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STATE OF COLc ~~~ ~~~~~~~~~~~~~~~~ <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />7313 Sherman St., Room 215 <br />Denver, CG 80203 <br />303 8663567 <br />Fa x: 303 832-8106 <br />Date: January 17, 1992 <br />To: Christine Johnston <br />Fr: Bruce Stover% Ly~ <br />RE: West Elk Mine Stack Tube Technical Revision <br />OF COr <br />~lr~$ <br />.`;.. <br />•\Y~y'\. <br />~87a ~ <br />Roy Romer. <br />Governor <br />Fretl R. Banta. <br />DiviS~on Direcmr <br />I have looked over the materials submitted in support of the Stack Tube <br />Technical Revision. The Geowest memo briefly outlines the approach of the <br />elope stability analysis, and concludes that a buttress of "clay fill's at least <br />fifty feet in thickness placed against the gob materials will be required to <br />meet the minimum safety factor for the stack tube pile. <br />In order to complete the review of this proposal, It would be appropriate for <br />us to have more specific geotechnical characterizations of the gob, "native <br />clay fill" and colluvium proposed to be used to construct the foundation pad. <br />Specific geotechnical materials parameters used in the numerical analysis, as <br />well ae the shear test results on the "similar samples" should be provided so <br />that we have a record of the assumptions that were made in performing the <br />analysis. <br />Some of this data may already exist in the current permit file. As I am still <br />new at finding my way through the volumes of permit materials, it would be <br />helpful to me if you could assist me in locating what geotechnical data we do <br />have on this particular aspect of the permit. If we do not already have the <br />geotechnical information noted above, then it should be provided by the <br />applicant. <br />i <br />