A contractor is excavating a trench 8 feet deep in Type C soil. What is the maximum allowable slope under Cal/OSHA regulations?
Correct Answer
C) 1.5:1 (34 degrees)
Cal/OSHA Section 1541.1 requires Type C soil to be sloped at 1.5:1 (1.5 horizontal to 1 vertical) which equals 34 degrees from horizontal.
Why This Is the Correct Answer
Option C is correct. Cal/OSHA Section 1541.1, consistent with OSHA 29 CFR 1926 Appendix B, classifies Type C as the least stable soil type. It requires the most conservative slope: 1.5:1 (1.5 feet horizontal for every 1 foot vertical), which produces an angle of approximately 34 degrees from horizontal. Type C includes fissured soil, previously disturbed soil, and soil with seeping water.
Why the Other Options Are Wrong
Option A: 1:1 (45 degrees)
Option A is incorrect. A 1:1 slope (45 degrees) is permitted for Type B soil, not Type C. Applying a 1:1 slope in Type C soil would be too steep and poses a significant collapse risk because Type C is inherently unstable.
Option B: 2:1 (26.5 degrees)
Option B is incorrect. A 2:1 slope (26.5 degrees) is more gradual than 1.5:1 and would actually be safer, but it is not the answer to what slope is 'maximum allowable.' The question tests knowledge of the required slope for Type C, which is 1.5:1 β and no steeper.
Option D: 3/4:1 (34 degrees)
Option D is incorrect because '3/4:1 (34 degrees)' is a misleading distractor. A 3/4:1 ratio means 0.75 feet horizontal per 1 foot vertical β that is steeper than 45 degrees and would be extremely dangerous in Type C soil. Additionally, 34 degrees is already the angle for the correct 1.5:1 slope, making this option numerically confusing by design.
Memory Technique
ABC slopes go 3/4, 1, 1.5 β getting flatter as soil gets worse. Type A is the best soil so it gets the steepest cut (3/4:1). Type C is the worst so it needs the widest berth (1.5:1). Think: C = Cut it wider.
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