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Method Statement 3.12 - Repair of Ductile Iron & PVC/HPPE Main

Document Information

Field Value
Document Reference MS 3.12
Issue Number 2
Issue Date 1 June 2026
Next Review 1 June 2027
Prepared By Sean Ashton
Approved By Aaron Mason, Director
Task No Task PPE to be worn Plant required Reference is made to the Team Pack risk assessment
3.12 Repair of Ductile iron & PVC/HPPE Main As defined by on-site risk assessment Cable avoidance equipment, works vehicle and hand tools (Excavator depending on depth/location of main) N/A

Hazards

  • Utilities exposed (Underground & Overhead)
  • Unstable Ground
  • Traffic
  • Hand Arm Vibration
  • Pressurised systems
  • Manual Handling
  • Confined Spaces
  • Entry into Third Party Property
  • Services Buried in concrete
  • Dewatering Excavations

Environmental Impacts

  • Carbon Emissions
  • Silt from dewatering
  • Waste
  • Light/Noise from Night working

Customer Impacts

  • Discoloured Water
  • Access
  • Dust
  • No Water
  • Inconvenience
  • Light/Noise from Night working

Training Required

As Per IMR specific contract training matrix

Additional Plant and Equipment

  • Dewatering pumps/systems
  • Excavation support systems

Permits Required

As Per IMR specific contract specifications and Client requirements.

COSHH Assessment Required

  • Diesel & Petrol
  • Co2
  • Chlorus
  • Coal Tar

Sequence of Operations and Control Methods

Site Setup and Service Location

  • Arrive on site and park vehicles in a safe area.
  • Set up traffic management signs and safe working exclusion zones in accordance with NRSWA Chapter 8 requirements. (Clancy Traffic Management (CTM) may have already erected the traffic management system).
  • Review all service drawings and conduct a comprehensive visual review of street/house furniture and road/location area for evidence of service installation.
  • Review location for overhead cables and other hazards and for any potential environmental concerns. In the event of overhead power lines contact your supervisor who will seek advice from the service provider (Northern Grid/Western Power Ltd). All work will be in accordance with GS6 exclusion requirements.
  • Complete the Excavation Dynamic Risk Assessment and the Permit to Dig documentation.
  • Using the Cat & Genny locate and mark-up services within the area adjacent to and beyond the intended excavation area.

Excavation

  • Hand dig to expose all known services within the intended work area, exposed services are to be supported at a maximum of one support per meter length.
  • Where required cut and remove tarmac and immediate sub-base.
  • If the excavation is within a carriageway test for the presence of Asphalt containing coal tar using the PAK spray.
  • Where excavators are to be used ensure safe-digging techniques/trial holes are used especially where gas services are present at the location.
  • In the event of a repair on a PVC main then the main water pressure shall be reduced/isolated prior to exposing the main.
  • If ground conditions dictate or excavation exceeds 1.2 metres complete a site specific risk assessment for trench support.
  • If trench support is required it must be installed by a competent person. Refer to Supervisor/Line Manager for an Approved Safe System of Work. Deep excavations that are not stepped or battered and require a support system to be installed will require a Temporary Works Design.

Dewatering

  • Where water has to be removed from the excavation then dewatering pumps should be used in conjunction with silt bags and the directed onto adjacent ground. Where suitable ground is not available the excavation water can be discharged into surface water drains.
  • For large excavations where considerable dewatering is required then a dewatering system and silt filtration tank system will be required.

Main Repair Process

  • Once the main has been exposed and the leak identified the type of repair can be established: Cut piece repair or encapsulation collar. The excavation must be sufficient to both expose all sides of the main and provide sufficient working room that the repair can be undertaken safely.

Cut Piece Repairs

  • Cut piece repairs will require the isolation of the main by the Anglian Water NT.
  • The methodology for cutting the main will depend on the size, thickness and material of the main and can include stihl-saw (Utilising the correct blade for the material), Keel-cutters or hand tools.
  • Once the damaged section of the main has been removed then the new section of pipe work can be installed. Where large sections of main have to be lifted into the excavation by the excavator then an Excavator Lift Plan will be required.
  • Where new pipe sections/valves are to be placed manually into the excavation then operatives should ensure that the manual handling activity risks are reduced to a minimum.
  • Once the new section of main has been installed and supported then both the existing and the new section of main will be thoroughly disinfected using the Chlorus solution. (Refer to COSHH assessment).
  • The repair can then be undertaken by the chosen method: electrofusion, push-fit or bolted flange.

Encapsulation Collar Repairs

  • Encapsulation Collar repairs may be undertaken with the main under pressure/reduced pressure at the discretion of the NT and the IMR repair team.
  • The large encapsulation collars Viking Johnson Easy-Clamp or AVK Supacollar can weigh up to 80 kg and therefore should be disassembled prior to being lifted into the excavation to reduce manual handling injuries. The encapsulation collar should then be reassembled and supported in situ and tightened securely.

Completion

  • Once the repair has been completed the main can be released to the NT for de-isolation/re-charging. PVC mains will require to be secured/weighted with excavation material to prevent movement prior to commencing de-isolation/re-charging.
  • When the water pressure is restored to the main a visual inspection of all joints is to be made. If a leak is observed then the main will require to be de-pressurised prior to the repair being made.
  • Following the de-isolation/re-charging of the main the excavation can be back-filled with material in accordance with the Hawk (Yellow Book) Specification or left for the Reinstatement team to complete.
  • The site is then to be cleared and left in a safe and tidy manner, be aware of the surrounding area and public access requirements. (Make sure the site is left in the correct manner to avoid section 74 charges).
  • Excavation barriers and traffic control/signage must be left in place until full reinstatement of the site has been completed. Where either a deep excavation or an excavation in a residential/populated area or other area of concern is present then the excavation must be protected by double-clipped Heras fencing.