Trenches and Excavations

When a construction project will involve digging trenches and excavation work, an owner builder should take particular note of the unique hazards that could arise, and the possible control measures to be implemented in an effort to eliminate or control such hazards.

Potential hazards that could arise include:

Water pipes and electricity cables could lie in the area to be dug up
Workers could fall when climbing in and out of a trench
The trench could collapse on a worker

No soil or rock can be relied on to support its own weight, therefore the sides of any excavation are likely to collapse at any time. A cubic metre of soil (about 80 shovels full) weighs at least 1.4 tonnes.

Possible control measures may include any or all of the following:

Check with the appropriate authority for the location of underground services (ie. gas, water, communications, electricity) before you dig.
Provide and secure a suitable barrier or guardrails around any excavation.
If workers are required to be in a trench 1.5 metres deep or more, the sides of the trench must be battered at an angle of 45 degrees or shored up with a trench support system. In some cases, trenches shallower than 1.5 metres in unstable ground should be battered. If you need advice, call your nearest WorkCover Construction Safety Inspector.
Trenches can be open graves, so owner builders should provide suitable ladders for entry and exit from trenches. If the right precautions are not taken, the sides of the trench can collapse and anyone working in it can be buried alive. Don't let this happen on your owner builder site.

Some special safety considerations for owner builders are asking themselves whether all trenches on site have:

a handrail or suitable barrier around the edge?
45 degree sloping sides or stepped sides - if not, are they shored up?
any access ladders?

For more general safety obligations of owner builders, CLICK HERE.