how many trench boxes can you stack ontop of eachother

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455 (2) An employer must ensure that if a worker is in a trench that is more than 1.5 metres deep, the trench is supported or sloped so that the worker can reach the safe point in order to enter and leave. ## Temporary protective structures - 456 (1) An employer must ensure that temporary protective structures in an excavation - (a) 3 metres deep or less are of sufficient strength to prevent the walls of the excavation from caving in or otherwise moving into the excavation, and - (b) more than 3 metres deep are designed, constructed and installed in accordance with the specifications of a professional engineer. - 456 (2) The specifications of a professional engineer for subsection (1)(b) must include - (a) the size and specifications of the structure, including the type and grade of materials used in its construction, and - (b) the loads for which the structure is designed. 456 (3) An employer must ensure that, before beginning an excavation, a foundation that may be affected by the excavation is supported by a temporary protective structure designed, constructed and installed in accordance with the specifications of a professional engineer. ## Alternatives to temporary protective structures 457 (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 …

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## OCCUPATIONAL HEALTH AND SAFETY, 2020 - (3) An employer or contractor shall ensure that a temporary protective structure in an excavation more than 3 metres deep is designed and certified as safe by a professional engineer and installed, used, maintained and dismantled in accordance with that design. 31 Dec 2020 c S-15.1 Reg 10 s17-6. ## Protection against cave-in of trenches - 17-7 (1) If a worker is present in a trench that is more than 1.2 metres deep, an employer or contractor shall ensure that the worker is protected from cave-ins or sliding material by: - (a) cutting back the upper portion of the walls of the trench in accordance with subsection 17-4(2); - (b) installing a temporary protective structure; or - (c) a combination of cutting back the walls to the slope specified in subsection 17-4(2) and installing a temporary protective structure that extends at least 300 millimetres above the base of the cut-back. - (2) An employer or contractor shall ensure that a temporary protective structure required by clause (1) (b) or (c) is: - (a) designed and installed using shoring made of number 1 structural grade spruce lumber having the dimensions set out in Table 14 of the Appendix for the type of soil and the depth of the trench or made of material of equivalent or greater strength; or - (b) designed by a professional engineer and constructed, installed, used, maintained and dismantled in accordance with that design. - (3) An employer or contractor shall ensure that a temporary protective structure in a trench more than 6 metres deep in type 1, type 2 or type 3 soil or in a trench more than 4 metres deep in type 4 soil is designed and certified as safe by a professional engineer and installed, used, maintained and dismantled in accordance with that design. - (4) An employer or contractor shall ensure that: - (a) shoring is installed and removed in a manner that protects workers from cave-ins and structural collapses and from being struck …

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## S-15.1 REG 10 ## OCCUPATIONAL HEALTH AND SAFETY, 2020 - (d) an excavation or trench that a worker may be required or permitted to enter is kept free from any accumulation of water; and - (e) the slope of a spoil pile adjacent to an excavation or trench has a slope at an angle not steeper than 1 horizontal to 1 vertical, or 45 measured from ° the horizontal. - (2) Subject to subsections (3) and (4), if a wall of an excavation or trench is cut back, an employer or contractor shall ensure that: - (a) in the case of type 1 or type 2 soil, the walls are sloped to within 1.2 metres of the bottom of the excavation or trench, with a slope at an angle not steeper than 1 horizontal to 1 vertical, or 45 measured from the horizontal; ° - (b) in the case of type 3 soil, the walls are sloped from the bottom of the excavation or trench, with a slope at an angle not steeper than 1 horizontal to 1 vertical, or 45 measured from the horizontal; and ° - (c) in the case of type 4 soil, the walls are sloped from the bottom of the excavation or trench, with a slope at an angle not steeper than 3 horizontal to 1 vertical, or 19 measured from the horizontal. ° - (3) If an excavation or trench contains more than 1 type of soil, the soil must be classified as the soil type with the highest number. - (4) Subsection (2) does not apply to an excavation or trench that is cut in sound and stable rock. - (5) If an excavation or trench is to be made in the vicinity of an overhead power line, an employer or contractor shall ensure that the work is carried out in a manner that will not reduce the original support provided for any overhead power line pole, unless permission has previously been obtained from the utility company responsible for the overhead power line. - (6) An employer or contractor shall ensure that no powered mobile equipment or vehicle is operated, and that no powered mobile equipment, vehicle or heavy load is located, near an excavation or trench so as to affect the stabili…