OSHA 10-Hour Construction ReviewFocus Four HazardsMedium
A construction crew is performing excavation work for a new building foundation. The excavation is 6 feet deep, 10 feet wide, and 20 feet long. Soil analysis indicates the soil is Type C. What is the maximum allowable slope for the sides of this excavation?
- A0.75:1 (53 degrees)
- B2:1 (26.6 degrees)
- C1:1 (45 degrees)
- D1.5:1 (34 degrees)
Show answer & explanationAnswer & explanation
Correct answer: D. 1.5:1 (34 degrees)
For Type C soil, OSHA requires a maximum allowable slope of 1.5 horizontal to 1 vertical (1.5:1), which corresponds to an angle of 34 degrees from the horizontal. This standard helps prevent cave-ins, which are a major hazard in excavation work.
Why the other options are wrong
- A. This slope is steeper than allowed for any soil type without additional protective systems.
- B. This slope is for Type A soil, which is the most stable type, or for stable rock.
- C. This slope is typically allowed for Type B soil, which is more stable than Type C.
Excavation Sloping (Type C Soil)
Sloping is a method of protecting workers in an excavation by cutting back the sides of the excavation to a safe angle. The maximum allowable slope depends on soil type, with Type C soil requiring a flatter slope due to its instability.
- Type C soil is cohesive soil with an unconfined compressive strength of 0.5 tsf or less, or granular soils such as gravel, sand, or loamy sand.
- OSHA standard 1926.652(b)(1)(iii) specifies the maximum allowable slopes.
- Sloping angles are crucial for preventing cave-ins, which are a leading cause of fatalities in excavation.
Memory trick: Slope Cautiously, Shoring Safely, Shielding Strong.