Cave-In Hazard
Excavation cave-ins are the #1 cause of construction worker deaths from caught-in/between hazards. One cubic yard of soil weighs up to 3,000 pounds — equivalent to a mid-size car. Cave-ins can occur without warning. NEVER enter an unprotected trench more than 5 feet deep. For trenches 4+ feet deep, a protective system is required.
Soil Classification
Type A: most stable (clay, hardpan). Type B: medium stability (silt, sandy loam, unstable due to vibration). Type C: least stable (sand, gravel, submerged soil). Soil is classified by the Competent Person using visual tests and the penetrometer test. When in doubt, classify as Type C.
Protective Systems
Options: Sloping (cut walls to safe angle — 1.5H:1V for Type C), Shoring (hydraulic or timber), Trench Box/Shield. The Competent Person selects the system. Inspect excavations daily and after rain, frost, or nearby vibration. Provide a ladder every 25 feet lateral travel.
Competent Person
A Competent Person must inspect excavations daily and after any hazard-increasing event. They must be able to identify hazards and have authority to take corrective action. Utility lines must be located (call 811) before ANY digging. Keep excavated material at least 2 feet from the trench edge.
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