Soils . . . and Their Classification

When employees must work in a trench or excavation, it is extremely important to know the characteristics of the soil where the excavation exists. Soil must be classified by the onsite “Competent Person,” and proper steps taken to ensure worker safety. It’s the law.

There are two important reasons to classify the soil:

• First, classifying the soil is the first step in choosing a protective system.
• Second, OSHA’s Subpart P (Appendix A) requires that the “Competent Person” classify the soil, based upon the properties and performance characteristics of the soil, and environmental conditions of exposure.

Although there are hundreds of different types of soils, OSHA classifies soils into just four categories: Stable Rock, Type A, Type B, and Type C (listed in decreasing order of stability).

The following introductory video from OSHA (11 minutes) describes the regulations for soil classification, and reviews three methods of testing soil to determine its type.

Ever-Changing Soil Conditions

It is important to remember that soil conditions can change as time passes. The on-site “Competent Person” must constantly monitor changing soil conditions and assess whether additional precautions are necessary. Work crews, whose attention is focused on other aspects of the job, may overlook deteriorating soil conditions, thus putting co-workers at risk.

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