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natural water means that there is sufficient acid-neutralizing ions such as hydroxyl <br />(OH-) or bicarbonate (HCO3-) in solution to absorb the acidic hydrogen (H+) ions <br />produced by the pyrite oxidation. Soluble sulfate (S04_2 ) ions are also produced <br />by the pyrite oxidation, and they are quickly taken up by the calcite to produce <br />calcium sulfate or gypsum (CaSOA which is not very soluble and also <br />precipitates out of solution, especially when the pH of the solution is near normal. <br />The (CO3 -2) anion in the calcite goes in solution to replace the sulfate. Calcium <br />stays as a solid in the new gypsum produced. Overall, the net change to the water <br />quality is not significant as compared to overburden water, but some pyrite has <br />been converted to other solid compounds: gypsum and iron oxides such as <br />limonite. Strong support for this occurring is seen in the water quality comparison <br />of overburden water to spoil water. Well GW-N9 is north of the mined areas of <br />New Horizon #1 and has been unaffected by the mine since the flow gradient is to <br />the. southwest, This wall is best to use in the comparison, Spoil Snring 1 xuhich <br />developed near the southwestern end of the reclaimed mine best represents the <br />spoil water. Table 2.05.6.(3)-2 in the permit application package shows the <br />chemistry of these waters sampled at the same time. <br />If the pyrite breakdown were occurring without any neutralization, the pH of the <br />spoil water would be lower than overburden water. This has not occurred; <br />however, the replacement of sulfate ion by carbonate ion from the calcite should <br />be seen as an increased carbonate or bicarbonate in solution. This is exactly what <br />is seen between the overburden water and the spoil water for each sampling <br />period except for the August 1998 sample, which must have had outside influence <br />of surface water flows since its total dissolved solids is much less than any other <br />sample. All other ions in solution are more or less proportional to the level of <br />TDS in the sample. Bicarbonate, on the other hand, has consistently increased by <br />approximately 33%. <br />There is no significant trend in TDS differences from the overburden water to the <br />spoil water, although averaging the samples from 1995, 1996, 2000 and 2001 <br />shows a difference of 200 ppm or a 6.6% increase. Overall, water quality of the <br />spoil water may be only slightly higher in TDS than the undisturbed overburden <br />water. The quality of both waters are relatively poor. However, the spoil water <br />quality is affected to a significant degree by the time of year when irrigation is <br />occurring on the surface. Table 2.05.6.(3)-3 in the permit shows the TDS levels <br />and flow rates for various samples taken from 1987 to the present for the Spoil <br />Spring and the NPDES 001 discharge. TDS for wells GW-N9 and GW-N15, <br />which are located in undisturbed overburden, are also included in the table. <br />The monthly flows and TDS values from the NPDES 001 discharge show a direct <br />correlation between TDS and flow rate. As the flow rate gets lower, the TDS gets <br />higher. <br />It is important to understand what is truly different from the pre-mine condition to <br />the spoil condition. In the pre-mine condition, very good quality water from <br />37