S-2.1, r. 14 - Regulation respecting occupational health and safety in mines

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46. An opening to the surface of a shaft or raise that is no longer in use and is not filled in to its collar shall be closed by a slab of reinforced concrete that shall:
(1)  rest on solid rock or a concrete collar;
(2)  be at least 1.5 m (4.9 ft) in width, and have eyebolts for raising;
(3)  be able to withstand a live load of 100 kN (22,481 lb) applied to its centre.
O.C. 213-93, s. 46.