Trenching and excavating are a regular part of construction operations and are required for a wide range of construction projects. According to the Occupational Safety and Health Administration, or OSHA, trenching is a leading jobsite hazard, which causes an average of 54 fatalities each year.* Understanding the risks associated with trenching and excavating can help you prevent bodily injury and fatalities. Learn about OSHA’s common trenching and excavation safety guidelines to help protect yourself and your crew the next time you dig.
Trenching and excavating: What’s the difference?
OSHA defines excavating as “any man-made cut, cavity, trench, or depression in an earth surface formed by earth removal.” A trench is a type of narrow excavation in which the depth is typically greater than the width, which does not exceed 15 feet. According to this definition, all trenches are excavations, but not all excavations are trenches. The specific safety requirements for trenches depend on the depth of the trench.
Trenches 5 feet to 19 feet: OSHA explains that any trench other than those made of stable rock exceeding 5 feet in depth must have a protective system in place. The protective system must be implemented by a competent person. This can be any worker who is qualified and capable of identifying rock and soil composition and hazardous excavating conditions in addition to possessing the knowledge and authority to take corrective action.
Trenches 20 feet and deeper: A registered professional engineer must implement a protective system for any trench exceeding 20 feet in depth as required by OSHA.
Top 5 excavation safety hazards
Trench collapses kill an average of two workers every month, making this a serious threat to worker safety. To prevent cave-ins, OSHA requires a professional engineer or a qualified professional to analyze soil composition, and then design and implement a system that:
Hiring a professional engineer or a qualified professional to design a system that prevents cave-ins is critical for preventing injury and jobsite fatalities.
Bonus tip: Because moisture and other weather conditions can affect soil stability, OSHA recommends that excavations be inspected at the beginning of each shift, after it rains, or after other extreme weather events.
2. Falls and falling loads
Workers and work equipment can fall into an excavated area. When possible, install a barrier and safety signage around the perimeter of the excavation to clearly mark the fall hazard. Falling loads, such as jobsite equipment or excavated dirt, can also fall into a trenched area and crush anybody who is working below. This is why OSHA requires jobsite materials to be stored at least two feet away from the edge of an excavation. Additionally, OSHA recommends that employers do not allow work to be conducted beneath suspended or raised loads.
3. Hazardous atmospheres
Trenched areas sometimes have depleted oxygen levels, which is safety hazard that must be taken into consideration on excavation sites. The atmosphere in trenched areas can also be contaminated by toxic gases and chemicals. For these reasons, OSHA requires atmospheric testing to be performed by a qualified professional in excavations that exceed four feet. If atmospheric hazards are present, then workers must wear the appropriate respiratory protection equipment depending on the hazard in the excavated area.
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4. Mobile equipment
Accidents involving construction vehicles, such as dump trucks or backhoe loaders, are a common hazard of trenching sites. Mobile equipment operators might have an obstructed view and therefore not be able to detect when they are approaching the perimeter of the trench. OSHA suggests that a spotter or a flagger be designated to direct the mobile equipment operator and prevent the vehicle from falling in the trench. When material is being loaded or unloaded from the construction vehicle, workers should be required to stand back in order to prevent being hit by flying debris.
Bonus tip: Wearing the right protective apparel will minimize the risk of working around mobile equipment. Make sure to wear a reflective vest to make yourself more visible to mobile equipment operators, and wear a hard hat to protect your head from construction debris.
5. Hitting utility lines
In addition to causing expensive damage to municipal infrastructure, hitting utility lines when digging can also cause electrocution and natural gas leaks,which can lead to worker fatalities. Fortunately, you can easily avoid hitting utility lines by contacting your local utility companies before you dig. Simply call your local 811 agency and allow the required time for the utility companies to mark their lines. Not only will this keep your crew safe, but this will help to prevent your company from being fined since digging without calling is illegal in many states.
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*According to the U.S. Bureau of Labor and Statistics, reported by the National Institute for Occupational Safety and Health