Trenching poses some of the most severe hazards in the construction industry, and sadly, trench failures are causing an increasing number of fatalities.
During the past year, workplace accidents involving trenching and excavation serve as a reminder of the hazards that come with this type of work. In April 2019, a worker in Marysville was killed while repairing a water line; two days prior, another worker died when he was buried in a trench collapse at a construction site for a housing development near Dayton.
Before You Dig
- Know the location of underground utilities before starting a new excavation project. Call OHIO 811 at least 48 hours before beginning any excavation project or use the free online ticket entry system.
- Have an emergency rescue plan in place with contact information for the local fire department or a specialized trench rescue unit.
Planning the Trench
- If a trench is more than 20 feet deep, a registered professional engineer must complete the protective system design.
- Review tabulated data that comes with all manufactured shoring and shielding equipment.
- Conduct the installation and removal of protective systems in a way that protects employees from cave-ins/collapses.
- Removal of shielding or shoring should start at the bottom of the excavation.
- Walkways or bridges are needed for crossing over trenches. When the trench is 6 feet deep or more, a guardrail must be installed on the walkway or bridge.
Use of Protective Systems
- Protective systems are required for trenches that are 5 feet or deeper, unless the excavation occurs in stable rock. If a competent person determines there is a potential for an excavation to cave in, a protective system must be used regardless of depth.
- Types of protective systems
- Sloping or benching – Slope the walls or create bench stepping for stability.
- Shielding – Use a trench box to protect from trench collapse.
- Shoring – Use a support system fashioned from posts, beams, shores or planking, and hydraulic jacks to prevent trench collapse.
Working in the Trench
- Have a competent person inspect trenches daily and as conditions change. A competent person should be able to identify soil classifications and protective systems to use in accordance with OSHA Excavation Standard, 1926 Subpart P.
- Review and follow Ohio Revised Code, Chapter 3781: Building Standards. The following sections are especially important for excavation and trenching:
- Before employees enter a trench, some form of protection must be in place. Use sloping and benching to modify the cut soil. If these two modifications are not allowed or otherwise not possible, use shoring (supporting the walls), or a trench box for protection prior to trench entry.
- Do not work outside of trench shoring or shielding protection in unprotected areas of trench.
- Ensure material and equipment for protective systems are in good working order and free from defects.
- Never have employees work alone in a trench; always have a lookout standing by.
- Provide safe access with ladders, ramps, or stairways.
- Keep excavated or other materials and heavy equipment at least 2 feet away from the edge of a trench.
- Inspect trenches following rain, snow, or ice.
- Employees should not work in a trench with water accumulation unless they follow necessary safety precautions, such as water removal to control the level of the water or special support or shielding systems.
- Do not allow employees to work under raised loads.
- Test for low oxygen, hazardous fumes, and toxic gases.
- Employees should wear high-visibility clothing when around traffic.