WA: new code of practice for excavation work issued

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Sunday, 27 February, 2022 - 12:45
Policy & legislation
Western Australia

Western Australia’s Department of Mines, Industry Regulation and Safety (DMIRS) recently issued a code of practice that provides practical guidance to prevent occupational injury and disease in all workplaces where excavation and associated earthworks are performed.

Excavation work may range from shallow trenching and simple foundation excavation to large and complex excavations for buildings and structures and deep sewers where the risk of serious injury is very significant.

DMIRS said the code of practice should be used by all persons involved in any aspect of work related to excavation, including designers, manufacturers, suppliers, employers, contractors, self-employed persons, managers, supervisors, persons in control of workplaces, employees and safety and health representatives to assist them to comply with the Act and Regulations.

Excavation is regarded as one of the most hazardous construction operations, and the DMIRS said excavation failure occurs very quickly, giving a worker virtually no time to escape, especially if the collapse is extensive and the excavation is a trench.

“Normally, a slab of earth collapses off the trench face under its own weight and breaks against the opposite wall of the excavation, burying and crushing any person in its path. This can result in potentially fatal injuries or suffocation,” the code of practice said.

The code provides advice on the provision of protective systems to prevent cave-ins, to protect workers when cave-ins occur and to protect workers from material that could fall or roll from an excavated face or from the collapse of adjacent structures.

Protective systems include support systems (steel, aluminium and timber), battering, benching and shield systems.

It also said an examination of site conditions by a competent person is necessary to determine safe slopes for excavations, and safe slopes depend on the height of the face, soil type and geological conditions, the moisture content of the soil and any surcharge loads.

“Soil moisture content and geological conditions may change as excavation progresses, causing safe slopes to become hazardous,” the code said.