United States
                        Environmental Protection
                        Off ice of Water
                        Washington, D.C.
EPA 832-F-99-032
September 1999
Collection  Systems
O&M  Fact Sheet
Trenchless Sewer Rehabilitation

As the infrastructure in the United States ages,
increasing  importance  is  being  placed  on
rehabilitating the  nation's  wastewater treatment
collection  systems.   Cracks,  settling, tree root
intrusion, and other disturbances that develop over
time deteriorate pipe lines  and other conveyance
structures  that comprise wastewater  collection
systems.   These  deteriorating  conditions can
increase the amount of inflow and infiltration (I/I)
entering the system, especially during periods of
wet  weather.   Increased  I/I levels  create an
additional hydraulic load on the system and thereby
decrease its overall capacity. In addition to I/I flow,
storm water may enter the wastewater collection
system through illegal connections such as down
spouts and sump pumps.  If the combination of
wastewater, infiltration, and  illegal  storm water
connections  entering the  wastewater treatment
plant exceeds  the capacity of the system  at any
point, untreated wastewater may be released into
the  receiving  water.  This bypass of untreated
wastewater, known as a Sanitary  Sewer Overflow
(SSO), may adversely affect human health  as well
as impair the usage and degrade the water quality of
the receiving water.

Under  the traditional  method of sewer relief, a
replacement or additional  parallel  sewer  line  is
constructed by digging along the entire length of the
existing pipeline. While these traditional methods
of sewer rehabilitation require  unearthing and
replacing  the deficient pipe (the dig-and-replace
method), trenchless  methods of rehabilitation use
the existing pipe as a host for a new pipe or liner.
Trenchless sewer rehabilitation techniques offer a
method of correcting pipe deficiencies that requires
less restoration and causes less  disturbance and
                      environmental degradation than the traditional dig-
                      and-replace  method.     Trenchless  sewer
                      rehabilitation methods include:

                      •     Pipe Bursting, or In-Line Expansion;

                      •     Sliplining;

                      •     Cured-In-Place Pipe; and

                      •     Modified Cross Section Liner.

                      These  alternative  techniques  must  be  fully
                      understood  before they are applied. These four
                      sewer rehabilitation methods are described further
                      in the following sections.

                      Pipe Bursting or In-Line Expansion

                      Pipe bursting, or in-line expansion, is a method by
                      which the existing  pipe  is forced outward and
                      opened by a bursting tool.  The Pipebursting™
                      method, patented by the British Gas Company in
                      1980, was successfully applied by the gas pipelines
                      industry before its applicability was identified by
                      other underground utility agencies.  Over the last
                      two decades, other methods of in-line expansion
                      have  been  patented  as  well.  During  in-line
                      expansion, the existing pipe is  used as a guide for
                      inserting the expansion head (part of the bursting
                      tool).  The expansion head, typically  pulled by a
                      cable rod and winch, increases the area available for
                      the new pipe by pushing the existing pipe radially
                      outward until it cracks. The bursting device pulls
                      the new pipeline behind itself.  The pipe bursting
                      process is illustrated in Figure  1. Various types of
                      expansion heads, categorized as static or dynamic,
                      can be used on the bursting tool to expand the
                      existing  pipeline.  Static heads, which have no

Source: Created by Parsons Engineering Science, Inc.,

moving internal parts, expand the existing pipe only
through the pulling action  of the bursting tool.
Unlike  static  heads,  dynamic  heads  provide
additional pneumatic or hydraulic forces  at the
point of impact.  Pneumatic heads pulsate internal
air  pressure  within the  bursting  tool,  while
hydraulic  heads expand and  collapse the head.
While the dynamic head pulsates or expands and
contracts, the bursting device is pulled through the
existing pipeline and breaks up the existing pipe,
replacing it  with the new pipe directly behind it.
Dynamic heads are often required  to  penetrate
difficult  pipe materials  and  soils.   However,
because dynamic heads can cause movement of the
surrounding soils-resulting in additional  pressure
and ground  settlement-static heads are preferred
where pipe and soil conditions permit.

During the pipe bursting process, the rehabilitated
pipe segment must be taken out of service by re-
routing flows around it. After the pipe bursting is
completed, laterals are re-connected, typically with
robotic cutting devices.


Sliplining is  a well-established method of trenchless
rehabilitation.  During the sliplining process, a new
liner of   smaller  diameter  is placed inside the
existing pipe.  The annulur space, or area between
the existing pipe and the new pipe, is typically
grouted to prevent leaks and to provide structural
integrity. If the annulus between the sections is not
grouted,  the  liner is not considered  a  structural
liner.  Continuous grouting of the annular space
provides a seal.  Grouting only the  end-of-pipe
sections can cause failures and leaks.

In most sliplining applications,  manholes cannot
function  as proper  access  points to perform the
rehabilitation. In these situations, an insertion pit
must be dug for each pipeline segment. Because of
this requirement, in most applications, sliplining is
not a completely trenchless technique. However,
the excavation required is  considerably less than
that  for  the  traditional dig-and-replace method.
System and site conditions will dictate the amount
of excavation spared.

Methods   of  sliplining   include   continuous,
segmental  and spiral wound.  All three methods
require laterals to be re-connected by excavation or
by a remote-cutter. In continuous sliplining, the
new pipe, joined to form a continuous segment, is
inserted into the host pipe at strategic  locations.
The  installation access point, such as a manhole or
insertion pit,  must be able to handle the bending of
the continuous pipe section.

Installation by the segmental  method  involves
assembling pipe  segments at the  access  point.
Sliplining  by the  segment  method  can  be
accomplished without rerouting the existing flow.
In many applications,  the  existing flow reduces
frictional   resistance  and  thereby aids  in  the
installation process.   Spiral wound sliplining  is
performed  within a manhole  or access point by
using interlocking edges on the ends of the pipe
segments to  connect  the  segments.  The spiral
wound pipe is then inserted into the existing pipe as
illustrated in Figure 2.

Cured-In-Place Pipe

During the cured-in-place pipe  (CIPP) renewal
process,  a  flexible fabric liner, coated with a
thermosetting resin, is inserted  into the existing
pipeline and cured to form a new liner. The liner is
typically inserted into the existing pipe through an
existing manhole. The fabric tube holds the resin in
place until the tube is inserted in the pipe and ready
to be cured.  Commonly  manufactured  resins
include unsaturated polyester,  vinyl  ester,  and

Source: Created by Parsons Engineering Science, Inc., 1999.

epoxy,  with  each   having  distinct  chemical
resistance to domestic wastewater.

The  CIPP method can be applied to rehabilitate
pipe lines with defects such as cracks, offset joints,
and   structurally  deficient   segments.    The
thermosetting resin material bonds with the existing
pipe materials to form a tighter seal than most other
trenchless techniques. The two primary methods of
installing CIPP are winch-in-place and  invert-in-
place.  These methods are used during installation
to feed the tube through the pipe.  The winch-in-
place method uses a winch to pull the tube through
the existing pipeline.  After being  pulled through
the pipeline, the tube is inflated to push the liner
against the existing pipe walls. The more typically
applied inversion-in-place method uses gravity and
either water or air pressure to force the tube through
the pipe and invert it, or turn the tube inside out.
This process of inversion presses the resin- coated
tube against the walls of the existing pipe. During
both the  winch-in-place  and inversion-in-place
methods, heat is then circulated through the tube to
cure the resin to form a strong bond between the
tube and the existing pipe. A typical CIPP process
by the  water-inversion method is illustrated is
Figure 3.

Under both CIPP methods, as the liner expands to
fit the new pipe, dimples occur in the line where the
laterals  exist. Dimples in the line can be found by
TV inspection  or  robotic equipment.   In some
applications, a Tee is placed  at the junction before
rehabilitation begins.  Tee's enable junctions to be
easily identified and modified after the pipeline has
been re-lined. Laterals are typically reinstated with
robotic cutting devices, or, for large-diameter pipes,
by manually cutting the liner.

Modified Cross Section Lining

The modified cross section lining methods include
deformed and reformed methods, swagelining™,
and rolldown.  These methods either modify the
pipe's cross sectional profile or reduce its cross-
sectional area so that the liner can  be extruded
through the existing pipe.  The liner is subsequently
expanded to conform to the existing pipe's size.

During deformed and reformed pipeline renewal, a
new flexible pipe is deformed in shape and inserted
into the host pipe. While the method of deforming
the flexible pipe varies by manufacturer,  with many
processes referred to as fold and form methods, a
typical approach is to fold the new liner into a "U"
shape, reducing  the pipe's diameter by about 30
percent.  After  the  liner is pulled  through the
existing line, the liner is heated and pressurized to
conform to  the  original  pipe shape.   A typical
deformed and reformed cross-section is illustrated
in Figure 4.

Another method of obtaining  a close fit between the
new lining  and existing  pipe  is to temporarily
compress the new liner before it is drawn through
the existing pipeline.  The swagelining™  and
rolldown processes use chemical and mechanical
means, respectively,  to reduce the cross-sectional
area of the new liner.

During   swagelining™,   a   typical   drawdown
process, the new liner is heated and subsequently
passed through a reducing die. A chemical reaction
between the  die and liner  material temporarily
reduces the liner's diameter by 7 percent to 15

    How Insituform® is installed
    Figure 1. A special needled felt recon-
    struction tube, Insitutube®, coated on
    the outside, is custom engineered
    and manufactured to fit the damaged
    pipe exactly. It is impregnated with
    a liquid thermosetting resin and low-
    ered into a manhole through an inver-
    sion tube. One end  of the Insitu-
    tube is firmly attached to the lower
    end of the inversion tube elbow.
    Figure 2. The inversion tube is then
    filled with water. The weight of the
    water pushes the Insitutube into the
    damaged pipe and turns it inside out,
    while pressing the resin impreg-
    nated side firmly against the inside
    walls of the old pipe. The smooth
    coated side of the Insitutube becomes
    the new interior surface of the pipe.
    Figure 3. After the Insitutube is
    inverted through the old pipe to the
    desired length, the water is circulated
    through a boiler. The hot water causes
    the thermosetting resin to cure within a
    few hours, changing the pliable Insitu-
    tube into a hard, structurally sound,
    pipe-within-a-pipe, Insitupipe™. It has
    no joints or seams and is usually
    stronger than the pipe it replaced. The
    ends are cut off and  the inversion tube
    and scaffolding are  removed. Normal-
    ly, there are no messy excavation re-
    pairs to be made since most work is
    done without digging or disruption.

i/MANHOLE     ss  C
Source: Iseley and Najafi, 1995 (from Insituform®)

percent and allows the liner to be pulled through the
existing pipe.  As the new liner cools, it expands to
its original diameter. The rolldown process uses a
series of rollers to reduce the pipe liner's diameter.
As  in  deform-and-reform  methods, heat  and
pressure are applied to the expand the liner to its
original pipe  diameter  after it  has been  pulled
through the existing pipe.

Unlike CIPP,  modified cross section methods do
not make use of resins to secure the liner in-place.
Lacking resin-coated lining,  these methods do not
have the curing time requirement of CIPP.  A tight
fit is obtained when the folded pipe expands to the
host pipe's inside diameter under applied heat and
pressure.  As  with the CIPP method, dimples are
formed at lateral junctions and similar methods of
reconnecting  the  laterals  can  be  employed.
Materials typically used for modified cross section
            linings include Polyvinyl Chloride (PVC) and High
            Density Polyethylene (HOPE).

            Trenchless sewer rehabilitation methods are now
            routinely applied to wastewater collection system
            improvement projects in the United States  and
            many  other   countries.     Trenchless   sewer
            rehabilitation has been successfully applied by both
            large municipalities such as New York, NY;  Los
            Angeles,  CA;  Boston,  MA;  Miami,  FL;  and
            Houston, TX;  and smaller municipalities such as
            Baton Rouge, LA; Madison, WI; and Amarillo, TX.
            Kramer  and Thomson  (1997) estimate that the
            market  value  for  sewer  and  pressure  pipe
            rehabilitation projects  will be $5 billion  dollars
            world-wide in the year 2000.

            In   many  municipalities,   sewer   rehabilitation
            projects are an essential  part of operation  and

Source: Created by Parsons Engineering Science, Inc., 1999.


maintenance (O&M) programs for the collection
system.  For example, as part of an O&M program
focused on pro-active maintenance, Fairfax County,
Virginia, has identified two older sewersheds for
rehabilitation.  All trunk and main lines within each
sewershed are television inspected. Results of the
TV inspection are used to prioritize cleaning needs
and to help determine appropriate  rehabilitation
measures. Projects within the targeted sewersheds
have  utilized  the  CIPP  and  fold-and-form
rehabilitation methods.

In an effort to monitor the effectiveness of the
rehabilitation  efforts,  the   department installed
permanent and  temporary  meters in  these two
sewersheds. Fairfax County's focused approach to
maintenance  has reduced  average  flows to the
wastewater treatment plant (WWTP) despite several
years of above- normal rainfall.


While trenchless techniques may be  applied to
rehabilitate  existing pipelines  in  a variety  of
conditions, they are particularly valuable in urban
environments  where   construction   impacts  are
particularly disruptive to businesses, homeowners,
and  automotive and  pedestrian traffic.   Other
underground utilities and existing infrastructure are
an  obstacle in  the traditional  dig  and replace
method,  and  trenchless  techniques  are  widely
applied where these are present. Most trenchless
techniques are applicable to  both  gravity  and
pressure pipelines. Many trenchless methods are
capable of performing spot repairs  as  well as
manhole to manhole lining.

For   most   applications,   trenchless  sewer
rehabilitation techniques require less installation
time-and therefore less pump-around time- than
traditional dig-and-replace methods.  Installation
time can be critical in deciding between trenchless
sewer rehabilitation methods and dig- and-replace
methods.  For example, when  considering sewer
repair or replacement options for a critical force
main crossing  the  Elbe River  in  Heidenau,
Germany, city officials determined that the  line
could not be out of service for more than 12 days
(Saccogna,  1998).   As  a  result  of this  time
constraint,  as  well  as   reduced  disruption  to
riverboat traffic, city  officials chose to rehabilitate
the sewer using the swagelining™ process.  The
successfully rehabilitated sewer was out of service
only eight days.

Trenchless sewer rehabilitation can be performed to
increase the hydraulic  capacity of the collection
system. While pipe  bursting typically yields the
largest increase in hydraulic capacity, rehabilitation
by other trenchless methods may  also  increase
hydraulic  capacity,  by  reducing  friction.   A
hydraulic analysis of the pre- and post-rehabilitation
conditions can be performed to evaluate the impact
on  collection  system  capacity. In  general,  the
hydraulic  analysis  is  performed  by  municipal
engineers  and/or   consultants  who  prepare
specifications for contractors.

Each of the  trenchless  rehabilitation methods
described has  been used for various applications
over  a  range of  pipe  sizes  and  lengths.   A
comparison of trenchless  techniques is shown in
Table 1.


By reducing  I/I levels in the  collection system,
trenchless  rehabilitation  projects   can  assist
communities in complying with the EPA's Clean
Water Act and thereby protect the aquatic integrity
of receiving water-bodies from potentially high

In-Line Expansion

Product Linings

Modified Cross-
Section Methods

Internal Point

Pipe Bursting
Spiral Wound

Fold and Form
Thin-walled lining
Robotic Repair
& Spray-on
Link Seal
Point CIPP

Diameter Range (mm) Maximum Installation (m) Liner Material
100-600 (4-24 in.)
100 -4000 (4-1 58 in.)
100 -1600 (4-63 in.)
150 -2500 (6-100 in.)
100-2700 (4-1 08 in.)
100 -1400 (4-54 in.)
76-4500 (3-1 80 in.)

100-400 (4-1 5 in.)
100-400 (4-1 5 in.)
62-600 (3-24 in.)
62-600 (3-24 in.)
500-1, 100 (20-46 in.)
200-760 (8-30 in.)
100-600 (4-24 in.)
100-600 (4-24 in.)

230 (750 ft.)
300 (1,000 ft.)
300 (1,000 ft.)
300 (1,000 ft.)
900 (3, 000 ft.)
150 (500 ft.)
150 (500 ft.)

210 (700 ft.)
800 (2, 500 ft.)
300 (1,000 ft.)
300 (1,000 ft.)
960 (3, 000 ft.)
15 (50 ft.)

Exopy Resins
Cement Mortar
Chemical Grouting
Special Sleeves
Note:   Spiral wound slipling, robotic repair, and point CIPP can only be used only with gravity pipeline.
       All other methods can be used with both gravity and pressure pipeline.

EPDM = Ethylene Polypelene Diene Monomer
GRP = Glassfiber Reinforced Polyester
HOPE = High Density Polyethylene
MDPE= Medium Density Polyethylene
PE = Polyethylene
PP = Polypropylene
PVC = Poly Vinyl Chloride
PVDF = Poly Vinylidene Chloride

Source: Iseley and Najafi (1995)

pollutant  concentrations by reducing SSOs.  In
addition to potential improvements  in  receiving
water-bodies,  trenchless   sewer  rehabilitation
requires substantially less construction work than
traditional dig-and-replace  methods.   In wetland
areas  and  areas  with  established  vegetation,
construction influences can be especially harmful to
the plant and aquatic habitat. Underground utility
construction can disrupt citizens living and working
in areas near the construction zone.  Trenchless
sewer rehabilitation, with the potential to reduce
surface disturbance over traditional dig- and-replace
methods,  can reduce the number  of traffic and
pedestrian detours,  spare tree  removal, decrease
construction noise, and reduce air pollution from
construction equipment.   In addition to   these
benefits,  reducing the amount  of underground
construction labor and  surface construction zone
area confines work zones to a  limited number of
access  points, reducing  the area where  safety
concerns   must   be  identified   and  secured.
Rehabilitation techniques should be selected based
on  site constraints, system characteristics, and
project  objectives.  A  comparison of economic,
cultural and social costs of sewer rehabilitation with
those of traditional  dig-and-replace methods can
               help determine whether or not a trenchless sewer
               rehabilitation is suitable and economically feasible
               for a particular site. Because some digging may be
               required for point repairs, construction limitations
               should  be  evaluated  when deciding  whether
               trenchless sewer rehabilitation techniques can be
               applied.  If there are major changes in cross section
               between manholes or  if the existing alignment,
               slope, or pipe bedding  material must be changed,
               each line must be rehabilitated as an independent
               segment, necessitating even more digging. Specific
               limitations of each trenchless rehabilitation method
               are listed in Table 2.   As  seen,  the sliplining,
               deform-and- reform methods, and  CIPP methods
               will reduce  the pipe diameter tending to decrease
               the  hydraulic   capacity  of the  sewer.    The
               rehabilitated pipeline, however, may be less rough
               than the original.   The  roughness coefficient
               depending  on  the  liner material.   New  high
               performance plastic materials tend to reduce pipe
               roughness   against  aged   concrete  materials.
               Additionally, the  hydraulic  capacity  may  be
               modified during  rehabilitation  as groundwater
               intrusion is inadvertently redirected to unlined side
               sewers.   An evaluation may  be performed to
               determine whether the change in pipe friction and
Pipe Bursting
Modified Cross Section
Bypass or diversion of flow required
Insertion pit required
Percussive action can cause significant ground movement
May not be suitable for all materials

Insertion pit required
Reduces pipe diameter
Not well suited for small diameter pipes

Bypass or diversion of flow required
Curing can be difficult for long pipe segments
Must allow adequate curing time
Defective installation may be difficult to rectify
Resin may clump together on bottom of pipe
Reduces pipe diameter

Bypass or diversion of flow required
The cross section may shrink or unfold after expansion
Reduces pipe diameter
Infiltration may occur between liner and host pipe unless sealed
Liner may not provide adequate structural support	

groundwater redirection will offset the decrease in
pipe diameter and meet project objectives for an
increase in peak flow and/or reduction in SSOs.
Most trenchless rehabilitation applications require
laterals to be shut down for a  24 hour period.
Coordinating shut-downs with property owners can
be  a difficult and unpopular task.   Unforseen
conditions  can increase construction  time  and
increase the risk and responsibility to the client and
contractor.  For example, during a rehabilitation
proj ect in Norfolk, Virginia, pipe bursting had to be
coordinated   with  the  relocation  of  a  nearby
electrical substation and the rerouting of flow from
a sanitary force main found in a manhole where an
insertion pit was to be located (Small, Gidley,  and
Riley, 1997).  In addition to these issues, numerous
abandoned underground utilities which were not
indicated on  city or private utility records were
encountered during the project. Such underground
conditions  are  found  in  many  other   urban
environments around  the United States.   When
trenchless rehabilitation is planned, public works
projects and utility work by other agencies should
be coordinated with sewer rehabilitation projects.


The performance  of  trenchless   techniques in
reducing I/I  can  be  determined  through flow
measurements  taken   before   and  after  the
rehabilitation. Effectiveness is typically calculated
by   correlating   flow   measurements   with
precipitation  data to determine the peak rate  and
volume  of I/I entering the collection  system.
Another method of calculating I/I is to isolate the
rehabilitated  line and  measure flows both before
and after the rehabilitation.

The performance of sewer rehabilitation projects in
three Northeastern  Illinois  communities  was
documented by Goumas (1995). Results of pre-
and  post-monitoring  within  these   three
communities  indicate that I/I reductions of 49
percent, 65 percent and 82 percent were achieved.
The Washington Suburban Sanitary Commission
(WSSC)  uses the isolation and measurement
method to assess the performance of rehabilitation
projects.    An  analysis   of 98  sewer  mains
rehabilitated between 1989 and 1995 indicates that
I/I  flow was  reduced by  70  percent in  the
rehabilitated sewers (WSSC, 1998).

The Miami-Bade Water and Sewer Department
(MDWASD) is completing  one  of the  country's
largest I/I reduction programs. The program, aimed
at reducing I/I thoughout the system, utilizes the
fold and form, CIPP, pipe bursting, and sliplining
rehabilitation techniques in conjunction with point
and  robotic  repairs.  MDWASD  has  already
experienced success with this program; an average
I/I reduction  of 19 percent  (20 MGD)  has been
achieved between January  1995 and May 1998
based on comparing plant  flow  and billed flow
(MDWASD,  1998)

In Fairfax County, VA,  between June 1994 and
June 1998, wet weather flows were significantly
reduced within the two sewer sheds identified in the
County's  focused  rehabilitation  program  even
though the program addresses only main and trunk
sewer lines and does not address I/I from private
laterals (Fairfax County, 1998).

These studies should only be used as an indicator of
potential I/I  removal.  Removal rates will vary
depending on the material and condition of the pipe,
local soil type, groundwater flow, and other site-
specific conditions.


Cost ranges for trenchless rehabilitation of a typical
size sewer main are provided in  Table 3. These
costs include a standard cleaning of the sewer line
(major blockages and  point repairs increase  the
cost) and inspection of the sewer line before and
after the sewer is rehabilitated. Sewer rehabilitation
by both trenchless and traditional dig- and-replace
methods can  reduce treatment and O&M costs at
the  receiving  treatment  plant  by  potentially
eliminating I/I flows to the plant.  In addition to
treatment cost savings, energy costs for transporting
flows to the treatment plant could also be reduced
due to the reduced flow volume.

A cost  comparison of trenchless and traditional
sewer rehabilitation methods must consider  the
condition and site characteristics of the existing

Pipe Diameter, mm (in.)
Cost Range, per linear meter (ft.)
 Pipe Bursting
 Modified Cross Section
       203 (8)


       203 (8)

       203 (8)
      $130-$260 ($40-$80)


Sources: Kung'u (1998), Burkhard (1998), Cost in 1998 dollars.
These costs are an indicator of some project costs but each project cost is site-specific.
pipeline.   Factors  influencing the  cost  of  a
trenchless sewer rehabilitation project include:

•      the diameter of the pipe;

•      the amount of pipe to be rehabilitated;

•      specific defects in the pipe (such as joint
       offsets, root intrusions, severe cracking or
       other defects);

•      the depth of the pipe to be replaced, and
       changes in  grade over the pipe length;

•      the locations of access manholes;

•      the number of additional access points that
       need to be excavated;

•      the location of other utilities that have to be
       avoided during construction;

•      provisions for flow by-pass;

•      the number of service connections that need
       to be reinstated; and

•      the number of directional changes at access

In general, the  less the amount of  excavation
required for a rehabilitation  operation, the more
cost-effective   trenchless  sewer  rehabilitation
becomes as compared with the traditional dig-and-
replace method.  In addition to excavation and
installation costs, sewer cleaning and inspection are
                   typically required before sewer rehabilitation


                   1.     Fairfax County  Department of  Public
                          Works, Burke, Virginia, 1998.  I. Khan,
                          Director of Line  Maintenance Division,
                          personal  communication  with  Parsons
                          Engineering Science, Inc.

                   2.     Goumas, J., 1995. "Tri-Villages of Greater
                          Chicago Reduce I/I with CIPP," Trenchless
                          Technology 4(3): 70-71.

                   3.     Iseley, T. and M. Najafi, 1995. Trenchless
                          Pipeline Rehabilitation.  Prepared for the
                          National Utility Contractors  Association,
                          Arlington, VA.

                   4.     Kramer, S. R. And J. C. Thomson, 1997.
                          "Trenchless Technology in the Year 2000
                          and  Beyond." In  Trenchless  Pipeline
                          Projects: Practical Applications, ed. Lynn
                          E. Osborn, pp. 174-182. New York: ASCE.

                   5.     Kung'u, Francis,  1998.  Excavation  and
                          Elimination: No-Dig Solutions to Sewer
                          Problems, Civil Engineering News 10 (7):

                   6.     Kutz, G.E.  Predicting I/I Reduction for
                          Planning Sewer Rehabilitation, 1997.  In
                          Trenchless Pipeline  Projects: Practical
                          Applications., ed. Lynn E. Osborn, pp. 103-
                          110. New York: ASCE.

7.     Miami-Bade Water and Sewer Department,
      (MDWASD)  Coral Gables, FL, 1998. L.
      Aguiar,  Assistant   Director,   personal
      communication with Parsons Engineering
      Science, Inc.

8.     Pipeline Rehabilitation Council, 1998. M.
      Burkhard,  president,      personal
      communication with Parsons Engineering
      Science, Inc

9.     Saccogna,  Laura  L., 1998. Swagelining
      Renews Force Main Under the Elbe River,
      Trenchless Technology International 2(1):
Missouri Western State College
Mohammad Najafi, Ph.D., P.E.
Department of Engineering Technology
St. Joseph, MO 64507

The  mention of  trade  names  or commercial
products does not  constitute  endorsement or
recommendation for use by the U. S. Environmental
Protection Agency.
10.     Small, A.B., J.S. Gidley, and D.A. Riley,
       1997.  "Design and Rehabilitation  of an
       Urban   Gravity  Interceptor  Using
       Pipebursting  in  Norfolk,  Virginia,"
       Trenchless Pipeline  Projects: Practical
       Applications., ed. Lynn E. Osborn, pp. 174-
       182. New York: ASCE.

11.     Washington    Suburban   Sanitary
       Commission,  Laurel,  MD,   1998.  A.
       Fitzsimmons,   Washington   Suburban
       Sanitary   Commission,   personal
       communication with Parsons Engineering
       Science, Inc.

Fairfax County, Virginia
Ifty Khan, Director -Line Maintenance Division
Fairfax County Department of Public Works
6000 Freds Oak Road
Burke, VA 22015

Louisiana Tech University
Raymond L. Sterling, Ph.D., P.E.
Trenchless Technology Center
West Arizona Avenue
P.O. Box 10348
Ruston, LA 71272-0046

Miami-Dade Water and Sewer Department
Luis Aquiar, Assistant Director
4200 Salzedo St.
Coral Gables, FL 33146
         For more information contact:

         Municipal Technology Branch
         U.S. EPA
         Mail Code 4204
         401 M St., S.W.
         Washington, D.C., 20460
          Excellence in compliance through optfmal technical solutions