A trench is a narrow channel that is deeper than it is wide, made below the surface of the ground. A trench can be up to 15 feet wide. Trenching is recognized as one of the most hazardous construction activities. The greatest risk is a cave-in. Even a small job can present serious safety hazards. The key to preventing this type of accident is good planning.
Each year trenching cave-ins result in more than 5,000 serious injuries and 100 deaths in the United States.
Trenches are needed for the installation and repair of utility lines, water and sewer lines, television cable, to build roads, and many other uses. Anyone whose work requires them to work in or around a trench should be aware of the hazards so they are not involved in or cause an accident to happen.
REQUIREMENTS FOR ALL EXCAVATIONS
- A utility locate must be conducted prior to the start of any excavation. Call 811.
- All employees working in an excavation must receive initial training
- A competent person must be clearly identified for all excavations. This person must be knowledgeable in assessing soil conditions, the use of protective systems, and WISHA/OSHA requirements.
- The daily trenching/excavation log must be completed, and a copy must remain on site
- The soil type must be identified by the competent person on site:
- Type A – clay, silty clay, sandy clay, clay loam and cemented soils (hardpan)
- Type B – angular gravel, silt, silt loam, and sandy loam
- Type C – gravel, sand, and loamy sand
- Excavated material must be placed at least two feet from the edge of any excavation
- Precautions must be taken to ensure vibrating equipment/vehicular traffic does not cause a cave-in
- No employee shall enter an excavation that contains standing or seeping water
- Access (ladder/ramp) must be provided and located so no worker must travel more than 25 feet to exit.
- Employees at the edge of an excavation 10 feet or more in depth shall be protected from falling
- If conditions change in or around the excavation, employees must exit the excavation and a competent person must re-inspect and give approval for employees to re-enter
EXCAVATIONS FIVE FEET OR GREATER IN DEPTH
- Sloping, benching, or other approved cave-in protection systems must be utilized
- Trench boxes/shoring must be a designed and approved system
- The trench box should extend at least 18 inches above the surrounding ground surface
- Excavations greater than 20 feet must be designed by an engineer