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pumped to the surface <br />The flows are measured at the discharges by totaling flow meter readings on the dewatering sump pumps. The mean <br />flow rate did not exceed the mine inflow predictions from the Probable Hydrologic Consequences (PHC) evaluation. <br />Year four of the PHC prediction, which corresponds most closely with the 1991 mining year indicated, combined <br />inflows of 850 to 1050 gpm for the No. 5 and No. 6 Mine operations. The 1991 average discharge was 454 gpm from <br />the No. 5 Mine sump, and 219 gpm from the 7 North Angle. The combined average discharge was 673 gpm. The <br />water produced in the No. 6 Mine is pumped underground to the No. 5 Mine sump and is accounted for at [he <br />discharge from that point. <br />The low discharge from the 7 North Angle sump during the first quarter and the decline at the end of 1991 was due to <br />the failure of the pump. The discharge from this sump generally ranges from 250 to 450 gpm when the pump is <br />working. <br />A mine inflow study performed for the No. 5 Mine in 1985 is presented in Exhibit 3Q 1985 Mine Inflow Study. The <br />results of this study indicated that almost half of the inflow to the No. 5 Mine was coming from a fault zone in the 2 <br />West Main. A report on the fault zone inflows in the 2 West area is presented in Exhibit 33, a Review of the Geology <br />and Geohydrology of the 2 West area, EC No. 5 Mine. <br />Based upon the observed flows in the mine, it appears that a significant portion of the inflow is coming from <br />dewatering of the coal beds. Additional flows are coming from fault zones and from overlying and underlying zones. <br />Because water level declines are being observed in the overlying Middle Sandstone unit, it can be assumed that some <br />of the inflow [o the mines is from this unit. However, it is no[ possible [o deterntine whether the Middle Sandstone <br />water reaches the mine through existing faults, through general seepage or through subsidence induced fractures. As <br />indicated in Figure 21, in Section 2.04.7, Hydrology Information, the No. 5 Mine discharge has declined slightly since <br />1986 despite the advance of mining into the E seam associated with the No. 6 Mine. <br />The water quality data for the fault zone inflow in the No. 5 Mine presented on Table 73, Ground Water Quality - <br />Faul[ Zone, indicates that the water is of similar chemistry to the Trout Creek Sandstone. This indicates that much of <br />the inflow to the fault may be derived from the Trout Creek Sandstone. Upward flow from the Trout Creek to the E <br />coal seam could also occur if fault zones are encountered. However, as the base of the E coal seam in the vicinity of <br />both Trout Creek Sandstone wells is above the current potentiometric Level in these two weds, it is not likely that the <br />fluctuations in potentiometric levels in the Trout Creek Sandstone is related to mine dewatering in the overlying E <br />coal seam. <br />Predicted Inflows <br />Ground water inflow analyses were performed on the No. 5 Mine inflow, (EC, 1983). An additional analysis was <br />also performed on the 2 Wes[ Main inflow in the No. 5 Mine. The projected mine inflows were made assuming an <br />aggressive mining sequence in both mines with completion of all mains in the No. 5 mine in 1984. Less aggressive <br />mining sequence would produce smaller maximum inflows for the mines. This prediction was subsequently altered to <br />take into account longwall mining and the acquisition of additional land (EC, 1984). <br />Three (3) types of analysis were performed to estimate future mine inflows. These were: 1) Theim's (1906) steady <br />state well formula, 2) Jacob & Lohman's (1952) formula for non-steady flow to a well of constant drawdown, 3) <br />McWhorter's (1981) methodology for calculating inflow to mines from a coal seam. Because EC has no direct <br />measurements of the hydrologic properties of the coal, estimates have been made. Transmissivity (T} and storativity <br />(S) values for equivalent coal beds at the nearby Northem Coal Mine were obtained (refer to Table 74, Coal Bed <br />Hydrology Data -Northern Coal Company). Specific yield (Sy) was estimated to be 0.10. Although the coal <br />thickness (b) can vary, an average thickness of 12 feet was used. These values were then applied to the McWhorter <br />method and used to try to duplicate the past measured inflows in the No. 9 Mine. The values of (T') and (S) were <br />Permit Revision 04-34 2.05-37 Revised 7/2/04 <br />