A 29-year-old construction worker employed by a small excavation contractor was killed when the trench he was working in collapsed and buried him in approximately six feet of dirt. The worker was part of a crew installing a sewer pipe at a residential property.
The property was heavily wooded (shown in Figure 1). It was reported that at the time of the incident, the excavation was 75 feet long and three feet wide. The trench depth ranged from five feet to 13 feet deep along its length. In the work area where the incident occurred, the trench was 10 feet deep. The contractor was using aluminum hydraulic shoring in the trench. Other equipment in use at various times on the job site included hand tools, a backhoe, and a dump truck.
The trench was 10 feet deep and approximately three feet wide in the area where the collapse occurred. The collapse occurred in an unprotected area of the trench, between two pieces of shoring that were spaced 15 feet apart.
When the trench collapsed, co-workers called 911 and attempted unsuccessfully to locate and dig the worker out. When emergency responders arrived, their first task before commencing rescue and recovery efforts was to shore up the trench to prevent the risk of additional collapse and injuries. Emergency responders spent several hours recovering the worker’s body.
Key factors identified in this investigation included an inadequate trench protective system; no ladder available for entry or egress; and a spoils pile being placed too close to the edge of the trench. Underlying contributing factors were the lack of oversight by a competent person; and insufficient employee training on recognizing and reporting hazards.
- Employers who have employees working in trenches that are five feet deep or deeper, must select and install appropriate protection systems for the conditions present, to protect workers from cave-ins. For trenches less than five feet deep, examination by a competent person for potential cave-in indicators is required.
- Excavation work requires a designated competent person on site who has both the knowledge and authority to identify and promptly correct hazards; this includes daily inspections prior to the start of work and as needed throughout the work shift, and any time site conditions change.
- To select appropriate trench protective systems for a given job site, the competent person should visually and manually test the soils, and also consult the shoring or shielding manufacturer’s tabulated data or OSHA’s tables and charts designed for this purpose.
- Employers must provide sufficient means of safe access and egress for workers in any trench excavation of four feet deep or deeper, which may include ladders, ramps, or stairs.
- Keep excavated soil (spoils) and other materials and tools at least two feet from the edge of any trench.
- Before working in and around trenches, employees should receive training on trenching safe practices, and on recognizing and reporting hazards.
- Employers should develop and maintain a safety culture where employees are encouraged to voice concerns about unsafe work conditions.