Trenches & Excavations

A trench with solid walls and an open "ceiling" can seem harmless. Workers can see the sky and their surroundings; often their heads are above ground level. Unfortunately this feeling can give workers a false sense of security.

Some Facts

• At about 100 fatalities a year, cave-ins are a prime cause of construction related deaths.

• Even shallow trenches can collapse and cause severe injuries or death. A trench only as deep as your shoulders could cave in and the weight of the soil could stop you from breathing.

• There are three ways to protect against excavation accidents. Protective systems include shoring, sloping, and a trench shield or box.

• Excavations 4 feet deep or more must have a safe means of entry and exit.

It Really Happens

A San Mateo sewer worker was carrying a pipe when he slipped on the edge of a trench. He fell down the side, twisting his knee. He missed 3 months of work and may require surgery in the future. Had the worker exercised caution by following proper safety procedures for work near trenches, this could have been avoided.

Employer's Role

• Know and understand the OSHA trenching standard.

• Survey sites for potential hazards and contact utility companies.

• Mark boundaries so heavy vehicles, equipment, and machinery don't come too close.

• Remove possible structure hazards and provide extra supports in trenches when needed.

Worker's Role

• Make sure you understand the potential hazards of excavation and trenches, and how to prevent them.

• Evaluate soil quality (or find a qualified person who can) to determine a trench's stability. While this won't prevent cave-ins, it will help identify the best practices to protect fellow workers.

• If you see dangers such as surface cracks, overhangs or bulges near the edge of a trench, evacuate the trench immediately. These are signs of a potential cave-in.

• Review the trench and its supports daily and after any weather changes.

Discussing Trenches and Excavations

• When would you use shoring? Why is it built from the top down?

• Whom would you notify first if you saw cracks at the edge of a trench?

• Why is rain a problem in a trench? What precautions can you take if you have to work in this situation?