Section 21-4. Precautions against landslides

The employer must ensure that trenches and shafts with vertical sides that are deeper than 2.0 m have shoring or other means of personal protection.
For trenches less than 2.0 m deep, vertical walls without shoring may be used unless special elements of danger exist. For all other unshored trenches and shafts, the sides must be given a safe angle of slope. The angle of slope shall be checked using an angle template and level, or equivalent.
In frozen soil, the trench or shaft may be excavated with vertical sides if the excavation is to be filled before there is a risk of thawing. If the trench or shaft is deeper than the ground frost level, the walls below ground frost level shall be shored where there is a risk of a collapse causing personal injury.
Nobody must occupy the trench unnecessarily during removal of the shoring.