A trench is being excavated to a depth of 8 feet in Type B soil. What is the maximum allowable slope ratio for the sides of this excavation?
Correct Answer
C) 1:1 (45 degrees)
For Type B soil, OSHA requires a maximum slope of 1:1 (45 degrees) for excavations. Type B soil includes angular gravel, silt, sandy loam, and previously disturbed soils.
Why This Is the Correct Answer
OSHA 29 CFR 1926.652 specifically requires a maximum slope ratio of 1:1 (45 degrees) for Type B soil excavations. This means for every 1 foot of depth, the excavation must slope back 1 foot horizontally from the vertical face. Type B soil has moderate cohesive strength and includes materials like angular gravel, silt, sandy loam, and previously disturbed soils. The 1:1 slope provides adequate stability to prevent cave-ins in this soil classification.
Why the Other Options Are Wrong
Option A: 2:1 (27 degrees)
The 0.75:1 slope ratio (53 degrees) is much too steep for Type B soil and would create dangerous conditions. This steep angle would likely result in soil failure and cave-ins, violating OSHA safety requirements for excavation work.
Option B: 0.75:1 (53 degrees)
The 1.5:1 slope ratio is actually steeper than required and would not provide adequate safety margin for Type B soil. While a flatter slope would be safer, OSHA specifically mandates 1:1 as the maximum allowable slope, meaning you cannot go steeper than this ratio.
Memory Technique
Remember 'Type B = 1:1' - the letter B looks like the number 1 stacked, helping you recall that Type B soil requires 1:1 slope ratio.
Reference Hint
OSHA 29 CFR 1926.652 - Requirements for protective systems, Table B-1 for soil classification and slope requirements
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