A contractor is digging a utility trench that is 8 feet deep and 3 feet wide in Type A soil. The trench will be open for 6 hours. What is the most appropriate protection method?
Correct Answer
C) Simple sloping at 1/2:1 ratio
For Type A soil (the most stable), trenches 5-20 feet deep can be sloped at 1/2:1 ratio (63 degrees). This is the most cost-effective protection method for this scenario given the soil type and depth.
Why This Is the Correct Answer
For Type A soil in trenches 5-20 feet deep, OSHA allows simple sloping at a 1/2:1 ratio (which equals 63 degrees from horizontal). This is the most cost-effective protection method since Type A is the most stable soil classification. The 1/2:1 slope provides adequate protection while minimizing excavation volume compared to more conservative slopes.
Why the Other Options Are Wrong
Option A: Benching or shoring system
While benching or shoring systems would provide adequate protection, they are not the 'most appropriate' method for this scenario. Simple sloping is more cost-effective and practical for Type A soil at this depth.
Option D: Sloping at 3/4:1 ratio
Even Type A soil requires protection when trenches exceed 5 feet in depth. OSHA mandates protective systems for all trenches 5 feet or deeper regardless of soil type due to cave-in hazards.
Memory Technique
ABC soil types with fractions: A=1/2, B=3/4, C=1/1. Think 'A is Awesome' so it gets the smallest fraction (steepest allowable slope).
Reference Hint
OSHA Construction Standards 29 CFR 1926 Subpart P - Excavations, specifically Table B-1 for maximum allowable slopes
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