how deep of an excavation needs sloping

OSHA standards require protective systems for trenches 5 feet or deeper, unless the excavation is made entirely in stable rock. If less than 5 feet, a competent person must examine the trench and determine if a protective system is required. Trenches 20 feet or deeper must have a protective system designed or approved by a registered professional engineer. [1] [1]

Common protective systems include:

• Sloping: Cutting back the trench wall at an angle inclined away from the excavation.
• Shoring: Installing aluminum hydraulic or other types of supports to prevent soil movement and cave-ins.
• Shielding: Using trench boxes or supports to protect workers from cave-ins.

[1] [1] [1] Specific sloping requirements depend on soil type:

• Type A Soil: 3/4H:1V (53°)
• Type B Soil: 1H:1V (45°)
• Type C Soil: 1 1/2H:1V (34°)

[2] [2] [2]