Trenching and Shoring — Safe Work Method Statement
Safe Work Method Statement for excavation of trenches and installation of shoring systems on construction sites, addressing risks of ground collapse, buried services, and working in confined spaces.
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Trenching is one of the leading causes of fatal construction injuries in Australia and internationally. The model WHS Regulations classify any trench deeper than 1.5 metres as HRCW because of the risk of ground collapse and entrapment, making a SWMS mandatory. The Safe Work Australia Model Code of Practice: Excavation Work sets out detailed requirements for safe trench design, shoring selection, and rescue planning that must be reflected in this document.
Ground collapse in trenches can occur with no warning — soil that appears stable can fail in seconds when disturbed, saturated, or subjected to vibration from nearby plant. A worker engulfed by 1 m³ of soil experiences approximately 1.5 tonnes of pressure on the chest, making self-rescue impossible. Shoring, trench boxes, or properly designed battered/benched walls are not optional — they are mandatory for any person working in a trench over 1.5 m deep. The shoring design must be prepared or approved by a competent person with geotechnical or structural engineering qualifications appropriate to the ground conditions.
Shoring systems used in Australia include hydraulic trench boxes (typically rated to AS 3799 or equivalent), timber box shoring, and steel sheet piling. The selection depends on trench dimensions, soil type, surcharge loads, and the duration of the excavation. Proprietary trench shields must be used strictly within the manufacturer's rated capacity and configuration — improvised use outside rated parameters voids the design basis.
A deep trench also constitutes a confined space under the WHS Regulations when it has restricted means of entry or exit and may develop a hazardous atmosphere. Atmospheric testing is required before entry into trenches adjacent to sewers, contaminated land, or where gas services are present.
Customise this template with the trench dimensions, the geotechnical report findings, the shoring type and rated capacity, the dial before you dig reference, and the emergency rescue procedure including how an injured worker would be extracted. This SWMS applies in all Australian states and territories.
Personal Protective Equipment
High Risk Construction Work Types
- •Excavation deeper than 1.5 metres
- •Work near live buried services
- •Confined space entry
Risk Assessment
1.Pre-excavation site investigation and service location
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Striking underground utilities (gas, electrical, water, telecom) | Catastrophic | Obtain dial before you dig (DBYD) plans from all relevant authorities prior to commencing work. Mark all known services on the ground surface using coloured spray paint per AS 5488 classification (red=electrical, yellow=gas, blue=water, orange=telecom). Use a calibrated cable and pipe locator (e.g. CAT4+) operated by a trained and competent person to scan the full excavation zone. Conduct hand digging or vacuum excavation (non-destructive digging) within 300 mm of any located service. Brief all workers on service locations during pre-start toolbox talk and display updated service plans in the site office. | Low | Site Supervisor / Excavator Operator |
| Inaccurate or missing as-built service records | High | Treat all service location information as indicative only. Where DBYD records are incomplete or absent, extend hand-dig exclusion zones to 500 mm either side of estimated service path. Engage a licensed vacuum excavation contractor to expose services prior to mechanical excavation commencing. Document all exposed services with photographs and GPS coordinates and update site plans accordingly. | Moderate | Site Supervisor |
2.Mechanical excavation of trench
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Plant collision with workers on foot | Catastrophic | Establish and enforce a clearly marked exclusion zone of no less than the full swing radius of the excavator plus 2 metres. Use a banksman/spotter at all times when other workers are within 10 metres of the plant. Spotter must be in constant visual contact with the operator and stand in a designated safe observation position. Operator must stop machine immediately if visual contact with spotter is lost. Fit excavator with reversing alarm and proximity warning system. Conduct pre-start plant inspection and record on checklist before each shift. | Low | Excavator Operator / Banksman |
| Trench wall collapse onto workers during excavation | Catastrophic | Assess soil classification (Types 1, 2, 3 per AS 4678) before excavation commences by a competent geotechnical person. For excavations exceeding 1.5 m depth in Type 2 or 3 soils, install hydraulic shoring, trench shields, or benching/battering to engineered design. Keep spoil a minimum of 600 mm from trench edge. Do not allow workers to enter the trench until shoring is fully installed and inspected. Review shoring condition after rainfall or ground disturbance events. | Moderate | Site Supervisor / Competent Person |
3.Installation of shoring or trench support
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Shoring system failure causing ground collapse | Catastrophic | All shoring systems must be designed by a structural or geotechnical engineer and installed strictly in accordance with the design drawings and manufacturer specifications. Only competent persons trained in the specific shoring system type may install, adjust, or remove shoring components. Inspect shoring daily before workers enter trench. Immediately evacuate and reassess if cracking, heave, or movement of trench walls or shoring is observed. Do not exceed rated loads on hydraulic struts. | Low | Competent Person / Site Engineer |
| Manual handling injuries during shoring component installation | Moderate | Use mechanical lifting aids (excavator attachment, chain block, or mechanical lifting frames) for shoring panels and struts exceeding 20 kg. Ensure workers use team-lift technique for components between 10–20 kg. Pre-position shoring materials adjacent to trench to minimise carry distances. Provide training in manual handling techniques. Workers with pre-existing back or musculoskeletal injuries must be assessed before undertaking this task. | Low | All Workers / Site Supervisor |
4.Working in and around open trenches
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Falls into open trench | High | Install compliant edge protection (safety mesh, barriers, or handrails) to all open trench edges not immediately being worked. Use secured trench covers when work in trench is not being actively performed. Mark all trench edges with high-visibility barrier tape and bollards. Ensure adequate lighting (minimum 80 lux) in trench. Provide fixed ladders or purpose-built trench access stairs at maximum 9 m intervals — workers must not climb up shoring panels or jump in/out. Implement pedestrian exclusion zones around the trench perimeter. | Low | Site Supervisor / All Workers |
| Water ingress and trench flooding | High | Monitor weather forecasts daily and implement trench dewatering plan before any rain event exceeding 10 mm expected. Install sump pump with automatic float switch at lowest point of trench. Workers must immediately evacuate trench if water begins to accumulate and not re-enter until trench is fully dewatered and walls inspected by competent person. Cover open trenches overnight with waterproof sheeting secured at edges. Check trench walls for softening or increased moisture after dewatering before re-entry. | Moderate | Site Supervisor |
5.Backfilling and compaction of trench
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Compaction plant overrunning workers | High | Establish an exclusion zone around vibrating plate compactors and trench rollers equal to the machine width plus 1 metre on each side. Workers must not stand in the trench while compaction is being conducted at the surface. Operator must perform a visual check before each pass to confirm zone is clear. Use dead-man switch compaction equipment where available. Brief all workers on exclusion zones during pre-start meeting. | Low | Compaction Operator / Site Supervisor |
| Noise and vibration exposure from compaction equipment | Moderate | Assess noise levels for compaction equipment against WHS Regulations exposure standard of LAeq,8h 85 dB(A) and LC,peak 140 dB(C). Provide hearing protection (Class 4 or 5 earmuffs) to all workers within 10 metres of operating compaction equipment. Rotate workers to limit individual exposure duration. Conduct hearing surveillance for workers regularly exposed. Vibration white finger assessment for operators using hand-held compactors on extended tasks. | Low | Site Supervisor / All Workers |
Relevant Codes of Practice
Worker Acknowledgement
By signing below, I confirm that I have read, understood and agree to comply with this Safe Work Method Statement.