Site Safety & Excavations

• Federal excavation rules (OSHA, 29 CFR 1926 Subpart P) require a protective system — sloping, benching, shoring or a shield — in trenches 5 ft deep or more unless they are in stable rock.
• Maximum allowable slopes for excavations under 20 ft: Type A soil ¾H:1V, Type B 1H:1V, Type C 1½H:1V.
• A trench 4 ft or deeper needs a ladder or other exit within 25 ft of lateral travel; spoil stays at least 2 ft back from the edge.
• Temporary erosion control — silt fence, inlet protection, sediment basins — is part of the site plan, not an afterthought.

Worked

• A 12 ft deep trench with a 4 ft bottom in Type B soil, sloped 1:1 both sides: top width = 4 + 2 × 12 = 28 ft.
• Three recordable injuries in 420,000 hours worked: 3 × 200,000/420,000 = 1.43.