The 5 ft rule and its two exceptions
29 CFR 1926.652(a)(1): every employee in an excavation must be protected from cave-ins by an adequate protective system. The OSHA fact sheet: trenches 5 ft or greater need one unless made entirely in stable rock.
Two exceptions:
- (a)(1)(i): the excavation is made entirely in stable rock, whatever its depth.
- (a)(1)(ii): it is less than 5 ft deep and examination of the ground by a competent person gives no indication of a potential cave-in.
Not the trigger: 4 ft; 6 ft is the fall protection height for construction edges; 20 ft is the depth at which the system must be designed by a registered professional engineer, not where protection starts.
Under 5 ft is not automatic
A 4 ft trench in soil may be entered without a protective system only if a competent person examines the ground and finds no indication of a potential cave-in.
Traps:
- Treating trenches under 5 ft as automatically exempt is the common error. The competent-person examination is required.
- Saying every trench needs a system ignores both exceptions.
- The engineer is tied to sloping or support designs outside the standard options and to trenches 20 ft or deeper.
Stable rock at any depth
A 7 ft trench cut entirely in stable rock needs no cave-in protective system under 1926.652(a)(1)(i).
Traps:
- Thinking 5 ft or deeper always requires a system is the common error; stable rock is the exception.
- The exception does not depend on an engineer certifying the rock.
- It does not depend on inspection; weekly inspection is not the standard.
Daily competent-person inspection
29 CFR 1926.651(k)(1): a competent person must inspect the excavation, the adjacent areas and the protective systems:
- daily, before the start of work,
- as needed throughout the shift, and
- after every rainstorm or other hazard-increasing occurrence,
whenever employee exposure can reasonably be anticipated.
Traps: weekly is the common error and is too infrequent. One inspection before first entry is not enough.