A trench is an excavation defined by its depth being greater than its width. The U.S. Occupational Safety and Health Administration, or OSHA, says that trenches have many safety hazards that trench workers must be wary of. To protect workers from accidents and injuries, trench depth standards are set by OSHA.
Ingress and Egress
In trench terminology, ingress and egress are words used to describe access into and exits from the trench. According to OSHA, trenches that are 4 feet or deeper require stationary egress options. Ladders, for example, must be provided and spaced such that trench workers do not have to travel more than 25 feet to the nearest ladder. This helps workers make quick getaways in a flood or cave-in.
OSHA says that the type of soil being excavated determines the horizontal-to-vertical ratio for benching. The rule is “the bottom vertical height of the trench must not exceed 4 feet for the first bench.” Benches after the first 4feet can be spaced to a maximum of 4 or 5 feet, depending on the soil type.
If the trench cut, depression or cavity is 20 feet or more, a professional, registered engineer must approve the procedure. This is because of the special accommodations that are needed, such as shoring and shielding.