OSHA 10-Hour Construction ReviewExcavationsMedium
A competent person is inspecting an excavation site. They observe that heavy equipment is operating near the edge of a trench, and spoil piles are placed directly at the trench lip. Which primary hazard is most likely to result from these conditions?
- AFalls from elevation into the trench.
- BAccumulation of hazardous atmospheres.
- CIncreased risk of cave-in due to surcharge loads.
- DElectrocution from overhead power lines.
Show answer & explanationAnswer & explanation
Correct answer: C. Increased risk of cave-in due to surcharge loads.
Heavy equipment and spoil piles at the trench edge create a surcharge load, which adds significant weight and pressure to the soil. This additional load directly increases the stress on the trench walls, making them more susceptible to collapse or cave-in.
Why the other options are wrong
- A. Falls into the trench are a risk, but the specific combination of heavy equipment and spoil piles at the edge primarily exacerbates the risk of cave-in, not just falling over the edge.
- B. While hazardous atmospheres can occur in trenches, they are not directly caused by heavy equipment or spoil piles at the edge.
- D. Electrocution is a separate hazard related to power lines, not specifically to equipment and spoil piles at the trench edge itself.
Surcharge Load
A surcharge load is any additional weight or pressure placed on the soil near an excavation, such as spoil piles, heavy equipment, or vehicles, which can increase the risk of a cave-in.
- Adds weight and pressure to excavation walls.
- Increases stress on soil, leading to instability.
- Common sources: spoil piles, heavy machinery, stored materials.
- Must be kept a safe distance from the trench edge.
Memory trick: Cave-ins: The Big Dig Danger