OSHA defines an excavation as any man-made cut, cavity, trench, or depression in the earth’s surface as formed by earth removal. This can include anything from excavations for home foundations to a new highway. A trench refers to a narrow excavation made below the surface of the ground in which the depth is greater than the width-and the width does not exceed 15 feet. Trenching is common in utility work, where underground piping or cables are being installed or repaired.
If an excavation is more than 5 feet in depth, there must be a protective system in place while workers are in the excavation. Excavations more than 4 feet in depth must have a way to get in and out, usually a ladder, for every 25 feet of horizontal travel.
OSHA says no matter how deep the excavation is, a competent person must inspect conditions at the site on a daily basis and as frequently as necessary during the progress of work to make sure that the hazards associated with excavations are eliminated before workers are allowed to enter. A competent person has the following qualifications:
Thorough knowledge of the OSHA standard 29 CFR 1926.650-652 /Subpart P
Understands how to classify soil types
Knows the different types and proper use of excavation safety equipment (e.g. protective systems.)
Has the ability to recognize unsafe conditions, the authority to stop the work when unsafe conditions exist, the knowledge of how to correct the unsafe conditions, and does it!
If someone else has to be called in order to stop the work, or the designated competent person does not stop unsafe acts and conditions, the person is not acting "competently" within the meaning of the standard.
It is the responsibility of the competent person to conduct daily inspections prior to the start of any work and as needed throughout the shift. He/she may use a checklist to ensure all operations are reviewed. Part of this inspection process includes determining the soil classification. OSHA has included in Appendix A of its excavation standard methods to make it easier for a competent person to classify soils. The ability to determine soil type correctly is critical, because soil type is one of the determining factors in specifying protective systems.
A protective system must be used if an excavation is 5 feet or greater in depth. The three most commonly used kinds of protective systems are: shoring, shielding, and sloping. Each of these protective systems are acceptable to OSHA; it is up to the competent person to determine which method will be most effective for the job. The competent person must inspect these systems regularly to ensure that they are functioning properly.