Laserfiche WebLink
2. Prevent additional contributions of suspended solids to streamflow and to runoff <br />outside the permit area; <br />3. Blend with the undisturbed drainage above and below the area to be reclaimed; <br />4. Safely pass the runoff from a 10 -year, 24 -hour precipitation event. <br />The reclaimed drainages are designed to safely pass the 10 -year, 24 -hour precipitation event and <br />to be stable. The peak flow was determined by using the SEDCAD+ Version 3.0 computer <br />program. A listing of the input parameters for obtaining the peak flows for the reclaimed drainage <br />channels are attached. The peak flow determination assumed the total watershed of the reclaimed <br />channel and was determined at the downstream end of the channel. Most of the reclaimed channel <br />reach will not have to handle that large a peak flow rate. This was done: to ensure that the drainage <br />channel capacity will be adequate and conservatively designed. <br />A limiting permissible velocity of 5.0 feet per second (fps) was used to insure that the postmining <br />drainage channels would be nonerodible and stable. The permissible velocity was obtained, Table <br />3.4, from "Red Book" by Barfield et al., 1981 for a grass mixture vegetated channel. The shape <br />of the reclaimed channel was assumed for design purposes to be trapezoidal with 10h:1v side <br />slopes as a worst case condition. The side slopes will be no steeper than 1 Oh:1 v. <br />The channel bottom was calculated using the SEDCAD+ Version 3.0 computer program. The <br />channel width was increased to insure that the peak velocity was below the limiting velocity. The <br />typical trapezoidal channel section was selected for design purposes only for the entire length of <br />the reclaimed channel. 'Reclaimed Drainage Channel Design" on the following pages contains the <br />specific design information of the reclaimed drainage channel in the eastern portion of the New <br />Horizon 2 permit area (San Miguel Draw). <br />The reclaimed drainage channels will be topsoiled and revegetated according to Sections <br />2.05.4(2)(d) and (e) respectively. Attachments 2.05.4(2)(C) -1 and 2.05.4(2)(C) -3, which <br />immediately follow this section, show the designs for these restored channels. <br />(Revised July 2006) 2.05.4(2)(c) -12 <br />