Laserfiche WebLink
<br /> <br />E:ME RGE NCY SP 1 L LWAY DES I GN - CLAR E POND <br />E:tisting data: <br />The following information was obtained from the Mined Land <br />Reclamation Division as the basis for spillway design: <br />drainage area: 23 square miles <br />80% hydrologic soil C <br />10A; hydrologic soil B <br />10!K hydrologic soil D <br />Average curve number: 74 <br />100 year 24 hour peak flow: 2136 cfs <br />Other information regarding the <br />conditions were determined from <br />visit. <br />Design Parameters: <br />dam dimensions and site <br />existing permit maps and a site <br />Initial computer modeling revealed that the presence of the pond <br />and trickle tube principal spillway provided little reduction of <br />the peak flow from the relatively large watershed (23 sq. miles). <br />The 100 year 24 hour storm produces an approximate discharge of <br />9!i0 acre-feet at this location. <br />The STORM program developed by the Office of Surface Mining was <br />u:>ed to determine the spillway design specifications. This <br />software uses the accepted Manning's equation for open channel <br />flow. <br />The site visit revealed that the north bank of the existing <br />channel is located in competent non-erosive sandstone. This <br />material should be utilized in the spillway design, where <br />possible. Where it is not practical, the channel should be lined <br />with a 6" thickness of shotcrete or other similar material. This <br />material and the sandstone has an average manning's n of 0.020. <br />