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Final Compensatory Mitigation and Monitoring Plan—Version 2.0 <br />Climax Mine Overburden Storage Facility Expansion (SPK-2013-00045) <br />March 2017 Bikis Water Consultants, a division of SGM Page 11 <br />typically around 10 acres. There is no defined outlet for the lake and the inflow is balanced by <br />infiltration into the subsurface and evaporation. Wetland plants have naturally invaded parts of <br />the shoreline of the lake that is adjacent to the natural hillside. Figure 3 shows the existing <br />conditions at the Lake Irwin area. Photographs of Lake Irwin are included in Appendix B. <br />5.2.1 Water Sources <br />Lake Irwin is fed by three perennial, intermittent drainages and several perennial seeps and <br />springs located at the base of Sheep Mountain. A water availability study was completed by <br />Tetra Tech to determine how much water is available at Lake Irwin to ensure sufficient water for <br />the created wetlands. A copy of this study is included in Appendix C. <br />Presently, water in two of the drainages, referred to as the West Drainage and East Drainage <br />No. 1 (Figure 3), mostly flows into a roadside ditch and south towards the Eagle River basin. As <br />discussed in Section 6.4, improvements will be made to more effectively route water to the Lake <br />Irwin mitigation site. <br />Based on the Tetra Tech water availability study, it is estimated that Lake Irwin could receive <br />around 315 acre-feet (AF) of water per year, with most of this (266 to 277 AF) during the <br />growing season. This amount of water equates to approximately 8 feet per acre, which is ample <br />to sustain the proposed wetland mitigation. <br />Climax has sampled surface water quality of two of the inflows to the lake and the lake itself <br />several times. The results of the water quality sampling show that the water quality in Lake Irwin <br />is very similar to that of the inflows. The water at all three locations is predominantly <br />calcium/magnesium and bicarbonate/carbonate water with pH of 7.5 to 8.3 standard units, which <br />indicates no problem with acidity. No parameters were found at levels of concern for use for <br />wetlands creation. These results would be expected given the relatively large amount of water <br />contributed to the lake from natural surface water sources. <br />5.2.2 Soils <br />To assess the soil and sub-soil conditions at the Lake Irwin site, Climax retained Habitat <br />Management, Inc. (HMI) to complete a soil investigation of the area in the fall of 2014. <br />Additional test pits were logged and sampled by Climax in the summer of 2016. At each