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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 />some portion of this upland area will likely not be impacted due to steeper grades in many of these <br />locations. <br />The remaining area of temporary habitat impact during cutoff wall installation activities includes 0.1 <br />acre of temporary impact to undisturbed riparian and 0.12 acre of temporary impact to previously <br />disturbed riparian areas (see Figures 7 and 8 and Table 8). Approximately 0.1 acre of undisturbed <br />riparian area is located between 50 to 100 feet upstream of the cutoff wall (see Figure 8). This area <br />will be impacted due to the 50 -foot width of trench needed west of the upstream cutoff and additional <br />area needed for dewatering activities such as coffer dam placement and pumping. This area also <br />allows for an additional 20 feet for construction access around the upstream portion of the Site. <br />The 0.12 acre of previously disturbed riparian area is located directly upstream and downstream of the <br />existing road crossing (see Figures 7 and 8 and Table 8). This section of Ralston Creek downstream <br />of the road crossing was altered during historic mining activities such that the riparian area appears to <br />be more narrow and linear than the original creek alignment. This approximately 0.12 acre of <br />previously disturbed riparian area will be temporarily impacted due to trench excavation, installation of <br />required BMPs, construction access, and the location of the construction dewatering discharge point <br />for the flexible pipe. Temporarily impacted sections of riparian area will be regraded and seeded; <br />however, they will be mitigated at the end of the overall Project due to the likelihood of these areas <br />being disturbed again during Phases 2 or 3 of the Project. <br />.5.3 Permanent Impacts <br />Permanent habitat impacts due to cutoff wall installation will total 0.22 acre (see Figures 7 and 8 and <br />Table 8). The 0.22 acre of permanent impacts will occur to previously disturbed PMJM riparian and <br />previously disturbed PMJM upland habitat. <br />There will be approximately 0.08 acre of permanent disturbance to previously disturbed PMJM upland <br />habitat (see Figures 7 and 8 and Table 8). This impact will be mainly due to regrading of these upland <br />areas to slope down into Ralston Creek. The purpose of the sloping will be in the event that flows in <br />Ralston Creek overtop the cutoff wall as weir flow across the reconstructed unpaved access road. The <br />sloped uplands will assist in directing water back into the creek to the east of the crossing. These <br />permanently impacted upland areas may also have cobbles or gravel installed for further armoring. <br />The upland road crossing itself will be armored with grouted boulders, as will the graded upland which <br />directs flows down into the creek over a boulder drop structure and energy dissipater. Loose riprap will <br />transition the grouted boulder area back down into the creek. <br />Page 29 August 2011 <br />