CSLB Law & Business ExamSafetyHard
A trench is being excavated in soil classified as Type C (the least stable classification) without a shoring or shielding system. What is the maximum allowable slope for the trench walls under Cal/OSHA excavation standards?
- A1.5:1 (34 degrees)
- B2:1 (27 degrees)
- C1:1 (45 degrees)
- D3/4:1 (53 degrees)
Show answer & explanationAnswer & explanation
Correct answer: A. 1.5:1 (34 degrees)
Cal/OSHA's soil classification system assigns Type C soil (the least stable) a maximum allowable slope of 1.5 horizontal to 1 vertical, or 34 degrees from horizontal, when sloping is used instead of a shoring or shielding system. Type A soil allows steeper slopes since it is more stable.
Why the other options are wrong
- B. 2:1 is steeper than required and not the standard Type C ratio.
- C. 1:1 slope corresponds to Type B soil, moderately stable.
- D. 3/4:1 slope corresponds to Type A soil, the most stable classification.
Soil Classification Slopes
Cal/OSHA assigns maximum allowable slope ratios based on soil type: Type A (3/4:1), Type B (1:1), and Type C (1.5:1), with Type C requiring the gentlest slope due to instability.
- Type A soil is most stable, allows steepest slope
- Type C soil is least stable, requires the gentlest slope
- Sloping is one alternative to shoring or shielding systems
Memory trick: C is for Careful—gentlest slope for the weakest soil