1. Purpose

The purpose of this method of statement is to define the safe and systematic procedure for the installation, testing, inspection, and commissioning of storm drainage water piping networks for construction projects.

By implementing this storm drainage water piping network method statement contractor shall ensure that all storm water drainage works are completed in accordance with:

• Approved shop drawings
• Project technical specifications
• Approved material submittals
• International plumbing and drainage standards
• Local authority regulations
• Health, Safety and Environmental requirements

The objective is to achieve a fully functional storm water drainage system capable of safely collecting and discharging rainwater and surface runoff without leakage, blockage, settlement, or structural failure.

2. Scope of Work

This method statement covers all activities related to storm water drainage piping systems including:

• Site preparation and setting out
• Excavation and trench preparation
• Dewatering works
• Pipe bedding installation
• Installation of GRP, HDPE, uPVC, RCC, and ductile iron pipes
• Pipe jointing and alignment
• Construction of manholes and inspection chambers
• Concrete encasement works
• Backfilling and compaction
• Hydrostatic and leakage testing
• Final inspection and approval

The procedure applies to underground storm drainage networks installed in any kind and size of residential, commercial, industrial, infrastructure, and utility projects.

3. References

The following standards and approved documents shall be referenced before commencement of work:

• Approved shop drawings
• Approved material submittals
• Project specifications
• Project Quality Plan
• Project HSE Plan
• Inspection & Test Plan (ITP)
• Municipality drainage specifications
• ASTM standards
• BS EN standards
• International Plumbing Code (IPC)
• National Plumbing Code (NPC)
• Manufacturer installation recommendations

4. Responsibilities

4.1 Project Manager

The Project Manager shall:

• Ensure proper planning and execution of works as per the project program.
• Coordinate with consultant and authorities for routine matters, clarifications and approvals.
• Arrange manpower, materials, and equipment as per the site requirements.
• Overall responsible to ensure quality and safety compliance.

4.2 Site Engineer

The Site Engineer shall:

• Verify approved drawings and site conditions before and during the storm drainage pipe installation works.
• Supervise installation activities for stormwater drainage system installation
• Coordinate inspections and testing as per the inspection and test plan for the storm water drainage system installation
• Ensure stormwater drainage system installation work is completed as per the project specifications

4.3 QA/QC Engineer

The QA/QC Engineer shall:

• Conduct inspections inline with project ITP
• Verify installation quality before calling the consultant for inspections
• Review installation and testing reports
• Maintain quality documentation inline with approved method statement for drainage pipe installation

4.4 Surveyor

The Surveyor shall:

• Establish benchmarks and reference points
• Carry out setting out works before and during the drainage pipe installation
• Verify line, level, and invert elevations during drainage pipe installation

4.5 HSE Officer

The HSE Officer shall:

• Conduct toolbox talks on daily basis on the subjects relevant to the daily activities.
• Monitor safety compliance during the routine site activities for storm drainage pipeline installation
• Ensure trench safety measures while storm drainage pipeline installations are in progress
• Verify PPE usage as per the site conditions
• Make sure permit to work system is imlemented as per the site HSE requirements

5. Materials

Approved materials to be used for storm drainage installation that may include:

• GRP pipes and fittings
• uPVC pipes and fittings
• HDPE pipes and fittings
• RCC pipes
• Ductile iron pipes
• Rubber gaskets
• Concrete for bedding and encasement
• Geotextile membrane
• Gravel and selected backfill material
• Warning tape
• Manhole covers and frames
• Precast manholes and chambers

All materials shall be approved prior to delivery and installation on the project site area.

6. Tools and Equipment

The following equipment shall be available at site:

Equipment	Purpose
Excavator	Trench excavation
Dewatering pumps	Groundwater control
Plate compactors	Soil compaction
Roller compactor	Backfilling compaction
Crane	Pipe lifting
Pipe laser level	Alignment and gradient
Total station	Survey works
Concrete vibrator	Concrete compaction
Generator	Power supply
Water tanker	Testing and curing
Hand tools	General installation

All equipment shall be inspected and certified before use.

7. Health, Safety and Environmental Requirements

Prior to commencement of works, the following HSE requirements shall be implemented.

Safety Requirements

• Approved Permit to Work (PTW) shall be obtained
• Underground utility survey shall be completed
• Excavation permit shall be approved before starting the excavations
• Barricades and warning signs shall be installed
• Safe access and egress shall be provided in all areas
• Trench shoring shall be installed where required
• Continuous atmospheric monitoring shall be conducted for confined spaces

Mandatory PPE

All personnel shall wear:

• Safety helmet
• Reflective vest
• Safety shoes
• Gloves
• Eye protection
• Dust mask where necessary

Environmental Controls

• Prevent water contamination
• Control dust generation
• Dispose excavated waste properly
• Prevent fuel or oil leakage
• Maintain housekeeping standards

8. Pre-Construction Activities

Before starting storm drainage installation works, the following shall be completed:

• Approval of shop drawings for underground drainage works
• Material approval
• Site inspection
• Utility clearance verification
• Trial pit investigation where required
• Survey benchmarks establishment
• Delivery inspections and approvals of pipes and fittings
• Toolbox talk for workforce

No excavation shall proceed without approval from the consultant and relevant authorities.

9. Survey and Setting Out

The surveyor shall establish the pipeline route based on approved shop drawings.

The following shall be verified:

• Pipe alignment
• Invert levels
• Pipe slope
• Manhole locations
• Existing utility crossings

Benchmarks and reference points shall be protected throughout the construction period as per the satisfaction of consultant/client.

10. Excavation Works

Excavation shall be carried out according to approved drawings and project specifications.

Excavation Procedure

1. Mark excavation boundaries
2. Install safety barriers
3. Excavate trench to required depth only
4. Maintain trench width as per pipe diameter as specified
5. Remove unsuitable materials
6. Keep trench dry and stable all the time

Where excavation exceeds safe depth limits, trench shoring or sloping shall be provided.

Excavated material shall be stockpiled away from trench edges to avoid collapse.

11. Dewatering Procedure

Where groundwater is encountered, dewatering shall be implemented before pipe installation.

Dewatering Activities

• Install wellpoint system where necessary
• Use submersible pumps
• Maintain dry trench conditions
• Prevent soil erosion and trench instability
• Discharge water to approved locations only

Continuous monitoring shall be conducted to ensure trench stability during installation activities.

12. Pipe Bedding Preparation

Pipe bedding shall be prepared according to approved specifications.

Bedding Requirements

• Remove loose material from trench bottom
• Lay consultant approved bedding materials only
• Compact bedding evenly as per backfilling method statement
• Maintain required bedding thickness as per the specifications
• Verify line and level before pipe laying

Bedding material shall typically consist of approved granular material or sand.

13. Storm Drainage Pipe Installation Procedure

General Installation Requirements

Storm drainage pipes shall be installed starting from downstream toward upstream direction.

The following requirements shall be maintained:

• Proper pipe alignment
• Correct slope and invert levels as per drawings
• Uniform support beneath pipes and provision of proper thrust blocks
• Proper approved jointing method
• Protection against pipe displacement

Pipe Jointing

Jointing shall be carried out according to manufacturer recommendations and as per approved method statements.

Typical jointing methods include:

• Rubber ring joints
• Solvent cement joints
• Butt fusion welding
• Mechanical couplings

Make sure that all the lubricants and jointing materials are approved for specific applications.

14. GRP Pipe Installation Procedure

For GRP pipe installation:

• To avoid any damages pipes shall be lowered carefully using nylon slings
• Pipes shall not be dragged on ground
• Gravel surround shall be installed around pipe taking care the pipes are not damaged
• Geotextile wrapping shall be provided where specified
• Side compaction shall be performed equally on both sides

Pipe joints shall be checked for proper seating before backfilling.

15. uPVC and HDPE Pipe Installation

uPVC and HDPE pipes shall be installed according to approved installation guidelines.

Installation Requirements

• Pipe interiors shall remain clean
• Pipe ends shall be capped during interruptions
• Correct insertion depth shall be maintained
• Thermal expansion allowance shall be considered
• Pipe slope shall comply with approved drawings

Pipe damage during installation shall not be permitted.

16. Concrete Encasement and Surround

Concrete encasement shall be provided where specified in approved drawings.

Concrete Works Procedure

1. Install formwork if required
2. Position pipe correctly
3. Verify alignment and slope
4. Pour approved concrete carefully
5. Compact concrete using vibrator
6. Protect pipe from movement during pouring

Concrete shall achieve required strength before further loading.

17. Manhole and Inspection Chamber Construction

Stormwater manholes and chambers shall be constructed as per approved structural details.

Construction Activities

• Excavation and formation preparation
• Blinding concrete
• Reinforcement fixing
• Formwork installation
• Concrete pouring
• Bench channel formation
• Frame and cover installation
• Waterproofing where specified

Manholes shall be aligned with incoming and outgoing pipe inverts.

18. Testing of Storm Drainage Network

Testing shall be conducted after completion of installation works.

Hydrostatic / Water Test Procedure

The testing sequence shall include:

1. Plug both ends of pipeline
2. Fill pipeline with water slowly
3. Release trapped air
4. Apply specified test pressure
5. Maintain pressure for specified duration
6. Inspect joints for leakage

No visible leakage or unacceptable pressure loss shall be permitted.

19. Backfilling Procedure

Backfilling shall commence only after successful inspection and testing approval.

Backfilling Requirements

• Use approved selected material
• Compact in layers
• Avoid displacement of pipe
• Hand compact around pipe zone
• Use mechanical compaction for upper layers

Warning tape shall be installed at specified depth before final backfilling.

Compaction testing shall be performed according to project specifications.

20. Inspection and Quality Control

The following inspections shall be conducted during the works:

Inspection Activity	Responsible
Excavation inspection	Site Engineer
Bedding inspection	QA/QC Engineer
Pipe alignment check	Surveyor
Joint inspection	QA/QC Inspector
Manhole inspection	Consultant
Testing inspection	Consultant / QAQC
Backfilling inspection	QA/QC Engineer

Inspection Request (IR) shall be submitted for each stage of work in compliance with the approved inspection and testing plan.

21. Acceptance Criteria

The storm drainage piping system shall be accepted when:

• Pipe alignment and slope comply with drawings
• Invert levels are within tolerance
• No leakage is observed during testing
• Compaction requirements are achieved
• Manholes and chambers are properly constructed
• Materials comply with approved submittals
• Consultant inspections are approved

22. Common Drainage Pipe Installation Problems and Solutions

Problem	Cause	Corrective Action
Pipe misalignment	Improper bedding	Reinstall and re-level
Leakage at joints	Poor jointing	Rejoint and retest
Pipe settlement	Inadequate compaction	Recompact bedding
Water accumulation	Incorrect slope	Correct pipe gradient
Trench collapse	Weak shoring	Reinforce trench support

23. Attachments

The following records shall be maintained:

• Material approvals
• Inspection reports
• Testing reports
• Calibration certificates
• Survey reports
• Compaction test results
• Concrete test reports
• As-built drawings

All documentation shall be submitted for consultant approval during project handover.

24. Conclusion

The proper installation of storm drainage water piping networks is essential to ensure long-term system reliability, effective stormwater management, and protection of surrounding infrastructure.

By following this detailed method statement, the contractor can ensure safe execution, proper quality control, compliance with specifications, and successful completion of stormwater drainage works in accordance with approved engineering standards.