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Post Mining Discharge-No. 9 Mine <br />• The "P'~ seam was mined from the No. 9 Mine from March 1978 to August 1981. The mine was driven northward in <br />a downdip direction. The approximate elevation of the bottom of the No. 9 mine portal was 6,305 ft.. and present <br />ground surface is approximately 6,350 ft. No significant full-extraction mining was performed in the mine. <br />The water level in the Twentymile Sandstone is estimated to be approximately 6.260 ft. at the point which has the <br />highest piezometric level in the Twentymile Sandstone anywhere it underlies the No. 9 Mine. This estimation is <br />based upon the water level contour map for water levels measured in November 1995 (1995 Annual Hydrology <br />Report, Permit C-81-044, Figure 12). The Twentymile Sandstone underlies the "P" seam by approximately 350 ft. <br />The historic water levels in the Twentymile Sandstone have alparently not been effected by the mining in the area as <br />they have been constant since 1981 (ibid., Figure ]0) indicating that there is not a good connection between the <br />aquifer and the mine. Also, [he mine was driven in adown-gradient direction so a]] ofthe workings are in lower head <br />areas than the portal. <br />The maximum piezometric level of the White Sandstone is estimated to be approximately 6,300 feet where it overlies <br />a location in the No. 9 Mine where measurable flow was encountered. This is based on the mine inflow study (Eagle <br />No. 9 Mine Inflow Study, Map N-l la, 5/8/83) and the December 1985 water level measurements (1985 Annual <br />Hydrology Report, Perini[ C-81-044, Figure 17). In addition, the maximum projected piezometric level of the White <br />Sandstone where it overlies any portion of No. 9 Mine is less than 6,320 feet, however, this is at the White <br /> <br />• <br />~f,~33 <br />Midterm Response 2.05-46.1 ~~;~~,Ll~•,>>;,~+^, i';;,~ ~_ ~ L'uJ2 7/30/01 <br />