Striking buried services remains one of the most predictable and preventable ways to injure people, stop a site, and damage reputations. Most incidents trace back to the basics being rushed: poor locating, weak briefings, or permits used as a tick-box rather than a live control. Getting the fundamentals right is not complicated, but it is disciplined work: gather reliable information, verify it with instruments and trial holes, brief the team with clear hold points, and dig in a controlled way with someone ready to call a halt.
TL;DR
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– Treat service plans as clues, then prove them with CAT/Genny sweeps and trial holes before any plant breaks ground.
– Run a live permit-to-dig with hold points, agreed hand-dig zones, and a named person who can stop the work instantly.
– Mark, photograph and protect located services; set exclusion zones and keep plant outside them unless the permit says otherwise.
– Adapt as you go: re-scan when layouts change, keep services visible while excavating, and close out with updated records.
Controls playbook for locating and digging around services
# Stage 1: Pre-plan with the right information
/> Start with complete utility information: recent statutory plans, previous phase as-builts, and any third-party diversions. If in doubt, ask for better detail rather than guessing; assume more is in the ground than the drawings show. Feed this into the RAMS and temporary works planning, considering trench support, edge protection, traffic routes and spoil management. Identify constraints like hospitals, substations, fibre backbones or sensitive clients nearby that raise the consequence of an error.
# Stage 2: Brief the team and set hold points
/> Turn the plan into a focused briefing for supervisors, machine operators, slingers, and the person operating the locator. Walk the line of the works and agree stop/go points: no digging until locating is completed and signed off; no machine within the hand-dig zone; cease work if anything unexpected appears or signals change. Clarify roles, radio channels, and how to escalate. The permit-to-dig sits at the heart of this: it starts closed and opens only when all pre-conditions are met, then stays live with daily verification.
# Stage 3: Locate using instruments and trial holes
/> Use a calibrated cable avoidance tool and signal generator with a methodical sweep in power, radio and generator modes. Mark suspected routes and depths cautiously, understanding that depth readings can be unreliable, especially in congested ground. Prove critical lines with trial holes by hand or vacuum excavation; expect multiple services in shallow ground on streets and entrances. Record what you find with photos and sketches stamped with date, location and names, then attach to the permit pack.
# Stage 4: Mark, protect and control access
/> Once located, make it obvious and hard to forget: durable paint, flags, stakes, and barrier protection where vehicle movements cross. Photograph the markings before you start and after any rain or trafficking that could scrub them off. Establish exclusion distances that keep plant out of hand-dig zones unless a specific control is in place and agreed on the permit. Use a banksman who is briefed on service routes when moving plant, not just on general pedestrian safety.
# Stage 5: Excavate safely and adapt
/> Within the hand-dig zone, use insulated tools and expose the service gently, working along its line rather than hacking across. Keep the service continually visible while machine digging proceeds nearby, with a dedicated spotter and a clear line of sight to the operator. Slow down in wet or salty ground where tools may track current and when electromagnetic signals are unreliable. If your alignment, depth or ground conditions change, stop and re-scan—don’t press on because the bucket is already in.
# Stage 6: Close out and update records
/> When the dig is complete or paused, tidy up the paperwork as diligently as you did the trench. Close the permit with photos of the as-left condition and mark-ups of actual service routes. Share updates with design, temporary works and the next trade, so no one repeats the locating effort or makes assumptions that are now out of date. Capture lessons in the supervisor debrief—what slowed you down, what surprised you, and what you’ll change next time.
A short site story
/> A small civils crew on a college expansion is installing drainage across a busy service yard. The programme is tight because term starts in three weeks and deliveries are stacking up at the gate by mid-morning. The supervisor has plans showing an 11kV cable at 1.2 m and a water main at 0.9 m, both sketched from a diversion two years earlier. The locator sweep flags a strong power signal 600 mm off the drawing and far shallower than expected. The team halts plant and hand-digs a trial hole, revealing a duct bank only 450 mm down with fibre and LV. The permit is updated, the trench is re-aligned, and temporary barriers are moved to create a safe corridor for plant. The delay costs half a day, but the site avoids an outage, a serious injury and a very awkward client call.
Common mistakes to stamp out
# Treating drawings as facts rather than hints
/> Utility plans are often outdated or generalised. Use them to target your locating, not to justify skipping it.
# Doing a single CAT sweep then cracking on
/> Ground is noisy and congested; one pass is rarely enough. Sweep in multiple modes, directions and at different times of day if interference is an issue.
# Treating the permit as paperwork, not a control
/> A permit that starts and ends in the cabin misses its purpose. Keep it live at the workface with signatures as conditions change.
# Letting plant creep into hand-dig zones
/> “Just a nibble” is how many strikes happen. Hold the line on agreed distances and assign a banksman who knows the red lines.
Immediate actions on live services control
# Seven-day push: get locating and permits tight
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– Map where ground will be broken in the next two weeks and compile a single, dated pack of plans for each zone.
– Schedule locator sweeps with a competent operator and make the supervisor walk every route before the machine arrives.
– Paint and photograph all marked services, then brief plant operators on the day with the images in hand.
– Establish and signpost hand-dig zones and hold points; put the permit board at the workface, not in the site office.
– Set up a standby plan: who calls stop, who informs the client/utility, and where first aid and isolation points are.
– Inspect excavations for temporary works needs—edge protection, trench boxes, safe access—and link these to the permit conditions.
Bottom line for site leads
/> Cable strikes thrive on assumptions and rush. If you control the information, the brief and the boundaries, you control the risk. Before any bucket bites ground, ask yourself: have we proven what’s under us and who has the authority to pause the work? And when the situation shifts, will the crew recognise the change and respect the hold point?
FAQ
# When should a permit-to-dig be used?
/> Use a permit-to-dig whenever there is a foreseeable chance of encountering buried or hidden services, including shallow trenches, fence posts, trial pits and sign foundations. It is equally relevant for soft digs near known routes as for major excavations. The permit ties together plans, locating, briefings, and hold points, and keeps the controls visible at the workface.
# Who is competent to carry out service locating with CAT/Genny?
/> Competence comes from training, practice, and understanding the site’s context, not just owning the kit. A supervisor should confirm the operator can use all modes, interpret signals, and explain limitations such as depth inaccuracy. Pair the operator with someone who can mark and document findings while maintaining safe separation from plant.
# How do we decide the hand-dig zone around a suspected service?
/> Set a conservative zone in your RAMS and permit based on the quality of information, ground conditions and the consequence of a strike. The zone should keep plant out until a trial hole confirms the exact position and depth. If congestion is high or visibility is poor, extend the zone and consider vacuum excavation.
# What if plans and the detector don’t agree?
/> Treat any disagreement as a stop-and-think moment. Pause excavation, expand the sweep area, and use different modes and orientations; then prove the route with a trial hole before resuming. Update the permit and inform affected trades so no one relies on the original assumption.
# What’s the right response to a near-miss with services?
/> Stop the activity, make the area safe, and gather the team for a quick debrief while the details are fresh. Capture what signalled the problem, which control failed or was missing, and what escalation should have happened earlier. Feed the learning into the permit conditions, the next briefing, and any temporary works or traffic plan that interfaces with the dig.
