WATER POLLUTION CONTROL RESEARCH SERIES 11022 EFF 01/71
Prevention and Correction
of Excessive Infiltration and Inflow
into Sewer Systems
A Manual of Practice
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and progress
in the control and abatement of pollution of our Nation's waters. They provide
a central source of information on the research, development and demonstration
activities of the Water Quality Office of the Environmental Protection Agency,
through in-house research and grants and contracts with the Federal, State,
and local agencies, research institutions, and industrial organizations.
Triplicate tear-out abstract cards are placed inside the back cover to facili-
tate information retrieval. Space is provided on the card for the user's
accession number and for additional key words. The abstracts utilize the
WRSIC system.
Inquiries pertaining to Water Pollution Control Research Reports should be
directed to the Head, Project Reports System, Planning and Resources Office,
Research and Development, Water Quality Office, Environmental Protection
Agency, Washington, D.C. 20242.
Previously issued reports on the Storm and Combined Sewer Pollution Control
Program:
11034 FKL 07/70 Storm Water Pollution from Urban Land Activity
11022 DMU 07/70 Combined Sewer Regulator Overflow Facilities
11024 EJC 07/70 Selected Urban Storm Water Abstracts, July 1968 -
June 1970
11020 --- 08/70 Combined Sewer Overflow Seminar Papers
11022 DMU 08/70 Combined Sewer Regulation and Management - A Manual
of Practice
11023 --- 08/70 Retention Basin Control of Combined Sewer Overflows
11023 FIX 08/70 Conceptual Engineering Report - Kingman Lake Project
11024 EXF 08/70 Combined Sewer Overflow Abatement Alternatives -
Washington, D.C.
11023 FDB 09/70 Chemical Treatment of Combined Sewer Overflows
11024 FKJ 10/70 In-Sewer Fixed Screening of Combined Sewer Overflows
11024 EJC 10/70 Selected Urban Storm Water Abstracts, First Quarterly
Issue
11023 --- 12/70 Urban Storm Runoff and Combined Sewer Overflow Pollution
11023 DZF 06/70 Ultrasonic Filtration of Combined Sewer Overflows
11024 EJC 01/71 Selected Urban Runoff Abstracts, Second Quarterly Issue
11020 FAQ 03/71 Dispatching System for Control of Combined Sewer
Losses
To be continued on inside back cover
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PREVENTION AND CORRECTION OF EXCESSIVE INFILTRATION
AND INFLOW INTO SEWER SYSTEMS
Manual of Practice
by the
AMERICAN PUBLIC WORKS ASSOCIATION
For the
ENVIRONMENTAL PROTECTION AGENCY
WATER QUALITY OFFICE
&
THIRTY-NINE LOCAL GOVERNMENTAL JURISDICTIONS
Program No. - 11022EFF
January, 1971
Contract 14-12-550
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, B.C. 20402 - Price $1.25
Stock Number 5501-0053
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SPONSORING LOCAL AGENCIES
City of Akron .Ohio
City of Albuquerque, New Mexico
City of Ann Arbor, Michigan
Arlington County, Arlington, Virginia
City of Baltimore, Maryland
Metropolitan District Commission, Boston, Massachusetts
City of Charlotte, North Carolina
City of Charlottetown, P.EJ.
City of Chattanooga, Tennessee
The Metropolitan Sanitary District of Greater Chicago, Illinois
City of Columbus, Ohio
City of Daytona Beach, Florida
City of Indianapolis, Indiana
Kansas City, Missouri
City of Ludington, Michigan
City of Miami, Florida
City of Middletown, Ohio
City of Milwaukee .Wisconsin
City of Minneapolis, Minnesota
City of Montreal, Quebec, Canada
City of Muncie, Indiana
City of Oshkosh, Wisconsin
City of Pittsburgh, Pennsylvania
Oakland County, Pontiac, Michigan
City of Puyallup, Washington
City of Richmond, Virginia
City of St. Clair Shores, Michigan
Metropolitan St. Louis Sanitary District, St. Louis, Missouri
City of San Carlos, California
City of San Jose, California
San Pablo Sanitary District, San Pablo, California
Santa Clara County Sanitation District No. 4, Campbell, California
City of Seattle, Washington
City of Springfield, Missouri
City of Topeka, Kansas
Municipality of Metropolitan Toronto, Ontario
City of Wichita, Kansas
Metropolitan Corporation of Greater Winnipeg, Manitoba, Canada
Also Contributing
City of Detroit, Michigan
EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents
necessarily reflect the views and policies of the
Environmental Protection Agency.
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ABSTRACT
As a result of ajnational study of the sources and
prevention of infiltration and inflow, a Manual of
Practice was proposed. The Manual is intended to
serve as asuide to local officials in evaluating their
S353W9'
construction practices, conducting surveys to
determine the extent and location of infiltration and
inflow, the making of economic analyses of the cost
of excessive infiltration/inflow waters; and instituting
corrective action.
Excerpts from sewer control legislation are given
as well as information on air and exfiltration testing.
This Manual of Practice was prepared for the
Environmental Protection Agency in partial
fulfillment of Contract 14-12-550. The study was also
supported by thirty-nine public agencies. A
companion document, "Control of Infiltration and
Inflow Into Sewer Systems", was also prepared.
Key Words: INFILTRATION, INFLOW, INVESTI-
GATION, CONSTRUCTION, LEGISLATION, TEST-
ING, ECONOMICS.
111
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APWA RESEARCH FOUNDATION
Project 69-Ib
STEERING COMMITTEE
Paul C. Soltow, Jr., Chairman, San Pablo Sanitary District
George E. Bums, Metropolitan Corporation of Greater Winnipeg
Richard L. Castle, Oakland County, Michigan, Department of Public Works
S. J. McLaughlin, The Metropolitan St. Louis Sewer District
Alfred R. Pagan, (ASCE), Bergen County, New Jersey, Engineer's Office
Lloyd Weller, (WPCF), Black & Veatch Consulting Engineers
Richard H. Sullivan, Project Director
Arthur T. Brokaw, Principal Investigator
Dr. Morris M. Cohn, Staff Consultant
ENGINEERING ADVISORY PANEL
Frank Kersnar, Brown and Caldwell
Walter Thorpe, Tolz, King, Duvall, Anderson and Assoc., Inc.
Charles R. Velzy, Charles R. Velzy & Associates
INDUSTRIAL ADVISORY PANEL
L. E. Gottstein, P.E., Chairman,
American Pipe Services
Charles M. Aiken, Raymond International, Inc.
James R. Alley, Certain-teed Products Corp.
Joseph P. Ashooh, The Assoc. General Contractors
of America
Donald M. Cline, Pacific Clay Products
Robert Hedges, Rockwell Manufacturing Co.
Quinn L. Hutchinson, P.E., Clow Corp.
Harold Kosova, Video Pipe Grouting, Inc.
Tom Lenahan, Environmental Control Research Center
W. J. Malcom, P.E., Cherne Industrial, Inc.
Joseph McKenna, Industrial Material Co.
Charles Prange, Rockwell Manufacturing Co.
John Roberts, Armco Steel Corp.
Harold Rudich, National Power Rodding Corp.
Joseph A. Seta, Joseph A. Seta, Inc.
H. W. Skinner, Press-Seal Gasket Corp.
E. W. Spinzig, Jr., Johns-Manville Sales Corp.
Edward B. Stringham, Penetryn System, Inc.
William M. Turner, Griffin Pipe Products Co.
Joe A. Willett, American Concrete Pipe Assoc.
John A. Zaffle, United States Concrete Pipe Co.
R. D. Bugher
R. H. Ball
Lois V. Borton
Marilyn L. Boyd
Doris Brokaw
APWA Staff*
R. B. Fernandez
John R. Kerstetter
Shirley M. Olinger
Violet Perlman
Ellen M. Filler
Frederick C. Ross
Terry Tierney
George M.Tomsho
Oleta Ward
Mary J.Webb
*Personnel utilized on a full-time or part-time basis on the project.
IV
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CONTENTS
Page
SECTION 1 Introductory Statement: The Infiltration and Inflow
Problem and Its Prevention and Control 1
SECTION 2 Design Standards and New Construction Methods for the
Control of Infiltration 5
SECTION 3 Correction of Infiltration Conditions,Existing Systems 29
SECTION 4 Controlling Discharge of Inflow 39
SECTIONS Economic Guidelines 51
SECTION 6 Trends and Developments 63
SECTION? Acknowledgements 69
SECTIONS Glossary of Pertinent Terms 75
SECTION 9 Appendices 79
TABLES
2.3.1 Standard Specifications for Selected Sewer Pipes 10
2.4.2 Design Flows Designated by State and Province Regulations 15
2.4.2.1 Illustration of Design Infiltration/Inflow Allowance Calculation
Example 1 17
2.4.2.2 Example 2 17
5.2.1 Community Profile 54
5.2.2 Unit Capital Costs of Sewage Collection System 55
5.2.5.1 Unit Treatment Plant Costs Per MGD (1967 Price Level) 57
5.2.5.2 Total System Costs - 100,000 Population . . 59
5.2.5.4 Total System Costs - 250,000 Population 60
5.2.5.6 Per Capita and Per 1000 GPD Costs-Municipal System 61
FIGURES
2.4.2.1 Ratio of Peak Sewage Flow to Average Flow 14
2.4.2.2 Intensity-Duration-Frequency Rainfall Curves 16
2.4.2.3 Stormwater Allowance for Design of Separate Sewers 18
2.5.1.3 Bedding for 84-Inch Interceptor 21
2.5.1.4 Placement of Rock Bed 72-Inch Interceptor 22
3.3 Ground Water Gauge ... 32
5.2.5 Total Capital Cost - Primary & Secondary Treatment . . . . 58
5.2.5.3 Annual Collection & Treatment Costs as Percent of Total
Annual Municipal Costs 59
5.2.5.5 Annual Collection & Treatment Costs as Percent of Total
Annual Municipal Costs 60
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AMERICAN PUBLIC WORKS ASSOCIATION
Board of Directors
Myron D. Calkins, President
William W. Pagan, Vice President
Ross L. Clark, Past. President
Ray W. Burgess Frederick R. Rundle Wesley E. Gilbertson Erwin F. Hensch
Timothy J. O'Leary Lt. Gen. Frederick J. Clarke Herbert Goetsch Lyall A. Pardee
Harmer E. Davis Donald S. Frady Leo L. Johnson Gilbert M. Schuster
Robert D. Bugher, Executive Director
APWA RESEARCH FOUNDATION
Board of Trustees
Samuel S. Baxter, Chairman
W. D. Hurst, Vice Chairman
Fred J. Benson William S. Foster
John F. Collins D. Grant Mickle
James V. Fitzpatrick Milton Offner
Milton Pikarsky
Robert D. Bugher, Secretary-Treasurer
Richard H. Sullivan, General Manager
VI
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SECTION 1
INTRODUCTORY STATEMENT: THE INFILTRATION AND
INFLOW PROBLEM AND ITS PREVENTION AND CONTROL
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SECTION 1
INTRODUCTORY STATEMENT: THE INFILTRATION AND
INFLOW PROBLEM AND ITS PREVENTION AND CONTROL
THE PROBLEM
A serious problem results from excessive
infiltration into sewers from ground water sources,
and high inflow rates into sewer systems through
direct connections from sources other than those
which sewer conduits are intended to serve. The
hydraulic and sanitary effects of these extraneous
flows are of particular importance now because urban
growth generally requires all available sewer capacities
to handle present flows and serve future expansion.
The pollutional effects of by-passed and spilled and
under-treated waste water flows caused by infiltration
and inflow are paradoxical at a time when higher
degrees of treatment are being demanded to protect
the nation's water resources.
The effects of these extraneous waters are of
primary importance in separate sanitary sewers. These
intrusion waters pirate greater proportions of the
relatively smaller sanitary lines than of combined
sewers and storm sewers. When sanitary sewers
become surcharged and produce flooding of street
and road areas and back-flooding into properties, the
spilled flows are a serious sanitary hazard. Similarly,
when by-passing of pumping stations, sanitary relief
and interceptor lines, and sewage treatment processes
occur because of excessive infiltration-inflow
volumes, the waste waters discharged to receiving
waters have great pollutional potential.
In combined sewers, such intruded waters offer
less threat of surcharging and back-flooding during
dry weather flows, but the hazard of local
overloading during storm periods should not be
discounted. Unnecessary and over-long overflows at
combined sewer regulator stations introduce
pollutional waste waters into receiving waters. (The
effects of overflows were investigated and reported
upon by the American Public Works Association for
the then Federal Water Pollution Control
Administration, Department of the Interior, and
participating local jurisdictions in a project covering
"Problems of Combined Sewer Facilities and
Overflows - 1967").
The effects of infiltration, and inflow are alike,
except for two specific conditions. Infiltration, and
its counterpart - exfiltration - often produce local
washout of soil bedding around defective pipe or
joints, followed by actual failure of the sewer barrel
or cave-in of roadways and pavements and loss of
nearby utilities and utility vaults. No such effects are
attributable to inflow connections. In infiltration, a
direct relationship exists between the entry of sewer
flows through defective pipe and joints and the
intrusion of water seeking tree roots through the
same cracks or openings. No such relationship exists
in the case of points of inflow into sewer systems.
The clogging of sewers with intruded sand, clay, or
gravel at points of infiltration is a specific infiltration
effect not duplicated in the phenomenon of inflow.
When infiltration waters and inflow waters
become commingled within sewer systems they are
not readily distinguishable from each other. The net
effect of their presence-is the same: robbed sewer
system capacities and usurped capabilities of system
facilities such as pumping, treatment, and
regulator-overflow structures. What is different about
these two types of extraneous waste waters is their
source.
This difference is borne out by the definitions of
"infiltration" and "inflow" chosen as guidelines for
the study of this problem in 1969-70 by the
American Public Works Association Research
Foundation for the Federal Water Quality
Administration and 39 participating local
jurisdictions in the United States and Canada. For a
clear understanding of the purposes of this Manual of
Practice (which is the end-product of the national
investigation of the infiltration and inflow problem),
it is essential to restate these basic definitions:
"INFILTRATION" covers the volume of
ground water entering sewers and building
sewer connection from the soil, through
defective joints, broken or cracked pipe,
improper connections, manhole walls, etc.
"INFLOW" covers the volume of any kinds of
water discharged into sewer lines from such
sources as roof leaders; cellar and yard area
drains; foundation drains; commercial and
industrial so-called "clean water" discharges;
drains from springs and swampy areas; etc. It
does not include, and is distinguished from,
"infiltration."
"INFILTRATION/INFLOW" is the volume of
both infiltration water and inflow water found
in existing sewer systems, where the
indistinguishability of the two components of
extraneous waters makes it impossible to
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ascertain the amounts of both or either.
These basic definitions serve two purposes - to
define the difference between the two extraneous
water flows, and to show that the difference relates
to sources, rather than characteristics, of such flows.
Definitions of other words and phrases used in this
Manual of Practice are contained in the Glossary of
Pertinent Terms, Section 8.
Infiltration results from soil conditions in which
sewer lines are laid; the quality of materials and
construction workmanship; ground water levels;
precipitation and percolation of surface waters;
waters retained in the interstices of surrounding soils,
and the stability of pipe and joints and appurtenant
sewer structures after periods of service.
Inflow is the result of deliberately planned or
expediently devised connections of sources of
extraneous waste water into sewer systems. These
connections serve to dispose of unwanted storm
water or other drainage water and wastes into a
convenient drain conduit. They are interpreted, in
terms of this Manual, to include the deliberate or
accidental draining of low-lying or flooded areas into
sewer systems through manhole covers.
Infiltration and inflow conditions have two
characteristics in common, in that each problem is
divided into two parts: prevention of excessive
extraneous flows, and correction of conditions
already imposed on existing sewer systems.
In the case of infiltration, prevention of
excessive entries into new sewer systems depends on
effective design; choice of effective materials of sewer
construction; imposition of rigid specifications
limiting infiltration allowances; and alert and
unremitting inspection and testing of construction
projects to assure tightness of sewers and
minimization of infiltration waters.
Correction of infiltration conditions in existing
sewer systems involves evaluation and interpretation
of sewage flow conditions to determine the presence
and extent of excessive extraneous water flows from
sewer system sources, the location and gauging of
such infiltration flows, and the elimination of these
flows by various corrective, repair and replacement
methods.
In the case of inflow onditions, the problem is
similarly two-faceted: prevention and cure.
Prevention of excessive inflow volumes is a matter of
regulating sewer uses and enforcement of such
precepts and codes by means of vigilant surveys and
surveillance methods. Correction of existing inflow
conditions involves location of points of inflow
connections; determination of their legitimacy or
illicit nature; evaluation of the responsibility f°r
correction of such conditions; establishment of
inflow control policies where none have been in
effect; institution of corrective policies and measures,
backed up by investigative and enforcement
procedures to make such policies potent.
THE NEED FOR GUIDELINES:
THE MANUAL OF PRACTICE
Control of infiltration and inflow in all future
sewer construction work, and the search for and
correction of excessive intrusion of excessive flows of
extraneous waters into existing sewer systems, is an
essential part of sewer system management.
Past practices often have been based on
inadequate technical policies, usually devoid of
substantiating data on causes and effects of
infiltration and inflow conditions. There has been a
dearth of standardization of such practices; the policy
of "standardization" has been limited to a
follow-the-leader attitude of accepting and using the
criteria of others without consideration of their
applicability to present-day materials and
methodologies.
In fairness to the great advances made in the
manufacture of pipe and joint materials, a review of
practices is long overdue. This Manual has been
prepared to provide a stimulus to improve practices in
the design, construction and operation-maintenance
of sewer systems.
One word of clarification and caution is
necessary. This Manual is designed as a compilation of
practices in the subjects outlined, in terms of their
applicability to the actual conditions under which
specific new sewer system projects are to be
constructed or existing systems are to be operated
and maintained. In short, what is offered here are
general guidelines for better practices - pointing the
way to improvements in control of infiltration and
inflow, sewer service, and water quality control. It is
hoped that the guidelines contained in this Manual
will result in the eventual development of so-called
"standards of practice," with the understanding that
each project, each sewer system, must be designed,
equipped, constructed, and operated to meet specific
local conditions.
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SECTION 2
DESIGN STANDARDS AND NEW CONSTRUCTION METHODS
FOR THE CONTROL OF INFILTRATION
IN SEWER SYSTEMS
2.1 Basic Factors
2.2 Predesign Investigations
2.3 Pipe and Jointing Materials and Practices
2.4 Design Criteria for New Sewers
2.5 Construction Methods and Inspection
2.6 Testing for Acceptance
2.7 Standards for Building Sewers
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SECTION 2
DESIGN STANDARDS AND NEW CONSTRUCTION METHODS
FOR THE CONTROL OF INFILTRATION
IN SEWER SYSTEMS
2.1 BASIC FACTORS
The initial area of concern in reducing or
eliminating infiltration involves the production of a
pipe system and appurtenances which are water-tight
and do not permit ground water leakage. The
realization of this objective begins during design; but,
in truth, a number of preliminary activities are
necessary to provide vital background information
before any design decisions are made.
This section proposes a logical, orderly approach
to the entire problem of producing an infiltration-free
sewer in the first instance, and one that will resist
deterioration in service due to improper design,
workmanship, or maintenance practices. Not every
detailed step which would be used in good sewer
design practice will be delineated. The emphasis is on
those factors in design and construction that are
particularly involved with infiltration control. Any
criteria which affect the installation of a sound and
well-built system will aid in reducing infiltration, but
there ' are many considerations of hydraulic and
structural significance that may have little bearing on
infiltration control.
References will be made to appropriate published
manuals on general sewer design and construction
techniques in lieu of any attempt to assemble
repetitive material that could be voluminous and not
totally applicable to infiltration control.
It is appropriate to point out at the outset that
the first step in producing infiltration-free sewers may
be the selection of a qualified and experienced civil
engineer. Even the larger communities or agencies
may not have sufficient personnel to execute the field
survey-and design activities required to produce plans
and specifications for extensive sewer system
construction. Small subdivision systems often are
engineered by a consultant for the private owner,
subject to agency approvals. The choice of a
consultant may involve the most important decision
of the project.
A number of professional .societies and groups
have published manuals and guides on how to select
consultants and set appropriate fees. They include:
American Society of Civil Engineers
National Society of Professional
Engineers — Salary and Fee Guide
Consulting Engineers Council — Selecting a
Consultant
2.2 PREDESIGN INVESTIGATIONS
2.2.7 Soil and Ground Water Investigations:
Soil and ground water conditions must be
considered if the design for a proposed sewer system
is to avoid infiltration. Section 3.7.1 describes in
detail effects of poor soil conditions.
The types of surveys and tests needed to obtain
the necessary information include:
a. Reconnaissance
Reconnaissance is the gathering of available
information on soils and groundwater conditions. For
small projects, it may supply all the necessary
information for proper design. For major projects, it
will serve as a basis for a more thorough subsurface
investigation, and may provide information on the
feasibility of alternate locations for a proposed sewer
system.
Geological maps, aerial photographs, flood
records, and the results of previous subsurface
investigations performed in the general vicinity of
proposed construction might be available in the
municipal engineer's office, libraries, universities and
utility companies.
Telephone calls or visits to builders familiar with
the area, municipal personnel, and local residents
often yield useful information or will point out
potential trouble areas.
The above information will give direction and
add to the effectiveness of a personal site review.
Investigation of construction excavations,
watercourses, high-water marks, lowland wet areas,
types of vegetation, and rock outcrops furnish
additional important information regarding soil and
ground water conditions.
b. Types of Subsurface Investigations
Subsurface investigations are performed to obtain
information more directly related to the proper
design of the proposed sewer.
Test pits of 10 to 15 feet in depth, depending on
the type of backhoe used, will economically provide
information on rock and soil types, layering and
compactness, safe soil slopes, and ground water level,
and they will permit soil and ground water sampling.
Probing consists of driving a rod through the
depth of soft or loose soils, with or without provision
for obtaining soil samples. Probes are usually used as
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a supplement to more reliable methods of
investigation.
Auger borings may be advanced either by hand or
by power equipment. Hand auger borings are limited
in depth. Auger borings produce information on soil
type and (under certain conditions), on ground water.
The "hollowstem auger," however, can supply
information similar to that outlined under machine
borings.
Machine borings produce the same information as
the machine augers. In addition, they are a means to
obtain undisturbed samples and rock core samples,
and can be used as ground water observation wells.
Geophysical exploration methods are used for
very large projects to supplement the more direct
methods listed above. They include seismic and
electrical refraction surveys and require highly
specialized personnel. The same applies to aerial
photographic interpretations.
Ground water readings can be obtained in
conjunction with the above methods of exploration,
but generally are limited to the time of investigation.
To observe ground water fluctuations over periods of
time, cased machine borings can be used for
observation wells. A perforated tubing is placed in the
cased hole and sealed to eliminate surface water
entrance. Ground water readings can then be made
periodically to monitor ground water level variations.
Existing manholes also can be used as ground water
observation wells by drilling through the bottom of
the manhole and installing a pipe perforated below
the manhole base and extended above maximum
anticipated height of water level. The system must be
sealed at the manhole bottom to avoid infiltration if
the ground water level rises above the manhole base.
Advice and assistance from qualified soil
engineers and ground water experts should be sought
in connection wtih sizeable jobs or where anticipated
exploration methods warrant such expertise.
c. Types of Laboratory Tests
Three general types of laboratory tests can be
performed: soil classification tests, soil performance
tests, and ground water analysis.
Classification tests, such as sieve and hydrometer
analysis, provide information on the physical
characteristics of the soils. Results of the tests are
useful in distinguishing (1) if a material is suitable as
backfill or bedding; (2) if it will produce problems
associated with dewatering as they pertain to
pumping of the fines, subsequent settlements, and
evaluation of ground water flow. Also the tests serve
as a basis for determining which performance tests are
needed to aid the design.
Performance tests provide information for
predicting the behavior of the soil under additional
loads, such as embankments to be constructed next
to or over a sewer installation. Such loads could cause
differential settlements of the sewer, with subsequent
cracking and infiltration. Permeability tests results are
used to assess the rate of ground water flow in
connection with infiltration problems.
Chemical ground water analysis, particularly tests
for the acidity of the water, is important in pipe
material selection.
d. Types of In-Situ Tests Available
Simple field classification tests are available to
determine if soils encountered are similar to those
anticipated. Also, in-situ field density tests are used
to monitor compaction. The most common methods
are the Sand Cone Method and the Rubber Balloon
Method.
2.2.2 Soil Clarification
In order to identify a specific soil and relate its
properties to the aspects of infiltration, it is necessary
to have some knowledge of soil classification. For
instance, a "Brown coarse SAND, little medium
Gravel" will indicate high permeability and,
therefore, excellent ground water flow characteristics,
while a "Silty CLAY" with its low permeability will
impede ground water flow for all practical purposes.
The suitability of soil for bedding or backfill
purposes and the need for specific types of trench
sheeting and dewatering methods become apparent
with the proper classification of a soil type.
Numerous soil classification systems are in use
throughout the United States. Soils are generally
classified as cohesionless or cohesive. Cohesionless
soils refer to boulders, gravels, sands, and silts or any
combination thereof. Cohesive soils are those
containing clay and exhibiting plasticity.
A soil description should contain the color of the
material and the relative proportions of the particle
sizes present in the soil. Standard proportion terms
are used in conjunction with classification
descriptions.
Soil identification and classification thus entail
an evaluation of the relative percentages of various
soil particles. Cohesionless soils classification involves
determining the predominate particle sizes, that is,
the major component representing more than half the
soil. Mentions of the remainder, the minor
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components, then forms the soil classification.
2,2.3 Analysis of Existing System
Except in the case of a totally new sewer system,
designers of new sewers plan at some point to
connect to an existing system, trunk line, or
treatment plant. Too often, a careful analysis of the
older sections is neglected. This may be because of
time limitations or fee limitations, or because the
importance of preplanning inspection and evaluation
was overlooked or no funds were made available for
such preliminary studies. This should be corrected in
the interest of improved sewer practices. Preplanning
investigations should be separately funded and
completed prior to design. At this time preplaning
inspection cannot be funded from Federal or state
construction grants. Local funds expended for this
purpose may result in lower construction costs and
better utilization of existing facilities.
The haphazard juncture of different parts of the
system over the years can result in poor hydraulic
characteristics which are not discovered until an
overall systems analysis is made to correct infiltration
and flooding problems. Most of these bottlenecks
never would have occurred if proper preliminary
investigations had been made before new sewer
extensions were connected. Although they are not a
cause of infiltration, they magnify the effects and
multiply the damage and destruction. Too often, land
subdivision sewer extensions are approved with only a
cursory examination of the adjacent trunk capacity
and the treatment plant at the end of the sewer
system. The condition and capacity of the intervening
system frequently are overlooked.
The connections of additional contributions to
an already overloaded system may be against the
public interest and welfare. The adoption of a
program of infiltration and inflow detection and
correction, as outlined in Sections 3 and 4 of this
Manual, may be necessary before acceptance of sewer
extensions. In some areas the state water pollution
control agencies have forced a halt to new home and
building construction until existing systems are
corrected.
The following items should be covered in the
analysis of the existing system when performed by
the municipal engineer or consultant or required from
the developer's consultant on new subdivisions:
1. Identification of the route of flow for the
added contribution from point of connection
to existing sewer system to the point of
ultimate treatment and disposal.
2. Selection of key manholes along the route
where major junctions or merging of flows
occur.
3. Opening of key manholes, observing flow
and general condition and taking invert and
pavement elevations.
4. Performing hydraulic analysis of route of
flow to determine present capacity and the
effect of new contributions from a sewer
extension.
Upon receipt and review of the preceding
information, the engineer in charge of the sewer
system should make a determination of acceptance or
rejection of the sewer extensions. Such decisions
should be made before extensive design is performed.
In decisions on boosting capacity, the officials also
should be involved — studies on the existing system,
making corrections, and removing bottlenecks. These
efforts are described more completely in Section 3.
Consideration of any existing system is mentioned at
this juncture mainly because it is so often overlooked
and the effects of existing infiltration and inflow may
well influence new design and construction.
2.3 PIPE AND JOINTING MATERIALS AND
PRACTICES
2.3.1 Types of Sewer Pipe to Con trol Infiltration
Improvements in pipe material ensure that the
designer can provide proper materials to meet rigid
infiltration allowances. The basic question of water
tightness of pipe material may not be a matter of
concern as much as problems of structural integrity
and strength of waste water character, or of local soil
or gradient conditions which would make one
material better suited than another, or preferable
under certain special installation conditions.
There are several common pipe characteristics
which affect a pipe's performance. These are ability
to:
1. Withstand handling during transport to the
job site, unloading, and laying;
2. Withstand the effects of corrosion from
hydrogen sulfide and resultant acid
formation as well as industrial chemicals; and
3. Withstand physical action of cleaning
equipment, such as saws, jets, and abrasion
from cables where circumlinear lines are
used.
In such cases or situations, pipe materials are
chosen for reasons other than their relative resistance
to infiltration.
The design of sewer lines which will be operated
-------
TABLE 2.3.1
STANDARD SPECIFICATIONS FOR SELECTED SEWER PIPES
NAME STANDARD
Asbestos-Cement Non Pressure Sewer Pipe
Asbestos-Cement Non Pressure Small Diameter Pipe
Asbestos-Cement Pipe, Standard Methods of Testing
Concrete Sewer, Storm Drain & Culvert Pipe
Concrete Culvert, Storm Drain & Sewer Pipe,
Reinforced
Concrete Sewer & Culvert Pipe, Joints for Concrete
Pipe using flexible, watertight Rubber Gaskets
Corrugated Metal Pipe
Rubber Rings for Asbestos-Cement Pipe
Solid Wall Plastic Pipe
Truss Pipe
Vitrified Clay Pipe
under pressure also must be evaluated. The pressures
to be used may effectively determine the type of pipe
which must be used.
The types of sewer pipe now in use are listed
alphabetically and briefly described below:
Asbestos-Cement sewer pipe is manufactured
from asbestos fiber, portland cement and silica, and is
divided into seven strength classes which are
designated for pipe sizes ranging from 6-inch diameter
up to 42-inch diameter. Types of pipe specified
depend on the usage intended.
Type I - for use where moderately aggressive
waste water and soil of moderate sulfate content
are expected to come in contact with the pipe.
Type II — for use where highly aggressive water
or water and soil of high sulfate content, or both,
is expected to come in contact with the pipe.
Type III — for use where contact with aggressive
water and sulfate is not expected.
Asbestos-cement pipe is in common usage in
many cities. Its particular advantages include reduced
number of joints due to longer laying lengths and its
relatively light weight. It is often used for pressure
sewers.
Cast Iron or Ductile Iron is utilized primarily in
building drain lines or laterals. However, it's also
specified where poor sewer foundation conditions
exist, such as in stream crossings; where a high water
table may require a very tight joint, or when the
sewage will be under pressure, as in a force main.
Concrete sewer pipe presently is in common
usage for new construction of sewers, storm drains,
ASTMC 428-70
ASTMC 644-69
ASTMC 500-70
ASTMC 14
ASTMC 76
ASTM C 443
AASHO M-36 &
Federal Specification
WWP-4059
ASTM D-1869-66
ASTM D-2751. &
D-2729
ASTM D- 2686
ASTMC-425
and culverts. Non-reinforced concrete pipe is available
in sizes ranging from 4 to 24 inches in diameter;
reinforced concrete pipe is used for sewers 12 to 156
or more inches in diameter. One of the advantages of
concrete pipe is the relative ease of providing the
required strength in a wide range of lengths. A variety
of jointing methods are available, depending on the
tightness required and the operating pressures
involved.
Fiber Qass pipe has not been used extensively
for sewer service in the United States and Canada. It
has been limited to special application such as
industrial waste drain lines. It reportedly is used more
widely in European practice. However, if recent
technical developments can be coupled with
production efficiencies and lower cost, this material
may find wider application. Fiber glass pipe is made
with polyester or epoxy resin and fiber glass material
for reinforcemnt. Other types of pipe are made with a
sand filler; these are available with bell and spigot
joints and "0" ring gaskets. Types of fiber glass pipe
joints include mechanical and chemical welded joints.
Plastic Sewer pipe use in sewer construction has
been limited to date, but plastic pipe can provide
essentially water-tight construction. Types of pipe
presently in use in sanitary sewer lines include
PVC (polyvinylchloride) and ABS (acrylonitrile-
butadiene-styrene). One type of plastic pipe that
has received recent attention is the so-called com-
posite "truss" type. Joints are obtained by use of
a sleeve-type coupling and chemical solvent welds
consisting of ABS in methyl-ethyl-ketone. Recent
10
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European practice has been to use plastic pipe of
exrremely long lengths without joints, in some cases
extruding the pipe on the jobe site to avoid shipping
problems.
Steel pipe is used for both gravity and force main
construction. Two types exist. Smooth wall welded
seam pipe with combinations of cement mortar and
coal tar coatings and linings and a variety of tight
jointing methods is used in pressure applications.
Corrugated galvanized steel with combinations of
asbestos bonding, coatings, pavings and smooth lining
and mechanical gasketed or "0" ring joints is used in
gravity sewer construction.
Vitrified Gay pipe is resistant to corrosion from
acids and alkalis and resists erosion and scour. It is
built in short laying lengths and therefore requires
more joints which can be subject to infiltration.
However, in the past few years application has been
made of a resiliant, flexible joint to clay pipe with
reported reduction of infiltration.
Table 2.3.1, Standard Specifications for Selected
Sewer Pipes Contains references to the American
Society for Testing and Materials (ASTM)
specifications and American Association of State
Highway Officials (AASHO) standard specifications
for various types of sewer pipe.
2.3.2 Sewer Jointing to Control Infiltration
So important is the effectiveness of sewer joints
for the control of infiltration that, axiomatically, no
sewer system is better than its joints. A good joint
must be water-tight, root penetration-tight, resistant
to the effects of soil and sewage, long-lasting, and
flexible.
Up to 30 years ago, cement mortar commonly
was used to make sewer pipe joints. As attention was
given to prevention of infiltration and root intrusion
into sanitary sewers, it became evident that mortar
was not a good material for this service. Such joints
were subject to shrinking and cracking; they were
rigid and tended to break loose from pipe bells and
spigots; they swelled because of hydrogen sulfide
action and caused the rupture of pipes; they were the
cause of root intrusion. To overcome these defects,
various forms of asphaltic compound joints came into
use. Some are hot-poured and others are pre-cast.
While these materials have desired characteristics,
they also require care and skill in application to
assure water-tightness.
Finally the compression-type gasket was
developed. It was first used on asbestos-cement pipe,
and then was found suitable for vitrified clay
by casting of a plastic ring on the spigot of the
pipe and a plastic lining on the bell of the pipe.
Compression-type gaskets were also made applicable
to concrete pipe. Manufacturers of plain and vitrified
clay pipes have developed a resilient or rubber-like
sleeve clamp for the pipe end in the form of a
non-corrosive metal band which makes a good joint
for plain end pipe.
The following types of joints are used in sewer
pipe service:
Cement Mortar is not recommended today. The
joints are rigid and tend to crack with any movement
or displacement of the pipe, including back-filling
operations.
Asphaltic or Bituminous joints have been and are
being used to overcome the objection to the rigidity
and failure of cement mortar joints. The
water-tightness of this type of joint will be affected if
such a joint compound shrinks away from the sides of
sewer pipe. In addition, the cementing with chemical
adhesives or solvents must be carried out with care to
achieve an adequate long-lasting seal.
Polyvinylchloride (PVC) and Polyurethane sewer
joints are in common usage with clay sewer pipe.
PVC, first utilized in the 1950's is cast both on the
spigot and in the bell of the pipe. Experience has
shown that because of dimensional changes of the
material a good water-tight seal cannot be assured
with PVC. Polyurethane has been found satisfactory
because of its high resilience. Clay pipe manufacturers
now provide pipe having a polyester compound cast
on the spigot and into the bell. A compression gasket
is used to make the seal between these surfaces, as the
spigot end is pushed into place inside the bell.
Compression Gasket joints have been in use for
over 30 years. Gasket components may consist of
natural rubber, synthetic rubber or various other
elastomeric materials. Compression-type joints are
used on asbestos cement pipe, cast iron pipe, concrete
pipe, vitrified clay pipe, and certain types of
composite plastic pipe. Demonstrations have shown
these to be the most effective seals against infiltration
into sewers; at the same time they provide for
deflection.
On most types of pipe the joint surfaces are
formed by the basic pipe material. These pipes use a
separate rubber gasket which acts as the sole sealing
element.
With vitrified clay pipe the joint surfaces are
formed by molding elastomeric material on the ends
of the pipe. This molded material may act as the
compression seal or may be used in conjunction with
a rubber ring gasket.
Chemical Weld joints are used to join certain
11
-------
types of plastic pipes and fiber glass pipes. This type
of joint has been reported to provide a water-tight
seal. However, neither plastic nor fiber glass pipe has
been used extensively, or for sufficient time to
demonstrate the longevity of this type of joint. As
mentioned under bituminous joints, some of the early
bituminous pre-cast welded in-the-field joints, which
used a solvent to effect the bonding of the pre-cast
bituminous material, required care in installation to
provide a complete seal throughout the circumference
of the joint.
Field practice indicates that the forming of a
joint at the bottom of a sewer trench is not
performed under the most ideal conditions; jointing
under such in-the-wet and often difficult-to-see
circumstances does not lend itself to precise and
careful workmanship. A type of joint which need
only be assembled in the trench, rather than formed
under such adverse conditions, would offer a desired
characteristic to prevent infiltration.
2.3.3 Effect of Subsurface and Ground Water
Conditions on the Selection of Pipe Joints
All soils, with the exception of soft organic
materials, will safely support a sewer installation as
long as no additional loads are being added. The
required strength of the pipe therefore is based on the
weight of the soil above the pipe and the method of
backfilling the trench. Under these conditions the
choice of joint type should not necessarily be
influenced by the soild type.
Immediate or future additional loads on the
pipe-supporting soils, however, can create
considerable differential settlements, resulting in
structural failure of pipes and joints and cause
infiltration or exfiltration depending on ground water
level. Examples of such loads are roadway
embankments next to or over the sewer line and
heavy foundations. A special case is sewer lines
constructed in man-made fill which are placed on
compressible soils. Such fills, increasingly used in the
reclamation of swamps and coastal land as well as
over solid waste disposal areas, can settle for many
decades. Most differential settling problems have
arisen from improper bedding and failure to replace
inadequate subgrade materials.
The magnitude of such settlements, varying from
fractions of an inch to several feet, defies standard
solutions and requires extensive soils explorations,
testing, and expert evaluation. Low magnitude
settlements can sometimes, but only after careful
study, be handled by the proper selection of pipe
strength and flexibility and the use of joints which
permit a certain amount of alignment change without
distress or loss of seal. The selection of the joint may
also be based on its shear transmitting capability as
differential settlement causes shear to be transmitted
through the joint.
A chemical analysis of ground water is
mandatory where the sewer will be installed at or
below ground water or in rock or tight clay because
the trench may act as an aquifer. The proper selection
of pipe materials and joints depends on these tests
and will prevent deterioration of the system and
subsequent infiltration.
2.4. DESIGN CRITERIA FOR NEW SEWERS
2.4.1 Type of System
There are many existing combined sewer systems.
Recent surveys, however, have indicated there is no
significant amount of new combined sewer
construction. In combined sewer systems, infiltration
and inflow tend to cause more frequent and
prolonged combined sewer overflows. Such flows in a
separate sanitary system may make the system
inadequate and, in effect cause it to simulate the role
of a combined sewer since it carries so much ground
water admixed with sanitary sewage.
It is assumed that the ultimate goal of every
sewer administrator is to design, construct, and
maintain his sanitary system in a way that will subject
as little excess water as possible and feasible. The cost
and -inconvenience of parallelling existing lines and
building larger treatment plants are more than
adequate justification for providing tight sewer
systems. Over and above such economic
considerations, many jurisdictions and industrial
wastes producers are being ordered to cease pollution
which may be induced or aggravated by excessive
infiltration. The aim, therefore, is to realize the
ultimate capabilities of the sewer construction
materials available.
2.4.2 Design Allowance for Infiltration/Inflow
A review of current practice in the use of
infiltration design allowances by design engineers has
revealed the need for standardization of terms and
units used in this field. This allowance is made in the
form of volume per unit of time and is added to the
design flows of domestic sewage and industrial
wastes. The total of all such flows at their peak is
used to establish pipe and waste water treatment
plant unit sizes.
The peak design flow is the maximum daily rate
of flow resulting from highest usage during certain
hours of the day, days of the week, and weeks of the
12
-------
year. It is based on the principle that at some specific
moment water and waste water flows will be at peak
volume because of the accumulation or combination
of maximum usage conditions. But it may never
actually occur. A number of state water pollution
control agencies stipulate peak design flow as a
specific volume or quantity per capita. The following
tabulation, Table 2.4.2, lists design flows required by
some states and provinces.
Other jurisdictions have developed peak rate
curves. Figure 2.4.2.1 is the rate chart used by
Washington, D. C.
Peak design flows must be examined carefully by
the design engineer to avoid the excessive impact and
importance of infiltration/inflow volumes. There has
been too great a tendency on the part of designers
and their design standards, as illustrated by Table
2.4.2 to lump all extraneous flows into some vague
TABLE 2.4.2
DESIGN FLOWS
DESIGNATED BY STATE REGULATIONS
Alberta
1) Maximum hourly flow =
/ 14 \
average daily x 11 + ' fi I
\ 4 + P '
when P = population in thousands, range of
maximum hourly flow is from 2 to 4 times
average daily
2) Per capita average daily flow =100 gallons.
Illinois
1) Laterals and sub mains—400 gallons per
capita per day.
2) Main, trunk and outfall sewers — 250 gallons
per capita per day.
3) Per capita average daily flow =100 gallons.
New Jersey
1) Sewers designed to carry at least twice the
estimated average design flow when flowing
half full.
2) Per capita average daily flow =100 gallons.
New Hampshire
1) All sanitary sewers shall be designed to carry
at least four times the estimated average
design flow when full.
2) Interceptors shall be designed to carry at
least two and one-half the average design
flow when full.
3) Per capita average daily flow =100 gallons.
Oklahoma
1) Laterals and submain sewers designed for
400 gallons per capita per day when running
full.
2) Main, trunk, interceptor and outfall sewers
shall have capacity of at least 250 gallons per
capita per day when running full.
3) Per capita average daily flow =100 gallons.
4) The 100-gallons-per-capita-per-day figure is
assumed to cover normal infiltration, but an
additional allowance should be made where
conditions are especially unfavorable. This
figure likewise is considered sufficient to
cover flow from cellar floor drains, but is not
sufficient to provide any allowance for flow
from foundation drains, roof leaders, or
unpolluted cooling water, which should not
be discharged to sanitary sewer systems.
Oregon
1) Because usually it is impossible to exclude all
ground water infiltration, it is recommended
that the capacity of sanitary sewers when
flowing full be equivalent to at least 300
gallons per capita per day and preferably 350
gallons per capita per day on the basis of
total estimated future population. Trunk and
interceptor sewers should in general have
capacities equal to at least 250 gallons per
capita per day.
Pennsylvania
1) Laterals and submain sewers—400 gallons
per capita per day. Main, trunk and outfall
sewers - 250 gallons per capita per day.
2) Per capita average daily flow =100 gallons.
Tennessee
1) Laterals and submain sewers—400 gallons
per capita per day. Main, trunk and outfall
sewers - 250 gallons per capita per day.
2) Per capita average daily flow =100 gallons.
Texas
1) Laterals and minor sewers shall be designed,
when flowing full, assuming flows equivalent
to four times average daily flow. Main trunk,
interceptor, and outfall sewers shall be
designed when flowing full, assuming flows
of 2.5 times the average daily flow.
2) Per capita average daily flow = 100 gallons.
Utah
1) Laterals and submain sewers — 400 gallons
per capita per day. Main, trunk and outfall
sewers - 250 gallons per capita per day.
2) "Per capita average daily flow = 100 gallons.
13
-------
FIGURE 2.4.2.1
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S::::::::E::::: = :5
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14
-------
multiplier for an assumed average daily flow. Actual
infiltration and inflow can vary tremendously from
jurisdiction to jurisdiction, e.g., from a minimal 10
percent of sanitary flow to 100 to 200 percent. Each
designer must evaluate the conditions existing in his
area and not simply use a convenient and
unsubstantiated design allowance. Without careful
examination of local conditions and the
establishment of realistic design criteria, the system
may be seriously over- or under-designed. In the first
case public funds are being wasted; in the second,
overload problems will plague the system. The design
engineer must never abdicate his responsibility to
produce a workable design for his project based on
thorough examination of all conditions present. No
reference manual can delineate all of the situations he
will encounter.
As previously discussed, the ideal goal in sewer
system and waste water management is to prevent the
entry of all waters which do not require treatment
and thereby keep associated sewer system costs at a
minimum and reduce environmental pollution.
Ideally, there should be little need for design
allowances in such a perfect system. In practice,
however, there always will be at least a small
increment of infiltration which it is usually not
economically feasible to find and correct. The fact
that it is not usually economical to either locate or
eliminate all infiltrations is important; this must be
recognized in the early planning stages.
In addition, since a design allowance covers both
infiltration and inflow, a considerable variation of
inflow can be effected, depending on the
effectiveness and permissiveness of local jurisdictional
control with respect to sewer-use ordinances and their
enforcement.
In the past some sewer designers have used such
flow units as gallons or cubic feet per acre per day.
However, this terminology was based on the old
concept of storm and combined sewer design. Since
an attempt now is being made to eliminate or
minimize all excess water intrusions, allowances for
them should be keyed to actual flow records or
estimates from sources of flow such as per capita or
per dwelling unit. Sometimes infiltration/inflow rates
are assumed as a percentage of the per capita flow, as
indicated by water use and recognized standards.
Such determinations may be adequate for overall
systems planning but are not sufficient for detailed
final design.
An accurate estimate of infiltration/inflow
allowances should be divided into two basic
components:
a. Infiltration Component
Since infiltration is related to tightness of
pipe and manholes, any design allowance
should be correlated with the maximum
allowable construction infiltration
allowances. While the full discussion of
construction allowances is contained later in
this section, it is sufficient to note that any
amounts of permitted infiltration must be
recognized in the design. In effect, then, the
construction infiltration allowance on the
project, including building sewers, becomes
the infiltration component of the design
allowance.
b. Inflow Component
Where a new sewer system is being designed
in a jurisdiction that forbids the introduction
of any ground, storm, or clean waters and
where enforcement is complete and effective,
there would be no inflow component. Such a
system is difficult to achieve; and to do it the
following inflow sources would have to be
prohibited and enforced:
1. Roof downspouts,
2. Foundation drains,
3. Basement drains,
4. Basement sumps and or capped
clean-outs,
5. Sump pumps,
6. Areaway drains,
7. Driveway drains,
8. Yard drains,
9. Street drains, and
10. Perforated manhole covers in areas
of potential flooding.
Since initial achievement and continued
realization of such restrictions are not completely
realistic, the inflow component must be varied and
tailored to fit the individual local situation. In terms
of an average per capita sanitary contribution of 100
gallons per day, an inflow component of five gallons
per capita per day might be chosen.
When local regulations permit connections of
"clean water" to the separate sanitary system and
cannot be tightened by any amount of logic and
persuasion used to convince local officials, the design
engineer should develop inflow or storm water
allowance curves for the system. These curves result
from studies of permitted inflow in terms of paved
areas per dwelling unit or per person and in
consideration of a certain maximum storm toleration.
Figure 2.4.2.2 is an intensity-duration frequency
curve developed by the Washington, D. C., Sanitary
15
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INTENSITY - DURATION - FREQUENCY RAINFALL CURVES
10
Fefr.28, 1957
o:
:D
o
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o:
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LU
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N \
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25 YR.
15 YR. FREQUENCY t =
- eoa/t
66.6
I3.2)0-75
— 10 YR.
y—SYR. ^-2YR. /-I YR.
-U.S.
VEATHER BUREAU (MINIMUM OF SPECIAL INTEREST)
o
3)
m
k»
ki
10 15 20 25 30 40 45 60
DURATION OF RAINFALL IN MINUTES = t
80
90
-------
Engineering Department, which has selected the
15-year storm as the design storm. Figure 2.4.2.3,
also from Washington, D. C., shows the storm water
allowance curves for this storm falling on various
acreage areas with varying population densities. These
represent an attempt to correlate lot or plot area with
population. A straight-forward use of infiltration or
inflow criteria on strictly an area basis becomes
meaningless when population development or
potential development is ignored.
The Washington, B.C., charts are useful as an
illustration of the concept of inflow component
allowances. However, they also incorporate a flat
700-gallons-per-acre-per-day figure representing
yearly average flow of ground water infiltration. Such
an assumption does not take into account varying
Table 2.4.2.1
Illustration of Design Infiltration/Inflow
Allowance Calculations
Assumed Conditions:
Area -1200 acres
Population Density - 20 persons per acre
Total population - 24,000
Separate Sanitary System -
4-inch building sewers - 36 miles
8-inch street laterals - 24 miles
10-inch sub-trunks - 6 miles
12-inch trunk - 6 miles
Average daily per capita sanitary contribution - 80
gallons
Peak design flow - 4 times average daily flow
Example 1 - Tight System with No Permitted Inflow
Additional assumptions -
Construction Infiltration Allowance = 100
gpimd
Maximum Inflow = 5 gallons/capita/day
Infiltration Component =
400 gpmd x 36 miles = 14,400 gal/day
800 gpmd x 24 miles = 19,200 gal/day
1000 gpmd x 6 miles = 6000 gal /day
1200 gpmd x 6 miles = 7200 gal/day
Total Infiltration Component =
46,800 gal/day
Inflow Component = 5 gpcd x 24,000 = 120,000
gal/day
Total Infiltration/Inflow = 166,800 gal/day
Peak Design Flow = 80 gpcd x 24,000 x 4 =
7,680,000 gal/day
Total peak Design Flow = 7,846,800 gal/day
lengths of pipe, population densities, and types of
buildings. Four hundred people per acre in high-rise
apartments would produce considerably less
infiltration potential than 400 people in 100
single-family homes on one-half acre lots. However, in
a combined system such as in Washington, D. C.,
which also permits outside areaway drains, the
infiltration load is less significant.
The following examples illustrate the use of
design infiltration/inflow allowances and the varying
impact on resultant flows. These may or may not
apply to conditions existent in other jurisdictions. A
basic design assumption is that infiltration and inflow
represent additional volume, over and above the peak
domestic flow of four times the average daily flow.
Table 2.4.2.2
System Slightly Less Tight and Some
Areaway Drains Permitted
Additional assumptions -
Construction Infiltration Allowance = 500
gpimd
Inflow Calculated from Washington, D. C.,
Stormwater Allowance Curve, Figure 2.4.2.3
Infiltration Component -
2000 gpmd x 36 miles = 72,000 gal/day
4000 gpmd x 24 miles = 96,000 gal/day
5000 gpmd x 6 miles = 30,000 gal/day
6000 gpmd x B miles = 36,000 gal/day
Total Infiltration^
Component =234,000 gal/day
Inflow Component (from figure 2.4.2.3 =
6,000,000 gal/day
Total Infiltration/Inflow = 6,234,000 gal/day
Peak> Design Flow = 80 gpcd x 24,000 x 4 =
7,680,000 gal/day
Total Peak Domestic Design Flow = 13,914,000
gal/day
The two preceding examples not only illustrate
the methods for arriving at peak design flows; they
also show how in the same theoretical design area
seemingly small variations in design criteria can effect
great differences in flows and pipe sizes.
In Example 2, the increase in allowable
construction allowance - from 100 to 500 gallons
per mile per day per inch diameter — raises the total
infiltration from 1 to 5 percent of the sanitary flow.
In terms of actual volumes the 500-inch-gallon
allowance, which is prevalent at this time, would
permit a maximum of 85.50 million gallons of
17
-------
BO Persons per acre
4Q Persons per acre, or more
20 Persons per acre
Note -that scales are nof -the same as be/ow
4O 50
Net area, acres
NOTE-
The allowance shown is based on -the
estimated runoff for a 15-year frequency
Storm, with a runoff coefficient of 0.9O,
for the following imperrious surfaces:
Impervious surface,
ft. per
t/7
146
179
2/0
DISTRICT OF COLUMBIA
DEPARTMENT OF SANITARY ENGINEERING
Note: For areas larger than /O,OOO
acres, either use the indicated
allowance per acre (gad.) for
IO,OOO acres or give special
consideration fo ihe area.
STORMWATER ALLOWANCE
FOR DESIGN OF SEPARATE SEWERS
See above for areas from O fo I0O acres
1,000
2,000
3,OOO
4,000 &floo 6,000
Nef area., acres
7,000
-------
extraneous water per year.
The most striking change in extraneous water
flow occurs in the inflow component of Example 2
utilizing the Washington, D. C., design curves for
storm water (inflow) into separate sanitary sewers. In
this case the inflow alone is 6 mgd which almost
equals the peak sanitary design flow and dwarfs the
infiltration component even in its increased
condition.
These illustrative examples are over-simplified in
order to emphasize the impact of differing design and
construction allowances. In actual practice pipe sizes
would be varied according to the design flows in a
slightly more involved procedure.
2.4.3 Manhole and Cover Design
Brick and block manhole construction methods
no longer are applicable, becuase of the reduced
availability of skilled masons in the sewer
construction field and the vulnerability of mortar
joints to corrosion and leakage. Precast manholes,
properly joined with rubber gaskets or sealing
compounds, have alleviated the problem. In recent
years the development of custom-made precast
manholes with pipe stubs already cast in place has
reduced *the problem of shearing and damage of
connecting pipes. They have also reduced the leakage
difficulties associated with breaking into a precast
manhole to insert the pipe line and then making an
adequate water-tight seal around the pipe. The use of
flexible connectors at all joints adjacent to manholes
reduce the possibility of differential settlement of the
manhole and the shearing of the connecting pipes.
The design of the joint between the precast
manhole sections and brick courses used to reach
grade, and the joint between the manhole ring and
the balance of the structure should be given special
attention. The details of these joints are seldom given
by designers, although if water follows the trench, or
the street sub-grade considerable hydrostatic forces
may be present and infiltration will occur.
The bedding and foundation beneath a manhole
also is a vital part of preliminary investigation and
design. All parts of the sewer system must maintain
their integrity and proper inter-relationship to sustain
a tight system.
Manhole cover design is attracting more serious
attention in view of evidence that even small
perforations can produce sizeable contributions of
extraneous inflow. It has been estimated that a single
1-inch hole in a manhole top covered with 6 inches of
water may admit 11,520 gallons per day; this exceeds
the infiltration or the inflow components in Example
1 of sub-section 2.4.2. Obviously, manholes that are
in areas subject to flooding should have solid, sealed
covers. Such covers, however, often prevent adequate
ventilation of the manhole and sewer, posing danger
to maintenance employees. Thus, the design of
sections requiring sealed covers should be given
special care. Maintenance employees should check all
manholes for hazardous gasses prior to entering.
2.4.4 Practical and Maintainable Design
Recent investigations into sewer design problems
have revealed a serious lack of understanding and
communication between design engineers and
maintenance personnel. There are many sewer
maintenance superintendents who are struggling with
problems caused not only by inadequate hydraulic
design but also by impossible physical structures with
extended lengths of pipe, omitted manholes, curved
lines on difficult radii, and inaccessable chambers.
Such maintenance problems result in inadequate
maintenance and unauthorized overflows, and usually
prevent rapid and adequate infiltration and inflow
surveys.
The sewer system cannot be buried and
forgotten. Every effort must be expended to
guarantee its maximum useable and economic life.
2.5 CONSTRUCTION METHODS AND
INSPECTION
2.5.7 Construction Considerations
The most critical factor relative to the prevention
of infiltration in new sewers is the act of
construction. All of the currently manufactured pipes
and joints are capable of being assembled into sewer
systems with minimal infiltration. This capability
must be coupled with good workmanship and
adequate inspection. The following items represent
some of the more important factors which relate to
infiltration control:
2.5.1.1 Construction Contract Documents
Related to Soils and Ground Water
Soils and ground water information used in the
design must be made available to the construction
contractor. These data are required to evaluate the
need for or the design of sheeting, dewatering,
borrow material, and a number of other
considerations which influence the estimate of his
costs. Since the nature of soils and location of ground
water anticipated is of prime importance for sewer
work, all subsurface information obtained should
form a part of the contract documents. Each
subsurface exploration should be clearly located on
19
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an overaD site plan since the data obtained from the
exploration is directly applicable to that particular
area. Care should be taken to avoid possible
misinterpretation or misrepresentation. For example,
ground water table elevation should be accompanied
with the date of such observation; soil and rock
profiles developed from subsurface explorations
should reflect extrapolation between investigation
locations and present the conditions most likely to
prevail. The widely used exculpatory notes which in
effect say, "We are not responsible for any
information supplied to you, Mr. Contractor", may
not be acceptable in a court of law and may result in
higher bid prices due to the contrator's uncertainty as
to what he will encounter.
2.5.1.2 Trenching and Excavation Methods
Trenches should be made as narrow as possible
but wide enough to permit proper laying of pipe,
inspection of joints, and consolidation of backfill.
Depending on the type of soil, space available, ground
water level, length of time the excavation is to remain
open, and depth of excavation, the slopes are
constructed as steeply as they will stand without
caving. In some areas a minimum slope of 1:1 is
specified or the placing of shoring in a vertical trench
is required. For deep excavations, particularly below
ground water table, the excavation should be braced
or sheeted to provide safe working conditions.
Construction should be accomplished in dry
conditions and thus, if water is encountered in the
excavation, dewatering should be done by sump
pumping, use of well points, or deep wells.
2.5.7.5 Bedding and Backfill
Trench excavation is done by hand or by
machines, depending on location and magnitude of
excavation necessary. For most trenching work,
excavation by machine is more economical and
efficient. Machines particularly adapted to sewer
trench excavation are continuous bucket excavators,
overhead cableway or .track excavators, power shovels
or backhoes and boom and bucket excavators. Figure
2.5.1.3, Bedding for 84-Inch Interceptor, is a
photograph of the bedding prepared for an 84-inch
concrete pipe laid on a curvilinear alignment.
Depending on ground water location, types of
soil, depth of excavation, available space and length
of time the excavation is to remain open, it may be
necessary to install sheeting or bracing to prevent
caving of the banks and prevent or retard entrance of
ground water into the trench.
2.5.1.4 Backfill and Bedding Material
Backfill directly around the sewer pipe should be
selected material. Compactable material should be
used around flexible pipe. The remainder of the
backfill generally is governed by the type of material
initially excavated. Figure 2.5.1.4, Placement of Rock
Bed, is a photograph of the placement of rock
bedding for a large (72-inch) interceptor. Frozen
earth, rubbish, old timber, and similar materials
should be avoided where permanent finished surfaces
are desired because they decompose or soften and
cause settlement. Differential settlements can lead to
ground water infiltration because of cracking of the
sewer or opening of the joints.
Depending primarily on the location of the sewer
and the anticipated development of the area,
specifications may require a specific gradation for
backfill material as well as definite compaction
requirements. In this case, the proposed fill must be
laboratory-tested to determine its gradation and
compactive characteristics.
In some instances materials with high void ratios
(such as trap rock or clam shells) produce a water
course around the pipe. It is extremely important
that pipe installation and inspection be carefully
performed to preclude heavy infiltration from this
aquifer.
Bedding material is that which forms the
foundation for the sewer. It may be original ground,
concrete, sand, or gravel, depending on the nature of
the soils present. Improper or non-uniform bedding
can result in settlements which subsequently cause
infiltration.
Specific information for backfilling and bedding
of various types of pipe are available from individual
pipe companies or associations.
It is obvious that the installation of backfill and
bedding can affect the infiltration characteristics of
the pipe. ASTM, ASCE and other references contain
installation practice instructions which, when applied,
will help produce tight pipes.
2.5.1.5 Compaction Techniques
Regardless of location, the most critical area with
respect to compaction is directly around the sewer
pipe. The backfill is placed and packed by hand under
and around the pipe being compacted by light hand
tampers. As backfilling is continued to original
surface level, compaction is achieved by machines.
The entire trench width must be compacted.
Depending on the size of excavation to be filled,
compacting equipment will range from hand operated
20
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FIGURE 2.5.1.3
BEDDING FOR 84-INCH INTERCEPTOR
Courtesy: United States Concrete Pipe Co.
-------
FIGURE 2.5.1-4
PLACEMENT OF ROCK
INCH INTERCEPTOR
Courtesy: United States Concrete Pipe Co.
22
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compactors to large rollers.
2.5.1.6 Dewatering Techniques
Excavation can be dewatered by sump pumping,
a well point system, deep wells, or soil solidification.
Pumping from sump pits is most widely used for
shallow excavations when the quantity of water is
small and the water table need not be lowered any
great distance. Well point systems and deep wells are
more complex and should be designed by an engineer.
It should be pointed out that in any wellpointing
procedure caution should be exercised in assuming
that the ground water table will be restored after
construction at the same rate or in an equal period of
time that it took to draw the water down. This
procedure will prevent any sudden "surge" of water
which could conceivably exert enough force to cause
disruption of new construction.
2.5.1.7 Construction Inspection and Testing of
Soils, Bedding and Backfill
Infiltration of groundwater into a proposed sewer
system can be minimized by proper construction
procedures, rigid inspection of materials and methods
of installation, and performance of soil and ground
water t&sts. To elaborate:
a. Field Inspection of Excavation,
Bedding and Backfill
Construction procedures and materials
should be inspected for conformance with
project plans and specifications. Rigid
inspection is mandatory.
b. Field Son Tests
Field soil testing is used in conjunction with
controlled backfill. When specifications
require backfill to be compacted to a high
percentage of maximum density, in-situ field
density tests are performed to determine if
such compaction is achieved. The most
common means of field density testing are
the Sand Cone Method and Rubber Balloon
Method, both yielding a field density to be
compared with laboratory maximum density
in order to monitor degree of compaction.
c. Laboratory Testing
For projects specifying a particular gradation
requirement for trench backfill or bedding,
the proposed material should be subjected to
a sieve and/or hydrometer analysis. Further,
a compaction test should be performed if
specifications call for a required degree of
compaction.
2.5.2 Construction Infiltration Allowance
One of the most effective ways to control
infiltration, and at the same time measure the quality
and condition of the new system, is to establish a
maximum infiltration rate. A national survey of
agencies and consultants revealed that although the
most commonly used allowance is 500 gallons per
mile per day per inch of sewer diameter
(inch-gallons), there is a definite trend in the
direction of lower limits. Pipe manufacturers
consistently claim that the rates of 250 gallons per
mile per day per inch diameter or less are readily
attainable.
In 1950 the Clay Pipe Engineering Manual
recommended a construction infiltration allowance of
1500 inch-gallons. The 1968 edition recommends no
more than 500 inch-gallons, indicating the improved
techniques now available. The Water Supply and
Pollution Control Commission of New Hampshire
places a 300 inch-gallon maximum on infiltration.
In 1965 a survey by Public Works magazine
revealed that 50 percent of cities surveyed used the
500 inch-gallons allowance, but even at that time 40
percent used lower rates and 15 percent were actually
specifying a low allowance of 100 inch-gallons. A
survey concluded in 1970 revealed allowances as low
as 50 inch-gallons with a few "zero" allowances
reported. Anotherrecent fact-finding survey, carried
out by the New York State Health Department,
Division of Pure Waters, indicated that ^80 percent of
responding consulting engineers in the state believed
the 500 inch-gallon standard should be lowered; 30
percent of those favoring reduction recommended an
allowance of 200 inch-gallons. Twenty-five percent
suggested 100 inch-gallons; 28 percent, a 250
inch-gallon allowance.
It is apparent that a maximum construction
infiltration allowance for all types of pipe of 200
gallons per mile per day per inch of diameter
(inch-gallons) can be obtained without additional
construction cost. The economic benefits,
cost-benefit ratio, should be determined for requiring
lower construction infiltration rates.
Manholes are subject to infiltration leakage over
and above the inflow component entering sewers
through cover perforations. Although the
contribution is recognized, actual construction
allowances are not always utilized. The Clay Pipe
Engineering Manual states that manholes should be
tested for leakage and that this infiltration amount
should be deducted from any infiltration tests of the
pipe section. The exfiltration leakage allowance
23
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specified by the State of New Hampshire is 1 gallon
per day per vertical foot of depth. It stipulates, also,
there shall be no visible leakage due to infiltration
where the ground water table is high.
2.5.3 Inspection of Construction
The importance of adequate inspection during
construction cannot be overemphasized. Material,
time, and money usually can be saved by supplying a
fully trained inspector for all phases of sewer
construction projects. Deliberate malpractices and
unintentional mistakes can result in contravention of
the designer's intent and jurisdiction's desire to
provide a sewer system of dependability and long life.
An alert inspector pays dividends by requiring
strict adherence to job standards, but he should not
assume so active a role in the project that he
preempts the supervisory direction of the contractor.
If the contractor does not have adequate supervision
on the job, the inspector should report this to the
contracting authority and the project should be
suspended until such supervisory personnel are
available. The inspector and the field engineer
logically may be asked to interpret specifications, but
they cannot assume direction of, or responsibility for,
the contractor's forces. If too many questions arise
about the plans and specifications, the design
engineer should visit the site and reassess the
adequacy of these documents. The need for this type
of job contacts affirms the need for the design
engineer, whether employed by the jurisdiction or by
a consulting engineering firm, to keep in touch with
the project during construction. The inspector should
not be expected to make engineering design decisions.
The inspector should have basic responsibilities
for adherence to specifications; the accounting or
verification of quantities of material supplied, and
time spent on the project. He should be provided
with a log book and whatever other forms are
necessary to produce an adequate record of all
activities of the contractor's forces. He should
observe and record weather conditions and all other
occurrences and conditions that affect the quality of
workmanship. It is not necessary that the inspector
be a licensed professional engineer, but he should
report to a professional engineer who should appear
on the job frequently enough to answer all questions
of the inspector or contractor. The consulting
engineer or the municipal design engineer should
recognize that construction is the ultimate realization
of his plans. He should be well represented during this
crucial period.
During the course of interviews the best
inspectors were often described as retired contractors
or former job superintendents who provide maximum
practical experience and knowledge. They are familiar
with all of the "tricks of the trade," both good and
bad. They speak the language of the workers and
engender respect because they know what they are
talking about.
2.6 TESTING FOR ACCEPTANCE
Testing and inspection are at times confused and
considered to overlap; however, it should be made
very clear that these are two separate quality-control
functions. Each may depend on the other but neither
can substitute for the other. Although many
engineers depend on criteria other than resistance to
infiltration as the main factor in controlling the
design and construction of sewers, the chief method
of guaranteeing a properly installed and workman-like
job has been the use of what can be described as
infiltration tests. Even though infiltration may not be
considered a prime factor in design, it still is
considered the most effective measure of the quality
of sewer installation and conformity with job
specifications. The owner should provide the testing
services and such services should not be a part of the
contractor's contractual responsibilities. An
alternative to this procedure could be the inclusion of
the method or methods to be used as a bid item in
order to provide a basis for reimbursement for the
performance of such sewers by the contractor.
A number of testing methods were reported,
including the following:
2.6.1 Infiltration Testing
The infiltration test is the most obvious method
of determining the tightness of the sewer. If a sewer
line has been laid under the ground water table, it is
obvious that any clear water flowing through the
pipes prior to any house connections represents true
infiltration. Despite the fact that a large percentage of
sanitary sewers are laid below ground water table,
either in wet or dry seasons, there always is a
question as to what effect this will have on
infiltration rates, since the head of water above the
pipe will have a great bearing on the quantity of
water intruding into the conduit due to pipe and joint
defects. Infiltration tests consist simply of measuring,
through use of weirs, the amount of flow in a sewer
before any building connections are made.
Unfortunately, this test has been used in many
cases where there are great lengths of pipe involved;
under these circumstances it is impossible to draw
firm conclusions as to compliance with specifications
24
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in any specific manhole-to-manhole section. As a
matter of fact, using an allowance of 500 gallons per
inch of sewer diameter per mile per day, a nominal
300-foot manhole-to-manhole section would yield an
infiltration quantity of less than 0.106 gallons per
minute, which is hardly measurable. Infiltration
testing, therefore, has been utilized mainly on
relatively long sections of sewer lines; even in these
cases the test is open to considerable question.
The infiltration test never should be used in dry
ground, since it is applicable only when the static
head is above the crown of the pipe at the upper
manhole. In some instances the flooding of the sewer
trench, usually associated with the puddling of
back-fill, has been used to simulate a high ground
water condition. This synthetic condition may not
offer a real simulation of the actual immersion of a
sewer line in ground water.
Another disadvantage of the infiltration test,
since it involves such small quantities, is that a very
large section of a sewer project must be completed
before any meaningful test can be made. This means
that a number of manhole sections with broken pipes
and infiltration rates considerably over the allowance
could be included in the long stretch of pipe tested;
the effects of such defective conduit could be masked
by the sections of the system which are water-tight.
Thus, the defective sections may never be detected
and located for corrective action. It must be
concluded that actual infiltration testing by
flow-gauging have to be ruled out as an adequate
method for approving new construction, except
under favorable circumstances.
26.2 Exfiltmtion Testing
The reverse of measuring actual infiltration is to
fill a pipe with water and observe the loss of water
during a specified test period. This exfiltration
method is far more positive since it involves
subjecting the pipe system and the manholes to an
actual pressure test. However, the presence of ground
water outside of the pipe, the effect of slopes, size of
pipe, and other factors will affect the validity of this
test. Gravity sewer pipe is not expected to be a
pressure system. Cases have been reported where the
surcharging of new sewer lines for testing purposes
has resulted in fractured pipes and manhole sections
not designed for the pressure head developed during
the test period. Unfortunately, the pressure effects of
a head of water in an upper manhole can produce
destructive results in lower sections of the sewer
because of the effect on downstream bulkheads,
house connections, "hookups," and even sewer joints.
However, during the testing of manhole-to-manhole
sections, the exfiltration test has fewer hazards,
though it cannot locate small fluctuations in sewer
leakage.
This test should be used mainly in dry areas
where the ground water level is below the crown of
the pipe. Development of correlations of heads, sizes
of pipe, slope, and other factors must be considered
prior to exfiltration testing. Attention should be
given to the presence of house service plugs in
exfiltration test programs. The elevation of such plugs
will have a bearing on exfiltration heads, and the test
head must exceed the highest house service elevation.
The ability to use the exfiltration procedure on
small sections of pipe allows a very sensitive test,
since the water pressure in the section of pipe under
test can be related to the water level in the
hydrostatic tube inserted in the plug or in the
manhole. There is no specific correlation between the
water exfiltration test and infiltration which covers
all sewer system conditions. It may be assumed that
there is some, but an unknown direct relationship
between exfiltration quantities and the infiltration to
which the sewer will be exposed but if exfiltration is
to be the test method, there is a need for dependable
hydraulic criteria which will clearly establish this
relationship.
ASTM C-425 established as a guideline that when
there is more than 2 feet of head, 10 percent should
be added for each 2 feet of additional head to
correlate exfiltration to infiltration.
A disadvantage of exfiltration testing with water
lies in the problem of finding enough water to fill the
sewer section and then disposing of it after the test is
completed. Water is a precious commodity in some
regions during certain seasons of the year, and may
not be readily available for testing purposes. In
addition, the disposal of the large amounts of water
used in exfiltration testing or in creating high water
levels in a trench may produce undesirable
construction conditions. Appendix 10, Examples of
Specifications for Exfiltration Testing of Gravity
Sewers, lists several specifications which might be
used.
2.6.3 Air Testing
In the last few years air testing has been
developed to a point where it appears to be highly
promising as a method for determining
sewer-construction tightness. Its advantages include
the fact that the air is readily available and will cause
no problems with the construction process or in the
trench. Air testing provides the inspector and
contractor a monitor of the construction
workmanship as the installation proceeds.
25
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Air testing is carried out by plugging both ends of
the sewer in adjacent manholes and pumping a certain
amount of low-pressure air into the sewer section
under observation. The pressure attained is usually
within the range of 2 to 5 pounds per square inch. At-
testing normally is limited to pipe under 24 inches in
diameter. Above this size, special air testing
provisions are required such as testing only the
individual joint.
Research work and actual field experience have
demonstrated that the maintenance of such pressures
for certain periods of time are a positive indication of
the water-tightness of the sewer section. This test
method requires the use of a compressor and sealing
equipment. There is need for an acceptable
correlation between air testing and true infiltration,
and for correction of air-testing data for existing
ground water conditions. It is essential to establish an
accurate measure of the static ground water table at
each manhole before the test can be made and
properly evaluated. Air testing is being used because
it offers a quick and easy method for evaluating new
sewer sections for acceptance. This test does not
determine the tightness of manholes which must be
tested separately, nor does it indicate differences such
as misalignment and small cracks and failures that
may be compacted from the outside with a tight soil
and would thereby pass the air test and yet be
deficient in structural integrity.
Appendix 9 contains typical specifications for
low pressure air testing of sewers for infiltration
control.
2.6.4 StUI Photography
Photography, including colorslides,
stereo-photos, etc., can provide a record of the
condition of new sewer lines. Its use is primarily for
new construction, since line conditions generally
allow an adequate view of defects as is true with TV
inspecting. It serves as an aid to the inspector by
providing a record of sewer construction
workmanship. It may reveal faulty joints or broken
pipe.
2.6.5 TV Testing
Television testing is a misnomer since television
is, more accurately, a method for observing the
condition of the interior of sewer pipes. For new
pipes, television detects cracks and other defects not
detected by other means of testing because the defect
had been packed with clay during backfilling. Efforts
have been made with some success to estimate actual
infiltration flows observed in television studies. TV is
also useful in the detection and eventual correction of
infiltration problems in existing sewer systems. After
building sewers have been connected, and the sewer
system is in use, infiltration, exfiltration, and air
testing cannot be used. TV appears to have the
following advantages:
a. Instantaneous viewing is permissable. If a
sewer line, new or old, cannot be viewed, this
is immediately discernable. Where lines are
restricted, causing sand or other debris to
cover the lens of the camera, flooded dips in
the lines, misalignments, and other such
deficiencies can be determined immediately.
b. "Development of Pictures" is not necessary.
Therefore, there is no delay in making a
decision especially where time is of the
essence.
c. Several people can "view the line" together
on the spot. In addition it is possible to take
video recordings off the screen in order that
permanent records can be made by means of
a Polaroid or a 35-milimeter camera. Sound
recordings onto the video tape are made at
the time of recording to specifically identify
the place, the time and the conditions found.
This saves unnecessary narration or
eliminates later questions as to areas or
conditions.
d. With the use of TV it is possible to limit
picture records to specific defects and those
areas that typify the general condition of
pipe free from defects.
e. TV provides the only means by which
moving water can be observed. In addition,
water of infiltration from house services that
are noted to be running, can be properly
evaluated by TV viewing. When a house
service is noted to be running, a check of the
building itself is possible to determine
whether the flow is, in fact, domestic flow or
water of infiltration. TV has certain
disadvantages:
a. Operation of the equipment requires a highly
qualified electronic technician.
b. Evaluation of TV reports, especially in the
case of infiltration studies, requires the
services of a skilled or specialized
professional engineer if optimum results of
the study are to be achieved.
2.6.6 Smoke Testing
Smoke is not an acceptable method of detecting
infiltration points. However, it has been used by some
26
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of the surveyed communities, and a number of
engineers feel it is effective in locating sewer cracks,
defective joints, and direct connection of a sanitary
sewer to a storm sewer. In this case, a smoke
generating unit is placed in a manhole with a blower,
and the smoke can be observed coming out of the soil
wherever there is a leak. It would appear to be a
method that has limited application on lines that are
seriously damaged or have been installed very poorly.
Smoke tests are useful in locating sources of inflow
waters which enter sewer systems through pipe
connections which are not trapped such as roof
downspouts. Where a high-water table is present, the
smoke will be absorbed by the overlying water.
2.6.7 Visual Observations
In large size sewer lines, and also by the use of
certain types of mirrors and lights in smaller sewers, it
is possible to inspect visually certain pipe lines.
Except in the case of large size pipe it would appear
that other methods of inspection are more
productive. In any case, this is not a quantitative test
of sewer conditions.
2.6.8 Conditions For Acceptance Tests
Another aspect of testing is the final acceptance
of a sewer line after construction. It is almost a
universally accepted fact, although not always so
practiced, that new sewer construction should be
tested and accepted in as short sections as feasible. It
becomes extremely difficult to assign responsibility
for correction of new sewer lines if building
connections have been installed since tests can not be
made properly after these connections. In addition,
the crucial role of the building sewer must be taken
into consideration; the sewer contractor cannot be
held liable for any inadequacies of plumbing
contractors who usually lay at least part of the
building connection line. If new sewer lines are tested
section by section and before connections are made
for final acceptance, the sewer contractor can be held
responsible for excessive infiltration rates which are
found and evaluated by effective methods of testing.
2.7 CORRECTIVE MEASURES
Testing prior to acceptance may indicate that
sections of the system do not meet the required
infiltration standards. The decision then must be
made as to whether or not the defective sections must
be excavated and replaced or repaired, or whether
internal sealing will be allowed. Where the defects are
not extensive, internal sealing generally will tighten
up the pipe to meet specifications. Excavation, on the
other hand, often results in the breaking of adjacent
joints.
The feeling that an internally sealed pipe is "less
than new" has led to the replacement of defective
sections. However, a realistic evaluation of the costs,
problems, and possible additional effects on the pipe
may indicate that the project specifications should
require or allow the contractor the option of such
sealing for minor defects when in the opinion of the
inspecting engineer there are no structural
deficiencies in the barrel of the pipe. Internal pipe
grouting can be a permanent solution if the technique
is applied in accordance with engineering principles
that consider the type of soil being grouted and the
nature of the defects being evaluated.
2.8 BUILDING SEWER STANDARDS
2.8.1 Jurisdiction and Control
Building sewers are the means of connecting
in-structure plumbing and drainage lines to street
sewers. They are the link between the production and
sources of sewage, commercial wastes, industrial
process waters, and the facilities provided by local
government for the removal and treatment of waste
waters. Building service conduits, which act as the~
bridge for the gap between the structures served and
the sewers which perform this service, represent a
vital gap in regulation and control. The portion of the
building sewer beween the structure and the property
line constitutes one part of the connection, while the
portion between the property line and the public
sewer in the street line completes the connection.
Reference is made to these two portions of
building sewers because separate parts have been
constructed and connected under the control and
supervision of separate governmental agencies. The
connection to the building plumbing and drain
system that extends to the property line often is
interpreted as an extension of the structure facilities,
is ordinarily installed under plumbing or building
code regulations, and tested and approved by
plumbing officials or building inspectors. The section
of the building sewer between the property line and
the street sewer, including the connection thereto,
usually is installed under sewer rules and inspection;
approval is within the purview of public works or
sewer officials.
One exception to this rule of split authority
often occurs in the case of industrial wastes
connections. Because of the effect of such wastes on
sewer structures and treatment facilities, the entire
length of these building sewers may be supervised by
sewer officials. This procedure gives them better
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control of such connections and the introduction of
wastes, when ruled to be amenable to sewer
transportation and treatment.
Building sewers play a vital role in the overall
infiltration and inflow volumes carried by separate
sanitary and combined sewer systems. This split in
authority impedes total control over building sewer
construction, testing and acceptance under present
circumstances when unified action is most needed.
Contributing to potential entry of infiltration water
into sewer systems are the relatively short lengths of
house sewer run, the multiplicity of these lines in any
given stretch of collection sewers in heavily built-up
urban areas, and the fact that each connection line
has two physical connection points — one at the
building line and the other at the junction with the
public sewer. One control agency should supervise the
building sewer as a single source of infiltration.
2.8.2 Codes, Construction and Testing
Regulations governing building sewers are often
contained in building or plumbing codes. They
represent a considerable range of interest and control.
Many codes make no reference to foundation drain
connections, although many make the distinction
between the building sewer and the building storm
sewer. A number of codes still permit various area
drains to be connected to the building sewer.
Most plumbing codes permit a wide range of
materials to be used, although some of the most
recent ones are more restrictive. A few codes require
the building sewer to be tested usually by holding a
10-foot head of water for 15 minutes with no
allowable leakage. Air testing is mentioned as a test
procedure, mainly on the interior system although
the building sewer also can be tested. Smoke tests
also can be used as the pipe lies in the trench before
backfilling and connection to the lateral. Small
defects are then readily apparent.
Because of the potential severity of the
infiltration and inflow contribution of building
sewers, they should be constructed of top quality,
water-tight materials with thorough inspection and
testing. The physical connection to the street lateral
sewer should be performed by the sewer agency or
department crews after careful training and
inspection.
Section 4 of this Manual gives specimen portions
of sewer-use ordinances that relate to prohibitions of
certain types of building connections and stipulate
the types of wastes which must be excluded from
public sewers. Other code excerpts involving
industrial process wastes and commercial operations
wastes are contained in Section 9 of this Manual.
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SECTION 3
CORRECTION OF INFILTRATION CONDITIONS
3.1 Objectives
3.2 Identify Systems
3.3 Identify Scope of Infiltration
3.4 Physical Survey of Sewer Systems
3.5 Economic and Feasibility Study
3.6 Sewer Cleaning
3.7 Television and Photographic Inspection
3.8 .Restoration of the Sewer System
3.9 Treatment Plant Design Criteria
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SECTION 3
CORRECTION OF INFILTRATION CONDITIONS, EXISTING SYSTEMS
The correction of infiltration involves a lengthy,
systematic approach or plan of action. The haphazard
deployment of investigative devices and sealing
equipment is ineffectual and extremely costly.
Interwoven with correction is maintenance.
Preventive Maintenance that restores the full capacity
of the pipe will permit the sewer to take the full
capacity for which it was designed, including
infiltration waters, and will, therefore, reduce the rate
of surcharge in upstream manholes.
There must be an orderly plan of approach when
investigating infiltration conditions. Excessive
infiltration is occurring and when it is determined
where visual inspection is needed, sewer cleaning is an
important consideration because of the cost and time
involved. It is impossible to run a camera through a
sewer that has restricted flow due to sand deposits or
other debris. Cleaning serves to produce the
maximum available carrying capacity in the sewer
pipe. Sewer cleaning will dictate the rate at which
inspection can be accomplished in accordance with
the availability and capability of the sewer cleaning
crews. The following general procedure for the
inspection of infiltration conditions is an adaptation
of a program developed by American Pipe Services,
Minneapolis, Minnesota.
3.1 OBJECTIVES
The first step in analyzing the extraneous water
problem is to define that problem as clearly as
possible. Before retaining consultants and sewer
service organizations, the public works director
should review and evaluate such questions as:
1. In what condition is the system?
a: How can this be determined?
b. What will it cost to determine the
condition?
2. Is there an infiltration/inflow problem?
a. How large is it?
b. What is its effect?
3. What will it cost to identify and correct?
4. Is adequate preventative maintenance being
performed?
5. Are state agencies forcing action?
6. Is correction an economically justified
procedure?
He may not have all the answers but it is essential
that he know the questions.
The goals and objections usually can be outlined
as an effort to:
1. Determine the need for a sewer system
analysis;
2. Establish an effective sewer maintenance
program;
3. Determine and project minimum and
optimum needs for equipment and
manpower;
4. Determine if infiltration is a significant
problem; and
5. Correlate cleaning and inspection with any
contemplated street paving program.
When the public works official has identified and
evaluated the problem, he may look for guidance
from a qualified consulting engineering firm,
supplemented by competent sewer service
organizations if he does not have adequate manpower
and equipment.
3.2 IDENTIFY SYSTEM
3.2.1 Plot Maps
The first request by a consultant or infiltration
analyst will be for detailed maps of the sewer system.
Only in rare instances are all such maps available.
Even in jurisdictions that take pride in maintaining
excellent records, the existing maps often will be
found inaccurate as to utility locations because
as-built records never were made or kept in past
practices.
It is imperative that the existing sewer maps be
completely checked in the field for verification of
line, grade, and sizes. Future studies and corrective
action will be rendered difficult and expensive unless
adequate attention is given at the very outset of
operations. Such mapping also is essential for routine
preventive maintenance programs.
Scales, types of maps, and information must be
tailored to each community or area. If the public
works department or sewer agency does not possess
such maps or if there are no personnel available to
produce them, a consultant or a separate land
surveying firm may be engaged for this vital step.
3.2.2 Identify Drainage Systems
Maps should be analyzed to develop a series of
small drainage areas or "mini-systems." Key manholes
should be selected for each "mini-system" through
which the total "mini-system" flow enters the trunks
or the" next area. A theoretical office analysis of key
manholes should be made to identify the sections and
manholes that are bottlenecks. This operation
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requires that true invert elevations and pipe sizes be
known so that hydraulic computations can be made.
At this point some feeling for the scope of the
problem can be gained.
3.3 IDENTIFY SCOPE OF INFILTRATION
3.3.1 Flow Measurements
In conjunction with the identification of drainage
systems, actual dry-weather and wet-weather flow
measurements should be made at key manholes. A
series of such measurements may extend over many
months of observation during daily periods of low
domestic and industrial flow.
The flow in the sewers can be obtained by
various methods:
1. Measure depth and obtain velocity by timing
floating material, appearances of dye,
conductivity of injected salt solutions,
radioactive tracers, or mechanical velocity
measuring devices.
2. Utilize various types and shapes of calibrated
measuring devices such as V-notch and sutro
weirs and orifices.
3. Use electronic flow recorders that can
transmit records to distant points.
4. Utilize photograpic installations that will
automatically record levels of water behind
weirs.
5. Install float-actuated devices that can record
depths of flow.
6. Evaluate pumping records at all pumping
stations, lift stations and treatment plants.
7. Make flow measurements at major metering
installations such as Parshall flumes, venturi
devices and wet well float meters at
treatment plants.
Ground water elevations also should be obtained
from ground water gauges installed in manholes
where wet ground conditions are suspected. These
gauges are like glass water level gauges in boilers, are
permanently placed by inserting a pipe with elbow
through the manhole wall, sealing it carefully, and
attaching a visible plastic viewing tube with a
calibrated scale behind it. Figure 3.3, Ground Water
Gauge, shows a gauge in place. Water rises in the
plastic tube to the height of the ground water outside
of the manhole.
Ground water elevation is extremely important in
planning an infiltration study. Unless the ground
water elevation is higher than the sewer pipe, little
actual infiltration — other than during storms — can
be expected. Thus, gauging and inspection should be
carried out on those sections located under the
FIGURE 3.3_
GROUND WATER GAUGE
SECURE TUBE
TO STEPS
GROUND WATER
GAUGE
I
INVERT-/
Courtesy of American Pipe Services Minneapolis, Minnesota
ground water table.
Ground water gauges should be inspected weekly
for an extended period, such as an entire year, to
determine seasonal variations. Inspection and gauging
then can be planned for maximum conditions.
The amount of infiltration flow as observed
within a pipe often can be judged when the head is
known.
All of this information should be collected
carefully, along with rainfall records for the area, and
evaluated in terms of variations of dry-weather to
wet-weather flows and time relationships to major
storms. When compared with the theoretical
computations and analysis of the drainage system as
outlined in 3.3, a clear picture of the actual situation
can be developed.
3.3.2 Rainfall Simulation
If the infiltration/inflow problem has been
identified as rain-connected and the system is
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supposedly separate, a rainfall simulation in the storm
sewers can help pinpoint the source. In this
simulation study, storm sewers that are adjacent to
sanitary sewers are plugged and filled with dyed
water. If this water shows up in the sanitary sewer,
there is serious infiltration or a direct inflow
connection between the two systems. Further
investigations, as described in Section 4, can be used
to identify inflow.
The preceding step has illustrated a basic factor
in such surveys — which is the identification of, and
distinction between, infiltration and inflow. Although
this section of the manual is devoted to the
infiltration component, it should be emphasized that
inflow is of equal or greater significance in some
systems. For that reason it is suggested that when
extraneous water flows are shown to be immediately
sensitive to rainfall, an inflow investigation be made
as described in Section 4.
3.4 PHYSICAL SURVEY OF SEWER SYSTEMS
In conducting a complete physical and lamping
survey of the entire sewer system, every manhole is
entered and sewers are examined visually for degree
and nature of deposition, flows, pipe condition, etc.
Manholes also are examined. Mirror and periscope
devices can facilitate viewing lines, but it is imperative
that someone physically enter each manhole. Very
little information can be obtained by peering into
even a shallow one. The proper safety checks for
combustible gas, oxygen deficiency, etc., must be
carried out prior to entry into any manhole.
If the static ground water gauges have not been
installed, they should be placed during the lamping
survey.
Smoke tests used in the inflow study also may
reveal infiltration sources under low ground water
conditions.
It should be emphasized that proper forms for
recording field data, experienced survey personnel,
and means for recording results on a visual plot map
are essential for subsequent evaluation. If local staff
personnel are not available, the consultant or the
professional survey team can perform these duties
and produce the data as well as analyzing them.
3.4.1 Effects of Poor Soil Conditions
Sewers constructed in poor soils may be
subjected to settlement that will tend to open the
joints or cause cracking of pipe, with subsequent
infiltration or exfiltration. Because such settlement
takes place over long periods of time and is
accelerated as new construction in the vicinity of the
pipe creates additional loads on the soils below the
sewer, the failure of the sewer installation can occur
after1 many years of satisfactory performance. This
indicates that, as increased infiltration has been noted
and poor soils conditions prevail, new construction
along or above the pipe is subject to suspicion and
investigation.
Man-made fill should be considered as poor soil
unless the- fill was placed under rigid construction
control. This is especially true where fill has been
placed on soft materials' such as clay, swamp, tree
roots, or debris.
An abrupt change of foundation conditions is
often the cause of cracking. Pipes connected to deep
manholes, the latter founded on harder material than
the pipes, can spell trouble. A pumping station on
pile foundation, with the sewer and adjacent
manholes laid in soft soils, always is cause for
suspicion.
Elimination of infiltration due to the above
sources usually will require complete reconstruction
of the affected portion of the system and should be
based on a revised design. This design must include
elimination of future settlements or the choice of
pipe and joint type as well as use of pipe cradles and
other means that will permit settlement without
failure of the sewer system.
3.4.2 Effects of Ground Water Conditions
If the ground water level is at or above the sewer
installation, the ground water can affect infiltration
in two basic .ways: attack on the pipe or joint
materials, and an increase in the rate of infiltration
once openings in the system haye occurred for a
variety of reasons, not necessarily connected with
ground water.
Chemicals in the ground water, such as sulfates
and organic acids, will attack certain pipe and joint
materials. The rate of attack depends on the rate of
flow through the ground and the resistance of the
sewer materials to the attack.
The presence of ground water may induce
electrolytic corrosion of metal pipes by stray
currents. Correction depends on the degree and type
of deterioration, and could involve replacement with
different materials, external coatings, and cathodic
protection.
Ground water has a very pronounced effect on
infiltration after a sewer system has lost its
water-tightness for any reason. Given a certain
number and size of openings in a portion of the pipe
system, infiltration will be influenced by the flow of
ground water through the surrounding soils, the
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distance between the pipe and top of ground water
surface (head), and the composition of the soils.
For soils of high permeability, such as gravel and
clean sand which permit a high rate of ground water
flow, the openings in the sewer will determine the
rate of infiltration, together with the ground water
head which dictates the hydrostatic pressure.
Conversely, soils of low permeability such as clay
may retard the rate of ground water entry through
openings in the sewer; for example, a dense clay may
seal openings and reduce or eliminate the effect of
the hydrostatic pressure of the ground water at sewer
level. The silt content of the soil can have a dual
effect on infiltration; it influences the permeability
but it can also increase the amount of solids entering
the sewer lines with the ground water.
Trench backfill and bedding materials different
from the in-situ soils should be taken into account in
the above described considerations. Trench backfill
can act as a ground water barrier or, on the other
hand, as an artificially created undergound stream.
3.5 ECONOMIC AND FEASIBILITY STUDY
Equaling in importance the identification of
infiltration is the evaluation of costs and benefits.
Although frequently there are overriding health and
environmental reasons for correcting infiltration,
exfiltration and inflow, there may be situations in
which the jurisdiction or agency has a choice between
either accepting the extraneous flows and treating
them, or eliminating them. Each choice has an
associated cost and requires a careful analysis prior to
any policy decision. Section 5 provides a detailed
economic analysis that most communities can apply
in arriving at meaningful conclusions.
The public works engineering staff or the
consulting engineer should make this economic
evaluation in conjunction with a review of existing
design features that would indicate the system's
adequacy. The current market value of the system
also should be weighed to illustrate the magnitude of
the investment which must be protected.
At this stage in the survey, fiscal decisions can be
made to proceed with correction programs only if
found economically and technically feasible. By this
time, cost estimates can be developed for the
subsequent correctional stages.
Generally, the pre-investigation will delineate
those sections of the system where high ground water
elevations, high flows, and defective pipe conditions
indicate the possibility of more than average
infiltration flows. Analysis at this point will enable
the identification of the areas with the most
infiltration and the drainage areas with less
infiltration where the economics of the corrective
actions dictate.
3.6 SEWER CLEANING
3.6.1 Initial Cleaning
A planned sewer cleaning program is essential for
the following reasons:
1. Full capacities and self-scouring velocities are
restored.
2. The difficult areas to dean are discovered.
Areas indicating possible breaks, offset
joints, restrictions, and poor house taps may
require photography or television inspection.
3. The most economical method and frequency
of cleaning can be established. This will
permit more realistic annual budgeting.
4. Individual flow readings by weir or recorders
will be more accurate in dean sewers.
5. Clean sewers are a necessary prerequisite for
any television inspection program and
correction sealing procedures.
Through past experience it has been found that
many municipalities are not equipped or experienced
enough to clean sewers adequately in preparation for
inspection by closed-circuit television or 'sealing by
pressure injection of sealants. Closed-circuit TV is
used basically to inspect the pipe line to determine
whether or not there are any structural failures,
misalignment, or points of infiltration. In this phase,
small amounts of debris left in the bottom of the line,
such as sand, stone, or sewage solids, may not
interfere with a good inspection except in pipe of less
than 10 inches in diameter. However, initial cleaning
preparatory to inspection should be done more
thoroughly than for routine maintenance. A full
diameter gage or "full gauge squeegee" should be
passed through the sewer to insure optimum
cleanliness.
Where repairs are going to be made by means of
internal pressure injection, it is also important that all
such deposits be removed. Two basic problems that
will result from debris left in the line are (1) the
damage that would be done to the inflatable ends of
the sealing machine or packing device, and (2)
inability of inflatable ends to create the perfect seal
required during the pumping period of sealants and
for pulling the sealing device through the line.
It is desirable to have little or no flow within the
sewer lines during the inspection or pressure sealing.
In most cases it is not possible to achieve this
condition. It has been found that flow depths of
one-third of the pipe or less are tolerable in the
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performance of these services. It should be
understood that inspections under submerged
conditions will give questionable results.
5.6.2 Sewer Cleaning Plan
OBJECTIVE:
Sewer pipe cleaning in preparation for television,
photography or internal injection
PRE-CLEANING INSPECTION:
Determine condition of pipe to be cleaned and
type of equipment to be used.
CLEANING EQUIPMENT:
The equipment can include, but not be limited
to:
1. Rodding Machine — sectional rodding
machine with 36-inch, 39-inch or 48-inch
sectional rods either 5/16-inch or 3/8-inch
diameter — hydraulically or mechanically
powered.
2. Rodding Machine—continuous rodding
machine with a minimum of ;375 diameter
rod.
3. Bucket Machine - 10.5 hp up to 100 hp;
buckets 6 inches up to any size for cleaning
round or square box sewers.
4. High Velocity Water Machine — air or
water-cooled power plant; sewer cleaning
hose 3/4-inch minimum with operating
pressure up to 1500 psi; maximum pressure
at the pump.
5. Hydraulically Propelled Devices or Cleaning
Tools — with or without harness.
CLEANING OPERATION:
The actual cleaning operation and the type of
equipment selected generally is determined by the
size and condition of the pipe to be cleaned. Ordinary
conditions in most cases may require the use of more
than one type of equipment or a combination of
more than one piece or type of equipment. These can
include, but not be limited to, the following:
1. Rodding machines, either sectional or
continuous, can be used to clean the pipe in
preparation for final inspection prior to
grouting; however, under severe cleaning
requirements they are .used primarily to
thread the sewer or pipe line for cleaning
operations and use of bucket machines.
There are many tools that can be attached to
the front of the rod which will effectively
remove debris, such as heavy conglomerates
. of grease, root intrusions, etc. The rodding
machine also can be used to pull such
cleaning tools as a stiff wire brush or swab,
to clean light debris from within sewer lines.
It should be noted that with those two tools,
a tag line connected to a bucket machine
should be used in order to pull the swab or
brush back if adverse conditions are
encountered.
It is necessary that in the above type of
cleaning methods a head of water, like that
which could be furnished by a fire hydrant,
should be used to help propel the solids
within the sewer line to the downstream
manhole.
2. Bucket machines provide a positive means of
cleaning pipe. Their operation allows a
positive connection of cable from one
manhole to the other, with applicable power
to pull a bucket loaded with sand or gravel
back to the manhole for dumping on the
street, into a container, or truck bed (if a
truck loader machine is used). This method
of cleaning removes solid materials such as
sand, gravel, and roots, and renders the pipe
clean for sealing if followed up with a stiff
wire brush and swab or squeegee.
It is important that final cleaning tools be as
close to pipe size as possible to obtain the
necessary results preparatory to a good
grouting job.
It also is necessary that a sufficient amount
of flushing water be available during the final
cleaning operation, to scour and flush the
pipe.
3. The high velocity or hydraulic pipe cleaning
machine is mobile and provides a fast and,
under most conditions, effective cleaning.
Operation of this machine with a specially
designed cleaning nozzle will produce a
cleaning or scouring action from streams of
water directed to strike the inside wall of the
pipe under high velocity. As a result of the
jet action from the rearward orifices, the
cleaning nozzle and hose is propelled
forward. As the hose and nozzle is pulled
back to the manhole, the high velocity spray
produces a hydraulic rake effect bringing the
debris back to the manhole. Care is necessary
in using hydraulic cleaning equipment. In
sandy soil where the sewer may be defective.
creation of voids may cause collapse of the
pipe.
4. Hydraulically propelled cleaning tools are
placed in the pipe with the proper tolerances
between the outside diameter of the device
and the inside diameter of pipe. Water is put
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into the manhole or sewage is allowed to
build up behind the ball to produce a head of
pressure moving the device down the sewer
line and allowing some water to escape. With
the rush of water, turbulence is created to
cause sand or solid materials to go into
suspension, thereby moving down the line.
Caution must be used in the operation of
these devices because the water pressure
created behind the ball can affect bad joints
in the pipe. The pressure may in some cases
damage private property because of water
entering basements through house laterals.
CLEANING EXAMPLE:
A 12-inch line with severe sand, gravel, and root
intrusion will require the use of bucket machines and
flushing equipment or a high water velocity machine.
In some cases where roots are the main problem, a
rodding machine with a saw or auger-type cutter may
be required, with a follow-up wire brush tool to clean
the pipe. In every case a swab-type tool incorporating
a rubber disc to clean or wipe the pipe to the full pipe
diameter can be used to free the inside pipe wall
completely from any obstruction. This is not only
important to effect the proper application of the
sealants; it will prevent possible damage to the
inflated rubber ends of the sealing machine or
packing device and create the perfect seal required
during the pumping period of the sealants.
3.7 TELEVISION AND PHOTOGRAPHIC
INSPECTION
As a result of the findings of the previous stages,
the best utilization of television or photographic
inspection can now be determined. Arbitrary use of
these techniques without pre-planning and budget
review is not recommended. The most economical
results are not achieved on a random basis. These
techniques are useless when flows in the sewer exceed
one-third of the depth.
The following are some of the more pertinent
factors associated with TV and photography:
3.7.7 Reasons for Inspection
a. As part of a planned sewer system
restoration as outlined in the previous stages.
b. As assurance of sound underground facilities
prior to a "permanent surface" type paving
program.
c. For the inspection of new construction prior
to final acceptance.
d. To determine deficiencies in "troubled
areas".
e. To pinpoint the cause, source, and
magnitude of infiltration problems.
3.7.2 Methods of Inspection
a. Draw the camera through the sewer and
record deficiencies on forms, polaroid
pictures, stereo slides, video tape, and/or
movie film. Take shots of adjacent "typical"
sound pipe for comparison purposes so that
the degree of the deficiencies may be
ascertained. Locate pertinent features.
b. Record results of the study and draft final
report.
c. Summarize and analyze, and recommend
corrective measures.
3.7.3 Testing and Sealing
A variation of the above mentioned method is to
use television and a testing device. Upon visual
inspection of a potentially leaky joint, the testing
device is pulled over the joint and a pressurized test
made. If the test indicates defects, sealing is
accomplished immediately. The cost of this method
may be high, although the cost of two setups, one for
inspection and then for sealing should be evaluated.
This method of "grouting as you go" does not
allow an economic and engineering analysis of the
optims which are available such as replacement of the
sewer or sealing only those defects which allow major
contributory flows.
3.7.4 Results of Inspection
a. Location of sources and magnitude of
infiltration.
b. Location and extent of structural
deficiencies.
c. Accurate location of wyes, taps, manholes,
lampholes, surreptitious connections of any
kind, cross-connections to the storm sewer,
and any other physical features of
consequence:
3.7.5 Benefits of Inspection
a. Provides the information necessary for the
drafting of a sewer system map or the
updating of an existing one.
b. Enables the engineer to recommend the
redesign, reconstruction, rehabilitation,
repair, or replacement of any specific part or
parts of the system.
c. Provides a permanent written and pictorial
record of the system which can be utilized at
any time.
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3.8 RESTORATION OF THE SEWER SYSTEM
Based on the results and recommendations of the
inspection report, sound budgeting and planning for
the restoration of the system can now be achieved.
The engineer can now appropriately decide how to
correct the structural deficiencies and eliminate the
infiltration. The following is a suggested approach:
3.8.1 Structural Deficiencies
a. Take into consideration the age, type, and
depth of the pipe and the severity and extent
of the damage.
b. Depending on the engineering and economic
evaluations, either repair the pipe on a partial
basis or replace the entire section between
manholes. (The economic evaluation must
include the cost of repair of the roadway
surface.)
c. Isolated or minor damage may be tolerable
or corrected at nominal cost.
d. It is obvious pavements should not be placed
over damaged or defective pipe. Remember
that marginal damage could become severe
before the life of the pavement expires.
3.8.2 Infiltration
a. In a structurally sound pipe, most infiltration
can be eliminated by the internal injection of
sealants. This method of repair precludes
excavation. Frequently this internal sealing is
performed simultaneously with internal
testing, as described in 3.10.3.
b. Weigh the cost of sealing against the cost of
treating this extraneous water.
c. Think in terms of the hydraulic load placed
on the collection system and on the
treatment plant. If, during periods of high
static head, the treatment plant must be
by-passed, compute the cost of plant
expansion to handle these peak loads.
d. Consider the fact that small leaks may
become larger with the passage of time
and/or increase in static head.
e. Compare grouting costs with partial and total
replacement costs.
f. Define those sources of infiltration that
could be considered livable.
5. & 3 Correction Alternates
a. Replacement of broken sections.
b. Insertion of sleeves or liners.
c. Internal sealing with gels or slurries.
d. External sealing by soil injection grouting.
3.8.4 Building Sewers
An internal grouting method for eliminating
waters of infiltration from building sewers has been
devised. A pilot project recently completed by_
American Pipe ervices indicates how sealing may be
accomplished if economically desirable.
The first step in the process was to identify the
building sewers that were leaking by the use of closed
circuit television in the mains. It must be determined
whether observed flows are from domestic usage,
footing drain tile discharge or as a result of
exfiltration from a flooded storm sewer and
subsequent infiltration into the building sewer which
crosses under the storm sewer.
Domestic usage can be determined by a check of
the house at the time ofvTV inspection to make sure
no water is being used and that there are no cooling
waters or cistern over-flows discharging to the system.
Footing drain tile contribution can be eliminated
from consideration by knowing what the elevation of
the ground water table is in the study area. This is
done through the use of groundwater gages installed
in the sanitary manholes nearby. If the groundwater
table is higher than the footing drain tile a check for
building sewer infiltration should not be initiated
until the groundwater subsides.
If the discharge from the building sewer can be
directly attributable to rainfall connected infiltration
as a result of flooding storm sewers, internal grouting
can be used if an economic analyses indicates a
favorable cost-benefit ratio. There must be enough
infiltration, either joint leaks and/or building sewer
leaks, in a specific run of pipe to make the cost of
both camera and packer in the line at the same time
worthwhile.
If the economic analyses indicates the advisibility
of sealing, the camera-packer tandem is placed in the
street sewer with the camera pulled into a position
such that it can view the building sewer discharge.
Simultaneously, the adjacent storm sewer is
re-flodded. When the infiltrating water appears in the
sewer a technician is sent into the connecting house
basement where he inserts a small inflatable bag into
the service cleanout and pushes it all the way out to
the main where the camera can view it. It is then
retracted toward the house in two foot increments
being inflated and deflated at each increment. Initial
inflations will stop the water from getting to the
main, but eventually the bag will be retracted to a
point where the full-flow infiltration will again be
evident. At this point the bag is left inflated in the
building sewer. Then the grouting "packer" in the
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main is positioned with its anular opening over the
house service connection and inflated. Grout is
pumped into the building sewer until sufficient
pressures have been reached. The catalyst is triggered
and the grout gels. At this point the "packer" is
deflated and moved away from the building sewer
and the bag in the building sewer itself if deflated and
removed. A domestic type sewer cleaning machine is
employed through the house sewer cleanout to
remove the gel from the line and the sealing process is
complete.
The cost range for this procedure has been found
to vary from $200 to $500 per house service,
depending on the number of services per manhole
setup and the amount of chemical used. It also has
been found that it is not economically justified to
seal building sewers when the infiltration flow is less
than 10 gpm. In some areas replacement of the
building sewer may be more economical than internal
sealing.
3.9 TREATMENT PLANT DESIGN CRITERIA
Besides the obvious advantages of restoring
needed capacities and reducing costs and pollution,
the final study goal of the complete restoration
program is the more accurate estimate of hydraulic
loading for future plant design. The design criteria
will be tempered by the knowledge that nominal and
predictable amounts of extraneous clean water can
now be anticipated.
The accomplishments and benefits of pursuing a
logical, orderly program for infiltration/inflow
correction can be listed as follows:
1. The sewer systems can now be reasonably
maintained, usually at lower unit costs.
Annual budget needs can be accurately and
realistically projected.
2. Serious structural deficiencies will be
corrected.
3. Any subsequent paving programs can be
carried out with reasonable assurance that
the sewers will not require repair at a later
date and can easily be maintained.
4. The waste water treatment plant, lift
stations, and other facilities will be of
adequate size to serve present and projected
needs.
5. Treatment or pumping costs in the future
will be reduced as much as possible.
6. Infiltration volumes will be reduced to a
minimum.
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SECTION 4
METHODS FOR CONTROLLING THE DISCHARGE
OF INFLOW WATERS INTO PUBLIC SEWER SYSTEMS
4.1 General
4.2 Causes, Effects and Control of Inflow
4.3 Location and Detection of Sources of Inflow
4.4 Removal and Elimination of Excessive Inflow:
Policies and Costs
4.5 Establishment of Official Policies by Sewer-Use Ordinances,
Regulations and Codes
4.6 Selected Excerpts from Sewer-Use Regulations
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SECTION 4
CONTROLLING DISCHARGE OF INFLOW WATERS
4,1 GENERAL
Discharges of excessive amounts of non-sanitary
wastes into public sewers is a costly misuse of such
sanitary systems. Included in such extraneous waters
are inflows from various sources through deliberately
connected pipes and drain lines. Separate sanitary
sewer systems are most seriously affected by such
inflows. Combined sewers suffer in somewhat lesser
degree, and storm sewers are designed for these flows.
Elimination of inflows of such waters, by
preventing and correcting direct discharges through
pipe connections, is in the best interests of
dependable and economical service from sewer
networks and appurtenant waste water facilities.
Inflow waters which have their sources in urban
structxires and other practices are not '"polluted," in
the sense that thay would require prompt removal
from the urban environment and subsequent
treatment to prevent the degradation of watercourses
into which they are discharged. In the case of
separate sanitary sewers, the use of carrying capacities
to handle such waste waters is unnecessary and
costly. For the purpose of providing proper and safe
drainage of such waters from private properties, their
discharge into storm sewer systems is more
appropriate.
National experiences have demonstrated the
advisability of following general guidelines for
handling the extraneous waters (referred to in this
Manual as inflow) in the design, construction, and
management of public sanitary sewer systems:
Roof leader connections — excluded.
Foundation and most are a way drain
connections - excluded.
Basement drain connections — permissible under
certain circumstances.
Residential, industrial, commercial cooling water
connections — excluded.
Other so-called "dean waters" — excluded.
Certain industrial-commercial
wastes — permissible when controlled and
authorized.
It is the purpose of this section of the Manual to
set forth general policies and lines of action by
jurisdictions for:
1. Determination of causes and effects of
inflow waters in sewer systems.
2. Detecting and locating sources of inflows and
determining their conformity with
jurisdictional regulations.
3. Planning workable and equitable prevention
and elimination of such waste water
connections, where necessary.
4. Establishment of official sewer-use
ordinances, codes and regulations upon
which jurisdictional actions can be taken to
(1) prevent future inflow connections and
(2) eliminate existing inflows detrimental to
the capacities and capabilities of sewer
systems, pumping and treatment facilities,
and other system appurtenances.
4.2 CAUSES, EFFECTS AND
CONTROL OF INFLOW
Sections 1 and 3 of this Manual relate to the
problems of infiltration. It is necessary here to draw
the distinction between the responsibility for actions
taken to control infiltration and for similar actions to
prevent and eliminate excessive inflow into sewer
systems.
The sources of infiltration are generally within
the control of the jurisdiction. The causes are
the responsibility of the jurisdiction, in terms of
design, choice of materials, construction control,
operation, and soil and water conditions in which
the sewer is laid and functions. The responsibility
for decisions in infiltration prevention and correction
is totally the jurisdiction's, as is the necessary
action to eliminate the detrimental effects of
excessive infiltration.
On the otlver hand-with the exception of
inflow through manhole covers — the sources of
inflow are, for all intents and purposes, from the
properties of private individuals and organizations.
The causes are their responsibility, except where
these have been authorized or condoned by official
actions. The responsibility for making decisions on
prevention and elimination of inflows may rest with
the jurisdiction; but real action will depend on total
or at least partial participation and expenditures by
property owners.
Inflow control is involved with other distinctions.
As a basis for corrective actions, it must be
determined if such connections haw been made
legally or illegally — with approval or condonement
on the part of the jurisdiction, or illicitly and
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surreptitiously. A further distinction must be drawn
between the types of sewers into which such inflows
intrude, with entry into storm sewers normally
acceptable and into combined sewers acceptable
under certain conditions.
The overall effects of inflow are much the same
as those attributable to excessive infiltration:
usurpation of sewer system capacities; local area and
private property flooding; surcharging of, and
deleterious effects on, pumping and treatment
installations; increases in combined sewer overflows,
and increased poUutional loadings on receiving
waters.
However, there is a distinction between the
volumetric and peak effects of inflow and infiltration.
It offers opportunities to differentiate between
sources of these two types of extraneous water flows
in existing sewer systems when the two waste waters
are commingled and generally indistinguishable from
each other. Inflow volumes increase and decrease
more markedly than infiltration flows, except in the
case of inflows due to certain industrial and
commercial "clean water" discharges.
The sources of actual inflow drainage are similar
to infiltration sources: the soil and ground water
therein. Inflows occur more rapidly following
precipitation conditions due to roof runoff. The
imperviousness of roof surfaces simulates urban areas
such as roads, streets, parking lots, and other surfaced
facilities. Inflows due to areaway and yard drains
occur rapidly, and even basement and foundation
drains may produce peak flows of inflow waters more
rapidly than the slower reaction of sources of
infiltration to ground water table changes.
Exclusion of inflow waters from sanitary sewers
is general practice, or at least a general goal, in
jurisdictions in the United States and Canada. This
was the disclosure of the 1969-1970 national
investigations and research studies. This general
statement is especially true of those systems which
have taken cognizance of this problem, have
established specific policies, and have taken actions to
control the effects of this type of waste water
intrusion. It is necessary to draw this distinction
because many jurisdictions have established no such
policies, enacted no such regulatory practices, or have
taken a permissive attitude on inflow connections by
overlooking or condoning conditions directly
affecting the serviceability of sewer systems and
appurtenant facilities.
The case for inflow control is clear. The effects
on sewer system management are unmistakable, but
no broad policy can cover all circumstances in all
local jurisdictions. Inflow conditions are the product
of local phenomena and policies. They reflect
building practices, including the use of basement or
other sub-grade building areas or the adoption of
on-slab construction; soil and ground water
conditions; precipitation experiences; climate, as it
applies to extensive air conditioning, and
industrial-commercial developments in any area,
followed by the generation of so-called "clean
waters" from processing operations. Proof of the
interlocking effect of a wide range of jurisdiction
conditions on inflow sources and rates is found in the
fact that availability of unrestricted amounts of
public water supply and the price thereof influences
the production of such "clean waters" in industrial
and commercial operations.
The upshot of these interlocking effects is that
inflows into jurisdictional sewer systems do not occur
in a governmental vacuum. They result from policies
and practices in other phases of urban life, including
not only sewer-use regulations but building code and
plumbing code provisions; control of
industrial-commercial construction by means of
zoning; water supply policies and pricing structures;
availability of storm sewer connections, and other
factors too varied to enumerate.
Inflow control practices by jurisdictions are
affected and influenced by location of storm sewers
in relation to property tie-ins, the geology and the
terrain of the community, local governmental actions
on control of ground water levels by draining and
topographic control. All of these factors must be
examined and evaluated by each jurisdiction which
has not yet established policies on inflow control or
taken adequate actions to enforce regulations already
in existence.
While this Manual urges the prevention and
control of excessive inflow into sewer systems,
particularly sanitary sewer facilities, it also stresses
the need for local decisions based on all local
conditions. Evaluation of all these local factors is the
first step in any inflow control program. The burden
of proof is to prove that inflow is detrimental and
that control is a foregone necessity if these adverse
effects are to be prevented and corrected. What about
the traumatic effect on the public of any sudden
decision to eliminate long-standing inflow sources? It
dictates that jurisdictions take actions based on this
type of evaluation of local conditions and on findings
that control needs are indisputable. In some cases, the
value of inflow has been advocated by some
engineering and operation personnel during prolonged
dry periods, on the basis that such extraneous flows
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inhibit sewer septicity and odor conditions.
These are the general factors involved in the
causes, effects, and means of control of the inflow
problem. No specific limits can be established for
inflow, such as the goals proposed for reduction in
infiltration allowances; the factors involved are too
indeterminate to permit the setting of determinate
guidelines. No built-in limits can be set for allowable
inflow, except in terms of broad policies covering
certain permissible connections — such as basement
drains entering sanitary sewers because of the nature
of the waste waters generated by in-structure
operations.
Certain sources of inflow can be exempted from
prohibitory regulations, such as basement drains and,
under certain circumstances, some types of so-called
"clean water" discharges. Whether certain exemptions
are permitted or not, policies must be firmly set and
enforced without favoritism.
4.3 LOCATION AND DETECTION OF
SOURCES OF INFLOW
Control of inflow, like control of infiltration,
resolves itself into two practices: prevention of new
inflows, and correction of existing inflows deemed
detrimental to sewer systems and wastes handling and
treatment work.
Prevention involves exclusion of inflow
connections by edict, and the rejection of any such
flows when new structures are built or present
building operations modified and their plumbing and
drainage lines installed. Correction involves the
location of existing sources and their elimination by
physical separation of any such connections in
accordance with set policies of the jurisdictions.
Elimination of existing inflow connections is not
merely a simple procedure of locating these sources
and ordering them discontinued. Not only are search
and surveillance procedures difficult, but matters of
principle are involved:
1. Have such connections been made in
violation of existing regulations? In this case
no official record of these connections will
have been filed, and no record of their
nature, size, and location will be available.
2. Have they been made in accordance with
authorized actions by the jurisdictions or
their agencies? In this case all pertinent
information on these drain connections may
have been mapped and recorded.
3. Have they been installed in the absence of
local prohibitions and/or with uncontrolled
permissiveness of public officials? In this case
their existence may or may not be recorded
and their sources listed in building or
plumbing plans, or in other drawings in the
possession of property owners.
Locating approved and recorded inflow
connections is relatively simple. It involves
examination of building connection plans and permits
an on-site check of their actual installation and
conformity with jurisdictional authorization. If
decisions are made to eliminate previously authorized
inflows because subsequent effects on sewer systems
have been greater than originally anticipated, a
careful search may be required to determine if the
connections are serving only the purposes intended
and authorized. This may involve gauging of inflow
volumes and testing of inflow composition. Gauging
and testing may require the location of the points
where inflow connections are made. This may be
directly into the building or "side sewer" at the
building line; at some point in the run of the building
connection between the structure and the street
sewer wye, or through a separate drain line which
enters the street sewer independently.
Similar search-and-find procedures can be
followed for all inflow connections which have been
installed without or in the absence of code
requirements but with the provision that all such
connections be indicated in applications for plumbing
or building permits. The problem in such cases is to
make certain that all inflow lines have been recorded
and that the sources of inflow waters are known and
traceable. This problem points out the importance of
prohibiting multiple-property drain connections to a
single building sewer line. Such multiple connections
make it difficult, if not impossible, to place specific
responsibility for excessive inflows on any one of the
connected structures.
The problem of locating illicit, surreptitious, and
unlisted inflow connections is a more difficult one. It
involves painstaking inspections and investigations of
all plumbing and drainage lines by expert persons and
the tracing of buried lines back to their original
sources. Every such source must be held suspect until
the point of discharge is located, either by tracing
piping plans or by detection methods.
In residential and related types of structures the
inflow sources are relatively few and less complicated,
but in industrial and commercial buildings they can
be more difficult to locate and evaluate.
Each jurisdiction must choose and use its own
techniques. This Manual can list only some of the
possible procedures:
1. Tracing roof leader connections with dye,
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pieces of paper, plastic chips, or confetti;
corks of varying colors placed in roof gutters,
the colors indicating specifically designated
buildings; chemicals such as salt, with tests
for chlorides in runoff water; use of safe
radioactive tracer materials of short-life
character, checked with Geiger counter-type
equipment, and other appropriate detection
methods. They all involve the observation of
sewer lines in the vicinity of the structures
being investigated. Observations can be made
during storm' periods or in flows induced by
water discharged onto roofs.
2. Tracing foundation drains by introduction of
dyes or chemicals into the ground surface
around the building being investigated, or by
injection of such tracer materials into the
ground at the foundation or footing level.
Such procedures must be followed by tests
or observations in sewer lines, as suggested in
(1)-
3. Tracing basement drain connections by
locating in-structure sources of such inflow
waters and introducing tell-tale materials
which can be detected in receiving sewers.
4. Applying tracer materials such as dyes or
chemicals, in areaways or areaway drains,
and introducing flows into them by hose
connections or waiting for storm flows to
flush the tell-tale materials into adjoining
sewers.
5. Applying tracer chemicals, radioactive
tracers, or dyes to industrial and commercial
equipment, such as water-using air
conditioners, refrigeration units,
stack-washing pits, or other wet-processing
points where drainage water is suspected of
being connected to sewer lines. This must be
followed by suitable detection means in
street sewers, in manholes or other chambers
located on such commercial-industrial
property.
6. Application of smoke bomb tests in street
sewers, followed by observations of the
appearance of smoke plumes at building
roofs, in basement and areaways, at
industrial and commercial connections or
building vents, or from the ground in the
area of foundation drains.
7. Actual excavation of building lines suspected
of being illicitly connected to public sewers.
This must be considered as a last-resort
measure in any inflow investigation.
4.4 REMOVAL AND ELIMINATION OF
INFLOW CONNECTIONS
Decision on removal and elimination of inflow
connections may be based not only on the existence
of such connections but also on the amount of inflow
volumes contributed to sewer systems. Determination
of the volume of inflow is difficult and often
impossible. These volumes change with climatic and
meteorological conditions, ground water levels, and
variations in industrial and commercial "clean water"
disposal operations. These factors must be considered
when tests are planned and undertaken.
Gauging of inflow volumes can be made, when
applicable, by use of the types of procedures
described in Section 3 of this Manual, covering
correction of infiltration conditions in existing
sewers. Points of gauging must be chosen specifically
to locate the. sources of inflow and pinpoint the
structure generating such waste waters.
Methods for removal and elimination of existing
inflow connections will depend on local conditions;
on whether they were made without specific approval
but with permissive failure of jurisdictional officials
to provide proper control; on whether they were
made illegally in contravention of regulations; on
whether other conditions prevailed at the time of
their original connection or at the time removal
actions were instituted.
In the case of illicit connections, property owners
can be ordered to discontinue such lines, and a fair
and reasonable period can be set for the necessary
corrective action. The cost should be borne by the
violator, but there is some responsibility on the part
of the jursidiction to suggest and/or provide alternate
means of inflow-water disposal. This problem will be
compounded if no existing storm sewer system is
available to receive drainage or industrial-commercial.
waste waters which cannot be safely and adequately
handled on the site.
While it is inadvisable to offer firm guidelines
for such disposal procedures, the following methods
have been applied with some success in representative
jurisdictions:
1. Discharge of roof leader drainage onto
property for seepage into soil. Roof leaders
should be extended for an adequate distance
beyond building walls to prevent the rapid
percolation of such waters into the soil and
thence into the ground water table around
the foundation, where it adds to the drainage
problem from this source. A distance of 5
to 10 feet has been specified in some
jurisdictions.
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2. Discharge of roof drainage in built-up areas
into street gutters.1 Many jurisdictions
prohibit the discharge of roof drainage onto
sidewalks or property areas which will drain
into public streets and cause pedestrian
hazards. In such cases, local regulations often
require the piping of roof drainage water
under the sidewalk and directly into the
gutter area.
3. Discharge of roof drainage, areaway drainage,
yard area drainage, or foundation drainage
into storm sewers or into surface ditches in
rural and suburban areas.
4. Discharge, under certain conditions, of
basement drainage into sanitary sewers or
combined sewers, rather than storm sewers,
in order to prevent pollution of the latter
with in-structure waste waters which require
treatment.
5. Reclamation and reuse of clean industrial
and commercial waters, such as air
conditioning and refrigeration cooling
waters, and other unpolluted process waters
for other on-stream purposes. These steps
reduce the water consumption demands of
such structures and eliminate large volumes
of avoidable inflows into sewer systems.
6. Connection of clean water discharges to
storm sewers, or discharge of such
unpolluted waters into nearby watercourses.
7. Internal on-stream separation of so-called
clean waters produced in industrial and
commercial operations, from industrial
wastes which can be discharged into sanitary
sewers if such wastes are deemed amenable
to transportation and treatment with
sanitary sewage flows. Once, such clean
waters are admixed with
industrial-commercial wastes which require
treatment, they become an inseparable part
of the total flow and must be accepted in
sanitary sewer systems which admit such
industrial wastes.
8. Disposal of industrial-commercial inflow
-waters with industrial wastes in
company-owned treatment facilities, in cases
where such ihstallations decide to go it alone
in the handling of their wastes.
Under any circumstance, acceptance of industrial
or commercial process wastes in public sewer systems
1Some local codes prohibit the practice, and require
connection to the storm drainage system or even the sanitary
sewers to reduce problems of erosion or icing of sidewalks.
must be based on the ability of sewer systems to
transport, and treatment works to handle, such
wastes without damage to physical structures,
impairment of waste treatment processes and
facilities, and danger to operational personnel. It is
the function of a sewer-use ordinance to stipulate the
types of wastes amenable to handling and treatment,
on the basis of quality and quantity, and set forth the
basis of charging for such sewer service.
These are some of the ways in which a
jurisdiction can accomplish the elimination and
control of inflow. Since it owns the sewer system, the
jurisdiction has ministerial responsibilities and police
rights to invoke fair and equitable standards for the
acceptance of inflow waters; exclude them if the
public interest so dictates, and impose costs for
corrective actions. However, the rule of reason must
prevail in establishing policies, in imposing costs, and
in determining who pays or shares in the cost of
corrective actions:
1. If inflow connections have been permitted
and it is then found that elimination of these
connections is needed to overcome the
deleterious effects oulined above in this
section and in Section 1 of this Manual, part
or all of the costs involved may have to be
borne by the jurisdiction.
2. If inflows were allowed by permissive
policies of the jurisdiction, either because no
prohibitions were enacted or were allowed
by nonenforcement policies, part of the cost
of elimination may rightly be a charge
against the community.
3. If illicit connections were made in violation
of known rules or regulations, the total cost
of corrective actions should be paid by the
property owner, or the builder if the latter
can be held responsible.
It is again stressed that decisions must be based
on local conditions and pertinent factors. Public
support and participation will be needed in all such
corrective programs because of the costs and
inconveniences involved. Jurisdictions are urged to
carry out carefully planned and judiciously executed
corrective programs to assure public compliance and
cooperation.
Every available means should be used to win
friends and influence people. Meetings with individual
property owners, citizens' groups, or local
improvement organizations should be held to explain
the reasons for corrective actions and the public
benefits that will result from inflow control. Every
communication device should be pressed into service,
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including radio, television, the press, bulletins and
brochures, motion pictures and slide presentations,
lectures and face-to-face confrontations.
Samples of informational material used by some
jurisdictions for this purpose are contained in Section
9.
Special problems of inflow control — and of
infiltration control — confront multi-community,
regional, or district sewer systems. A jurisdiction may
have police and ministerial control over the use of its
sewers by its own residents yet find that it is
powerless to regulate sewer uses in communities
contributing waste water flows to the system
operated by the primary jurisdiction.
In such cases, the incentive for such contributory
communities to prevent and eliminate excessive
inflows must stress local benefits, in terms of better
community sanitation and lower costs of sewer
service. The jurisdiction which renders interceptor
and treatment service to such satellite communities
can:
1. Point out the hazards of local flooding and
property damage due to sewer lines
surcharged by inflow and infiltration.
2. Impose rules which must be enforced by
contributing communities if their wastes are
to be accepted and handled by the recipient
jurisdiction.
3. Establish charges for handling contributed
flows, based on volumes of flow — thereby
placing a penalty on uncontrolled intrusion
of excessive amounts of extraneous waters.
4. Use any other means for accomplishing
inflow control, either voluntary or
compulsory, and for bringing the importance
of the problem to the officials and residents
of contributing communities.
4.5 ESTABLISHMENT OF OFFICIAL POLICIES
BY SEWER-USE ORDINANCES AND
REGULATIONS
The establishment of sewer-use laws, rules,
regulations, or codes of practice must be the basis for
enforcement actions. Such regulations remove doubts
and indecisions as to jurisdictional policies; apprise
builders, developers, and property owners of their
rights and responsibilities; guide installers and
suppliers of sewer, building, and plumbing facilities in
their operations; establish standards for engineering
and architectural designers, and assure uniform
treatment for all persons and organizations.
Enactment of such ordinances, codes, or
regulations is strongly urged. For this reason, this
Manual presents excerpts from sewer regulations of
representative jurisdictions in the United States and
Canada. These excerpts have been chosen from scores
of workable ordinances and rules for the purpose of
offering guidance to jurisdictions considering
enactment of initial regulations and those intending
to modify and modernize their practices and policies.
These excerpts have been divided into two parts:
(1) quotations from ordinances relating specifically to
connection of so-called inflow waters from
residential, commercial, and industrial structures, and
(2) code terms referring to the discharge of industrial
and commercial process wastes which, if amenable
and allowable, become an integral part of the sanitary
sewage flow of a jurisdiction and, as such, are handled
as an admixture component of its total waste water
flows.
The excerpts in part 1 are given below, under
appropriate headings. The regulations relating to
industrial wastes discharges are contained in Section 9
because of their significance to the problems of
waste-water discharge and handling from such
sources, over and above the inflow waters that must
be minimized or totally eliminated.
4.6 SELECTED EXCERPTS FROM
SEWER-USE REGULATIONS
4.6.1 Drainage Connections Prohibited
"Storm waters, surface waters, ground waters,
roof runoff, subsurface drainage, cooling waters or
other uncontaminated waters shall not be admitted
into any sanitary sewer but shall be discharged into
such sewers as are specifically designated as storm or
combined sewers or to a natural outlet." — Kansas
City, Missouri.
"No person shall discharge, or cause to be
discharged, any storm water, surface water, ground
water, roof runoff, subsurface drainage,
uncontaminated cooling water, or unpolluted
industrial process waters to any sanitary
sewers." — Cedar Rapids, Iowa and Jacksonville,
Florida.
"No person shall discharge, or cause .to be
discharged, any storm water, surface water, ground
water, roof runoff, subsurface drainage or cooling
water, such as from boilers, air conditioning systems
and the like, to any sanitary sewer." — Knoxville,
Tennessee.
"No leaders from roofs and no surface drains for
rain water shall be connected to any sanitary
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sewers." - Enterprise Public Utility District, Shasta
County, California.
"No person shall make connection of, roof
downspouts, exterior foundatfon drains, areaway
drains, or other sources of surface runoff or
groundwater to a building sewer or building drain
which in turn is connected directly or indirectly to a
public sanitary sewer." — Rome, New York.
"No person shall cause or permit the roof water
downspouts of any building or surface or ground
water drains in or about any building, to be
connected into, or to remain connected into, and soil,
pipe, drain, or lateral sewer tributary to any sanitary
sewer of the city, or shall cause or permit any other
physical condition to exist in, on or about any
building, or in the yard around any building whereby
either the roof water or surface water, from or about
such building is caused or permitted to flow into any
soil, pipe, drain or lateral tributary to any sanitary
sewer of the City." — Akron, Ohio.
"It shall be unlawful for any person to discharge
the contents of a swimming pool into a sanitary
sewer." - Enterprise Public Utility District, Shasta
County, California.
4.6.2 Methods and Points of Disposal Specified
"Storm water, cooling water and all other
unpolluted waters shall be discharged to such sewers
as are specifically designated as combined sewers or
storm sewers, or to a natural outlet approved by the
City Engineer." — Jacksonville, Florida.
"Storm water and all other unpolluted drainage
shall be discharged to such sewers as are specifically
designated by the City as combined sewers or storm
sewers. Cooling water may be discharged with
approval of the City to a storm sewer, combined
sewer or natural outlet." — Knoxville, Tennessee.
"Storm water and all other unpolluted drainage
shall be discharged to such sewers as are specifically
designated as combined sewers or storm sewers, or to
a natural outlet approved by the Water Pollution
Control Superintendent. Industrial cooling water or
unpolluted process waters may be discharged, on
approval of the Superintendent, to a storm sewer,
combined sewer, or natural outlet." — Cedar Rapids,
Iowa.
"No person shall suffer any particular drain from
any building or land of which he is the owner or
occupant to leak or be out of repair; and no person
shall, except in accordance with a permit from the
Commissioner of Public Works, enter or attempt to
enter a particular drain into a public drain or
sewer." — Boston, Massachusetts.
"Rain water from roofs or other approved areas
exposed to rain water may be drained into the storm
drainage system, or the combined sanitary and storm
water drainage, but shall not drain into any sewer
intended for sanitary sewage only. Rainwater from
roofs or other approved areas exposed to rainwater
may drain into a public street gutter, provided that
such gutter is paved and runs to a catch basin
connected to a public storm drain, and provided
further that such drainage has the approval of the
City Engineer or other public authority having
jurisdiction over public streets or public storm
drains." — Burlingame, California.
"Paved areas, yards, courts, courtyards, public
garage drainage areas and all other areas not having
natural drainage, and .building roofs as required by
the Irving Building Code, shall be drained into the
storm sewer systems where such systems are available;
otherwise, they shall be drained to a lawful place of
disposal approved by the City Engineer. When rain
water from any roof is conducted underneath the
sidewalk to the street curb, the pipes under the
sidewalk shah1 be of cast iron with an area equal to
twice that of the downspout or a concrete trough
may be used which shall be fitted with a cast iron
cover held in place with non-corrodible screws and
such covers shall be made preferably in one piece and
shall be set flush with the surface of the sidewalk.
Storm water shall not be drained into sewers intended
for sanitary sewage except by special permission of
the Chief Plumbing Inspector." —Irving, Texas.
"For residences, multiple residences, churches,
schools, hotels, motels, industrial and commercial
buildings, planned developments, hospitals and all
similar installation and appurtenances thereto: Storm
plumbing outlets, downspouts, parking lot drainage,
footing drains, and unpolluted water must be
connected to any storm drain existing on the same
side of the centerline of the abutting street and
within 60 feet of a side property line. In the event a
natural outlet is available abutting the property, it
may be used for storm water disposal. In the event
neither of the two above outlets are available, storm
water may be disposed of in dry wells or by draining
the water to the street gutter, but storm water shall
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not be directed over the surface of a public sidewalk
or walkway. The method for their being connected to
a combined sewer when there is no accessible storm
drain: downspouts, storm plumbing outlets, parking
lot drainage, unpolluted water and footing drains
must be carried in a side sewer pipe separate from the
sanitary side sewer pipe to the property line, as
designated by the City Engineer, and shall be joined
with the sanitary side sewer at that point and then
connected to the combined sewer, provided that the
City Engineer may permit or require storm drainage
to discharge upon the surface of a public place or into
a natural outlet or dry wells, even though a combined
sewer is accessible, when it is planned to provide a
storm relief sewer in the vicinity of said combined
sewer." - Seattle, Washington.
"The sanitary and storm drainage systems of a
building shall be entirely separate except where only
a combined sewer is available." —Metropolitan
Toronto, Ontario.
"It shall be unlawful for any person to connect
or cause to be connected, any drain carrying, or to
carry, any toilet, sink, basement, septic tank,
cesspool, industrial waste, or any fixture or device
discharging polluting substances to any storm water
drain in the City." — Rockford, Illinois.
"No person, other than a municipality having
such right by contract with the county, shall make or
cause to be made any connection or attachment to
any county sewer facility, nor shall any person
maintain, use or cause or permit any such connection
or attachment to be maintained or used without
having obtained a permit therefore from the
Commissioner of Public Works." — Nassau County,
New York.
4.6.3 Existing Inflow Connections Eliminated
"All existing connections between rainspout
drains on all residential dwellings and commercial
buildings in the City of Transcona which are
connected to the sanitary sewer system shall be
disconnected on or before the effective date of this
by-law." — Transcona, Manitoba
4.6.4 Protection from Damage
Protection of sewer facilities is usually accorded
special attention, apart from general penalty
provisions.
"It shall be unlawful for any person to
maliciously, willfully, or negligently break, damage,
destroy, uncover, deface or tamper with any
structure, appurtenance, or equipment which is a part
of the municipal sewage works." — Santa Cruz,
California.
"No person shall maliciously, willfully, or
negligently break, damage, destroy, uncover, deface,
or tamper with any structure, appurtenance or
equipment which is a part of the sewage works. Any
person violating this provision shall be guilty of
disorderly conduct." - Oklahoma City, Oklahoma.
"No unauthorized person shall maliciously, willfully,
or negligently break, damage, destroy, uncover,
deface, or tamper with any structure, appurtenance,
or equipment which is a part of the sewage works.
Any person violating this provision shall be subject to
immediate arrest under charge of disorderly
conduct." -Rome, New York.
4.6.5 Penalties for Violations of Regulations
"Any person found to be violating any provision
of this ordinance except Article VI, ("Protection
from Damage") shall be served by the city with
written notice stating the nature of the violation and
providing a reasonable time limit for the satisfactory
correction thereof. The offender shall, within the
period of time stated in such notice, permanently
cease all violations. Any person who shall continue
any violation beyond the time limit shall be guilty of
a misdemeanor, and on conviction thereof shall be
fined in the amount not exceeding $200.00 for each
violation. Each day in which any such violation shall
continue shall be deemed a separate offense. Any
person violating any of the provisions of this
ordinance shall become liable to the city for any
expense, loss, or damage occasioned the city by
reason of such violation." - Rome, New York.
"Any person found to be violating any provisions
of this or any other ordinance, rule or regulation of
the District, except Section 10.1 hereof ("Protection
from Damage") shall be served by the District
Inspector or other authorized person with written
notice stating the nature of the violation and
providing a reasonable time limit for the satisfactory
correction thereof. Said time limit shall not be less
than two nor more than seven working days. The
offender shall, within the period of time stated in
such notice, permanently cease all violations. All
persons shall be held strictly responsible for any and
all acts of agents or employees done under the
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provisions of this or any other ordinance, rule or
regulation of the District. Upon being notified by the
District Inspector of any defect arising in any sewer
or of any violation of the ordinances, rules or
regulations of the District, the person or persons
having, charge of said work shall immediately correct
the same." - Enterprise Public Utilitv District, Shasta
County, California.
"Any person who shall violate any provision of
this Ordinance- shall be served by the City with a
written notice stating the nature of the violation and
providing a maximum of ten days of grace; provided,
however, that in case of serious danger to public
health, or potential damage to the sewer system, a
forthwith notice to cease the violation may be served,
which notice shall have immediate effect. Any person
who shall violate any provision of this ordinance
shall, upon conviction of such violation, be punished
by a fine of not to exceed One Hundred ($100.00)
Dollars, or by imprisonment for a period of not to
exceed ninety (90) days, or by both such fine and
imprisonment, in the discretion of the Court. Each
day in which any such violation shall continue shall
be deemed a separate offense." - Wyoming,
Michigan.
"Any person violating any provision of this
ordinance, or who shall fail to do any act he is
required to do under the provisions of this ordinance,
shall, upon conviction, b.e punished by a fine not
exceeding $500.00 or imprisonment not exceeding
six months, or by both such fine and imprisonment.
Each day any violation of this ordinance shall
continue shall constitute a separate
offense." — Salem, Oregon.
"(1) The owner of any commercial or industrial
establishment found to be violating any provisions of
this ordinance shall be notified in writing by the
director, stating the nature of the violation and
providing a reasonable time limit for the correction
thereof. The owner of such establishment shall
permanently cease all violations within the period of
time stated in the notice, and shall certify to the
director that the corrections have been accomplished.
(2) The owner of any commercial or industrial
establishment found to be violating any provision of
this ordinance who shall continue such violation
beyond the time limit provided in paragraph one,
above, shall be guilty of a misdemeanor, and upon
conviction thereof shall be fined in an amount not
exceeding Two Hundred Dollars ($200.00) for each
violation. Each day in which such violation shall
continue shall be deemed a separate offense. (3) In
cases of repeated violations, the director may revoke
the permit for the discharge of wastes into the sewer
system, and effect the discontinuation of water or
sewer service, or both. (4) Any person violating any
of the provisions of this ordinance shall become liable
to the city for any expense incurred as a result of
such violation." - Kansas City, Missouri.
4.6.6 Inspectors'Right of Entry
Many ordinances assert the .city's right of
inspection, plus entry onto premises for the purpose.
The timing, objectives, and circumstances of the
inspectional visits may be differently regulated; but
possession of proper identification and credentials is
almost universally required of the inspector:
"Any duly authorized representative of the City,
bearing proper credentials and identification shall be
permitted to enter upon all properties for the purpose
of inspection, observation, measurement, sampling
and testing, in accordance with the provisions of
these regulations." — Jefferson City, Missouri.
"Authorized representatives of the City of
Yakima are hereby empowered to, at all reasonable
times, enter and inspect all buildings and premises for
the purposes of ascertaining whether the provisions of
this chapter are being violated." — Yakima,
Washington.
"That the Superintendent or any member of his
department so authorized by him may enter into and
upon any lands and premises for the purpose of
inspecting the sewer connections and any pipe or
other apparatus or thing connected therewith,
particularly rain downspouts." — Transcona,
Manitoba.
"The City Engineer and other duly authorized
employees of the City bearing proper credentials and
identification shall be permitted at all reasonable
hours to enter upon all properties for the purpose of
inspection, observation, measurement, sampling and
testing, in accordance with the provisions of this
Ordinance." - Wyoming, Michigan.
"The officers, officials, servants, employees and
workmen of the City shall have the right at all
reasonable times to enter upon any land to which this
section applies, to inspect the works installed thereon
and generally for the purpose of ascertaining whether
the provisions of the said subsection are being
compiled with." - Yorktown, Saskatchewan.
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'The officers, inspectors and any duly authorized
employee of the District shall carry evidence
establishing his position as such and upon exhibiting
the proper identification shall be permitted during
reasonable hours to enter in and upon any and all
buildings, industrial facilities and properties for the
purpose of inspection, reinspection, observations,
measurements, sampling, testing or otherwise
performing such duties as may be necessary in the
enforcement of the provisions of the ordinances, rules
or regulations of the District." — Enterprise Public
Utility District, Shasta County, California.
"The Engineer in Charge and other duly
authorized employees of the City bearing proper
credentials and identification shall be permitted to
enter all properties for the purposes of inspection,
observation, measurement, sampling and testing in
accordance with the provisions of this ordinance. The
Engineer in Charge or his representatives shall have no
authority to inquire into any processes including
metallurgical, chemical, oil refining, ceramic, paper,
or other industries beyond that point having a direct
bearing on the kind and source of discharge to the
sewers or waterways or facilities for waste treatment.
While performing the necessary work on private
properties referred to above, the Engineer in Charge
or duly authorized employees of the City shall
observe all safety rules applicable to the premises
established by the company and the company shall be
held harmless for injury or death to the City
employees and the City shall indemnify the company
against loss or damage to its property by City
employees and against liability claims and demands
for personal injury or property damage asserted
against the company and growing out of the gauging
and sampling operation, except as such may be
caused by negligence or failure of the company to
maintain safe conditions. The Engineer in Charge and
other duly authorized employees of the City bearing
proper credentials and identification shall be
permitted to enter all private properties through
which the city holds a duly negotiated easement for
the purposes of, but not limited to, inspection,
observation, measurement, sampling, repair, and
maintenance of any portion of the sewage works
lying within said easement. All entry and subsequent
work, if any, on said easement, shall be done in full
accordance with the terms of the duly negotiated
easement pertaining to the private property
involved." - Knoxville, Tennessee.
4.6.7 Testing for Sewer Infiltration
"No house connections will be permitted until
sections of sewers are completed between completed
manholes and inspected for infiltration and other
tests which the City Inspector deems
necessary." -NewBritain, Connecticut.
'The inspection shall include a test to determine
that the side sewer is of tight construction and does
not allow infiltration or exfiltration of water.
Specifications for such a test shall be included in the
rules and regulations (the City Engineer may make)
referred to in Section 35 of this
ordinance." — Seattle, Washington.
"Infiltration testing shall take place when the
natural ground water table is above the crown of the
higher end of the test section. The maximum
allowable limit for infiltration shall be four-tenths
(0.4) gallon per hour per inch of internal diameter per
100 feet of length with no allowance for external
hydrostatic head." — Anchorage, Alaska.
"If, in the construction of 'a section of sewer
between any two structures, excessive ground water is
encountered, the test for leakage shall not be used,
but instead the end of the sewer at the upper
structure shall be closed sufficiently to prevent the
entrance of water, and the pumping of the ground
water shall be discontinued for at least three days
after which the section shall be tested for infiltration.
The infiltration, as measured by the amount of water
intercepted at the structure below the plugged end of
the sewer, shall not exceed 0.1 gallon per minute per
inch of nominal diameter of pipe per 1,000 feet of
length of sewer being tested. If the sewer main being
tested contains laterals, the allowable leakage shall
not exceed 0.2 gallon per minute per inch of nominal
diameter per 1,000 feet of length of sewer main being
tested. The length of laterals shall not be used in
computing the length of sewer main being
tested." - Escondido, California.
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SECTION 5
ECONOMIC GUIDELINES
5.1 The Economic Factors Involved
5.2 Guideline For Economic Evaluation
5.3 Example: Infiltration and Inflow Costs
5.4 Evaluation of Costs vs. Benefits of Corrective Measures
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SECTION 5
ECONOMIC GUIDELINES
5.1 THE ECONOMIC FACTORS INVOLVED
When excessive amounts of infiltration and
inflow waters enter sanitary or combined sewer
systems, the immediate effects are "physical." As
important as these physical effects on the capacities
and capabilities of sewer conduits, pumping facilities,
treatment works and regulator-overflow structures
may be, the full impact of such extraneous waters
cannot be known until the "financial" factors are
computed and evaluated.
The evaluation of the economic factors of
infiltration and inflow has been given little attention
because of the unavailability of rational fiscal
guidelines that will permit the computation of the
tangible costs of handling excessive amounts of
extraneous waters and balancing these costs against
the cost of constructing relatively infiltration-free
sewer systems in the future and of financing projects
to correct infiltration and inflow conditions in
existing systems.
This Manual outlines a rational approach to the
economic factors involved in surcharged sewer
systems and over-taxed waste water handling,
treatment and disposal works. It stresses the two
factorial effects of excessive infiltration and inflow:
"sanitation" and "cents." These include, but are not
limited to, the following:
1. Increased size and cost of new sewers if
excessive infiltration and inflow are
permitted;
2. Need for construction of relief or
supplementary collection and interception
sewers, at dates prior to those originally
estimated as the economic life of existing
seweis;
3. Operation and maintenance costs for
handling local sewer surcharges, clean-up of
flooded areas, and damages to flooded
private properties;
4. Increased operation and maintenance costs
for pumping excess flows;
S. Cost of repairing pavement cave-ins and
wash-outs of subsurface utilities caused by
infiltration and exfiltration;
6. Cost of removing soil and debris and tree
roots entering sewers through defective sewer
pipes and joints;
7. Cost of excessive wear on pumping station
equipment and power requirements;
8. Increased operation and maintenance costs at
waste water treatment plants;
9. Need for increases in treatment capacity
because systems are overloaded with
excessive infiltration and inflow volumes,
and
10. Regulating agencies will no longer tolerate
the bypassing of flows from sewers or waste
water treatment plants.
The hidden costs of infiltration-inflow usurpation
of system capacities and capabilities generally have
been overlooked when jurisdictional officials are
planning corrective action. Even the readily
computable costs of such extraneous water intrusion
into systems seldom have been evaluated and
properly interpreted in terms of the economics of
urban services.
Where preventive measures have been taken to
reduce infiltration in new sewer systems, designers
and utility officials have been concerned about any
added cost of projects covered by specifications for
tighter systems. Little consideration has been given to
immediate and long-range savings that might accrue in
terms of reduced size of new sewer lines and longer
service life of such systems.
If and when correction of infiltration in existing
overtaxed sewer systems has been considered or
undertaken, the main concern has been the
out-of-pocket or bond investment for sealing or
replacing defective sewer structures. Little thought
has been given to the comparative economies of costs
vs. the benefits to be derived in sewer system service
and in the pumping and treatment of waste waters.
Few jurisdictions actually have evaluated the volumes
of flow due to infiltration and inflow and the marked
economic effect of these extraneous flows.
Emphasis has always been on the adverse effects
of surcharged sewers on the public which uses
thoroughfares and on property owners
inconvenienced and injured by the back-flooding of
overtaxed sewers into their properties. Sanitation and
convenience thus have been considered to the
exclusion of the dollar cost of such flooding
conditions.
No meaningful evaluation of this problem, in all
of its ramifications and implications, can be made
without taking up the costs of such intruded flows
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and the capital investments required to eliminate or
alleviate the difficulties previously mentioned.
Otherwise no rational relationship between costs and
benefits can be developed.
For this reason a guideline approach to an
economic evaluation g of these problems is offered. It
is based on a theoretical community "profile" for
two different size jurisdictions, under two different
conditions. In this sense, it is a sample of an
economic concept because there is no such thing as
an average community and an average sewer system.
Each jurisdiction has its own character; its sewer
system and treatment and disposal facilities are
individualized.
The cost assumptions and other factors used in
the guideline may or may not reflect conditions in
any individual jurisdictional system. Each community
has its own cost experiences, its own sewer system
needs, its own pumping and treatment requirements,
and other factors than those outlined.
Such local "known" factors can be used to
replace the arbitrarily chosen physical and economic
assumptions used in the sample analysis. The value of
the guideline is that it illustrates a method whereby
the costs and benefits of infiltration and inflow, and
of their prevention and correction, can be
determined. Admittedly, such economic analyses may
be subject to errors, but any such computations will
be an improvement over past practices of disregarding
the economics of sewer services in an era when all
urban functions deserve such evaluations.
5.2 GUIDELINE FOR ECONOMIC EVALUATION
5.2.1 General
The first step in an economic analysis of the
infiltration and inflow problem in any jurisdiction is
to tabulate the so-called "community profile" in
terms of pertinent sewer service factors. Table 5.2.1
shows the community profiles chosen as the basis of
the analysis for two jurisdictions. Population sizes of
100,000 and 250,000 were chosen because there are
numerous communities of these sizes in the United
States. A key explanation of terms and data sources
will enable jurisdictional officials and consulting
engineers to prepare specific profiles for any
communities under consideration.
5.2.2 Collection System
The capital or construction costs of a sewer
system show wide variations among cities. Differences
in topography and climate are two of the several
reasons. The sewer pipe and manhole costs presented
in this analysis reflect approximate values from
28,570 71,430
TABLE 5.2.1
COMMUNITY PROFILE
Population 100,000 250,000
1. Area (acres) 12,000 28,000
2. Density (persons/acre) 8.3 8.9
3. Housing Units
(3.5 persons/unit)
4. Housing Structures
(75% of units) 21,430 53,570
5. Mfg. Establishments 112 333
6. Business Establishments 1,470 3,900
7. Business Structures
(75%ofest.) 1,100 2.900
8. All Structure Connections
(ft./structure) 60 60
9. Diameter (inches) 6 6
10. House Connections
(feet)
11. Mfg. Connections
(feet)
12. Business Connections
(feet)
1,285,800 3,214,200
6,720 19,980
66,000 174,000
TOTAL 6 inch
Building Sewer Connections 1,358,520 3,408,180
Municipal System
13. Sewer Miles/Acre .022 .02!
14. Total Sewer Miles 264 588
15. Pipe Size as Percent of Total
System (feet)
6 in. to 8 in. @ 75% 1,045,440 2,328,480
10 in. to 12 in. @ 14% 195,149 434,650
15 in. to 18 in. @ 6% 83,635 186,278
21 in. to 27 in. @ 4% 55,757 124,186
30 in. to 42 in @ 1% 13,939 31,046
Total Length of Sewer Sys. 1,393,920 3,104,640
16. Manholes 3,485 7,762
several midwestern areas. It was assumed that the
presented values include all costs, such as landscaping
and street cut repairs, and other phases of
construction and reconstruction. Not included in this
analysis were the costs of sewage pumping stations.
Table 5.2.2 shows the assumed unit capital costs by
pipe size, and for manholes. Operation and
maintenance costs, including overhead for collection
systems, are arbitrarily estimated at 1 percent of
capital costs.
Also included in the costs for a collection system
are estimates for emergency repairs resulting from
street cave-ins, and for pumping and clean-up due to
wet-weather flooding of local areas. The inclusion of
these costs is justified because sewer infiltration
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KEY - TABLE 5.2.1
1- Area — Average sewered area of cities in
these population ranges. Taken from a
survey summary prepared by APWA for a
study on combined sewer overflows.
Problems of Combined Sewer Facilities
and Overflows 1967. Federal Water
Pollution Control Administration, U. S.
Dept. of the Interior; December, 1967.
2. Density — Based on average area and
population by city size, from overflow
report summary (Ibid).
3. Housing Units - Average for all SMSA's in
1960. 7960 Census of Housing, Bureau of
the Census, U. S. Dept. of Commerce.
4. Housing Structures — Average for all
SMSA's in 1960 (Ibid).
5. Manufacturing Establishments — Based on
average number for appropriate SMSA size.
Each establishment assumed to occupy
separate structures. 1963 Census of
Manufacturers. Bureau of the Census, U.S.
Dept. of Commerce.
6. Other Business Establishments — Based on
average number of retail and service
establishments by appropriate SMSA size.
-7963 Census of Business. Bureau of the
Census, U. S. Dept. of Commerce.
1. Other Business Structures — Assumed to
be 75 percent of business establishments.
8/9. All connecting sewers were assumed to be
6-inch vitrified clay pipe with a length of
60 feet between the structure and the
municipal sewer
10. Presented in feet. Number of structures
times 60 feet.
11. Presented in feet. Number of structures
times 60 feet.
12. Presented in feet. Number of structures
times 60 feet.
13. Sewer Miles/Acre — Based on overflow
survey cited in (1), above.
14. Total Sewer Miles — Sewer miles/acre,
times average area.
15. Pipe Size and Percen t of System — Average
sizes as percent of system based on U. S.
totals estimated by BSDA. Picton, Walter
L.; "2.7 Billion Feet of Sewer Pipe Will
Serve Communities by 1975." Wastes
Engineering. November, 1959
16. Manholes — One manhole for each 400
feet of municipal sewers. Merritt,
Frederick S. Ed. Standard Handbook for
Civil Engineers. New York: McGraw-Hill
Book Co. 1968.
TABLE 5.2.2
UNIT CAPITAL COSTS OF
SEWAGE COLLECTION SYSTEM
Unit UNIT Capital Cost
Pipe:
6 inch Building Connections $ 6.00/1. ft.
6 & 8 inch Municipal Sewers 10.00/1. ft.
10 & 12 inch 12.00/1. ft.
15 & 18 inch 20.00/I. ft.
21 to 27 inch 30.00/I. ft.
30 to 42 inch 40.00/I. ft.
Manholes 300.00 each
Source: Bid prices supplied by Streater Division,
Clow Corporation for new systems
contributes to street substructure undermining and
erosion and wet-weather flooding due to surcharged
sewers.
The cost figures for repairs and cleanup are
arbitrary; they are presented to illustrate typical costs
directly attributable to infiltration and inflow. Any
jurisdiction can substitute its own cost experiences in
making a similar analysis.
The costs for emergency street repairs have been
assumed as $10,000 per 100 miles of sewer per year.
Pumping and clean-up due to flooding also is
estimated'at $10,000 per 100 miles of sewer per year.
5.2.3 Treatment Plant
The plant chosen for this model is one providing
three stages of waste water treatment. The costs
presented are those for an activated sludge
primary-secondary system and an activated carbon
tertiary treatment system.
The capital costs of primary and secondary
treatment are based on a study conducted by the U.
S. Public Health Service in 1963.1 The cost of
tertiary treatment has been estimated at 100 percent
of the costs of primary-secondary treatment.2 Plant
operating and maintenance costs are based on a study
Modern Sewage Treatment Plants — How Much Do They
Cost? Public Health Service, Division of Water Supply and
Pollution Control. U. S. Department of Health, Education
and Welfare, Washington, D.C., 1964.
Cost and Performance Estimates For Tertiary Waste Water
Treating Processes. Federal Water Pollution Control.
Administration, U. S. Department of the Interior, Cincinnati,
Ohio, June, 1969.
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carried out by P. P. Rowan, K. L. Jenkins and D. H.
Howells of the Public Health Service.3 The operating
costs of tertiary treatment are again assumed to be
100 percent of primary-secondary treatment.
The capital costs of primary and secondary
facilities were computed on a per-capita basis. These
were converted to gallons per day by assuming an
average flow of 100 gallons per day, per person. For
each of the two city sizes presented (100,000 and
250,000 population) two plant sizes are shown. The
first is based on a 100 gallons/capita flow and the
second includes a 70 percent industrial population
equivalent.4 Operation and maintenance costs also
were computed on a per-capita basis. Regardless of
the sources of flow to the plant, the analysis gives a
basis for making decisions as to effect of the volume
on increased plant costs.
5.2.4 Capital Costs
As stated previously, the capital costs were based
on a Public Health Service study. Data on activated
sludge "plants were available from 133 construction
projects in all parts of the country. The included
projects represented design populations up to
100,000. The expected costs were estimated by
regression analysis from the formula:
log lOy = 3.6533024 - 0.2782395 log X
y = expected per capita cost
X = design population (r = —0.73)
(r = coefficient of correlation)
The resulting values represent contract
construction costs. Not included are engineering, legal
and administrative costs. Also not included are land
acquisition costs. The study points out that the
non-construction costs, exclusive of land, could add
20 percent to the expected costs. These costs have
been added, as has 10 percent for land acquisition.
All study capital costs were stated in 1957-59 dollars.
Those presented herein were inflated to 1967 levels
using the FWQA treatment plant U. S. cost index
(1967 = 120.28).
Annual capital costs are based on an average
useful life of 25 years5 and a 5-percent interest rate,
3Rowan, P.P.; Jenkins, K.L; Howells, D. H., "Estimating
Sewage Treatment Plant Operation and Maintenance Costs."
Journal of the Water Pollution Control Federation, Vol. 23;
February, 1961.
This is the average proportion, for the areas surveyed, of
industrial waste population equivalent to total population
from the APWA overflow study survey, Problems of
Combined Sewer Facilities and Overflows. 1967. Federal
Water Pollution Control Administation, U. S. Department of
the Interior, December, 1967, p. 69.
SKeefer, C. E., "Estimating the Life of Sewage Treatment
Facilities," Public Works. Vol. 93 July 1962, pp. 79-82.
despite the fact that present rates on municipal bonds
are considerably higher.
It should be noted that the projects included in
the Public Health Service study were limited to those
with design populations of 100,000 or less.
Therefore, the values obtained for plants of over
10-mgd capacity may or may not reflect the actual
costs of larger treatment facilities. The lack of
applicable cost data for larger plants necessitated the
extension of the cost curve beyond the sample range.
However, the resulting values appear reasonable and
are presented for illustrative purposes only.
5.2.5 Operating Costs
Plant operation and maintenance costs also are
based on a Public Health Service survey. Included in
this were operating and maintenance costs for 60
activated sludge treatment facilities. In this study the
valid design population range is up to 200,000. As
before, extension of the curve may or may not
accurately reflect these costs for larger plants. The
expected values were estimated from the formula:
log Y = l/(-0.50927) + 0.13791 log X
y = the expected annual per capita cost x 10
X = population served x 0.01 (No r is given)
All costs were stated in 1957-59 dollars. They have
been inflated to the 1967 level by use of the
OBE-IPD of state and local government purchases of
goods and services (1967 = 133.3). Included in the
operation and maintenance costs are all costs other
than central administration and capital maintenance.
Figure 5.2.5 shows the capital and operating
costs of treatment from the formulas above. The
figures have been adjusted and inflated to 1967 price
levels. Table 5.2.5.1. shows the various treatment
costs for the four plant sizes. All figures are per
million gallons of daily design flow.
Tables 5.2.5.2. and 5.2.5.4. summarize the total
direct costs of sewage collection and treatment. The
annual capital costs for the collection system were
computed by using a 20-year life and 5-percent
interest rate. The 20-year life reflects an accepted
practice of bonding sewage construction costs. The
collection system itself may have a useful life of from
50 to 100 years, but can be paid for in about 20
years.
Figures 5.2.5.3 and 5.2.5.5 show the various
annual collection and treatment costs as a percentage
of the total direct annual municipal costs.
Table 5.2.5.6 presents the various system costs as
a cost per unit. From these figures, estimates of the
costs of infiltration and inflow can be illustrated. As
discussed earlier, the costs of pumping stations have
56
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TABLE 5.2.5.1
UNIT TREATMENT PLANT COSTS PER MGD (1967 PRICE LEVEL)
10mgd
$290,389
20,604
Population
Average Plant Size
Capital Costs
Primary & Secondary Treatment
Total Capital Costs/mgd
Annual Capital Costs/mgd
Tertiary Treatment
Total Capital Costs/mgd
Annual Capital Costs/mgd
Total Treatment Capital Costs/mgd
Total Annual Capital Costs/mgd
Annual Operation & Maintenance Costs
Primary & Secondary Treatment/mgd $ 16,129
Tertiary Treatment/mgd
Total O & M Costs/mgd
Total Annual Treatment Costs/mgd
Total Annual Treatment Cost
100,000
250,000
17mgd
$ 250,538
17,776
25 mgd
$ 224,976
15,962
42.5 mgd
$ 194,176
13,777
290,389
20,604
$580,778
41,208
250,538
17,776
$ 501,076
35,552
224,976
15,962
$ 449,952
31,924
194,176
13,777
$ 388,352
27,554
$ 16,129
16,129
$ 32,258
$ 73,466
$734,660
$ 14,930
14,930
$ 29,860
$ 65,412
$1,192,544
$ 13,997
13,997
$ 27,994
$ 59,918
$1,497,950
$ 13,063
13,063
$ 26,126
$ 53,680
$2,281,400
discussed earlier, the costs of pumping stations have
not been included in this analysis.
5.3 INFILTRATION AND INFLOW COSTS
To illustrate these costs, an example is presented
using the cost data from the 100,000-population city.
In this case it is assumed that 10 gallons per
capita per day is ground water infiltration and inflow.
Initially, the relevant costs are those that will vary
with changes in flow. When considering costs over a
short period of time, the capital costs are not variable
and should not be considered.
For a city with a population of 100,000,
infiltration is assumed to add 1 mgd to the total flow.
For the municipality, the costs attributable to this
infiltration would be a portion of the 0 & M costs of
collection and treatment. From Table 5.2.5.6 the
costs of 1000 gpd are $10.44 for collection and
$29.86 for treatment. At 1 mgd, the total annual cost
of infiltration/inflow would be about $40,000.
To this, the annual costs of emergency street
repairs and wet-weather basement flooding must be
added, inasmuch as the elimination of infiltration and
inflow will end these occurrences. The costs of both
emergency street repairs and flooding each have been
estimated at $10,000 per 100 miles of sewer per year.
A city of 100,000 people has approximately 264
miles of sewer (Table 5.2.1). Therefore, the annual
cost of street repairs and flooding damage would be
about $53,000.
The total avoidable costs of 0 & M and
emergency repairs and flooding will be approximately
$93,000 per year.
5.4 COSTS VS. BENEFITS EVALUATION
It must now be determined if this annual saving is
great enough to offset the cost of eliminating
infiltration and inflow. By assuming that correction
costs will be capitalized at 5 percent for 20 years, the
break-even point can be determined. That is, what
capital investment with a 20-year payback period at 5
percent will have an annual capital cost of $93,000?
The investment would be approximately $1,160,000.
The 20-year payback may or may not represent
the true useful life of the capital expenditure. Should
the useful life be longer, the savings also will be
realized for the longer period. This would raise the
break-even points. Also not reflected is the trend
toward increasing unit costs. Any increases would
permit a higher break-even point.
However, for illustration purposes, the
$1,160,000 figure will be used. An investment up to
$1,160,000 to eliminate infiltration and inflow
costing $93,000 per year in avoidable costs will result
57
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£
'5.
3
I
FIGURE 5.2.5
TOTAL CAPITAL COST - PRIMARY & SECONDARY TREATMENT
( 1967 Dollars)
$35
$30
$10
50 100 150 200 250 300 350 400 450 500
Population x 1,000
a
'5.
3
I
1
u
*
1.60
.50
1.40
$1.30
^
50
ANNUAL OPERATION & MAINTENANCE COSTS
PRIMARY & SECONDARY
(1967 Dollars)
LI
J-U
100 150 200 250 300 350 400 450 500
Population x 1,000
58
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TABLE 5.2.5.2
TOTAL SYSTEM COSTS
100,000 POPULATION
Collection
Private Connections
Municipal System
6 & 8 Inch Pipe
10 & 12 Inch Pipe
15 & 18 Inch Pipe
21 to 27 Inch Pipe
30 to 42 Inch Pipe
Total Municipal Sewer Pipe
Manholes
Treatment:
Primary & Secondary
Tertiary
Total Treatment
Total Municipal Collection
& Treatment
Total System
Unit
1.358,520 ft.
1,045,440ft.
195,149 ft.
83,635 ft.
55,757 ft.
13.939 ft.
3,485
17mgd
17mgd
—
__
—
Unit
Capital
Cost
$
6.00/ft.
10.00/ft.
12.00/ft.
20.00/ft.
30.00/ft.
40.00/ft.
300.00 ea.
250,538/mgd
250,538/mgd
—
—
Total
Capital
Cost
$
8,151,120
10,454,400
2,341,788
1,672,700
1,672,710
557,560
16,699,158
1,045,500
4.259,146
4,259,146
8,518,292
26,262,950
34,414,070
Annual
Capital
Cost
$
654,070
—
-
—
—
—
1,339,991
83,894
302,192
302,192
604,384
2,028,269
2,682,339
Total
Annual
O & M Cost
$
81,511
—
-
-
—
—
166,992
10,455
253,810
253,810
507,620
685,067
766,578
Total
Annual
Cost
$
735,581
—
-
-
-
—
1,506,983
94,349
556,002
556,002
1,112.004
2,713,336
3,448,917
FIGURE 5.2.5.3
ANNUAL MUNICIPAL COLLECTION & TREATMENT COSTS
AS PERCENT OF TOTAL ANNUAL MUNICIPAL COSTS
22%
19%
Annual Capital Cost —
Collection
i i i i .,.,.
O&M
o
K
j>
Annual
Capital
Cost-
Treatment
i i i
O&M
Treatment
10 20 30 40 50 60 70 80 90 1C
Percent
59
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TABLE 5.2.5.4
TOTAL SYSTEM COSTS
250,000 POPULATION
Unit
Collection
Private Connections 3,408,180 ft.
Municipal System
6 & 8 Inch Pipe 2,328,480 ft.
10 & 12 Inch Pipe 434,650 ft.
15 & 18 Inch Pipe 186,278 ft.
21 to 27 Inch Pipe 124,186 ft.
30 to 42 Inch Pipe 31,046ft.
Total Municipal
Manholes
7,762
Treatment:
Primary & Secondary 42.5 mgd
Tertiary 42.5 mgd
Total Treatment —
Total Municipal —
Collection & Treatment —
Unit
Capital
Cost
6.00/ft.
10.00/ft.
12.00/ft.
20.00/ft.
30.00/ft.
40.00/ft.
300.00 ea.
194,176/mgd
194,176/mgd
Total System — —
Total Annual Total Total
Capital Capital Annual Annual
Cost Cost O&M Cost Cost
20,449,080 1,640,896 204,491 1,845,380
23,284,800 - -
5,215,800 -
3,725,560 - -
3,725,580 - - -
1,241,840 - - -
37,193,580 2,984,524 371,936 3,356,460
2,328,600 186,854 23,286 210,140
8,252,480 585,523 555,178 1,140,701
8,252,480 585,523 555,178 1,140,701
16,504,960 1,171,046 1,110,356 2,281,402
56,027,140 4,342,424 1,505,578 5,848,002
76,476,220 5,983,320 1,710,069 7,693,389
FIGURE 5.2.5.5
ANNUAL MUNICIPAL COLLECTION & TREATMENT COSTS
AS PERCENT OF
0
Annual Capital Cost
Collection
I I i
10 20 30
TOTAL ANN
1 1
i 1
40 50
UAL MUNICIPAL COSTS
O&M Annual
c Capital ° & M
o
** Cost — Treatment
= Treatment
I I '
60 70 80 90 100
Percent
60
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TABLE 5.2.5.6
PER CAPITA AND PER 1000 GPD COSTS
MUNICIPAL SYSTEM
Population
Per Capita Cost - Municipal System
Total Capital - Collection
Annual Capital - Collection
Annual 0. & M. - Collection
Total Capital - Treatment
Annual Capital - Treatment
Annual O. & M. - Treatment
Annual Cost Per 1000 Gallon Daily Flow
Total Capital - Collection
Annual Capital — Collection
Annual O. & M. - Collection
Total Capital — Treatment
Annual Capital - Treatment
Annual O. & M. — Treatment
Cost Per 1000 Gallons
Capital — Collection
O. & M. - Collection
100,000
(17 mgd)
$ 177.45
14.24
1.77
$ 85.18
6.04
5.08
Municipal System
$1,043.80
83.76
10.44
250,000
(42.5 mgd)
$158.09
12.69
1.58
$ 66.02
4.68
4.44
$
501.08
35.55
29.86
0.2295
0.0286
$929.93
74.62
9.30
$388.35
27.55
26.13
0.2044
0.0255
Capital — Treatment
O. & M. - Treatment
0.0974
0.0818
0.0755
0.0716
in a net saving to the community. For example: If the
investment necessary is $1,'000,000, and this is
amortized at 5 percent for 20 years, the annual cost
would be approximately $80,000. The annual
infiltration and inflow cost of $93,000, less the
annual cost of its elimination, would result in a net
savings of $13,000 per year.
It is uncertain if total infiltration and inflow to a
total system of the size described could be corrected
for $1,160,000. However, there may be relatively
short sections within the system accounting for a
large portion of the extraneous flow. In such cases,
investment in correction may result in an appreciable
net savings.
In addition to possible variable cost savings,
future capital system expenditures to meet increasing
demand may be reduced or postponed. If either or
both the collection and treatment plant are operating
at or near capacity, a reduced flow would eliminate
the need for immediate construction to increase
system capacity.
A case may arise where a city finds it necessary
to extend service to a new subdivision or a new
satellite urban area, or to a formerly unsewered area
within its jurisdiction. Here the choice could be
between expansion of treatment and interceptor
capacity and the reduction of present flow.
The cost data from Table 5.2.5.6 will permit the
determination of the low cost alternative. For
simplification, assume that the increased demand will
be 1 mgd and that any increments to plant capacity
will be made at constant costs.
To expand collection and treatment facilities to
handle 1 mgd, a capital expense of $1,544,880 would
be required [Table 5.2.5.6 ($1,043.80 + 501.08) x
1000].
61
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The annual capital cost of this investment would
be approximately $119,000 [Table 5.2.5.6: (83.76 +
35.55) x 1000]. For comparison, the annual costs of
0 & M ($40,000) and street repair and flooding
($53,000) must be added. Therefore these three cost
factors are the annual avoidable costs accruing from
the correction of infiltration and inflow. This is how
much a city could spend on the correction of
infiltration and inflow to reduce the daily flow by 1
mgd, and save money by doing so.
In the above example, the total annual cost of
the capacity expansion alternative is $212,000.
Assume again a 20-year payback at 5 percent for the
cost of correcting infiltration and inflow. In this case
the break-even point will be about $2,640,000. Any
investment for infiltration and inflow reduction
resulting in a reduced flow of 1 mgd and costing less
than $2,640,000 will produce a net savings to the
community.
The examples cited above are admittedly
over-simplifications. However, they do serve to point
out the need for more comprehensive examinations
of both the present and future costs of any capital
investment decision. A lower initial cost is not always
the least expensive way to achieve a desired objective.
Before the true costs of alternatives can be
determined, all inputs must be outlined and stated in
compatible terms. The figures presented herein show
the required inputs for two moderate-size cities. They
may serve as yardsticks for comparison with like-size
communities. However, the major value of this
analysis is in the illustration of the total system cost
considerations needed when making an investment
decision. Each jurisdiction can evaluate its own fiscal
policies by using data relating to its own sewer costs,
sewage flows, treatment processes, infiltration and
inflow corrective measures, local bond-financing
practices and other factors considered in the analysis
presented above.
Jurisdictional officials and consultants are
reminded that the decision to undertake infiltration
and inflow correction may have to be based on local
sanitation and water pollution control factors such as
a no bypass policy, over and above the economic
considerations.
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SECTION 6
TRENDS AND DEVELOPMENTS
6.1 Intensification of the Problem
6.2 Improvements in Pipe and Joint Products
6.3 Tightening Infiltration Allowances
6.4 Improvements in Construction and Inspection Practices
6.5 Elimination of Existing Infiltration
6.6 Improvements in Inspection, Testing and Sealing Products
6.7 Improvement in Building Sewer Construction Practices
6.8 Better Prevention and Elimiantion of Inflow Connections
6.9 Summary
63
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SECTION 6
TRENDS AND DEVELOPMENTS
6.1 INTENSIFICATION OF THE PROBLEM
Today's recognition of the infiltration and inflow
problem springs from urban growth and the essential
role which sewer system capacities and wastes
handling facility efficiencies play in environmental
sanitation and water pollution control. The 2,942
million feet of sewers now in service represent an
investment generally estimated to be upwards of $50
billion. It is predicted that an additional 1,240
million feet of public sewers must be installed in the
next decade, and 649 million feet of new sewers will
be needed to replace inadequate lines now in service.
These additions and replacements will represent a
further investment of some $20 billion.
It would be inexcusable to shorten the service life
of existing sewer systems by allowing extraneous
waters that do not require collection and treatment
to usurp capacities required for present and future
flows. This Manual has offered guidelines for
evaluating the dollar value of infiltration and inflow
in terms of their effects on sewer systems and
waste-water treatment facilities.
Every 100 gallons per day of unnecessary
infiltration and inflow removed from an existing
system, or prevented from entering a new system,
provides capacity for a new urban resident or for an
industrial wastes equivalent unit in an expanding
urban era. On the basis of causes, sources, and effects
of infiltration and inflow in its own system, each
jurisdiction must evaluate its problem on the basis of
its own conditions, its own cost factors, and its own
policies.
6.2 IMPROVEMENTS IN PIPE AND
JOINT PRODUCTS
Improvements have been made by manufacturers
through research and development of improved sewer
pipe and sewer jointing materials. Effective choice
and use of these products is the keystone to, better
control of infiltration. Still further progress in pipe
and jointing methods can be anticipated in the next
few years. Designers, contractors, and jurisdictional
administrators must maintain close contact with
manufacturers to keep informed on product progress.
Cooperation between sewer officials and those who
serve them, and manufacturers, will stimulate greater
product developments which can assist in the
reduction and elimination of infiltration.
6.3 TIGHTENING INFILTRATION ALLOWANCES
A quarter-century ago many sewers were built
under specificatipns which permitted infiltration rates
as high as 1,000 gallons per day per mile of length per
inch of pipe diameter. These are the sewers which are
still in service in many jurisdictions at the outset of
the 1970's. The common infiltration rate in present
practice is sharply reduced from the earlier
specification allowances, judging from the findings of
the national investigatory project recently completed
by the American Public Works Association for the
Federal Water Quality Administration and
participating jurisdictions. The general use of the 500
gpd/mile/inch of pipe diameter was given impetus by
the adoption of this criterion by the so-called 'Ten
States Standards" nearly two decades ago.
Better pipe products — and particularly the
development and application of better jointing
materials and methods for these new pipe types with
proper construction and rigid inspection — offer
unmistakable opportunities for markedly lower
infiltration allowances in all future construction
work. Better equipment and tighter control of
construction methods can produce approaches to
watertight sewers; examples of this type of sewer
construction already are in service. It is physically
possible and economically feasible to limit infiltration
allowances to 200 gallons per day per mile of sewer
per inch of pipe diameter, a level which can be
specified and conformed to without any appreciable
increase in construction costs.
6.4 CONSTRUCTION AND INSPECTION
IMPROVEMENTS
The best pipe and jointing material in the world
cannot assure a watertight sewer job. Construction
methods must make the proper use of such materials,
because no sewer job is any better than its
construction quality. The sewers of the future must
be laid in dry trench, on proper bedding, with good
backfill and compaction methods, and under
conditions that will assure physical stability while the
line is in service. Joints must be made carefully.
Every sewer job must be inspected adequately to
assure adherence to construction specifications. Alert
65
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inspection is as important as proper materials and
construction methods. Modern methods of inspection
and testing to determine the tightness of sewer lines,
from section to section, are available. They must be
applied in every sewer construction project.
6.5 ELIMINATION OF INFILTRATION IN
EXISTING SEWERS
The total problem of infiltration cannot be
solved by even the best design and construction
practices for new sewer systems. The greater footages
of sewers now in service — antedating today's better
pipe, joint materials, and construction
methods — allow excessive infiltration which must be
eliminated or minimized to overcome the usurpation
of sewer capacities and the capacities of pumping,
treatment, and disposal facilities.
Jurisdictions affected by infiltration must carry
out surveys to locate sources of such extraneous
waters, determine their volumes, and correct defects
in sewer pipe, joints, manholes, and other
appurtenant structures.
6.6 IMPROVEMENTS IN INSPECTION,
TESTING AND SEALING PRACTICES
Survey procedures must be planned carefully
and executed expertly. Lines must be cleaned prior
to internal inspection or sealing. Inspection methods
«and devices of great sophistication can assist in
visual observation. Closed-circuit television equipment,
photographic devices, physical observation facilities,
and other internal inspection systems are available to
jurisdictional agencies. Commercial firms with wide
experience and highly specialized equipment can
carry out the multiple functions of infiltration
inspection-location-correction and be retained for
this purpose.
Effective and economical methods for correcting
points of defect in sewer systems include methods for
internal sealing of pipe and joints with chemical
compounds and physical grouting materials. Other
sealing methods are applicable by means of external
corrective procedures. The present capabilities of
such sealant methods will be increased by further
research and development. The use of such
infiltration control, methods will increase. Physical
replacement of defective sewer pipe and joints will
remain a workable procedure, but in areas of urban
densities such reconstruction methods may result in
disruption of traffic and impediments to other public
services. Success has been reported in lining larger
sewers, especially those constructed of brick.
6.7 IMPROVEMENT IN BUILDING SEWER
CONSTRUCTION PRACTICES
Infiltration through building sewer connections
must be recognized as a serious problem. Future
infiltration from such sources must be eliminated by
improved construction, inspection, and approval
practices. Every jurisdiction must examine its present
regulations for such construction, and evaluate the
effectiveness of the agency or agencies now charged
with regulating these connection-line installations.
What if supervisory control of building sewer
connections is divided between (1) multiple agencies,
such as building and plumbing officials for the section
between the building and the property line, and (2)
sewer, engineering, or public works officials for the
section between the property line and the street
sewer, together with connection thereto? In that case,
consideration should be given to consolidating total
authority in a single agency or to. planned
cooperation and coordination of multiple-agency
actions.
Improved building sewer construction will
involve more rigid regulations, stronger enforcement
and inspection practices, and more effective testing of
such lines before approval. The choice of available
pipe and jointing materials should be made on the
basis of local needs and conditions. Connections of
building sewers to dissimilar materials should be made
with an approved fitting.
Poor conditions of existing building sewer
connections are the cause of a large percentage of the
total infiltration flows being handled by sewer
systems. Efforts should be made to locate and
evaluate such infiltration sources. Programs of
correction should be instituted, where this is feasible,
with the use of sealing methods similar to those
utilized for public sewer rehabilitation programs.
Excavation and replacement of defective building
sewers may be required despite its costliness and
inconvenience to the public.
Building sewers should not be connected to street
sewers by any means other than through a suitable
wye fitting. Other connections can cause obstructions
in the street sewer or result'in connections that are
not tight. All wye-connections installed on sewers
prior to building connections must be capped or
plugged to prevent infiltration. All abandoned
66
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building connection stubs must be sealed to prevent
open sources of infiltration.
6.8 PREVENTION AND ELIMINATION OF
INFLOWS IN SEWER SYSTEMS
Inflows into sanitary sewers must be eliminated
to the greatest possible extent. All future connections
to sewer systems should be regulated by sewer-use
ordinances or other legislative edicts. Existing inflow
connections should be eliminated, to the greatest
extent possible and feasible, by surveys to locate
sources, followed by corrective actions that will be
equitable to property owners and made acceptable to
them by carefully planned and executed public
information and educational procedures. Costs of
such corrections should be allocated on the basis of
responsibility for originally installed inflow lines.
The importance of a well-planned public relations
program cannot be overstressed; endorsement of the
inflow control program by both the elected officials
and the public is essential. Inflow control affects
individual property owners, and correctional action
may cause a great deal of inconvenience as well as
cost; but the eventual benefits make such efforts
worthwhile.
6.9 SUMMARY
Guidelines have been given for the control of
infiltration and inflow conditions. Each jurisdiction
must determine its own policies and practices, using
these indicators as to what can be accomplished by
new criteria and actions.
The control of infiltration and inflow is not
merely an academic exercise in urban planning and
development. It can be translated into the public
services purpose: service to the public. The fact that
investments in control of extraneous water flows in
overtaxed systems can be economically rewarding is
further reason why all jurisdictions should investigate
their problems and take necessary actions to protect
the capacities and capabilities of their sanitary
facilities.
67
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SECTION 7
ACKNOWLEDGEMENTS
69
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SECTION 7
ACKNOWLEDGEMENTS
The American Public Works Association is deeply indebted to the following persons and their
organizations for the services they rendered to the APWA Research Foundation in carrying out this
study for the local governmental jurisdictions and the Environmental Protection Agency who
co-sponsored the study. Without their cooperation and assistance the study would not have been
possible. The cooperation of the American Society of Civil Engineering (ASCE) and the Water Pollution
Control Federation (WPCF) is acknowledged for their participation on the project Steering Committee.
STEERING COMMITTEE
Paul C. Soltow, Jr. (Chairman)
George E. Burns
Richard L. Castle
S. J. McLaughlin
Alfred R. Pagan (ASCE)
Lloyd Weller (WPCF)
PANEL OF CONSULTANTS
Frank Kersnar, Brown & Caldwell, Consulting Engineers
Walter Thorpe, Toltz, King, Duval, Anderson & Associates, Consulting Engineers
Charles R. Velzy, Charles R. Velzy & Associates, Consulting Engineers
CONSULTANTS
Dr. Morris M. Cohn, Consulting Engineer
Richard Fenton, Consulting Engineer
Harry Grounds, Toltz, King, Duval, Anderson & Associates, Consulting Engineers
H. Storch, Storch Engineers
FIELD INTERVIEWERS
William L. Bryant, Flood & Associates, Jacksonville, Florida
Robert E. DeLoach, Flood & Associates, Jacksonville, Florida
Robert S. Gemnell, Professor, Northwestern University
John Morin, Former City Engineer, Oakland, California
Dean Sellers, Chief Engineer, Construction, Wichita, Kansas
Steve M. Slaby, Professor, Princeton University
ENVIRONMENTAL PROTECTION AGENCY
Darwin R. Wright, Project Officer
William A. Rosenkranz, Chief, Storm and Combined
Sewer Pollution Control Branch, Division of Applied
Science and Technology
71
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INDUSTRIAL ADVISORY PANEL
Leland E. Gottstein (Chairman), American Pipe Services
Charles M. Aiken, Raymond International, Incorporated
James R. Alley, Certain-teed Products Corporation
Joseph P. Ashooh, Associated General Contractors
Donald M. Cline, Pacific Clay Products
Robert H. Hedges, Rockwell Manufacturing Company
Quinn L. Hutchinson, Clow Corporation
Harold Kosova, Video Pipe Grouting, Incorporated
Tom Lenahan, Halliburton Services
W. J. Malcolm, Cherne Industrial, Incorporated
Joseph McKenna, Industrial Material Company
Charles Prange, Rockwell Manufacturing Company
John Roberts, Armco Steel Corporation
Joseph A. Seta, Joseph A. Seta, Incorporated
Harry W. Skinner, Press Seal Gasket Corporation
E. W. Spinzig, Jr., Johns-Manville Sales Corporation
Edward B. Stringham, Penetryn System, Incorporated
William M. Turner, Griffin Pipe Products Company
Joe A. Willett, American Concrete Pipe Association
John A. Zaffle, United States Concrete Pipe Company
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ADVISORY COMMITTEE
Paul C. Soltow, Jr., San Pablo, California (Chairman)
E. Nay Bentley, Indianapolis, Indiana
C. A. Boeke, Middletown, Ohio
Philip A. Boiler, Muncie, Indiana
G. Briere, Montreal, Quebec
G; E: Burns, Winnipeg, Manitoba
Richard L. Castle, Pontiac, Michigan
Milton R. Christensen, Minneapolis, Minnesota
William R. Davis, Pittsburgh, Pennsylvania
Robert Grant Dietrich, Baltimore, Maryland
David W. Duncan, Charlotte, North Carolina
John E. Eastus, San Jose, California
W. T. Eefting, Miami, Florida
Walter A. Fielding, Akron, Ohio
W. D. Gilman, Richmond, Virginia
Stephen H. Goodman, Campbell, California
Forrest Grant, Jr., Columbus, Ohio
Allison C. Hayes, Boston, Massachusetts
Paul T. Hickman, Springfield, Missouri
R. J. Horgan, Toronto, Ontario
Joseph Irons, Chicago, Illinois
Roy L. Jackson, Kansas City, Missouri
W. I. Jefferies, Arlington, Virginia
Roy W. Likins, Daytona Beach, Florida
Robert P. Lowe, Albuquerque, New Mexico
Frederick A. Mammel, Ann Arbor, Michigan
0. H. Manuel, Charlottetown, Prince Edward Island
Herbert D. McCullough, Milwaukee, Wisconsin
Marvin J. Miller, San Carlos, California
E. W. Ott, Seattle, Washington
John W. Schneider, Oshkosh, Wisconsin
Philip W. Slagel, Topeka, Kansas
R. Marlin Sumner, St. Clair Shores, Michigan
George H. Wilton, Wichita, Kansas
John Winden, Puyallup, Washington
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SECTION 8
GLOSSARY OF PERTINENT TERMS
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SECTION 8
GLOSSARY OF PERTINENT TERMS
Efforts to attain better levels of infiltration and
inflow control must be based on a uniform
understanding of the "language" of the field. In fact,
one of the findings of the national investigation of
this problem of extraneous water intrusion into sewer
systems was that there has been no "standardization"
of nomenclature among jurisdictional authorities,
state and provincial agencies and those who serve and
supply the sewer system field. Out of this "babel" of
misconceptions of intent and purpose has come
misinterpretations of community-to-community data
and a confused inability to arrive at better sewer
system practices.
To assist in the interpretation of the findings of
. the national investigations, a Glossary of Terms is
included in the report of which this Manual is an
integral part. To make this Manual document a
self-contained guide to better practices, the following
clarification of the meaning of pertinent terms is
provided.
Areaway A paved surface, serving as an entry
area to a basement or sub-surface portion of a
building, which is provided' with some form of
drainage device that may be connected to a sewer
line.
Building Sewer The conduit which connects
building waste water sources to the public or street
sewer, including lines serving homes, public buildings,
commercial establishments, and industry structures.
In this report, the building sewer is referred to in two
sections: (1) The section between the building line
and the property line, frequently specified and
supervised by plumbing or housing officials, and (2)
the section between the property line and the street
sewer, including the connection thereto, frequently
specified and supervised by sewer, public works or
engineering officials. (Referred to, also, as house
sewer, and building connection.)
By-pass A pipe line which diverts waste water
flows -away from, or around, pumping or treatment
facilities — or by-passes such facilities — in order to
limit the flows delivered to such facilities and to
prevent surcharging or' adversely affecting their
operation or performance.
Cellar Drain A pipe or series of pipes which
collect waste waters which leak, seep, or flow into
subgrade parts of structures and discharge them into a
building sewer, or by other means dispose of such
waste waters into sanitary, combined or storm sewers.
(Referred to, also, as "basement drain.")
Clean Waters Waste waters from commercial
or industrial operations which are uncontaminated,
do not need, and could not benefit from waste water
treatment processes, and which for sanitary purposes
do not require disposal into public sewers,
particularly separate sanitary sewers.
Collector Sewer A sewer located in the public
way which collects the waste waters discharged
through building sewers and conducts such flows into
larger interceptor sewers and pumping and treatment
works. (Referred to also as "street sewer.")
Compression Gasket A device which can be
made of several materials in a variety of
cross-sections, which serves to secure a tight seal
between two pipe sections (frequently referred to as
"o" ring.)
Exflltration The leakage or discharge of flows
being carried by sewers out into the ground through
leaks in pipes, joints, manholes or other sewer system
structures; the reverse of "infiltration."
Foundation Drain A pipe or series of pipes
which collects ground water from the foundation or
footing of structures and discharges these waters into
sanitary, combined or storm sewers, or to other
points of disposal, for the purpose of draining
unwanted waters away from such structures.
Grouting The cementing together of loose
particles of soil in such a manner that the soil so
grouted becomes a solid mass which is impervious
to water.
Inch-Gallons A designation for the commonly
used expression, referring to units of infiltration
allowances. The full expression is gallons per inch of
diameter per mile of pipe per day.
Infiltration The discharge of ground waters into
sewers, through defects in pipe lines, joints, manholes
or other sewer structures.
Inflow The discharge of any kinds of water into
sewer lines from such sources as roof leaders, cellar,
and yard-area drains, foundation drains, commercial
and industrial so-called "clean water" discharges,
drains from springs and swampy areas, etc. It does
not include "infiltration" and is distinguished from
such waste water discharges, as previously defined.
Infiltration/Inflow A combination of
infiltration and inflow waste water volumes in sewer
lines, with no way to distinguish either of the two
basic sources, and with the same effect of usurping
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the capacities of sewer systems and other sewer
system facilities.
Infiltration Allowances The amount of
infiltration anticipated in sewer systems; considered
inevitable under sewer construction and sewer service
conditions, and authorized and provided for in sewer
system capacity design and in sewer construction
practice. A distinction is made between "sewer design
infiltration allowances" which the designer provides
for in structuring the total sewer system and
"construction infiltration allowances" permitted in
the specifications covering the construction of
specific projects and specific sections of the total
sewer system.
Interceptor Sewer A sewer which receives the
flow from collector sewers and conveys
the wastewaters to treatment facilities.
Joints The means of connecting sectional
lengths of sewer pipe into a continuous sewer line,
using various types of jointing materials with various
types of pipe formations that make possible the
jointing of the sections of pipe into a continuous
collecting sewer line. The number of joints depends
on the lengths of the pipe sections used in the specific
sewer construction work.
Jurisdiction Any governmental entity, such as
city, town, village, county, sewer district, sanitary
district or authority, or other multi-community
agency which is responsible for and operates sewer
systems, pumping facilities, regulator-overflow
structures and waste water treatment works.
Overflow A pipe line or conduit device, together
with an outlet pipe, which provides for the discharge
of portions of combined sewer flows into receiving
waters or other points of disposal, after a regulator
device has been allowed the portion of the flow
which can be handled by the interceptor sewer lines
and pumping and treatment facilities to be carried by
and to such water pollution control structures.
Pipe Sealing A method of correcting leaks or
defects which permit infiltration of excessive
extraneous waters into sewers, by means of physical
or chemical materials, applied by interior or exterior
means, and which seals such points of defects and
reduces or eliminates such infiltration waters.
Pipe Tests Various methods of testing sewer
lines, after construction, and in service, to ascertain
whether or not infiltration allowances have been met,
and locating the sources of infiltration which exceeds
construction specifications. Such tests include:
infiltration tests; exfiltration tests; air tests; and other
means of locating sources of infiltration in new and
existing sewer lines, such as smoke bomb tests.
Precipitation Rainfall or thawing snow and ice
which produce storm water runoff from streets,
roads, and other impervious surface's, and which
percolate into the soil and augment the ground water,
are held in the interstices of the soil, affect the
ground water table, or produce inflows into sewer
systems.
Regulator A device or apparatus for controlling
the quantity of admixtures of sewage and storm
water admitted from a combined sewer collector line
into an interceptor sewer, or pumping or treatment
facilities, thereby determining the amount and
quality of the flows discharged through an overflow
device to receiving waters or other points of disposal.
Roof Leader A drain or pipe that conducts
storm water from the roof of a structure, downward
and thence into a sewer for removal from the
property, or onto or into the ground for runoff or
seepage disposal.
Sewer Inspection Methods for determining the
condition of new or existing sewer systems, in terms
of infiltration conditions, by visual inspection,
closed-circuit television viewing, photographic
methods, or other means.
Sewer-Use Ordinance A regulation, code, or
ordinance enacted by a jurisdiction to specify the
types and volumes of waste waters which can be
discharged into sewer systems, the waste waters
which cannot be so discharged, and the fees or
charges to be imposed for the privilege of discharging
those wastes and volumes which are permitted.
State Provincial Water Pollution Control Agency
A branch of government which imposes and enforces
water quality standards, establishes standards 'of
design for sewer systems and pumping and treatment
facilities, and has responsibility for maintaining
established water pollution control standards in
receiving waters.
The "TWO I's" A phrase adopted for this
report, to designate the two factors of infiltration and
inflow which affect sewer systems and the other
waste water handling facilities evaluated in this
project and report.
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SECTION 9
APPENDICES
1 Why Regulate the Use of Your Sewer System?
2 Regulation of the Discharge of Industrial, Commercial and
Other Special Wastes into Sewer Systems
3 Milwaukee, Wisconsin, In-Depth Study of Sewer Cleaning Practices
4 Sewer Connection Requirements, Oakland County Department of
Public Works, Pontiac, Michigan
5 Samples of Maintenance Report Forms
6 Sample Forms Used to Inspect Existing System by Opening Manholes
7 Sample of Letters and Forms Used to Investigate and Correct Inflow Conditions
8 Recommended Lot Grading Requirements Reported by Hubbell,
Roth & Clark, City Engineers, Southfield, Michigan
9 Typical Engineering Specifications for Low Pressure Air Testing of
Sewers for Infiltration Control
10 Example of Specifications for Exfiltration Testing of Gravity Sewers
11 A Method for Gauging Infiltration Flow in Sewer Testing
12 Correction of Infiltration by Means of Grouting with Sealants and Gels
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APPENDIX 1
WHY REGULATE THE USE OF YOUR SEWER SYSTEM?
In October 1969, the New York State
Department of Health's Division of Pure Waters,
Bureau of Water and Waste Water Utilities
Management, distributed a memorandum outlining its
position on the question: "Why Regulate the Use of
Your Sewer System?"
The reasons presented by the State agency are so
relevant to the guidelines expressed in this Manual, in
Section 4, that the memorandum is included here.
Each jurisdiction is urged to evaluate the New York
State presentation in terms of its own conditions.
Why are Sewer Use Ordinances Valuable?
1. The objective is to have legal authority to
protect life and limb and sewers and
wastewater treatment facilities, to minimize
overall expense of treatment to the taxpayer,
and to prevent unwarranted abuse of the
sewerage system.
2. Protect Sewer System from:
(a) damage, deterioration and destruction
from discharges of gasoline, fuel oil,
cleaning solvents, and paint particles;
(b) hazardous explosive substances;
(c) acids or alkaline wastes which eat out
joints and cause infiltration;
(d) ashes, tar, sand, cinders, metal, broken
glass, wood, clay and slag which clog
sewers;
(e) grease which adheres to sewers and
causes stoppages;
(f) hazardous wastes, such as sulphur
dioxide, hydrogen sulphide and
sulphur-oxidizing bacteria which may
cause disintegration of some sewers; and
(g) excessive high-temperature wastes.
3. Protect Biological Treatment Units of a
waste water facility from:
(a) excessive acidity or alkalinity harmful to
biological waste water treatment
processes;
(b) greases, oil, etc., which cause scum
formation; and
(c) toxic substances such as copper,
chromium, lead, zinc, arsenic and nickel
which kill off or inhibit biological
activity.
4. Protect Receiving Water Users and Aquatic
L ife from:
(a) poisonous compounds or radioactive
wastes which may also pass through
waste water utility facilities in dangerous
concentrations that are hazardous to
human life or injurious to edible fish
and/or shellfish;
(b) high temperature wastes which disturb or
destroy natural aquatic life; and
(c) high or low pH wastes which may
interfere with natural aquatic life.
What Are the Problems that
Municipalities Face?
1. There has been frequent evidence of cases
where municipalities experience trouble from
one or more of the above sources. As a
result, they are forced to:
(a) spend considerable sums of money to
repair the sewer system; and
(b) spend sums to repair the damage done to
treatment units of' the waste water
facility. And, municipalities may be sued
because of pollution of a body of water
caused by inadequately treated
discharges.
2. In many cases, industry has made no effort
or very little effort to cut down on the
volume and/or concentrations of the waste
waters until an ordinance is enacted and/or
steps are taken to enforce it. Sometimes
investigation and action of communities to
enforce ordinances has resulted in industry
finding out that they have suffered losses in
their uncontrolled discharges.
3. When an industry approaches the officials of
a community on the discharge of their
industrial wastes into the public sewer
system, the officials must find out first
whether the cost of their handling these
wastes will be too high for municipal
treatment.
4. Many communities permit runoff from roofs,
footing drains, cistern overflows, etc. This
adds considerably to the capital cost and
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operating expenses and affects operation of
waste water facilities.
What are the Rules and Interrelationships?
Article 12 of the Public Health Law (New York
State) Reg. 1220, contains a general prohibition
against pollution; namely, "It shall be unlawful for
any person, directly or indirectly to throw, drain, run
or otherwise discharge into such waters, organic or
inorganic matter that shall cause or contribute to a
condition in contravention of the Standards adopted
by the Water Resources. Commission pursuant to
section one thousand two hundred five of this
article." The community is therefore responsible for
any violation of standards promulgated by the Water
Resources Commission because it allows the
condition to exist.
Alternates
Most users of public sewer systems will
cooperate, but some willful violators always attempt
to take unfair advantage of a municipality and
discharge undesirable wastes. A good ordinance
fitting the particular needs of the sewerage system
which can be properly and promptly enforced by
local officials is needed in each community.
Solution
1. Water pollution abatement and prevention is
the sole aim of a municipal waste water
treatment plant. Therefore, the ordinance
must regulate the concentrations and
volumes of waste water to the plant to
obtain the maximum practical reduction of
pollutants.
2. The sewer ordinance should control the
concentrations and volumes of waste water
to minimize the capital cost and operating
expenses of treatment that is paid by
taxpayers, both individual and corporate.
3. The sewer ordinance to be effective must
provide for penalties in* case of violations
together with procedures for their
inspection. It must empower the officials to
prohibit the discharge of any wastes at any
time which can harm life, limb, structures or
property; that is, if necessary, have legal
machinery available to take immediate
action.
4. In many cases, industry may agree to
pre-treatment of their wastes, while in
others, industry may prefer to pay
municipalities for expenses of treatment.
5. The inability of a waste water treatment
plant to effectively process a new industrial
load does not necessarily constitute a
permanent banning of industrial load from
sewerage system. Provisions may be worked
out for altering or extending the plant to
handle the load with the industry or
industries concerned paying their proper
share of construction costs and operation
expenses of such modifications which would
benefit them.
6. Exclusion of existing roof water, footing
drains, cistern overflows, etc., is a difficult
problem, but the municipality should not
shirk its responsibility fpr saving the
taxpayer's money. One way of speeding up
elimination is to chwge taxpayers who have
connection for continuing the connection.
7. Cooling and condensing waters containing no
organic matter or reducing gases which are
incapable of causing objectionable conditions
in an open watercourse, should be segregated
from polluted wastes and discharged into
storm sewers or to a natural outlet.
8. Under no circumstances should the
responsibility for industrial waste water
control be delegated to an agency or a
department which does not have the
authority and responsibility for regulating
the condition of receiving water.
9. The ordinance should be flexible enough to
cover all known conditions as well as those
which may arise in the future.
10. Pre-treatment of certain wastes which cannot
be accepted in sewer systems must be
required.
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APPENDIX 2
REGULATION OF THE DISCHARGE OF INDUSTRIAL, COMMERCIAL
AND OTHER SPECIAL WASTES INTO SEWER SYSTEMS
Sewer-use ordinances or other types of local laws,
codes and regulations provide a valuable means for
controlling the types of wastes discharges into sewer
systems which may be deleterious to sewer lines,
detrimental to wastes handling, treatment and
disposal works, or hazardous to operation and
maintenance personnel involved in these municipal
installations.
Section 4 of this Manual contains sample
excerpts from representative ordinances relating to
the control of sewer connections and discharges of
inflow waters into public sewer systems. Research
work on sewer-use regulations covering inflow control
provided valuable references to the control of
industrial, commercial and other special wastes of the
nature referred to above.
This special waste material is so closely related to
the regulation and control of inflow waters that it is
included here as a valuable source of information for
jurisdictions which are planning to enact new
sewer-use legislation or to improve and modernize
their present powers to enforce rules and protect
their sewer systems.
The following excerpts are presented under
specific categories for ease of reference. They are
intended for guidance purposes only, rather than as
actual parts of any codes or ordinances to be drafted
by any jurisdictions. The applicability of all
regulatory items to actual jurisdictional conditions
must be judged by local officials who intend to devise
such regulations and who will be required to enforce
them.
Prohibited Substances - General
General provisions to bar a broad range of
substances from the sewers are often included in
sewer-use regulations:
Substances which are not amenable to standard
wastewater treatment plant processes or may affect
the quality of water supplies derived from
watercourses receiving solid waste should be
prohibited.
"No property owner or sewer user shall be
allowed to discharge sewage into the sewer disposal
system which shall be deemed deleterious to such
system, or which shall endanger the employees,
operation or treatment processes of sewage disposal,
or which shall cause incrustations or chemically or
physically attack so as to corrode or erode the sewer
or sewage disposal system or facilities." — Boise,
Idaho
"No substances which will clog the drains,
produce explosive mixtures or injure the pipes or
their joints shall be allowed to enter the drainage
system or the sewer." — Boston, Massachusetts
"It shall be unlawful for any person to disturb,
tear up, or injure any public drain or sewer, manhole,
or catch basin or other appurtenances connected with
any public sewer or cause any public sewer to become
clogged by permitting oils, or greases, rags, lime,
sodium cyanide, garbage, fruit or vegetable parings,
ashes, cinders, poisonous or explosive liquids or gases,
household foods, offal, swill, bottles, tin cans, dead
or live animals, tree limbs, lawn clippings, rubbish, or
any material of any nature whatsoever other than
normal' domestic sewage to accumulate
therein." —Rockford, Illinois
"No person shall release or discharge into any of
the City's sewers any of the following: (a) animal
grease or oil; (b) horse, cattle, sheep or swine manure;
(c) solids in particles larger than will go through a
quarter-inch screen; (d) oil or petroleum, or wastes
therefrom; (e) any acid or alkali waste which may
injure or damage any such sewer, the City Sewage
System, or its sewage treatment or sewage at such
plant; (f) any other deleterious matter, substance or
thing, whether liquid or solid, which will injure,
damage or pollute any such sewer, thfe City's Sewage
System or it's Sewage Disposal Plant, or interfere
with the proper operation of such
plant." — Yorktown, Saskatchewan
"Under no conditions will the City consider
accepting sewage that is detrimental to pipe lines,
hazardous because of explosive liquid or gases, or
may cause stoppage of the lines. Any customer found
allowing any of the above listed types of sewage to
enter the system will be subject to paying all costs
necessary to stop such flow and remove the
objectionable item from the system, and repair it if
necessary, as. well as all penalties as further outlined.
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In the determination of what materials may be
harmful and the degree of correction necessary, the
City will generally follow the recommendations of
the Water Pollution Control Federation." -St.
Petersburg, Florida
"The following materials shall be excluded from
the sewerage system: (a) Gasoline, cleaning solvent,
fuel, oil, etc. These are highly inflammable
compounds and serious damage due to explosions of
these liquids or their vapors have occurred within
sewerage systems; (b) Ashes, sand, cinders, rock, etc.
These inorganic compounds add excessive solid
loading on the sewerage causing unnecessary cleaning
and maintenance; (c) Tar, plastics, and other water
insoluble viscous materials. These compounds do not
break down by bacterial action and add to the solid
loading of a sewerage system, (d) Mineral oils,
lubricating oils, etc. do not decompose in the normal
course of sludge digestion. They cause potential fire
hazards throughout -the sewerage system, cause
excessive cleaning and impose an unnecessary solid
loading upon the sludge system, (e) Feathers, hair,
rags, etc. These' materials cause excessive
maintenance throughout the sewerage system.
Feathers and hair do not readily digest in sludge
digestion processes and create excessive matting on
top of the decomposing sludge, (f) Metal, broken
glass, shavings, etc. These materials will readily plug
up sewer lines, pumps and appurtenant equipment.
(g) Unshredded garbage. Large pieces of unshredded
garbage cause sewer lines and pumps to clog and
excessive maintenance will occur. Garbage ground in
domestic and industrial grinders to a size of & inch or
less is satisfactory, (h) Wastes which contain or result
in the production of toxic, corrosive, explosive and
malodorous gases." — San Diego, California
Prohibited Substances — Specifics
Numerous types and characteristics of specific
wastes ruled inadmissible to sewers are covered in
many ordinances. (Where the quoted portion seems
more an itemization than an explicit ban it is because
the specific item is one of a series following a
prohibitory introduction.)
1. Temperature
"Any liquid or vapor having a temperature higher
than 150° F." -Jacksonville, Florida
"Any liquid or vapor having a temperature higher
than 150 degrees F (65 degrees C)." - Cedar Rapids,
Iowa
"Any liquid or vapor having a temperature higher
than 160 degrees F." — Wilson, North Carolina
"Any liquid or vapor having a temperature
greater than 140 degrees Fahrenheit." - Salem,
Oregon
"Steam, vapor, and water at a temperature above
one hundred and thirty degrees Fahrenheit shall not
be discharged into the sewer. The blow-off of boilers,
steam exhaust or drip, or hot water from any other
source destined to be discharged into a sewer shall be
condensed and cooled to one hundred and thirty
degrees Fahrenheit in a blow-off tank or other
approved device of which the size, arrangement,
location, venting and all connections shall be subject
to the approval of the Commissioner of Public
Works." — Boston, Massachusetts
"No person shall discharge into a sewer or storm
drain any industrial waste, water, or liquid having a
temperature greater than 100 degrees Fahrenheit,
except upon written advance permission of the Board
of Public Works." — IMS Angeles, California
"Any liquid or vapor having a temperature higher
than 100 degrees Fahrenheit (37 degrees
Centrigrade)." — KnoxvUle, Tennessee
2. pH (Hydrogen Ion Concentration)
"Any liquids having a pH lower than 5.5 or
higher than 9.0, or having any corrosive property
capable of causing damage or hazards to structures,
equipment, or personnel of the sewage disposal
works." — Salem, Oregon
'The pH of industrial wastes shall average
between 5.5 to 9.0 daily. The maximum variation on
a temporary basis during any twenty-four hour period
shall not be less than 5.0 or greater than 10.0." - San
Diego, California
"Any industrial waste with a hydrogen-ion
concentration less than 5.5 (for acidity), or greater
than 9.0 (for alkalinity)." - Los Angeles, California
"Hydrogen ion concentration (pH) — 4.5 to
9.5." — Nassau County, New York
"Any water or waste, acidic or alkaline in
reaction, and having corrosive properties capable of
causing damage or hazard to structures, equipment
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and personnel. Free acids and alkalies in such wastes
must be neutralized, at all times, within a permissible
range ofpHbetween 5.5 and 10.0." -Jefferson City,
Missouri
"Waters having a pH below 6.0 or above
8.5." - Yakima, Washington
"Any waters or wastes having a stabilized pH
lower than 6 or higher than 9, or having any other
corrosive property capable of causing damage or
hazard to structures, equipment, and personnel of the
sewage works, provided accumulated pH does not
exceed our limits as specified." — Wilson, North
Carolina
"Wastes having a pH less than 6.0 or greater than
10.0 or otherwise having chemical properties which
are hazardous or are capable of causing damage to the
sewage works or personnel." — Kansas City, Missouri
"Any waters or wastes having pH lower than 6.0
or greater than 10.5 or having any other chemical or
corrosive property which are hazardous or capable of
causing damage to structures, equipment and
personnel ok the sewage works." — Oklahoma City,
Oklahoma
"Wastes having a pH less than 6.5 or greater than
9.75 or otherwise having chemical properties which
are hazardous or capable of causing damage to the
sewage works or personnel." - Omaha, Nebraska
3. Fats, (Ms, Greases
"Waste water which contains more than one
hundred parts per million by weight of fat, oil or
grease." — Seattle, Washington
"Any water or waste which may contain more
than 100 parts per million by weight, of fat, oil, or
grease, exclusive of soap." - Oak Ridge, Tennessee
"Any water or waste containing fats, wax, grease,
or oils, whether emulsified or not, in excess of one
hundred (100) mg/1 or containing substances which
may solidify or become viscous at temperatures
between thirty-two (32) and one hundred fifty (150)
degrees F (0 and 65°:C)." - Rome, New York
"Insoluble oils, fats arid greases. So-called soluble
oils may be admitted to the extent of 100 ppm,
provided subsequent dilution in the sewers or
treatment plant does not result in
separation." —Kansas City, Missouri
"Any water or waste containing fats, wax, grease,
or oils, whether emulsified or not, in excess of 100
mg/1 or containing substances which may solidify or
become viscous at temperatures between 32 degrees
and 150 degrees F (0 and 65 degrees C)." - Cedar
Rapids, Iowa
"Any water, or waste containing grease, as
follows: (1) floatable grease in excess of 50 parts per
million. Grease is an oil, fat, grease, or other ether —
soluble matter. Floatable grease is grease which rises
to the surface of quiescent sewage or waste or upon
dilution of the sewage or waste with fresh or salt
water. (2) Dispersed grease, other than soap, in excess
of 500 parts per million. Dispersed grease is grease
which is not fleatable." - Watsonville, California
"Any water or waste containing fat, oil, or grease
of such character or quantity that unusual attention
or expense is incurred." — Janesville, Wisconsin
4. Suspended Solids
"Suspended Solids - 300 ppm. max."
County, New York
- Nassau
"Industrial wastes having suspended solids in
excess of 500 ppm. will be considered individually. If
the sewerage system can safely receive said wastes,
wastes having higher suspended solids can be
allowed." - San Diego, California
"Any waters or wastes containing more than 700
parts per million by weight of suspended
solids." - Oak Ridge, Tennessee
"Liquid waste material in which the suspended
solids exceed 1000 parts per million, determined by
weight." — Los Angeles, California
"Any waters or wastes containing suspended
solids of such character and quantity that unusual
attention or expense is required to handle such
materials at the sewage treatment
plant." — Jacksonville, Florida
"Any waters or wastes containing suspended
solids of such character and quantity that unusual
provision, attention or expense is required to handle
such materials at the Waste Water Treatment
Plant." — Knoxville, Tennessee
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5. Biochemical Oxygen Demand (BOD)
'The admission into the public sewers of any
water or wastes having a 5-day BOD (Biochemical
Oxygen Demand) greater than 400 parts per million
by weight shall be subject to the review and approval
of the City Engineer." - Watsonville, California
"Any waters or wastes having a Biochemical
Oxygen Demand in excess of 500 parts per million by
weight." — Wilson, North Carolina
Materials which exert or cause ... unusual BOD,
chemical oxygen demand, or chlorine requirements in
such quantities as to constitute a significant load on
the sewage treatment works." — Rome, New York
"Materials which exert or cause ... unusual
BOD, chemical oxygen demand, or chlorine
requirements (such as, but not limited to, whey,
whole or separated milk, yeast, whole blood, etc.) in
such quantities as to constitute a significant load on
the sewage treatment works." — Oklahoma City,
Oklahoma
6. Phenols
"Wastes containing phenolic compounds over .50
ppm expressed as phenol." — Omaha, Nebraska
"Wastes containing pheolic compounds over 1.0
ppm expressed as phenol." — Kansas City, Missouri
"Any water or wastes that contains phenols in
excess of 0.50 parts per million by weight. These
limits may be modified if the aggregate of
contributions create treatment difficulties or produce
a plant effluent discharge to the receiving waters
which may be prohibitive." - Oak Ridge, Tennessee
7. Gases and Fumes
"Any water or waste that contains more than 10
milligrams per liter of gases such as hydrogen
sulphide, sulfur dioxide, or nitrous oxide." —
Jefferson City, Missouri
"Any waters or wastes containing more than 1.0
parts per million of dissolved sulfides." — Watsonville,
California
"Any water or wastes containing more than ten
parts per million by weight of the following gases:
Hydrogen sulphide, sulphur dioxide, or nitrous
oxide." - Knoxvttle, Tennessee
"Wastes containing cyanides or compounds
capable of liberating hydrocyanic acid gas over 2 ppm
expressed as hydrogen cyanide." - Kansas City,
Missouri
"Any noxious or malodorous gas or substance
capable of creating a public nuisance." — Santa Cruz,
California
8. Flammables
Flammables are generally regulated in the terms
first shown below, but generalized provisions are
sometimes encountered:
"Gasoline, benzene, naptha, fuel oil or other
flammable or explosive liquid, solid or
gas." - Lethbridge, Alberta
"Any solid, liquid or gas which by reason of its
nature and/or quantity could cause fire or
explosion." — Kansas City, Missouri
"Any petroleum product or other product which,
by reason of its nature or quantity may cause a fire or
explosion, or in any way be injurious to persons or to
the sewers or storm drains or other
appurtenances." — Los Angeles, California
9. Solid and Viscous Substances
"Any ashes, cinders, sand, mud, straw, shavings,
metal, glass, rags, feathers, tar, plastics, wood, paunch
manure, or any other solid or viscous substance
capable of causing obstruction to the flow in sewers
or other interference with the proper operation of the
sewerage system." —Jacksonville, Florida
"Any ashes, cinders, sand, mud, straw, shavings,
metal, glass, rags, feathers, tar plastics, wood, paunch
manure, hair and fleshings, entrails, lime slurry, lime
residues, chemical residues, paint residues, cannery
waste bulk solids, or any other solid or viscous
substance capable of causing obstruction to the flow
in sewers, or other interference with the proper
operation of the sewer system or sewage treatment
facilities." - Jefferson City, Missouri
"Any solid or viscous material which could cause
an obstruction to flow in the sewers or in any way
interfere with the treatment process. Examples of
such materials include, but are not limited to, ashes,
wax, paraffin, cinders, sand, mud, straw, shavings,
metal, glass, rags, lint, feathers, tars, plastics, wood
and sawdust, paunch manure, hair and fleshings,
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entrails, lime slurrys, beer and distillery slops, grain
processing wastes, grinding compounds, acetylene
generation sludge, chemical residues, acid residues,
and food processing bulk solids." - Kansas City,
Missouri
"Industrial wastes having a viscosity exceeding
1.10 poises (absolute Viscosity) upon discharge or
after acidification (pH below 5.5), or alkalization (pH
above 8.5.)" -Nassau County, New Yprk
"Paunch manure or intestinal contents from
horses, cattle, sheep or swine; hog bristles; pigs'
hooves or toenails; animal intestines or stomach
casings; bones; hides or parts thereof; animal fat or
flesh in particles larger than will pass through a
quarter inch screen; manure of any kind; poultry
entrails, heads, feet or feathers; eggshells; fleshing and
hair resulting from tanning operations." —
Lethbridge, Alberta
"Any waters or wastes containing strong acid
iron pickling wastes, or concentrated plating solutions
whether neutralized or not." — Rome, New York
"Septic tank sludge, except that such sludge may
be discharged into selected treatment plants at
locations designated for this purpose by the
director." — Kansas City, Missouri
Scavenger wastes shall mean putrid or offensive
matter, the contents of all privies, septic tanks and
cesspools. ... Scavenger wastes will be admitted into
the sewerage system only by approval of the City
Engineer and subject to the payment of fees or
charges fixed by the City Commission." —
Jacksonville, Florida.
10. Toxic Substances and Chemicals
"Any waters or wastes containing a toxic or
poisonous substance in sufficient quality to injure or
interfere with any sewage treatment process,
constitute a hazard to humans or animals, or create
any hazard in the receiving waters of the
Plant." — Watsonville, California
"Any waters or wastes containing toxic or
poisonous solids, liquids, or gases in sufficient
quantity, either singly or by interaction with other
wastes, to injure or interfere with any sewage
treatment process, constitute a hazard to humans or
animals, create a public nuisance, or create any
hazard in the receiving waters of the sewage
treatment plant, including but not limited to cyanides
in excess of two (2) mg/1 as CN in the wastes as
discharged to the public sewer." - Oklahoma City,
Oklahoma
"Any waters or wastes containing strong acid
iron pickling wastes, or concentrated plating solutions
whether neutralized or not." — Cedar Rapids, Iowa
"Waters and wastes containing metallic ions such
as copper, zinc, and chromium. Such wastes shall be
subject to the control of the City as to volume and
concentration of wastes from individual
establishments." — Jefferson City, Missouri
"Any waters or wastes containing strong acid
iron pickling wastes, or concentrated plating solutions
whether neutralized or not. Any waters or wastes
containing iron, chromium, copper, zinc, and similar
objectionable or toxic substances; or wastes exerting
an excessive chlorine requirement, to such a degree
that any such material received in the composite
sewage at the sewage treatment works exceeds the
limits established by the Commissioner for such
materials." — Rome, New York
"Any waters or wastes containing a toxic or
poisonous substance in sufficient quantity to injure
or interfere with any sewage treatment process,
constitute a hazard to humans, or animals or create
any hazard in the receiving waters or storm water
overflows or the effluent of a Waste Water Treatment
Plant. Materials such as copper, zinc, chromium, and
similar toxic substance shall be limited to the
following average quantities in the sewage as it arrives
at the Treatment Plant and at no time shall the
hourly concentration at the Waste Water Treatment
Plant exceed three (3) times the average
concentration: Iron as FE-15 parts per million;
Chromium as Cr. (hexavalent)-5 parts per. million;
Copper as Cu-3 parts per million; Zinc as Zn-2 parts
per million; and with contributions from individual
establishments subject to control in volume and
concentration by the City." — Knoxville, Tennessee
"The term 'objectionable waste' shall mean:
... (b) Any chemicals or chemical compounds of the
following nature or characteristics, or having similarly
objectionable characteristics: alcohols; arsenic and
arsenicals; cresols; formaldehyde; iodine; manganese;
cyanide and other metal plating wastes; mercury and
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mercurials; phenols and their derivatives; silver and
silver compounds; sulfanamides; toxic dyes (organic
or mineral); zinc; all strong oxidizing agents such as
chromates, dichromates, permanganates, peroxide,
and the like." - Nassau County, New York
"The following chemical substances shall not
exceed the specific listed concentrations in
Mg/1: ... Arsenic, 0.10; Barium, 1.0; Cadmium, 0.10;
Chloride, 300.0; Chromium trivalent (Cr. + 3), 2.00;
Chromium, hexavalent (Cr. + 6), 0.20; Copper, 0.50;
cyanide, 0.20; (Cr. + 3), 2.00; Fluoride, 3.00; Lead,
0.10; Methylene Blue Active Substances, 1.0; Nitrate
nitrogen, 20.0; Phenols, 0.20; Selenium, 0.10; Silver,
0.10; Sulfate, 200.0; Zinc, 5.0; Other
Constituents — shall not contain other substances
which are or may become injurious or detrimental to
the sewage system." —Janesville, Wisconsin
11. Colored Materials
"Any waters or wastes having an objectionable
color which is not removable in the existing sewage
treatment plant processes." — Wilson, North Carolina
"Concentrated dye wastes or other wastes.which
are either highly colored or could become highly
colored by reacting with other wastes." — Kansas
City, Missouri
"Blood in sufficient quantities so as to cause
discoloration of... effluent." — Omaha, Nebraska
12. Radioactive Wastes
"Any radioactive waste in an amount greater
than recommended by local or state public health
agencies." — Watsonville, California
"Any radioactive wastes or isotopes of such
half-life or concentration as may exceed limits
established by the Superintendent in compliance with
applicable state or federal regulations." — Cedar
Rapids, Iowa
"Pretreated wastes shall conform to the following
minimum standards: Radioactive wastes — Not to
exceed 1,000 micro micro-curies, in the known
absence of Strontium 90 and alpha
emitters." — Janesville, Wisconsin
"Radioactive material: Any institution or
industry using radioactive material or fission products
must be registered with the City Engineer as well as
such other control agencies as the law requires. The
active elements and their local concentration
permitted to be discharged into the sewers shall be
based upon the latest knowledge available to this
technology." — Jacksonville, Florida
"The introduction of radioactive wastes into the
city sewers shall be permitted only if a special permit
is obtained prior to introducing such wastes. While
each case will be decided on its own merits, in
general, decisions will be in accordance with the
principles laid down in the Atomic Energy Acto of
1954
"The introduction of radioactive wastes into the
city sewers shall be permitted only if a special permit
is obtained prior to introducing such wastes. While
each case will be decided on its own merits, in
general, decisions will be in accordance with the
principles laid down in the Atomic Energy Act of
1954 (68 Stat. 919), Part 20, Sub-Part D-Waste
Disposal, Section 20.303, or successor principles as
established by the Atomic Energy Commission." -
Kansas City, Missouri
"No person shall discharge or cause to be
discharged any radioactive wastes into any public
sewers or appurtenances thereof, except where: (a)
The person is authorized to use radioactive materials
by the Atomic Energy Commission or other
governmental agency empowered to regulate the use
of radioactive materials; (b) The waste is discharged
in strict conformity with current Atomic Energy
Commission recommendations for safe disposal of
radioactive wastes; (c) The person discharging the
radioactive wastes assumes full responsibility for any
injury to personnel or damage to the sewerage system
that may result from such discharge and submits
evidence satisfactory to the Director of Public Works
that he has assumed this responsibility. Any person
discharging a radioactive waste to a public sewer in
accordance with the provisions of the preceding
paragraph shall submit to the Director of Public
Works such reports as the Director may deem
necessary. If any radioactive material is accidentally
discharged into any public sewer, the person
responsible shall: (1) Immediately notify the Director
of Public Works. (2) Render such technical or other
assistance to the Department of Public Works within
his power to prevent the sewerage system from
becoming contaminated with radioactivity; and (d)
The person has secured a permit from the Director of
Public Works to discharge radioactive materials into
the public sewers." - Santa Cruz, California
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13. Garbage and Garbage Grinders
"Garbage that has not been properly
shredded." - Seattle, Washington
"Any garbage that has not been properly
shredded. Properly shredded garbage shall mean the
wastes from the preparation, cooking and dispensing
of food that has been shredded to such degree that all
particles will be carried freely under the flow
conditions normally prevailing in public sewers, with
no particle greater than one-half inch in any
dimension." — Enterprise Public Utility District,
Shasta County, California
"Any garbage that has not been ground or
shredded." - Salem, Oregon
"The term 'minced garbage' shall mean food
waste resulting from the normal occupancy of any
residential building, no particle of which shall have
any dimension greater than one-half inch. Such
'minced garbage' shall not be deemed an
'objectionable waste'." —Nassau County, New York
"The installation and operation of any garbage
grinder equipped with a motor of three-fourths (3/4)
horsepower or greater shall be subject to the review
and approval of the Director of Public Works/City
Engineer." — Oklahoma City, Oklahoma
"Garbage, fruits, vegetables, animal or other solid
kitchen waste materials from individual dwelling units
resulting from the preparation of any food or drink
may be admitted to the sanitary sewer if first passed
through a mechanically operated grinder so designed:
(a) that it will operate with cold water flowing into
the grinder and through the sink drain line in such
manner as to congeal and aerate the solid and liquid
greases within the grinding unit; (b) that it shall
discharge wastes at a reasonably uniform rate in fluid
form, which shall flow readily through an approved
trap, drain line or soil line in a manner which prevents
clogging or stoppage of the drain line;(c) that it shall
be of such construction and have such operating
characteristics that not more than five percent by
weight of all material discharged from it shall have
any dimension larger than one-fourth inch, and no
particle shall be greater than one-half inch in any
dimension; (d) that it shall be self-scouring, with no
fouling surfaces to cause objectionable odors; (e) that
it shall be free from electrical or mechanical hazards
and shall adequately protect the user against injury
during operation; (f) that the installation shall be free
from cross-connection to any water pipe; (g) that the
entire installation shall comply in all particulars with
the provisions of the plumbing and electrical codes of
the City. The final decision as to the sufficiency of
the design to meet these requirements shall: rest with
the Director of Public Works." - Santa Cruz,
California
"Under no circumstances will the discharge of
garbage or refuse whether shredded or unshredded be
permitted into the sewer system. The installation of
'Garbage Grinders' for the purpose of grinding or
shredding garbage into the sewer system is expressly
prohibited." -Jacksonville, Florida
"Household garbage grinders, garbage disposal
units, or garburetors, of any nature or kind shall not
be affixed to any plumbing or other fixture or
otherwise used so that the waste therefrom is
discharged into either the sanitary or storm sewer or
open ditch or watercourse, provided however, that
should any household garbage grinder, garbage
disposal unit or garburetors installed and in use
within the City on the date of the enactment of this
By-law, become worn out and in need of
replacement, they shall not be so
replaced." — Kamloops, British Columbia
14. Installation of Interceptors
"All wastes discharged into the industrial wastes
sewer shall be adequately screened by a twenty mesh
or finer screen before discharge. An additional screen,
with openings not to exceed one-fourth inch square,
shall be installed in a fixed position so that all
material must pass through said screen immediately
before entrance into sewers." - Yakima, Washington
"Grease, oil and sand interceptors shall be
provided on private property for all garages, gasoline
service stations and vehicle and equipment washing
establishments; interceptors will be required for other
types of businesses when in the opinion of the
Director, they are necessary for the proper handling
of liquid waste containing grease in excessive
amounts, or any flammable wastes, sand and other
harmful ingredients, except that such interceptors
shall not be required for private living quarters or
dwelling units. All interceptors shall be of a type and
capacity approved by the Director and shall be so
located as to be readily and easily accessible for
cleaning and inspection. Where installed, all grease, oil
and sand interceptors shall be maintained by the
occupant at his expense in continuously efficient
operation at all times." — Lethbridge, Alberta
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"Screen type interceptors, in addition to other
required interceptors, may be required for handling
industrial waste." — Santa Cruz, California
"Grease and oil interceptors shall be constructed
of impervious materials capable of withstanding
abrupt and extreme changes in temperature. They
shall be of substantial construction, water tight, and
equipped with easily removable covers which, when
bolted in place, shall be gas tight and water
tight." — Wyoming, Michigan (and Knoxville,
Tennessee)
"(a) An interceptor shall be so designed that it
will not become airbound and be so located as to be
readily accessible for cleaning; (b) a grease or oil
interceptor shall be of sufficient capacity to intercept
all grease or oil likely to flow into it under normal
conditions; (c) the interceptor for motor vehicle wash
floors shall have a capacity sufficient to retain the
sand or grit reaching the interceptor during any
ten-hour period, but in no case shall it be less than
four feet long, two feet six inches wide and two feet
deep, measured from the floor of the interceptor to
the invert of the overflow."—Metropolitan
Winnipeg, Manitoba
Rate Structures for Sewer Service
Where sewer service charges are levied upon all
connected properties, special charges or surcharges
are often assessed against contributors of "problem"
wastes.
"Industrial rates shall be based on the following
unit charges; (1) Industrial Schedule — $23.83 per
million gallons, (2) Biochemical oxygen demand
(BOD) - 0.0035 per pound, (3) Suspended
solids — 0.0056 per pound. Unit charges are to be
applied against the total monthly measured quantities
of flow, biochemical oxygen demand and suspended
solids from each industry, using the calendar month
at which the maximum biochemical oxygen demand
load occurs at the industry. The resultant monthly
charge is applied uniformly each month over the
calendar year." — Salem, Oregon
"Industrial and Commercial Surcharge. All
persons, firms, corporations or institutions
discharging wastes into the public sewers, shall be
subject to a surcharge, in addition to any other sewer
service charge, if their sewage has a concentration
greater than "normal" concentrations. The amount of
surcharge shall reflect the cost incurred by the City in
removing the excess B.O J). and suspended solids. (1)
Computation of Surcharge. The excess pounds of
Biochemical Oxygen Demand (B.O.D.) and suspended
solids (S. S.) will be computed by multiplying the
flow volume in million gallons per day (M.GD.) by
the constant 8.345 and then multiplying the product
by the difference between the persons' concentration
in ppm by weight. This product will then be
multiplied by the number of days in the billing period
to determine the surcharge. (2) Rates of Surcharge.
The rates of surcharge for each of the aforementioned
constituents will be at the prevailing rate at the time.
Said prevailing rate at the time is as follows: (a) For
Biochemical Oxygen Demand (B.O.D.) $0.01 per
pound, (b) For Suspended Solids (S.S.) $0.01 per
pound." — Janesville, Wisconsin
"When the suspended solids content or the
B.O.D. of a waste exceeds the maximum
concentration of these components in normal sewage,
a surcharge, in addition to the normal sewer charge,
shall be levied and established by either of the
formulae hereinafter set forth, but in no event shall
said surcharge be less than $1.00 per month. The
surcharge shall be computed by using formulae as
outlined below, providing that the surcharge shall be
limited to the maximum amount established by either
of the following formulae:
"S (ss) = .0000625 x Va x $ .014 x (SS-400),
which shall signify that the amount of the surcharge
of the suspended solids basis shall equal the factor of
.0000625 for converting parts per million by weight
to pounds per cubic foot multiplied by the volume of
sewage in cubic feet multiplied by $ .014, the
estimated cost for treatment of one pound of
suspended solids in raw sewage, multiplied by the
concentration of suspended solids in the waste in
parts per million by weight minus 400, with the
minimum charge to be $ 1.00, or
"S.(B.OD.) = .0000625 x Va x .0075 x
(B.O.D.-300), which shall signify that the amount of
the surcharge on the B.OJ). basis shall equal the
factor of .0000625 for converting parts per million
by weight to pounds per cubic foot, multiplied by the
volume of sewage in cubic feet, multiplied by the
concentration of B.O.D. (biochemical oxygen
demand of the waste) in parts permillion by weight
minus 300, with the minimum charge to be $1.00.
'The symbols, letters or figures employed in the
aforesaid formulae signify the following: Va = volume
of sewage in cubic feet, S (ss) = amount of surcharge
on suspended solids basis, S (B.O.D.) = amount of
surcharge on biochemical oxygen demand basis,
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.0000625 = factor for converting parts per million by
weight to pounds per cubic feet, SS - concentration
of suspended solids in the waste in parts per million
by weight, BOD = biochemical oxygen demand by
the waste as defined in .... this ordinance.
Determination of the suspended solids and BOD
concentration shall be made in accordance with
standard laboratory methods." — Kansas City,
Missouri.
"A surcharge (is) established herein, in addition
to the charge now or hereafter fixed for 'Normal
Sewage'. The basis of the surcharge shall be
determined on each of three constituents of the water
or wastes: (a) total suspended solids as herein
provided; (b) BOD five (5) days at 20 degree
centigrade where applicable as outlined elsewhere in
this section; (c) recoverable grease and as herein
provided. When anyone or all of the total suspended
solids, BOD and recoverable grease of a water or
wastes accepted for admission to the city sewage
works exceeds the values of these constituents for
'normal' sewage, the excess concentration in each
case shall be evaluated volumetrically in terms of
'Normal' sewage and be subject to surcharge on the
volume derived in accordance with the following:
Sv = (Sw - 2500) x .90 x F x 133690
2500
Sv = F ( (Sw - 2500) 48 ) Suspended Solids
Sy = (Bw-2000)x .85 x F x 133690
2000
Sv = F ( (Bw - 200) x57 ) BOD
Sv = (Gw - 833) x .70 x F x 133690
Sv = F ( (Gw - 833) 112 ) Grease
Note: Where Sv is the derived volume of wastes
in cubic feet 'subject to surcharge, Sw is pounds per
million gallons of suspended solids from the wastes as
discharged, 2500 is the pounds per million gallons of
suspended solids in the 'Normal' Sewage, Bw is
pounds per million gallons of B.O.D. in the wastes as
discharged, 2000 is the pounds per million gallons of
B.OX)., in 'Normal' Sewage, Gw is the pounds per
million gallons of grease from the wastes as
discharged, 833 is the pounds per million gallons of
grease in 'Normal' Sewage, 0.90 is factor allowance
for 90% degree of purification of suspended solids,
0.85 is factor allowance for 70% degree of
purification of grease, F is the flow expressed in
million gallons of the waste discharge, and 133,690 is
equal to the factor to convert million gallons to cubic
feet.
The equivalent volume of 'normal' sewage as
derived from the excess above the normal strength of
any water and waste shall be subject to a surcharge
for the volume of equivalent 'normal' sewage as
computed from the formula for the Papillion Creek
Plant Service Area at the flat rate of $ .0175 for each
one hundred cubic' feet on the highest single value
applicable to the contributing wastes as above
computed." — Omaha, Nebraska
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APPENDIX 3
MILWAUKEE, WISCONSIN, IN-DEPTH STUDY OF
SEWER CLEANING PRACTICES1
Prior to 1965, the City of Milwaukee's sewer
cleaning operations were carried out purely on a
reactive-type basis geared to complaints and random
inspections.
Late in 1964, a study was made of the city's
experience with clogged sewers. All locations where
the city had experienced obstructed sewers during the
ten-year period from 1955 through 1964 were
tabulated and coded for the cause of the obstruction,
such as grease, roots, rags, etc.
These incidences of system failures were plotted
on a city map. Those areas of the city having a group
or cluster of incidences were programmed for regular
and periodic cleaning. The frequency of cleaning was
dependent upon the suspected causes for the clogged
sewers. This was the city's first real attempt to
establish a planned, preventative maintenance
program for the cleaning of its local sewers.
As a result of this program, the incidences of
clogged sewers decreased in these "programmed"
areas, but new locations were springing up and
property owners' increasing awareness of the
possibility of collecting damages caused by these
clogged sewers was apparent from the increasing
number 'of claims being filed against the city.
Apparently, an increase in the acceptable standard for
cleaning sewers was needed — but by how much?
How many crews and what kind were needed? How
many miles of sewers were now being cleaned by each
crew and how effective were the techniques being
used? How many additional miles of sewers should be
added to the existing program? What type, or
methods, of cleaning should be phased out and what
new sewer cleaning techniques should we add?
To answer these questions, the Bureau of Street
and Sewer Maintenance, in 1968, began a
comprehensive study of its sewer cleaning program,
methods, and techniques.
The study was divided into two separate phases
of investigation. The first was comprised of a
block-by-block analysis of every foot of sewer in the
city's sewer system. The second phase consisted of
sending out questionnaires to 136 major cities in the
United States. The date and information gathered was
Abstracted from a report by Milwaukee's Department of
Public Works, entitled, Sewer Cleaning, A Determination of
Needs and Methods
assembled, analyzed, and included in a final study
report. Conclusions and recommendations for
improving Milwaukee's sewer cleaning operation was
the final step in this study. The following excerpts
from the Milwaukee report are included in this
Manual because of the correlation between sewer
cleaning and infiltration conditions:
OBJECTIVES
WHY CLEAN SEWERS?
Most municipalities have a multi-million dollar
investment in their sewer systems. It is designed to
furnish a collection network for sewage, a by-product
of their industries, businesses, and residential
properties.
The service that a sewer system provides is most
often measured in terms of "capacity" to carry
sewage. The amount of flow that a sewer is capable of
handling is directly in proportion to the square of the
pipe's diameter.
In the 1968 issue of the "American Public Works
Manual", is found the following statement regarding
the need for regular maintenance. "When a sewer is
constructed, capacity is purchased. With use, this
capacity is reduced and can only be restored by
regular maintenance."
Without regular cleaning, the capacity of a sewer
can be drastically affected and reduced below
originally designed requirements.
Any obstruction, or collection of debris, inside
the pipe, such as grease and roots, will reduce this
capacity. For example, the efficiency of a 12-inch
diameter sewer will be reduced by 75 percent of its
originally designed capacity if a three-inch layer of
grease, roots, or other debris, is permitted to
accumulate around the circumference of the pipe. A
sewer cleaning program that permits a 75 percent
decrease in the capacity of a sewer is substandard.
(The effect of sewer clogging on infiltration is
self-evident.)
Water use in the past decade has changed
considerably. There is a greater use of garbage
disposals, automatic washers, air conditioning units,
etc., that has radically changed the per capita water
use formula. This has increased the flow in the sewer
above that amount originally anticipated in the earlier
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a sewer system very often affects another portion of
the system upstream; i.e., a loss of effectiveness in
one section of a system can be hydraulically reflected
upstream to a relatively clean portion of sewer.
The principal reasons for establishing an effective
sewer cleaning operation are based upon two
premises: Maintenance of the sewer system's
efficiency; and the savings that result from a
preventive maintenance program.
A clean sewer assures continuous service and
reduces the chance of surcharging and resulting
backwater problems. The monies saved by
anticipating problems, and eliminating the cause
before the problem occurs, has been proven
worthwhile in dealing with other maintenance
problems, such as surface sealing.
This philosophy can be applied to the
maintenance of sewers. By determining the critical
areas involved, and establishing a sewer cleaning
program that will give reasonable assurances that the
system will perform in an acceptable manner, more
work can be done by each crew and the efficiency of
the sewer system increased.
The objectives of this sewer cleaning study are as
follows:
1. Determine the recommended level of sewer
cleaning that will give reasonable assurances
that the City of Milwaukee's sewer system
will function effectively.
2. Compare the City of Milwaukee's present
sewer cleaning capability with the
recommended level of sewer cleaning and
determine if additional crews are required to
provide an efficiently operating sewer
system.
3. Evaluate present methods of cleaning sewers
and determine relative effectiveness of each
type of cleaning.
4. Compare the City of Milwaukee's sewer
cleaning capability with those of other cities
and seek guidelines for improving present
cleaning services.
METHODS AND PROCEDURES
This study is divided into two phases.
The first phase offers a critical evaluation of the
City of Milwaukee's sewer cleaning techniques and
concerns itself with the first two objectives outlined
above.
The procedure used in the first phase consisted of
interviews and meetings between each of five District
Sewer Supervisors and the Assistant Superintendent
of Sewer Maintenance.
Each block of sewer in all five Districts was
studied. The District Sewer Supervisor was asked to
describe any special problems that he might have
encountered with that particular section of sewer. In
addition, he was asked the following pertinent
questions.
1. Do you clean this section of sewer now? If
so, what sewer cleaning method do you use?
How frequently do you clean this section?
How long does this cleaning operation take?
How many lineal feet are you cleaning?
2. Assume that you were asked to provide your
department with reasonable assurances that
this section of sewer will provide efficient
and reliable service, what would be your
recommendation on the type and frequency
of sewer cleaning required?
In answering these questions, each Supervisor was
asked to consider the following factors:
(a) His experience and knowledge of this area
with respect to special problems consisting of
unusual waste from abutting properties; to
include industrial plants, restaurants, and
schools, root penetration from extensive tree
population, high density housing
developments, etc.
(b) Age of sewer
(c) Type of sewer
(d) Size of sewer
(e) Length of sewer
(f) Street traffic conditions encountered
(g) The Department's records of complaints and
service.
The second phase concerns the third and fourth
objectives and consists of an evaluation of what other
cities are doing in the cleaning of their sewers and a
comparison with Milwaukee's present cleaning
program. The procedures used in the second phase of
this Study consisted of the preparation and mailing of
a questionnaire to 136 municipalities in the United
States.
An attempt was made to sample most major
cities in the United States and obtain opinions and
information from various sections having the greatest
variety of geographic and climatic conditions. An
attempt was made to obtain a greater number of
samples from the northeastern section of the country.
This permits the City of Milwaukee maximum
opportunity to compare its sewer cleaning operations
94
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TABLE 1
MILWAUKEE STUDY
CURRENT SEWER CLEANING OPERATIONS
District Bucket
1
2
3
4
5
Total
1967-68
Dept. Avg.
Per Crew
Lin. Ft.
2.600
43.150
197,890
14,320
25,350
283,310
300,000
Crews
Used
1
.5
2.5
.5
1
5.5
Rodder
Lin. Ft.
0
58,230
96,420
523,360
163,000
841,010
600,000
Crews
Used
0
.5
.5
1
0
2.0
Wayne
Lin. Ft.
0
410,920
138,905
1,320
111,050
662,195
700,000
Ball
Crews
Used
0
.5
.5
0
J5
1.5
Flushing
Lin. Ft.
175,000
0
9
6,120
4,400
185,590
200,000
Crews
Used
1
4
0
0
0
Total
177,600
512,300
433,285
545,120
303,800
1,972,105
TABLE 2
MILWAUKEE STUDY
SEWER CLEANING REQUIREMENTS
RECOMMENDED BY SUPERVISORS
District
1
2
3
4
5
Total
Bucket
Lin. Ft.
651,630
235,000
450,580
294,350
144,015
Crews
Used
9.50
3.80
7.75
4.40
1.25
Rodder
Lin. Ft.
0
133,950
95,770
540,720
191,685
Crews
Used
0
0.363
0.236
1.33
0.228
Wayne Ball
Lin. Ft.
0
1,129,300
264,435
639,700
497,300
Crews
Used
0
2.56
0.524
1.56
1.0
Flushing
Lin. Ft.
282,800
800
24,105
6,120
4,400
Crews
Used
1
0
0
0
0
Total
Lin. Ft.
934,430
1,499,050
834,890
1,480,890
837,400
1,775,575 26.70 962,125 2.157 2,530,735 5.6444 318,250
1 5,586,660
with other cities under similar geographic and
climatic conditions. A total of 88 cities responded to
this questionnaire.
ANALYSIS OF RESULTS
FIRSTPHASE
The first phase of this study was designed to
provide information and data concerning the first two
objectives. Each supervisor was asked to give
thoughtful and critical consideration to his existing
cleaning techniques and problems. What were his
problems? Was he satisfied with the methods used
and the results?
A summary of the results obtained in this phase
is shown in Tables 1 and 2. Table 1 is the current
operations, while Table 2 depicts the recommended
level of operations . that will provide "reasonable
assurances" that the sewer system will function
efficiently. The difference, between the "current
operations" and the "recommended level of
operations", represents the additional work capability
required to meet the supervisors' recommended level
of sewer cleaning.
95
-------
The supervisors' recommendations propose an
increase of 18 bucket crews and 3% wayne ball crews.
This represents an expansion of approximately 300
percent in the present cleaning program at an
estimated annual cost of $500,000.
SECOND PHASE
The second phase of this Study was designed to
gather information and data concerning the third and
fourth objectives. This phase involves the evaluation
of the relative merits of various methods for cleaning
sewers. The questionnaire was intended to help in the
evaluation and provide a means of comparing the City
of Milwaukee's capability with those of other cities.
From the information reported relating to miles
of sewers, and relating to cleaning methods, each
municipality's relative ability to clean sewers was
computed. The relationship between a city's ability
to clean sewers and the total miles of sewers in its
system is defined as the "Capacity Index1", i.e. -
Capacity Index = Total Miles Cleaned -r Total
Miles in System x 100
The Capacity Index was tabulated for each
reporting municipality. The Capacity Index and the
Total System Mileage was plotted to produce Figure
1.
The City of Milwaukee has 2,150 miles in its
sewer system and operates near the 350 mile work
line with a Capacity Index of 16.2. The
recommended increase for the City of Milwaukee, as
shown in Table 3, amounts to a shift from the 350
mile line to a point above the 1,000 mile line with a
potential Capacity Index of 51.5.
The principal factors determining a
municipality's position in the Capacity Index curve is
believed to be the following:
1. Velocity of Flow. (Design Requirements)
This factor will determine the self-cleaning
characteristics of a sewer.
2. Type of Sewer. (Sanitary, Combined, and
Storm)
3. Nature and Character of the
Municipality. The number and type of
industrial complexes, or commercial
developments, will affect the type of
cleaning problems encountered; i.e., what is
the economy based upon — industry,
commerce, tourist trade, etc?
For the capacity index to have meaning it must be
determined that:
a. all reporting agencies have used the same definition of
a clean sewer - that is that a full guage squeegee has been
passed through the line, and
b. that all sewers have the relatively same degree of
deposition.
TABLE 3
MILWAUKEE STUDY
DATA ANALYSIS OF QUESTIONNAIRE
Number of Cities Reporting = 88
CAPACITY INDEX ANALYSIS
Average index of all Cities reporting = 34.9
Average index of all Cities reporting cleaning footage
= 40.4
Average index of all Cities with total system above
2,000 miles = 10.61
Average index of all Cities with total system above
1,000 miles = 18.65
Average index of all Cities with total system above
500 miles = 29.3
Average system mileage of all Cities reporting (index
above 100%) = 312
Average system mileage of all Cities reporting (index
above 50%) = 428
Average system mileage of all Cities reporting (index
above 25%) = 558
Average system mileage of all Cities reporting (index
above 20%) = 551
Average system mileage of all Cities reporting (index
above 16.2%) = 668
Average system mileage of all Cities reporting (index
below 16.2%) = 1507
Average system mileage of all Cities reporting (index
below 10%) = 1781
Average system mileage of all Cities reporting (index
below 5%) = 2346
Total number of Cities reporting Combined Sewers =
39
Mileage:
High 2600
Low 2 Average 494
Total number of Chic's reporting Combined Sewers
only = 7
Mileage:
High 1500
Low 50 Average 438
4. Citizen Demands and Resulting Pressure
Groups. In Milwaukee, the level of citizen
demands vary, even between neighborhoods
or wards. The difference in citizen demands
could be even greater between major cities.
96
-------
150
* 100
50
FIGURE 1
MILWAUKEE STUDY
CAPACITY INDEX CURVES
1000
2000
3000 4000
SYSTEM MILEAGE
5000
6000
-------
100
Figure 2
Milwaukee Study
AVERAGE INDEX CURVE
FOR
ALL REPORTING CITIES
O
-------
TABLE 4
MILWAUKEE STUDY
DOMINANT CLEANING PROBLEMS FOR REPORTING CITIES
Cleaning Problem: Grease Roots Sand Gravel Sludge
No. Cities Reporting 65 74 49 24 35
Industrial Waste
11
Problem
Preference Tabulation from Survey
Bucket Rodder Wayne Ball Hyd. Jet
Old
Flushing Chemicals
New Old New Old New Old New Old New Old New Old
Sewers Sewers Sewers Sewers Sewers Sewers Sewers Sewers Sewers Sewers Sewers Sewers
Grease
Roots
Sludge
Sand&
Gravel
ndustrial
Waste
17
23
16
49
18
25
28
19
53
20
40
71
15
5
12
36
72
20
9
12
6
4
9
18
6
7
1
7
16
5
32
6
24
26
16
21
6
22
21
12
24
10
39
23
16
22
13
38
24
16
25
15
14
2
10
23
25
16
3
8
5. Climate and Topography of Land. The
elevation above sea level, and the chemical
and physical structure of the soil, can affect
the design and construction of the sewers.
This can, also, mean a difference in the
maintenance problems encountered.
6. Efficiency of Present Cleaning
Operations. The type of cleaning used may
be obsolete. or poorly planned. In addition,
the municipality might be only responding to
emergencies and not be capable of
implementing a Preventive Program.
7. Tax Limitations. The ability of the
municipality to pay the cost for a better and
more efficient cleaning operation.
In addition to establishing the "Capacity Index"
for sewer systems responding to the national
questionnaire survey, and comparing these indexes
with its own operations, the city computed and
plotted the so-called "Performance Factor" for each
responding municipality and compared this factor
For the performance factor to have meaning it must be
determined that all agencies have used the same definition of
cleaning; that is that a full gauge squeegee has been passed
through the sewer.
with the national average. The "Performance Factor"
was defined as:
P»F.=Total miles cleaned/type/yr.
No. of crews =ft./crew/day
The city also summarized the sewer clogging
problems reported by responding systems, and
evaluated the effectiveness of sewer cleaning method.
These data are included in this excerpted report.
(Table 4, Dominant Cleaning Problems for Reporting
Cities)
The Bucket Method is slow and most costly, but
offers a solution to almost all difficult sewer cleaning
problems.
The Rodder Method is very mobile at a relatively
low cost, but the final cleaning results are not as
reliable.
The Wayne Ball Method has a high production
rate and removes a high percentage of debris from the
sewers.
The Hydraulic Jet Method has a high production
rate, is very mobile, but could leave a high percentage
of debris in the sewers.
The sewer Flushing Method is the cheapest, but it
leaves a high percentage of debris in the sewers and
the final cleaning results are not reliable.
The use of Chemicals is a relatively new method,
and may be effective where grease deposits are a
problem.
99
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APPENDIX 4
SEWER CONNECTION REQUIREMENTS
OAKLAND COUNTY DEPARTMENT OF PUBLIC WORKS
PONTIAC, MICHIGAN
OAKLAND COUNTY DEPARTMENT OF PUBLIC WORKS
PONTIAC, MICHIGAN
SEWER HOUSE LEADS: Sewer connection requirements
1. ALL WORK TO BE PERFORMED UNDER 0. CO. D.P.W. INSPECTION.
2. NOTIFY WATER AND SEWAGE MAINTENANCE, 24 HOURS IN ADVANCE OF WORK.
3. NO SANITARY SEWER WILL BE USED FOR A CLEAN OUT OR A DEWATERING OUTLET.
4. ALL WORK IS TO BE PERFORMED IN THE BEST TRADE PRACTICES.
5. THE TYPE OF PIPE IN THE GROUND, USED FOR A HOUSE LEAD, WILL BE CARRIED ALL THE WAY
TO THE HOUSE UNLESS A FACTORY MADE D.P.W. APPROVED ADAPTER IS USED TO CONVERT TO
ANOTHER TYPE OF PIPE.
example: "TYLOX" PIPE TO "WEDGE LOCK" PIPE USE A FACTORY MADE D.P.W. APPROVED "TYLOX
SPIGOT" TO "WEDGE LOCK BELL", CONVERSION ADAPTER.
6. APPROVED PIPE FOR HOUSE LEADS: FULL DIAMETER, SIX INCH (6 in.)
A. VITRIFIED CLAY PIPE - NCPI - ER 4 - 67 - EXTRA STRENGTH
(1) ASTM C - 425 - 60T (TYPE I)
(a) "AMVIT" AMERICAN VITRIFIED PRODUCTS CO.
(b) "UNILOX" U.S.CONCRETE PIPE CO.
(c) "WEDGE LOCK" CLAY PIPE ASSOCIATION JOINT
(2) ASTM C - 425 - 60T (TYPE III)
(a) "LOXON" LARSON PIPE CO.
(b) " '0' RING" CLAY PIPE ASSOCIATION JOINT
(c) "TYLOX" U. S. CONCRETE PIPE CO.
B. ASBESTOS - CEMENT (AC) PIPE - CLASS 2400 (TYPE III)
(1) "FLUID-TITE" KEASBEY-MATTISON CO.
(2) "RING-TITE" JOHNS MANVILLE*CO.
(3) "WELD-TITE" FLINTTITECO.
C. CAST IRON PIPE - SERVICE WEIGHT
(1) "LEAD JOINT" (HOT POURED AND COMPACTED)
(2) "TY-SEAL" TYLER PIPE CO.
D. CONVERSION JOINT SEALER; VITRIFIED PIPE TO CAST IRON PIPE, FOUR (4 in.) INCH
(1) POLYVINYL CHLORIDE (PVC) DONUTS OR EQUAL FERNCO JOINT SEALER CO.
(2) MASTIC DONUTS (SEE NINE (9) BELOW. STANDARD
7. DIRECT TAP. SEE PAGE 2
8. "SPRINGING IN" PIPE AND WYE, SEE PAGE 2
101
-------
OAKLAND COUNTY D.P.W.
PONTIAC, MICHIGAN
Direct House Lead Connections to Main Sewers
7. Direct Tap-15" or larger only.
•.':V;>\#IO or equal Ml**;
Undisturbed Ground
a. Wye opening to be made
by star drill or hand-
chiseled.
b. Do not permit house
lead pipe to protude in
the main sewer. Contour
end to inside radius of
receiving pipe to provide
smoothest possible joint.
"Spring in" wye pipe
a. Break out half =
of bells as
shown;
b. Center the
pipe with
oakum;
c. Fill the broken out
sections with a st.iff
(summer) mastic for a
joint sealer.
Dewitt's *IO or equal Mastic
Ground
102
-------
OAKLAND COUNTY D.P.W.
PONTIAC, MICHIGAN
ACCEPTABLE PIPE JOINTS FOR ASBESTOS-CEMENT AND CAST IRON PIPE
CAST IRON PIPE
2.
3.
ASBESTOS-CEMENT PIPE
COUPLING
ASTM C428
FLUID-TITE
KUtSE* GASKET1-
ASTM C 428
RING-TITE
COUPLING
SPIGOT
KUBtER BASKET
ASTM C 428
WELD-TITE
SPIGOT
SASKET.
HUB
SERVICE WEIGHT CAST IRON PIPE
TY-SEAL JOINT
POLYVIMYL CHLORIDE
2.
CONVERSION JOINT SEALER 6X4
FERNCO PVC DONUT
103
-------
3.
5.
7.
OAKLAND COUNTY DEPARTMENT OF PUBLIC WORKS
PONTIAC, MICHIGAN
ACCEPTABLE PIPE JOINTS FOR VITRIFIED .CLAY PIPE
(APPROVED VIT. CLAY PIPE SPEC. N.C.P.I. ER 4-67, EXTRA STRJ
ASTM C425-66T TYPE I
AMVIT
POLYYIHYL CHLORIDE
ASTM C425-66T TYPE I
WED6ELOCK
POLYVIHYL CHLORIDE
ASTM C425-66T TYPE I
UNILOX
BELL
1 ^
fOLYURETHAME
J_
SPIGOT
ASTM C425-64 TYPE I
STRE-TITE
2.
6.
8.
ASTM C425-66T TYPE III
LOXON
ASTM C425-66T TYPE III
•O'-RING
SILICA AMD SULFUR
PAINTED SURFACE
ASTM C425-66T
TYLOX
TYPE UI
CHLORIOC
ASTM C425-66T TYPE III
AMVIT'A' RING
104
-------
APPENDIX 5
SAMPLES OF MAINTENANCE REPORT FORMS
Example of Report Form
COMPLAINTS OR REQUEST FOR REPAIRS
JOB NO:
LOCATION
Nature of Complaint:
Received By: Time: Date:
From:
Investigated By: Time: Date:
Repairs Requested By: Time Date:
Assigned To: Time Date:
Action Taken on Complaint or Request:
TIME:
DATE COMPLETED; SIGNATURE:
WATER
H
CUBIC
YDS. SIL
SIZE
FT. SEWERS
2
3
8
i
BASINS CLEANED
U
i
o
1
1
|
SEWERS FLUSHED
n
TRUNK SEWERS CLEAN
STREAMS CLEANED
STREAMS PLAYED
BASINS SPRAYED
O
GARAGE TRAPS INSPEC
n
il
GARAGE TRAPS CLEAN
LIGHTS & BARRICADES
INVESTIGATIONS
Ba
ODORS
:k
RATS
MOSQUITOES
ROACHES
FLOODING
BROKEN SEWERS
OBSTRUCTED SEWERS
DAMAGED MANHOLES
BROKEN BASIN TOPS
OBSTRUCTED BASINS
BROKEN COVERS
LOST ARTICLES
OIL SPILLS
DYE TEST
JOB NO.:
Front roHM SE'561
MAINTENANCE BRANCH DAILY REPORT
DATE: / /
EQUIPMENT:
MATERIALS
BRICK
BRANCHES
CEMENT
CONCRETE SAND
SCREENED SAND
PEBBLES
RED SEWER BRICK
MANHOLE IRONS
PIPE VC
PIPE CONCRETE
24" COVERS
30" COVERS
36" COVERS
24" FRAMES
30" FRAMES
36" FRAMES
BASIN TOP SIDE
BASIN TOP CORNER
JUTE
LATEX ADDITIVE
SEWER CLEANER COMP.
DISINFECTANT
USED
MATERIALS
LUMBER
NAILS
OTHER (SPECIFY)
USED
105
-------
o
-J
STREET NAME
Tapper Drive
Uncas Re
_,
Ursula Place
Vanbuskirk Ave. '
MANHOLE
NUMBER
§1
62
—ft-
AC 1
55 —
67
33$
. .^3§
•vq
336
' Illl/
2U(
2t'
2«
2U
25(
§51
— Is1
25
25
25
-H>
2__
j
r
3
)
4
j —
*
2^2
— 3§7—
328
$°2
MANHOLES
MISSING STEPS
X
DETERIORATED
STEPS
1 INFILTRATION
| OBSERVED
RIM OR COVER
REPAIRS REQUIRED
MASONRY REPAIRS
REQUIRED.
WATER FAUCET
IN MANHOLE
. CLEANING
REQUIRED
X
X
X
X
X
X
x
X
X
~~x
X
X
X
X
UTILITY PIPE
IN MANHOLE
sk
i3s
BS
"'p.
» o
OK
is
CQ i-}
~x
£
K
rife
w a,
Jg
gg
M n
w<
X
X
SEWAGE FLOW
STOPPED
x
X CONDITION
ADEQUATE
x
x
NOT INSPECTED
PIPES
CLEANING
j| REQUIRED
~X
X
X
X
x
X
X
x
"3E —
"~5C —
I] INFILTRATION
OBSERVED
JOINT
MISALIGNMENT
X
BROKEN PIPE
1 1 SAG OR HORIZONTAL
SWING
X
X
X
1 1 CONDITION
1 ADEQUATE
X
NOT INSPECTED
X
X
~~x
X
X
X
X
TABLE II
INVESTIGATION OF EXISTING SANITARY SEWERS
SOUNDVIEW AVENUE INTERCEPTOR SEWER AREA
SEWER CONDITIONS OBSERVED
REMARKS
M.H.No. 63, not found.
M.H.No. 66, not found.
Pipes too full to Inspect.
Pipes blocked with sludge.
M.H. troughs too narrow to permit Inspection
Pipes blocked with sludge.
M.H. No. 330, pulsating flow of soap suds
observed.
W
vi r-s
£ "
i|
w s
if
i 1
O 5
1Q
o
w
en
-o
TJ
m
Z
D
X
O)
-------
APPENDIX 7
SAMPLE OF LETTERS & FORMS USED TO
INVESTIGATE AND CORRECT INFLOW CONDITIONS
1. SEWER OPERATING COMMITTEE
102 Witherspoon Street
Princeton, New Jersey
Tel.: 924-3495
Date:
Tests of the sanitary sewer located in your area
indicate the following violations and/or deficiencies
on your property at
These violations and/or deficiencies must be
corrected within thirty days in order to insure your
safety and the proper operation of the sanitary
system.
Will you please notify this office when the
necessary repairs have been completed.
SEWER OPERATING COMMITTEE
ah-300
5/19/67
2. Washington Suburban Sanitary Commission
4017 Hamilton Street
Hyattsville, Maryland 20781
RE: Plumbing Violations
Dear
In connection with your property this
Commission made an inspection prior to the final
approval of the plumbing work performed therein. It
is the responsibility of the property owner to be sure
that his property in no way violates the Regulations
of the Sanitary Commission.
The Commission recently adopted a policy of
making another inspection on all properties within
the Sanitary District in an effort to eliminate
plumbing violations that occur subsequent to the
final inspection. The Commission regards a violation
of its Plumbing Regulations as a serious matter. The
accumulated effect of such violations has created
health problems in certain areas as well as increase the
operating cost of the Commission.
A recent inspection of your property revealed the
following violation:
The Commission realizes that the situation on
your property referred to was possibly not created by
you or that you may not have been aware of its
existence. However, it is one that must be corrected
for the welfare of the community.
It is necessary that this condition be corrected as
soon as possible and you are therefore allowed fifteen
(15) days from the date above to make the necessary
changes.
A representative will visit the premises at the end
of this time to ascertain if the violation has been
eliminated. Your cooperation in eliminating this
condition is earnestly solicited.
If you desire to discuss this matter prior to
making the correction, will you please come to this
office between 8:15 A.M. and 5:00 P.M. on . It
may be to your interest to have your builder or seller
accompany you at this time.
Yours very truly,
FB/jg
Frank Bliss
Chief Plumbing Inspector
3. Washington Suburban Sanitary Commission
4017 Hamilton Street
Hyattsville, Maryland 20781
RE: Illegal Sewer Connection
Dear Sir or Madam:
In connection with a recent study, made by the
Commission's Engineers, of the cause of the backing
up of sewers in your locality during times of heavy
rainfall, it was discovered that your
connected to the sanitary sewer is in excess of the 30
square feet allowed by the W.S.S.C. Plumbing
Regulation, which reads as follows:
"608.1 No rain water leaders or other pipes
carrying roof, surface or ground water shall be
connected to pipes conveying sewage. However,
cellar drains in cellars ordinarily dry or not
subject to flooding may be connected to the
building drain unless expressly disapproved, and
paved areas containing not over 30 square feet
109
-------
or horizontal surface entirely unprotected by
roof, and not receiving drainage from other
surfaces, may be drained to the building sewer
or building drain."
This situation on your premises not only
contributes to the occasional flooding of some of the
cellars (possibly even your own) in the community
with the attendant inconvenience and damage, but is
a violation of the Plumbing Regulations, adopted for
the protection and benefit of this metropolitan area.
The Commission realizes that the situation on
your property referred to was quite possibly not
created by your or that you may not have been aware
of its existence. However, it is one that must be
corrected for the welfare of the community.
It is appreciated that it may not be feasible for
you to correct the condition mentioned immediately
and you are therefore allowed sixty (60) days from
the date above to make the necessary changes.
A representative will visit the premises about 10
days before this time to ascertain if the violation has
been eliminated.
Your cooperation in eliminating the flooding of
cellars in your community is earnestly solicited. If
you require further information regarding this matter,
please call the PLUMBING DIVISION, Appleton
7-7700, Ext. 344, before 10:00 AJVL, and we will be
glad to promptly furnish you with it, if at all possible.
Very truly yours,
Washington Suburban Sanitary Commission
Secretary
110
-------
APPENDIX 8
RECOMMENDED LOT GRADING REQUIREMENTS
REPORTED BY
HUBBELL, ROTH & CLARK, CITY ENGINEERS
SOUTHFIELD, MICHIGAN
protective slope
drainage divide
side swale or channel
/
rear drainage easement
running to proper outfall
lot grading type B
lot grading type B
example o block grading type 4, valley along rear lot lines
-------
protective slopes
side swale or channel
street
lot grading type A
lot grading type A
street
lot grading type A
all drainage to street
example g bbck grading type I, ridge along rear lot lines
112
-------
rear drainage swales
protective slopes-
side swale
or channel
rear slope to
lower lot
rr~M t
lot grading type A
lot grading type B
lot grading type B
drainage both to street and to rear
lot line"
side swale
example o block grading type 2, gentle cross-slope
113
-------
drainage divide
rear drainage swales
1
front drainage swales
protective slopes
side swale or channel
side swale
or channel
"*—--~^T possible locations of rear drainage
.X'j~~easements to proper outfall
jr f
lot grading type A
lot grading type C
lot grading type C
all drainage to rear lot line
example § block grading type 3, steep cross-slope
114
-------
APPENDIX 9
TYPICAL ENGINEERING SPECIFICATIONS FOR
LOW-PRESSURE AIR TESTING OF SEWERS FOR INFILTRATION CONTROL
Testing of the tightness of sewers with
low-pressure air has become a recognized substitute
for the use of water testing methods, to simulate
infiltration or exfiltration rates into or out of gravity
sewers.
Development of the air-testing procedure in
California has been highlighted by work carried out in
the 1950's and 1960's by an informal organization in
the San Francisco-Oakland Bay Area, composed of
sewer utility officials, sanitary engineers and
manufacturers. This group, known as the Bay Area
Committee on Air- Testing, utilized the same type of
coordinated inter-disciplinary knowledge and
experience which was the pattern of the studies of
infiltration and inflow problems carried out by the
American Public Works Association, as described in
the Report to the Environmental Protection Agency
titled Control of Infiltration and Inflow Into Sewer
Systems, a companion document to this Manual of
Practice.
Much of the following material on air testing was
excerpted from a paper on air-testing experiences at
the City of Seattle, Washington, presented by William
J. Chase and Harvey W. Duff before the Pacific
Northwest Pollution Control Association, November
5, 1965. This paper, in turn, quoted the work of Roy
Edwin Ramseier and George C. Riek, on behalf of the
Bay Area Committee (ASCE Journal, Vol. 90, Part 1,
April 1964).
Description of the Air Test
Test Procedure The low:pressure air test is a test
which determines the rate at which air under pressure
leaves an isolated section of pipeline. This rate
indicates the presence, or absence, of pipe damage.
The test procedure, thus far, is described as follows:
1. Isolate Pipe To Be Tested The section of
pipe to be tested is plugged at each end. The ends of
all branches, laterals and wyes which are to be
included in the test are plugged. All plugs are
carefully braced to prevent slippage and blow-out due
to the internal pressure. One of the plugs provided
must have an inlet tap, or other provision, for
connecting an air hose.
2. Connect Equipment Connect one end of an
air hose to the plug used for the air inlet. Connect the
other end of the hose to the protable air-control
equipment. This equipment consists of valves and
pressure gauges used to control the rate at which the
air flows into the test section and to also provide a
means of monitoring the air pressure inside the pipe.
Connect an air hose between the compressor, or other
source of compressed air, and the control equipment.
3. Add Air - Supply Air to the Test-Pipe
Section Monitor the air pressure so that the pressure
inside the pipe does not exceed 5.0 psig.
4. Stabilize When pressure reaches 4.0 psig,
throttle the air supply so that the internal pressure is
maintained between 4.0 and 3.5 psig for at least 2
minutes. These two minutes allow time for the
temperature of the air to come to equilibrium with
the temperature of the pipe walls. During this time,
check all of the plugs with soap solution to detect
any plug leakage. If plugs are found to leak, bleed off
the air, tighten the plugs, and begin again by
supplying air.
5. Determine Rate of Air Loss This step can be
performed in two ways: (a) Flowmeter Method. This
procedure is used when the rate of air loss is high
(greater than 10 c.f.m.). The control equipment
includes rotameters or other air-flow measuring
devices. Air is supplied to the pipe section at such a
rate that the internal pressure is maintained at 3.0
psig. The flow rate is read in cubic feet per minute.
The pressure of the metered air is read. The rate of air
flow is corrected for pressure and temperature, and is
reported in cubic feet per minute of air under
standard conditions of pressure and temperature.
(Standard pressure is 14.7 psi; standard temperature
is 68° F.). (b) Stopwatch Method. This procedure is
being used for pipeline inspection on new
construction where air losses are usually very small.
The control equipment consists of pressure gauges,
valves and a pocket stopwatch. After the temperature
has been allowed to stabilize for the two-minute
period, the air supply is disconnected, and the
pressure is allowed to decrease to 3.5 psig. At 3.5 psig
the stopwatch is started to determine the. time
required for the pressure to drop to 2.5 psig. This
time required for a loss of 1.0 psi at an average
pressure of 3.0 psig can be used to compute the rate
of air loss. For a precise calculation of the rate of air
loss, the temperature of the air inside the pipe section
and the barometric pressure should be determined
and reported; however, this refinement has been
found unnecessary for the usual acceptance test.
115
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Test Equipment
Plugs Small diameter pipes (4 inch to 12 inch)
have been successfully plugged with plumbers' test
plugs. The air-supply connection is made by removing
the cap from the continuously threaded pipe and
substituting the cap from the continuously threaded
pipe and substituting a hose-adapter fitting.
Pipes of diameters larger than 12 inch can be
plugged by the same plugs used for the
water-exfiltration test, with the addition of an
air-hose inlet connection.
Safety Braces are required to hold the plugs in
place and to prevent the sudden release of the
compressed air. Braces are particularly important on
plugs 12 inches and greater in diameter. A pressure of
4.0 psig against a 12 inch diameter plug will cause a
force of approximately 450 pounds. The compressed
air acts like a spring. Proper precaution must be taken
to prevent this spring from propelling the plug from
the pipe like a bullet."
Recommended Air-Test Specification
Discussion
The recommended specification is that based on
the data collected by Ramseier and Riek, and which
was generally and independently corroborated by
City of Seattle work. While some of the other test
criteria in use result in a simpler specification, they
have, in most cases, somewhat less logic to them per
se, or in their development. In specifying a new
testing concept, it has been found advantageous in
gaining acceptance to be able to show that the test is,
in both theory and practice, a logical one.
Fundamentally, the recommended specification
is based on an allowable air loss of 0.003 c.f.m. per
square foot of internal pipe area. This relates,
primarily, to pipe wall porosity. There is also
included in the specification, however, a
provision that in no case will the allowable air leakage
be less than 2 c.f.m. This becomes of some
importance on short runs of small pipe (6 in. and 8
in.). It was found by Ramseier and Riek that, using
the double plug leak-locating equipment, it is very
difficult to specifically locate the particular piece of
porous pipe in a buried pipeline which leaks only 2
c.f.m. A crack or poorly-installed joint will result in
substantially greater leakage. They concluded that if
the leaking pipe could not be readily identified it was
not a serious leak, and that it was not reasonable to
require its repair.
The recommended specification allows for
establishing the rate of air loss from the pipe either
by measuring the pressure drop in a given period of
time, or, by measuring the rate at which air must be
added to maintain a constant pressure. Photographs
and/or schematic diagrams for equipment to measure
either method are shown in the appendix.
Recommended Specification
The owner will furnish all facilities and personnel
for conducting the test.
The contractor may desire to make an air test
prior to backfilling for his own purposes. However,
the acceptance air test shall be made after backfilling
has been completed and compacted.
All wyes, tees, or end of side sewer stubs shall be
plugged with flexible-joint caps, or acceptable
alternate, securely fastened to withstand the internal
test pressures. Such plugs or caps shall be readily
removable, and their removal shall provide a socket
suitable for making a flexible-jointed lateral
connection or extension.
Prior to testing for acceptance, the pipe should
be cleaned by passing through the pipe a full gauge
squeegee. It shall be the responsibility of the
contractor to have the pipe clean.
Immediately following the pipe cleaning, the'pipe
installation shall be tested with low-pressure air. Air
shall be slowly supplied to the plugged pipe
installation until the internal air pressure reaches 4.0
pounds pe; square inch greater than the average back
pressure of any ground water that may submerge the
pipe. At least two minutes shall be allowed for
temperature stabilization before proceeding further.
The pipe line shall be considered acceptable,
when tested at an average pressure of 3.0 pounds per
square inch greater than the average back pressure of
any ground water that may submerge the pipe, if: (1)
the total rate of air loss from any section tested in its
entirety between manhole and cleanout structures
does not exceed 2.0 cubic feet per minutes, or, (2)
the section under test does not lose air at a rate
greater than 0.0030 cubic feet per minute per square
foot of internal pipe surface.
The requirements of this specification shall be
considered satisfied if the time required in seconds
for the pressure to decrease from 3.5 to 2.5 pounds
per square inch greater than the average back pressure
of any ground water that may submerge the pipe is
not less than that computed according to the
attached page entitled, "Recommended Procedure for
116
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Conducting Acceptance Test."
If the pipe installation fails to meet these
requirements, the contractor shall determine at his
own expense the source or sources of leakage, and he
shall repair (if the extent and type of repairs
proposed by the contractor appear reasonable to the
engineer) or replace all defective materials or
workmanship. The completed pipe installation shall
meet the requirements of this test, or the alternative
water exfiltration test, before being considered
acceptable.
NOTE: It has been found that in many instances clay and
concrete sewer pipe must be wetted before an acceptable
test can be performed. In as much as under actual field
conditions when infiltration would occur, the pipe would
wet from ground water, it appears reasonable to allow the
contractor at his expense to wet the pipe prior to retesting.
AIR TEST
RECOMMENDED PROCEDURE FOR CONDUCTING ACCEPTANCE TEST
1. Clean pipe to be tested by propelling snug fitting Inflated rubber ball through the
pipe with water.
2. Plug all pipe outlets with suitable test plugs. Brace each plug securely.
3. If the pipe to be tested is submerged In ground water, Insert a pipe probe, by
boring or jetting. Into the backfill material adjacent to the center of the pipe, and de-
termine the pressure In the probe when air passes slowly through it. .This Is the back
pressure duo to ground water submergence over tho end of tho probe. All gauge pres-
sures in the test should be Increased by this amount.
4. Add air slowly to the portion of tho pipe installation under teat until the internal
air pressure is raised to 4.0 psig.
5. Checkexposedpipeandplugsforabnormal leakage by coating with a soap solution.
If any failures are observed, bleed off air and make necessary repairs.
G. After an internal pressure of 4.0 psig is obtained, allow at leapt two minutes for
airtempcraturetostabilize.addingonly the amount of air required to maintain pressure.
7. Alter the two minute period, disconnect air supply.
6. When pressure decreases to 3.5 psig, start stopwatch. Determine the time in
seconds that is required for the internal air pressure to reach 2.5 psig. This time In-
terval should then be compared with the time required by specification as computed
below.
9. Ustsizeondlengthof all portions of pipe under test in table similar to one shown
here.
Diameter
Inches
Length
Feet
K = .011 d2L
C =. 0003882 dL
Time required
10. By use of nomograph compute K and C. Use acalea d and L, read K
and C, and enter these values in uie table above.
11. Add all values of K and all values of C for pipe under test.
12. If the total of all C values is less than one, enter the total of all K values Into the
space for •Time Required by Specification.*
13. If thetotalof all C values Is greater than one, divide the total of all K values, by
the total of alt C values, to get t,. To moke this division with the nomograph, use scales
C and K, and read tq.
L
-1000
lao~=
9.0-|
8.0 -E
7.0 -=
60-1
5.0-I
40 -=
0.9 -=
0 S -§
15000 —
5000 -=
4000
1105-=
1Q2Q_I
935
900 -=
425-=
400 —=-.
300—;
283.3
226.7
200 —
170 -
-NOMOGRAPH FOR THE SOLUTION OF K
tq = K4- C
= .011d2L, C = .0003882dL,
117
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APPENDIX 10
EXAMPLE OF SPECIFICATIONS FOR EXFILTRATION
TESTING OF GRAVITY SEWERS
The use of exfiltration testing of sewer pipe to
determine the watertightness of construction is
widely utilized instead of infiltration tests. To assist
sewer system management personnel in evaluating the
procedures used by representative jurisdictions for
this purpose, the following excerpts of specifications
are included he re.
1. Example 1
The owner will provide for the conduct of
exfiltration tests on the sanitary sewer in the presence
of the contractor. Final acceptance of the sewer shall
depend upon the satisfactory performance of the
sewer under test conditions. The tests shall be
performed on pipe between adjacent manholes after
the trench has been backfilled.
The test will be performed up to an average
maximum hydrostatic head of 10 feet. The
exfiltration from the sewer shall not exceed 0.23
gallons per inch of internal diameter per 100 feet of
pipe per hour. Head measurement will be made at the
flow line elevation of the upstream manhole.
The owner will provide for the necessary
watertight hose having a minimum diameter of 3/4
inch. The hose shall be of sufficient length that it can
be extended from the nearest hydrant to the
downstream manhole of the pipe to be tested. The
owner will provide for the necessary control valve,
water meter, adapters, and plugs adapted to air and
water entry and release and any other equipment that
may be necessary to perform the test.
In the event • that city water mains are not
installed and water available therefrom at the time of
the test, the owner will provide water from some
other source to make the test.
Procedure
In inspecting exfiltration tests, the following
minimum requirements and precautions should be
adhered to.
The sewer plug used at the highest end of the
sewer shall have a suitable air vent to allow removal
of trapped air. The hose between the air vent and the
calibrated container shall be of 3/4 inch minimum
diameter and a maximum of 10 to 15 feet long. Do
not allow the hose to become linked or blocked as
this may cause the sewer to be subjected to city water
main pressures. To prevent leaks and plug movement
during the tests, the sewer plugs should be supported
in position by bracing to the opposite wall of the
manhole. Do not refill the sewer under test through
the calibrated container as this will allow the air to
become trapped.
Place the calibrated container at the average
height of ten feet above the flow line of the sewer.
Check the entire system for leaks in hoses, plugs,
calibrated container, etc., while filling through the
positive shut off valve. When the water overflows the
calibrated container, close the input valve and tests
may begin.
Record the elapsed time to empty the container
of water and calculate the loss in gallons per hour. If
the container has not emptied after 15 minutes,
measure the loss and calculate the gallon per hour
rate. Take two or more tests at this level. If the test
results at the 10 foot average level do not vary more
than ten percent, the container can be repositioned at
the five foot average level. Take two or more tests at
the average five foot level. Open the valve slowly
during test runs to avoid building up too high a
pressure in the sewer. If more than one section of
sewer is to be tested the water used to test the higher
section can be saved by placing another sewer plug in
the next downstream manhole.
2. Example 2
Vitrified Clay Pipe Unless otherwise specified in
the Special Provisions or otherwise directed by the
engineer, all vitrified clay pipe installations and
laterals adjacent thereto will be tested for leakage.
The owner will provide for water and all equipment
necessary to make the required tests. The owner, at
his discretion, may test only a portion of the lines
installed, but in no case will less than twenty-five (25)
percent of the lines be tested. In no case will the
minimum percentage be allowed unless all sections
tested pass the required leakage test the first attempt.
All lines will be tested in areas where underground
water is or may be encountered.
A section of sewer line shall.be prepared for
testing by plugging the upper side of the downstream
manhole and all openings in the next upstream
manhole except the downstream opening. Where
grades are slight, two or more sections between
manholes may be hydrostatically tested at once.
Where grades are steep, the maximum head on any
119
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section under test will not exceed ten (10) feet.
Branch sewers running from Y-branches on the mains
shall be plugged at their upper end if the test head
would cause them to overflow.
A section of sewer line prepared as above shall be
tested by filling with water to an elevation of four- (4)
feet above the invert at the midpoint of the test
section, or four (4) feet above the existing ground
water elevation or one (1) foot above the top of the
pipe in the upstream manhole, whichever is greater.
The water should be introduced into the test section
at least four (4) hours in advance of the official test
period to allow the pipe and joint material to become
saturated with water. All entrapped air is to be
removed from test section prior to performing the
test. At the beginning of the test the elevation of the
water in the upper manhole shall be carefully
measured from a point on the manhole rim. After a
period of one (1) hour, or less, with the approval of
the engineer, the water elevation shall be measured
from the same point on the manhole rim and the loss
of water during the test period calculated. If directed
by the engineer, enough water shall be precisely
measured into the upper manhole to restore the water
to the level existing at the beginning of the test, and
the amount added shall be used to determine leakage.
Should an initial test show excess leakage in a
section of line, it is permissible to draw the water off
and test the manhole that contained water. This test
shall be made by plugging all the openings in the
manhole and filling with water to the same elevation
as existed during the test. The leakage from the
manhole may be deducted from the total leakage of
the test section in arriving at the test leakage. After
testing is complete, the manhole shall be
waterproofed by grouting and/or painting the interior
with sodium silicate or other approved water-proofing
agent. If it is necessary or desirable to increase the
test head above four (4) feet, the allowable leakage
will be increased to allow for the increase in head.
Sewer sections showing leakage in excess of that
allowed shall be repaired or reconstructed as
necessary to reduce the leakage to that specified.
The maximum allowable exfiltration for this test
shall be 200 gallons/inch of diameter/mile/day, plus
ten percent for each two foot of head over two feet
or as indicated in Special Provisions. The contractor's
attention is, however, directed to the fact that the
stipulation of a maximum allowable leakage shall in
no way relieve the contractor of his obligation to
correct, stop or otherwise remedy individual leaks in
the system due to defective workmanship or material
even though such leakage might come within the
allowable maximum.
The air test may be substituted for the water test
only with specific approval of the engineer. When
allowed, the air test shall be conducted in
conformance with the requirements and procedures
on file in the engineer's office.
Concrete Pipe .Leakage tests on concrete pipe
with cement mortar or other joints, may be specified
in the Special Provisions or on the drawings. The
testings on these installations will be in accordance
with specifications indicated in "Testing of Sewer
Lines, Vitrified Clay Pipe," and as directed by the
engineer.
3. Example 3
The owner will provide an exfiltration test on all
sanitary sewers. Final acceptance of the sewer shall
depend upon the satisfactory performance of the
sewer under test conditions.
The owner will provide the necessary watertight
hose having a minimum diameter of 3/4-inch. The
hose shall be of sufficient length that it can be
extended from the nearest hydrant to the
downstream manhole of the pipe to be tested. The
owner will provide the necessary one-gallon calibrated
container, control valve, water meter, adaptors, and
plugs adapted to air and water entry and release and
any other equipment that may be necessary to
perform the test.
In the event that city water mains are not
installed and water available therefrom at the time of
the test, the owner will provide water from some
other source to make the test.
The test shall be performed on pipe between
adjacent manholes after the trench has been
backfilled and the pipe cleaned. After filling the line
completely, the hose connection from the water
source shall be disconnected and the test begun.
The test shall be performed up to a hydrostatic
head of ten feet above the average elevation of the
sewer line. The exfiltration from the sewer shall not
exceed 0.23 gallons per inch of internal diameter per
100 feet of pipe per hour. Head measurement will be
made from the flow line elevation of the upstream
manhole.
The- allowable exfiltration is shown in the table
for various pipe sizes.
Where conditions warrant, the owner may
perform an infiltration test. The rate of infiltration of
water into any sanitary sewer or appurtenance shall
not exceed 0.4 gallons per inch diameter per 100 feet
of sewer per day. This allowable infiltration,
expressed in gallons per hour, is shown in the table
for various pipe sizes.
120
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ALLOWABLE LIMITS OF EXFILTRATION
295 Gal/Inch Dia/Mi/Day (at 10ft. head)
Diameter
of Sewer
Sin.
10 in.
12 in.
15 in.
18 in
21 in.
24 in.
27 in.
30 in.
Maximum Allowable Loss
In Gals./Hr./100 Ft. of Pipe
1.9
2.3
2.6
3.5
4.2
4.9
5.6
6.3
7.0
ALLOWABLE LIMITS OF INFILTRATION
200 Gay/Inch Dia/Mi/Day
Diameter Infiltration Diameter Infiltration
of Sewer Gals/hr/100 ft. of Sewer Gals/hr/100 ft.
Inches
8
10
12
15
18
21
24
27
30
36
42
48
Gallons
1.3
1.6
1.9
2.4
2.8
3.3
3.8
4.3
4.8
5.7
6.6
7.6
Inches
54
60
66
72
78
84
90
96
102
108
114
120
Gallons
8.5
9.5
10.4
11.4
12.3
13.3
14.2
15.2
16.1
17.0
18.0
18.9
Allowable M.H. Infiltration
41 In. Dia. M.H. 0.07 Per Vertical Ft. Per Hr.
48 In. Dia. M.H. 0.08 Per Vertical Ft. Per Hr.
121
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APPENDIX 11
A METHOD FOR GAUGING INFILTRATION
FLOW IN SEWER TESTING
(excerpted from literature of Cherne Industrial, Inc.)
The following discussion of the use of a V-notch
for gauging the amount of ground water which
infiltrates into sewer lines is presented here only for
general information. Its inclusion in this Manual is
not to be interpreted as any confirmation of the data
by the American Public Works Association or the
Environmental Protection Agency.
Infiltration testing methods and standards are
discussed in detail in Section 2 of this Manual of
Practice. Further information on testing procedures
can be found in standard text books on sewer
construction and testing.
WATER INFILTRATION
Two basic types of equipment are used to
determine the actual rate of infiltration. One, the
flow meter is used in existing sewers to determine
flow through a manhole; the other is the weir. We will
devote the majority of this discussion to the weir,
since it is the most economical and most widely used
measuring device for determining infiltration into
newly constructed sewers.
The term, "weir", as it is commonly used, applies
to a structure containing a notch with a shape such as
a rectangle, a trapazoid, or a triangle (also called a
V-notch). Weirs are classified according to the shape
of the notch and this discussion will be confined to
the most common type, the 90° V-notch, sharp
crested, weir. Discharge over this weir is computed by
the following formula:
Q = 3240 H2 s Gallons/Day (H is measured in inches)
This basic formula neglects the velocity of fluid
approaching the weir, so that only one measurement
need be taken to compute the quantity of water
flowing through the weir. This one dimension, "H" is
the head of water flowing over the crest. (Note Figure
1)
In Figure 1 the "H" decreases in height as it
approaches the weir. This is because the velocity of
the fluid increases as it approaches the weir. The "H"
reading must be taken at such a point (distance "D"
in Figure 1) that the velocity of approach is not a
factor. The rule of thumb is that the "H" dimension
must be taken at least 18 inches upstream from the
crest of the weir or 3 times the height of "H",
whichever is greater. This becomes even more
complicated, since some V-notch weirs have been
modified by their manufacturers so that the reading
at the crest of the weir is the actual reading that
should be taken. But, in these cases one must be
careful not to use the corrected weirs for sizes other
than those for which it was designed, otherwise the
corrections are useless.
The next consideration in the infiltration test is,
"What length of pipe do we check at one time?"
Many engineers will specify the total project cannot
leak more than a specified number of gallons per inch
of diameter per mile of pipe per day, but a single
manhole to manhole reach of pipe may be allowed to
leak 2 to 3 times this amount. This allows the
contractor to average out bad construction over the
whole job and is extremely unfair to the buyer and
actually unfair to the contractor, since an extremely
bad portion of pipe can cause many other pipe
sections to apparently fail. The most important thing
to consider here is that leakage is a symptom of bad
workmanship.
Figures 2 and 3 indicate the details of testing for
infiltration in various lengths of sewer lines.
The proper use and reading of the weir is
extremely important, both to the contractor and the
engineer. To demonstrate this importance, take a
typical installation of an 8 inch diameter line,
manhole to manhole. It would be about 300 feet long
with 8 homes connected to the line by means of 6
inch laterals brought to the property line. It is
generally assumed that each lateral will be
approximately 20 feet long and suitably capped with
a good quality stub seal. Figure 4 is a rough drawing
of this setup. We will assume that the infiltration
standard is 250 gallons per inch diameter per mile per
day, therefore, the allowable infiltration rate for the
above installation will be:
250 GPD [(300 ft. x 8 in.) + (8 homes x 20 ft.
x 6 in.)] = 160 Gallons/Day
123
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r\
BALL
n
Figure 82
•WEIR
n
^-WEIR
BALL
Figure #3
3 GO-
S HOUSE LATERAL
20' LONG
ALL CAP LATERAL STUB SEAL
Figure 8k
124
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APPENDIX 12
CORRECTION OF INFILTRATION BY MEANS OF
GROUTING WITH SEALANTS AND GELS
The following material is presented for general
information purposes only. Its inclusion does not
constitute any approval of the data offered by
manufacturers of products or processes, nor does it
represent any endorsement of such materials or
methods used for sealant purposes by the American
Public Works Association or the Environmental
Protection Agency.
Further information can be obtained from he
manufacturers and suppliers listed and from others
not covered by the data contained in this Appendix.
Grouting is the cementing together of loose
particles of soil in such a manner that the soil so
grouted becomes a solid mass which is impervious to
water. It is not a method of cementing pipes together.
The ability of any chemical, or combination of
chemicals, to penetrate the soil is directly related to
the amount or percent of suspended solids in the
grout material used to the void ratio of the soil to be
grouted. Grouting technology is an old procedure
dating back to the turn of the century.
With the advent of television inspection, soil
grouting techniques (especially with the use of
sodium silLcates and calcium chloride) were
attempted in conjunction with internal TV
inspection. However, because of the lack of control
of the gel time, external piping was required and costs
were high. After development of control gel time and
reactions, it was possible to utilize internal packing
procedures for sewer sealing. American Cyanamid
holds the patent for AM-9 and is the major
formulator of chemical sealants.
Chemical Grouting with AM-9
American Cyanamid has a policy of "licensing
the applying contractor" before agreeing to selling
the chemical. Attendance is required at a special
grouting school held in their plant in New Jersey.
They also check the. company who asks to be
licensed, as to their professional, capabilities, their
past experience, the availability of registered
engineers, and other factors.
The following data have been excerpted from the
"Chemical Grout Field Manual" and other literature
of the American Cyanamid Company.
CHEMICAL DATA
Description of AM-9
AM-9 CHEMICAL GROUT is a mixture of two
organic monomers - acrylamide and N, N
methylenebisacrylamide - in proportions which
produce very stiff gels from dilute, aqueous solutions
when properly catalyzed. The process by which
gelation occurs is a polymerization-crosslinking
reaction.
Description of Catalysts
|3-Dimethylaminopropionitrile (Catalyst
DMAPN). This is a liquid, somewhat caustic, chemical
used as an activator for the reaction. The density of
Catalyst DMAPN, between 32°F and 104°F, is about
0.86 gm./ml. or 7.1 Ib./U.S. gal. There are 529 cubic
centimeters per pound of Catalyst DMAPN.
Ammonium Persulfate (AP). Ammonium
persulfate is a granular meterial and a very strong
oxidizing agent. It is the initiator that triggers the
reaction and is therefore the last material to be
added. The induction period (gel time) begins with its
addition. Generally, it is dissolved in water and added
as a 5 to 20 percent solution to the AM—9 solution
through a separate pump or by gravity.
Description of Inhibitors
Potassium Ferricyanide (KFe). Potassium
ferricyanide is a reddish, granular material which may
be used to control the reaction. It behaves as an
inhibitor in very small quantities and must be used
cautiously for this reason.
Description of Buffers
Buffers are chemicals used to control the pH of
the catalyzed AM—9 solution. In rare cases, acidic
mixing water will necessitate the use of buffers to
bring the solution pH to 8. When ammonium
persulfate is used alone for catalysis, buffers will
generally be required. Disodium phosphate
heptahydrate is recommended. Sodium carbonate
may be used in soft water.
125
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Chemical Reactions
The gel is formed by the following two-step
process:
Step 1. An aqueous solution of AM—9,
containing DMAPN (one component of the catalyst
system) and KFe (if required), is prepared.
Step 2. The remaining component of the catalyst
system, AP (usually in water), is added to the
solution of AM-9 prepared in Step 1. Timing of the
induction period (gel time) is started.
Two reactions occur in sequence:
Catalysts -> Free Radicals
Free Radicals + AM-9 -> Polymer
The first reaction starts almost immediately after
the second component of the catalyst system is added
to the AM-9 solution. The rate of formation of free
radicals and their rate of decomposition is strongly
influenced by a number of factors. Control of these
by proper selection of the catalyst system and the
environment allows a predetermined amount of time
to elapse before polymerization of AM—9 occurs.
This is known as the induction period or gel time,
during which the viscosity of the solution remains
almost constant. At the end of the induction period,
heat is evolved, and long, flexible, polymer chains are
formed. As these chains form, they simultaneously
crosslink to form a stiff complex matrix which binds
the water into a gel. The gel reaches its maximum
strength in a matter of minutes.
Gel Charts
The relationships between gel time and catalyst
concentrations, as influenced by inhibitor
concentration and temperature, have been
determined for a wide range of conditions.
Factors Affecting Gel Time
1. AM-9 CONCENTRATION. Reducing the AM-9
concentration in the range of 15 percent causes a
slight increase in gel time.
2. CATALYST CONCENTRATION. Changes in the
concentration of one or all components of the
catalyst mixture have a very marked effect on the gel
times. Too much KFe or too little AP or Catalyst
DMAPN will produce weak gels or none at all. The
recommended lower limits are 0.4 percent for
Catalyst DMAPN1, 0.25 percent for AP, and the
upper limit for KFe is 0.035 percent.2
3. TEMPERATURE. The gel times for any catalyst
system increase with decreasing temperature and
Under special conditions it may be lower.
Under special conditions it may be higher.
decrease with increasing temperature. A rough rule of
thumb is that the gel time is cut in half if the
temperature goes up ten degrees Fahrenheit.
4. pH. The pH of the solution, after catalyst
addition, may affect the gel time. For best control up
to about a one-hour gel time, the pH should be in the
range of 7 to 11. Except under very unusual
conditions where large amounts of acid are present,
Catalyst DMAPN maintains the pH between 8 and 9.
Below a solution pH of 6.5, the gel times can become
long and indefinite.
5. AIR. AM-9 solutions that are saturated with air gel
much slower than those containing no air. In general,
allowance must be made for the air that is entrained
and dissolved during vigorous mixing.
6. METALS. Certain metals such as iron, copper and
copper-containing alloys, have an accelerating effect
on the gel time of AM—9 solutions. However, the
presence of Catalyst DMAPN in the solution makes it
possible to use standard equipment and materials in
handling and placing AM—9. Where iron storage tanks
are used for AM—9 solutions, they should be painted
with aluminum paint to prevent iron rust from
entering the injection system. Aluminum, stainless
steel, plastic or rubber containers, pipes and valves
must be used to handle solutions of AP.
7. MIX WATER. Formation water or water from the
local supply may be used in the field depending on
which is the more suitable for the application. Some
of the factors described in this section may occur in
the mix water. Therefore, it is very important to
check gel times by carrying out a gel test with the
water which will be used in the application.
8. SUNLIGHT. Direct sunlight, due to the ultraviolet
rays, sometimes will cause local gelation in tanks
containing AM—9 solutions. To avoid this in the field,
solution tanks should be covered.
9. INHIBITORS. Most of the ordinary
polymerization inhibitors, i.e., hydroquinone,
oxygen, ferric ions and sodium nitrite can be used to
stop or slow down the gelation of AM—9. These
materials, however, cause the formation of weak gels
which cannot be improved. KFe, when used in the
recommended concentrations, does not affect the
strength of the final gel. Under special conditions, it
may be aflded repeatedly in small quantities to delay
the gelation of a catalyzed solution.
10. HYDROGEN SULFIDE. Hydrogen sulfide has a
very complicated effect on the gelation of AM-9. In
general, it behaves as an accelerator and may be
considered as such under ordinary working
conditions.
11. SALTS. The presence of soluble salts, such as
126
-------
sodium chloride, calcium chloride, sulfates and
phosphates, has an accelerating effect on the rate of
gelation. The amount of acceleration depends on the
salt concentration and should be determined by a test
in the field. Salts may also have the effect of
increasing the gel strength. Certain ones, such as
calcium chloride, decrease the rate at which water is
lost from gels under dehydrating conditions.
12. FREEZING. The freezing of AM-9 solutions has
little effect on their activity. To avoid freezing during
application, salt, alcohol or any commercial
antifreeze may be added. The effect of these additives
on the gel time must be checked.
13. PARTICULATE MATERIALS. Most fine,
insoluble materials such as clay, bentonite, etc., slow
down the gelation to some extent. If such fillers are
used,....
GROUTING SPECIFICATIONS
The material which follows is suggested by
American Cyanamid for inclusion in specifications
when it is desired to use AM—9 Chemical Grout. (A
"maximum" limit on the amount of chemicals used
per size of pipe should not be specified. A range of
gallon usage would be preferable. The amount of
chemical used is dependent soley on the type of soil
to be grouted. The static or hydro-static conditions of
the ground water, the approximate volume of
chemcial required to assure a permanent, long-lasting
seal, and many other factors.)
Materials
Materials shall conform to the requirements listed
below. All materials shall be delivered to the site in
undamaged, unopened containers bearing the
manufacturers original labels.
a. Chemical Grout. The chemical grout shall consist
of an intimate mixture of dry Acrylamide and
dry N, N1- Methylenebisacrylamide, in such
proportions that dilute aqueous solutions, when
properly catalyzed, will form stiff gels.
The grout must make a true solution at
concentrations as high as three pounds per gallon
of water.
The chemical solution shall have the ability to
tolerate ground water dilution, and to react in
moving water.
The viscosity of the chemical solution, shall have
a viscosity of less than 2 cps, which remains
constant until gelation occurs.
The reaction time shall be controllable from 10
seconds to an hour.
The reaction shall produce a continuous and
irreversible gel at chemical concentrations as low
as 0.4 pounds per gallon of water.
b. Catalyst. The catalyst for the chemcial grout
shall be Ammonium Persulfate. This material
shall normally be used in combination with an
activator, but it may be used in combination with
a buffer for high temperature work.
c. Activator. The activator shall be
jS-Dimethylaminopropionitrile or other suitable
compounds.
d. Inhibitor. Under some conditions it may be
necessary or desirable to control the chemical
reaction by inhibition. The inhibitor used shall be
Potassium Ferricyanide.
Supervision
The entire chemical grouting operation shall be
supervised by a professional engineer experienced
with chemical grouts and grouting equipment. Such
engineer shall be present whenever grouting is being
performed.
Equipment
The chemical grout pumps shall be of a type
approved by the manufacturer of the grout, and shall
be able to operate continuously at the volumes and
pressures required by the job. The pumps shall be
capable of proportioning catalysts mechanically, and
shall be calibrated prior to use. Materials used for
tanks, packers and other equipment shall be
compatible with the chemicals.
APPLICATION EQUIPMENT
There are three basic types of equipment which
have been used to apply AM—9 solutions. These are
designated as the proportioning system, the
two-solution system and the batch system. Of these
the proportioning system is the best and easiest to
use, (as described here).
Proportioning System
Flexibility is designed into the proportioning
system because it is usually important to vary gel
times, pumping rates and pressures over a moderate
range during any application. This system allows one
man to control all of these factors rapidly and
precisely by mechanical means. The need to adjust
the compositions or concentrations of solutions
during an application is eliminated.
AM-9, Catalyst DMAPN, and KFe (if required)
are mixed in TA!; AP is made up in TA2. The pump
(P2) is selected to handle a small volume of AP
127
-------
KEY OF COMPONENT PARTS
TA, - Muring Tank for AM-9
Chemical Grout,
Catalyst DMAPN. and KFe.
TA, - Mixing Tank for
Ammonium Parsulfate.
S. G. - Sight Gauges.
P, Positive Displacement Pump.
Pj - Positive Displacement Pump.
V.S.,- Variable Speed Drive.
V.S.,- Variable Speed Drive.
G, - Diaphragm Pressure Gauge.
G2 — Diaphragm Pressure Gauge.
V, - Quick Opening Valve.
V, - Spring Loaded Check Valve.
O - Orifice.
TA, to Injection Pipe should be
aluminum. Type 316 stainless
steel, rubber or some plastics.
TAt through V, can be mild steel,
aluminum, stainless steel, rubber
or plastics.
Proportioning System.
solution (5 to 20 percent AP in solution) relative to
the volume of AM-9 solution handled by pump Pi.
Thus the flow through P2 can be varied on the job to
produce large changes in gel time without materially
changing the concentration of AM—9 in the final mix
or the total volume of solution entering the ground.
Changes can also be made in total volume pumped
without changing the gel time. A typical gel chart for
use with field proportioning equipment is shown in
Figure 6. The capacity of Pj is usually about 5 to 15
times that of P2.
The sizes of all pumps, lines and valves must be
chosen according to the pressures and flow rates
anticipated. For all applications a separate water
source should be available so that water may be
pumped through P, or another pump to clear the
injection points or the formation adjacent to them.
A proportioning system can be constructed to
handle a wide variety of pressures. It is also possible
to have a low pressure system which can be used to
proportion AM—9 and catalyst solutions into the
suction side of many standard grouting pumps. The
latter then determines the pressures that may be used.
Asphaltic Base Soil Sealing Treatment
The City of Richmond, California used this
process on a trial section of sewer in 1962. It was
found that infiltration was reduced 50 percent, as
shown by the hydrostatic head test.
The treatment compound is an asphaltic base
product produced by the Standard Oil Company and
was originally used for sealing and soil stabilization of
irrigation canals. Before application, the asphaltic
compound is diluted with water in proportions of one
to a hundred. The treatment is carried out by
blocking off a section of sewer and the sealant
solution is pumped into this section in exactly the
same manner as in carrying out a hydrostatic head
test. At the saturation limit, or when the sewer
section no longer absorbs sealant, the treatment is
considered completed. The sealant is then drawn
from the section and reused. The hydrostatic head
test is carried out before and after treatment to
determine treatment effectiveness.
The lasting quality of this process is not yet
known. Its effectiveness in areas of extremely high
infiltration is questionable, and more testing is
needed. The low cost of this process may make it
desirable in cases where partial reduction of flow is
sufficient to serve an immediate need.
The City of Richmond is planning to carry out
further trials with this process. The product details
may be obtained from Mr. P.L. Chapdelaine,
Research Engineer, California Research Corporation
of the Standard Oil Company, Limited.
Compared to other sealing methods this process
is very economical. The cost of the asphaltic
compound before dilution is about 50 cents a gallon;
128
-------
the greatest cost is in the labor involved. No figures
are available at present on the basis of cost per lineal
foot of sewer treated, but it would depend on the
condition of the sewer and the soil conditions around
the sewers.
Cement Grouting Process
A process of sealing sewers using cement grout
containing certain additives and accelerators, such as
calcium chloride, can be utilized as a fairly
economical process by properly trained sewer
maintenance crews. This method has been used by
various agencies, some of which are:
Los Angeles County Sanitation Districts,
California
Imperial Beach, California
Menlo Park Sanitary District, California
The necessary equipment is basically simple;
operation involves the pulling of a telescopic cable
and disc system through the sewer. The discs are
metal .with a leather or felt perimeter. The term
"telescopic" means that there are four or five discs
attached to the cable system and spaced about two
feet apart. Grout is loaded up between the discs; the
head disc is fixed, and as the system is pulled through
the pipe, the discs pull and squeeze the sealant into
the cracks and leaks in the sewer. Application is
repeated as required.
The immediate results after treatment appear to
be excellent according to the sources interviewed.
Unfortunately, no concrete information was available
on tests of durability.
A drawback in this system is that it is necessary
to protect side laterals at the street main and lateral
connections to prevent grout blockage of the lateral
sewers. This might mean excavation. Because of this
fact, utilization of this process may be economical
only in areas where there are few lateral sewer
connections or where the sewers are very shallow in
depth and where cost of excavation of lateral
connections is low.
The cost of this method lies mostly in the labor
involved. As mentioned, this system could be carried
out by the sewer maintenance staff. Contractor costs
can be expected to run approximately $2.50 per foot
of sewer treated.
Other Methods of Sewer Sealing
In addition to the methods of sewer sealing
described, other means have been used in American
sewer practice. The following information is
excerpted from an infiltration study report prepared
by W. Long and Associates, Consulting Engineers,
Berkeley, California.
This material is presented for information
purposes only. Its inclusion in this Manual does not
constitute any approval of the data, and/or
endorsement of the processes and products described.
Internal Packing Method
A number of major national sewer service
companies are experienced in the sealing of sewer
system defects by means of bdth external and
internal methods.
The external packing method involves the use of
a closed-circuit television unit, a sealing device and
related control equipment. The sealing operation
begins by introduction of the TV camera and sealing
device into the sewer. When a leak comes into view
the sealing device is moved into place and by
expanding the inflatable ends of the sealing device,
the leaking section is isolated. Sealant compounds are
pumped into the isolated section under pressures in
excess of ground water pressures. The compounds,
which have low viscosity, pass through the leakage
point and seal the path of leakage and the adjacent
soil area. The sealing device is then deflated and the
• immediate results inspected by the television camera.
The principal chemical used is ordinarily AM—9.
The "set" time required for the solution to gel
depends on field conditions and is controlled by the
quantity of catalyst added to the solution. The gel
time may vary from seconds to hours as field
conditions demand.
This method has only recently been employed on
the West Coast areas (since 1962). Some typical costs
in California are given below.
Area
1. City of Richmond
2. Santa Clara County
Sanitation District
No. 4
3. City of Live Oaks
4. San Pablo
Sanitary District
5. City of Concord
Size- Length- Total
in. ft. Cost
21,24 3,000 $4,000
8
15
890
4,400
15 3,000
15 4,000
1,400
14,000
2,400
5,000
The average costs in the above list fall in a range
of $0.80 to $3.20 per foot. The final cost is generally
dependent on the number of seals which must be
made per length of sewer.
129
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Because the cost of the process is directly
proportional to the number of seals made, it merits
consideration in those cases where only a few leaks
are present or where the number of sewer joints are
less because of longer pipe sections in larger diameter
pipes such as trunk sewer lines. The agencies
interviewed indicated their interest in continuing to
use the system. Many agencies were found to be
unfamiliar with the method. Without a planning
investigation as described in Section 3 of the Manual
of Practice, an agency cannot properly evaluate the
desirability of grouting as contrasted to replacement.
Sonoma County, California Asphaltic Treatment
Process
The County developed a sewer sealing process
which involves impregnating the soil around the
outside of the sewer pipe with applications of SC-1
and RS-1 asphalts. These asphalts are applied to the
soil about 6 inches above the sewer by an applicator
made of 3/4-inch steel pipe with a perforated nipple
at the discharge end. The applicator is placed in a
hole drilled down to the sewer, and the inlet is
connected to the asphalt drum resting on the ground
surface. The applicators are spaced 15 feet apart
along the center line of the existing sewer. The line is
considered sealed when the asphaltic penetration into
the sewer ceases. Penetration into the sewer is
determined by the color of the sewage at a manhole;
carrying asphalt, the sewage is brown-colored.
Considerable success has been reported by the
County on this process, with results being recorded at
two locations by the County. Recording stations have
been located in L.I.D. No. 1 in two manholes, T-71
and 1-60, each having a separate drainage area
including approximately 5 miles or more of tributary
sewers.
Despite this sealing, recent flow records at these
two stations indicated flows increased 5 times to the
average flow in 2 hours during a moderate rainfall
with an intensity of 0.3 inch per hour for 3 hours.
However, these flow figures could not be completely
attributed to the limitations of the sealing process at
this time, due to the fact that neither of the two areas
is completely treated to date. Flow records after
completion of treatment or repairs should then give
the true effectiveness of the process used. It is
suggested that detail testing of the treated sections be
carried out in order to provide additional
information.
Bentenoite
Another common chemical used in bentenoite.
Bentenoite is essentially a clay type material mined in
various parts of the country. It has a physical
property of expanding when wet and contracting
when dry. However, because of its high suspended
solid content, its use is limited to very pervious soils
such as gravel.
Study of "Improved Sealants for Infiltration
Control"
The following tabulation of "Preliminary
Estimates of the Properties of Grouting Materials,"
has been excerpted from the report of the Western
Company, Richardson, Texas, to the Federal Water
Quality Administration, Department of the Interior,
June 1969, under Contract No. 14-12-146. The
report has been published as Water Pollution Control
Research Series, WP-20-18.
Inclusion of this tabulation is for information
purpose only. It does not constitute any acceptance
of the accuracy of any of the data, or any
endorsement of the products listed. The purpose of
the research study was an attempt to determine if
structural deficiencies could be corrected as well as
"welding a new joint together." This is in contrast to
the existing concept of grouting, that is, stabilizing
the material around the pipe.
130
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PRELIMINARY ESTIMATES OF THE PROPERTIES OF GROUTING MATERIALS*
Material
IDEAL MATERIAL
CEMENT
Probable Achievable
Concrete (1-2-4)
Cement (1-4-0)
Cement Mortar(l-i-O)
Pozzolantc
Hydromite
Cal-Seal
Latex
Diesel Oil
Fast-Fix
Putty- Fix
ASPHALTS
Probable Achievable
SC-70
S-l
AC- 20
OA-90
OA-55
GELS
Probable Achievable
AM-9, Penetryn, PWG,
Wes Grout and VPG
Terra Flnna and Blox-all
Slroc, Slljel and
Formasll
POLYMERS
Probable Achievable
Epoxy plus ,
Herculox, Epo sand
or Whlteslde
HG-10
PC- 12
Polyesters
Cost ($)
Z
a
5
1.50/gal
1.20/ft'
1.20/ft'
1.20/ft1
1.00/ft1
7. 00/gal
5.00/100 1
1.50/ft1
1.40/ft1
1.30/ft'
1.50/ft5
1.50/gal
1.00/gal
1.00/gal
1.00/gal
1.00/gal
1.00/gal
2.00/gal
2.00/gal
2.00/gal
2.00/gal
3.50/gal
3. 00/gal
4.55/gal
4.55/gal
2. 50/gal
>
•a
o
1
30.00
38.50
38.50
38.50
38.50
38.50
38.50
38.50
38.50
38.50
38.50
30.00
30.00
38.50
38. 50
38. 50
30.00
38.50
38.50
38.50
38.50
<
*
100
70
20
30
50
50
40
50
50
50
60
40
60
60
30
20
20
20
90
90
70
70
85
40-70
30-70
50-70
30-70
>
3"
FT
100
80
10
20
30
35
35
35
35
20
50
40
30
20
20
20
20
20
20
10
10
10
90
60
70
60
30
Properties
Ul
5f
S
100
100
80
85
90
80
80
80
80
60
95
90
40
10
20
20
20
20
50
20
30
30
100+
60-100
40-90
50-80
60-1004
Shrinkage
0
Ij
100
95
80
85
85
85
80
85
85
80
90
85
80
80
80
80
80
80
70
70
70
70
100+
95
100
100
60
M
^
£J
m
100
95
95
95
95
95
95
80
95
80
90
85
90
90
90
90
90
90
40
10
20
30
100
100
100
100
100
H]
8
cr
§
100
60
50
50
50
50
50
50
50
50
50
50
90
90
90
9u
90
90
100+
100+
100+
100+
100
50-90
50-90
40-70
50-90
O
o
B
3
3
0)
3
100
80
60
60
60
60
60
60
60
80
60
60
100
100
100
100
100
100
40
40
40
40
85
40
30+
30+
70
•d
it
f1
100
80
50
50
50
60
50
50
50
60
60
60
40
30
10
10
10
10
80
80
80
80
90
40
80
80
80
Remarks
The ideal material will have a viscosity of water during placement.
adhesion equivalent to breakage, strength equal to sewer pipe, no
shrinkage, flexible as the sewer pipe, contamination to not affect
set or materially affect strength and a pot life which Is adjustable.
By using special additives and formulations, these results are expected.
The ratios 1-2-4, 1-4-0, and 1- 1-0 refer to the ratios of cement-
sand-gravel in the formula.
Volcanic materials which will react with lime to form a cementlous
material or may be used as additives In cement.
Special cement formulations.
Blend of cement In dlesel oil which has a retarding effect until water
Is added.
Rapid set cements developed by Western for specfal applications.
The formulas can be further Improved for sewer pipe grouting use.
A number of additives to modify the properties of cement are available.
Limited because of pour point of asphalt in relation to temperature
of sewer pipe (200°F vs 60 F). Placement and strength are disadvantages
Typical road asphalt diluted with solvent.
Typical road asphalt.
Special asphalt of the Texas Highway Department.
200°F pour point asphalt.
200°F pour point asphalt for pavement crack repair.
Chief gel disadvantages are the strengths and environmental cure
characteristics.
Trade names for the acrylamlde £ype or grouting gel.
Trade names for the llgnosulfate type of gel.
Trade names for the silicate type of gel.
Gel starting materials are basically water soluble and are
severely affected if diluted with water or dehydrated.
Primary disadvantage Is cost of materials, however, this Is small
compared to total cost.
Tradenames for epoxy resin plus amlne, acid, anhyhide, etc. as
a crosslinking agent.
Prepolymer plus polyol, etc, as a crosslinking agent.
Unsaturated polyester resin plus vinyl crosslinking agent, styrene.
The properties are estimates of anticipated values since there are
no known commercial products.
NOTE: An almost unlimited number of materials are available for formula modifications. Each different material In comblnat Ion "1* 'ha. base polymer material ™*"}ts ln
a finished nroduct with different properties. Example base chemical suppliers are: Polyesters - American Cyanamlc, Chevron, Allied, Hooker, ADM, Dow,
Urethane Union Carbide Monsanto DuPont Gllddem Epoxy - Shell/General Mills/Humble. In addition to the base materials available, other methods
IxTsTwhlch permit modification of the properties of the poTy^Ss (1. e. , fillers, coupling agents, plastlclzers, solvents, catalyslsts).
+ If contaminant Is water the Urethane may foam (expand) which may be an advantage.
* These estimates of the properties of grouting materials ware made prior to the beginning of the program. The estimates were based upon general knowledge of the various
grouting materials. A number of properties of the grouting materials were selected which were anticipated to be Important In their evaluation. An Ideal property was assigned
a value of 100; the closer the estimated properties approached 100, the better the material property.
131
-------
r
BIBLIOGRAPHIC: American Public Works Association,
Research Foundation. Prevention and Correction of Excessive
Infiltration and Inflow Into Sewer Systems - A Manual of
Practice EPA Publication No. 11022 EFF 01/71
ABSTRACT: As a result of n national study of the sources and
prevention of infiltration and inflow, a Manual of Practice
was proposed. The Manual is intended to serve as a guide to
local officials in evaluating their construction practices,
conducting surveys to determine the extent and location of
infiltration and inflow, the making of economic analyses of
the cost of excessive infiltration/inflow waters; and instituting
corrective action.
Excerpts from sewer control legislation are given as well as
information on air and exfiltration testing.
This Manual of Practice was prepared for the Environmental
Protection Agency in partial fulfillment of Contract
14-12-550. The study was also supported by thirty-nine
public agencies. A companion document, "Control of
Infiltration and Inflow Into Sewer Systems", was also
prepared.
KEY WORDS
Infiltration
Inflow
Investigation
Construction
Legislation
Testing
Economics
BIBLIOGRAPHIC: American Public Works Association,
Research Foundation. Prevention and Correction of Excessive
Infiltration and Inflow Into Sewer Systems - A Manual of
Practice EPA Publication No. 11022 EFF 01/71
ABSTRACT: As a result of a national study of the sources and
prevention of infiltration and inflow, a Manual of Practice
was proposed. The Manual is intended to serve as a guide to
local officials in evaluating their construction practices,
conducting surveys to determine the extent and location of
infiltration and inflow, the making of economic analyses of
the cost of excessive infiltration/inflow waters; and instituting
corrective action.
Excerpts from sewer control legislation are given as well as
information on air and exfiltration testing.
This Manual of Practice was prepared for the Environmental
Protection Agency in partial fulfillment of Contract
14-12-5SO. The study was also supported by thirty-nine
public agencies. A companion document, "Control of
Infiltration and Inflow Into Sewer Systems", was also
prepared.
KEY WORDS
Infiltration
Inflow
Investigation
Construction
Legislation
Testing
Economics
I—
t
BIBLIOGRAPHIC: American Public Works Association,
Research Foundation. Prevention and Correction of Excessive
Infiltration and Inflow Into Sewer Systems - A Manual of
Practice EPA Publication No. 11022 EFF 01/71
ABSTRACT: As a result of a national study of the sources and
prevention of infiltration and inflow, a Manual of Practice
was proposed. The Manual is intended to serve as a guide to
local officials in evaluating their construction practices,
conducting surveys to determine the extent and location of
infiltration and inflow, the making of economic analyses of
the cost of excessive infiltration/inflow waters; and instituting
corrective action.
Excerpts from sewer control legislation are given as well as
information on air and exfiltration testing.
This Manual of Practice was prepared for the Environmental
Protection Agency in partial fulfillment of Contract
14-12-550. The study was also supported by thirty-nine
public agencies. A companion document, "Control of
Infiltration and Inflow Into Sewer Systems", was also
prepared.
L_
KEY WORDS
Infiltration
Inflow
Investigation
Construction
Legislation
Testing
Economics
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Accession Number
w
Subject Field & Group
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
The American Public Works Association, Chicago, Illinois 60637
Title
PREVENTION AND CORRECTION OF EXCESSIVE INFILTRATION AND INFLOW
INTO SEWER SYSTEMS - A MANUAL OF PRACTICE
1 Q Author(s)
The American Public Works
Association
16
21
Project Designation
Program No. 11022 EFF 01/71
(APWA69-16)
Note
22
Citation
23
Descriptors (Starred First)
* Infiltration, *lnflow. Investigation, Construction, Legislation, Testing, Economics
25
Identifiers (Starred First)
27
Abstract
As a result of a national study of the sources and prevention of infiltration and inflow, a Manual of Practice was
proposed. The Manual is intended to serve as a guide to local officials in evaluating their construction practices,
conducting surveys to determine the extent and location of infiltration and inflow, the making of economic analyses
of the cost of excessive infiltration/inflow waters; and instituting corrective action.
Excerpts from sewer control legislation are given as well as information on air and exfiltration testing.
This Manual of Practice was prepared for the Environmental Protection Agency in partial fulfillment of Contract
14-12-550. The study was also supported by thirty-nine public agencies. A companion document, "Control of
Infiltration and Inflow Into Sewer Systems", was also prepared.
Abstractor
Richard H. Sullivan
Institution
APWA Research Foundation
WR: ">2
WRSIC
(REV. JULY 1969)
SEND, WITH COPY OF DOCUMENT, TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 20240
ft U. S. GOVERNMENT PRINTING OFFICE : 1971 O - 424-250
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Continued fron inside front cover
11022 — 08/67
11023 — 09/67
11020 — 12/C7
11023 --- Q5/G8
11031 —- OC/68
11030 DNS 01/69
11020 DIM 06/69
11020 DES 06/69
11020 --- 06/69
11020 EXV 07/69
11020 DIG 08/G9
11023 DPI 08/69
11020 DGZ 10/69
11020 EKO 10/69
11020 — 10/69
11024 FKi'l 11/69
11020 DUF 12/69
11000 --- 01/70
11020 FKI 01/70
11024 DOK 02/70
11023 FDD 03/70
11024 DMS 05/70
11023 EVO 06/70
11024 --- 06/70
Phase I - Feasibility of a Periodic Flushing Systen
for Combined Sewer Cleaning
Demonstrate Feasibility of"the Use of Ultrasonic
Filtration in Treatinn the Overflov/s from Combined
and/or Storm Sewers
Problems of Combined Sewer Facilities and Overflows,
1967, (UP-20-11)
Feasibility of a Stabilization-Retention Basin in Lake
Erie at Cleveland, Ohio
The Beneficial Use of Storm 1,'ater
Uater Pollution Aspects of Urban Runoff, (IT-20-15)
Improved Sealants for Infiltration Control, (UP-20-18)
Selected Urban Storm Hater Runoff Abstracts, (WP-2C-21)
Sewer Infiltration Reduction by Zone Pumping, (DAST-3)
Strainer/Filter Treatment of Combined Sewer Overflows,
(UP-20-1C)
Polymers for Sewer Flow Control, (UP-20-22)
Rapid-Flow Filter for Sewer Overflows
Design of a Combined Sewer Fluidic Regulator, (DAST-13)
Combined Sewer Separation Using Pressure Sewers, (ORD-4)
Crazed Resin Filtration of Combined Sewer Overflows, (DAST-4)
Storm Pollution and Abatement from Combined Sewer Overflows-
Bucyrus, Ohio, (DAST-32)
Control of Pollution by Underwater Storage
Storm and Combined Sewer Demonstration Projects -
January 1970
Dissolved Air Flotation Treatment of Combined Sewer
Overflows, (WP-20-17)
Proposed Combined Sewer Control by Electrode Potential
Rotary Vibratory Fine Screening of Combined Sewer
Overflows, (DAST-5)
Engineering Investigation of Sewer Overflow Probler.i -
Roanoke, Virginia
Microstraining and Disinfection of Combined Sewer
Overflows
Combined Sewer Overflow Abatement Technology
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