Trench collapses happen fast and leave little chance of escape. Here is what every contractor needs in the plan before the first bucket goes in the ground.
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Why trenching needs its own plan
Trench collapses happen fast and leave little chance of escape. A cubic yard of soil weighs about as much as a car. Trenching and excavation work shows up on almost every job, from utilities to footings, which is why it deserves a written plan instead of a quick decision in the field.
Know the protection rule
OSHA requires protective systems for trenches 5 feet deep or more, unless the excavation is made entirely in stable rock. At 20 feet or deeper, the protective system must be designed by a registered professional engineer. Shallower trenches still need a competent person's judgment.
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Choose the right protective system
- Sloping: cutting the walls back at a safe angle.
- Benching: stepping the walls in levels.
- Shoring: supporting the walls with hydraulic or other supports.
- Shielding: trench boxes that protect workers inside.
The competent person
A competent person must inspect the trench daily before work and after rain or other events that could change conditions. This person must understand soil classification and have the authority to stop work.
Access and spoils
Trenches 4 feet or deeper need a safe way in and out, such as a ladder or ramp, within 25 feet of workers. Keep spoils and equipment at least 2 feet back from the edge.
Call before you dig
Call 811 before excavating and wait for utilities to be marked. Hitting a gas or electric line creates a second emergency on top of the trench hazard.
Other hazards
Water accumulation, hazardous atmospheres in deeper excavations and nearby traffic or vibration all affect trench safety. Include them in the pre-task plan.
Make stopping normal
The most important rule is that anyone can stop work in an unprotected trench without being questioned. Build that into toolbox talks and back it up in the field.
Plan for rescue
Never let workers jump into a collapsed trench to dig out a coworker without protection. Secondary collapses are common. Have an emergency plan, know the local rescue response and keep the area clear until trained responders arrive.
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Frequently asked questions
At what depth does a trench need protection?
OSHA requires protective systems for trenches 5 feet deep or more unless the excavation is entirely in stable rock, and trenches 20 feet or deeper need a system designed by a registered professional engineer.