Reviewing OSHA Trench Safety Requirements

By Russell Spruill, P.E. | April 2014, Vol. 69 No. 4

It’s an everyday occurrence on the job. Whether you are the contractor, the inspector or even the engineer you may have to get in a trench. Most of us don’t give it a second thought and get the job done. Trenches however, are a dangerous environment and accidents can occur quickly and often without warning. The Occupational Safety and Health Administration (OSHA) states that fatality rate from trench related work is 112 percent higher than general construction work. A basic knowledge of trenching and the dangers it presents is essential to staying safe.

There are different types of trenching. The first is an open trench where the sides are usually back-sloped, depending on the soil type. This trench may have steep walls for the majority of the excavation but includes “bell holes” where it anticipated that workers will need to enter the trench. Another type uses a prefabricated shoring box that provides protection for workers. The trench box is moved as the work progresses forward. These are used in congested areas where there is minimum space to work in.

The final type of trench uses constructed on site methods such as sheet piling and cross bracing. These are used for deep excavation and for areas where groundwater may present a problem. They are usually designed by an engineer.

Regardless of the trenching technique OSHA requires a “competent person” to be on site. OSHA defines this person as “an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate or control these hazards and conditions.”

After you have identified the trench type, you should asses the possible hazards. This includes ingress and egress. There should be an easy path such as a gentle slope or a ladder so you don’t fall in the event you have to exit the trench quickly in an emergency. Exposure to vehicle and heavy equipment is another hazard. Heavy equipment next to a trench can cause an otherwise safe wall to collapse. Falling objects are another hazard to be aware of. Hazardous atmospheres and confined space issues should be addressed. The trench should be monitored for the presence of poison or explosive gases. The final item to watch for is the stability of the soil and how it may change with influences such as weather conditions.