Safe Use of Trench Boxes

When it comes to open excavations or trenches, OSHA allows four different types of protection: benching, sloping, shoring, and shielding. Shielding involves the use of trench boxes, shields, or other types of support to prevent cave-ins. This blog will discuss when a trench box can be used and how to safely use them while working below grade.
 
When to Use Trench Boxes
Per OSHA requirements (1926.652), employees must be protected when excavations are more than 5ft in depth. Trench boxes are a great protection system when workers are needed where benching or sloping of the soil is not possible. Trench boxes can also be utilized for utility work where large excavations are unnecessary. When selecting a trench box or other type of support, it is important to consider factors such as soil classification, depth of cut, water content within the soil, and other loads in the vicinity. When using trench boxes, some rules to follow include:

• Trench boxes must extend 18” above the surface
  • This helps prevent the potential for cave-ins from shifting soils on the surface
• Excavations 24” (2ft) below the bottom of the trench box are prohibited
  • Undercutting the trench box has the potential for soil to enter from below
• Means of Egress is required every 25ft
  • Workers must have access to a ladder which must be secured and extend 3ft beyond the trench at the surface
• All excavations exceeding 20ft in depth must have a system designed by an engineer
  • System should include size, type, and configuration of boxes to be used

 
Installing Trench Boxes
When installing or removing trench boxes, the protection of workers is always critical. Make sure to identify your soil type as well as the limitations of your trench box before it is used. Some rules to installing/removing trench boxes include:

• Do not allow employees in trench boxes while they are moving
  • Employees are only authorized to remain in a trench box while moving it horizontally
• Trench boxes can be used together
  • When boxes are stacked or placed alongside each other, properly secure them to each other
• Remove from the bottom of the excavation
  • Trench boxes should be removed from the bottom first, reducing the potential of a failure or cave-in
• Working on or around trench boxes is prohibited
  • When employees are in a trench box, all additional excavation work around or above is prohibited to prevent potential cave-ins or sliding material/equipment

 
Excavations and trenches have potential hazards that are fatal if not handled correctly. Make sure your competent person understands the types of protective systems and which is best for their situation. To keep the conversation going, download the Trenching & Excavation Toolbox Talk (TBT) or comment below.

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