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<br /> RECOMMENDED UNIFORM INFILTRATION RATES <br /> SOIL TEXTURE CLASS , INFIL TRA TION RATE linlhrl <br />Send 4.00 - 8.00 <br /> , <br />Loamy Sand 1.20 - 2.40 <br />Loam 0.50 - 1.00 <br />Silt Loam 0.15 - 0.30 <br />Sandy Clay Loam 0.10 - 0.20 <br />Clay Loam 0.05 - 0.10 <br />Silty Clay Loam 0.05 - 0.10 <br />Sandy Clay 0.03 - 0.05 <br />Silly Clay 0.02 - 0.04 <br />Clay 0.01 - 0.02 <br /> <br />These values are based on the saturated hydraulic conductivity for soils ' <br />in each texture class. In addition to the values listed in the table above, the SCS has <br />developed a soil classification system that consists of four groups of soils. Group A <br />includes deep sand, deep loess, and aggregated silts. Group B consists of shallow <br />loess and sandy loams. Group C includes clay loams, shallow sandy loam, and soils <br />low in organic content and high in clay. Group D consists of soils that swell <br />significantly when wet such as heavy plastic clays and certain saline soils. <br />Recommended infiltration rates for each soil group are as follows: <br /> <br />GROUP <br /> <br />SOIL TYPE <br /> <br />INFILTRATION RATE linlhrl <br /> <br />A <br /> <br />Sand, Aggregated Silts <br /> <br />0.30 - 0.45 <br /> <br />B <br /> <br />Shallow Loess, Sandy Loams <br /> <br />0.15 - 0.30 <br />0.05' 0.15 <br /> <br />C <br /> <br />Low Organics, High Clay <br /> <br />D <br /> <br />Plastic Clays, Saline <br /> <br />0.00 - 0.05 <br /> <br />3. SCS CURVE NUMBER METHOD. <br /> <br />Probably the most widely used and misused method for estimating <br />infiltration losses is the SCS Curve Number method. This method was developed by <br />the SCS in the 1950's in order to predict the effects of proposed changes in land use <br />and treatment on direct runoff. It was based on observed daily rainfall and runoff data <br />from field test plots located in the Midwest in order to develop average relationships <br />between rainfall and runoff and was not intended to be used for the simulation of <br />individual events. Since the method is the only one available for estimating loss rates <br /> <br />7-3 <br />