Excavation cave-ins cause about 75 deaths and 1,000 injuries a year in the US, including about140 that result in permanent disability.
Much more hazardous than they may appear, excavations can collapse unexpectedly and bury a worker or a bystander.
It is unsafe to enter an excavation unless it is properly supported. A hole dug for a basement, or a trench dug for utilities are some of the kinds of excavations which need to be shored up or sloped properly. The support must be adequate to handle the pressure of the soil and water content, as well as other pressures, such as piles of excavated dirt and rock, nearby buildings, traffic and heavy equipment.
You might be surprised to learn you can be killed by a cave-in even if you are not totally buried. Many cave-in victims suffocate before they can be dug out. Others buried only to the waist have died because of injuries caused by pressure from the soil.
Particularly dangerous are holes in or near soil previously excavated because the dirt remains loose. Moisture also increases the likelihood of a cave-in, as water pressure causes the walls of the excavation to collapse. Also hazardous is clay, which may crumble as it dries.
Frozen ground is no guarantee of safety and is not considered an alternative to proper support of excavation walls.
An excavation can be called a confined space, with the possibility of an atmosphere contaminated by toxic gases or other problems that make it unsafe to breathe the air.
An excavation could be located near an old chemical dump, a leaky underground gasoline tank or a sewer.
If your work takes you in to trenches, remember these safeguards:
- The excavation must be inspected by a competent person such as a certified engineer to determine if it is safe to enter.
- All equipment such as pumps and ventilators must be working properly.
- You need a way to exit quickly, such as a ladder.
- Your employer must have marked all utilities before digging so you don’t run into an energized electrical cable, a natural gas line or a water pipe.
- The edge of the excavation must be properly sloped, benched or shored up so it won’t collapse.
- Keep the excavated soil at a safe distance from the edge of the trench.
- Use a barrier if necessary to keep dirt and rocks from falling back into the trench.
- A barrier around the excavation to keep bystanders away is also recommended, particularly near sidewalks and crosswalks.
If, in spite of all precautions, a cave-in begins, get out fast. Call for emergency help for your workers from outside the trench. Don’t jump in, even for a rescue, because you could be killed.
Excavations are hazardous not only for the construction or utility crews who work in them, but anyone in the area. Keep a safe distance from construction sites, and keep your children away too.