Cable strikes remain one of the most stubborn causes of serious harm and programme damage on UK projects. Most “near misses” sound the same: the team had a plan, but the digline shifted, the locator stayed in the van, and the permit was treated as a form rather than a control. A permit-to-dig that actually prevents strikes is a live process: it blends reliable service information, competent locating, clear markings, controlled excavation and a supervisor who calls time when anything changes.
TL;DR
/>
– Make the permit-to-dig a live control with clear hold points, not just a piece of paper.
– Locate, mark and verify services using competent people and the right kit before any bucket goes in.
– Hand dig trial holes to prove positions and keep updating the plan as ground conditions change.
– Stop the dig immediately on any unexpected find, marker tape or signal change, and re-brief before restarting.
Permit-to-dig: a staged playbook that actually prevents strikes
# Stage 1: Build a reliable picture before breaking ground
/> Start with utility searches and client records, then challenge them. Arrange competent locating using a cable avoidance tool and signal generator, and consider a specialist survey where records are poor or the area is congested. Walk the area with the foreman, mark suspected routes, and note visible clues such as street furniture, joint boxes, scar lines and ducts. Agree where the “tolerance zones” are likely to be and plan your trial holes.
# Stage 2: Fix the boundaries on the ground
/> Transfer the paper plan onto the workface using durable paint, flags or pinned boards where paint won’t hold. Colour code and label directions so plant operators and banksmen can understand them at a glance. Establish a physical exclusion zone around marked services with barriers or bunting, not just cones, and place signage at all approach points. Keep a weatherproof copy of the permit and plan at the point of work.
# Stage 3: Issue a live permit with real hold points
/> The supervisor issues the permit only after seeing the markings, the locator results and the briefed team. Set explicit hold points: before the first trial hole, before exposing any suspected service, at depth changes, and at shift handovers. Define methods: hand digging with insulated tools in tolerance zones, vacuum excavation where feasible, and banksman control for plant. State stop-work triggers and escalation paths in plain language that the crew can repeat back.
# Stage 4: Prove, expose, and only then proceed
/> Open trial holes to confirm service positions and depths; record locations with photos against fixed references. Keep the locator in use as you progress, as signals can drift with ground conditions and coupling. Once a service is exposed, support and protect it with timber or guards, and brief the team on the new risks before continuing. Never allow toothed buckets or aggressive attachments near unproven ground in a tolerance zone.
# Stage 5: Manage change like a hazard, not an inconvenience
/> On any unexpected find—marker tape, duct cluster, altered signal strength, or a service where none was expected—down tools, clear plant away and re-issue the permit after reassessment. If the digline, depth or method changes, treat it as a new job: update markings, re-brief and reset hold points. Keep a simple log of changes and photos; those notes will protect the workforce today and the next trade tomorrow. Reinstate markings that fade or wash off; a wet morning can erase your boundaries by lunch.
# Stage 6: Hand back the ground safely
/> Before closing the permit, confirm services are undamaged and correctly supported or backfilled per specification. Update as-built information with confirmed locations, levels and photos and pass it to the project team. Remove temporary markers only after records are captured, and leave the area safe for follow-on trades or the public if it’s a live environment.
Site scenario: weekend drainage tie-in on a live retail park
/> A civils gang is booked for a weekend tie-in to a new drainage run across a car park outside a supermarket. The utility plans show a medium-voltage ring main and multiple comms ducts near the route, but the as-builts are old. The foreman and locator walk the line early Saturday, pick up strong signals and alter the trench by a metre to avoid a suspected cluster. The plant arrives, and pressure mounts to start; the permit is issued with a hold point at the first trial hole. At 400 mm, the team finds yellow marker tape and stops; the locator shows a different reading than earlier. The supervisor calls the DNO contact, confirms a slight deviation of the HV route, and revises the trench alignment. After re-marking and re-briefing, the gang uses vacuum excavation to expose and protect the cable before finishing the tie-in by hand on Sunday.
Common mistakes
# Treating the permit as paperwork
/> Issuing permits in the office without walking the workface leads straight to blind digging and missed changes on the ground.
# Over-reliance on old plans
/> Utility drawings are a starting point, not the truth. Failing to locate and prove positions causes false confidence.
# “One and done” locating
/> Doing a single scan and never re-checking ignores signal drift, coupling and ground changes as the excavation progresses.
# Letting pressure override hold points
/> Skipping trial holes or switching to bigger buckets to claw back time often leads to contact with unproven services.
Quick supervisor checklist for live digs
/>
– Walk the route with the locator operator and foreman; agree tolerance zones and planned trial holes.
– Confirm the permit states hold points, stop-work triggers, and the exact excavation method in risk areas.
– Check barriers, markings and signage are in place and readable from plant cabs and approach routes.
– Verify competence: who is trained to use the locator, who briefs the plant op, and who can stop the dig.
– Watch the first bucket: ensure hand digging happens where required and the locator stays in the work area.
– Re-brief at shift handover; update markings and the permit if the scope or conditions have changed.
Bottom line on permits and buried services
/> A permit-to-dig only works if it controls behaviour at the trench edge, not just ticks a box in the site office. The strongest sites make finding and proving services part of the method, bake in hold points, and stop the dig the moment anything doesn’t match expectations. The coming months will likely see more scrutiny on service strikes and permit quality; supervisors who can defend their controls with photos and clear briefings will be on solid ground. Ask yourself at the next briefing: who owns the hold points, what will make us stop, and how will we prove the ground before we touch it?
FAQ
# When should a permit-to-dig be used for small excavations?
/> Use a permit whenever there’s a chance of interacting with buried services or when the dig is within areas with previous utilities. Even shallow trial pits and fence post holes can hit cable or duct routes near buildings and roads. Treat the permit as a scaled control, not something reserved only for big trenches.
# Who should operate the cable locator and interpret results?
/> A competent person who understands the tool’s modes, limitations and how services behave underground should do this. They should work with the supervisor and foreman so the findings translate into markings and method. Rotate the scan as the dig progresses, and don’t let the device sit unused in the van.
# What’s the right response to unexpected marker tape or ducts?
/> Stop the dig, move plant out of the immediate area, and secure the trench. Re-scan, open a controlled trial hole by hand or with vacuum excavation, and seek guidance from the service owner if needed. Only restart after updating the permit, markings and briefing to reflect what you’ve found.
# How do we manage permit controls across multiple shifts or crews?
/> Build hold points that force a pause at shift changes, and keep the permit and plan at the point of work. Re-brief incoming crews, refresh markings that have faded, and confirm everyone understands stop-work triggers. If the method or line changes, re-issue rather than “carry on under the old permit”.
# Is vacuum excavation always required near suspected services?
/> It’s a strong option where ground allows and services are likely or poorly recorded, but it’s not the only method. Hand digging with insulated tools and controlled trial holes can be effective when space is tight or the ground is hard. Choose the method that keeps energy and metal away from unproven ground, and set clear hold points either way.
