Method Statement for GRP (Glass Reinforced Plastic) Pipe Installation

1. Purpose

This method statement for GRP formalizes the requirements for the installation and testing of GRP (Glass Reinforced Plastic) pipes & fittings for the underground external stormwater networks.

The specifications, procedures, and guidelines contained in this method statement specify the technical requirements to be followed and also act as a reference to clearly establish defined standards for work assessment.

Moreover, this document shall provide guidelines to check that specified materials are installed and agreed procedures are implemented during the execution of work and to define the responsibilities for controlling the execution.

2. Scope

This method statement describes the sequence of activities involved in the installation and testing of GRP pipes and fittings for the stormwater network as per the requirements derived from the scope of work, contract specifications, codes, and standards of the project.

3. Definitions

Project Management-Construction Management (PM-CM)

Construction Supervision Consultant (CSC)

Main Contractor – xxxxx

Supplier/Vendor – Seller of material as defined in the project specification

4. References

Approved material submittals

Approved shop drawings

Project Specifications

5. Abbreviations

HSE-Health Safety and Environment

QA/QC-Quality Assurance and Quality Control

MST-Method Statement

RA-Risk Assessment

ITP-Inspection and Test Plan

PQP-Project Quality Plan

INR-Inspection Request

PPE-Personnel Protective Equipment

STARRT-Safety Task Analysis Risk Reduction Talk

6. Responsibilities

A. General

1. Project Manager (MEP) will be responsible to manage, executing, completing, and handover the construction activities within approved budgets and resources in compliance with Project Requirements as specified in Project Specifications. He will be overall in charge of implementing the Method Statement for GRP installation in accordance with QA/QC and HSE requirements.

2. Construction Manager will be responsible for managing construction activities and will lead and communicate with site Supervision, Subcontractors, and Vendors to assist them in working to the Project Schedule by conforming to QA/QC and HSE requirements at the site.

3. HSE Manager will be responsible for planning, coordinating, and implementing issues and directives within the organization. He ensures safe environmental working conditions for all employees.

4. QA/QC Manager will be responsible for supporting the project team in implementing and maintaining Quality Management System for the project through POP, ITP, MST, and Procedures in compliance with Project specifications, Codes, and Standards.

5. HSE Officer will ensure the enforcement of safety procedures in accordance with the approved HSE Plan. Will be closely monitoring the site engineer’s strict implementation of the MST and Risk Assessment, the use of proper tools and equipment to maintain safety, certifications of equipment and their adherence to safety regulations, reporting of any unsafe work, or stopping work that does not comply with HSE procedures.

6. Site Engineer will be responsible for carrying out all construction-related activities with compliance to HSE and QAQC requirements as per contract specifications, drawings/documents, codes, and standards.

7. QA/QC Engineer will be responsible for conducting inspections as per PQP.

8. Supervisor/Foreman will be responsible for coordinating all works and workers related to the job.

9. Electrician / other tradesmen will be responsible for assisting his superiors during all construction work-related activities following HSE and QAQC requirements.

10. Store In-charge receives and inspects all incoming materials and reconciles them with documents; processes and distributes documentation; reports, documents, and tracks damages and discrepancies.

11. Security guards will be clearly visible, and vigilant, respond quickly and correctly during the crisis, observe and report, check and monitor, maintain order among workers, and offer safety warnings and tips.

7. List of Subcontractors

Subcontractors for MEP: xxxx

8. Transportation, Handling, and Storage

Ensure that flatbed trailers are used for transporting the GRP pipes and that the trailer’s bed is free from nails/sharp objects.

Pipes should be uniformly supported throughout the length by flat timber placed beneath each pipe layer with spacing not greater than 4 meters.

Check the pipe with wooden wedges to maintain stability and operation. Ensure no pipe-to-pipe contact (in between each layer) to avoid abrasion during transit.

Stack height should not exceed 2.6 meters.

While in transit, strap the pipes to the vehicle over the support points using pliable straps or nylon ropes. Never use steel cables or chains without having adequate padding to protect the pipes from abrasion.

While loading and offloading the pipes, do not drop impact, or bump the pipe particularly at the pipe ends.

While loading and offloading the pipes by forklift/crane, fork and steel ropes must be protected with rubber pads to avoid their direct contact with pipes to prevent damage.

When loading/offloading the single pipe, use pliable straps, slings, or ropes to lift with two support points placed at an equal distance to handle the pipe easily.

While in transit, ensure that the maximum diametrical deflection must not exceed the value as shown in the below table:

The following timber sizes should be used to support the pipes

Handling & Storage:

Ensure that the storage surface is clean and clear from rocks or any other solid objects.

Pipes should be stored separately according to their class and diameter.

Stacked height should be stacked in layers with each pipe socket placed at alternate ends.

Pipes should be placed on flat timber supports at a maximum of 4 meters spacing with wooden wedges to prevent sliding of the pipes from the stack.

While shifting the GRP product by forklift/crane, metal slings, chains, and forks do not come into direct contact with the product.

Fittings are normally stored on top of the pallets. Direct contact between products should be prevented in the storage area.

The spool should be stored in a flat area. Ensure that wooden seating beneath the spool is provided as required. Also, ensure that contact between products is avoided.

Care must be taken that the storage is leveled, firm, and clear of rocks or solid objects that might damage the pipes and spools. If it is necessary to stack pipes, it is best to stack on flat timber supports and a maximum of 4 meters of spacing. The maximum stack height is approximately 2.8 meters. Stacking of pipes from dia.1500mm up to dia. 4000mm is not recommended. This height is limited for safety purposes and to avoid excessive load on the pipe during storage.

Ensure suitable supports are used for example wooden beams, measuring 10 x 5cm. to avoid damage to machined pipe ends. Stacking should be undertaken with care. It is recommended to protect machined ends for example with polyethylene-covered straw mats or polyethylene netting. The socket and spigot end must not touch each other.

The pipe can be stacked economically by alternating the spigot with the socket in order to avoid bending of the pipes, the beams should be laid directly above each other in a vertical line.

Wooden wedges which are used in order to prevent the pipe stack from sliding should be placed on both sides of the stack on the timber bearers.

While shifting the GRP/GRE product by forklift/crane, metal slings, chains, and forks must not come into direct contact with the product.

Fittings are normally stored on top of the pallet. Direct contact between products should be prevented in the storage area.

Spools should be stored in a flat area. Ensure that wooden seating beneath the spool is provided as required. Also, ensure that contact between products is avoided

Important:

The pipe has to be segregated based on the same diameter, pressure classes, and thickness since two pipes of the same diameter can be of different pressure classes and hence have to be stored separately with a tag identifying each pile

If the product is stacked too high for long storage periods (6-12 months) and subjected to high temperatures, the supports may cause flattening. It is recommended that the product (in particular machine parts) be stored under tarpaulins or (white) polyethylene sheeting.

Pipe stacks should have side supports or blocks to roll or slip off the stack during stormy weather.

The pipe stack should have side supports or blocks to prevent the rolling or slipping of the stack during stormy weather.

Unprotected flange faces should never be placed directly on the ground or on concrete floors.

Storage of Jointing Material:

Store gaskets, adhesives kits, resins, hardeners woven roving, lubricants, and consumables in their original packaging in AC controlled room between 20° – 30°C. Keep dry, away from frost, direct sunlight, and ozone.

Observe the self-life of the adhesive and resins (For the resin-The shelf life is 3 months from the date of shipment from FPI Factory to the site). It is preferable to order these as required, however, it is recommended to follow MSDS for better storage.

Handling of Nested Pipes:

Always lift the nested bundle using at least two pliable straps limitations, if any for spacing between straps, and lifting locations will be specified for each project. Ensure that the lifting slings have sufficient capacity for the bundle weight. This may be calculated from the approximate pipe weights.

It is recommended to use soft liquid or rubber inside the nesting pipe to make more smoothen the nesting process.

There should be a minimum gap/size difference between 2 pipes with 200mm.

The lifting boom should be covered with corrugated paper or it should be laminated

The nested pipe is usually stored in the transport packaging. Stacking of these packages should not occur unless specified otherwise.

Nested pipe bundled can only be safely transported in the original transport packaging. Special requirements, if any, for support, configuration, and/or strapping to the vehicle will be specified for each project.

Package removal and de-nesting of the inside pipe(s) is best accomplished at a de-nesting Station. Typically, this consists of three or for-fixed cradles to fit the outside diameter of the largest pipe of the bundle. Inside pipes starting with the smallest size may always be removed by lifting slightly with an inserted padded boom to suspend the section and carefully move it out of the bundle without touching the other pipes.

When weight, length, and /or equipment limitations preclude the use of this method, the procedure for sliding the inside pipe(s) out of the bundle will be recommended for each project

There should be proper attention or care to be taken while de-nesting pipes and pipes should not be de-nested from the trailer bed directly.

Ensure that the boom should be laminated in order to avoid direct damage.

9. Material Inspection

For materials to be inspected after receiving at the site, the following points are to be followed:

Each material item shall be allotted a distinct and separate reference number and mentioned on the material requisition. Make sure that material is approved/examined by the consultant and QA/QC and associated documents/test certificates are approved.

The Store In-charge shall ensure that all approved supplies be delivered to the site as per the approved material submittal; with the manufacturer’s seals, labels, or other proof of origin intact. These labels and seals shall not be removed until the material is required for use and shall be retained for inspection by the consultant and QA/QC.

Store In-charge shall initiate material inspection for all incoming material to QA/QC and the material shall be inspected against reference documents and as per approved material submittal. Moreover, the physical condition of the material shall be checked. Afterward, an INR shall be raised by QA/QC to the consultant and an inspection will be carried out by the consultant.

Materials, which do not conform to the given specification/approved material submittal, shall be rejected. Any discrepancy or damages will be notified and reported for further action.

For any materials inspection (especially pipes, fittings, and other accessories), the items shall be segregated as per their type/sizes and placed items separately in racks or on different pallets.

Each rack/pallet shall have an identification posted on laminated paper with the description of the items clearly written on it.

There shall be appropriate spaces between the pallets so that the engineer/inspector can freely go around them and inspect the materials thoroughly.

Staking the materials all over each other & in one corner is strictly not allowed.

All items shall be kept in a protective environment and shall not be kept directly on the floor; they shall have wooden pallets underneath them.

10. Resources

A. Tools and Equipment

Tools

a. Pipe fitter standard toolbox

b. Chain Cutter, Cutting ring

c. Chain block

d. Come-Along-Jack (cap. 1.5 Ton)

e. Wooden Pushers Sprit Level

f. Steel clamps with rubber liner and accessories

g. 4″X4″ Timbers

h. Shovels

i. Wooden Plank

j. Wooden spacer (16mm width)

k. Working gloves and goggles

I. Paintbrush 4″ and 6″

m. Rags

n. Marker

Note:

All testing equipment and measuring tools to be used shall have valid calibration certificates prior to usage.

All lifting equipment and machines shall be 3rd party certified with valid certificates.

B. Materials

GRP Pipes and Fitting as per approved material submittal

Geotextile

Warning tape

Double bell coupling

Gasket

Note:

Material shall be used after being approved by Approved Material Submittals.

All material to be used shall conform to the Project Specification and Authorities’ regulations (where required).

C. List of Manpower

Construction Manager

Pipe installers

QA/QC Engineer

Helpers

HSE Officer

Mobile Crane Operator

Site Engineer

Trailer Driver

Supervisor

Forklift Driver

Foreman

Riggers

11. Mobilization

A Preparation and Planning

The contractor shall ensure that all gate passes, permits, tools, materials for safety precautions, manpower, and equipment are available before the commencement of work.

The site team shall make sure that access roads are always clear from any obstruction and that the site is always accessible.

B. Site clearance

Before commencing the work, the area shall be cleared of all debris, materials, or other obstructions.

C. Traffic Management

The Site Team with the assistance of the Safety Officers shall coordinate logistics and materials movement through the site following the direction and road signs displayed on site.

The required diversion routes shall be marked on drawings including the required traffic signs.

The Work Permits and Operator Certificates shall be compiled and filed for reference by authorized personnel.

Temporary traffic signs, barriers, and flagmen will be deployed to control traffic flow in accordance with and Traffic Management of the HSE Plan.

At the end of each ramp, there will be a transition area to give the driver the opportunity to watch the access roads before joining thereto.

D. Pre-construction Safety Meetings:

The meeting shall be scheduled prior to the beginning of the work and before any Subcontractor starts on the project.

Safety awareness meetings will be conducted every working day morning/every other Day to brief the workforce on the safety prevention measures. The equipment check for safety shall be recorded/ documented during the daily Safety Awareness Meeting.

Traffic safety will be discussed to emphasize these meetings.

Each worker will be instructed to follow specific safety requirements related to his trade. They will be required to follow installed safety signs, observe barricades and use PPEs.

The contractor safety officer will perform hazard risk analysis by identifying all steps, and hazards identified in those steps, with a focus on the relationship between the work task, the tools, and the work environment. After identifying uncontrolled hazards; The contractor will take steps to eliminate or reduce them to an acceptable risk level.

General Contractual Safety, Health, and Environmental requirements:

Roles of the contractor, subcontractors, authorized representatives, and all project workers.

• Accident reporting requirements.
• Specific details of the work to be performed along with the use of personal protective equipment.
• Emergency procedure.

E. Operating Procedures:

A site investigation has to be carried out to develop safety precautions and measures prior to the commencement of the work. After such investigation, relevant signboards will be displayed and barricades will be installed where and as necessary, such as but not limited to the following:

• Relevant information, advanced signs, warning, and mandatory signs will be placed as required.
• A Radio Communication system would be used where normal communication is impossible.
• After completion of the work, safety cones and barricades have to be removed accordingly.

12. Methodology

Pre-Installation

All necessary work permits shall be obtained prior to the commencement of any activity at the site and shall remain valid throughout the entire duration of the operation.

Site interface permits are to be taken from other contractors before placing pipe at the tie-in point to reconfirm IL and coordinates.

All activities for earthwork, trench excavation, pipe bedding in trenches, initial backfilling and final backfilling, laying of marker tapes, and all associated jobs relates to civil shall be done by the civil contractor.

Dewatering shall be added if the excavation level is lower than the water table. Dewatering shall be performed by the civil contractor.

Check & verify that the civil work is completed in compliance with all requirements for installation as per the approved shop drawing and handed over for mechanical works. A joint inspection of the location shall be carried out by the consultant & contractor before releasing the excavated trench for installation works.

For the waterlogged area, gabbro material as gravel shall be used.

Prior to the commencement of work, inspect areas and access to confirm that the site is ready to commence the work and coordinate with other trades and subcontractors.

Please refer attachment checklist for site readiness.

Ensure that proper and dry trench beddings are placed.

Ensure that gridlines, reference levels, etc. are marked.

Ensure trenches are free from obstruction, rocks, and other debris prior to laying pipes.

All relevant documentation approved shop drawings, and material applicable to a particular section of works will be checked by Site Engineer prior to the commencement of work.

Ensure that the material received is in compliance with the Project Specifications/Authority’s Regulations and is approved.

Ensure that all required materials and accessories are delivered, inspected, and approved by the Consultant and are readily available at the site to carry out the work.

The site engineer and his Supervisor/Foremen will carry out a site survey and mark the route of piping as per approved shop drawings. In the event of any discrepancies or difficulties in executing the work, these shall be brought to the notice of the Construction Manager for corrective action.

All relevant documentation (including method statement for GRP installation and risk assessment are approved, obtain necessary work permits, fill up STARRT cards after completion of daily toolbox talk), will be checked by Site Engineer prior to commencement of work.

The Site Engineer/Site Supervisor will give necessary instructions to tradesmen (Plumbers/pipe installers) and provide necessary approved construction/shop drawings.

The Site Engineer/Site Foreman will check that proper tools and equipment are available to carry out the work and are in compliance with contract specifications.

The Site Engineer will explain to his team about HSE precautions to be observed.

Trial pits shall be carried out for all existing services prior to any excavation activities.

Cut-off walls shall be formed in granular bedding and surrounded by pipes to prevent the bedding from acting as a subsoil drain. Cut-walls shall be provided at a maximum spacing of 40m with one at each manhole and structure and at least one cut-off wall between two adjacent manholes and structures.

Cut-off walls shall be made from an impervious fine-grained clay mixture, prepared with the addition of water where necessary, to suitable trench spoil of available, or imported. Concrete cut-off walls shall be Grade 20 SRC concrete. Cut-off walls shall be installed across the full cross-section of the granular bedding material and shall be at least 300mm wide along the axis of the pipeline.

Installation Steps:

Setting Out

Pipe centerline coordinates are provided as part of the approved shop drawings together with the pipeline level. Meanwhile, as the primary out is carried out during the excavation of the trench of which its survey marks could be removed during excavation works, the Glass Reinforced pipe will be installed at the trench centerline, unless otherwise shown in the shop drawings as might be the case according to actual site conditions.

However, stormwater pipeline strings i.e. from manhole to manhole will be marked by setting out manholes centerline and pipe bottom level by short steel bars firmly placed in the natural rock by means of drilling, hammering, or mortar for every manhole and 5m of pipelines, as well as at every slope change if required. Setting out a survey will be checked by the engineer and surveyor.

As-built excavated trench width and formation level are jointly surveyed by the contractor and Main contractor and recorded as part of excavated trench handover procedure which shall involve a joint survey record for the trench bottom level, pipe centerline, and trench coordinates as well as status of groundwater: the same shall be verified against pipeline route and layout shop drawings, before releasing the area being surveyed for further works.

The top of the pipe level shall be marked by surveyors using the string wire and timber’/steel braces; at the same time and according to pipe diameter and ground conditions, aggregate bed and surrounding top levels will be marked by spray paint on trench sidewalls.

Pipe levels will be reviewed with as-built trench level and cross-checked by MEP subcontractor and main contractors engineers representative prior to/and during the course of construction made in stages, including:

• Bedding material placement (and compaction, if needed)
• Pipe installation
• Surround material placement (and compaction, if needed)

Further, the following location levels and coordinates have to be mutually checked and marked carefully prior to installation, subject to the engineer’s acceptance or instructions.

• Each pipe/joint level and coordinate
• Change in gradient (slope), if any
• Manholes centerlines and offset, if any.

Dewatering

If the final excavation level is lower than the groundwater level, the dewatering will be performed to make the dry condition at the final excavation level as per the submitted method statement for dewatering work. During the excavation, a submersible pump will be used to discharge the water to the approved discharge location.

Trench Specifications

The Trench:

The trench excavation should not be too far ahead of the pipe-laying team to ensure better control of the trench and for safety reasons. The excavated soil should be placed on one side of the trench leaving the other side, clear for equipment and pipe handling. If the trench consists of various layers of soil, these should be placed separately in order to use the stone-free granular material for backfill.

Minimum trench width:

The trench width must be maintained within certain limits. A very wide trench will increase the volume of backfill material required, and compaction labor and effort. A very narrow trench will render laying, handling, and jointing of pipes, as well as compaction of side, and backfill difficult.

Note:

► In poor native soil conditions and depending on pipe stiffness and burial depth, a wide trench (up to 4XDN) might be required.

► The distance between the pipe and the trench wall should be at least 10 cm wider than the width of the equipment used for the compaction of the backfill material.

Parallel pipes installed in the same trench:

Where two or more pipes are installed parallel in the same trench, the following minimum distance should be maintained in order to allow for sufficient room to place and compact the backfill material under the pipe haunches, for all the pipes in the trench.

The distance between the pipes should be at least 10 cm wider than the width of the equipment used for the compaction of the backfill material. Where pipes of the same or different diameters are installed in the same trench, a minimum spacing equal to (DN pipe a + DN pipe b)/4, but not smaller than 300mm is required.

Trench Depth:

Minimum Cover Depth:

Generally, the cover depth of the pipe is specified by the design Engineer. When there is no traffic load over the pipe, the minimum burial depth is 0.6 m. In the presence of traffic loads, a minimum cover above the pipes shall always be maintained as follows for all stiffness classes.

High Water Table:

In the case of a high groundwater table, a minimum cover depth equal to 0.75 times the pipe diameter of granular soil (minimum dry density of 1300 kg/m3) must be provided to prevent pipes from floating. Always ensure that this minimum coverage is available before turning off dewatering systems.

Maximum Cover height:

The maximum cover height depends on the pipe stiffness, type of installation, backfill material, and compaction, as well as native soil conditions.

Lowering the pipe into the trench:

Handloading should be executed by at least two men. It is recommended that the weight carried by one man does not exceed 30 kg. Pipes weighing up to 175 kg can be lowered by means of two ropes. The ropes must be anchored to stakes.

Lowering with ropes

Mechanical lowering is used for larger-diameter pipes, especially when combined with pipe assembly in the trench. Two straps or slings can be used from an excavator boom if no separate lifting equipment is available.

Pipe Joining

Pipe joining will consist of the following steps:

The rubber ring needs to be installed on both grooves of the double bell coupler while the double bell coupler is still at ground level

One double bell coupler needs to be inserted on each pipe (ie. one side only) while the pipe is at ground level, before being lifted to be laid inside trenches.

Rubber Ring Assembly:

The rubber ring should be fitted into the coupling when the coupling is in a horizontal position, as shown in Figure.

Clean the grooves of the double bell coupler and rubber gaskets with a brush or rag. Ensure that these areas are totally free of dust or any other dirt. In dusty and windy weather conditions, the area where the rubber ring assembly is taking place needs to be protected from all sides to avoid dust, sand, and dirt. If such protection cannot be provided, the work shall be stopped.

Insert the gasket into the groove, leaving enough loops to ensure a uniform distribution of the stress along the gasket length. Then, with uniform pressure, push each loop into the groove, Check that the ring is uniformly fitted into the groove of coupling.

Apply lubricant on the outer surface of the rubber ring. After lubricating, ensure to keep the coupling and rubber ring clean and free from sand particles.

Mounting the coupling onto the pipe:

The below step should be followed while pipe P1 is still at ground level and properly supported with temporary wooden supports. Clean the grooves of the double bell coupler and rubber gaskets with a brush or rag.

Clean the dust and foreign material from the outer surface of the pipe spigot with a firm brush or rag and ensure the pipe spigot has a smooth and glossy appearance.

Apply vegetable base soap on the outer surface of the pipe spigot.

Fix a pipe installation clamp on the home line, which will also act as a stopper to stop the coupler exactly on the home line.

Hold the coupler with a sling wrapped around it. The coupler shall be held until it has been fully mounted on the pipe spigot.

The coupler is mounted on the spigot using come-along- jacks which will pull the coupler towards the pipe. Keep the installation clamp in its position.

The pipe with a coupler mounted is then ready to be lifted by a crane and laid inside the trench before jointing it to another pipe.

Pipe Assembly:

In the following steps, it is assumed that previously a pipe along with its mounted Coupler has been already laid with the pipe support clamps.

Place temporary nylon or pressure-treated wooden spacers 16mm thick at 12, 3, 6, and 9 o’clock positions on the pipe edge. These spacers will ensure that the gap Of 16mm between the two pipes is maintained as specified by the manufacturer.

Pipe P2 with its mounted coupler (coupler mounted as described in the above steps) Is carefully held by a crane and positioned along the final axis of the line before joining it to pipe P1 using P1 ‘s coupler. (Note: P2’s coupler would be used for installing a pipe P3 for example). Ensure that the two pipes are aligned Horizontally & vertically before joining them.

Make sure that pipes P1 & P2 still have the installation clamps clamped over them.

Clean the outer surface of the pipe spigot end with a firm brush or rag. Ensure that the area is totally free of foreign particles.

Apply vegetable-based soap on the outer surface of the pipe spigot.

Attach pullers to the pipe installation clamp of pipe P1 to the pipe installation clamp of P2. Pull the pipe by jacking the pullers until the edge of the coupling reaches the home line of the new pipe. At this stage, the edge of the new pipe would be touching the wooden spacers.

Loosen and detach the pullers.

Install the support clamp on both ends of pipe P2.

The current setup is ready for installing pipe P3 & Jointing it to pipe P2 etc.

All spacers must be removed before hydro testing and commissioning.

Laying of pipes in Trench Bedding

All civil-related works are mentioned here for reference only. Civil works shall be performed by the civil contractor.

The laying of drainage pipes in trenches shall be in accordance with the relevant provisions of the project specification/ manufacturer’s recommendations.

General

GRP pipe shall be installed in trenches that shall not exceed the maximum trench width at 300mm above the crown of the pipe as shown in Table 2.1 of Part 2 of Section 8.

Pipe bedding shall be provided as shown on the Drawings or stated in the approved methods statement.

Pipe bedding shall be well compacted and shall completely fill the whole width of the trench excavated.

Wet conditions: In the wet ground, sloppy working conditions can be alleviated by first placing a layer of hard granular material, or by de-watering the area in and around the trench. If patches of ground area are so wet that there is a risk of subsidence and possible damage to sections of the pipeline, these areas are to be consolidated by the addition of fill material. (Details shall be included in the shop drawings).

Any over-excavation adjacent to a structure or beneath the formation level of a pipeline, either to be constructed under the Contract or in a future contract, shall be backfilled with Grade 20 SRC concrete.

In case the trench width exceeds the limits, the contractor shall provide plain or reinforced concrete cradles and/or reinforced concrete arches to the requirement shown in the drawing and to the approval of the Engineer at no additional cost

Table 2.1 – Minimum pipe trench width at 300mm above pipe crown:

Granular bedding material for rigid pipes shall conform to the following requirements:

Shall be cleaned gravel or broken stone from a source approved by the Engineer. Gabbro shall be used in waterlogged ground.

The granular material size shall be according to the following grading limits given in Table 2.2

Table 2.2 – Gravel size grading limits

Bedding for pipes shall be constructed by spreading and compacting granular bedding material over the whole width of the pipe trench.

Bedding material shall be in accordance with the project specifications unless otherwise specified.

Nominal single-sized aggregate and graded aggregate shall comply with Table No. 4 of BS 882.

Sand for bedding material shall comply with the relevant provisions of BS 882.

Bedding systems other than those specified in this clause may be allowed upon approval of the Engineer or as recommended by the pipe manufacturer.

Where socketed pipes are required to be laid on a granular or sand bed, or directly on a trench bottom, joint holes shall be formed in the bedding material or final excavated surface to ensure that each pipe is uniformly supported throughout the length of its barrel and to enable the joint to make.

Pipes shall be laid on setting blocks only where a concrete bed or cradle is used and is required by approved drawings and project specifications.

Where pipes are required to be bedded directly on the trench bottom, the final excavated surface shall be trimmed and leveled to provide even bedding for the pipeline and shall be free from all extraneous matter that may damage the pipe, pipe coating, or sleeving. Where rock is encountered, the trench shall be cut at least 150 mm deeper than other ground and made up with well-compacted selected fill material.

No protective cap, disc, or other appliance on the end of a pipe or fitting shall be removed permanently until the pipe or fitting that it protects is about to be jointed. Pipes and fittings, including any lining or sheathing, shall be examined for damage and the joint surfaces and components shall be cleaned immediately before laying.

Suitable measures shall be taken to prevent soil or other material from entering pipes and to anchor each pipe to prevent flotation or other movements before the works are complete.

Where pipeline marker tape is specified in approved drawings/specifications, it shall be laid between 100 mm and 300 mm above the pipe.

Marker tape wording and color shall be in accordance with project requirements. For foul water red color tape.

Protective Coatings

Coatings, sheathings, or wrappings shall be examined for damage, repaired where necessary, and made continuous before trench excavations are backfilled.

Backfilling

Backfilling shall, wherever practicable, be undertaken immediately after the specified operations preceding it have been completed. Backfilling shall not, however, be commenced until the parts of the works to be covered have achieved a strength sufficient to withstand all loading imposed thereon.

Suitable material shall be used for backfilling. All required tests shall be performed prior to bedding surround/backfilling.

Backfilling around existing structures shall be undertaken in such a manner as to avoid uneven loading or damage.

Selected fill material for the pipe surround shall be placed in a layer of not greater than 150 mm compacted thickness until the fill has been carried up at least 300 mm above the top of the pipe.

Where the excavations have been supported and the supports are to be removed, these, where practicable, shall be withdrawn progressively as backfilling proceeds in such a manner as to minimize the danger of collapse. All voids formed behind the supports shall be carefully filled and compacted.

All safety measures shall be taken during excavation, bedding, compaction, and backfilling.

An open trench will be barricaded by warning tape. A warning sign shall be in place i.e. “Danger” “Deep Excavation” “Keep Away” “Do Not Enter” “Work Under Progress” etc. Trench barricade requirements shall not be limited to warning tape, and adequate barricade to be provided to suit site conditions and area.

After completion of backfilling the pipe trench all warning signage, and warning tape shall be removed and the area will be cleaned.

Geotextile filter membrane shall be placed in the trench after formation level.

Concrete surround shall be provided around the pipe if the minimum cover depth is less than 1200 mm.

Note: For the GRP pipes it is required to maintain the level to achieve the required earth cover to be 1200 mm. Furthermore, this will be mentioned in the shop drawing.

Installation Procedure for underground piping:

The laying/lowering of pipes shall be performed according to the manufacturer’s recommendations, and project specifications.

The trench will be made clear of any debris or any sharp object before laying the pipe in. The trench bottom will be level to provide uniform bearing and support of pipes.

A trench survey will be done for ensuring the required pipe elevation as per the approved drawings.

Lower the pipes and fittings into the trench with the crane or any suitable lifting/lowering machinery or manually depending upon the weight, size, and length of the pipe. As per the approved material and specification, any external treatment or protection (sleeves, etc) are not applicable.

Wire rope or any metallic lifting sling will not be in direct contact with vitrified clay pipe while lifting or lowering into the trench. Cotton Jute or soft rubber material will be wrapped to avoid damage to the pipe at the place where the sling will tie for lifting the pipe.

Care shall be taken to avoid damage to pipes during lowering into the trench.

Care should be taken in lowering the pipe into the trench to prevent damaging the joint material or disturbing trench conditions. Never allow the pipe to be damaged along the ground or even at the trench bottom.

The pipe shall be laid in the upstream direction with the bell end laid upstream.

Make/dig the pit (hole) in the soil under each pipe socket (bell) for firmly resting the pipe barrel on the trench bottom or bedding material so that load is supported by the pipe barrel and not the pipe socket.

Connect/Join the pipe and fitting ensuring its invert elevation is as per the latest approved shop drawings. Please refer section jointing procedure of this method statement.

For jointing methods, the manufacturer’s recommendation shall be followed where applicable.

A pipe passing through the concrete/wall shall be installed in the sleeve. Sleeve material will be as per approved material submittals. The pipe sleeve diameter is 13 mm larger than the outside diameter of the pipe.

If required to prevent misalignment, underground piping shall be stabilized and secured as per approved drawings or by thrust block at intervals, every branch, and every change of direction as specified in the specification or drawings.

Protective caps shall be removed from pipes and fittings end prior to making joints and at every end of the working day, pipe ends will be covered or will close with end caps.

After installation check for correct leveling, position, alignment, straightness, and required slope as per International Plumbing Code.

Installation inspection will be offered for the part or complete portion of the entire underground piping. Air Testing Inspection will be offered after approval of installation.

Both inspections will be independent.

Piping will be backfilled and compacted as per project specifications. The minimum top coverage shall be 300 mm. This shall be in accordance with finalized specification document.

Back-Drop Connection- In some instances, there may be a significant level difference between the incoming pipe and the invert level of the manhole. To accommodate this, and to avoid having to excavate to full depth for the incoming pipe, a Drop shaft connection may be used.

The incoming pipe is projected through the chamber, to enable rodding and CCTV access, and then stoppered. A tumbling bay junction will be used to divert the flow downward, through the vertically set backdrop pipe, and then via the knuckle bends to enter the chamber at the invert level.

Typical Backdrop Connection Detail:

Rocker Pipe- If tanking is not provided to concrete surround to pipes, the concrete surround shall be in SRC20, and tanking shall be turned and lapped 150 DN to the pipe surround

The rocker pipe connecting sewers to the manhole shall have sufficient cast-in-situ concrete surround and an extended concrete base.

Swabbing/Cleanliness of Pipelines:

Before Testing, cleaning, and swabbing of the pipeline shall be carried out.

Pipelines and manholes shall at all times be kept free of all silt, mortar, debris, and other obstructions. When work is not in progress the open ends of the pipeline shall be securely plugged with an approved watertight plug or stopper firmly fixed to resist unauthorized removal.

The inside of each fitting and pipe length shall be cleared immediately before jointing and shall swab all fittings and pipe lengths to remove all dirt, sand, or other matter that may clog the pipeline or contaminate the fluid to be transported in the pipeline.

After joining, the interior of the pipes shall be freed from any dirt, stones, or other matter that may have entered them. For this purpose, a rubber disc, brush, or other suitable implements that will not harm the internal lining of the pipe shall be pulled through the pipe after jointing.

Testing:

Testing a pipeline shall be carried out before any backfilling takes place and shall be repeated after backfilling is completed, and should be in accordance with the standard specifications of water and air testing of drain and sewers.

Each pipeline 600 mm or less in diameter shall be tested by air test. If any pipe fails the air test, the Consultant /Engineer may order a water test (of 5m head/half bar) to be carried out.

Acceptance of the pipeline will then be based on the results of the water test. All pipelines up to and including 1200 mm shall be tested by air test in accordance with the requirements of BS EN 752.

Pipelines shall be tested in lengths between manholes.

Each pipeline shall be tested before backfilling and also after backfilling before carrying out road reinstatement or laying new road surfacing. Where the pipeline is located under a new road alignment, the pipeline will be tested after the sub-base compaction is complete.

All pipelines shall be subjected to pass infiltration tests as specified herein. All pipes are to be clean and empty at the time of testing. Tests shall be performed in the presence of the consultant/Engineer.

Air Testing of a Pipeline:

Prior to Air Testing INR will be raised for approval of the installation of piping work.

Air testing of drainage will be carried out prior to closing/backfilling the trench.

Piping may be tested in sections or in total, depending on on-site requirements.

Trained Personnel will conduct the test monitored by a responsible site engineer and safety department.

Methodology:

Ensure that the pipes and fittings are capable of withstanding air leak tests.

Air testing can be applied to the system in its entirety or in sections. Once the above is checked and found acceptable, proceed with the test.

Inspect the pipeline for possible damage during or subsequent to laying.

Thoroughly check all plugs and equipment. The average drain plug is quite often not airtight and rubber tubing used in connections must be in good condition and not perished.

Ensure that the ends of the line are adequately strutted against movement with all plugs held firmly in position.

Pump or blow in the air until a pressure of slightly in excess of 4 inches (100mm) water gauge is indicated on the manometer connected to the system. Pumping or blowing warms the air so a minute or two should be allowed for this to cool to the pipe temperature.

If necessary, then reduce the pressure to 4 inches (100mm) water gauge. During a further period of 5 minutes, the air pressure should not fall below 3 inches (75mm) water gauge.

The testing team will conduct a soap test at the joints if an air leak is identified.

If any leaks are detected then they are to be attended to prior to proceeding further.

Repeat the procedure after attending to the leaks (if any).

Once it is confirmed that there is no leak in the system and maintain pressure in the piping for 5 minutes.

INR will be raised for the client/ consultant to witness the Air Test.

After consultant inspection, the system will be vented until normal pressure is attained.

Procedures for Handling Air Test Failure:

I) Before Backfill

a) Readjust the pipe pressure to the specified test pressure and examine for leakage by pouring a solution of soft soap and water over the exposed joints if the test fails.

b) Repair leaks and repeat testing where leaks are found at joints.

c) Where leaks are not found at joints, move the plug, the one that is not used to exert air pressure, along the pipeline to isolate lengths with leakage. Uncover pipe barrels in the isolated lengths where leakage in pipe barrels is suspected. Replace leaking pipe lengths and repeat testing.

d) Conduct low-pressure water testing to verify that the air test was not erroneous where the test length fails the air test but no source of leakage can be identified. Consultant’s consent is required as per site conditions.

II) After Backfilling

a) Move the plug up from the other end along the sewer pipeline to isolate the lengths that fail the air test.

b) Exhume the failed length of the pipeline and replace pipe lengths.

c) Repeat the air test.

d) Conduct water testing to check that the air test was not erroneous when failed lengths could not be isolated using the air test. Consultant’s consent is required as per site conditions.

e) Use CCTV or a suitable recording medium, when required or available, to identify the leakage if the failed section cannot be isolated by the air test or water test.

Water Testing of a Pipeline:

(Shall be done after consultant’s approval where Air Test failed)

Preparation

Before testing, attention should be paid to the following points:

1. Inspect the pipeline for possible damage during or subsequent to laying.

2. Plugs, should be thoroughly checked. Faulty plugs will invalidate test results.

3. Close all openings in the line with watertight seals (Test Stoppers) ensuring against movement. i.e. all plugs held firmly in position.

4. Ventilating valve should be fixed at the high point of the section.

Methodology:

All the joints of the pipeline shall be able to withstand a pressure of a minimum 5m head of water, above the crown of the pipe at the highest point of the pipeline without leakage. A layer of embedding soil equal to the diameter of the pipe shall be laid over the pipe to prevent the lifting of the pipe while applying test pressure. However, all the joints shall be left open for the purpose of inspection for leakage if any. All branches and open ends shall be closed with stoppers, and secured with longitudinal braces/thrust blocks before testing begins.

Water shall be filled from the lowest point and air allowed to escape through an air vent fixed for the purpose at the high points of the pipeline section under test. The diameter of the air vent shall be about one and a half times the diameter of the water inlet pipe to allow easy escape of air. No entrapped air shall remain in the pipeline while testing.

A pressure of 5 m head of water shall be maintained for one hour to allow the initial absorption of water. After that, the test pressure shall be maintained for 15 min and the water added shall be measured. If water consumption in 15 min does not exceed 0.1 l/m2 of wetted inner pipe surface and if there is no visible leakage through joints, the pipeline shall be treated as passed.

Infiltration Testing a Pipeline:

General

This test method defines procedures for hydrostatic infiltration testing of new installations of vitrified clay pipelines, to demonstrate the structural integrity of the installed line as per ASTM C 1091 – 03a.

This test method is suitable for testing gravity-flow pipelines constructed of vitrified clay pipe or combinations of clay pipe and other pipe materials.

This test method is applicable to the testing of the pipelines only.

The upper ends of the sewer and service connections shall be closed sufficiently to prevent the entry of water and pumping of groundwater shall be discontinued until the groundwater surface reaches its natural level before beginning the infiltration test.

The dewatering system shall be stopped, but not be removed until the infiltration test has been successfully completed or as otherwise permitted by the Consultant/Engineer.

Procedure

The hydrostatic infiltration test procedure is applicable where the measured water table is 2 ft (610 mm) or greater above the pipe barrel at the lower manhole of the test section. Where the groundwater elevation is indeterminate, less than 2 ft (610 mm) above the top of the pipe barrel, or the line is partially below the water table, use a combination of both the air test and infiltration procedure.

Note 1- the most practical method for testing is Air Test Method which is recommended.

However, where groundwater is present and meets the criteria established in this procedure, the infiltration test procedure outlined in this practice is recommended.

Note 2- what can be called false infiltration represents condensate on the pipe walls.

The infiltration shall not exceed 6 liters per mm diameter per kilometer per day of the portion of the sewer being tested, including the length of service connection entering that section.

The total length tested in one section shall not exceed 400 m in length. This length is dependent upon the type of deflection measuring equipment proposed by the contractor if flexible pipes are used.

No gravity pipeline will be accepted if the total infiltration exceeds the above-mentioned limit and joints will not be accepted if, during an internal inspection, any infiltration is visible.

If the test section includes more than one pipe size, calculate the allowable test rate for each size and add to arrive at the total allowable test rate for the test section.

External drainage pipelines shall be tested for infiltration after backfilling. All inlets to the system shall be effectively closed, and any residual flow shall be deemed to be infiltration.

The pipeline shall be accepted as satisfactory if the infiltration, including infiltration into manholes, in 30 minutes does not exceed 0.5 liters per linear meter per meter of the nominal bore. This relationship in equation format, with water infiltration measured in liters, can be written as follows:

Maximum volume of infiltration over a 30 minute period = 0.5 x L x D Where: L = pipe diameter (m) D = Length of test section (m)

CCTV survey:

CCTV survey shall be carried out on a representative sample of no more than 12% of the length of constructed pipelines if the Consultant/Engineer’s representative requires it.

In case this survey indicates sections of the pipeline fail to meet the specification requirements, undertake additional CCTV after remedial works will be carried out.

Note: CCTV & Deflection tests shall be carried out by a specialized party approved and listed in the updated list of vendors. The pipeline locations and diameters to go under this test may be selected by the concerned authority.

Setting-up of equipment:

Place visible signage i.e. “System under Pressure”, “Keep Away”, “Danger”, “Caution”.

Warning notices and barricades (if deemed necessary) will be used to identify the system under test.

Clean-up and restoration

After a successful test, remove carefully all temporary plugs.

Remove warning signage and temporary barricades in a safe and orderly manner such that the work area is restored as is prior to conducting the test.

Clean the work area thoroughly prior to transfer to another test location.

13. Health Safety and Environment

A. HSE Risk Assessment

Please refer to the attached document in Appendix A.

B. Permit and Licensing Requirements

The required permit to work shall be obtained prior to the commencement of work. This shall be coordinated with HSE. Site interface permits are to be taken from other contractors before placing pipe at the tie-in point to reconfirm IL and coordinates.

C. Pre-Start Safety Briefing Arrangements

C.1 Protective and Safety Equipment

All workers involved shall be equipped with adequate PPE as stated below:

Safety Helmet with Company Logo

Safety Boots

High Visibility Vest

Safety Goggles

Hand Gloves

Coveralls

Proper safety harness

C.2 Information to Personnel

Safety Induction

Job training

– All the personnel involved in this task shall be provided training and only trained personnel shall be authorized to work around this area.

Toolbox talks

STARRT Card

C.3 Special Safety Requirements:

All necessary personal/protective equipment (PPE), as well as harness, be provided.

Rigging Team, wearing distinctive vests, shall be assigned to help operators maneuver their equipment.

The equipment operators shall possess the required licenses and certificates.

The required permit to work shall be obtained prior to the commencement of work.

The project safety officer is responsible along with the project zone site engineer for ensuring that all operations are carried out with due regard to the safety of all project personnel & property.

• Working at height to be monitored with due care.

• In case of working at night, please refer to Method Statement for Night Works

• Contractor must provide a safe place of work, with safe access and egress. Provide a safe working environment that is without risk to health.

14. Quality Assurance and Quality Control

A. Quality Assurance Requirements

The contractor shall provide the required documents for the Consultant’s approval prior to initiating the execution of this activity as per project specification.

The Quality Control requirement shall include related ITPs and other related documents as applicable.

B. Quality Assurance Process

The contractor shall notify the Engineer 24 hours in advance prior to the start of activity and comments from the site instruction will be complied with the satisfaction of the consultant. The contractor shall consult the public utility authorities not less than one month before it is proposed to commence work to ascertain whether any underground installations will be affected by the proposed work, in which event the contractor shall make all necessary arrangements with the public utility authorities to safeguard the installation.

C. Follow-up and Evaluation

Follow-up on quality performance shall be carried out through an in-house monitoring system such as progress reporting to the planning department, and daily, weekly, and monthly reports generated by the planning department to closely monitor site performance.

All of the above shall be conducted in close coordination with the quality department to monitor any deviations from the Quality Management System requirement and induce corrective actions whenever required to eliminate non-conformance or quality deviations.

D. Records

Checklists (CL)

Inspection Request (INR)

Inspection and Test Record (ITR)

14. Attachments

A. Appendices

Appendix A: HSE Risk Assessment for Installation and Testing of Glass Reinforced Pipe (GRP) for Storm Water Network

Appendix B: Inspection and Test Plan for Installation and Testing of Glass Reinforced Pipe (GRP) For Storm Water Network

Appendix C: Checklist for Installation & Testing of Glass Reinforced Pipe (GRP) for Storm Water Network

Appendix D: Checklist for Site Readiness for Installation & Testing of Glass Reinforced Pipe (GRP) for Storm Water Network

Appendix E: Pressure Test Report for Glass Reinforced Pipe (GRP) for Storm Water Network

Appendix F: Sewer Record Sheet

Appendix G: Permanent Material Delivered Approval Form

Appendix H: Location, drawing for stormwater network

Appendix I: BOQ for stormwater network

Appendix J: Installation guide for underground pipe

Appendix K: Manufacturer’s method statement for installation of the stormwater network (GRP Pipe)

tag: Method Statement for GRP