Type-C soils—Generally benching is not permitted in Type-C soils unless used in combination with a trench box or shoring. Exceptions are made for layered soils where Type-C soils are above Type-B or Type-A soils. In such conditions, the Safety and Health Manager or company official must be notified for authorization.
Benching is permitted in Type-C soils for any depth excavation provided that the upper bench or benches are excavated back far enough from the edge of the next lower top of slope to virtually make the upper bench non-affecting the lower bench; for example, scalping an area 4 ft. deep and 50 ft. wide for a proposed trench 10 ft. deep and 10 ft. wide. The result would be a trench 6 ft. deep so that the closest bench to the top of its slopes would be back 20 ft., which would allow an 8 ft. high trench box to be used safely.
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