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IRIS <br />MITIGATION AND DESIGN, INC. <br />SCHWARTZWALDER MINE PHASE 1 - UPSTREAM CUTOFF WALL AND LOW FLOW BYPASS <br />PIPELINE - BIOLOGICAL ASSESSMENT <br />The majority of PMJM riparian habitat impact will occur down - gradient of the cutoff wall. This section of <br />Ralston Creek was previously disturbed due to mining activities. The proposed low flow bypass <br />pipeline will begin as a buried pipeline due to elevation constraints, will daylight on the south side of the <br />creek, and will follow the existing unpaved road through the Site to re- connect with Ralston Creek east <br />of the Site (see Figure 3). The majority of impacts from the proposed low flow bypass pipeline, <br />construction equipment and materials staging and access will be to previously heavily disturbed upland <br />areas that are not considered PMJM upland habitat (see Figures 2 and 3). <br />2.2.1 Anticipated Steps <br />Phase 1 construction is proposed to start November 2011 and will be completed in three to four <br />months. The sequence of major activities associated with Phase 1 includes: <br />• Establish stabilized staging areas for Phase 1. Multiple staging areas are anticipated for this <br />Project. <br />• Move equipment and materials into the staging areas. <br />• Blade and gravel the access road from the staging areas to the work area associated with the <br />cutoff wall. <br />• Install a coffer dam upstream of the cutoff wall location to temporarily dewater the area for <br />construction of the cutoff wall. <br />• Establish a relatively small work area near the coffer dam. Most equipment and materials will be <br />stored in the stabilized staging areas; however, construction materials that are actively being <br />used may be stored temporarily near the cutoff wall work area. <br />• Commence construction dewatering of the upstream cutoff via alluvial wells. <br />• Install perimeter best management practices (BMPs) down - gradient of areas anticipated to be <br />disturbed during cutoff wall installation. Perimeter BMPs will include a combination of silt fence, <br />sediment control logs, and a rock check dam. <br />• Clear and grub the area where the cutoff wall will be constructed. <br />• Excavate the cutoff wall foundation, dewatering as needed. <br />Page 6 August 2011 <br />