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<br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1 J13 Sherman 51., Room 215 <br />Deover, Colorado 80203 <br />Phone: 13031 866-3 567 <br />FAX: (303) 832-8106 <br />DATE: January 10, 1997 <br />T0: Bill Carter <br />Roy Romer <br />Governor <br />lames 5. Lochhead <br />E>teculive Duector <br />Michael 8. Lonq <br />Division Duector <br />FROM: Jim Pendleton <br />RE: "Coal Mine~lAf< <br />Creek Mine" <br />iii iiiiiiiiiiiu iii <br />9 9 <br />STATE OF COLORADO <br />Bank Design for the Sanborn <br />(Permit No: C-81-022) <br />I have completed a preliminary review of the geotechnical aspects of the <br />design analysis prepared for Oxbow by WESTEC, which you forwarded to <br />my attention. During our visit to the proposed waste pile site last fall, I <br />indicated my willingness to preliminarily review the document, in an <br />effort to expedite the process. <br />Design Report & Stability Analysis <br />WESTEC has done a good job of preparing the design documents and the <br />accompanying stability analysis. A combination of laboratory analysis and <br />field blow count conversion was used to develop material strength <br />properties for the waste and three materials encountered within the site <br />foundation. All of the analytical techniques and field observations appear <br />appropriate. The stability analyses, performed for both rotational and <br />planar failure scenarios project a minimum static slope safety factor of <br />2.1 for the circular failure mode and 2.3 for planar failure. Corresponding <br />pseudo static factors of safety are 1.5 for the circular case and 1.8 for <br />the planar case. As such these safety factors easily satisfy the <br />requirements of our regulations. <br />I~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />My review of the design report and analysis discerned only one concern. <br />During our reconnaissance of the site last fall, I mentioned a concern <br />