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MINE ENGINEERING CIVIL ENGINEERING <br />MINE RECLAMATION CONST. MANAGEMENT <br />July 9, 2012 <br />Brock Bowles <br />Division of Reclamation, Mining & Safety <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />Re: Bowie Resources, LLC, Bowie No. 2 Mine <br />MR -131, Revise design of Ditch D -3 - Adequacy Response #1 <br />Permit C- 1996 -083 <br />Dear Mr. Bowles: <br />J. E. STOVER & ASSOCIATES, INC. <br />2352NORTH 7 STREEET, UNIT B <br />GRAND JUNCTION, COLORADO 81501 <br />PHONE: (970) 245 -4101, FAX 242 -7908 <br />BRL: Please see revised page EXH. 8 -29i. <br />?owe° <br />707 <br />o� ; eclama <br />0, W t and Safety <br />M`n►n9 <br />The DRMS' letter dated July 5, 2012, 2012 requested additional information. On behalf <br />of Bowie Resources, LLC, enclosed is the requested data. <br />1. DRMS: The newly revised page EXH. 8 -29i does not coincide with the currently <br />approved page. The currently approved pages EXH. 8 -29 and 29i have ditches C10 <br />and C11 at the bottom of page 8 -29 and C11 and C12 at the top of page 8 -29i. The <br />new page 8 -29i starts off with C13, so C12 is omitted. Please revise page 8 -29i to <br />include C12. <br />2. DRMS: The rip rap sizing calculations on pages EXH 8 -252 and EXH 8 -253, <br />resulting in require D50 of 0.83' for Ditches D3 -1 and D3 -2 and 1.17' for Ditch D3 -3 <br />appear to be in error. Using the same equation, DRMS calculations show a required <br />D50 of 1.64' for Ditches D3 -1 and D3 -2 and 2.55' for Ditch D3 -3. Please review the <br />calculation and verify and correct the calculations and revise the pages <br />accordingly. <br />BRL: The equation in Excel used to calculate the rip rap size for Ditch D -3 had an <br />incorrect cell reference and has been corrected. Ditch sections D3 -1 and D3 -2 remain <br />specified with D50 =12" riprap, the flow depth changed from 1.0' to 0.6'. Ditch section <br />D3 -3 (50 %) was changed from D50 =15" to D50 =18" and the flow depth changed from <br />1.0' to 0.6'. Both sections maintain the minimum freeboard requirement of 0.3'. <br />A site inspection of Ditch D -3 was conducted on July 8, 2012, and it was confirmed that <br />the 50% ditch section has D50 =18" installed, and, the majority of Ditch Section D3 -3 <br />has D50 =15" installed, which exceeds the design specification of D50 =12 ". Please see <br />revised pages EXH. 8 -246 and 247, and EXH. 8 -252 and 253. In addition, since the <br />flow depths have been changed for ditch sections D3 -1, through D3 -3, please see <br />