Design Considerations For Corrosion Protection in Large Diameter by djd18436

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									            North American Society for Trenchless Technology (NASTT)
                                  NO-DIG 2005

                                     Orlando, Florida
                                     April 24-27, 2005




DESIGN CONSIDERATIONS FOR CORROSION PROTECTION IN
LARGE DIAMETER SEWER TUNNEL CONSTRUCTION
David R. Chapman P.E.1, and Glen Frank P.E.2
1
    LACHEL FELICE & Associates Inc., Morristown NJ
2
    LACHEL FELICE & Associates Inc., Columbus OH


ABSTRACT: The phenomenon of corrosion in sanitary and combined sewers has been identified for
some time, but the condition was thought to be specific to warmer climates. Now it is recognized that
designers of sewer systems must consider corrosion when determining the life expectancy of the facility
no matter where the facilities are located. Sanitary sewers will continue to become more corrosive as
inflow and infiltration is reduced, and more combined sewers will develop corrosive conditions as
separation projects are completed.
This paper explores the use of techniques and products during new construction in order to lower the
cost of installing “corrosion proof” sewers. The paper will focus on large diameter sewer construction
appropriate for storage tunnels being planned or constructed to reduce wet weather overflows, but will
address methods appropriate for small diameter installations as well.




1.     INTRODUCTION

Municipal sanitary sewer utilities are facing numerous challenges as they seek to develop new projects to
meet system growth needs and regulatory requirements, while keeping existing facilities operational
through rehabilitation of degraded sections. Older facilities are being pressed to serve much longer than
their designers envisioned. Major rehabilitation costs are being incurred by wastewater utilities in dealing
with corrosion-damaged concrete pipe and structures. Protection of new concrete sanitary sewer
facilities from such corrosion will prolong infrastructure life and reduce future maintenance costs.
Integration of an appropriate corrosion protection (CP) system into the design and construction process
can strongly influence the design concepts, construction methods and installed costs for new sanitary
sewer tunnels. This paper discusses some aspects of the problem and solutions that are being
employed, including attention to the potential for rehabilitation methods to be applied to providing
corrosion protection in new construction involving larger diameter sewers, particularly tunnels. Topics
covered by the paper include:
     • Background – The Corrosion Problem in Sewers
     • Factors Influencing Sewer Design Incorporating CP Systems
     • Previously Used CP Systems
     • Design Criteria for CP Systems
     • Candidate CP Systems for Future Works



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2.    BACKGROUND - THE CORROSION PROBLEM IN SEWERS

Concrete has long been used for sanitary sewer system infrastructure, in the form of concrete pipe for
conveyances cast-in-place structures for junction chambers, manholes, sumps, and treatment basins.
Corrosion of concrete in this aggressive environment has been known for some time, particularly for
manholes and structures at treatment plants. In addition, increased inspection is disclosing that significant
concrete loss has occurred in the pipe conveyance systems themselves. Much effort and expense is
being applied to protect against and remediate corrosion damage.

This problem has traditionally been associated with warmer climates and higher ambient temperatures
thought to better support the microbial growth that gave rise to the particular mechanism of concrete
attack. It may indeed be more severe in such climates. Houston, Texas is known to have great problems
with concrete deterioration in sewers, and the City of Houston has studied many alternatives to provide
protection against such corrosion. The University of Houston has a significant research program under
the Civil Infrastructure System Initiative that is sponsored by the National Science Foundation (University
of Houston, 1997). Large testing chambers allow performance of research on corrosion mechanisms and
helps determine means for preventing or mitigating concrete deterioation . However, corrosion problems
have increasingly been observed and required attention in more northern locations with cooler climates
as well, including in Canada (Joyce, (2001).

Mechanisms for concrete corrosion have been thoroughly documented, and a detailed treatment of this
subject is beyond the scope of this paper. Simply stated, sulfides can be generated in sewers under
certain conditions, namely: low dissolved oxygen content, high strength wastewater, long detention times,
extensive pumping, and high wastewater temperatures. Part of the equilibrium that results in the sewer
environment involves the generation of hydrogen sulfide gas. Bacteria that colonize surfaces above the
water line in sewer pipes and structures can consume hydrogen sulfide and oxidize it to generate sulfuric
acid. This process can result in the cultivation of colonies of bacteria that can live in progressively lower
pH environments. Surfaces of sanitary sewer pipes have been found to exhibit conditions with pH values
as low as 0.5.

The sulfuric acid attacks the cement matrix of the concrete and this attack is not prevented by the use of
sulfate-resisting cement of Type II or Type V. Sewer flows can then remove softened cement, exposing
aggregate particles to removal by sewer flows. This successively exposes new surfaces to attack, and
eventual progression to the steel reinforcement that is also attacked by the acidic environment.

Certain factors may exacerbate the corrosion mechanism in today’s sanitary sewer conveyances. First,
environmental regulations require that industrial generators pre-treat sewage for metals removal. Metals
are toxic to bacteria and it is thought that their removal has allowed bacteria that were previously kept in
check to flourish. Second, regionalization of sewage treatment through closure of older treatment plants
that cannot meet current effluent standards and conveyance of sewage to larger modern treatment plants
significantly increases residence time, contributing to greater sulfide generation. Joyce (1995)


3.    FACTORS INFLUENCING SEWER DESIGN INCORPORATING CP SYSTEMS

The increased understanding of corrosion effects on concrete sewer structures and conveyances is
influencing design for new projects, with the potential need to specify a corrosion protection (CP) system
being addressed for many new projects. Besides variables specific to corrosion potential including the
characteristics of the sewage streams and previous measurements of hydrogen sulfide concentrations in
sewer system components, there are several factors that are important in consideration of sewers to be
installed by tunneling.

Sewer Diameter - Although tunneling technologies exist for installation of both small and large sewer
conveyances, many newer projects involve interceptor sewers to collect flows from trunk sewers and
convey them to regional treatment plants designed to meet present and future treatment standards.



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These are typically larger in diameter and often deeper than typical sewer construction, in order to
provide the required flow capacity and to be at sufficiently low elevation to maximize their potential to
collect flows from other system components. Such sewers are also oversized in some cases to provide
storage capacity for peak flow events to reduce treatment plant wet weather bypass occurrences to meet
regulatory requirements. Diameter is important because some CPL systems are more practical up to
some limiting diameter. For example, a polymeric sheet liner that is attached to precast concrete pipe
during the casting process is practical for application to pipe up to 12 feet or so in diameter, but larger
pipe than that may not be practical because of large load transportation requirements (escort, advance
scheduling with police, etc.)

Tunnel Route Geology – The geology of the area that a sewer tunnel must traverse can influence CP
system selection because of the influence it has over tunnel construction method and feasible lining
system options, which in turn influence feasible CP system alternatives. Sound rock, fairly impermeable
soils that are not too soft, and minimal or controllable levels of groundwater allow tunneling systems that
are more amenable to permitting the widest range of CPL systems. Conversely, soft clays and silts, and
permeable soils with high groundwater tables may require tunneling methods that narrow feasible tunnel
support possibilities and thereby constrain CP system design.

Tunnel Support System – Large sewers in the diameter range of 5 to 10 feet have been installed by
tunneling typically utilizing a “two-pass” support system. During tunneling, initial structural support is
installed to resist the ground loads and to provide for the placement of a final support system which acts
as both the final structural support and the sewage conveyance conduit. One of the most frequently
employed initial support systems is steel ribs and timber lagging, commonly termed “ribs and boards.”
This system employs steel ribs bent to the required diameter in circular arc sections and fitted with flange
plates. These are assembled within the tail shield of a tunnel boring machine (TBM), timber lagging is
then placed to span between the flanges of adjacent ribs, and the TBM advances by pushing off the
completed rib. Lagging can be partial or complete depending on the soil or rock conditions and level of
support required. When tunneling of a section of tunnel is complete, final support in the form of concrete
pipe can be installed by casting in place, or by installing precast pipe sections within the initial ribs and
board structure and grouting the annular space. This support system is shown in Figure 1. Precast
concrete pipe is very amenable to provision of a CP system by casting an anchored polymeric sheet liner
onto the inside surface of the pipe at the precast plant.




Figure 1 – Steel Ribs and Timber Lagging Support System.

For finished tunnel diameters larger than 9 to 10 feet, more complex tunnel support technology may be
warrented or required. Particularly if these larger tunnels are required in locations with less favorable
geological conditions involving less stable soils and high groundwater levels. Tunnel boring machines
involving EPB (earth pressure balance) or slurry pressure balance technology are capable of balancing



                                             Paper A-3-02 - 3
earth and groundwater pressures at the tunnel face, permitting tunneling below the groundwater table. It
may be necessary in this case to install a “one-pass” support system, in which the permanent structural
support is installed by the tunnel boring machine. This type of tunneling frequently involves the use of a
precast concrete segmental system, whereby five or more segments comprise a ring. Once the ring is
installed it acts to supports a four to five foot section of the tunnel. These segments are cast in precision
molds, installed with gasket systems to render them effectively water-tight, assembled into rings within the
tail shield of the TBM, and bolted and/or dowelled together. The TBM advances by shoving against the
previously installed ring. Figure 2 shows precast concrete segments individually and assembled into a
completed ring. This lining system presents much more of a challenge to CP system design as will be
discussed further below.




Figure 2 – Individual Precast Concrete Segments and Assembled Rings.


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Hydrostatic Pressure – A CP system for larger tunnels is typically a liner, which implies an interface (or
more than one) between the liner or liner components and the structural liner or sewer conveyance. For
sewers located below the groundwater table, the consideration of hydrostatic pressure forces is essential,
and it is typically assumed that these forces must also be resisted by any lining system that is employed.
This can result in significant cost differences. For example, one rehabilitation system that has been used
involves placing an anchored polymeric membrane liner over a form, leaving a small space between the
liner and the concrete. The space is then filled with grout material to bond to the concrete and in which to
embed the anchors of the polymeric liner, as shown in Figure 3. If hydrostatic pressure is involved, both
the anchor pullout resistance and the ring of grout created must be capable of resisting pressure forces.
It must be decided to what extent cracking of the grout could occur, and what thickness of grout is
required to provide sufficient ring thickness to resist the applied pressure forces. This CP liner system will
be less attractive from a cost standpoint with a greater grout thickness, both because of its cost and
because of the greater loss of existing flow area.




Figure 3 – Grouted-In Polymeric Membrane Liner.

The Water Research Centre in Swindon, England performed intensive research on sewer rehabilitation
and published the Sewerage Rehabilitation Design Manual. (Water Research Centre, 2001) This outlines
various design criteria depending on the type of rehabilitation being performed and the external loading
system. Type 1 designs consider vertical loadings from overlying ground and embankments as well as
road loadings. Type 2 designs consider only hydraulic loadings from external groundwater pressures.
Type 3 designs consider no external loadings and provide only corrosion protection. It appears that many
design situations would require Type 1 and Type 2 loadings to be considered, termed by the manual as a
Type 2 design with a Type 1 check.

Cost – Cost is one of the most important considerations in CPL system selection and design. The owner
must decide how much of a premium will be paid for corrosion protection, and must also consider the
consequences of that decision relative to operations and maintenance requirements for the sewer. Los
Angeles County in California takes a very conservative line on this, and have recently installed several
large sewers which were constructed by placing an oversized precast concrete segmental tunnel support
(one-pass) system followed by placement of the final conveyance consisting of precast concrete pipe
sections lined with Ameron’s T-Lock PVC material, grouted inside the segmental liner. (Redner, 2003)
This is based on experience gained with severe corrosion of existing sewers and having incurred major
expenditures for their rehabilitation. Other municipal utilities will be reluctant to incur the premium
associated with this type of construction, which is approximately double the cost of installing a precast
concrete segmental lining system of the required diameter. For conveyances larger than 12 feet in



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diameter the difficulties associated with precast pipe transport render this type of construction even more
unattractive.

Other CP systems can range in initial installed cost from 20 to 100 percent or more of basic tunnel cost.
(Chapman, 2002)


4.    PREVIOUSLY USED CP SYSTEMS

A fairly limited range of CP systems has been employed to date for new sewer construction, and as
described above, the need to install a sewer by tunneling methods may further restrict the options. Some
smaller diameter sewers have historically been constructed using vitrified clay pipe, which had a high
resistance to corrosion, but being unreinforced, had practical diameter limitations. Some larger, older
sewers were lined with corrosion resistant tiles or brick, but had to be installed with mortar systems which
was not corrosion resistant and which ultimately failed.

Coatings - One class of CP system for which there is a lot of evaluation and performance data and which
is primarily used for rehabilitation, are coatings. They have less frequently been utilized in new
construction since their expected life is often short and the cost of reaplication high.

Glass Fiber Reinforced Polymer Pipe - Pipe constructed from polymers and reinforced with glass fibers
has been developed and used very successfully for sewer pipe conveyances, manholes, etc. in diameters
up to about 10 feet. These pipes are significantly lighter than concrete pipe of the same diameter, and
may be more costly, but provide a corrosion resistant system. Larger diameter molds are being
developed by manufacturers, but economical transport considerations dictate a practical limit to the
possible diameter increase that is achievable.

Polymer Concrete – Polymer concrete is already in use to make sewer pipe that is resistant to corrosion,
particularly in the small to medium size range. It typically has a high compressive strength by virtue of the
resins used, and is unreinforced. Work is underway to potentially apply polymer concrete to the
manufacture of precast concrete segments, which are typically reinforced. The cost is higher than that of
concrete pipe, but manufacturers claim that depending on the specific project details, its cost may
compare favorably with that of other CP systems.

Anchored Polymeric Sheet Liners - Polymeric sheet liner systems with integral profile anchors on one
side have been cast onto the face of precast concrete elements, most notably precast concrete pipe. The
best known, with a 50-plus year performance record is the polyvinyl chloride (PVC) material T-Lock by
Ameron, with linear T-shaped anchorage protrusions on one side. It has been widely used on precast
sewer pipe for direct burial and placement by tunneling. There are a number of competitive systems that
utilize high density or linear low density polyethylene (HDPE, LLDPE), and that have either linear T-
shaped anchorage systems similar to T-Lock or that have cone-shaped, X-shaped, or other integral point-
anchorage devices in a grid pattern on one side. These materials are also used successfully in applying
corrosion protection to rectangular basins used in sewage treatment and other types of industrial
processes. Peggs and Hammer, (1999). The record of successfully casting these materials in place as a
tunnel lining is much more limited. Some problems with this have been recorded, and the ease of
installing polymer sheet lined pipe seems to have eclipsed the use of cast-in-place concrete linings when
CP systems are specified.

These materials have not been installed on precast concrete segments, but to do so is certainly feasible.

Mechanically-Anchored Polymeric Liners - Corrosion resistance of polymeric sheet liners is well
established and so a variety of systems for applying them has been considered and attempted over the
years. Application of a HDPE liner in tunnels for corrosion protection was done on a large scale in the
Northside Sewer Relief Tunnel in Houston, Texas, using stainless steel batten strips (longitudinal and
circumferential) held in place by anchors drilled into the concrete. This has been termed as a
mechanically-anchored liner. The design was faulty, and several large sections of the liner failed less


                                             Paper A-3-02 - 6
than three years after commissioning of the system during several intense rainstorms. Ultimately, the
entire liner was removed from the tunnel, and the City of Houston embarked on an extensive study of
rehabilitation methods for the tunnel, some aspects of which will be discussed below.

King County Wastewater Treatment Division (Seattle area, Washington) installed three sections of sewer
with mechanically attached liners, the oldest having been installed in the early 1990’s. All three either
have been replaced or are scheduled for replacement. Being familiar with the failure of a similar system in
Houston, they increased the number of longitudinal battens to reduce the spacing between them. Their
experience has been that this lining system does not prevent corrosive gases from contact with the
concrete and concrete deterioration has progressed anyway. They have not had any catastrophic failures,
and the liners have stayed attached. By means of an active inspection program, they have observed
progressive loss of concrete at the anchor locations, which would eventually permit a catastrophic failure
and have proceeded with removal of these liners. Browne (2001).

Some sections of the Onion Creek Interceptor in Austin, Texas were lined with a mechanically anchored
HDPE lining system, installed by the manufacturer as a subcontractor to the tunnel contractor, in the mid-
1980’s. This 10-foot diameter tunnel was lined for 270o of its circumference; with HDPE liner anchored
using a batten strip at the tunnel crown and a batten strip at each lower edge of the liner. Twenty-foot
sections of liner were installed, with an overlap at the joints, where circumferential battens were installed.
Although the liner was still in place in 2001 and there had been no dramatic failures (Vallejo (2001)),
indications of developing problems led to inspection which disclosed problems and the liner has since
been removed.

It seems doubtful that this system will see further use, considering the design pitfalls, the need to provide
relief for hydrostatic pressure coming from outside the sewer, the ventilation of air which will be forced out
by water filling the tunnel during high flow events, and the potential for corrosion of the concrete around
the anchors that will likely lead to eventual liner failure.

“Chemically Attached” CP System – An evaluation of lining technologies for rehabilitation and
corrosion protection was developed by Joyce, 1998. Several categories of systems were described, one
of which was termed “chemically attached.” One of these, a system termed a “co-lining” system by its
manufacturer, Linabond, was evaluated for the Big Walnut Augmentation/Rickenbacker Interceptor Sewer
Project in Columbus, Ohio. (Chapman, 2002). It was ultimately selected and specified for the project,
although its application has not yet begun. This system includes a hydrophyllic primer, a spray-on
structural polymer (polyurethane), to which is attached a specially treated PVC liner sheet that will cross-
polymerize and strongly bond to the structural polymer. It is applied in circumferential strips four feet in
width with joints welded by a higher strength polymer. It had previously been used primarily in sewer pipe
rehabilitation and in lining of wastewater treatment plant structures.


5.    DESIGN CRITERIA FOR CP SYSTEMS

The trend described above toward larger diameter sewers, and the development of the one-pass tunnel
support system using precast concrete segments present some additional CP system design challenges.
In considering CP design for a precast concrete segmental tunnel support system, one obvious candidate
was an anchored polymeric sheet liner attached to the segments in the casting process. The precast
concrete segmental tunnel support is placed as the tunnel is mined. Thus, would be in the tunnel
throughout construction subject to various forms of damage, complicating normal placement of concrete
anchors for placement of utilities in the tunnel, and presenting a very smooth surface and thereby
increasing slipping hazards. The other negative feature of such a system is the great amount of welding
required to apply joint strips at circumferential joints (welding both sides of joint required), longitudinal
joints, and all penetrations for lifting inserts, grout holes, etc. Figure 4 shows a closeup of various types
of anchors for these materials and Figure 5 shows a section view of the required weld joint. These factors
indicate that it would be an advantage if a CP system could be devised that consisted of a lining installed



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after the tunnel mining was complete. Consideration of CP systems typically applied for rehabilitation
could potentially identify systems that would be suitable for application in new construction.




Figure 4 – Closeup of Anchors for Various Polymeric Membrane Liners.




Figure 5 – Joint Detail for Anchored Polymeric Sheet Liner On One-Pass Tunnel Support Segments.


City of Houston Rehabilitation Study - Specific design criteria for a CP system for any project must be
developed by the project designers, but various studies and design efforts offer some useful models for
consideration. Following the failure of the mechanically anchored polymeric liner failure in Houston
described above, the City of Houston Department of Public Works and Engineering – Greater Houston
Wastewater Program undertook a study to determine the best methods for rehabilitation of the sewer. A
comprehensive evaluation of the technical issues and economics associated with rehabilitation of the
deteriorated sewer was performed by a team consisting of utility and consulting personnel, and a final
report, “Evaluation of Alternative Cleaning and Rehabilitation Methods for the Northside Sewer Relief
Tunnel,” was issued in October, 1995. City of Houston (1995) This report provides significant useful
material for CP system design because a large number of rehabilitation methods were screened in the
Houston study, some of which were applicable to new construction.



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The rehabilitation study identified 27 possible systems for rehabilitating the sewer tunnel, which can be
grouped into coatings, liners, and slipliners. Of the 27 products, 14 coatings, 8 liners, and 5 slipliners
were identified from extensive product surveys. The 27 methods were then evaluated by a set of
minimum qualifying criteria that were developed based on the physical conditions existing in the NRST.
These criteria were:
− Resistant to corrosion with pH ≥ 0.5 and H2S concentration ≤ 200 ppm
− Can be applied at 100% relative humidity
− Ability to withstand 210 kPa (30 psi) hydrostatic head
− Construction method allows evacuation of the tunnel within a 2-hour time period in response to a wet
   weather warning
− Cure time < 6 hours
− Suitable for rehabilitation of pipe diameters in the range of 1.8 to 3.66m (72” to 144”)
− Has a history of successful application under conditions similar to those existing in the Northside
   Sewer Relief Tunnel.

Screening of the 27 potential methods according to the above criteria resulted in elimination of 12
methods, with 15 methods remaining for final ranking and consideration. Included were 6 coating
systems, 6 liner systems and 3 sliplining systems. Of these methods, coatings were considered the least
desirable based on permanence (unknown design life and higher frequency of failure) and experience
(less than 10 years). Liner systems were ranked second most desirable, with greater permanence
(estimated at 25 to 50 years design life and moderate ease of repair) than coatings. They also exhibit
longer experience records, have been more frequently installed than coatings, and were rated best in
constructibility. Slipliner systems were ranked most desirable because of greatest permanence (study
stated 50 year design life), greatest experience in terms of years and quanitity of materials installed. They
were rated least constructible because of shape conformance problems, loss of flow capacity, need for
jacking pits, etc.

Costs were estimated for each system, and a ranking based on cost and risk again separated the
methods based on a combined evaluation into the following categories:
− Low Cost/Low Risk – This category included some of the liner systems.
− High Cost/Low Risk – This category included slip liner systems.
− Medium Cost/Medium Risk – This category included liner systems that had higher costs and less
  performance history than the Low Cost/Low Risk category.
− High Cost/High Risk – This category included coating systems. The coatings were in the high cost
  category because the analysis was a present worth analysis that included replacement provisions for
  the coatings given the uncertainties regarding their service life.

Systems recommended for potential application included two Low Cost/Low Risk liner systems and two
slip lining systems for cases where slip lining would be more suitable. It was also recommended that the
two lowest-risk coating systems be tested in a demonstration project in an accessible location where
routine inspection can be performed to document performance. If the coatings perform better than
expected, this could improve the risk rating and potentially reduce the present worth cost.

Slipliners may have more potential for new construction application than they were considered to have in
the Houston study because shape conformance may be less of a concern. However, in the larger
diameters of interest for many new tunnels, multiple pieces are likely to be required to form a ring,
necessitating extensive field jointing and such a built-up section must be analyzed to ensure desired
performance. They are also likely to have relatively high costs compared to other potential systems.

Singapore Deep Tunnel Sewer System – The government of Singapore has adopted an ambitious
deep tunnel sewerage system (DTSS), which will be developed over the years ahead, with tunnels in soft
ground and hard rock. The total planned length is 48 km (29.8 mi) of tunnel ranging in diameter from 3.3
to 6.0m (10.8 to 19.7 ft). The first phase of the work will involve six major contracts to be executed using


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a design-build approach, the basic design having been performed by a joint venture of CH2M Hill and
Parsons Brinckerhoff.

The specified design life of the facility is 100 years and to satisfy that requirement considering the high
temperatures and humidity presented by Singapore’s climate, a thick composite tunnel lining was
specified. The primary tunnel support is a precast concrete segmental lining, inside which a dual CP
system consisting of a PVC or HDPE anchored liner cast into a minimum 22.9 cm (9”) thickness of
unreinforced cast-in-place concrete to be installed, over 330 to 350o of the circumference. The designers
of the design-build teams will perform the detailed design of this system. Singapore (undated)

The General Conditions section of the Instructions to Design-Build Contractors were reviewed and some
of the key requirements are listed below: Singapore (undated)
− No chemical dosing is permitted for corrosion protection
− H2S concentration ≥100 ppm
− Very limited capability for future inspections and maintenance
− Design for full hydrostatic pressure, “applied as point sources at various points around the CPL.”
− The bottom ends of the lining must be secured
− All manufacturers’ recommendations to be met
− Use of trained personnel required with material supplier representative on-site
− Liner anchor to withstand a test pull of 19.6 kN/m (1340 lb/ft) at the liner crown perpendicular to the
    concrete surface for one minute without rupture or pullout of liner anchors
− Color choice to facilitate future video inspection (light color)
− Stationing marks to be applied
− Full welded joints between sections and of joints at intersecting structures
− Same lining system applies to shafts and other structures
− A 10m (33 ft) long test section is required prior to production installation.
− Implement an inspection and test plan to address integrity of joints, anchorage of liner, voids, and
    tolerances. Necessary elements include drilling of a grout hole every 5m (16.4 ft) for contact grouting
    (between precast segments and cast-in-place concrete liner) and probe holes to determine CPL
    system thickness.

This is a rigorous specification for a severe design condition and ambitious design life. A full dual CP
system is to be provided (i.e., the polymeric liner and the sacrificial concrete). It should be noted that the
application of liner materials with integral anchors to cast-in-place concrete is not a simple task, and that
the greatest success with these materials in the past has been when they were applied to precast
concrete pipe in the casting yard. When applied to precast pipe, the forms are vertical and vibration can
be properly performed to ensure flow of concrete and encapsulation of the anchor elements. This is
much more of a challenge in a cast-in-place system inside of a tunnel where the liner material must be
secured to a form in a confined annular space and access for vibration is much more difficult.

These examples offer a reasonable checklist of factors to be considered in CP system design for large
sewer pipes and sewer tunnels.


6.    CANDIDATE CP SYSTEMS

Provision of CP systems for larger diameter sewers is a dynamic issue, one that is already attracting
significant attention and one that will attract more as additional owners are faced with decisions to provide
CP systems for new sewer pipes and tunnels. Besides the systems described herein, there are additional
systems that warrant consideration for designers faced with the need to provide CP systems.

Segments Faced with Corrosion Resistant Material– As described above and as is common for
precast concrete pipe, segments can also be faced with corrosion resistant materials such as polyvinyl



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chloride (PVC) or high density or linear low density polyethylene (HDPE, LLDPE). This produces many
joints requiring welding, as discussed above.

Bernold Ceresola, an Italian company that specializes in equipment and services to the tunneling
industry, together with Herrenknecht AG, Microtunneling Division, has developed a patented process for
applying an integrated glass fiber-reinforced “inliner” to precast concrete segments that extends into the
segment joint, eliminating the need for welding identified for other liners that could be cast onto segment
faces. This was introduced at the BAUMA 2004 trade fair in Munich, Germany. This is a very promising
development, currently described as available in diameters ranging from 2.0 to 3.5 meters (6.6 to 11.5 ft).

Construction Polymers of Chagrin Falls, Ohio has developed another lining system to be cast onto
segment faces, utilizing a non-woven geotextile fabric bonded to the back of Seaman Corporations XR-5
polymeric membrane liner. Cut pieces are placed in segment molds and when the concrete is poured,
the cement paste penetrates the geotextile layer, bonding the composite liner system to the concrete.
This system has not been applied on a project yet, but it was applied to a full-scale mockup liner and the
system developers report favorable testing results. Developers are also considering enhancements
including how welding requirements may be simplified and a means of provision of inserts planned for
use in hanging utility systems, etc. on tunnel walls during construction. (Peterka, 2004)

Glass Fiber Reinforced Panels – Various manufacturers have developed systems involving different
forms of glass fiber reinforced panels which can be manufactured to fit custom shapes, providing good
qualifications for rehabilitation projects. These shapes can be designed and fabricated to resist the
necessary loadings, greater loadings requiring greater thicknesses and or additional reinforcing and
therefore higher costs. These shapes are then transported in the sewer or tunnel environment and joints
are made using an appropriate welding technology. Available shapes range from rectangular panels cast
such that an upper and lower panel form a circular section to custom shapes that can be fabricated to fit
non-standard cross sections. Such systems would certainly be suitable for new construction, and may
offer advantages relative to installation time compared to competing systems. Costs will be relatively
high, but performance characteristics appear to be excellent. Several case histories for such systems are
documented in the North American No-Dig 2004 proceedings.

Polymer Concrete – Various manufacturers are working on provision of structural shapes suitable for
tunnel lining projects. Polymer concrete systems that are compatible with placement of steel reinforcing
and other metallic inserts are expected to be more successful than those for which kiln curing is required
and which intend to depend entirely on high compressive and tensile strength. Handling loads and other
potential loading conditions typically require steel reinforcing in precast concrete segments. At this time,
polymer concrete costs are sufficiently high that this system could be competitive only with a concrete
tunnel support system with a significant CP system.

Concrete Admixtures – A new biotech material Conshield, has been developed and is undergoing
testing in some markets, which when used as a concrete admixture is claimed to make the concrete
surface unreceptive for bacteria colonization. According to the manufacturer the product has no adverse
affect on the concrete strength and workability but combines with the molecules of the cement paste to
become a permanent part of the concrete matrix.
If bacteria will not grow on the concrete containing this admixture, then the generation of sulfuric acid will
not occur and there is no need for a corrosion proof liner. This would prove to be a very elegant solution
to the concrete corrosion problem in new sewer construction. Careful investigation of such a material
would be required before relying on it as a CP system for any major underground work.

The other systems described in this paper and references such as the Houston study and in the Los
Angeles County evaluation (Redner et al, 2002) also have potential for use in provision of CPL systems
for sewer pipes and tunnels. Numerous opportunities exist for manufacturers and specialty contractors to
develop CPL systems for application in both rehabilitation and new construction.




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7.       RECOMENDATIONS

There is a lack of unbiased information currently available, making it extremely difficult to specify CP
systems that don’t have a long track record. The Los Angeles and Houston studies provide important
information on candidate systems, but only cover the products that were on the market at the time of the
study. There is a significant need for an ongoing “benchmarking” system to provide an independent
evaluation of new products entering the market in this field, or at least for owners to document and share
their experience with such products. Such information sharing would provide owners and design
engineers with the necessary performance data to permit incorporation of new technologies and new
products into system design.

The following recommendations should aid designers in formulating plans to evaluate and include CP
systems in sewer designs where required:

     •    Determine service conditions and assess if corrosion is likely to be a problem
     •    Consider structural design, construction sequence, means and methods, operations and
          maintenance considerations and life cycle costs.
     •    Perform life cycle cost analysis considering actual application costs, crew, equipment, etc for the
          specific sewer project. Provide additional applications at likely intervals and include inspection
          and surface preparation costs as well as shutdown and bypass operation costs in the economic
          analysis.
     •    Where possible, design in flexibility to divert or bypass flow in parallel systems and provide
          shutoff gates, stop logs, etc. to permit future access for inspection and maintenance.
     •    Attend industry conferences and trade shows and communicate desirable design characteristics
          to manufacturers and specialty contractors to facilitate communication and encourage
          development of systems providing desirable characteristics.
     •    Document testing of candidate CP systems in technical papers and conference presentations and
          share experiences by means of work groups, online forums, etc.


8.       REFERENCES

Browne, Roger. 2001. Personal communication – Civil Engineering Supervisor – King County Wastewater
Treatment Division Seattle, Washington.

Chapman, David R. 2002. Selection and Design of Corrosion Protection Liner for Precast Concrete
Segment Tunnel Liner. Proceedings, North American Tunneling Conference 2002, May, 2002, Seattle,
Washington.

City of Houston, Texas. 1995. Final Report – Evaluation of Alternative Cleaning and Rehabilitation
Methods for the Northside Sewer Relief Tunnel. Study Report for Greater Houston Wastewater Program,
October 1995. Houston, Texas.

U.S. Government. Federal Specification TT-P-1411A, Paint, Copolymer Resin, Cementitious (for
Waterproofing Concrete and Masonry Walls. 1973 and 1977 amendment. June 28, 1977.

Joyce, James, 1995. Odor and Corrosion Control in Collection Systems: A Growing Problem?
Proceedings, Water Environment Federation Specialty Conference entitled, “Sewers of the Future,”
September 1995, Houston, Texas.

Joyce, James, 1998. An Evaluation of Lining Technologies for Corrosion Protection and Rehabilitation of
Large Diameter Sewer Tunnels and Interceptors. Water Environment Federation WEFTech Asia
Conference. March 1998. Singapore.

Joyce, James, 2001. Personal communication.


                                             Paper A-3-02 - 12
Peggs, I.D. and Hammer, H.I., 1999. Cast-in Liners Gain Foothold. Geotechnical Fabrics Report, Vol. 17,
No. 5, July, 1999, p 24-30. Roseville, Minnesota.

Peterka, Andrew, 2004. Personal communication.

Public Works. 1998. Lining System Does the Job. Public Works, Vol 129, No. 2, February 1998, pp 46-48.
Redner, John, 2003. Personal communication – Sewerage Departmental Engineer, County Sanitation
Districts of Los Angeles County.

Redner, John et al. 2002. Evaluation of Protective Coatings for Concrete, Presented at the Water
Environment Federation’s National Conference. Updates presentations made at several conferences
1986-1991. Based on Internal Report, County Sanitation Districts of Los Angeles, 1986.

Singapore Wastewater Utility, undated. Design and Construction of Sewer Tunnels for the Deep Tunnel
Sewerage System – Contract T-04 and Mo Kio Tunnel – Instructions to Design-Build Contractors.

University of Houston. 1997. University of Houston Environmental Engineer Searches for Solution to
Wastewater        Pipe      Corrosion.       Press       Release.     August      15,        1997.
http://www.uh.edu/admin/media/nr/archives97/0897/roberts.html

Vallejo, Yvonne, 2001. Personal communication – Engineering Associate – Austin Water and Wastewater
Utility. Austin, Texas.

Water Research Centre. 2001. Sewerage Rehabilitation Manual – 4th ed.. Water Research Centre.
Swindon, England.




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