Cal. Code Regs. tit. 8, § 7062 – Mine Housekeeping.

(a) Combustible rubbish shall be promptly removed from the mine.
(b) All oily rags or waste shall be deposited in covered metal receptacles. The contents shall be sent to the surface every week, and also when the receptacle is full.
(c) Old timber, waste timber, scraps, and chips shall not be permitted to accumulate underground, but shall be removed from the mine as soon as practical.
Exception: Old timber, waste timber, wood scraps, and chips in stopes may be left in the mine if buried in filling material.
(d) Active manways, shafts, and winzes shall be kept clear of loose rocks and other obstructions.