Occupational Safety and Health Administration OSHA

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Trenching and Excavation

Hazards and Solutions

The primary hazard of trenching and excavation work is employee injury from a cave-in. Before workers enter a trench, a soil analysis should generally be conducted to determine the appropriate employee protection methods such as sloping, benching, shoring or shielding. Employers should also consider potential struck-by hazards associated with heavy equipment, falling loads, and public vehicular traffic in close proximity to the excavation operations. Also consider potential hazards from undermining sidewalks and buildings. Other unsafe conditions that may be encountered include hazardous atmospheres and electrical hazards from overhead and underground power lines. These five key trench safety tips will help keep workers safe:

What are the hazards?

To prevent injuries during normal entry and exit of a trench or excavation at a job site, employers must provide ladders, stairways, ramps, or other safe means of egress. In some circumstances, when conditions in a trench or excavation become hazardous, survival may depend on how quickly workers can climb out.

To manage the hazards:

  • Provide stairways, ladders, ramps, or other safe means of egress in all trenches that are 4 feet deep or more.
  • Position the means of egress within 25 lateral feet of workers.
  • Ensure means of entering and exiting the trench is within the protective system.
  • Structural ramps that are used for access or egress from excavations must be designed by a competent person.
  • When two or more components form a ramp or runway, they must be connected to prevent displacement, and be of uniform thickness.
  • Cleats or other means of connecting runway components must be attached in a way that would not cause tripping (e.g., attached to the bottom of the structure).
  • Structural ramps used in place of steps must have a non-slip surface.
  • Use earthen ramps as a means of egress only if a worker can walk them in an upright position, and only if they have been evaluated by a competent person.

More Information:

Example: Every trench must have safe access and egress.

Example: Every trench must have safe access and egress.

What are the hazards?

All excavations are hazardous because soil can be unstable. If workers are not using protective systems or equipment while working in trenches or excavations that are five feet or greater in depth, they are in danger of being crushed by a cave-in.

To manage the hazards:

Pre-job planning is vital to incident-free excavation work; safety cannot be compromised as work progresses. The following concerns must be addressed by a competent person:

  • Evaluate soil conditions and select appropriate protective systems. [29 CFR 1926 Subpart P Appendix A and 29 CFR 1926 Subpart P Appendix F].
  • Construct protective systems in accordance with the standard requirements. [29 CFR 1926.652]
  • Plan ahead; contact utilities (gas, electric, water and sewage) to locate underground lines, plan for traffic control if necessary, be prepared to support utilities (pipes/ducts) passing through excavations when necessary, and determine proximity to structures that could affect choice of protective system.
  • Test for hazardous atmospheres such as low oxygen, hazardous fumes, and toxic gases, especially when gasoline engine-driven equipment is running, or when the soil has been contaminated by leaking lines or storage tanks. When necessary, ensure that there is adequate ventilation or respiratory protection.
  • Provide appropriate protections if water accumulation is a problem (i.e., remove water, divert water flow).
  • Maintain safe access into and out of the excavation.
  • Inspect the excavation, adjacent areas, and protective systems daily at the start of the shift, after a rainstorm or after any other hazard increasing event. The inspection shall be conducted by a competent person, who looks for evidence of a situation that could result in a possible cave-in, indication of failure of the protective system, hazardous atmospheres or other hazardous conditions.
  • Keep excavations open only for the minimum amount of time needed to complete operations.

More Information:

Example: Select appropriate protective systems based on existing soil conditions and soil analysis.

Example: Select appropriate protective systems based on existing soil conditions and soil analysis.

What are the hazards?

Excavations may present risks of hazardous atmosphere and water accumulation. If any of these conditions exist, workers could be exposed to the possibility of suffocating, inhaling toxic materials, being burned or engulfed by fire, or drowning.

To manage the hazards:

Employers can ensure that excavations are safe to work in by directing the competent persons to inspect excavations:

  1. Before construction begins.
  2. Daily before each shift.
  3. As needed throughout the shift.
  4. Following rainstorms or other hazard-increasing events (such as a vehicle or other equipment approaching the edge of an excavation).
    • Plan ahead; contact utilities (gas, electric, water and sewage) to identify the location of underground lines and determine proximity to structures that could enter the excavation.
    • Test for hazardous atmospheres where hazardous atmospheric conditions are likely to occur, such as when equipment is running or work is being conducted that could generate a hazardous atmosphere. Examples: low oxygen, hazardous vapors and toxic gases, especially when gasoline engine-driven equipment is running (e.g. when pumping water accumulation from the bottom of the trench), or the soil has been contaminated by leaking fuel lines or storage tanks. When necessary, ensure that there is adequate ventilation or respiratory protection.
    • Provide appropriate protections if water accumulation is a problem (i.e., remove water, use PPE, divert water flow).

More Information:

Example: Ensure a trench with an accumulation of water is inspected by a competent person before entering.

Example: Ensure a trench with an accumulation of water is inspected by a competent person before entering.

What are the hazards?

Excavated material (spoils) at your site are hazardous if they are set too close to the edge of a trench/excavation. The weight of the spoils can cause a cave-in, or spoils and equipment can roll back on top of workers, causing serious injuries or death.

To manage the hazards:

Provide protection by one or more of the following:

  • Set spoils and equipment at least two feet back from an adequately protected excavation.
  • Use retaining devices, such as a trench box that will extend above the top of the trench to prevent equipment and spoils from falling back into the excavation.
  • Where the site does not permit a two-foot setback, spoils may need to be temporarily hauled to another location.

More Information:

Example: The spoil pile is required to be at least 2 feet from the edge of the trench and/or retained to prevent it from falling into the trench.

Example: The spoil pile is required to be at least 2 feet from the edge of the trench and/or retained to prevent it from falling into the trench.

What are the hazards?

The conditions of an excavation can change during the course of work. Even a properly protected excavation or trench can become compromised.

To manage the hazards:

Employers can help ensure that excavations are safe to work in by directing a competent person to inspect excavations:

  1. Before construction begins.
  2. Daily before each shift.
  3. As needed throughout the shift.
  4. Following rainstorms or other hazard-increasing events (such as a vehicle or other equipment approaching the edge of an excavation).

Inspections must be conducted by a competent person. OSHA defines a “competent person” as “one who is capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.”

A "competent person" –

  1. Has training in the use of protective systems.
  2. Is knowledgeable about OSHA requirements.
  3. Has authority to immediately evacuate workers from the excavation and ensure that hazardous conditions are addressed.

Note: Even if all the inspections are conducted, workers may still be in danger due to changing conditions. Workers must be trained to report changes to the competent person/supervisor. 29 CFR 1926.21(b)(2) states: “The employer shall instruct each employee in the recognition and avoidance of unsafe conditions and the regulations applicable to his work environment to control or eliminate any hazards or other exposure to illness or injury.” Training for excavation/trench work must follow the provisions in 1926 Subpart P and its appendices.

To help evaluate different protection systems and identify the warning signs of excavation failure, see the Guide for Daily Inspection of Trenches and Excavations.

Soil Classification

More Information:

Example: A competent person is required to conduct daily inspections of excavations and protective systems to identify possible cave-ins, failure of protective systems, hazardous atmospheres, or other hazardous conditions.

Example: A competent person is required to conduct daily inspections of excavations and protective systems to identify possible cave-ins, failure of protective systems, hazardous atmospheres, or other hazardous conditions.

Other Resources

The following references aid in recognizing and controlling hazards in trenching and excavation:


Note: Original images provided by:

  • OSHA Region 9
  • KTVX News4Utah; Salt Lake City, UT
  • Utah Occupational Safety and Health Division; Salt Lake City, UT
  • National Trench Safety
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