Workplace fatality: retaining wall collapse
The following story contains language and references which some readers may find distressing and the content is confronting and may be triggering.
Workplace Health and Safety Queensland (WHSQ) published a safety alert in May highlighting risk control measures to help prevent the collapse of retaining walls.
The information contained in the alert is relevant to builders, principal contractors, sub-contractors and workers who undertake excavations at or near the base of retaining walls and other structures.
Retaining wall collapses can occur suddenly and without warning. The weight of retaining wall materials and supported earth can make retaining wall collapses particularly hazardous to those in the vicinity.
In Queensland, retaining walls greater than one metre in height require engineering design and certification. The design and certification will specify the conditions for which the retaining wall has been designed.
If the existing ground conditions near the retaining wall are altered in any way, such that it is outside of the original certification, instability and failure could occur.
Persons Conducting a Business or Undertaking (PCBUs) planning excavation works must identify hazards and risks associated with the works and then, as far as is reasonably practicable, control these risks. This includes hazards and risks associated with excavation works in the vicinity of retaining walls and other structures.
The Work Health and Safety Regulation 2011 sets out requirements for trenches of at least 1.5 metres deep. However, excavations shallower than this may still pose serious risks to health and safety, especially if they are performed adjacent to existing buildings and structures, such as retaining walls.
To minimise the risks of retaining wall collapse, the following should be considered and implemented:
- adequate investigation before excavating;
- safe systems of work; and
- an effective emergency plan.
Retaining walls often rely on the earth at the base of the wall to prevent the wall from sliding, overturning or collapsing. Disturbing this earth or performing excavations at the base of retaining walls can reduce or remove this support, leading to failure of the wall and collapse of the retained earth.
More information
Read the full Safety alert - Retaining wall collapse on construction site.