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It is important to understand what is truly different from the pre -mine condition to the spoil <br />condition. In the pre -mine condition, very good quality water from precipitation and from the <br />irrigation ditches infiltrates through the soil and through the more permeable strata and picks up <br />dissolved solids. The water quality becomes poor (approx. 3000 ppm TDS), but this process takes <br />a very long time since the water moves very slowly through the tight strata with low hydraulic <br />permeabilitites, which 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 <br />breaks down at a faster rate but is buffered by the calcite, as described above. Therefore, the <br />overall 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 <br />picks up some TDS in the fields and is gathered in return ditches. In the post -mine <br />condition, a large portion of the irrigation water will infiltrate and recharge the spoil due <br />to the increase in porosity. The TDS of the spoil water at the New Horizon #1 Mine will <br />increase approximately 6% compared to that of the overburden water immediately after <br />re-establishment of irrigation. This is approximately 3300 ppm of TDS. Since the <br />flowpath through the New Horizon #2 spoil is greater than the New Horizon #1 spoil, the <br />expected increase in TDS for this water is 10% over background TDS in the overburden <br />water. This is approximately 3425 ppm of TDS. A potential maximum is 4000 ppm <br />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 <br />the spoil water to the surface. This is an impact since no spoil springs existed in the pre -mine <br />condition. <br />C) Once the pyrite and easily dissolved salts are washed out of the spoil, the water in both <br />spoil springs will gradually get lower in TDS until sometime many years from now, the <br />spoil spring water quality will get better than the overburden quality. At a time much <br />more distant in the future and much more difficult to calculate, the spoil water will <br />approach the irrigation water quality. Time periods for this to occur are given later in <br />this section. <br />July 2016 (TR -74) 2.05.6(3)-24 <br />