A permit to dig should be a hard stop until you can show how buried services are located, isolated or protected, and what proof you have in your hand. Ground strikes still happen on tidy jobs because teams rely on drawings, skip the isolation evidence, or let permits drift beyond their shift. The test is simple: can the supervisor demonstrate, on the spot, that each identified service is either de-energised, shut, or kept live with a safe method around it? If not, you are relying on luck, not control.
TL;DR
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– Treat the permit as a hold point: no digging until isolation is proven and evidenced, not just discussed.
– Combine utility plans, on-site locating, and trial holes; never trust a single source.
– Lock-off, tag, and physically prove dead where you can; if a service must stay live, set a safe clearance method and have a spotter.
– Record everything: photos of locks and tags, locator screenshots, marks on the ground, and signatures with times.
– Re-brief and re-scan whenever the area, depth, or shift changes; permits expire with conditions, not dates.
Proving isolation before ground is broken: the controls playbook
# Stage 1: Assemble the service picture and plan your method
/> Start with all available utility stats, previous as-built drawings, and any site records from earlier phases. Assume they’re incomplete. Pull in local knowledge from maintenance teams and neighbours, especially on private networks inside industrial estates, schools, and hospitals. Define likely corridors and conflict points with your new works. Plan for a staged approach: scan, trial holes, isolation or protection, then controlled excavation. Build time for approvals from utility owners; rushing this stage just moves delay to the dig face.
# Stage 2: Locate and mark what’s underfoot
/> Use a competent locator operative with calibrated equipment, in multiple modes, and mark findings clearly on the ground with paint and flags. Pin your marks to fixed references so they survive weather and foot traffic. Scan from different angles and heights; re-scan after any ground change or plant movement. Capture evidence: photos of markings, locator screenshots, and a simple sketch with offsets. Expect depth to vary—services snake and rise around old obstructions. Trial holes by hand or vacuum excavation should confirm each critical service before machines go in.
# Stage 3: Isolate, lock, and prove you’ve controlled energy
/> For water and gas, coordinate planned shut-offs or pressure reductions with the utility or asset owner, and record valve locations and tag numbers. For electric, isolate at the correct point in the private or DNO system; apply lock-off and a visible tag; then prove dead with a suitable tester before any contact. Watch for backfeeds from generators, PV arrays, or temporary supplies—confirm these are captured in the isolation plan. Fibre and comms may need to stay live; if so, define a clearance method, tool restrictions, and an agreed hand-dig or vacuum window. Around any service that remains live, set minimum approach clearances as good practice and reinforce with insulated tools and a named spotter.
# Stage 4: Evidence and authorise with a tight permit
/> Build a simple “isolation pack”: utility drawings, locator evidence, photos of locks/tags, valve plans, trial-hole results, and contact details for the asset owner or responsible manager. State exactly which services are isolated, which are live, and the safe system for each. Fix boundaries, depth limits, and an expiry time tied to shift or condition changes, not just a date. Include hold points: first bucket, each new bay or depth step, and any switch from hand to machine. Only a competent authoriser who has seen the evidence—not hearsay—signs the permit.
# Stage 5: Excavate under control and keep proof current
/> Start every bay with hand or vacuum exposure where services are expected. Keep an exclusion zone so the excavator can’t sweep into marked corridors, and use a spotter who’s fully briefed on what’s live and where. Re-brief the gang at shift handover, and re-scan if the footprint extends or levels change. If you hit unexpected material, a duct, or inconsistent depths, stop and treat it as a new job: re-locate, re-brief, re-permit. Close the loop by recording as-dug photos and updating sketches for the next shift.
Scenario: drainage connection at a busy retail park entrance
/> A civils team is tying new drainage into an existing line near the park entrance. Drawings show a LV electric feed and water main; the locator also picks up an uncharted signal cutting across the bay. The supervisor arranges a water shut and tag with the utility, isolates a private LV panel feeding car park lights, and proves dead at the pillar. Vacuum excavation exposes a telecoms duct where the unknown signal was found; it must stay live. The permit is updated: telecoms corridor is hand-dig only, insulated shovels, and a spotter. A late delivery forces a change in the dig sequence, so the team re-briefs and re-marks the adjusted area. Work proceeds without a strike, and the as-dug info is kept with the day’s permit pack.
Supervisor walk-round checklist before the first bucket
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Before authorising the dig, the supervisor should be able to point to physical proof, not just paperwork.
– Isolation points identified, locked off, tagged, and photographed; contact name and time recorded.
– Locator marks visible and tied to fixed references; latest scan evidence on file and understood by the gang.
– Trial holes completed where services were expected; findings marked and briefed.
– Live services clearly indicated on the ground with protected corridors and stated approach method.
– Exclusion zone set, spotter appointed, and hand tools/insulated kit staged for the first exposure.
– Permit boundaries, depth limits, and expiry time stated; hold points agreed with the machine operator.
– Escalation plan in place: who to call and what stops work if anything unexpected appears.
Common mistakes when signing off isolation
# Assuming one valve or breaker controls the whole area
/> Private and backfed supplies often bypass the obvious point. Without confirming the exact circuit or section, you can leave parts energised.
# Treating drawings and CAT marks as enough to authorise digging
/> A line of paint is not proof. Trial holes and photos of exposed services are what confirm location.
# Leaving telecoms and data out of the risk conversation
/> Cutting a fibre may not injure someone, but it can shut a client’s operations and trigger claims. Treat it with the same planning discipline.
# Letting the permit run past its conditions
/> Shifts, weather, or a small layout change can make yesterday’s controls unsafe today. Time-bound permits and re-briefs prevent drift.
Keep the programme moving without cutting corners
# Over the next week: make isolation visible on the ground
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Turn isolation from paperwork into something anyone can point to.
– Tag isolations with unique numbers and hang printed photos at the workface so crews know what “good” looks like.
– Paint service corridors with clear legends and arrows, then refresh markings after rain or heavy traffic.
– Hold a face-to-face pre-dig huddle at the bay, walking the limits, live routes, and hold points with the operator and spotter.
– Stage vacuum excavation kit and insulated tools at the pit, removing excuses to “just nudge it with the bucket”.
– Capture as-dug updates daily and pin a simple sketch by the permit board to steer the next shift.
Bottom line: dig only when isolation is proven
/> Permits mean very little until you can show locks, tags, exposed services, and a crew that understands the plan. The strongest defence against strikes is slow at the start—locate, isolate, prove—so the rest of the dig can run fast and uneventful.
FAQ
# What evidence should sit with a permit to dig?
/> Keep utility plans, locator screenshots, photos of on-ground markings, images of locks and tags in place, and trial-hole photos. Add a simple sketch with offsets and contact names for anyone who authorised an isolation or attended site. This creates a shared picture for the crew and a record if conditions change.
# How often should we re-scan an area that’s already been marked?
/> Re-scan whenever the footprint changes, levels are reduced, or heavy plant has tracked across your marks. It’s also good practice to re-scan at the start of each shift or when weather has washed off paint. Fresh scans catch set-out drift and unexpected services exposed by earlier digging.
# Can we dig near a service that must stay live?
/> Yes, but only with a defined safe system that everyone understands. That normally means hand or vacuum excavation within a set clearance, insulated tools, a named spotter, and an exclusion zone for plant. Build these controls into the permit and stop work if the route isn’t where it was expected.
# Who should authorise isolations on private networks?
/> Use someone competent who understands that network—often the client’s facilities lead or a qualified electrician for electrical systems. Make sure their name, time, and scope of isolation are recorded, with locks and tags applied where practical. If there’s doubt, pause and get the right person involved; assumptions on private systems are a common strike cause.
# What triggers a stop and re-permit during excavation?
/> Finding any uncharted duct or pipe, inconsistent depths, damaged protection (like broken tiles or marker tape), or a deviation from the planned bay should trigger a stop. Treat it as a new job: locate, expose, update the plan, and brief again. Building these stop points into the permit avoids on-the-spot compromises.
