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3.2.2 Hydrologic Data <br />A. Clear Creek is the significant surface water feature within 2 miles of the proposed facility. <br />B. There are no perched zones or traditionally defined aquifers in this mountainous area. The site is <br />completely composed of crystalline Precambrian rocks, i.e. gneisses and schists, and tertiary intrusive rocks <br />such as quartz monzonites overlain by 0-24" of soil. <br />C. Ground water wells within one mile of site boundary are detailed in Appendix I, sourced from the Colorado <br />Division of Water Resources. <br />Unconsolidated materials, soils, of between 0 and 18"-24" overlay the crystalline rocks. The rocks themselves <br />have essentially no porosity or permeability. Fractures due to jointing and faulting provide the only <br />groundwater transmissivity and relative porosity. The site is underlain by numerous mine openings, the most <br />important of which is the workings of the Shafter Mine. The vein of the Shafter Mine outcrops within 100 <br />yards of the proposed disposal area, strikes N 40-60° W and dips 78-80° NW. The Shafter vein is cut by the <br />Big Five Tunnel at 4,250 feet from the portal, and at a depth of 893 feet on the dip of the vein. The mine <br />workings effectively drain the area underneath the site. Hydraulic conductivity for the undisturbed rock types <br />present at the site, in-situ before mining, ranges from 10'2 -10+2 gallons per day per square foot (as reported by <br />Freeze and Cherry (1979)) due to joints and fractures in the rock. These joints and fractures will be sealed with <br />hydraulically applied clay that is part of the waste stream. The existence of the underground mine openings <br />provide a direct hydraulic conduit for groundwater beneath the site. The Big Five tunnel, the major drainage for <br />the area, lies 1,000 feet directly below the site. The Big Five Tunnel drainage is monitored, collected, and <br />pumped to the Argo Tunnel Treatment Facility located in Idaho Springs. <br />D. According to the most current FEMA Flood Plain Map (reference FEMA Map #08019C00931) effective <br />March 19, 2007 in Appendix H) the proposed disposal site is in Zone X. <br />E. There is no surface water present directly at the site. The potential impacts to surface waters are managed <br />through the Stormwater and BMP plan as attached in Appendix D, and the structures of the Tailings <br />Impoundment Design (Appendix Q. The proposed processing of the existing waste rock dumps in the <br />Clear Creek watershed will significantly lower the potential for pollution to surface waters and <br />groundwater in the vicinity of the facility. <br />F. For existing quality of ground water beneath the proposed facility please refer to Appendix G, "Explanation <br />of Significant Differences Big Five Tunnel Discharge". The Big Five Tunnel is within the vicinity beneath <br />the proposed disposal area at a depth of approximately 1,100 feet. The condition of the existing ground <br />water (see Table 1.0 in Appendix G) is significantly worse than the mill process water (see lab analysis of <br />proposed waste stream attached in Appendix F). In the event there is infiltration into the groundwater <br />table, the quality could only significantly improve. <br />3.2.3 Engineering Data <br />1) Daily and intermediate cover: During operations the potential for windblown debris is confined to the <br />exposed face of the impoundment. Temporary cover consisting of geotextiles will be used to control <br />windblown debris from this area. The area behind the dam is inundated with water during normal <br />operations. During periods of in-activity, the potential exists for windblown debris from this portion of the <br />cell. In the event of this situation, water will be applied with sprinklers and/or the area will be covered with <br />geotextile fabric. <br />2) Liner and final cover: See 3.2.5.A Liner design components and 2.5, 3.5 Closure plan. <br />3) Maps & Plans: See Appendices A, Parcel Plat and Boundary Line Survey; and C, Tailings Impoundment <br />Design Drawings. <br />3.2.4 Construction details of monitoring points <br />Surface and ground water quality will be monitored quarterly at a well located down-gradient of the <br />impoundment as shown in the Tailings Impoundment Design, Appendix C. Section 9.5.8 describes the <br />construction specifications of these wells. <br />19