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.