Cal. Code Regs. tit. 8, § 7031 – Conveyor Passage.

(a) (11-9) Safe passageway shall be provided along every pit conveyor where employees are required or permitted to travel in the course of their operating duties.
(b) Conveyor tunnels constructed after April 7, 1953 shall have an unobstructed passageway at least 2 feet wide and 6 ½ feet high.
When a tunnel constructed before April 7, 1953 is extensively repaired or rebuilt, an unobstructed passageway shall be provided as required in the foregoing paragraph of this subsection.
(c) (11-16) Passageways adjacent to conveyors shall be kept free of spillage from the conveyor. Means shall be taken to minimize spillage on the passageway.