A cubic yard of soil weighs approximately 3,000 pounds — as much as a compact car. A trench cave-in gives you no warning and no time to react. In New York City, where ground conditions range from solid Manhattan schist to unstable Queens fill to waterlogged Brooklyn clay, every excavation is unique and every one must be treated with full cave-in protection from Day 1.

• OSHA requires cave-in protection for any excavation 5 feet deep or greater — not 20 feet, not when it "looks unstable." Five feet.
• If unstable soil or known hazards exist, protection may be required at depths less than 5 feet — Competent Person makes this call
• Three acceptable protection methods: Sloping (cutting back the trench walls), Shoring (hydraulic shores, timber, or sheet piling), or Shielding (trench box)

• Type A (most stable): Clay, silty clay. Maximum slope 3/4:1 (53°). Manhattan bedrock — if you hit it, you likely don't need sloping
• Type B (medium): Angular gravel, silt, previously disturbed soil. Slope 1:1 (45°)
• Type C (least stable): Sandy soil, gravel, soil submerged or with water seeping in. Slope 1½:1 (34°). Much of Brooklyn and Queens excavations fall here
• Only the designated Competent Person may classify soil — they must perform visual and manual tests daily

• Ladder or ramp within 25 feet of every worker — no exceptions
• Spoil piles 2 feet minimum from the edge of the trench — never pile directly at the edge
• Competent Person inspects trench before each shift, after rainstorms, and after any event that could affect stability
• Atmospheric testing required before entry if depth exceeds 4 feet and any hazardous atmosphere is possible
• If water is seeping in: stop work, get out, call the Competent Person