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RULE 2 - PERMITS <br />mine will be into the mine. The only anticipated effect during mining will be in the undisturbed <br />• bedrock between the spoils aquifer and the mine workings, because groundwater from the spoils <br />aquifer will flow through that area into the mine workings, displacing the native groundwater. <br />Consequently, the groundwater in that area will take on the quality of the spoils aquifer <br />groundwater. <br />Inflow to the mine from the spoils aquifer will occur in the portal area through any saturated, <br />exposed, spoils and bedrock units in the unmined area between the spoils and the PSCM workings. <br />In the mine workings away from the portal area, inflow to the mine will be primarily through the <br />coal. Consequently, the chemical quality of the groundwater entering the mine will be a mixture of <br />the qualities of all the source waters. The rate of inflow to the mine workings from the spoils aquifer <br />can be estimated using the following equation (Freeze and Cherry, 1979): <br />Q =T•I•W <br />where: Q = volumetric flow rate <br />T = transmissivity <br />I = hydraulic gradient <br />W = width of aquifer for which the flow is calculated <br />Flow from the spoils aquifer to the PSCM workings would occur through the Wadge coal and <br />overburden where both units are exposed in the portal area. For the portal area calculation, the <br />combined transmissivity (T) for these two units applies to the calculation and ranges from is 0.01 <br />ft /d (0.006 ft /d for the Wadge coal plus 0.005 ft /d for the overburden) to 4.2 (0.026 ft /d for the <br />Wadge coal plus 4.2 ft'` /d for the overburden). The hydraulic gradient (I) is the head difference <br />between the spoils aquifer water table and the base of the Wadge coal divided by the horizontal <br />distance between the spoils aquifer and the PSCM workings. For the portal area, the head difference <br />from the spoils to the workings (based on spoils well water level elevations, spoils springs <br />elevations, and Wadge coal elevations) ranges from about 2 to 60 feet (averaging about 35 feet), <br />and the horizontal distance, from the spoils to the workings ranges from about 10 to 150 feet <br />(averaging about 100 feet). The average hydraulic gradient is about 0.35. The width of aquifer (W) <br />through which flow would occur is the saturated, exposed east side of the portal area, about 200 <br />feet. Thus, the flow from the spoils to the north main part of the mine workings is: <br />Q =T •I •W <br />= (0.01 to 4.2 ft'/d) • ( 0.35) - ( 200 ft) <br />= 0.7 to 294 ft /d <br />= 0.004 to 1.5 gpm <br />Flow from the spoils aquifer to the PSCM workings would occur through the Wadge coal away <br />from the portal area. This area includes the easternmost mine workings south of the portal area, <br />which will be opened during the first 13 months of mining. For this calculation, the Wadge coal <br />transmissivity (T) applies to the calculation; it ranges from 0.006 ft` /d to 0.026 ft /d. In this area, <br />both the head difference and the distance from the Seneca II Mine spoils aquifer start at about 200 <br />• feet and increase to the south. The distance to the Seneca II Mine spoils from the mine opening <br />increases to 6,000 feet at the southern -most extent of the eastern mine opening. The head difference <br />between the spoils and the mine workings increases steadily also, from about 200 feet to about 650 <br />PSCM Permit App. 2.05 -80 Revision 03/05/10 <br />