Every excavation must be inspected by a designated competent person before work begins.

OSHA defines a competent person as someone capable of identifying existing and predictable hazards and authorized to take prompt corrective action.

The competent person evaluates soil conditions, identifies excavation hazards, and determines whether protective systems are appropriate for the work.

OSHA requires inspections before the start of work and as needed throughout the shift. Additional inspections are required following rainstorms or other events that could increase excavation hazards.

Excavated soil, construction materials, and equipment placed too close to a trench can create additional hazards.

Spoil piles may increase pressure on excavation walls and allow loose material to fall or roll into the trench.

OSHA requires employees to be protected from excavated materials and equipment that could fall or roll into excavations.

One common method is maintaining a minimum 2-foot setback between these materials and the excavation edge. Retaining devices or other compliant protective measures may also be used.

Heavy equipment operating near an excavation can introduce additional surcharge loads that must be considered when selecting a protective system.

Workers need a reliable way to enter and exit an excavation.

When a portable ladder is used for access to an upper landing surface, OSHA generally requires its side rails to extend at least 3 feet above the landing surface. On most ladders, 3 rungs above the top of the trench is equal to 3 feet above the trench.

This extension provides a secure handhold while workers transition between the ladder and the ground surface.

Where a 3-foot extension is not possible because of the ladder's length, OSHA provides specific alternative securing and grasping-device requirements.

Ladders must be properly positioned, inspected, and maintained in safe condition.

OSHA requires a safe means of access and egress in trench excavations 4 feet deep or greater.

A ladder, stairway, ramp, or another safe means of egress must be positioned so workers do not have to travel more than 25 lateral feet to reach it.

Access routes must remain unobstructed and workers must be protected from excavation hazards while entering or leaving the trench.

Crews should verify that access points remain properly positioned as excavation work progresses.

OSHA generally requires a protective system for excavations 5 feet deep or greater, except excavations made entirely in stable rock.

A protective system may also be required in excavations less than 5 feet deep when a competent person identifies a potential cave-in hazard.

Common methods of cave-in protection include:

• Sloping and Benching: Excavating soil at approved angles or in stepped configurations.
• Shoring: Supporting excavation walls with hydraulic, aluminum, steel, or other approved support systems.
• Shielding: Using trench boxes or trench shields to protect workers within the shielded area.

Manufactured trench boxes and shoring systems must be selected and installed according to applicable OSHA requirements and manufacturer tabulated data.

Excavation depth, soil classification, surcharge loads, groundwater, and protective system configuration must all be considered.

A trench box must be installed to restrict lateral or other hazardous movement if a cave-in occurs.

The space between the outside of a trench shield and the excavation wall is an important installation consideration.

A commonly recommended industry practice is to maintain no more than approximately 6 inches of clearance between the trench shield and the excavation sidewall.

Excessive clearance can allow collapsing soil to strike the shield and potentially cause hazardous movement.

Where appropriate, the space between the shield and excavation wall should be backfilled or otherwise controlled to restrict hazardous shield movement.