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<br />-4- <br />The total area of disturbance of Mine l/1 and Eckman Park is approximately 4000 <br />acres, (some of this includes prior disturbance due to previous mining). <br />Assuming an annual percipitation rate of 16 inches per year and that 25 <br />percent of this precipitation will infiLtra[e into the overburden, the <br />postmining recharge rate should be 1330 acre-feet per year or 190,000 gpd/sq. <br />mi.. This increased rate of recharge will enable rapid recovery of the <br />piezometric surface. I[ should be noted that post-mining infiltration may <br />decrease for a period of time however infiltration should approximate <br />pre-mining conditions. <br />The average permeability of the undisturbed overburden aquifer as determined <br />by pumping tests is 2.9 gpd /ft.2. The total recharge area of boxcut highwall <br />is 1,060,000 ft.2. The boxcut highwall is that porion of the mine farthest <br />down gradient where the spoil abuses against the undisturbed overburden <br />aquifer. Recharge to the overburden aquifer should therefore be <br />3,074,000 gallons per day or z potential of 3,450 ac-ftivr. not accounting for <br />water contributed by present recharge area. When accounting for the quantity <br />of water contributed by the present recharge area these values only increase <br />by 2 percent. The means that the intact portion of overburden aquifer along <br />the boxcut highwall.in Eckman Park mine area can transmit more water in to the <br />ground water basin than the increased recharge capacity resulting from mining <br />can supply. This is significant in orrlnr ro demonstrate that the mine spoil <br />will not become satur ed and cause s n develo alon the toe of <br />t poi . <br />Because the recharge area affected by the mine comprises only 5 percent of the <br />area of the ground water basin, the increased recharge capacity is expected to <br />leave no significant impact on water quantity in the ground water basin. <br />In order to address the effects of the leaching of soluble ions from the spoil <br />and the transport of those ions into the waters of the ground water basin, EFC <br />cooperated with Dr. Herber[ Gardner on his research on the leaching of <br />overburden material. Seventeen leaching tests were performed. The summation <br />of these tests are described in table 103. From this data, a leaching rate <br />was determined in order to access the time required to leach the soluble salts <br />from [he spoil and thereby bring the ground water quality parameters back to <br />baseline conditions. Based on this study, the recharge capacity of the spoil, <br />and volume of spoil, it was determined that the ground water will return to <br />baseline conditions approximately 74 years after reclamation has taken place. <br />Because of the long time until baseline ground water quality conditions are <br />again attained in the affected area the applicant has undertaken an analysis <br />of solute transport since the increased ionic concentration of these waters <br />will potentially affect the entire ground water basin. This could occur <br />because a plume of relatively saline water will emanate from the mine plan <br />area through the overburden aquifer. Dilution will occur as the salt plume <br />spreads away from the mine plan area. In order [o quantify at what point [he <br />increased salt load will be indis[inguisable from baseline conditions. Frieds <br />two-demensional solute dispersion equation was used. This equation yields [he <br />solute concentrations above the baseline level at a point some distance from <br />