2016-01-07_PERMIT FILE - C2010089A (11)

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over time. Six months prior to NI -IN 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 1/4, SW 1/4, NW 1/4 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. Unlike SS #1, SS #4 does not have an existing analogy to draw on or that has been previously monitored and therefore flow and quality must be projected. The expected highwall seepage rate is calculated by Q = (K, ft/day)(area, ft2)(gradient)(365days)/43,560ft3 to get acre -ft per year. Hydraulic conductivity or K is different for each of the bed rock zones: OB = 2. 1, Coal = 0. 19, and UB = 1.61, (see Tables 7-5 and 7-6 in Appendix 2.04.7-2 this application). Height of each of the bedrock zones is also different: OB = 20.3 ft. during irrigation season and 14 ft during non - irrigation season; Coal 6.Oft.; and UB 5.Oft. Gradient is estimated from the draw down (cone of depression) around the old Peabody highwall at 0.053. The maximum highwall length from the north and east high walls is 4005 ft. During irrigation season (165 days) it is projected that maximum seepage into the pit will be: OB = 34.3 ac -re; Coal = 1.07 ac -ft; and UB = 7.77 ac -ft for a total of 43.14 ac -ft, or about 59 gpm. During non -irrigation season (200 days) it is projected that maximum seepage into the pit will be: OB = 28.7; Coal = 1.29; and UB = 9.41 for a total of 39.4 ac -ft or about 44.6 gpm. This is a total of about 82.6 ac -ft per year, not all of which will accumulate to issue as a spoil spring. As noted above (see discussion of seepage into "low wall" Section 2.05.6(3) Page 29 Sept. 2015 (TR -11)