Service strikes remain one of the most disruptive, high-risk events on UK sites. A cable flash can injure in seconds; a gas main rupture can shut a site and half a street; a severed fibre can halt nearby businesses and your programme. Permits to dig are meant to be the controlled gateway into ground-breaking work, not a last-minute signature. Used properly, they stitch together planning, service detection, supervision, and pause-points. Used poorly, they become the tick-box you skim before the teeth hit the ground.
TL;DR
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– Treat the permit to dig as the go/no-go control that links plans, locating, supervision, and stop-work triggers.
– Combine utility plans, on-site visual checks, locating kit, and trial holes before machine digging.
– Mark services clearly, brief the team, set exclusion zones, and keep plant and pedestrians apart.
– Revalidate permits after design or sequence changes, and whenever evidence on the ground doesn’t match the drawing.
– Stop immediately on unknowns, near misses, or suspicion of a strike; escalate, make safe, and only resume under a fresh permit.
Clear-headed principles for safe digging
/> Most service strikes happen because assumptions beat evidence. Good practice starts with a desk-based sweep of statutory plans and any as-builts, followed by a walkover to spot clues: covers, cabinets, markers, previous reinstatements, and private feeds. Combine that with competent locating using a cable avoidance tool and signal generator, and then prove what you’ve found with careful trial holes. Only then should machine excavation be permitted, and only within the marked, briefed, and supervised area.
A permit to dig should coordinate these steps. It names the work area, sets limits and depth, lists the services expected, and defines safe methods for proving, exposing, supporting, and working around them. It specifies who’s competent to supervise and who is authorised to operate plant near services. It also records edge protection, access, and traffic routes so plant and pedestrians don’t mix around open excavations.
Don’t forget temporary works. If the excavation depth or ground conditions demand it, temporary works design and inspection need to be in place before the permit is live. Likewise, emergency arrangements should be clear: how to stop, who to call, how to isolate, and how to secure the area if something goes wrong.
On-site flow from first query to backfill
/> In practice, the process starts when a dig is proposed. The site team requests service plans early, checks for private feeds from nearby buildings, and overlays everything on the latest setting-out. A competent locator surveys the area and marks detected routes with clear colour codes and notes. A pre-start briefing walks the team through the drawing and the markings, points out no-go strips, and agrees the hand-dig zones for proving. Only when trial holes confirm the picture do machines come in, with a dedicated banksman and clear barriers. The permit stays at the point of work, and the supervisor pauses the job to revalidate if anything changes.
Scenario: A civils gang on a retail park extension needed to install drainage across a service corridor feeding existing units. Programme pressure was heavy because night-time delivery windows had been lost to weather. The supervisor had the utility plans, but a private LV cable installed two years earlier wasn’t on them. The locator traced a feed from a cabinet and marked a suspected route; the team agreed to hand-dig trial holes ahead of the trench line. The first trial hole didn’t show anything, but the second uncovered a small duct at a shallow depth, running slightly off alignment. They widened the exclusion zone, adjusted the trench route by half a metre under a revised permit, and installed shoring before proceeding. A day was lost, but the buried service stayed intact, the units kept power, and the client avoided a public incident.
# Actions for the coming week on live digs
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– Walk all planned dig zones with the locator and the supervisor, and refresh markings where weather or traffic has scuffed them.
– Pin a laminated service key at the workface with photo references of markings and trial hole locations.
– Brief operators on hand digging around service crossings and define the max machine approach before re-briefing.
– Set up barriers and signage so plant routes and pedestrian access don’t pass over suspected service runs.
– Stage materials and spoil so nothing loads ground over service corridors; include this in the permit conditions.
– Agree and display the stop-work triggers: unexpected duct, conflicting depth, loss of signal, or change in ground cue.
Pitfalls and fixes on buried services
/> Relying on a single method is the common trap. Drawings are a start, not the truth. Locating kit can mislead without good technique. Trial holes can miss if set in the wrong place. Blend all three, then keep testing your assumptions as the excavation progresses.
Private services complicate most commercial and refurbishment sites. Look for feeder pillars, small cabinets, recently reinstated tarmac, and direct routes between plant rooms and outbuildings. Engage the client or landlord early to surface any contractor-installed feeds that never made it to statutory maps.
Controls must be visible at the workface. Marking is no use if the digger can’t see it. Keep paint lines topped up, use short pegs and flags where appropriate, and photograph everything into the permit pack. Assign one named banksman for plant around services; swapping in a spare labourer mid-morning is how context gets lost.
Permit discipline matters after lunch as much as at 8am. If the design changes, the trench shifts, or the ground tells a different story, treat it as a new job. Suspend the permit, regroup, and brief a new method. It’s slower for an hour, quicker for the week.
# Relying on old utility plans
/> Plans are often out of date and rarely show private runs. Treat them as clues to be verified, not a green light to dig.
# Sweeping once with a locator, then cracking on
/> A single pass can miss, especially over reinforced concrete or congested corridors. Use multiple modes, change orientations, and confirm with trial holes.
# Letting a permit drift past its scope
/> When the trench line moves or depth increases, reissue the permit. A scribble on the margin won’t hold the line under pressure.
# Treating PPE as the control
/> Gloves and boots won’t stop a cable flash or gas leak. The real protection is planning, proving, supervision, and stop-work authority.
FAQ
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Who should issue and sign a permit to dig?
A competent person with authority on the project, typically the site manager or an appointed supervisor, should issue it. They must understand the service information, the proposed method, and the site interfaces so they can judge whether controls are adequate.
# When does a permit need revalidating?
/> Any time the scope, location, depth, sequence, or site conditions change in a way that affects risk. If what you find on or under the ground doesn’t match expectations, pause, update the information, and issue a fresh permit with a new briefing.
# Is a CAT and Genny enough, or do we need more advanced surveys?
/> A CAT and Genny used by a competent locator is good practice for most digs, but it has limitations. In congested or sensitive areas, you may need additional techniques or specialist support to build confidence before breaking ground.
# How do we control plant and pedestrian interfaces around excavations?
/> Plan routes so people and machines don’t share space near open trenches or suspected service runs. Use barriers, spotters, clear signage, and keep the permit conditions visible at the workface so everyone understands the no-go areas.
# What should trigger a stop-work and escalation?
/> Unknown ducts, loss of signal where one was expected, unexpected depth or orientation, a near miss, or any strike suspicion should stop the job. Secure the area, inform the site lead, follow isolation and emergency procedures as applicable, and only resume under a revised permit and method.
As enforcement attention stays high on service strikes, expect more scrutiny on how permits tie planning to execution at the workface. The bottom line: permits to dig are only as strong as the evidence you gather, the brief you give, and the pause-points you enforce.
