Trenching and excavation continue to place workers in the construction and utility industries in dangerous positions.
The private construction industry was responsible for 80% of trenching fatalities between 2011 and 2016, according to data from the Bureau of Labor Statistics.
OSHA's National Emphasis Program (NEP) in Trenching and Excavation specifically requires agency investigators to concentrate enforcement of standards for employers performing these activities.
United Rentals recommends the following seven trench safety topics to include in upcoming toolbox safety talks:
1. OSHA 12 Specific Requirements
Review the 12 specific requirements related to excavations specified by the Occupational Safety and Health Administration (OSHA 1926.651 General Requirements). Discuss these requirements, which address areas such as access and egress, exposure to vehicular traffic, warning systems and more, to promote greater awareness. Create a “Trenching & Excavating by the Numbers” exercise to build worker retention of excavation standards, such as five – the number of feet at which a protective system becomes mandatory – and 25 – the maximum distance in feet a worker may travel to reach a means of egress.
2. Soil Classification
Soils are among the most important factors to consider when following the required manual and visual tests to identify the correct protective system solution. The soil type dictates the trench protective system that can be used – sloping, bench, shielding or shoring. Remind workers that soil needs to be reevaluated anytime site conditions change.
3. Protective Systems – Sloping/Benching
Sloping and benching protect workers from cave-ins by cutting back trench walls. With sloping, the wall is cut at an angle inclined away from the excavation. Benching involves excavating the sides of an excavation to form one or a series of horizontal levels or steps. A toolbox talk can review common mistakes associated with benching, such as benching in Type C soil, which OSHA does not allow and benching in granular soil, OSHA allows benching in cohesive soil only – never in granular soil.
4. Protective Systems – Shoring
Shoring is an active system designed to prevent cave-ins by applying positive pressure against trench walls. Conduct a hands-on talk with a hydraulic vertical shore, reviewing available sizes, limitations, installation instructions and proper usage. Remind workers it is essential positive shoring be placed correctly, according to the manufacturer’s tabulated data.
5. Protective systems – Shielding and Trench Boxes
These are passive systems; they don’t prevent cave-ins like shoring does. They are designed to withstand a cave-in and protect workers provided the shield is properly installed. Review shielding options available, including aluminum boxes and steel boxes. Perform an inspection on a shield to show how to check that all components are present and intact.
6. Tabulated Data
Review different types of tabulated data that come with all manufactured shielding and shoring equipment. This data details proper equipment use and limitations, covering areas such as assembly instructions, soil types and maximum depth rating. Remind workers this information must always be onsite, either on paper or electronically. If the scope of work is outside what the equipment is rated for per the tabulated data, another protective system needs to be considered or an engineer needs to get involved to create a site-specific plan.
7. Site-Specific Engineering
Excavations near adjacent structures, underground utilities and roadways may come with unique and complex challenges that require professional input. Although contractors can usually utilize manufactured systems with tabulated data, there are times where additional guidance and stamped drawings from a professional engineer are necessary. A toolbox activity can be reviewing when to call upon a professional engineer, which include when heavy surcharges – such as heavy equipment, stockpiled equipment, roads, bridges and buildings – are close to the excavation.
“The challenges of trenching and excavation jobsite safety are something companies face every day,” said Todd Hayes, region vice president – trench safety, United Rentals. “Everyone working at these sites needs to be knowledgeable with trench safety practices and toolbox talks keep safety top-of-mind with workers.”