HSE figures show this isn't a "bit of a shock" risk -- people die every year from hitting buried cables and overhead lines, and a single strike can finish your business as well as your day.
4.26.1 Why this matters
HSE stats show contact with electricity kills around a dozen people and seriously injures hundreds every year in the UK, with a big chunk caused by hitting cables and lines during work. Over five recent years, 354 people suffered life-changing injuries just from striking underground electricity cables, mostly construction and utilities workers. Add gas mains, water mains, telecoms and sewers and every strike becomes a mix of danger, delay, cost and investigation.
The two big HSE guides here are:
- HSG47 -- Avoiding danger from underground services.
- GS6 -- Avoidance of danger from overhead power lines.
This guide is how to actually follow the spirit of those books when you're stood in a garden or on a small site with a bucket and a deadline.
4.26.2 The core rule: plan, locate, then dig
HSG47 can be summed up in three words: plan, locate, dig -- in that order.
Plan
- Decide exactly what you're doing and where -- trench routes, post holes, footings, duct runs, plant access.
- Get service information before anyone breaks ground, on anything more than the tiniest hole.
- Allow time and money for scans, trial holes and possible diversions -- not just "turn up and dig".
Locate
- Use utility plans to understand what might be there, but never treat them as precise -- position and depth are often only approximate.
- Scan with a CAT and Genny (cable avoidance tool and signal generator) or equivalent, used by someone who's had proper training.
- Mark suspected routes on the ground before you start.
Dig
- Start with hand digging and trial holes in risk areas.
- Use insulated tools near suspected electricity cables.
- Only bring in plant once you've proved where services are and set no-go strips.
If you skip the first two steps, you're not "being efficient" -- you're gambling with lives and your insurance.
4.26.3 Legal duties and key regulations
Several bits of law sit behind this:
- Electricity at Work Regulations 1989 -- require you to prevent danger from electrical systems, including underground cables and overhead lines, so far as reasonably practicable.
- Gas Safety (Management) Regulations 1996 -- put duties on gas network operators to manage gas safely; from your side it means you must avoid damaging mains and follow emergency procedures if you do.
- CDM Regulations 2015 -- put duties on clients, designers and contractors to avoid foreseeable risks, give information, and plan work safely (services included).
In practice:
Contractor / person doing the work
- Has to plan and carry out work to avoid damaging services where it's reasonably practicable to do so.
- Must follow recognised guidance like HSG47/GS6 if they want to show they've done the right thing.
Client / site owner
- Under CDM, must provide relevant information they hold about existing services and not hide or ignore known risks.
If you ignore the guidance and clout a main, expect HSE to take an interest -- they prosecute where people are killed or put at significant risk, and fines in this area are often heavy.
Your public liability might cover some damage costs, but it won't get you off the hook with HSE or the courts if they decide you've been negligent.
4.26.4 Getting utility information (plans and where they fall short)
Before you dig anything meaningful, you want to know what's down there -- or at least what might be.
How to get plans
Linesearch Before U Dig (LSBUD) and similar
- Online "dial before you dig" services used by many major utilities for free plan requests.
- You enter the site area and it notifies participating asset owners, who then send you plans or contact you.
Direct from utilities
- Local DNO (electric network operator), gas transporter, water company, telecoms -- all can provide network plans, usually via online forms.
Client / principal contractor
- On proper sites, they should already have gathered this info as part of the pre-construction pack.
Limits
- Plans are often approximate -- a cable shown might be a metre or more out from where it actually lies, and depths are rarely guaranteed.
- Private services (garden feeds, private site cabling, homeowner-installed drains) might not appear anywhere.
So you treat plans as a warning, not a map -- they tell you where to be extra careful, not where you can switch off your brain.
4.26.5 CAT and Genny, training and trial holes
Using a CAT properly is a skill, not "wave it till it beeps."
Good practice
- Use the CAT with a signal generator (Genny) wherever possible, to improve detection of metallic services.
- Make sure the operator has had real training, not just a two-minute toolbox talk -- EUSR/Energy & Utility Skills run recognised courses, and many hire firms offer half-day CAT training with the kit.
- Scan the whole work area and a buffer either side in multiple modes (power, radio, Genny).
- Mark suspected lines on the ground -- paint, flags, pegs.
- Use trial holes by hand at key points to confirm position and depth.
You don't assume "no beep = nothing there." You assume "no beep = nothing detected -- still dig carefully until you've proved it."
4.26.6 Safe digging -- what "careful" looks like
Once you know where services might be, you change how you dig rather than just cracking on.
Near suspected cables/pipes
- Establish a "danger strip" either side of the expected line where you only hand dig until the service is exposed.
- Use insulated spades/shovels for electric risk areas.
- Dig in thin slices, pulling material back towards you, not stabbing downwards.
- Support and protect exposed services; don't leave them hanging in mid-air or where plant can clip them.
Avoid
- Mechanical diggers, breakers, impact moles (underground boring tools used to punch a hole for services) or augers (powered drill bits for post holes and similar) in unknown ground or directly over known service routes.
- Concrete with cables in it is a particular killer -- a lot of serious arc-flash incidents come from breaking out slabs without isolating the buried cables first.
4.26.7 Overhead lines -- distances, plant and step potential
Overhead power lines kill people every year, mostly through plant, ladders or long materials getting too close.
Key points from GS6 and related guidance
- You must keep people and plant well clear -- clearances are measured in metres, not inches.
- For lower-voltage lines (up to 33kV), guidance typically works with minimum approach distances of around 3--4 metres for plant and people, with larger clearances for higher voltages and passing beneath.
- No part of your operations -- excavator arms, telehandlers, scaffold, ladders, long pipes -- should be able to swing or fall into that exclusion zone.
If you can't maintain safe distance
- Stop and speak to the network operator before any work starts.
- Options are: switch the line out (make it dead) while you work, fit protective barriers/insulation, or divert the line -- all at the DNO's discretion and usually at the client's cost.
Step potential -- why you don't walk towards a fault
If a live cable or overhead line hits the ground, electricity can spread through the ground around it -- the voltage can be different between your two feet, and that difference can kill you.
That's why the advice is not to stride towards the fault, but to shuffle away with your feet close together or hop clear if you're very close, keeping both feet at similar potential.
You never use a ladder or handle long metal sections under live lines unless you're absolutely sure you're outside the safe zone.
4.26.8 Special case: asbestos cement pipes
On older sites, some water mains and drainage pipes are asbestos cement.
If you hit and break one:
- You've now got a utility strike and an asbestos incident.
- Don't dry sweep; keep people away, damp down to reduce dust if safe, and treat fragments as asbestos-containing waste.
- Follow your asbestos procedures (see guide 4.4) and involve specialists where required.
It's another reason to identify and expose services carefully rather than smashing straight through.
4.26.9 Small domestic jobs vs bigger sites
You're not commissioning a full utility survey for a short garden wall, but "just dig it" still isn't good enough.
Small domestic job (garden wall trench, small extension footings, drive)
Minimum you should do:
- Ask the client what they know: Where do gas, electric and water enter the house? Where are the meters and manholes?
- Look for clues: Meter boxes, service heads, external cables, inspection covers, old repair patches in drives.
- Assume services run in sensible lines: From the road to the meter, from the house to the garage, from stacks to manholes.
- If you're digging near those routes: Use a basic cable locator if you have one, or dig trial holes by hand to prove depth and position before you go deeper.
- Avoid using impact moles or deep augers in unknown ground.
If you're going to be close to obvious services and you're not sure, be honest with the customer: either you price in extra careful work, or you walk.
Bigger contractor-run site
You should expect:
- Utility plans provided as part of the construction phase plan.
- Ground marked up with known service routes.
- RAMS that cover CAT scanning, trial holes, safe dig zones and overhead line controls.
- Briefings/toolbox talks on where you can and can't dig and what plant is allowed where.
You still have a duty to follow the system and speak up if it doesn't look right. If you can see a conflict between the paperwork and reality and say nothing, "I was just following orders" won't impress HSE later.
4.26.10 If you hit a service -- what to do
When it goes wrong, your job is not to be a hero -- it's to keep people alive and not make it worse.
Hitting a live electricity cable
- Stop work immediately.
- If you're in a machine in contact with the cable, stay put if you can and call for help; stepping out can be deadly because of step potential.
- Keep everyone else away; treat the area as live.
- Don't touch the cable, the damaged tool, or any exposed metalwork.
- Call 999 and your local DNO emergency number.
Hitting a gas main
- Stop work; no smoking or ignition sources.
- Evacuate the area -- gas can travel into buildings and low spots.
- Call 0800 111 999 (National Gas Emergency Number).
- Call 999 if there's a fire or major escape.
- Don't try to stop the leak yourself -- leave it to the gas emergency team.
Bursting a water main
- Stop work and keep people away from undermined ground -- water can wash out trenches and supports.
- If safe, try to channel water to avoid flooding buildings.
- Call the local water company emergency number (on bills and their website).
After any strike
- Report it -- on bigger sites this may be RIDDOR reportable, especially if there was potential for serious harm.
- Expect questions from the client, the utility, insurers and possibly HSE.
- Being able to show you followed HSG47/GS6 -- plans, scans, trial holes, safe system of work -- makes a huge difference to how that conversation goes.
What to do next
For your own jobs, at a minimum:
- Build "plan, locate, dig" into your normal routine -- don't let anyone put a bucket in the ground until you've at least asked about services and walked the site.
- Get yourself or someone on your team properly trained on CAT and Genny use -- look at EUSR/Energy & Utility Skills or hire-firm courses.
- Decide how you'll handle small domestic work: a simple checklist for asking about meters, manholes and obvious routes, plus trial holes where needed.
- For anything near overhead lines, set a hard rule: if plant could reach it, we stop and speak to the DNO before work starts.
- Write this down in your RAMS so it's not just "what we usually do when we remember."
Sources
- HSE -- HSG47: Avoiding danger from underground services -- hse.gov.uk/pubns/books/hsg47.htm
- HSE -- GS6: Avoidance of danger from overhead power lines -- hse.gov.uk/pubns/gs6.htm
- Electricity at Work Regulations 1989 -- legislation.gov.uk/uksi/1989/635/contents/made
- Gas Safety (Management) Regulations 1996 -- legislation.gov.uk/uksi/1996/551/contents/made
- Construction (Design and Management) Regulations 2015 -- legislation.gov.uk/uksi/2015/51/contents/made
- Energy Networks Association -- utility strike data and prevention guidance.
- HSE electrical injury statistics -- annual reports on workplace electrical fatalities and injuries.
- Academic study on causes, impacts and costs of strikes on buried assets -- cited in HSE and utility industry publications.
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