51. In an underground mine, any opening more than 1.2 m (3.9 ft) deep shall be:
(1) surrounded by a guard rail that complies with paragraph 5 of section 66; or
(2) closed by a cover able to withstand a load at least equal to the greater of the following values:
(a) a single point load of 2 kN (450 lb) applied to any point on the cover; and
(b) a distributed load of 3.8 kN/m2 (79.4 lb/ft2).
Where a motorized vehicle is likely to travel over a cover, the cover shall have a resistance at least equal to 3 times the maximum load that may be exerted by the vehicle.
O.C. 213-93, s. 51; O.C. 1326-95, s. 15.