OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 32 Excavating and Tunnelling

Section 456 Temporary protective structures

Subsection 456(1) and 456(2)

In an excavation 3 metres or less deep, the type of temporary protective structure used is left to the discretion of the employer, as long as the structure is of sufficient strength to protect workers. In common practice, protective structures are often pre-fabricated from steel, or built in place from wood materials for shoring, stringers and bracing.

If an excavation is more than 3 metres deep, the risk of injury to workers increases dramatically. It is therefore mandatory that any temporary supporting structure be designed and certified by a professional engineer. The engineer’s specifications must indicate all details related to the design, including the type and grade of materials to be used and the calculated loads the structure is designed to support.

Subsection 456(3)

Where an excavation could affect an existing foundation, the foundation must be supported by a temporary protective structure. The structure must be designed, constructed and installed in accordance with the specifications of a professional engineer. This extra precautionary measure reduces the risk of injury to workers working near the foundation, as well as the risk to persons in or near the structure supported by the foundation.