Trenching and Excavation Safety (Part 5)

Trench Protective Systems

There are four basic ways to protect workers in a trench. Trenches that are more than 20 feet deep must be protected by a protective system that was designed by a registered professional engineer.

  1. Sloping
    The type of soil will determine the ratio of the slope:
    1. Type A soil should have a ¾ to 1 ratio
    2. Type B Soil should have a 1 to 1 ratio
    3. Type C soil should have a 1 ½ to 1 ratio

    If different layers of soil are encountered as you go deeper, the slope must be adjusted in order to have the right ratio for each.

  2. Benching
    Benching follows the same ratios as for sloping with the last 4 feet being straight down (without a slope) and the top of this 4 foot deep trench within a trench being at least 4 feet from the slope of the rest of the trench
  3. Shoring
    Shoring is essentially plating that is held in place with expandable braces. There are different types of shoring systems but the basic system is similar. The plates are lowered in and the brace is expanded until it holds them in place and keeps the soil on either side of the trench from collapsing.
  4. Shielding
    Shields are similar in nature to shoring except that the plates and the braces are permanently fixed together. The braces are not expandable.