Every year in the United States, more than 100 people are killed in trench cave-ins. Most of these accidents happen on smaller jobs in excavations less than 20 feet deep. Even if the excavation is only 5 feet deep, a cave-in can kill or maim workers setting forms, placing concrete, stripping forms, placing drain tiles or waterproofing walls.
WHY TRENCHING ACCIDENTS CAN BE DEADLY
A cubic yard of undisturbed soil weighs about 2700 pounds. When cave-ins occur, the material falls at speeds up to 35 miles per hour. Usually it pulls away at the top and falls across to the other side, crushing victims between the collapsing soil and the opposite wall of the trench. Based on personal opinion and past experience, many contractors decide there is no danger from cave-ins on smaller jobs. By allowing employees to work unprotected in trenches they not only endanger workers but risk prosecution and fines for violating regulations enforced by the Occupational Safety and Health Administration (OSHA).
RECOGNIZING HAZARDOUS TRENCHING CONDITIONS
OSHA regulations require contractors to provide safety training and education for all employees. Foremen and workers should be trained to watch for conditions that can cause trench failure and to recognize indicators of potential cave-ins. Several conditions that can be direct causes of trench failure are listed below:
- Material or equipment too near the edge
- Previously excavated areas
- Intersecting trenches
- Vibration caused by traffic or blasting
- Wet soils
- Load from existing structures
- Changes in the weather
- Layers of different soils