What Is a Trench Box and What Is It For?

Trench boxes, also known as trench shields, are of the utmost importance for construction workers’ safety. When dealing with an excavation site, it’s of paramount importance to protect workers from potentially deadly cave-in situations. 

If you are unfamiliar with trench boxes or trench shields, we discuss this below. You will be able to answer the question, "What is a trench box?" after reading this article. 

What Are Trench Boxes?

Trench boxes offer protection to workers while they’re working within an excavation area. They’re also called "trench shields." or "sewer boxes." These boxes are made of steel or aluminum that are inserted into a trench in order to secure the walls of dirt, preventing a cave-in. 

Trench boxes can be made of aluminum or a combination of aluminum/steel materials. Aluminum shields are usually used in more shallow excavation when doing service connections or point repairs. They are available in panel construction, allowing the user to use them as a two, three, or four-sided shield. The user can pick panels from a number of lengths up to 12 feet and widths up to 12 feet. Most of these panels are two feet tall and can be stacked to achieve the height required.

Another type of aluminum sheet is a three-foot wall foam-filled aluminum panel reinforced with a steel frame to add durability when used in more severe situations. This is known as an SFA shield and comes in four-foot, six-foot, and eight-foot heights. They range from four feet to 16 feet in length and are often used when smaller excavators or backhoes are operating.

Are trench boxes required for every excavation?

In March of 1990, the Occupational Safety and Health Administration added additional rules and guidelines for the Subpart P Excavation Standard. These revisions were made to clarify the current rules and make them easier to understand and implement. This revision dealt with excavation being accepted as one of the most dangerous types of construction. More workers are injured or killed in the excavation process of construction than in any other area.

All trenches greater than five feet require a protective system, though the engineer on a site may require the depth to be as low as four feet. OSHA also requires that a competent person trained in the Subpart P Excavation standard determines the correct level of protection needed for the job.

All trench boxes must be designed and constructed according to the design of a registered professional engineer, within the structural field. Manufacturer tabulated data, with a signed P.E. stamp, is required during the installation. It must be available at the request of any OSHA official. 

Trench boxes are one of the most critical components of worker safety on a construction/excavation site. Without such protection in place, the safety of any work is severely in jeopardy. Crucial rules and regulations regarding trench boxes help keep the workers safe and prevent catastrophe. 

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