14 Jan Excavations

Excavations

Cave-ins are one of the most serious hazards associated with excavation and trenching work. Other hazards include falling materials, underground utilities, hazardous atmospheres, water accumulation, mobile equipment, and falls into the excavation.

Excavation work must be planned and inspected by a competent person. Never enter an excavation until required protective systems are installed and the competent person has determined that conditions are safe.

Guide for Discussion

Before Excavation Begins

Before digging or allowing employees to enter an excavation, determine:

• Have underground utilities and installations been located and marked?
• Has the appropriate 811 utility-locate service been contacted before digging?
• Are overhead or surface hazards present, such as equipment, structures, loose soil, rock, or materials?
• Will vehicles or heavy equipment operate near the excavation?
• What is the anticipated depth and configuration of the excavation?
• What type and condition of soil will be encountered?
• Is groundwater or surface-water accumulation possible?
• Could a hazardous atmosphere be present?
• What protective system will be used?
• How will employees safely enter and exit?
• Are barricades, guardrails, warning lines, or other fall protection needed around the excavation?
• Have emergency procedures been reviewed with affected employees?

Protect Employees from Cave-Ins

Employees in excavations generally must be protected from cave-ins when the excavation is 5 feet or more deep, unless it is made entirely in stable rock.

Excavations less than 5 feet deep also require cave-in protection when a competent person determines that there is an indication of a potential cave-in.

Depending on soil conditions and the work being performed, protection may include:

• Sloping the excavation walls to a safe angle.
• Benching, where permitted.
• Shoring to support excavation walls.
• Shielding, such as an appropriately designed trench box.

Never assume that an excavation is safe simply because the soil appears solid or the work will only take a few minutes.

Competent Person Inspections

A competent person must inspect excavations, adjacent areas, and protective systems:

• Before employees begin work.
• Daily before the start of work and as needed throughout the shift.
• After rainstorms.
• After vibration, water intrusion, soil movement, or other events that could increase hazards.

Look for warning signs such as cracks, fissures, sloughing soil, bulging excavation walls, sinking near the edge, water accumulation, or movement or damage to the protective system.

If a hazardous condition is identified, employees must leave the affected area until the hazard has been corrected.

Spoil Piles and Falling Materials

Keep excavated soil, materials, tools, and equipment at least 2 feet from the excavation edge, or use retaining devices or other effective controls to prevent material from falling or rolling into the excavation.

Remove or secure loose rock, soil, and other materials that could fall onto employees.

Employees must never work underneath loads handled by lifting or digging equipment.

Safe Access and Egress

For trench excavations 4 feet or more in depth, provide a stairway, ladder, ramp, or other safe means of egress.

The means of egress must be positioned so employees do not have to travel more than 25 feet laterally to reach it.

Keep access routes clear and ensure ladders and ramps are properly installed and secured.

Working Around Protective Systems

• Never work outside the protected area of a trench box or shield.
• Never enter beneath unsupported excavation walls.
• Do not modify shoring, shields, or other protective systems without authorization.
• Do not assume a trench box prevents a cave-in; it is designed primarily to protect employees if surrounding soil collapses.
• Follow the manufacturer’s tabulated data and applicable design requirements for protective systems.

Hazardous Atmospheres

Excavations near sewers, landfills, tanks, pipelines, contaminated soil, or other sources may contain oxygen-deficient, toxic, or flammable atmospheres.

Where a hazardous atmosphere exists or could reasonably be expected in an excavation greater than 4 feet deep, atmospheric testing must be performed before employees enter. Required ventilation, respiratory protection, monitoring, and emergency equipment must be provided when applicable.

Water and Changing Conditions

Employees should not work in excavations where water is accumulating unless adequate precautions have been taken.

Rain, groundwater, leaking utilities, and runoff can quickly change soil stability. Water-control measures may include pumps, drainage, diversion ditches, dikes, or specially designed protective systems.

Following rain or other conditions that could increase hazards, the competent person must inspect the excavation before employees re-enter.

Mobile Equipment and Excavation Edges

When equipment operates near an excavation and the operator does not have a clear view of the edge, use an appropriate warning system such as:

• Barricades.
• Stop logs.
• Hand or mechanical signals.
• Other effective warning methods.

Employees working around traffic or mobile equipment must remain visible to operators and wear required high-visibility garments.

Discussion Questions

• Who is the competent person for today’s excavation?
• What protective system are we using?
• Where are the nearest safe access and egress points?
• Have all underground utilities been located?
• Could hazardous gases or oxygen deficiency be present?
• What conditions would require everyone to immediately exit the excavation?
• What is our procedure if water begins entering the excavation?
• Are barricades or other controls needed to protect employees around the excavation?

Remember

Never enter an unprotected excavation. Soil conditions can change without warning, and there may be little or no time to escape a cave-in.

Have the excavation inspected, use the required protective system, maintain safe access and egress, and get out immediately if conditions become unsafe.