OSHA 10-Hour Construction ReviewFocus Four HazardsHard
A trench is being excavated for a utility line. The trench is 7 feet deep, 3 feet wide, and 50 feet long. Soil analysis indicates the soil is Type B. What is the maximum vertical side of the trench that can remain unsloped or unshored before protective systems are required for Type B soil?
- A0 feet, all trenches require protection regardless of depth.
- B5 feet
- C4 feet
- D20 feet
Show answer & explanationAnswer & explanation
Correct answer: B. 5 feet
OSHA 1926.652(a)(1) states that each employee in an excavation shall be protected from cave-ins by an adequate protective system, except when excavations are made entirely in stable rock or are less than 5 feet in depth AND examinations by a competent person provide no indication of a potential cave-in. Since this trench is 7 feet deep, it exceeds the 5-foot threshold, requiring protective systems.
Why the other options are wrong
- A. This is incorrect; trenches under 5 feet may not require protection under specific conditions.
- C. 4 feet is not the standard threshold for requiring protective systems for trenches.
- D. 20 feet is the maximum depth for sloping or shoring, beyond which a registered professional engineer must design the system.
Excavation Protective System Threshold
OSHA generally requires protective systems (sloping, shoring, shielding) for all excavations 5 feet or deeper, unless the excavation is entirely in stable rock. Even for shallower excavations, a competent person must assess for hazards.
- The 5-foot depth rule is a critical trigger for trenching and excavation safety.
- A 'competent person' must inspect excavations daily and after any changes.
- Cave-ins are a major 'Caught-In/Between' hazard and are often fatal.
Memory trick: Five Feet Deep, Protection You Keep.