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
- Mark excavation boundaries
- Install safety barriers
- Excavate trench to required depth only
- Maintain trench width as per pipe diameter as specified
- Remove unsuitable materials
- 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
- Install formwork if required
- Position pipe correctly
- Verify alignment and slope
- Pour approved concrete carefully
- Compact concrete using vibrator
- 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:
- Plug both ends of pipeline
- Fill pipeline with water slowly
- Release trapped air
- Apply specified test pressure
- Maintain pressure for specified duration
- 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.