EPA-520/9-74-018
GUIDANCE FOR
SEWER SYSTEM
EVALUATION
MARCH 1974
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF WATER PROGRAM OPERATIONS
WASHINGTON, D.C. 20460
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BIBLIOGRAPHIC DATA
SHEET
1. Report No. 2.
EPA/520/9-74/018
4. Title and Subtitle
Guidance for Sewer System Evaluation.
7, Author(s)
9. Performing Organization f
Environmental Prot
Office of Water Pr
12. Sponsoring Organization
lame and Address
ection Agency, Washington, D. C.
•ogram Operations
Name and Address
3. Recipient's Accession No,
PB-259 451
5. Report Date
Mar 74
6.
8. Performing Organization Rept.
No.
10, Project/Task/Work Unit No.
11, Contract/Grant No.
1 3. Type of Report & Period
Covered
14.
15. Supplementary Notes
16. Abstracts
Extraneous water from infiltration/inflow sources reduces the capability of
sewer systems and treatment facilities to transport and treat domestic and
industrial wastewaters. Infiltration occurs when existing sewer lines undergo
material and joint degradation and deterioration as well as when new sewer lines
are poorly designed and constructed. The elimination of infiltration/inflow by
sewer system rehabilitation can often substantially reduce the cost of wastewater
collection and treatment, both a logical and systematic evaluation of the sewer
system is necessary to determine its cost-effectiveness. This document in
intended to provide engineers, municipalities, and regulatory agencies with
guidance on sewer system evaluation.
17, Key Words and Document Analysis.
*Sewers,
*F1uid infiltration,
Evaluation,
Methodology,
Water influx,
Flow rate,
Rainfall,
Waste water,
Soil properties,
I7b. Identifiers/Open-Ended Terms
17o. Descriptors
Classifications,
Surveys.
I7c. COSATI Field/Group 1 3B
18. Availability Statement
National Technical Information Service
Springfield, Va. 22161
19. Security Class (This
Report)
|2t. No. of Pages
20. Security Class (This
Paee
UNCLASSIFIED
FORM NT1S-»» (REV. 10-73)
ENDORSED BY ANSI AND UNESCO.
THIS FORM MAY BE REPRODUCED
USCOMM-DC S26S-«"7«
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Guidance For
Sewer System Evaluation
Table of Contents
Page Number
1.0 INTRODUCTION 1
2.0 INFILTRATION/INFLOW ANALYSIS 1
3.0 SEWER SYSTEM EVALUATION SURVEY 4
3.1 Physical Survey 5
3.2 Rainfall Simulation 5
3.3 Preparatory Cleaning 6
3.4 Internal Inspection 6
3.5 Survey Report 7
APPENDIX
Rules and Regulations, 40 CFR Part 35, Excerpts 9
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1.0 INTRODUCTION
Extraneous water from infiltration/inflow sources reduces the capability
of sewer systems and treatment facilities to transport and treat domestic
and industrial wastewaters. Infiltration occurs when existing sewer lines
undergo material and joint degradation and deterioration as well as when new
sewer lines are poorly designed and constructed. Inflow normally occurs when
rainfall enters the sewer system through direct connections such as roof
leaders and catch basins. The elimination of Infiltration/inflow by sewer
system rehabilitation can often substantially reduce the cost of wastewater
collection and treatment. However, a logical and systematic evaluation of
the sewer system is necessary to determine the cost-effectiveness of any
sewer system rehabilitation to eliminate infiltration/inflow.
The Federal Water Pollution Control Act Amendments of 1972 require that
after July 1, 1973, all applicants for treatment works grants must demonstrate
that each sewer system discharging into the treatment works is not subject to
excessive infiltration/inflow. The requirement was implemented in the Rules
and Regulations for Sewer System Evaluation and Rehabilitation, 40 CFR 35.927
(pages 9 and 10).
This document is intended to provide engineers, municipalities, and regula-
tory agencies with guidance on sewer system evaluation.
2.0 INFILTRATION/INFLOVJ ANALYSIS
The infiltration/inflow analysis should provide the information necessary to
establish the non-existence or possible existence of excessive infiltration/inflow
in the sewer system(s) and justify any proposed sewer system evaluation survey.
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The analysis should include each sewer system tributary to the
treatment works project. The sewer system(s) should not be limited by
political jurisdictions or sewer types. The treatment works grant applicant
is responsible for the entire sewer system evaluation and any rehabilitation
to eliminate excessive infiltration/inflow. The sewer system included in
the evaluation should originate at the wastewater sources, such as com-
mercial buildings or private residences, and terminate at the wastewater
facility.
The estimated flow rates of infiltration/inflow, infiltration and
inflow entering the sewer system should be stated in the analysis. The
following diagram identifies these terms:
INFILTRATION/INFLOW IDENTIFICATION (IDEALIZED)
BYPASSES AND
OVERFLOWS
INFILTRATION
/INFLOW
INFLOW
INFILTRATION
DOMESTIC
AND
INDUSTRIAL
TOTAL
FLOW
TIME
LEGEND
FLOWS 1NCLUDIN8 INFILTRATION/INFLOW
FLOWS NOT INCLUDING INFILTRATION/INFLOW
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The difference between the maximum domestic and industrial flow rate and
total flow rate would represent the total infiltration/inflow entering the
sewer system. The difference between the maximum domestic and industrial
flow rate and the maximum flow rate during periods of high ground water
(with no rainfall) normally represents the infiltration entering the sewer
system. The amount of flow increase during storm events (including bypasses and
overflows) normally represents the inflow entering the sewer system.
Data sources for the analysis should include maps, operation and maintenance
records, observations by past and present municipal employees, and previous
engineering reports. When complete flow records are not available, estimated
flow rates may be computed from observed flow depths. Data presented in the
analysis does not have to be based on absolute measurements. A physical
examination of key manholes is normally conducted to obtain data for the analysis.
Estimated flow data should be related to rainfall intensity or other pertinent
data. A rainfall and sewage flow hydrograph should be included in the analysis.
Each bypassed flow and when possible overflows should be identified by location,
cause, duration, quantity, frequency, rate and method of discharge from the
system.
The total domestic and industrial wastewater flow rates and their relationship
to water consumption plus the domestic wastewater flow per capita should be stated
in the analysis.
A general description of the geographical and geological characteristics of
the area served by the sewer system should be presented in the analysis. This
description should include soil types, topography, rainfall data, known ground
water levels and other pertinent information.
The general discussion of a sewer system in the analysis should include: the
type of sewer system, i.e. sanitary or combined sewers; the known methods of sewer
construction; the maximum, minimum, and average depth of the sewers; major known
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sources of inflow; the structural condition, operation and maintenance practices,
amount and type of deposits, degree of root intrusion, and other pertinent sewer
system information; plus an evaluation of the probability of future decreases or
increases in the quantities of infiltration/inflow.
A comparison of the cost estimates for transportation and treatment of the
infiltration/inflow versus correction of the infiltration/inflow is normally
sufficient to determine if infiltration/inflow is non-excessive or possibly
excessive. Treatment costs should be based on achieving the effluent limitations
that are or will be included in the NPDES permit(s) for discharges from the
system.
When a sewer system has bypasses or overflows due to combined sewers and
there is or will be no control or treatment required of the bypasses or over-
flows in the NPDES permit, treatment costs should be based on treatment of the
total flow minus the bypasses or overflows attributable to the combined sewer
inflow. In those cases where control or treatment of combined sewer bypasses
or overflows is required, the cost-effectiveness analysis should be based on
control or treatment of the total flow in the system. In all instances, the
excessive infiltration should be eliminated from the entire sewer system In-
cluding the combined sewer portions.
Infiltration/inflow correction cost estimates should include the costs of
an evaluation survey, sewer system rehabilitation, and transportation and treat-
ment of the infiltration/inflow not eliminated by rehabilitation.
3.0 SEWER SYSTEM EVALUATION SURVEY
The sewer system evaluation survey is a systematic examination of the
sewer system to determine the specific location, flow rate and rehabilitation
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costs of the infiltration/inflow problem. The following approach is designed
to avoid over-study of the infiltration/inflow problem, including unnecessary
sewer cleaning and internal inspection. Each phase of the evaluation survey
is supported by the preceding phase.
The evaluation survey is normally divided into five consecutive phases:
(1) physical survey, (2) rainfall simulation, (3) preparatory cleaning,
(4) internal inspection, and (5) survey report. However, in certain situa-
tions, it will be possible to acquire the desired information and results more
economically by combining or eliminating certain phases of the survey. The
physical survey and rainfall simulation phases may provide sufficient data
to determine the existence or non-existence of excessive infiltration/inflow.
In such cases, the cleaning and internal inspection phases could be eliminated.
3.1 Phys i c a1 S u ryey
The first phase of the sewer system evaluation survey should be a physical
survey to determine the flow characteristics, ground water levels and physical
conditions of the sewer system.
In the first step of the physical survey, flow characteristics, and, if
infiltration is a problem, ground water levels at key manholes in the sewer
system are determined. Evaluation of this data would enable identification
of segments of the sewer system requiring further study. In certain instances,
the study area for the sewer system can be determined from data acquired during
the infiltration/inflow analysis.
The second step of the physical survey should be an examination of each
manhole in the study area to determine the actual physical condition of the
sewer system. This examination involves a physical lamping of each pipeline
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connected to the manholes. This data should aid in the identification of
infiltration/inflow sources and provide a factual base for any sewer cleaning,
3.2 Rainfall SImulation
The second phase of the evaluation survey should be rainfall simulations
to identify sections of sewer lines which have infiltration/inflow conditions
during periods of rainfall.
Dyed water flooding of storm sewer sections which parallel or cross sanitary
sewer sections (including service connections) and have crown elevations greater
than the invert elevations of the sanitary sewers is a method of conducting the
rainfall simulation phase. Stream sections, ditch sections, and ponding areas
located near or above sanitary sewer sections should be dyed tfater flooded to
identify other sources of infiltration/inflow. The downstream sanitary man-
hole is monitored for evidence of dyed water. The observed presence, concentra-
tion, and travel time of the dyed water into the sanitary sewer can be correlated
with the soil types to obtain an estimate of the sources and quantities of
infiltration/inflow. If the sewer system does not contain water traps or sagged
lines, smoke testing could be used to identify connections from catch basins,
roof leaders, yard drains and area drains.
3.3 Preparatory Cleaning
The third phase of the evaluation survey should be the preparatory cleaning
of selected sewer lines to provide for unobstructed internal inspection. The
selection of sewer sections for internal inspection is determined by analysis
of the data from the physical survey and rainfall simulation phases. Selected
sewer sections should have obvious potential for excessive infiltration/inflow
and warrant the necessary preparatory cleaning and internal inspection.
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3.4 Internal Inspection
The fourth phase of the evaluation survey should be the internal inspection
of selected sections of the sewer system. This phase should determine the
specific location, condition, estimated flow rate, and cost of rehabilitation
for each source of infiltration/inflow defined in the selected sections. A
descriptive record of all structural defects, service connections, abnormal
conditions and other pertinent observations should be obtained during the
inspection. The source of service connection flows should be identified.
An estimated flow rate is determined for each infiltration/inflow source.
Internal inspection for infiltration conditions is normally conducted
during periods of maximum ground water levels. One exception to this pro-
cedure is when the sewer is located above the maximum ground water level. All
storm sewers sections, stream sections, ditch sections, and ponding areas
related to the infiltration/inflow conditions are normally flooded during
the internal inspection.
The method used for internal inspection of sewer sections should be the
best and most cost-effective method of obtaining the necessary information.
Television is an acceptable method of obtaining the necessary information.
Inspection of large sewers may be accomplished by actual observation. Photo-
graphs or video tapes of infiltration/inflow sources can be used to support
the field data.
3.5 Survey Report
The final phase of the evaluation survey should be a survey report of the
data gathered during the survey, plus a justification for each sewer section
cleaned and internally inspected, (costs not justified will be unallowable
grant costs) and a proposed rehabilitation program to eliminate all defined
excessive infiltration/inflow.
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Each source of infiltration/inflow found during the survey should be
identified in the report by specific location, condition, flow rate, method
and cost of rehabilitation, and cost of transportation and treatment. An
infiltration/inflow source should be proposed for rehabilitation if the
rehabilitation cost does not exceed the cost of transportation and treat-
ment.
Rehabilitation costs for an infiltration/inflow source should be based
on the most cost-effective method of rehabilitation. (Several sources in
a sewer segment between two consecutive manholes could be combined to achieve
this objective.} Methods of rehabilitation can include: (1) replacement
of sewer sections or service connections; (2) insertion of sewer liners',
(3} internal or external pressure grouting with chemical sealants; (4) re-
moval or plugging of inflow connections; (5) manhole grouting; and (6) re-
placement, elevating and/or sealing of manhole covers. Cement mortar grouting
is not an effective method of rehabilitation except for manholes. Chemical
sealants used for pressure grouting should have the demonstrated capability
to eliminate infiltration under similar soil and sewer conditions. When
pressure grouting is the selected method of rehabilitation, the estimated
cost for the chemical sealant must be included in the rehabilitation costs.
When the sewer system contains a portion of combined sewers, the major
sources of inflow in the sanitary sewer portions tributary to the combined
sewer portions, such as cross connections from storm sewers, yard and area
drains, roof leaders, manhole covers and catch basins should be proposed for
rehabilitation. If control or treatment is or will be required for bypasses or
overflows in the NPDES permit, the remaining inflow sources in the sewer
system should be proposed for rehabilitation if the cost of rehabilitation
does not exceed the cost of transportation and treatment.
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EXCERPTS
Title 40—Protection of Environment
CHATTER I—ENVIRONMENTAL
PROTECTION AGENCY
EUBCHAPTFR B—GRANTS
PART 35—STATE AND LOCAL
ASSISTANCE
Final Construction Grant Regulations
§ 33.903—a Excessive infiltration/inflow.
The quantities of Infiltration/inflow
which can ba~ economically eliminated
from a sewer system by rehabilitation, as
determined by a cost-effectiveness anal-
ysis that eompaies the costs for correct-
ing tJie laflltrfttion/inflow conditions
•with the total costs for transportation
and treatment of the infiltration/inflow,
subject to the provisions in 5 35.927.
§ 35.905-9 Infiltration.
The water entering a sewer system,
Including sewer service connections,
from the ground, through such means as,
but not limited to, defective pipes, pipe
Joints, connections, or manhole walls. In-
filtration does not include, and is dis-
tinguished from, inflow.
§ 35.905-10 Infiltration /inflow.
The total quantity of water from both
infiltration and inflow without distin-
guishing the source.
§ 3S.90S-11 Inflow.
The water discharged into a sewer
system, including service connections
from such sources as, but not limited to,
roof leaders, cellar, yard, and —area
drains, foundation drains, cooling water
discharges, drains from springs and
swampy areas, manhole covers, cross
connections from storsn sewers and com-
bined sewers, catch basins, storm waters,
iurface run-off, street wash waters, or
drainage. Inflow does not include, and
is distinguished from, infiltration.
I 35.905-18 Sanitary sfwfr.
A sewer intended to carry'only sanS-
t«ry or- sanitary and industrial waste
waters from residences, commercial
bttlldlr.RS. industrial plants, and institu-
tions,
| 35.905-22 Slornt sewer.
A sewer Intended to carry only storm.
waters, surface run-off, street wash
waters, and drainage,
§ 35.905-2 Combined sewer,
A sewer intended to serve as a sanitary
sswer and a storm sewer, or as an In-
dustrial sewer and a storm sewer.
§ 33.927 Sewer system evaluation and
reliabilUation.
(a) All applicants for grant assistance
awarded after July 1,1973, must demon-
strate to the satisfaction of the Regional
Administrator that each sewer system
discharging into the treatment works
project for which grant application is
mad* is not or will not be subject to
excessive infiltration/inflow. The deter-
mination whether excessive infiltra-
tion/inflow exists, may take into account,
In addition to flow and related data,
other significant factors such as cost-
RUtES AND REGULATIONS
effectiveness (including the cost of sub-
stantial treatment works construction
delay, see Appendix A to this subpart),
public health emergencies, the effects of
plant bypassing or overloading, or rele-
vant economic or environmental factors.
(b) The determination whether or not
excessive infiltration/inflow exists will
generally be accomplished through a
sewer system evaluation consisting of (1)
certification by the State ngenc;.-, as ap-
propriate; and, when necessary <2j an
infiltration/inflow analysis; and, if ap-
propriate, (31 a sewer system evaluation
survey followed by rehabilitation of the
sewer system to eliminate an excessive
infiltration/inflow defined in the sewer
system evaluation. Information sub-
mitted to the Regional Administrator for
such determination should be the mini-
mum necessary to enable a judgment to
be made.
(c) Guidelines on sewer system evalu-
ation published by the Administrator
provide further advisory information.
§ 55.927-1 Infihrmlion/Inflow OB»ly«».
(a) The infiltration/inflow analysis
shall demonstrate the non-existence or
possible' existence of excessive infiltra-
tion/inflow to each sewer system tribu-
tary to the treatment works. The
analysis should identify the presence,
flow rate, and type of infiltration/inflow
conditions, which exist in the sewer sys-
tems. Information to be obtained and
evaluated in the analysis should include,
to the extent appropriate,, the following:
(1) Estimated flow data at the treat-
ment facility, all significant overflows
and bypasses, and, if necessary, flows at
key points within the sewer system.
(2) Relationship of existing popula-
tion and industrial contribution to flows
in the sewer system.
(3) Geographical and geological con-
ditions which may a-lect the present and
future- flow rates or correction costs for
the infiltration/inflow.
(4) A discussion of age, length, type,
materials of construction and known
phvsical condition of the sewer system,
Sb) For determination of the possible
existenee~of excessive infiltration/inflow,
the analysis shall include an estimate of
the cost of eliminating the innltratian/
inflow conditions. These costs shall be
compared with estimated total costs for
transportation end treatment of the
infiltration/inflow. Cost-Effectiveness
Analysis Guidelines (Appendix A to this
subpart), which contain advisory infor-
mation, should be consulted with respect
to this determination.
(c) U the infiltration/inflow analysis
demonstrates the existence or possible-
existence of excessive infiltration/inflow
a detailed plan for a sewer system evalu-
ation survey shall be included in th«
analysis. The plan shall outline the tasks
to be performed irx the survey and their
estimated costs.
§ 35.927—2 Sewer system evaUuUion
survey.
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required, an evaluation survey, is an es-
sential element of Step 1 facilities plan-
nr.53 <*nd ;•- a prer Step I. Facilities plan and related
elements required to apply for Step ?
grant assistance. An application for a
grant for Step I shall include:
(DA plan of study presenting Required comments or approvals of
relevant State, local, and Federal agen-
cies (including "clearinghouse" require-
ments' of OMB Circular A-95. promul-
gated at 38 FK 32874 on November 28,
1973>.
Step 2. Preparation of construction.
drawing's and specifications. Prior to the
award of a grant or grant amendment
lor a Step 2 project, the following must
have been furnished:
CD A facilities plan (including an en-
vironmental assessment in accordance
with Part 6 of this chapter) to accord-
ance with }£ 35.317 through 35.917-9.
(2) Satisfactory evidence of compli-
ance with the user charge provisions ol
15 38.928-11 aad 33,935-13;
(3) Satisfactory evidence of compli-
ance with the industrial cost recovery
provisions Of §§ 35.925-12, 35.928, and
35.S35-13, If applicable:
(4) A statement regarding availability
of the proposed site, i£ relevant;
(5) Satisfactory evidence of a pro-
posed or existing program for compliance
with, the Relocation and Land Acquisi-
tion Policies Act of 1970 in accordance
with,! 30.403(d> and Part 4 of this chap-
ter, If applicable; .
(6) Satisfactory evidence of compli-
ance with, other applicable Federal statu-
tory and regulatory requirements (see
Part 30, Subpart C of this chapter); -
(7) Proposed subagreements or an ex-
planation of the intended method of
awarding subagreements for perform-
ance of any substantial portion of the
project work.
(8) Required comments or approvals
at relevant State, local, and Federal
agencies (including "clearinghouse" re-
quirements of OMB Circular A-95; if a
grant application has not been previously
submitted
(c) Step 3. Building and erection of a
treatment works. Prior to the award OL a
grant or grant amendment for a Step 3
project, each of the items specified in
paragraph (b) of this section, and in ad-
dition (I) two sets of construction draw-
Ings and specifications, suitable for bid-
ding purposes, and (2) a schedule for or
evidence of compliance with §§ 35.925-10
and 35.935-12 concerning aa operation
and maintenance program, must have
been furnished,
(d) Step 2/3. Design/Construct Proj-
ect. Prior to the award of a grant or
grant amendment for a design/construct
project the items in paragraphs tb> and
(c) of this section must have been fur-
nished, except that, in lieu of construc-
tion drawings and specifications, the pro-
posed performance specifications and
other relevant design/construct criteria
for the project must hare been submitted.
§35.917-1 Content of Facilities Plan.
Facilities planning which is initiated
after April 30, 1974, must encompass tha
following to the extent deemed appro-
priate by the Regional Administrator: -
(a) A description o* the treatment
works for which construction drawings
and specifications are to be prepared.
This description shall include prelimi-
nary engineering data, cost estimates lor
design and construction of the treatment)
works, and » schedule for completion of
design and construction. The preliminary
engineering data may Include, to tha
extent appropriate, such information as
a schematic flow diagram, unit processes,
design data regarding detention times.
flow rates, sizing ol units, etc.
Cb> A description o! the selected com-
plete waste treatment system (s) of which
the proposed treatment works is a part.
The description shall cover all elements
of the system, from the service area and
collection sewers, through treatment, to
the ultimate discharge of treated waste-
waters and disposal of sludge.
(c) Xafiltraiion/iaflcrw documentation
in accordance with I 35.927.
(d) A cost-effectiveness analysis of
alternatives for the treatment works and
for the waste treatment system(s) of
which toe treatment works is a part.
The selection of the system(s) and the
choice of the treatment works on which
construction drawings and specifications
are to be based shall reflect the cost-
effectiveness analysis. This analysis shall
include:
(1) The relationship of the size and
capacity of alternative works to the needs
to be served, including reserve capacity;
(2) An evaluation of alternative flow
and waste Deduction measures;
(3) An evaluation of improved effluent
quality attainable by upgrading the op-
eration and maintenance and efficiency
of existing faculties as an alternative or
supplement to construction of new
facilities;
(4) An evaluation of the capability of
each alternative to mcot applicable ef-
fluent limitations. The treatment works
design must be based upon not less than
secondary treatment as denned by the
Administrator pursuant to sections 301
(a) (1) An evaluation of the alternative
means by which ultimate disposal can be
effected for treated wastewato and
for sludge materials resulting from the
treatment process, and a determination
of the means chosen.
(7) An adequate assessment of the ex-
pected environmental impact of alter-
natives including sites pursuant to Part
8 of this Chapter. This assessment shall
be revised as necessary to Include infor-
mation developed during subsequent
project steps,
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