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III IIIIIIIIIIIIIIII <br />999 <br />STATE OF COLORADO <br />DIVISION Of MINERALS AND GEOLOGY <br />Depanment of Natural Resources <br />t 313 Sherman 51., Room 275 <br />Denver, Colorado 80203 <br />Phone: (703) 866-3567 <br />FAX: 1303) 83?-8106 <br />Ms. Christine Johnston <br />Mountain Coal Company LLC <br />P.O. Box 591 <br />Somerset CO 814;4 <br />Dear Ms. Johnston: <br />.~,tirhael B. Long <br />Oveaor <br />The Division has completed review of Mountain Coal Company's submittal of Technical Revision Number <br />87, As-built diagrams for the Run-of-Ivtine Pad Expansion. Barr Engineering Company, consultant [o <br />MCC on many of the recent slope stabilization projects at the West Elk Mine, completed the required <br />analysis which reflected the lack of groundwater encountered during the construction and related auger <br />investigations of the foundational vicinity. The stability analysis, whhcih appears to have been conducted <br />in accordance with acceptable methodology, determined that the steepened outslope has a static factor of <br />safety of l .3 (. As such the as-built outslope is acceptable. <br />The stability analysis assumes non-saturation of the foundational bedrock and soils, 'the storage pad fill, <br />and the cut slope bedrock and soils above the pad. Because the safety factor of the outslope is slightly <br />above the required minimum, it is important that the materials involved remain unsaturated. For this <br />reason, we believe it is appropriate to impose two monitoring requ'vements upon approval of Technical <br />Revision #87. <br />(I) MCC should install and monitor three (3) piezometers at the crest of the outslope. These piezometers <br />should be installed to refusal in bedrock. The piezometers should be monitored to determine if any <br />groundwater is present within or beneath the fill slope. <br />(2) MCC should install slope stability monument profile lines on the outslope of the expansion to verify <br />that the slope is stable. These profile lines may include the piezometers as their upper members. MCC <br />may install simple line-of-sight monuments similar to those previously installed and monitored at <br />numerous locations throughout their permit area, such as the waste pile expansion and road cut slopes <br />throughout Sylvester Gulch. These monuments should be monitored at least quarterly in July, <br />October, and January, and monthly from April through June. <br />With the imposition of these two monitoring conditions, the Division will approved the revision. <br />Please call if you have any questions. <br />Sincerely, <br />!/N~ <br />~ ~/~[/1. ~~t~i%~~~C. <br />im Burnell <br />Environmental Protection Specialist <br />ulrl )ION of <br />MINERALS <br />-&- <br />GEOLOGY <br />NcCLAnAiION <br />MIN iNG•SAFETT <br />dill Owens <br />Governor <br />February 9, 1999 Greg E. watcher <br />E.ecmrve Dkeaor <br />