A construction worker watches while another worker operates an excavator digging a trench on a construction site.
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5 common trenching and excavation safety hazards

A wide range of projects at construction sites require trenching and excavating, but this regular part of the job is a leading hazard for workers. The Occupational Safety and Health Administration, or OSHA, has made reducing hazards in trenching and excavation its priority goal.

Discover OSHA’s digging safety guidelines and how to avoid trenching and excavation safety hazards to keep you and your crew safer on the jobsite.

What’s the difference between trenching and excavating?

A simple way to remember the difference is that all trenches are excavations, but not all excavations are trenches. Specifically, OSHA says an excavation is when soil is removed from the surface of the earth to create “any man-made cut, cavity, trench, or depression.”

A type of narrow excavation, a trench is below the surface of the ground, and its width—measured from the bottom—cannot be greater than 15 feet. Typically, a trench is deeper than it is wide.

OSHA’s requirements for trenches vary and depend on the depth of the trench as well as soil type. Find the excavation safety standards in 29 CFR 1926.650-652, Safety and Health Regulations for Construction.

Trenches less than 5 feet deep: A “competent person,” designated by the employer, can investigate a trench less than 5 feet deep and determine whether a protective system for workers is required. This person can inspect the construction site and eliminate existing or potential hazards in working conditions.

Trenches between 5 feet through 19 feet: If a trench deeper than 5 feet but less than 20 feet is made in any soil type other than stable rock, it requires a protective system that must be implemented by a competent person. They’re responsible for determining soil type, monitoring equipment that removes water, inspecting protective systems and designing structural ramps to keep workers safe.

Trenches equal to or greater than 20 feet deep: For trenches more than 20 feet deep, OSHA requires a registered professional engineer to implement, prepare or approve a protective system.

Trenching safety: top 5 excavation hazards

Make sure you and your crew take excavation safety hazards seriously. The National Institute for Occupational Safety and Health (NIOSH) reports that more than 80% of trenching fatalities happen in the construction industry. Explore the top five excavation hazards to keep your workers safe and your business running.

1. Trench cave-ins and collapses

The Bureau of Labor Statistics reports that between 2011-2018, trench collapse, or cave-in, was the most frequent cause of fatal occupational injury in the confined spaces category of ditches, channels, trenches and excavations, killing 166 workers.

To prevent this serious threat to worker safety, OSHA requires soil composition analysis from a professional engineer or qualified professional. This person will then design and implement a system to prevent worker injury and death. The three steps to avoid collapse hazards include:

  • Slopes: Ensure trench walls are benched.

  • Supports: Shore walls to brace them.

  • Shields: Protect workers from sidewalls with trench boxes.

Bonus tip: Inspect excavations after rain or extreme weather events as well as at the beginning of each shift. Soil stability can shift due to moisture and other weather conditions.

2. Falls into excavations and falling loads

Workers and work equipment or materials falling into trenches represents a safety hazard. If possible, use barriers and signage to mark the area of a fall hazard. Not only construction equipment but also excavated dirt can become a falling load and crush workers.

In order to prevent falling loads, OSHA requires jobsites to have materials stored at least two feet away from the edge of an excavation. The agency also recommends not allowing loads to be suspended or raised above workers.

In addition, make sure workers have a safe and secure means of egress in trenches 4 feet deep or more. The competent person who designed the structural ramps must make sure that these don’t create a tripping hazard. Provide trench excavation safety training, so workers appreciate the risks and understand if they’re in unsafe conditions.

3. Hazardous atmospheres in trenches

Not only can excavated areas sometimes have diminished oxygen levels, but a trenched area’s atmosphere can also be contaminated with toxic gases and chemicals. Either or both of these situations can represent a risk for workers.

In excavations deeper than 4 feet, a qualified professional must perform atmospheric testing. Depending on the hazardous atmosphere in the excavation, workers must wear proper respiratory protection equipment to minimize the risk.

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4. Mobile equipment on the construction site

Accidents on the construction site, with vehicles like dump trucks or backhoe loaders, are also one of the common excavation hazards. Mobile equipment operators may have an obstructed view and might not be aware when they’re approaching the trench perimeter.

OSHA suggests minimizing hazards by using a spotter or flagger for vehicles on the jobsite. In addition, require workers to stand back when a construction vehicle is loading or unloading material to prevent them from being hit by flying debris or soil.

Bonus tip: Reduce the risk of working around mobile equipment by making sure you and your crew wear the right protective apparel, including reflective vests. Make sure you also protect your head from construction debris with a hard hat.

5. Hitting utility lines while excavating

Trenching hazards also include electrocution and natural gas leaks from hitting utility lines. To prevent worker fatalities as well as damaged infrastructure, make sure to contact local utility companies prior to excavating.

In many states, digging without calling first is illegal. The easiest digging safety tip is to call your local 811 agency and allow the utility companies the time they require to mark their lines. This will help keep your crew safe and your company from receiving financial penalties.

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