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بسى الله انرحًٍ انرحيى

(شثكاخ الصرف الصحي تأهيل أعادجو الفحوصاخ )تقنياخ

Rehabilitation Technologies of Sewers -3rd

Class Dr. Sataa A. Al-Bayati(09-10)

Dictionary:

Deterioration =تهف, trenchless = وٌ حفربد , integrity = سلايت, defects = عيىب,

variety = تُىع, replacement =أستبدال, constraints =يحدداث, disruption = عرقهت,

reinstatement = أرجاع, , conjunction = أرتباط, Spot Repair =تصهيح يحدود ,

blockages = أَسداد, liner = بطاَت , Resin = راتُج, grouting = تحشيت ,

cost-effective = أقتصادي, installation =أَشاء , option =أختيار , fabric =انياف

overflow = طفح أو فيض انشبكت

Infiltration/inflow = I/I

Inspection = test

high-density polyethylene = HDPE

Polyvinyl chloride = PVC

Titles: process, materials, conditions, uses, limitations, advantages,

disadvantages, & actual applications

All actual applications in this literature are in USA.

Introduction:

The need for collection system rehabilitation arises from several factors:

1. Deterioration of structural integrity of the aging)قدو( sewer systems,

2. Excessive infiltration/inflow(I/I) due to defects in the system, and

3. Additional hydraulic capacity needs for the sewer system.

Trenchless pipe rehabilitation techniques may offer a variety of advantages

over traditional open-cut pipeline replacement techniques, such as:

1. More cost-effective than open cut

2. Avoidance of many surface constraints

3. Disruption of other services minimized (e.g., power lines)

4. Surface reinstatement needs minimized

5. Surface disruption including traffic disruption kept to a minimum

6. Reduced surface settlement, particularly important in sensitive areas,

such as under railways, motor ways, services and adjacent to buildings

7. Environmental disturbance minimized e.g. dust, noise, & sewer

blockage.

8. Installation of services at greater depths than would normally be

considered cost effective for trenching.

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Rehabilitation Technologiesتقنياخ أعادج التأهيل

1. Pipes (Sewer Mains)

2. Manholes

3. Pipes (Lateral Sewers)

4. Spot Repair

1. Pipes (Sewer Mains)

1.1 Open Cut)المفتوح(:

Open cut has been the traditional method of installing lines.

Material:

Any type

Advantages:

It does not need sophisticated يعقدّة() equipment and extra skilled personnel.

There is opportunity to inspect the pipe fully and ensure it is constructed

according to the specifications.

It is cost-effective option under certain conditions. For example: when the

depth of installation is shallow, the soils are stable, and no ground water is

present.

Disadvantages:

Surface disruption and traffic impact.

Costly for deep sewer

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1.2 Cured-In-Place Pipe, CIPP)أنثوب السقي الموقعي(:

Types of cracks:

Structural cracks: e.g. along the pipe

Nonstructural cracks: hair cracks

CIPP is a fabric liner saturated with a liquid resin is placed inside the

existing sewer main, inflated ينُف(() , and then cured. The technology is used

to provide a lining inside a host يفّ(يضن) pipe to prevent infiltration through

defects in the pipe, or it may be used to form a structurally sound new pipe.

The process may be used on an entire segment جنءء() of sewer main between

manholes.

The design condition is for fully or partially deteriorated pipe.

Process: Pipes must be thoroughly cleaned and dried.

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A CCTV camera is run through the pipe to ensure the pipe wall is clean and

ready for installation of the liner.

The liner is pulled in (usually with a cable) or inverted in the host pipe.

Cure method is usually by steam, hot water, ultraviolet light, or ambient air.

A CCTV camera should be run through the pipe to inspect the condition of

the liner and open the lateral connections by a robotic machine.

Material:

Resin types are epoxy, vinylester, or polyurethane.

Fabric types are polyester felt or fiberglass.

Advantages:

1. The liner will slightly reduce the inside diameter of the pipe, however,

this reduction may be offset by the smoother surface of the material.

2. CIPP liners can be used both for structural and semi-structural

rehabilitation of sewer lines.

Disadvantages:

Costly

Actual application: In 1999, The City of Boca Raton, FL 14000 ft force main was failing in

many areas due to sulfide attack at the pipe crown and was rehabilitated by

CIPP. The contract was awarded for this work at $985,000. The estimate for

doing this work using traditional open cut methods was $2,000,000.

1.3 Pipe Bursting)تفجير الانثوب( :

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Pipe bursting is used to replace an entire segment of sewer main between

manholes.

Process:

- A CCTV inspection must be performed on the pipeline before starting

the process of bursting the pipe.

- Replacing an existing pipe by pulling in a new high-density

polyethylene (HDPE) pipe and simultaneously bursting the old pipe

into fragments with a steel- bursting head.

- The broken pipe fragments remain in place in the surrounding soil.

Existing Pipe Materials can be bursted: Vitrified clay pipe, asbestos cement pipe, reinforced and unreinforced

concrete pipe, and cast iron pipe.

Advantages: 1. Increase the capacity of pipes.

2. Replace corroded and leaking sewer pipes.

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3. Solve structural problems and extensive root intrusion.

4. Without extensive excavation and all the other costs of surface

restoration.

5. Because it's trenchless, pipe bursting is the preferred method for

replacing old pipes in urban areas where disruption to surrounding

utilities, local residences, businesses and the environment are a

consideration.

6. While the range of pipe size and length is constantly increasing, pipe

rehabilitation projects have involved pipe diameters of 3" to as much

as 30" and straight pulls of HDPE pipe as long as 1500 ft.

7. Because of its flexibility HDPE pipe will be able to replace some

elbow fittings on both vertical and horizontal bends.

8. The technology has now developed to the point of handling even three

and four diameter increases 8-in to 16-in.

Disadvantages:

Costly

Actual application: In 1999, pipe bursting is used at West Valley Sanitation District, Santa Clara

County, CA. Replacement of 38,000 ft of collection system was done.

1.4 Sliplining)التثطين الانزلاقي( :

It is used to line an entire length of sewer main between manholes, although

it can be used in shorter portions of the sewer main.

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Process:

1. The existing line must be cleaned.

2. A CCTV inspection must be performed.

3. At an access pit location, a winch cable is inserted يندخّم() through the

existing line and then attached to the front of the new liner.

4. The new liner pipe is then pulled into the existing pipe, and the new

liner pipe reconnected to the system. If needed, the void between the

new and old pipes can be filled by grouting.

5. The pipe is typically grouted at the ends.

Condition:

New line has the largest possible diameter that can fit inside existing pipe.

Material:

It is HDPE, fiberglass, PVC or polymer concrete, although some other

materials may be used.

: Advantages

Sliplining can be used on most types of pipe.

The inserted pipe is not deformed or cured.

It is rapid and causes little disturbance to other utilities.

It is a fully structural solution.

It improves hydraulic performance because of an improved friction

coefficient

It can be installed in live lines without bypass pumping.

: Disadvantages When the new pipe is pulled into an existing pipe, there is a reduction

in the inside diameter which means a loss of capacity.

Sliplining requires a long area of space for assembly.

Poorly applied grouting can lead to buckling.

It does not work well in pipelines with a lot of elbows.

Many excavations are required if there are too many service and

branch reconnections involved.

Actual application:

Location: St. Thomas, U.S. Virgins Islands (1999).

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Characteristics: A 24-in force main conveyed wastewater from a wastewater

pumping station with an average daily flow of 2.2 mgd. The force main was

3560 ft long and was made of ductile iron.

Problem: Overflows were occurring at the top of a hill, when the pumping

station was operating with more than one pump. The overflows were caused

by corrosion of the force main and hydraulic inefficiencies. The pump

station could not be put out of service for more than eight hours.

Solution: Sliplining with HDPE was used.

1.5 Chemical Grouting)التحشيح الكيمياويح( :

Chemical grouting of sewer mains is a process where acrylamide grout is

pressure-injected into a crack, joint, or lateral connection in a sewer main. A

remotely operated grout packer جهنناا انتحشننيت() delivers the grout to the

selected location. The grout packer uses air to inflate bladders at each end of

the plug. The grout is then injected under pressure into the annular space

between the plug and the sewer main, and then migrates into the cracks and

open joints. The flexible and non-cohesive grout remaining on the pipe wall

when the grout packer is removed is pulled out, leaving grout in the joint

spaces of the pipe.

1.6 Spiral Wound Pipe)أنثوب الجرح الحلزوني(:

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Spiral wound pipe is a type of pipe used to slipline an existing pipe.

Process:

Bypassing of flow, if necessary.

Cleaning of the line.

Plugging of laterals.

Lowering the winding machine into the manhole and feeding it with PVC

strips from the surface.

Spiral wound pipe is formed by spirally winding a continuous strip into a

pipe.

Grouting of the liner.

Reinstatement of laterals by local excavation or by a remote-controlled

cutter.

The strips are typically 2 to 6-in (50-150mm) wide and have a locking

mechanism such that the strips “lock” into adjacent portions of the strip.

Conditions:

Applicable to sewer lines smaller than 30-in in diameter.

Material:

PVC, HDPE, or steel.

Advantages:

It increases the hydraulic capacity. Although the cross-sectional area

decreases slightly, the relatively smooth surface of PVC liner reduces the

friction to flow and more than offsets the effect of diameter reduction.

Actual application: In 2000, the City of Santa Monica utilized spirally wound pipe for

rehabilitation of 110000 ft of sewer lines. This was part of a five year

comprehensive program that the City of Santa Monica embarked on to

rehabilitate the sewer lines which had been damaged during the Northridge

earthquake.

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1.7 Fold and Formed PVC)طي وتشكيل الانثوب( :

Fold and formed PVC is a method for installing a new PVC pipe inside the

entire segment of sewer main between manholes, and expanding it through

pressure, heat or mechanical means to restore its original circular shape.

Process:

1. The new PVC pipe is heated and then folded into a smaller diameter

at the factory.

2. The old pipe must be brushed or scraped and cleaned of all debris and

build-up.

3. The PVC pipe is pulled into the sewer main.

4. The PVC pipe is heated and pressurized to unfold and form to the

shape of the host pipe.

5. The PVC pipe is then cooled to form a rigid pipe inside the host pipe.

6. Laterals are reinstated by robotic machines.

Material:

PVC, or HDPE.

Conditions:

It was not used on line segments which had broken or collapsed section.

Advantages:

The “folding” allows easy installation of the liner throughout the length of

the pipe.

Disadvantages:

It is limited to smaller diameters (up to 15 in).

It does not negotiate يتقبمّ() bends as well.

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Actual application:

In 1999, Miami-Dade Water and Sewer Authority, FL, utilized fold and

form liners to rehabilitate approximately 10% of the sewer lines which had

been identified to be in need of rehabilitation.

1.8 Segmental Lining)الثطانح المقطّعح(

This technique is based on forming a pipe in-situ by using PVC-ribbed

panels قطع() with interlocking edges.

Process:

1. The panels are placed inside the sewer line and locked together on the

edges to form a continuous liner.

2. The PVC panels incorporate male and corresponding female double

locking edges.

3. The edges form a circumferential joint, which is simply snapped

together by a smaller joiner strip.

4. The joiner strip utilizes a flexible polymer co-extrusion to make the

joints water tight.

Conditions: Used for man-entry sewers ( ≥ 30-in in diameter)

Material: PVC

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Advantages: The panels and joiner strip are light and easily handled and can be passed

through a narrow opening or manhole eliminating any need for excavation.

Actual application:

The Hampton Road Sanitation District in Hampton, VA used this method for

rehabilitation of approximately 2000 ft of a 42-in reinforced concrete pipe

which had been severely damaged due to hydrogen sulfide crown corrosion.

2. Manholes It is estimated that there are now over 20 million manholes in municipal

wastewater systems throughout the USA. These manholes are sources of

costly inflow and infiltration. This is due to:

1. Late stages of design life.

2. Poor construction.

3. Inflow into a manhole originates from the cover, frame or frame seal.

4. Infiltration occurs due to cracked, loose or missing mortar or at joints

between precast sections and pipe joints.

Fig. Manhole details

2.1 Open Cut Replacement Open cut removal and replacement is a proven method for renewing

deteriorated manholes. Often times, rehabilitation is a less costly option than

full replacement.

2.1.1 New Concrete Manholes:

Base

Barrel

Cone

Chimney

Frame & cover

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2.1.2 Fiberglass Manholes:

They are used to replace the base, barrel, cone, and in some cases the

chimney portions of existing manholes. The manholes are typically pre-

fabricated to ship to the site in one unit. The fiberglass manholes require

excavation and full installation, as is required for new concrete manholes.

2.1.3 HDPE Manholes:

HDPE manholes are used to replace the base, barrel, cone, and in some cases

the chimney portions of existing manholes. The manholes are typically pre-

fabricated to ship to the site in one unit. The HDPE manholes require

excavation and full installation, as is required for new concrete manholes.

2.2 Chemical Grouting:

Chemical grouting is used to reduce I/I in manhole structures.

The service life of grouting solutions is between 5 to 25 years.

:Condition

Since chemical grouts do not add to the structural integrity of manholes, they

only should be used when the overall structural integrity of the manhole is

sound.

:Process

It used to fill voids and stabilize soils behind manhole walls.

It applied under pressure through grout holes drilled into the

manhole walls.

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:Materials

Grouts can be divided into four categories: acrylamide, acrylate, urethane

foam, and urethane gel.

a) Acrylamide grouts are carcinogens and should be handled with care.

b) Urethane foams are normally used in the upper 5 ft of the manhole,

with the urethane gel and acrylate grout used in the lower sections.

Actual application: In 1999, the Miami-Dade Water and Sewer Department utilizes chemical

grouting in conjunction with lining or coating systems such as prefabricated

fiberglass, polyurethane, and cementitious manhole liners. Chemical

grouting is used to seal the pipe entrances.

2.3 Interior Epoxy Coatings)الطلاء الذاخلي( :

Coating systems may be used as a corrosion protection barrier and/or to

enhance structural integrity of manhole structures.

Process:

- The surfaces be properly cleaned and prepared. High pressure water

blasting may be used to remove loose mortar, grease and oil.

- Coatings can be applied by spraying, or handapplied.

Material:

- Cementitiousbased coating systems have low corrosion resistance.

The corrosion resistance can be improved by using calcium aluminate

cement.

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- Epoxy and polymer (polyurea and polyurethane) base have excellent

corrosion protection properties.

Actual application:

The municipalities in Harrisburg, PA (2001) utilized 1/2-in thick cement

mortar coating for manhole rehabilitation.

2.4 Exterior Coatings)الطلاء الخارجي( : Exterior coatings are used on all or portions of the barrel, cone, and chimney

sections of manholes.

Types: spray-on cementitious, epoxy, or polyurethane; shrink-wrap plastic;

and/or adhesive rubber tapes.

These coatings require excavation around the manhole.

2.5 Structural Lining)التثطين ألانشائي( :

Structural linings restore the structural integrity of manhole structures.

:Types

:place concrete liner-in-Poured1.

It is often combined with epoxy coating or a PVC liner for corrosion

protection. The PVC liner has T-lock ribs which get embedded in the

concrete liner.

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:Actual application

The City of Pensacola, FL (1995) has utilized poured-in-place concrete with

a T-lock PVC lining for structural rehabilitation of several of its severely

deteriorated manholes.

2. PVC Manhole Liners:

PVC manhole liners are used to line all or portions of the interior surface of

the manhole. They are made of sheets of PVC and are mechanically or

adhesively connected to the manhole.

3. Pre-Formed Fiberglass or HDPE Manhole Liners:

Pre-formed fiberglass or HDPE manhole liners are rigid shapes fabricated at

a plant to match the interior size of the manhole.

They are used to line the interior surface of the manhole in the base, barrel,

cone, and sometimes in the chimney sections.

The liner is installed by excavating and removing the manhole cone section.

Then the liner is inserted and the cone section replaced.

For installations in portions of the manhole, the edges of the liners are

grouted to form a seal with the manhole surface.

Frame, Cover & Chimney2.6 Most inflow into a sewer system occurs through the defects in the upper

components of the manholes. The inflow can significantly be reduced by

rehabilitating or replacing these components.

The manhole covers with pick holes or cracks can either be replaced with

watertight covers, or be sealed with mastic compounds and pick hole plugs.

Alternatively, watertight inserts may be installed under the manhole cover.

Reset Frame and Raise to Grade:

Resetting the frame is a method intended to adjust a frame that has moved

horizontally and/or to raise the cover above grade to prevent inflow. The

installation involves minimal excavation – only enough to allow replacement

of damaged concrete leveling rings and addition of new rings to bring the

top of the frame above grade.

Actual Application:

In 1997, the Plainfield Area Regional Sewerage Authority developed a

manhole rehabilitation program.

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3. Laterals and Side Sewers)الاناتية الفرعيح( Laterals are a major source of infiltration/ inflows (I/I) to the collection

system.

The following methods are available for lateral rehabilitation:

� Removal and replacement

� Cured-in-place pipe (CIPP) lining,

� Chemical grouting, and

� Pipe bursting.

Removal & Replacement3.1

Open cut removal and replacement of sewer laterals is a proven method for

renewing sewer laterals.

3.2 Cured-In-Place Pipe:

:Process

The lateral should be cleaned of all debris and roots.

Access to the service lateral may be from either the sewer line or from the

cleanout. If a cleanout is not available, a small entry point outside the

building can be made to install one.

The process of liner installation in the service lateral is very similar to the

CIPP lining of sewer lines.

Actual application:

In 1999, the South Palos Township Sanitary District (SPTSD), IL, used

CIPP lining for rehabilitation of 117 clay pipe service laterals.

3.3 Pipe Bursting:

Lateral bursting is very similar to main pipe bursting.

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:Process

Access pits are excavated at both the upstream and downstream ends of the

service lateral.

One entry is for the insertion of the replacement pipe led by a bursting head,

while the other end is for access to pull the head through the lateral by cable

or rods.

The existing service line is burst into pieces and pushed into the surrounding

soil.

The new pipe is pulled in place behind the bursting head.

Actual application:

In Jacksonville, FL, lateral bursting was done. It involved bursting six

laterals, approximately 8 to 9 ft deep, and with an average length of 30 ft.

The 4-in VCP laterals were replaced with 6-in HDPE.

3.4 Chemical Grouting:

Chemical grouting is frequently used to reduce infiltration/inflow (I/I) in

laterals.

:Conditions

Since chemical grouts do not add to the structural integrity of laterals, they

should only be used when the overall structural integrity of the laterals is

sound.

:Process

A section of the sewer line containing the lateral is isolated by bladders.

Very-low-viscosity chemical grout is then pumped into the isolated area

under pressure.

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The grout is delivered remotely to the location by a mechanism that has two

sealing devices; the grout is injected into the entire space between the two.

The flexible and non-cohesive grout is pulled out of the pipe in the area

between the sealing devices, leaving grout in the joint spaces of the pipe.

The grout penetrates through the cracks into the surrounding soil and seals

off the cracks and other defects.

:Materials

Acrylamide grout

Actual application:

In 1996, a one-year warranty inspection on approximately 1300 chemical

grouting applications for lateral rehabilitation in Broward and Miami-Dade

counties indicated that less than 2% of the laterals were leaking at the

junction of the service lateral and sewer line.

Spot Repair4.

Spot repairs may be used to correct isolated or severe problems in a pipeline

segment. Spot repairs are usually limited to the rehabilitation or replacement

of only a short portion of the sewer line.

The following techniques are available for spot repairs of short deficient

sections of a pipeline:

� Open cut repair/replacement,

� CIPP,

� Internal grouting,

� External grouting, and

� Rubber Seals with stainless mechanical bands.

Cut Repair/Replacement-Open.1 4

Open cut has been the traditional method for spot repair.

:Uses

1. For emergency repairs

2. In cases when they are only a few spot repairs to be made.

3. The severity of the condition requiring repair

When the depth of the sewer line is shallow, the soils are stable, and no

ground water is present.

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:Advantages

It does not need sophisticated equipment and extra skilled personnel.

The opportunity to inspect the repaired pipe fully and ensure it is constructed

according to the specifications.

Pipe (CIPP) Lining-Place-In-Cured.2 4

CIPP liners for spot repair can vary from 3 ft to 60 ft in length.

:Process

A composite section consisting of a polyester wearing surface and a resin

soaked fabric is pulled to the desired repair location.

A chemical reaction that cures within a few hours creates a pipe within a

pipe repair.

Actual application:

In 2002, The City of Portland, OR has used this process for spot repairs in

locations with extremely poor access. One case dealt with a service branch

that had been missed during a fold-and-form repair project.

Internal Chemical Grouting.3 4

Internal chemical grouting may be used for spot repairs of defective pipe

joints. Grouting is also used to seal the junction of the sewer pipe and

manholes.

External Grouting.4 4

When access to the inside of the pipe is not practical, external grouting may

be used from above the ground surface.

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:Materials

Both cementitious and chemical grouts may be used.

Uses:

1. Soil movement,

2. Pipe settlement,

3. Soil voids, and

4. Groundwater.

:Types

1. Portland cement grouts: they can be used to form impermeable subsurface

barriers.

: They can be divided into four broad categories: Chemical grouts2.

acrylamide: it is carcinogens and should be handled with care.

Acrylate,

Urethane foam, and

Urethane gel

:Limitation

It is limited to large size interceptors.

Actual application

In 2000, The City of Niagara Falls, NY utilized external grouting to reduce

infiltration into the Fall Street Tunnel (FST), a three-mile long tunnel

crossing from east to west.

This tunnel was constructed between 1894 and 1923, and ranges from a 6 ft

by 7 ft section 30 ft below ground level, to an 8 ft by 8 ft section 70 ft below

groundwater level.

A series of grouting holes drilled along each side of the tunnel allowed the

creation of a concrete cocoon around the tunnel.

Over the course of the three month construction duration, about 150 tons of

grout was pumped into 81 holes. The Fall 2000 leakage rate of 5.8 mgd was

reduced to a Spring 2001 rate of 1.6 mgd, a difference of about 4.2 mgd.

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Rubber Seals.5 4

Rubber seals are used to repair leaky joints.

:Process

Prepare the joint to be sealed by removing any grease and scale before the

seal is positioned.

The rubber seal is secured in place by two stainless expansion steel bands.

Limitation:

They can be used in systems ranging from 16-in to138-in in diameter.

:Advantage

A problem joint can be repaired without excavation.

:Disadvantage

High ground water pressures may eventually overwhelm the seal.

:Actual applications

In 2002, The City of Portland, OR has used rubber seals for man-entry sized

sewers (72-in diameter).

Reference:

ASCE & USEPA, 2004, “Sanitary Sewer Overflow Solution”, USA