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• Minimizine Subsidence <br />In order to minimize the possibility of subsidence in areas where creeks, pipelines, or other <br />permanent structures overlay the mine the extraction ratio is lowered to less than 50 %. This has <br />specifically been the case underneath the Palisade Water Lines Ute Water Line,, and,Cottonwood, <br />Rapid, Jerry and Coal Creeks. h1 azeas where more~sfabihty is needed-by structures, a block of c al <br />is le$~xnderrieath tfie st cfu~re to further mimmize the possibility of subsidence. Current_plans and <br />this <br />Conclusion <br />To comply with Stipulation 12 of the Mining and Reclamation Permit C - 81 - 041, two <br />regular inspections were conducted during the 1995 year. Two azeas were located during inspections <br />in 1994 and two areas were located this year with cracks that might be the result of underground <br />mining. Surface cracks found during these inspections were measured and located on the attached <br />map. Due to the 70 - 75% extraction in much of the RSS mining area, subsidence has occurred and <br />is expected to occur in the future. The 34 - 49% extraction for the majority of the RSN has not <br />shown and is not expected to show subsidence affects over the currently developed area. The 49% <br />. maximum extraction projected for mined azeas this next year is not expected to show subsidence <br />affects in the future. Observations made of subsided areas has not indicated any destructive or <br />dangerous affects. The cracks found aze no more dangerous than the normal hazards of steep terrain <br />and cliffs already common to the area. Also due to the high relief of the surface, azeas lowered by <br />subsidence will not create depressions or other obvious surface affects. There has been no evidence <br />that the 50% maximum extraction under the creeks is not adequate. Limited extraction practices <br />under the creeks and pipelines will continue. This was the first yeaz for surveys at the RSN and the <br />creeks were the only structures or features which will need special protection. <br />• Page 4 <br />