6.27.4 Soil Classifications

1. There are basically (4) types of soil classifications used to determine stability of soils:

• Stable Rock
• Type A (cohesive)
• Type B (mildly cohesive)
• Type C (non-cohesive)

When in doubt as to the soil type in a particular excavation Type C is to be assumed for the purpose of safety in trenching and excavating. All sloping, benchings, and protection systems used on our projects must conform to Type C soil requirements. Exceptions will only be allowed when authorized and classified by the Safety Department.

2. The immediate supervisor (Competent Person) must make at least one visual test and one physical or manual test to determine the soil classification.
   1. Visual
      By looking at the soil around the excavation, the soil that is excavated, or the walls of the excavation and deciding whether it is:
      1. Cohesive A-Type
         (high clay or cemented soil content)
      2. Mildly Cohesive B-Type
         (high loam or silt mixed with clay or sand)
      3. Non-Cohesive C-Type
         (sandy, granular soil or extremely wet soil or clay).
   2. Physical
      By seeing how difficult it is to press your thumb into an undisturbed section or clump of soil and how deep a penetration is obtained
      1. Cohesive A-Type
         (hard pressure with little to no penetration)
      2. Mildly Cohesive B-Type
         (mild pressure and full penetration)
      3. Non-Cohesive C-Type
         (easily penetrated several inches).

Remember: Work in A and B soil classifications must be authorized by the Safety and Health Manager.