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Overburden and Wadge Coal aquifer characteristics used in the McWhorter analysis are <br />summarized in Table 17-1. These data are discussed in the "Site Specific Aquifer - <br />Characteristics" section of Tab 7. Geometric mean values for hydraulic conductivity and <br />transmissivity are used, and hydraulic gradient values were determined from mine plan maps <br />with superimposed po tentiometric surface contours. Overburden aquifer tests provide a <br />_y _7 <br />range of stora tivity values of 10 to 10 which are quite low for an unconfined aquifer. <br />_p <br />Therefore, a sto rativity value of 10 is used for the overburden pit inflow analyses <br />which will provide more liberal (i.e., higher) estimates of pit inflows. Since Wadge Coal <br />aquifer tests did not yield stora tivity values, storativity for this aquifer is estimated <br />_p <br />to be 10 <br />Estimates of the overburden and Wadge Coal ground water inflow are presented in Tables <br />17-2 and 17-3. These estimates were prepared assuming that the total inflow would be <br />derived from two principal sources: 1) the interception of premi ning flow rates under a <br />natural hydraulic gradient; and 2) the drainage of ground water from storage in the <br />aquifers. The following is a list of assumptions made in using the McWhorter pit inflow <br />analysis technique. <br /> • <br />1. Mining intercepts the saturated portion of the pit at the start of each year. <br />2. The length of pit opened on a daily basis is equivalent to the total pit length <br />divided by the number of days required to open the pit. <br />3. Each daily pit increment is instantaneously opened. <br />4. Total pit inflow per year is equal to the sum of incremented daily inflows for that <br />year. <br />5. Pit inflows for each year are independent of residual effects from preceding years. <br />The method therefore tends to overestimate the amount of water coming into the pit. <br />6. Hydraulic conductivity, storage coefficient, and depth of saturation are constant for <br />each mine pit for each year. <br />7. Pit inflow is from two sides for the first year and from one side for all remaining <br />years (i.e., there is no additional flow from the reclaimed spoils). <br />8. Natural - gradient flow is over the entire saturated length of the pit, no <br />corrections are made for the orientation of the pit in relation to the gradient <br />direction; hence, the saturated pit length is assumed to be perpendicular to the <br />gradient direction. <br />9. Natural gradient flux is unaffected by reclaimed spoils from the preceding year. <br />2 <br />