OSHA Soil Classifications

A Summary of OSHA Soil Classifications

 

When performing an excavation on a jobsite it is important to determine the soil type. Failure to comply with their standards can result in a costly OSHA violation. OSHA has divided the types of soil that construction workers would be working with into three categories, Type A, Type B, and Type C. The first category, Type A is the most stable and safe ground to work in and the third category, Type C is the least stable.

Knowing your soil type will help you choose the correct trench box. Iron Lot is a good source to buy one from.

The first is High Stability (Type A Soil), also known as Class A Soil. This first category consists of clay, silty clay, sandy clay, and clay loam. OSHA states that no soil is Type A if it is fissured, is subject to vibration, has previously been disturbed, or has seeping water.

The second classification is Medium Stability (Type B Soil), also known as Class B Soil. This second group of soil consists of silt, sandy loam, medium clay, and unstable dry rock. Type B soil also includes previously disturbed soils, except those that would be classified as Type C soil. Further, Type B Soil includes soil that meets the requirement of Type A soil, but is fissured or subject to vibration.

The third and final category is Low Stability (Type C Soil), also known as Class C Soil. This third group of soil includes gravel, sand, loamy sand, soft clay, submerged soil, dense unstable rock, or soil from which water is freely seeping.

Understanding Soil Classifications Lead to Safer Job Sites

Understanding these three types of soil defined by OSHA is a key factor in making key decisions concerning the safety of the excavation. These factors play a role in determining the proper trench shield to use on the job. The depth rating of the trench shield should meet or exceed the depth of the trench and corresponding soil type. For example, if the soil type is Class C and the depth of the trench is 12', the Class C depth rating of the trench box should be at least 12'.