Unless the excavation is in stable rock, OSHA requires a protective system (sloping, benching, shoring, or shielding) when a trench is:

1. 2 feet deep or greater, with no exceptions
2. 5 feet deep or greater, unless a competent person finds no cave-in potential in a shallower excavation
3. 20 feet deep or greater only
4. Any depth if a ladder is present