2016-10-28_PERMIT FILE - C2010089A (27)

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measurements from 1987 through 2000 and likewise reported, (see Table 2.05.6(3)-4 of the New Horizon #2 Area permit), as taken at surface water site SW -N3. Table 2.05.6(3)-2b included in Appendix 2.05.6(3)-2 shows this information for these as well as other sample points. Table 2.05.6(3)-2 shows the predicted impact of the NHN backfill spring discharge on the receiving waters of Tuttle Draw. During the irrigation season, the predicted TDS for Tuttle Draw is an increase of about 9 mg/1 or about 0.5%. During the non -irrigation season the predicted TDS for Tuttle Draw is an increase of 26 mg/1 or about 1.2%. The spoil water inflows from NHN Mine will influence the quality of Tuttle Draw to a minor degree. However, within about 2 miles, this flow enters the San Miguel River where the flow is so much larger than the Tuttle Draw flow that the impact is negligible. Further, the water in Tuttle Draw is too high in dissolved solids for domestic drinking water or for use in irrigation without treatment. Also, these impacts are for the time when the spoil material is leaching salts at a maximum. As described earlier, the TDS levels will drop over time as pyrite is oxidized and other salts are leached out of the spoil which will lessen the impact to the waters downstream over time. Six months prior to NHN Mine startup, monitoring of Spoil Spring #1, 001 discharge site, and SW -N3 (on Tuttle Draw) will be resumed if at that time it has been suspended. The approved "hydrologic monitoring plan" is described in Appendix 2.05.6(3)-3 at the end of this section. Impacts to receiving Waters — Meehan Draw The Meehan Draw barrier pillar will serve as a dam of sorts (see discussion on "Spoil Water Infiltration Into Low Wall" on page 23 above and Figure 2.05.6(3)-1) for water in the backfill of the reclaimed pit. It is anticipated that water accumulating behind the low wall will eventually issue as a "spoil spring", (Spoil Spring #4 (projected)). Based on the structure contour map (see Map 2.04.6-1 in Section 2.04.6), the overburden depth, and the topography the expected location of this spring is in the vicinity of NW 1/, SW 1/, NW 1/ of Section 25, T. 17 N., R. 16 W., (see SS #4 Map 2.04.7-1 in Section 2.04.7). There are two basic differences in the spoil water that will eventually issue from Spoil Spring #4 (SS#4): • The area north of Meehan Draw will be reclaimed as "dry land pasture" and will not be affected by the percolation of irrigation water. Therefore, water entering the pit will be the result of seepage from the bedrock zones (due to the low annual precipitation and high evaporation rate very little precipitation remains for percolation). • The quality of the water in the bedrock zones in the area north of Meehan Draw is lower in TDS (see groundwater monitoring data in Appendix 2.04.7-1 of this application) than the area north of the old highwall. Section 2.05.6(3) Page 26 April 2016 (PR -01)