3.15.3. (1) The employer shall ensure that the banks of an excavation or trench are shored solidly with quality materials in accordance with the plans and specifications of an engineer. Shoring is not required in the following cases:
(1) where the trench or excavation is dug out of solid rock or where no workers are required to descend into it;
(2) where there is no risk of the banks of the trench or excavation collapsing and where they slope less than 45º from a point less than 1.2 m from the bottom;
(3) where there is no risk of the banks of the trench or excavation collapsing and where an engineer attests that it is not necessary to shore up the banks, given the slope, nature and stability of the ground. A copy of the engineer’s attestation shall be available on the construction site at all times.
Solid rock means rock that cannot be excavated otherwise than by blasting.
(2) The shoring shall extend 300 mm above the excavation, except where the trench dug in on a public road and must be covered over to allow for the passage of traffic during periods when works are not in progress.
When the shoring consists of unjoined stays, the 300 mm extension above the excavation shall be fitted with a plinth 300 mm wide.
(3) The banks shall be shored as the work progresses unless the shoring can be carried out before the digging.
(4) During the work the employer shall ensure that the walls are inspected and maintained so as to remove:
(a) rocks or materials liable to become detached therefrom;
(b) overhanging matter.
Where the banks have been subject to environmental or climatic stress, inspections shall be more frequent.
(5) It is prohibited:
(a) to place materials less than 1.2 m from the rim of the banks;
(b) to drive or park vehicles or machines less than 3 m from the rim of the banks, unless reinforced shoring has been used;
(c) to let banks deteriorate.
(6) Shoring shall be removed by an experienced person or under his supervision:
(a) from the bottom upwards; and
(b) only in places to which workers no longer have access.