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with particular emphasis on areas mined order low overburden. <br />• No visual indications of subsidence were noted during surveying or <br />hydrology monitoring efforts during the 1990 calendar year. <br />Projected Subsidence Impacts 1991 <br />S~bsidenoe i~acts during 1991 are projected to be minimal bard upon <br />subsidence patterns established to date. Mining during 1991 will be <br />primarily located in panels A and A+. Cevelopment and retreat mining is <br />scheduled to occur in these areas. Additional development mining will <br />occur in the II West SUbmains as work to access the west thick coal pod is <br />initiated.. None of the areas scheduled to be mined during :1991 are <br />significantly different from areas previously mined in terms o:E depth, <br />topography, or mining technique and should not, therefore, exhibit <br />significantly different subsidence effects. <br />Projected Subsidence Monitoring 1991 <br />In the 1983 subsidence survey conducted by Geo-Hydro Consulting Inc., <br />predictions as to the nature and extent of subsidence in the area were <br />• formulated. 'Ihe subsidence survey called for subsidence monitoring to be <br />conducted to verify the predictions contained therein. A conservative <br />angle of draw was estimated to be 21 degrees and maximum elevation <br />adjustments of approximately 7 feet were anticipated. <br />A subsidence control plan was developed, submitted, and approved based <br />upon the projection of worst case impacts stemming from the aforementioned <br />subsidence developments. All survey data gathered to date support the <br />conservative nature of the initial predictions for both draw angles and <br />subsidence magnitudes. Survey data has consistently shown that subsidence <br />magnitudes are in fact nn~ch less than predicted and that draw angles may <br />be more typically on the older of 16 degrees although a draw angle of as <br />high as 20 degrees was calculated in the 1986 analysis. <br />Cyprus orchard Valley Coal Corporation believes that adequate sutsidence <br />data has been collected to show that the initial predictions are <br />reasonably conservative. ~VCC hereby requests the Colorado Mined Iand <br />Reclamation Division to consider the discontinuation of the surveying <br />aspect of the subsidence monitoring program. COVCC believes that <br />continuation of the visual monitoring and subsidence repair progru~s will <br />adequately protect any structures, roads, or renewable resources <br />potentially impacted by the mining operation. <br />C~ <br />9 <br />