Trench Sloping & Benching Calculator

OSHA 29 CFR 1926 Subpart P (Standard 1926.652 and Appendices A and B) governs safety requirements for excavations and trenches.

A protective system (sloping, benching, shoring, or trench shield) is required for excavations 5 feet (1.5 meters) or deeper, or any depth where a Competent Person identifies cave-in hazards.

Under OSHA 1926 Subpart P App B: Type A soil allows 3/4:1 (53°); Type B soil allows 1:1 (45°); Type C soil allows 1.5:1 (34°).

Top Opening Width = Base Width + 2 × (Slope Ratio × Depth). For Type C soil (1.5:1) at 8 ft depth and 3 ft base: 3 + 2 × (1.5 × 8) = 27 ft.

An OSHA Competent Person is capable of identifying existing and predictable hazards in the surroundings and has authorization to take prompt corrective measures to eliminate them.

No. Benching is prohibited in Type C soil under OSHA 1926 Subpart P. Type C soil must be sloped at 1.5:1 or protected with shoring/trench boxes.

Per OSHA § 1926.651(j)(2), excavated spoil piles and equipment must be kept at least 2 feet (0.6 meters) away from the edge of the excavation.

A stairway, ladder, ramp, or other safe means of egress is required in trench excavations that are 4 feet (1.2 meters) or more in depth, located so as to require no more than 25 feet of lateral travel.

OSHA requires a protective system (sloping, benching, shoring, or shielding) for all trenches 5 feet (1.52m) or deeper, unless excavated in stable rock.

Type A is cohesive soil with an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater (e.g., clay, silty clay).

Type A soil requires a maximum sloping angle of 3/4:1 (53° above horizontal) for excavations up to 20 feet deep.

Type B soil (angular gravel, silt, sandy loam, strength 0.5 to 1.5 tsf) requires a maximum sloping angle of 1:1 (45° above horizontal).

Type C soil (granular soil, sand, gravel, submerged soil, strength < 0.5 tsf) requires a maximum sloping angle of 1.5:1 (34° above horizontal).

OSHA 1926.651(c)(2) requires a stairway, ladder, or ramp in trenches 4 feet or deeper, located so workers travel no more than 25 feet laterally to reach egress.

OSHA requires keeping spoil piles and equipment at least 2 feet (0.61m) back from the edge of the excavation to prevent cave-ins.

A Competent Person must classify soil type, inspect trenches daily before worker entry, monitor atmospheric hazards, and order immediate evacuation if instability is detected.

Shoring uses hydraulic or timber props to apply active pressure against trench walls to prevent soil movement. Shielding (trench boxes) protects workers inside if a collapse occurs.

OSHA standards mandate that excavations deeper than 20 feet (6.1m) require a protective system designed and stamped by a licensed Professional Engineer.