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0 SedCAD Notes: Culverts in road between TS -1 and RDH -3 <br />Curve Numbers <br />Curve numbers were derived through the process of first reviewing the available soil survey data to <br />preliminarily determine appropriate hydrologic soils group (HSG). The watersheds involved were then <br />field checked to determine the accuracy of the surveys and to access the hydrologic conditions on site. <br />The attached map depicts the resulting mosaic of area with common curve numbers (CN). <br />Subwatersheds (SWS) were delineated for the main drainage. This was done to better model a faster <br />response from the higher curve numbered areas closer to the culvert. Weighted curve numbers were <br />calculated based on the relative area of each classification within the subwatersheds. <br />The following curve numbers were used in obtaining appropriate weighted values. All values are based <br />off of Table 2 -2d in 210- vl- TR -55, Second Ed., 1986 (Runoff curve numbers for arid and semiarid <br />rangelands): <br />51 HSG: B Sagebrush with grass understory - fair hydrologic condition. <br />62 HSG: B Herbaceous - good hydrologic condition <br />63 HSG: C Sagebrush with grass understory - fair hydrologic condition <br />70 HSG: D Sagebrush with grass understory - fair hydrologic condition <br />73 HSG: C Pinyon - juniper -fair hydrologic condition <br />89 HSG: C Pinyon - juniper - poor hydrologic condition <br />Curve Number weighting: <br />MAIN CULVERT (24 ") <br />SWS #1 <br />SWS #2 <br />CN <br />Acres <br />Weight <br />CN <br />Acres <br />Weight <br />51 <br />16.81 <br />857.31 <br />51 <br />13.48 <br />687.48 <br />63 <br />16.67 <br />1050.21 <br />63 <br />6.17 <br />388.71 <br />73 <br />12.9 <br />941.7 <br />70 <br />0.45 <br />31.5 <br />46.38 <br />61.4 <br />73 <br />12.41 <br />905.93 <br />32.51 <br />61.9 <br />SWS #3 <br />CN <br />Acres <br />Weight <br />62 <br />1.06 <br />65.72 <br />SMALL CULVERT (12 ") <br />63 <br />17.89 <br />1127.07 <br />SWS #1 <br />70 <br />8.57 <br />599.9 <br />CN <br />Acres <br />Weight <br />73 <br />11.75 <br />857.75 <br />63 <br />12.92 <br />813.96 <br />89 <br />3.85 <br />342.65 <br />73 <br />2.06 <br />150.38 <br />43.12 <br />69.4 <br />14.98 <br />64.4 <br />