Under Cal/OSHA, a trench generally must be protected by sloping, shoring, or shielding once it reaches what depth?

Giải thích

Cal/OSHA requires cave-in protection such as sloping, benching, shoring, or a trench box for excavations 5 feet deep or greater, and even shallower trenches if a competent person identifies a hazard. Unprotected trenches can collapse and bury workers in seconds. A competent person must inspect trenches daily.