Striking a live cable or service pipe is one of those mistakes that turns a routine dig into an emergency. A permit-to-dig is the control that draws a hard line between planning and action, and it lives or dies on the quality of the work that leads up to it. Good permits don’t just say yes or no; they define where, how and by whom the ground will be opened, and what must happen if something unexpected appears. The aim is simple: know what’s beneath, control how you approach it, and stop the job going off-plan.
TL;DR
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– Get all utility information early, then verify it with scanning and marked-up trial holes before any plant breaks ground.
– The permit must set boundaries, methods, supervision, hold points and stop triggers; if anything changes, the permit is paused.
– Use insulated hand tools and vacuum excavation near suspected live services; keep people out of the swing and trench zones.
– Re-scan after breaks or when conditions change; if in doubt, stop, escalate and re-brief.
Controls that prevent underground service strikes
# Stage 1: Plan the dig and gather service intelligence
/> Start by pulling together every source of underground info you can get: statutory plans, client as-builts, previous survey data, and any recent installation records from other trades. Treat all drawings as indicative; they’re a starting point, not permission to dig. Build the scope, methodology and sequencing into RAMS, including how traffic, deliveries, and other site activities will be kept away from the excavation footprint. Decide early where you’ll need temporary works for support or edge protection. Nominate who will issue and hold the permit, and agree escalation routes if something doesn’t look right.
# Stage 2: Locate and mark with CAT, Genny and competent people
/> Use a cable avoidance tool with a signal generator to actively trace services and to sweep the area in multiple passes and frequencies. Only competent, briefed operators should do this. Mark all detected routes clearly on the ground and on a sketch, including suspected service corridors and no-dig zones. Don’t rely on one sweep; scan again after layout changes, before plant arrival, and after breaks. Keep a record of the scan results with photos, so the permit has proof of what was checked, where and when.
# Stage 3: Prove the ground with controlled trial holes
/> Before the main dig starts, expose key points by hand or vacuum excavation to confirm location and depth. Use insulated tools and proceed from the expected “safe” side, peeling back small amounts and maintaining visual control. If you find a service out of position, stop and re-mark the route; if you find something not on the plan, treat it as live until proved otherwise and escalate. Space trial holes to match the route and complexity, not convenience. Capture photos with a tape or identifiable marker in shot so your records are meaningful later.
# Stage 4: Issue the permit with hard limits and active supervision
/> The permit should define exact boundaries, maximum depth, method (hand, vacuum, plant), who can operate, and the conditions for stopping. Include hold points: for example, before switching from hand to machine, or at a set depth until the supervisor inspects. Build in controls for segregation, edge protection, and spoil management, along with plant/pedestrian interfaces and banksman duties. Brief the whole team in a pre-start talk using the marked-up sketch, not just the permit holder. Date and time-limit the permit; a new shift or weather change can make yesterday’s controls unfit today.
# Stage 5: Run the dig, manage change and close out
/> Keep people out of the slew radius and trench edges, and maintain barriers as the excavation advances. Use spotters with clear hand signals when operating near suspected services, and approach at shallow angles rather than digging straight down onto a target. If you lose markings, the weather turns, or another trade works nearby, pause and re-validate with a re-scan and a re-brief. Unknown object? Stop, make safe, and escalate; do not probe blindly. On completion, record what you found with photos and an updated sketch, reinstate any markers you removed, and close the permit formally so there’s a clear line of accountability.
Scenario: civils team under programme pressure
/> A civils gang arrives to install a new drainage run on a commercial refurbishment where the client’s compound was moved the week before. The original plans show LV cables along the old fence line, clear of the proposed trench. The supervisor runs a quick scan, picks up a signal but assumes it’s the same LV in its old position. Plant starts breaking out and immediately uncovers an orange duct 600 mm from the new fence, right where the trench is planned. The team stops, but one operative steps in to “have a look” and kicks loose material off the edge. A second scan reveals a parallel route – the LV was re-routed when the compound shifted. The permit is pulled, the route is re-marked, and the trench is offset with additional trial holes before works resume, this time with vacuum excavation at the crossing.
On-the-day essentials checklist
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– Confirm the permit is in date, signed, and matches the exact area marked on the ground.
– Verify the latest utility pack and marked-up sketch are present and match visible markings.
– Check CAT/Genny functionality and that the named operator is on shift and has re-scanned.
– Walk the route with the team; identify trial holes, no-dig zones, and hold points.
– Set up barriers, signage and plant/pedestrian segregation before any breakout.
– Agree stop signals, radio channels, and who escalates if an unknown service is found.
Common mistakes
# Treating plans as accurate location data
/> Drawings are a clue, not a map. If you don’t scan and prove, you’re gambling with plant and lives.
# Scanning once, then relying on memory
/> Conditions change through the day. Re-scan after breaks, layout shifts, or when new kit arrives.
# Issuing open-ended permits
/> Permits without time limits or hold points drift into box-ticking. Set expiry and defined checks.
# Hand-digging like machine-digging
/> Even with insulated tools, speed kills. Pull soil away from suspected routes slowly and keep fingers and blades out of line with the service.
Bottom line: permits that hold the line
/> A permit-to-dig only works if it’s the capstone of careful planning, competent locating and active supervision. When teams see it as the on/off switch for ground disturbance, it stops rushed starts and sloppy assumptions. Watch for drift: yesterday’s markings and controls don’t survive new deliveries, weather or re-routed services. Ask yourself three questions at each briefing: what’s changed, who’s watching, and where do we stop if the picture isn’t right?
FAQ
# When do we actually need a permit-to-dig?
/> Use a permit when there’s any risk of contacting underground services or disturbing unknown ground, even for small holes or posts. It’s also sensible where temporary works, existing structures or adjacent public areas could be affected by the excavation. The permit ties planning, scanning and supervision into one controlled decision point.
# Who should operate the CAT and Genny, and how often?
/> Only trained, competent people should use locating equipment, and they should be named on the permit or RAMS. Scan before marking out, again before plant arrives, and after any break or change that could affect the ground picture. If the operator changes mid-shift, have the new person re-scan and confirm markings.
# What if services are private and not on the statutory plans?
/> Assume services exist until you prove otherwise with scanning and trial holes. Ask the client, FM team or principal contractor for as-builts and recent works records, and speak to other trades who may have installed temporary power or water. Mark unknown routes conservatively and escalate if you find anything unrecorded.
# How should we control interfaces with other site traffic and trades?
/> Set physical barriers and clear no-go zones around the dig and slew area, and route deliveries away from the excavation. Brief neighbouring trades at the start of shift and update them if the dig moves or expands. Keep access routes for emergency services unobstructed and maintain housekeeping to prevent slips into the excavation.
# What’s the right response if we expose or strike a service?
/> Stop work immediately, secure the area, and keep people back from the excavation edge. Escalate to the site manager or permit issuer, and contact the relevant utility or emergency services if needed. Do not attempt makeshift repairs; the next steps are to make safe, re-assess the method and controls, and only resume under a re-issued permit.
