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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />DepaRment of Natural Resources <br />1313 Sherman St., Room 215 C O L D RA D O <br />Denver, Colorado 80203 DIVISION O F <br />Phone: (303! 8663567 MINERAL S <br /> <br />FAX: (303) 832-8106 G E O L O G Y <br /> 0.E ClA MATION•MINING <br /> EAEETY•SLIENCE <br /> Bill Owens <br /> Governor <br />June 28 <br />2005 Russell George <br />E <br />i <br />Di <br />, xecut <br />ve <br />rector <br /> Ronald W. Cattany <br />Mr. Roy Karo Division DireROr <br />Seneca Coal Company Natural Resource Truztee <br />P.O. Box 670 <br />Hayden, CO 81639 <br />Re: Seneca II Mine (Permit No. C-1980-005) <br />Technical Revision No. 39 -Adequacy Review <br />Deaz Mr. Karo: <br />The Division of Minerals and Geology (Division) has reviewed Seneca Coal Company's <br />Technical Revision No. 39 application, which proposes changes to the principal spillway <br />locations and configurations at Sedimentation Ponds 004 and 008 and abandonment plans <br />for the existing spillways. The Division has the following comments. <br />I. The Hydrologic Input Parameters tables for both Ponds 004 and 008 indicate <br />Vegetation Cover > 70% for Reclaim > 3 years. The 2004 Revegetation Monitoring <br />Report does not support this for average total vegetation cover. With exception of the <br />2002 Reclaimed Area, the report does indicate that Ground Cover (Liter + Rock + Veg.+ <br />St. Dead) for reclaimed areas is greater than 70%. Please revise the Hydrologic Input <br />Parameters tables for both ponds to indicate Ground Cover > 70% as opposed to <br />Vegetation Cover. Please also review and revise the SEDCAD demonstrations and <br />watershed azeas (including the 2002 Reclaimed Area) to ensure that accurate curve <br />numbers are reflected for all areas where the cover is less than 70%. <br />2. Exhibit 7-22 is incorrectly labeled as 17-22. The curve number is also incorrect <br />for SWS-1 for Structure #9 on this exhibit based on information presented in the <br />SEDCAD demonstration. Please revise Exhibit 7-22 accordingly. <br />3. The principal spillways for Ponds 004 and 008 are proposed for redesign with fl- <br />inch plastic straight pipes. Based on review of Annual Hydrology Reports (AHRs), <br />quarterly Dischazge Monitoring Reports (DMRs) and other related hydrology data, it <br />appears that the elevations of the principal spillways may be inadequate to prevent flow <br />through the emergency spillways during a storm event equal to or less than the 10-year, <br />24-hour precipitation event. Based on this information, the amount of flow entering the <br />Office of Office of Colorado <br />Mined Land Reclamation Active and Inactive Mines Geological Survey <br />