CSLB Law & Business ExamSafetyMedium
A contractor excavates a trench 7 feet deep entirely within a formation of stable rock. Under Cal/OSHA excavation standards, what protective system requirement applies?
- AOnly atmospheric testing is required, with no protective system needed
- BNo protective system is required because the excavation is entirely in stable rock
- CA protective system is still required because the trench exceeds 5 feet in depth
- DA trenching permit is required but shoring may be omitted
Show answer & explanationAnswer & explanation
Correct answer: B. No protective system is required because the excavation is entirely in stable rock
Cal/OSHA excavation standards exempt excavations made entirely in stable rock from the protective system (sloping, shoring, shielding) requirements that otherwise apply to trenches 5 feet or deeper, because stable rock does not present the same cave-in risk as soil.
Why the other options are wrong
- A. Atmospheric testing relates to hazardous atmospheres, not the protective system exemption for rock.
- C. The 5-foot rule applies to soil excavations, but stable rock is specifically exempted.
- D. Permits may still apply for depth, but this option incorrectly implies shoring is normally needed and only sometimes omitted.
Stable Rock Exception
Excavations made entirely within stable rock formations are exempt from Cal/OSHA's protective system requirements that normally apply to deeper trenches.
- Applies only if excavation is entirely in stable rock
- Exempts sloping/shoring/shielding requirement
- Does not exempt other excavation safety duties like inspections
Memory trick: Solid rock, no shoring shock — stable rock skips the protective system.