Working in a trench is one of 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 (3 ft. by 3 ft. by 3 ft.) can weigh as much as a small pickup truck. If a person is buried, there is little chance of survival.
- There are many things that 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.
- About half of the people killed each year in trenches die trying to rescue someone else who has been buried by a cave-in. Call 911 for help. Do not attempt a rescue unless you have been properly trained in trench-rescue techniques.
- Other hazards include falling objects, hazardous atmospheres, and exposure to mobile equipment and traffic.
- Remember, if you are buried by a cave-in, your chance of survival is very low. 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.
SOURCES OF HAZARDS:
- Cave-ins and Collapses: The walls of trenches can collapse, burying workers and causing fatalities. This is the leading cause of trench-related accidents.
- Falling Objects: Tools, equipment, or soil can fall into the trench, striking workers below.
- Workers working in trenches and excavations are exposed to the hazard of falling into the trench or excavation. This is more common when workers must cross over excavations to get to the other side.
- Hazardous Atmospheres: Trenches can have low oxygen levels, toxic gases, or flammable atmospheres.
- Superimposed Load or Surcharge Hazard: When excess loads or weight are placed at the top of a trench, there is a risk of such vertical loads (e.g., excavated soils and other materials, vehicles, or equipment) resulting in reducing the stability of a trench or excavation area. This excessive pressure on the soil could cause the trench edge to collapse resulting in the machine or the excavated soil falling inside the trench and risking serious injury to workers.
- Mobile Equipment: Heavy equipment operating near trenches can be a striking hazard.
- Flooding: Water accumulation can destabilize trench walls and create drowning hazards.
- Exposure to Utility Lines: Hitting underground utilities like gas or electrical lines can cause serious injury or fire.
- Soil Stability: Soil can be unstable, leading to collapses or slides.10. Superimposed Loads: Heavy equipment or materials stored near the
- trench edge can increase the risk of cave-ins.
- Drowning and Flooding Hazards.
- Traffic: Vehicular traffic near excavation sites can pose a striking hazard.
- Lack of Training.
REGULATIONS:
1926.651(b)(1) – The estimated location of utility installations, such as sewer, telephone, fuel, electric, water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work, shall be determined prior to opening an excavation.1926.652
1926.651(b)(3) – When excavation operations approach the estimated location of underground installations, the exact location of the installations shall be determined by safe and acceptable means.
1926.651(c)(2) – Means of egress from trench excavations. A stairway, ladder, ramp or other safe means of egress shall be located in trench excavations
that are 4 feet (1.22 m) or more in depth so as to require no more than 25 feet (7.62 m) of lateral travel for employees. 1926.651(d) – Exposure to vehicular traffic. Employees exposed to public vehicular traffic shall be provided with and shall wear warning vests or other suitable garments marked with or made of reflectorized or high-visibility material.
1926.651(g)(1) – Testing and controls. In addition to the requirements set forth in subparts D and E of this part (29 CFR 1926.50 – 1926.107) to prevent exposure to harmful levels of atmospheric contaminants and to assure acceptable atmospheric conditions, the following requirements shall apply.
1926.651(g)(2)(i) – Emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, shall be readily available where hazardous atmospheric conditions exist or may reasonably be expected to develop during work in an excavation. This equipment shall be attended when in use.
1926.651(h)(1) – Employees shall not work in excavations in which there is accumulated water, or in excavations in which water is accumulating, unless adequate precautions have been taken to protect employees against the hazards posed by water accumulation. The precautions necessary to protect employees adequately vary with each situation but could include special support or shield systems to protect from cave-ins, water removal to control the level of accumulating water, or use of a safety harness and lifeline.
1926.651(i)(1) – Where the stability of adjoining buildings, walls, or other structures is endangered by excavation operations, support systems such as shoring, bracing, or underpinning shall be provided to ensure the stability of such structures for the protection of employees.
1926.651(k)(1) – Daily inspections of excavations, the adjacent areas, and protective systems shall be made by a competent person for evidence of a situation that could result in possible cave-ins, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions. An inspection shall be conducted by the competent person prior to the start of work and as needed throughout the shift. Inspections shall also be made after every rainstorm or other hazard increasing occurrence. These inspections are only required when employee exposure can be reasonably anticipated.
1926.651(l) – Walkways shall be provided where employees or equipment are required or permitted to cross over excavations. Guardrails which comply with §1926.502(b) shall be provided where walkways are 6 feet (1.8 m) or more above lower levels.
EXAMPLE INCIDENTS THE FACTS:
In the U.S., trenching, which kills, on average, 40 workers every year. Workers can suffer death or serious injury within minutes of being caught in a trench cave-in.
08/28/2024, San Diego, CA, Joel Olea Gomez (27) died in trench collapse. 1771818, State, No. 08/28/2024, Mooresville, NC, Luis Alberto Flores Mendez (23) …
THE BASICS:
- Proper Training: Workers should be trained on trench safety procedures and the use of protective systems.
- Soil Testing and Classification: A competent person should assess soil types and classify them to determine appropriate protective systems.
- Cave-in Protection: Protect trenches from collapse using methods like sloping, benching, shoring, or shielding.
- Locating Utilities: Identify and mark all underground utilities before digging.
- Ventilation and Atmosphere Testing: Ensure proper ventilation and test for hazardous atmospheres.
- Safe Access and Egress: Provide safe entry and exit points for the trench.
- Distance and Spoil Storage: Keep excavated materials at a safe distance from the trench edge.
- Traffic Control: Implement traffic control measures to protect workers from vehicular hazards.
- Regular Inspections: Conduct daily inspections of the trench and protective systems. These increased precautions should last for 1-2 weeks. After that time, new workers should be acclimatized to the heat and can safely work a normal schedule.
WHAT YOU NEED TO KNOW:
- A trench is an excavation (or hole in the ground) where the depth is greater than the width.
- There are three types of protective systems – Sloping, Shoring, and Shielding.
- Types in Construction:
- Utility Trenches: Dug to install or repair utility lines such as water, sewer, or electrical lines. They are usually shallow but can vary in depth.
- Foundation Trenches: Excavated to provide a base for building foundations. These trenches are deeper and require careful planning and preparation.
- Drainage Trenches: Constructed to manage surface water or groundwater. They are designed to redirect water away from structures or areas prone to flooding.
- Access Trenches: Used to provide access to underground structures such as basements or tunnels. They are often deeper and may require additional support.
HERE ARE IMPORTANT DO’S TO KEEP IN MIND ABOUT TRENCHES:
- Do locate all underground utilities before digging.
- Do enter only trenches that have been sloped at the proper angle, shored, or shielded.
- Do eliminate or control water accumulation before entering the trench.
- Do stay alert when working in or near previously disturbed soil conditions.
- Do check regularly for hazardous materials and oxygen levels in the trench.
- Do use a ladder or ramp to get in and out of the trench. Place the ladder inside the protective system.
- Do wear hard hats when working in or around trenches.
- Do stay out from under raised loads.
HERE ARE IMPORTANT DON’TS TO KEEP IN MIND ABOUT TRENCHES:
- Don’t go outside the area that has been sloped, shored, or shielded, not even for a moment.
- Don’t permit vehicles near the edge of the trench.
- Don’t allow machines to run unattended.
- Don’t climb on shoring or shields. Never ride in equipment buckets or on crane hooks.
“Trenching | Transcript.” Osha.gov, www.osha.gov/sites/default/files/publications/osha2226.pdf. Accessed 9 June 2025.
CDC. “Trenching and Excavation Safety.” Trenching, 29 Feb. 2024, www.cdc.gov/niosh/trenching/about/index.html.
