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SINE BY: III ~~~~~~~~~~~~~ ~~~ <br />- sss <br />3~-95 :I1=19PM : <br />0 S• 303 832 8106:# 5/ 8 <br />United States Department of the Interior <br />OFFICE VF SURFACE MINING <br />Itcdauounn a~ L'ntormnlrnc <br />I `J`)'1 Brr.rd.~.2. Suirc 3330 <br />Drn.cr. (;~Lrndo 80202-5711 <br />IV RLI'LY OEYER IU <br />February 28, 1995 <br />Mrs_ Ann Tatum <br />P.O. Box 23 <br />12630 Highway 12 <br />Weston, CO 81091 <br />Dear Mrs. Tatum: <br />Enclosed are several documents we discussed relative to <br />subsidence and your home. <br />The first is a map depicting the relationship to your home and <br />well and the completed mined-out areas. This map is prepared by <br />the operator to meet the requirements of the Mine. Safety and <br />Health Administration (MSHA). This federal agency is primarily <br />concerned with the safety of underground miners. MSHA requires <br />the submittal of accurate maps of the mined-out areas as a safety <br />measure. If there would be an accident or fire underground, <br />there may be the need to access that area of the mine from the <br />surface. Therefore, MSHA requires maps to assure timely and <br />accurate access. MSHA inspectors regularly inspect underground <br />to verify the accuracy of these maps, thereby assuring miner <br />safety and mine conformance with the plans and maps. <br />It is these maps that are used by osM to check mine plan <br />compliance and, in your case, to verify extraction ratio and the <br />limits of extraction. <br />The second document included in this package is the calculation, <br />utilizing our subsidence prediction model, needed to approximate <br />a 35-degree angle of draw you suggested to me. <br />As background, predictive models are dev <br />research and actual site verification of <br />research and the field measurements have <br />physical characteristics relating to the <br />the mining plan establish the subsidence <br />angle of draw. <br />_loped from years of <br />subsidence. This <br />verified that certain <br />geology of the area and <br />pattern, including the <br />The calculations submitted with our report reflected the actual <br />conditions that existed at the mine site and are presented as <br />"input llata." These included panel width, overburden depth, <br />extraction thickness, percent hardrock in the overburden, and <br />cool extraction ratio. These five factors are those most <br />critical to the subsidence prediction. Subsidence and the angle <br />