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• Post-MiningDischazge-No.9Mine The "P" seam was mined from the No. 9 Mine from August 1988 to March 1985. The mine was driven northward in a downdip direction. The approximate elevation of the bottom of the No. 9 mine portal was 6,305 ft., and present ground surface is approximately 6,350 ft. No significant full-extraction mining was performed in the mine. The water level in the Twentymile Sandstone is estimated to be approximately 6,260 ft., at the point which has the highest piezometric level in the Twentymile Sandstone anywhere it underlies the No. 9 Mine. This estimation is based upon the water level contour map for water levels measure in November 1995 & (1995 Annual Hydrology Report, Permit C-81-044, Figure l2). The Twentymile Sandstone underlies the "P" seam by approximately 350 ft. The historic water levels in the Twentymile Sandstone have apparently not bee effected by the mining in the area as they have been constant since 1981 (ibid., Figure 10) indicating that there is not a good connection between the aquifer and the mine. Also, the mine was driven in adown-gradient direction so all of the workings are in lower head areas than the portal. The maximum piezometric level of the White Sandstone is estimated to be approximately 6,300 feet where it overlies a location in the No. 9 Mine where measurable flow was encountered. This is based on the mine inflow study (Eagle No. 9 Mine [nFlow Study, Map IV-lla, 5/8/83) and the December 1985 water level measurements (1985 Annual Hydrology Report, Permit C 81-044, Figure 17). In addition, the maximum projected piezometric level of the White Sandstone where it overlies any portion of No. 9 Mine is less than 6,320 feet; however, this is at the White Sandstone's outcrop area where it is probably not saturated. The White Sandstone overlies the mine by approximately 125 feet and outcro0ps approximately 1,000 feet north of the portal. The historic water levels in the • White Sandstone were probably no effected by the mining (1985 Annual Hydrology Report, Permit C-81-044, Figures l2 -14. Indicating that there is not a good connection between the aquifer and the mine. Also, the mine was driven in adown-gradient direction so all of the workings are in lower head areas than the portal. The vertical groundwater gradient, based upon a comparison of the piezometric surfaces in the overlying and underlying sandstones, indicates that it is downward in the No. 9 Mine area. Even if there is a good connection between either aquifer, and the mine, the downward gradient indicates that the mine would not fill to the surface. Instead, it would refill to an equilibrium level that would be between the levels of the two aquifers. None of the historic underground mines in the area are known to discharge. This includes the Wisehill No. 4, which had opening in a "bottom area" and was filled with discharge the No. 5 Mine. It discharged when water from the No. 5 Mine was injected; however, when injection stopped, it ceases to discharge. • The piezometric surface in the aquifer below the mined seam is lower than the portal elevation • The piezometric suface in the aquifer above the mined seam is lower than the ground surface at the portal site • Where there was measured inflow to the No. 9 Mine, the highest piezometric head in the overlying aquifer was lower than the portal elevation • The vertical component of the gradient in the area is downward • The mine was driven in a down-dip and down-gradient directions • The mine portal is located at the crop line. • There are no historic springs in the area • None of the historic underground mines in the area are know to discharge, and the No. 9 Mine portal is at a higher elevation than any of the old mines. Effect of Seepage from No. 9 Portal Backfill Permit Renewal No. 3 2.05-29 7/15/98