United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/024 June 1987
SEPA Project Summary
Water Main Evaluation for
Rehabilitation/Replacement
Robert M. Clark, Martin Allen, and D. Kelly O'Day
This report describes a series of
studies that identified factors
contributing to water main failures
and developed decision strategies
on main rehabilitation, replacement,
and preventive maintenance. The
objective of this report is to provide
the water utility industry with
practical methods to assess long-
term changes in the condition of
distribution systems and to assist in
rehabilitation/replacement planning
decisions.
Written as a guidance manual, the
report discusses the following
topics:
1. A comparison of utility repair
recordkeeping practices with
recommended procedures for
analysis of leak and break trends.
2. Description of structural
properties of water mains and the
role external environmental
conditions and corrosion
processes play in water main
deterioration.
3. Description of techniques to
evaluate water main conditions
with a recommended physical
testing program that determines
internal and external corrosion
rates.
4. Presentation of economic models
related to leakage control, main
rehabilitation, and main
replacement
5. Description of suggested water
distribution system inventory
procedures including geographic
referencing systems, computer
mapping, and hardware/software
requirements.
6. Discussion of approaches to
monitor distribution system
conditions, to determine repair
rates and patterns, and to
coordinate the cost of monitoring
with long-term benefits.
7. Presentation of independent
planning steps that can be
adopted by all utilities depending
on system needs, budget, and
personnel. The steps include
standardized assessment
programs, economic models for
decision making, and
computerized rehabilitation/re-
placement
This Project Summary was
developed by EPA's Water Engineering
Research Laboratory, Cincinnati, OH,
to announce key findings of the
research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
In recent years, the condition of water
distribution systems nationwide has
attracted a great deal of media, political,
and research attention. A number of
divergent views have resulted regarding
the magnitude of water distribution
problems and the level of capital
expenditures needed to address these
problems.
These conflicting viewpoints arise
from the lack of extensive research
undertaken in the past into the
effectiveness of water distribution system
planning and maintenance activities.
Standard analytical procedures have not
been developed by the water utility
industry to assess distribution system
conditions. For this reason, no
benchmark or set of procedures has
been established to compare distribution
system conditions.
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Recently, several institutions or
organizations have surveyed water
utilities nationwide to determine the type
and magnitude of existing infrastructure
problems. The surveys, conducted by
the American Water Works Association
(AWWA) and CH2M Hill Consultants,
indicate that a significant variation exists
within utility infrastructure improvement
planning systems. Different sizes of
systems tend to emphasize different
types of program. The larger systems
tend to be more sophisticated systems.
Availability of useful information is
indicative also of differing levels of
planning and programming.
Research efforts in recent years have
focused primarily on methods to assess
current conditions of water distribution
systems, including realistic evaluations of
the structural, hydraulic, and water
quality problems encountered. These
important research needs have not been
addressed until recently by the industry.
Results from the surveys as well as
other sources of information have
indicated a number of different types of
research needs.
Research Needs
The development of a standard
condition assessment terminology that
can be utilized by all water utilities is a
major research priority. The
establishment of standardized
nomenclature would enable water utilities
to compare capital programming
approaches and results. This standard
should include an accepted set of terms
and definitions as well as a consistent
method to assess current and future
performance levels of distribution
systems. Variations in distribution
system problems by region of the
country should not hinder the
development of such a standard.
Although the type of distribution system
affected ranges from older, established
systems in the midwest and northern
regions to younger, growing systems in
the southern and western regions, water
quality, hydraulic, and structural
deterioration problems are not limited to
any one region.
Research must also address the need
for an increased understanding of the
structural deterioration process. There is
a particularly critical need for more
research into the causes of internal
corrosion. Internal corrosion of water
mains can lead to several problems,
including the loss of hydraulic capacity,
water discoloration, and a decrease in
the effective main wall thickness. The
impact of internal corrosion on water
quality has taken a back seat in the
research community compared with
other drinking water quality research
issues.
Although most water quality research
has focused on the use of various
disinfection treatment processes to
control and mitigate system-wide
bacterial growth, the effect of a localized
deterioration of the distribution grid on
water quality must also be recognized. A
research need is to draw correlations
between internal corrosion levels and
water quality deterioration. Future
research must seek new techniques and
materials for the replacement,
rehabilitation, and repair of water mams.
More economical approaches should be
found to counter inflationary trends and
to assist utilities in many sections of the
country to increase their maintenance
efforts.
Research is needed to develop an
objective framework for water utility
managers to better compare and
understand various strategies available to
them for distribution system
maintenance. This report primarily
addresses this critical research need.
In addition to defining the above
mentioned research needs, the study
reported in this project summary was
conducted with five major objectives:
analyze leak and break patterns from a
selected set of utilities; examine the
major causes of water main deterioration;
survey analytical techniques used by
utilities to evaluate water mam
conditions; discuss the economies of
leakage control, main rehabilitation, and
replacement; develop a series of
recommendations focusing on the types
of information necessary in building a
water distribution system inventory;
provide a series of recommendations for
monitoring distribution system
conditions; and, present a series of
planning steps for rehabilitation that may
be adopted by all size utilities depending
on their system needs, budget, and
personnel.
Analysis of Utility Leak and
Break Patterns
The study team analyzed records on
broken water mains for six utilities:
Denver Water Department, East Bay
Municipal District (California), Kenosha
Water Utility (Wisconsin), Louisville
Water Company (Kentucky), New York
City Water Supply Bureau, and
Philadelphia Water Department. The
utilities varied in size of service area,
geological conditions, and geographic
location. Comparative information on
mam break patterns by age, diamete
construction period, and material in th
six utilities studied is presented in thi
section. Each utility's recordkeepm
system was examined. A recommende
procedure is included for the analysis c
leak and break repair data. Eight exhibit:
including a sample repair form and
series of data plots, are presented.
It was concluded from this study th<
water main leak and break patterns var
widely among utilities and within a give
utility. Variations in pipe materials, joir
materials, design practices, constructio
practices, soil conditions, corrosio
conditions, external loadings, an
weather conditions all contribute t
variations in leak and break experience;
Even with these variations across utilities
there are similar patterns which must b
recognized.
Water Main Deterioration
The causes of water mai
deterioration are the focal point of thi
section Structural properties of wate
mains are discussed, including
technical subsection describing thi
interplay of external loads, beddmi
conditions, and corrosion on thi
deterioration process The genera
principles of corrosion are described witl
respect to both internal and external pipi
conditions. A series of photographs c
pipe samples that underwent variou
types of corrosion is presented. Thesi
samples were obtained under thi
Philadelphia Water Department's materie
testing program. A discussion of thi
relationship between the age of wate
mams and their rate of deteriorate
encompasses changes in castmi
techniques, construction practices, am
materials over time.
It was concluded that a water main wi
fail when the forces exerted on the man
exceed the main's effective strength
This strength decreases from its origine
design strength as a result of internal an<
external corrosion, reducing the mam'
ability to withstand various appliei
forces. Many environmental factor
should be investigated for their roles n
this process.
Assessing Water Main Conditions
A survey of analytical techniques use<
by utilities to evaluate water mail
conditions is provided in this section
Descriptive analysis techniques evaluati
the frequency and patterns of mail
breaks for several utilities, including Eas
Bay Municipal Utility District (California]
Philadelphia Water Department, am
several utilities in Great Britain am
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Canada. Three predictive model case
studies from Des Moines, the USEPA,
and the Massachusetts Institute of
Technology are reviewed. Physical
analysis to estimate water main
conditions is outlined. Analyses from
Vancouver, Philadelphia, and the Army
Corps of Engineers Construction
Engineering Research Laboratory are
presented.
The predictive model approach offers
utilities an evaluation method for
assessing the interplay of environmental
and structural factors which lead to water
main deterioration and failure. Utilities
are cautioned that this approach will
require continual enhancement to refine
predictive capabilities as each utility
collects information on the interplay of
loads, environmental factors, and failures
of its main.
Economics of Distribution System
Rehabilitation
The economics of leakage control,
main rehabilitation, and replacement are
examined in this section. Economic
trade-offs of alternative maintenance
and capital programs are shown in
models and discussed through sensitivity
analyses. Simple work sheets are
presented so that managers can examine
and develop unit costs for their individual
utilities.
Water Distribution System
Inventory
This section presents recommen-
dations focusing on information
necessary in building a water distribution
system inventory. Geographic reference
system requirements, inventory
procedures, computer mapping
capabilities, and hardware/software
requirements are discussed. The
recommended inventory system includes
a combination of coordinate, link node,
and street address reference capabilities.
Monitoring Distribution System
Conditions
By monitoring its distribution system,
a water utility can obtain the important
information needed to establish a cost-
effective rehabilitation/replacement
planning system. A series of
recommendations that water utility
managers can use to monitor distribution
system conditions is presented. Trend
analyses of both leak and break rates as
well as hydrant, valve, and service
repairs are suggested as means to
assess system conditions. The need for
annual assessment of distribution
systems is examined. These annual
assessments include analysis of current
and anticipated future trends and
identification of those portions of the
system experiencing higher or lower
failure rates.
Developing a Rehabilitation
Planning System
Several water distribution planning
system approaches developed by water
utilities across the country are presented
in this section. The series of planning
steps presented may be adopted by all
utilities depending on their system
needs, budget, and personnel. These
planning steps include a- standardized
main repair recordkeeping system for the
annual assessment of distribution
network conditions, the analysis of repair
patterns by geographic area, the
establishment of repair pin maps, a main
testing program, the development of
economic models for maintenance
decision making, the preparation of a
computerized inventory of the water
distribution system, and the development
of both water main condition predictive
models and computer-based
rehabilitation/-replacement screening
and selection systems. Reactive and
predictive planning system approaches
by four utilities are illustrated in this
section as case studies. Various
combinations of the planning system
components described above are used
by each utility.
Summary and Conclusions
Designing and implementing a water
main decision planning system is an
on-going evolutionary process. It begins
with an assessment of the distribution
system condition. From this assessment
a reactive planning system may be
designed and implemented. This, in turn,
can lead to the development of a
predictive planning system.
Regardless of the level of
sophistication and computerization
involved, each utility should collect
information concerning system
conditions, implement preventive
maintenance measures, identify
chronically failing mains, and prioritize
these mains for repair or replacement.
The utility policy and replacement criteria
may change from year to year, but the
basic process remains the same. Case
studies of live utility planning systems
were presented to illustrate various
approaches to these primary planning
tasks.
If a utility decides that a predictive
planning method is desirable, the first
step is the development of a
comprehensive water main inventory and
maintenance history database. This
database should include the location of
inventory, maintenance history, and
environmental description for each
record. A variety of options for
inventorying water mains are available
and span a wide cost range.
The second step in the
implementation of a predictive planning
approach is the development of a
physical condition assessment model.
This model enables the utility to
approximate the deterioration process
based on engineering principles, and
estimate the relative break and leak
frequency for the main. This ability to
better estimate the future condition of the
main makes preventive maintenance and
replacement activities more cost-
effective due to more precise
prioritization and scheduling capabilities.
Additional criteria assessment models
such as hazard assessment or economic
evaluation models may also be
developed. These criteria assessment
models may be coupled with a physical
condition assessment model to select
and prioritize mains for replacement or
other maintenance activities. Field data
collection and testing should take place
to verify critical model assumptions.
Increased planning system
sophistication will increase
implementation cost, particularly the cost
of building and updating a water main
information database. These costs must
be weighed against the benefits of more
effective decision-making regarding
repair, replacement, abandonment, and
preventive maintenance activities.
Improved budgetary planning can be a
means of justifying additional funding for
system improvements. Improved system
reliability and water quality conditions are
other important benefits which should be
measured. These costs and benefits
should be investigated thoroughly before
a commitment is made to implement a
predictive planning system.
The full report was submitted in
fulfillment of Cooperative Agreement No.
CR810988 by American Water Works
Association Research Foundation under
the sponsorship of the U.S.
Environmental Protection Agency.
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The EPA author. R. M. Clark (also the EPA Project Officer, see below), is with
Water Engineering Research Laboratory, Cincinnati. OH 45268; M. Allen is
with American Water Works Research Foundation, Denver, CO 80235; and
D. Kelly O'Day is with Peer Systems, Inc.. Philadelphia, PA.
The complete report, entitled "Water Main Evaluation for Rehabilitation/
| Replacement, (OrderNo. PB87-175378/AS; Cost: $18.95. subjecttochange) \
'; will be available only from: '
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-87/024
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