Excavations in Type A less than 8 feet deep can have a maximum 3.5 foot unsupported vertical side.
Excavations Type A between 8 to 12 feet deep can have a maximum 3.5-foot unsupported vertical side.
Excavations in Type A less than 20 feet deep that use a shield can/must have a slope of 3/4: 1. The top of the shield must extend 18" above the vertical portion of the trench.
Maximum bench dimension with cohesive Type B soils.
Excavations in Type B of 20 feet or less 1 H:1V
Excavations less than 20 feet deep in Type B that use shield must have a slope of 1: 1.
The top of the shield or support extends 18" above the vertical portion of the trench
A registered professional engineer shall design sloping or benching for excavations of greater than twenty feet deep. If soil conditions allow, and upon approval of a registered professional engineer to certify a site specific trench safety sloping plans, this chart and slope angles may be used as part of such plan.
Excavations in Type C soil less than 20 feet deep that use a shield can/must have a slope of 1 1/2: 1. The top of the shield must extend 18" above the vertical portion of the trench.
Excavations of 20 feet or less Type C Soils 1 1⁄2:H:1V Slope
