When is a SWMS Required for Excavation and Earthmoving?
A Safe Work Method Statement is legally required under WHS Regulation 2025 Part 6.1 Division 3 before any high-risk construction work commences. Schedule 1 of the Regulation identifies the 18 categories of HRCW, and excavation and earthmoving work routinely triggers several of them at once.
The most obvious trigger is work in or near a trench or shaft with an excavated depth greater than 1.5 metres. This is the point at which trench collapse becomes reliably fatal, because the weight of soil above a worker's head is sufficient to cause compressive asphyxiation and blunt-force internal injury. Note that the 1.5 metre threshold applies to the excavated depth, not the depth at which a worker is standing — a 2 metre trench with a worker standing on backfill at 1.2 metres is still regulated as a 2 metre excavation.
Additional HRCW triggers routinely activated by excavation include: work on or near energised electrical installations (underground power cables); work on or near pressurised gas distribution mains; work on or near chemical, fuel, or refrigerant lines; work in an area that may have a contaminated or flammable atmosphere (brownfield sites, landfill cells, former service station sites); work in an area where there is any movement of powered mobile plant; work involving a confined space (deep excavations with restricted access, valve chambers, sumps); and work in or near water that involves a risk of drowning (excavations below the water table, work near rivers or stormwater).
In Victoria, the equivalent trigger is contained in Part 5.1 of the OHS Regulations 2017 and uses employer/employee terminology rather than PCBU/worker. The substantive threshold of 1.5 metres excavation depth is the same. Tasmania, Queensland, South Australia, Northern Territory, ACT, and Western Australia all follow the harmonised WHS model.
Trench Collapse — The Primary Fatal Hazard
Trench collapse is the defining hazard of excavation work. The Code of Practice: Excavation Work (Safe Work Australia, 2018) identifies unsupported excavation as a significant cause of fatality in Australian construction, and state regulator investigations routinely find that fatal collapses occurred in trenches that had no shoring, no battering, and no benching.
The physics are unforgiving. One cubic metre of dry soil weighs approximately 1.5 tonnes; saturated clay or silty soils can exceed 1.9 tonnes per cubic metre. A worker buried to chest height under collapsed soil cannot expand their ribcage against that weight, and suffocation occurs within three to five minutes. Even partial burial from knee height can cause crush injuries to pelvis and lower limbs that require immediate technical rescue. Because the weight of soil progressively compresses the worker's chest, the time between collapse and cardiac arrest is often shorter than the time required for a rescue team to arrive on site.
Ground conditions change without visible warning. A trench that stood open for two days may collapse on day three because of overnight rain, vibration from nearby plant, surcharge loading from spoil piled too close to the edge, or simple relaxation of the soil mass. The Code of Practice requires that excavations deeper than 1.5 metres must be battered, benched, or shored unless a competent person has assessed the soil and certified that the walls are stable for the duration of the work. 'We didn't think it would collapse' is not a defence — the regulator expects ground support or certified stability, full stop.
Shoring systems used in Australia include hydraulic aluminium shores, trench shields (sometimes called trench boxes), timber shoring, steel sheet piling for deeper or waterlogged excavations, and soldier pile and lagging systems for larger civil works. Each system has load ratings and installation requirements that must be followed in accordance with the manufacturer's instructions and, where required, a geotechnical engineer's design.
Underground Service Strikes
Underground service strikes are the second category of fatal excavation hazards. Striking a live 11 kV or 33 kV underground cable with an excavator bucket can electrocute the operator through the machine, eject molten copper and vaporised soil at the strike point, and cause explosive failure that injures ground crew within several metres. Striking a pressurised gas main can release natural gas or LPG that ignites on contact with the excavator exhaust or any ignition source on site, causing fire and explosion. Striking a high-pressure water or wastewater main can erode surrounding soil and destabilise the excavation, precipitating collapse on workers inside.
The primary control is a Before You Dig Australia (BYDA) plan obtained before any ground disturbance. BYDA is a free service that coordinates with asset owners — electricity distributors, gas networks, water authorities, telecommunications carriers, and local councils — to provide plans of known underground services at the excavation location. Plans must be obtained within the previous 30 days because networks are extended and modified continuously. A plan obtained six months ago may no longer accurately reflect what is in the ground.
BYDA plans do not eliminate the need for physical verification. Plans have a stated tolerance (typically ±500 mm to ±1 metre depending on the asset owner) and may be inaccurate due to historic survey errors, undocumented relocations, and private services that were never registered. The Code of Practice: Excavation Work requires that mechanical excavation within the plan tolerance zone of any underground service must be preceded by hand-digging, hydro-excavation (vacuum truck), or cable-locating using an electromagnetic locator. This process is sometimes called 'potholing' and is mandatory for any excavation near known services.
A SWMS for excavation must document the BYDA process, the physical verification method, the exclusion zones around located services, and the escalation procedure if an unknown service is encountered during digging. The SWMS should name the asset owner emergency contact for each category of service and specify the stop-work threshold that triggers notification.
Powered Mobile Plant and Plant-Pedestrian Interaction
Earthmoving sites operate multiple powered mobile plant simultaneously: excavators, wheel loaders, skid steer loaders, dump trucks, articulated dump trucks, graders, rollers, scrapers, and dozers. Plant-pedestrian interaction — where a worker on foot is struck, crushed, or run over by moving plant — is a persistent cause of fatality and serious injury on civil sites.
The hierarchy of controls for plant-pedestrian risk begins with elimination: physically separating workers from plant operating areas using exclusion zones, fencing, or designated pedestrian-only routes. Where separation is not reasonably practicable, the next control is ensuring that every operator has direct line-of-sight to any worker within the plant's operating envelope, supplemented by 360 degree camera systems, proximity sensors, and RFID-based proximity warning systems for machines with known blind spots.
All plant operators must hold the relevant High Risk Work Licence where required, or demonstrate verifiable competency where a licence is not mandatory. The unit of competency for excavator operators is RIIMPO320F (Conduct civil construction excavator operations), which is the current national code. Older codes such as RIIMPO320E are superseded and should not be referenced in current SWMS. Wheel loaders, dozers, graders, and scrapers each have their own RII competency codes.
The SWMS must document the traffic management plan for the site — the routes that plant will take, the locations where workers will be on foot, the spotters and traffic controllers who will manage interactions, and the communication protocol (two-way radio, hand signals, horn signals) that will coordinate plant movements with worker activity. For larger civil sites, the traffic management plan should be a separate controlled document referenced from the SWMS.
Hierarchy of Controls for Excavation Work
The WHS Regulation 2025 requires that risks be managed in accordance with the hierarchy of controls, from most effective (elimination) to least effective (personal protective equipment). For excavation and earthmoving, the hierarchy applied to the critical hazards is as follows.
Elimination: wherever reasonably practicable, eliminate the need for workers to enter excavations at all. This can be achieved by specifying trenchless methods (horizontal directional drilling, microtunnelling, pipe bursting) for service installation; by using remote-operated or long-reach excavators for the final trim rather than hand-finishing; and by designing drainage and services to run in shallow trenches where workers can complete connections from above.
Substitution: where excavation cannot be eliminated, substitute hand-digging or mechanical excavation with vacuum excavation (hydro-excavation) in the vicinity of underground services. Vacuum excavation eliminates the risk of cable or pipe strike from a tool or bucket and is now the standard method for exposing services in tolerance zones.
Isolation: isolate workers from unstable ground by using trench shields, hydraulic shoring, or steel sheet piling. Isolate workers from moving plant by establishing exclusion zones marked by physical barriers and signage. Isolate the excavation from surface water by using bunding, diversions, and pump sumps to prevent inundation.
Engineering controls: specify battering of trench walls to the natural angle of repose for the soil type (typically 45 degrees for firm clay, 34 degrees for loose sand); specify benching for excavations deeper than 3 metres; design ground support systems and have the design certified by a Chartered Professional Engineer where required; use geotechnical assessment to determine whether the ground can stand unsupported for the duration of the work.
Administrative controls: obtain BYDA plans before any ground disturbance; conduct daily pre-start inspections of all excavations and ground support before entry; implement a permit-to-enter system for excavations deeper than 2 metres; train all workers in excavation hazards (unit of competency RIICWD503D); implement atmospheric monitoring for deep excavations or excavations in contaminated ground; establish and communicate emergency rescue procedures.
Personal protective equipment: high-visibility clothing to AS/NZS 4602.1; safety helmet to AS/NZS 1801; steel-capped safety boots to AS/NZS 2210.3; eye protection to AS/NZS 1337; hearing protection to AS/NZS 1270 when working near plant; gas detectors (four-gas) for deep excavations or contaminated ground.
Training and Competency Requirements
Every worker carrying out excavation or earthmoving work must hold the General Construction Induction (White Card) under unit of competency CPCCWHS1001. This is the minimum prerequisite for any work on a construction site in Australia. Workers also require training in the specific hazards of the work they will carry out, delivered before the work commences and documented on the worker sign-on sheet for the SWMS.
Excavator operators should hold RIIMPO320F (Conduct civil construction excavator operations). Wheel loader operators should hold the relevant RII unit for wheeled or tracked loaders. Dozer operators should hold RIIMPO318F or equivalent. Roller operators should hold RIIMPO317F. Dump truck operators on haul roads should hold RIIMPO321F. Where the plant is used on a public road, the operator must also hold an appropriate driver licence class issued by the relevant state road authority.
Forklifts and order pickers require a TLILIC0003 or TLILIC0004 High Risk Work Licence depending on the specific machine. Elevated work platforms with a boom length over 11 metres require a WP class HRWL. Dogging and rigging on civil sites involving crane operations require the relevant DG or RB/RI/RA HRWL.
Workers entering deep excavations that meet the definition of a confined space must be trained in confined space entry to AS 2865:2009 (note that AS 2865 explicitly excludes trenching and general excavation work from its scope, but applies where the excavation meets the confined space definition due to restricted access, atmospheric hazards, or limited egress). Confined space training is delivered as unit MSMWHS217 (Gas test atmospheres) combined with MSMPER205 (Enter confined space) or equivalent industry training.
Codes of Practice and Australian Standards
The following regulatory instruments apply to excavation and earthmoving SWMS and must be referenced where relevant: Code of Practice: Excavation Work (Safe Work Australia, 2018), which is the primary practical guidance document for excavation in the model WHS jurisdictions; Code of Practice: Construction Work (Safe Work Australia, 2018); Code of Practice: Managing the Risks of Plant in the Workplace (Safe Work Australia, 2020); Code of Practice: Confined Spaces (Safe Work Australia, 2020); and Code of Practice: Managing Electrical Risks in the Workplace (2022) where underground electrical services may be encountered.
In Victoria, the equivalent documents are Compliance Codes rather than Codes of Practice, issued by WorkSafe Victoria. Victoria uses the Compliance Code: Excavation and the Compliance Code: Confined Spaces. The legal status differs slightly — Victorian Compliance Codes provide practical guidance on compliance with the OHS Act 2004 and OHS Regulations 2017, but Codes of Practice in WHS jurisdictions are admissible in proceedings as evidence of what is known about a hazard.
Relevant Australian Standards include AS 2187.2 (Explosives — Use of explosives, for blasting operations); AS/NZS 4576 (Guidelines for scaffolding); AS 2865:2009 (Confined spaces, where the excavation meets the confined space definition); AS 1742.3 (Manual of uniform traffic control devices — Traffic control for works on roads, for civil sites interacting with public roads); and AS 4970 (Protection of trees on development sites) where excavation occurs near trees protected under planning instruments.
Each template in this guide references the specific standards applicable to that activity.
Emergency Rescue and Notifiable Incidents
The Code of Practice: Excavation Work requires that every excavation SWMS include an emergency rescue plan capable of retrieving an injured or buried worker within the shortest possible timeframe. Because compressive asphyxiation from trench burial can cause death within three to five minutes, emergency services (000) will in most cases not arrive in time to rescue a worker who has been fully buried. The rescue plan must therefore provide for immediate on-site response using the plant and equipment already present.
On-site rescue equipment for excavation work should include: a second competent excavator operator and machine capable of clearing spoil quickly without further endangering the buried worker; shovels and hand tools for the final exposure once the victim is located; a trauma first aid kit including oxygen, trauma dressings, and a spinal board; and a means of immediate communication to emergency services. All workers must be briefed on the rescue procedure before entry, and the site supervisor must confirm that the rescue equipment is present and operational at the start of every shift.
Under WHS Act 2011 section 38, a notifiable incident must be reported to the regulator as soon as practicable. A notifiable incident includes any death at a workplace; any serious injury or illness requiring hospital admission; and any dangerous incident, which explicitly includes the collapse or partial collapse of an excavation. This means that even a trench collapse with no injury must be notified to the regulator. The site must be preserved in the state it was in immediately after the incident until an inspector authorises disturbance, unless preservation would create further risk.
Industrial manslaughter is now an offence in every Australian state, territory, and at the Commonwealth level. The maximum penalties for industrial manslaughter range from 20 years imprisonment to life imprisonment depending on the jurisdiction, and corporate fines can exceed $18 million. A SWMS that specifies shoring which was not installed, or that identifies a rescue plan which was not rehearsed, becomes key evidence in any such prosecution.