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Hydrologic Soil Group-Rifle Area, Colorado, Parts of Garfield ancf Mesa <br />Counties <br />USDA . <br />Description <br />Hydrologic soil groups are based on estimates of runoff potential. Soils are <br />assigned to one of four groups according to the rate of water infiltration when the <br />soils are not protected by vegetation, are thoroughly wet, and receive precipitation <br />from long-duration storms. <br />The soils in the Un~ed States are assigned to four groups (A, B, C, and D) and <br />three dual classes (AID, BID, and CID). The groups are defined as follows: <br />Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly <br />wet. These consist mainly of deep, well drained to excessively drained sands or <br />gravelly sands. These soils have a high rate of water transmission. <br />Group B. Soils having a moderate infillration rate when thoroughly wet. These <br />consist chiefly of moderately deep or deep, moderately well drained or well drained <br />soils that have moderately fine texture to moderately coarse texture. These soils <br />have a moderate rate of water transmission. <br />Group C. Soils having a slow infiltration rate when thoroughly wet. These consist <br />chiefty of soils having a layer that Impedes the downward movement of water or <br />soils of moderately fine texture or fine texture. These soils have a slow rate of water <br />transmission. <br />Group D. Soils having a very slow inflftration rate (high runoff potential) when <br />thoroughly wet. These consist chiefly of clays that have a high shrink-swell <br />potential, soils that have a high water table, soils that have a claypan or clay layer <br />at or near the surface, and soils that are shallow over nearly impervious material. <br />These soils have a very slow rate of water transmission. <br />If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is <br />for drained areas and the second is for undrained areas. Only the soils that in their <br />natural condition are in group D are assigned to dual classes. <br />Rating Options <br />Aggregation Method: Dominant Condition <br />Natural Resources <br />Conservation Service <br />Web Soli Survey 2.0 <br />National cooperative Soil SUivey <br />RTZ lndustr1al Sile <br />2128/2008 <br />Page 4 of 5