Gas, Electric & Water Strikes on Site: Method Statement Requirements for Excavation Near Services

Table of Contents

• Why Utility Strikes Are One of Construction's Deadliest Risks
• Gas Services: Specific Risks and Controls
• Electrical Cables: Specific Risks and Controls
• Water, Telecoms, and Other Services
• Emergency Procedures: What Your Method Statement Must Include
• Exclusion Zones for Different Service Types
• Method Statement Requirements
• Frequently Asked Questions
• Next Steps

Why Utility Strikes Are One of Construction's Deadliest Risks

A utility strike is not just a property damage incident. Striking a live electrical cable can cause electrocution and arc flash injuries that can be fatal at distances of several metres. Striking a gas main can lead to a gas release that, if ignited, can cause a catastrophic explosion. Striking a water main can cause flooding, ground collapse, and secondary electrical hazards. Despite the well-known risks, the HSE estimates that around 60,000 utility strikes occur annually on UK construction sites.

Your method statement must demonstrate that you have identified the service risks at your specific site and implemented controls proportionate to those risks. A generic "look for services before digging" instruction is not sufficient. This guide explains what the method statement must include for each type of service.

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Gas Services: Specific Risks and Controls

Gas distribution networks in the UK operate at two primary pressure levels: Low Pressure (LP, up to 75 mbar) — typically the supply pipe to individual properties — and Medium Pressure (MP, up to 2 bar) — the distribution mains. High Pressure (HP) transmission pipelines are managed by National Gas Transmission and carry gas at pressures up to 85 bar.

Key controls for excavation near gas services include:

• Record searches — Obtain drawings from National Gas (National Gas Transmission), Cadent, SGN, Northern Gas Networks, or Wales & West Utilities as applicable for the distribution region. Records should be read in conjunction with LSBUD data.
• HP pipeline additional controls — For work near high-pressure transmission pipelines, National Gas Transmission has specific working requirements including minimum separation distances, agreement of safe working methods, and standby procedures.
• Mechanical plant exclusion distance — Do not use mechanical plant within 500 mm of a located gas service. Within this zone, use hand tools only.
• Gas detection — Where gas services are known or suspected in the vicinity, a 4-gas monitor (LEL, O2, CO, H2S) should be deployed in the excavation area during works.
• Emergency procedure — If a gas pipe is struck: stop all work, evacuate and keep clear of the area, do not use any ignition sources (no smoking, no mobile phones near the leak), call National Gas Emergency 0800 111 999 immediately.

Electrical Cables: Specific Risks and Controls

Electrical cables in the UK range from low-voltage service cables (230V single phase to individual properties) to high-voltage distribution cables (11 kV, 33 kV) and extra high-voltage transmission cables (132 kV and above). The severity of the risk increases with voltage, but even 230V single-phase cables can be lethal.

Key controls for excavation near electrical cables include:

• Record searches — Obtain drawings from National Grid Electricity Distribution (NGED), UK Power Networks, SP Energy Networks, or Northern Powergrid as applicable. Records from LSBUD and individual DNO requests.
• High-voltage cable additional controls — For work near HV cables (11 kV+), the DNO's network requirements must be obtained and followed. This may include notification requirements, standby requirements, or minimum separation distances.
• CAT & Genny survey — Provides additional confidence on cable location beyond records alone.
• Mechanical plant exclusion distance — Do not use mechanical plant within 500 mm of a located cable (further for HV cables — confirm with DNO). Hand digging only in the exclusion zone.
• Insulation and PPE — Operatives hand digging near electrical cables should wear electrically insulated gloves (Class 0 minimum for LV work) and use insulated tools where practicable.
• Emergency procedure — If a cable is struck: stop work, do not touch the cable or any plant in contact with it, evacuate all non-essential personnel, call the DNO emergency number immediately. Do not attempt to assess damage or repair.

Water, Telecoms, and Other Services

While strikes on gas or electrical services typically attract most attention, water main strikes can also cause significant harm:

• Water mains — A high-pressure water main strike can cause ground collapse, flooding of adjacent excavations, and failure of surrounding ground. Saturated ground can lead to trench collapse. Contact details for the local water company emergency number must be in your method statement.
• Telecoms and fibre optic cables — These carry lower risk of direct personal injury, but striking a major fibre optic trunk can cause significant disruption and lead to significant claims for consequential loss. Non-metallic fibre optic cables are not detectable with standard CAT & Genny equipment. Ground-penetrating radar or PAS 128 surveys may be needed.
• Drainage and sewers — Sewers carry foul water and may produce hydrogen sulphide gas. A struck sewer can flood an excavation rapidly. Sewers should be included in all service searches (contact Water Utilities and local authority for drainage records).
• District heating and chilled water mains — Present in many city centres and hospital campuses. Can operate at elevated temperatures and pressures. Often not included in standard utility searches — check with the site client and local authority.

Emergency Procedures: What Your Method Statement Must Include

Your method statement must include specific emergency procedures for each type of service present. These should be communicated to all site operatives in the site induction and toolbox talks before excavation begins.

• Gas strike — Stop work, evacuate, no ignition sources, call National Gas Emergency 0800 111 999
• Electrical cable strike — Stop work, do not touch, evacuate, call DNO emergency number
• Water main strike — Stop work, evacuate if flooding, call water company emergency number
• Sewer strike — Stop work, do not enter excavation (H2S risk), call water company emergency number

Emergency numbers must be displayed at the point of work, not just in the RAMS document in a site office. Consider laminated cards posted at the site entrance and near excavation areas.

For more detail on utility strike prevention RAMS, see our guide on Utility Strike Prevention RAMS: CAT & Genny Surveys, Permits & Risk Controls.

Exclusion Zones for Different Service Types

Your method statement should specify mechanical plant exclusion distances from located services. As a general guide (always verify with the network operator for specific requirements):

• LV electrical cables (up to 1 kV) — 500 mm minimum from located cable. Hand dig only within exclusion zone.
• HV distribution cables (11 kV–33 kV) — 1 metre minimum. Confirm with DNO. Additional notification may be required.
• EHV transmission cables (132 kV+) — Confirm with National Grid. Extensive controls required.
• Low pressure gas (LP) — 500 mm minimum.
• Medium pressure gas (MP) — 500 mm minimum. Notify network operator for works within 3 m.
• High pressure gas transmission — Confirm minimum distances with National Gas Transmission. Standby requirements likely.
• Water mains — 500 mm minimum. Confirm with water company for large mains.

Method Statement Requirements

A compliant method statement for excavation near buried services must include:

• List of service types identified from record searches
• Service drawings obtained and referenced
• CAT & Genny survey procedure and limitations acknowledged
• PAS 128 survey if required
• Ground marking system and exclusion zones
• Permit to dig system description
• Safe excavation sequence: trial holes, hand digging, machine exclusion distances
• Emergency procedures for each service type with emergency numbers
• Gas detection arrangements if applicable
• Competency requirements: CAT operator, NRSWA operatives
• Supervision: constant supervision during excavation near services

Frequently Asked Questions

Q: Can we use a mechanical digger right up to the edge of a located gas pipe?
A: No. The exclusion zone for mechanical plant around located gas services is 500 mm minimum. Within this zone, only hand digging with spade and bar is permitted. Pneumatic tools must not be used within the exclusion zone.

Q: Do we need to notify utility companies before we dig?
A: You must obtain records from all relevant utility companies before work begins. Some network operators (particularly for high-pressure gas and high-voltage electricity) require formal notification of works near their assets and may have specific requirements or standby arrangements. Check the conditions on each set of service records.

Q: What is a PAS 128 survey and when is it needed?
A: PAS 128 is the British Standard specification for underground utility surveys. It defines four quality levels of survey, from desktop records review (Level D) through to advanced detection methods including ground-penetrating radar (Level A). PAS 128 surveys are recommended for higher-risk excavations and are increasingly required by network operators and principal contractors for works near critical infrastructure.

Next Steps

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