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I • Section 780.21(c) Continued. Revised 11/20/80 Based on field observations of water inflow at the existing Marr Mine active pit, it can be determined that mining to date has barely intercepted the saturated zone of the coal aquifer. No seeps or other discharge from the highwali or low-wall have been observed during operations. Therefore, no measurable dewatering of the coal aquifer has resulted from mining to date. As documented in Section 779.15, with data from exploration drilling, well monitoring, and pump test data, the coal aquifer is confined within the area to be mined. The coal aquifer is confined by shale layers above the coal seam within a syncline. An analogy of this occurrence could be a "U" shaped tube containing water. At the top of the limbs of the "U", which are equivalent to the out- crops of the coal aquifer, there is a free water surface. The water is under increasing pressure along the limbs toward the • bottom of the tube. Thus, artesian water levels can be measured just beneath the top of the tube, or just downdip from the outcrop of the coal aquifer. This condition is shown graphically on Maps 7a - 14a, Geologic Cross-Sections, in which the water levels in the coal aquifer, measured within the approximate mining limit, are shown to be artesian. Also shown are the confined layers of shale overlying the• coal seam throughout the area to be mined. The knowledge of confined, artesian aquifer conditions is used con- sistently in the following analyses of ground water inflow and drawdown. The mine plan calls for mining and contemporaneous reclamation in incremental stages in three pits from south to north. Excavation will expose the coal aquifer where it is saturated under a piezo- metric head of as much as 250 feet. The exposed portion of the coal aquifer will yield water into the active pit. The rate of dewatering through time has been estimated using the methods of 780-112 as