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MaY 1998 Sturm 17Mini"PoitMimt Dmwotr Corlro! ~ 5 <br />• <br />Rnr•him~d Aen~n <br />Soil Type: B <br />Ground Cover Type: Herbaceous <br />Ground Cover. Good <br />CN : G2 <br />CHANNEL DESIGNS <br />The surface water diversion dimensions were determined using Mannings Equation Eor open channel <br />flow. All channels will be either riprap, gravel, or vegetated lined channels. <br />All existing channels were evaluated assuming a worst case scenario, which is; a V-shaped, vegetated <br />ditch with 3H:1V sideslopes. If the channel is stable assuming a worst case configuration, no <br />additional aunoring is required. If not, the channel will be riprapped as indicated on the channel <br />design drawings. <br />For newly designed channels, if the flow velocity is less than G feet per second, the channel will be <br />gravel lined. IF flow velocities exceed G feet per second the channels will be lined with riprap. Riprap <br />sizes were determined using the SEDCAD+ subroutine for designing riprap lined channels, utilizing <br />either the OSM/Simons Method or the PARER Method. Given the uncertainty in determining <br />riprap sizes for steep grades where the PARER Method was used, a factor of safety of 3 inches was <br />added to the Dso of riprap in these azeas. <br />CULVERT DESIGNS <br />The culverts were sized using the U.S. Bureau of Public Roads nomograph. The culvert design <br />nomograph can he found in Appendix C. Culverts 19A, 24A, and 45A were removed from the <br />permanent light-use road and will be replaced with a dry stream crossing. A figure showing the <br />typical dry stream crossing is included at the end of Appendix C. <br />L~ <br />7-12-5 Revised 08/04/98 <br />