OSHA 10-Hour Construction ReviewExcavationsMedium
A utility crew is installing new pipes in an existing right-of-way. They encounter a trench where the soil has been classified as Type B. What is the maximum allowable slope for this trench if no other protective system is used?
- A1:1 (45 degrees)
- B0.75:1 (53 degrees)
- C2:1 (26.5 degrees)
- D1.5:1 (34 degrees)
Show answer & explanationAnswer & explanation
Correct answer: A. 1:1 (45 degrees)
For Type B soil, OSHA allows a maximum allowable slope of 1:1 (horizontal to vertical). This corresponds to an angle of 45 degrees from the horizontal, providing a balance between safety and excavation practicality for this soil type.
Why the other options are wrong
- B. This slope ratio is typically allowed for Type A soil, which is more stable than Type B.
- C. This slope is overly conservative for Type B soil and not required by OSHA, potentially increasing excavation costs unnecessarily.
- D. This slope is required for Type C soil, which is less stable than Type B and needs a gentler slope.
Type B Soil Sloping
Type B soil has an intermediate level of cohesion and strength, requiring a maximum allowable slope of 1:1 (45 degrees) when open excavation is used, as per OSHA standards.
- Intermediate stability between Type A and C.
- Maximum allowable slope is 1:1.
- Angle of 45 degrees from the horizontal.
- Common for silts, sandy loams, and some clays.
Memory trick: Slopes Classify Safety Carefully