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infiltrating into the spoil at the upper end of the New Horizon #1 spoil may only spend 15-45 <br />days in the spoil before the water is discharged at the spring. Yet, during this short time, it has <br />managed to become approximately the same quality as the overburden water. Due to the <br />increased porosity and higher level of oxygen in the rapidly infiltrating water, the pyrite breaks <br />down at a faster rate but this reaction is buffered by both the higher pH of the water and the <br />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- Spoil <br />GW- <br />Spoil <br />GW- Spoil <br />GW- <br />Spoil <br />GW- Spoil <br />GW- <br />Spoil <br />N9 Spr. <br />N9 <br />Spr. <br />N9 Spr. <br />N9 <br />Spr. <br />N9 Spr. <br />N9 <br />Spr. <br />Sulfate <br />1820 2020 <br />2010 <br />2000 <br />2020 790 <br />1240 <br />1840 1890 <br />2200 <br />1980 <br />Magnesium <br />157 222 <br />224 <br />220 <br />218 102 <br />151 <br />158 190 <br />236 <br />215 <br />b <br />Q <br />0 <br />Z <br />Iron Total <br />14.8 0.06 <br />1.64 <br />0.09 <br />0.74 1.3 <br />0.62 <br />0.42 0.73 <br />0.27 <br />1.18 <br />Bicarbonate <br />292 1 415 <br />323 <br />1 411 <br />330 295 <br />322 <br />280 368 <br />302 <br />419 <br />Calcium <br />564 537 <br />549 <br />555 <br />550 269 <br />398 <br />555 542 <br />567 <br />541 <br />TDS <br />2950 3280 <br />3120 <br />1 3210 <br />3350 1560 <br />2120 <br />2740 3280 <br />3210 <br />3050 <br />Flow in cfs <br />- 0.09 <br />- <br />0.17 <br />- 0.26 <br />0.40 <br />- 0.26 <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 />Section 2.05.6(3) Page 22 April 2016 (PR -01) <br />