Breaking ground without discipline is one of the quickest ways to end up with an electrocution, a gas release or a flooded trench. Permits to dig and proper cable avoidance are your front line against service strikes, but they only work when planning, competence and supervision stick together. The control is simple in theory: know what’s under you, set boundaries, verify before you dig, and stop when anything changes.
TL;DR
/>
– Get the permit right, mark the dig limits, re-scan often, and hand-dig to positively locate services before machines get involved.
– Use CAT and Genny correctly: power, radio and Genny modes, different passes, and rescans after breaks or depth changes.
– Keep supervision tight: one appointed controller for the permit, clear stop-work triggers, and no out-of-hours digs without a fresh permit.
– Record what you find, adjust the plan on the day, and brief every person who picks up a spade or gets in the cab.
What’s buried and why it matters to your controls
/> Underground services are rarely where the old drawing says they are. Electricity, gas, water, drainage, telecoms and district heating can cross and zig‑zag, be at unpredictable depths, or sit in plastic ducts that don’t trace well. A service strike brings real harm fast, from arc flash and ignition to ground collapse and contamination.
A permit to dig is a controlled green light for breaking ground in a defined area, for a short window, with specific methods. It pulls together utility plans, survey findings, trial holes, method statements, hold points and supervision. Cable avoidance tools (CAT and Genny) are best used as part of a system, not as reassurance after the fact. Good practice is to combine scans, physical verification by hand, and constant re-checking as the excavation develops.
Permits should set out: where you can and cannot dig, by what method, who is in charge, how services will be located and protected, and what will trigger a stop. They should expire quickly, so that yesterday’s assumptions don’t leak into tomorrow’s conditions.
How control should run on a UK site
/> Before a spade is lifted, gather the available service information and walk the line. Flag inspection covers, cabinets, meter positions and any visible clues. Mark the dig limits, likely service corridors and exclusion zones on the ground with durable paint and pegs. Brief the team and confirm they can explain the hold points and stop-work triggers. The CAT and Genny scan is carried out by a competent person with a second set of eyes. Only after positive locating with hand tools and trial holes should a machine approach, at a controlled distance and under full-time watching brief.
Plant and people need clear separation. Use barriers, spotters and a banksman who is not doing any other job. Maintain trench edge protection, access/egress and spoil placement to avoid collapsing onto the work area or tracked plant. If the ground or weather changes, pause and reassess; water and soft spots hide services and swallow shoring.
# Scenario: civils gang chasing programme on a housing streetworks tie-in
/> A civils subcontractor is forming new kerb lines and utility crossings on a housing site, working to open the road by Friday. The permit to dig was issued on Monday after a scan and mark-up. By Wednesday, rain has washed out several paint marks and the team has moved 4 metres to avoid a parked delivery trailer. The ganger asks the 3‑tonne excavator to “just scratch the surface” to keep the crew moving. The machine clips a duct marker and the spotter sees a change in the soil colour where a reinstatement strip crosses. Work is stopped, the permit area is re‑scanned, and a trial hole confirms a low-voltage cable sitting shallower than expected. The team adjust the method to hand-dig under watching brief to expose, protect and bridge the cable before machine digging resumes. The day’s output drops, but the service remains intact and the site avoids a street outage.
Pitfalls and practical fixes
/> Old utility drawings lull teams into a false sense of security. Treat them as clues, not the truth. Fix: run multiple scan passes (power, radio and Genny) in both grid directions and along likely service paths; then prove or disprove by trial holes.
CAT use is often rushed. A single pass on “power” mode misses dead cables and plastic services. Fix: energise the Genny to induce a signal where possible, switch modes deliberately, and log each pass. If the signal is vague or intermittent, assume risk is higher and slow the job.
Painting the ground once is not enough. Rain, footfall and traffic remove marks. Fix: remark frequently, use flags or pegs where safe, and keep a sketch that can be re-marked quickly. Never extend the dig beyond marked limits without a fresh scan and permit amendment.
Permit drift is common by mid‑week. People move the dig a few metres, change depth, or split crews. Fix: keep permits short-dated, name the appointed supervisor, and require a verbal pause-and-brief before any change. Out-of-hours works need an explicit decision and competent cover, not a copy of the earlier permit.
# Common mistakes
/>
– Assuming a trench is “clear” because yesterday’s section was fine. Services can dog-leg unexpectedly; every shift and each new stretch needs its own verification.
– Hand-digging with a pick or breaker in suspected service zones. Controlled shovel work and insulated tools are your last line, not brute force.
– Letting the excavator operate within unproven areas under “slow and careful” instructions. Machines should not enter a zone until services are located and protected.
– Failing to record and brief what was actually found. Without sketches and photos, the next crew or the night shift repeats the same risks.
Site-ready checklist for breaking ground
/>
– Confirm permit boundaries on the deck with fresh marks, flags or pegs that match the permit sketch.
– Prove all suspected service corridors with CAT/Genny in multiple modes, followed by trial holes using insulated hand tools.
– Set minimum machine stand-off distances and approach angles; appoint a watching brief who does nothing else.
– Protect exposed services with suitable coverings and supports; never leave a service hanging or unguarded.
– Maintain barriers, signage and edge protection; keep spoil, plant and materials away from trench edges and service runs.
– Keep a live record: photos, depths, offsets and unexpected finds; update the permit before continuing.
– Define stop-work triggers: unexpected signals, unmarked covers, change in ground conditions, or loss of markings.
Interfaces, supervision and change control
/> Service avoidance only holds if supervision is visible. The appointed person controlling the permit should be on the ground at key points: first breakthrough, first exposure of any service, depth changes and when plant enters a sensitive area. Keep the client and principal contractor informed about finds and deviations so design or sequencing can shift early, not in crisis.
Temporary works and shoring belong in the same conversation. If trench support is needed, plan how it will be installed without loading or damaging nearby services. Traffic management should prevent third parties from driving over marked routes or exposed services; include deliveries in the briefing so they don’t cut across your zones. Housekeeping helps: tidy leads, clear spoil, and staged materials reduce trip hazards and make service markers visible.
# Over the next 7 days: ring‑fence ground‑breaking activities
/>
– Tighten permit durations to 24–48 hours and require a short re-brief at each shift start.
– Walk all active and pending dig zones with the CAT/Genny and remark worn or washed-out markings.
– Photograph and sketch every exposed service with offsets to fixed features; file them in the daily record.
– Remove any “just scratch it” instructions from the culture by backing supervisors who stop and reset.
– Bring utilities and temporary works coordinators into the weekly look‑ahead to de-conflict plant routes and shoring.
A permit is not paperwork; it is the site’s collective decision to break ground with eyes open. The pressure to keep programme will always be there, but the quickest job is the one that does not stop for a strike, an investigation and a repair gang.
FAQ
# When should a permit to dig be used?
/> Use a permit whenever you plan to break ground, including small trial pits, posts, and kerb lines. It’s good practice to treat any change in location, depth or method as requiring a fresh permit or a signed amendment. Short durations help stop assumptions drifting. If in doubt, pause work and escalate to the site manager or H&S adviser.
# How often should the CAT and Genny be used during the works?
/> Scan before you start, after breaks, when the dig line moves, and whenever the ground or weather changes. Use multiple modes and passes, and repeat after exposing any service to confirm what’s nearby. If the operator or supervisor can’t explain the signal, stop and bring in someone competent. Don’t rely on a single early-morning pass for a full shift’s digging.
# What should we do if we suspect we’ve hit or uncovered a service?
/> Stop immediately, make the area safe and prevent re-energising or further damage. Keep people and plant clear, control ignition sources, and inform the site lead so the utility owner and principal contractor can be contacted. Do not attempt makeshift repairs. Record the location and circumstances and hold a quick learning brief before any restart.
# How do permits link with temporary works and trench support?
/> If excavation depth or ground condition suggests support, involve the temporary works coordinator at planning stage. The method must show how shoring is installed and removed without loading services or destabilising the trench. Permits should reference the temporary works design and any hold points. Supervisors should check that edge protection, access and exclusion zones align with the temporary works plan.
# How do we manage interfaces with plant, deliveries and other trades near live digs?
/> Set and maintain clear barriers and banksman control, with plant routes that avoid service corridors and open trenches. Include nearby trades and drivers in the daily briefing so they understand the marked zones and stop-work triggers. Good housekeeping keeps markings visible and prevents trip hazards from obscuring service indicators. If another trade needs to cross your area, pause and coordinate rather than letting them thread through.
