Trenches and excavations can collapse and trap or crush workers.
Before digging
- Locate buried services first. Contact the owners of any underground utilities in the area and have them identify and mark the locations.
- Identify overhead power lines.
- Look at the soil and anything that could make it less stable, such as water or vibration from nearby vehicles and equipment.
Protective systems
In general, trenches 1.2 m (4 ft) deep or more need a protective system unless they're entirely in stable rock. The exact rules depend on your jurisdiction and the soil. The two basic methods are:
- Sloping or benching: cutting the walls back at an angle away from the work area.
- Temporary protective structures: shoring, trench boxes and engineered systems.
Working in and around trenches
- Keep spoil piles, pipe, tools and other materials at least 1 m from the edge.
- There must be a safe way in and out, such as a long enough, secured ladder.
- A competent person should inspect the excavation regularly, including at the start of each shift and after anything that could affect its stability.
- Never enter an unprotected trench, even “just for a minute.”
Excavation rules differ by province and territory. Check with your regulator.
Key takeaways
- Locate and mark buried services before you dig.
- Trenches 1.2 m (4 ft) or deeper generally need protection unless in stable rock.
- Keep spoil and materials at least 1 m back from the edge.
- Never enter an unprotected trench.