United States
Environmental Protection
Agency
Water Engineering Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/132 Jan. 1986
Project Summary
Insituform and Other Sewer
Rehabilitation Techniques
Michael R. Olson
Four methods were examined for
rehabilitating defective sanitary sewers
with respect to (1) logistic problems, (2)
equipment and labor required by each,
(3) the environmental impact as related
to noise, air, and water pollution, (4) the
social impacts, including public incon-
veniences from traffic disruption, utility
relocation, and the temporary disruption
of sanitary service, (5) economic pa-
rameters, including adjusted cost com-
parisons and the cost effectiveness of
each alternative, (6) the effectiveness
of the technique in reducing mainline
infiltration, (7) durability of the prod-
ucts, and (8) before-and-after flow
properties of the rehabilitated sections.
The four methods studied were Insitu-
form* lining, test-and-seal, point repair,
and conventional sliplining. The study
emphasizeslnsituform lining, especially
as installed in Hagerstown, Maryland,
and it includes discussion of installation
procedures and problems, product lim-
itations, spatial requirements of the
equipment, and safety hazards and
procedures.
This Project Summary was developed
by EPA's Water Engineering Research
Laboratory. Cincinnati, OH. to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The public works industry shares a
widespread concern about the progres-
sively deteriorating condition of sewer
collection systems across the nation.
Larger and larger wastewater treatment
'Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use
plants are being designed and constructed
every day, in many cases to treat flows
that result from the infiltration and inflow
(I/I) of stormwater into the sanitary sewer
system. Engineers are increasingly hesi-
tant to attack the I/I problems existing
within collection systems because of the
uncertain results of any anticipated sewer
rehabilitation program. Less risk is in-
volved in designing an oversized treat-
ment plant to accommodate extraneous
flows than in attempting to control and
limit these flows. However, the engineer
can be doing a disservice to his client by
overlooking some cost effective measures
of eliminating extraneous flows in the
sewer network. Engineers, municipal
employees and officials, and regulatory
agencies must pay increased attention to
the collection system. This study attempts
to present methods by which substandard
conduits can be repaired, and it compares
the advantages and disadvantages of each
alternative.
The four sewer rehabilitation methods
included in this study were Insituform
lining, test-and-seal, point repair, and
conventional sliplining. Insituform lining
is a new technique in which a thermo-
setting-polymer-soaked bag is blown into
the existing sewer line, usually with water
pressure. Hot water or steam is then used
to cure the polymer producing a rigid liner
conforming to the original pipe. Because
the liner offers structural stability, it can
be used to rehabilitate badly deteriorated
sewers. The test-and-seal procedure
makes use of chemical grout that is
injected into imperfections in the pipe.
Equipment has been developed for testing
and sealing in one operation. This method
cannot be used with badly deteriorated
sewers. Point repair refers to replacement
of pipe where pipe condition is too poor to
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permit application of any less complete
rehabilitation procedure. Sliplining in-
volves the insertion of a slightly smaller
diameter pipe inside the original pipe. The
availability of slightly flexible plastic pipe
allows long lengths of sewer to be relined
in one operation. This method is appli-
cable to badly deteriorated sewers so long
as there are not large offsets that would
prevent passage of the liner.
Procedures
Field studies were performed primarily
in Hagerstown, Maryland, but some were
also conducted in LaGrange Highlands,
Illinois, and in 13 other North American
sites. The field studies were supplemen-
ted with data gathered during the prepa-
ration of earlier reports on the Insituform
process. These data were used to compare
and evaluate various sewer rehabilitation
techniques, considering parameters such
as the effectiveness and durability of the
product in eliminating infiltration, the
procedures and problems associated with
each rehabilitation option, the economic
aspects of each option, and the socio-
logical ramifications of each technique.
Each rehabilitation alternative considered
in this report has its place in the overall
scheme of collection system renovation;
hence defective segments of sewers must
be considered individually, using the
inspection tools available, to establish the
best rehabilitation application for each
instance
Potential Insituform userswantto know
how effective and durable the product is
when exposed to a typical sewerage
environment over an extended period. To
answer this question, sites were visited
where Insituform liners had been in place
for a considerable time. Officials respon-
sible for each installation were questioned
about the need for the Insituform con-
struction procedures, problems associ-
ated with the work, the effectiveness of
the liner, and the durability of the repair
material over time. Evaluations based on
these visits are presented here with ap-
propriate conclusions. This approach
should enable prospective users to judge
the feasibility of using Insituform liners in
each circumstance.
Some attention must be paid to the
problem of rehabilitating service laterals
on private property without damaging the
property. To eliminate infiltration from a
sewer collection system, defective laterals
must be rehabilitated as much as possible
within cost constraints. Groundwater that
repair work prevents from entering a
mainline will seek out other avenues of
entrance to the collection system, often
migrating to deteriorated service lines or
manholes.
Results and Conclusions
Sites Other Than Hagerstown
The site studies, interviews, and video
tapes reviewed indicate that the Insitu-
form method of sewer lining is a viable,
cost-effective alternative for rehabilita-
tion in various circumstances. Each situa-
tion must be considered individually to
determine the appropriateness of the
technique.
Sewers have been lined by the Insitu-
form method in vastly different locations
and geologies. Climatic conditions have
varied from those in Winnipeg, Canada,
in the middle of the winter to those in
central Florida in the summer. Sewers
transporting domestic-strength waste
from municipalities and sewers carrying
high-strength chemical wastes from in-
dustrial situations have been lined with
the product and are holding up reasonably
well under the conditions imposed on the
liner.
The Insituform liner was chosen over
other repair alternatives for a variety of
reasons, but the deciding factor was
generally the logistics of the site. Many
industrial plants chose Insituform lining
for sewers running under buildings. The
cost in such cases was not only below
that for other options, but the no-
excavation procedure provided for mini-
mal disruption of production during
construction. Where the restoration costs
of excavation were considerable or pro-
hibitive(e.g., in built-up areas, areas with
numerous services or land of great value),
Insituform was found to be the most
economical method of sewer rehabilita-
tion. In some areas, the lejal problems of
gaining access to a site necessitated the
use of Insituform because of its non-
destructive and nondisruptive nature.
Since lining by Insituform takes much
less time than conventional Sliplining,
situations in which lengthy construction
cannot be tolerated lend themselves to
this method. Sites favor Insituform when
project staging areas are limited or when
traffic control might cause problems;
Insituform requires less equipment space
and can easily be adapted to the remote
location of installation and curing equip-
ment.
The lining was implemented to elimi-
nate either infiltration or exfiltration from
sewer stretches, or to provide structural
integrity to defective or severely deterior-
ated pipes. The parties interviewed gen- f
erally agreed that the product was effec-
tive in performing this designated task. In
three cases where weak spots and
bubbles were detected in the post-
rehabilitation television inspection before
client acceptance, the lining was either
removed and redone or a point repair was
made.
Hagerstown Rehabilitation
Study
1. For all mainline sewer rehabilitation
techniques studied, effectiveness
in eliminating infiltration depends
directly on the rehabilitation of
appurtenant facilities such as
manholes, service laterals, etc.
2. The sanitary sewer rehabilitation
program within any municipality
must be an ongoing maintenance
activity. Rehabilitated sewers, lift
stations, manholes, etc., begin to
deteriorate as soon as the repair is
complete; this fact is evidenced by
the gradual increase in wet weather
flows seen at the treatment plant
following completion of a collection
system rehabilitation project.
3. Before-and-after flow data from this
study revealed that test-and-seal,
point repair, conventional sliplining,
and Insituform lining were all suc-
cessful in reducing the mainline
infiltration of groundwaters.
4. The durability of each technique
studied over the 3-year study period
was very good. Specifically impor-
tant was the apparent lack of de-
terioration in the point repairs and
seal rehabilitations after 2 to 3
years. Recent discussions with the
City of Hagerstown staff have indi-
cated that a number of sections that
received test-and-seal repairs were
displaying a return of infiltrating
groundwater. Plans are now in
preparation to line these stretches
with Insituform. During collection
system rehabilitation, it was de-
termined that some manhole sec-
tions in which grouting was planned
could not be successfully sealed
because of large voids or incom-
patible material in the sewer back-
fill. These sections were lined with
Insituform after an analysis was
made for cost effectiveness. City
staff had indicated that much grout-
ing performed in previous programs
within Hagerstown had deteriorated
to the point of ineffectiveness. In
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many instances, these lines were
successfully rehabilitated using
Insituform in the recent program.
5. In some study sections lined with
Insituform, flow data indicated the
technique to be relatively ineffective
in reducing infiltration. This result
could have been dueto either of the
following causes:
a. Groundwater may have been
prevented from entering the
collection system mains but
mitigrated to deteriorated system
elements such as services or
manholes, where it eventually
infiltrated.
b. Tolerances associated with flow
measuring equipment and meth-
ods may have resulted in data
that were not totally representa-
tive. Numerous inconsistencies
in the flow metering data strong-
ly indicate that this item is the
major contributing factor.
Considering all data presented and
the recent deterioration of grouting
sections (not shown by flow data
but determined by the City to be
present), Insituform appears to be
quite effective in eliminating the
infiltration of groundwater from
mainline sewers.
6. Though the Insituform manufac-
turer contends that the liner's
smoothness and thinness provide
the conduit with a greater hydraulic
capacity than before repair, this
result was not borne out in every
test section.
7. The Insituform method of reinstat-
ing services without excavation is
an excellent concept, but a devel-
opment effort with respect to the
Insitucutter is apparently necessary
to render the system totally reliable.
The Insitucutter is designed to be
pulled through a sewer to cut a
circular opening in the line at each
service lateral.
8. Methods of lining service laterals
without excavation are currently
being developed by various lining
firms, with some of the techniques
appearing quite feasible.
9. Each repair technique has its ad-
vantages and problems. Individual
applications should be considered,
weighing costs versus benefits for
each alternative at each site.
10. Initial construction cost figures
indicate that the most cost-effective
method of sewer system rehabilita-
tion is a combination of point repair
and test-and-seal, followed in order
by conventional sliplining and In-
situform lining. These rankings may
change when we consider the life
and serviceability of each alterna-
tive, especially in view of apparent
problems Hagerstown has noted in
test-and-seal work. In addition, it
should be noted that the conven-
tional lining project studies were
very small compared with the
Hagerstown Insituform work, with
limited service reinstatement and
surface restoration. In built-up
areas with access problems, high
restoration costs, and numerous
service connections, Insituform lin-
ing would most likely be more
economical than conventional lin-
ing. Each application must be anal-
yzed individually.
Recommendations
Sites Other Than Hagerstown
A certain amount of follow-up study
should be pursued in this case to establish
the long-term effects of a potentially
destructive environment on Insituform.
Essentially, the sites visited in this report
were lined within the past 5 years and
might not be good examples of the far-
reaching results of continued exposure to
wastewater. Possibly some early Insitu-
form installations in Europe might be
studied.
The ongoing technical advances asso-
ciated with this product should be moni-
tored. Research is currently being
performed on an advanced internal
service-cutting system, and a technique
is being developed for lining service
laterals without excavation. As most of
those involved with sewer rehabilitation
will attest, extraneous flows will not be
successfully eliminated from the sanitary
sewer system until an acceptable, cost-
effective means of rehabilitating sewer
laterals is developed and refined.
The Insituform procedure is an advance-
ment in the field of sewer rehabilitation.
As such, it deserves a great deal of
attention in the future.
Insufficient quality control was evi-
denced in three of these early installa-
tions, both in installation techniques and
materials. Liner arrived at the site too
long or too short, or with skin or seam
imperfections that resulted in installation
problems. Lack of preparation or attention
to detail in the inversion and curing
phases contributed to problems in the
field. Preventive equipment maintenance
should also receive a higher priority.
Hagerstown Rehabilitation
Study
Insituform installers should pay careful
attention to safety problems associated
with their technique. The use of hot water
under pressure to supply the resin-curing
medium for this process deserves specific
concern. This factor, coupled with the
height at which the water is drawn from
and discharged into the inversion tube,
creates a very dangerous construction
situation, especially during curing. Nor-
mal safety precautions should also be
exercised with respect to construction
scaffolding and work in enclosed areas.
The manufacturer should work to de-
velop a reliable mechanical means of
internally reinstating services in all sizes
of sewers. The Insitucutter should be
modified with this end in mind.
Finally, a detailed technical study
should be conducted to establish the
feasibility of rehabilitating sewer laterals
in a cost-effective manner without exca-
vating.
This report, prepared by Thomas I. Sim-
mons and Associates, Rochelle, IL, was
submitted by the City of Hagerstown, MD
in fulfillment of CR 806625 under the
partial sponsorship of the U.S. Environ-
mental Protection Agency.
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Michael R. Olson is with Thomas I. Simmons and Associates, Rochelle, IL 61068.
Richard Field is the EPA Project Officer (see below).
The complete report, entitled "Insituform and Other Sewer Rehabilitation
Techniques," (Order No. PB 86-130 192/A S; Cost: $ 16.95, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U. S. Environmental Protection Agency
Cincinnati. OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAI
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-85/132
0169064 WERL
60604
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United States
Environmental Protection
Agency
Water Engineering Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/133 May 1986
&EPA Project Summary
Alternative Sewer Studies
This report provides new design and
operational information on two of the
most effective and widely applied alter-
native sewer systems—small-diameter
gravity and pressure sewers. The infor-
mation provided here will help system
designers and operators avoid or
rectify problems resulting from sulfides
and downhill hydraulics that could
otherwise represent major impairments
to the successful application of these
technologies.
This Project Summary was developed
by EPA's Water Engineering Research
Laboratory, Cincinnati, OH, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Small communities in need of new or
expanded sanitary sewers are faced with
a severe financial burden. Low popula-
tion densities and unfavorable geological
situations increase per capita costs of
conventional sewers, which often ac-
count for up to 80% of the total capital
costs of a new wastewater management
system.
Conventional sewers are expensive. To
insure that raw sewage flows freely,
conventional sewer systems use large-
diameter pipes set in the ground at
minimum slopes. Pumping stations are
often required as well. Extensive exca-
vation is usually necessary to achievethe
desired slopes. Flat terrain, high ground-
water, and waterfront areas all add to
construction costs and difficulties. Finally,
infiltration and inflow (l&l) of extraneous
water cannot be eliminated entirely in
large pipes. The added wastewater vol-
ume and solids mean that the treatment
plant must have a greater capacity than
would be required to treat only the dry
weather flow.
Alternative approaches to sewering
that address some of the problems en-
countered with conventional systems can
reduce collection and treatment costs.
Three types of alternative sewers are
discussed below:
• pressure sewers
• vacuum sewers
• small-diameter gravity (SDG) sewers
Discussion
Alternative sewers offer the dual ad-
vantages over conventional sewers of
small-diameter pipes and a greater ability
to follow the natural topography without
risk of clogging, which reduces excavation
and construction costs. Furthermore, all
three of these sewers provide reduced I/I.
The two major types of pressure sewer
systems are grinder pump(GP) and septic
tank effluent pump (STEP). These two
systems differ in the onsite equipment,
layout, and quality of the wastewater
conveyed to the pressure sewer. In GPs,
solids are ground to a slurry and dis-
charged through pressure lines. I n STEPs,
wastewater from a home first flows into a
septic tank from which treated effluent is
pumped to pressurized lines.
Vacuum sewers use a central vacuum
source to constantly maintain a vacuum
on small-diameter collection mains. Per-
iodically, the pressure differential created
by the vacuum source draws a slug of
sewage from a holding tank at each home
into the line. When sufficient volume of
sewage is collected at a central vacuum
station, it is pumped to the treatment
plant or main interceptor.
Like the STEP system, a small-diameter
gravity (SDG) sewer is used with indi-
vidual septic tanks. Because solids are
removed by the septic tank, pipes of 4 in.
in diameter can be used at very shallow
slopes without risk of clogging. The'
effluent requires little or no pumping,
generally flowing by gravity to the treat-
ment facility.
Despite their many advantages, several
concerns have been raised about alter-
native sewers. The most important of
these potential problems are:
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• Excess sulfide generation, and
• Two-phase flow in pressure and SDG
sewers
Sulfide generation affects all types of
sewers. The problem manifests itself in
unpleasant odors and corrosion produced
by hydrogen sulfide. Years of experience
have gone into the design of conventional
sewer systems to minimize sulfide gen-
eration. Experience with sulfides in con-
ventional sewer systems has raised two
main concerns about alternative systems:
(1) That the septic effluent in SDG and
STEP systems may be more prone to
sulfide generation, and (2) that the an-
aerobic nature of the pressure and the
SDG sewers may contribute to sulfide
generation.
Two-phase flow refers to a hydraulic
problem of particular concern in pressure
systems. In downhill sloping sections of
pressure sewers, gas bubbles present in
the pipeline can adversely affect flow.
The typical solution is to install air-release
valves at summits within the pipeline.
However, in many cases this technique
does not work efficiently, and additional
steps must be taken to solve the problem.
Conclusions
Although a significant number of pres-
sure and SDG sewers have been de-
signed and constructed, there remain
some significant gaps in understanding
the technology. These studies provide
some insights into two of the major
technology gaps. The major conclusions
are as follows:
1.
2.
3.
GP systems can produce sulfides at
a rate of three to four times that of
STEP systems and about twice that
of conventional sewer force mains
because of the high organic strength
of the wastewater.
STEP systems show unexplained
losses of sulfide and gams in dis-
solved oxygen based on analyses
performed in this study and prev-
ious data for septic tank effluents.
Both pressure systems (i.e., GPand
STEP) ca n be expected to have some
sulfide concentration m their waste-
waters, with values varying from 1
to 14 mg/L based on this study.
4. GP sulfide concentrations will gen-
erally increase in the direction of
mainline flow, but random locations
of service lines and branches may
mask this trend.
2
5. Concentrations of sulfides in pres-
sure sewers cannot yet be quanti-
fiably predicted because of the
empirical nature of the available
equations and their derivation from
weaker conventional wastewaters.
6. SDG sewers should not be designed
to minimize pipe sizes, to flow full
for substantial periods, or to pro-
liferate substantial inundated sec-
tions of mainline if sulfide mini-
mization is desired.
7. For conventional gravity sewers,
equilibrium sulfide concentrations
result from long pipe segments of
relatively uniform conditions. Ap-
plying the equilibrium equation for
conventional gravity sewers to SDG
sewers results m concentrations
comparable with those observed in
SDG sewers. These concentrations
are much lower than the higher
levels reported to occur in septic
tanks.
8. Because of the phenomenon of
conclusion No. 7, SDG sewers
appear to be capable of producing
terminal wastewater sulfide con-
centrations lower than those of
pressure sewers.
9. Conventional placement of air-re-
lease valves at high points of a
pressure sewer system does not
preclude the entrainment of air,
which results m headlosses greatly
exceeding design calculations.
10. In downhill runs where the pres-
sure main intersects the dynamic
hydraulic grade line (HGL), a hy-
draulic jump is formed that gen-
erates gas bubbles that pass on to
downstream segments of the main.
11. Placement of sewage-type auto-
matic air-release valves at points at
least 14 pipe diameters below hy-
draulic jump locations was effective
in removing entrapped air and
reducing headlosses to near theo-
retical levels.
12. Backpressure sustaining valves
were found to be inadequate for
control of downhill hydraulics in the
pressure sewer because of high
capital cost, intensive maintenance
requirements, and unreliable opera-
tion.
13. On downhill runs with irregular
terrain that provide numerous op-
portunities for the formation of
smaller hydraulic jumps, standpipes
were shown to be inexpensive and
reliable The standpipes used large-
diameter downlegs to prevent the
escape and conveyance of air bub-
bles into the downstream segment
of the mains and automatic air-
release valves at their summits to
expel the trapped gases.
14. Soil absorption beds were success-
fully used for the vented gases from
the air-release valves to prevent
hydrogen sulfide odors.
Recommendations
The designer needs improved capability
to predict sulfide concentrations in pres-
sure and SDG sewers. Toward this end,
comprehensive studies of sulfides should
be made from the septic tank to the
terminus of a number of these systems to
identify the gains and losses of sulfide
concentration, to quantify the mechan-
isms responsible, and to develop predic-
tive equations. Once this goal is accom-
plished, a study should be undertaken to
develop a corrosion-based methodology
for evaluating the alternatives of design-
ing a transition station or modifying a
receiving conventional sewer. Such a
methodology would provide a quantitative
solution to one of the major design
obstacles in the design of pressure and
SDG sewers that terminate at larger
conventional sewers.
A need also exists for more quantitative
assessment of the requirements for,
location of, and design and operating and
maintenance requirements for air-re-
lease valves in pressure and SDG sewer
systems. Further assessment is also
needed for soil absorption and other low-
maintenance odor control methods ap-
propriate for these alternative sewers.
The full report was submitted in partial
fulfillment of Contract No. 68-03-3057 by
Urban Systems Research and Engineer-
ing, Inc., under the sponsorship of the
U.S. Environmental Protection Agency.
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Urban Systems Research and Engineering, Inc., is located in Cambridge, MA
02138.
James F. Kreissl and Robert P. G. Bowker were the EPA Project Officers (see
below).
The complete report, entitled "A Her native Sewer Studies, "(Order No. PB 86-131
224/AS; Cost: $9.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
For further information, contact James F. Kreissl at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES
EPA
PERMIT No. G-3
Official Business
Penalty for Private Use $300
EPA/600/S2-85/133
0169064 WERL
CHlc!rnEARBO*N ST-
CHICAG0 IL
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