Striking buried services remains one of the most serious groundworks risks on UK sites. A permit to dig, used properly, is not just paperwork; it is the control that sequences planning, detection, supervision and stop-work triggers into a single, auditable process. The aim is simple: no breaking ground until you can explain, on the spot, where services are, what the safe method is, and when you’ll stop.
TL;DR
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– Treat every excavation as live until proven otherwise by up-to-date plans, detection and trial holes.
– Build a staged permit process: early mapping, method selection, permit brief, locate-before-you-dig, controlled break, adapt, close-out.
– Use competent people for scanning and trial holes; hand-dig near suspected services and keep a trained spotter on task.
– Stop immediately if markings don’t match, unknown apparatus is found, or plant/traffic changes the risk picture.
– Record what you actually find and update as-builts before closing the permit.
Controls playbook for safe breaking ground
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Stage 1 – Map what’s underground before you plan the dig
Start with all available information: utility enquiries, client O&M packs, previous as-builts, private network information, and recent surveys. Walk the area; look for street furniture, route logic (valves, kiosks, marker posts), and recent reinstatements. Overlay everything onto one drawing and mark uncertainty zones. Identify high-risk corridors such as footway strips, site entrances, and previous carriageway crossings. Define areas where invasive work should be avoided until further proved.
# Stage 2 – Align methods with risk and temporary works
/> Select a method that fits what you think is below. Hand-dig first where services are suspected; consider vacuum excavation where congestion is likely. Coordinate with temporary works for shoring, trench boxes, edge protection and support to existing structures or slabs. Plan plant routes and pedestrian interfaces so excavators aren’t slewing across service corridors. Build in safe access/egress and lighting for early starts and late finishes.
# Stage 3 – Build the permit and brief the team
/> Draft the permit with supporting risk assessment and method statement. Confirm responsibilities: who issues, who holds, and who closes out. Set competence requirements for cable avoidance tool users and spotters; verify calibration and training records. Brief everyone at the workface with a marked-up plan and ground markings, explain the safe dig sequence and explicit stop-work triggers. Put the permit on display at the excavation with the latest drawings.
# Stage 4 – Locate before you excavate
/> Use multiple detection modes and sweep patterns with a cable avoidance tool and signal generator; don’t rely on a single pass. Mark both positive finds and no-go zones on the ground and on the plan. Open trial holes to confirm position and depth—photograph and tag findings. Treat all apparatus as live unless isolated and proven otherwise by a competent person. If findings differ from expectations, stop and re-plan; do not “press on”.
# Stage 5 – Controlled break of ground
/> Do a last-minute risk assessment and confirm the permit is in date and signed. Establish an exclusion zone and keep plant and deliveries out of marked service strips. Use insulated hand tools when approaching indicated lines and keep mechanical excavation away from unproven ground; within about half a metre of suspected services, hand-digging is typical good practice. Keep a dedicated, briefed spotter focused on the operation—no dual roles. Communicate clearly between operator, banksman and ground workers; if vision is lost or markings fade, pause and re-establish controls.
# Stage 6 – Monitor, record and adapt to change
/> Conditions change quickly with weather, lighting, plant swaps and new trades nearby. If you expose an unknown service, a void, or damaged protection, stop, make safe, and escalate. Protect exposed apparatus with suitable coverings or supports; never leave live services hanging or buried under spoil. Record actual positions with measurements and photos, and update the marked-up plan daily. Note any deviations from the method and revise the permit if the scope shifts.
# Stage 7 – Close out and hand back safely
/> Before backfilling, confirm inspections are complete and any statutory or client checks arranged. Reinstatement should include suitable bedding, marker tiles or tapes, and clear surface markers where needed. Remove temporary supports only when it is safe and agreed. Update as-built information and share it with the site team and client so the next dig starts from a better baseline. Close the permit formally and archive it with key photos and notes.
A very familiar near-miss: civils tie-in at a site entrance
/> A roads and sewers crew on a housing development had a weekend window to install a new drainage connection across the entrance. Utility plans were on file, but the private LV supply to the marketing suite wasn’t shown clearly. Under programme pressure, the excavator opened up after a single CAT sweep and marked water and telecoms only. At 600 mm, the bucket exposed a bitumen-wrapped cable in the trench wall; the banksman shouted and the operator froze. They halted works, fenced off, and the DNO confirmed it was a live low-voltage feeder across the gate installed years earlier. Monday’s re-plan brought in vacuum excavation, extended the exclusion zone, and the team updated the site services plan with photos and coordinates. The permit process was revised to include private networks and weekend staffing arrangements for isolations and support.
Permit-to-dig essentials: a quick walk-round checklist
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– Verify the permit on display is current, signed, and matches the exact area and depth of work.
– Confirm ground markings, latest service drawings, and photos of trial holes are available at the workface.
– Ask the spotter to explain the safe dig sequence and stop triggers; check they’re not doubling as another role.
– Inspect insulated tools, CAT/genny calibration date, and evidence of operator competence.
– Check exclusion zones, plant routes, and pedestrian controls are holding up under real site traffic.
– Look for exposed or newly found services; ensure they’re supported, protected, and recorded.
– Confirm as-builts and mark-ups are being updated daily before closing or extending the permit.
Common mistakes during groundworks permits
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Relying on utility plans as the sole truth
Plans can be outdated, incomplete, or mis-scaled, especially for private networks. Use them to guide detection, not to replace it.
# Treating the permit as a one-off green light
/> A permit is live only while conditions match the plan. Scope creep, plant changes or fading markings require a pause and reissue.
# Letting scanning become a tick-box exercise
/> Single-pass, single-mode sweeps miss complex or shallow services. Use multiple modes, repeat passes, and open trial holes to confirm.
# No clear stop-work authority at the trench
/> If nobody feels empowered to halt the dig, small doubts get ignored. Make it explicit who can stop and how escalation works out of hours.
Bottom line for permit-to-dig discipline
/> A good permit to dig gives you confidence that people, plant and plan are aligned, and that stopping is as easy as starting. The control lives or dies on supervision at the trench, the quality of locate-before-you-dig activity, and the willingness to adapt when the ground tells a different story.
# In the next 7 days: harden buried-services control
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– Map private supplies by speaking to the client/FM and walking the site for informal markers and recent reinstatements.
– Convene a 15-minute trench-side brief on stop-work triggers and the escalation route, including weekends.
– Audit CAT/genny use by silently observing a sweep and asking the operator to explain their method.
– Swap generic insulated tools for clearly tagged, voltage-rated sets at each excavation, not just in the stores.
– Ring-fence scanning and spotting as dedicated tasks on the programme so they aren’t squeezed by plant productivity.
The push on buried services is not going away, and enforcement attention tends to follow repeat strike trends and weak supervision. Ask yourself before any dig: where do we think services are, how do we know, and who will stop us if that changes?
FAQ
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Who should issue and hold a permit to dig?
On most sites, the principal contractor designates a competent permit issuer who understands the service risks and the method. The permit is held at the workface by the supervisor in charge, who keeps it current and visible. Issuing and holding should never be the same unchecked person for high-risk digs.
# What if utility plans are missing or obviously incomplete?
/> Treat the area as high risk and extend locate-before-you-dig steps with more scanning and trial holes. Speak to the client about private networks and look for on-site clues like kiosks, duct entries, or recent reinstatements. No plans plus no detection means no digging.
# How often should we rescan and remark during a job?
/> Rescan when the area extends, when conditions change (lighting, weather), after any long break, or if markings are unclear. Markings fade fast with traffic and rain, so refresh them and re-brief the team. Use photos to capture initial markings and trial holes for later cross-checking.
# How do we manage subcontractors working under our permit system?
/> Make the permit process part of their package and brief it before mobilisation. Check their competencies for scanning, spotting and excavation, and require their method to align with your permit controls. Stop the work if they attempt to vary methods or bring in different plant without reauthorisation.
# What should trigger an immediate stop during excavation?
/> Stop if you find uncharted apparatus, depths differ materially, the method changes, or exclusion zones are not holding due to traffic or access needs. Pause when communication breaks down or visibility of markings is lost. Make it routine to stop, reassess, and reissue the permit rather than pushing on.
