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Unified Soil Classification System (USCS) <br />MAJOR DIVISIONS <br />COARSE <br />GRAINED <br />SOILS <br />(more than 50% <br />retained on <br />No. 200 sieve) <br />FINE GRAINED <br />SOILS <br />(50% or more <br />passes the <br />No. 200 sieve) <br />HIGHLY OR( <br />SOILS <br />Gravels <br />(more than 50% <br />of coarse fraction <br />retained on No. 4 <br />sieve) <br />Sands <br />(50% or more <br />of coarse fraction <br />passes the No. 4 <br />sieve) <br />Silts and Clays <br />(liquid limit less <br />than 50) <br />Silts and Clays <br />(liquid limit 50 or <br />more) <br />Clean Gravels <br />(less than 5% <br />fines) <br />Gravels with <br />Fines <br />(more than 12% <br />fines) <br />Clean Sands <br />(less than 5% <br />fines) <br />Sands with <br />Fines <br />(more than 12% <br />fines) <br />Inorganic <br />Organic <br />Inorganic <br />Organic <br />Primarily organic matter, dark in color, <br />and organic odor <br />Classification of Soil Constituents <br />MAJOR constituents compose more than 5o percent, <br />by weight, of the soil. Major constituents are capitalized <br />(i.e., SAND). <br />Minor constituents compose 12 to 50 percent of the soil <br />and precede the major constituents (i.e., silty SAND). <br />Minor constituents preceded by "slightly" compose <br />5 to 12 percent of the soil (i.e., slightly silty SAND). <br />Trace constituents compose o to 5 percent of the soil <br />(i.e., slightly silty SAND, trace gravel). <br />Relative Density <br />Consistency <br />'Coarse Grained Soils) <br />(Fine Grained Soils) <br />N, SPT, <br />Relative <br />N, SPT, <br />Relative <br />BlowsFf <br />Density <br />Blows FT <br />Consistency <br />0-4 <br />Very loose <br />Under 2 <br />Very soft <br />4-10 <br />10 - 3o <br />Loose <br />Medium dense <br />2-4 <br />4 - 8 <br />soft <br />Medium stiff <br />30 - 50 <br />Over 50 <br />Dense <br />Very dense <br />8 -15 <br />15 - 3o <br />Stiff <br />Very stiff <br />Over 30 <br />Hard <br />Cobalt Geosciences, LLC <br />P.O. Box 82243 <br />Kenmore, WA 98028 <br />(2o6) 331-1097 <br />www.cobaltgeo.com <br />cobaltgeo (@ email.com <br />TYPICAL DESCRIPTION <br />Well -graded gravels, gravels, gravel -sand mixtures, little or no fines <br />Poorly graded gravels, gravel -sand mixtures, little or no fines <br />i <br />Silty gravels, gravel -sand -silt mixtures <br />Clayey gravels, gravel -sand -clay mixtures <br />gravelly Well -graded sands, g Y sands, little or no fines <br />Poorly graded sand, gravelly sands, little or no fines <br />n <br />Silty sands, sand -silt mixtures <br />Clayey sands, sand -clay mixtures <br />FL Inorganic silts of low to medium plasticity, sandy silts, gravelly silts, <br />or clayey silts with slight plasticity <br />-� Inorganic clays of low to medium plasticity, gravelly clays, sandy cla <br />silty clays, lean clays <br />>L <br />Organic silts and organic silty clays of low plasticity <br />aH Inorganic silts, micaceous or diatomaceous fine sands or silty soils, <br />elastic silt <br />=H Inorganic clays of medium to high plasticity, sandy fat clay, <br />or gravelly fat clay <br />DH <br />Organic clays of medium to high plasticity, organics is <br />PT Peat, humus, swamp soils with high organic content (ASTM D4427) <br />Moisture Content Definitions <br />Dry Absence of moisture, dusty, dry to the touch <br />Moist Damp but no visible water <br />Wet Visible free water, from below water table <br />Soil Classification Chart <br />Figure C1 <br />