The United States National Institute for Occupational Safety and Health (NIOSH)
offers guidance on engineering controls, protective equipment, and safe work
practices to minimize hazards and protect workers who are at risk of injury and
death from cave-ins during trenching and excavating.
Excavation sites can be hazardous and workers who dig the trenches are at risk
of serious injury or death if the walls collapse. A trench can fail suddenly
before workers have time to move out of the way. Soil is heavy. A single cubic
yard of dirt can weigh more than 1360 kilograms (3,000 pounds) - enough to
crush or suffocate a person.
There are precautions employers and employees can take to prevent injuries and
deaths and address the hazards they face in trenching and excavation work.
What employers can do
Before the job begins:
- Train and designate a competent person to ensure safety measures are in place.
- Contact utility companies before digging to have utility lines marked, then hand dig test holes or potholes to expose utilities and determine their exact location and depth before excavating.
- Evaluate the soil to determine its stability, keeping in mind that soil conditions can change substantially over a few days.
- Plan the job layout to identify safe locations, well away from the trench, for spoil piles (excavated material) and heavy equipment routes.
- Determine what type of protective system (shoring, shielding, or sloping) will be used for the job and have the system in place before workers enter.
- Consult an engineer for more complex trenches greater than 20 feet deep, to determine the appropriate protective system that should be used.
- Ensure that everyone working in the trench is aged 18 or over.
- Ensure that workers involved in the job are trained about hazards and work practices in a language and literacy level that they understand.
- Develop a trench emergency action plan to describe steps to be taken in case of an emergency, and ensure it includes emergency contact information.
Operating safely during the job:
- Inspect the excavation, adjacent areas, and protective systems each day before the start of work, as needed throughout the shift, and after every rainstorm.
- Notify subcontractors of the trench location and precautions, and ensure that vehicles are kept a safe distance from the excavation. Ensure that ladders and other means of exit are never more than 25 feet away from any worker in the trench.
- Remove workers from the trench if any situation is detected that could cause a cave-in, such as water in the trench or problems with the protective systems.
- Monitor other types of trench-related hazards that can occur such as falls from the edge, rigging hazards, or toxic and combustible gases.
- Implement and enforce procedures to ensure that work in an unprotected trench is not permitted.
- Do not enter an unprotected trench.
- Inspect the protected trench before entering.
- Exit the trench and call your supervisor if you see any evidence of problems with a protective system.
- Do not assume there will be a warning sign before a cave-in or that you will have time to move out of the way so immediately report potential problems at the first sign of any trouble.
AplusA-online.de - Source: National Institute for Occupational Safety and Health (NIOSH)