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��� V V V V ENGINEERING <br />611 SKYLINE ROAD - LARAMIE,. WY $2070 - (307) 742.0031 FAX (307) 721.2913 MEMO <br />TO: CMI EDNA MINE FILE, WWC JN 2011 -180.1 FILE, CDRMS PERMIT C -1980 -001 FILE <br />FROM: MURRAY SCHROEDER, P.E. <br />SUBJECT: NORTH ROAD DITCH CAPACITY <br />DATE: 08/21/12 <br />1.0 COMMENT <br />The Colorado Division of Reclamation, Mining and Safety (CDRMS) Coal Program Inspection <br />Report dated 8/10/12 provides the following comment: <br />"At the intersection of the North Road and the Lower Moffat Road, no construction has been <br />performed to address the low spot where water could potentially pond and flow over the road. <br />DRMS is awaiting survey results (or other information) to determine if the low spot warrants <br />improvements to the roadside ditch." <br />2.0 RESPONSE <br />The attached drawing provides a profile of the North Road edge and the flowline of the easterly <br />roadside ditch. Along this profile, the ditch is (in all areas) lower than the edge of the road as it <br />trends north. This indicates that the ditch has some capacity to convey water. <br />The approximate capacity of the ditch will be limited where the ditch is shallowest and the slope <br />is flattest, assuming that the cross - section of the ditch is uniform. <br />The profile exhibits that the ditch in the area of station 4 +80 has the least potential capacity. A <br />cross - section at this location shows the ditch to be approximately 1 foot deep, 15 feet wide, with <br />a vee shape. The slope of the ditch between station 4 +80 and station 6+40 is about 0.0163 ft/ft <br />(2.6 feet of fall in 160 feet of length). <br />Using an open channel hydraulic calculator (printout attached), the maximum capacity of the <br />ditch is roughly 30 cubic feet per second, before flow would encroach the North Road. <br />1/1 <br />