A trench box (trench shield) is being used in an excavation that is 12 feet deep. The shield extends to 10 feet deep. What is the maximum allowable distance the shield can extend above the bottom of the excavation?
Correct Answer
D) 2 feet
OSHA 29 CFR 1926.652 allows shields to extend up to 2 feet above the bottom of an excavation, provided other protection is used for the remaining depth.
Why This Is the Correct Answer
According to OSHA 29 CFR 1926.652, trench shields are permitted to extend up to 2 feet above the bottom of an excavation. This regulation recognizes that shields don't always need to reach the full depth of the trench, provided that adequate protection is maintained for workers. The 2-foot maximum ensures worker safety while allowing practical flexibility in shield positioning and installation.
Why the Other Options Are Wrong
Option A: 3 feet
18 inches (1.5 feet) is less than the maximum allowable distance. While this would be acceptable, it's not the maximum permitted distance that the question asks for. OSHA allows up to 2 feet, making this answer unnecessarily restrictive.
Option B: 18 inches
OSHA does not require shields to extend to the top of trenches in all cases. The regulation specifically allows shields to be positioned up to 2 feet above the bottom, recognizing that other protective measures can address the remaining depth.
Option C: The shield must extend to the top of the trench
3 feet exceeds the maximum allowable distance specified in OSHA regulations. This would create an unsafe condition where workers could be exposed to cave-in hazards in the unprotected portion of the excavation above the shield.
Memory Technique
Remember '2 feet from the feet' - trench shields can extend up to 2 feet above the bottom (where workers' feet are) of the excavation.
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