United States
Environmental Protection
Agency
Water Quality in Small Community
Distribution Systems
A Reference Guide for Operators
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EPA/600/R-08/039
March 2008
Water Quality in
Small Community Distribution Systems
A Reference Guide for Operators
U.S. Environmental Protection Agency
Office of Research and Development
National Risk Management Research Laboratory
Water Supply and Water Resources Division
Cincinnati, Ohio
Recycled/Recyclable
Printed with vegetable-based ink on
paper that contains a minimum of
50% post-consumer fiber content
processed chlorine free
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Notice
The document was prepared by Shaw Environmental, Inc. (Shaw) under EPA Contract No. EP-C-05-056,
Work Assignment No. 0-10 and 1-10, with Pegasus Technical Services, Inc. Mr. Radha Krishnan, P.E.,
was the Shaw Program Manager for this contract and Mr. Srinivas Panguluri, PE. was the Shaw Project
Leader for this Work Assignment. Dr. Walter Grayman, P.E., and Dr. Robert Clark, P.E., D.E.E. were
consultants to Shaw on this Work Assignment. Ms. Lucille M. Garner served as EPA Work Assignment
Manager and Mr. Craig L. Patterson, P.E., served as the Alternate EPA Work Assignment Manager. Mr.
Roy C. Haught served as EPA Technical Advisor.
Disclaimer
Any opinions expressed in this document/reference guide for utilities are those of the author(s) and do
not, necessarily, reflect the official positions and policies of the U.S. Environmental Protection Agency
(EPA). Any mention of products or trade names does not constitute recommendation for use by EPA.
This document has been reviewed in accordance with ERA'S peer and administrative review policies and
approved for publication.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's
land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to
formulate and implement actions leading to a compatible balance between human activities and the ability
of natural systems to support and nurture life. To meet this mandate, ERA'S research program is providing
data and technical support for solving environmental problems today and building a science knowledge
base necessary to manage our ecological resources wisely, understand how pollutants affect our health,
and prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for investiga-
tion of technological and management approaches for preventing and reducing risks from pollution that
threaten human health and the environment. The focus of the Laboratory's research program is on meth-
ods and their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface
resources; protection of water quality in public water systems; remediation of contaminated sites, sedi-
ments and ground water; prevention and control of indoor air pollution; and restoration of ecosystems.
NRMRL collaborates with both public and private sector partners to foster technologies that reduce
the cost of compliance and to anticipate emerging problems. NRMRL's research provides solutions to
environmental problems by: developing and promoting technologies that protect and improve the envi-
ronment; advancing scientific and engineering information to support regulatory and policy decisions;
and providing the technical support and information transfer to ensure implementation of environmental
regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is
published and made available by EPA's Office of Research and Development to assist the user commu-
nity and to link researchers with their clients.
Sally Gutierrez, Director
National Risk Management Research Laboratory
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Abstract
The U.S. Environmental Protection Agency (EPA) has developed this reference guide to assist the
operators and managers of small- and medium-sized public water systems. This compilation provides a
comprehensive picture of the impact of the water distribution system network on distributed water quality.
This reference guide provides information on the following topics:
• Water supply and distribution process overview
• Distribution system infrastructure
• Drinking water regulations
• Distribution system water quality issues
• Distribution system monitoring, control and security
• Operational, financial and management strategies to address
distribution system water quality
In addition, to make this document appeal to a diverse group of small system operators and managers,
graphical elements such as pictures, tables, blue sidebars, and cartoon illustrations have been used
throughout the document. Although every water distribution system is different (in terms of specific
layout and operations), all water distribution systems generally have the same components and operate
under similar principles and operational strategies. To illustrate solutions to some of the common issues
faced by the small community distribution system operators, an example of a small water distribution
network (SmallWater, USA) has been included in this document. At the end of many chapters, one
or more SmallWater problem scenario(s) are presented along with some guidance on resolving these
problems.
Other related EPA reference guides in this area include the following:
• Small Drinking Water Systems: State of the Industry and Treatment Technologies to Meet
the Safe Drinking Water Act Requirements. EPA Publication Number: 600-R-07-110
• Water Distribution System Analysis: Field Studies, Modeling and Management - A
Reference Guide for Utilities. EPA Publication Number: 600-R-06-028
• Small Drinking Water Systems Handbook: Guide to "Packaged" Filtration and Disinfection
Technologies with Remote Monitoring and Control Tools. EPA Publication Number: 600-
C-03-041
IV
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Table of Contents
1.0 Introduction 1-1
1.1 Purpose and Scope of the Document 1-1
1.2 Graphical Elements and Cartoon Illustrations 1-1
1.3 SmallWater, USA- Problem Scenarios 1-2
1.4 Content Development and Description 1-2
2.0 The Supply, Distribution, and Quality of Water: An Overview 2-1
2.1 Protecting Source Water Quality 2-1
2.2 Water Treatment, Supply and Distribution 2-2
2.3 History of Water Supply and Treatment in the United States 2-3
2.4 History of Water Quality Regulations and Standards in the United States 2-3
2.5 Public Water System 2-4
2.5.1 Type and Size of Systems 2-4
2.5.2 Type of Source Water Used 2-5
2.5.3 Type of Ownership 2-6
2.6 Common Problems Faced by Small and Medium Utilities 2-6
2.6.1 Water Quality Problems 2-6
2.6.2 Operational Problems 2-7
2.6.3 Regulatory/Compliance Problems 2-7
2.6.4 Institutional Problems 2-7
2.7 SmallWater, USA Scenario 2-7
3.0 Distribution System Infrastructure 3-1
3.1 The Impact of Distribution System on Water Quality 3-1
3.2 Distribution System Pipes 3-2
3.2.1 Pipe Connectivity, Placement and Configuration 3-2
3.2.2 Pipe Material 3-3
3.2.3 Common Problems, Troubleshooting and Pipe Repair 3-4
3.3 Distribution System Pumps 3-5
3.3.1 Common Problems, Troubleshooting and Maintaining Pumps 3-6
3.4 Distribution System Storage Facilities 3-6
3.4.1 Types of Storage Facilities 3-6
3.4.2 Common Problems, Troubleshooting and Maintaining Tanks 3-7
3.5 Distribution System Valves 3-8
3.5.1 Gate Valves 3-8
3.5.2 Butterfly Valves 3-8
3.5.3 Check Valves 3-9
3.5.4 Other Valves 3-9
3.5.5 Common Problems, Troubleshooting and Maintaining Valves 3-9
3.6 Distribution System Hydrants 3-10
3.6.1 Common Problems, Troubleshooting and Maintaining Hydrants 3-10
3.7 Water Meters and Service Lines 3-11
3.7.1 Water Meters 3-11
3.7.2 Service Lines 3-11
3.7.3 Common Problems, Troubleshooting and Repairs 3-11
3.8 Distribution System Asset Management 3-12
3.9 Distribution System Modeling 3-13
3.10 SmallWater, USA-Asset Management Problem Scenario 3-16
4.0 Drinking Water Regulations 4-1
4.1 Highlights of 1974 SDWA and its Amendments 4-3
4.1.1 1986 Amendments to SDWA 4-3
4.1.2 1996 Amendments to SDWA 4-3
4.1.3 Variances and Exemptions 4-3
4.2 Regulations to Control Microbial Contaminants 4-4
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4.3 Regulations to Control Chemical Contaminants 4-5
4.4 Public Notification and Consumer Confidence Rules 4-5
4.5 SmallWater, USA - Regulatory Scenario Problems 4-9
5.0 Distribution System Water Quality Issues 5-1
5.1 Taste, Odor, and Color 5-1
5.1.1 Taste and Odor Problems 5-1
5.1.2 Color Problems 5-2
5.2 Biofilm 5-3
5.2.1 Factors Aiding Biofilm Growth 5-4
5.2.2 Operational Factors Inhibiting the Growth of Biofilm 5-4
5.3 Disinfection and Disinfection Byproducts 5-5
5.4 Nitrification 5-6
5.5 pH Stability and Scale Formation 5-6
5.6 Contamination Events 5-7
5.6.1 Cross-connections and Backflow 5-7
5.6.2 Permeation and Leaching 5-8
5.6.3 Intrusion and Infiltration 5-8
5.6.4 Storage Facility Contamination 5-8
5.7 SmallWater, USA-Water Quality Problem Scenarios 5-9
6.0 Distribution System Monitoring, Control, and Security 6-1
6.1 Monitoring a Distribution System 6-1
6.2 Distribution System Hydraulic Monitoring 6-2
6.2.1 Flow and Velocity Monitoring 6-2
6.2.2 Pressure Monitoring 6-4
6.3 Distribution System Water Quality Monitoring 6-5
6.4 Controlling a Distribution System 6-6
6.4.1 SCADA Instrumentation and Hardware 6-6
6.4.2 SCADA Operator Interface 6-6
6.4.3 Communication Media 6-7
6.4.4 Selection of SCADA Systems 6-7
6.5 Securing a Distribution System 6-8
6.5.1 Distribution System Vulnerabilities 6-8
6.5.2 Operational and Emergency Response Mechanisms 6-9
6.6 SmallWater, USA - Monitoring, Control and Security Problem Scenarios 6-10
7.0 Strategies to Address Distribution System Water Quality Issues 7-1
7.1 Operational Strategies 7-1
7.1.1 Reducing Water Age in the Distribution System 7-1
7.1.2 Adapting Operations to Meet System-Specific Water Demands 7-2
7.1.3 Changing Disinfectants 7-2
7.1.4 Implementing Corrosion Control 7-3
7.1.5 Preventing Sedimentation and Scale Formation 7-4
7.1.6 Implementing a Flushing Program 7-4
7.1.7 Infrastructure Replacement and/or Treatment Upgrades 7-5
7.2 Financial Strategies 7-5
7.2.1 Drinking Water State Revolving Fund 7-6
7.2.2 Community Development Block Grants 7-7
7.2.3 Rural Utilities System 7-7
7.2.4 Economic Development Administration 7-7
7.2.5 Other Entities and Private Foundations 7-8
7.3 Management Strategies 7-8
7.3.1 Small Systems Working Together 7-8
7.3.2 Change in Ownership and/or Management 7-9
7.4 SmallWater USA - Cell Tower Installation 7-9
8.0 Bibliography 8-1
VI
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List of Tables
Table 3.1 Infrastructure Components 3-1
Table 3.2 Potential Negative Impacts to Water Quality Based on Pipe Material and Changes in
Water Quality 3-3
Table 3.3 Common Problems that Lead to Pipe Failure for Various Pipe Materials 3-5
Table 3.4 Listing of Low-cost CADD and CIS Application Software 3-14
Table 3.5 Available Hydraulic-Water Quality Network Modeling Software Packages 3-16
Table 3.6 Hydrant Inventory Information 3-17
Table 3.7 Event Table 3-17
Table 4.1 Summary of Regulations Designed to Control Microbial Contamination 4-6
Table 4.2 Summary of Regulations Designed to Control Chemical Contamination 4-7
Table 6.1 Flow Meters 6-3
Table 6.2 Cost of SCADA Implementation at Coalwood, WV. 6-7
List of Figures
Figure 1.1 "Rogue's Gallery" of fictional characters used in this reference guide 1-1
Figure 2.1 The Hydrologic Cycle or"Water Cycle" 2-1
Figure 2.2 Multiple Risks to Public Health 2-2
Figure 2.3 A Typical Water Supply System Using Surface Water as Source 2-3
Figure 2.4 A Schematic Representation of a Water Distribution System 2-3
Figure 2.5 Classification of PWSs in the U.S 2-5
Figure 2.6 Distribution of PWSs by Size 2-5
Figure 2.7 Distribution of Small- and Medium-Sized PWSs by Source of Water Used 2-6
Figure 2.8 Distribution of Small- and Medium-Sized PWSs by Ownership 2-6
Figure 2.9 SmallWater, USA - Schematic Layout 2-8
Figure 3.1 A Branched Distribution System 3-2
Figure 3.2 A Grid/Looped Distribution System 3-2
Figure 3.3 NSF-Approved PVC Pipe for Potable Water Use 3-3
Figure 3.4 Pipe Wall Interactions that Affect Water Quality 3-3
Figure 3.5 Storage Tank Volume Design Requirements 3-7
Figure 3.6 Gate Valve (side view) 3-8
Figure 3.7 Butterfly Valve (top view) 3-9
Figure 3.8 Swing Check Valve (side view) 3-9
Figure 3.9 Dry Barrel Hydrant 3-10
Figure 3.10 Arenas Valley Pipe Inventory and Main Break Map 3-12
Figure 3.11 Screen-shot Showing the Results of an Analysis for the SmallWater Distribution
System 3-14
Figure 3.12 EPS Plots of Tank Water Levels and Flow in a Water Main Over a 2-Day Period 3-15
Figure 3.13 Components in the SmallWater Distribution System 3-17
Figure 3.14 Hydrant locations in part of SmallWater 3-17
Figure 3.15 Sample Asset Management Database Design or Schema 3-17
Figure 4.1 The Evolution of Federal Drinking Water Standards 4-2
Figure 4.2 Disease-Causing Microorganisms - E. coli, Giardia and Cryptosporidium (not to scale) 4-5
Figure 4.3 Sample Public Notice 4-8
Figure 5.1 Drinking Water Taste and Odor Wheel 5-3
Figure 5.2 Biofilm Growth Inside the Pipe 5-4
Figure 5.3 Water Age Within SmallWater, USA 5-10
Figure 6.1 Manual Water Quality Sampling and Field Testing 6-2
Figure 6.2 Automated Water Quality Monitoring 6-2
Figure 6.3 Hydrant Flow Gages 6-4
Figure 6.4 Digital and analog pressure meter attached to fire hydrant 6-5
Figure 6.5 Readout meters for flow, water level and pressure from a SCADA system 6-5
Figure 7.1 Crowded Cell Tower Installation 7-11
Figure 7.2 A Well-Designed and Constructed Cell Tower Installation 7-11
VII
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Acronyms and Abbreviations
AM Asset Management
AMR Automatic Meter Reading
ANSI American National Standards
Institute
AOC Assimilable Organic Carbon
ARC Appalachian Regional Commission
ASTM American Society for Testing
Materials
AWWA American Water Works Association
AwwaRF American Water Works Association
Research Foundation
BAT Best Available Treatment
BDOC Biodegradable Organic Carbon
CaCOS Calcium Carbonate
CADD Computer-Aided Design and Drafting
CCR Consumer Confidence Report
CDBG Community Development Block
Grant
CWA Clean Water Act
CWS Community Water System
DBP Disinfection Byproduct
D/DBPR Disinfectants/Disinfection Byproducts
Rule
DWSRF Drinking Water State Revolving Fund
EDA Economic Development
Administration
EPS Extended Period Simulation
ERP Emergency Response Plan
EPA United States Environmental
Protection Agency
FBRR Filter Backwash Recycling Rule
fps Feet per Second
CIS Geographic Information System
gpm Gallons Per Minute
GPS Global Positioning System
GWR Ground Water Rule
GWUDI Ground Water Under Direct Influence
(of Surface Water)
HAA Haloacetic Acids
HOPE High-Density Polyethylene
HPC Heterotrophic Plate Count
IESWTR Interim Enhanced Surface Water
Treatment Rule
IDSE Initial Distribution System Evaluation
IMS Indian Health Service
I/O Input/Output
IOC Inorganic Compounds
IRS Internal Revenue Service
LCR Lead and Copper Rule
LOS Level of Service
LRAA Locational Running Annual Average
LSI Langelier Saturation Index
LT1ESWTR Long-term 1 Enhanced Surface
Water Treatment Rule
LT2ESWTR Long-term 2 Enhanced Surface
Water Treatment Rule
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
MCPSD McDowell County Public Service
District
ug/L Micrograms per Liter
mg/L Milligrams per Liter
NDWC National Drinking Water
Clearinghouse
NIPDWR National Interim Primary Drinking
Water Regulations
NKWD Northern Kentucky Water District
NMEFC New Mexico Environmental Finance
Center
NPDES National Pollutant Discharge
Elimination System
NRWA National Rural Water Association
NSDWR National Secondary Drinking Water
Regulations
NTNCWS Non-Transient Non-Community Water
System
O&M Operation and Maintenance
OSHA Occupational Safety and Health
Administration
PD Positive Displacement
POE Point of Entry
POU Point of Use
PRV Pressure Reducing Valve
PVC Polyvinyl Chloride
PWS Public Water System
RAA Running Annual Average
REM Roentgen Equivalent Man
RTU Remote Terminal Unit
RUS Rural Utilities System
VIM
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SBREFA Small Business Regulatory
Enforcement Act
SCADA Supervisory Control and Data
Acquisition
SCWIE Small Community Water
Infrastructure Exchange
SDWA Safe Drinking Water Act
SMF Standardized Monitoring Framework
SOC Synthetic Organic Compounds
SSCT Small System Compliance
Technology
STEP Simple Tools for Effective
Performance
SWTR Surface Water Treatment Rule
TCR Total Coliform Rule
THM Trihalomethanes
TMDL Total Maximum Daily Load
TNCWS Transient Non-Community Water
System
TOC Total Organic Carbon
TT Treatment Technique
UF Ultrafiltration
UL Underwriters Laboratory
USDA U.S. Department of Agriculture
U.S. United States
USA United States of America
VA Vulnerability Assessment
VOC Volatile Organic Compounds
WV West Virginia
IX
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Acknowledgements
The principal authors of this document, titled "Water Quality in Small Community Distribution Systems
- A Reference Guide for Operators," were: Mr. Srinivas Panguluri, RE., Dr. Walter M. Grayman, RE., Dr.
Robert M. Clark, RE., D.E.E., Mr. E. Radha Krishnan, RE., Ms. Lucille M. Garner, Mr. Craig L. Patterson,
RE., and Mr. Roy C. Haught.
The authors wish to acknowledge the contributions of the following individuals and organizations towards
the development of this document:
EPA technical reviews of the document were performed by:
Mr. Thomas Grubbs, RE., Environmental Engineer, EPA Office of Ground Water and Drinking
Water (OGWDW)
Mr. Michael Finn, RE., Environmental Engineer, EPA OGWDW, Standards and Risk Reduction
Branch
Mr. Steve Clark, Environmental Health Scientist, EPA OGWDW, Drinking Water Protection Branch
EPA Office of Research and Development (ORD) Quality Assurance, editorial and graphical reviews
were performed by:
Mr. Stephen M. Harmon, Quality Assurance Manager- Quality Assurance Review
Dr. Jean Dye - Editorial Review
Mr. Patrick Burke - Publishing Review
Mr. Steve Wilson - Review of Illustrations
Ohio EPA Drinking Water Division staff for coordination of site visits to small water distribution systems
and providing state perspective on key issues:
Mr. Dan Cloyd, Environmental Specialist 3
Mr. Jeff G. Davidson, Environmental Manager
Mr. Daniel J. Stine, Environmental Supervisor
External technical reviews of the document were performed by:
Mr. Jerry C. Biberstine, RE., of the National Rural Water Association
Mr. Gary Burlingame of the Philadelphia Water Department
Mr. Gary Lynch of the Park Water Company
Mr. Lee Larue with the National Park Service at Mt. Rainer, Washington
Assistance during the conduct of site visits to small water distribution systems:
Mr. Jeremy Fite and Mr. Jason Barger at Williamsburg, Ohio
Mr. Fred Freeman at Blanchester, Ohio
Mr. Ken Shearwood and Mr. Don Caudel at New Richmond, Ohio
Illustrations and Graphical layout assistance:
Dr. Robert Probst of the University of Cincinnati (DC) Design, Architecture, Art, and Planning
(DAAP), for arranging the services of DAAP graduate students to prepare the illustrations
Ms. Shereen Puthenpurackal, graduate student at UC-DAAR for preparing the stand-alone
illustrations
Mr. Abhijeet Bhattacharya, graduate student at UC-DAAR for developing the character-based
illustrations
Mr. James I. Scott of Shaw for performing the document setting and layout
x
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Context-specific information and illustrations for inclusion into the document were provided by:
Mr. Ira M. Cabin, Dixon Engineering
Ms. Heather Himmelberger, RE., New Mexico Environmental Finance Center
Dr.Yeongho Lee, RE., Greater Cincinnati Waterworks
Mr. Adam Levine, Historical Consultant, Philadelphia Water Department
Ms. Charlotte D. Smith, Consultant
Mr. Gordon W Thompson, Shaw
Cover Photo Credits (starting from top left clockwise) are as follows:
Rural water tank - photograph by Mr. James I. Scott
Children drinking from a faucet- pictured are Mr. Ravi R. Panguluri and Ms. Isabella M. Panguluri
- photograph by Ms. Jennifer S. Panguluri
Small town picture - Aerial view of Stowe, Vermont - Royalty-free image from American Spirit
Images purchased from www.fotosearch.com
Operators flowing a hydrant - Montgomery County Sanitary Engineering Department Operators
- photograph by Dr. Walter M. Grayman.
XI
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Chapter 1
Introduction
In the United States, there are thousands of miles of
water distribution pipes which convey drinking water
to consumers. However, there are many changes that
occur within a distribution system that may result in
degraded water quality. Suspended and/or dissolved
solids in finished water can settle under low-flow con-
ditions and can be re-suspended during high-flow con-
ditions. Various disinfection agents (e.g., chlorine,
chlorine dioxide, and chloramines) can react with or-
ganic matter contained in the source water and gener-
ate potentially harmful byproducts to which consumers
are exposed. In addition, microorganisms can attach
to pipe surfaces, producing a complex microbiologi-
cal environment known as "biofilm." Contaminants
may infiltrate a distribution system during pipe breaks
or through finished water storage facilities. Some of
these undesirable water quality changes result in taste,
odor or red-water problems that can be detected imme-
diately. Potential contamination by pathogens (e.g., E.
coli or Salmonella) may only be identified by sampling
and analysis after a contamination event or following
a waterborne disease outbreak. In order to minimize
the degradation of water quality within distribution
systems, the United States Environmental Protection
Agency (EPA) publishes drinking water regulations.
It is important that water distribution system operators
and water utility managers understand changes occur-
ring in water distribution systems, the related water
quality concepts, and associated regulations in order to
maintain a high degree of water quality within a distri-
bution system. As emphasized in this document, prop-
er operation and management of distribution system
components is essential to protect the customer against
both aesthetic and public health threats that may result
due to undesirable water quality changes in the distri-
bution system.
1.1 Purpose and Scope of the
Document
EPA has developed this reference guide to assist op-
erators and managers of
small- and medium-sized
public water systems
(PWSs). It presents a
compilation of informa-
tion designed to provide
small- and medium-sized
water utility operators
with a comprehensive
picture of the water distribution system network. Be-
cause the technical background level of the target audi-
ence (small- to medium-size system operators and deci-
sion makers) varies widely, some very basic concepts
have been included in this document. For the purposes
of this reference guide, PWSs are interchangeably re-
ferred to as water utilities.
1.2 Graphical Elements and
Cartoon Illustrations
To make this document appealing to a wide audience,
graphical elements (pictures, tables and blue sidebars)
and cartoon illustrations have been used throughout the
document. Many of these graphical elements and car-
toons are borrowed or adapted from existing publica-
tions (as referenced). Others were developed exclusive-
ly for use in this reference guide. Many of the cartoons
were developed to illustrate basic distribution system
concepts in a humorous manner but bear no relation to
any real individuals or organizations. Figure 1.1 shows
a "rogue's gallery" of the characters that populate this
\
Carl, a utility
consultant
Stan, a state
regulator
Fred, a federal
regulator
Dale, a small utility
decision-maker
Liz, a small utility
laboratory technician
&
-ji* '
- ' A *-
:i:i.. i i'"*?A.- '
*
^" /
r-fc-^-i
•f
uA_K'
V
^
4^
1\r^
•;'i Bob, a small
utility operator
Figure 1.1 "Rogue's Gallery" of fictional
characters used in this reference guide.
1-1
-------
manual and their roles. In addition to these fictional
characters, other "stand alone" cartoons are also used
throughout the document as necessary. None of the car-
toon illustrations are meant to provide any "real-world"
solutions. The sole purpose of the cartoon illustrations
is to provide humor without offending any race, nation-
ality, gender, politics, or religion.
1.3 SmallWater, USA- Problem
Scenarios
Every water distribution system is different in terms of
specific layout and operations. However, water distri-
bution systems generally have the same components
and operate under similar principles and operational
strategies. SmallWater, USA is an example of a water
distribution system, utilized in this document to illus-
trate a drinking water utility serving a small- to medi-
um-sized town. This exam-
ple system includes all
of the components that
are typically found
in the majority of
small- and medium-
sized PWSs and is
used to illustrate
many of the issues
and potential prob-
lems facing a small
water utility. SmallWa-
ter, USA problem scenarios
are used throughout this reference guide to explore a
number of water quality, operational, regulatory/com-
pliance, and institutional problems faced by many of
the small- and medium-sized utilities in the nation.
At the end of each chapter, one or more SmallWater
problem scenario(s) are presented along with some
guidance on how to address these problems.
1.4 Content Development and
Description
Between January and February of 2007, during the
initial stages of development of this reference guide,
several of the authors met with the staff at three small
water utilities to discuss their operational and manage-
ment procedures. The various utility staff members
were very helpful in discussing their approaches to
solving common problems. The authors also met with
various state regulatory agency personnel to get their
perspective on the critical issues facing small-commu-
nity water utility operators and managers. In addition,
the authors consulted with several technical and edi-
torial reviewers to refine the material presented in the
document to make it suitable for the target audience.
These individuals are listed in the Acknowledgement
section immediately preceding this chapter. The fol-
lowing is a brief description of the content in each of
the subsequent chapters of this reference guide.
Chapter 2 provides an overview of the water supply
and distribution process with an emphasis on how the
distribution system impacts the quality of water sup-
plied to the consumer. First, the concept of "water
cycle" is illustrated along with strategies employed
by EPA to protect source water quality. Subsequent-
ly, the process for treating, stor-
ing and distributing water is
described. A brief history
of water treatment and
water quality regu-
lations is provided
as it relates to pro-
tecting water qual-
ity. Summary sta-
tistics documenting
the size, source water,
and ownership of PWSs
is presented. Finally, a listing of
common problems faced by small- and medium-sized
water utilities is presented along with the description
of SmallWater, USA.
Chapter 3 describes distribution system infrastructure
and how each component can potentially impact water
quality. Each of the major distribution system com-
ponents is discussed in this chapter. The first subsec-
tion of this chapter discusses distribution system pipes
and how their functionality varies
with connectivity, place-
ment and configuration.
Pipe types and mate-
rial are also discussed
along with common
problems, as well
as troubleshoot-
ing and pipe repair
techniques. Options
for minimizing pipe
leaks and water loss
during distribution
system line breaks
are also presented.
This is followed by a discussion on distribution sys-
tem pumps, storage facilities (tanks), valves, and hy-
drants. Common problems associated with each of
these components, along with troubleshooting and
suggested maintenance techniques for these compo-
nents, are also presented. Finally, the distribution
system asset management concept is presented along
with a SmallWater, USA problem scenario.
Distribution System
Infrastructure
1-2
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Chapter 4 presents a summary of
the drinking water regula-
tions. The highlights of
the 1974 Safe Drinking
Water Act (SDWA)
and its subsequent
amendments are dis- -•>
cussed. The regula-
tions to control mi-
crobial and chemical
contaminants are tab-
ulated. Public notifi-
cation and consumer
confidence rules un-
der the SDWA are discussed. Two SmallWater, USA
regulatory problem scenarios are presented.
Safe Drinking Water Act
Water Quality
Chapter 5 summarizes various distribution system wa-
ter quality issues such as taste, odor, and color. The
concept of "biofilm" is presented, along with the fac-
tors contributing to
biofilm growth and
operational factors
that could inhibit the
growth of biofilm.
Subsequently, distri-
bution system water
quality issues such as
disinfection byproducts
(DBFs), nitrification, pH
stability and scale forma-
tion are discussed. These
sections are followed by a
discussion on contamination
events including cross-connections, permeation/leach-
ing, intrusion/infiltration and reservoir/storage facility
contamination. Finally, the concept of hydraulic mod-
eling is introduced followed by two SmallWater, USA
regulatory problem scenarios.
Chapter 6 provides a summary of the
available methods for monitoring,
controlling, and securing dis-
tribution systems. The physi-
cal state of the distribution
system changes over time and
techniques for monitoring pa-
rameters such as flow, veloc-
ity, and pressure are present-
ed. Distribution system water
quality monitoring techniques
and methods for controlling a
distribution system are discussed. Common control
automation equipment such as Supervisory Control and
Data Acquisition (SCADA) instrumentation, SCADA
hardware, SCADA interface, and SCADA communica-
Water Distribution
Automation
Strategy
tion media are presented. This is followed by a discus-
sion on distribution system vulnerabilities, operational
responses, and emergency response mechanisms. Fi-
nally, two SmallWater, USA problem scenarios related
to monitoring, control and security are presented.
Chapter 7 contains a summary of operational, man-
agement and financial strategies to address distribution
system water quality issues. Operational strategies
such as reducing water age,
adapting operations to meet t,-v
demand, initiating or chang-
ing disinfectants, and con-
trolling corrosion are pre-
sented. Financial strategies
such as obtaining loans and
grants through various gov-
ernment and private sources
are discussed. Management
strategies such as regionali-
zation and change in ownership are presented. Finally,
two SmallWater problem scenarios are presented.
Chapter 8 includes a bibliography for this reference
guide. Some of the documents included in the bibliog-
raphy are referenced within the text of this guide. The
references in the bibliogra-
phy contain additional
detailed informa-
tion and provide
valuable read-
ing material for
readers who wish
to pursue any of the
specific topics dis-
cussed in this guide in
greater detail. Additional Information and
T ,u A i * * Bibliography
In the development of J r J
this reference guide, care has been taken to keep the
guide simple, short, and concise. The guide contains
additional references for supplementary reading mate-
rial (as necessary and appropriate). Acronyms and ab-
breviations used in each chapter are defined in a sepa-
rate listing as well as at their first occurrence in each
chapter. In addition, to help explain many of the con-
cepts, a variety of graphic illustrations, crossword puz-
zles and example problem scenarios have been utilized
throughout the document.
1-3
-------
-------
Chapter 2
The Supply,
Distribution, and
Quality of Water:
An Overview
Water is a renewable resource that is in continuous
movement at the earth's surface (e.g., rivers, streams,
and oceans), below the ground in aquifers and in the
atmosphere. The natu-
ral movement of water
is powered by the sun
and the earth's gravity,
This natural continu-
ous movement of water
is called the hydrologic
cycle or the "water cy-
cle." In this cycle, wa-
ter precipitates as rain
and falls onto surface
storage areas such as
lakes, rivers, streams,
and oceans. The water
on the land and these surface storage
areas infiltrates and recharges un-
derground sources called aq-
uifers. Additionally, the
water from the surface
sources and plants evaporates to form rain-bearing
clouds. Figure 2.1 is a graphical representation of the
natural water cycle.
Aquifers (ground water) and rivers (surface water) are
the main sources of water for utilities in the United
States (U.S.).
2.1 Protecting Source Water
Quality
During the natural cyclic movement and storage of wa-
ter in both surface and subsurface sources, water may
be exposed to a variety of natural or human activity-
related contaminants. Depend-
ing upon the location, the source
water may be exposed to surface
or subsurface sources of physical,
chemical, biological and/or radio-
logical contamination. Examples
of contamination sources include:
• Rain water run-off collected by storm
sewers (physical and/or chemical/biological
contamination)
• Concentrated Animal Feeding Operations
(biological and chemical contamination)
Agricultural Pesticide
and Fertilizer Application
(chemical contamination)
Figure 2.1 The Hydrologic Cycle or "Water
Cycle" (Adapted from: EPA, 2002f)
2-1
-------
• Septic Systems and Leaking Sewers (biological
contamination)
• Construction Activities (chemical
contamination)
• Wastewater and Industrial Discharges (chemical
and biological contamination)
• Mining Wastes (chemical and radiological
contamination)
• Naturally occurring chemical and radiological
material in contact with underground
water resources (chemical and radiological
contamination)
These multiple risks to public health, illustrated in Fig-
ure 2.2, are only a few of the potential sources of con-
tamination that can threaten both surface and ground
water supplies used by the water utilities. EPA man-
dates various water quality standards and regulations
that are designed to serve as barriers to the risk of
source water contamination.
If the amount (or concentration) of the contaminant
material present in the source water supply exceeds
drinking water standards, water utilities are required to
treat the source water to reduce (or eliminate) the con-
taminant material to the required standard levels prior
to distributing the water to their customers.
2.2 Water Treatment, Supply and
Distribution
Source water is often treated by unit processes such
as coagulation, filtration, and disinfection to remove/
reduce the contamination, to meet the maximum con-
taminant levels (MCLs). These treatment processes
are generally not considered to be part of the distri-
bution system. The finished water may be directly
delivered to the consumer through the distribution
system or temporarily stored in underground/elevated
tanks before it is delivered to the consumer through
the distribution system to faucets in their homes or
work places. Figure 2.3 is a graphical representation
of a typical water supply system that uses a surface
water source.
A drinking water distribution system is a complex net-
work of pipes, tanks and reservoirs that delivers finished
water to consumers. The consumers of water include:
residential households, commercial businesses, indus-
trial users, and agricultural users. Collectively, water
distribution system infrastructure consists of a variety
of equipment such as pumps, pipes, tanks, valves, hy-
drants and meters, that are built to deliver water from
the surface (e.g., river) and/or subsurface source (e.g.,
wells drilled into aquifers) to the customer. Figure 2.4
shows a schematic representation of a generic water
distribution system.
Agricultural Pesticide
& Fertilizer Application
Figure 2.2 Multiple Risks to Public Health
(Adapted from: EPA, 2002f)
2-2
-------
Figure 2.3 A Typical Water Supply System Using Surface
Water as Source (Adapted from: EPA, 2002f)
A more detailed discussion of the distribution system
components is presented in Chapter 3.0 of this report.
2.3 History of Water Supply and
Treatment in the United States
The first water supply utility was established in the U. S.
in Boston, Massachusetts in 1652, for the purpose of
providing domestic water and fire protection. Other
cities followed Boston's example and established water
utilities for fire protection and to provide commercial
and residential water service. The first water treatment
plant in the U.S. was constructed in Richmond, Virginia
in 1832 and the second was constructed in 1855 in Eliz-
abeth, New Jersey. The water treatment system in Eliza-
beth consisted of a small charcoal sand and gravel filter.
By 1860, only 136 water systems had been constructed
in the U.S. Because most of the early utilities supplied
water from springs low in turbidity and relatively free
from pollution, they were also relatively problem-free.
By the end of the nineteenth century, however, water-
borne disease had become a serious problem in indus-
trialized watersheds. For example, during one year in
the 1880s, the typhoid death rate was 158 deaths per
100,000 in Pittsburgh, Pennsylvania. This led to the
more routine use of water treatment; by 1935, the ty-
phoid death rate had declined to 5 per 100,000. Another
study of typhoid case rates and associated death rates in
the City of Cincinnati between 1898 and 1928 shows a
significant decline in these rates after the city initiated
filtration in 1907, and after implementation of chlorina-
tion in 1915. Water treatment in the U.S. has proven to
Source Treatment Distribution/Storage
s2£2ws2£2£> — *•
\
}
L
Figure 2.4 A Schematic Representation of a Water
Distribution System
be a major benefactor to the nation's public health. The
use of chlorine in particular has been recognized as a
breakthrough in public health.
2.4 History of Water Quality
Regulations and Standards in
the United States
EDITORIAL PAGE
PHILADELPHIA RECORD
SUNDAY, MARCH 14, 1937
WATER, WATER EVERYWHERE.
BUT NOT A DROP FIT TO DRINK.
(Courtesy: PWD, 2007)
The first federal drinking water regulation was prom-
ulgated in 1912 under the Interstate Quarantine Act of
1893. At that time, interstate railroads provided a com-
mon cup for train passengers to share for drinking water
while on board. The Act prohibited this practice. By
1962, several sets of federal drinking water standards
Sorry, honey, the first drinking water
regulation passed in 1912 under the
Interstate Quarantine Act of 1893
specifically prohibits the use of a "common
cup" on carriers of interstate commerce!
2-3
-------
Fix the leak, open the valve,
flush the hydrant, and take the
water samples by 4:00 pm.
had been issued, but they applied only to interstate car-
riers. By the 1960s, each of the states and trust ter-
ritories had established its own drinking water regula-
tions, although there were many inconsistencies among
them. Reported waterborne disease outbreaks had de-
clined from 45 per 100,000 persons in 1938-40 to 15
per 100,000 persons in 1966-70. However, the annual
number of waterborne disease outbreaks had stopped
declining around 1951 and may have actually increased
slightly. These conditions, in part, led to the passage of
the Safe Drinking Water Act (SDWA) of 1974.
The SDWA defines drinking water quality as a measure of
its suitability for human consumption, based on selected
physical, chemical, and biological characteristics. The
regulations established under the SDWA became the first
set of national drinking water regulations. These regula-
tions require that utilities meet specific guidelines and/or
numeric standards for drinking water quality. The SDWA
defines a public water system (PWS) as a system that pro-
vides water for human consumption through pipes or other
constructed conveyances, provided that such a system has
at least 15 service connections or regularly serves an aver-
age of at least 25 individuals daily for at least 60 days out
of the year. The SDWA established two types of numeric
standards. The first is an enforceable standard commonly
referred to as an MCL. The other (non-enforceable) stand-
ard is referred to as a maximum contaminant level goal
(MCLG). MCLGs are set at a level at which no known or
Water quality in the distribution system has been of major
interest to regulators and drinking water utilities. Main-
taining a high level of water quality in the distribution sys-
tem can pose a major challenge to some drinking water
utilities because of the age and type of pipes used in their
system. Corroded and decaying pipes may deteriorate
water quality significantly during transportation of water
through the distribution system. Contaminants that can
potentially increase in a distribution system include lead,
copper, disinfection byproducts (DBFs), and coliform.
Cross-connections are another major source of distribu-
tion system contamination.
anticipated adverse human health effects occur.
Where it is not economically or technologically feasible
to determine the MCL for a contaminant, an enforce-
able treatment technique (TT) is prescribed by EPA in-
stead of an MCL. For example, Giardia lamblia is a
microbial contaminant that is difficult to measure. To
ensure proper treatment, experimental work has been
conducted by EPA and others to establish optimum
treatment conditions. EPA and other researchers have
identified treatment technologies for ensuring proper
treatment. Therefore, the TT describes a specified pH,
temperature, and disinfectant concentration along with
a specified length of "contact time" to achieve a spe-
cific level of inactivation (or microbial kill). EPA has
also set operational conditions that systems must meet
to demonstrate removal by physical removal processes
(e.g., rapid granular filtration, membranes).
The major rules and requirements of interest to small-
and medium-system operators are discussed in Chapter 4
of this document.
EPA has identified several Best Available Technologies
(DATs) under SDWA for the treatment of drinking wa-
ter. The identified BATs include: Activated Alumina, Co-
agulation/Filtration, Direct Filtration, Diatomite Filtration,
Electrodialysis Reversal, Corrosion Control, Granulated
Activated Carbon, Ion Exchange, Lime Softening, Reverse
Osmosis, Polymer Addition, and Packed Tower Aeration.
Note that using BAT is not the same as employing speci-
fied TT. However, BATs can be used for requesting the
issuance of variance or exemption.
2.5 Public Water System
There are nearly 160,000 water utilities in the U.S. These
water utilities vary greatly in size, ownership, and type
of operation. The SDWA defines PWSs as consisting of
community water systems (CWSs), transient non-com-
munity water systems (TNCWSs), and non-transient
non-community water systems (NTNCWSs). A CWS
is a PWS which serves at least 15 service connections
used by year-round residents or regularly serves at least
25 year-round residents. An NTNCWS is a PWS that is
not a CWS and it regularly serves at least 25 of the same
persons for more than six months per year. A TNCWS
is a not a CWS and it does not regularly serve at least 25
of the same persons for more than six months per year.
Figure 2.5 shows examples of this classification.
2.5.1 Type and Size of Systems
Of the nearly 160,000 water utilities in the U.S., 33 per-
cent are classified as CWSs, 55 percent are classified as
TNCWSs, and 12 percent are classified as NTNCWSs.
PWSs serve 297 million residential, transient, and
2-4
-------
Public
Water System
Community
Water System (CWS)
Municipal Systems
Rural Water Districts
Mobile Home Parks
Non-Transient,
Non-Community
Water System
(NTNCWS)
• Office Buildings
• Schools
• Factories
• Daycare Facilities
Transient,
Non-Community
Water System
(TNCWS)
• Restaurants
• Parks
• Motels
Figure 2.5 Classification ofPWSs in the U.S.
commercial customers. PWSs servingfewerthan3,300
people are categorized as small systems and those serv-
ing 3,300 to 10,000 people are categorized as medium
systems. Although a vast majority (98 percent) of sys-
tems are categorized as small and medium, they serve
only about a quarter of the U.S. population. Other size
classifications such as that specified by the Small Busi-
ness Regulatory Enforcement Act (SBREFA) generally
define small systems to include all distribution systems
that serve less than 10,000 people. Figure 2.6 shows a
distribution of PWSs by size in the U.S.
"Consecutive systems" are those PWSs that receive some
or all of their finished water from one or more wholesale
systems. Delivery may be through a direct connection or
through the distribution system of one or more consecutive
systems.
As shown in Figure 2.6, a very large number of the
PWSs in the U.S. are represented by small- and me-
dium-size water utilities. The large number of small
and medium utilities creates a major administrative and
oversight challenge for state and federal water supply
regulatory agencies.
131,291
82.2%
19,632
12.3%
4,913
3.1%
I Small 501-3,300
I Large 10,001-100,000
U Very Small 25-500
D Medium 3,301-10,000
• Very Large >100,000
Figure 2.6 Distribution of PWSs by Size (EPA, 2007a)
We have 85 customers and we spent
1.4 million dollars to build this
double reverse osmosis system
Wealthy Falls Water
Treatment Plant
SmallWater, USA
Flea Market
I sure hope we can buy a spare
hydrant at the flea market, I don't
think we can fix this one again
2.5.2 Type of Source Water Used
Some utilities rely primarily on surface water supplies.
while others rely primarily on ground water. Surface
water is the primary source of 22 percent of the CWSs,
while ground water is used by 78 percent of CWSs. Of
the TNCWSs and NTNCWSs, 97 percent are served by
ground water. In addition, many systems serve commu-
nities using multiple sources of supply such as a com-
bination of ground water and/or surface water sources.
In these systems, the mixing of water in the distribution
system poses a challenge for managing water quality.
Figure 2.7 shows a distribution of PWSs by primary
source of water used.
As shown in Figure 2.7, the vast majority of small and
medium water utilities in the U.S. use ground water.
2-5
-------
11,909
7.6%
143,927
92.4%
107,976
69.3%
6,610
4.2%
,787
.4%
18.6%
Ground Water Systems
Surface Water Systems
Figure 2.7 Distribution of Small- and Medium-Sized
PWSs by Source of Water Used (EPA, 2007a)
2.5.3 Type of Ownership
The ownership of water utilities in the U.S. is also di-
verse and has a long history of local government control
over operation and financial management, with varying
degrees of oversight and regulation by state and fed-
eral government. The water utilities serving cities and
towns are generally administered by departments of
municipalities or counties (public systems) or by inves-
tor-owned companies (private systems).
Public systems are predominately owned by local mu-
nicipal governments, and serve approximately 78 per-
cent of the total population. Approximately 82 percent
of urban water systems (those serving more than 50,000
persons) are publicly owned.
About 33,000 privately owned water systems serve the
remaining 22 percent of people served by CWSs. Pri-
vate systems are usually investor-owned in the larger
population size categories, but can include many small
systems as part of one large organization. These inves-
tor-owned utilities are in business to generate profit for
their shareholders. In the small-and medium-sized cat-
egories, the privately owned systems tend to be owned
by homeowners, associations, or developers.
Other types of system owners include several classifica-
tions of state-chartered public corporations, quasi-gov-
ernmental units, and municipally owned systems that
operate differently from traditional public and private
systems. These systems include special districts, inde-
pendent non-political boards, and state-chartered cor-
porations. Figure 2.8 shows the distribution of PWSs
by ownership.
Figure 2.8 indicates that the vast majority of small and
medium water utilities in the U.S. belong in the private
ownership category, followed by the local government
category. The difference in financial structure between
D Private
D Public/Private
D State Government
• Unknown
D Federal Government
• Local Government
DTribal Government
Figure 2.8 Distribution of Small- and Medium-Sized
PWSs by Ownership (EPA, 2007a)
the government and private entities makes the manage-
ment of small system operations challenging.
2.6 Common Problems Faced by
Small and Medium Utilities
The problems faced by operators of a small- and me-
dium-sized utility are as diverse as the system statistics
presented in Section 2.5. However, for the purposes of
this document, the common problems have been broad-
ly categorized as follows:
"Help!"
Water Quality
Problems
Operational
Problems
Regulatory/
Compliance
Problems
Institutional
Problems
Key considerations associated with the management
of these problems for small-and medium-sized utilities
will be the focus of this document.
2.6.1 Water Quality Problems
Water quality issues faced by small-and medium-sized
utilities are geographically diverse and complex. The
common consumer-reported problems include taste,
odor, and color. These problems generally do not have
an immediate impact on consumer health or result in
regulatory non-compliance. However, they must be ad-
dressed quickly to retain customer support for the sys-
tem. Examples of taste and odor issues reported by the
2-6
-------
"This should take care of
the smell issue!"
customers include:
• earthy smell
• chlorine smell
• rotten egg smell
• petroleum smell
• fishy smell
• metallic taste
Examples of common color issues reported include:
• red water
• green water
• black water
• milky water
2.6.2 Operational Problems
Common operational problems faced by small-and me-
dium-sized utility operators include:
• pressure problems
• main breaks, leaks
• valve problems
• excessive
sediments in pipes
and reservoirs
• cross-connection
and backflow
• replacement and/or repair of tanks and water
mains
• network and supply expansion
• adequate fire flow
2.6.3 Regulatory/Compliance Problems
Common regulatory and compliance issues faced by
small-and medium-sized utilities include:
Monitoring and
reporting problems
MCL exceedances (e.g.,
elevated lead, copper,
and arsenic levels)
Treatment technique
violations
Loss of disinfectant
residual
2.6.4 Institutional Problems
Common institutional issues faced by small-and me-
dium-sized utilities include:
• money constraints (small population and low
water rates)
• limited asset management
• poorly trained and low-paid operators (even
volunteers)
• inadequate metering
• unaccounted-for water loss
• lack of system security
I'm using a miracle fertilizer.
Hopefully, we'll have enough money
to buy a water tank next summer.
To focus on these problems and to evaluate potential so-
lutions, a hypothetical example of a community with a
small water utility called "SmallWater, USA" has been
developed. The problems and solutions discussed and
presented in this document will be related to SmallWa-
ter, USA. The following section presents a brief over-
view of SmallWater, USA.
2.7 SmallWater, USA
Scenario
SmallWater is a hypothetical rural town in Midwestern
U.S. The current population is about 2,700 with a small
commercial downtown area and a small industrial park.
The original water system was installed in the 1930s us-
ing cast iron pipe and was served by a well field on the
western edge of the town and an adjacent standpipe. The
town grew with additional development in the 1970s to
the north of the original town using asbestos-cement
pipe. In the 1990s, the well supply became inadequate
and an alternate source was developed in the form of an
interconnection to the surface water supply for a larger
2-7
-------
system located to the southeast. The well field was
maintained as a supplemental and emergency supply.
At that time, additional development also occurred in
the form of a subdivision at the eastern edge of the town
and on the ridge to the north of the town. A pump sta-
tion was built to serve this high zone (ridge) and a small
elevated tank was constructed. A commercial develop-
ment (shopping center) was also added to the system
and served via a pressure-reducing valve (PRV) from
the high zone. Polyvinyl chloride (PVC) pipe was used
for these modifications. Figure 2.9 is a schematic of the
water system in SmallWater, USA.
SmallWater, USA purchases finished water from the
adjacent system via the interconnection. Well water is
chlorinated without any additional treatment. At the cur-
rent time, the town uses an average of 210,000 gallons/
day with approximately 70 percent of that total attribut-
ed to residential use and the remainder for commercial.
industrial, and institutional use. Maximum daily usage
is approximately 400,000 gallons. Total revenue for the
water utility is approximately $250,000/year. The wa-
ter system is run by the town water board. Employees
include a full-time clerk, a full-time water director and
a part-time assistant.
The SmallWater, USA scenario will be used in this refer-
ence guide to explore a number of water quality, operation-
al, regulatory/compliance, and institutional problems faced
by many small- and medium-sized utilities in the U.S.
So what is the solution
to our problem?
Tank
PRV
N
Land Use Category
Residential
Industrial
Commercial
Well Field
(Stand pipe)
Figure 2.9 SmallWater, USA -Schematic Layout
Inter-Connect
2-8
-------
Crossword
The Supply, Distribution, and Quality of
Water: An Overview
ACROSS
2 Regulatory acronym for water system serving
restaurants, parks, motels that serve different
customers
4 U.S. City where first water utility was estab-
lished
6 Term for preventing source water contamina-
tion
7 Regulatory acronym for utilities serving 25 or
more people year round
8 U.S. City where first water treatment plant was
established
9 Regulatory acronym for expressing the
enforceable limits for a particular contaminant
DOWN
1 Term for natural movement of water from
rains, to lakes and streams, and evaporation
3 Regulatory acronym for water system
serving schools, hospitals and factories that
have their own water supply and serve the
same people for at least six months in a
year.
5 Term for microbial organisms that attach to
interior pipe surfaces
10IAI (6 PUB 'puoiuipiy (9 'SAAO (Z 'uo
sojnos (9 '
(g 'uojsog fc 'SAAON1N (C 'SAAONlfe 's
:uo!in|os PJOMSSOJQ
2-9
-------
-------
Chapter 3
Distribution System
Infrastructure
Distribution system infrastructure consists of a network
of pumps, pipes, tanks, valves, hydrants, and meters
through which finished water is supplied to customers.
This infrastructure is designed to deliver water to the
customer. The physical integrity of the distribution sys-
tem, from entry point to the customer's faucet, is a pri-
mary barrier against the entry of external contaminants.
Figure 2.4, in the previous chapter, showed a schematic
representation of a typical water distribution system.
A variety of components and materials make up a drink-
ing water distribution system. These include: (1) pipes,
including mains and service lines; (2) fittings and ap-
purtenances such as crosses, tees, ells, hydrants, valves,
and meters; (3) storage facilities including reservoirs
(underground, open, and covered), elevated storage
tanks, ground level storage tanks, and standpipes; and
(4) backflow prevention devices.
Table 3-1 provides examples of the infrastructure
components and the common materials of construc-
tion. These components serve as a physical barrier to
protect the distribution system water quality from ex-
ternal contamination threats. For example, the piping
material and fittings serve to protect the water from ex-
ternal contamination sources such as soil, ground wa-
ter, sewer exfiltration, surface runoff, human activity,
animals, insects, microbial pathogens, and other life
forms. The premise plumbing and storage facilities
are designed to protect from air contamination, rain,
algae, surface runoff, human activity, animals, birds,
insects and other sources of non-potable water.
3.1 The Impact of Distribution
System on Water Quality
Although water entering the distribution system may
meet the regulatory standards, water quality may de-
grade during transportation within the distribution
system before reaching the consumer. Some of these
undesirable water quality changes such as taste, odor
or red-water problems can be detected immediately,
whereas others may only be identified by sampling and
analysis. A waterborne outbreak caused by organisms
such as E. coli or Salmonella, for example, may be later
traced back to accidental contamination of water in the
distribution system. A variety of components make up
the physical barrier that protects against the deteriora-
tion of water quality in a distribution system. In ad-
dition, the proper management of these components is
essential to protecting the customer against both aes-
thetic and public health threats to distribution system
water quality. This chapter presents an overview of the
key distribution system infrastructure components, the
common problems associated with these components,
and some potential solutions to these problems. Spe-
cifically, the following infrastructure components are
discussed in this chapter:
• Pipes
• Pumps
• Storage facilities
• Valves
• Hydrants
• Water meters and service lines
Table 3.11nfrastructure Components (NRC, 2006)
Pipe
Pipe wrap and coatings
Pipe linings
Service lines
Customer building plumbing
Fittings and appurtenances (meters, valves,
hydrants, ferrules)
Storage facility walls, roof, cover, vent hatch
Backflow prevention devices
Gaskets and joints
Asbestos cement, reinforced concrete, steel, lined and unlined cast iron, lined
and unlined ductile iron, polyvinyl chloride (PVC), polyethylene and high-den-
sity polyethylene (HOPE), galvanized iron, copper, polybutylene, and lead
Polyethylene, bitumastic, cement-mortar
Epoxy, urethanes, asphalt, coal tar, cement-mortar, plastic inserts
Galvanized steel or iron, lead, copper, chlorinated PVC, cross-linked polyethyl-
ene, polyethylene, polybutylene, PVC, brass, cast iron
Copper, lead, galvanized steel or iron, iron, steel, chlorinated PVC, PVC,
cross-linked polyethylene, polyethylene, polybutylene
Brass, rubber, plastic
Concrete, steel, asphalt, epoxy, plastic
Brass, plastic, stainless steel
Rubber, leadite (a lead substitute), asphalt, plastic
3-1
-------
'N
Whoops... I should V
have called 811! J
The U.S. Federal Communications Commission in
March 2005 made 811 the universal number for
coordinating location services for underground public
utilities. This was required by the Pipeline Safety
Improvement Act of 2002.
3.2 Distribution System Pipes
Pipe materials used by the water utilities have changed
greatly over time. Cast iron pipe (lined or unlined) has
been largely phased out primarily due to its suscepti-
bility to both internal and external corrosion. Early
on, ductile iron pipe (with or without a cement lin-
ing) took its place because of its durability, strength
and good resistance to external corrosion from soils.
However, ductile iron pipe also needs corrosion pro-
tection in certain soils and may require multiple types
of joints. Subsequently, concrete, asbestos cement,
and polyvinyl chloride (PVC) plastic pipe were used
to replace metal pipe because of their relatively good
resistance to corrosion. More recently, high-density
polyethylene (HDPE) pipe is being used as a replace-
ment because of its ease of installation, toughness,
flexibility, and corrosion resistance.
3.2.1 Pipe Connectivity, Placement and
Configuration
Distribution system pipe networks consist of wa-
ter "mains," also called "primary feeders" or "trunk
lines." The mains are generally 12 inches or greater
in diameter (for small systems, the mains may be only
6- to 8-inches in size), and carry water from the treat-
ment plant to the local service areas where they are
connected to smaller-diameter "branches" also called
"secondary feeders." The branches that are tied into
the mains are usually greater than six inches in diam-
eter. At the other end, the branches are tied to other
smaller diameter pipes (4, 6 or 8 inches) that connect
with service connections to customers (residential,
commercial, and industrial). Water pipes are typically
placed three to six feet below ground level to protect
them from traffic, freezing, damage from excavation
and construction activities. These pipes are placed
within the public right-of-way so that workers can in-
stall service connections for all potential water users.
Branch and grid/loop are the two basic configurations
used by most water distribution systems. A branch
system is similar to a tree where smaller pipes branch
off larger main pipes (similar to a tree trunk) through-
out the service area. This type of system is most
frequently used in rural areas, and generally in this
type of system, water has only one pathway from the
source to the consumer. A grid/loop system consists
of interconnected pipe loops throughout the area to be
served. In this type of system, there are several path-
ways that the water can follow from the source to the
consumer. A grid/loop system is the most widely used
configuration in medium-and large-sized utilities. The
grid/looped systems provide a high degree of reliabil-
ity should a line break occur, because the break can
be isolated with little impact on customers outside the
immediate area. Figures 3.1 and 3.2 depict a branched
and grid/looped distribution system, respectively.
•—4—i
•-H
Figure 3.1 A Branched Distribution System
Figure 3.2 A Grid/Looped Distribution System
3-2
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3.2.2 Pipe Material
Distribution system pipes are generally made of asbes-
tos cement, unlined cast iron, cement-mortar-lined cast
or ductile iron, plastic (PVC, HDPE), reinforced con-
crete, steel or fiberglass. Pipes used in water systems
must be approved for potable water use. NSF Interna-
tional, American National Standards Institute (ANSI),
American Society for Testing Materials (ASTM), and
Underwriters Laboratory (UL) are among the organiza-
tions that test and approve pipe for potable water ap-
plications. Figure 3.3 shows the NSF potable water use
approval depicted on a PVC pipe.
Additional Information
Pipe Material Voluntary
Standards
AWWA - M9, Concrete Pressure Pipe, Second Edition,
1995
AWWA - Mil, Steel Pipe—A Guide for Design and In-
stallation, Fourth Edition, 2004
AWWA - M23, PVC Pipe—Design and Installation, Sec-
ond Edition, 2002
AWWA - M41, Ductile-Iron Pipe and Fittings, Second
Edition, 2003
AWWA - M55, PE Pipe—Design and Installation, First
Edition, 2006
Figure 3.3 NSF-Approved PVC Pipe for Potable Water
Use
The condition of pipe, source water quality, and the soil
conditions around the buried pipe can negatively impact
the water quality. Degradation of plastic (PVC or HDPE)
pipes located in soils contaminated with organic com-
pounds may result in softening of the pipe wall and subse-
quent permeation of organic matter through the pipe wall,
leading to contaminated water. Table 3.2 presents a sum-
mary of potential negative impacts to water quality based
on pipe material and changes in source water quality.
As presented in Table 3.2, depending upon the pipe ma-
terial and relative changes in source water quality, the
pipe wall interactions may negatively impact the water
quality. Figure 3.4 depicts the various pipe wall inter-
actions that may adversely affect water quality.
CorauMi
Surface (Chemicals Biological)
Ruction*
Paniculate* H*t«fOtfOph* Colilorma
Biofilmiregrowth
Figure 3.4 Pipe Wall Interactions that Affect Water
Quality (Adapted from: MSU, 2005)
Table 3.2 Potential Negative Impacts to Water Quality Based on Pipe Material and Changes in Water
Quality (Adapted from AwwaRF, 2005)
Pipe Material
Unlined cast iron, steel, or old
galvanized steel
Cement-mortar lined ductile iron
Asbestos cement (Transite)
All pipe types including fiber glass
Changes in Water Quality
1) pH increase or decrease, or
2) Alkalinity decrease, or
3) Dissolved oxygen increase or decrease
Chlorine residual increase
1) pH decrease, or
2) Alkalinity decrease
1) pH decrease, or
2) Alkalinity decrease
Chlorine residual decrease
Potential Negative Impacts
May result in discolored water
May mobilize iron and/or manganese
oxides and result in discolored water
May trigger localized pH and alkalin-
ity increases with associated negative
impact of discolored water
May trigger localized pH and alkalin-
ity increases and increased levels of
asbestos fibers in water
May result in increase in microbiological
population such as HPCa and possibly
coliformb levels
aHeterotrophic Plate Count —A bacterial counting procedure used to estimate bacterial density in a water sample. Other names for the procedure
[within the water industry] include total plate count, standard plate count, or plate count.
bColiform - A specific class of bacteria found in the intestines of warm-blooded animals and people. The presence of conform bacteria in water
indicates that there is a possibility, but not a certainty, that disease-causing organisms may also be present in the water.
3-3
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3.2.3 Common Problems, Troubleshooting and
Pipe Repair
Excessive scale buildup, corrosion, pipe leaks and main
breaks are the most common pipe-related problems
faced by water utilities. Excessive scaling in pipe results
in loss of delivery capacity overtime. Internal corrosion
of pipes can result in discolored water or high lead and
copper levels. For example, reddish-brown water is the
result of corrosion of iron pipes, bluish stains on fixtures
are the result of corrosion of copper lines, and black wa-
ter generally results from sulfide corrosion of copper or
iron lines, or can be the result of precipitation of natural
occurring manganese in water. External corrosion leads
to pipe leaks and water main breaks. There are several
types of leaks, including valve leaks and service line
leaks, but in most cases the largest amount of water is
lost through water main leaks. Leaks occur due to fac-
tors such as pipe material, pipe composition, pipe age.
finished water quality, temperature, pressure, and pipe
joining methods. External conditions, such as contact
with other structures (that can cause movement or elec-
trical current flow), stray electric currents, traffic load.
aggressive soils, vibrations, and frost conditions can
also contribute to leaks. Pipes also break due to factors
such as water freezing, traffic load, and corrosion. In
addition, pipes may be defective, installed improperly,
or simply not strong enough to handle pressure surges.
Somebody get me a
! clamp, quick!
3.2.3.1 Minimizing Leaks and Water Loss
Leakage results in loss of revenue to a utility. Larger
leaks are usually detected faster, because they usually
lead to water reaching the surface which results in quick
identification, isolation and repair. Small undetected
leaks can often lead to large amounts of water loss over
time. Leak detection methods usually involve sonic or
ultrasonic leak-detection equipment, which identifies
the sound of water escaping a pipe. These devices in-
clude pin-point listening devices that make contact with
valves and hydrants, or geophones that listen directly
to sound moving through the ground. In addition, there
are other devices that can listen at two locations simul-
taneously to correlate "leak" sounds and determine
the exact leak location. Leak detection efforts should
Pipe Leak Management by a Small System (EPA, 2002c)
Gallitzin, a small town in western Pennsylvania (popula-
tion -2,000), services approximately 1,000 connections.
The system was experiencing water losses exceeding 70
percent. In November 1994, the system was using an av-
erage of 310,000 gallons per day. Gallitzin experienced a
peak usage in February 1995 of 500,000 gallons per day.
The water authority identified five major problems in the
system: 1) high water loss, 2) recurring leaks, 3) high over-
all operational costs, 4) low pressure complaints and 5) un-
stable water entering the distribution system.
The water utility decided to implement a comprehensive
program for water leak detection. For this purpose, the
utility first developed accurate water production and dis-
tribution records using 7-day meter readings at the plant
and pump station. A system map was then created to lo-
cate leakage. Through the use of a leak detector, the utility
was able to identify approximately 95 percent of its leaks.
Thereafter, the utility initiated a leak repair program and
a corrosion control program at the Water Treatment Plant.
Gallitzin was one of the first systems to receive technical
assistance from the Pennsylvania Department of Environ-
mental Protection Small Water Systems Outreach Program.
The training helped the authority repair distribution system
leaks, replace inaccurate meters, and improve customer
billing. Accuracy of water meters is critical for determin-
ing water loss as part of a good leak management program.
By November 1998, 4 years after implementation of the
program, the system delivered an average of 128,000 gal-
lons per day to the town—down from 310,000 gallons per
day in November 1994. Unaccounted-for water dropped
to only 9 percent. The financial savings from the program
have been highly beneficial. The city saved $5,000 on total
annual chemical costs and $20,000 on total annual pow-
er costs between 1994 and 1998. The significant savings
helped the utility keep water rates down.
focus on the portion of the system where the greatest
problems are expected. These problem areas generally
include areas with excessive leak and break rates, high-
pressure areas, and areas where pipes are old. As a gen-
eral guideline, a water conservation and leak detection
Additional Information
Leak Detection and Water
Loss
A National Drinking Water Clearinghouse (NDWC) Tech
Brief on leak detection and water loss control can be ob-
tained online from: http://www.nesc.wvu.edu/ndwc/pdf/
OT/TB/TB_LeakDetection.pdf
AWWA - M36, Water Audits and Leak Detection, Second
Edition, 1999
3-4
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program should be implemented when the "unaccount-
ed-for" water (water produced - metered water usage at
customer locations) exceeds 15 percent.
3.2.3.2 Distribution System Line Breaks
Distribution system pipes can break for a variety of
reasons such as excessive traffic load, extremely cold
temperatures, accidents during excavation/construction
activities, pressure surges, and corrosion. Procedures
for dealing with major main breaks are usually outlined
in a utility's emergency response plan (ERP). If a util-
ity suffers a major main break, law enforcement, fire
protection, and city officials should be notified since the
leak may pose significant hazard to life or property. Af-
fected customers should be notified since valves must
be shut off to isolate the break and to perform needed
repairs. For smaller leaks, it is preferable to perform the
repair without shutting off the water service. Allowing
a line to remain under pressure prevents back siphoning
and back pressure that can cause contaminants to enter
into the pipe. In some cases, nearby hydrants can be
opened to lower the water pressure to facilitate the re-
pair. If the pipe break is small, it can be repaired using
a pipe clamp or sleeve that serves as a "bandage." For
larger breaks, portions of pipe are cut off and replaced
by new sections. As a general rule when conducting
repairs, safety precautions are necessary with regard to
Additional Information
Line Repair and
Rehabilitation
A NDWC Tech Brief on repairing distribution line breaks
can be obtained online from: http://www.nesc.wvu.edu/
ndwc/articles/OT/SP04/TechBrief_LineBreaks.pdf
AWWA - M28, Rehabilitation of Water Mains, Second
Edition, 2001
AWWA - M22, Sizing Water Service Lines and Meters,
Second Edition, 2003
trenching and shoring, in addition to following proper
procedures for pipe installation and repair.
Table 3.3 summarizes some of the common problems
that lead to pipe failures for pipes of differing materi-
als. These include some of the principal factors, but
they are not the only factors that act individually or in
combination to cause a main break. Other factors could
include a street excavation that accidentally disturbs a
water main or the misuse of fire hydrants.
3.3 Distribution System Pumps
Within a distribution system, pumps are used to dis-
charge water under pressure to the pipe network, to
boost pressure within a system and also to lift water
to a higher elevation where it can then be delivered by
gravity (e.g., elevated water storage tanks). Pumps can
be classified into two basic groups: positive displace-
ment and variable displacement pumps. A positive
displacement pump delivers the same volume or flow
of water against any "head" within its operating capac-
ity. Head is the vertical distance between a pump and
water outlet, usually measured in feet or converted and
expressed in equivalent pressure scale. Examples in-
clude: piston pumps, screw pumps, diaphragm pumps
and gear pumps. Variable displacement pumps deliver
water with the volume or flow varying inversely with
the operating head (i.e., the greater the head, the less
the volume of the flow). Examples include: centrifugal
pumps, jet, and airlift pumps. Appropriate pumps are
selected based on the desired application.
Centrifugal pumps are used widely in water distribution
systems because of several advantages including: 1)
low cost and small footprint for a given capacity, 2) a
rotary mechanism that allows for adaptability to high-
speed driving mechanisms such as electric motors and
gas engines, 3) simple mechanism, easy for operations
and repair, and 4) safety against damage from high-
pressure because of limited maximum pressure that can
be generated.
Table 3.3 Common Problems that Lead to Pipe Failure for Various Pipe Materials (NRC, 2006)
Pipe Material (common sizes) Common Problems
PVC and Polyethylene (4-36 in.)
Cast/Ductile Iron (4-64 in.)
(lined and unlined)
Steel (4-1 20 in.)
Asbestos-Cement (4-35 in.)
Concrete (12-1 6 to 144-1 68 in.)
(prestressed or reinforced)
Excessive deflection, joint misalignment and/or leakage, leaking connections, exposure
to sunlight, high internal water pressure or frequent surges in pressure, exposure to
solvents, manufacturing flaws
Internal corrosion, joint misalignment and/or leakage, external corrosion, leaking connec-
tions, casting/manufacturing flaws
Internal corrosion, external corrosion, excessive deflection, joint leakage, imperfections
in welded joints
Internal corrosion, cracks, joint misalignment and/or leakage, small pipe can be dam-
aged during handling or tapping
Corrosion in contact with ground water high in sulfates and chlorides, pipe is very heavy,
alignment can be difficult, settling of the surrounding soil can cause joint leaks
3-5
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Many brands of centrifugal pumps are available in the
U.S. with capacities ranging from a few gallons per
minute (gpm) to several thousand gpm. Working heads
can range between 5 to 700 feet, but the efficiency of
each pump is limited to a narrow range of discharge
flows and head. Careful consideration must be given to
these factors prior to pump selection.
'We got the pump, and the
, horses to power it!
3.3.1 Common Problems, Troubleshooting and
Maintaining Pumps
During startup, centrifugal pumps require "priming."
Priming is a procedure in which the pump is filled with
water before turning the switch on. The unit does not
operate efficiently if it is not properly primed. In gener-
al, pumps have an adjacent priming chamber that draws
water when the pump is turned on to keep the impeller
submerged. After priming, the pump must be started
with the discharge valve fully closed. Thereafter, the
discharge valve must be opened slowly to allow any air
in the system to escape and prevent water hammer or
pressure surges. A surge of pressure occurs when a valve
is suddenly closed or opened. This surge can cause the
pipes to vibrate or create a hammering noise. Also, at
shutdown or during power failures, the discharge valve
must be programmed to close in order to avoid backflow
and prevent the impellers from running in reverse.
Because of the variety of pumps available, individual
procedures for proper operation of each pump vary by
manufacturer. A utility operator should refer to manu-
facturer instructions while operating and troubleshoot-
ing the pumps. Centrifugal pumps require regular in-
spection and maintenance. Bearings on the motor may
become worn and must be checked and kept well-lubri-
cated. The packing seals must be examined for wear
due to friction that can result in pump leakage. Bearing
and motor temperature must be monitored for excessive
heat. If a surface is substantially hotter than normal,
the unit must be shut down and examined for the cause.
Any unusual noises or vibrations from the pump should
also be thoroughly investigated by shutting down the
unit first. Prior to performing any maintenance activity
on the pump, the pump must be shut down and drained
of all liquids before servicing. Electrical safety pro-
cedures must also be followed while servicing motors.
All safety instructions provided by the manufacturer
must be followed during the performance of mainte-
nance activities.
Additional Information
Pumps
AWWA - Water Transmission and Distribution: Principles
and Practices of Water Supply Operations, 3rd edition,
2003
AWWA- Design and Construction of Small Water Sys-
tems, 2nd edition, 1999
3.4 Distribution System Storage
Facilities
Distribution system storage facilities (tanks and reser-
voirs) are necessary to accommodate peak flow (equal-
izing storage), emergency demand, and firefighting
capabilities. In addition, they help maintain uniform
pressure and allow for reduction in the size of distri-
bution mains that would otherwise be much larger to
accommodate peak flow requirements. Storage also re-
duces pumping costs under peak energy periods. Gen-
erally, these storage facilities are designed and located
such that they can provide water at the required pres-
sure to the farthest location in the service area.
3.4.1 Types of Storage Facilities
Ground level reservoirs and tanks, elevated tanks and
hydro-pneumatic tanks are designed for multiple uses
including: equalizing storage, maintaining pressure
in the system, and providing firefighting capabilities.
Equalizing storage is necessary when the source pump
capacity is less than the peak system demand. This
storage is also essential for water production facilities
to run at a constant rate. Smaller distribution systems
with wells and relatively flat topography may use a
hydro-pneumatic tank to maintain water pressure. A
hydro-pneumatic tank is an air-pressurized water tank.
The air in the tank acts as a cushion that can exert or
absorb pressure as required. The two common methods
employed for air-charging the tanks are: motor-driven
air compressors and hydraulic-powered air chargers.
3-6
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I am thankful that you guys
approved our funding request
perform some minor repairs
to this tank.
The storage volume requirements for tanks are classi-
fied by function: operating, equalizing, fire and/or emer-
gency, and dead storage volume. The typical minimum
municipal fire flow requirement for a single-family resi-
dential area is 500 to 1,000 gpm for two hours, which is
equivalent to a minimum storage requirement of 60,000
to 120,000 gallons. For commercial and industrial ar-
eas, the fire flow requirement ranges between 2,000 and
8,000 gpm for several hours which is equivalent to a
storage requirement of -500,000 gallons to over a mil-
lion gallons. Some local fire and state agencies allow
for combining fire and emergency storage requirements.
Figure 3.5 illustrates the typical storage tank volume de-
sign parameters.
Water In/Out
Figure 3.5 Storage Tank Volume Design Requirements
Depending upon the size and location-specific require-
ments, tanks may be constructed using steel (welded or
bolted, carbon or stainless), concrete, fiberglass, or plas-
tic (polyethylene, polypropylene). The type of material
used for the tank depends upon many factors including:
1) location of the water tank (indoors, outdoors, above
ground or underground), 2) volume (larger tanks are
generally made of steel), 3) temperature and wind in
the area where water will be stored (concern for freez-
ing and structural strength requirements). In addition
to selecting appropriate tank material, all piping, joints
and fittings should conform to regulatory design speci-
fications. Steel tanks are most widely used by water
utilities in the U.S. Steel tanks are required to be painted
and to have cathodic protection to resist corrosion.
Additional Information
Storage Tanks
AWWA - M25, Flexible-Membrane Covers and Linings
for Potable-Water Reservoirs, Third Edition, 2000
AWWA - M31, Distribution System Requirements for Fire
Protection, Third Edition, 1998
AWWA - M42, Steel Water-Storage Tanks, First Edition,
1998
3.4.2 Common Problems, Troubleshooting and
Maintaining Tanks
Water storage facilities (tanks) must have covers or
hatches that keep out birds, rodents, insects, dust and
surface runoff. They must also have a screened vent
which allows air to enter and leave as the water level
drops or rises in the tank. Outside access to the stor-
age facility must be lockable and weather-tight. Lack
of proper hatches and vents may result in dead animals
and/or birds floating in the tank which can create serious
health problems. Tanks should be routinely inspected
(for corrosion and structural integrity) and cleaned. Wa-
ter tanks are confined spaces and a confined-space warn-
ing label must be placed on tank access. Confined-space
entry procedures must be followed by anyone entering
the tank. For larger tanks, commercially trained divers
and/or remotely controlled underwater robotic systems
can be used for inspection and/or cleaning. The use of
divers and/or robotic devices requires special precau-
tions and procedures, especially if the tank is allowed to
remain in service during inspection/cleaning procedures.
Tanks that are improperly operated can lead to excessive
"aging of water" or areas of poor circulation. Excessive
storage time can lead to a loss of disinfectant residual
(chlorine/chloramine) which can result in bacterial re-
3-7
-------
growth. In addition, the disinfectant can react with nat-
urally occurring organic matter to form greater levels of
undesirable byproducts that may pose long term health
problems. Poor circulation can lead to "dead" or stat-
ic zones where the water may be much older than the
average age in the storage facility. Stratification is an
example of poor mixing where the water age and char-
acteristics vary in the vertical direction in the tank. This
is most common in tall standpipes and in tanks where
there is insufficient energy in the inflow during the fill
cycle to create a well-mixed tank. Water aging can be
reduced by changing the tank operation so that there is
a greater exchange of water between the tank and the
distribution system. Mixing problems can frequently
be relieved by modifying the inlet-outlet configuration
and/or increasing the inflow rate and velocity.
3.5 Distribution System Valves
Valves are critical for management of the distribution
system. Valves control flow/pressure, and isolate por-
tions of the water distribution system for servicing. If
valves are properly placed, distribution system pipe re-
pairs and maintenance can be conducted with minimal
loss of service to the customer. Most valves require
some mechanical or externally devised system to open/
close or change the position of the valve. Manually op-
erated actuators, or electromechanically actuated mech-
anisms are installed on valves to allow proper operation.
Cover your ears dear... he is^
closing the valve real fast, he |
is sure to produce a bang!
*«*"* « „
V* C
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/*•. *•
(
In newer installations, it is common to use automatic
valves. The valve types generally used in water distri-
bution systems include: gate, butterfly, check, control,
pressure reducing, pressure relief, altitude, and air-and-
vacuum relief. A brief overview and general function
of the most commonly used valves are presented in the
following sections.
3.5.1 Gate Valves
Gate valves are used to isolate distribution system sec-
tions. A sliding gate is moved up or down to block the
flow. The purpose of the valve is to completely stop
the flow and not to regulate it. These valves should not
be opened or closed too rapidly. Rapid valve operation
can cause a phenomenon known as "water hammer" or
pressure surge that can seriously damage distribution
system components. Water hammer is caused by the
sudden increase in pressure of water caused by the con-
version of the kinetic energy of the water in motion to
static energy when it is forced to stop. Under extreme
conditions, this pressure surge may cause the pipes to
vibrate and/or create a hammering noise. Figure 3.6
illustrates a gate valve.
Open
Jfjt
Jfjt
Flow
Closed
Flow
Figure 3.6 Gate Valve (side view)
3.5.2 Butterfly Valves
A butterfly valve consists of a round disk attached to
a shaft in the pipe. Rotating the shaft by 90 degrees
(one quarter turn) opens or closes the valve. In the
open position, the disk is parallel to the flow of water.
These valves are commonly used for larger diameter
pipes. Similar to gate valves, these valves should not
be opened or closed too rapidly in order to avoid water
hammer. Figure 3.7 illustrates a butterfly valve.
3-8
-------
Open
Jit
Jit
Open
Disk-
Flow •
-Shaft
Closed
Jit
Jit
Flow i
Figure 3.7 Butterfly Valve (top view)
3.5.3 Check Valves
Check valves are designed to allow flow in only one di-
rection. One common application of this valve is on the
discharge side of a pump to prevent backflow when it is
shut down. A variety of devices (e.g., weights, springs,
motors) are available to dampen the closing of valves to
minimize water hammer. Figure 3.8 illustrates a swing
check valve.
3.5.4 Other Valves
Control valves are used to regulate flow between a ful-
ly opened and a fully closed position. Control valves
are almost always equipped with some sort of actuator
mechanism to provide ease of operation.
There are many types of pressure regulating and flow
control valves. For example, a pressure sustaining
valve tries to maintain a constant upstream pressure,
whereas a pressure reducing valve maintains a constant
downstream pressure. An altitude valve is a serf con-
tained pressure regulating valve that is used to control
the flow into a tank in order to prevent water overflow.
These valves are balanced to use the line water pressure
as the operating motive. For example, when the tank
level rises to a specified upper limit, the valve closes to
prevent any further flow from entering, thus eliminating
overflow. When the flow trend reverses, the valve reo-
pens. In some places, high- and low-level tank indica-
tors are also used to control flow.
Pressure relief valves are installed to relieve excessive
internal pressures (such as surge pressures) in a hydro-
pneumatic tank as the excessive pressure may lead to
ruptures.
Air and vacuum valves, commonly referred to as air
release/vacuum breaker valves, are used to remove
Flow'
Closed
4ft ^
1
•a
r 4ft
i
/ -^^™ Backflow
\ \
Figure 3.8 Swing Check Valve (side view)
air from system components. For example, deep-well
pumps are equipped with air release valves to exhaust
large quantities of air very rapidly from a deep-well
pump column when a pump is started.
3.5.5 Common Problems, Troubleshooting and
Maintaining Valves
Valves in constant use have parts that wear out and re-
quire routine maintenance. In addition, valves that are
not used regularly may not function when the need
arises. Valves can stick (due to deposition or rust for-
mation and growth of biofilm on the operating sur-
face) and even break (weakened by corrosion) if ne-
glected. A valve exercise program is a necessary part
of water distribution system maintenance.
We have initiated a valve |
exercising program J
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Ur~
In cases where there is a high-pressure drop through
a valve, it can lead to a number of immediate prob-
lems such as cavitation, flashing, choked flow, high
noise levels and vibration. Over the longer term,
it degrades system efficiency and results in higher
pumping costs.
3-9
-------
Additional Information
Valves
A NDWC Tech Brief on valves can be obtained online
from: http://www.nesc.wvu.edu/ndwc/pdf/OT/TB/OT_
TB_Su02.pdf
AWWA - M44, Distribution Valves: Selection, Installation,
Field Testing, and Maintenance, Second Edition, 2006
AWWA -M49, Butterfly Valves: Torque, Head Loss, and
Cavitation Analysis, First Edition, 2001
AWWA - M51, Air-release, Air/Vacuum and Combination
Air Valves, First Edition, 2001
3.6 Distribution System Hydrants
Two types of hydrants are used in a distribution system:
flush hydrants and fire hydrants. Flush hydrants are
generally installed in a pit and have nothing projecting
above ground. These hydrants are placed at the end of
lines to remove accumulated corrosion products from
dead-ends. Flush hydrants should also be installed
throughout the system to provide for periodic flush-
ing to maintain high water quality. Sometimes, flush
hydrants are mistaken for fire hydrants. Fire hydrants
are larger in size. Fire hydrants are classified into two
basic categories: wet barrel and dry barrel. Wet bar-
rel hydrants are designed to be used only in areas of
the country where the temperature never drops below
freezing, since these units are always charged with
water. Dry barrel hydrants are predominantly used in
the U.S., and designed to automatically drain water
Operating
Nut
Outlet
Cap
Upper Standpipe
or Barrel
Ground Surface
Main Valve
Drain Valve
Fire Hydrant History (Adapted from Rader, L. undated):
In colonial America, cisterns were used to store water
for early fire fighting purposes. Around the time of the
American Revolution, several American communities had
built water distribution systems. These early systems used
wooden main lines that workers had built using bored-out
logs. The logs were fitted together and buried. When fire
fighters needed water, they uncovered the wooden line and
bored a hole in the pipe wall. They used the water that
collected around the pipe for fighting the fire. After the
fire was put out, a tapered wooden plug was driven into
the hole in the pipe wall and the location of the hole was
marked with the "fireplug." Later, when cast iron became
the material of choice for water lines, it became harder to
bore the hole. However, water systems installed tees with
wooden plugs at convenient locations and the wooden fire-
plug continued for several more years. The hydrant's evo-
lution included a standpipe that fire fighters shoved into
the tee after they removed the fireplug. It conveyed water
above ground to a hose connection and a ball valve, and
it finally made the wooden plug obsolete. This setup was
the forerunner of the dry-barrel compression hydrant. Cis-
terns continued to be used even after the introduction of the
hydrant in many cities. As late as 1861, the city of Louis-
ville, Kentucky employed 124 cisterns but no fire hydrants.
Cisterns are still used today for firefighting.
after the water is turned off.
dry barrel hydrant.
Figure 3.9 illustrates a
Figure 3.9 Dry Barrel Hydrant
3-10
3.6.1 Common Problems, Troubleshooting and
Maintaining Hydrants
Hydrants should be opened and closed slowly to avoid
water hammer effect. Dry barrel hydrants should al-
ways be fully opened because operation of the drain
mechanism is linked to the main valve. A partially
opened hydrant causes water to leak through the base
which can cause erosion around the base of the hydrant.
Dry barrel hydrants need a supply of air to drain prop-
erly. Therefore, the caps should not be tightened until
the unit finishes draining. Hydrants should be inspect-
ed on a routine basis for operability and leaks. Many
different brands and models are available in the U.S. It
is important that parts provided or recommended by the
manufacturer be used for servicing each unit. Hydrant
Additional Information
Hydrants
A NDWC Tech Brief on how to begin a fire hydrant op-
eration and maintenance program can be obtained online
from: http://www.nesc.wvu.edu/ndwc/pdf/OT/TB/OT_
HowTo_f02.pdf
-------
repair requires specialized tools that are available from
the manufacturer; using other tools may result in unnec-
essary damage and lead to the early failure of the unit.
3.7 Water Meters and Service
Lines
Water meters are generally considered to be the last con-
nection in the portion of the distribution system owned
by a utility before water is delivered to the customer.
They are extremely important because they measure the
customer's water usage and are the basis for billing cus-
tomers for money to support the utility's operation. In
larger utilities, wastewater charges are frequently based
on water meter readings. A service line carries water
from the main to the water meter and/or curb stop or to a
customer's building plumbing. Meters are generally the
property of the water utility, but there are wide differ-
ences across the country with regard to the ownership of
service lines. Residential or building plumbing is almost
always the property of the home or building owner.
3.7.1 Water Meters
A water meter is a device used to measure the volume
of water usage. Water meters are used at the service line
inlet to a residential and commercial building in a PWS.
Water meters can also be used at the water source, well, or
throughout a water system to determine flow through that
portion of the system. Water meters in the U.S. typically
measure and display total usage in cubic feet, or U. S. gal-
lons on a mechanical or electronic register. Water meters
are also used to generally define ownership and responsi-
bility. For example, maintenance and repair of pipes on
the "street side" of the water meter is the responsibility of
the PWS, and the customer/property owner is responsible
for the maintenance and repair of pipes and plumbing on
the "customer side" of the water meter.
There are several types of water meters in common use.
Selection is based on different flow measurement meth-
ods, the type of end user, the required flow rates, and
accuracy requirements. In U.S., standards for manufac-
turing of water meters are made by the American Water
Works Association. Positive Displacement (PD) meters
are most commonly used and are generally very accu-
rate at low to moderate flow rates typical of a residential
user and a small commercial user. Common PD meters
are sized between 5/8 and 2 inches. Because these me-
ters rely on water flowing through the meter to "push"
the measuring element, they are generally not practical
in large commercial applications requiring high flow
rates or low pressure loss. See Section 6.2.1 for other
types of flow meters.
PD meters normally have a built-in strainer to protect
the measuring element from rocks or other debris that
could stop or break the measuring element. PD meters
normally have bronze, brass or plastic bodies with in-
ternal measuring chambers made from molded plastics
and stainless steel. Most meters in a typical water dis-
tribution system are designed for cold potable water
only. There are other water meters manufactured for
specific uses. For example, hot water meters are de-
signed with special materials that can withstand higher
temperatures. Meters for reclaimed water have special
lavender register covers to signify that the water is non-
potable and should not be used for drinking.
Water meters are generally owned, read, and maintained
by the PWS. In some cases, an owner of a mobile home
park, apartment complex or commercial building may
be billed by a utility on one meter, and the cost of the bill
is shared among the tenants. In these cases, the complex
owner may purchase private water meters to separately
track usage of each unit in what is called submetering.
3.7.2 Service Lines
A service line carries water from the main to the water
meter and/or curb stop. A curb stop box refers to the
enclosure which houses a valve. In case of an emergen-
cy or service disconnection, this valve is used to shut-
off water service to the individual customer. Most curb
stop boxes are not boxes, but cast iron housings with
a pipe that extends to the ground level with a remov-
able cover. The valve is accessed with a special wrench
which is slid down the pipe and turns the valve off and
on. A meter stop is a valve placed on the street side of
the water meter to isolate the water meter for installa-
tion or maintenance. Many codes require a gate valve
on the customer side of the meter to shut off water for
performing customer plumbing repairs.
3.7.3 Common Problems, Troubleshooting and
Repairs
Water meters are generally well built, and require mini-
mal maintenance if installed correctly. If a meter is in
need of repair, it will generally under-register rather than
over-register the customer's water use. Because they
are very accurate, they can be used to identify leaks in
a customer's plumbing. For example, if a customer re-
ports excess usage bill, the first step would be to shutoff
all water use in the building and observe if the meter is
still moving. In case the meter registers usage, it is very
likely that the customer plumbing contains a leak. The
customer should be recommended to obtain the services
of a licensed plumber to isolate and correct the problem.
Even small leaks over time can result in significant wa-
ter loss and resulting cost to the customer.
The majority of water leaks in a distribution system
occur in service lines, service fittings, and connections
including ferrules, curb stops, valves and meters. In
3-11
-------
addition, customer's plumbing and service lines have
longer residence times, more stagnation, lower flow
conditions and elevated temperatures than normally
found in distribution systems and can have a negative
effect on the quality of water supplied to the customer.
Therefore, service lines and their fittings provide the
greatest potential for intrusion and subsequently for
outside contamination to enter the distribution system.
Compared to the main water distribution systems, less
is known about the types and causes of service-line fail-
ures than for other components of the distribution sys-
tem. Some possibilities include:
• Internal and external corrosion
• Poor installations such as improper backfilling
techniques and materials
• Damage during handling
• Improper tapping
Many times during landscaping of the home, the curb
stop access is buried or damaged. The cover lid can also
be damaged, allowing debris to block access to the valve.
Locating and marking the curb stop on a customer's
property line can save time and money during an emer-
gency when water needs to be shut off. The curb and
meter stop valves are not designed for frequent use and
can be ruined in a short time if used very frequently.
Because of the wide variation in ownership service
lines, it is difficult to identify the party that should take
responsibility for their maintenance. This lack of clear
responsibility can complicate the extent to which serv-
ice lines are inspected, replaced, and repaired. In most
cases, a drinking water utility only assumes responsibil-
ity for the quality of water delivered to the curb stop or
water meter. For the portion of the service line owned
by customers, the responsibility and cost of repairs falls
on the customer.
Service Line/Water Meter Repair (NRC, 2006)
A recent report published by the National Research Coun-
cil of the National Academies highlighted the issue of serv-
ice lines and residential plumbing and their contribution to
the deterioration of water quality. A waterborne disease
outbreak that occurred in Cabool, Missouri, in the winter
of 1989-1990 was partially attributed to the need to replace
a large number of water meters in the distribution system at
the same time as the sewage overflow occurred. The town
had a population of approximately 2,100 people. A total
of 243 cases of E. coli O157:H7 was reported, with 32 hos-
pitalizations and four deaths. It was the first documented
waterborne outbreak of E. coli O157:H7 ever reported.
3.8 Distribution System Asset
Management
Distribution systems typically represent a water utility's
largest capital investment. In order for a distribution sys-
tem to operate at peak performance, its status must be
continuously assessed. The Asset Management (AM)
concept has emerged as an important mechanism for
tracking and evaluating distribution system operation
and maintenance (O&M) needs. The key focus of as-
set management is to minimize the amount of money
necessary to own, operate, and maintain a distribution
system asset (e.g., pumps, pipes, hydrants, and tanks)
over its useful life. One key feature of an AM system is
to track the installed life of a distribution system asset.
Asset Management (NMEFC, 2007)
In 2005, the New Mexico Environmental Finance Center
(NMEFC) conducted an AM study for the Arenas Valley
water distribution system in New Mexico. The Arenas val-
ley water system purchases finished water from Silver City.
The primary distribution system assets included: relatively
new PVC pipe installed in the 1980's (approximately 20
miles of pipe), approximately 430 service connections, 25
hydrants and 100 valves. When the study was initiated, the
utility was concerned that a substantial portion of the sys-
tem's PVC pipe had degraded/failed and needed replace-
ment. During the process of developing a comprehensive
AM database, a pipe break event map was created depict-
ing the 26 breaks previously recorded. Figure 3.10 shows
the pipe break event map, which indicates that the majority
of the breaks were service-line leaks and two of the 26
breaks were caused by a service-line tap. This pipe break
map allowed the utility board to see that these pipes were
not degrading as originally suspected, and therefore did
not need replacement. Also, a better grasp on assets and
Level Of Service requirements allowed the utility board to
see that it was more valuable to install new pipe that would
create some loops in the distribution system, improving
both service and possibly water quality.
Figure 3.10 Arenas Valley Pipe Inventory and Main
Break Map
3-12
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The missing fire hydrant serial number obtained from
your asset management database helped us catch the
crooks trying to sell it on the Internet."
The "expected useful lives" of distribution system com-
ponents are theoretically known and depend upon con-
struction material, location, and environmental condi-
tions. For example, the expected useful life of distribution
system components is as follows: pipes - 35 to 50 years;
hydrants - 40 to 60 years; valves - 35 to 40 years; storage
tanks - 30 to 60 years; pumps - 10 to 15 years. Though
these are typical values for expected useful life, there are
always exceptions and it is not unusual, for example, to
find some 100-year old pipes that are still in good condi-
tion. Generally speaking, when a specific asset begins
to exceed its "useful life," it needs to be inspected peri-
odically and reevaluated for replacement. For example,
if the average age of the hydrants is documented as 50
years in the AM database, it is likely that a majority of the
hydrants are near the end of their useful lives and would
need to be replaced fairly soon or evaluated on a regular
basis. Basically, a good AM system contains a compre-
hensive equipment inventory, and is closely linked to the
Level of Service (LOS) concept. LOS clearly defines
performance goals and can be periodically used to define
where, when, and how resources must be expended. The
LOS defines a utility's commitment to the customer and
its goals must be measurable. For example, a water utility
might define its LOS as follows:
• Main breaks will be repaired within 8 hours of
initiation of repair 90 percent of the time.
• Regulatory water quality requirements will be
met 100 percent of the time.
• Monthly water losses will be kept to less than
15 percent.
• Customer complaints will be responded to
within 24 hours.
These LOS requirements make it possible for a utility
to prioritize its O&M activities in order to meet these
goals. For example, if monthly water losses average
greater than 20 percent, the utility would initiate some
type of water audit and leak detection program.
The heart of any utility AM system is a complete inven-
tory of the pipes, tanks, pumps and other facilities that
make up the distribution system, coupled with a system
for recording and tracking the status of those assets.
Historically, information on distribution system assets
has been kept in the form of maps and paper records.
In recent years, many larger water utilities have moved
to computerized mapping and database management
systems. Commercial AM software packages are now
readily available. However, most small- to medium-
sized water utilities continue to use paper records as
the primary method for tracking assets. In many cases,
electronic AM takes a backseat to other utility func-
tions such as electronic billing and electronic reporting
(which may be required by regulations). Expenditures
for commercial AM software packages and their asso-
ciated labor costs are generally perceived as being too
expensive for most small- and medium-sized systems.
The resulting lack of effective tracking often results in
a delay or deferment of needed repair and maintenance
of distribution systems.
An economical solution to AM inventory and record-
keeping is the use of general spreadsheet or database
management software typically available on most per-
sonal computers. These systems can be augmented
by mapping software (Geographic Information Sys-
tem [GIS] or Computer Aided Design and Drafting
[CADD]). As an alternative, a utility may continue to
use paper-based maps.
CADD and GIS are more advanced geographic-based
computer systems that allow the user to store, display
and analyze spatial data. Historically, CADD packages
have been used by engineers and draftsmen in the design
of facilities. GIS grew out of the planning and mapping
fields as a means of constructing maps and analyzing
spatial data. The two fields have moved closer together
in terms of concepts and software and both are used
today as a basis for designing, analyzing and displaying
water distribution systems.
Table 3.4 provides a listing of the popular low-cost
CADD and GIS mapping software.
3.9 Distribution System Modeling
Distribution systems are designed to provide custom-
ers with needed flow at an acceptable pressure level.
Some questions frequently asked regarding the design
and operation of a distribution system are as follows:
3-13
-------
Table 3.4 Listing of Low-cost CADD and GIS Application Software
CAD Mapping Software
Product
Vendor
Web site
Cost
Ease of Use
Operating
systems
supported
Virtual Drafter
V2.2
Softsource
http://www.
vdraft.com/
vdraft.html
$250
Medium
Microsoft
Windows 95,
98, ME, NT,
2000 and XP
IntelliCAD
lintelliCAD
Technology
Consortium
http://www.
intellicad.org/
Basic -$149,
w/ Service
Contract $249
Pro Version
-$349
Easy/Medium
Microsoft
Windows
2000, XP and
Vista
TurboCAD
Deluxe V1 4
IMSI/Design
http://www.
turbocad.
com/
Deluxe - Price
Varies from
$100-$150
Easy/Medium
Microsoft
Windows XP
and Vista,
Macintosh
10.4+
GIS Mapping Software
GRASS V6.2
GRASS
Technology
Consortium
http://grass.
itc.it/
Free (Open
Source)
Difficult
Microsoft
Windows
2000, XP, Mac
10+, Linux
JUMP V1 .2
Vivid Solution
http://www.
vividsolutions.
com/
Free (Open
Source)
Difficult
Microsoft
Windows 2000,
XP, Mac10+,
Linux
Map Window
GISV4.4
Map Window
Open Source
Team
http://www.
mapwindow.
org/
Free (Open
Source)
Medium/Hard
Microsoft
Windows 95,
98, ME, NT,
2000 and XP
Forestry GIS
V1.0
Forest Pal
http://www.
forestpal.
com/Toolbox.
html
Free; Version
of software is
frozen in time
Medium
Microsoft
Windows 95,
98, ME, NT,
2000 and XP
Manifold
System V6.5
Manifold. Net
http://www.
manifold.net/
Personal
- $245/$295;
Professional
- $295/$345
Medium/Hard
Microsoft
Windows 95,
98, ME, NT,
2000, XP and
Vista
Tatuk GIS Editor
V1.8
TatukGIS
http://www.
tatukgis.com/
products/Editor/
Editor.aspx
$350, Free
Viewer Available
Medium/Hard
Microsoft
Windows 95, 98,
ME, NT, 2000, XP
and Vista
• How is a distribution system designed and
operated to satisfy the acceptable flow and
pressure objectives?
• How can one determine the flow available to
fight a fire in a particular neighborhood on a hot
summer day?
• How can one determine the consequences
of taking a tank out of operation to perform
maintenance activities such as painting?
• If an extension to the water system is built to
serve a new development, what will be the
pressure and will there still be an acceptable
chlorine residual in the water delivered to the
new service area?
Computerized network models can assist in provid-
ing answers to these questions. These models are also
referred to as distribution system models or hydrau-
lic and water quality models. Computerized network
models perform calculations based on mathematical
descriptions of flow and pressure. The basic formula-
tion of these models dates back to the work of Profes-
sor Hardy Cross in the 1930s. Today, these models
are packaged in an interactive graphical format that
makes the data entry and analysis of results relatively
easy. Figure 3.11 is a computer screen shot depicting
the results of an analysis of the SmallWater distribution
system using the EPANET software package (available
from EPA). Color coding and arrows are displayed in
order to show flow magnitude and direction, and pres-
sure at junctions.
A distribution system is represented as a network
model of links and nodes. Links represent pipes, while
nodes represent junctions, sources, tanks or reservoirs.
Valves and pumps are represented as either nodes or
links depending on the specific software package. In
order to "build" a network model, the location and con-
nectivity between each network component must be
known. Additionally, the following basic information
is required for the various types of components:
• Pipe: length, diameter, roughness
• Junction: elevation, water use
• Tank: diameter or dimensions, elevations
• Reservoir: water level
Figure 3.11 Screen-shot Showing the Results of an
Analysis for the SmallWater Distribution System
3-14
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I need some fresh pictures for my portfolio, I have
a new hydraulic modeling gig coming up!
Tank Water Level
• Pump: head-discharge curve, intial status
• Valve: type, settings
There are two types of hydraulic analyses that may be
conducted using a drinking water distribution system
network model: steady-state and extended period simu-
lation (EPS). In a steady-state analysis, all water de-
mands and operations are treated as constant over time
and a single solution is generated. Steady state analysis
is useful for assessing a distribution system under a par-
ticular set of circumstances. For example, a steady state
model could be used to estimate the amount of water
available to fight a fire and the resulting pressures in a
particular neighborhood on a hot summer day.
In the EPS mode, variations in demand, tank water lev-
els and other operational conditions are simulated by a
series of steady-state analyses that are linked together
in order to represent the changes in flows and pres-
sures over time. EPS can be used to investigate dis-
tribution system operation, study the behavior of tanks
and pumps, assess energy usage, and serve as the basis
for water quality modeling. Figure 3.12 illustrates plots
from an EPS model of SmallWater showing the varia-
tion in tank water levels and flow in a water main over
a 2-day period. EPS models are "built" starting with
a steady-state model. Additional information that is
needed for an EPS model include: variation in water use
(demands) over the course of a day, operating rules that
describe how pumps and valves are operated and mini-
mum and maximum allowable water levels for tanks.
Water quality models use the output from hydraulic
models in conjunction with additional inputs to pre-
dict the temporal and spatial variability of a variety of
constituents within a distribution system. These con-
stituents include:
• the fraction of water originating from a
particular source
12 16 20 24 28 32 36 40 44 48
Time (hours)
Figure 3.12 EPS Plots of Tank Water Levels and Flow in
a Water Main Over a 2-Day Period,
• the age of water (i.e., duration since leaving the
treatment plant)
• the concentration of a non-reactive tracer
compound either added to or removed from the
system (e.g., fluoride or sodium)
• the concentration of a reactive compound
including the concentration and loss rate
of a secondary disinfectant (e.g., chlorine
or chloramines) and the concentration and
growth rate of disinfection by-products (e.g.,
trihalomethanes [THMs])
EPANET was initially developed in 1993 as a distri-
bution system hydraulic-water quality model to sup-
port research efforts at the EPA. The development of
the EPANET software has also satisfied the need for
a comprehensive public sector hydraulic/water quality
distribution system model. It has been a key compo-
nent in providing the basis for water quality modeling
incorporated into many commercial models and has
been used by many utilities throughout the country.
In addition to EPANET, there are several commercial
software packages that are widely used in the United
States and internationally. Many of these packages
are based on the EPANET formulation and include
value-added components that increase the capability of
the software. Table 3.5 provides a summary listing of
available commercial software and a Web link where
additional details may be obtained on specific features,
current versions, availability and pricing.
3-15
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Table 3.5 Available Hydraulic-Water Quality Network Modeling Software Packages
Network Modeling Software Company Website
AQUIS
EPANET
InfoWater H2ONET/H2OMAP
InfoWorksWS
MikeNet
Pipe2000
PipelineNet
STANET
SynerGEE Water
Wadiso
WaterCAD/WaterGEMS
7-Technologies
U. S. EPA
MWHSoft
Wallingford Software
DHI
Univ.of Kentucky
TSWG, SAIC
Fisher-Ulrig Eng.
Advantica
GLS Eng. Software
Bentley Systems
http://www.7t.dk/company/default.asp
http://www.epa.gov/ORD/NRMRL/wswrd/epanet.html
http://www.mwhsoft.com
http://www.wallingfordsoftware.com/
http://www.dhisoftware.com/mikenet/
http://www.kypipe.com/
http://www.tswg.gov/tswg/ip/PipelineNetTB.htm
http://www.stanet.net
http://www.advantica.biz/
http://www.wadiso.com
http://www.bentley.com
3.10 SmallWater, USA-
Asset Management
Problem Scenario
SmallWater has been experiencing a rapid turnover of
operators. Often, during these personnel changes, one
operator has left before another is fully trained. Conse-
quently, much of the on-duty operator's time has been
spent in locating seemingly misplaced maintenance
records. Repair problems seem to be increasing. The
utility's managers are increasingly concerned that the
loss of trained operators, personnel turnover and mis-
placed records are jeopardizing the utility's ability to
meet long-term water quality goals, to develop an O&M
plan, and to meet their overall LOS requirements.
Issues to Consider
SmallWater does not have an AM system in place. It has
limited finances to purchase commercially available AM
software and is limited in its ability to provide training
to operators for developing an in-house AM system.
Guidance
In order to solve these problems, it is recommended that
the utility investigate the use of a simple spreadsheet-
or database-based AM system. Prior to selecting an
AM system to track inventory and event data, the utility
staff should examine its needs and determine which AM
system provides the best fit. If utility personnel are not
familiar with the use of spreadsheet or database man-
agement software, there are many readily available re-
sources that can help provide training. These resources
include local software specialists, community colleges,
and vendors. Also, there are many books that can pro-
vide a good overview of available software packages.
Once data are entered into a spreadsheet or database
management system, the data can be sorted or filtered
and custom reports can be generated. To be effective,
this system should be viewed as a means for efficient
O&M, not merely a recordkeeping tool.
The key to successful inventory and recordkeeping is
the identification of all distribution system assets and
assignment of a unique identifier to each separate asset
component. Figure 3.13 shows the SmallWater distri-
bution system with each component color coded. Each
component type is assigned a letter (or letters) and with-
in that component type, individual items are assigned a
unique number. For example, T-2 refers to tank number
2 and P-30 refers to pipe number 30. Individual pipes
are categorized as continuous "runs" between junctions,
where pipe characteristics (diameter or material) may
(or may not) change at other important locations such as
a tank, pump or major water users.
For each component, additional information of interest
can be collected and stored in the database. For exam-
ple, the following information would likely be stored for
pipes:
• Pipe number
• Street name
• Diameter
• Length
• Material
• Date installed or replaced
Other types of information could easily be stored. For
example, in addition to the components shown in Fig-
ure 3.13, inventory data on hydrants and isolation valves
could be kept. Figure 3.14 shows the location of hydrants
in parts of SmallWater and the accompanying Table 3.6
contains useful hydrant inventory information. This
type of data could be useful and provide the basis for an
inventory of assets. It is usually referred to as static data
since it remains relatively constant over time.
Other data that can be collected and stored in a data base
include information on pipe breaks, valve exercising,
hydrant flushing, hydrant flow tests, water quality events
such as "red water," or any other distribution system
events or activities of interest. This type of O&M infor-
mation is especially useful for evaluating the perform-
ance of assets and making decisions on future repair and
3-16
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Table 3.6 Hydrant Inventory Information
HyNdr J5L Add- *""°- Avai;agpm)Flow
H014
H015
H016
H017
H043
H044
H045
H046
H047
H048
1996
1996
1996
1996
1952
1952
?
?
2005
1968
202 Main St.
224 Main St.
248 Main St.
286 Main St.
140 Spring St.
110 Spring St.
78 Spring St.
95 Spring St.
112 Lincoln St.
82 Lincoln St.
P-3
P-5
P-17
P-17
P-16
P-9
P-8
P-8
P-12
P-13
1100
375
420
\ WELL-1
replacement programs. Table 3.7 shows a portion of an
event table for SmallWater.
The inventory and event tables serve as a permanent re-
pository for information on all actions taken related to
the distribution system. Figure 3.15 presents an exam-
ple schema (structure) that can be used to design such
a system within a spreadsheet or database management
system. The solid boxes show the elements in the water
system. The dashed boxes refer to maintenance events
for various elements, and the dashed lines show the re-
lationship between the elements and the maintenance
events. This schema can be modified, based on the spe-
cific needs of the utility. Some types of information may
not be of immediate interest to some utilities and other
data may be added as needed.
Figure 3.13 Components in the SmallWater Distribution
System
PIPE
Pipe ID
Diameter
Length
Material
Year installed
!••-•••
! PIP.E.BREAK
• Pipe ID
; Date
! Action
! Active?
HYDRANT
Pipe ID
Elevation
Fire Flow
Material
Year installed
ISOL. VALVE
IsolValve ID •
i Pipe ID
Turn direction
Year installed
PUMP TANK CONT. VALVE
Pump ID Tank ID Valve ID
Pump station Diameter Valve type
Pump name Height Setting
Manufacturer Max level Diameter
Design flow Min level Year installed
Design head Year installed
Year installed
HYPRANT.MA1NT
Hydrant ID
Date
Maintenance
Active?
i VALVE MAINT.
; Date
! Maintenance
Active?
Figure 3.14 Hydrant locations in part of SmallWater
Table 3.7 Event Table
Figure 3.15 Sample Asset Management Database
Design or Schema
Component Date of Event Type of Event Notes
Type y|J
Pipe
Valve
Valve
Hydrant
Hydrant
P-4
V-55
V-55
H016
H047
2/5/03
2/5/03
6/14/03
8/07/06
9/12/06
Break
Flow Test
Replaced
Flush
Replaced
Valve cannot be closed
3-17
-------
Crossword
Distribution System Infrastructure
10
11
ACROSS DOWN
3 The longest components of a distribution 1
system infrastructure
4 Abbreviation for a commonly used plastic pipe 2
in U.S. water distribution systems
7 Configuration of distribution system that 5
provides a higher degree of reliability of
service to customers in case a main break 6
occurs 8
9 Centrifugal pumps require this at startup
10 Term for keeping an inventory of distribution
system components
11 Type of valve that allows flow in one direction
only
Mechanical device that moves water from
surface to elevated storage tanks
Types of pumps most commonly used in
distribution systems
Can be a "turn on" or a "turn off" for water
utilities
Provides a water connection for fire-fighters
Two letters of the NSF logo designating pipe
approved for potable water use
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Chapter 4
Drinking Water
Regulations
Drinking water regulations are designed primarily to
protect public health. As discussed in Section 2.4, the
Safe Drinking Water Act (SDWA) was passed by the
U.S. Congress in 1974 to protect public health by regu-
lating the Nation's drinking water supplies. The 1974
SDWA and its amendments established the following
four key elements:
• a framework (including schedule and
procedures) for developing drinking water
standards
• drinking water standards designed to include
health-based goals, known as Maximum
Contaminant Level Goals (MCLGs)
• technically achievable enforceable standards
known as Maximum Contaminant Levels (MCLs)
• use of treatment techniques (TTs) instead of the
MCLs (as necessary)
The SDWA works in conjunction with the Clean Water
Act (CWA), which controls the discharge of pollutants
into lakes, rivers and streams. The CWA regulations are
designed to protect the source water, whereas SDWA
regulations are designed to protect water quality sup-
plied to the general public (consumer) by public water
systems (PWSs).
Even though CWA and SDWA generally work in con-
junction with each other, some conflicts may arise be-
tween the two acts as they have separate and distinct
measures of water quality. As mentioned previously, the
CWA prescribes Total Maximum Daily Loads (TMDLs)
for different pollutants based on the designated use of a
water body, whereas the SDWA prescribes MCLs.
Regulated by
Safe Drinking Water Act
Clean Water Act (EPA, 2002a)
The 1977 amendments to the Federal Water Pollution
Control Amendments of 1972 are commonly known as the
CWA. The goal of the CWA is to eliminate the releases of
toxic amounts of pollutants into waters of the United States
(e.g., rivers, lakes, streams). The CWA established the fol-
lowing three major programs:
• National Pollutant Discharge Elimination System
(NPDES) Program - A system for granting and
regulating discharge permits which regulates both
point (industrial) and non-point (agricultural)
discharges into waters of the U.S.
• Total Maximum Daily Load (TMDL) Program - A
TMDL is the sum of the allowable loads of a single
pollutant from all contributing point and non-point
sources to a water body (e.g., river, stream, lake).
The TMDL calculation includes a margin of safety
to ensure that the receiving water body can be used
for the state-designated purposes (e.g., drinking
water supply, swimming, fishing). The TMDL
calculation also accounts for seasonal variation in
water quality.
• State Water Pollution Control Revolving Fund
- To assist municipalities in creating wastewater
treatment plants that were capable of meeting the
standards, the CWA established a system to provide
federal financial assistance. Initially, funding was
provided in the form of construction grants. This
mechanism was modified several times and later
replaced by the State Water Pollution Control
Revolving Fund in 1987.
In response to the CWA, EPA finalized effluent guidelines
that regulate water pollution from 56 industrial categories.
It also established pretreatment requirements for industrial
users contributing wastewater to Publicly Owned Treat-
ment Works. It is estimated that these EPA regulations are
responsible for preventing the discharge of nearly 700 bil-
lion pounds of pollutants each year.
Regulated by;
Clean Water Act
4-1
-------
From a compliance perspective, PWS operators who
discharge wastewater and/or storm water (during con-
struction activities) from their facilities need to ensure
that the applicable requirements of CWA are met. How-
ever, the focus of this reference guide is distribution
system water quality; therefore, only SDWA-related
regulations are discussed in this chapter. A summary
of the evolution of federal drinking water regulations
since the passage of the 1974 SDWA is presented in
Figure 4.1.
The regulations presented in Figure 4.1 are designed to:
control microbiological contamination, control chemi-
cal/radioactive contamination, and establish procedural
requirements for meeting MCLs. The following three
factors determine if a specific regulation or rule applies
to a utility's operations:
• classification and size of the utility
• type of source water used (e.g., surface water,
ground water, or ground water under the
influence of surface water)
• type of water treatment used by the utility (e.g.,
filtration, disinfection)
Based on these factors, if it is determined that a particu-
lar rule applies, the utility must then meet the sampling,
monitoring, reporting, treatment, and management
practices as outlined in the regulation. These applica-
bility decisions are typically made by the state regu-
latory agencies. Failure to meet these requirements
Bioterrorism Act
Public Health Security and Bioterrorism Preparedness and Response Act of 2002
enacted Jun 12, 2002 (PL 107-188)
ACCNSCMn
Arsenic and Clarifications to Compliance and New Source Contaminant Monitoring
promulgated Jan 22, 2001
SDWA
Safe Drinking Water Act, enacted 1974
Phase I Rule
promulgated July 8,1987
TTHMR
Total Trihalomethane Rule
promulgated Nov 29,1979
Public Notification Rule
promulgated May 4, 2000
Total Coliform Rule
promulgated Jun 29,1989
SWTR
Surface Water Treatment Rule
promulgated Jun 29,1989
Phase V Rule
promulgated Jul 17,1992
RDWR
Radon in
Drinking Water Rule
scheduled for promulgation
NIPDWR I
National Interim Primary Drinking Water Regulations
enacted between 1975 and 1976 I
86SDWAA -I
Safe Drinking Water Act Amendments of 1986
enacted Jun 16,1986
LCR
Lead and Copper Rule
promulgated Jun 7, 1991
-Phase II and MB Rule
promulgated Jan 30 and Jul 1,
ICRH
Information Collection Rule
promulgated May 14,1996; effective Jun 18,1996
96SDWAAJ
Safe Drinking Water Act Amendments of 1996
enacted Aug 6,1996
IESWTRH
Interim Enhanced Surface Water Treatment Rule
promulgated Dec 16,1998
DBPR1
Stage 1 Disinfection By-Product Rule
promulgated Dec 16,1998
Consumer Confidence Rule
promulgated Aug 19,1998
1991
GWR
Ground Water Rule
promulgated Nov 8, 2006
DBPR2
Stage 2 Disinfection
I 'By-Product Rule
promulgated Jan 4, 2006
Figure 4.1 The Evolution of Federal
Drinking Water Standards
(Adapted from EPA, 2005a)
LT1ESWTRJ
Long-Term 1 Enhanced Surface Water Treatment Rule
promulgated Jan 14, 2002
Long-Term 2 Enhanced Surface Water Treatment Rule
promulgated Jan 6, 2006
4-2
-------
constitutes a violation under the SDWA and can lead
to enforcement actions and penalties. The following
sections present a summary of the key regulations that
apply to small- and medium-sized utilities.
4.1 Highlights of 1974 SDWA and
its Amendments
Between 1975 and 1976, EPA adopted a set of Na-
tional Interim Primary Drinking Water Regulations
(NIPDWR). The NIPDWR provided the basis for the
first national drinking water standards. These stand-
ards included limits for ten inorganic chemicals, six
organic pesticides, turbidity and five radionuclides.
In addition, the NIPDWR established standards for
microbiological contamination based on total col-
iform organisms. In order to ensure that the water
quality supplied to the public met these standards,
the SDWA required that utility operators routinely
monitor drinking water by sampling and testing the
water entering the distribution system for most con-
taminants and in their distribution system for other
contaminants. The SDWA also required utilities to
notify their customers if the standards or sampling
requirements were not met. State regulatory agen-
cies were given the primary enforcement responsibil-
ity ("primacy") over their water supply systems, pro-
vided the individual State program met the national
criteria. Furthermore, the SDWA required EPA to
assume the enforcement responsibility in case a State
was unable or unwilling to do the job of enforcing the
national standards.
4.1.1 1986 Amendments to SDWA
In 1986, the SDWA was amended and the NIPDWR
standards were declared to be final. In addition, the
1986 amendments required EPA to:
• regulate 83 contaminants within three years after
enactment
• regulate an additional 25 contaminants every
three years
• mandate disinfection for all PWSs
• mandate filtration for surface water systems
• designate best available technology for each
contaminant regulated
• allow for TT instead of MCL
The non-community water systems were subdivided
into transient and non-transient systems. States with
primacy were required to adopt these regulations and
begin enforcing them 18 months after they were pub-
lished by EPA.
4.1.2 1996 Amendments to SDWA
The SDWA was amended again in 1996 to address these
concerns and provide funds for PWS infrastructure and
state program management. The 1996 amendments
made the following changes to the SDWA:
• allowed EPA to establish a process for selecting
contaminants to regulate based on scientific
merit and eliminated the need to regulate an
additional 25 contaminants every three years
• established the Drinking Water State Revolving
Fund (DWSRF) to help PWSs finance the costs
of drinking water infrastructure needs
• added an emphasis on source water protection
and enhanced water system management
• allowed for flexibility of regulations and
monitoring for small systems
• required EPA to conduct cost-benefit analyses of
new regulations and analyze the likely effect of
the regulations on the viability of the utility to
implement them cost-effectively
• provided all systems additional time to come
into compliance, plus allowed up to two more
years if capital improvements were required
• established consumer confidence reporting
requirements
Hmm... maybe it's time for
us to amend the SDWA!
4.1.3 Variances and Exemptions
Each drinking water regulation includes provisions for
states to issue variances and exemptions. Affordabil-
ity-based variances are available for small-to-medium
systems (serving fewer than 10,000 people) that allow
utilities to deviate from MCL or TT requirements under
4-3
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The EPA Regulatory Process (EPA, 2003b)
To continually increase the effectiveness of the multiple
barrier approach and protect drinking water customers,
EPA develops regulations as new scientific or health infor-
mation becomes available. Each new regulation strength-
ens or adds a needed barrier at one or more stages of the
water supply process. After an extensive review of scien-
tific and health information, EPA works with stakeholders
and concerned citizens to draft a proposed regulation. The
proposed regulation is published for public comment. EPA
considers all comments and revises the regulation, if ap-
propriate. A final regulation is then published. A listing
and details on specific current and proposed standards can
be found on the EPA website at: http://www.epa.gov/safe-
water/standards.html
certain conditions. Exemptions are designed to give
utilities additional time to comply with the new regula-
tions. To use these variances and exemptions, the utility
must first prove that the requested variance or exemp-
tion does not pose an unreasonable risk to public health
as determined by EPA. Also, variances and exemptions
are not allowed for meeting the regulatory requirements
for controlling microbial contaminants.
General Variance A general variance from meeting an
MCL requirement can be requested if the utility cannot
comply with the MCL because of the characteristics of the
source water. This variance is granted only if the utility
has already installed the EPA-designated Best Available
Technology (BAT) for treatment to remove the contami-
nant for which the MCL is being exceeded. In addition,
the variance should not result in an unreasonable risk
to public health, and the state agency must prescribe a
schedule for compliance when granting this variance.
Small System Variances States can grant small-system
variances to systems serving fewer than 3,300 people
without EPA approval. However, they must get EPA
concurrence for variances to systems serving between
3,300 and 10,000 people. EPA needs to identify afford-
able variance technology for each regulation based on
affordability criteria. As of 2005, no such small-system
variances have been granted because EPA has not identi-
fied any affordable small-system variance technology.
Exemptions States may exempt PWSs from an MCL
or TT requirement if the following three conditions are
met:
• The utility is unable to comply because
of compelling factors, which may include
economic factors.
• The exemption must not result in unreasonable
risk to public health.
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Variance Technology...
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• The system was in operation as of January 1,
1989, or, if it was not, no reasonable alternative
source of drinking water is available to the new
system.
In summary, the variances and exemptions are tempo-
rary. Only under an extreme condition should a utility
consider these as options.
4,2 Regulations to Control
Microbial Contaminants
Disease-causing microbial contaminants such as fecal
coliform (e.g., E. coif), Giardia, and Cryptosporidium
are frequently found in surface waters and ground-
waters under the influence of surface water. Figure
4.2 shows microscopic photographs of the disease-
causing microorganisms E. coli, Giardia, and Crypt-
osporidium. Some of the major rules that are intended
Dad, I heard you talking about affordable virus
removal technology. This tool is guaranteed to
remove all viruses, and best of all it's free!
4-4
-------
Cryptosporiftitfm
Figure 4.2 Disease-Causing Microorganisms - E. coli,
Giardia and Cryptosporidium (not to scale)
to control these microbial contaminants include:
• Total Coliform Rule (TCR)
• Surface Water Treatment Rule (SWTR)
• Interim Enhanced SWTR (IESWTR)
• Long-term 1 Enhanced SWTR (LT1ESWTR)
• Filter Backwash Recycling Rule (FBRR)
• Long-term 2 Enhanced SWTR (LT2ESWTR)
• Ground Water Rule (GWR)
Table 4.1 presents a summary overview of each of these
regulations and its applicability to small- and medium-
sized systems, along with the associated monitoring,
treatment, and management practice requirements.
The information presented in the table is only meant
to provide a general overview of the regulation. EPA
has developed many regulation-specific factsheets and
guidance documents that are much more thorough and
cover the nuances of each regulation.
4.3 Regulations to Control
Chemical Contaminants
Some of the major rules under the SDWA that are in-
tended to control chemical contaminants include:
• Arsenic Rule
• Lead and Copper Rule (LCR)
• Stage 1 Disinfectants/Disinfection Byproducts
Rule (Stage 1 D/DBPR)
• Stage 2 Disinfectants/Disinfection Byproducts
Rule (Stage 2 D/DBPR)
• Radionuclides Rule
• Radon Rule
Table 4.2 presents a summary overview of each of
these regulations and its applicability to small- and me-
dium-sized systems, along with the associated monitor-
ing, treatment, and management practice requirements.
The information presented in the table is only meant
to provide a general overview of the regulation. EPA
has developed many regulation-specific factsheets and
guidance documents that are much more thorough and
cover the nuances of each regulation.
Additional Information
Regulatory Guidance
Documents
EPA has prepared many rule-specific guidance documents
for public use. In addition, EPA has prepared the follow-
ing guides which are tailored for small system operators:
1. Small Systems Guide to Safe Drinking Water Act
Regulations: The First STEP to Providing Safe and
Reliable Drinking Water - One of the Simple Tools
for Effective Performance [STEP] Guide Series.
2. Complying with the Ground Water Rule: Small
Entity Compliance Guide - One of the Simple Tools
for Effective Performance (STEP) Guide Series.
These and the other rule-specific regulatory guidance doc-
uments can be downloaded for free from the EPA website
at: http://www.epa.gov
4.4 Public Notification and
Consumer Confidence Rules
Public notification is intended to ensure that consum-
ers will know if there is a problem with their drinking
water. PWSs must notify their customers if: the level
of a contaminant in the water exceeds EPA/state drink-
ing water regulations; there is a waterborne disease
outbreak or any other situation that may pose a risk to
public health; the water system fails to test its water
as required; or the system has a variance or exemption
from the regulations. Depending on the severity (tier)
of the situation, PWSs have a time limit of 24 hours to
one year to notify their customers. The three EPA des-
ignated tiers are as follows:
1. Tier 1, for MCL violations and situations with
significant potential to have serious adverse
effects on human health as a result of short-term
exposure. Notice is required within 24 hours
of the violation. A consultation with the state
agency is also required within 24 hours.
2. Tier 2, for other violations and situations with
potential to have serious, but not immediate,
adverse effects on human health. Notice is
required within 30 days, or as soon as possible,
with extension of up to three months for
resolved violations at the discretion of the state
or primacy agency.
4-5
-------
Table 4.1 Summary of Regulations Designed to Control Microbial Contamination (Adapted from AWWA, 2006a)
Rule/Applicability to Small-and-
Medium Systems
Total Coliform Rule - Applies to all
PWSs.
Rule Overview/Objective
Conforms are abundant in the feces
of warm-blooded animals. In most
instances, coliforms themselves
are not the cause of sickness, but
they are easy to culture and their
presence is used to indicate that
other pathogenic (disease-caus-
ing) organisms of fecal origin may
be present which can cause seri-
ous illnesses.
Related General Monitoring
Requirements
Sampling is required. The number
and frequency of samples is based
on population served by the PWS
and results of the sanitary survey.
Repeat samples are required within
24 hours if a positive total coliform
sample is found. Furthermore, the
positive samples must be analyzed
for £ co// (a fecal coliform). Cer-
tain strains of £ co// are known to
cause illness in humans.
Related Treatment Requirements
The rule does not mandate any
specific treatment. However, if
monitoring indicates the presence
of coliform, treatment may need to
be added or modified as neces-
sary to resolve the issue.
Related Management Practice
Requirements3
The rule does not mandate any
specific management practices.
However, management practices
may need to be adjusted to meet
the problems uncovered during
monitoring.
Surface Water Treatment Rule
-Applies to all PWSs that use sur-
face water or ground water under
the influence of surface water.
Disease-causing microorganisms
such as G/ard/a and Leg/onella are
present in most surface waters.
This rule establishes criteria for
determining if both filtration and
disinfection are required for re-
moval of these organisms.
Unfiltered systems need to moni-
tor turbidity every 4 hours (source
water), residual disinfectant con-
centration continuously (finished
water), maintain distribution sys-
tem disinfectant residual, and the
total coliform levels (source water)
1-3 times per week, depending
upon the population served.
Filtered systems need to monitor
turbidity at least every 4 hours and
residual disinfectant concentration
continuously (finished water).
Systems may avoid filtration if
they have low coliform and tur-
bidity in source water and meet
other site-specific criteria. Sys-
tems that do not meet this crite-
ria must install filtration treatment
and the state must determine
that filtration in combination with
disinfection achieves the desired
G/ard/a (99.9% removal) and virus
(99.99% removal) removal/inacti-
vation efficiency.
Unfiltered systems are required to
meet source water quality criteria
and maintain a watershed control
program. They are also subject to
annual inspection and watershed
control program evaluation.
Interim Enhanced SWTR and
Long-term 1 Enhanced SWTR.
This regulation builds upon the
SWTR to address Cryptosporid-
ium - a microorganism that can
spread due to contamination of
water from human or animal feces
leading to severe diarrheal illness.
Continuous turbidity monitoring is
required for each conventional and
direct filtration process, with val-
ues recorded every 15 minutes.
States are required to perform
sanitary surveys.
Combined filter effluent must be <
0.3 NTU for 95 percent of monthly
readings and may at no time ex-
ceed 1.0 NTU.
Systems requiring compliance
must establish disinfection profile
and benchmark. Any changes to
disinfection practice must be ap-
proved by the state.
Long-term 2 Enhanced SWTR
-Applies to all PWSs that use sur-
face water or ground water under
the influence of surface water.
This regulation builds upon the
SWTR, IESWTRandLT1ESWTRto
address Cryptospor/d/um - a mi-
croorganism that can spread due
to contamination of water from
human or animal feces leading to
severe diarrheal illness.
Required to initially monitor £
co// for a year and if the annual
mean concentration in the source
water exceeds specified levels,
Cryptospor/d/um monitoring is
required.
Depending upon the initial moni-
toring results, the PWS is further
classified into four "bins" (Bin 1 <
0.075 oocyst/L, Bin 2 - between
0.075 and 1.0 oocyst/L, Bin 3 -
between 1.0 and 3.0 oocyst/L, and
Bin 4 > 3.0 oocyst/L). Each bin
(except Bin 1) requires the PWS to
install a treatment technology and
establish a monitoring schedule
based on contamination levels in
the source water. The treatment
options range from improving
watershed control, reducing influ-
ent concentrations and additional
pre-treatment to membranes and
advanced oxidation.
The rule does not mandate any
specific management practices.
However, management practices
may need to be adjusted to meet
the problems uncovered during
monitoring.
Filter Backwash Recycling Rule
-Applies to all PWSs that use sur-
face water or ground water under
the influence of surface water; if
they employ conventional or direct
filtration, and recycle spent filter
backwash water, thickener super-
natant, and liquids from dewater-
ing process.
Spent filter backwash water, thick-
ener supernatant, and liquids from
dewatering process can contain
microbial organisms such as
Cryptospor/d/um. This rule mini-
mizes the risks associated with
recycling these types of water.
The FBRR requires utilities to sub-
mit a plant schematic showing
recycle flow and plant flow to the
regulatory authority. They must
also retain any records on recycle
practices to document that the re-
cycling of the regulated streams is
performed correctly.
The recycle streams must be sent
to a point where they will pass
through all the treatment process
steps before entering the distri-
bution system. The PWSs can
request approval for an alternate
location.
The rule does not mandate any
specific management practices.
However, management practices
may need to be adjusted to meet
requirements of the regulation.
Ground Water Rule -Applies to all
PWSs that use ground water.
This rule is designed to protect the
consumers of ground water from
bacteria and viruses. It also seeks
to identify defects through sanitary
surveys in water systems that
could lead to contamination.
Systems not achieving mandated
level of microbial removal/inacti-
vation must, after a positive total
coliform result, take a source
water sample and conduct further
tests (e.g., for£ co//, enterococci,
orcoliphage). States also conduct
hydro-geological assessments to
identify if a particular source is
sensitive to such contamination
in which case further monitoring
requirements are applicable.
Systems that detect fecal contam-
ination would be required to take
corrective action that may include
disinfection, removal of the con-
tamination source, or switching
sources.
The rule does not mandate any
specific management practices.
However, management practices
may need to be adjusted to meet
deficiencies noted in the sanitary
survey requirements of the regula-
tion.
aAII of the rules have recordkeeping and reporting requirements associated with the monitoring, treatment and/or management requirements.
4-6
-------
Table 4.2 Summary of Regulations Designed to Control Chemical Contamination (Adapted from AWWA, 2006a)
Rule/Applicability to
Small-and-Medium
Systems
Arsenic Rule - the revised
rule is called -Arsenic and
Clarifications to Compli-
ance and New Source Con-
taminants Monitoring Rule.
All CWSs and NTNCWSs.
Rule Overview/Objective
The revised Arsenic Rule reduced the MCL from
0.05 mg/L to 0.01 mg/L. Arsenic is shown to
cause cancer and other health effects.
Related General Monitoring
Requirements
The rule makes monitoring requirements
of arsenic consistent with those for other
inorganic compounds (lOCs) regulated un-
der the standardized monitoring framework
(SMF)*.
Related Treatment Requirements
The rule specifically lists BATs and
small system compliance technolo-
gies (SSCTs). The SSCTs including
Point-of-Use (POU)/Point of Entry
(POE) technologies most likely to be
used by small systems include: acti-
vated alumina treatment, reverse os-
mosis, and modified lime softening.
Related Management
Practice Requirements'1
The rule does not mandate
any specific management
practices. However, sys-
tems employing treatment
for the first time to meet
the MCL need to focus
and develop appropriate
technical, managerial and
financial capacity. Sys-
tems employing POU/POE
systems must maintain
excellent customer rela-
tionship.
Lead and Copper Rule - All
CWSs and NTNCWSs.
This rule establishes a 90th percentile action level
for lead at 15 micrograms/L (/jg/L) from the 50
jug/L previous level and copper action level of 1.3
mg/L. Lead is a toxic metal that can cause a range
of health effects including learning disabilities in
children. Long-term (more than 14 days) expo-
sure to copper in drinking water at levels higher
than 1.3 mg/L may cause kidney and liver dam-
age in infants.
The number of samples required (ranging
between 5 and 60 for small- and medium-
sized systems) depends upon the system
size. Sampling frequency is annual, every
3 years, or every 9 years (depending upon
the system size and previous monitoring
results). If lead or copper concentrations
exceed the specified action levels in more
than 10% of customer taps sampled, the
PWS must undertake a number of additional
actions to control corrosion.
Corrosion control treatment is re-
quired unless the monitoring data
indicates levels below the action
level for two consecutive 6-month
sampling periods. Source water
monitoring and treatment may be
required if the action levels are ex-
ceeded because of elevated levels
in source water. If the service lines
are the cause of the exceedance and
the problem is not corrected by cor-
rosion control, service lines must be
replaced.
The rule does not mandate
any specific management
practices. However, man-
agement practices may
need to be adjusted to
meet the problems uncov-
ered during monitoring.
Stage 1 Disinfectants/ Dis-
infection By-products (D/
DBPs) Rule-All CWSs and
NTNCWSs that add chemi-
cal disinfectant to water
during the treatment proc-
ess. Certain requirements
apply to TNCWSs that use
chlorine dioxide.3
DBPs result from a reaction between the disin-
fectant (such as chlorine) and the organic and
inorganic compounds present in water. The rule
sets MCLs for haloacetic acid 5 (HAAS) at 0.060
mg/L, chlorite (chlorine dioxide by product) at 1.0
mg/L, bromate (ozone byproduct) at 0.010 mg/L,
and total trihalomethanes (TTHMs) at 0.080 mg/L.
It also sets maximum residual disinfectant levels
(MRDL) for chlorine (4.0 mg/L), chloramines (4.0
mg/L) and chlorine dioxide (0.8 mg/L). DBPs can
potentially cause cancer and impact reproductive
health of humans.
For small and medium systems, 1 sample
per plant annually are required for THMs and
HAAs, generally in the warmest month, or
quarterly. Plants using ozone are required to
monitor monthly, and chlorine dioxide plants
are required to monitor daily at the entrance
to distribution system and monthly within
the distribution system. For systems using
conventional filtration, monthly sampling is
required for total organic carbon (TOG) and
alkalinity which are precursors that impact
the DBP formation.
Systems that use surface water or
ground water under the influence of
surface water and employ conven-
tional filtration must remove a speci-
fied percentage (15 to 50%) of TOG
using either enhanced coagulation or
enhanced softening. The specific %
requirement depends upon TOG con-
centration and alkalinity of source
water.
The rule does not mandate
any specific manage-
ment practices. However,
management practices
may need to be adjusted
to balance the need for
disinfection while minimiz-
ing the potential for DBP
formation.
Stage 2 D/DBPs Rule - All
CWSs and NTNCWSs that
add chemical disinfectant
(other than UV light) to
water during the treatment
process or deliver water
that has been disinfected.3
The rule builds upon the Stage 1 D/DBP Rule. The
covered PWSs are required to perform an initial
distribution system evaluation (IDSE) to identify
monitoring locations for eventual compliance with
the current standards for TTHM and HAAS. Very
small systems (serving fewer than 500 people)
may seek waiver from IDSE. The other option
is to obtain a "40/30" certification. The term
"40/30" refers to a system that under the Stage
1 D/DBP monitoring shows all samples <, 0.040
mg/L for TTHMs and 0.030 mg/L for HAAS.
The IDSE determines the monitoring site
locations. The frequency of monitoring is
based on both source water type and sys-
tem size. Generally, for small to medium
systems it is 2 samples per quarter or year.
Changes in treatment may be re-
quired to remove the DBP precur-
sor (TOG) for the reduction of DBP
concentrations. Systems should
explore operational changes, distri-
bution system modifications, and
alternative disinfection strategies as
necessary.
The rule does not mandate
any specific manage-
ment practices. However,
management practices
may need to be adjusted
to balance the need for
disinfection while minimiz-
ing the potential for DBP
formation.
Radionuclides Rule - All
CWSs
This rule builds upon the MCLs for combined ra-
dium-226/228 of 5 pico curies/liter (pCi/L), gross
alpha particle activity 15 pCi/L, and beta particle
and photon activity of 4 milliremt/year. It adds a
uranium MCL of 30 pg/L. These radionuclides
are known to cause cancer and death at elevated
levels of exposure.
Monitoring of the radionuclides other than
beta particle and photon emitters is consist-
ent with the SMFt. Monitoring is required
at each entry point to the distribution sys-
tem. Monitoring of beta particle and photon
emitters is not required for most CWSs. If
the system is designated by the state as
"vulnerable" or "contaminated," monitor-
ing of beta particle and photon emitters is
required.
The small system compliance tech-
nologies listed in the rule are green
sand filtration, co-precipitation with
barium sulfate, electrodialysis, ac-
tivated alumina and ion exchange
POU/POE devices. Special consid-
eration for spent media or cartridge
disposal may be required.
The rule does not mandate
any specific management
practices. However, man-
agement practices may
need to be adjusted to
meet requirements of the
regulation.
a Stage 1 D/DBP Rule compliance is based on running annual average (RAA), monitoring is plant-based. Stage 2 D/DBP Rule compliance is based on locational running annual average (LRAA),
monitoring is population-based.
bAII of the rules have recordkeeping and reporting requirements associated with the monitoring, treatment and/or management requirements.
t The Standardized Monitoring Framework (SMF) was finalized by EPA in 1991 to simplify and consolidate monitoring requirements across contaminant groups. The SMF increases public health
protection by simplifying monitoring plans and synchronizing monitoring schedules leading to increased compliance with monitoring requirements. The SMF reduces the variability within monitoring
requirements for chemical [inorganic compounds (lOCs), volatile organic compounds (VOCs), and Synthetic organic compounds (SOCs)] and radiological contaminants across system sizes and
types. Monitoring for asbestos, fluoride, nitrate and nitrite are different from monitoring requirements for other lOCs because these chemicals have unusual characteristics. The SMF established a
9-year "compliance cycle" composed of three 3-year "compliance periods." Newly regulated contaminants will be subject to the SMF. During the initial monitoring period, the rule requires PWSs to
sample four consecutive quarters for each contaminant at each entry point to the distribution system. Depending upon the results, systems may be able reduce their monitoring frequency to annually
or once every 3,6, or 9 years. The SMF allows states to waive all monitoring requirements for all contaminants except nitrate (MCL of 10 mg/L) and nitrite (MCL of 1 mg/L).
t millirem is a unit of radiation dose equivalent to one-thousandth of a rem. Roentgen equivalent man (rem) - A unit used to express different types of ionizing radiations on a common
scale to indicate its relative biological effects. For beta and gamma radiations: Exposure to 1 Roentgen delivers a dose of 1 Rad, which is equivalent to 1 Rem.
4-7
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3. Tier 3, for all other violations and situations not
included in Tier 1 and Tier 2, such as monitoring
and reporting violations. Notice is required
within 12 months of the violation, and may be
part of a single annual report, including, in some
cases, the annual consumer confidence report
(CCR) already required by EPA.
EPA sets strict requirements on the form, manner,
content, and frequency of public notices. Figure 4.3
contains a sample public notice. Public notification
is provided in addition to the annual water quality
report (or CCR), which provides customers with a
more complete picture of drinking water quality and
system operations for the preceding year. The annual
CCR informs consumers what is in their water, where
it comes from, and where they can obtain additional
information.
"Hi Stan. Our contractor dropped his
cell phone into the finished water tank.
Is this a Tier 1, 2 or 3 violation?"
2) When the
violation
occurred —
6) Actions -—
consumers
should take
3) Potential
health
effects ,,
7) What is
being done to
correct the
violation
10) Required
distribution
language
IMPORTANT INFORMATION ABOUT YOUR DRINKING WATER
Tests Show Coliform Bacteria in [System] Water
The Jonesville water system routinely monitors for coliform bacteria.
• During the month of July, 7 percent of our samples tested positive. .
The standard is that no more than 5 percent of samples may test
positive.
What should I do?
You do not need to boil your water or take other corrective
actions. However, if you have specific health concerns, consult
your doctor. ^/
Jf
You do not need to use an alternate (e.g., bottled) water supply.
People with severely compromised immune systems, infants, and •
some elderly may be at increased risk. These people should seek
advice about drinking water from their health care providers.
General guidelines on ways to lessen the risk of infection by
microbes are available from EPA's Safe Drinking Water Hotline at
1-800-426-4791.
What does this mean?
This is not an emergency. If it had been, you would have been notified
immediately. Coliform bacteria are generally not harmful themselves.
Conforms are bacteria which are naturally present in the environment
and are used as an indicator that other, potentially-harmful, bacteria
may be present. Conforms were found in more samples than allowed
and this was a warning of potential problems.
Usually, conforms are a sign that there could be a problem with the
system's treatment or distribution system (pipes). Whenever we detect
coliform bacteria in any sample, we do follow-up testing to see if other
bacteria of greater concern, such as fecal coliform or E. coli, are
present We did not find any of these bacteria in our subsequent
testing.
What was done?
We took additional samples for coliform bacteria which all came back
negative. As an added precaution, we chlorinated and flushed the
pipes in the distribution system to make sure bacteria were eliminated.
This situation is now resolved. -4
For more information, or to learn more about protecting your drinking
water please contact John Jones at 555-1212.-
Please share this information with all the other people who drink this
water, especially those who may not have received this notice directly
(for example, people in apartments, nursing homes, schools, and
businesses). You can do this by posting this notice in a public place or
distributing copies by hand or mail.
This is being sent by the Jonesville Water System.
State Water System ID#1234567. Date Distributed: 8/8/06
Figure 4.3 Sample Public Notice (EPA, 2007c)
4) Should alternate
/water supplies be
used
5) The
-^*** population
at risk
8) When the
system will
— return to
compliance
• 9) Phone
number for
more
information
4-8
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Sanitary Surveys (EPA, 1999)
A sanitary survey is an on-site survey of the water source, fa-
cilities, equipment, operation, and maintenance of the PWS for
the purpose of evaluating the adequacy of such source, facili-
ties, equipment, operation, and maintenance for producing and
distributing safe drinking water. They are used to prevent and
correct sanitary deficiencies and are indispensable for ensuring
the delivery of safe water on a sustainable basis. When conducted
properly and with appropriate follow-up, sanitary surveys fulfill
the following objectives:
• Reduce the risk of waterbome disease;
• Provide an opportunity to educate system operators;
• Identify systems needing technical or capacity
development assistance; and
• Identify candidates for enforcement action.
Sanitary surveys have been a critical component of state drink-
ing water programs for decades. States regulatory agencies are
required to complete sanitary surveys for all surface water sys-
tems and systems using ground water under the direct influence of
surface water (GWUDI) on the following schedule:
System Type
Noncommunity water system
Community water system
Community water system with
outstanding performance based
on prior sanitary surveys
Minimum Frequency
Every 5 years
Every 3 years
Every 5 years
The recent ground water rule extends sanitary survey require-
ments to ground water systems. Sanitary surveys may also be re-
quired when compliance problems arise. The PWSs are required
to cooperate with their regulatory agency and provide supporting
information when requested by the agency. Sanitary surveys can
be very useful for small utilities and provide them outside assist-
ance to identify weaknesses in the system before they cause seri-
ous problems. They can also help the utility regain control and re-
solve current weaknesses and avoid repeat compliance problems.
Sanitary surveys help evaluate the following issues:
• The capability of the PWS to monitor and manage water
quality data
• System management and operational weaknesses
• Regulatory compliance weaknesses
• The integrity of supply sources
• Treatment adequacy and operational weaknesses
• Potential impacts of pumping
• Integrity of storage facilities, and
• Distribution system weaknesses
After the sanitary survey is completed, the inspector generally
provides a follow-up report addressed to the PWS manager or
chief operator. The purpose of the report is to summarize any
problems that have been identified, as well as recommendations
for necessary improvements. The report generally discusses each
of the items listed above in detail and provides dates by which the
deficiencies (if any) should be corrected. Sanitary surveys can be
a preventive tool, helping water utilities address weaknesses.
]L 4.5 SmallWater, USA -
T Regulatory Scenario
Problems
Problem #1 Scenario
As previously presented in Section 2.7, in the 1990s,
the well (ground water) supply in SmallWater became
inadequate. Therefore, an alternate source was devel-
oped in the form of an interconnection to the surface
water supply from a larger system located to the south-
east. The well field was maintained as a supplemental
and emergency supply. What regulations would cur-
rently apply?
Issues to Consider
1) Is the source considered a surface water source
from a regulatory standpoint because it has
switched supply from ground water wells to
purchased surface water?
2) If the ground water source is used for
supplementing for peak summer demand, what
compliance issues are raised?
3) Since SmallWater is buying treated surface
water from another source which is in
compliance with all surface water source
requirements, does SmallWater have any
compliance requirements?
Regulatory Guidance
SmallWater should first contact its state (primacy)
regulatory authority and present the entire operating
scenario. From a regulatory standpoint, SmallWater is
considered as the supplier to the customers who live in
the SmallWater service area. At the point where the
bulk purchase takes place, it is SmallWater's respon-
sibility to ensure that the water quality supplied to the
consumer meets the surface water requirements man-
dated by the SDWA.
If ground water is used as a supplement to meet summer
demand, the supplier has to comply with both ground
and surface water treatment requirements. SmallWater
should consult the state regulatory agency to make sure
the mixed water supply meets all regulatory require-
ments.
Problem #2 Scenario
Last July, one of the three required monthly routine
total coliform samples in SmallWater showed positive
results. This triggered a series of actions including no-
tification to the state, additional testing, and public no-
tification.
4-9
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Issues to Consider
1) What is the procedure to identify if
contamination is isolated to the plumbing
system of an individual building from where the
routine sample was drawn, or if contamination
was in the distribution system itself?
2) What should be done if a repeat sample is total
coliform-positive?
3) How is the overall monitoring schedule affected
by this event?
Regulatory Guidance
In response to the notification of positive total coliform
sample, SmallWater was required to take action within
24 hours. This response includes collection of a set of
three repeat samples to assess the extent of the problem.
For water systems that collect one or fewer samples per
month, a fourth repeat sample is required. One of the
repeat samples must be collected from the original sam-
ple tap, one within five service connections upstream,
and one within five service connections downstream.
This pattern of repeat sampling helps to determine the
extent of contamination and potential cause of the posi-
tive sample. If a repeat sample is total coliform-positive
at the same service connection, but negative at upstream
and downstream service connections, the state may in-
vestigate to determine if it is appropriate to waive the
total coliform-positive sample as being a plumbing sys-
tem problem in the individual building.
If any routine or repeat sample is total coliform-positive,
the positive sample is tested either for the presence of
fecal conforms orE. coli. The test is done automatically
by the lab and does not require an additional sample. A
potential urgent health risk exists if any sample, routine
or repeat, tests positive for fecal coliform/E1. coli. When
notified by the laboratory that one of the samples tested
positive for fecal coliforms or E. coli, SmallWater was
required to notify the state by the end of the day. This
notification is required on or before the end of the next
business day if the state office is closed. The occurrence
of a positive routine and repeat sample in conjunction
with a positive fecal or E. coli sample creates an acute
violation of the MCL. In addition to notifying the state,
SmallWater is also required to notify the public within
24 hours by television, radio, hand delivery, or other
methods approved by the state, and consider advising
their customers to boil their water.
coliform-positive sample results, they are required to
notify the state by the end of the next business day and
to notify the public within 30 days by mail, hand deliv-
ered notices, or other methods approved by the state.
In the month following detection of total coliforms in
any routine or repeat sample, SmallWater is required to
collect five routine samples. If none of these tests are
positive for the presence of total coliforms, they may
resume collecting their usual three routine samples the
next month. A total coliform-positive sample is cause
for concern. However, if a set of repeat samples that
month and five routine samples the next month are all
negative, and their other multiple barriers to contamina-
tion are adequate, SmallWater should have confidence
that their water is safe.
Beyond the strict requirements for responding to a posi-
tive coliform sample, SmallWater may also consider the
following progressive steps to avoid further problems.
1. The sample-tap and sample collection
procedures should be examined and reviewed.
Coliform bacteria can come from unclean
faucets, biofilm in the premise plumbing, and
poor sample collection and handling procedures
such as sample bottles sitting in melted ice in a
cooler. Sample collectors may need to take more
care in the collection process and sample faucets
may need to be repaired and sanitized.
2. Local water main conditions should be
reviewed. If the water system is chlorinated,
chlorine test results should be evaluated to
ensure that there is adequate chlorine residual.
Local main breaks, flushing, unusual flow
reversals, valve and hydrant operations can all
stir up or dislodge coliforms from sediments or
biofilms.
3. Storage facilities that influence the water
provided to the sample location from which the
positive coliform sample was taken should be
checked for possible contamination.
A less serious but still significant potential health risk
exists if more than one sample (routine and/or repeat)
in a month is total coliform-positive. This creates a
monthly MCL violation. When SmallWater is notified
by their laboratory of the repeat or second routine total
4-10
-------
Crossword
Drinking Water Regulations
6 7
ACROSS
3 The action level for this compound is 15 |jg/L
under the Lead and Copper Rule
4 A microbial contaminant that is used as a
general indicator of the presence of other
disease-causing organisms
6 Acronym for the regulation designed to control
Cryptosporidium in drinking water
DOWN
1 Time period within which a notice is required
to the regulatory agency in case of a Tier 1
violation
2 Term for special allowances by the regula-
tors to exempt small systems from meeting
the regulatory MCL or treatment technique
requirements
5 Abbreviation for the act passed by congress
to protect drinking water in 1974
7 Acronym for the sum of four disinfection
byproducts formed due to reaction of
chlorine with naturally occurring organic
matter
IAIH11 (Z '
(9 'VAACS (9 'WJOJHOQ fc 'pes~\ fe 'SSOUEUEA fe 'sjnon K ( \,
suounios P.IOMSSOJO
4-11
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Chapter 5
Distribution System
Water Quality Issues
Drinking water exiting the water treatment plant enters
a distribution system which is a complex network of
pipes, tanks and reservoirs designed to deliver finished
water to consumers. Although water entering a distri-
bution system may meet drinking water standards, the
quality of the transported water may degrade within
the distribution system before it reaches the consumer.
Some of these undesirable changes such as objection-
able taste, odor or color can often be detected imme-
diately, whereas other changes in quality such as the
intrusion of dangerous pathogens may only be noticed
after a waterborne disease outbreak. Some of these
pathogens include Salmonella and E. coli. Therefore,
proper distribution system management is essential to
protect consumers from both aesthetic and public health
threats due to deteriorating water quality. The following
sections in this chapter discuss common water quality
issues faced by water utilities, including small- and me-
dium-sized systems. These issues include taste, odor,
and color; biofilm formation; disinfection and disinfec-
tion byproducts (DBFs); nitrification; pH stability and
scale formation; and contamination events.
5.1 Taste, Odor, and Color
In most cases, taste and odor do not pose a public health
threat, and color in water can stain household applianc-
es and plumbing fixtures. These aesthetic problems can
result due to various factors including the following:
poor source water quality, inadequate treatment, initiat-
ing disinfection of well with iron or manganese, chang-
es in water quality in the distribution system, and exter-
nal contamination events. The Safe Drinking Water Act
(SDWA) established National Secondary Drinking Wa-
ter Regulations (NSDWR or secondary standards) that
are non-enforceable guidelines regarding contaminants
that may cause cosmetic effects (such as skin or tooth
discoloration) or aesthetic effects (such as taste, odor,
or color) in drinking water. EPA recommends second-
ary standards for water systems, but does not require
these systems to comply. However, states may choose
to adopt them as enforceable standards and may require
monitoring and reporting.
All customers want their water to look, taste and smell
good; therefore, the utility operator should investigate
customer complaints and try to resolve these issues.
When complaints are filed, as a first step, the utility op-
erator should try to identify if the water quality problem
has occurred in the customer's plumbing or is due to
poor source water quality or treatment and/or changes
in the distribution system that can be controlled by the
utility operator. If more than one customer has reported
similar problems, it is likely that the issue is related to
source water, inadequate treatment or distribution sys-
tem problems. The following sections discuss typical
customer concerns, their most common causes and ba-
sic troubleshooting techniques.
5.1.1 Taste and Odor Problems
Petroleum, gasoline, turpentine, fuel or solvent odor
Generally, the source of these types of odors is external
contamination (e.g., leaking underground fuel storage
tanks). Therefore, it is recommended that the utility
perform on-site investigations to isolate and remedi-
ate the problem. Contaminated soil or ground water
can enter a well or it can permeate through plastic pipe
buried in a contaminated area. Small systems that lack
resources and expertise for tackling this problem should
notify the state agency.
Sulfur or rotten egg odor These types of odors are
commonly caused by bacteria growing in a sink drain
or in a water heater in the customer's home. In some
cases, the smell may be caused by naturally occurring
hydrogen sulfide. As a first step, it is recommended that
the utility ask the customer to collect a small amount of
water in a cup, step away from the odor-causing sink,
swirl the water around inside the cup and smell it. If the
water has no odor, the likely source is bacteria in a sink
drain. If the water continues to have an odor, a possible
source is the customer's water heater. This problem can
occur 1) if the hot water has not been used for a long
time, 2) if the heater has been turned off for a while, or
I Do you have anything that will mask a
"rotten egg" smell in drinking water?
5-1
-------
3) if the thermostat on the heater is set too low. If the
sink drain and the water heater have been eliminated as
the potential source of the problem, additional investi-
gations will be needed. Sulfur odors can also originate
from unmaintained household water treatment devices
and from stagnant plumbing. Sulfur odors can appear
in dead-end mains or through a backflow event and
the distribution system piping may require flushing to
remove the odor-causing material. If the problem is
system-wide, additional water treatment (such as car-
bon filtration) prior to distribution may be necessary to
eliminate organic compounds in the source water that
may be causing the problem.
Moldy, musty, earthy, grassy or fishy odor These
odors can also be caused by bacteria growing in a sink
drain or stagnant water. As indicated in the previous
section, the customer should be requested by the water
utility to collect a small amount of water in a cup, step
away from the tap, swirl the water around inside the
container and smell it. If the water has no odor, the
likely cause is bacteria in the sink drain. If the water
continues to have an odor, the source is most likely al-
gal bloom in the main water. Although generally harm-
less, it may result in abnormal odor at very low con-
centrations. Temporarily, this problem can be alleviated
by flushing (running the faucet for several minutes).
However, it is possible that the distribution system may
require flushing to remove the odor-causing material.
If an algal bloom in the surface water source is deter-
mined to be the cause, additional water treatment (such
as ozonation or carbon filtration) prior to distribution
may be necessary to eliminate the problem.
Chlorine, chemical or medicinal odor These types
of odors are usually caused by the presence of excess
chlorine in the water. Chlorine odors can result from
disinfection of new pipe installations or due to poor con-
trol of chlorine residual. Chemical or medicinal odors
may occur due to the interaction of excess chlorine with
organic matter present in source water or the distribu-
tion system piping. If the organic matter in the source
water is not a problem and there are no nearby custom-
ers reporting similar problems, it is recommended that
the customer contact a licensed plumber and have the
building pipes cleaned or replaced. If organic matter in
the source water is found to be causing the problem, ad-
ditional water treatment (such as carbon filtration) prior
to distribution may be necessary to resolve the issue.
Salty taste This type of taste is usually caused by natu-
rally occurring sodium, magnesium or potassium com-
pounds that are present in a coastal area where sea water
may be affecting the fresh water supply. Naturally occur-
ring high levels of total dissolved solids (e.g., Colorado
River water) can also cause this problem. A utility should
work with the state, and additional site investigation may
be required to isolate and remediate the problem.
Metallic taste Metallic tastes may be caused by met-
als, such as aluminum, zinc, iron, copper or manganese
that leaches from distribution system piping as corro-
sion byproducts, or arise from the source water, or a
residual chemical contaminant from water treatment.
Possible sources of these tastes are treatment process
chemicals (e.g., coagulants or corrosion inhibitors) or
the source water. The corrosive potential of the finished
water must be evaluated to determine if the distribution
system piping could be a source (see Section 5.5, pH
Stability and Scale Formation, for additional details).
Appropriate sampling and analysis may be required to
isolate the problem. Once the problem is identified,
corrective techniques can be applied which may include
modification of the treatment process.
5.1.2 Color Problems
Green or blue water Corrosion of copper plumbing will
frequently cause a bluish-green stain on porcelain fix-
tures. The cause of this problem is generally in the cus-
tomer's piping or due to corrosive water supplied by the
utility. Copper corrosion can sometimes appear in new
building plumbing. Also, backflow of carbon dioxide
or other corrosive chemicals can cause copper corrosion
in plumbing. The corrosive potential of water should be
checked and, if necessary, adjustments need to be made
during treatment such that the water supplied is not cor-
rosive. Phosphate is commonly added to reduce corro-
sion in the distribution system. If the water supplied by
the utility is not corrosive, the customer should contact a
licensed plumber and possibly have the residential pipes
replaced. A short-term acute exposure (above the maxi-
mum contaminant level (MCL) of 1.3 mg/L) can cause
gastrointestinal distress. Long-term acute exposure can
result in liver or kidney damage. People suffering from
Wilson's disease should consult their doctor if the cop-
per in their water exceeds the MCL.
Brown, red, orange or yellow water Rusty water can
cause brown, red, orange or yellow water due to cor-
roding galvanized iron, steel or cast iron pipes in build-
ing plumbing or in the distribution system pipes. Local
water main conditions (valve operating, flow reversals,
and flushing) can upset corroded iron mains and stir
up rust. While unpleasant and potentially damaging to
clothes and fixtures, iron in drinking water is not an im-
mediate human health concern. The SDWA has a (non-
enforceable) secondary standard of 0.3 mg/L for iron.
The corrosive potential of water should be checked by
the utility and, if necessary, appropriate adjustments
should made during treatment. Phosphate addition and
pH adjustment are commonly used to reduce corrosion
in the distribution system.
5-2
-------
I'm feeling a bit flushed... |
I think it is more than just
iron rust contamination J
Black or dark brown water Manganese or other pipe
sediment can cause a black or dark brown color but
generally clears up without further action after the
sediment settles in the water main. Flushing of cold
water faucets and toilets is recommended. Manganese
does not pose a threat to human health. The SDWA has
a (non-enforceable) secondary standard of 0.05 mg/L
for manganese. The utility should investigate to deter-
mine if the household is located in an area with chronic
low-flow issues that could lead to pipe sediments and
deposits. If the problem is caused by the presence of
manganese in source water, additional treatment pri-
or to distribution may be required to resolve the
problem.
Milky white or cloudy water En-
trapment of air bubbles can result
in milky or cloudy water. The
customer should fill a
glass with water and set it on
a flat surface. If the water
starts to clear at the bot-
tom of the glass first, the
cloudy or white appear-
ance is a natural occur-
rence. Presence of air
bubbles is not a health
threat and should clear in
about five minutes. If the
water does not become
clear, additional studies
should be conducted to
isolate and remediate the
problem. Galvanized pipe
(zinc coating) or aluminum
oxide can also make the water
appear milky.
Figure 5.1 depicts a taste and odor
wheel that can assist t
activities.
5.2 Biofilm
Biofilm consists of microbial organisms that attach
to the interior surfaces (e.g., pipes, tanks) of water
distribution system pipes and tanks. These organ-
isms excrete a slimy glue-like substance that allows
them to adhere to the piping or other water distribu-
tion system components. Figure 5.2 shows a picture
of biofilm growth inside a pipe. Generally, biofilm
in distribution system piping contains various species
of bacteria: most commonly coliforms, heterotrophic
and nitrifying bacteria. However, biofilm can contain
fungi, algae, protozoa, dead cells, corrosion products.
organic, and inorganic matter. Typically, biofilms are
benign and do not cause health problems. However,
in many cases, their excessive growth leads to various
types of problems and requires control. For example.
biofilms can shield disease-causing microorganisms
such as mycobacteria, aeromonads and Legionella
from residual disinfectants. In addition, biofilms can
allow the growth of bacteria to reach a level that in-
terferes with total coliform compliance testing or
support the growth of coliform organisms to a level
that jeopardizes compliance with the total coliform
;ar .
i %
*
-------
Figure 5.2 Bio film Growth Inside the Pipe
monthly standard. Furthermore, biofilms can also
produce taste- and odor-causing compounds, especial-
ly after initiation of disinfection, leading to consumer
complaints. Therefore, it is important to understand
the factors that promote biofilm growth and the opera-
tional techniques that can be employed to minimize
biofilm growth as discussed in the following subsec-
tions.
5.2.1 Factors Aiding Biofilm Growth
Drinking water is not sterile. Thus, bacteria in water
will form biofilm as water always has enough nutrients
(carbon, nitrogen and phosphorous) to allow biofilm
growth to occur. However, the rate of biofilm growth is
influenced by the finished water quality and other con-
tributing factors such as disinfectant type, residual disin-
fectant concentration, pipe material, system hydraulics,
corrosion activity and distribution system maintenance
practices. The basic process begins with the seeding of
Just like the "fire triangle,"
for the biofilm to grow it
needs three key nutrients....
the microbial organism in the system and the growth
rate is a function of nutrient availability and other con-
tributing factors which are discussed in this section.
The overall composition of the biofilm in a distribu-
tion system depends upon the organisms that initiate
the growth. For example, water main construction and
repair activities can create an opportunity for some
undesirable organisms to enter the system and act as
"seeds" for growth. Thereafter, the availability of nu-
trients in the finished water is a key factor in biofilm
growth. The key nutrient that impacts biofilm growth
is total organic carbon (TOC) in water. Some research
has pointed to specific components of TOC, notably as-
similable organic carbon (AOC) and biodegradable or-
ganic carbon (BDOC), as the key factors in influencing
biofilm growth. However, there is still much uncertainty
associated with the biofilm growth process.
Biofilm growth is amplified by factors such as flow,
high temperature, corrosion, and low residual disin-
fectant levels. In general, low flow conditions tend to
favor formation of biofilms. Higher temperatures favor
the development of biofilms and increase the diversi-
ty of microorganisms present in the biofilm. A rule-
of-thumb is that water temperature at or above 15°C
(~60°F) tends to experience greater bacterial activity.
Corroded pipes are more supportive of biofilm growth
than non-corroded pipes, because the corrosion deposits
and tubercles (blister-like growth of iron oxides) can act
as a shelter to the organisms to protect them from the
disinfectant. Most disinfectants are effective in control-
ling the organisms that comprise a biofilm provided that
it comes in contact with the organisms. However, the
dead cells, extra cellular molecules, and other compo-
nents of a biofilm react with the disinfectant to limit
their destructive ability. The type of disinfectant used
can also affect biofilm growth. In some instances, the
use of chloramines may yield better biofilm control.
5.2.2 Operational Factors Inhibiting the
Growth of Biofilm
Biofilm growth in distribution system piping is inevi-
table, given that small quantities of microorganisms
are always present in source water and pass through
treatment or can be introduced accidentally during con-
struction and repair activities. Operational techniques
can be implemented to inhibit biofilm growth by the
following: reducing available nutrients, optimizing dis-
infectant dosage, controlling corrosion and periodic
flushing.
Reducing nutrient availability As mentioned in the
previous section, TOC is usually the key nutrient that
impacts biofilm growth in drinking water systems.
Utilities should consider treatment techniques such as
5-4
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enhanced coagulation and/or activated carbon nitration
in conjunction with source water protection measures
to reduce the overall TOC levels in water. For some
utilities, another option is to move the point of disinfec-
tion (to a point after the filtration process). This allows
bacteria to grow in the filter media and consume the
biodegradable fraction of TOC, even though the over-
all TOC levels are not significantly reduced. In some
systems, nitrogen may be the limiting nutrient factor.
Ammonia, nitrate or nitrite removal technologies may
be employed by the operator to reduce nitrogen avail-
ability. For systems using chloramines, careful control
of ammonia addition may help to reduce residual free
ammonia in the finished water.
Optimizing disinfectant dosage Disinfectants can re-
duce the growth of biofilm in a distribution system.
However, residual disinfectant must be available
throughout the distribution system. In many cases, it
may not be practical to maintain residual levels based
on disinfection at one central location. Distributed
booster chlorination stations may be more effective in
maintaining residual levels in areas of low-flow and
stagnation, especially during warmer water tempera-
ture months.
This automated antibiotic
drip system is designed to
control Biofilm
Corrosion control As discussed previously, corrosion
deposits and tubercles can act as a shelter to help pro-
tect biofilm from a disinfectant. In moderate to severe-
ly corroded iron pipes, the exposed surface may take up
a vast majority of the available disinfectant. Proactive
corrosion control practices may result in better control
of biofilm growth. Water main rehabilitation or replace-
ment is another option.
Flushing Flushing at velocities greater than 2 feet/sec-
ond can physically remove some biofilm by scouring.
Flushing can also remove accumulated debris and cor-
rosion products that shield the biofilm from disinfec-
tion. Flushing is only a temporary measure; the under-
lying conditions that support biofilm growth need to be
addressed simultaneously.
5.3 Disinfection and Disinfection
Byproducts
All utilities using surface water sources are required
by EPA to disinfect the water prior to delivery to their
consumers. The intent of this requirement is to pro-
vide a barrier against disease-causing microorganisms.
The process which destroys or removes disease-causing
organisms is termed "disinfection." Chlorine and chlo-
ramines are the most commonly used disinfectants in
the U.S. Furthermore, it is necessary that a residual
disinfectant be maintained throughout the distribution
system. Loss of disinfectant residual is one of the most
common water quality concerns. The availability of a
disinfectant residual is a function of time and rate of de-
cay or loss caused by consumption of disinfectant at the
pipe wall and in the bulk water. Excess disinfectant lev-
els lead to undesirable changes in water quality when
the disinfectants react with naturally occurring organic
matter or compounds, such as TOC or bromide, in the
source water/distribution system to form DBFs.
I wonder if the new disinfectant
soap we are using for handwashing
causes any disinfectant byproducts
to form on our hands...
5-5
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Although studies are ongoing to determine the long-
term health effects of exposure to DBFs, EPA has
already set monitoring requirements and MCLs for
some of the more common DBFs including: tri-
halomethanes (THMs), haloacetic acids (HAAs),
bromate, and chlorite. If DBFs are a problem, the
utility should carefully evaluate the key variables
that impact their formation including: residual dis-
infectant levels, water age in the distribution system,
TOC concentration, pH, and water temperature. A
DBF problem scenario is described in Section 5.7 at
the end of this chapter.
5.4 Nitrification
Nitrification in drinking water distribution systems is
the transformation of ammonia to nitrate. In this proc-
ess, ammonia is first transformed to nitrite by bacteria
and subsequently, nitrite is transformed to nitrate as a
bacteriological process or simply in the presence of
oxygen. Nitrifying bacteria are slow-growing organ-
isms, and nitrification problems usually occur in large
reservoirs or low-flow sections of distribution sys-
tems. Ammonia is present in drinking water through
either naturally-occurring processes or through the
addition of ammonia during disinfection to form chlo-
ramines. Given similar levels of TOC and temperature
in the source water, chloramines form less DBFs than
chlorine. Therefore, chloramine use is expected to in-
crease as a direct result of more stringent DBF MCLs
associated with the Stage 1 and Stage 2 D/DBP Rules
(see Chapter 4).
If you paid attention in your
chemistry class, you would know
they stand for nitrite and nitrate!
Nitrate and nitrite levels in water are required to be
monitored at the entrance to the distribution system.
If the levels are greater than one-half of the MCL,
additional proactive monitoring and troubleshooting
should be performed. Nitrate and nitrite have direct
health implications. Nitrate is transformed to nitrite
in the human digestive system. The nitrite ion oxi-
dizes iron in the hemoglobin of the red blood cells to
form methemoglobin, which lacks the oxygen-carry-
ing ability of hemoglobin. This creates the condition
known as methemoglobinemia (commonly referred
to as "blue baby syndrome"), in which blood lacks
the ability to carry sufficient oxygen to the individ-
ual body cells causing the veins and skin to appear
blue. Infants under 6 months of age and older persons
with genetically impaired enzyme systems are unable
to reduce toxic methemoglobin to oxyhemoglobin.
Therefore, ingestion of nitrite and nitrate can be fatal
in these susceptible population groups. To protect the
susceptible population, EPA has mandated the MCL
for nitrate to be 10 mg/L (measured as nitrogen) and
1 mg/L for nitrite (measured as nitrogen). Most indi-
viduals over one year of age have the ability to rapidly
convert methemoglobin back to oxyhemoglobin.
It is important to recognize that nitrate and nitrite may
come from sources other than nitrification. It has been
found that 93 percent of all U.S. water supplies contain
less than 5 mg/1 nitrate, but these values may be chang-
ing as a result of the increased use of nitrate-contain-
ing fertilizers that enter source waters. Increased use
of chloramination may also result in higher levels of
nitrate in drinking waters because of partial nitrification
in the distribution system. The nitrification process in
a distribution system can be controlled by utility op-
erators by controlling the presence of ammonia, mini-
mizing the low-flow areas in distribution systems and
controlling the growth of biofilm that may contain the
nitrifying bacteria.
5.5 pH Stability and Scale
Formation
It is important to maintain a stable pH as part of main-
taining distribution system water quality. Excessive
changes in pH can lead to water quality problems. For
example, low pH values (less than 7.0) can accelerate
the internal corrosion of metallic pipes, and can lead
to leaching of lead and copper in pipes and plumbing
fixtures. Therefore, a certain level of scaling in me-
tallic pipes is helpful in passivating the pipe by de-
positing a protective carbonate layer on it. However,
higher pH (greater than 9) can cause excessive scale
formation which can significantly reduce the carrying
capacity of a pipe and provide a shelter for biofilm
growth. Scales in pipes are formed due to the precipi-
5-6
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tation of mineral constituents in water onto the pipe
walls. Scale formation is a complicated process that
depends on a variety of system-specific physical and
chemical conditions and pH is only one of the factors.
Scale-forming potential is often measured by the Cal-
cium Carbonate Precipitation Potential or the Lange-
lier Saturation Index (LSI).
Langelier Saturation Index (LSI) (CD, undated)
In order to calculate the LSI, it is necessary to know the
alkalinity (mg/1 as calcium carbonate [CaCO3]), the cal-
cium hardness (mg/1 Ca2+ as CaCO3), the total dissolved
solids (mg/1), the actual pH, and the temperature of the
water (°C).
LSI = pH-pHs
Where: pH is the measured water pH and pHs is the pH at
saturation in calcite or calcium carbonate and is defined as:
pHs = (9.3+A + B)-(C + D)
Where:
A = (Log10 [total dissolved solids] - 1) /10
B = -13.12 x Log10 (°C + 273) + 34.55
C = Log10 [Ca2+ as CaCO3] - 0.4
D = Log10 [alkalinity as CaCO3]
A negative LSI value indicates that there is no potential for
scaling to occur, the water will dissolve CaCO3. A positive
LSI indicates that scaling can result from CaCO3 precipita-
tion. An LSI close to zero is the desirable in most cases.
5.6 Contamination Events
Drinking water distribution systems are vulnerable to
external contamination from cross-connections, perme-
ation/leaching, intrusion/infiltration and reservoir/stor-
age facility contamination. These problems are briefly
discussed below.
5.6.1 Cross-connections and Backflow
Almost all distribution systems contain locations
where accidental cross-connections between pota-
ble drinking water and non-potable water can occur.
These cross-connections can provide a pathway for
backflow of non-potable water (i.e., contaminated
water into potable supplies). Backflow occurs either
because of reduced pressure in the distribution system
(termed backsiphonage) or due to the presence of in-
creased pressure from a non-potable source (termed
backpressure). Backsiphonage may be caused by a va-
riety of circumstances, such as main breaks, flushing,
pump failure, hilly terrain, limited pumping capacity,
high demand by consumers, or emergency firefighting
water drawdown. Backpressure can occur when heat-
ing/cooling, waste disposal, or industrial manufactur-
The extensive scaling has reduced
the pipe diameter to 20% of design
capacity. If we adjusted the pH and
cleaned the pipes, we could meet the
new demand in this service area.
ing systems are connected to potable supplies and the
pressure in these external systems exceeds the pres-
sure in the distribution system. In both cases, the di-
rection of water flow is reversed, causing non-potable
and potentially contaminated water from industrial,
commercial, or residential sites to flow back into the
distribution system through a cross-connection.
The risk posed by cross-connection and backflow can
be minimized. For example, it can be prevented by
installing backflow prevention devices and assemblies
and through formal programs to seek out and cor-
rect cross-connections within the distribution system.
Some water systems have programs to identify cross-
connections or the potential for cross-connections
in individual service connections. Some corrective
measures include activities such as flushing and clean-
ing a distribution system after an incident.
There is no easy way to detect and monitor for the oc-
currence of cross-connection and backflow. Also, there
are no national reporting requirements for backflow in-
cidents, and no central repository exists for backflow
incident information. Some states have detailed re-
quirements and other states have minimal requirements
for cross-connection control. The number of reported
incidents is believed to be a small percentage of the to-
tal number of backflow incidents that actually occur in
the U. S. There is a lack of general awareness about
the threat posed by cross-connections and backflow
through illegal and unprotected taps. PWS operators
should be aware that there is a potential for intentional
contamination of a distribution system through such
cross-connections.
5-7
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5.6.2 Permeation and Leaching
Permeation of piping materials and non-metallic joints
is denned as the passage of contaminants external to
the pipe, through porous, non-metallic materials, into
the drinking water and is generally limited to plastic
and other non-metallic materials. Volatile organic com-
pounds present in the ground can permeate plastic pip-
ing and gaskets.
Leaching is denned as the dissolution of metals, solids,
and chemicals into drinking water. Leaching from ce-
ment linings can occur in soft, aggressive, poorly buff-
ered waters. Under static conditions, metals such as alu-
minum, arsenic, barium, chromium, and cadmium can
leach from cement linings, even when NSF-approved
materials are used and linings are applied according to
AWWA standards. Vinyl chloride can leach from PVC
pipe manufactured prior to 1977. The SDWA has estab-
lished an MCL of 0.002 mg/L (2 ug/L) for vinyl chloride;
however, no instances of MCL violations have been cited
in connection with PVC pipe manufactured after 1977.
Permeated plastic piping must be replaced since the
piping retains its swollen porous state after permea-
tion. Operators of small PWSs using non-metallic pipes
should be aware of permeation and leaching problems
and address them appropriately. Operators should avoid
placing plastic pipes (mains or service lines) in soils
and ground water environments that may be contami-
nated with organic solvents and petroleum products.
5.6.3 Intrusion and Infiltration
A pressure transient in a drinking water pipeline caused
by an abrupt change in the velocity or direction of water
can cause a surge or "water hammer." When a valve
is closed rapidly, it suddenly stops water flowing in a
pipeline and the associated pressure energy is trans-
ferred to the valve and pipe wall. Similar action can
occur when a pump is shut off rapidly, as may happen
with a power outage. Shock waves circulate within the
distribution system and pressure waves sometimes pro-
duce a banging noise as it travels back and forth. A less
severe form of water hammer is called a surge where
a slow motion mass oscillation of water is caused by
internal pressure fluctuations in the system. If these
pressure transients are not controlled, they can damage
pipes, fittings, and valves, causing leaks and shortening
the life of the system. The production of this transient
low- and negative-pressure creates the opportunity for
contaminated water to intrude and infiltrate the pipe
from outside. Such pressure transients can back-siphon
environmental water in soil (or flooded valve and meter
pits) into the mains through leaking joints or cracks.
5.6.4 Storage Facility Contamination
Reservoirs and neglected finished water storage facili-
ties such as reservoirs and tanks can be a dangerous
source of contamination. When unchecked, animals,
birds and pests can inhabit and contaminate these fa-
cilities. If these facilities are improperly maintained,
they can quickly spread the contamination throughout
a distribution system. Storage facilities should be thor-
oughly inspected on a regular basis.
Looks like we have
a storage facility
contamination problem!
Storage Tank Contamination (Clark et al, 1996)
In December 1993, a Salmonella outbreak was identified in
the Gideon, Missouri, municipal water system. This out-
break affected around 486 of the 1,104 residents and caused
seven deaths among nursing home residents. Ensuing EPA
investigations supported by other federal, state and local au-
thorities concluded that all the affected residents had con-
sumed municipal water. The investigations revealed that a
large municipal storage tank was in a state of disrepair with
bird parts and other floating debris which was determined
to be the source of contamination. During November 1993,
the residents of Gideon reported objectionable tastes and
odors in the drinking water supply. The utility superintend-
ent initiated an aggressive and comprehensive flushing
program and flushed the hydrants in the system. Unfortu-
nately, the flushing program resulted in water being drawn
from the municipal tank that was severely contaminated
with Salmonella which dispersed throughout the network.
This preventive action led to a major waterborne disease
outbreak. Initially, it was suspected that the sediments in
the tank owned by the private company also connected to
the distribution system and was the source of the outbreak.
However, a pressure test confirmed that the backflow pre-
vention valve connecting the private tank to the Gideon
network was functioning properly. A modeling analysis
confirmed that the earliest reported cases of disease were
found to be from areas receiving water predominantly from
the contaminated municipal tank.
5-8
-------
Additional Information
Taste, Odor, Flushing, DBF,
Nitrification and Cross-
connection
NESC. Tech Brief: Taste and Odor Control. 2006.
AWWA. Water Supply Operations: Flushing and Cleaning
- DVD. 2006.
AWWA. Cost and Benefit Analysis of Flushing. 2004.
EPA. Technologies and Costs for Control of Disinfection
By-Products. October, 1998
EPA. Nitrification. August 15, 2002.
EPA. Cross-Connection Control Manual. February, 2003.
|L 5.7 SmallWater, USA -
7 Water Quality Problem
Scenarios
Problem #1 DBF Scenario
SmallWater purchases water from another supplier and
has discovered a compliance problem with DBFs (par-
ticularly THMs and HAAs) in its purchased water. The
supplier chlorinates the water and the long travel time to
SmallWater and within the SmallWater distribution sys-
tem frequently leads to the formation of excess DBFs.
Issues to Consider
Elevated DBF levels can be a difficult problem to al-
leviate. This is especially true in this situation where
SmallWater purchases most of its water from another
utility and has little control over the source water and
treatment process. Issues that should be considered in-
clude:
• Does the water comply with DBF levels in the
new Stage 2 DBF Rule?
• If it is not in compliance, what are the primary
causes for the elevated DBF levels? Potential
problems could be high levels of DBF
precursors in the source water coupled with
insufficient or incorrect treatment, long travel
times for the finished water to reach the town,
and/or excessive travel times from the entry
points into the town until the water reaches the
town's customers.
Regulatory Guidance
The initial question that SmallWater should address is
whether or not the elevated DBF levels are due prima-
rily to the characteristics of the source water and treat-
ment. Another question is whether or not excessive wa-
ter age has led to high levels of DBF formation during
the time when the water is traveling to SmallWater and
within the SmallWater distribution system.
Sampling data showed that THM levels at the point of
entry to the town were in compliance and typically av-
eraged around 40 to 50 ug/L while samples within the
SmallWater distribution system frequently exceeded 80
ug/L and, in some cases, exceeded 100 ug/L. This sug-
gested that THM formation within the town was the pri-
mary cause of the elevated DBF levels. A quick calcula-
tion of the travel time for the water from the treatment
plant to the town for the purchased water showed that,
under average conditions, it took about 20 hours. This
was compared to the map of maximum water age (from
the entry points to the town) that the town's consultants
produced from their hydraulic model.
Figure 5.3 indicates that maximum travel times within
the town were typically in the range of 1 to 5 days. This
far exceeded the 20-hour travel time for the purchased
water to reach the town. Both the sampling data and
the travel time calculations clearly indicated that the
primary problem leading to excessive DBF levels was
the operation of SmallWater's water distribution system
rather than the source water/treatment. SmallWater's
consultant was asked to work with the town's water
staff to determine operational changes for reducing the
water age within the town.
Problem #2 Contamination Scenario
SmallWater has received several sporadic complaints
over the past year from the residents in the trailer park
in the southwestern part of town about water that oc-
casionally tastes and smells bad. The water system op-
erator has visited the area on a few occasions and has
not found any obvious problems. There haven't been
any positive conform samples in the town for the past
year. Recently, one resident mentioned that both their
children and elderly mother have experienced severe
stomach aches.
Issues to Consider
The patterns of complaints in the trailer park suggest
that there may be some intermittent contamination
occurring in the distribution system serving this area.
Since the complaints are from more than a single resi-
dence, it is likely that the location of the contamination
is in the distribution system itself or possibly within the
customer's plumbing that has then migrated through
the distribution system. Also, since the trailer park is
served by a single connection to the main part of the
distribution system, it is likely that the contamination
usually will stay in the trailer park piping rather than
move more widely into the distribution system. There
are no Total Conform Rule (TCR) sampling sites in the
5-9
-------
Figure 5.3 Water Age Within Small Water, USA
Inter-Connect
trailer park which may explain why there have been no
positive coliform readings.
Regulatory Guidance
The town has fulfilled the sampling requirements as-
sociated with the TCR and has not experienced any
positive readings. However, the repeated complaints
within a small area and especially the recent indications
of possible gastrointestinal illness should alert the town
to a potential serious problem. SmallTown officials
should contact the state primacy and health agency and
solicit its assistance. Other activities should include (1)
a cross-connection investigation in the trailer park area;
(2) additional coliform sampling in the trailer park area;
and (3) medical testing of the sick residents for possible
exposure to disease-causing coliforms such as E. coli.
5-10
-------
Crossword
Distribution System
Water Quality Issues
10
11
ACROSS
4 Odor commonly caused by bacteria growing
in a sink drain
7 Plastic pipes are susceptible to contamination
from surrounding soils when this occurs
8 Water appearance caused by entrapment of
air bubbles
9 Shock-waves caused by abrupt changes in
velocity and direction of water
10 Technical term for process that converts
ammonia to nitrate in distribution system
11 Water colors associated with manganese or
other pipe sediments
DOWN
1 Forms due to precipitation of minerals in
water on to the pipe walls
2 Water colors associated with corroding iron
pipes
3 Water colors associated with corrosion of
copper plumbing
5 A result of a cross-connection where
nonpotable water contaminates drinking
water distribution system
6 Common technique used for biofilm control
which can sometimes lead to undesirable
byproducts
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5-11
-------
-------
Chapter 6
Distribution System
Monitoring, Control,
and Security
There are many questions that arise when attempt-
ing to monitor, control and/or secure a distribution
system. Some of these questions include the fol-
lowing:
• What is happening at any moment in the
underground pipes, elevated tanks, pump
stations and other components that make up
the distribution system?
• Are pressures sufficient to meet customer
demands, prevent infiltration, and provide fire
flow?
• Is there sufficient chlorine residual to protect
the water in the distribution system?
• Is there enough water in the tank in case of a
major fire?
• Has a contaminant entered the water system
that could lead to a waterborne disease
outbreak?
• When opening a hydrant, how much flow is
available?
• Does the distributed water quality meet the
standards set by EPA and the state regulatory
agency?
In order to answer these questions with some de-
gree of accuracy and reliability, data must be col-
lected and reviewed periodically by the utility per-
sonnel from a variety of sources. If any problems
are observed, corrective actions must be taken by
the utility personnel. Utility managers may want
to consider automated monitoring for operating and
controlling a distribution system. Automation assists
in obtaining a continuous set of records that can be
examined for improving system operations. A distri-
bution system is one of the most vulnerable aspects
of a water utility because its components are geo-
graphically dispersed, making it difficult to ensure
physical integrity. However, some key distribution
system components, such as finished water storage
tanks, can be adequately secured. Automation may
therefore help improve the overall security of the
distribution system. This chapter discusses options
for monitoring, controlling and securing a distribu-
tion system.
6.1 Monitoring a Distribution
System
Monitoring can be broadly categorized as measuring
the hydraulic state of the water in a distribution sys-
tem, or measuring water quality parameters. These
two aspects of distribution system monitoring are
discussed further in Sections 6.2 and 6.3. Hydraulic
state monitoring includes: measuring flow rate, water
pressure, velocity and/or water levels within a tank
or reservoir. Water quality monitoring involves meas-
urement of the intrinsic characteristics of the water.
For example, a representative sample of water may be
analyzed for temperature, conductivity, and pH. In
addition, the water can be analyzed for specific wa-
ter quality parameters such as chlorine residual and
coliform.
Doc, the sampling guide said to grab
a sample and store at 39°F
t-t-til the t-t-time of analysis!
Specific monitoring procedures may range from sim-
ple manual sampling to a highly automated process of
sample collection and analysis. In manual sampling, a
water sample is taken from the distribution system and
is either analyzed in the field (Figure 6.1) or transport-
ed for analysis in the laboratory. Automated moni-
toring typically requires more sophisticated and costly
equipment, but provides savings in labor costs and the
added benefit of a greater number of measurements.
Historically, small water utilities have generally relied
upon manual sampling procedures in order to avoid the
capital investments associated with automated equip-
ment. However, as technology costs decrease, there
are many cases where automated monitoring equip-
ment is cost-effective for smaller utilities. Figure 6.2
shows an example schematic of an automated sampling
unit that measures and analyzes the sample in the field
and sends the information back to a central office for
assessment.
6-1
-------
Figure 6.1 Manual Water Quality Sampling and Field
Testing
Since monitoring activities are expensive, they are usu-
ally performed to meet a specific objective or multiple
objectives. These objectives may include:
• Regulatory requirement - Taking samples of
water to determine if it meets the requirements
established by federal or state agencies
• Process control requirement - Providing real-
time information that assists in operating the
system
• Baseline data collection - Establishing normal
ranges for data values from the system
• Contaminant identification - Detecting the
presence of a contaminant that has intentionally,
accidentally or naturally entered the water
system
• Computerized model calibration - Collecting
hydraulic or water quality data to be used in
adjusting a hydraulic and/or water quality model
of the distribution system
Figure 6.2 Automated Water Quality Monitoring
(GCWW, 2007)
6-2
• Improving system performance - Collecting
real-time information that may be used to
understand and improve system performance
In the following sections, various available options for
distribution system state and water quality monitoring
are discussed.
6.2 Distribution System Hydraulic
Monitoring
As water moves through a distribution system and its
various components, hydraulic characteristics such as
flow, velocity, and pressure change over time. In order
to understand a system's operation, to identify potential
problems, or to operate the system more efficiently, it is
useful to monitor these characteristics. Measurements
may be made continuously at key locations using auto-
mated monitors (if affordable) or be measured manually
at selected locations and times.
6.2.1 Flow and Velocity Monitoring
Flow is an important factor in understanding the opera-
tion of a distribution system. Low flows in some pipes
may indicate a constriction or closed valve. High flows
can result in high velocities which cause large friction
losses and even damage to the pipe. Water sold to cus-
tomers is typically billed based on flow. Therefore, un-
derstanding flow is important to the proper operation and
maintenance of a water distribution system.
Meters are used to measure flow rates and velocities in
an open channel or closed pipe. They may be perma-
nently placed in the distribution system or in a treatment
plant to provide continuous measurements. They may
also be temporarily installed as part of a testing program
to provide measurements over a period of a few days
or weeks. They may also be used manually to measure
flow from a hydrant as part of a system calibration or fire
flow analysis. Flow meters can provide continuous flow
measurements and/or totalized volumes over a period
between readings.
There are several different types of flow meters. Most
meters can be broadly classified based on the following
operating principles: differential pressure, positive dis-
placement (PD), velocity measurement and level meas-
urement. Differential pressure meters and velocity meters
are most commonly used in the water industry. Within
each of these categories, there are alternative methods for
achieving these measurements. Table 6.1 illustrates sev-
eral different types of flow meters and the basic principle
upon which each is built. More detail on the limitations
and advantages of each type of meter can be found in
American Water Works Association's (AWWA's) M33
Manual of Water Supply Practices "Flowmeters in Water
Supply" (second edition published in 2006).
-------
Table 6.1 Flow Meters (Partially adapted from AWWA, 2006b)
Meter Type
Venturi Meter
Diagram
- High-Pressure Port
Principles of Operation
A constricting section is placed in the pipe causing
an increased velocity and corresponding pressure
drop. Pressures are measured at the upstream end
of the constriction and within the constriction. Flow
is calculated from the square root of the measured
pressure differential multiplied by a meter factor
that accounts for dimensional units and discharge
coefficient.
Turbine and Propeller
Meters
Straitening
Vanes v
In turbine and propeller flowmeters, flowing water
strikes rotor blades that rotate at a rate proportional
to the flow velocity. The turbine wheel of a turbine
meter generally fills the cross-section of the pipe
and is mounted to spin freely between two central
bearings supported in the pipe wall. The propeller
of a propeller meter is mounted on bearings at the
downstream end of the pipe and does not fill the
meter cross-section.
TransitTime Ultrasonic
Flow Meter
A pair of transceivers is positioned diagonally across
the meter body. The transceivers transmit and re-
ceive an ultrasonic pulse in the direction of flow, fol-
lowed by a return pulse against the direction of flow.
The time difference between the two pulse transmis-
sions through the stream is a function of fluid veloc-
ity and, by computation, the rate of flow.
Averaging Pitot Flow
Meters
Multiple ports in an insertion tube face upstream
into the flow to provide sampled pressures at
selected points along the vertical pipe diameter to
provide an averaged pressure over the pipe cross-
section while ports facing downstream register
static pressure. The device produces a differential
pressure reading which is used to calculate velocity
(proportional to the square root of the pressure
differential).
Insertable Averaging
Magnetic Flowmeter
Multiple magnetic fields are generated by electro-
magnetic coils placed inside a sensor inserted in
the pipe section through a tap connection. Water
passing around each sensor encounters the mag-
netic field, which induces a small electric charge
that is proportional to the velocity of the water in
the magnetic field. The electric charge is sensed by
multiple pairs of electrodes in contact with the water
adjacent to each of the electromagnets. Each coil
and pair of electrodes becomes an electromagnetic
velocity sensing point along the sensor.
Variable Area Flow
Meter
Also known as a rotameter, the area through which
the liquid flows is permitted to vary so that a con-
stant differential pressure is maintained. The basic
elements are a vertical conical tube and a cylindri-
cal float that is free to rise and fall in the tube. The
greater the entering volumetric flow, the larger the
required flow through area, and the higher the float
rises. Therefore, the rise of the float is proportional
to the rate of flow.
6-3
-------
Flow measurements may also be taken at hydrants
and used to estimate fire flow availability (or as part
of a distribution system model calibration study). Pitot
gages are typically used to measure hydrant flow and
are available in three forms: hand held, clamp-on, or in
combination with diffusers (see Figure 6.3). They are
all based on the principle that virtually all of the veloci-
ty head in the hydrant flow is converted to pressure head
that is read by the pitot gage. Pressure measurements
can then be converted to hydrant discharge rates based
on the diameter of the hydrant port, the characteristics
of the port and the specific instrument.
Figure 6.3 Hydrant Flow Gages
6-4
Water Meters and Automation
Positive displacement (PD) water meters are normally
used to measure usage in residences and commercial
buildings. Other types of flow meters can also be used
at specific locations in a distribution system to determine
flow through that portion of the system. These flow me-
ters utilize a variety of flow measurement methods and are
generally selected for specific use based on the type of end
user, the required flow rates, and accuracy requirements.
PD meters employ oscillating pistons or a nutating disk to
measure flow. Both methods rely upon the physical dis-
placement of the measuring element in direct relation to
the amount of water passing through the meter. The piston
or disk moves a magnet that drives the register. PD meters
are generally very accurate at low to moderate flow rates
typical of residential and small commercial users, and are
common in sizes from 5/8 to 2-inch pipe-size. However,
this measuring methodology is not practical in large com-
mercial applications that experience high flow rates or low
pressure loss. A velocity type meter is commonly em-
ployed for higher flows where the velocity is converted
into volume. Common velocity-based meters include: jet
meters (single-jet and multi-jet), turbine meters, propeller
meters, and magnetic meters.
Manufacturers have now developed pulse or encoder reg-
isters to produce electronic output for radio transmitters,
reading storage devices, and data logging devices that
are employed with Automatic Meter Reading (AMR). In
AMR technology, the usage data is automatically collected
from customer water meter and transferred to a central da-
tabase for billing and/or analyzing. AMR systems provide
customers and utilities a more accurate way of tracking
and billing of actual water usage rather than depending
on a flat rate system or an estimate. AMR technologies
include handheld, mobile and network technologies based
on wired, wireless, or radio frequency transmission.
6.2.2 Pressure Monitoring
Pressure measures the amount of internal energy within
water at any location in the distribution system. Most
importantly, pressure serves as an important indicator of
how a water system is operating and is closely related to
hydraulic integrity. Routine low pressures in a distribu-
tion system indicate design deficiencies or operational
problems in the system. Unusually low pressures may
indicate a problem such as a main break, closed valve
or low water levels in a tank. Therefore, pressure is
frequently monitored to assess system operation and
integrity.
Pressure can be monitored continuously using pres-
sure meters installed in the system or can be measured
manually at hydrants or any faucet in the distribution
-------
My dad put automatic water meters and
valves throughout the house and the
shower shuts off after 15 gallons use!
system. Permanently installed continuous monitors
are frequently connected to a Supervisory Control and
Data Acquisition (SCADA) system (See Section 6.4
for an overview on SCADA and automation). These
pressure values are transmitted to a central control
room. Pressure meters may also be used to measure
tank water levels. Figure 6.4 shows a pressure gage
attached to a fire hydrant. Figure 6.5 shows typical
SCADA readouts of the distribution system hyraulic
measurements.
6.3 Distribution System Water
Quality Monitoring
Water utilities strive to deliver water that meets or
is better than the Safe Drinking Water Act (SDWA)
standards and is aesthetically acceptable. Other goals
may include minimizing treatment costs and deliver-
ing a product that is consistent in quality for all uses.
Water quality monitoring serves as the mechanism for
measuring how well the utility meets these goals and
Figure 6.4 Digital and analog pressure meter attached
to fire hydrant
may serve multiple purposes including:
1. Satisfying regulatory compliance requirements
2. Assisting in process or operational control
3. Identifying contaminants in the water
4. Characterizing the water quality for use in future
decisions
Because water quality monitoring can be expensive,
most small utilities emphasize its use only in meeting
regulatory compliance requirements. However, ad-
ditional monitoring can frequently pay off in terms of
an improved product and lower treatment and chemi-
cal costs. Routine or automated online monitoring can
also assist in screening for the possible occurrence of:
loss of disinfection residual, pathogen contamination,
disinfectant byproduct formation, nitrification, metal
accumulation, and intentional (e.g., terrorist) contami-
nation.
Design of a monitoring or sampling program involves
the following decisions:
1. What constituents should be monitored?
2. Where should the monitoring locations be
placed?
3. What type of sampling (continuous, composite
or grab) should be employed?
4. How often should sampling occur?
5. What type of analytical procedures should be
used?
6. Is the sampling routine, seasonal, or being
conducted for a special study?
•*
Figure 6.5 Readout meters for flow, water level and
pressure from a SCADA system
6-5
-------
For compliance monitoring, the answers to most of
these decisions are spelled out in the regulations and
operating permits. However, for other types of moni-
toring, the water utility is responsible for designing the
monitoring program that meets its specific needs and
fits within its budget.
Honestly ma'am, the computer |
virus ate our monitoring and h
compliance records! J
6.4 Controlling a Distribution
System
The smaller utilities have historically limited the use
of SCADA to control the treatment process. However,
SCADA is routinely employed by larger utilities to moni-
tor and control distribution system operations. A SCADA
system consists of three components: instrumentation
and hardware, a software program or operator interface,
and communication media. In the past, most small sys-
tems could not afford SCADA systems because the initial
equipment cost was high and it required a highly trained
technical person to effectively operate the SCADA on a
routine basis. However, with more sophisticated technol-
ogy updates, costs have become more reasonable. Fur-
thermore, the degree of sophistication (and customiza-
tion of the programming) allows for a less skilled person
to operate the system effectively. The implementation
of appropriate automation and control technology (e.g.,
SCADA) can greatly enhance operations and mainte-
nance activities for small utilities. The key components
of SCADA systems, along with some basic selection cri-
teria, are described in the following subsections.
6.4.1 SCADA Instrumentation and Hardware
Instrumentation and hardware are generally the most
expensive components of a SCADA system. In order
for an instrument to be connected to a SCADA system,
it must generate an output signal that the SCADA can
read. Sophisticated monitoring instruments generally
have a local display and an optional standard external
analog or digital output. The analog output is usually a
direct current output of 1 to 5 volts or 4 to 20 milliam-
peres which can be interfaced with standard SCADA
input/output (I/O) hardware. Through calibration, this
signal can then be directly related to the instrument
reading, such as chlorine concentration in milligrams
per liter or turbidity in nephelometric turbidity units.
Similarly, a pump's operating state would have a pre-
defined digital output (e.g., 1 or 0) where the value re-
turned would directly correspond to the operating state
of the pump (i.e., 1 = off and 0 = on, orvice versa).
Information also travels in the opposite direction
through the SCADA system. In this case, the central
system sends an analog or digital signal to the instru-
ment in order to initiate some action by the instrument.
The digital signals are used to control all system com-
ponents from relays to motor starters. The analog sig-
nals are used to control variable frequency drives and
other variable speed pumps and motors.
Would we be able to send an alarm to
our vendor when the cookie supplies are
running low on the vending machine?
The analog and digital I/O values are aggregated, com-
puted and communicated by field SCADA devices such
as programmable logic controllers or micro-processor
based remote terminal units (RTUs). Field RTUs may
be connected to other master RTUs or computing devic-
es such as a personal computer that contains customized
software which provides the human machine interface
or the SCADA operator interface. The cost of the RTUs
can range between $200 and $20,000, depending upon
the features and complexity desired.
6.4.2 SCADA Operator Interface
The price of commercially available customizable
SCADA software usually depends on the number of
I/O channels licensed for use along with the number
of computers or workstations from which the system is
operated. The cost of SCADA software has decreased
6-6
-------
over the past few years and the ease of customizing
SCADA software has improved dramatically. The most
sophisticated packages, designed to work with a variety
of hardware, are relatively expensive (between $1,000
and $20,000 for a utility with I/O channels numbering
between 50 and 1,000) and generally require a trained
programmer for the initial setup. For less complicat-
ed uses, such as by a small water utility with minimal
staffing, a package arrangement (where the software
is included with the hardware and basic programming
setup) is usually sufficient.
6,4.3
Generally, SCADA equipment that is located within
a treatment plant is hard-wired. Distribution system
components, such as tanks and pumps that are scattered
throughout the distribution system, need alternative
communication media such as leased lines or wireless
transmission capability. Small systems that are rela-
tively compact should explore the use of standard in-
dustrial wireless radio modem connectivity where pos-
sible. Other hard-wired and wireless options available
to commercial carriers (such as the phone company)
require a monthly fee that may range between $20 and
$200 per month, depending upon the selected solution
and required data bandwidth requirement.
of
If a small system operator is considering the installation
of a new SCADA system, the following factors should
be carefully considered:
• Does the treatment and distribution system
justify the need for a SCADA system (is
it spatially dispersed and are its various
components difficult to access)?
• Is the treatment plant and the distribution system
amenable to automation?
• What types of communication media can be
used (phone, radio, cellular, etc.) at the critical
locations in the system?
• How much existing automation and control
instrumentation is available in the system that
could be incorporated into the SCADA system?
• What type of SCADA system is needed (is the
goal to monitor and /or control operations)?
• How many parameters need to be monitored
and/or controlled?
• Are there any specific regulatory monitoring and
reporting requirements that can be met by using
a SCADA system?
• Can the selected SCADA system be made
compatible with existing or future use of AMR?
Remote Monitoring - Coabvood, West Virginia (EPA, 2003d)
In 1992, EPA, in collaboration with the McDowell County Public
Service District (MCPSD), installed a prefabricated semi-auto-
mated ultrafiltration (UF) drinking water treatment package plant
in Coalwood, West Virginia (WV). The UF system was located
approximately 12 miles from the MCPSD office in the Appa-
lachian Mountains. The UF system has been in operation since
1992, and has been providing water of good quality to the com-
munity. However, upon completion of the two-year project, it be-
came apparent that the MCPSD would be unable to meet the WV
Department of Health monitoring and reporting guidelines. These
regulations require that the treatment operator(s) maintain daily
records of specific operating and treatment parameters. Routine
monitoring of the water distributed from the UF treatment process
was resulting in significant costs for associated time and travel.
Furthermore, during inclement weather conditions, completion
of these routine tasks became extremely difficult. Similar moni-
toring requirements at other remotely located sites also required
MCPSD to dedicate a considerable amount of staff time to com-
plete these routine tasks. Therefore, in 1998, the EPA extended
the research project by installing and testing an off-the-shelf user-
friendly Windows-based SCADA system. The SCADA system
selected was fairly inexpensive, smart, user-friendly and scalable.
The total cost for the hardware and software for setting up the
SCADA system at the WV test site was $35,000. Table 6.2 pro-
vides a breakdown of the SCADA system costs:
6,2 Cosf of SCADA at
Coalwood, WV.
Computer, Instrumentation, Software, and
Upgrades
Communication Modem and Phone Line
Data Collection and Transportation Terminal
Instrumentation for Monitoring and Control
Setup and Installation
Total Capital Cost
$6,000
$1,000
$5,200
$21,000
$1,800
$35,000
The remote capability allowed the utility to save on labor and
mileage for performing daily monitoring. A simple cost-benefit
(retum-on-investment) analysis showed the advantages of such
a system. The site was approximately 24 miles round trip from
MCPSD headquarters and it took the operator one hour per day to
perform this task. The annual labor savings (based on an operator
labor rate of $15/hour) amounted to: $15 per hour X 1 hour/day
X 365 days/year = $5,475. In addition, the vehicle cost savings at
the rate of $0.40 per mile amounted to: $0.40 per mile X 24 miles/
day X 365 days/year = $3,504. In total, a minimum of $8,979
in annual savings to the utility was achieved immediately for
this site. A direct payback, based on cost savings to satisfy daily
monitoring requirements, was achieved in less than 4 years. This
simplified cost model was based on direct operating costs only
and assumed that the cost of upkeep of monitoring instrumenta-
tion was similar to other laboratory devices used by the opera-
tor. Additional benefits included the ability to maximize the effi-
ciency of the water treatment operations, creation of an advanced
knowledge of the systems condition prior to performing any site
visits for troubleshooting and repair, improving the security of the
system, and improving regulatory monitoring compliance.
6-7
-------
• Can the SCADA system be classified as a capital
improvement project and acquired through
outside sources of funding such as grants and
interest-free loans?
• What is the return-on-investment or labor cost
savings resulting from installing a SCADA
system?
Considering these factors will help a utility determine
the need, affordability, and the basic design of a SCADA
system. These factors will also help to determine if the
SCADA system will complement general utility opera-
tions. Retrofitting a treatment and distribution system for
a SCADA system can be cost-prohibitive because many
currently operating small utilities were not originally de-
signed for remote operations. Therefore, they have lit-
tle or no existing electronic instrumentation or hardware
that can be integrated into a SCADA system, and the cost
of upgrading the utility for remote operations could be
significant. It is essential that a cost-benefit analysis be
performed prior to such implementation.
[Under this new water rate plan, anyone can reduce
| their current water bills by 10%... if they take
showers and cook during off-peak hours!
6.5 Securing a Distribution System
The Public Health Security and Bioterrorism Prepared-
ness Act of 2002 mandated that drinking water utilities
serving more than 3,300 persons conduct vulnerability
assessments (VAs) and develop emergency response
plans (ERPs). EPA provided funding or training as-
sistance to utilities to assist in compliance with the
Act. The compliance schedule was staggered based
on system size. The last scheduled date for preparing
a certified ERP was December 31, 2004, for systems
serving between 3,300 and 50,000 persons. For sys-
tems serving fewer than 3,300 persons, EPA developed
a guidance document titled, "Drinking Water Security
for Small Systems Serving 3,300 or Fewer Persons."
There are a variety of guidance documents and tools
available on the Internet for addressing small systems
security that were collaboratively developed and fund-
ed by a variety of organizations including: EPA, state
environmental agencies, Department of Homeland Se-
curity, National Rural Water Association, and the Rural
Community Assistance Program. Small water utilities
are strongly encouraged to use these sources as much
as possible.
The VA process identifies the critical water utility as-
sets that may be subject to potential threats. If these
assets are successfully targeted, the consumer's health
could be compromised or there could be severe infra-
structure and economic damage. The ERPs address the
risks associated with these vulnerabilities and contain
procedures that eliminate, minimize, and/or manage
these security breaches. An overview of distribution
system vulnerabilities, operational and emergency re-
sponse mechanisms is presented in the following sub-
sections.
6.5.1 Distribution System Vulnerabilities
Distribution systems and their components are vulner-
able to two types of attacks. In one scenario, the system
component could be physically destroyed or disabled;
in the other scenario, the component may be contami-
nated with a chemical and/or biological threat agent. In
Our security budget only had
enough money to buy these signs.
Go ahead and post them... they
might discourage the vandals,
6-8
-------
addition to security threats, distribution system compo-
nents are vulnerable to aging and corroded pipes. Pipes
located below the water table provide an opportunity for
intrusion of water and contaminants (e.g., animal and
human wastes) if low or negative pressure conditions
occur. Maintaining the hydraulic integrity (positive
pressure) of a water distribution system is important,
given that insufficient pressure can lead to infiltration
or backflow through cross-connections (see Chapter
5). Infiltration or backflow can occur during fluctuating
water use patterns (e.g., fire prevention activities/fire
hydrant use, power outages, and flushing exercises).
Post-treatment contamination can occur during the stor-
age of drinking water. Storage facilities are particularly
vulnerable to contamination due to the failure of pro-
tective covers or barriers, or open hatches and vents.
Birds, insects, animals, rain, and microorganisms can
even contaminate covered finished water storage tanks.
Routine inspections and maintenance are necessary to
address this vulnerability.
6.5.2 Operational and Emergency Response
Mechanisms
EPA strongly recommends that utilities develop a for-
mal ERP that contains the following eight core ele-
ments:
1. System-Specific Information - At a minimum,
identify the utility staff and contact person(s)
with the location of critical documents, such as
distribution system maps, as-built drawings, site
plans, source water locations, current equipment
inventory and operations manual(s).
2. Community Water System Roles and
Responsibilities - The plan should designate an
Emergency Response Lead with an alternate.
This person should be designated as having
the responsibility for evaluating incoming
information, managing resources and staff, and
deciding on appropriate response actions. This
person should also have the lead responsibility
of coordinating emergency response efforts with
first responders.
3. Communication Procedures: Who, What,
and When - The plan should clearly identify
communication channels for utility staff and
personnel, external non-utility entities (such as
other city, state and federal agencies), and the
public/media. The plan should contain internal
and external notification lists with information
on all appropriate entities to be contacted,
including their names, titles, mailing addresses,
e-mail addresses, all applicable land line and
cellular phone numbers, and pager numbers.
These lists should be updated as necessary.
4. Personnel Safety - During an emergency,
personnel may be at risk of harm, injury, or
even death. Therefore, protecting the health
and safety of the utility, first responders, and
the surrounding community should be a key
priority. An ERP should provide direction to
personnel on how to safely implement a variety
of response actions.
5. Identification of Alternate Water Sources - The
plan should contain information on the amount
of water needed to address both short-term
(hours to days) and long-term (weeks to months)
outages. The ERP should identify potential
alternate water supplies that can be quickly
mobilized during both types of outages.
6. Replacement Equipment and Chemical Supplies
- The plan should identify the location of the
current equipment inventory that contains the
listing of equipment, repair parts, and chemicals
that would be needed to respond adequately
to a particular vulnerability. The utility should
consider establishing mutual aid agreements
with other nearby water utilities to address any
deficiencies. These agreements should identify
the equipment, parts, and chemicals available to
the utility under the agreement.
7. Property Protection - Protecting the utility
facilities, equipment and vital records at the
utility is essential to restoring operations once
a major event has occurred. Therefore, the
ERP should identify measures and procedures
that include: "Lock down" procedures; access
control procedures; establishing a security
perimeter following a major event; evidence
protection measures for law enforcement
(should the major event also be declared a crime
scene); securing buildings against forced entry;
and other property protection procedures and
measures.
8. Water Sampling and Monitoring - The ERP
should clearly identify water sampling and
monitoring requirements. To the extent
possible, the ERP should identify and address
special water sampling and monitoring issues
that may arise during and after a major event.
Some water sampling and monitoring issues to
consider include: identifying proper sampling
procedures for different types of contaminants;
obtaining sample containers; determining the
quantity of required samples; identifying who
is responsible for taking samples; identifying
who is responsible for transporting samples (in
time-sensitive situations); confirming laboratory
capabilities and certifications; and interpreting
monitoring or laboratory results.
6-9
-------
I! only have $100 in our emergency
communications budget but I got a I-
great deal on 5 miles of string. J
An ERP containing these eight core elements provides
the necessary information to effectively coordinate and
respond to an emergency event. In addition, the util-
ity staff should be trained on procedures and conditions
that necessitate the activation of the ERP. Thereafter,
operational actions must be implemented to identify the
source of contamination, to isolate the source (if pos-
sible), and to determine the operational changes neces-
sary for containing the damage to public health and the
distribution system. Finally, steps must be undertaken
to discharge or transport the contaminated water to a
location where it can be effectively treated for disposal.
An ERP should be viewed as a "living document" that
is frequently updated as changes are made in the sys-
tem, its operation and its personnel.
6.6 SmallWater, USA -
Monitoring, Control
and Security Problem
Scenarios
Problem #1 Monitoring and Control
Water samples from the distribution system indicate
that SmallWater has had trouble maintaining residual
chlorine levels in the distribution system. Residual
chlorine levels were frequently near zero at the most
distant locations (supplied by the elevated tank) in the
distribution system. SmallWater is considering booster
disinfection at the tank and installing a continuous chlo-
rine monitor to collect data for optimal disinfectant dos-
age and to control the chlorine dosage rate.
Issues to Consider
Maintaining adequate residual disinfectant levels is es-
sential from a compliance perspective and to ensure
a safe water supply. However, the cost of installing a
booster chlorine station and an online chlorine monitor
with an analyzer can be quite costly. Costs may range
between $1,000 and $2,000 for the monitor and con-
necting it to a SCADA interface to control the booster
dosage of chlorine will require additional funds (new
SCADA remote terminal unit ~$2,500, installation and
testing ~$3,000). Additional funds are required for the
chlorine storage unit and the injection pump.
Guidance
In order to take better advantage of the costs associ-
ated with the booster chlorination station, other uses of
the SCADA at this location should be investigated. The
utility may achieve some operational efficiency if the
operation of the tank can be optimized by using the tank
level indicators and integrating them with the SCADA
system for booster chlorination. Understanding tank hy-
draulics and mixing processes within the tank and their
potential impact on loss of chlorine residual may result
in further efficiencies and better performance. Online
residual chlorine data are also useful if there is a great
deal of variation in the regular weekday, weekend and
seasonal data.
Problem #2 Security Scenario
Security at the elevated tank has been an ongoing issue.
The tank property is not fenced and has been broken
into several times. Birds, animals and insects have pe-
riodically contaminated the tank and dead species have
been found in traps at access locations.
Guidance
First and foremost, the tank access must be physically
secured. Barriers (e.g., doors, wire mesh or iron bars)
and locks must be placed on all hatches, vents, gates,
and other points of entry to prevent access by unau-
thorized personnel, birds, animals and insects. Dead
bolt locks and lock guards are fairly inexpensive and
provide additional security at minimal cost. A daily
check of critical system components enhances security
and ensures that there has been no unauthorized entry.
Doors to critical facilities, and their hinges, should be
constructed of heavy-duty reinforced material. Hinges
on all outside doors should be located on the inside.
To further enhance security, SmallWater should consid-
er installing access alarms on all points of entry utiliz-
ing the SCADA system (see Problem #1). Integrating
SCADA with security and monitoring/compliance re-
quirements is extremely cost-effective.
6-10
-------
Crossword
Distribution System Monitoring,
Control, and Security
ACROSS
4 Type of commonly used pressure-based
flowmeter
6 Flowmeter using sound waves to measure
flow
8 A term for protecting utility property from
tampering
DOWN
1 Term for periodic measurement of water
quality in distribution system
2 Abbreviated term for most commonly used
water meters for residential applications
3 Acronym for a plan to address risks associ-
ated with vulnerabilities
5 Recommended number of core elements of
an Emergency Response Plan
7 Acronym for Supervisory Control and Data
Acquisition System
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6-11
-------
-------
Chapter 7
Strategies to Address
Distribution System
Water Quality Issues
In the U.S., a concept called the "multiple barrier ap-
proach" (as discussed in Chapter 2) has been applied
widely to drinking water treatment. This includes the
use of both disinfection and nitration to treat surface
water prior to supplying it to the consumer. However,
under the Safe Drinking Water Act (SDWA) and its
amendments, this concept has been expanded by EPA to
include source water protection and distribution system
integrity. The 1996 Amendments to the SDWA empha-
sized source water protection; more recently, EPA has
focused on drinking water distribution systems. The
most recent "report card" issued by the American So-
ciety of Civil Engineers addressing the nation's drink-
ing water infrastructure reveals that distribution system
infrastructure improvements will require a tremendous
investment if they are to provide an effective barrier in
protecting the nation's drinking water.
Many small- and medium-sized distribution systems
built prior to World War II (especially those serving ru-
ral areas) have received little or no recent capital invest-
ment. Some of these systems are facing water quality
problems that are associated with aging infrastructure.
In addition, some utilities are experiencing a higher
rate of pipe failures and problems with specific pipes
manufactured during a certain period of time, or when
they are subjected to certain environmental conditions.
Common problems include: corrosion, biofilm growth,
frequent breaks and leaks, and difficulty in minimiz-
ing disinfectant loss and disinfection byproduct (DBF)
levels. Cross-connection and backflow issues are also
i- \
[Ah! here is the quarterly compliance
report for Small Water. I knew they
were cutting back on mail costs. ,
frequently observed in these systems. To address these
issues and find long-term solutions, small- and medi-
um-sized utilities need to step back from a "crisis man-
agement mode" and engage in strategic planning. For
example, when a water quality problem is discovered
and the cause isolated, the utility must address immedi-
ate problems related to public health. However, util-
ity mangers should also explore strategies that address
long-term issues. Some of these changes may require
long-term, phased infrastructure investment. This chap-
ter provides an overview of these operational, financial
and management strategies.
7.1 Operational Strategies
Operational changes are generally less expensive and
easier to implement than changes that require signifi-
cant infrastructure investment. For example, if DBFs
are an issue, the utility should consider actions that
minimize DBF formation in the distribution system.
The utility might consider reducing water age and/or
changing disinfectants (e.g., chlorine to chloramine) or
both. Switching disinfectants to chloramine will likely
require some capital investment. In some cases, these
operational changes may only provide temporary relief
and eventually an infrastructure investment may be nec-
essary. The utility may need to find an alternative source
of water or treat the water in such a way as to lower
the total organic carbon (TOC) content in the finished
water. A summary of available operational strategies
is presented in the following sections of this chapter.
Some of these operational strategies are not presented
in detail here as they have been previously described
within various chapter-specific problem scenarios (see
Chapter 4 and 5).
7.1.1 Reducing Water Age in the Distribution
System
There are several indicators of excessive water age in-
cluding: taste and odor complaints, discoloration, low
disinfectant residual concentration, elevated DBF level,
elevated bacterial count, and elevated nitrite or nitrogen
levels. "Old" water, especially in warm environments,
promotes the growth of microorganisms. Such micro-
organisms impart taste and odor issues or enhance nitri-
fication. Low-flow and dead-end areas within a distri-
bution system generally accumulate sediments; during
high-demand periods, these sediments may be stirred
up, resulting in discolored water.
From an operational perspective, tanks, valves, main
size and pumping rates have a direct impact on water
age. Finished water storage facilities may exhibit poor
mixing conditions because tank turnover is limited by
minimum fire-fighting capacity requirements. Tank
mixing can also be optimized either by cycling the tanks
periodically or installing mechanical devices, such as
7-1
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diffusers and nozzles to achieve higher velocities which
results in better mixing. Valve settings and pumping
rates determine water velocities and flow direction. Ve-
locity, in turn, impacts hydraulic pathway and retention
time. In some cases, operators can adjust system pres-
sures and position the valves in such a way as to induce
flow within the distribution system in a direction that
can minimize water age. The utility can also initiate
flushing programs to displace "old" water.
Hold it, young drop... this is a "dead-end" of
the distribution system; I have been here for
almost 8 days now — that is roughly 120 in
water droplet years, so I'm next to be used!
1 *
7.1.2 Adapting Operations to Meet System-
Specific Water Demands
Water demand is a driving force that affects all public
water system (PWS) operations. However, water de-
mands vary significantly and system operators must
have a good understanding of the amount of water be-
ing used, where it is being used, and how this usage
varies with time. For example, for most PWSs, the
ratio of daily average to daily maximum water demand
ranges from 1.2 to 3.0, and the ratio of the daily aver-
age to the peak hourly demand ratio may vary between
3.0 and 6.0. Seasonal variations may make these ra-
tios even more extreme. Fortunately, these demand
values are system-specific and can be quantified based
on experience. Demands are generally classified as
follows:
• Baseline demands - Corresponds to consumer
demands and unaccounted-for water associated
with daily average operating conditions.
• Seasonal Demand - Water use typically
varies over the course of the year with higher
demands occurring in the warmer months, due
to watering of lawns and recreational use (e.g.,
swimming pools).
• Fire demands - Typically, the most important
consideration for water system design.
• Diurnal (daily) demand variations -
Continuously varying demands which are
inherent in a PWS and typically increase during
the daytime hours.
As discussed previously, water distribution systems are
basically a networked conveyance mechanism in which
pumps move water through the system, control valves
allow water pressure and flow direction to be regulat-
ed, and storage facilities such as reservoirs and tanks
smooth out the effects of fluctuating demands (flow
equalization). Storage facilities also provide reserve
capacity for fire suppression and other emergencies.
Generally, pumping operations are optimized based on
cost of electricity and demand requirements. A utility
might consider operational changes based on overrid-
ing demand type in an attempt to minimize water age.
For example, a storage tank might normally be cycled
to only 50 percent of its capacity because of fire-fight-
ing needs. The utility could consider a change in strat-
egy in which it cycles the tank to utilize 65 percent of
its capacity and then make arrangements to meet the
additional 15 percent fire-fighting demand from alter-
nate sources such as other tanks, or even the purchase
of bulk water from a nearby utility.
7.1.3 Changing Disinfectants
If DBF formation or nitrification is a problem, the util-
ity could consider switching disinfectants on a periodic
or permanent basis. For example, a drinking water util-
ity that normally uses chloramines might temporarily
switch to free chlorine as a preventative nitrification
control measure. This switch to chlorination would be
accomplished system-wide by simply turning off the
ammonia feed facilities. However, to switch to free
chlorine in an isolated pressure zone or storage facil-
ity, enough chlorine must be added to exceed the break-
point and thereby achieve a free chlorine residual. If
strategies such as adjustments in chlorine to ammonia
ratio, increased turnover, or flushing have not solved
the problem, breakpoint chlorination is a commonly
utilized approach in storage tanks.
Utilities that normally chlorinate could consider a tem-
porary switch to chloramines. Recently, many utilities
have switched from chlorine to chloramines because
chloramines are more stable and associated DBF forma-
tion is lower. Whether disinfectant changes are long- or
short-term, utilities should be aware that these changes
may have implications for protecting public health, es-
pecially during an intrusion event. Chloramine is a less
powerful disinfectant than chlorine and may be inad-
equate for protection against microorganisms entering
the distribution system. Giardia cysts and enteric viruses
are known to be less easily inactivated by chloramines
than chlorine. However, any significant intrusion event
7-2
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will likely overwhelm either types of residual disin-
fectant. In addition, the utility should inform dialysis
centers that chloramines are being used so that they can
have their water treatment system enhanced to remove
chloramine. In addition to chloramines, other substanc-
es found in tap water can also interfere with dialysis.
For example, copper, fluoride, sulfate, nitrate, zinc and
aluminum also impact dialysis operations. Remember,
chlorine and chloramines are both toxic to fish. Gener-
ally, the operators of dialysis centers and fish breeders
know that disinfectants in tap water must be removed
before being used in their facilities. Therefore, utilities
changing disinfectant techniques must notify the public
of the change, contact kidney dialysis facilities, and fish
breeders. Disinfection changes may also cause a change
in pH levels in a distribution system resulting in tempo-
rarily elevated lead or copper levels.
7.1.4 Implementing Corrosion Control
Corrosion in drinking water systems can be control-
led by adjusting pH, alkalinity or by introducing
corrosion inhibitors. Increase in pH is one of the
effective methods for reducing lead and copper cor-
rosion. According to research studies, the optimal
pH for lead and copper control falls between 7.5 and
9.5 (the value depends upon the system and inhibitor
Changing Disinfectants (AwwaRF, 2006b)
In November 2003, the American Water Works Asso-
ciation Research Foundation (AwwaRF) sponsored a
project to evaluate the long-term effects of disinfection
changes on distribution system water quality. The re-
search team evaluated 19 utilities that had changed their
primary and/or secondary disinfectants. Specifically,
seven utilities changed from chlorine to chloramines,
six changed from chlorine to ozone, two changed from
chlorine to chlorine dioxide, two changed from chlo-
rine to ultraviolet disinfection, and two added booster
chlorination. The study concluded that, in general, the
results were positive. The following specific improve-
ments in the distribution system water quality were ob-
served as a result of changing disinfectants:
• Better microbial quality - lower coliform levels
and heterotrophic plate counts
• Lower DBFs - reduced levels of trihalomethanes
and haloacetic acids
• Reduced numbers of customer complaints
regarding red water or discolored water
• Reduced numbers of customer complaints
regarding tastes and odors
Despite the positive effects of changing disinfectants,
there was one participating utility that experienced an
increase in lead levels. Therefore, a utility should care-
fully evaluate the effect of making such changes.
Mommy, I cleaned the fish
bowl and filled it with tap
water. Nobody told me using
tap water with disinfectants
would kill my fish!
used). The higher pH level can also help reduce iron
concentrations. However, high pH can also result in
precipitation and scale on the pipe that significantly
impact the hydraulics of a distribution system.
Increasing alkalinity can also assist in corrosion con-
trol, and the optimal alkalinity for lead and copper
control lies between 25 and 75 mg/L as calcium car-
bonate. Higher alkalinity levels (>60 mg/L as calcium
carbonate) are favorable for controlling iron corrosion
and result in better buffer intensity, which in turn pro-
vides a stable pH.
Phosphate- and silicate-based corrosion inhibitors are
often used by water utilities. The most commonly
used inhibitors include orthophosphate, polyphos-
phate and sodium silicate, with or without zinc. Or-
thophosphate and zinc orthophosphate have reported-
ly been successful in reducing lead and copper levels;
polyphosphates are reported to prevent iron corrosion.
Sodium silicate has been shown to reduce lead and
copper levels. It should be noted that sodium silicate
is basic and always results in pH increases. Therefore,
it is difficult to determine if reductions in lead or cop-
per are due to the use of sodium silicate or higher pH
levels. Nevertheless, sodium silicate has been shown
to be an effective inhibitor. Utilities using inhibitors
should periodically monitor the inhibitor concentra-
tion within the distribution system.
Use of corrosion inhibitors and pH and/or alkalinity
adjustments to control lead, copper and/or iron levels
in drinking water should be employed with caution.
Pilot studies should be conducted to determine the ef-
fectiveness of a specific control method.
7-3
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7.1.5 Preventing Sedimentation and Scale
Formation
Under low velocity conditions, suspended solids may
deposit on the pipe surface. Scale and mineral deposits
may accumulate on pipe surfaces if the mineral content
in the water is high and the pH/alkalinity of the water
is supportive of scale formation (as addressed previ-
ously in Section 5.5). The accumulated sediment and
scale reduces the carrying capacity of the pipe and can
also create a more favorable environment for microbial
growth. Although sediments and scales themselves do
not necessarily pose a serious health risk, they can cause
water quality deterioration, taste and odor problems, or
discoloration. Furthermore, the deposited solids may
be re-suspended by sudden changes in flow. Significant
changes in flow (velocity and direction) can scour sedi-
ments, tubercles, and scale deposits from pipe walls and
result in degradation of water quality. It is possible that
these re-suspended particles may contain adsorbed con-
taminants such as arsenic and other metals that origi-
nated in the source water. Rapid changes in velocity
and flow direction can occur during main breaks, when
service reservoirs are being filled or drained, when
pumps are going on or offline, or during hydrant flush-
ing activities.
As metal pipes corrode, roughness tends to increase,
and cross-sectional area tends to decrease. Microbial
slimes can also result in a decrease in the hydraulic car-
rying capacity of water mains. This loss in carrying
capacity can result in a water system that cannot deliver
necessary fire flow. Increases in pumping rates may be
necessary to overcome the increasing friction losses and
local deficiencies in system pressure. These increased
pumping requirements can overload motors and result
in a significant increase in energy consumption, and in
operating and maintenance costs. Furthermore, the ad-
ditional pressure can over-pressurize weaker portions
of the distribution system, potentially increasing the
number of leaks and breaks. To avoid these negative
consequences, utilities should operate their distribu-
tion systems in a manner that minimizes sedimentation
and scaling by maintaining appropriate flow and water
chemistry (e.g., pH and alkalinity levels) throughout
the distribution system.
7.1.6 Implementing a Flushing Program
Flushing involves moving water through the distri-
bution system at a high rate, and then discharging it
through hydrants or blow-off ports. A flushing pro-
gram is designed with one or more specific objectives
such as replacing aged water, removing loose deposits
and sediments, and/or scouring internal pipe surfaces.
Utilities typically implement a flushing program in re-
sponse to consumer complaints. Terms such as "direc-
tional flushing" or "unidirectional flushing" are used to
describe the operation of valves during a flushing pro-
gram to maximize velocity and control flow direction,
starting with the largest mains and moving to the small-
est. Flushing is usually accomplished by opening one
or more hydrants in a planned pattern. A good rule of
thumb for flushing is to start at the location with "best"
water quality in the system and move outwards.
Residual disinfectant concentration in a distribution
system can be reestablished or stabilized by displacing
"old" water and replacing it with fresh water containing
a measurable residual disinfectant. Flushing can also
remedy or prevent nitrification in systems that utilize
chloramines for disinfection. Water that has elevated
levels of ammonia is replaced with water containing a
higher disinfectant residual. However, flushing is not
required by all state agencies. Of 34 states responding
to a survey by the Association of State Drinking Water
Administrators, only 11 require flushing/cleaning/pig-
ging, with 20 others encouraging the practice.
The new prototype pressurized flush system
SP17 flushes pipes up to 1,000 feet long.
We could save thousands of gallons of water
during routine flushing operations.
Flushing Velocities (AwwaRF, 2004b)
AwwaRF sponsored a project to evaluate a range of site-
specific flushing velocities. The study report indicates that
utilities which had previously never flushed their systems
benefited significantly from a high velocity (~5 feet per
second [fps]) unidirectional flushing program. Utilities
that had flushed within the last 4 to 6 years could receive
approximately the same benefit (and save water) by flush-
ing at a lower velocity (2 to 4 fps). The AwwaRF study
also determined that loose particles, including corrosion
particles, iron sludge, sand, and iron floe, are removed
from smooth or slightly tuberculated pipes at lower flush-
ing velocities (2 to 4 fps). In most cases, distribution sys-
tem lines should be flushed until the water is clear.
7-4
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Some systems may choose to clean pipelines that are
suspected of contributing to the decay of disinfectant
residuals in finished water. A variety of cleaning meth-
ods are available which include:
• swabbing
• scraping
• pigging
• chemical cleaning, and
• jet flowing
Swabbing, scraping, and pigging refer to methods that
remove scale and deposits from the inside of the pipes.
Chemical cleaning involves the injection of chemi-
cal cleaners. Jet flowing uses a high-pressure method
to wash the inside of the pipe. Each technique has its
benefits and disadvantages and should be tailored to a
specific site. In addition, depending upon the age of the
pipes, some utilities may want to consider pipe lining
or replacement.
7.1.7 Infrastructure Replacement and/or
Treatment Upgrades
Proper treatment methods, tailored to the utility's source
water characteristics, can also solve potential problems
in the distribution system. If optimum treatment is em-
ployed, it can greatly improve the biochemical stability
of the finished water. Biochemical stability is closely
related to the amount and kind of organic matter present
in the water. Problems associated with the formation of
DBFs increase with the amount of organic matter left
in the water. Treatment to remove organics, inorganics,
and turbidity will also curb chlorine decay. The most ef-
fective treatment methods for maintaining biochemical
stability include:
• enhanced coagulation
• biological filtration
• ultrafiltration/nanofiltration
• granular activated carbon treatment
Water main breaks commonly occur in older or in poor-
ly designed systems. Main breaks are disruptive and
expensive to fix. Furthermore, for rusting and aging
pipes and finished water storage facilities, replacement
may be the only viable option. Therefore, utility opera-
tors and managers must develop a long-term strategy
for timely maintenance and replacement. However,
these types of infrastructure replacement and treatment
upgrade projects require a significant amount of finan-
cial resources and time. Possible financial strategies
designed to accomplish these goals are discussed in the
next section of this document.
7.2 Financial Strategies
Small- and medium-sized systems face unique finan-
cial challenges because they cannot take advantage of
the economies of scale associated with larger drinking
water systems. For example, in a small system, a piece
of equipment costing $1,000 may be spread over a cus-
tomer base of 100 to 1,000 customers. In a larger sys-
tem, the cost of this same piece of equipment may be
spread over 10,000 to 100,000 customers. Simply put,
any capital investment for smaller systems is generally
higher on a per customer basis or per capita basis than
in a larger system.
Financial Strategy (EPA - EFAB, 2005)
In rural and developing areas, back-end loading could be
used in financing water projects where hook-up fees and
user charges only begin to flow after a project is complet-
ed. Infrastructure projects in such areas are often judged
unaffordable because the debt associated with the capital
investment needed for new facilities cannot be immediate-
ly serviced by user charges. In fact, new hook-ups/connec-
tions often occur slowly. As connections are made and the
service area rate base increases, user charge revenues grow
to support debt repayment. Back-end loading can enable
projects to proceed because it solves immediate environ-
mental needs by deferring financial issues of "affordabil-
ity" of debt repayment to a later time.
This approach has proven to be valuable for San Benito,
Texas, along the US-Mexican border. The North American
Development Bank guaranteed a bond issue for San Benito
with a highly skewed amortization schedule that allowed
for the build-out of the system and the build-up of oper-
ating revenues to sustain long-term debt service. In this
case, the new water system would enjoy the very low inter-
est rates provided by the bank guaranty until such time as
the system revenues could provide substantial debt service
coverage.
In cases where the price of water cannot be simply
passed on to the customer, small- and medium-sized
utilities can apply for grants and low-interest loans. A
grant is a form of financial assistance that is given to a
utility which does not have to be repaid. Loans must be
repaid along with the appropriate interest. These terms
are defined more carefully in the following paragraphs:
• Grant Programs: Grants are generally awarded
to states, local governments or other nonprofit
organizations. The primary advantage of grants
is that the recipients do not have to use their
own resources to pay the costs that the grant
covers. Applying for grants, however, can
require a significant commitment of time by
utility personnel. In addition, the availability
7-5
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Sustainable Pricing (EPA, 2005b)
Individual customers are the most important source of rev-
enue for a drinking water system. The income provided
by customers is critical to ensuring that systems are op-
erated properly and efficiently both in the present and in
the future. Charging customers the actual cost of service
ensures that water systems guarantee themselves a stable
source of funds that is sufficient to cover the cost of opera-
tion (including treatment, storage, and distribution costs).
This policy also allows for the acquisition of funds for in-
frastructure investments. Asking customers to pay for a
commodity or service sends a signal about the value of
the product or service they are purchasing. Fees and other
charges that reflect the full cost of water service help cus-
tomers recognize the value of water service. Customers
also become more aware of how much water they use and
how they use it. To support this approach, EPA has devel-
oped a sustainable infrastructure initiative which is based
on the following four pillars:
• Better Management - Similar to asset management,
environmental management systems, consolidation,
and public-private partnerships can offer significant
savings for small water utilities.
• Full-Cost Pricing - A key consideration in
constructing, operating, and maintaining
infrastructure is ensuring that there are sufficient
revenues in place to support the costs of doing
business. Sensible pricing can also have the added
benefit of encouraging efficient water use.
• Efficient Water Use - One way to reduce the
need for costly infrastructure is efficient use of
water. There are many options for enhancing
water efficiency including metering, water reuse,
water-saving appliances, landscaping, and public
education.
• Watershed Approaches to Protection - In
addressing infrastructure needs for the purposes
of water supply and water quality, it is important
to look at water resources in a coordinated way.
Directing resources towards high priorities, such as
permitting on a watershed basis, and water quality
trading are all means of ensuring that investments
achieve the greatest benefit.
and timing of the grant award may not match
the utility's needs. Most grant programs have
limited funds, and usually there is significant
competition for this type of funding. Grants also
have project eligibility requirements, and some
programs may specify that the grantee contribute
a share of the total project funds.
x x.
I have solved our financial crisis,N
here is a "cash cow" and a
"goose that lays the golden egg!"
Loan Programs: Loans are available from
governments, banks or other financial
institutions and the application process can be
relatively quick. Commercial interest rates are
generally higher with less favorable pay back
rules than government loans. State programs
generally have better rates and terms for those
systems that do not qualify for conventional
types of financing. The terms of loans vary
significantly and the utility should carefully
evaluate these terms before a loan is secured.
Some of these financial options (both grants and loans)
are briefly summarized in the following sections.
7,2,1
Congress established the Drinking Water State Revolv-
ing Fund (DWSRF) as part of the 1996 SDWA Amend-
ments to provide states with a financing mechanism to
ensure safe drinking water for the public. EPA, through
the various state agencies, administers the DWSRF in
order to provide financial resources to upgrade and re-
place drinking water infrastructure. PWSs can receive
loans with very low or zero percent interest rates with
repayment periods of up to 20 years. However, in some
cases, drinking water utilities in disadvantaged commu-
nities may find even low-interest loans unaffordable. In
these types of cases, states can provide DWSRF funds
at a negative interest loan rate, or under a principal for-
giveness loan with an extended repayment period of up
to 30 years. Each state has specific eligibility criteria to
determine funding priorities. Funding requests under
the DWSRF program are allocated based on the follow-
ing order of priority:
• Requests that address the most serious health
risks to consumers
• Requests necessary to comply with SDWA
standards
7-6
-------
Creative Funding (Hudson, 2007)
Recent SDWA revisions to reduce the Arsenic Maximum
Contaminant Level (MCL) to 0.010 mg/L affected approx-
imately 80 small Indiana PWSs. As a result, many small
utilities needed assistance to comply with the new stand-
ard. A majority of these affected systems were rural (serv-
ing fewer than 500 people) and the Indiana DWSRF Loan
Program estimated that the average arsenic remediation
project would cost $44,000. Unfortunately, this amount
was too small to justify a DWSRF loan. If a utility cannot
justify a project under the DWSPJ7, these funds cannot be
used for small systems. To solve this problem, the Indiana
DWSPJ7 created the Arsenic Remediation Grant Program
in May 2006. By combining DWSRF set-aside funds for
planning and design costs and state monies for construc-
tion costs, the DWSRF Loan Program was able to offer
grants up to $100,000 to small PWSs to cover the entire
cost of arsenic remediation projects.
• Requests that assist water systems which are
most in need, on a per-household basis (as
determined by the state affordability criteria)
Similar funding assistance is also available to Indian
tribes in the U.S.
7.2.2 Community Development Block Grants
The U.S. Department of Housing and Urban Develop-
ment administers a Community Development Block
Grant (CDBG) program through the individual states.
The program provides small communities with re-
sources to address a wide range of needs. The program
gives each state the opportunity to administer CDBG
funds for "non-entitlement areas." Generally speaking,
I received your application for loan, I
am afraid we need more information
than what you currently have provided
for us to process this application.
"non-entitlement areas" are cities with populations of
less than 50,000 and counties with populations of less
than 200,000. The primary objective of this CDBG
program is to develop viable communities by providing
decent housing and a suitable living environment. This
general objective is achieved by prioritizing activities
which benefit low- and moderate-income families or
aid in the prevention or elimination of slums or blight.
Under unique circumstances, states may also use their
funds to meet urgent community development needs.
A need is considered urgent if it poses a serious and
immediate threat to the health or welfare of the com-
munity and has arisen in the past 18 months. Local
governments have the responsibility to consider local
needs, prepare grant applications for submission to the
state, and carry out the funded community development
activities. The list of eligible activities under this pro-
gram includes construction or reconstruction of water
and sewer facilities.
7.2.3 Rural Utilities System
One of the six basic mission areas of the U.S. Depart-
ment of Agriculture (USDA) is the Rural Utilities Sys-
tem (RUS). Under the RUS umbrella, USDA provides
a variety of water loan and grant programs. Along with
EPA and other federal agencies, USDA supports organ-
izations such as the National Rural Water Association
(NRWA) and the Rural Community Assistance Partner-
ship. The USDA's RUS issues contracts to NRWA for
providing rural water circuit rider technical assistance.
In addition to supporting these national organizations,
USDA provides emergency community water assist-
ance grants to rural communities that have experienced
a significant decline in the quantity or quality of drink-
ing water. Grants are provided to rural areas and cities
or towns with low income and a population of fewer
than 10,000. Grants can cover up to 100 percent of
project costs. The maximum grant is $500,000 when
a significant decline in quantity or quality of water oc-
curred within two years, or up to $150,000, to make
emergency repairs and replace facilities in existing sys-
tems.
7.2.4 Economic Development Administration
The U.S. Department of Commerce provides grants
through the Economic Development Administration's
(EDA) Public Works and Development Program. Ap-
plications must be submitted to the state economic de-
velopment agency; states are authorized to administer
the funds. A drinking water project must be located in
a community or county determined to be economically
distressed, and the project must be directly related to
future economic development. Some restrictions apply
when grants are provided in conjunction with other fi-
nancial assistance. The combined funding is generally
limited to 80 percent of the total project cost.
7-7
-------
7.2.5 Other Entities and Private Foundations
Appalachian Regional Commission (ARC) ARC sup-
ports qualifying applicants in the designated Appalachi-
an Regions of 13 states. The ARC's local development
districts provide assistance in preparing an applicant's
proposal. Priority funding is determined each year by
the state governors, Appalachian district personnel,
and ARC members. All projects that qualify for grant
funding must be directly related to economic develop-
ment, housing development, or downtown revitalization
and improvement. Drinking water projects are among
the types of projects eligible for assistance. It should
be noted that ARC grants are limited to 50 percent of
project costs and require the recipients to supply the
other 50 percent. An exception is made for economi-
cally distressed counties, which can receive 80 percent
and must supply only 20 percent. To raise the remain-
ing 20 percent of funds, owners of small systems in dis-
tressed counties should innovatively and aggressively
seek other sources of funding.
Indian Health Service (IHS) IHS is a part of the De-
partment of Health and Human Services, and provides
grants for projects undertaken by American Indians and
Alaska Natives. In 1959, Congress passed the Indian
Sanitation Facilities Act to provide improved health
conditions by improving sanitation, sewer, solid waste,
and drinking water facilities. IHS grants support public
health rather than economic development or environ-
mental preservation and do not include funding for op-
eration and maintenance. No matching funds are nec-
essary, and IHS grants can be consolidated with those
from other agencies.
Small Community Water Infrastructure Exchange
(SCWIE) SCWIE is a network of water funding offi-
cials. Under the auspices of the Council of Infrastruc-
ture Financing Authorities, a group of public and non-
profit environmental funding and technical assistance
officials combined their efforts to create SCWIE.
Private Foundations Private foundations are another
possible source of funding for small- and medium-sized
PWSs. These are often overlooked by small PWS man-
agers. Information about smaller foundations can be ob-
tained from a local Internal Revenue Service (IRS) of-
fice. The IRS annually collects Form 990-PF (Return on
Private Foundations) from foundations of all sizes, and
compiles information about the foundations' interests,
restrictions, application procedures, and deadlines.
7.3 Management Strategies
If the operational and financial strategies currently avail-
able to a utility do not have long-term sustainability, a
utility should consider management and institutional
changes. Some options to consider are merging with a
Additional Information
More information on the DWSRF is available at: http://
www.epa.gov/safewater/dwsrf/index.html
More information on state CDBGs is available at: http://
www.hud.gov/local/index.cfm
More information on RUS assistance is available at: http://
www.usda.gov/rus/water/programs.htm
More information on EDA assistance is available at:
http ://www. eda. gov/InvestmentsGrants/Investments. xml
More information on ARC assistance is available at: http://
www.arc.gov/index.do ?nodeld=101
More information on IHS assistance is available at: http://
www.ihs.gov/
More information on SCWIE assistance is available at:
http ://www. scwie.org/ContactSearch. asp
A commercial source of private foundation listing online
is: http://foundationcenter.org/
larger utility, or changing ownership and/or management
of the water utility (from private to public or vice versa).
7.3.1 Small Systems Working Together
In general, state and federal regulatory agencies encour-
age small water systems to work together if it makes
financial sense. Working together generally results in
a regulatory agency having more effective control over
water quality and regional development. Furthermore,
the economies of scale associated with working together
tend to ensure the long-term financial viability of a sys-
tem. One challenge in working together is the difficulty
in servicing a geographically diverse distribution system
from a central location. In such cases, remote monitor-
ing and reporting is recommended to ensure prompt local
service even if bulk water is purchased from a larger util-
ity. Each manager of a small- and medium-sized utility
should consider the pros and cons of working together,
for developing regional water usage rates and/or central-
ized purchasing. In addition to concerns of financial via-
bility, managers should consider the geographical spread
and type of source water of the combined systems. The
number one concern of the partners is the potential im-
pact of the combination on the quality of the water served
to the consumer. Again, remote monitoring and reporting
is recommended to ensure the quality of the water in the
combined distribution system. EPA's Community Water
System Survey, conducted in the year 2000, indicated
that there was a continued decline in the number of sys-
tems serving fewer than 3,300 people, while the number
serving more than 3,300 people grew by 20 percent.
7-8
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Utility Merger (KEPPC, 2006)
The Northern Kentucky Water District (NKWD) was
formed in 1997 from the merger of water districts in
Kenton and Campbell counties. In recent years, it has also
acquired the Newport and Taylor Mill water utilities. By
2006, NKWD had 78,000 retail customers in Campbell
and Kenton counties and provided wholesale water service
to the Pendleton County, Bullock Pen water districts, and
to the city of Walton.
In 2003, the Kentucky Public Service Commission granted
NKWD a rate adjustment that equalized the water rates in
the former Kenton and Campbell county districts. In 2004,
PSC granted rate adjustments to equalize water rates in
Newport with the rest of the district. In 2006, the PSC
granted a rate adjustment to equalize the rates for custom-
ers in Taylor Mill. The 2006 rate increase was estimated to
raise the quarterly bill for the average NKWD residential
customer consuming 18,000 gallons/quarter, from $78.65
to $83.70 (an increase of $5.02, or 6.4 percent). It is es-
timated that the 2006 rate increase will increase NKWD's
annual revenues from water sales by 6.8 percent, to $36.3
million.
7.3.2 Change in Ownership and/or
Management
In general, there are four options to consider when
changing ownership and/or management of water utili-
ties including:
• Efficiency Improvement Program: Implementing
operational and management changes to improve
efficiency.
• Municipalization: The assets, operations
and ownership of private water systems are
transferred to a public entity.
• Privatization: The assets, operations, and
ownership are transferred to a private entity
• Public-Private Partnership: In general, the
public retains the ownership and control
of the system, but privatizes operation and
maintenance.
Private utilities are generally perceived as being profit-
oriented and hence more efficient than public or mu-
nicipal utilities. Because they are for-profit entities
there is a perception that they may fail to invest in long-
term growth which may lead to poor system mainte-
nance and upgrade practices. Municipalities, because
they are non-profit entities and represent the people, are
perceived as likely to invest in the system and have a
plan for long-term growth. On the other hand, because
municipal systems are non-profit entities, there is con-
cern that there are inefficiencies built into the system
which may increase costs to the consumer. The general
perception about public-private partnerships is that they
represent the "best" of both municipal and private sys-
tems. These perceptions are generally anecdotal and
based on individual cases where information is avail-
able. There are no long-term data or analyses that con-
clusively support any of these general perceptions.
7.4 SmallWater USA -
Cell Tower Installation
Problem #1 Water Storage Tank Antenna
Scenario
Several telephone companies approached SmallWater,
USA officials and made financial offers to the town if
they were permitted to install cell phone antennas on the
top of the elevated tank in the northern part of the water
system. It sounded like a good source of needed funds
but the official wanted to make sure that there would
not be any problems. He talked to an engineering firm
that specialized in tank construction and maintenance
procedures. Following is a summary of the information
that he received from the engineer.
Issues to Consider
The rapid expansion of wireless communication serv-
ices throughout the United States has resulted in the
construction of many cellular antenna towers. To save
on the cost of erecting these towers, communications
companies look for existing structures that are suitable
for locating their antennas. Also, in some areas, zoning
restrictions have severely limited the ability of cellular
companies to locate their towers. For these reasons, wa-
ter storage tanks are prime sites for antennas. Existing
tanks are often the highest structure in a community and
usually have pre-existing Federal Aviation Authority
and zoning approvals.
Leasing revenue from antenna installations has been
a welcome development for hard-pressed water utility
budgets. Leasing rates range from a few hundred dollars
to over $ 1,000 per month depending on the location and
suitability of the storage tank. Since tanks usually have
room for multiple antenna installations, leasing revenue
can be doubled or tripled by adding cellular carriers.
In some cases, it is possible to pay for all future tank
maintenance and painting with these revenues. While
the income provided to water utilities from placement
of antennas is certainly worth considering, care must be
taken to avoid the adverse effects of these installations.
Guidance (Source: Cabin, I.M., 2007)
Many problems have occurred from antenna installa-
tions that were improperly designed and constructed.
Many installers have viewed the tank as simply a plat-
7-9
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form for their antennas, without understanding the im-
portant function that the tank serves and the purpose of
tank appurtenances. Problem areas include:
1. Structural damage
2. Coating and corrosion damage
3. Occupational Safety and Health Administration
(OSHA) violations
4. Restriction of access to ladders, manholes and
hatches with resultant confined space and safety
concerns
5. Contamination of water supply through
improperly sealed penetrations
6. Potential for interference with future painting
7. Poor aesthetic appearance
A few basic steps should be followed by storage tank
owners to avoid these problems. First, the cellular
company should be required to provide a drawing of
its complete installation including site utilities, ground
structures, equipment panels, cable routing, and anten-
na structures. Secondly, a qualified engineering firm ex-
perienced with both storage tanks and antenna installa-
tions should be retained to inspect the tank, and review
the drawings, welding procedures and coating repair
specifications. Structural analysis should be performed
to ensure that the tank can safely support the antennas.
Also, care must be taken that the new installation does
not interfere with existing cellular or utility antennas.
Only after all necessary drawing and specification revi-
sions are completed should the installer be allowed to
begin. Keys to the tank or tank site should be returned
when the project is finished. It is not recommended that
antenna companies be allowed to access the tank to
service their equipment without utility personnel pro-
viding authorization and access.
The final step is inspection of the completed installa-
tion. The same firm that reviewed the drawings should
inspect the entire installation including the interior paint
repairs. In some cases, paint repairs can only be com-
pleted during low demand times of the year. In other
cases, the repairs must wait for warmer weather. This
will require coordination with the cellular company to
ensure that the interior paint is properly repaired.
When negotiating a lease with the cellular company, the
design review and inspection services should be includ-
ed in the contract at the company's expense. Most cel-
lular companies are very cooperative in including these
services in the lease. It is a minimal expense and also
provides them with the assurance that their equipment
will be properly installed. A number of other legal and
financial considerations should be carefully evaluated
including length of contract, cost of living adjustments,
access, liability, exclusivity clauses, and future painting
expenses. Since many utilities already have antenna in-
stallations, it would be worthwhile to inquire about their
leases and hopefully benefit from their experience.
Water storage tank antennas are certainly worth investi-
gating. By following these steps, one should be able to
obtain the benefit of this new source of revenue while
avoiding the problems that can be caused by deficient an-
tenna design and installation. Figures 7.1 and 7.2 show
pictures of bad and good cell-tower designs, respective-
ly. The crowded design shown in Figure 7.1 could lead
to operational, maintenance and structural problems.
Problem #2 Operational Changes to Reduce
Water Quality Degradation in Storage
Tank
During the past summer, SmallWater, USA officials
received frequent taste and odor complaints from resi-
dents in the trailer park located near the old standpipe.
Discussions with the town consulting engineer led to
the likely conclusion that these taste and odor problems
were probably due to water quality degradation in the
standpipe. Some options for dealing with this problem
were discussed and will be tried out next summer.
Issues to Consider
Because water sometimes spends a large amount of
time in a storage tank, it is susceptible to degradation
of water quality. Some specific forms of water quality
degradation can include: loss of disinfectant residual,
regrowth of bacteria, formation of DBFs, nitrification
and sedimentation. In all of these phenomena, the deg-
radation is associated with two physical processes in a
tank: aging of water and mixing within the tank.
Guidance
Since it is not uncommon for water to spend several
days or sometimes even weeks in a storage facility,
tanks are prime candidates for potential water quality
problems. There is no fixed standard for allowable wa-
ter age, but some experts suggest that 3 to 5 days is a
reasonable maximum residence time within a tank. Al-
lowable water age varies based on the chemical content
of the water and the type of disinfectant that is utilized.
An approximate value for the average residence time
can be easily calculated based on the turnover within
the tank using the following equation:
Average Residence time (days) =
Average water volume in tank (gallons) -^
Average daily inflow (gallons per day)
7-10
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Figure 7.1 Crowded Cell Tower Installation
encourage good mixing - namely, the water that is en-
tering the tank during the fill cycle should mix well with
the water that is already in the tank. A poorly mixed
tank can result in zones or pockets of older, deteriorated
water. In some cases, the tank may become stratified
(poor vertical mixing), primarily when the inflow water
is colder than the water in the tank. Tall tanks, such as
the SmallWater, USA standpipe, are especially suscep-
tible to mixing and stratification problems. Good mix-
ing will generally occur if 1) the inflow "jet" enters at
a relatively high velocity (at least 1 foot per second), 2)
the inlet is oriented to encourage mixing with the water
in the tank, 3) the water level in the tank is allowed to
fluctuate over a range of several feet over the course of
each day, and 4) the water temperature of the inflow is
approximately the same as the temperature of the water
in the tank. The average inflow velocity for the stand-
pipe was calculated by dividing the average inflow rate
(100 gpm) by the cross-sectional area of the 16-inch
inlet. This showed a typical inflow velocity of only 0.16
feet per second (fps) - far less than the recommended
velocity of 1 fps.
Based on this analysis, the engineer suggested that no
modification in operations was needed but that some
minor modifications in the standpipe inlet configura-
tion should be made. The primary recommendation was
that a "reducer" be placed on the inlet-outlet line where
it entered the standpipe so that the effective diameter
would be reduced from 16 to 6 inches. Other situations
may require the addition of more complex inlet-outlet
designs or the use of mechanical mixers to encourage
circulation in the tank. There are a variety of modeling
and monitoring procedures that can be used to assess
whether there are mixing problems in a tank and to test
alternative schemes for improving mixing in a tank.
Figure 7.2 A Well-Designed and Constructed Cell
Tower Installation
The standpipe typically contains about 150,000 gallons
of water. Based on Supervisory Control and Data Ac-
quisition (SCADA) records, the daily inflow is about
75,000 gallons per day. Using this equation, the aver-
age residence time in the standpipe was calculated as
150,000 - 75,000 = 2 days. This was considered to be
reasonable.
Mixing is another issue in tank operation and design.
Distribution system storage tanks should be designed to
7-11
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Crossword
Operational, Financial, and Management
Strategies to Address Distribution
System Water Quality Issues
ACROSS
4 Type of disinfectant that can be more toxic to
fish
5 Financial assistance that must be repaid with
the applicable interest
7 Financial assistance that does not have to be
paid back
8 Commonly used base-chemical for corrosion
inhibition
DOWN
1 Acronym for EPA-established financing
mechanism
2 Term for a publicly-owned non-profit water
utility
3 Common procedure for removing loose
sediments and deposits in pipes
6 Reduce "this" in distribution system to
control DBP formation
(8 IUEJO d 'sBy (9 'sueon (g 'suj
(t? '
fe 'A)!|edp!un|/\| fe 'dySAAd U
suounios P.IOMSSOJO
7-12
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Chapter 8
Bibliography
The references included in this bibliography contain
additional detailed information for readers who wish to
pursue, in greater detail, the specific topics discussed
in this guide. Many of these references (especially the
EPA references) are freely available on the Internet.
The references are listed alphabetically, based on
the last name of the first author(s). In cases where
there are two or more works by the same author (e.g.,
AWWA, AwwaRF, and EPA), the entries are listed by
the year, with the most recent document listed first.
The reverse chronological order makes it easy for the
reader to look up the most recent publication first.
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