Working the right way means working the safe way. The challenges of trenching and excavation jobsite safety are faced by utility employees and contractors daily. Every employer and employee working at these sites needs to be knowledgeable about trench safety practices including recognizing hazards, site evaluation and safety precautions.
Toolbox talks provide informal, topic-specific, short-format meetings to offer an opportunity to teach employees how to recognize trenching hazards, abate the recognized hazard, and reinforce basic trench safety procedures. As a Dodge Data & Analytics Report noted, “toolbox talks continue to be the most effective means of communicating with jobsite workers about safety.”
The Occupational Safety and Health Administration (OSHA) has made reducing trenching and excavation hazards a priority at the agency. Trench collapses, or cave-ins, pose the greatest risk to employee safety. Employees working on a trenching site should know that trenches deeper than five feet require a trench support system. More information can be found at: https://www.osha.gov/Publications/trench_excavation_fs.html
Toolbox Talk Topics
Here are seven topics that can be the foundation for a toolbox talk series to advance worker knowledge about trench hazards and safe work practices in trenching and excavation operations. They can serve as a starting point in building the more detailed information needed to create meaningful toolbox talks.
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). The competent person must know these, but anyone working in or around a trench or excavation should be aware of these minimum requirements.
Discuss the 12 specific 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.
Soil Classification. Proper soil-type identification through visual and manual tests is required to identify the correct protective system solution. The soil type dictates the trench protective system that can be used – sloping, benching, shielding or shoring. The weight of a cubic yard of soil is over 3,000 lbs. An average cave-in consists of 3 to 5 cubic yards. Soil needs to be reevaluated any time site conditions change. A good toolbox talk activity can be using soil from a jobsite to have everyone perform a manual soil test with the instructor walking participants through visual soil tests.
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. These include benching in Type C soil, which OSHA does not allow; failing to bench Type B soil appropriately – OSHA allows for a 4-ft vertical rise, but requires the horizontal run be 8 ft; and benching in granular soil, OSHA allows benching in cohesive soil only – never in granular soil.
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 critical that positive shoring be placed correctly, according to the manufacturer’s tabulated data. A toolbox talk activity can be having workers determine the number of shores needed for a particular-sized excavation/trench.
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. A toolbox talk activity can be performing a daily inspection (one of the 12 general specific requirements) on a shield to show how to check that all components are present and intact.
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.
A toolbox talk activity can be reviewing a few different types of tabulated data, from different manufacturers. Ask workers to identify the depth rating of a steel shield in B soil and an aluminum box of the same size in B soil. Also ask workers to identify the type of backing allowed to be used with hydraulic vertical shores.
Site-Specific Engineering. Contractors can often utilize a protective system simply by following the OSHA charts or the manufacturer’s tabulated data. However, 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 using protective systems not covered by a manufacturer’s tabulated data or the OSHA charts, such as steel sheet piling or when heavy surcharges – such as heavy equipment, stockpiled equipment, roads, bridges and buildings – are close to the excavation.
Employees must be trained to never enter a trench until it has been inspected by a competent person and deemed safe to enter. A trench can collapse in seconds, burying workers under the weight of thousands of pounds of soil making it very difficult to be safely rescued. Working together and educating on the use of appropriate protective systems, we can reduce employee injury and death in this high-risk industry. Employers should also ensure there is a safe way to enter and exit a trench and always keep materials at least two feet away from trench edges.
OSHA offers several resource pages with valuable information that can be used in developing toolbox talks:
- OSHA’s trenching operations QuickCard provides information on protecting workers around trenches, including daily inspections, and trench wall safety.
- OSHA’s “Protect Workers in Trenches” poster provides a quick reminder of the three ways to prevent dangerous trench collapses: SLOPE or bench trench walls, SHORE trench walls with supports, or SHIELD trench walls with trench boxes. The poster is available in Englishand Spanish.
- OSHA’s trenching and excavation webpage provides additional information on trenching hazards and solutions.
Advancing Trench Safety Knowledge
Maintaining up-to-date training on safety regulations and equipment solutions is a cornerstone to keeping utility construction workers safe, healthy and productive. Reviewing the fundamental principles covered in these toolbox topics with all employees will ensure that everyone has a good foundation and understanding of the basics of trench safety.
Tina Davis is a Customer Training Program Marketer for the Trench Safety Region of United Rentals. In her role, Davis orchestrates training and outreach events, helping customers advance worker knowledge about trench hazards and safe work practices in trenching and excavation operations as well as in confined spaces.
This article is for informational purposes only and generally discusses common industry processes and procedures. This article is not intended to be a substitute for site-specific professional/expert advice, instruction and supervision. United Rentals recommends consulting with Shoring and Excavation Experts to ensure full compliance with Federal OSHA 29 CFR, Part 1926, Subpart P-Excavations and Trenches, and any other applicable rules and regulations.