A buried service strike is one of the quickest ways to turn a routine dig into an injury, outage and claim. A permit-to-dig isn’t paperwork for its own sake; it’s the control that pulls together utility searches, locating, supervision and change management into a single, unambiguous decision to break ground. On UK sites, the strongest permits are specific, time-limited and actively supervised. They define where you can dig, where you absolutely cannot, and the behaviours expected around the tolerance zone. If your permit doesn’t do that, it isn’t protecting anyone.
TL;DR
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– Treat utility plans as clues, not certainty; verify with scan and trial holes before any machine works.
– A permit-to-dig must be specific, short-lived, and linked to a clear mark-out, briefing and hold points.
– Hand dig with insulated tools in the tolerance zone; keep plant out until you’ve proved the route and depth.
– Stop, make safe and re-permit when conditions or information change—never “just carry on”.
– Photograph the mark-out, record scans, and close out with as-builts to avoid repeat risk.
Risk and control concepts that stop strikes
# Records are not reality
/> Utility plans and statutory searches are a starting point, not a green light. Depths change with ground movement, past alterations and unrecorded services; some assets aren’t on any plan. Good practice is to combine desk-top information with site locating and an agreed tolerance zone where only hand tools are used.
# Scanning is a process, not a sweep
/> A CAT and signal generator can only tell you what you ask it to find, and only if the operator is competent. Multiple passes, different modes, and induced signals are needed to build confidence, plus effective marking that all trades understand. Where ground or service type makes detection uncertain, plan for further verification such as trial holes or vacuum excavation.
# Trial holes confirm the truth
/> Controlled test pits at agreed locations verify the presence, route and depth of services in the work area. They also set realistic stand-off distances for plant. Insulated tools, careful technique and a spotter reduce strike risk while exposing enough to make decisions.
# The permit defines boundaries and behaviours
/> A useful permit-to-dig is not a generic form; it’s a map-backed instruction that fixes the exact area, method, exclusions, supervision, and stop-work triggers. It ties into the programme (validity per shift or day), names competent persons, and includes hold points before plant enters the tolerance zone or changes method.
How the permit-to-dig works on the ground
# Before the bucket moves
/> Start with up-to-date utility searches and available records, overlaid on a site plan and the latest setting-out. A competent locator undertakes a structured scan and mark-out, photographed and referenced to fixed features. The supervisor walks the line with the dig team and plant operator, highlighting the tolerance zone and no-go strips, and agreeing trial hole locations. The permit is raised with these specifics, briefed at a toolbox talk, and signed by those actually doing the work.
# During excavation
/> Trial holes are completed first, logged, and depths/routes reconciled against the mark-out. Exclusion zones keep plant away from the tolerance zone until verification is complete. Where plant is authorised, a banksman stays in clear view, with agreed signals and a halt if accuracy is in doubt. Spoil, materials and barriers are positioned so that markings are not obscured and access remains controlled.
# If anything changes
/> Discovering an uncharted cable, a depth discrepancy, lost markings after rain, or a route diversion are all automatic stop points. The supervisor makes safe, re-scans if needed, updates the plan, and either amends or re-issues the permit before work restarts. If a service is damaged or suspected to be live and compromised, isolate the area, keep people clear, and call the relevant emergency services and utility owner—do not attempt makeshift repairs.
Site scenario: civils crew on a live business park
/> A groundworks team is forming a drainage run between two retail units over a weekend possession. Searches and plans show power and comms crossing the line somewhere near a service yard; the programme is tight, with a surfacing crew due Monday. The locator completes a scan on Friday, marks two likely routes and sets three trial holes for Saturday morning, with the permit valid for that shift only. The first trial hole confirms a shallow fibre duct at a slightly different angle than shown, and the second finds an older power cable deeper than expected. The supervisor adjusts the line, extends the exclusion, and pauses plant entry pending a re-brief. Rain smears the paint; before restarting, the locator re-marks and photographs the line. The team finishes the trench with plant kept outside the tolerance zone, hand digging across crossings, and the permit is closed with updated sketches for the as-built pack.
Common mistakes
# Treating utility plans as gospel
/> Plans can be wrong, incomplete or out of date. Without scanning and trial holes, you’re relying on hope.
# Issuing permits that are vague or open-ended
/> Permits that cover whole zones or multiple days invite drift and shortcuts. Keep them specific and time-bound.
# Letting plant close the gap to the mark-out
/> Encroaching on the tolerance zone before verifying depth and route is where most strikes happen. Hold plant back until the ground proves safe.
# Failing to pause when the ground tells a different story
/> When markings wash off, depths don’t tally, or you expose an unexpected duct, stopping is the control. Re-brief and re-permit before continuing.
Practical fixes that stick
/> Make the permit-to-dig a living control that crews respect by tying it into your daily rhythm, not just your forms. Supervisors should own the mark-out and briefing, and managers should make it easy to pause and re-permit without blame when information shifts. Capture what you learn—photographs and redlines today prevent tomorrow’s strike.
# Seven-day push: tighten permit-to-dig practice
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– Map and photograph every mark-out with fixed references; store it in a shared folder crews can access on their phones.
– Nominate named permit issuers per shift and publish their contact numbers at the site gate and welfare.
– Run a 10‑minute stand-up with the dig team and plant operators to walk the tolerance zones before work each morning.
– Add hold points to permits: “no plant within X metres until trial holes 1–3 signed off” and “re-permit required after rainfall or loss of markings”.
– Stock insulated hand tools and cable avoidance equipment in a dedicated lockable box; sign them in/out to ensure competence and accountability.
– Agree an escalation phrase (“Red Line”) that any worker can call to halt digging when uncertainty appears, without debate.
A strong permit-to-dig is simply disciplined ground truthing wrapped in clear authority and stop points. Expect more scrutiny on service avoidance as outages and utility damage remain hot topics. The sites that stay out of trouble are the ones where permits are briefed on the ground, not filed in a folder, and where stopping to re‑permit is treated as professionalism, not delay.
FAQ
# Who should issue a permit-to-dig on a UK site?
/> A competent person who understands buried services, scanning, and the planned method should issue it, typically a supervisor or site manager delegated by the principal contractor. They must be separate enough from the digging task to make unbiased decisions, yet close enough to the work to brief and enforce controls. Naming the issuer and the duty holder for supervision keeps responsibility visible.
# How long should a permit-to-dig be valid?
/> Short durations reduce drift—think per shift or per day as a sensible baseline. If conditions change, markings fade, or the scope moves even slightly, pause and re-issue. Treat a rolling, multi-day permit as a red flag unless the area is fenced and unchanged.
# What’s the minimum I should do before a machine digs near services?
/> Combine current utility records with a structured CAT and Genny scan and visible mark-up, then verify with trial holes at key crossings or uncertainty points. Keep plant outside the tolerance zone until those verifications are signed off, and use insulated tools for hand digging. Brief all involved, including banksmen, on the no-go areas and stop-work triggers.
# What if we find a service that isn’t on the drawings?
/> Stop, make the area safe, and inform the site supervisor immediately. Re-scan and adjust the plan, then amend or re-issue the permit with the new information before any further digging. Record the discovery with photos and a sketch so the information benefits others on site and future works.
# How should we respond to a service strike or suspected damage?
/> Do not touch or attempt ad-hoc repairs. Stop work, evacuate to a safe distance, control ignition sources, and contact emergency services and the utility owner through established numbers. Secure the area, brief the workforce, and preserve information for investigation and lessons learned before any restart.
