Across the United States and Canada, a booming oil and natural gas sector is putting many Laborers to work on pipeline projects. These construction projects are a great source of important, long-term work, but there are also potential hazards that Laborers need to be aware of.
Construction laborers’ role in pipeline work is primarily in digging trenches and laying pipe. That means spending a lot of time working around and inside trenches and ongoing excavations. Unprotected trenches can easily collapse, and if workers are inside or nearby, serious injuries and fatalities are almost always the result.
Research by the Department of Transportation shows that 25 percent of incidents on pipeline sites are related to excavation, and the Bureau of Labor Statistics reports that cave-ins account for three quarters of trench-related fatalities. Fatalities from cave-ins and collapses can be prevented if proper protections are in place.
Digging trenches causes pressure from the surrounding soil to build on the walls of the trench, forcing it inward. On trench jobs, protection for workers comes in several forms:
- Sloping, the most common way to protect workers, involves cutting back the trench wall at an angle inclined away from the excavation. This helps alleviate the downward pressure on the soil by removing weight from the walls of the trench. This method is not always used in tight confines because of the space needed to widen the trench.
- Benching, a form of sloping, protects workers by excavating the sides of a trench to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels. Benching cannot be done in all soils.
- Shoring requires installing aluminum, hydraulic or other types of supports to prevent soil movement and cave-ins.
- Shielding protects workers with trench boxes or other supports when sloping and shoring aren’t practical or are not being used. Because trench boxes don’t lessen pressure on the walls of the trench, workers must stay inside the confines of the trench box to be protected.
“Too often, pipeline trenches are left unprotected because workers are not expected to be in them, or are ‘only’ in them for very short periods of time. Supervisors don’t think it’s worth sloping and workers hop in without being shielded by a trench box. This has to change,” says Walter Jones, Associate Director of the LHSFNA’s Occupational Safety and Health (OSH) Division. “A collapse can occur with no warning, in a blink of the eye, and strike with over 10,000 pounds of force. More often than not, trench rescue becomes body recovery.”
Environmental conditions like rain, cracks in the trench wall or the type of soil present, as well as worksite activities or an increase in nearby traffic, can all affect the stability of an unprotected trench very quickly. More than a third of trench-related fatalities occur on Mondays, most likely due to rain or other environmental factors changing conditions over the weekend.
A number of other factors can cause a trench to fail:
- External loads from construction equipment near the edge of the trench
- Soil piled too close to the edge of the trench
- Trench walls too steep for the type of soil present
- Pressure from moisture in the soil during winter and early spring
Visit the LHSFNA’s Trenches and Excavations page to learn more about following safe trench practices on your site, or call the OSH Division at 202-628-5465. The Safety in the Trenches pocket guide is also available through the online Publications Catalogue.