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Excavation Protective Systems

Each employee in an excavation shall be protected from a cave-in by using either an adequate sloping/benching system or an adequate support/protective system.

Exceptions to this requirement are limited to:

  • Excavations made in stable rock; 
    • Note: "Stable rock" is not recognized by Virginia Occupational Safety and Health (VOSH) in the commonwealth and should not be considered as an option. 
  • Excavations less than 5 feet in depth where examination of the ground by a Competent Person provides no indication of a potential cave-in.

Protective systems shall be capable of resisting all loads that could be reasonably expected to be applied to the system.

Trench boxes are pre-built shield systems designed to the manufacturer's tabulated data. These boxes must be used in accordance with all specifications, recommendations, and limitations issued or made by the manufacturer. A copy of the manufacturer's instructions must be available for review, upon request.

  • Trench boxes must not be used at a depth greater than that for which they were designed. 
  • The shield must be installed in a safe manner to restrict lateral or another hazardous movement of the shield in the event of a sudden cave-in. The closer a properly constructed trench shield/box is to the trench wall, the less chance that it could be dislodged by a lateral force.
  • Personnel shall not be allowed in trench boxes when they are being installed, removed, or moved vertically/horizontally (where hazardous).
  • Personnel shall not work outside of the protective structure of the trench box where protective systems are not provided.

Sloping and benching system requirements are specified below for excavations between 4 and 20 feet deep. The angle of the slope or bench is determined by the class of soil present at the excavation site. 

  • (Best Practice) The competent person may assume the worst class of soil (i.e. the most unstable), class "C", and angle the sides of the excavation 34 degrees (i.e. 1 1/2 H to 1 V).
  • If the competent person has classified the soil and determined that it is class "B," the angle of the sides of the excavation must be 45 degrees (i.e. 1 H to 1 V). 
  • Class "A" soil is not recognized at Virginia Tech because all soil has been previously disturbed, and therefore does not meet the criteria for class "A" soil properties. 

Personnel shall not be permitted to work above other personnel on the faces of sloped or benched protective systems except when personnel at lower levels are protected from the hazards of falling, rolling, or sliding materials or equipment.

For more information on sloping and benching systems - 29 CFR 1926, Subpart P, Appendix B. 

Where preassembled shield systems or sloping/benching is not available or feasible, the competent person must implement an appropriate system designed to OSHA criteria (i.e. timber or aluminum hydraulic shoring), or have written approval by a registered professional engineer to implement the system designed by him/her. 

For more information on timber shoring refer to 29 CFR 1926, Subpart P, Appendix C. 

For more information on aluminum hydraulic shoring refer to 29 CFR 1926, Subpart P, Appendix D.