Cable strikes still rank among the most disruptive and high-consequence events on UK sites. They injure people, shut down programmes, trigger claim chains, and wreck client confidence. The fundamentals have not changed: good planning, competent locating, and a permit-to-dig that actually governs the work, not just the paperwork. If you’re breaking ground anywhere near built environments or known corridors, treat service avoidance as a controlled operation in its own right.
TL;DR
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– Don’t dig without a live permit-to-dig that matches the exact line, depth and method.
– Use a competent person to CAT and Genny scan, in multiple modes, immediately before starting.
– Prove positions with trial holes and hand-dig within marked tolerance zones.
– Keep controls live: re-scan after layout changes, weather, or delays; stop at uncertainty.
A staged control plan for live-service avoidance
# Stage 1: Gather records and map the risk
/> Request all available utility plans early, including statutory, private, and recent as-builts from previous phases. Plot likely corridors on a site plan and walk them with the supervisor, the excavator driver, and the person who will operate the locator. If plans conflict or are missing, assume services are present and set out a conservative search area. Record the assumptions; they drive the permit conditions.
# Stage 2: Build the permit-to-dig with the method, not after it
/> Draft the permit alongside the RAMS so they agree on line, depth, plant, hand-dig zones, and stop points. The permit should specify who scans, what locator is used, marking colours, and where trial holes are required. Include plant exclusion distances, standby person arrangements, and immediate stop/escalation triggers. Time-limit the permit so it can’t go stale as the programme shifts.
# Stage 3: Competent CAT and Genny scanning, then mark and brief
/> Use a known, calibrated CAT and Genny, operated by someone competent with that model. Scan in multiple modes (power, radio, and Genny with direct connection or clamp) and in two directions. Mark the ground with durable paint and pins, photograph the markings, and transfer the results back to the permit sketch. Brief the crew at the workface so they know what the lines mean and where they cannot use mechanical plant.
# Stage 4: Prove by trial holes and safe hand-digging
/> Treat scan results as indicative until proven. Excavate trial holes at pinch points and crossings, using insulated tools and careful arisings control. Once services are found, expose sufficient length to confirm direction and depth and protect them with boards or matting. Update the permit with confirmed positions and agree revised method if tolerances are tighter than expected.
# Stage 5: Control the dig — spacing, exclusion and stop rules
/> Maintain a clear buffer either side of plotted lines and never allow buckets to pass over exposed services. Keep the excavator and banksman in constant radio or eye contact and prohibit mobile phone distraction. Stop work if markings wash off, the route deviates, or the digging feels “different” (unexpected resistance or backfill change). Isolate ignition sources if gas is suspected and call the service owner if damage or exposed conductors are seen.
# Stage 6: Backfill, sign-off and update the record
/> Before backfilling, photograph exposed services with measurements from fixed features and record any protective measures installed. Backfill with suitable material and warning tape to a consistent depth. Remove or revise markings so future crews don’t rely on outdated information. Close out the permit, file the records, and feed confirmed service data into site orientation briefings.
Site scenario: EV charger trench across a retail car park
/> A civils subcontractor is asked to trench 120 metres across a live retail car park to feed new EV chargers. The client provides several drawings, but they don’t agree: one shows a high-voltage route along the kerb; another shows it crossing the bays. Under programme pressure, the team plans to scan on the morning and dig the same day. Rain the night before washes off some of the spray marks, and the labourer replaces them from memory. The excavator clips a duct that wasn’t on the plan and trips a local supply; the car park is evacuated. Post-incident, the root causes include a stale permit that didn’t reflect the marked deviation, no trial hole at the crossing, and a rushed brief. The remedial effort and client complaint consume the rest of the week and add costs that nobody priced.
Common mistakes that still cause strikes
# Treating a service drawing as gospel
/> Plans are often out of date or approximate. Use them to guide scans and trial holes, not to justify digging fast.
# Scanning in ‘power’ only and missing comms
/> Relying on a single CAT mode misses dead or screened cables and plastic ducts. Use the Genny and multiple modes; prove by excavation.
# Letting the permit go stale during programme slips
/> A two-week-old permit is not permission to break ground today. Re-validate after delays, heavy weather, or route changes.
# Using metal tools close to suspected cable lines
/> Non-insulated crowbars and picks are unforgiving near live conductors. Use insulated hand tools and proceed in thin layers.
Supervisor walk-round checklist before breaking ground
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– Permit-to-dig aligns with the exact line, depth and method stated in the RAMS.
– Latest utility records and marked-up plan are at the workface and match site markings.
– Today’s CAT and Genny scan completed by the named competent person, with modes noted.
– Markings are legible, protected where needed, and photographed; tolerance zones are obvious.
– Trial holes identified on the ground; hand-dig zone physically demarcated with barriers.
– Stop points, contact numbers for service owners, and emergency actions briefed to every person in the dig team.
Programme pressure vs permits: keep control
# Priorities for the coming week on service avoidance
/> Schedule a short demonstration with your actual locator model for supervisors and banksmen. Walk the planned trench with the client or facilities contact to uncover any private feeds not on statutory plans. Refresh faded markings after wet weather and replace tape barriers so the route is respected. Remove casual language from RAMS like “no services present” unless you have proved it by scan and trial holes. Stand up a simple rule: if anyone is unsure of a service position, the dig pauses until a re-scan is done.
Bottom line on avoiding buried services
/> Safe digging is a managed process, not a morning task to be ticked off. Permits, scanning, and trial holes must control the work in real time, not just satisfy a pre-start document. Watch for programme pressure and competence drift; those are the cracks where strikes happen. Ask yourself: would I be happy to put my bucket over that spot based on the evidence I have?
FAQ
# When is a permit-to-dig necessary?
/> Use a permit whenever there’s potential to contact buried or hidden services, including small excavations, fence posts, and trial pits. It’s good practice to extend the same control to core drilling and breaking near suspected routes. If in doubt, treat it as a permit-required task and scale the controls to the risk.
# How often should CAT and Genny scans be repeated?
/> Scan immediately before breaking ground and again if the route, weather, or surface conditions change. Re-scan after any delay or shift handover so the incoming team owns the information. If you deviate from the line or deepen the excavation, treat it as a new search area.
# Who is competent to operate a CAT and Genny?
/> Competence comes from training on the specific device and enough field experience to interpret signals and recognise limitations. Supervisors should confirm the named operator understands all modes, battery checks, calibration status, and how to use direct connection or clamps. Keep a simple record of training and familiarisation with the model used on site.
# What’s sensible practice for hand-digging near suspected cables?
/> Use insulated spades and shovels, take thin layers, and never stab downwards. Keep arisings clear so you can see the excavation face and stop immediately if you uncover anything unexpected. Establish a narrow hand-dig corridor where mechanical plant is excluded until services are proven.
# How do service-avoidance controls tie in with temporary works and traffic management?
/> Coordinate excavation support, edge protection, and crossing points so exposed services aren’t undermined or struck by vehicles. Mark plant routes and pedestrian walkways to keep pressure off tolerance zones and prevent over-run of markings. Where temporary works designs are affected by service positions, involve the TWC early and capture confirmed locations in the design risk register.
