Excavation
permit to work

Any excavation, trench, pit, or ground penetration work.

These are the precautions the issuer confirms before signing. Each one says what good looks like, when it passes, the regulation it rests on and how it usually fails. Critical precautions are marked: if one cannot be confirmed, the permit is not issued.

Precautions before issue

1. 1.

   Service drawings obtained and reviewed
   What to look forStatutory undertakers searched within last 28 days (LSBUD or equivalent for gas, water, electricity, telecoms, district heating). Plans reviewed and translated onto site mark-up showing depth, type, owner, and emergency contact. Where drawings are absent the area is treated as having unknown services and full proving by hand-dig is required. Plans printed and on site, NOT just on the project manager phone in the office.
   Acceptable whenDrawings <28 days old (services move, get added, get cut over). All four utilities searched (electric, gas, water, telecoms) plus district heating, fibre, fuel pipelines, MoD/Network Rail signalling where applicable. Site mark-up cross-referenced to drawings before scanning.
   StandardHSG47 Avoiding danger from underground services (4th ed). New Roads and Street Works Act 1991. Health and Safety at Work Act 1974 s.3. CDM 2015 reg 13 (principal contractor).
   Common defectsPlans 6+ months old, recent service not shownOnly electricity searched, gas main struck during digDrawings reviewed in office, not brought to site, operative unable to cross-referenceNetwork Rail / MoD assets not searched, high-voltage signalling cable struckPrivate services (site cabin power, on-site fuel line) not on statutory plans, no separate site search
2. 2.

   CAT and Genny scan completed

   Critical: a fail stops the work
   What to look forCalibrated CAT4+ (or equivalent) scan of the full excavation footprint AND a 1m perimeter, in all three modes (Power, Radio, Genny) with operator using sweep technique, slow, low to the ground, overlapping passes. Genny applied to known services (e.g. the visible MV pillar) to induce a signal that traces the cable run. Scan repeated AFTER each 300mm of dig depth, not just once at surface. CAT calibration valid (annual cert).
   Acceptable whenCAT4+ with current calibration cert (annual). Three-mode scan (P, R, G). Sweep speed <0.25 m/s. Repeat scan every 300mm of depth. Genny used on traceable services. Operator trained and competent (e.g. EUSR Locator or equivalent).
   StandardHSG47 4th ed. EUSR / SHEA-Power locator competence schemes. PAS 128:2022 (utility detection survey).
   Common defectsCAT scan in Power mode only, radio-frequency-only services and inert pipes missedCAT calibration certificate >12 months, readings unreliable, court-inadmissibleSingle surface scan, no re-scan as depth increases, service struck at 800mm by mini-excavatorGenny not used to confirm direction of known cable, service direction assumedOperator with no training using the unit, readings misinterpretedScan footprint smaller than excavation, service struck just outside scan zone
3. 3.

   Hand dig within 500mm of detected services
   What to look forOnce a service is detected by CAT/Genny, mechanical excavation stops at least 500mm clear of the indicated position. Trial holes by hand using insulated tools (insulated shovel, fork, no picks). Operator wears arc-flash PPE for cable risk. Service exposed, identified, marked, then mechanical dig resumes only past the service. Where multiple services run parallel, each is exposed individually.
   Acceptable when500mm hand-dig buffer (HSG47). Insulated tools EN 60900. Insulated gloves class 0 minimum (EN 60903) where electrical risk. Service positively identified by colour/marker tape/duct type before mechanical dig resumes.
   StandardHSG47 4th ed s.5. EN 60900 insulated hand tools. EN 60903 insulating gloves. Electricity at Work Regs 1989 reg 14.
   Common defectsMini-excavator scrapes "carefully" through 500mm zone, service hitPick or pneumatic breaker used in hand-dig zone, pierces service jacketCable assumed to be the LV one shown on drawing, actually MV, flash incidentService not exposed for the full crossing length, struck 2m further alongNo insulated PPE, hand-dig operative shocked through contact
4. 4.

   Trench support/battering design adequate

   Critical: a fail stops the work
   What to look forFor trenches >1.2m deep, sides supported (trench box, sheet piles, hydraulic shores) OR battered to a safe angle for the soil. Design by a competent temporary works engineer where the system is non-standard. Battering angle: 1:1 (45 deg) cohesive firm clay, 1:1.5 to 1:2 for granular/loose, 1:3 for waterlogged/running sand. Trench box top 150mm above ground level. Battering AND boxes cannot mix freely, get a TWC sign-off.
   Acceptable whenSupport designed for the soil and depth. >1.2m always supported or battered (HSG185). Trench box top above ground level by 150mm. Soil category assessed by competent person (CIRIA C760 / BS 6031). Daily inspection by trained inspector.
   StandardCDM 2015. PUWER 1998. HSG185 Health and safety in excavations (1999). BS 6031:2009 Earthworks. CIRIA C760 Guidance on embedded retaining wall design.
   Common defectsVertical sides at 1.5m in clay assumed self-supporting, collapse during wet weatherTrench box too short, ends of trench unsupported, side collapse from endBox not stepped properly when trench deepens, operative below the box baseBattering angle from a generic table, soil never tested, wrong angle for actual groundSpoil pile loading the battered slope, surcharge collapse
5. 5.

   Edge protection barriers in place
   What to look forPhysical barrier 1m clear of the excavation edge, Heras fence pinned with feet, trench-edge handrail (top rail 950mm-1100mm, mid rail, toeboard), or proprietary edge-protection system. Continuous around the full perimeter, not just the obvious side. Lit at night (red flashing lamps) where pedestrian risk. Pedestrian routes diverted with signage.
   Acceptable whenTop rail 950-1100mm, mid rail max 470mm gap, toeboard 150mm. Continuous closed perimeter. Standoff 1m minimum from edge. Heras feet weighted not just placed. Night lighting where public access.
   StandardWork at Height Regs 2005 sch.2. CDM 2015 reg 22 (excavations). HSG150 Health and safety in construction.
   Common defectsHeras panels free-standing on hard surface, no feet, blow over in windSingle-rail safety tape only, no fall arrest if person leans on itGap left for wheelbarrow access, never closed, pedestrian route to fallEdge protection inside the 1m zone, surcharge from feet plus barrier weightNo night lighting at public boundary, fall hazard after dark
6. 6.

   Safe access/egress provided (ladders)
   What to look forLadder, ramp, or stairway sited so any operative is within 7m of safe access at all times along the trench length. Ladder secured top and bottom (lashed or stake-pinned), extends 1m above the platform/ground level, 4:1 angle (1m out for every 4m up). Class 1 industrial or BS 2037 / EN 131 professional. Inspected pre-shift.
   Acceptable whenAccess within 7m walking distance throughout trench. Ladder EN 131 / BS 2037 class 1. Extends 1m above landing. 4:1 angle. Both ends secured. Pre-shift inspection log.
   StandardWork at Height Regs 2005 sch.6 (ladders). HSE INDG402 Safe use of ladders and stepladders. BS 2037 / EN 131.
   Common defects60m trench, single ladder at one end, operative 30m from accessLadder unsecured at top, slips when descending operative leans backwardsLadder too short, 700mm step from top rung onto ground levelDomestic-grade ladder (class 3) used, bends under loadWooden plank as a ramp on saturated ground, slips
7. 7.

   Materials stored >1m from edge
   What to look forSpoil heaps, pipes, kerbs, manholes, plant outriggers all stored or sited a minimum 1m clear of the trench edge, preferably 2m where the trench is deep. Surcharge from stored material is the classic cause of progressive collapse. Plant tracking parallel to a trench is at least one-trench-depth away.
   Acceptable when1m minimum to spoil/material edge. 2m where trench >1.5m deep. Plant standoff = trench depth (i.e. 3m deep trench = 3m plant standoff) OR battered with engineering check.
   StandardCDM 2015 reg 22. HSG185. BS 6031.
   Common defectsSpoil tipped at edge to "save double-handling", surcharge collapse onto operativePipe stack within 500mm of edge, battered face failsExcavator outrigger within 1m, slips into trench during digStored material height equal to trench depth, equivalent to a wall of soil pushing on the side
8. 8.

   Dewatering provisions if required
   What to look forWhere groundwater inflow is expected, dewatering pump (typically electric submersible 110V CTE or diesel) sited at the deepest sump with a settlement tank before discharge. Discharge consented by the EA / SEPA / NRW where to a watercourse, or to foul sewer with water company consent. Pump auto-cuts on float. Backup pump on site. Saturated soil reduces support capacity by ~50%, battering angle reduces accordingly.
   Acceptable whenDewatering rate matches measured inflow. Discharge consented. Settlement tank capacity >2 minutes pump output. 110V CTE or IP rated pump. Backup pump available. Soil re-assessed once saturated.
   StandardWater Resources Act 1991. Environmental Permitting Regulations 2016. CIRIA C750 (groundwater). BS 6031.
   Common defectsPump discharge to surface water without EA permit, silt-laden discharge prosecutedNo backup pump, primary fails overnight, trench fills, side collapses on resumptionPump cable run through the trench unprotected, abraded by trafficNo settlement tank, silt plume in watercourseSaturated battered face not reassessed, collapse
9. 9.

   Competent person to inspect daily

   Critical: a fail stops the work
   What to look forDocumented inspection by a competent person (P401-equivalent for excavations or trained TW Coordinator) at the start of each shift, after any event likely to have affected stability (rain, plant impact, freeze-thaw, surcharge change), and before any operative re-enters. Inspection report kept on site for 3 months and at the office for 3 years (CDM reg 24/25). Signed and timed.
   Acceptable whenInspection at start of every shift, after substantive events, after 7 days continuous occupation. Inspector competent (formal training, demonstrable experience). Form F91 part 1 section B or equivalent. Records retained 3 months on site, 3 years off.
   StandardCDM 2015 reg 22(1)(b), 24, 25. PUWER 1998. HSG185.
   Common defects"Eyeball" inspection by site agent with no formal training, defects missedNo written record, inspection deniable post-incidentInspection not repeated after weekend rain, saturated face collapses Monday7-day occupation passed without re-inspectionInspector failed to look behind shoring panels, voids between panel and soil
10. 10.

    Exclusion zone for plant near edge
    What to look forA clearly defined zone around the excavation where wheeled and tracked plant cannot encroach, physical barrier (Heras, kerb stop block) plus banksman where plant must operate adjacent. Standoff distance equal to trench depth at minimum, or per the temporary works design. Plant operator briefed and signaller present where reversing toward the edge.
    Acceptable whenStandoff = trench depth (1:1) OR per TWC design. Stop blocks / Heras at the limit. Banksman at any plant approach within 2x standoff. Reversing alarms enabled. Plant on outriggers or tracks confirmed.
    StandardCDM 2015. PUWER 1998. HSG144 The safe use of vehicles on construction sites. HSG185.
    Common defectsNo stop block, telehandler reverses into trenchBanksman doubles as ground-worker, leaves the standoff zoneStandoff measured from plant track edge not from outermost point, counterweight overhangs trenchSlewing crane counterweight passes over trench, operatives below in collapse fanReversing alarm disabled by tape, pedestrian struck

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