A construction crew is excavating a trench that is 8 feet deep and 4 feet wide in Type B soil. What is the minimum allowable slope ratio for the sides of this excavation?
Correct Answer
C) 1:1 (45 degrees)
For Type B soil, OSHA requires a minimum slope of 1:1 (45 degrees) for excavations. This means for every foot of depth, the excavation must be sloped back one foot horizontally.
Why This Is the Correct Answer
OSHA 29 CFR 1926.652 specifically requires a minimum slope ratio of 1:1 (45 degrees) for Type B soil excavations. This means that for every foot of vertical depth, the excavation must slope back horizontally one foot from the edge. Type B soil has moderate cohesive strength and requires this specific slope ratio to prevent cave-ins and ensure worker safety. The 8-foot depth and 4-foot width mentioned in the question don't change this fundamental requirement.
Why the Other Options Are Wrong
Option A: 1/2:1 (63 degrees)
While a slope ratio of 1 1/2:1 (34 degrees) would be safer than the minimum requirement, it's not the minimum allowable slope. The question asks for the minimum allowable slope, making this option incorrect despite being acceptable.
Option D: 3/4:1 (53 degrees)
A slope ratio of 3/4:1 (53 degrees) is still too steep for Type B soil according to OSHA standards. While less steep than option A, it still doesn't meet the minimum safety requirements.
Memory Technique
Type B = 1:1 = 45 degrees. Remember 'B for Basic 45' - Type B soil needs the basic 45-degree angle slope for safety.
Reference Hint
OSHA 29 CFR 1926.652 - Requirements for protective systems, Table B-1 for soil classification and sloping requirements
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