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iii iiiiiiiiiiiuiii STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Depanmem of Natural Resources 1 J 1 3 Sherman 51 . Room 215 Denver, Colorado 80203 II~ Phone. IJ031 86fi-7567 FAX:110J183L8106 DEPARTMEIJT OI NATURAL RESOURCE Roy Romer Governor April 25 1997 , IamesS luihheaJ E ~emu.c Uim~ ini Mi~hnrl8 Long Urv~sion Dne~w~ Mr. Lary Reschke Powderhom Coal Company P.O. Box 1430 Palisade, CO 81526 RE: Roadside North & South Portal Mine (C-81-041) Midterm Bond Calculations Dear Mr. Reschke, The Division received the disk containing ACAD R-12 file of the existing and proposed final contours at the Roadside South Portal Mine. The Division evaluated the maps and the material balance using SurvCADD, a software package developed by Carlson Software. A 3D polyline perimeter was drawn around the postmining topography representing the limits of the earthwork and the daylign[ point where the cuts and fills tie to the original ground. The perimeter was drawn as a distinct layer and made a pan of both existing and final surfaces. Volumes were then determined from the layers and the inclusion perimeter. The Division came up with 133, l45 CY of cut material and 129,446 CY of fill material. These numbers compare to Powderhorn's estimate of 138,000 cy of cu[ and 146,800 cy of fill. See attached report for further detail. The Division located a number of data errors in the postmining map generated by Powderhom. The data errors included a series of contour intervals labeled 4,790 located adjacent to the regraded refuse pile. The Division deleted these lines to determine a more precise cut and fill balance. The Division is satisfied [hat the cut and fill material at the South Portal Mine will balance when the site is reclaimed. The difference between the cut and fill volume is less than 4,000 cy of material, a relatively small margin of error. Exhibits 6C and 26 do not need to be revised to account for any discrepency in the material balance.