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J. E. STOVER & ASSOCIATES <br />2768 COMPASS DRIVE, SU17'E 101 <br />GRAND NNCTION, COLORADO 81506 <br />PRONE: (970) 245-4101, FAX 242-7908 <br />MINE ENCUVeeRINc <br />MINE RECLAMATION <br />May 24, 1999 <br />J. J. Dudash <br />Division of Minerals & Geology <br />1313 Sherman St., Room 215 <br />Denver. CO 80203 <br />Re: Bowie No. 2 Mine <br />Minor Revision Application (MR-012) <br />Permit C-91-083 <br />Dear Mr. Dudash: <br />III IIIIIIIIIIIII III <br />999 <br />CIVIL ENGWEERING <br />CONST. MANAGEMENT <br />RECEIVED <br />MAY 2 61999 <br />Division of Minerals 8 Geology <br />Enclosed is an application for a minor revision to provide for erosion protection for the coverfil] <br />pile upper diversion ditch. The peak flow for the ditch is obtained from Volume IV Gob Pile, <br />Appendix BHydrology/Sedimentology Output. The design flow is the 10-year event from two <br />ditches. The first is flow from the gob pile upper diversion ditch (A4b) which flows into the <br />coverfill pile upper diversion ditch drainage basin. The second is the coverfill pile drainage basin, <br />reach A6. The total design flow is 6.26(A4b) + 13.74(A6) = 20 cfs. <br />Two types of erosion protection are proposed for the ditch. The first is PEC-MAT for the upper <br />275 feet of ditch. This ditch section has relative flat slopes and low velocities. The second is one- <br />half of a 24-inch diameter pipe (corrugated metal or ADS) for the lower 150 feet of ditch. This <br />ditch section has steep slopes, high velocities and high shear stresses. <br />I recommend the enclosed calculation sheet for the Coverfill Pile -Upland Diversion Ditch be <br />inserted in Volume III, Exhibit 8, page Exh-8 - 29ii -. <br />Please call if you have any questions. <br />Sincerely, <br />~~~Q~ <br />J. E. Stover, P.E. <br />Consulting Engineer <br />cc: Wm. A. Bear, Jr. <br />