Excavation & trench collapse

Worker buried by collapse of unshored excavation wall. 1 m³ of soil weighs ~1.5 t — sufficient to fatally crush. HRCW under WHS Reg 291(1)(g) for trenches >1.5 m.

Controls (hierarchy of controls order)

1. Engineering controls

   Residual MEDIUM

   Battered or benched walls to safe angle of repose

   Walls battered to angle of repose for soil class (typically 45° for cohesive, 30° for granular); benched at every 1.5 m vertical; verified by competent person prior to entry.

   Cited: WHS Reg 304 · Excavation Work CoP

2. Engineering controls

   Residual MEDIUM

   Trench shields / shoring system

   Engineered trench shield or hydraulic shoring system designed by a structural engineer for the soil class and depth; installed top-down before any worker entry; inspected daily and after any rain/disturbance.

   Cited: WHS Reg 305 · Excavation Work CoP s 5

3. Administrative controls

   Residual MEDIUM

   DBYD search + hand-expose all services

   Dial Before You Dig search completed within 30 days of works; underground services hand-exposed (potholed) to a minimum 0.5 m clearance before any mechanical excavation within 3 m of indicated services.

   Cited: WHS Reg 304(1)(d) · Excavation Work CoP s 4.3

4. Administrative controls

   Residual MEDIUM

   Excavation permit + spoil setback

   Excavation permit valid for the shift; spoil set back ≥600 mm from edge or higher of (a) 600 mm or (b) depth-equivalent for granular soils; ladders every 7.5 m and within 3 m of any worker.

   Cited: WHS Reg 297(2) · Excavation Work CoP

PPE

• Industrial safety helmet — Type 1 industrial safety helmet with chin strap where required by site rules or wind exposure. Replace at expiry date or after impact.Standard: AS/NZS 1801
• Steel-cap safety boots — Type 1 safety footwear with steel toecap, slip-resistant sole, ankle support; electrical hazard rating where exposed to live electrical work.Standard: AS/NZS 2210.3
• Hi-visibility vest or shirt (day use) — Class D fluorescent hi-visibility garment for daytime use on site.Standard: AS/NZS 4602.1