A 6-ft trench is not entirely in stable rock. Which protective-system rule controls?
Correct Answer
B) 5 ft or deeper unless an exception applies
Because the trench is deeper than 5 ft and not entirely in stable rock, cave-in protection is generally required.
Why This Is the Correct Answer
Because the trench is deeper than 5 ft and not entirely in stable rock, cave-in protection is generally required.
Why the Other Options Are Wrong
Option A: Set the trench protective system trigger threshold at 2 ft
The trap in A is 2 ft. That selection is wrong because 2 ft uses the wrong excavation protective-system trigger or exception.
Option C: Set the trench protective system trigger threshold at 8 ft
Choice C (8 ft) is rejected because 8 ft uses the wrong excavation protective-system trigger or exception.
Option D: Base the trench protective system trigger response on 20 ft
In site construction, 20 ft only is the wrong selection for Trench protective system trigger - stable rock exception: 20 ft only uses the wrong excavation protective-system trigger or exception.
Memory Technique
Make trench protective system trigger - stable rock exception a tabbed card: cite the exact condition, then choose 5 ft or deeper unless an exception applies.
Reference Hint
Open 29 CFR Part 1926 (OSHA Construction Standards), 1926-2023 / PSI OSHA Excerpts 2025; use 29 CFR 1926 Subpart P - §1926.652; related §1926.651(d), §1926.651(i), §1926.651(l) to confirm that Because the trench is deeper than 5 ft and not entirely in stable rock, cave-in protection is generally required.
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