Method Statement: Laying of Ductile Iron (DI) Water Main Pipes with Bedding, Joint Assembly, Anchor Blocks, and Initial Pressure Class Verification – Method Statement

Overview

This method statement defines the controlled procedures for installing ductile iron (DI) potable water mains, including:
- Setting out, trench excavation, shoring and dewatering where required.
- Bedding preparation and pipe surround.
- Pipe receipt, inspection, initial pressure class and markings verification.
- Pipe lowering and joint assembly (push-on/gasket or mechanical joints).
- Installation of anchor (thrust) blocks at bends, tees, reducers, dead-ends, and hydrant branches.
- Initial pressure class verification vs. test pressure and operating pressure.
- Hydrostatic pressure testing (pre-commissioning) and reinstatement to safe temporary backfill level (final reinstatement by others if specified).

Exclusions/Interfaces

• Disinfection, flushing, and bacteriological testing are excluded unless stated otherwise (to be performed post-pressure test) [Verify per project specifications].
• Permanent surface reinstatement, valve chamber construction, and appurtenance installation may be covered under separate method statements if not explicitly included.
• Utility diversions and relocation works are by others unless specified.

Key Performance Requirements

• Alignment and level tolerances, bedding thickness and compaction, joint integrity, and thrust restraint adequacy to comply with referenced standards and project specifications.
• Materials, equipment, and measuring devices to be approved and calibrated.
• HSE controls and environmental protection measures implemented throughout.

• Approved IFC drawings, method statement, risk assessment, and ITP available on site.
• Permits to Work (excavation, dewatering, lifting, hot works if any, traffic management) issued [Verify per project HSE plan and local regulations].
• Utility search and permits obtained; trial pits completed and services positively identified/marked; isolation/consent from utility owners if required.
• Materials MIRs approved; pipes, gaskets, fittings, and concrete mix design (if site mixed) approved; certificates of conformity (ISO 2531/EN 545) available.
• Calibration certificates for gauges, levels, torque wrenches, and test pump current and valid.
• Lifting plan approved with rigging study for longest/heaviest pipe and fittings; appointed person and riggers briefed.
• Dewatering and groundwater control plan approved, including discharge consent if applicable.
• Survey control established; benchmarks protected; trench line set out with offsets.
• Pre-start briefing/toolbox talk conducted; emergency and rescue plan tested (trench collapse, lifting incident, flooding).
• Weather and ground conditions assessed; stop work if conditions jeopardize trench stability or joint integrity.
• Thrust block design calculations signed off or standard details selected for each fitting/bend angle and test pressure.
• Test water source identified; disposal route/consent defined (avoid chlorinated discharges at this stage).

Identify, assess, and control the following task-specific hazards:

• Hazard: Trench collapse/engulfment
• Likely consequence: Serious injury/fatality by burial or crushing
• Engineering/procedural control: Design shoring/trench boxes to suit soil class and depth; keep surcharge loads/set plant ≥1 m from edge; step/bench where allowed; daily inspections by competent person; install safe access/egress every ≤7.5 m [Verify per local code]
• Required PPE: Helmet with chin strap, high-visibility vest, safety boots, gloves
• Collective preventive measure: Physical barriers, guardrails, trench edge stop blocks, exclusion zones

• Inspection/permit/supervision: Excavation permit; daily trench inspection record; appointed competent person sign-off

• Hazard: Underground utility strike (gas, power, telecom)

• Likely consequence: Electrocution, explosion, service outage
• Engineering/procedural control: Utility maps + electronic locating + trial pits; hand-dig in tolerance zones; maintain minimum clearances; liaison with utility owners; live services support; permit to dig
• Required PPE: Dielectric gloves when appropriate, insulated tools near electrical
• Collective preventive measure: Marked corridors, barriers, spotter

• Inspection/permit/supervision: Permit-to-dig; supervision by Site Engineer

• Hazard: Lifting and lowering pipes/fittings

• Likely consequence: Crush injuries, dropped loads, rigging failure
• Engineering/procedural control: Approved lift plan; use spreader bars/web slings (no chains on coating); tag lines; controlled communication; wind limits [Verify]; no personnel under suspended load
• Required PPE: Helmets, steel-toe boots, gloves, eye protection
• Collective preventive measure: Exclusion zones, banksman control, spotters

• Inspection/permit/supervision: Lifting equipment certification; pre-lift checklist; Appointed Person and competent operator on site

• Hazard: Working in/near water and dewatering operations

• Likely consequence: Slips, drowning in sumps, electrocution (pumps)
• Engineering/procedural control: Secure pump cables/hoses; GFCI/RCD protection; covered sumps; non-slip access; emergency plan for flooding
• Required PPE: Waterproof boots, gloves; life jacket if near deep water
• Collective preventive measure: Barriers around sumps; spill kits

• Inspection/permit/supervision: Electrical PAT; weekly pump checks

• Hazard: Pressurization and hydrostatic testing

• Likely consequence: Pipe/joint burst, projectile end caps, high-energy release
• Engineering/procedural control: Verify end restraints/thrust blocks strength and curing; rated test end caps; exclusion zone during pressurization; pressure increase gradual; calibrated gauges; relief valve
• Required PPE: Eye/face protection, helmet, gloves
• Collective preventive measure: Barriers and signage; remote monitoring where possible

• Inspection/permit/supervision: Test permit; Engineer witness; test log

• Hazard: Manual handling and musculoskeletal strain

• Likely consequence: Sprains/strains
• Engineering/procedural control: Team lifts; use dollies/rollers; rotate tasks
• Required PPE: Gloves, supportive footwear
• Collective preventive measure: Mechanical aids

• Inspection/permit/supervision: Supervisor oversight; training records

• Hazard: Traffic interface (public roads/site plant)

• Likely consequence: Struck-by incidents
• Engineering/procedural control: Traffic Management Plan; segregated routes; banksman; work during off-peak where feasible
• Required PPE: High-visibility clothing, helmets
• Collective preventive measure: Barriers, signage, lighting at night

• Inspection/permit/supervision: Road opening permit; daily checks; [Verify per local authority]

• Hazard: Silica dust and noise from cutting/compaction

• Likely consequence: Respiratory and hearing damage
• Engineering/procedural control: Wet cutting; dust suppression; use quieter plant; exposure time limits
• Required PPE: FFP2/FFP3 mask as needed, hearing protection, eye protection
• Collective preventive measure: Water suppression units; acoustic screens where practicable

• Inspection/permit/supervision: Noise monitoring if required; COSHH assessments [Verify]

• Hazard: Contact with cement/concrete for thrust blocks

• Likely consequence: Chemical burns/dermatitis
• Engineering/procedural control: Avoid skin contact; wash stations; correct mixing; safe delivery access
• Required PPE: Alkali-resistant gloves, long sleeves, goggles
• Collective preventive measure: Barriers around fresh concrete
• Inspection/permit/supervision: Material SDS on site; supervision during pour

Where exact legal requirements apply, implement them in addition to the above [Verify per project HSE plan and local regulations].

• Groundwater and surface water management:
• Dewatering discharge via silt bags or settlement tanks; obtain discharge consent if needed. Prevent trench fines from entering watercourses.

• Maintain pumps to prevent leaks; place drip trays under generators/pumps.

• Spoil and material handling:

• Segregate reusable granular material from unsuitable spoil. Stockpile outside root protection zones and away from drains. Cover dusty stockpiles in dry/windy conditions.

• Noise and vibration:

• Use compliant equipment; restrict high-noise activities to permitted hours; monitor if near sensitive receptors [Verify per local consent].

• Dust and air quality:

• Water spray during cutting/backfilling; speed control on haul routes; wheel-wash as required.

• Concrete works:

• Use lined washout; no washout into ground or drainage. Collect and dispose of hardened waste via licensed facilities.

• Water for hydrostatic testing:

• Source from approved hydrant or tanker; measure volumes. Discharge only clean, non-chlorinated water to approved points; use energy dissipation to prevent erosion.

• Waste management:

• Collect gasket/bolt packaging; recycle metals where possible. Dispose of contaminated materials via licensed carrier with waste transfer notes.

• Ecology and heritage:

• Stop work and notify if protected species or archaeological finds encountered. Follow project-specific method statements if in sensitive areas.

• Monitoring and records:

• Keep environmental log (pumping hours, discharge turbidity if required, complaints register). Corrective actions tracked to close-out.

• Standards and acceptance:

• Installation complies with ISO 2531/EN 545, AWWA C600, and project specifications.

• Tolerances:

• Alignment: ±50 mm horizontal; Level: ±20 mm vertical [Verify per project].
• Bedding thickness: 100–150 mm, tolerance ±10 mm [Verify].
• Surround compaction: ≥95% MDD (ASTM D698) unless specified otherwise.
• Joint deflection: within manufacturer’s published limits (typically 1–3° for push-on joints) [Verify].

• Coating repairs: DFT per product datasheet; no bare metal exposed.

• Thrust/anchor blocks:

• Bearing area sized using test/design pressure, pipe area, and fitting angle; allowable soil bearing from geotechnical data [Verify].

• Concrete class and curing meet design; no testing before minimum strength achieved.

• Pressure testing:

• Gauges and test pump calibrated within 6 months; dual gauges cross-checked.
• Soak period observed for cement mortar lining (typically ≥24 h) [Verify].

• Test pressure and duration per spec (typ. 1.25–1.5 × operating pressure, 2 h) within pipe class limits; acceptable leakage per AWWA C600 formula. No visible leaks permitted.

• Records and traceability:

• Material certificates, heat numbers, and lot traceability maintained.
• ITP sign-offs at each hold/witness point.

• As-built drawings with chainages, valve/hydrant locations, and changes recorded daily.

• Nonconformance and corrective action:

• NCR raised for deviations; corrective works agreed with Engineer; re-test/re-inspect as required.

• Typical trench and bedding detail (sketch) with dimensions and tolerances.
• Standard thrust/anchor block details for bends (11.25°, 22.5°, 45°, 90°), tees, reducers, and dead ends, including calculation template.
• Manufacturer torque tables for mechanical joints by DN size.
• Lifting plan and rigging diagram for longest pipe section.
• Pre-start checklist and daily trench inspection form.
• Hydrostatic pressure test procedure and data sheet, including leakage calculation sheet (AWWA C600 formula and metric conversion guide).
• Material submittal approvals and certificates (ISO 2531/EN 545 compliance).
• Calibration certificates (gauges, torque wrenches, levels, test pump).
• Environmental management plan excerpts (dewatering/discharge method).
• Emergency response plan for trench collapse and pressure testing incidents.