Cal. Code Regs. tit. 8, § 7094 – (5-1). Dust--Mucking and Transferring Rock.

(a) The muck pile shall be wet down before mucking begins and shall be kept wet during the entire mucking operation to control the dust.
It is recommended that a continuous spray of water be maintained on muck piles where mucking machines are being operated.
(b) Water sprinklers shall be installed and used on all chutes from which dusty rock is taken, or other equally effective means acceptable to the Division shall be used to prevent harmful accumulations of dust in the atmosphere.
(c) Whenever a sprinkling device is installed at a chute, it shall be so placed that it can be operated by the workmen who operate the chute gates.
The spray shall be directed into the chute and away from the operator's position at the chute.
(d) To prevent spillage from loaded cars and trackless haulage vehicles from adding to the mine dust, the loaded car or vehicle shall not be moved away from the loading spot until the load has been trimmed and leveled so as to prevent spillage.
(e) Effective means shall be used to control the dust in manways, haulageways and other parts of the mine.
It is recommended that dust on haulageways be controlled with water, treating with calcium chloride, or other equally effective means.
In areas of water scarcity, it is recommended that water for dust control be treated with a wetting agent to increase its efficiency.