Utility Strike Prevention RAMS: CAT & Genny Surveys, Permits & Risk Controls

Table of Contents

• Utility Strikes in UK Construction: The Scale of the Problem
• Legal Framework: CDM 2015 and HSG47
• CAT & Genny Surveys: What Your RAMS Must Address
• Service Records, Drawings, and PAS 128
• Permit to Dig Systems
• Safe Excavation Methods Near Services
• What Your RAMS Must Cover
• Frequently Asked Questions
• Next Steps

Utility Strikes in UK Construction: The Scale of the Problem

Utility strikes — damage to underground cables, gas pipes, water mains, or telecoms during excavation — kill and seriously injure construction workers every year. The Health and Safety Executive estimates there are around 60,000 utility strikes on UK construction sites annually. Many are not reported. Those that are often result in prosecutions, significant fines, and in the worst cases, fatalities from gas ignition, electrocution, or flooding.

Under CDM 2015, the duty to identify and manage buried service risks lies with the contractor carrying out excavation works. This cannot be delegated or ignored. Your RAMS must demonstrate that you have taken all reasonably practicable steps to identify services before excavating and that you have implemented adequate controls to prevent strikes during excavation. This guide explains what a compliant utility strike prevention RAMS looks like.

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Legal Framework: CDM 2015 and HSG47

The primary sources of duty and guidance for utility strike prevention are:

• CDM 2015 — Requires the principal contractor to ensure that the preconstruction information provided to all contractors includes details of services in the ground. Contractors must risk assess all excavation works in the context of buried services.
• HSG47 (Avoiding Danger from Underground Services) — The HSE's primary guidance document on buried service risks. It describes the full process of service identification, safe digging practice, and permit systems. Your RAMS should reference HSG47 and demonstrate compliance with its principles.
• Health and Safety at Work Act 1974 — The overarching duty to ensure, so far as reasonably practicable, that workers and others are not exposed to risks from the work.
• Electricity at Work Regulations 1989 — Specific duties in respect of work near live electrical conductors, including buried cables.
• Gas Safety (Installation and Use) Regulations 1998 — Duties in respect of gas pipework, including avoiding damage to buried gas infrastructure.

CAT & Genny Surveys: What Your RAMS Must Address

A Cable Avoidance Tool (CAT) and Signal Generator (Genny) survey is the minimum baseline requirement for excavation near buried services in the UK. Your RAMS must specify:

• Who carries out the survey — The CAT & Genny survey must be carried out by a trained and competent operative. CAT & Genny training is available from NRSWA and various specialist providers. Untrained operatives should not use these instruments.
• When the survey is carried out — The survey must be carried out immediately before excavation begins in each area. A survey carried out days or weeks earlier is insufficient because services can be temporarily installed and removed.
• How the survey is documented — Survey results should be marked on the ground using spray paint or flags and recorded on a service drawing. Your method statement should describe how survey results are communicated to the excavation crew.
• Limitations of CAT & Genny — Your RAMS must acknowledge that CAT & Genny surveys have limitations. They cannot detect plastic pipes, fibre optic cables without metallic sheathing, or non-metallic service markers. Additional survey methods may be required where these service types are suspected.

CAT & Genny surveys are a critical control but not a guarantee. Your RAMS must include further controls for safe digging in addition to the survey.

Service Records, Drawings, and PAS 128

Before any ground investigation or excavation begins, service records from all utility companies and asset owners must be obtained. Your RAMS should confirm:

• Dial Before You Dig (LSBUD) — Searches through the Land and Sea Underground Damage (LSBUD) service and individual utility companies. Records must be obtained for all service types: electric, gas, water, telecoms, and drainage.
• As-built drawings — Service drawings from utility companies show the recorded position of services. Your RAMS should acknowledge that these drawings are indicative and not always accurate to the position of actual services.
• PAS 128 surveys — For higher-risk excavations (near high-voltage cables, high-pressure gas mains), a utility mapping survey to PAS 128 (Specification for underground utility detection, verification, and location) may be required. PAS 128 surveys use ground-penetrating radar, electromagnetic induction, and other technologies to improve service location accuracy.

Permit to Dig Systems

A permit to dig (PTD) system provides a formal check before any ground-breaking activity begins. Your RAMS should specify whether a PTD is required and, if so, describe the system. A typical PTD process includes:

• Service records review and confirmation that records have been obtained
• CAT & Genny survey completed and results documented
• Ground marking completed with service positions and exclusion zones
• Safe digging method confirmed (trial holes, hand digging, vacuum excavation)
• Authorised signatory (supervisor or above) signing the permit before work begins
• Any deviation from the approved method requiring re-authorisation

For works involving high-voltage cables or high-pressure gas mains, PTD systems must be applied. For all other excavation works in areas with known services, PTD represents best practice.

Safe Excavation Methods Near Services

Your method statement should specify safe excavation methods to be used in areas with buried services:

• Trial holing — Before machine excavation proceeds in a service corridor, hand-dug trial holes should locate services precisely. Trial hole positions should be agreed with the supervisor.
• Hand digging in service corridors — Within 500 mm of a located service, hand digging (spade and bar) must replace mechanical excavation. Pneumatic tools should not be used within this exclusion zone.
• Vacuum excavation (suction excavation) — The safest method for exposing buried services. Vacuum excavation is non-percussive, minimises the risk of striking and damaging services, and is increasingly required by network operators for works near their assets.
• Mechanical plant exclusion zones — Define the exclusion distance from located services within which mechanical plant cannot operate. Typically 500 mm to 1 m depending on service pressure/voltage.

What Your RAMS Must Cover

• Reference to HSG47 and relevant service operator requirements
• Service record searches: LSBUD, individual utility companies, PAS 128 if required
• CAT & Genny survey procedure: who, when, how, limitations
• Ground marking system: colours, flags, exclusion zones
• Permit to dig system if applicable
• Safe digging methods: trial holing, hand digging, vacuum excavation
• Machine exclusion distances from located services
• Emergency procedures: what to do if a service is struck (gas: evacuate and call National Gas Emergency 0800 111 999; electric: do not touch, call DNO)
• Supervision requirements: constant supervision during excavation near services
• Competency requirements: CAT & Genny operator training evidence

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Frequently Asked Questions

Q: Is a CAT & Genny survey always enough to identify buried services?
A: No. CAT & Genny surveys cannot detect non-metallic services (plastic pipes, fibre optic cables). They are also limited by ground conditions, service depth, and the skill of the operator. CAT & Genny surveys must be supplemented by service records and, for higher-risk excavations, PAS 128 surveys or other detection methods.

Q: What is the emergency procedure if a gas pipe is struck?
A: Stop all work in the area immediately. Evacuate all personnel to a safe distance. Do not use any ignition sources. Call the National Gas Emergency Service on 0800 111 999. Do not attempt to repair the pipe. Your RAMS must include this procedure and operatives must be briefed on it before work begins.

Q: Do we need a permit to dig for all excavation works?
A: A formal PTD system is a legal requirement in some circumstances (e.g., under network operator rules for works near their assets). For other excavation works in areas with known services, PTD represents best practice and is strongly recommended. Your RAMS should confirm whether a PTD is required for the specific project.

Next Steps

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