A trench is 12 feet deep with vertical sides in Type B soil. The contractor wants to use a trench box. What is the minimum width required for the trench box under Cal/OSHA?
Correct Answer
B) 24 inches wider than the maximum width of the structure being installed
Cal/OSHA Section 1541.1 requires trench boxes to be at least 24 inches wider than the maximum width of the structure being installed to provide adequate protection.
Why This Is the Correct Answer
Option B is correct. Cal/OSHA Section 1541.1 specifies that when a trench box (shield) is used, it must be at least 24 inches wider than the maximum width of the structure being installed. This clearance ensures workers have adequate room to work safely and that the shield properly protects the work zone.
Why the Other Options Are Wrong
Option A: 18 inches wider than the maximum width of the structure being installed
Option A is incorrect because 18 inches is below the Cal/OSHA minimum clearance requirement. While 18 inches may seem like a reasonable workspace, Cal/OSHA specifically mandates 24 inches of additional width beyond the structure being installed.
Option C: The trench box width equals the structure width
Option C is incorrect because a trench box that matches the structure width exactly provides zero lateral clearance for workers. The trench box must be wider than the structure to protect the workers installing it, not just contain the structure itself.
Option D: 36 inches wider than the maximum width of the structure being installed
Option D is incorrect because 36 inches exceeds the minimum requirement. While a wider box is technically safe, the question asks for the minimum required under Cal/OSHA, which is 24 inches β not 36 inches.
Memory Technique
Remember '2 feet for the box to fit' β the trench box needs 24 inches (2 feet) more width than whatever you are installing. Picture a pipe in a trench: the box surrounding it must be 2 feet wider on each side to protect the workers installing it.
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