Journeyman Plumber ExamTools, Equipment, and SafetyHard
A plumber is working in a trench that is 5-feet deep and the soil is classified as Type C. According to OSHA regulations, what is the maximum allowable slope for the trench walls?
- A0.75:1 (53 degrees)
- B1:1 (45 degrees)
- C0.5:1 (63 degrees)
- D1.5:1 (34 degrees)
Show answer & explanationAnswer & explanation
Correct answer: D. 1.5:1 (34 degrees)
OSHA regulations (29 CFR 1926.652(b)(1)(iii)) specify that for Type C soils, the maximum allowable slope for an excavation less than 20 feet deep is 1.5 horizontal to 1 vertical (1.5:1), which corresponds to an angle of 34 degrees from the horizontal. This is the least stable soil type commonly encountered, requiring a gentler slope.
Why the other options are wrong
- A. 0.75:1 (53 degrees) is the maximum allowable slope for Type A soil, the most stable category.
- B. 1:1 (45 degrees) is the maximum allowable slope for Type B soil, which is more stable than Type C.
- C. 0.5:1 (63 degrees) is much steeper than allowed for Type C soil, which is the least stable of the common soil classifications.
OSHA Trench Sloping - Type C Soil
OSHA's requirement for the maximum angle at which a trench wall in Type C soil can be sloped to prevent cave-ins.
- Type C is the least stable soil classification
- Maximum slope is 1.5:1 (34 degrees)
- Applies to excavations less than 20 feet deep
- Competent person must classify soil type
Memory trick: A is sharp, B is balanced, C is flat.