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procedure also applies to soils and sediments collected using other techniques (e.g., post hole <br />digger, scoop, Van Veen sampler, and backhoe). <br />The USCS categorizes soils into 15 basic groups, each with distinct geologic and engineering <br />properties. The following steps are required to classify a soil sample: <br />Observe basic properties and characteristics of the soil. These include grain-size grading <br />and distribution and influence of moisture on fine-grained soil. <br />Assign the soil a USCS classification and denote it by the standard group name and symbol. <br />Provide a written description to differentiate between soils in the same group, if necessary. <br />Many soils have characteristics that are not clearly associated with a specific soil group. These soils <br />might be near the borderline between groups, based on either grain-size grading and distribution, or <br />plasticity characteristics. In this case, assigning dual group names and symbols might be <br />appropriate (e.g., GW/GC or ML/CL). <br />The three basic soil groups are: <br />Coarse-Grained Soils — For soils in this group, more than half of the material is larger than <br />No. 200 sieve (0.074 mm). <br />Fine-Grained Soils — For soils in this group, one half or more of the material is smaller than <br />No. 200 sieve (0.074 mm). <br />Highly Organic Soils — This group includes soils with high organic content, such as peat. <br />Note: No. 200 sieve is the smallest size that can be seen with the naked eye. <br />B.4.2 Classification of Coarse-Grained Soils <br />Coarse-grained soils are classified on the basis of: <br />Grain size and distribution <br />Quantity of fine-grained material (i.e., silt and clay) <br />Character of fine-grained material <br />Classification uses the following symbols: <br />Basic Symbols <br />G - gravel <br />S - sand <br />Modifying Symbols <br />W - well graded <br />P - poorly graded <br />M - with silt fines <br />C - with clay fines <br />The following are basic facts about coarse-grained soil classification: <br />Additional Soil and Groundwater Sample Work Plan, Page 2 <br />BNSF Mormon Yard, Stockton, California <br />111wybnsf2tnsfwptwp1201811899020 00_mormon_yardtwork_plan_idtappb_sogboreholelogging acpt chng_wp.doc