Excavation SWMS Australia: Trenching, Hazards and Controls

When does excavation work need a SWMS?

The clearest trigger is depth: under the model WHS Regulations, construction work involving a trench or shaft deeper than 1.5 metres is high-risk construction work, so it needs a SWMS before it starts. But depth is not the only trigger, and a shallow excavation can still need one — for example where the work is near underground or overhead services, or involves powered mobile plant, each of which is its own high-risk construction work category. So the question is not only "how deep?" but "does this excavation involve any high-risk category?" Requirements can vary by jurisdiction; check your state or territory regulator.

Ground collapse — the risk that defines trenching

The hazard that makes trenching so dangerous is the one people underestimate: the collapse of the excavation face. A cubic metre of soil is heavy enough to kill, and collapses happen without warning. The SWMS must set out how the ground is controlled — benching, battering, or shoring and shielding with trench boxes — chosen for the actual ground conditions and depth, not assumed. Ground conditions, previous excavation, water and weather all change the risk and belong in the assessment.

Services, above and below

Striking a buried gas main, water main or electrical cable, or contacting overhead powerlines with plant, is a leading cause of serious excavation incidents. The SWMS should cover how underground services are located and identified before digging — plans, location tools, potholing — and how overhead services are kept clear, with exclusion zones and controls for plant working near them.

Plant, people and the edge of the hole

Excavators and other powered mobile plant working alongside people on foot is a hazard in its own right, so the SWMS should separate plant and pedestrians, control the swing and reversing zones, and use a spotter where needed. Spoil and materials placed too close to the edge add load and cause collapse, so their placement is a control. Safe access and egress into and out of the excavation, and exclusion zones around the open hole, complete the picture.

Competence, monitoring and review

Set out who is competent to do the work and operate the plant, induct every worker into the SWMS and record sign-ons, and — because excavation conditions change as you dig and as the weather turns — monitor the excavation and review the SWMS whenever conditions, method or plant change. Water entering a trench, a change in soil, or a service found unexpectedly are all review triggers.

Excavation SWMS checklist

• Whether the work is high-risk (trench/shaft over 1.5m, near services, or mobile plant)
• Ground control for the actual conditions: benching, battering, shoring or shielding
• Locating and identifying underground services before digging
• Overhead services kept clear, with exclusion zones for plant
• Separation of powered mobile plant and people on foot
• Spoil and material placement away from the edge
• Safe access and egress, and exclusion zones around the excavation
• Competent workers and plant operators
• Worker consultation, induction and recorded sign-ons
• Monitoring changing conditions and review triggers (water, soil, services)

Keep your excavation SWMS with the project rather than in a ute or an inbox: Complys can keep the SWMS and the associated worker, plant and contractor records organised against the work. See also SWMS software Australia, how to write a SWMS, construction compliance software and contractor management software. You can create and manage SWMS free for 90 days.