Surcharge Loads & Vibration Near Trenches

Anything heavy near the edge of a trench, such as a spoil pile, an excavator, a stack of pipe or a loaded truck, pushes down on the soil and out against the trench wall. Add vibration from traffic or compactors, and a wall that looked stable can let go.

• Construction
• Equipment operators
• Competent persons

Common surcharge loads

• Spoil piles (excavated soil)
• Excavators, loaders and cranes working next to the trench
• Dump trucks and concrete trucks backing up to the edge
• Pipe, precast structures and materials stockpiled nearby
• Nearby buildings, walls and foundations. See Excavations Near Structures

The rules

• Keep spoil, materials and equipment at least 2 feet from the edge, or use retaining devices to keep them from falling or rolling in (or both).
• When mobile equipment works near the edge and the operator can’t see it well, use a warning system such as barricades, hand or mechanical signals, or stop logs.
• Protective systems (sloping, shoring, shields) must be designed for the surcharge loads that will be present. Tabulated data often assumes limited surcharge; heavier loads need an engineer’s design.
• Don’t let workers be under loads handled by lifting or digging equipment.

Vibration

• Traffic, trains, pile driving, compactors and running equipment shake soil loose.
• Soil subject to vibration can’t be classified as Type A. See Soil Tests.
• Watch for small soil falls and new cracks when vibration starts.

Daily checks

• Spoil piles at least 2 feet back and not sliding toward the trench
• Material stockpiles and equipment parked back from the edge
• Stop logs or barricades where trucks back up
• No new cracks parallel to the edge
• Protective system designed for the loads actually present

Last updated: October 2, 2026