Here are some sobering facts: Trench collapses kill two to three workers every month, according to the OSHA. In addition, data from the U.S. Bureau of Labor Statistics shows that 250 workers died in trenching or excavation cave-ins from 2000 through 2009. 

And historically, according to a review of multiple national databases by the National Institute for Occupational Safety and Health, employees at smaller companies are typically most at-risk for trenching/excavation deaths. Of the 488 workers killed in trenching/excavation accidents between 1992 and 2000, for instance, 68 percent occurred in companies with fewer than 50 workers and 46 percent occurred in companies with 10 or fewer workers. 

Cave-ins, which can crush or suffocate workers, pose the greatest risk; according to OSHA, they’re more likely to result in fatalities than any other kind of excavation-related accident. That’s not surprising, considering that just one cubic yard of soil weighs about 3,000 pounds — or as much as a decent-size car. Other causes of death range from asphyxiation from lack of oxygen, falling loads and inhalation of toxic fumes within small, under-ventilated confined spaces to employee falls, electrocutions and drowning, to name a few. Clearly, working in a trench or excavation is risky business. 

But as grim as these statistics sound, there is some good news: Most trenching accidents could be avoided by following simple, commonplace and inexpensive-to-implement guidelines. Here are some of the most basic OSHA standards to follow:

• Install a protection system in all trenches 5 feet deep or more; trenches 20 or more feet deep requires a protective system designed by a registered professional engineer. Protective systems could include:

           • Sloping the ground at an angle inclined away from the excavation.
           • Benching, or cutting horizontal levels or steps into the sides of excavations.
           • Installing some kind of shoring system, such as planks or hydraulic jacks.
           • Shielding workers with trench boxes or other support devices. 

• Require a competent employee to inspect trenches daily, or after conditions change (after a rainstorm or some other water intrusion, for instance). A “competent person” is generally defined as anyone who can capably identify existing and predictable hazards or unsafe working conditions, and has the knowledge and authority to take corrective steps to fix problems. 

• Provide a safe entrance to and exit from all trenches (such as ladders, steps, ramps, etc.) that are 4 feet deep or more. Safe access and egress must be located within 25 feet of all workers. 

• Keep all heavy equipment away from the edges of trenches.

• Identify factors that could affect trench stability. These could include, but are not limited to, accurately classifying the kinds of soils in an excavation, the stability of adjacent structures and foundations; vibrations from heavy traffic, pile driving, or similar effects near the trench or excavation; warning sign of failures, such as tension cracks in sidewalls or surfaces adjacent to excavation; any indications of failure of protective systems; and degradation of soils in the excavation through freezing/thawing and/or significant rainfall. 

• Pile all excavated soil and other materials at least two feet away from the trench edges. This helps to prevent excavated or other materials — or even equipment — from falling or rolling into excavations. 

• Locate all underground utilities before excavating. 

• Test for atmospheric hazards, such as low oxygen levels or the presence of hazardous fumes and toxic gases, in trenches more than 4 feet deep. 

• Do not work under suspended or raised loads and materials.

Overall, OSHA officials note that trench safety has improved during the last decade (see chart shown below). “We estimate that the average number of fatalities per year in trench/excavation related activities to be 33 from fiscal year 2004 through 2013,” an OSHA spokesperson says. “However, the average annual number is 27 from 2009 to 2013, indicating that fewer average fatalities occurred per year during the last five years, compared to the last 10 years. 

“Although the number of fatalities seems to fluctuate, the general trend shows a reduction in number of fatalities during the past five fiscal years,” the spokesperson adds. “The average number of injuries has shown a smaller but steadier decline during the same period, averaging 20 per year during from 2004 through part of 2013, to 17 per year from 2008 through part of 2013.” (2013 data was incomplete when this article was published.)

OSHA provides many resources for companies that want to improve trenching safety. To ensure compliance with OSHA safety standards, employers can contact OSHA’s On-site Consultation Program, which offers a free and confidential service for small- and medium-size businesses with less than 250 employees at a work site and less than 500 employees overall. Consultants work with employers to identify workplace hazards, provide advice on standards compliance and assist in establishing injury- and illness-prevention programs. On-site consultation services are separate from enforcement and do not result in penalties or citations. Visit OSHA’s On-site Consultation page for more details. 

Employers can also contact one of OSHA’s compliance-assistance specialists, who can provide general information about OSHA standards and compliance-assistance resources. Visit OSHA’s online directory to find out how to contact a local compliance-assistant specialist.