General Trenching and Excavation Rules
- Keep heavy equipment away from the edges of the trench. Also, keep excavated soil (spoils) and other materials at least 2 feet from trench edges. This is crucial to preventing cave-ins.
- Be aware of the space surrounding the trench, and any objects or environmental fixtures that could affect trench stability.
- Know where underground utilities are located before digging.
- Test for atmospheric hazards (such as low oxygen and toxic gases) when the trench is deeper than four feet.
- Inspect trenches at the start of each shift, and after a rainstorm, water intrusion, or other occurrence that could change the trench condition.
- Do not work under suspended or raised loads.
- All workers should wear high visibility clothing when exposed to vehicular traffic, as well as any mandatory PPE.
Benching is a protective system that involves excavating the sides of the trench to form horizontal levels, usually with vertical or near- vertical surfaces between levels. Benching results in a step-like appearance along the sides of a trench.
Sloping is a protective system that cuts back the trench wall at an angle inclined away from the excavation.
Shoring is a protective system that requires the installation of supports (typically aluminum hydraulic) to prevent soil movement and cave-ins.
Shielding is a protective system that uses trench boxes or other types of supports to prevent soil movement and cave-ins.
To determine the appropriate protective system for a trench, one must consider the soil classification, trench depth, climate, surcharge loads, and other operations in the vicinity.