Site Construction
Site work (15 of 115 items) covers excavation safety, soils, and earthwork. This chapter reviews OSHA's excavation standard, soil classification, and compaction testing.
Excavation safety (OSHA Subpart P)
OSHA's excavation standard (29 CFR 1926 Subpart P) requires a protective system, sloping, shoring, or shielding, for trenches 5 feet or deeper unless the excavation is entirely in stable rock. For trenches 20 feet or deeper, the protective system must be designed by a registered professional engineer. Trenching cave-ins are a leading cause of construction fatalities, so this standard is heavily tested.
Soil classification and stability
OSHA ranks excavation stability from stable rock (most stable) through Type A and Type B to Type C (least stable). Less stable soils require flatter sloping and stronger protective systems, so correctly classifying the soil, using visual and manual tests by a competent person, drives the protective design and the maximum allowable slope.
Earthwork and compaction
Structural fill under slabs and pavements must be compacted to a specified percentage of maximum dry density. The Proctor test (standard or modified) establishes that maximum dry density and optimum moisture content in the lab; field density tests then compare compacted fill to that reference. A '95% compaction' specification is meaningless without a Proctor value to measure against.