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• <br />New Horizon 2 <br />Reclaimed Krill Drainage Channel Design <br />West Lateral <br />• <br />• <br />Introduction <br />The design of the reclaimed drainage channel in the New Horizon 2 permit area was based on DMG <br />regulations for conveyance of overland flow of watersheds less than one square mile. The reclaimed <br />channel is shown on Map 2.05.4-2 between points BB to BB'. The premine drainage channel slope is <br />2.67 percent and the postmining drainage channel will be 2.67 percent. <br />Design <br />For the design of this reclaimed channel, the SEDCAD + model was used to predict runoff from the <br />watershed (see AttachmentA). A 10-year, 24-hour precipitation event was used in the design. The peak <br />flow was determined at the downstream end of the drainage channel. Following is a list of main input <br />factors. <br />Input Channel BB-BB' <br />Precipitation 2.0 in <br />Drainage Area 13.19 ac <br />CN 81 <br />L 1500 ft <br />Y 40 ft <br />Output <br />Q 4.49 cfs <br />Based on this discharge, SEDCAD+ was used to design the reclaimed drainage channel bottom width <br />based on Manning's equation calculation. The shape of the channel was assumed to be trapezoidal with <br />3h:1v side slopes. The channel bottom width was increased to insure that the peak velocity was below <br />the limiting velocity of 5.0 fps. Below is a summary of the input factors and the results determined by the <br />computer program. <br />(Revised 2-21-96) ATTACHMENT 2.05.4(2)(C)-2-1 <br />