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r- ~i <br />_li <br />~. <br />DIVISION OF MINERALS AND GEOLOGY <br />Deparimenl of Natural Resources <br />171 }Sherman 51., Room 215 <br />Denver, Colorado &0'_03 <br />Phona~. (3031 865-3567 <br />FAY: (3031 832-8106 <br />DATE: October 7, 1997 <br />III IIIIIIIIIIIII III <br />STATE OF COLC~I~Uv <br />TO: Mike Boulay <br />FROM: Jim Pendleton <br />RE: West Elk e - T.R. 8 - PHC Adequacy Responses #20 & #21 <br />It No: C-80-007) <br />II~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />~ame~S. LOChhead <br />Ezennive Dircuor <br />Michael B. Long <br />Division Duedor <br />As you requested, I have reviewed Mountain Coal Company's (MCC) responses to our original <br />adequacy comments #20 & #21, which you forwarded to my attention. <br />Comment #20 <br />MCC has modified the two apparently contradictory statements to render them acceptable to the <br />Division. <br />Comment #21 <br />Wright Water Engineer's (WWE) has completed a subjective evaluation of the relationship <br />between projected lumping of waters in the B Seam, invasion into the Bear and Edward's mines <br />abandoned workings, migration through the subcrop into the colluvial wedge, and slope stability <br />of the colluvial wedge downslope from the B Seam subcrop. WWE's conceptual assumptions <br />are plausible and it's conclusions appear appropriate. <br />Simply stated WWE concludes that historically the instability of the colluvial slope below the B <br />Seam subcrop is directly related to the availability of moisture; i.e. landslides occur <br />predominantly in the wet years. Further, instability of [he colluvial wedge below the B Seam <br />subcrop is predominantly "shallow" in nature. WWE projects that the increase in soil moisture <br />due to increased migration from the B Seam workings should be insignificant in relation to the <br />annual variability in soil moisture related to differences in precipitation infiltration. All of <br />WWE's rationale appears plausible. Unfortunately, no quantitative soil water moisture or related <br />slope stability monitoring data exists with which to objectively verify WWE's conceptual <br />evaluation. <br /> <br />~` <br />