Construction Safety (Depth)
Concepts
OSHA 29 CFR 1926 and the Focus Four: falls, struck-by, caught-in/between, and electrical. Fall protection at 6 ft general, 10 ft for scaffolds, and 15 ft for steel erection; guardrails, personal fall arrest, and rescue. Excavations: competent person, protective system at 5 ft, access within 25 ft, spoil 2 ft from edge, and utility locating. Scaffolds: 4:1 height-to-base, fully planked, and inspected. Cranes, rigging, confined space, PPE, HazCom, and recordkeeping.
Traps
6 ft versus 10 ft versus 15 ft. Competent person versus qualified person. A trench box does not eliminate the competent-person inspection. Ladders must extend 3 ft above the landing. Excavation access is required at 4 ft, not 5 ft. Fall protection is required at 6 ft, but some tasks require it sooner.
Worked example
An excavation is 8 ft deep in Type B soil. A protective system is required because depth exceeds 5 ft. Type B allows sloping at 1:1 (45°), so horizontal offset from the bottom edge is 8 ft on each side, plus the 2-ft spoil setback. If sloping is impractical, use a tabulated trench shield and inspect daily by a competent person.
Rule of thumb
When in doubt, protect: 5 ft for excavations, 6 ft for falls, 4:1 for scaffolds, and 3 ft for ladder extension.