cross-connection and intrusion. 

How are research conducted and information collected in this project area likely to inform 

opportunities for mitigation and risk reduction? 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 56

The results from this project area will inform future efforts to determine whether and what type 

of policies might be implemented to reduce potential risks. Research conducted and information 

collected in this project area will also inform the activities for the distribution system 

optimization program specified in the AIP, and possibly identify candidate utilities for 

participation.

What types of distribution system decisions could be supported by research and information 

collection in this project area? 

Research conducted and information collected in this project area will contribute to the 

determination of whether guidance or regulation is more appropriate to limit low or negative 

pressure events nationally. 

Project area constraints and timing: 

Relationship to 

other RICP project

areas

Project

area 

document

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project

areas or what will be 

used in follow-on 

project areas

This project area 

depends on. . .

No other project areas. NA

Project areas that this 

project area builds on

Sur1 Survey of Large Drinking Water 

Utility Distribution Systems

Survey results may 

aid in refining the 

project area design of 

Pres1.

Project areas that 

build on this project

area

Pres3 Develop strategies to diagnose and 

monitor pressure fluctuations in 

water distribution systems

Survey results may 

provide a range of 

pressure management 

practices that are 

being implemented 

throughout the US. 

Relevance to the Agreement in Principle: 

This research and information collection project area will provide information relevant to needs 

identified in Section 4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and 

specifically the following items:

Exposure and Vulnerability to the Public

o Identify situations that may result in contamination of public health significance

o Assess the exposure to contaminants

Health Effects and Risk to the Public
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 57

o Monitor for situations that pose a public health concern

o Measure and track the national significance of the described situations

Effectiveness of mitigation measures

o Quantify the national significance of additional mitigation measures

This research and information collection project is specifically relevant to the Tier 1 priority 

topic areas of intrusion and cross connection/backflow. It also has relevance to the Tier 1 

priority topic areas of storage and main construction/repair. In addition, it will inform the 

distribution system optimization partnership identified in the AIP.

Key References:

Fleming, K.K., R.W. Gullick, J. P. Dugandzic, and M. W. LeChevallier. 2006. Susceptibility of 

Distribution Systems to Negative Pressure Transients. AWWARF, Denver, Colorado, 

USA.

Friedman, M., Radder, L., Harrison, S., Howie, D., Britton, M., Boyd, G., Wang, H., Gullick, R., 

LeChevallier, M., Wood, D. & Funk, J. 2004. Verification and Control of Pressure 

Transients and Intrusion in Distribution Systems. AWWARF, Denver, Colorado, USA.

Gullick, R.W., LeChevallier, M.W., Svindland, R.C. & Friedman, M.J. 2004. Occurrence of 

Transient Low and Negative Pressures in Distribution Systems. Journal of the American 

Water Works Association. 96 : 11. 52-66.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 58

Project Area Document Code: Pres2

Project Area Title: Characterize Propagation of Pressure Events through Water Distribution 

Systems to Improve Pressure Management Approaches

Goal(s): Evaluate the propagation of pressure events through the distribution system and 

compare field data with surge model results for the same events. Evaluate pressure propagation 

events at a number of systems and investigate the impact and cost of changes intended to 

mitigate the number and extent of such events. 

Rationale: While pressure management has been a long-term focus in distribution system 

management, there is a growing awareness that pressure and pressure fluctuations may be more 

important in distribution system management than previously thought. The practical use of surge 

models as management tools to aid identification and mitigation of pressure events will also be 

advanced in this work. The results of this work could lead to improved pressure management in 

distribution systems. 

Objectives: 

Promote further understanding of risk and mitigation factors associated with pressure 

events by generating field and modeled data on the occurrence and propagation of 

pressure events through water distribution systems.

Implement changes expected to eliminate or minimize pressure events (or the area of the 

distribution system impacted by pressure events) and generate field and modeled data on 

the occurrence and propagation of pressure events under the new conditions (e.g. hydrant, 

valve, pump or storage structural or operational changes, or main repair procedural or 

operational changes).

Evaluate the effectiveness of the changes in eliminating or minimizing pressure events.

Describe the use, application and limitations of surge models as tools in pressure 

management. 

Suggested Approach: 

This project area involves full-scale field monitoring and modeling studies. Research will be 

conducted at 4 - 5 utilities that represent a variety of distribution system attributes that are 

significant for pressure propagation such as systems with and without elevated storage, and with 

a variety of geography/geology, climate, size, and infrastructure age and types. These attributes 

will be determined in conjunction with the pressure information collection project area and by 

the project area examining the frequency of pressure events. 

- Each utility will be evaluated with field monitors and through the use of surge models.

Participating systems will be extensively instrumented with high-speed electronic 

pressure data loggers in areas susceptible to low or negative pressures or to wide pressure 

variations, as well as areas expected to be unaffected by pressure events. A number of 

monitors will be needed at each utility studied.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 59

- Monitoring at a utility will be conducted for at least one year in order to capture data 

from a variety of predictable and unpredictable causes of pressure events (such as fire 

flows).

- Field data will be compared with modeled data to verify and evaluate the usefulness of

surge models in terms of predict and aid management of pressure events. 

- Pressure data from district metered areas or mini-pressure districts should be considered 

if available.

- Analysis of field and model data will be used to determine the likely number of service 

connections and associated populations impacted by system events which lead to low or 

variable pressure (e.g. main breaks, power outages, fire flows, pump or control valve 

failures, tank or fire hydrant operations). 

- Once baseline conditions are understood, the design or operations of the system will be 

changed at some of the utilities in ways expected to reduce low pressure events. Field 

monitoring will be conducted following the change, and field data will be compared with 

model results following the change. This comparison will be used to evaluate the impact 

of the change, and the predictive value of the model in that situation.

- The cost of potential strategies to reduce the impacts of pressure events will be estimated 

in order to inform the value of enhanced pressure management. Data associated with 

distribution system operations will be compiled in parallel with pressure monitoring data 

to help illustrate and explain causes of each pressure event recorded, including main 

breaks, and the value of surge models to evaluate these pressure events. 

Results and Applications:

o Research in this project area will improve the understanding of risk factors that lead to 

pressure events, as well as propagation of events throughout distribution systems.

o Provide a better understanding for how to mitigate risk factors that lead to the occurrence 

or greater propagation of pressure events.

o Help to establish the value of surge models and pressure monitors in predicting areas 

susceptible to low or variable pressure events, and the use of these models in predicting 

the quantitative impact of mitigation measures. 

o Further characterize the relationship of pressure and pipe break incidence and the 

potential for contamination related to intrusion, cross connection or storage events.

o Investigate the relative balance of field data to modeled data so that models with 

adequately predictable results can be run with a minimum of field data, and situations 

where field data are absolutely needed will be better understood.

o Help to estimate the potential health risks associated with pressure events through 

improved understanding of the occurrence and propagation of the event through the 

distribution system.

o Inform improved pressure management approaches that could lead to improved 

distribution system water quality (due to reduced intrusion, backflow, and mobilization of 

contaminants from sediments or simply mobilization of the sediments), reduced 

quantities of non-revenue water (lost due to leakage), and reduced pipe breaks. 

o The beneficiaries of work in this project area will be utilities, environmental consultants, 

and environmental regulators with a focus on public health. Utilities are expected to gain 

practical insights and methods of evaluation regarding pressure management in their 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 60

distribution systems. Environmental consultants will benefit from this work because the 

general risk factors, evaluation, and management approaches developed in this work will 

be described to allow adaptation to the specific situation at other utilities. Environmental 

regulators are expected to be provided with an additional understanding of the number 

and propagation of pressure events in the distribution system, which can be used to better 

estimate public health risks and means to reduce those risks.

o Critical research and information collection needs addressed by this project area include:

- Percent of service area (or number of service connections) exposed to low pressures. 

- Number of service connections provided with stable and reliable operating pressures.

- Effect of increasing or variable water pressure on current infrastructure conditions in 

low pressure areas. 

- Further understanding of the relationship of pipe breaks and pressure conditions.

- More application of transient analysis (modeling) to full-scale distribution systems 

and comparison of predicted pressures to field pressure data.

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk? 

Research in this project area will improve the understanding of the number of distribution 

systems likely to be impacted by pressure events of different severity. This information will be 

useful to help estimate how many people may have been ―exposed‖ to low pressure events, and 

can be used together with information obtained from other projects to evaluate the magnitude of 

potential health risks associated with propagation of pressure events in distribution systems. The 

analysis is particularly relevant to intrusion, cross-connections and backflow, main repair, and 

storage topics. 

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction? 

Research in this project area will assess potential design and operational changes that could be 

used to eliminate or minimize pressure events. If implemented and effective, these changes 

could reduce potentially exposed populations. Also, the use and limitations of surge models as 

tools to aid pressure management objectives will be further established so that these models can 

be appropriately and effectively applied. 

What types of distribution system decisions could be supported by research in this project 

area? 

Design, engineering, and operational changes to distribution systems to improve pressure 

management could be informed by this project area. Limited research to date indicates that in 

many cases, relatively low-cost system changes may provide more stable distribution system 

pressures.

Project Area Constraints and Timing:

This project area could go forward almost immediately, but more benefit may be gained if it is 

implemented after the Large Systems Survey project area (Sur1) is substantially underway, or 

complete. The Large Systems Survey project area could provide relevant information on the 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 61

incidence of pressure events, which could focus efforts in this project area on cases that would be 

helpful in better management of pressure in distribution systems.

Targeted utilities are those that will allow a considerable amount of monitoring of their systems. 

Monitoring may prove somewhat disruptive and time consuming for utility employees and 

operations. Also, changes to operations or design and engineering of at least some of the utilities 

are also anticipated from research in this project area. Participating utilities will need to be 

willing to conduct this work with limited data and limited indications of the possible value of the 

outcomes.

Relationship to 

other RICP project

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be used in 

follow-on project

areas)

This project area

depends on. . .

No other project areas. NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project

None. NA

* Although the Hea2 project area is not dependent on this project area, there would be 

advantages to the same utilities participating in Hea2 as this project area since the field 

monitoring data generated under this project area would be useful for Hea2.

Relevance to the Agreement in Principle: 

Research conducted in this project area will provide information relevant to needs identified in 

Section 4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the 

following items:

Exposure and vulnerability of the public

o Identify situations that may result in contamination of public health 

significance.

o Characterize the contamination or conditions of public health significance 

that are introduced during those situations.

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

o Identify and implement remediation steps when contamination occurs.

o Quantify the national significance of additional mitigation measures.

This project area is highly relevant to the all of the Tier One priority topic areas: intrusion, cross 

connection/backflow, storage and main construction/repair.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 62

Key References:

Fleming, et al. 2006. Susceptibility of Distribution Systems to Negative Pressure Transients. 

Water Research Foundation and American Water. Denver, Colorado. 

Friedman, et al. 2004. Verification and Control of Pressure Transients and Intrusion in 

Distribution Systems. Water Research Foundation. Denver, Colorado.

Pearson, et al. 2005. Searching for N2: How does Pressure Reduction Reduce Burst 

Frequency? Presented at the 2005 Leakage Conference, Halifax, Nova Scotia, Canada. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 63

Project Area Document Code: Stor1 

Project Area Title: Best Practices for Minimizing Risks Associated with Storage Facilities.

Goal(s): Identify and characterize the best practices (BPs) for storage that can be used to 

mitigate potential contamination exposure concerns.

Help industry personnel to:

1. Better diagnose potential problems

2. Better understand the conditions that influence storage-related contamination events, 

3. Provide operators with best practices to reduce those risks

4. Provide information on the cost effectiveness of BPs

Rationale:

While storage-related industry standards exist, there are no national requirements to design or 

operate storage for effective mixing or regular cycling, or to monitor quality of stored water, or 

to regularly inspect or maintain storage. Storage facility configuration and operations vary 

widely, with decisions often driven by cost and fire flow needs. Due to large volumes of water in 

storage, and often limited monitoring of storage, undetected storage breaches and/or contaminant 

accumulations could potentially impose health risks that impact large areas of the system and 

associated consumer populations. Finished water storage facilities have been associated with a 

range of health risks that can include acute or fatal illness from exposure to waterborne 

pathogens, exposure to intermittent, chronic or persistent contamination that can result from 

breaches in tank integrity or internal reactions including nitrification, solids accumulation and 

mobilization, and release of pathogens from biofilms. In addition, aesthetics concerns (taste and 

odor) may be linked to perturbations in storage operations and associated water quality 

variations. 

Information collected in this project area will characterize BPs (design, operations, maintenance, 

inspection, and costs) for use by water utilities and support entities (states, inspectors, 

contractors, and researchers). Such BPs will help users understand, prevent, diagnose, and 

mitigate storage-related risks in distribution systems.

Objectives: 

Document the elements of effective storage best practices currently in use. Information 

related to implementation costs and other barriers to implementation will also be compiled.

Provide a single reference resource for evaluation of storage facility design, operations or 

maintenance-related risk factors, and risk mitigation options (including costs, and other 

potential implementation obstacles).

Determine key barriers to development, implementation and enforcement of storage related 

best practices, and provide case study examples of how these barriers have been overcome.

Develop strategies to quantify and benchmark the effectiveness of BPs and document case 

studies of successful programs.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 64

Suggested Approach: 

Develop a “State-of-Knowledge” Synthesis of Existing Knowledge and Information Relative to 

Storage — Provide a review and summary of key existing information and knowledge from 

literature, references, industry surveys, and existing storage guidance.

Collect and summarize available information on potential risk factors.

Collect and summarize evidence of links between storage-related contamination events, 

contaminant exposure, and waterborne disease outbreak and potential ―lessons learned‖. 

Compile relative costs of components of existing storage facility maintenance and 

operation programs (including diagnostic approaches, and mitigation measures).

Develop a glossary with illustrations, definitions, units of measure, etc., that can be used 

by the water industry to promote dialog and to more fully characterize storage physically 

and operationally, including relative costs of various structural and/or operational 

alternatives for storage.

Provide easy-to-use examples and case studies of storage risk-related regulations, 

standards, policies, and BPs (assimilated from States/EPA, storage manufacturers, 

fabricators, and modifiers, inspectors, utility operators/managers) and provide comparative 

costs and constraints for adoption of risk minimization or mitigation measures where 

needed.

Provide case study examples of how some systems have overcome key barriers to 

development, implementation and enforcement of storage related best practices.

Conduct follow-up as needed to gather, assemble and summarize key information and 

knowledge.

Assess the Effectiveness of Storage BPs –Incorporate key information useful to evaluate: (1) 

potential storage related risk and (2) storage risk mitigation. 

Describe BPs for industry personnel to better evaluate storage risks and risk mitigation, 

including costs and implementation obstacle comparisons.

Collect information about online monitoring of water quality parameters that have been 

obtained and how the information was used to improve storage operations and 

maintenance.

Conduct expert review of BPs.

Strategies Gauge Industry Application of BPs 

Develop strategies and approaches to assess industry application, usefulness and 

effectiveness of BPs and to assimilate data from applications of project results. 

Develop metrics and benchmarks of effectiveness of BPs.

Results and Applications: 

BPs identified through this project area will help utilities (and other industry professionals, such 

as storage operators, designers, regulators, inspectors, tank fabricators, modifiers, and trainers) to 

more effectively inspect, operate, and maintain storage to diagnose and mitigate storage-related 

contamination risks. BPs will also aid identification, selection, implementation and ongoing 

evaluation of performance and cost-effectiveness of risk mitigation alternatives. Information 

collected in this project area will document the status, costs and limitations of existing storage 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 65

design, operations and maintenance as well as ongoing cost and effectiveness of storage risk 

mitigation options. Information collected will facilitate more informative/effective storagerelated surveys, sampling, and data analysis, and may also be useful in sanitary surveys required 

under the SWTR and GWR. Under this project area utilities and others will verify and document 

storage-related contamination risks. The results will inform choices regarding the benefits, costs 

and constraints relative to various risk mitigation options. Use of BPs by utilities, contractors, 

and states could lessen DS health risks during the interim while other DS research and 

information collection project areas are ongoing and regulatory decisions are still pending. 

Decision Relevance: 

How is information collected in this project area likely to inform evaluation of the magnitude 

of health risk? 

Information developed through this project area will include descriptions of storage 

contamination incidents where exposure to contamination has occurred. These accounts illustrate 

severity and extent of outcomes that can occur where there are failures in storage design, 

operation and/or maintenance. Case studies from actual storage events can help inform industry 

personnel of potential risks relative to storage and may be helpful in selection of risk mitigation 

options. Storage risk evaluations and data regarding mitigation resulting from BPs have the 

potential to yield more representative and useful storage risk-related (performance and cost) 

information and knowledge than is currently available. 

How is information collected in this project area likely to inform opportunities for risk 

reduction?

The results will assist the industry in planning and evaluating storage structure design and 

performance relative to contamination risk, and in reducing potential risks. Cost and performance 

effectiveness of existing storage structures and operations (e.g. sampling, continuous monitors, 

inspections, cleaning, repairs) can be evaluated as well. Information collected in this project area 

will highlight the effects of a variety of typically-used facility configurations and will increase 

the understanding of various storage evaluation, monitoring and control techniques and 

approaches. Examples from existing studies of storage and storage modifications (including 

costs) can be used to evaluate potential effectiveness and obstacles to utilization of various risk 

mitigations. 

What types of distribution system decisions could be supported by information collected in this 

project area?

Enhanced knowledge and understanding gained through information collected in this project area 

will enable collection of more useful information in DS surveys, and can improve other DS 

research projects. Data from future utility use of BPs and subsequently improved surveys and 

research will provide better understanding of national status of storage and related risks and the 

obstacles to implementation of risk mitigation measures. Need, focus, and feasibility of new DS 

and storage-related guidance or regulations will be informed by information collected in this 

project area.

Project Area Constraints and Timing:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 66

This project area is not dependent on other project areas and can begin immediately and be 

completed within two years. The results of this project area may influence Sur4, under 

consideration by the DS RICP. See the table below for more details. 

Relationship to 

other RICP project

areas

Project

area 

document 

code

RICP project area document 

title (under consideration by the 

DS RICP)

Information needs 

(what will be used in 

follow-on project

areas)

This project area 

depends on. . .

No other project areas. NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project

area

Sur4 Targeted surveys to obtain 

information on state and local 

regulations, policies, 

manufacturing practices and 

guidelines for distribution systems

Stor1 results may aid 

in refining the project 

design of Sur4. Also, 

information on 

storage facilities 

practices from Stor1 

could be compared 

with information 

collected in Sur4.

Factors that might influence the timing of completion of this project area include:

Knowledge of industry personnel regarding storage-related design and operational 

concepts and BPs, existing research publications (literature), guidance, industry 

standards, and other resources;

Access to existing storage infrastructure-related state and federal database databases, 

existing industry surveys, and other unpublished resources and information;

Relevance to the Agreement in Principle:

This project area is directly relevant to the storage which is a Tier One priority area. This project 

area will contribute towards fulfillment of the AIP objective of optimizing distribution system 

integrity by assembling BPs associated with storage design, operation and maintenance and 

providing the tools needed for utilities and other responsible parties to evaluate existing storage 

risk and risk mitigation options. 

Key References: 

Clark, R.M., E.E. Geldreich, K.R. Fox, E.W. Rice, C.H. Johnson, J.A. Goodrich, J.A. Barnick, F. 

Abdesaken, J.E. Hill, and F.J. Angulo. 1996. A Waterborne Salmonella typhimurium

Outbreak in Gideon, Missouri: Results from a Field Investigation. International Journal 

of Environmental Health Research 6:187-193. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 67

USEPA. 2002. Finished Water Storage Facilities. Washington D.C.: USEPA. Distribution 

System Issue Paper. 

Walski, Thomas M., Donald V. Chase, Dragan A. Savic, Walter Grayman, Stephen Beckwith, 

Edmundo Koelle. 2003. Advanced Water Distribution Modeling and Management. 

Waterbury, CT: Haestad Press. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 68

Project Area Document Code: Sur1 

Project Area Title: Survey of Large Drinking Water Utility Distribution Systems

Goal(s): To identify characteristics of drinking water distribution and storage systems that serve 

> 50,000 people.

Rationale: 

This information collection project area will evaluate the current status of distribution system 

conditions and practices. It will provide data on the type, condition and vulnerabilities of 

drinking water and storage systems that serve >50,000 people; inform potential risk implications; 

and characterize the use of risk management strategies. This project area could also identify

opportunities and impediments to mitigate and manage risks pertinent to systems that serve 

>50,000 people. 

Objectives: 

Identify drinking water distribution and storage systems at public water supplies to target 

for surveys conducted in this project area.

Identify key variables related to the type, quantity, and condition of distribution system 

infrastructure elements that may contribute to increased public health risks in distribution 

systems.

Assess the prevalence and use of various risk management strategies on distribution 

systems. 

Provide baseline information on distribution system conditions, operations, and 

management practices.

Identify additional research and information collection needs.

Identify a subset of utilities with varied infrastructures, distribution system conditions, 

and/or water quality conditions to assist in construction of a representative sample for 

subsequent distribution system related research and information collection projects.

Suggested Approach:

This project area will proceed in two sequential phases: Phase 1 - Review and analyze available 

data and information, and Phase 2 - Survey targeted utilities based on findings in Phase 1. 

Phase 1 – The first phase of this project area is a comprehensive review of literature and 

available data relevant to water distribution systems. Examples of data sources include the 

Community Water System Survey (CWSS), the Water Utility Distribution Surveys (WaterStats), 

the 2007 Drinking Water Infrastructure Needs Survey (DWINS), the 2006 Water Research 

Foundation Study – Susceptibility of Distribution Systems to Negative Pressure Transients. 

Implementation data from sanitary surveys for drinking water regulations (e.g., Surface Water 

Treatment Rule, Total Coliform Rule, etc.) may also provide information. Key variables will be 

identified and the data sources will be mined to compile, synthesize, and evaluate the available 

data.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 69

Information collected will be analyzed to determine characteristics of drinking water distribution 

and storage systems, and identify information gaps.

Phase 2 - Based on the results from Phase 1, survey instruments will be developed targeted at 

utilities that serve populations > 50,000. The survey should be developed with a statistical 

design to yield meaningful results. All key terms used in the surveys will be carefully and 

explicitly defined in order to ensure there is no confusion between the survey respondents and 

those using the results. To facilitate responses, it is recommended the surveys be organized into 

sub-surveys that correspond to the expertise of individual utility departments such as: 

Operations/Maintenance, 

Design/Engineering/Infrastructure, and 

Water Quality/Monitoring. 

The below list includes examples of types of information that may be available, compiled, and 

analyzed in Phase 1. The survey designs should include measures to anonymize security-related 

survey data to avoid security concerns. Survey designers will organize questions into groups 

based on the expertise of individual departments of utilities. This will improve efficiency and 

accuracy of responses by ensuring that the most qualified people answer each question and do 

not waste effort on questions which are not related to their area of expertise.

 

Phase 1 

Operations / Maintenance Type and frequency of rehabilitation activities performed 

per year, 

Number of service connections with stable/reliable 

operating pressure, 

Percent of water loss through pipe leaks, 

Number of emergency main breaks per mile per year, 

Storage disinfection practices (type, usage, frequency, 

dosage, and application point),

Determination of representative system‘s operation / 

configuration (storage tanks, detention times, dead-end 

mains). 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 70

Phase 1 

Design / Engineering / Infrastructure Frequency of power failures that affect pump operations, 

Miles of new mains constructed and old mains with 

planned replacement per year, 

Frequency of main breaks by pipe diameter and pipe 

material

Frequency of construction on distribution/transmission 

mains, 

Number of pressure zones and storage facilities per zone, 

Number and types of storage facilities (e.g. cylinder, 

spheroid, standpipe, pedestal, in-ground; above-ground 

elevation; populations served),

Location of storage relative to supply source, and 

volume of storage relative to piping.

Each sub-survey will be designed in an easy-to-use electronic format to minimize the amount of 

effort that systems must exert in order to complete the surveys (e.g. yes/no, multiple choice, and 

simple short-answer questions). The list below includes examples of the types of information 

that may be collected in the surveys in Phase 2. The actual information to be collected will be 

based on information gaps identified in Phase 1.

Phase 2 

Operations / Maintenance Status of implementation of cross-connection control 

programs, 

Number of direct cross-connections and cross connections 

with health risks, 

Frequency of temporary or illegal connections, 

Number and size of systems without floating storage 

tanks, 

Fraction of flooded underground vaults, height of water 

above submerged meters and air vacuum valves, 

Percentage of emergency main repairs that required 

depressurization, 

Practices for removal of solids accumulated in storage 

(amount removed, percent removed of total solids, and 

frequency of removal).
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 71

Phase 2 

Design / Engineering / Infrastructure Presence and type of surge suppression, 

Number of pumps on universal power supply, 

Number of service connections with backflow prevention 

devices, 

Percentage of piping submerged beneath water table (and 

depth), 

Number air-vacuum valves and meters installed in 

underground vaults, meter orifice sizes, 

Existence and use of calibrated hydraulic or water quality 

models for the distribution system, 

Number and types of storage facilities with specific types 

of internal coating. 

Parameter Monitoring Stored water volume monitoring (e.g. levels, sensors, 

SCADA) frequency, type, content, cost, reporting, rationales, 

data use.

Current and planned installation of online water quality 

monitoring instruments

Results and Applications:

The survey results will be used to identify distribution system characteristics including the 

prevalence of specific infrastructure components, perceptions of infrastructure condition in large 

systems, and the extent to which specific risk management practices are employed. The survey 

results are expected to enable a comparison of engineering, operations, and maintenance 

practices and effectiveness. The survey results are expected to help explain and estimate the 

prevalence of risk factors and the degree of use of specific risk management strategies, as well as 

barriers to implementation. 

Specifically, the data from these surveys are intended to help in better understanding: 

Number of high-hazard cross-connections and degree of implementation of various crossconnection control program elements,

Potential for occurrence of low pressures or highly variable pressures,

Potential for intrusion through leaks and other orifices,

Degree of implementation of surge control strategies, 

Types of storage facilities and the degree to which storage facilities are 

configured/operated for sufficient turnover, breach avoidance, etc.

Frequency and characteristics of planned and emergency main installations and repairs.

The results of these surveys may provide a baseline for follow-up research or information 

collection projects that inform the magnitude of public health risks and/or the use and 

effectiveness of risk management strategies. The survey results are expected to provide baseline 

information on distribution system conditions, operations, and management practices. These 

surveys are expected to provide information on practices already in use to help utilities make 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 72

informed decisions about distribution system operations, maintenance, rehabilitation, or 

replacement. The information can provide a reference point of current conditions from which the 

effectiveness of potential actions such as guidance, regulations, or policies that arise from the 

RICP process may be assessed. 

The results of these surveys may also identify a pool of utilities with varied infrastructures, 

distribution system conditions, and/or water quality conditions. Such recognition will assist in 

the identification of a representative sample for subsequent distribution system related research 

and information collection projects. Screening of survey participants will identify potential 

candidate utilities for follow-up field research or additional information collection projects. 

Decision Relevance:

How is information collected in this project area likely to inform evaluation of the magnitude 

of public health risk? 

Information collected in his project area will provide a perspective of the quantity, type and

condition of existing distribution system infrastructure. This information combined with 

information from RisM1 and Hea2 is expected to better estimate the frequency of events which 

carry with them increases in public health risk.

How is information collected in this project area likely to inform opportunities for mitigation 

and risk reduction?

Information collected in this project area will provide an initial understanding of the degree to 

which various risk management practices are used. This information can help the drinking water 

community (PWSs, States, EPA) determine whether and what type of policies might be 

implemented to reduce potential risks.

What types of distribution system decisions could be supported by information collected in this 

project area?

Information from this project area could be used to inform national policy on distribution system 

issues. Possible policy outcomes that could be supported may include guidance, regulation, or 

other options.

Project Area Constraints and Timing:

The completion of this information collection project area may influence several other project 

areas under consideration by the DS RICP. In most cases, the baseline data from Phase 1 will 

improve design of follow-on projects or be used to identify appropriate subpopulations for indepth sampling, field work, or modeling. See the table below for information on the project 

areas that build on Sur1. 

Relationship to 

other RICP project

areas

Project

area 

document

code

RICP project area document 

title (Projects under 

consideration by DS RICP)

Information needs 

(what will be used in 

follow-on project

areas)
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 73

This project area

depends on. . .

No other project areas. NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project

area

Con1 Characterization of pathogens and 

chemicals in soil and water 

adjacent to distribution system 

infrastructure 

Survey results may 

aid in refining the 

project designs of 

Con1.

Con2 Distribution system contamination 

associated with repair of water 

main leaks and breaks

Survey results may 

aid in refining the 

project designs of 

Con2.

Con4 Estimation of contaminated water 

volumes and contaminant 

concentrations introduced into DSs 

from cross-connection 

contamination events based on 

model predictions and field and 

pilot-scale experiments

Survey results may 

aid in refining the 

project designs of 

Con4.

Con6 Understanding the growth 

potential within distribution 

systems of indigenous bacterial 

pathogens (Legionella and 

Mycobacterium)

Survey results may 

aid in refining the 

project designs of 

Con6.

Con7 Understanding the survival of 

enteric pathogens and ammoniaoxidizing organisms under 

different DS conditions and 

disinfection practices

Survey results may 

aid in refining the 

project designs of 

Con7.

Con8 Baseline data on episodic 

release/mobilization of chemical 

contaminants from biofilms and 

accumulated solids in distribution 

and storage systems

Survey results may 

help target sample 

locations.

Pres1 Survey of Distribution System 

Pressure Management Practices

Survey results may 

provide information 

on attributes leading 

to low or negative 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 74

pressures.

Pres3 Develop strategies to diagnose and 

monitor pressure fluctuations in 

water distribution systems

Survey results may 

provide information 

regarding pressure 

management 

strategies.

Pres4 Toolkit for pressure management Survey results may 

provide insightful 

information that may 

aid in refining the

design of Pres4.

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Survey results could 

be used to refine the 

menu of risk 

management 

strategies.

Sur4 Targeted surveys to obtain 

information on state and local 

regulations, policies, 

manufacturing practices and 

guidelines for distribution systems

Survey results will 

identify data gaps. 

Sur4 design may help 

to fill data gaps.

Factors that might influence the timing of completion of this project area include:

Familiarity of investigators with distribution system concepts and survey design and data 

analysis

Complexity and scope of survey design and survey data analysis

Survey response/data quality review

Ability of surveyors to solicit or require sufficient responses

Willingness of recipients to participate

o Issues associated with providing potentially sensitive information (data 

confidentiality)

o Lack of information in utility files

o Lack of utility resources (personnel-time, computer expertise) to complete survey 

responses

Participation by enough (and sufficiently diverse) recipients to provide meaningful results

Communication/approvals for survey data use in follow-on project areas

Relevance to the Agreement in Principle:

The AIP specifically recommends in section 4.1.e that the RICP explore several mechanisms for 

collecting and analyzing data, including surveys implemented through research project areas or 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 75

by interested organizations such as EPA, AWWA, AMWA, NRWA, WaterRF, and others. The 

completion of this project area is relevant to all seven priority topic areas. 

Key References:

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 76

Project Area Document Code: Sur4

Project Area Title: Targeted Surveys to Obtain Information on State and Local Regulations, 

Policies, Manufacturing Practices and Guidelines for Distribution Systems

Goal: To evaluate extent to which distribution system risk management and mitigation practices

are implemented by states or through manufacturing, installation, or inspection programs.

Rationale: 

This information collection project area will provide data on state and local regulations, industry 

standards/guidelines, and manufacturing and inspections practices that may affect potential 

health risks associated with distributions systems. 

Objectives: 

Evaluate inspection practices and results (e.g., plumbing/backflow prevention devices, 

main installations, storage).

Evaluate certification requirements for inspecting distribution system components 

(storage tanks, backflow prevention devices, new construction, main repair, etc).

Evaluate fire department practices for operating and maintaining hydrants and level of 

coordination with water utilities.

Evaluate the extent to which backflow prevention device are used and failure frequency 

(manufacturers).

Evaluate trends in storage tank types, configurations, construction materials, and ages 

(tank fabricators and designers). 

Estimate the frequency of state and/or local sewer leak and breaks and repair strategies 

that might impact water distribution systems (wastewater utilities and municipalities).

Compare requirements in state laws, regulations, policies, and industry 

standards/guidelines concerning distribution systems.

Suggested Approach:

This project area will proceed in two sequential phases: Phase 1 - Review and analyze available, 

and Phase 2 - Survey targeted utilities based on findings in Phase 1.

Phase 1- The first phase of this project area is a comprehensive review of literature and available 

data relevant to water distribution systems including: state laws, regulations, and policies. 

Possible sources of data include the primacy application packages which EPA requires from 

States. Key variables will be identified and these data sources will be mined to compile, 

synthesize, and evaluate the available data quality. The information collected will be analyzed to

identify information gaps.

Phase 2 – Based on the results from Phase 1, survey instruments will be developed to obtain 

specific information from inspectors, manufacturers, fire departments, and wastewater treatment 

utilities, and consultants. Suitable entities to target for the surveys will be determined by 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 77

consulting with States and industry consultants. To the extent practicable, electronic surveys 

will be used. The surveys will be designed and administered to facilitate the compilation and 

assessment of needed data by survey participants. All terms used in the surveys will be carefully 

and explicitly defined in order to ensure there is no confusion between the survey respondents 

and those using the results. Examples of information that could be obtained include:

Source of Information Examples of Data that May be Obtained Examples of Data 

Sources

Inspectors, Certifiers 

of Inspector 

Inspector certification criteria

Extent of cross connections and backflow 

prevention devices found at service 

connections and inspection frequency

Frequency and scope of inspections of 

distribution systems

Internal and external status of 

distribution system infrastructure

Guidance 

manuals

Fire Departments Hydrant operation practices, policies, and 

flow requirements.

State and local 

codes and 

insurance 

requirements

Backflow Prevention 

Device Manufacturers

Number of devices produced by type

Historic sales records

Failure rate and pressure ratings of 

backflow prevention devices

Device 

certification 

standards

Storage Tank 

Manufacturers, 

Inspectors and 

Cleaners

Number and configuration of storage 

facilities produced per year

Materials used in storage tanks and their 

frequency

Device/materials 

certification 

Industry 

standards

States Laws, regulations, and policies 

concerning 

o Distribution system 

design/engineering (function, 

capacity, etc.)

o Cross connection control programs

o Distribution system inspections

o Sanitary practices

o Storage facilities

o Operations

o Operator training

Training on regulations, policies, 

guidances and best practices

US EPA records

State websites 

and guidance 

documents

Results and Applications:

The project area results will be used to help assess the prevalence of specific infrastructure 

components and the extent to which specific risk management and mitigation practices are 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 78

employed including design/engineering, inspection, operations, and maintenance. The survey 

results are expected to help explain and estimate the prevalence of risk factors, and the degree of 

use of specific risk management strategies, as well as help identify barriers to implementation.

Specifically, the data from these surveys may help in better understanding: 

Number of high-hazard cross-connections and degree of implementation of various crossconnection control program elements,

Practices associated with cross-connection control program,

Protocols for preventing and detecting health hazards associated with sewage intrusion 

into distribution systems including inspection programs, responsible parties, and 

communication strategies,

Frequency of activities which can result in low pressure events that can cause intrusions, 

Types of storage facilities and the chemical and use of storage risk mitigation options. 

The degree to which training is used to improve utility personnel understanding of State 

and Federal regulations, policies, guidance, and best practices.

The results of these surveys may provide a baseline for follow-up research or information 

collection projects that inform the magnitude of public health risks or the effectiveness or risk 

management and mitigation strategies. These surveys are expected to provide information on 

practices already in use to help utilities make informed decisions about distribution system 

operations, maintenance, rehabilitation, or replacement. This information can provide a 

reference point of current conditions from which the effectiveness of potential actions such as 

guidance, regulations, or policies that arise from the RICP process may be assessed. 

Decision Relevance: The survey results will help characterize the prevalence of risk factors.

They will also help to understand the extent that best practices are currently implemented.

How is information collected in this project area likely to inform evaluation of the magnitude 

of public health risk? 

Information collected in this project area will provide a description of the quantity, types, and 

conditions of existing distribution infrastructure. This information is expected to better estimate 

the frequency of events which carry with them increases in public health risk. 

How is information collected in this project area likely to inform opportunities for mitigation 

and risk reduction?

Information collected in this project area will provide an initial understanding of the degree to 

which various risk management practices are used. These surveys will also inform the extent of 

risk-related activities and the level of surveillance. This information can help the water supply 

community (PWSs, States, EPA) determine whether and what type of policies would be prudent 

to reduce risks.

What types of distribution system decisions could be supported by information collected in this 

project area?
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 79

Information from these projects could be used to inform national policies on distribution system 

issues. Possible policy outcomes that could be supported may include guidance, regulation, or 

other options.

Project Area Constraints and Timing:

This project area does not strictly depend on the completion of other project areas, but 

completion of CC1 and Stor1 might provide useful information. These surveys may yield results 

which need to be verified or expanded upon by the inspector surveys. 

Relationship to 

other RICP project

areas

Project

area 

document

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas

This project area

depends on. . .

No other project areas. N/A

Project areas that this 

project area builds on

CC1 Best Practices to Minimize Risks 

Associated with Cross 

Connections and Backflow

Information on cross 

connection and 

backflow best 

practices that systems 

use from CC1 will 

inform survey 

questions. 

Stor1 Best Practices for Minimizing 

Risks Associated with Storage 

Facilities.

Information on 

storage best practices 

that systems use from 

Stor1 will inform 

survey questions.

Project areas that 

build on this project

area

None. N/A

Factors that might influence the timing of this project area include:

Agreement on key terms to be used in the survey instruments

Completion of pre-survey alternative exploration and analysis

Development of multiple, different, concise survey requests for a variety of non-utility 

entity groups

Assembly/selection of appropriate samples of, and contacts for, non-utility entities

Cooperation from certifying agencies and other non-utility entities

Willingness for entities to share information

Completion of alternative resource studies, such as the 2011 Drinking Water 

Infrastructure Needs Survey
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 80

Relevance to the Agreement in Principle:

The AIP specifically recommends in section 4.1.e that the RICP explore several mechanisms for 

collecting and analyzing data, including surveys implemented through research projects or by 

interested organizations such as EPA, AWWA, AMWA, NRWA, WaterRF, and others. The 

completion of this project area is relevant to all seven priority topic areas. 

Key References:

ANSI/AWWA (2004). Standard G200-04, Distribution Systems Operation and Management, 

Denver, CO.

TCRDSAC Agreement in Principle (2008).

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac_2008-

09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 81

Appendix A – Steering Committee Members

Language concerning the Steering Committee from the AIP:

―The RICP will be directed by a Steering Committee (SC)comprised of three members from 

EPA, three members from water utilities, plus three members, one each representing public 

health (e.g. CDC), environmental advocate, and state regulator perspectives. The Committee 

recommends that one or more members of the SC bring a small system perspective.‖

RICP Steering Committee members as of April 2010:

EPA

Nick Ashbolt

U.S. Environmental Protection Agency

26 West Martin Luther King Drive

Mail Code: 564

Cincinnati, OH 45268

ashbolt.nick@epa.gov

Audrey Levine

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W.

Mail Code: 8101R

Washington, DC 20460

levine.audrey@epa.gov

Stig Regli

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W.

Mail Code: 4607M

Washington, DC 20460

regli.stig@epa.gov

Water Utilities

Gary Burlingame

Philadelphia Water Department

1500 E. Hunting Park Avenue

Philadelphia, PA 19124 

gary.burlingame@phila.gov

Stephen Estes-Smargiassi

Director of Planning

Massachusetts Water Resources Authority

Charlestown Navy Yard

100 First Ave, Building 39

Boston, MA 02129

Stephen.Estes-Smargiassi@mwra.state.ma.us
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 82

Mark LeChevallier

Director, Innovation and Environmental Stewardship

American Water

1025 Laurel Oak Rd

P.O. Box 1770

Voorhees, NJ 08043

Mark.LeChevallier@amwater.com

Public Health Perspective

Joan Brunkard

Division of Parasitic Diseases

Centers for Disease Control and Prevention

4770 Buford Hwy NE Mailstop F22

Atlanta, GA 30341

jbrunkard@cdc.gov

Environmental Advocate Perspective

David M. Gute

Associate Professor of Civil & Environmental Engineering

Tufts University

113 Anderson Hall

Medford, MA 02155

david.gute@tufts.edu

State Perspective

Cindy Forbes*

Chief, Southern California Section Drinking Water Field Operations Branch

California Department of Public Health

265 W. Bullard Ave., Suite 101

Fresno, CA 93704

Email: cindy.forbes@cdph.ca.gov 

*also represents the small systems perspective

April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 84

Appendix B – Project Area Titles and Codes

Code Project Area Title

CC1 Best Practices to Minimize Risks Associated with 

Cross Connections and Backflow

CC2 Assess Distribution Systems Characteristics that May 

Lead to Cross Connection and Backflow Problems and 

Potential Health Risks

Con1 Characterization of Pathogens and Chemicals in Soil 

and Water Adjacent to Distribution System 

Infrastructure 

Con2 Sampling to Determine Potential Distribution System 

Contamination Associated with Repair of Water Main 

Leaks and Breaks

Con3 Contaminant Entry from Breaches in Storage 

Facilities

Con4 Estimation of Contaminated Water Volumes and 

Contaminant Concentrations Introduced into 

Distribution Systems Due to Backflow Events from 

Unprotected Cross-Connections Based on Model 

Predictions and Field and Pilot-Scale Experiments

Con5 Computation of Intrusion Volumes through Orifices

Con6 Understanding the Growth Potential within 

Distribution Systems of Indigenous Bacterial 

Pathogens (Legionella and Mycobacterium)

Con7 Understanding the Survival of Enteric Pathogens and 

Ammonia-Oxidizing Organisms under Different 

Distribution System Conditions and Disinfection 

Practices

Con8 Baseline Data on Episodic Release/Mobilization of 

Chemical Contaminants from Biofilms and 

Accumulated Solids in Distribution and Storage 

Systems
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 85

Hea1 Quantitative Microbial Risk Assessment (QMRA) to 

Evaluate Exposure to Pathogens through Drinking 

Water Distribution Systems 

Hea2 Epidemiological Studies of Health Effects Associated 

with Low or Negative Pressure Events in Distribution 

Systems 

Hea3 Response Teams to Prepare Case Studies on Adverse 

Public Health Effects from Distribution System Events 

Hea4 Molecular Epidemiology of Distribution System 

Associated Pathogens

Mon1 Collection of Distribution System and Storage 

Monitoring Data for Nitrite, Nitrate, and Related 

Physical and Chemical Constituents

Pres1 Survey of Distribution System Pressure Management 

Practices

Pres2 Characterize Propagation of Pressure Events through 

Water Distribution Systems to Improve Pressure 

Management Approaches

Pres3 Develop Strategies to Diagnose and Monitor Pressure 

Fluctuations in Water Distribution Systems

Pres4 Toolkit for Pressure Management

RisM1 Decision Support for Managing Potential Distribution 

Systems Public Health Risks from Potential 

Contamination Events and Daily Operations

RisM2 Improving Hydraulic Models for Distribution Systems

RisM4 Tracking How Water Quality Modifications and 

Distribution System O&M Impact Stability and 

Release of Chemical Contaminants from 

Accumulated Solids and Biofilms in Distribution and 

Storage Systems
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 86

RisM5 Develop Next Generation Models for Informing 

Distribution System and Storage Water Quality 

Including Episodic Release/Mobilization of Chemical 

Contaminants from Accumulated Solids and Biofilm

Stor1 Best Practices for Minimizing Risks Associated with 

Storage Facilities

Stor2 Assess Distribution Systems Characteristics that May 

Lead to Storage Related Problems and Potential 

Health Risks

Sur1 Survey of Large Drinking Water Utility Distribution 

Systems

Sur2 Survey of Small and Medium Drinking Water Utility 

Distribution Systems

Sur3 Field Survey to Collect Information on Risk 

Management Practices Employed in Water 

Distribution Systems

Sur4 Targeted Surveys to Obtain Information on State and 

Local Regulations, Policies, Manufacturing Practices 

and Guidelines for Distribution Systems
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 87

Appendix C – Lower Priority Project Area Documents

Note that the Steering Committee focused their review and comments mainly on the high priority 

project area documents. Therefore, the project area documents in this appendix did not get the 

same level of review as the ten high priority project area documents. They are listed here in 

alphabetical order.

Project Area Document Code: CC2

Project Area Title: Assess Distribution Systems Characteristics that May Lead to Cross 

Connection and Backflow Problems and Potential Health Risks

Goal(s): To better understand the potential public health risks and the magnitude of the health 

risks related to cross connection and backflow contamination events.

Rationale: 

The presence of an unprotected cross-connection represents a potential distribution system (DS) 

vulnerability, through which backflow can occur. This situation can provide a conduit for 

chemical, microbial and/or radiological contaminants to enter a DS, particularly when the 

pressure in the potable source is lower than the pressure in the contaminant source. These lower 

pressures result from common events in DS, including valve and pump operations, power 

outages, main breaks, high demand, flushing, and even a rise in pressures from the contaminant 

source (e.g., a boiler). 

Contamination of the distribution system through unprotected cross-connections has resulted in 

documented public health impacts. US EPA has compiled information describing 469 backflow 

incidents which occurred between 1971 and 2006. In 164 of these events (35 percent), 

contaminants reached the distribution system serving the public. Contaminated water was 

contained within the premise plumbing for 185 events (39 percent). The contaminant entry point 

to the distribution system was undocumented or undetermined for the remaining 120 events.

The extent and magnitude of health risks associated with backflows is site-specific and depends 

on the source of contamination (sewage, industrial discharges, etc.), the location of the backflow, 

the distribution system characteristics, and the effectiveness of prevention and inspection 

programs. The durations of consumers‘ exposures to the contaminants is highly variable and 

depends on water use practices, system hydraulics, the nature of the cross connection, an 

understanding by the system that a risk may exist and the ability of the system to find and 

remedy the problem. Given that limited monitoring occurs in DS, these events often escape 

detection. Frequently events are detected through customer complaints rather than routine 

monitoring. Even then, the event will often have passed by the time the utility investigates. As a 

result, undetected and uncorrected cross connections may result in recurring backflow 

occurrence, imposing unquantifiable health risks. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 88

Research in this project area will examine distribution system characteristics that may contribute 

to backflow through cross connections. In particular, the research will examine the potential 

frequency at which the convergence of three distribution system characteristics exist that must 

simultaneously occur for backflow contamination from cross connections to result. The three

factors that must occur are the presence of a contaminant in a contaminant source, the presence 

of an unprotected cross connection, and the failure of a barrier to prevent contamination (in this 

case a pressure differential between the contamination source and the potable water supply). To 

estimate the potential public health impacts from cross connections and backflow research in this 

project area will examine data on these characteristics from other RICP project areas, as well as 

existing data.

Objectives:

1. Collect and synthesize information that may inform the frequency and magnitude of 

potential health risks related to cross connection and backflow contamination events 

2. Conduct additional targeted literature searches, if needed, that may provide information 

on the frequency and magnitude of potential health risks related to cross connection and 

backflow contamination events 

Suggested Approach:

This project area has two suggested approaches to obtain information needed to assess 

distribution system characteristics that may lead to cross connection and backflow problems 

and potential health risks

1. Collect and synthesize information from completed RICP project areas related to cross 

connection and backflow and that may inform the magnitude of potential health risks related to 

cross connection and backflow contamination events. This step includes determination of the 

extent to which barriers to contamination (e.g., sufficient pressure levels) exist and the causes 

and frequencies of barrier failure.

- Presence of a pathway for contamination

- Number of direct cross-connections and cross connections with health risks (Sur1)

- Frequency of temporary or illegal connections (Sur1)

- Number of service connections with backflow prevention devices (Sur1)

- Failure of a barrier

- Number of service connections with stable/reliable operating pressure (Sur1)

- Number of pressure zones (Sur1)

- Frequency of power failures that affect pump operations (Sur1)

- Frequency of main breaks by pipe diameter and pipe material (Sur1)

- Percentage of emergency main repairs that required depressurization (Sur1)

- Model magnitude and duration of pressure events (Con4)

- Determination of the extent of a distribution system affected by a pressure event (Pres2)

- Presence of a contaminant

- Identification of contaminants of concern (Con4)

- Estimated contaminated water volumes introduced to the distribution system from cross 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 89

connections and backflow events (Con4)

- Estimated contaminant concentrations from cross connection and backflow contamination 

sources (Con4)

2. If needed, conduct additional targeted literature searches for existing information that may 

provide information on the frequency and magnitude of potential health risks related to cross 

connection and backflow contamination events. These searches would fill in gaps in the areas of 

knowledge that are listed in section 1, but were not able to be obtained from RICP completed 

project areas. Evaluate resulting information to estimate the frequency and magnitude of

potential public health risks resulting from cross connections.

Results and Applications:

The results of research in this project area will inform the magnitude of potential public health 

risks associated with distribution system contamination from backflow through cross 

connections. Specifically, the research will assess information from other RICP project areas 

and information from research and information collection efforts outside of the RICP, if needed,

to determine the frequency at which various distribution system characteristics occur which 

contribute to cross connections and backflow. These pieces of information are essential inputs to 

a calculation of risk from cross connections and backflow.

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk? 

Research in this project area will evaluate information on the occurrence of distribution system 

characteristics that lead to contamination from cross connections and backflow. The information 

evaluated under this project area includes information from other RICP project areas and may 

also include research and information generated outside of the RICP. The characteristics 

evaluated are those that lead to contamination of distribution systems from cross connections and 

backflow, and the resultant public health risks from the contamination.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

Research in this project area will help identify the prevalence, frequency and magnitude of 

problems related to cross connection and backflow. 

What types of distribution system decisions could be supported by research in this project 

area?

Research in this project area will support future decisions regarding the need for regulation, 

guidance, policy statements, or other actions be taken to control potential public health risks 

from cross connections and backflow. 

Project Area Constraints and Timing:

The focus of research in this project area is to analyze information generated through other 

research and information collection efforts, including some conducted as part of the RICP. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 90

Therefore, research in this project area cannot be completed until the information generated from 

those other RICP project areas is available. These project areas are listed in the table below.

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by 

the DS RICP)

Information needs 

(what will be 

learned from the 

predecessor project

areas or what will 

be used in followon project areas)

This project area 

depends on. . .

Sur1 Survey of Large Drinking 

Water Utility Distribution 

Systems

The presence of 

distribution system 

characteristics that 

contribute to 

contamination from 

cross connections 

and backflow.

Con4 Estimated contaminated water 

volumes and contaminant 

concentrations introduced into 

DSs due to backflow events 

from unprotected crossconnections based on model 

predictions and field and pilotscale experiments

The estimated 

concentrations of 

contaminants 

entering the 

distribution system 

during a backflow 

event, and the 

volumes of 

contaminated water.

Pres2 Characterize Propagation of 

Pressure Events through Water 

Distribution Systems to 

Improve Pressure Management 

Approaches

The estimated 

occurrence of 

pressure events that 

enable 

contamination from 

cross connections 

and backflow to 

occur.

Project areas that 

this project area 

builds on

None. NA

Project areas that 

build on this project 

area

CC1 Best practices to minimize risks 

associated with cross 

connections and backflow

The problem 

identification 

assessment from 

CC2 may be used to 

evaluate the 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 91

effectiveness of 

existing best 

practices.

Pres1 Survey of Distribution System 

Pressure Management Practices

Information on 

barriers to cross 

connection and 

backflow 

contamination.

RisM1 Decision support for managing 

potential distribution systems 

public health risks from 

potential contamination events 

and daily operations

Information on 

barriers to cross 

connection and 

backflow 

contamination.

Factors that might influence the timing of completion of research in this project area include:

Completion of research in preceding RICP project areas listed in the table above

Quality and completeness of information from the preceding project areas

Availability of supplemental information from sources other than RICP project areas

Relevance to the Agreement in Principle:

Research in this project area is relevant to the cross-connection which is a Tier One priority area. 

Research in this project area focuses on the analysis of information on cross connection and 

backflow contamination to inform local and national risk management decisions by the drinking 

water community. Support for these risk management decisions through the RICP was a 

recommendation in the Agreement in Principle.

Key References:

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf

EPA. (2001) Potential Contamination Due to Cross-Connections and Backflow and the 

Associated Health Risks. Distribution System White Paper. 

www.epa.gov/safewater/disinfection/tcr/pdfs/issuepaper_tcr_crossconnectionbackflow.pdf.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 92

Project Area Document Code: Con1

Project Area Title: Characterization of Pathogens and Chemicals in Soil and Water Adjacent to 

Distribution System Infrastructure

Goal: To identify types of contaminants and their concentrations in soil and water adjacent to 

distribution system infrastructure relevant to intrusion events and main 

installation/repair/rehabilitation procedures

Rationale: External contaminants that are found in the vicinity of the distribution system can 

find their way into the system if there is a breach in physical integrity. The characterization of 

microbial indicators of contamination and of some viruses in the soil and water adjacent to 

drinking water mains was the topic of two studies (Karim et al., 2003; Besner et al., 2008). This 

is a limited set of data, characterized by conflicting results between the two studies regarding the 

frequency of detection for both the indicators of fecal contamination and viruses. In addition, 

only one study has looked at the microbial characterization of the water found in flooded airvalve vaults, another potentially major intrusion pathway into a distribution system (Besner et 

al., 2009). The primary purpose of this study is to provide more data regarding the presence of 

pathogenic microorganisms (not only indicators) and chemical contaminants in the vicinity of 

drinking water mains, to allow for a more thorough exposure evaluation associated with intrusion 

events due to low/negative pressure events and contamination from main 

installation/repair/rehabilitation procedures. 

Objectives: 

Develop plans for representative sampling of contamination sources (soil/water) adjacent 

to possible entry pathways (such as pipe leaks, flooded air-vacuum valves) from a 

number of case study systems targeting a variety of system characteristics.

Characterize and quantify contaminants of public health concern in soil and groundwater 

around drinking water mains, and in flooded vaults in several U.S. distribution systems 

with a variety of system characteristics

o Determine types and concentrations of microbial indicators and pathogenic 

microorganisms representing a range of distribution system characteristics (such 

as Cryptosporidium, Giardia, Norovirus, E. coli O157:H7); determine viability of 

pathogens.

o Identify and analyze organic and inorganic contaminants (regulated and 

emerging) representing a range of distribution system characteristics.

o Considering the different types of entry pathways (pipe leaks, flooded air-vacuum 

valves, etc.) and circumstances studied, identify relationships between 

contaminant presence, concentrations and system characteristics (e.g., proximity 

to leaking sewer lines) to provide a framework upon which different 

circumstances could be evaluated as to the probable risk of contributing to 

distribution system contamination.

o Identify model baseline conditions to evaluate. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 93

Suggested Approach: 

This project area involves field investigations to identify the some of the contaminants that can 

enter distribution systems from the external environment.

- Design sampling plans to capture the range of system vulnerability to external 

contamination (based on influencing factors such as height of water table, proximity 

between sewer and drinking water mains, type of soil, etc.). Plans should include a 

systematic approach for determining statistically-significant number of sample sites, 

types of samples (soil, water, etc), appropriate analytes and detection limits, the number 

of samples to be collected per site, and the total number of scenarios to be sampled to 

inform a national estimate of the magnitude of risk. The designs should include plans for 

how non-detects will be reported and interpreted.

- Collect soil and groundwater samples from pipe trenches at pipe repair sites and water 

samples from flooded valve and meter vaults.

- Analyze samples for a suite of pathogens and indicators using molecular tools. Conduct 

supplemental analyses on a subset of the samples to evaluate potential viability and likely 

source. 

- Analyze samples for organic and inorganic constituents that may present a hazard.

- Collect system data and associated metadata (distance between sewer and drinking water 

main if reliable data can be generated, age/type of sewer, height of water in vault, etc.). 

Results and Application:

- Research in this project area will provide information regarding the presence (or absence) 

and concentrations of contaminants of public health concerns that could be introduced 

into the distribution system under various pressure scenarios

- Research in this project area will provide information useful for the evaluation of the 

relative risks associated with different system characteristics (e.g. submerged pipes, 

sewer overflows, and flooded vaults) by providing for a linkage between the presence of 

a condition and the occurrence of the contaminants.

- The range of concentrations obtained for microorganisms and chemicals will provide 

inputs for fate and transport/risk models to estimate exposure/health risks from intrusion

and main repair contamination events. 

Decision Relevance:

How is research in this project area likely to inform the evaluation of the magnitude of public 

health risk? 

Research in this project area will provide information regarding the presence and concentrations 

of contaminants of public health concern that could be introduced into distribution systems under 

various pressure scenarios. This is fundamental information needed to conduct a risk assessment 

of the public health impacts associated with intrusion events and contamination from main 

installation/repair/rehabilitation procedures. It will reduce the current uncertainty in possible 

pathogen concentration levels external to distribution system pipes and provide new information 

on the presence of organic/inorganic constituents that is not available at this time.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 94

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction? 

Research in this project area is oriented towards the assessment of the potential levels of 

contamination external to water mains. The results are not likely to directly inform on the effect 

of mitigation strategies but will rather provide incentives to apply such strategies (such as leak 

detection/reduction, underground vaults inspection, sewer replacement/rehab, 

flushing/disinfection after repairs, etc.) to reduce the risk of contaminant introduction into the 

system. They will help identify the breach, which will help in determining appropriate corrective 

strategies.

What types of distribution system decisions could be supported by research in this project

area? 

Research in this project area will provide information on the possible need to: (i) emphasize the 

application of leak detection/reduction strategies, (ii) establish inspection programs for 

underground vaults in distribution systems, (iii) establish requirements for installation/retrofitting 

of air-vacuum valves in distribution systems, (iv) establish requirements for cleaning/disinfection 

after pipe repairs, (v) emphasize the need for sewer replacement/rehabilitation, (vi) provide 

supporting evidence for the need to upgrade certain distribution system components that may be 

experiencing significant decay. 

Project Area Constraints and Timing:

This project area could benefit from being implemented after the Large Systems Surveys (Sur1) 

and Small and Medium Systems Surveys (Sur2) are substantially underway or complete. These 

surveys could provide candidate water utilities for research in this project area. For example, the 

surveys will help determine if these utilities have high leakage rates, high pipe break rates, high 

frequency of rehab activities or flooded underground vaults. The studies would then inform 

external contaminant conditions at sites highly vulnerable to contamination in order to establish 

estimates of contamination in reasonable worst case scenarios. Other systems could be selected 

and compared to these high risk systems. 

Depending on how the research is structured, there is a need for coordination between 

participating utilities, samplers (if not conducted by utility crews), and laboratories performing 

the sample analyses. The time between sample collection and analysis is sometimes critical, 

especially for microbiological analyses. To collect soil and water samples at sites of pipe repairs, 

there is a need for repairs to take place. The predictability of these is also difficult. The same 

situation arises with flooded underground air-valve vaults, where there is a need for flooded 

vaults, hence the selection of more vulnerable water utilities as discussed above. 

Relationship to 

other RICP project

areas

Project 

area 

document 

code

RICP project area document

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project

areas or what will be 

used in follow-on 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 95

project areas)

This project area

depends on. . .

No other project areas. N/A

Project areas that this 

project area builds on

Sur1 Survey of large drinking water 

utility distribution systems

Baseline data, 

identification of 

additional information 

gaps, pools of 

potential participants.

Sur2 Survey of small and medium 

drinking water utility distribution 

systems

Baseline data, 

identification of 

additional information 

gaps, pools of 

potential participants.

Project areas that 

build on this project 

area

None. N/A

Relevance to the Agreement in Principle: 

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Exposure and vulnerability of the public

o Identify situations that may result in contamination of public health 

significance.

o Characterize the contamination or conditions of public health significance 

that are introduced during those situations.

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

This project area is highly relevant to the Tier One priority topic areas, namely of intrusion, and 

main construction/repair. 

Key References:

Karim, M.R., Abbaszadegan, M. and LeChevallier, M. 2003. Potential for pathogen intrusion 

during pressure transients. J. Am. Water Works Assoc. 95 (5), 134-146.

Besner, M.C., Lavoie, J., Morissette, C., Payment, P. and Prévost, M. 2008. Effect of water main 

repairs on water quality. J. Am. Water Works Assoc. 100 (7), 95-109.

Besner, M.C. and Prévost, M. 2009. Microbial characterization of intrusion pathways and pitfalls 

of modeling negative pressure events. In Proceedings of AWWA-WQTC, Seattle, WA. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 96

Project Area Code: Con2

Project Area Title: Sampling to Determine Potential Distribution System Contamination 

Associated with Repair of Water Main Leaks and Breaks

Goal(s): To develop a greater understanding of the public health risk associated with microbial 

and chemical drinking water contamination occurring during the repair of water main leaks and 

breaks and to characterize the effectiveness of available mitigation strategies employed 

following these repairs.

Rationale: Though voluntary standards exist to prevent drinking water contamination following 

water main repair activities (AWWA Standard C651; Pierson et al., 2001), there is a need to 

validate the effectiveness of existing industry standards. Previous research has detected 

microbial contaminants in flushed water from planned repairs of pipe leaks which can result in 

contamination of the distribution system (Besner et al, 2008). This previous research indicates 

that flushing alone (without pipe disinfection) following planned pipe leak repairs successfully 

avoided contaminated water from reaching consumers (Besner et al, 2008). However, the result 

is dependent upon a variety of factors including the level of contamination present in the soil and 

groundwater surrounding the repaired main and the degree to which industry guidance is used 

during repairs. Additionally, very limited data exists to characterize the level of microbial 

contamination that may occur following catastrophic pipe failures that require emergency repair. 

The purpose of research in this project area is to characterize the extent of contaminant 

introduction associated with planned and emergency water main repairs. This research also 

seeks to validate existing industry guidance on shock disinfection following main repair, 

rehabilitation and replacement activities that systems use for the prevention of microbial drinking 

water contamination.

Objectives:

To characterize the extent of possible contamination associated with planned and emergency 

water main repairs.

To characterize the effectiveness of shock disinfection as a mitigation strategy for systems 

using shock disinfection following water main repair, rehabilitation and replacement.

To provide data to better predict health risks associated with drinking water contamination 

during repair of water main leaks and breaks.

Suggested Approach:

Research in this project area consists of both field surveys to estimate the extent of 

contamination that occurs before and during water main repairs as well as controlled laboratory 

or pilot scale studies to characterize the effectiveness of existing industry guidance.

To conduct these studies sampling protocols with a statistically significant representative 

number of sites are needed to determine the extent of contamination introduced before 

and during planned and emergency water main repairs. The methods used by Besner et 

al. (2008) provide an ideal starting point for the development of these sampling protocols. 

The data will be generated in a manner that will enable the estimation of the national 

public health risk.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 97

Laboratory or pilot scale pipe systems will be constructed to simulate field repair 

conditions under controlled conditions and to validate industry guidance for preventing 

microbial contamination following main repair activities.

Results and Application:

The results generated in these studies are expected to:

1. Provide data to contribute to the estimation of the magnitude of public health risk associated 

with construction activities.

2. Generate a greater understanding of the effectiveness of existing industry standards intended 

to prevent drinking water contamination during construction.

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of health 

risk?

Research in this project area will provide data to enable a quantitative estimate of contaminant 

introduction, to estimate the public health risk associated with main installation, repair and 

rehabilitation activities.

How is research in this project area likely to inform opportunities for risk reduction?

Existing industry guidance to prevent drinking water contamination during construction activities 

will be validated. In doing so, the research may also provide data that indicates a need to revise 

existing industry guidance.

What types of distribution system decisions could be supported by research in this project 

area?

The results of these studies are needed to identify risks and the associated risk reduction 

opportunities associated with main installation, repair and rehabilitation activities. The results of 

research in this project area are also likely to confirm or identify areas of improvement for 

existing technical guidance.

Project Area Constraints and Timing:

The results of Con1: ―Characterization of pathogens and chemicals in soil and groundwater 

adjacent to distribution system infrastructure” are required for the development of the sampling 

protocol used here. 

A number of systems with a variety of distribution system characteristics willing to participate 

must be identified. Furthermore, the logistics of collecting samples to document contamination 

associated with emergency water main repairs may present some challenges.

Relationship to 

other RICP project 

areas

Project 

area 

document

RICP project area document

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 98

code predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area

depends on. . .

Con1 Distribution system contamination 

associated with repair of water 

main leaks and breaks

Identification of 

microbial and 

chemical constituents 

for sampling. 

Sampling protocol 

from Con1.

Project areas that this 

project area builds on

Sur1 Survey of large drinking water 

utility distribution systems

Baseline data, 

identification of 

additional information 

gaps, pools of 

potential participants.

Sur2 Survey of small and medium 

drinking water utility distribution 

systems

Baseline data, 

identification of 

additional information 

gaps, pools of 

potential participants.

Project areas that 

build on this project 

area

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Identification of the 

effectiveness of risk 

mitigation strategies 

will inform the most 

appropriate best 

practices for 

controlling 

contamination.

Relevance to the Agreement in Principle: 

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Exposure and vulnerability of the public

o Identify situations that may result in contamination of public health 

significance.

o Characterize the contamination or conditions of public health significance 

that are introduced during those situations.

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

o Identify and implement remediation steps when contamination occurs.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 99

o Quantify the national significance of additional mitigation measures.

Research in this project area is highly relevant to the AIP Tier One priority topic area of main 

construction/repair.

Key References:

American Water Works Association. 1992. ANSI/AWWA 651-92 - AWWA Standard for

Disinfecting Water Mains. Denver, CO: AWWA.

Besner, M. C.; Lavoie, J.; Morissette, C.; Payment, P.; and Prevost, M. (2008) Effect of water 

main repairs on water quality. Journal of the American Water Works Association. 100(7) 

95-109.

Pierson, G., K. Martel, A. Hill, G. Burlingame, A. Godfree. (2001) Practices to Prevent 

Microbiological Contamination of Water Mains. Denver, CO: Water Research 

Foundation.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 100

Project Area Document Code: Con5

Project Area Title: Computation of Intrusion Volumes through Orifices

Goal(s): Conduct experiments to determine if the orifice equation used to calculate intrusion 

flow rates is adequate to correctly quantify intrusion volumes through various types of pipe leaks 

(circular holes, longitudinal cracks, and circumferential cracks) and to allow for a better 

prediction of the public health risks.

Rationale: The orifice equation (

Qi Cd A 2g H

) is generally used to compute the intrusion 

flow rate through holes in pipes when a difference in pressure exists between the exterior and 

interior of the pipe. Although it may provide a first estimation of the volumes of water (flow rate 

x duration of event) that could be coming in during an intrusion event, there is some uncertainty 

associated with the use of an exponent value of 0.5. Investigation of the pressure-leakage 

relationship (under positive pressure conditions in pipes) by several researchers has shown that 

the exponent value may differ from 0.5 when the effective leak area may, in some cases, be 

pressure-dependent (Lambert, 2001; Greyvenstein and van Zyl, 2007). Exponent values higher 

than 2 have been reported, increasing the importance of the pressure differential and significantly 

increasing estimated flow rates compared to those mediated by the standard equation. However, 

much uncertainty exists whether these results are also applicable to leaking pipes under negative 

pressure conditions. No studies have been conducted to validate the use of this equation for the 

several types of pipe leaks that may be found in distribution systems (round holes, longitudinal 

and circumferential cracks) under negative pressure conditions. Computation of realistic 

intrusion volumes is essential to adequately assess the resulting public health risk from such 

events. 

Objectives: 

1. Synthesize findings from ―surveyable‖ variables (for potential sizes of intrusion orifices) 

and pressure-related variables (for potential difference in pressure between the outside 

and the inside of a pipe) and use these findings as input into the equation used to estimate 

intrusion flow rate (variables A and H). 

2. Under the reported conditions, assess the potential intrusion volumes from various 

pathways (pipe leaks, flooded air-vacuum valves, and meters).

3. Assess accuracy of the equation used to calculate intrusion flow rates

(

Qi Cd A 2g H

), especially for intrusion through pipe leak orifices, which may take 

various forms (holes, cracks) by evaluating the applicability of the equation for difference 

forms. 

4. Determine the range of discharge coefficient values to be used in the intrusion flow rate 

equation for various types of orifices (leaks, air-vacuum valve outlet orifices, meter 

orifices-if needed).
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 101

Suggested Approach: 

This project area involves pilot-scale experiments:

- Synthesize the following information obtained from surveys or pressure-related project 

areas to recreate conditions under pilot-scale experiments: 

o Characteristics of pipe leaks (shape, diameter)

o Height of groundwater above pipes

o Size of outlet diameters of air-vacuum valves installed in DSs

o Height of water above submerged air-vacuum valve orifice

o Meter orifice sizes that could allow water in pipe if submerged

o Height of water above submerged meters

o Number of pipe leaks (i.e., holes, cracks, etc.)

o Relative locations of leaks

o Ranges of leak sizes

o Duration, magnitude of low/negative pressure events 

- Perform pilot-scale experiments recreating real-system conditions and compute intrusion 

flow rate for pipes with several orifice shapes and diameters; Validate the exponent value 

and determine if the use of the orifice equation (exponent of 0.5) is adequate under 

realistic negative pressure conditions (pipe internal pressures and external heads). 

- Conduct validation experiments with air-vacuum valve vault outlet orifices and meter 

orifices to confirm whether the use of an exponent value of 0.5 is adequate for these 

orifices. 

- Calculate the discharge coefficient values of the various leak forms. 

Results and Application:

- Research in this project area will confirm the adequacy of or need to modify the equation 

used for the calculation of intrusion flow rates when modeling is used (e.g., transient 

models). 

- The project area results will provide input to fate and transport/risk models which can be 

used to estimate the exposure/health risk associated with intrusion. 

- This will improve our ability to estimate the impacts of intrusion on contaminant volumes 

and concentrations. 

Decision Relevance:

How does research in this project area inform the evaluation of the magnitude of public 

health risk? 

Research in this project area will provide assessments of the adequacy of the orifice equation to 

compute intrusion flow rates through pipe leaks in distribution system. Intrusion volumes, which 

are obtained from multiplying the intrusion flow rate by the duration of the event, constitute a 

fundamental piece of information need to conduct a risk assessment of the public health impacts 

associated with intrusion events. 

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction? 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 102

These are theoretical investigations of the basic mechanisms used to estimate intrusion flow rates 

(and subsequently, volumes) into orifices found in distribution systems. The results are not likely 

to directly inform the effect of mitigation strategies. However, the results will increase the 

reliability of model results and data on subjects such as leak detection/reduction and inspection 

programs for underground vaults in distribution systems. This information can be used to 

mitigate and reduce risks by minimizing water loss and contaminant entry into distribution 

systems. 

What types of distribution system decisions could be supported by research in this project 

area? 

Research in this project area will inform the possible need to: (i) establish inspection programs 

for underground vaults in distribution systems, (ii) establish guidance, technical assistance or 

requirements for installation/retrofitting of air-vacuum valves in distribution systems, and (iii) 

emphasize the need for application of leak detection/reduction strategies. Research in this 

project area supports these decisions by providing information to help determine how important 

of a contamination pathway intrusion represents.

Project Area Constraints and Timing:

What factors influence the timing of research in this project area? Research in this project 

area could start immediately, but could also benefit from additional data obtained from RisM2. 

This is a relatively simple stand-alone project area. 

What are potential constraints to the implementation of research in this project area? 

Research in this project area requires a working space large enough to accommodate a pilot-scale 

system built to simulate actual distribution system conditions, especially in terms of pressure 

conditions. The investigators would also need tested pipes (with leaks) from water utilities that 

would agree to remove leaking pipe sections as part of repairs. 

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area 

depends on. . .

No other project areas. N/A

Project areas that this 

project area builds on

RisM2 Improving hydraulic models for 

distribution systems

Determination of 

appropriate orifice 

equation developed 

by Con5 will enhance 

hydraulic models.

Project areas that None. N/A
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 103

build on this project 

area

Relevance to the Agreement in Principle: 

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Exposure and vulnerability of the public

o Identify situations that may result in contamination of public health 

significance.

o Characterize the contamination or conditions of public health significance 

that are introduced during those situations.

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

Research in this project area is highly relevant to the Tier One priority topic area, namely 

intrusion, and could provide some informative value for cross connections and backflow. 

Key References:

Lambert, A. 2001 What do we know about pressure-leakage relationships in distribution 

systems. In Proceedings of IWA System approach to leakage control and water distribution 

systems management, Brno, Czech Republic. 

Greyvenstein, B. & van Zyl, J.E. 2007 An experimental investigation into the pressure-leakage 

relationship of some failed water pipes. Journal of Water Supply Research and Technology–

Aqua. 56(2), 117-124. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 104

Project Area Document Code: Con6

Project Area Title: Understanding the Growth Potential within Distribution Systems of 

Indigenous Bacterial Pathogens (Legionella and Mycobacterium)

Goal: To provide quantitative data on both the physical/chemical characteristics of distribution 

systems, and the distribution of various potentially pathogenic Legionella and Mycobacterium

spp within biofilms in distribution systems. Correlations between these data will be useful in 

developing predictive risk assessment models. 

Rationale: Legionella and Mycobacterium are bacterial genera that include species that are 

pathogenic for humans. While there are other potential sources of these pathogens (food, soil), 

their documented presence in drinking waters is evidence that consumption of or exposure to 

treated finished water after it has been distributed could pose a risk of infection to humans in the 

US. Their presence in water that has been specifically treated to remove pathogens is explained 

by the high resistance of Mycobacterium to halogen disinfectants and to the observation that 

Legionella can survive ingestion by protozoan amoebae and thus be protected from disinfection.

While these pathogens have been isolated from drinking water, both from bulk water and biofilm 

samples, it has not been established under what conditions Legionella or Mycobacterium are 

most likely to occur and grow. There appears to be some association with organic carbon levels 

and perhaps geography and Mycobacterium occurrence; and little association with chlorine 

residuals and Mycobacterium occurrence. But difficulties in isolating Mycobacterium from 

water and biofilm samples due to interference from background microflora has prevented a 

comprehensive picture of occurrence in a wide variety of water systems. 

Because of the potential for growth and virulence enhancement, drinking water biofilms will be 

analyzed in this study. There have been few systematic surveys of water biofilm samples to 

determine occurrence of these pathogens in distribution systems. From these studies, few clues 

are available of the important distribution system characteristics that must exist for Legionella

and Mycobacterium to occur at significant levels to impact human health. The significance of 

varied operational practices, such as switching from free chlorine to monochloramine residuals, 

as well as the competing microbial composition of the biofilm (including specific amoeba hosts) 

are expected to influence the selection for virulent pathogens within these genera. It is expected 

that better management of opportunistic Legionella and Mycobacterium is reliant upon 

understanding the differences in distribution system biofilm communities located in different 

climatic regions of the U.S., along with the impacts of different secondary disinfectants, source 

water chemistry and management practices.

Objectives:

1. Determine the occurrence of potentially pathogenic Legionella and Mycobacterium spp. in 

distribution system biofilms and the diversity of potential amoebae hosts, versus nonpathogenic species of these genera.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 105

2. Quantify the density of potential Legionella and Mycobacterium pathogens within biofilms 

and growth rates by water temperature and disinfectant residual type/concentration.

3. Evaluate interrelationships between the presence of specific amoeba host species, water 

quality parameters and operational regimes and the occurrence of potentially pathogenic 

Legionella and Mycobacterium spp.

4. Identify biofilm community characteristics associated with the occurrence of either 

Legionella or Mycobacterium pathogens and their amoebae hosts.

Suggested Approach:

This project area includes field studies on biofilm samples collected from a variety of 

distribution systems and is a companion project area to the occurrence and risk management 

monitoring project areas.

Conduct surveys of utilities to determine those which might provide opportunities for 

biofilm samples and which differ in the following respects:

 -source water chemistry characteristics and treatment resulting in different 

levels of carbon/nutrient levels;

 -types of primary and secondary disinfection;

 -types of pipe materials used;

 -temperature/pH/corrosion control program

Choose utilities that are willing to supply biofilm samples and which represent 

 -low (<100ug/L) and high (>200ug/L) AOC levels in finished water;

 -free chlorine primary and secondary residual

 -monochloramine primary and residual

 -monochloramine primary and free chlorine residual

 -ozone primary and chlorine/monochloramine residual

 -those which are located in more temperate zones, which experience four 

distinct seasons and those from consistently warmer zones.

 -other management practices which may influence biofilms.

Assess water meters as sources of biofilm samples and use available cultural and 

molecular methods to analyze for Legionella, Mycobacterium and protozoan amoebae. 

Characterize the microbial and protozoan biofilm communities from different systems 

such that differences in biological composition can be determined (e.g. T-RFLP analysis, 

Sanger sequencing of amplified DNA fragments to determine predominant genera, 

pyrosequencing).

Determine statistical significance of the presence of pathogens, amoebae and 

physical/chemical characteristics of the source water and distribution system.

Research in this project area would lead to lab- or pilot- scale studies designed to test 

hypotheses relating to what conditions are ideal for the growth of these pathogens in 

distribution systems. 

Results and Application: 

Research in this project area will provide assessments of the occurrence of these pathogens in 

U.S. distribution systems using state of the art methodologies that will enable a more 

comprehensive picture of this occurrence than has been generated in past studies. Culture only 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 106

studies have provided an inaccurate picture and have not included the larger community in which 

these pathogens exist and grow. Especially useful information would include associations 

demonstrated between specific operational parameters of distribution systems and the occurrence 

of these specific pathogens or their protozoan hosts, in that this information could result in 

management changes leading to lower risks from these pathogens. Occurrence/growth/survival 

data of Legionella and Mycobacterium pathogens would be important inputs into drinking water 

quantitative microbial risk assessments. Field data could be complementary to proposed 

epidemiology studies.

Decision relevance: 

How is research in this project area likely to inform the evaluation of the magnitude of public 

health risk? Previous studies have used methods which provide a limited view of the magnitude 

of the occurrence of these pathogens, as well as providing no information that could be used to 

evaluate the risks due to increased virulence of these pathogens. A better understanding of 

conditions that favor the growth and enhance virulence of indigenous biofilm pathogens will aid 

in predictive model development which could provide quantitative assessments of risk.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

Information that allows us to understand better the association between the occurrence of these 

pathogens, their protozoan hosts and distinguishing characteristics of the distribution system 

might allow utilities to alter their treatment, flushing activities and/or pipe replacement practices 

to reduce the potential for these organisms to grow.

What types of distribution system decisions could be supported by research in this project 

area? Decisions related to the use of chlorine vs monochloramine as a residual; the need for 

additional treatment to remove a greater proportion of carbon from source water; more informed 

choices when considering types of new replacement pipes.

Project Area Constraints and Timing:

What factors influence the timing of research in this project area? We are just now seeing 

more reports on the use of metagenomics in environmental studies. There are a variety of 

hierarchical approaches for community composition analysis. The methods chosen for these 

studies would incorporate the latest methods. Research in this project area could be informed by 

the results of proposed epidemiology studies on Mycobacterium infections. There would be 

advantages to targeting distribution systems from which others are gathering clinical data and 

isolates from treated drinking water consumers.

What are potential constraints to the implementation of research in this project area? The 

primary constraint will be finding utilities willing to participate in these studies, as they involve 

the collection of information on pathogen occurrence in treated drinking water. Other constraints 

include having access to biofilm samples that can be transported to analytical laboratories under 

conditions where there is no degradation of the sample, and the fact that genomic analyses,

especially large-scale pyro-sequencing, requires a significant investment of money. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 107

Research in this project area is not dependent on any other RICP project areas. See the table 

below for information about project areas that research in this project area builds on.

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by 

DS RICP)

Information needs 

(what will be 

learned from the 

predecessor project 

areas or what will 

be used in followon project areas)

This project area 

depends on. . .

None NA

Project areas that 

this project area 

builds on

Sur1 Survey of Large Drinking 

Water Utility Distribution 

Systems

Identify pools of 

utilities with varied 

infrastructures, 

distribution system 

conditions, and/or 

water quality 

conditions.

Sur2 Survey of Small and Medium 

Drinking Water Utility 

Distribution Systems

Identify pools of 

utilities with varied 

infrastructures, 

distribution system 

conditions, and/or 

water quality 

conditions.

Project areas that 

build on this project 

area

None NA

Relationship to WaterRF projects:

Project Number Project Title

4092 The Role of Amoebae in the Protection and Proliferation 

of Pathogens in Distribution Systems 

Will determine the extent to which amoebae shelter 

pathogenic organisms and enable proliferation of 

pathogens such as Legionella and Macobacterium avium 

complex in distribution systems. Research partner:

UKWIR.

Relevance to the Agreement in Principle:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 108

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Exposure and vulnerability of the public

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

Research in this project area is relevant to the Tier One priority topic area, storage; and the Tier 

Two priority topic areas, biofilms and nitrification.

Key References:

Falkinham et al. (2001) Factors influencing numbers of Mycobacterium avium, Mycobacterium 

intracellulare and other mycobacteria in drinking water distribution systems. Applied 

and Environmental Microbiology 67(3): 1225-31.

Lau, H.Y. and Ashbolt, N.J. (2009) The Use of Acanthamoeba as a tool for understanding 

Legionella pathogenesis: Implications for drinking water. Journal of Applied 

Microbiology 107: 368-78.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 109

Project Area Code: Con7

Project Area Title: Understanding the Survival of Enteric Pathogens and Ammonia-Oxidizing 

Organisms under Different Distribution System Conditions and Disinfection Practices

Goal: To provide data to better predict health risks associated with the impacts of water 

distribution and storage system biofilms on the survival of microbial populations (including 

enteric pathogens and ammonia oxidizing bacteria) that enter distribution systems through 

pathways including intrusion, cross-connections, storage breaches, and during main 

replacement/repair/rehabilitation.

Rationale:

Naturally occurring microorganisms found in treated drinking water will attach to and colonize 

exposed internal surfaces (e.g., pipe walls, storage tank walls, sediment particles) within a DS, 

forming biofilms. These biofilms are generally thought to be composed of a wide variety of 

bacteria, protozoa and fungi and are characterized by carbohydrate-rich extracellular polymers 

that serve to bind cells together. The specific microbiological and chemical properties of 

biofilms in a specific DS will likely be determined by such parameters as the chemical 

composition of the source water, the chemistry of the treated water in the DS, disinfectants used, 

any chemical additions to the water (e.g. corrosion control agents), presence of contaminants 

organisms that can enter through contamination pathways (e.g., intrusions), temperature, pipe 

material and flow characteristics. Biofilm microorganisms will be released into the bulk water at 

rates determined by physical, chemical and biological conditions. 

Water utilities rely on residual disinfectants in their DS to inactivate harmful microorganisms 

that make it through the treatment regime, as well as to guard against and inactivate any 

contaminants that gain entry into the DS post-treatment. In addition residual disinfectants are 

relied upon to control biofilm build up and help in preventing the growth of bacterial pathogens 

in DS. Free chlorine and monochloramine represent the most commonly used residual 

disinfectants. It is well established in the published literature that free chlorine is far less 

effective in inactivating microorganisms that are part of a biofilm, as opposed to the same 

organisms freely floating in water and this is especially true of biofilms formed on ironcontaining surfaces, as opposed to other commonly used materials such as copper or PVC. It is 

generally acknowledged that this difference in disinfectant effectiveness is largely due to the fact 

that free chlorine reacts to a wider variety of chemical compounds compared to monochloramine. 

And so the oxidizing power of free chlorine is spent quickly in a biofilm, reacting with the 

carbohydrate polymers, while the bacterial cells remain unaffected. Monochloramine on the 

other hand, is less reactive chemically with polysaccharides and thus is able to penetrate biofilms 

with enough oxidizing power to inactivate the microbes present. However, monochloramines are 

less effective than chlorine at inactivating microbial contaminants that enter the distribution 

system bulk water through breaches. The presence of ammonia in the DS, through the 

production of monochloramine can support the growth of ammonia-oxidizing bacteria, which in 

turn can lead to elevated levels of nitrate and nitrite.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 110

Situations that allow contaminated water to enter a DS, through cross-connections, backflows, 

intrusions through cracks during low pressure events and pipe repair operations, will involve the 

exposure of pipe biofilms to pathogenic microorganisms, as well as creating large disinfectant 

demands that use up added residuals. Because of the porous nature of biofilms, these 

microorganisms can become entrapped, shielded from disinfectants and possibly released back 

into the bulk drinking water through shearing or erosion of the biofilms. Reports exist that 

document the adsorption and release of pathogenic bacteria from distribution system biofilms 

following incidents such as wastewater cross-connections. In a pilot-scale study designed to 

investigate this scenario under controlled conditions, a 2 month long simulated wastewater crossconnection documented the adsorption of bacterial pathogens to the biofilms and re-released 

back into the water column in a more concentrated  ̳parcel‘. 

A better understanding of the role of biofilms as contaminant reservoirs is needed in identifying 

management practices to reduce the potential for survival of enteric pathogens in distribution 

systems. 

Objectives: 

- Determine the relative biofilm uptake and survival kinetics for reference enteric 

bacterial, viral and protozoan pathogens, and ammonia-oxidizing organisms associated 

with biofilms on DS pipe and storage internal surfaces and in accumulated sediments, 

with varying types and concentrations of secondary disinfectants.

- Describe the biological and physical mechanisms and extent to which enteric 

pathogens are released into the bulk water from the biofilms.

- Evaluate relationships between ammonia oxidizing bacteria and other microbial 

flora resident in distribution and storage system biofilms and factors that influence 

survival and die-off.

Suggested Approach: 

These are laboratory studies of biofilms on pipe walls and sediments developed from different 

source waters and surface materials;

- Develop laboratory-scale biofilms on pipe materials which span the range of those 

currently used, including new materials being proposed as resisting biofilm growth. 

- Develop biofilms using pure cultures of selected bacterial strains, ammonia-oxidizing 

organisms, and wastewater inocula.

- Study adsorption of enteric pathogens (including bacterial, protozoan and viral 

pathogens) and appropriate indicator organisms to biofilm and quantify microbial 

viability/infectivity over time.

> target pathogens will include Salmonella typhimurium strains, 

Shigella spp., Giardia cysts, norovirus (or best surrogates), enterovirus (echocoxsackie virus.)

- Conduct parallel tests of alternative secondary disinfectants to evaluate impacts of free 

chlorine and monochloramine on pathogens/indicators viability/infectivity and activity of 

ammonia oxidizing bacteria. Include source water quality considerations.

- Evaluate pathogen/indicator release from biofilms and sediments under a variety of 

simulated distribution system operational modes; and
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 111

- Investigate whether the use of mathematical models, such as those that describe the 

adsorption of particles to surfaces (Langmuir Isotherm), could be useful in predicting 

attachment/release of specific pathogens from biofilms.

Results and Application: 

Sorption, survival and release kinetics for a range of enteric pathogens and indicators are key 

input parameters required to model the interaction of pathogens with surfaces as pathogens make 

their way through distribution systems, and ultimately provide densities for input into 

quantitative microbial risk assessments. Data could be useful in refining existing and modified 

EPANET models to include the modeling of the movement and fate of both chemical and 

biological reactive contaminants that interact with biofilms throughout distribution systems. 

Field data will be complementary to proposed epidemiological studies and to the refinement of 

best operating practices for distribution systems.

Decision relevance: 

How is research in this project area likely to inform the evaluation of the magnitude of public 

health risk? 

Published reports to date have been limited in the conditions under which adsorption/release of 

pathogens from biofilms have been conducted. More comprehensive studies will provide 

information on the extent to which specific pathogens adsorb to biofilms generated under 

commonly observed DS conditions. These studies, focusing on the differences in the chemical 

nature of the biofilms and the adsorption characteristics of different pathogen types could 

highlight conditions which favor survival of specific pathogens and aid in predictive model 

development which could provide quantitative assessments of risk.

How is research in this project area likely to inform opportunities for risk mitigation and risk 

reduction?

If associations can be found between DS conditions and opportunities for introduced pathogens 

to survive and even replicate in biofilms, then utility operators could establish best management 

practices that would reduce these opportunities. It is likely that many operators are unaware of 

the potential for introduced pathogens to evade disinfection if entrapped in biofilms. And it is 

also likely that many operators would be unaware that such biofilms will form on any internal 

surfaces- pipe walls, storage tanks, sediment particles, etc. Increasing the awareness of operators 

as to the possibilities for pathogens to exist in their systems should provide the impetus for some 

systems to seek ways to avoid these risks, such as when they are deciding on secondary 

disinfectants, when they decide on what pipes to use when replacements are needed and perhaps 

other operational parameters under their control. 

What types of distribution system decisions could be supported by research in this project 

area? 

Research in this project area could provide information on the ability to control biofilm 

formation and sediment accumulation on DS internal surfaces by managing pipe and storage 

materials, operations, finished water chemistry, and type of primary and secondary disinfectants.

Project Area Constraints and Timing:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 112

What factors influence the timing of research in this project area? 

Because these are largely laboratory studies, they are not dependent on other research in project 

areas being proposed. However, information from fate and transport components of Hea2 

could inform the specific parameters in the lab experiments. 

What are potential constraints to the implementation of research in this project area? 

There are possible technical issues associated with growing and determining viability of certain 

pathogens, including certain viral pathogens (e.g., noroviruses) without current effective viability 

assays. Another possible technical constraint is the identification of a representative wastewater.

See the table below for information about project areas that research in this project area builds 

on.

Relationship to 

other RICP project 

areas

Project 

area

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area

depends on. . .

None. NA

Project areas that this 

project area builds on

Hea1 Quantitative Microbial Risk 

Assessment (QMRA) to evaluate 

exposure to pathogens through 

drinking water distribution 

systems

Fate and transport 

models and results.

Project areas that 

build on this project 

area

None. NA

Relationship to WaterRF projects:

Project Number Project Title

4116 Microbial Ecology in Distribution Systems

4165 Microbial Ecology during Nitrification Events,

Relevance to the Agreement in Principle:

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Exposure and vulnerability of the public:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 113

o Characterize the contamination or conditions of public health significance 

that are introduced during those situations.

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

o Identify and implement remediation steps when contamination occurs.

Research in this project area is relevant to the Tier One priority topic area, storage facilities; and

the Tier Two priority topic areas, biofilm, nitrification and contaminant accumulation.

Key References:

Gibbs et al. (2004). Evaluation of the ability of chlorine to inactivate selected organisms from 

the biofilm of a drinking water distribution system simulator following a long-term 

wastewater cross-connection. Journal of Environmental Engineering Science 3: 97-105.

LeChevallier et al. (1988) Inactivation of biofilm bacteria. Applied and Environmental 

Microbiology 54(10): 2492-99.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 114

Project Area Code: Con8

Project Area Title: Baseline Data on Episodic Release/Mobilization of Chemical Contaminants 

from Biofilms and Accumulated Solids in Distribution and Storage Systems

Goal: Obtain data documenting levels of selected chemical contaminants in drinking water 

distribution systems collected under ―normal‖ conditions. 

Rationale: 

A number of researchers have reported that trace contaminants in water can accumulate in solids 

found in drinking water distribution systems. Studies have shown, for example, that arsenic, 

radium, uranium and vanadium can accumulate to significant levels on iron and lead corrosion 

by-products and other solids in the distribution system (Lytle et al. 2004; Valentine and Stearns 

1994; Snoeyink et al. 2003; Schock 2005; Schock et al. 2008; Morris and Lytle 2007). Given the 

likelihood that contaminants have accumulated in some distributions systems, the possibility that 

an event (such as a pressure fluctuation) could trigger the release of the contaminant back to the 

water resulting in elevated levels in the consumer‘s tap water exists. Physical, chemical and 

biological factors can result in intermittent, episodic, or continuous release of contaminants from 

solids into the bulk water. These contaminants can be chronic, sub-chronic or acute in nature.

Although the potential for contaminants to be released back to the water from distribution 

systems exist, very little real data documenting levels of released contaminants in the distribution 

system exists. Regulatory sampling requirements for most regulated contaminants are at the 

point of entry into the distribution system. Research in this project area will identify levels of 

contaminants (such as arsenic, nitrite and uranium) in drinking water distribution systems in real 

communities when no events that could trigger major release episodes are occurring or under 

―normal‖ conditions. The data will serve as a ―baseline‖ to compare how levels of contaminants 

of concern differ from the water entering the distribution system. The data can also be used to 

compare how contaminant levels change when an ―event‖ occurs that could impact contaminant 

release (RisM4). 

Objectives: Research in this project area establishes a baseline for occurrence of some 

contaminants of concern in drinking water at consumer‘s taps and other locations in the 

distribution system. The research will include intensive field investigations of consumer‘s tap 

water and other locations for water quality parameters of concern and corresponding treated 

water chemistries.

1. Establish baseline levels of contaminants at consumer‘s taps and elsewhere within the 

distribution system.

2. Evaluate the impact of finished water quality on water quality at consumer‘s taps and 

other locations such as storage tanks under ―normal‖ operation.

3. Evaluate the impact of distribution system materials (iron, cement, etc.), on water quality 

at consumer‘s tap. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 115

Suggested Approach: 

The team will coordinate with utility participants to identify locations that currently have or in 

the past had measureable levels of contaminants (such as arsenic, radium, and uranium) in their 

source water. Also, communities with specific materials in the distribution system that can 

contribute to elevated levels of contaminants will be targeted. Complete water quality 

monitoring programs of sites in the distribution system, source water and finished water will be 

initiated. The research will:

- Develop distribution system sampling protocols designed to collect samples at 

consumer‘s taps and other locations in distribution systems under ―normal‖ operating 

conditions. Researchers should take into account routine distributions system operations 

that could lead to release of contaminants.

- Analyze samples for potential contaminants of concern and indicator parameters (e.g. 

iron, color, TSS, metals, carbonates, phosphates, silicates, pH, alkalinity, ORP, TDS, 

conductivity, chloride, sulfate, coliforms, HPC, turbidity, chlorine residual, nitrite). 

- Compare source and finished water parameters with distribution samples and interpret 

data to identify relationships.

Results and Applications: 

Results will provide a baseline for comparing water quality, particularly contaminants of 

concern, in the distribution system under ―normal‖ operating conditions. In some cases, some of 

the contaminants may increase in concentrations in distribution systems to levels above the 

MCLs, even under ―normal‖ conditions. The utilities may be unaware of this increase since the 

monitoring occurs before distribution. Therefore, the results of the studies will provide baseline 

data to help determine whether changes to monitoring locations need to be considered.

Decision relevance: 

Research in this project area will support risk management decisions targeted at controlling 

health risks associated with chemical contaminants that are released from biofilms and 

accumulated solids in distribution and storage systems.

How does research in this project area inform the evaluation of the magnitude of public 

health risk?

Research in this project area will yield new data carefully collected in targeted systems and 

scenarios, to enhance the understanding of effects of risk management practices on stability or 

release of selected chemical contaminants from distribution system biofilms and accumulated 

solids. 

How does research in this project area likely inform opportunities for mitigation and risk 

reduction?

Research in this project area will provide data from actual systems that can be used as a baseline 

for making changes toward mitigation of system contamination risks. Levels of contaminants 

measured and patterns of release can help inform potential exposures and risk.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 116

What types of distribution system decisions could be supported by research in this project 

area?

Research in this project area will enhance the understanding of the range possible consequences of risk 

management actions aimed at minimization of sediment accumulation- or biofilm-related chemical 

contamination. As such, research in this project area will inform the need for consideration of revisions 

to current regulatory monitoring strategies for inorganic contaminants.

Project Area Constraints and Timing: 

This project area does not depend on any other RICP project areas. Project area timing has been 

projected as 2 – 5 years.

Relationship to 

other RICP project 

areas

Project 

area 

document

code

RICP project area document

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area

depends on. . .

None. NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project 

area

None. NA

What are the potential constraints to the implementation of research in this project area?

Investigator knowledge of complex operational conditions and factors affecting accumulation 

potential, access to analytical resources and qualified sampling staff.

Access to and assimilation of findings from R&ICP project areas upon which this project area

builds. 

Sampling protocols to accommodate sample integrity and analytical processing needs and to 

collect water and sediments under clearly described conditions.

Willingness of utilities to participate by facilitating or taking samples and providing metadata.

Relevance to the Agreement in Principle: 

As stated in section 4.2.a, accumulation and release of contaminants from distribution system 

scales and sediments was identified by the TCRDSAC as being one of the seven issues most 

relevant to protecting public health and maintaining the integrity of distribution systems.

Research in this project area helps address multiple issues across the AIP priority topic areas in 

Section 4.2 of the AIP (e.g., storage facilities, nitrification and contaminant accumulation). This 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 117

project area, as part of a phased R&ICP project area approach also addresses AIP directives to 

conduct focused and coordinated research and information collection to inform potential 

additional risk management actions (e.g. regulations, guidance). 

Key References:

Lytle, D.A.; Sorg, T.J.; Frietch, C. 2004. ―The Accumulation of Arsenic in Drinking Water 

Distribution Systems.‖ Environ. Sci. Tech. 38:20:5365-5372.

Valentine, R.L.; Stearns, S. 1994. ―Radon Release from Water Distribution System Deposits.‖ 

Environ. Sci. Technol. 28(3):534-537.

Snoeyink, V.L.; Schock, M.; Sarin, P.; Wang, L.; Chen, A.S.C.; Harmon, S. 2003. ―AluminumContaining Scales in Water Distribution Systems: Prevalence and Composition.‖ Journal 

of Water Supply: Research and Technology. 52(7):455.

Schock, M.R. 2005. Distribution Systems and Reservoirs and Reactors for Inorganic 

Contaminants (Chapter 6). In: Distribution System Water Quality Challenges in the 21st 

Century. AWWA. Denver, CO.

Schock, M. R.; Hyland, R.N.; Welch, M.M. 2008. "Occurrence of Contaminant Accumulation in 

Lead Pipe Scales from Domestic Drinking-Water Distribution Systems." Environ. Sci. 

Tech. 42(12): 4285-4291.

Morris, E. and Lytle, D.A., "The Accumulation of Radium and Other Radionuclides in Drinking 

Water Distribution Systems." Presented at AWWA Water Quality Technology 

Conference, Nov. 4-8, 2007, Charlotte, NC. 2007.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 118

Project Area Document Code: Hea3

Project Area Title: Response Teams to Prepare Case Studies on Adverse Public Health Effects 

from Distribution System Events 

Goal: To deploy trained response teams to collect and analyze information on any reported 

public health consequences associated with distribution system events where the introduction 

and/or mobilization of one or more contaminants is known or believed to have resulted in human 

population exposures at levels presenting potential public health risks.

Rationale: 

Real-time data linking adverse public health consequences to distribution system contamination 

events are limited. Contamination events such as intrusion, main breaks, cross connections and 

backflow may cause harm to individuals consuming tap water. The purpose of the response 

teams and case studies is to compile information in a coordinated and systematic way to describe 

associations between observed distribution system events and adverse health effects. Activities 

in this project area will involve close collaboration with CDC and other federal, state, or local 

entities and EPA Regional offices as appropriate. It is envisioned that this project area will 

involve a large number of systems with evidence of a contamination event. The investigations 

will occur as close in time to the actual contamination event and will focus on the population 

most likely to have experienced the elevated exposure levels during the contamination event. 

This project area will augment the data obtained from more comprehensive long-term 

epidemiological studies that tend to focus on a limited number of specific systems where the 

occurrence of distribution system events may or may not be observed. Results from these studies 

may also inform the design and data collection needs in epidemiological studies that are focused 

on distribution systems. In addition to characterizing the extent and severity of adverse health 

effects among the exposed population, researchers will document differences in public health 

consequences associated with various response and intervention measures implemented by water 

system managers to address those distribution system events.

Objectives: 

Establish, train, and maintain the readiness of response teams of public health 

professionals to deploy to locations where a significant event has occurred in public 

water distribution systems (e.g., a major main break, significant pressure loss due to 

power outages, storage related events) to study potential resulting adverse public health 

effects.

Collect and analyze data on: illnesses or other adverse health effects following 

documented distribution system contamination events; relevant information on 

distribution system characteristics, operations, and water quality; and supporting 

demographic data.

Prepare case study reports that characterize the nature of the distribution system 

contamination events (including relevant conditions leading up to the event), the water 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 119

system response to addressing / controlling that event, and the incidence and severity of 

any illnesses occurring among exposed populations following those events.

Suggested Approach: 

This research effort will involve three main phases.

The first phase would be to identify representative sets of water systems (in terms of 

types of water systems and geographic distribution) and enter into advance agreements 

with them (and with relevant local public health agencies) to notify the response teams 

when events occur and to allow them access to the information needed for conducting the 

case studies (e.g. security clearances for viewing sensitive DS characteristic information). 

The second phase would be to select and train the response team members for this effort, 

to provide on-going training and support to ensure their readiness, and to provide all 

needed logistical support for the teams to deploy when events occur that will be studied.

The third phase is the actual mobilization of the teams into the field to collect information 

from drinking water supply customers or local public health agencies concerning 

gastrointestinal (GI), respiratory and other diseases, in the period following a significant 

disruption in normal service at public water systems as well as the associated information 

on the events themselves. This third phase will also include the preparation and 

dissemination of the case study analysis results to EPA and the research partners for their 

use in assessing the health risks and risk reduction potential from those events.

It should be noted that the purpose of these response teams is gathering information about 

the events, and not to provide the type of emergency response support that is the 

responsibility and purview of a range of federal, state and local entities (see, for example, 

HHS 2007). However, it is anticipated that there would be considerable cooperation with 

those entities and that the training and deployment logistics would be modeled to some 

extent on those developed by such emergency response groups.

Results and Application: 

The key products from the case studies are expected to be characterizations of the extent 

and severity of public health risks associated with the actual occurrence of different types 

of distribution system events.

The application of this information is expected to contribute to an understanding of the 

potential health benefits to be gained from implementing risk mitigation strategies 

through technical assistance, industry guidance, policy statements, or technical guidance 

and/or regulations developed locally, at the State level or nationally.

Decision Relevance: 

How is research in this project area likely to inform evaluation of the magnitude of health 

risk? Research in this project area will directly inform the potential magnitude and severity of

public health risks associated with different types of distribution system events, including major 

main breaks, significant pressure loss due to power outages, and storage related events. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 120

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction? Research in this project area could identify differences in public health outcomes for 

similar events where systems have important differences in operating characteristics or event 

response strategies. This would inform the relevant risk mitigation and reduction strategies.

What types of distribution system decisions could be supported by research in this project 

area? The results of these studies will help inform the basis to determine whether the current 

risks and risk reduction potential regarding various types of distribution system events merit 

regulatory action, technical guidance, both, or neither.

Project Area Constraints and Timing: 

Research in this project area can begin without dependence on any other effort. As indicated in 

the suggested approach section, research in this project area does depend upon establishing 

advance agreements with public water systems, and possibly with other local public health 

agencies, to deploy to those locations and have access to needed information. 

The completion of this information collection project area may influence several other project 

areas. See the table below for information on the project areas under consideration by the DS 

RICP that build on Hea3.

 

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by the 

DS RICP)

Information needs 

(what will be used in 

follow-on project 

areas)

This project area 

depends on. . .

No other project areas. NA

Project areas that this 

project area builds on

None. NA

Project areas that 

build on this project 

area

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Information from the 

case study reports 

(e.g., relevant 

conditions leading up 

to the contamination 

event) may aid in 

refining the project 

area designs of RisM1 

and Pres4. 

Pres4 Toolkit for pressure management

Note: Although research in this project area does not explicitly build on other project areas, nor 

do other project areas depend on it, it is possible that this project area and Hea2 (Epidemiological 

Studies of Low Pressure Events) may be mutually informative of one another with respect to 

improving their respective methodologies for gathering information and identifying health 

effects end-points and subpopulations on which to focus.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 121

Relevance to the Agreement in Principle: Research in this project area will provide 

information relevant to needs identified in Section 4.2.b of the AIP ―Conceptual Framework for 

Knowledge Gaps‖, and specifically the following items:

Health Effects and Risk to the Public

o Measure health consequences from exposure to contaminants

o Monitor for situations that pose a public health concern

o Measure and track the national significance of the described situations

Effectiveness of mitigation measures

o Characterize preventative measures or steps to minimize or prevent exposure

o Identify and implement remediation steps when contamination occurs

o Quantify the national significance of additional mitigation measures

Research in this project area is highly relevant to all of the Tier One priority topic areas: main 

construction/repair, storage, cross-connection and backflow and intrusion (e.g., from significant 

pressure loss due to power outages).

Key Reference:

 

HHS 2007. U.S. Department of Health and Human Services. Public Health Emergency 

Response -- A Guide for Leaders and Responders. Office of the Assistant Secretary for 

Public Affairs. http://www.hhs.gov/emergency (August 2007).
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 122

Project Area Document Code: Hea4

Project Area Title: Molecular Epidemiology of Distribution System Associated Pathogens

Goal: Evaluate potential linkages between distribution system characteristics and disease 

transmission by comparing the molecular signatures of distribution system-associated pathogens 

and clinical samples from hospitals and clinics. A key focus will be comparing distribution

system samples of biofilm-associated pathogens including Legionella and Mycobacteria with 

samples from patients with suspected cases of Legionella-like respiratory disease or infection by 

non-tuberculous mycobacteria.

Rationale:

Various Mycobacterium and Legionella spp. and other pathogens are known to colonize drinking 

water biofilms. A recent study using genomic analyses of household showerhead water and 

biofilm samples found that 78- 90% of the samples were positive for M. avium, by either qPCR 

or sequence analysis of rRNA clone libraries. Another study found Legionella spp present in 

22% of household hot water samples. However, data are lacking on the extent to which these 

opportunistic pathogens colonize water distribution and storage systems. These pathogens can 

persist under ambient disinfectant conditions in drinking water distribution systems, either 

through protection by amoebal ingestion (Legionella and Mycobacterium), through resistance to 

inactivation by halogen disinfectants due to an unusually protective cell wall (Mycobacteria), or 

through the microbial ecology of biofilms. In fact, numbers of mycobacteria are higher in water 

systems that use some disinfectant (as opposed to untreated groundwater systems), likely due to 

the fact that mycobacteria are extremely slow growing and cannot compete with other halogensensitive bacteria found in water.

Drinking water is not the only possible source of these pathogens. Mycobacteria are present in 

many household environments, including food and soils. And Legionella were originally 

recognized as pathogens that came from aerosols from air-conditioning units. So the link 

between municipally treated drinking water and exposure is unclear. 

By using molecular epidemiology to compare high-resolution molecular fingerprints of 

environmental sample isolates with isolates/molecular fingerprints directly from infected 

patients, it can be determined if drinking water is a possible source of pathogens causing human 

respiratory illness. Such an approach has provided evidence for drinking water as a potential 

source of Mycobacterium avium complex (MAC). Here we seek to investigate a wider selection 

of clinical and environmental strains and link the microbiological findings to distribution system 

water quality and operating parameters to identify plausible control and management strategies.

Objectives:

1. Develop culture and direct molecular fingerprint approaches to apply to lung/sputum 

samples and environmental isolates.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 123

2. Work with clinicians and local utilities at patients‘ households to collect paired samples.

3. Conduct molecular identification of isolates and then appropriate high-resolution 

fingerprinting for the different species identified.

Suggested Approach: 

Phase 1:

- Research in this project area will depend on access to hospitals and clinical patients 

suffering from Legionella and Mycobacterium respiratory disease and the isolates from 

these patients. Therefore medical practices/clinics which cater to these patients will need 

to be identified and enrolled in the studies.

- Institutional Review Board approval for human subject research must be obtained.

- Once households are identified for analysis, a sampling plan must be developed for each 

house. The plan should include both water and biofilm samples from as many taps as 

there are in the house and include how samples will be collected and how frequently 

samples are to be taken. In addition, plans must be developed to receive clinical isolates 

of Legionella and Mycobacterium from targeted patients.

- Information on the drinking water systems should be collected, including the source 

water, treatment regime, location of the house in the distribution system, physical 

characteristics of distribution system (pipe material, storage facilities, dead ends), 

distribution system operational and management parameters and in premise plumbing 

water quality parameters.

Phase 2:

- Tap water and biofilm samples will be processed for recovery of Legionella and

Mycobacterium using current best practices (including enrichment culturing.)

- Samples should also be processed for recovery of DNA targets for molecular analyses for 

these pathogens. 

- All isolates, both clinical and water, should be analyzed by amplified fragment length 

polymorphism analysis (AFLP) to determine if the pairs (isolates from the patient and 

from his/her home environment) are clonal, indicating that the home tap water is the 

source of the clinical infection.

- Based on the culture/molecular identifications, fingerprinting and distribution system

parameters, identify potential covariates in characterizing risk and system vulnerability.

Results and Application: 

These studies should add to the understanding of drinking water as a transmission vehicle for 

Legionella and Mycobacterium infections. In addition, these studies should yield critical 

information needed to determine whether the occurrence of Legionella and Mycobacterium

strains, those which are the causative agent of human infections, can be predicted based on the 

physical and chemical characteristics of particular distribution systems. It is likely that if such 

predicted associations can be determined for these pathogens, then there are likely to be present 

other pathogens in water inhabiting the same ecological niches as the pathogens targeted in these 

studies. Preventing the survival and/or the growth of Legionella and Mycobacterium will also 

serve to decrease exposure to other pathogens. Data from these studies could be useful in 

refining quantitative microbial risk assessment models to include the risks from exposure to 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 124

these biofilm pathogens, evaluate potential management strategies to reduce distribution-system 

associated respiratory disease and enable estimation of the national significance of drinking 

water respiratory pathogens.

Decision relevance:

How does research in this project area inform the evaluation of the magnitude of public 

health risk?

Because there are other potential sources of Legionella and Mycobacterium other than home 

water taps, a better understanding of role of distribution systems and household premise 

plumbing in supporting the survival/growth of these pathogens will enable a more accurate 

evaluation of the magnitude of the public health risk.

 

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction? 

If it can be established that specific parameters of the distribution system or premise plumbing 

are associated with exposure to Legionella or Mycobacterium pathogens, then altering 

distribution system management practices or consumer actions in the home could provide 

meaningful opportunities for mitigation and risk reduction.

What types of distribution system decisions could be supported by research in this project 

area? 

The choice of secondary disinfectant could be informed by the results of these studies. The use 

of monochloramine introduces potential public health risks (nitrification) and the lack of 

inactivation of intruded contaminants due to lack of necessary contact time in the DS, balanced 

by the potential for more effective disinfection of biofilm pathogens. These studies could 

provide further evidence that the use of monochloramine is associated with lower levels of 

biofilm pathogens. Also any water quality parameters or physical characteristics of distribution 

systems that are found to be associated with the occurrence of these human pathogens could 

form the basis for identification of how/where possible management activities could be focused 

to reduce the disease burden.

Project Area Constraints and Timing:

What factors influence the timing of research in this project area? While research in this 

project area is not dependant on any other project areas, research in this project area would build 

on the successful completion of Con 6- Understanding the growth potential within distribution 

systems of indigenous bacterial pathogens (Legionella and Mycobacterium).

What are potential constraints to the implementation of research in this project area? 

Finding clinics willing to participate in the study and receiving IRB approval could be a timeconsuming and lengthy process. Also it will be difficult to gain access to homes for sample 

collection or to rely on patients or their family to take samples. Shipping of samples to lab will 

need to be accomplished such that any target organisms remain viable. And, it is likely that most 

clinical cases will be from either exposure to pathogens in other matrices or that the water 

exposure occurred in the past and the pathogens are no longer present in the household water 

taps.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 125

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas)

This project area 

depends on. . .

None NA

Project areas that this 

project area builds on

Con6 Understanding the growth 

potential within distribution 

systems of indigenous bacterial 

pathogens (Legionella and 

Mycobacterium)

Information would 

inform sampling plan.

Project areas that 

build on this project 

area

None NA

Relevance to the Agreement in Principle:

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Exposure and vulnerability of the public

o Assess the exposure to contaminants (considers occurrence, pathway and 

host susceptibility).

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

Research in this project area is relevant to the Tier One priority topic area, namely storage; and 

the Tier Two priority topic areas, biofilms and nitrification.

Key References:

Falkinham et al. (2001) Factors influencing numbers of Mycobacterium avium, Mycobacterium 

intracellulare and other mycobacteria in drinking water distribution systems. Applied 

and Environmental Microbiology 67(3): 1225-31.

Feazel et. al. (2009) Opportunistic pathogens enriched in showerhead biofilms. PNAS 106(38):

16393-399.

Lau, H.Y. and Ashbolt, N.J. (2009) The Use of Acanthamoeba as a tool for understanding 

Legionella pathogenesis: Implications for drinking water. Journal of Applied 

Microbiology 107: 368-78. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 126

Project Area Document Code: Mon1

Project Area Title: Collection of Distribution System and Storage Monitoring Data for Nitrite, 

Nitrate, and Related Physical and Chemical Constituents

Goal: To establish a national perspective on the levels of nitrite, nitrate, and other contaminants 

in distribution and storage systems (water and sediments) and their relationship with system 

characteristics, water chemistry, disinfection approaches, and operating practices, etc.

Rationale: 

Federal drinking water regulations require monitoring of nitrate and nitrite at the entry point to 

the distribution system. However, nitrification can occur within distribution systems and excess 

nitrate and nitrite can lead to significantly higher levels in distribution systems. These high 

levels could exceed maximum contaminant levels (MCLs).

Objectives: 

Develop programs to monitor distribution system mains, storage tanks, and premise 

plumbing for nitrite, nitrate, ammonia, disinfection residuals (including organic and 

inorganic chloramines). Consider issues such as source water quality, time of year, 

treatment methodologies, and distribution system hydraulics in developing monitoring 

procedures.

Evaluate relationships between system characteristics, source water characteristics 

(including blending), disinfection approaches, operating practices, consumer complaints, 

and monitoring results to identify possible causes of the contamination and if 

contaminant detection outcomes result.

Suggested Approach:

This is an information collection project area for monitoring of water in distribution systems and 

sediments in storage tanks. Research in this project area will proceed in three sequential phases:

Phase 1 - Identify participating utilities and review available data and information.

Phase 2 - Develop sample collection and processing methods.

Phase 3 - Develop and conduct utility specific monitoring programs, and collect and 

analyze samples.

Phase 1 - The first phase includes the identification of utilities to participate in the monitoring 

programs, representing systems with a variety of distribution and storage system characteristics: 

size, age, sources of water, disinfection approaches, and geographical and climate distribution. 

After utility identification, comprehensive analyses of the available utility data will be 

conducted.

Phase 2 - The second phase will be the development of new sample collection and processing 

methods required to conduct the proposed sampling (e.g. methods related to sediment analysis 

from storage tanks).
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 127

Phase 3 - Based on the results of the previous phases, utility specific monitoring plans will be 

developed. Following the development of the monitoring plans sample collection will take 

place. After collection, the data will be analyzed and interpreted to identify relationships 

between system properties and monitoring results.

Results and Applications:

Research in this project area will develop a national perspective on nitrite, and nitrate in 

distribution and storage systems. Results may also lead to alternative monitoring approaches. In 

addition, sample collection and processing methods will be developed.

Specifically, the data to be collected includes:

Distribution system influent levels and occurrence of ammonia, nitrite, nitrate, and 

chloramines (inorganic and organic).

Distribution system levels and occurrence of ammonia, nitrite, nitrate, and chloramines 

(inorganic and organic).

Premise plumbing levels and occurrence of ammonia, nitrite, nitrate, and chloramines 

(inorganic and organic).

Storage tank sediment analyses to determine sediment accumulation rates.

Decision Relevance:

Research in this project area could inform new monitoring strategies for regulation, such as 

revising monitoring requirements for nitrate/nitrite. Research in this project area could also 

inform the need for potential guidance or policies relevant to nitrification.

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk? 

Research in this project area will provide a national perspective of the levels of nitrite and nitrate 

in distribution and storage systems. This will inform the extent and frequency at which various 

potential public health vulnerabilities are occurring on a national basis.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

Research in this project area will provide an initial understanding of the degree to which nitrite 

and nitrate occur in distribution and storage systems.

What types of distribution system decisions could be supported by research in this project 

area?

Research in this project area would inform the local, state and national policies on distribution 

system issues, including monitoring requirements for nitrite/nitrate. It will also support 

monitoring decisions undertaken at individual utilities. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 128

Project Area Constraints and Timing:

Factors that may influence the timing of project area completion include:

Identification and willingness of utilities to participate.

Participation by enough (and sufficiently diverse) utilities to provide meaningful results

between system characteristics, source water characteristics (including blending), 

operating principles, disinfection approaches, consumer complaints, and monitoring 

results.

Issues associated with providing potentially sensitive information (data confidentiality).

The complexity and scope of monitoring plan design and data analysis.

o Lack of information in utility files.

o Lack of utility resources (personnel-time, computer expertise, sampling expertise) 

to complete the monitoring plan.

o Identification of relevant sampling points.

o Development of required sample collection and processing methods.

Research in this project area does not depend on the completion of other project areas. See the 

table below for information on project areas that research in this project area builds on and 

project areas that build on research in this project area.

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area 

depends on. . .

None. NA

Project areas that this 

project area builds on

Sur1 Survey of Large Drinking Water 

Utility Distribution Systems

Candidate utilities 

where to conduct 

research based on 

information such as: 

source water 

ammonia levels, 

secondary 

disinfectants used and 

distribution system 

attributes. 

Sur2 Survey of Small and Medium 

Drinking Water Utility 

Distribution Systems

Candidate utilities 

where to conduct 

research based on 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 129

information such as: 

source water 

ammonia levels, 

secondary 

disinfectants used and 

distribution system 

attributes. 

Project areas that 

build on this project 

area

RisM4 Tracking how water quality 

modifications and distribution 

system O&M impact stability and 

release of chemical contaminants 

from accumulated solids and 

biofilms in distribution and storage 

systems

Identification of 

candidate utilities that 

could be studied in 

RisM 4. 

Identification of areas 

of potentially 

increased contaminant 

concentrations in 

candidate utilities.

Relevance to the Agreement in Principle (AIP):

The completion of research in this project area is directly relevant to two AIP topic areas listed in 

section 4.2.a: (1) contamination due to storage facility design, operation, and maintenance and 

(2) nitrification issues that lead to public health effects. In addition, the analysis of sediments in 

storage facilities provides information for two additional AIP topic areas listed in section 4.2.a: 

(1) significance and control of biofilm and microbial growth and (2) accumulation and release of 

contaminants from distribution system scales and sediments.

Key Reference:

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 130

Project Area Document Code: Pres3

Project Area Title: Develop Strategies to Diagnose and Monitor Pressure Fluctuations in Water 

Distribution Systems

Goal: To optimize where and how to monitor for low and negative pressure events and to 

develop a better understanding of the frequency, magnitude and causes of low and negative 

pressure events.

Rationale:

Distribution systems prone to low or negative pressures are more susceptible to water quality 

deterioration due to backflow and intrusion. Furthermore, wide pressure fluctuations in 

distribution systems may increase leakage rates and main breaks, and decreasing service life. 

Previous research has demonstrated that certain critical locations in the distribution system may 

be especially prone to low or negative pressures (Fleming et al., 2006). Identification and 

effective monitoring of these critical locations is necessary for successful distribution system 

pressure management and optimization. The purpose of research in this project area is to build 

on previous research (Fleming et al, 2006; Friedman et al, 2004) and available pressure 

optimization guidance (Ongoing Water Research Foundation project 4109, ―Criteria for 

Optimized Distribution Systems‖ ) to refine strategies to identify and monitor critical distribution 

system locations. Furthermore, limited data exist on the frequency and magnitude of low or 

negative pressure events. Pressure data loggers will be installed in these critical locations in an 

effort to capture the frequency and magnitude of low and negative pressure events and pressure 

events will be investigated to determine their possible causes. The results of this work could 

lead to improved pressure management, reducing the public health risks that may be associated 

with low and negative pressure events.

Objectives:

Refine strategies to identify and monitor critical distribution system locations susceptible to 

low or negative pressure events.

Evaluate the effectiveness of passive monitoring strategies for pressure management.

Develop a greater understanding of the risk and mitigation factors associated with low or 

negative pressure events by generating field data on the cause, frequency and magnitude of 

these pressure events across a variety of distribution system attributes.

Suggested Approach:

This research involves full-scale field studies that will be conducted at a minimum of 25 utilities 

that will be selected to represent the range of conditions prevalent in distribution systems 

nationally. It is anticipated that some utilities with representative distribution system attributes 

will have optimized pressure management programs while pressure management at others could 

be improved.

Participating systems will be instrumented with high-speed electronic pressure data 

loggers in areas vulnerable to pressure events. These areas will be identified based on 

existing pressure optimization guidance from ongoing Water Research Foundation 

Project 4109 ―Criteria for Optimized Distribution Systems.‖ Current guidance suggests 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 131

that monitored locations should be selected to be representative of areas of high and low 

pressure in every pressure zone of a distribution system. 

Control data will also be obtained from analogous distribution system areas expected to 

be relatively free from risk factors related to pressure events. The comparison of data 

from vulnerable and control areas will help evaluate the effectiveness of critical location 

determination based on existing guidance.

Pressure monitoring will be conducted at relatively short intervals (two to three weeks). 

Current guidance suggestions that pressure data should be collected at least hourly for a 

minimum of four days. Pressure monitors are intended to be temporarily installed at 

utilities for short periods of time to maximize the data collection provided from data 

loggers used for the research.

Metadata associated with the distribution system operations will be compiled in parallel 

with pressure monitoring, allowing pressure events occurring during the monitoring 

periods to be investigated to document potential causative factors.

Methods for selection of critical distribution system locations and pressure monitoring at 

those locations should reflect the current state-of-the industry practice.

Results and Application

The results of this study are expected to:

- Enhance pressure management optimization strategies by testing the effectiveness of 

passive monitoring approaches.

- Generate a greater understanding of the risk factors associated with low or negative 

pressure events, therefore providing insights into the cost and applicability of available 

mitigation strategies.

- Provide improved estimations of the nationwide prevalence of low or negative pressures 

in distribution systems through extrapolation of the results collected from representative 

distribution systems. 

Decision Relevance:

How does research in this project area inform evaluation of the magnitude of health risk?

Research in this project area does not directly inform the magnitude of public health risk, but the 

results of this work will help to further inform an estimate of the nationwide prevalence of low or 

negative pressure events. The research will directly provide information to the participating 

utilities on the magnitude of risk from low to negative pressure events in those utilities. 

Understanding the prevalence of these events is an intermediate step in evaluating the national 

public health risk associated with water quality deterioration due to backflow or intrusion.

How does research in this project area inform opportunities for risk reduction?

The goals of research in this project area are to refine strategies for pressure management. 

Improved pressure management should directly reduce the risk associated with backflow and 

intrusion. Furthermore, identification of the causes of low or negative pressure events will allow 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 132

the applicability of available mitigation strategies to be evaluated, including how and when to 

apply them.

What types of distribution system decisions could be supported by research in this project 

area?

The results of these studies will help determine what type of risk reduction response 

opportunities associated with low or negative pressure events are warranted on a local, regional, 

State or national level. The results of research in this project area are also likely to confirm or 

expand on existing technical guidance related to distribution system pressure management. The 

research will inform the magnitude of risks from low to negative pressure events in the 

participating utilities.

Project Area Constraints and Timing:

What factors influence the timing of research in this project area? Research in this project area

could move forward without dependence on other project areas. However, more benefit may be 

gained if it is implemented after the Survey of Large Drinking Water Utility Distribution 

Systems (Sur1), the Survey of Small and Medium Drinking Water Utility Distribution Systems 

(Sur2) and the Survey of Distribution System Pressure Management Practices (Pres1) because 

these project areas will help identify nationally representative distribution system attributes that 

could be further understood through work on this new project area. 

Surge models may help identify critical distribution system areas and can confirm the choice of 

critical locations based on other factors. Therefore, information developed through the 

Characterize Propagation of Pressure Events through Water Distribution Systems to Improve 

Pressure Management Approaches (Pres2) could be beneficial to this project area though the 

results are not critically dependent of the Pres2 project area.

What are potential constraints to the implementation of research in this project area? A large 

number of utilities willing to participate must be identified and convincing poorly optimized 

systems to participate may be difficult. Systems may have security concerns with making 

distribution system information available. In addition, for some systems there may be logistical

issues associated with accessing parts of the distribution system that may be of interest for 

research in this project area. The installation of the pressure monitors, which are expensive 

pieces of equipment, will need to be coordinated to ensure the timeframe of data collection 

provides the highest value for each utility monitored.

Relationship to 

other RICP project 

areas

Project area 

document 

code

RICP project area 

document title

(under consideration 

by DS RICP)

Information needs 

(what will be learned 

from the predecessor 

project areas)

This project area 

depends on. . .

None NA

Project areas that 

this project area 

Sur1 Survey of Large 

Drinking Water 

Identification of 

nationally 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 133

builds on Utility Distribution 

Systems

representative 

distribution system

attributes

Sur2 Survey of Small and 

Medium Drinking 

Water Utility 

Distribution Systems

Identification of 

nationally 

representative 

distribution system 

attributes

Pres1 Survey of Distribution 

System Pressure 

Management

Identification of 

nationally 

representative 

distribution system 

attributes

Pres2 Characterize 

Propagation of 

Pressure Events 

through Water 

Distribution Systems 

to Improve Pressure 

Management 

Approaches

Understanding of 

frequency and severity 

of pressure events

Project areas that 

build on this project 

area

None. NA

Relevance to the Agreement in Principle: 

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

o Identify and implement remediation steps when contamination occurs.

o Quantify the national significance of additional mitigation measures.

Research in this project area is highly relevant to the following Tier One priority topic areas of 

the AIP: intrusion and cross connection/backflow. The other Tier One priority topic areas that 

this project area relates to are storage and main construction/repair.

Key References:

Fleming, et al. 2006. Susceptibility of Distribution Systems to Negative Pressure Transients. 

Water Research Foundation and American Water. Denver, Colorado. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 134

Friedman, et al. 2004. Verification and Control of Pressure Transients and Intrusion in 

Distribution Systems. Water Research Foundation. Denver, Colorado.

Ongoing Water Research Foundation Project 4109. ―Criteria for Optimized Distribution 

Systems,‖ particularly the information on preliminary Distribution System Optimization SelfAssessment Criteria (DOSAC). 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 135

Project Area Document Code: Pres4

Project Area Title: Toolkit for Pressure Management

Goal: To develop guidance on the use of tools and operational strategies to minimize low and 

negative pressure events and to optimize distribution system pressure management

Rationale:

Distribution systems prone to low or negative pressures are more susceptible to water quality 

deterioration due to backflow and intrusion. Minimization of low and negative pressure events 

can help reduce the public health risk associated with these events. Furthermore, wide pressure 

fluctuations in distribution systems may increase leakage rates and main breaks, decreasing 

service life and providing opportunities for the direct introduction of contaminants into the 

distribution system. The purpose of research in this project area is to build on previous research 

(Fleming et al, 2006; Friedman et al, 2004), currently available pressure optimization guidance 

(ongoing Water Research Foundation Project 4109, ―Criteria for Optimized Distribution 

Systems) and the findings of other project areas developed and executed as part of the Research 

and Information Collection Partnership (RICP) to synthesize the use of available tools and 

operational strategies to optimize distribution system pressure management. The results of this 

work are intended to improve pressure management strategies, reducing the public health risks 

that may be associated with low and negative pressure events.

Objectives:

To critically evaluate the effectiveness and cost of various strategies to optimize pressure 

management based on existing knowledge and information and on information collected 

through the RICP.

Support utility decision making by compiling the findings from other work into suites of 

easy-to-use, practical tools to optimize distribution system pressure management.

Suggested Approach:

The key results from other project areas such as the frequency of low or negative pressures 

nationwide, the causes of low or negative pressures, the effectiveness of available mitigation 

strategies, and the use of enhanced hydraulic and surge models and passive pressure monitoring 

for pressure management will be critically evaluated to determine the most cost-effective and

efficient approaches to optimize distribution system pressure management. These critical 

evaluations will support decision making on the most appropriate approach to optimize pressure 

management.

Results and Application:

The results of these studies are expected to:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 136

- Integrate the results from previous project areas to provide multiple approaches to 

improved pressure management. 

- Integrate the results from previous project areas to provide a critical evaluation of the 

costs associated with improved pressure management, and to help identify the most costeffective and efficient approaches to minimizing low or negative pressures and generally 

optimizing distribution system pressure management.

- Support decision making on the most appropriate approach for controlling the risks 

associated with low and negative pressure events.

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of health 

risk?

Research in this project area does not directly inform the magnitude of public health risk. 

However, since it does inform the effectiveness of pressure management strategies it could help 

inform national risk magnitude for utilities already using those strategies.

How is research in this project area likely to inform opportunities for risk reduction?

The goals of research in this project area are to determine the most cost-effective, efficient 

approaches to distribution system pressure management. Therefore, the research will inform the 

potential decrease in public health risks through the application of the tools evaluated.

What types of distribution system decisions could be supported by research in this project 

area?

The results of research in this project area will expand on existing technical guidance related to 

distribution system pressure management. Research in this project area will also support 

decision making on the most appropriate approach for addressing risks from low and negative 

pressures locally, regionally, at the State level and nationally.

Project Area Constraints and Timing:

Research in this project area does not depend on any other project areas. However, the project 

area could benefit from the completion of other relevant project areas because it builds on their 

results. The project areas that research in this project area builds on are listed in the table below.

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by 

DS RICP)

Information needs 

(what will be 

learned from the 

predecessor project 

areas)

This project area 

depends on. . .

None NA

Project areas that this Sur2 Survey of Small and Medium Identification of 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 137

project area builds on Drinking Water Utility 

Distribution Systems

nationally 

representative 

distribution system 

attributes

CC1 Best Practices to Minimize Risks 

Associated with Cross 

Connections and Backflow

Best practices for 

addressing cross 

connections

Pres1 Survey of Distribution System 

Pressure Management

Identification of 

nationally 

representative 

distribution system 

attributes

Con4 Estimation of contaminated water 

volumes and contaminant 

concentrations introduced into 

DSs from cross-connection 

contamination events based on 

model predictions and field and 

pilot-scale experiments

Total volume and 

contaminant 

concentrations 

introduced during 

pressure events

Hea3 Response Teams to Prepare Case 

Studies on Adverse Public Health 

Effects from Distribution System 

Events

Real world examples 

from pressure related 

incidents

Project areas that 

build on this project 

area

None NA

Relevance to the Agreement in Principle: 

Research in this project area will provide information relevant to needs identified in Section 

4.2.b of the AIP ―Conceptual Framework for Knowledge Gaps‖, and specifically the following 

items:

Effectiveness of mitigation measures:

o Characterize preventative measures or steps to minimize or prevent 

exposure.

o Identify and implement remediation steps when contamination occurs.

Research in this project area is highly relevant to the Tier One priority topic areas, namely

intrusion and cross connection/backflow. The project area is also relevant to the Tier One 

priority topic areas, storage and main construction/repair.

Key References:

Fleming, et al. 2006. Susceptibility of Distribution Systems to Negative Pressure Transients. 

Water Research Foundation and American Water. Denver, Colorado. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 138

Friedman, et al. 2004. Verification and Control of Pressure Transients and Intrusion in 

Distribution Systems. Water Research Foundation. Denver, Colorado.

Ongoing Water Research Foundation Project 4109. ―Criteria for Optimized Distribution 

Systems,‖ particularly the information on preliminary Distribution System Optimization 

Self-Assessment Criteria (DOSAC). 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 139

Project Area Document Code: RisM1 

Project Area Title: Decision Support for Managing Potential Distribution System Public 

Health Risks from Potential Contamination Events and Daily Operations

Goal: To understand advantages and disadvantages of current risk management practices and to 

identify the best risk management strategies 

Rationale:

Water utilities currently have a wide range of options to manage and mitigate distribution system 

risks, including those listed in industry standards, utility-specific practices, and state and local 

guidelines. However, in a given situation, it is not always easy for utilities to identify the best 

option and to fully understand the implications of the options. Because distribution systems are 

interconnected, risk management practices in one area can negatively impact another area. For 

example, flushing to increase chlorine residual may cause pressure fluctuations or contaminated 

sediment re-suspension. Therefore, the need exists to better understand the risk management 

practices used across the country, the effectiveness, and barriers to implementation of risk 

management strategies for different types of utilities. A decision support system that synthesizes 

national practices and outlines steps for utilities to follow in various situations is a critical 

resource for public health protection, which directly depends upon effective risk management.

Objectives: 

1. Synthesize survey data from project areas Sur1, Sur2, Sur3, and Sur4 to develop a 

comprehensive understanding of how different risk management practices are used to 

address distribution system risks, differences in best management practices, factors that 

affect differences, and barriers to implementation.

2. Identify some of the possible unintended consequences of applying the best management 

practices from the survey information.

3. Identify ways to avoid situations where management practices intended to mitigate one 

specific problem may result in other unintended negative consequences, including 

political/managerial consequences (e.g., public concern over the use of chloramines).

4. Suggest monitoring programs that may be used to generate data to inform how to best 

address the possible problems anticipated, and to avoid unintended consequences of 

changed management schemes.

5. Develop decision support products on how to select the best risk management option to 

prevent, predict, diagnose, and/or respond to contamination under specific scenarios.

Suggested Approach:

Research in this project area should proceed in four sequential phases: Phase 1 – Compile and 

synthesize risk management strategies currently being implemented as observed in Sur1, Sur2, 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 140

Sur3, and Sur4, identify key differences in risk management practices, and develop lists of 

optimized risk management practices; Phase 2 – Evaluate information compiled in Phase 1 and 

identify possible unintended consequences that could result from implementation of the risk 

management practices; Phase 3 - Suggest monitoring programs that may be used to generate data 

to inform how to best address the possible problems anticipated, and to avoid unintended 

consequences of changed management schemes; and Phase 4 - Develop decision support 

products on how to select the best risk management options to prevent, predict, diagnose, and/or 

respond to contamination under specific scenarios

Phase 1 – The first phase is compilations of survey data from project areas Sur1, Sur2, Sur3, and 

Sur4 and summarization of existing industry standards (e.g., ANSI/AWWA G200-09, Ten State 

Standards). From the compiled data, identify key differences in risk management practices along 

with factors that affect differences and lessons learned regarding barriers to implementation 

(including political/managerial) and suggest ways current risk management practices may be 

optimized to better protect public health. The outcomes should be short lists of optimized risk 

management practices and how they can overcome implementation barriers.

Phase 2 - For the optimized risk management practices, identify and evaluate the possible 

negative consequences that could result. Where it is not possible to fully avoid negative 

consequences, use cost/benefit analyses to clearly document the situations where the given risk 

management practice should still be used.

Phase 3 – Evaluate existing monitoring programs that may provide early warning of possible 

problems that may occur when implementing risk management practices and suggest which 

monitoring programs may be appropriate for systems with different characteristics (e.g., size, 

location, etc.) to avoid unintended consequences of changed management schemes. 

Phase 4 - Build decision support systems that incorporate the findings on risk management 

practices in a comprehensive manner. The decision support systems should be easy to use tools 

that systems can use to help make optimal decisions concerning their risk management practices. 

The systems should be developed to incorporate all relevant factors including system size, 

prevalence and type of vulnerabilities for which risk management strategies are lacking, ease of 

implementation, potential barriers to implementation, and additional criteria identified 

throughout the project area. 

Results and Applications:

Research in this project area provides a critical link between the fundamental understanding of 

contamination events and the field-based application of practices for intervention and public 

health protection. The anticipated products are decision support systems that can be used by 

utilities and regulators to better select the appropriate risk management practices, allowing for 

quicker response to events and minimization of adverse public health outcomes. Pulling from 

data collected from Sur1, Sur2, Sur3, and Sur4 will allow for a comprehensive perspective on 

risk management within the context of real-world distribution system operation.

Decision Relevance:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 141

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk?

Research in this project area will not provide a direct evaluation of the magnitude of public 

health risk. However, as the understanding of the implications, particularly the unintended 

negative consequences, of different risk management options is increased, the information 

learned will also provide insight into the magnitude of public health risks, particularly when 

those risks are related to distribution system operations.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

The primary focus of research in this project area is to identify the best risk management 

practices so that water utilities can make solid decisions about risk mitigation and reduction. 

Quick and effective intervention is important in reducing the potential public health risks and for 

sustained public health protection.

What types of distribution system decisions could be supported by research in this project 

area?

A variety of important decisions regarding distribution system operation and selection of risk 

management practices will be directly supported by research in this project area through the 

creation of the decision support systems.

Project Area Constraints and Timing:

Research in this project area is dependent on the findings of Sur1, Sur2, Sur3, and Sur4. The 

design of the survey questions related to risk management practices within project areas Sur1, 

Sur2, Sur3, and Sur4 should be coordinated with research in this project area to ensure that the 

correct data are collected. In addition, there are other project areas that research in this project 

area could build on. These project areas are summarized in the table below. 

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the predecessor 

project areas)

This project area 

depends on. . .

Sur1 Survey of Large Drinking Water 

Utility Distribution Systems

Data on risk 

management practices 

from representative 

subsets of large systems 

Sur2 Survey of Small and Medium 

Drinking Water Utility 

Distribution Systems

Data on risk 

management practices 

from a representative 

subset of small and 

medium systems

Sur3 Field Survey to Collect 

Information on Risk Management 

Practices Employed in Water 

Distribution Systems

Information on the 

effectiveness of risk 

management practices 

and information on 

challenges related to 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 142

implementing certain 

risk management 

practices

Sur4 Targeted surveys to obtain 

information on state and local 

regulations, policies, 

manufacturing practices and 

guidelines for distribution systems

Information on risk 

management and 

mitigation strategies as 

listed in industry 

standards, utilityspecific practices, and 

state and local 

guidelines

Project areas that this 

project area builds on

Con2 Distribution system contamination 

associated with repair of water 

main leaks and breaks

Extent of 

contamination due to 

main repairs.

Effectiveness of 

mitigation strategies

Con3 Contaminant entry from breaches 

in storage facilities

Effectiveness, costs 

and barriers to 

implementation of 

storage related risk 

mitigation measures

Con4 Estimation of contaminated water 

volumes and contaminant 

concentrations introduced into 

DSs from cross-connection 

contamination events based on 

model predictions and field and

pilot-scale experiments

Total volume and

contaminant 

concentrations 

introduced during 

pressure events

RisM4 Tracking how water quality 

modifications and distribution 

system O&M impact stability and 

release of chemical contaminants 

from accumulated solids and 

biofilms in distribution and storage 

systems

Extent of the 

mobilization/release 

of contaminants as a 

result of various DS 

actions

Project areas that 

build on this project 

area

None NA
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 143

Factors that might influence the timing of completion of research in this project area include:

Need to supplement the data collected in Sur1, Sur2, Sur3, and Sur4 project areas. Sur1,

Sur2, Sur3, and Sur4 must have adequate detail to ensure they will capture the type of 

information needed/anticipated.

Coordination with state and local jurisdictions with overlapping 

regulations/requirements to identify core best management practices.

Ability to conduct the necessary research to fully understand the potential negative 

consequences associated with each risk management practice.

Ability to accurately identify and assess the most significant political/managerial barriers 

to implementation from regional and local perspectives.

Relevance to the Agreement in Principle:

Research in this project area is relevant to all seven priority topic areas and is cross-cutting in 

that it addresses the inter-relationships between areas. 

Key References:

ANSI/AWWA (2004). Standard G200-04, Distribution Systems Operation and Management, 

Denver, CO.

Great Lakes Upper Mississippi River Board (2007). Ten States Standards: Recommended 

Standards for Water Works, Health Research Inc., Albany, NY.

TCRDSAC Agreement in Principle (2008).

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 144

Project Area Document Code: RisM 2 

Project Area Title: Improving Hydraulic Models for Distribution Systems

Goal(s): To enhance hydraulic modeling software so that it can more accurately simulate 

pressure transients, pressure management options, and the impact of hydraulics on contaminant 

fate and transport. 

Rationale:

Hydraulic models to simulate distribution system performance are used widely throughout the 

industry for design and operational evaluations. These models currently rely primarily on 

empirical pipe flow equations developed in the early 1900s and are best suited for simulating 

typical operating conditions. There are limited current capabilities for modeling very short 

duration events like pressure transients, mixing dynamics that are non-uniform, pipe wall 

interactions with bulk fluid, the impact of certain pressure management devices and contaminant 

dispersion factors. Research in this project area provides the necessary fundamental research 

along with the recommendations for using existing modeling options for a broader range of 

contaminant events to advance the state of hydraulic modeling. Research in this project area will 

work to improve existing models to provide an excellent tool for design of monitoring and risk 

management strategies for water utilities. 

Objectives: 

- Build upon existing knowledge and research about cross-connections, intrusions, and 

pressure management to enhance existing modeling tools.

- Enable identification of new risk management strategies related to pressure and hydraulics 

through the application of the enhanced modeling capabilities.

Suggested Approach:

1. Compile and synthesize the findings of fundamental research related to pressure and 

pressure management strategies from project areas Pres1, Pres2, Sur1 and any other 

relevant sources. Summarize the current capabilities of hydraulic modeling software and 

identify data gaps to be filled, which may include data on specific types of contamination 

events (e.g. intrusions), field practices from water utilities, contaminant dispersion 

factors, ties to GIS and related case studies.

2. Create algorithms, equations, and supporting model inputs to more accurately simulate 

the full range of pressure events, fluid dynamics, and contaminant fate and transport that 

can occur in a distribution system.

3. For the new algorithms and equations, recommend field data collection procedures and 

develop typical ranges of input parameters based on factors that water utilities can 

determine from their system characteristics. Conduct sensitivity analyses on the input 

parameters to assist water utilities in prioritizing data collection to determine parameters.

4. Conduct full-scale field trials to validate the enhanced models.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 145

Results and Applications:

Research in this project area provides enhanced tools that will enable water utilities to better 

understand pressure management vulnerabilities, contaminant dispersion through the system and 

mitigation options. These types of tools will play an important role in the development of risk 

mitigation strategies for distribution system operation. With the inclusion of field verification 

studies to assist in parameterization of the models developed, the results will be readily usable by 

water utilities.

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk?

Research in this project area will provide enhanced tools for individual water utilities to estimate 

the magnitude of pressure events and the dispersion potential for contaminants introduced during 

these events for their particular system configuration and operation. In conjunction with related 

project areas to characterize the magnitude of health risk from pressure events, the health risk 

can be estimated at an individual system level with these tools.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

The primary focus of research in this project area is to provide tools to assist with risk 

identification, mitigation and management strategies. Tools are needed to design appropriate 

monitoring and management systems for distribution system pressure management and overall 

operation.

What types of distribution system decisions could be supported by research in this project 

area?

Decisions related to placement of pressure sensors, adjustments of operational practices related 

to pumping, identification of vulnerable locations and parts of distribution systems affected, 

evaluation of the effectiveness of different risk management strategies and response to 

contamination events can all be supported by research in this project area.

Project Area Constraints and Timing:

Research in this project area will build upon the findings of Sur1, Pres1 and Pres2. The design 

of the survey questions related to pressure management practices within project area Pres1

should be coordinated with research in this project area to ensure that the correct data is 

collected.

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area Sur1 Survey of Large Drinking Water Identification of 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 146

depends on. . . Utility Distribution Systems nationally 

representative 

distribution system 

attributes

Pres1 Survey of Distribution System 

Pressure Management

National data on 

pressure management 

practices

Pres2 Characterize Propagation of 

Pressure Events through Water 

Distribution Systems to Improve 

Pressure Management Approaches

Understanding of 

frequency and 

severity of pressure 

events

Project areas that this 

project area builds on

None NA

Project areas that 

build on this project 

area

Pres4 Toolkit for pressure management Hydraulic models 

could be a tool to 

assess and improve 

pressure conditions in 

the DS

Factors that might influence the timing of completion of research in this project area include:

Need to supplement the data collected in Sur1, Pres1 and Pres2 project areas

Ability to conduct the necessary research to fully understand the pressure events

Ability to field verify the findings and develop a database of parameter values that is 

broadly applicable

Modeling complexity

Relevance to the Agreement in Principle:

Research in this project area is most relevant to intrusion, cross-connection, and storage, which 

are all Tier One priority topic areas. Because pressure is a cross-cutting issue for all distribution 

system reactions, research in this project area will also have relevance for biofilms, contaminant 

accumulation, and nitrification. 

Key References:

Rossman, L.A. (2000). EPANET 2 Users Manual. National Risk Management Research 

Laboratory, Environmental Protection Agency. Cincinnati, OH.

Walski, T., Chase, D., Savic, D., Grayman, W., Beckwith, S., and Koelle, E. (2003). 

―Introduction to Water Distribution Modeling.‖ Advanced Water Distribution Modeling 

and Management, Haestad Method Inc. 1st Ed, Waterbury, CT.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 147

Project Area Document Code: RisM4

Project Area Title: Tracking How Water Quality Modifications and Distribution System O&M 

Impact Stability and Release Of Chemical Contaminants from Accumulated Solids and Biofilms 

in Distribution and Storage Systems

Goal: To provide data to support risk management decisions targeted at controlling health risks 

associated with chemical contaminants that are released from biofilms and accumulated solids in 

distribution and storage systems. 

Rationale: 

Risk management decisions require sound data to understand the influence of source water 

changes, treatment strategies, storage operations, and operation and maintenance (O&M)

practices on accumulation and release of chemical contaminants from biofilms and sediments in 

distribution and storage systems. Biofilms and solids which may form and accumulate in 

distribution systems can contain toxic chemical substances which may be mobilized at levels of 

health concern when system hydraulic, physical or chemical conditions (Schock 2005, Lytle 

2008, NASNRC 2006). For example, changes to source water quality or treatment can 

contribute trace levels of chemical contaminants which can accumulate undetected in low flow 

areas of system piping or storage, or can destabilize existing accumulations or biofilms. System 

changes which affect pressure or flow affect the likelihood that contaminants will accumulate

and/or mobilize (NASNRC 2006). 

Several approaches are available to address potential risks from the accumulation of solids and 

biofilms in distribution systems. In some cases the full effect of these approaches are not 

completely understood. More research is needed to measure, document and understand systems 

status and effects of O&M modifications. Specifically, real system data provided through 

research in this project area will enhance the understanding of the effects of a variety of water 

quality (treatment or source changes) or O&M-related risk mitigation measures on release of 

chemical contaminants from biofilms and solids accumulations in distribution systems and 

storage. Research in this project area will help utilities to better manage system O&M activities 

by using improved knowledge of factors affecting stability and release of chemical contaminants 

from solids and biofilms. Data from research in this project area will also assist in identification 

of obstacles to implementation of good O&M practices and the need for risk management 

decisions.

Objectives: Research in this project area builds on the baseline data project area (RisM3) and 

includes intensive field investigations before, during, and after planned modifications to water 

quality or distribution system O&M.

Suggested Approach: 

The project area requires coordination with utility participants to:

- Identify existing or planned actions that could potentially impact the extent to which 

chemical contaminants are mobilized/released from biofilms or solids including: 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 148

o Changes in source water that impact nutrients, organics, microbial community 

structure, pH, alkalinity, sulfur, nitrogen, chloride, and other water quality 

parameters

o Changes in treatment including disinfectant type/dose/ratio, pH adjustment, 

corrosion control, coagulant chemicals, reverse osmosis, ion exchange, advanced 

oxidation

o O&M activities such flushing, storage cycling, and mixing, storage or pipe 

cleaning.

o Short-term or seasonal change to primary or secondary disinfectant (e.g. free 

chlorine, ozone, chloramines or chlorine dioxide)

- Determine which inorganic, organic, and microbial parameters will be used as indicators 

in these studies (e.g. iron, color, TSS, metals, carbonates, phosphates, silicates, pH, 

alkalinity, ORP, TDS, conductivity, chloride, sulfate, turbidity, chlorine residual, nitrite).

- Conduct monitoring before, during, and after planned action using sampling approaches 

developed in the baseline study (RisM3) to collect representative samples of system 

biofilms, sediment, bulk water, and associated metadata surrounding the timeframe of the 

action. 

- Analyze samples for accumulated chemical contaminants and indicator parameters and 

interpret data to identify relationships between baseline conditions, conditions during and 

after the changes in source water or treatment, operations, maintenance procedures, or 

structural changes to piping or storage.

Results and Applications: 

Results will provide assessments of how system or storage O&M changes impact release of 

chemical constituents from distribution system biofilms and solids. This will allow for a greater 

understanding and more effective application of O&M changes studied.

Decision relevance: 

This project area will support risk management decisions concerning the most effective O&M 

activities for controlling health risks associated with chemical contaminants that are released 

from biofilms and accumulated solids in distribution and storage systems.

How does research in this project area inform the evaluation of the magnitude of public 

health risk?

Research in this project area will yield new data carefully collected in targeted systems and 

scenarios, to enhance the understanding of effects of risk management practices on stability or 

release of chemical contaminants from distribution system biofilms and accumulated solids. 

How does research in this project area likely inform opportunities for mitigation and risk 

reduction?

Research in this project area will provide detailed analyses of data from actual systems making 

changes toward mitigation of system contamination risks. Levels of contaminants measured and 

patterns of release can help inform potential exposures and risk.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 149

What types of distribution system decisions could be supported by research in this project 

area?

Research in this project area will enhance the understanding of the range of possible consequences of risk 

management actions aimed at minimization of chemical contaminant accumulation and release in 

sediments or biofilms. The need for risk management decisions that address monitoring within 

distribution systems will be further informed.

Project Area Constraints and Timing: 

Project area timing influences and considerations. Research in this project area has been 

developed as a companion project area to Con8 ―Baseline data on episodic release/mobilization 

of chemical contaminants from biofilms and accumulated solids in distribution and storage 

systems.‖ Project area timing is expected to take 2 – 5 years to complete. 

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the predecessor 

project areas or 

what will be used in 

follow-on project 

areas)

This project area 

depends on. . .

Con8 Baseline data on episodic 

release/mobilization of chemical 

contaminants from biofilms and 

accumulated solids in distribution 

and storage systems

Baseline data on 

release/mobilization is 

needed to compare to 

the situations studied 

in this project area.

Project areas that this 

project area builds on

None NA

Project areas that 

build on this project 

area

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Extent of the 

mobilization/release 

of contaminants as a 

result of various DS 

actions

What are potential constraints to the implementation of research in this project area?

Investigator knowledge of complex operational conditions and factors affecting accumulation 

potential, and access to analytical resources and qualified sampling staff.

Access to and assimilation of findings from R&ICP project areas upon which research in this 

project area builds. 

Identification/selection of water quality and O&M change scenarios/systems to study.

Sampling protocols to accommodate sample integrity and analytical processing needs and to 

collect water, biofilm and sediment samples under clearly described conditions.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 150

Willingness of utilities to participate by facilitating, conduction and/or allowing sampling, and 

providing metadata.

Relevance to the Agreement in Principle: 

As stated in section 4.2.a, accumulation and release of chemical contaminants from distribution 

system scales and sediments was identified by the TCRDSAC as being one of the seven issues 

most relevant to protecting public health and maintaining the integrity of the distribution system.

Research in this project area helps address multiple issues described in Section 4.2 of the AIP 

(e.g., storage facilities, biofilms, nitrification and contaminant accumulation). Research in this 

project area, as part of a phased R&ICP project area approach also addresses AIP directives to 

conduct focused and coordinated research and information collection to inform potential 

additional risk management actions (e.g. regulations, guidance). 

Key References:

Schock, M.R. 2005. Distribution Systems and Reservoirs and Reactors for Inorganic 

Contaminants (Chapter 6). In: Distribution System Water Quality Challenges in the 21st 

Century. AWWA. Denver, CO.

Lytle, D.A. 2008. "Additional USEPA Accumulation and Release Studies" Presented at AWWA 

Water Quality Technology Conference, Nov. 16-20, 2008, Cincinnati, OH.

NASNRC 2006. National Academies of Science National Research Council Report. Drinking 

Water Distribution Systems: Assessing and Reducing Risks. The National Academies 

Press. Washington, DC, USA.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 151

Project Area Document Code: RisM 5 

Project Area Title: Develop Next Generation Models for Informing Distribution System and 

Storage Water Quality Including Episodic Release/Mobilization of Chemical Contaminants from 

Accumulated Solids and Biofilm

Goal(s): Develop computer-based models that can be used to identify vulnerable portions of 

distribution systems and optimize risk management activities associated with controlling 

chemical contaminants that are released from biofilm and accumulated solids in distribution and 

storage systems. 

Rationale:

Water quality models currently in use are first-generation simulations that are built upon a 

hydraulic model of flows and pressures. Research continues to advance regarding the 

fundamental mechanisms of distribution system reactions; particularly those that are least 

understood which include biofilm and solids accumulation reactions. There is a need to apply 

the findings to better simulate water quality dynamics in real distribution systems. Current 

capabilities to model complex, multi-phase and multi-species phenomena within distribution 

systems are limited. Most models rely on the use of simplified first-order reaction equations and 

segmented pipe wall reactions. Research in this project area applies the findings of fundamental 

research on accumulation of solids and biofilms to modeling frameworks and develops tools to 

support design of monitoring and risk management strategies for water utilities. 

Objectives: 

- Develop mechanistic representations and input parameters to enable water quality models to 

incorporate biofilm attachment and detachment, particle transport and deposition, and 

adsorption/desorption reactions.

- Conduct field studies to test, validate and optimize these advanced water quality models in 

distribution and storage systems.

- Develop modules to link these advanced water quality models to existing hydraulic models.

Suggested Approach:

- Compile and synthesize the findings of fundamental research related to biofilms and 

solids accumulation from project areas RisM3 and RisM4. Supplement where necessary 

with data from laboratory studies, water utilities, and related case studies.

- Create algorithms, equations, and supporting model input parameters to more accurately 

simulate the processes of biofilm attachment and detachment, particle deposition, transport 

and re-suspension, pipe wall reactions such as adsorption/desorption and associated water 

quality dynamics affecting contaminant fate and transport in a distribution system.

- For the new algorithms and equations, recommend field data collection procedures and 

develop typical ranges of input parameters based on factors that water utilities can determine 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 152

from their system characteristics. Conduct sensitivity analyses on the input parameters to 

assist water utilities in prioritizing data collection to determine parameters.

- Conduct full-scale field trials to validate the enhanced models and develop databases of 

input parameters that can be used in individual applications of the advanced water quality 

models.

Results and Applications:

Research in this project area provides enhanced tools that enable water utilities to better 

understand the full dynamics and inter-relationships among factors that govern water quality 

reactions in distribution systems. These models will provide a more realistic understanding of 

conditions in real distributions systems and will therefore allow utilities to have more complete 

information with which to make decisions. These tools that represent water quality reactions in a 

mechanistic manner can then be used by individual water utilities to develop risk mitigation 

strategies and guidance for the characteristics of their particular distribution system and its 

operation. With the inclusion of field verification studies to assist in parameterization of the 

models developed, the results will be more readily usable by water utilities.

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk?

Research in this project area will provide tools for water utilities to simulate a wide range of 

important water quality reactions for their individual system configuration and operation. In 

conjunction with related project areas to characterize the magnitude of health risk from different 

chemical contamination events, the health risk can be estimated at an individual system level 

with these tools. In addition, a national perspective on distribution system conditions can be 

informed from case studies conducted using these improved models.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

The primary focus of research in this project area is to provide tools to assist with risk 

identification, mitigation and management strategies at individual utilities. Additional tools are 

needed to design appropriate monitoring and management systems for distribution system 

management.

What types of distribution system decisions could be supported by research in this project 

area?

Decisions related to adjustments of operational practices, identification of vulnerable locations, 

evaluation of the effectiveness of different risk management strategies and response to 

contamination events can all be supported by research in this project area.

Project Area Constraints and Timing:

Research in this project area will build upon the findings of project area RisM4. While research 

in this project area is intended to be a later application of the findings of several project areas, the 

researchers conducting RisM4 should consider the modeling application desired as they design 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 153

and carry out their studies so that the findings will support this desired modeling end products as 

much as possible.

Relationship to 

other RICP project 

areas

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas)

This project area 

depends on. . .

RisM4 Tracking how water quality 

modifications and distribution 

system O&M impact stability and 

release of chemical contaminants 

from accumulated solids and 

biofilms in distribution and storage 

systems

Fundamental 

understanding of 

biofilm and solids 

accumulation 

processes, field data 

on these processes

Project areas that this 

project area builds on

Con3 Contaminant entry from breaches 

in storage facilities

Information on 

storage related 

pathogens that may be 

found in distribution 

systems

Project areas that 

build on this project 

area

None NA

Factors that might influence the timing of completion of research in this project area include:

Need to supplement the data collected in RisM4

Availability of sufficient research to fully understand the complex series of reactions 

affecting biofilms and solids accumulation

Ability to field verify the findings and develop a database of parameter values that is 

broadly applicable

Relevance to the Agreement in Principle:

Research in this project area is most directly relevant to biofilms, contaminant accumulation, and 

nitrification. However, robust water quality modeling tools will have wide range of applications 

with relevance to most topic areas.

Key References:

Rossman, L.A. (2000). EPANET 2 Users Manual. National Risk Management Research 

Laboratory, Environmental Protection Agency. Cincinnati, OH.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 154

Project Area Document Code: Stor2 

Project Area Title: Assess Distribution Systems Characteristics that May Lead to Storage 

Related Problems and Potential Health Risks

Goal(s): To better understand the potential public health risks and the magnitude of the health 

risks related to storage contamination events.

Rationale: 

Finished water storage facilities have been associated with a range of health risks that can 

include acute or fatal illness from exposure to waterborne pathogens, exposure to intermittent, 

chronic, or persistent contamination that can result from breaches in tank integrity or internal 

reactions including nitrification, solids accumulation and mobilization, and release of pathogens 

from biofilms. In addition, aesthetics concerns (taste and odor) may be linked to perturbations in 

storage operations and associated water quality variations. Due to large volumes of water in 

storage, and often limited monitoring of storage, undetected storage breaches and/or contaminant 

accumulations could potentially impose health risks that impact large areas of the system and 

associated consumer populations. Finished water storage facilities have been directly linked to 

reported waterborne disease outbreaks. For example, a well-documented, extensively studied, 

drinking water storage-related Salmonella typhimurium disease outbreak occurred in December

1993 in Gideon, Missouri. This outbreak resulted in more than 650 illnesses and seven deaths.

It was ultimately determined that system-wide hydrant flushing distributed contaminated water 

from a bird-infested elevated storage tank. While high profile events such as the outbreak in 

Gideon have pointed to finished water storage as a potential public health risk, more work is 

needed to fully understand the national implications of storage on public health.

Research in this project area will examine distribution system characteristics that may contribute 

to contamination due to storage related events. In particular, the research will examine the 

potential frequency at which the convergence of three distribution system characteristics exist 

that must simultaneously occur for storage contamination. The three factors that must occur are 

the presence of a contaminant in storage or in proximity to storage, the presence of pathways or 

mechanisms for contaminant entry to the distribution system, and the failure of a barrier to 

prevent contamination. To estimate the potential public health impacts from storage related 

events, research in this project area will examine data on these characteristics from other RICP 

project areas, as well as existing data.

Objectives:

1. Collect and synthesize information that may inform the frequency and magnitude of 

potential health risks related to storage contamination events 

2. Conduct additional targeted literature searches, if needed, that may provide information 

on the magnitude of potential health risks related to storage events 

Suggested Approach:
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 155

This project area has two suggested approaches to obtain information needed to assess 

distribution system characteristics that may lead to storage problems and potential health risks

1. Collect and synthesize information from completed RICP project areas related to storage and 

that may inform the magnitude of potential health risks related to storage events. This includes 

determination of the extent to which barriers to contamination (e.g., disinfection) exist and the 

causes and frequencies of barrier failure.

- Presence of a pathway for contamination

- Number and types of storage facilities (Sur1)

- Populations served by storage facilities (Sur1)

- Number and size of systems with floating storage tanks (Sur1)

- Storage tank operation/configuration information (Sur1)

- Location of storage relative to supply source (Sur1)

- Volume of storage relative to piping (Sur1)

- Characterization of breaches in storage tanks (including causes, sizes, durations, and 

frequencies) (Con3)

- Failure of a barrier

- Storage disinfection practice information (including type, usage, frequency, dosage and 

application point)

-Number of pressure zones and storage facilities per pressure zone (Sur1)

-Practices for removal of solids accumulated in storage (amount and percent removed, frequency 

of removal) (Sur1)

- Presence of a contaminant

- Number and types of storage facilities with specific types of internal coating (Sur1)

- Frequency of pathogen occurrence in storage tanks (Con3)

- Extent to which accumulation, amplification or die-off of pathogens occurs due to storage 

conditions or operations (Con3)

2. Conduct additional targeted literature searches, if needed, for existing information that may 

provide information on the frequency and magnitude of potential health risks related to storage 

contamination events. These searches would fill in any gaps in the areas of knowledge that are 

listed in section 1, but were not able to be obtained from RICP project areas. Evaluate resulting

information to estimate the frequency and magnitude of potential public health risks resulting 

from storage.

Results and Applications:

The results of research in this project area will inform the magnitude of potential public health 

risks associated with distribution system contamination from storage related events. 

Specifically, the research will assess information from other RICP project areas and, if needed,

information from research and information collection efforts outside of the RICP to determine

the frequency at which various distribution system characteristics occur which contribute to 

storage related contamination. The estimated occurrence of contamination from storage from 

these data will provide information to support local and national risk management decisions. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 156

Decision Relevance:

How is research in this project area likely to inform evaluation of the magnitude of public 

health risk? 

Research in this project area will evaluate information on the prevalence, frequency, and 

magnitude of occurrence of distribution system characteristics that lead to storage related

contamination. The characteristics evaluated are those that lead to contamination of distribution 

systems from storage, and the resultant public health risks from the contamination. These pieces 

of information are essential inputs to a calculation of risk from storage related contamination.

How is research in this project area likely to inform opportunities for mitigation and risk 

reduction?

Increased understanding of the risk factors associated with contamination due to storage events 

will lead to better decisions on how to mitigate those risks. 

What types of distribution system decisions could be supported by research in this project 

area?

Research in this project area will support future decisions regarding the need for regulation, 

guidance, policy statements, or other actions be taken to control potential public health risks 

from storage. 

Project Area Constraints and Timing:

The focus of research in this project area is to analyze information generated through other 

research and information collection project areas, including some conducted as part of the RICP. 

Therefore, research in this project area cannot be completed until the information generated from 

those other RICP project areas is available. These project areas are listed in the table below.

Relationship to 

other RICP 

project areas

Project 

area 

document 

code

RICP project area 

document title (under 

consideration by the DS 

RICP)

Information needs 

(what will be 

learned from the 

predecessor 

project areas or 

what will be used 

in follow-on 

project areas)

This project area 

depends on

Sur1 Survey of Large Drinking 

Water Utility Distribution 

Systems

The presence of 

distribution system 

characteristics that 

contribute to 

contamination from 

storage.

Con3 Contaminant entry from 

breaches in storage facilities 

Extent of 

contamination of 

storage tanks.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 157

Project areas that 

this project area 

builds on

Con8 Baseline data on episodic 

release/mobilization of 

chemical contaminants from 

biofilms and accumulated 

solids in distribution and 

storage systems

Frequency and 

extent of release of 

accumulated 

contaminants, 

especially from 

storage.

Project areas that 

build on this 

project area

Stor1 Best practices for minimizing 

risks associated with storage 

facilities

The problem 

identification 

assessment from 

Stor2 may be used 

to evaluate the 

effectiveness of 

existing best 

practices.

RisM1 Decision support for 

managing potential 

distribution systems public 

health risks from potential 

contamination events and 

daily operations

Information on 

barriers to 

implementation of 

storage 

contamination 

mitigation 

activities.

Factors that might influence the timing of completion of research in this project area include:

Completion of preceding RICP project areas listed in the table above

Quality and completeness of information in the preceding project areas

Availability of supplemental information from sources other than RICP project areas

Relevance to the Agreement in Principle:

Research in this project area is relevant to storage topic area described in the Agreement in 

Principle, which is a Tier One priority area. Research in this project area focuses on the analysis 

of information on storage to inform local and national risk management decisions by the drinking 

water community. Support for these risk management decisions through the RICP was a 

recommendation in the Agreement in Principle.

Key References:

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf

EPA. (2001) Potential Contamination Due to Cross-Connections and Backflow and the 

Associated Health Risks. Distribution System White Paper. 

www.epa.gov/safewater/disinfection/tcr/pdfs/issuepaper_tcr_crossconnectionbackflow.pdf.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 158

Project Area Document Code: Sur2

Project Area Title: Survey of Small and Medium Drinking Water Utility Distribution Systems

Goal(s): To identify the characteristics of drinking water distribution and storage systems that 

serve < 50,000 people.

Rationale: 

Information collection in this project area will evaluate the current status of distribution system 

conditions and practices. It will provide data on the type, condition, and vulnerabilities of small 

and medium systems infrastructure; inform potential risk implications; and characterize the use 

of risk management strategies. This could also identify opportunities and impediments to 

mitigate and manage risks pertinent to systems that serve < 50,000 people. 

Objectives: 

Use relevant data sources to identify drinking water distribution and storage systems to 

target for these surveys.

Identify key variables related to the type, quantity, and condition of distribution system 

infrastructure elements that may contribute to increased public health risks.

Assess the prevalence and use of various risk management strategies on distribution 

systems.

Provide baseline information on medium and small drinking water distribution and 

storage systems.

Compare results to findings from large system survey(s) (see Sur1).

Identify additional research and information collection needs.

Identify pools of utilities with varied infrastructure, distribution system conditions, and/or 

water quality conditions to assist in construction of a representative sample for 

subsequent distribution system related research and information collection project areas.

Suggested Approach:

Information in this project area will proceed in two sequential phases: Phase 1 - Review and 

analyze available, and Phase 2 - Survey targeted medium and small utilities based on findings in 

Phase 1. 

Phase 1 - The first phase is comprehensive reviews of literature and available data relevant to 

water distribution systems that serve small communities. Examples of data sources include the 

Community Water System Survey (CWSS), the 2007 Drinking Water Infrastructure Needs 

Survey (DWINS), and the 2006 Water Research Foundation Study – Susceptibility of 

Distribution Systems to Negative Pressure Transients. Implementation data from sanitary survey 

for drinking water regulations (e.g., Surface Water Treatment Rule, Total Coliform Rule, etc.) 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 159

may also provide information. Key variables will be identified and these data sources will be 

mined to compile, synthesize, and evaluate the available data.

Information collected will be analyzed to determine characteristics of drinking water distribution 

and storage systems, and identify information gaps.

Phase 2 - Based on the results of Phase 1, survey instruments will be developed targeted at 

utilities that serve populations < 50,000. Systematic methods will be developed to collect data 

from representative utilities that serve medium or small-sized populations. All terms used in the 

surveys will be carefully and explicitly defined in order to ensure there is no confusion between 

the survey respondents and those using the results. Because smaller systems tend to have fewer 

staff members with less specialized training, it is anticipated that the desired level of detail will 

require considerable follow up effort on the part of the researchers. States may be able to 

provide assistance in these survey processes due to their familiarity with the small systems 

within their jurisdiction. Supplemental information could be collected through workshops or 

meetings with groups of utility representatives. 

Results and Applications:

The survey results will be used to identify distribution system characteristics including the 

prevalence of specific infrastructure components, perceptions of infrastructure condition in 

medium and small systems, and the extent to which specific risk management practices are 

employed. The survey results are expected to help explain and estimate the prevalence of risk 

factors, and the degree of use and effectiveness of specific risk management strategies, as well as 

barriers to implementation.

Specifically, the data from these surveys may help in better understanding: 

Number of high-hazard cross-connections and degree of implementation of various crossconnection control program elements,

Potential for intrusion through leaks and other orifices,

Degree of implementation of surge control strategies, 

Types of storage facilities and the degree to which storage facilities are 

configured/operated for good cycling/mixing, breach avoidance, etc.

Frequency and characteristics of planned and emergency main installations and repairs.

The results of these surveys may provide a baseline for follow-up research or information 

collection project areas that inform the magnitude of public health risks or the effectiveness of 

risk management strategies. The survey results are expected to provide baseline information on 

distribution system conditions, operations, and management practices. The surveys are expected 

to provide information on practices already in use to help utilities make informed decisions about 

distribution system operations, maintenance, rehabilitation, or replacement. The information can 

provide a reference point of current conditions from which the effectiveness of potential actions 

such as guidance, regulations, or policies that arise from the RICP process may be assessed. 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 160

The results of these surveys may also identify pools of utilities with varied infrastructures, 

distribution system conditions, and/or water quality conditions to assist in construction of 

representative samples for subsequent distribution system related research and information 

collection project areas. Screening of survey participants and associated responses will identify 

potential candidate utilities for follow-up field research or information collection project areas. 

Decision Relevance:

How is information collection in this project area likely to inform evaluation of the magnitude 

of public health risk? 

Information collection in this project area will provide a perspective of the quantity, type and 

condition of existing distribution system infrastructure. This information coupled with 

information from RisM1 and Hea2 is expected to inform the frequency at which various potential 

public health vulnerabilities are occurring throughout the nation.

How is information collection in this project area likely to inform opportunities for mitigation 

and risk reduction?

Information collection in this project area will provide an initial understanding of the degree to 

which various risk management practices are used across the nation. This information can help 

the water supply community (PWSs, States, EPA) determine whether and what type of policies 

would be prudent to reduce risks.

What types of distribution system decisions could be supported by information collection in 

this project area?

Information from this project area could be used to inform national policies on distribution 

system issues. Possible policy outcomes that could be supported may include guidance, 

regulation, or other options.

Project Area Constraints and Timing:

The completion of information collection in this project area may influence several other project 

areas. In most cases, the baseline data from Phase 1 will improve design of follow-on project 

areas or be used to identify appropriate subpopulations for in-depth sampling, field work, or 

modeling. See the table below for information on the project areas that build on Sur2. 

Relationship to 

other RICP projects

Project 

area 

document 

code

RICP project area document 

title (under consideration by DS 

RICP)

Information needs 

(what will be learned 

from the 

predecessor project 

areas or what will be 

used in follow-on 

project areas)

This project area 

depends on. . .

Sur1 Survey of large drinking water 

utility distribution systems

Lessons learned from 

Sur1 will help 

determine the extent 

of Sur2.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 161

Project areas that 

build on this project 

area

Con4 Estimation of contaminated water 

volumes and contaminant 

concentrations introduced into DSs 

from cross-connection 

contamination events based on 

model predictions and field and 

pilot-scale experiments

Survey results may 

provide insightful 

information that may 

aid in refining the 

design of Con4.

Con6 Understanding the growth 

potential within distribution 

systems of indigenous bacterial 

pathogens (Legionella and 

Mycobacterium)

Survey results may 

aid in refining the 

project area design of 

Con6.

Pres3 Develop strategies to diagnose and 

monitor pressure fluctuations in 

water distribution systems

Survey results may 

provide insightful 

information that may 

aid in refining Pres3.

RisM1 Decision support for managing 

potential distribution systems 

public health risks from potential 

contamination events and daily 

operations

Survey results could 

be used to refine the 

menu of risk 

management 

strategies.

Sur3 Field survey to collect information 

on risk management practices 

employed in water distribution 

systems

Baseline conditions 

and inventory; 

identify pools of 

utilities to select for 

Sur3. Survey results 

could perhaps reduce 

or eliminate elements 

of Sur3.

Factors that might influence the timing of completion of this project area include:

Familiarity of investigators with distribution system concepts and survey design and data 

analyses

Complexity and scope of survey design and survey data analyses

Survey response/data quality review

Ability of surveyors to solicit or require sufficient responses

Willingness of recipients to participate

o Issues associated with providing potentially sensitive information (data 

confidentiality)

o Lack of information in utility files
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 162

o Lack of utility resources (personnel-time, computer expertise) to complete survey 

responses

Participation by enough (and sufficiently diverse) recipients to provide meaningful results

Communication/approvals for survey data use in follow-on project areas

Relevance to the Agreement in Principle:

The AIP specifically recommends in section 4.1.e that the RICP explore several mechanisms for 

collecting and analyzing data, including surveys implemented through research project areas or 

by interested organizations such as EPA, AWWA, AMWA, NRWA, WaterRF, and others. The 

completion of this project area is relevant to all seven priority topic areas. 

Key Reference:

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 163

Project Area Document Code: Sur3

Project Area Title: Field Survey to Collect Information on Risk Management Practices 

Employed in Water Distribution Systems

Goal(s): To develop a detailed understanding of the types of risk management practices (that are 

used to control distribution systems against contamination events and maintain water quality), 

the extent of their use, their perceived effectiveness, and challenges related to implementation.

Rationale: 

Conducting field surveys of representative subsets of Sur1 (Survey of large drinking water utility 

distribution systems) and Sur2 (Survey of small and medium drinking water utility distribution 

systems) participants provides an opportunity to systematically collect more detailed information 

with regard to use and effectiveness of risk management practices without imposing undue costs 

on the larger population of systems.

These surveys build on Sur1 and Sur2. Certain types of information being requested in Sur1 and 

Sur2 may not be readily available from all participating systems. Sur3 will try to collect such 

information. Additionally, there are information collection needs that cannot necessarily be fully 

captured using a paper or electronic survey formats. 

Objectives: 

Collect information on risk management practices that are used to control pressure, 

intrusion, cross-connections and backflow, main repair contamination, storage facility 

contamination, excess biofilm formation and release, nitrification, and solids 

accumulation.

Collect information on the effectiveness of risk management practices and identify 

challenges in implementing them.

Suggested Approach:

This project area will proceed in two sequential phases: Phase 1 - Review results of Sur1 and 

Sur2 to assess additional information collection data gaps identified in Sur 1 and Sur2, and to 

identify potential survey participants for these surveys; and Phase 2 – Develop and implement 

follow-up field surveys of subsets of Sur1 and Sur2 participants. 

Phase 1 – The first phase of this project area is detailed reviews of the Sur 1 and Sur 2 results to 

assess the degree to which those project area objectives were fulfilled, and areas in which more 

in-depth data collection, field observations, interviews, etc. are needed to more fully and 

accurately estimate the prevalence of risk factors, the degree of use of specific risk management 

strategies, as well as barriers to implementation. Systematic processes will be developed to 

select respondents from Sur1 and Sur2 for participation in Sur3. Factors such as system size, 

type, location (state), level of detail and consistency of responses, perceived willingness to 

participate and share information, etc. will be considered to maintain representativeness. The 
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 164

survey developers will need to define categories of participation (e.g., representing which 

physical, chemical, or high/low risk conditions) and appropriate justifications. While 

participation will need to be broad enough and comprehensive enough to allow for extrapolation 

to other systems, the purpose of Sur3 is to provide more detailed information from a smaller 

number of ―representative‖ systems.

Phase 2 – Once the information gaps have been assessed and participant pools have been 

identified, Sur3 will be developed and implemented. Sur3 will likely involve a combination of 

targeted phone interviews, field investigations, requests for additional information collection and 

evaluation, modeling, and follow-up. Utilities could be asked to identify critical distribution 

system challenges and then queried on methods used to prevent, diagnose, predict, respond, and 

manage water quality problems generated within their distribution systems. They could also be 

asked for information on the types of monitoring that are used routinely, how they document and 

respond to distribution system issues, and how they gauge the effectiveness of risk management 

strategies. A key issue for consideration as Sur3 is being carried out is to determine how, 

whether, and to what degree the results can be extrapolated nationally. 

Other information that may be collected includes the following: 

Level of training provided to staff, 

Asset management, 

Assessment of costs of risk mitigation and prevention, and 

Perceived barriers to implementation of various risk management strategies (cost, public 

relations, conflicting requirements, lack of authority, political barriers, etc). 

Results and Applications:

The survey results will be used to develop a more detailed perspective on the use, effectiveness, 

and barriers to implementation of risk management practices relevant to managing distribution 

system water quality. Sur1 and Sur2 results will be used to develop identify distribution system 

characteristics including the prevalence of specific infrastructure components, perceptions of 

infrastructure condition in large systems, and the extent to which specific risk management 

practices are employed. Specific information gaps that may be addressed by the Sur3 

participants include but are not limited to the following: 

Additional field surveys (including site visits by surveyors) and review of existing crossconnection surveys to better estimate the number of cross connections per service 

connection and the number of cross-connections with health hazards

Frequency of valve operations by valve type and crew type (e.g., utility vs. fire 

department, etc.)

Frequency of hydrant operations and type of operations (e.g., fire flow testing, flushing, 

fire department practice, maintenance, etc.)

Distance (horizontal/vertical) between sewer mains and drinking water mains

Effect of increasing water pressure on current infrastructure condition in low pressure 

area

Ability to maintain sanitary conditions during main installations and repairs
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 165

Use and effectiveness of existing risk management strategies and intervention options 

Economic impacts of implementing various risk management options

Impacts of storage facility set points on mixing and turnover

Impacts of storage facility inlet/outlet configurations on mixing and turnover 

Decision Relevance:

How is information collection in this project area likely to inform evaluation of the magnitude 

of public health risk? 

Information collection in this project area will support development of a more in-depth 

understanding of the occurrence and magnitude of potential health risks for the systems surveyed 

in Sur3 by identifying aspects of systems‘ risk management practices and the prevalence of risk 

factors across the nation. 

How is information collection in this project area likely to inform opportunities for mitigation 

and risk reduction?

Information collection in this project area will provide a substantially greater understanding of 

the degree to which various risk management practices are used across the nation. It will also 

help to probe more deeply into understanding barriers to implementation of risk management 

strategies that are already known to be effective, but perhaps under-utilized. This information 

can help the drinking water community (PWSs, States, EPA) determine whether and what type 

of actions might be appropriate for reducing potential risks. 

What types of distribution system decisions could be supported by information collection in 

this project area?

Information collection in this project area would inform local, regional, State and national policy 

on distribution system issues. Possible policy outcomes that could be supported may include the 

need for technical assistance, guidance, or regulation, or other options.

Project Area Constraints and Timing:

Ideally, this information collection will build on the findings Sur 2, and therefore will occur 

sequentially with Sur2. In most cases, the baseline data obtained from Sur 2 will improve the 

design of Sur 3, and can be used to identify a subset of representative systems for in-depth 

sampling, field work, or modeling. However, there may be good opportunities to recruit utilities 

prior to the completion of Sur 2. 

Relationship to 

other RICP 

projects

Project 

area 

document 

code

RICP project area 

document title (under 

consideration by DS RICP)

Information needs 

(what will be 

learned from the 

predecessor 

project areas or 

what will be used 

in follow-on 

project areas)

This project area No other project areas. NA
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 166

depends on. . .

Project areas that 

this project area 

builds on

Sur2 Survey of small and medium 

drinking water utility 

distribution systems

Baseline data, 

identification of 

additional 

information gaps, 

pools of potential 

participants.

Project areas that 

build on this 

project area

RisM1 Decision support for 

managing potential 

distribution systems public 

health risks from potential 

contamination events and 

daily operations

Survey results 

could be used to 

refine the menu of 

risk management 

strategies.

Factors that might influence the timing of completion of this project area include:

Complexity and scope of survey design and survey data analyses

Survey response/data quality reviews

Technical capability of respondents

Ability of surveyors to solicit ―representative‖ participants so that the ability to 

extrapolate can be determined

Willingness of recipients to participate

o Issues associated with providing potentially sensitive information (data 

confidentiality)

o Lack of utility resources (personnel-time, expertise) to complete survey 

responses

Communication/approvals for survey data use

Relevance to the Agreement in Principle:

The AIP specifically recommends in section 4.1.e that the RICP explore several mechanisms for 

collecting and analyzing data, including surveys implemented through research project areas or 

by interested organizations such as EPA, AWWA, AMWA, NRWA, WaterRF, and others. The 

completion of this project area is relevant to all seven priority topic areas, and will use multiple 

data collection mechanisms including phone interviews, field inspections and surveys, use of 

hydraulic models, more detailed review of databases, plus others. 

Key References:

TCRDSAC Agreement in Principle (2008). 

http://www.epa.gov/safewater/disinfection/tcr/pdfs/tcrdsac/agreementinprinciple_tcrdsac

_2008-09-18.pdf
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 167

Appendix D – Scoring System Description and Initial Results

How the Scoring System Works

The partners completed the scoring by assessing the ability of the project area documents to fill 

the needs identified, and by applying the appropriate weighting to the Tier One and Tier Two 

issues, as recommended by the SC. For each of the seven topics areas each project area 

document received two scores, one for magnitude of risk and one for mitigation of risk. 

Therefore each project area document received a total of 14 scores, which were then summed to 

obtain the final score. Scores of 0, 5 or 10 were used. The standards used to assign these 

scores were:

10 – The project area is critical to informing risk magnitude/risk mitigation for this 

framework topic. 

5 – This project area provides some information relevant to risk magnitude/risk 

mitigation but is not considered to be critical for this framework topic.

0 – This project area provides no information relevant to risk magnitude/risk mitigation 

for this framework topic.

Once the partners completed the scoring, they provided an initial ranking for each project area 

based on the sum of the weighted scores. The partners then provided this initial ranking to the 

SC for review and discussion.

Initial Scoring Results

The following are the results of the scoring and ranking process executed by the partners. The 

partners presented this information to the SC for their final review.

Project Area 

Document 

Code Score

Project Area 

Document 

Code Score

Sur1 155 Hea3 55

Sur2 155 Con7 55

Sur3 120 RisM5 50

Pres1 120 Con3 50

Pres2 120 Con4 50

Hea1 120 Mon1 45

RisM1 110 CC* 40

Hea2 95 Stor* 40

Sur4 90 Hea4 25
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 168

Pres3 90 RisM3 25

Con1 65 RisM4 25

Con2 65 Con6 25

Pres4 60 Con5 20

RisM2 60

* At the time of the scoring, only the CC1 and Stor1 project area documents had been completed, so the scores here 

reflect the partner scores of those projects. Subsequently, the partners included two additional projects, CC2 and 

Stor2, that served to compliment the CC1 and Stor1 projects. While CC2 and Stor2 did not undergo the formal 

scoring process described above, they would have likely received similar scores to CC1 and Stor1 based on the 

scoring criteria used.
April 2010 – Priorities of the Distribution System Research and Information Collection 

Partnership Page 169

Appendix E – First Generation Project Area Documents

Project Area 

Document Code Project Area Title

CC1 Best Practices to Minimize Risks Associated 

with Cross Connections and Backflow

Con3 Contaminant Entry from Breaches in Storage 

Facilities

Hea1 Quantitative Microbial Risk Assessment 

(QMRA) to Evaluate Exposure to Pathogens 

through Drinking Water Distribution Systems 

Hea2 Epidemiological Studies of Health Effects 

Associated with Low or Negative Pressure 

Events in Distribution Systems 

Hea3 Response Teams to Prepare Case Studies on 

Adverse Public Health Effects from Distribution 

System Events 

Pres2 Characterize Propagation of Pressure Events 

through Water Distribution Systems to Improve 

Pressure Management Approaches

Stor1 Best Practices for Minimizing Risks Associated 

with Storage Facilities

Sur1 Survey of Large Drinking Water Utility 

Distribution Systems