The hazard
Soil is heavy, and a trench wall can give way with little or no warning. A cave-in can bury or crush a worker before they can react, and a coworker who jumps in to help can be caught by the next collapse. These rules keep the walls off people and give everyone a way out.
The action
Trenches 4 feet or more deep must have a stairway, ladder, ramp or other safe way out, so no one travels more than 25 feet sideways to reach it. Move the ladder as the work moves. In a trench box, you must be protected from cave-ins while getting in and out, and no one may be inside while it is installed, removed or moved vertically (29 CFR 1926.652(g)(1)(iii) and (iv)). (29 CFR 1926.651(c)(2))
ASK THE CREW
Where is the nearest ladder or ramp to your work spot?
From the talk: Trenching and excavation. Read it in full, free, with the questions and the sign-in sheet.