CSLB General Building (B)Site Work, Foundations and ConcreteEasy
A crew is excavating a 10-foot-deep trench in Type B soil and wants to use the benching method instead of sloping the trench walls back at an angle. According to OSHA/Cal-OSHA excavation rules, in which soil types is benching a permitted protective method?
- ABenching may be used in any soil type as long as a trench box is also installed
- BBenching is prohibited in all soil types over 5 feet deep
- CBenching is permitted only in Type C soil
- DBenching is permitted in Type A and Type B soil, but not Type C
Show answer & explanationAnswer & explanation
Correct answer: D. Benching is permitted in Type A and Type B soil, but not Type C
OSHA/Cal-OSHA excavation standards allow benching (cutting the trench wall into a series of horizontal steps) only in Type A and Type B soils, because these soils have enough cohesion to hold a stepped face safely. Type C soil is too unstable for benching and requires sloping, shoring, or shielding instead.
Why the other options are wrong
- A. A trench box is a separate protective system and does not make benching valid in Type C soil.
- B. Benching is allowed, just not in unstable Type C soil.
- C. Backwards — Type C is the least stable soil and cannot be benched.
Benching Method
An excavation protection method that cuts trench walls into a series of horizontal steps or benches, permitted only in soils with sufficient cohesion (Type A or B).
- Allowed in Type A and B soil only
- Not permitted in Type C soil
- Alternative to sloping or shoring for trench protection
Memory trick: 'Benching needs backbone' — only cohesive soils (A & B) can hold a stepped shape.