June 30 2015


Historical incidents have highlighted the need for workers to be vigilant when conducting excavation, trenching or other earth moving activities. Underground and overhead services have been impacted upon, collapses have occurred, members of the public have been injured in unprotected excavations, environmental incidents have occurred and damage caused to or the integrity of adjacent structures has been effected.

Excavating and trenching is an activity that trades are likely to engage in on a regular basis, often involving mobile plant which then introduces another hazard and subsequent risks, which you as the person in control of the work, are required to effectively manage to prevent injury or damage.

As a reminder, below is a summary of your legal requirements for excavation works under the present WA Occupational Safety and Health legislation:

  • As a ‘catch all’ under the Regulations – You are responsible for identifying, assessing and considering the means by which the risks at your workplace may be reduced. This can done by considering:
    1.  Temporary support systems
    2.  Benching
    3.  Shoring
    4. Retaining structures (either temporary or permanent)
    5. De-watering systems
  • Suitable barriers are to be erected around excavations between a person that may be put at risk and the likely cause of danger.
  • Suitable signs that warn of the risk are erected at the place where the excavation work is to be done are required.
  • Ensure that existing services (whether overhead or underground) that may impact upon you, others, or you may impact upon them are positively identified, marked, protected and isolated where required (water, gas, electricity, communications, etc.). Consider:
    1. Dial before your dig
    2. Safe job planning (SWMS, JSA’s, etc.)
    3. Thoroughly inspecting site prior to commencing
    4. Spatial drawings
    5. Site plans
    6. Potholing
    7. Initial hand excavating
    8. Cable locating wands
    9. Ground penetrating radar
  • Ensure that people can move safely in, around, and across the top of, the area.
  • Ensure that any plant can be moved safely in, around, and across the top of, the area.
  • Position spoil, plant and materials in a position away from the excavation edge to prevent collapse or plant / material from falling into excavation.
  • Where there is any risk of collapse or a worker is required to work within an excavation deeper than 1.5m deep, the excavation edge must be shored, benched or have temporary or permanent retaining structures installed in order to prevent collapse.
  • If any worker is required to work within an excavation deeper than 1.5m a spotter must be present in the immediate vicinity.
  • If excavating adjacent to a building, structure or road that could adversely affect the stability of the structure, sheet piling, shoring or bracing must be implemented.
  •  Where plant is used on order to conduct the excavation or trench, ensure that:
    1. The plant is set up correctly
    2. Operators are appropriately trained and competent
    3. Excavation areas are barricaded off
    4. Services are identified and protected
    5. Plant is maintained, fit for purpose and pre-start log book check completed
  • For any excavation of a depth greater than 1.5m a site specific Safe Work Method Statement (SWMS) must be prepared, signed by all involved in the activity and remain on site until completion of the task. Safety Solutions WA recommend this is considered for all excavations, not just those deeper than 1.5m.

The above are the MUST DO elements as detailed within the WA OSH Regulations. In addition, a WA Code of Practice is available for further guidance and recommended control methods in order to lessen the risks associated with excavation works.

For more information on this topic, a copy of the Excavation Code of Practice, or any other OSH inquiry, please do not hesitate to contact Safety Solutions WA.