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It is important to understand what is truly different from the pre -mine condition to the spoil condition. <br />In the pre -mine condition, very good quality water from precipitation and from the irrigation ditches <br />infiltrates through the soil and through the more permeable strata and picks up dissolved solids. <br />The water quality becomes poor (approx. 3000 ppm TDS), but this process takes a very long time <br />since the water moves very slowly through the tight strata with low hydraulic permeabilitites, which <br />are in the range of 3.5 to 5.5 ft/day. <br />In the case of the spoil, the hydraulic permeability is increased to 40 ft/day and much more <br />irrigation water is recharged rapidly through the permeable, broken spoil material. This good quality <br />water picks up dissolved solids as in the case of the overburden, it simply does it much more <br />rapidly. Water infiltrating into the spoil at the upper end of the New Horizon #1 spoil may only spend <br />15 -45 days in the spoil before the water is discharged at the spring. Yet, during this short time, it <br />has managed to become approximately the same quality as the overburden water. The average <br />TDS of the irrigation ditch water is only 100 to 280 ppm. Due to the increased porosity and higher <br />level of oxygen in the rapidly infiltrating precipitation water and irrigation water, the pyrite breaks <br />down at a faster rate but is buffered by the calcite, as described above. Therefore, the overall <br />impacts to water quality are the following: <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 and recharge the spoil due to the increase in porosity. <br />The TDS of the spoil water at the New Horizon #1 Mine will increase approximately 6% compared <br />to that of the overburden water immediately after re- establishment of irrigation. This is <br />approximately 3300 ppm of TDS. Since the flowpath through the New Horizon #2 spoil is greater <br />than the New Horizon #1 spoil, the expected increase in TDS for this water is 10% over background <br />TDS in the overburden water. This is approximately 3425 ppm of TDS. A potential maximum is <br />4000 ppm TDS. Water movement through the spoil will also be considerably faster than the <br />movement in the overburden. <br />B) Spoil springs will be present at both reclaimed mine areas which discharge the majority of the <br />spoil water to the surface. This is an impact since no spoil springs existed in the pre -mine condition. <br />C) Once the pyrite and easily dissolved salts are washed out of the spoil, the water in both spoil <br />springs will gradually get lower in TDS until some time many years from now, the spoil spring water <br />quality will get better than the overburden quality. At a time much more distant in the future and <br />much more difficult to calculate, the spoil water will approach the irrigation water quality. Time <br />periods for this to occur are given later in this section. <br />REVISED August 2010 2.05.6(3) -31 <br />