Key points to cover
- Before any excavation or ground penetration, obtain up-to-date utility plans from the asset owners and use a cable avoidance tool (CAT) and signal generator (Genny) to locate services
- Treat all located services as live until confirmed otherwise by the asset owner
- Plan and manage any work within 10 metres of an overhead power line, and keep plant out of a safety zone at least 6 metres from the outermost wire on each side of the line (GS6)
- Hand dig within 500mm of a known service — no mechanical excavation
- Mark the location of identified services with paint or markers before work begins
- Use insulated hand tools (spade, pick) when digging near known electrical cables
- Report any damage to underground services immediately, even if apparently minor — gas leaks and cable damage can escalate rapidly
Do's and don'ts
Do
- Obtain up-to-date utility plans from all asset owners before starting any excavation
- Use a CAT and Genny to scan the full work area before breaking ground — even if plans show nothing
- Hand dig within 500mm of any known or suspected service using insulated tools
- Mark the positions of identified services clearly on the ground
- Keep plant and equipment out of the barriered safety zone — at least 6 metres from the outermost wire on each side of the line, wider if the line owner advises
Don't
- Never assume an area is free of services because plans don't show any — plans can be incomplete or inaccurate
- Never use a mechanical excavator within 500mm of a known service
- Never use a metal pickaxe or bar near an electrical cable — use insulated hand tools
- Never drive plant or equipment under overhead power lines without a specific risk assessment and goalposts or barriers in place
- Never attempt to repair a damaged service yourself — evacuate the area and call the asset owner
Questions to check understanding
Q1: What is a CAT and Genny and why must they be used before excavation?
Show the answer
A CAT (Cable Avoidance Tool) is a handheld device that detects electromagnetic signals from underground cables and metallic pipes. A Genny (signal generator) is used with the CAT to apply a signal to a specific service so it can be traced more accurately. They must be used together before any excavation because utility plans alone are not reliable — they can be inaccurate, incomplete, or out of date, and should never be relied on for distances or depths. The CAT and Genny provide on-the-ground confirmation of service locations. Only trained and competent operators should use them.
Q2: How far should plant be kept from overhead power lines?
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HSE guidance GS6 says to manage the risk for any work within 10 metres of an overhead line, and to mark out a safety zone at least 6 metres from the outermost wire on each side of the line — wider if the line owner advises or a jib could reach into it. Physical measures such as goalposts, barriers, and defined crossing points should be installed to prevent plant from breaching the exclusion zone. If work must take place closer, consult the line owner about diverting the line or switching it off — if the work can't be done safely, it shouldn't be done.
Q3: Why must you hand dig within 500mm of a known underground service?
Show the answer
Because mechanical excavators can easily sever or damage buried cables, gas mains, and water pipes, causing electrocution, explosion, flooding, or loss of essential services. Hand digging with insulated tools allows the operative to feel for and carefully expose the service without striking it with force. HSE HSG47 says mechanical excavators must not be used within 500mm of a gas pipe or pipeline — hand dig to expose any known service before an excavator works near it.
This is general guidance for UK construction sites. Check it against your own risk assessment, method statement and the site before you deliver it.