Safe system of work: Unstable or collapsed natural or built environments

Control Measure Knowledge

An incident involving an unstable or collapsed opening may require:

  • Shoring
  • Removal of fallen or collapsed materials
  • Isolation of machinery or vehicles
  • Relocation of loads, such as vehicles, machinery or building materials
  • Reducing movement in the hazard area
  • Appropriate location of fire and rescue service vehicles, equipment and personnel

The opening should be assessed at the earliest opportunity. Although the initial assessment can be carried out by first responders, it may be necessary to seek specialist advice.

Specialist advice may be available from a competent person, structural engineer or tactical adviser and should be sought prior to committing personnel to the hazard area.

If personnel need to enter where any of the support system has been compromised, it will be essential to consult with the responsible person or competent person to determine a safe system of work. This could be the contractor or a civil engineer.

The hazard area should be monitored for signs of collapse; this may include distortion or deflection of supports, tension cracks or soil movement.

The minimum number of personnel should be committed to the hazard area, especially if the assessment or monitoring indicates the potential for further collapse. There should also be emergency procedures in place, which can be initiated if required.

Additional loading such as fire and rescue service vehicles, equipment and personnel is to be avoided, as this can further contribute to secondary collapse.

Where it is necessary to work around the opening, appropriate working at height procedures should be adopted. Any additional load placed in the area should be risk assessed and consideration given to spreading the load, for example by using trench sheets or plywood. It should be considered that using methods that cover large areas can prevent early signs of collapse being identified. For more information refer to:

Other safe systems of work or procedures may be involved in rescue operations, such as those for:

  • Confined spaces; for example a trench may collect flammable or toxic vapours or have an oxygen-deficient atmosphere
  • Working at height, for example, personal protective equipment (PPE) may be required for unguarded edges
  • Access and egress, as this may be restricted

Strategic Actions

Tactical Actions