Cal. Code Regs. tit. 8, § 7051 – (11-12). Winzes, Raises, and Openings.

(a) Winzes or other openings in the floor of mine workings shall be guarded so that persons will not fall into them.
(b) (11-12) Manways intersecting overhead workings through which material is dropped shall be closed to the passage of persons whenever material is dropped through such working.
(c) (11-1) Every raise while under construction shall be provided with a safe means of access from the bottom to the face at all times when employees are working in the raise.
1. (1) For slopes up to 20 degrees, a walkway may be used where there is safe footing.
  If footing is slipping or otherwise insecure, a rope, chain, or other aid to climbing shall be provided.
2. (2) For slopes from 20 degrees to 45 degrees, chains, or ladders shall be provided.
3. (3) For slopes greater than 45 degrees, ladders shall be provided.
4. (4) Other means that will afford at least equal safety.
Such means of access shall be as follows: