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calcite in the replaced overburden. Therefore, the overall impacts to groundwater water quality <br />are the following: <br />Table 2.05.6(3)-1 <br />Water Quality Comparison -Overburden Water (GW -N9) vs. Spoil Water (Spoil Spring #1) <br />Sample <br />11/1995 <br />08/1996 <br />08/1998 <br />08/1999 <br />08/2000 <br />03/2001 <br />Date <br />Parameter <br />GW- <br />Spoil <br />GW- <br />Spoil <br />GW- <br />Spoil <br />GW- <br />Spoil <br />GW- <br />Spoil <br />GW- <br />Spoil <br />N9 <br />Spr. <br />N9 <br />Spr. <br />N9 <br />Spr. <br />N9 <br />Spr. <br />N9 <br />Spr. <br />N9 <br />Spr. <br />Sulfate <br />1,820 <br />2,020 <br />2,010 <br />2,000 <br />2,020 <br />790 <br />0 <br />Z <br />1,240 <br />1,840 <br />1,890 <br />2,200 <br />1,980 <br />Magnesium 157 222 224 220 218 102 <br />151 158 190 <br />236 <br />215 <br />Iron Total 14.8 0.06 1.64 0.09 0.74 1 1.3, <br />0.62 0.42 0.73 <br />0.27 <br />1.18 <br />Bicarbonate 292 415 323 411 330 295 <br />322 280 368 <br />302 <br />419 <br />Calcium 564 537 549 555 550 269 <br />398 555 542 <br />567 <br />541 <br />TDS 2,950 3,280 3,120 3,210 3,350 1,560 <br />2,120 1 2,740 31280 <br />1 31210 <br />3,050 <br />Flow in cfs - 0.09 - 0.17 - 0.26 <br />0.40 1 0.26 <br />1 <br />A) In the pre -mine condition, a large portion of the irrigation water runs off the surface and picks <br />up some TDS in the fields and is gathered in return ditches. In the post -mine condition, a large <br />portion of the irrigation water will infiltrate the backfill due to the increase in porosity. The TDS <br />and pH of the backfill water at the New Horizon North Mine is expected to approximate that of <br />the overburden water quality, resulting in minimal impact to the ground water quality. Water <br />movement through the spoil will be considerably faster than the movement in the overburden. <br />B) Spoil springs will be present at the SS #1 location and will discharge the majority of the <br />backfill water to the surface. This is an impact since it will decrease the recharge to the ground <br />water zones and increase flow at the existing spring; however, it will also quickly return water to <br />the San Miguel River by way of Tuttle Draw. The quality of water in Tuttle Draw is not suitable <br />for drinking water or irrigation water but is suitable for livestock and the spring water flow will <br />not change that. <br />C) Once the pyrite is oxidized and easily dissolved salts are washed out of the spoil, the water in <br />the spoil springs will gradually get lower in TDS until sometime in the distant future, the spoil <br />spring water quality will get better than the overburden quality. As dissolution of the backfill <br />continues, the backfill water will approach the irrigation water quality. Time periods for this to <br />occur are given later in this section. <br />Spoil Water Infiltration Into Backfill Any accumulated spoil water may enter one or more of <br />the minor sandstone beds of the overburden in the backfill. This annual infiltration is calculated <br />below assuming a 10' average backfill height, a hydraulic conductivity of 2.1'/day (from GW - <br />N9) and a hydraulic gradient of 0.053 (based on the water level gradients along the old Peabody <br />Highwall). <br />Section 2.05.6(3) Page 22 March 2018 (TR -16) <br />