An excavation permit authorises a specific excavation in a specific location for a specific time window, recording the underground services survey, the chosen excavation method, the support / battering design, and the daily inspection regime. It is required by every UK principal contractor working under CDM 2015 and is the practical mechanism for discharging the HSG47 'Avoiding danger from underground services' duty.
Underground service strikes are the single most-investigated incident category in UK groundworks. HSG47 (Avoiding danger from underground services) sets the framework, but it is not a permit by itself — the permit is the site-level document that ties together the service plans (drawn from utility records and confirmed by a CAT and Genny survey), the chosen excavation method (mechanical, hand-dig in proximity zones, vacuum excavation around live services), the support design, and the supervisor sign-off.
The permit also satisfies regulation 22 of CDM 2015 — the principal contractor's duty to plan and monitor excavation works — and provides the audit trail that the HSE looks for after a strike or collapse.
HSG47 requires a three-step approach: plans, locate, dig. The permit records all three. Service plans must be obtained from every utility owner in the area (LinesearchBeforeUDig is the standard UK portal); the survey on site must use a CAT (Cable Avoidance Tool) and Genny in power, radio and generator modes; and the dig must respect the proximity rules — hand-dig within 500 mm of a known service location, vacuum excavation within 100 mm of live LV cables.
Reviewers reject permits that record a CAT scan without naming the operator, the equipment serial number, the calibration date, or the scan pattern (parallel passes 250 mm apart, repeated in two directions). Generic 'CAT scanned' entries are not sufficient.
The Construction (Design and Management) Regulations 2015, regulation 22(1), require excavations to be supported as necessary to prevent collapse. The permit references the support design — trench box specification, sheet piling, or battered sides at the angle of repose for the soil class (typically 1:1 in clay, 1:2 in sand / gravel, but always per a competent person's design). For excavations over 1.2 m deep, support is the default; deeper than 4 m, a temporary works designer (TWD) sign-off is normally required.
The permit also records the spoil heap setback (minimum 1 m from the edge), the access / egress arrangement (ladders within 7.5 m horizontal travel, extending 1 m above the edge), and the plant proximity rule (no plant tracking within 1 m of the excavation edge unless designed for it).
CDM 2015 regulation 22(2) requires excavations to be inspected by a competent person at the start of each shift, after any event likely to have affected its stability (heavy rain, vibration from plant, accidental fall), and after any unintentional fall of material. The permit references the inspection register (Form 91 Part 1, Section A is the standard UK record) and names the competent person.
A permit that doesn't reference the inspection regime is functionally one-shot and does not discharge the regulation 22(2) duty. Most insurers and principal contractors now require permits to expire daily, with re-issue after the shift inspection has been signed.
The numbered sections a reviewer expects to see, in order.
Sequential number, exact location (grid reference / drawing reference), proposed depth and dimensions.
Utility plans obtained (list owners), CAT and Genny survey with operator, equipment serial, calibration date, scan pattern recorded.
Mechanical, hand-dig zones, vacuum excavation areas — with proximity rules to known services.
Trench box / sheet pile / battering — design reference and temporary works designer sign-off for deep excavations.
Spoil setback ≥ 1m, edge guardrails / barriers, ladder access within 7.5m travel, extending 1m above edge.
No plant within 1m of edge unless designed for it; banksman arrangements.
Where excavation may meet Confined Spaces Regs 1997 criteria, atmospheric testing regime and reference to confined space permit.
Competent person named, inspection register reference (Form 91 Part 1A), expiry / re-issue schedule.
Issuer signature, operative briefing, permit cancellation when excavation backfilled or area handed back.
Why a permit gets sent back — these are the patterns we see most often.
The legal framework this permit operates inside. Links go to the official source.
SI 2015/51 reg 22
The statutory duty to prevent collapse and to inspect — the core regulation the permit operates under.
HSE HSG47
The reference document for service surveys, CAT / Genny use and proximity rules.
HSE HSG185
Standard reference for excavation support, access and inspection.
SI 1997/1713
Applies where the excavation meets the regulation 1(2) test (specified atmospheric risk).
Not directly named in statute, but it is the standard mechanism for discharging the CDM 2015 regulation 22 duties to plan, support and inspect excavations and the HSG47 duty to avoid services. Every UK principal contractor operating under CDM 2015 will require one.
There is no fixed depth in statute, but in practice excavations over 1.2 m are presumed to require support unless battered to the angle of repose for the soil class by a competent person. HSE prosecutions under CDM reg 22 frequently involve unsupported excavations between 1.2 and 2 m where 'we were only in for a minute' was the operative's defence.
Operator name, equipment make / model and serial number, calibration date (within manufacturer's interval), the modes used (power, radio, generator), the scan pattern (parallel passes at ≤ 250 mm spacing, repeated perpendicular to the first pass), and any anomalies detected with their location marked on a sketch or plan.
No. The plans are a precondition to the permit. The permit records that plans were obtained from every utility owner (via LinesearchBeforeUDig in most UK locations) and confirms the on-site survey reconciled with the plans. Permits issued without the plan-request audit trail are routinely rejected.
Most principal contractors require daily re-issue, paired with the regulation 22(2) shift inspection. This is because excavation stability can change overnight (rain, frost, vibration from adjacent plant) and the shift inspection is the regulatory mechanism for verifying continued safety.
Trade-specific RAMS guidance for the contractors who typically produce this permit.
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Final RAMS must be reviewed and approved by a competent person before use.