EPA 670-9-74-004
Excerpts from
Control of Infiltration and Inflow
into Sewer Systems
and
Prevention and Correction
of Excessive Infiltration and Inflow
into Sewer Systems
A Manual of Practice
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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PREFACE
Two publications were developed under contracts DI-14-12-550
and EPA-WQO-14-12-550 by the American Public Works Associ-
ation, Chicago, Illinois, for the U.S. Environmental Protection
Agency's Water Quality Office and 39 local governmental juris-
dictions.
The publications are:
Prevention and Correction of Excessive
Infiltration and Inflow into Sewer Systems,
Manual of Practice, January 1971
NTIS PB 203 208
GPO 5501 0053
and
Control of Infiltration and Inflow Into
Sewer Systems, December 1970
NTIS PB 200827
GPO (number not available)
This publication (revised 1974) contains excerpts from these
two reports. It provides a brief and quick reference source of
information on infiltration and inflow problems and on correction
of infiltration conditions.
Copies of the complete reports may be obtained from the
National Technical Information Service, U.S. Department of
Commerce, Springfield, Virginia 22151, or Sliderintendent of
Documents, U.S. Government Printing Office, Washington, D.C.
20402.
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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
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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.
Key Words: INFILTRATION, INFLOW, INVESTI-
GATION, CONSTRUCTION, LEGISLATION, TEST-
ING, ECONOMICS.
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SECTION 1
INTRODUCTORY STATEMENT: THE INFILTRATION AND
INFLOW PROBLEM AND ITS PREVENTION AND CONTROL
THL PROBLEM
A seiious 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 suicharging 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 theii 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 tne 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 for
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
necessaiy. 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 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
is 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 ami
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 he
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 irunks
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 thai true invert elevations and pipe sizes be
known so that hydraulic compulations 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
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, i 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
wate.. 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
after 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
cumulation 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 bask .ways: attack on the pipe or joint
materials, and an increase in the rate of infiltration
once openings in the system have occurred for a
variety of reasons, not necessarily connected wiiii
pound 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 cathotiic
protection.
Ground water has a very pronounced eflect 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 clean 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 clean 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.
3.6.2 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 ;37S 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 ihe 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 will) sand or gravel
back to the manhole for dumping on Ihe
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 lo pipe size as possible lo obtain the
necessary results preparatory to a good
grouting job.
It also is necessary that a sufficient amount
of flushing water be available during (he final
cleaning operation, to scour and flush the
pipe.
3. The high velocity or hydraulic pipe cleaning
machine is mobile and provides a fust and,
under most conditions, effective cleaning.
Operation of this machine wilh a specially
designed cleaning no/./.le will produce j
cleaning or scouring action from streams of
water directed to strike the inside wall of ihe
pipe under high velocity. As a result of Ihe
jet action from the rearward orifices, ihe
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 necessary1
in using hydraulic cleaning equipment. In
sandy soil where ihe sewer may be defective.
creation of voids may cause collapse of the
pipe.
4. Hydraulically propelled cleaning tools arc
placed in the pipe with the proper tolerances
between the outside diameter of ihe 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:
3.7.1 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.^.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.
3.8.3 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 Sewen
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
ex filtration 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 of'TV 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 pulkd 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 it 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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CONTROL OF INFILTRATION AND INFLOW INTO SEWER SYSTEMS
by the
AMERICAN PUBLIC WORKS ASSOCIATION
for the
ENVIRONMENTAL PROTECTION AGENCY
WATER QUALITY OFFICE
and
THIRTY NINE LOCAL GOVERNMENTAL JURISDICTIONS
c,itr«>ci 14-J2-5SO
December, 1970
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ABSTRACT
Two hundred and twelve public jurisdictions in the
United States and Canada were contacted, and
twenty-six communities were visited. Practices of
consulting engineers and state and provincial water
pollution control agencies were also surveyed.
The surveys indicated that infiltration and inflow
are widespread problems.
Reduction of infiltration should be stressed in both
new and old systems. For new sewers a construction
allowance of no more than 200 gallons per day per inch
of diameter per mile of pipe is recommended. Existing
systems must be extensively investigated to determine
the extent and location of infiltration. Reduction of
inflow waters can be accomplished after sources of such
flows have been identified, alternate methods of disposal
identified, and the backing of public and governing
bodies secured.
Twenty recommendations are given indicating the
need for extensive investigation of the extent of the
infiltration/inflow problem before relief sewers are
constructed or wastewater treatment plants built or
enlarged.
The report includes 43 tables, an extensive review of
reports concerning local infiltration studies, and a
bibliography of 135 references.
This report was prepared for the Environmental
Protection Agency in fulfillment of Contract 14-12-550.
The study was also supported by thirty-nine public
agencies. A companion document, "Manual of Practice,
Prevention and Correction of Excessive Infiltration and
Inflow into Sewer Systems," was also prepared.
Key Words: INFILTRATION, INFLOW, INVESTI-
GATION, INSPECTION, SURVEY.
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