Service strikes remain one of the most stubborn causes of injury, disruption and unexpected programme damage on UK sites. A permit-to-dig is supposed to stop them, but too often it’s a photocopied form and a handshake. The control only works when it drives the right sequence: confirm, locate, prove, control and supervise. If any one of those steps is skipped or compressed, the risk jumps back up.
TL;DR
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– Treat every dig as if live services are present until proved otherwise.
– Build your permit around hold points: surveyed, marked-up, trial holed, then controlled excavation.
– Use competent people and functioning kit for CAT/Genny and GPR; record what you find, not what you hoped to find.
– Keep the permit at the point of work and brief the actual crew; stop if conditions change.
– Support, protect and signpost exposed services; photograph, sketch and update as-built records before you cover.
Permit-to-dig that prevents strikes: the playbook
# Desktop and utility verification before any kit turns a wheel
/> Start with current utility information from statutory undertakers and any client-held records. Consolidate it onto a clear drawing with a defined dig zone and likely service corridors. If the risk is non-trivial, commission a competent survey (for example EML with Ground Penetrating Radar where appropriate) and define the detection quality. Choose your plant and method with that information in mind; a 13-tonner on a tight footpath with suspected shallow services is asking for trouble.
# Locate and mark: CAT/Genny, GPR and visible cues
/> Scan the proposed dig area using a calibrated locator by a trained operator, using the generator to induce signals as needed. Don’t just trace one pass; sweep systematically, perpendicular and parallel, and extend beyond the trench lines to catch crossings and tees. Mark detected routes on the ground with clear colour coding and arrows, and photograph the markings with a scale and reference points. Look for surface clues: service markers, repaired patches, inspection covers, telecom boxes, and changes in surfacing that betray previous trenches.
# Trial holes and proving: hand-dig smart, not blind
/> Prove the presence and location by trial holes at key points and at changes in direction or depth. Use vacuum excavation as a preferred method where feasible; where hand-digging, use insulated tools and a gentle technique, scraping rather than stabbing. Never assume depth or protective coverings; shallow plastic gas and fibre drops are common on housing and retail refurb. Once you expose a service, clean enough length to confirm direction and mark offsets to fixed features. Record what you find on the permit pack with photos and a sketch.
# Control the dig: permits with hold points and boundaries
/> A working permit defines more than permission; it sets hold points, equipment limits and supervision levels. Enforce exclusion distances from proved services—mechanical excavation limits, bucket guards, and a spotter dedicated to the service interface. Mark red-line boundaries on the ground and brief the crew daily. If you need to cross a service, plan supports, bridging or temporary works; never undercut a cable or pipe and leave it unsupported. Keep plant and materials away from exposed services to avoid crushing or rubbing damage.
# Supervise and adapt: changes, backfill and handover
/> Nominate a supervisor to stay close during service interfaces and to pause the task if new information appears. If actual findings differ from drawings or previous marks, stop, update the permit and re-brief before continuing. Protect exposed services with timber, matting or proprietary guards, and sign them so other trades cannot step on or snag them. Before backfilling, photograph and measure, then agree any insulation, cover or warning tape requirements with the principal contractor. Issue updated as-built sketches so the record is better for the next phase.
Housing streetworks scenario: the near-miss that reset the approach
/> A civils gang on a new-build housing plot is chasing kerbs to hit a paving milestone before tarmac. The supervisor relies on week-old spray marks from a utility survey and a laminated plan on the dash. After lunch, the mini-digger tracks onto the verge for a quick pull of spoil where the kerb-line jogs out. The banksman sees a yellow marker peg half-buried in the sod and shouts, but the bucket has already scraped the top of a plastic gas service. The pipe scuffs but holds; work stops, and the gas network is called to check integrity. The review finds the verge was regraded by landscapers two days earlier, burying the marker peg and shifting the visible cues. The new permit flow now includes re-scan after any ground works, hold points at every deviation, and a vacuum-excavated trial hole at kerb-jogs.
Permit-to-dig essentials: supervisor checklist
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– Confirm utility searches are current and cover the exact dig footprint plus a sensible buffer.
– Function-test the CAT/Genny and verify operator competence; capture scan photos with reference points.
– Mark services clearly on the ground and in the permit pack; include offsets to fixed features and a simple sketch.
– Plan trial holes at entries, crossings, bends and depth changes; prefer vacuum excavation where practicable.
– Define mechanical excavation limits near proved services and brief a dedicated spotter for the interface.
– Put physical protection on exposed services and keep plant/materials off them; set a no-lift zone overhead.
– Establish stop triggers: unexpected find, missing marks, rain/flooding in the trench, or a change in method/crew.
Common mistakes that keep causing strikes
# Treating old markings as gospel
/> Ground conditions, landscaping and other trades can alter or obscure marks within days. Always re-scan and re-brief before you break ground.
# Confusing a clean sweep with competence
/> A locator in untrained hands gives false confidence. Make sure the operator understands induction, clipping-on, nulls and limitations.
# Letting the permit live in the site office
/> If the permit isn’t at the point of work, it isn’t controlling the task. Keep it with the supervisor and update it as findings emerge.
# Assuming service owners will rescue you quickly
/> Relying on rapid attendance leads to risky “just a quick dig” decisions. Build time for proving and isolation planning into the programme.
Over the next week on your job: make it stick
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– Map your highest-risk digs and assign a named supervisor to each, with time protected to observe the interface with services.
– Ring-fence service corridors with durable markings and small stakes where allowed, so rain and foot traffic don’t erase your controls.
– Swap any tired or unverified locators for units with current function checks; retrain one operative per gang on good scanning technique.
– Drill crews with a five-minute “prove and pause” routine: scan, mark, trial hole, then stop for a short hold-point sign-off.
– Stage materials and plant away from exposed services and set visual barriers so other trades can’t wander into the dig zone.
Bottom line
/> A permit-to-dig only earns its keep when it changes behaviour at the trench edge. The strongest permits hard-wire proving, supervision and stop triggers into the job, and they adapt when the ground tells a different story. If you keep that discipline, service strikes stop being a lottery and become a preventable risk.
Expect increasing scrutiny on how you verify and brief, not just on having a form signed. Before your next excavation, ask: What has changed since we last scanned? Who is watching the interface? Where are we forced to stop if anything looks wrong?
FAQ
# Who should sign the permit-to-dig and who keeps it?
/> A competent supervisor with authority to pause the task should sign, along with the person in control of the work area. Keep the live permit at the point of work so the crew can reference limits, hold points and sketches. The site office should hold a copy, but the working document belongs by the trench.
# How long is a permit-to-dig valid for?
/> Treat it as valid only while the conditions match what was assessed and briefed. Weather, new trenches, service diversions or a change of crew can all invalidate it, triggering a revisit and re-brief. It’s better to refresh too often than to continue on stale assumptions.
# What if the scan and the utility plan don’t agree?
/> Stop and resolve the discrepancy before you dig. Extend the scan area, use different modes, and add a trial hole to prove the route. Update the permit pack with what you actually find, and escalate to the principal contractor or asset owner if you suspect an unrecorded service.
# How do we manage interfaces with other trades working nearby?
/> Coordinate start/stop times and exclusion zones through the daily coordination meeting and point-of-work briefings. Sign and barrier the dig, protect exposed services, and control deliveries and plant routes so no one runs over your workface. If another trade changes levels or reinstates, require a re-scan before resuming.
# Is vacuum excavation mandatory near services?
/> It isn’t universally required, but it’s good practice on congested or high-consequence digs because it reduces contact risk. Where it isn’t practical, use hand-digging with insulated tools and a proven method statement that limits force and defines approach distances. Choose the method based on risk, ground conditions and the service criticality, then build it into the permit.
