ACI Concrete Finisher Practice Test 2026 – Your Complete Exam Prep

Keep the wheels from the edge by at least the depth of the trench. For a six-foot-deep excavation, that six-foot buffer creates a safe zone where the soil is less likely to cave in under wheel load or vibration and where the operator has space to maneuver without threatening the edge. It also accounts for any slight wheel deflection or tire swing as the truck passes.

A smaller distance would put the wheel close enough to the edge to increase the risk of a cave-in or edge failure, while a much larger distance, though safer, isn’t necessary for this depth and would unnecessarily limit access.