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Excavation,Trenching Shoring Safety and the OSHA Excavati tandard- ... Page 2 of 2 In many construction projects,the soil that is being excavated has been previously disturbed.This means the soils has been dug up or moved in the past. This is another factor a competent person must consider when typing soils. Previously disturbed soils are rarely as strong as undisturbed soils, and are usually typed as"C"soil.Previously disturbed soil is commonly foundaboveexisting utilities, such as water,sewer,electrical and gas lines. This makes work around these utilities more dangerous due to the unstable nature of the soil. Much of the work AFSCME members perform in excavations are along right- of-ways,where the soil is almost always likely to be Type C. Because of where we dig, it's important to understand that once soil has been excavated, it will never be returned to the way it was naturally formed. Per 1926 Subpart P,Appendix A(c)(2), a competent person must type soils by using at least one visual and one manual test.A visual test can include inspecting the soil as it is being removed, and examining the spoil pile and the color and make-up of the excavation walls.A manual test means working with the soil with either your hands or with an instrument designed to measure soil strength. For example, if you can roll the soil in your hands into a long"worm" or ribbon, the soil is cohesive and may be classified as A or B,depending on other conditions. One useful instrument for measuring soil strength is a penetrometer.When you press this instrument into a soil sample, it measures its unconfined compressive strength in tons per square foot(tsf). Regardless of the methods used,the typing of soils must be done by the competent person prior anyone entering the excavation.The weaker the soil,the greater the need for protective systems. Mote:if you are uncertain of the soil type,ALWAYS assume Type C soill http://www.afscme.org/health/excav04.htm 8/25/2005