United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-85/020 Apr. 1985
<>EPA Project Summary
Selected Topics Related to
Infiltration and Inflow in
Sewer Systems
Richard H. Sullivan and James W. Ewing II
The currant state of the art in sewer
system infiltration/inflow control was
reviewed to gather information not in-
cluded in earlier manuals and reports
on this subject. A series of nine
regional seminars was conducted to
explore local problems and practices
for solutions. The report includes an
overview of information on problem
determination as approached by the
Washington Suburban Sanitary Com-
mission, methods for flow determina-
tion (including a discussion of ac-
curacy), economics of sewer rehabili-
tation, methods of rehabilitation,
long-term rehabilitation programs, and
long-term flow monitoring. Also in-
cluded is a brief discussion of the ma-
jor problems covered at the regional
seminars.
This Project Summary was de-
veloped 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
With the passage of Public Law 92-500
in 1972, increased emphasis was placed
on sewer rehabilitation for reducing the
hydraulic loads on municipal sewage
treatment plants during wet weather. In-
creased flow results from the leakage of
ground water into the sanitary sewer
system through open joints, cracks, and
holes. In addition, flow increases through
above-ground discharges from building
drains of various kinds, and stormwater
can enter manholes directly. The com-
bination of these sources of infiltration
and inflow can cause very significant in-
creases in the total flow to a treatment
plant.
In response to the increased importance
of sewer rehabilitation and other control
techniques to reduce infiltration and in-
flow (I/I), a number of manuals have
been written on the subject by both the
U.S. Environmental Protection Agency
(EPA) and by other scientific and profes-
sional organizations.
This project was undertaken to review
the state of the art for I/I control and to
make additional information available to
users. A series of nine regional seminars
was conducted to determine the most
significant I/I problems in various parts of
the United States. Topics were for-
mulated from a list of significant prob-
lems, and new information was sought on
these topics. The results were combined
to make the full report. The seminars also
aided information exchange between EPA
officials, representatives of state and loca
governments, and consultants.
Overview
The regional seminars highlighted the
diversity of problems encountered by
public agencies in various parts of the
country. Because of existing physical con-
ditions such as age of the system, local
practices, and soil and groundwater con-
ditions, national guidelines must be broad
to allow for loca) needs. In addition, the
regional seminars provided an extensive
review of the EPA regulations governing
I/I studies. The review determined many
potential trouble spots for local agencies
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in adhering to the national guidelines.
Those who attended the seminars also
identified two agencies that are conduct-
ing extensive local programs for I/I con-
trol—the Washington Suburban Sanitary
Commission (WSSC) of the city of Hy-
attsville, Maryland, and the City of Salem,
Oregon.
This report is based on comments made
at the regional meetings. Chapters were
developed to cover the major points
discussed. The topics for each section are
described here briefly.
Problem Determination by the
Washington Suburban Sanitary
Commission
The program of the WSSC is a very
comprehensive attempt to overcome
many of the identifiable failings of the
standard sewer system evaluation survey
program. Under the program, internal in-
spection is scheduled to allow final
rehabilitation recommendations by
autumn of 1985. The approach being
followed is designated as the "systems
approach to sewer system evaluation."
The systems approach, in turn, is based
on the concept that collection systems
have "individual personalities." Since cer-
tain system personalities behave similarly,
they can generally be compared and
defined where pipe type, joint material,
and other accepted grantee compliance
requirements are similar. An accelerated
pilot study of the systems approach to
subarea rehabilitation has been approved
by the local regulatory agency. The
results of the study should be available at
approximately the time the sewer system
evaluation is completed.
Determining Excessive I/I and
Precise Flow in Sewers
The full report includes an analytical
listing of the various methods, including
smoke testing, used to determine whether
I/I should be considered excessive.
Difficulties are encountered in determin-
ing precise flow in leaking house laterals.
Such difficulties are the result of the inac-
cessibility of the point of discharge from
the house lateral to the street sewer. Care
must be taken to minimize the error in-
herent in each item of measurement. The
final report reviews interpretation of
monitoring data and the potential range of
error in discharge data. The report also
reviews the range of error experienced in
flow monitoring, together with an error
analysis scheme for estimating energy
slope. The error in the parameters for
various flow-estimating formulae is also
covered.
Economics of Rehabilitation
The economics of rehabilitation are
reviewed with the aim of helping the in-
vestigator ta make decisions by discussing
the problems associated with current
rehabilitation practices. One of the easiest
rehabilitation techniques available on the
market is sealing and grouting. Associated
problems arising from this technique are
traffic control, mobilization, and cleaning.
They are presented in detail in the full
report. Similarly, other techniques are
discussed with the view of what is needed
to evaluate a rehabilitation project
economically.
Techniques for Rehabilitating
Sewer Mains
The full report evaluates six basic
techniques involved in rehabilitating sewer
mains. A decision tree outlining steps re-
quired for various methods of sewer
rehabilitation is included. Techniques are
examined briefly and the positive and
negative aspects of each are discussed.
Processes reviewed are classified as
follows:
(1) -Spot repair
(2) Reconstruction in place
(3) Construction of a bypass
(4) Grouting
(5) Sliplining
(6) Inversion lining
A flowchart presents guidelines for the
use of each technique.
Inspection and Maintenance
The materials and workmanship used in
the inspection and maintenance processes
of sewer systems are listed in the full
report. The inspection process discussed
consists of two phases: cataloguing
through inventory and inspection by
television surveillance. Also discussed are
the two phases that make up the
maintenance process —the repair of
deteriorated sections and cleaning of the
lines to allow free flow.
Long-Term Flow Monitoring
The phases of long-term flow monitor-
ing are separated into three sections:
preparation of location, purchase and in-
stallation of equipment, and evaluation of
the project before and after completion. A
rehabilitation project must consider fac-
tors such as prior moisture conditions,
flow versus rainfall, flow versus intensity,
flow versus duration, and existing condi-"
tions.
Comments of Participants
The full report summarizes comments
of the participants at the various meetings
held by the American Public Works
Association for the project. Topics sum-
marized are:
House lateral construction problems
House lateral contributions
House lateral rehabilitation techniques
Single point versus multi-point monitor-
ing
Illegal connections
Cross connection
Manhole inflow
Groundwater migration
Cost effective I/I removal
New development standards
Improved building lateral access
A key concept of this report is the need
for local agencies to initiate continuing
preventive maintenance programs. This
step is necessary to maintain the
minimum level of extraneous water flows.
A sewer system cannot be rehabilitated
on a one-time basis and never develop ad-
ditional points of infiltration or inflow.
Multiple factors may be responsible for
various types of defects that allow I/I to
enter the system.
The full report was submitted in partial
fulfillment of Cooperative Agreement No.
CR 808934-01 by the American Public
Works Association Research Foundation
under the sponsorship of the U.S. En-
vironmental Protection Agency.
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Richard H. Sullivan and James W. Ewing II are with the American Public Works
Association Research Foundation, Chicago, IL 60637.
Carl A. Brunner is the EPA Project Officer (see below).
The complete report, entitled "Selected Topics Related to Infiltration and Inflow in
Sewer Systems," (Order No. PB 85-177 202/AS; Cost: $11.50, subject to
change) 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
ft US GOVERNMENT PRINTING OFFICE: 1985-559-016/27034
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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