Striking underground services remains one of the most preventable causes of serious harm and programme pain on UK projects. A permit-to-dig is only as good as the thinking, planning and supervision behind it. When done properly, it stitches together utility records, modern locating methods, competent people and real-time controls at the excavation face. When rushed, it becomes a paper comfort that falls apart under schedule pressure, subbie interfaces and weather.
TL;DR
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– Treat permits to dig as a live control: pause work if conditions, drawings or line-up change.
– Use layers of verification: plans, survey, locate, mark-up, supervised trial holes, then controlled digging.
– Define tolerance zones and excavation methods clearly; hand-dig or vacuum within them.
– Keep a competent supervisor at the face and stop at every transition, depth change or plant changeover.
A staged permit-to-dig playbook
# Stage 1: Desktop prep and utility intelligence
/> Start by gathering all available utility information early: client packs, local authority records, statutory undertaker plans, and any previous as-builts. Treat drawings as indicative only; note discrepancies, suspected abandoned services and areas of limited confidence. Overlay information on current setting-out models and agree a zone of influence for the task, including haul routes and spoil areas, not just the trench line. Build in time for surveys and stakeholder callbacks—utility owners can take time to respond or attend.
# Stage 2: Detection, verification and mark-up
/> Commission competent service location using appropriate techniques for the ground and service type. Combine electromagnetic locating and ground-penetrating radar where it adds value, and have results interpreted by someone who understands the kit’s limits. Brief the site engineer and supervisor to verify critical lines with supervised trial holes, then mark the confirmed services on the ground and on a controlled plan. Use clear, durable markings and stake flags where needed; record photos with measurements to fixed features.
# Stage 3: Plan the dig and define safe methods
/> Translate the findings into a method that crews can follow. Set tolerance zones around known or suspected services and specify the method for each zone: hand-digging with insulated tools or vacuum excavation for initial exposures, then carefully managed machine work outside the zones. Agree plant type, bucket selection and approach angles; many strikes occur when slewing or trimming, not during the first bite. Build in temporary works considerations for trench support, edge protection and access, because collapsing ground can push plant or operatives into harm’s way.
# Stage 4: Controls at the face and permit issue
/> Write a permit that ties the plan to the ground: location references, depth ranges, identified services, photos, isolation status if applicable, and the exact area it covers. Set permit life with a clear expiry trigger: change of crew, change of plant, significant weather, or any deviation from the mark-up. Fence off the excavation zone, establish plant-pedestrian segregation and position a banksman who knows the service locations. Brief the team at the trench edge; bring the mark-up map, not just words, and record attendance.
# Stage 5: Supervise, pause and verify as you go
/> Keep a competent supervisor present for the initial break of ground and at all transitions: new chainage, crossing services, deeper lifts. If anything doesn’t tally with expectations—unexpected duct, missing cable, depth variance—stop, re-locate and expand the trial exposure. Manage spoil so it doesn’t bury service markers or overload the trench edge, and keep the excavation tidy to maintain visibility. Refresh exclusion zones as the dig extends, and ensure lighting is adequate for early or late shifts.
# Stage 6: Close, record and hand back safely
/> When the task is complete or suspended, close the permit formally. Record the final as-dug position and any services found or disproved; pass those back to design so the next team isn’t starting blind. Make the area safe: backfill or protect exposed services, remove temporary markings that could mislead others, and reinstate fencing as needed. Debrief the crew for learning points and adjust the standard method if you found surprises.
Scenario: civils trench across a live access road
/> A groundworks contractor on a housing scheme needs to trench across the main access road to pick up a new drainage run. Programmed plant and deliveries are pressed up against the weekend, and the client wants the road open by Monday. Utility plans show low to medium confidence on telecoms and LV power. The supervisor arranges a Friday morning locate and marks two telecom ducts diagonally across the route, with uncertain depth. The permit limits machine digging and calls for vacuum excavation across the marked zone first. As the team starts, the vac reveals a third, shallow duct not on the plans, clipped to the edge kerb. The method is adjusted on the spot, the line is hand-dug and supported, the crossing is completed by Saturday, and the road is made safe without a strike.
Supervisor checklist for service-safe digging
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– Confirm you have current utility plans and the latest mark-up at the face; no photo, no dig.
– Walk the line with the operator and banksman; agree tolerance zones and plant approach.
– Prove or disprove all suspected services with controlled trial holes before live machine digging.
– Keep a visible permit-to-dig at the workface and re-brief when crews or methods change.
– Maintain plant-pedestrian segregation and a banksman focused on services, not just traffic.
– Control spoil and water; don’t bury markers, and keep trenches dry to maintain visibility.
– Stop work immediately if anything doesn’t match expectations and escalate for re-verification.
Common mistakes on service avoidance
# Relying on plans as if they’re gospel
/> Utility drawings are guidance, not truth. Without on-site locating and trial holes, you are guessing.
# Issuing a permit miles from the trench
/> Desk-based sign-offs miss context. Permits should be issued and briefed at the exact location.
# Hand-digging too aggressively
/> “Hand-dig” doesn’t mean smashing the ground with insulated tools. Gentle exposure and shallow, progressive lifts prevent nicks and pulls.
# Forgetting interfaces after hours
/> Night shifts, weekend crews and follow-on trades often carry on past the permit scope. If the permit expires, the ground is closed—no exceptions.
Bottom line on permits to dig
/> The strongest control for buried services isn’t the paper—it’s the layered verification, site visibility and supervision that sit behind it. If crews see clear markings, understand the tolerance zones, and feel empowered to stop at the first sign of doubt, strikes drop and productivity improves, not the other way round.
# Actions to lock down service safety this week
/> Walk your live and upcoming digs with the people doing them and compare what’s on the plans to what’s in the ground. Refresh permit templates so they demand photos, tolerance zones and expiry triggers. Line up competent locating support before the programme squeezes you. Identify your most at-risk interfaces—road crossings, service corridors and late shifts—and raise the level of control there.
Underground service strikes are avoidable with disciplined planning, sharp supervision and the confidence to pause. Expect more attention on verification quality and permit credibility during site inspections. Ask at your next briefing: Where are we guessing, who is supervising the first bite, and what will make us stop without debate?
FAQ
# When should a permit to dig be used on a UK site?
/> Use a permit whenever breaking ground where buried services could be present, including small trial holes, fence posts and sign bases. It’s also sensible for work within known service corridors or where confidence in utility records is low. Treat it as a trigger to bring plans, survey and supervision together before the first bite.
# What’s the best way to locate services before excavation?
/> Layer your approach: gather utility plans, then use competent locating by EM and/or radar as appropriate, followed by supervised trial holes to prove positions. Each technique has limits, so combining them reduces blind spots. Record and mark what you find both on the ground and in a controlled drawing or photo log.
# Can machine digging ever happen near known services?
/> Yes, but only outside agreed tolerance zones and with a defined method that manages approach angles, bucket type and supervision. Within tolerance zones or where uncertainty remains, use hand-digging with insulated tools or vacuum excavation to expose services first. Pause machine work at every crossing and depth change to reassess.
# How should permits be managed across shifts and subcontractors?
/> Keep the permit at the workface and brief each crew change, including nights and weekends. Set clear expiry points—change of conditions, methods or personnel—and reissue when any trigger is met. If another subcontractor is affected by the dig, involve them in the briefing and make the interface part of the permit scope.
# What should I do if the ground doesn’t match the drawings?
/> Stop the dig, secure the area and bring in the supervisor and locator to re-verify. Update markings, adjust the method and only restart when the permit reflects the new information. Capture photos and measurements so future work isn’t caught by the same surprise.
