Live buried services are one of the quickest ways a routine dig turns into a life-changing incident. A permit to dig is not a form to satisfy a client; it’s the control spine that keeps the crew, the public and the programme safe. When utilities are live, the permit must lock in planning, competence, survey results, control zones and hold points. The people who sign it need to own it on the ground, not just in the site office.
TL;DR
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– Treat the permit as a live control: scope fixed, survey proven, crew briefed, and hold points enforced.
– Locate, mark and verify with competent people using current drawings and calibrated locators; expose by hand or vacuum first.
– Control the dig: exclusion zones, plant limits, insulated tools, and a supervisor present whenever tolerance is tight.
– Close out properly: as-builts updated, services reprotected, permit returned, and lessons fed into the next task.
Staged controls for live-service excavations
# Define the dig and freeze the scope
/> Write down exactly what is being dug, to what dimensions, and why. Drawings alone aren’t enough; add a simple sketch with service corridors, plant positions and access routes. If the task changes more than trivially, stop and reissue the permit rather than “making do”.
# Interrogate records and request searches
/> Pull service records from your client, utility search results, and any previous as-builts. Treat missing or vague information as a risk in itself. If results are still pending, the safe assumption is that services may be present; adjust the method to trial and verify before committing.
# Survey and mark out with competent locators
/> Use trained people with a CAT and Genny (or equivalent) to scan and mark detected services. Confirm calibration and check batteries before starting. Mark tolerances, direction of run and depth indications on the ground in a durable way, then photograph and date them. Where depth is critical, plan trial holes at set offsets to physically prove location.
# Agree the method: trial, expose and then excavate
/> Set the method to reflect the highest risk service in the area. Good practice is hand digging or vacuum excavation for initial exposure, with insulated tools and a no-mechanical zone around known or suspected lines. Detail plant limits (buckets, breakers, augers), access for spoil removal, and weather stoppages if visibility or ground conditions deteriorate.
# Temporary works and service supports
/> If services are to be supported, diverted or bridged, involve temporary works early. Specify support kits, gap distances and sequencing so that pipes and cables are never left hanging. Include trench support where required; a safe service dig is still a collapse risk if sides are unsupported.
# Set control zones, plant exclusion and pedestrian routes
/> Physically segregate the dig from people and traffic with barriers that suit the risk. Mark no-go areas for plant slewing, and fit slew restrictors if the space is tight. Keep the public and other trades out with clear signage and a banksman where site traffic interfaces with the dig.
# Permit issue, briefing and hold points
/> Only competent issuers should sign the permit, and the receiving supervisor must brief the crew before the first spade goes in. Build in hold points: after service marks are set, after the first trial hole, before bringing in plant, and if conditions change. Document these on the permit and use a simple tag or stop card at the dig to make it obvious what stage you’re at.
# Supervise the dig and record as you go
/> The supervisor stays within sight and reach whenever work is inside the tolerance zone or near a critical service. Photograph exposures, supports and protection as they’re installed. If anything deviates, pause and escalate rather than arguing with the ground.
# Protect, reinstate and close out
/> Before closing, verify that services are protected with tape, tiles, ducting or covers to suit the utility and depth. Remove temporary supports only once permanent protection is in place. Update as-builts with measured positions and hand back the permit with notes on surprises, changes and lessons.
A real-world scenario: unexpected LV near a school entrance
/> A civils crew are installing bollards at a refurbished school’s main entrance during half term. The client drawings show a telecoms duct on one side and an LV cable crossing further along the footway. The locator survey picks up the telecoms duct but struggles with the LV due to nearby street furniture and interference. The permit sets a hold point after the first trial hole and bans mechanical digging within 500 mm of any suspected line. On day one, the gang exposes the telecoms duct where expected. When hand digging the second position, they find an LV service at a shallower depth than the plan suggested, running diagonally into the building. The supervisor extends the no-mechanical zone, calls the permit issuer, and shifts two bollard positions by agreement. The job finishes a day late but without a strike, and the as-built is updated so maintenance teams don’t repeat the near miss.
Permit-to-dig walk-round checklist
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– Survey marks visible, dated, initialled and matched to the latest records.
– Calibrated locator and insulated tools on site; competent users named in the briefing.
– Exclusion barriers, signage and a designated spoil area set before any digging starts.
– Method statement reflects live-service risks; hand-dig or vacuum first is explicit.
– Hold points written on the permit and physically flagged at the workface.
– Temporary works requirements identified for trench support and service supports.
Common mistakes
# Assuming old drawings equal certainty
/> Record plans are often indicative; treating them as exact leads to overconfidence and strikes.
# Letting the permit live in the folder, not at the dig
/> If the permit isn’t visible and referenced at the workface, crews drift back to habit and shortcuts.
# Forgetting interfaces with other trades and traffic
/> Adjacent activities can push barriers, alter plant routes or create distractions that defeat controls.
# Mixing up “service found” with “service made safe”
/> Exposure is not the same as protection; leaving a live cable uncovered or unsupported invites damage later in the shift.
Bottom line for supervisors and permit issuers
/> A permit to dig for live services is a control process that begins days before the first hole and ends only when the ground is made safe again. It aligns information, competence and behaviour so that surprises in the ground don’t become injuries in the news. The strongest sites make the permit visible, the hold points non-negotiable, and the briefings short but specific.
# Immediate site week priorities (next 7 days)
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– Map upcoming digs and group utility searches so results arrive before the programme crunch.
– Walk the next two permit areas and pre-plan barrier lines, plant access and spoil locations.
– Line up a vacuum excavation unit for trial holes in high-risk corridors rather than hoping to hand-dig quickly.
– Refresh locator competence: quick on-site practice checks and reissue the scan sketch standard.
– Agree a simple stop-and-call rule: any uncharted service, depth variance or broken marker triggers a pause and a supervisor visit.
If scrutiny on utilities bites anywhere, it’s on whether your permit controls exist at the kerb, not just in the office. Three questions for the next briefing: Who is competent to scan and brief? Where are our hold points printed at the workface? What will make us stop if the ground disagrees with the plan?
FAQ
# When is a permit to dig actually needed?
/> Use a permit whenever there’s a reasonable chance of encountering buried services or when the client or principal contractor specifies it. That includes minor hand digs if plans are unclear or services are known nearby. Treat it as good practice for all intrusive ground works in live environments.
# How close to a marked service can I use plant?
/> Good practice is to define a no-mechanical tolerance zone and start with hand or vacuum excavation until the service is exposed and its exact position confirmed. The width of that zone depends on confidence in the survey and site conditions. If in doubt, expand the zone and bring plant in only after a hold point sign-off.
# Who should sign and brief the permit?
/> A competent permit issuer, usually from the principal contractor or the responsible subcontractor, should sign, and the working supervisor should brief the crew. The people using the locator and leading the dig must understand the controls and hold points. Keep the briefing at the workface, using the marked ground and sketches, not just paperwork.
# What if utility search results are delayed?
/> Do not treat the absence of records as the absence of risk. Adjust the method to trial and verify more cautiously, expand exclusion zones, and push the programme to wait where sensible. Escalate to the client or PC if the delay affects safety-critical decisions.
# How should temporary works tie in with service digs?
/> If excavation sides need support, or services must be bridged or propped, bring temporary works into the planning stage. Get simple designs or standard solutions agreed before you break ground, and make sure the crew understand when supports go in and come out. Temporary works checks should be hold points on the permit, not an afterthought.
