Cal. Code Regs. tit. 8, § 6988 – (3-8). Face Inspection and Control.

(a) A daily inspection shall be made of faces and banks where men are exposed to falling or rolling materials. The inspection shall be made by a competent person who shall dislodge or make safe any material dangerous to employees, or shall cause such material to be dislodged or made safe.
(b) (3-9) No person shall be permitted to work near a face made unsafe by primary blasting, rains, freezing or thawing weather, or earthquakes, until the face has been inspected and made safe.
(c) At least once a week, or oftener if necessary, a competent person shall inspect the top of the face or bank for cracks that may indicate the imminence of slides or movement of the face.
(d) (3-5) Overhanging banks in pits are forbidden, except in:
1. (1) Pits where material is moved away from the face by mechanical equipment having controls located at a safe distance so that no employee is required to approach the face in the course of normal operations.
2. (2) Hydraulic pits where the bank is undercut with a stream of water and the monitor is located at a safe distance from the bank.
(e) Where necessary, a watchman shall be employed at the face, to give warning when loose rock or other materials are about to fall.
The watchman shall be provided with a whistle, siren, or other device that will give adequate warning to employees in the pit.
The watchman shall have no other work to distract his attention from his duties as a watchman.
(f) Work shall not be permitted on or near any bank or face at night unless the bank or face above the working area is adequately illuminated to make any movement of rock or other material readily observable.
(g) Provision shall be made to keep employees away from dangerous areas that are not working places. Signs shall be posted warning employees to keep away, or such dangerous areas shall be barricaded or otherwise guarded.