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BIE Safety Advisor | June 2024

Lisa Ramirez | May 28, 2024

The National Utility Contractors Association is once again sponsoring the 2024 Trench Safety Stand Down, June 17-23, 2024, an annual opportunity for employers to discuss trench and excavation hazards and reinforce the importance of protective systems.

In 2022, 39 people died while working in trenches or excavations. Employers must provide a workplace free of recognized hazards and comply with the trenching and excavation requirements of 29 CFR 1926.651 and 1926.652 or comparable OSHA-approved state plan requirements.

A “trench” is a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but its width - measured at the bottom - is not greater than 15 feet.

An “excavation” is any human-made cut, cavity, trench, or depression in an earth surface formed by earth removal.

Dangers of Trenching and Excavation Dangers

Cave-ins pose the greatest risk and are much more likely than other excavation-related accidents to result in fatalities. Other hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. 

One cubic yard of soil can weigh as much as a car. An unprotected trench is an early grave. Do not enter an unprotected trench.

OSHA standards require that trenches be inspected daily and as conditions change by a “competent person” before worker entry. A competent person is an individual capable of identifying existing and predictable hazards or conditions that are hazardous, unsanitary or dangerous; soil types, and protective systems required. The competent person is also authorized to take prompt corrective measures.

Trenches 5 feet deep or greater require a protective system unless the excavation is made entirely in stable rock. If less than 5 feet deep, a competent person may determine that a protective system is not required.

Trenches 20 feet deep or greater require that the protective system be designed by a registered professional engineer or be based on tabulated data prepared and/or approved by a registered professional engineer in accordance with 1926.652(b) and (c).

Access and Egress

OSHA standards require safe access and egress to all excavations, including ladders, steps, ramps, or other safe means of exit for employees working in trench excavations 4 feet or deeper. These devices must be located within 25 feet of all workers.

Protective systems include:

  • Benching: Protects against cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels. Benching cannot be done in Type C soil.
  • Sloping: Cutting back the trench wall at an angle inclined away from the excavation. 
  • Shoring: The installation of aluminum hydraulic or other types of supports to prevent soil movement and cave-ins.
  • Shielding: The use of trench boxes or other supports to prevent soil cave-ins.

Designing a protective system can be complex because many factors - soil classification, depth of cut, water content of soil, changes caused by weather or climate, surcharge loads and other operations in the vicinity - must be considered.

Monthly Toolbox Talk | Trench Safety

Working in a trench is among the most hazardous jobs in construction. Dozens of people die and hundreds are seriously injured each year due to cave-ins.

Soil weighs between 90 and 140 lbs. per cubic foot. Therefore, one cubic yard can weigh as much as a small pickup truck. If a person is buried there is little chance of survival.

Many factors can affect soil stability, such as the type of soil, water, and vibration. Soils saturated with water and previously disturbed soils are very dangerous to work in or around.

But don’t be fooled, even hard soil and rock that appears stable can cave in. Therefore, always be sure that the trench walls are sloped, shored, or shielded with a trench box and that the trench is safe before you enter.

Before entering a trench, the competent person at the jobsite must inspect the trench and

the protection system to ensure it is safe to enter. There are recorded incidents of people buried and killed in trenches 3- to 4-ft. deep, so even shallow trenches must be inspected.

Trench Safety Tips

  • Locate all underground utilities before digging.
  • Only enter trenches that have been sloped at the proper angle, shored or shielded.
  • Never go outside the area that has been sloped, shored, or shielded, not even for a moment.
  • Eliminate or control water accumulation before entering.
  • Stay alert.
  • Do not permit vehicles near the trench edge.
  • Check regularly for hazardous materials and oxygen levels in the trench.
  • Never allow machines to run unattended.
  • Use a ladder or ramp to get in and out of the trench. Place the ladder inside the protective system.
  • Never climb on shoring or shields.
  • Never ride in equipment buckets or on crane hooks.
  • Wear a hard hat.
  • Stay out from under raised loads.

About half of the people killed in trenches die trying to rescue someone who has been buried by a cave-in. Call 911. Only attempt rescue if you have been properly trained in trench-rescue techniques.

Prepared and edited by Michael Ballantine, Occupational Safety Consultants, www.WorkRiskFree.com