OHS Code

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

Section 457 Alternatives to temporary protective structures

(1) Despite section 456, an employer may install the following as temporary protective structures in trenches:

(a) if the trenches vary in depth from 1.5 metres to 6 metres, shoring, stringers and bracing constructed of lumber that complies with Schedule 9, or a material that has equal or greater properties to those of the lumber;

(b) exterior grade plywood as a substitute for 38 millimetre shoring elements if

(i) the plywood meets the requirements of CSA Standard O121-08, Douglas Fir Plywood or CSA Standard O151-04, Canadian Softwood Plywood,

(ii) the plywood is at least 19 millimetres thick,

(iii) the trench is not more than 2.7 metres deep,

(iv) uprights are installed at intervals of not more than 600 millimetres centre-to-centre,

(v) cross braces do not bear directly on the plywood, and

(vi) cross braces bearing on uprights or walers are located at all joints in the plywood sheathing.

(2) Despite subsection (1)(a), screw jacks, hydraulic equipment or other apparatus may be used as shoring, stringers or bracing if they are at least equivalent in strength and reliability to the shoring, stringers or bracing described in Schedule 9.

(3) Despite subsection (1)(a) if the trench is less than 2.4 metres deep and in soil classified as “hard and compact” an employer does not have to use stringers.

(4) Despite section 456, an employer may install additional protection certified by a professional engineer in trenches to compensate for passing vehicular traffic, working machinery or a heavy object placed within a distance equal to the depth of the trench, measured from the near edge of the bottom of the trench to the traffic, machinery or heavy object.

(5) Despite section 456, an employer may install additional protection certified by a professional engineer in a trench to compensate for the stress created because the trench is adjacent to or abuts a building or other structure.