When is a trench high risk construction work?

In construction work, work in or near a trench or shaft with an excavated depth of more than 1.5 metres is high risk construction work under model WHS Regulation reg 291. That combination — construction work plus a depth greater than 1.5 metres — makes it high risk construction work needing a Safe Work Method Statement (SWMS) before the work starts. If the work is not construction work, or the trench is 1.5 metres or less, it is not high risk construction work on that basis, but the duty to manage the risk of ground collapse still applies.

Do I need a SWMS to dig a trench?

You need a Safe Work Method Statement (SWMS) when the work is construction work and the trench or shaft is more than 1.5 metres deep — that is high risk construction work under WHS Regulation reg 291, and the SWMS must be prepared before the work starts (reg 299). For shallower trenches or non-construction excavation a SWMS is not specifically required, but you must still manage the risk of the ground collapsing and of a person or object falling in.

How do I prevent an excavation from collapsing?

Under the model WHS Regulations Part 6.3, a PCBU must manage the risk of ground collapse so far as is reasonably practicable. The main engineering controls are benching (cutting the walls into steps), battering (sloping the walls back to a safe angle), and shoring or shielding (supporting the walls with trench shields, props or sheet piling designed by a competent person). You must also keep excavated material (spoil), plant and stored loads back from the edge so the extra weight does not cause a collapse or material to fall in.

What is Dial Before You Dig?

Before You Dig Australia (formerly Dial Before You Dig) is a free service that helps you locate underground services — gas, electricity, water, telecommunications and other buried assets — before you excavate. Lodge an enquiry at byda.com.au, review the asset plans you receive, and have services marked, potholed or hand-dug as needed before machine excavation. Locating services is a key step in managing excavation risk and avoiding strikes.

What depth of excavation is safe without controls?

There is no depth at which an excavation is automatically safe. Any excavation can collapse — even a shallow trench can trap or bury a worker, because a cubic metre of soil can weigh more than a tonne. The duty to manage the risk of ground collapse and of a person or object falling in applies at any depth under model WHS Regulations Part 6.3. The 1.5 metre figure is only the trigger for high risk construction work needing a SWMS in construction; it does not mean shallower excavations are safe or unregulated.

Excavation & Trenching Safety Checker

Answer a few questions about your excavation. The tool tells you the ground-collapse controls to consider, whether the work is high risk construction work needing a SWMS (a trench deeper than 1.5 metres in construction), the Before You Dig step, and your safe access and egress duties.

Last verified: 21 June 2026

You must manage the risk of an excavation collapsing and of a person or object falling in, at any depth (model WHS Regulations Part 6.3). In construction work, a trench or shaft more than 1.5 metres deep is high risk construction work needing a SWMS (reg 291).

Your state or territory

Roughly how deep is the excavation or trench?

The duty to manage ground collapse applies at any depth. Depth only affects whether the work is high risk construction work needing a SWMS (more than 1.5 metres in construction).

Is this construction work?

Construction work includes building, alteration, repair, maintenance, demolition and excavation work on a structure. It only affects the high risk construction work / SWMS question — the ground-collapse duty applies either way.

Might there be underground services near the dig?

Gas, electricity, water and telecommunications assets are often buried near work sites. Locate them with Before You Dig Australia before you excavate.

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