Keep the jobsite safe by making sure your construction company and employees comply with these requirements.

Look at various jobsite safety websites, and you will see numerous accounts of OSHA citations, employee fatalities and accidents involving excavations and trenches. Some of the headlines have been:

  • OSHA cites New York contractor for cave-in hazards after employee is caught in 16-foot deep hole.
  • OSHA cites contractor for willful and serious violations following trench fatality in Atlanta, Ga.
  • OSHA proposes $178,000 in fines for contractors for Newton, Mass. cave-in hazards.
  • OSHA cites contractor following trench fatality at Idaho worksite.
  • OSHA proposes $57,000 in penalties for trench safety violations at Fort Bragg, N.C.

What Does OSHA Say?

OSHA wrote a standard specifically to protect employees working in excavations and trenches. Subpart P of 29 CFR Part 1926 applies to all open excavations made in the earth's surface, including trenches.

Defining the Terms

There are two terms that are often used interchangeably: excavation and trench. OSHA defines an excavation as any man-made cut, cavity, trench or depression in the earth's surface formed by earth removal. A trench is defined as a narrow underground excavation that is deeper than it is wide and no wider than 15 feet at the bottom.


When you think of trenching accidents you think of cave-ins.  Cave-ins are potentially fatal, but there are other excavation hazards to consider, like lack of oxygen, inhaling toxic fumes, drowning, electrocution and explosions.  The following types of issues cause most injuries and deaths:

  • Failure to inspect the trench
  • Not using protective systems
  • Failure to keep spoil-piles back far enough
  • Not supplying proper access and/or egress

Initial Jobsite Inspection

It is a good idea to inspect the jobsite to determine how to safely perform the work. When doing the inspection, look for hazardous conditions that can lead to accidents. Some of the questions you should ask include:

  • Traffic-How close is the moving traffic? Barricades, high-visibility vests and signal persons may be needed to protect workers from being struck.
  • Proximity and physical conditions of nearby structures-Are there any hazards from buildings? Will soil displacement affect the stability of these structures?
  • Soil-What is the soil type?
  • Surface and groundwater-Is groundwater or surface water present? What is the depth of the water table?
  • Overhead and underground utilities-Are underground utilities marked? How close are overhead utilities?

If these conditions are not readily observable, you will need to perform test boring for soil conditions and talk to utility companies for locations of underground lines.

Contacting the Utility Companies

OSHA requires you to:

  • Determine the approximate location of utility installations: sewer, telephone, fuel, electric, water lines and any other underground installations.
  • Contact the utility companies involved, and let them know of the proposed work.
  • Ask the utility companies to find the exact location of the underground installations. If they cannot respond within the period required or cannot find the exact location of the buried installations, proceed with caution.

When you do expose underground installations, you have to protect, support or remove them.

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."

There are several concerns which need to be addressed by your competent person. He/she must:

  • Evaluate soil conditions and select appropriate protective systems. Construct protective systems in accordance with the standard requirements.
  • Preplan by contacting utilities (gas, water, cable and electric) to locate underground lines, planning for traffic control if necessary and determining proximity to structures that could affect choices of protective systems.
  • Test for low oxygen, hazardous fumes and toxic gases, especially when gasoline engine-driven equipment is running, or the soil has been contaminated by leaking lines or storage tanks. Ensure adequate ventilation or respiratory protection if necessary.
  • Provide safe access into and out of the excavation.
  • Provide appropriate protections if water accumulation is a problem.
  • Inspect the site daily at the start of each shift, following a rainstorm or after any other hazard-increasing event.
  • Keep excavations open the minimum amount of time needed to complete operations.

Soil Types

Identifying the type of soil you will be excavating is important because the soil type determines the type of sloping, benching and the protective system (if any) you will need to use. OSHA categorizes soil and rock deposits into four types:  Stable rock, Type A, Type B and Type C. These types can also be found together in layered geological strata.

The strongest and safest material to work in is stable rock. OSHA defines stable rock as "natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed."

Soil Testing

Soil classification tests are not required if excavations are 20 feet or less in depth and the slope is not greater than 34 degrees measured from the horizontal. In addition, if you assume Type C soil is present, and provide protection (sloping, shoring or shielding) as required for Type C soil, the intent of the requirement for soil classification tests would be met. However, soil classification tests are required if the employer elects to use any other option.

Protective Systems-Choosing the Right One

Some of the factors to consider when deciding what protective system to use are:

  • Soil classification
  • Excavation depth
  • Water content of the soil
  • Other operations in the vicinity that could create vibration
  • Weather and climate

Ways to protect your employees when they could potentially be exposed to cave-ins are:

  • Sloping or benching the sides of the excavation
  • Supporting the sides of the excavation with some type of bracing (hydraulic or timber shoring) or
  • Placing a shield (usually a trench box) between the sides of the excavation and the work area


You don't need to provide this protection if the excavation is made entirely in stable rock, or is less than 5 feet in depth, and examination of the ground by a competent person provides no indication of a potential cave-in.

Excavation work is hazardous, and it's the employer's duty to protect employees performing this type of work. As always, keeping employees safe is a good way to keep OSHA from knocking on your door.

Construction Business Owner, August 2010