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- ~ ~ III IIIIIIIIIIIII III <br />STATE OF COLOlZADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Geparlmenl of Nalmal Resources ~~~~~ <br />I l I3 Sherman St., Room ?15 <br />Derner, Colorado 80203 <br />Phone: (3113) 866-1567 <br />FAX. (1031 832-810( <br />DEPART MENT OF <br />DATE: January 14, 1997 RESOLUTRRC S <br />Roy Romer <br />Governor <br />TO: Dave Berry lames S. LOChhead <br />6ecuL Ve D~reaur <br />Michael B. LOnR <br />FROM: Jim Pendleton Division Direnor <br />RE: "Geotechnic`al-~dGoratory Testing, Proposed Gob <br />Pile, Bowie No. 2 Mine, Bowie, Delta County, <br />Colorado" (Permit No: C-96-083) <br />I have reviewed the above referenced additional geotechnical study, which you <br />forwarded to my attention. This study was prepared by MAXIM Technologies, <br />Inc., a geotechnical subcontractor to Morrison Knudsen, the primary design <br />contractor for Bowie Resources Limited (BRL). This study was prepared to <br />address adequacy comments included in my original geotechnical adequacy <br />memorandum, dated July 6, 1996. The WESTEC gob pile design report was <br />submitted by J. E. Stover & Associates, the general permit consultant for the <br />Bowie No. 2 Mine, as a portion of the original permit application. <br />The Original Concern <br />The Division expressed a concern because WESTEC assumed material properties <br />for three of the four involved earthen materials in completing its slope <br />stability analysis for the proposed waste pile. Only strength parameters for <br />the coal waste, material "1" were determined by performing a direct shear test <br />in the laboratory. Strength parameters for existing sandstone-derived colluvial <br />material underlying the proposed waste pile, material "2", were theoretically <br />developed from interpretation of the Standard Penetration Test (SPT) blow <br />counts recorded in the field. Strength parameters for the Mancos Shale bedrock, <br />material "3", were similarly deduced from SPT blow counts. Strength <br />parameters for the historic coal mine waste fill material located beneath the <br />