Laserfiche WebLink
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 13 <br />around the lake excavated to provide the required mitigation. Wetland plants and soil salvaged <br />from McNulty Gulch along with transplants, cuttings (for willows) and containerized nursery <br />stock will be used for revegetation. A total of 0.022 acre of shallow aquatic habitat will be <br />created, with an average water depth of 2 feet. A total of 0.044 acre of emergent wetland will be <br />created along the shallow aquatic bed, as shown on Figure 4. This emergent wetland will be <br />planted 3-foot, on-center with transplants and containerized nursery stock of wetland species. <br />The maximum depth of water in the emergent wetland will be 0.25 feet. <br />The remainder of the existing Lake Irwin area will be filled and graded to allow for placement of <br />salvaged wetland plant/soil material from the impacted wetlands in McNulty Gulch, or with other <br />salvaged soil and cuttings, transplants, and containerized plants. The remainder of the site <br />outside of the existing Lake Irwin will be over-excavated and backfilled with soil. If available, <br />salvaged wetland plants and soil from McNulty Gulch will be placed in portions of this area, and <br />the remainder of the area will be planted. A total of 36.146 acres of scrub shrub wetland will be <br />created. <br />As discussed in more detail in Section 6.5, the mitigation site will be constructed in three phases <br />cells) to provide mitigation that corresponds to timing of impacts from the OSF expansion. <br />6.2 GRADING AND EARTHWORK <br />A preliminary grading plan for the three cells of the Lake Irwin mitigation site is included in <br />Figure 5a, details are included on Figure 5b, and a cross section is shown on Figure 5c. <br />Earthwork will generally include the following: <br />Dewatering of the area by diverting clean inflows to the Eagle River watershed and <br />constructing a temporary de-watering sump adjacent to the existing pond to lower the <br />water level of the lake and underlying materials. It will be necessary to lower the lake <br />water surface as much as possible and below the new design elevation of the lake of <br />11,135 feet above mean sea level. All de-watering water will be conveyed to the <br />Tenmile TSF which is part of the Climax water management and treatment system. No <br />dewatering water will be discharged to the upper Eagle River watershed. <br />Salvaging and stockpiling the existing soil cap, as needed for later reuse.