2010-07-27_PERMIT FILE - M2009076 (12)

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• American and Edgar) is cut by the 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 workings effectively drain the area underneath the site. Refer to USGS Bulletin 1208, Plate 3, Geologic Section Along the Big Five Tunnel Idaho Springs District Colorado at the end of this Exhibit C. Another example supporting this is the Colorado School of Mines Edgar Mine Facility (approx. 350' south of the proposed Tailings Impoundment). After a meeting with them on August 31, 2009, it was learned that their mine is "dry". So "dry" in fact that they are working on permitting a well on premises to supply a marginal water supply for drilling operations to keep the dust down. The starting elevation of their well is 7,793' and the borehole was drilled to-254'. Water was determined at -172'. This elevation, 7,621', just so happens to match the Big 5 Tunnel elevation. Safe to say another example of the drainage in this area. A copy of this well log is attached in the appendix of this Exhibit C. Hydraulic conductivity for the undisturbed rock types present at the site, in-situ before mining, ranges from 10"2 - 10+2 gallons per day per square foot (as reported by Freeze and Cherry (1979)) due to joints and fractures in the rock. The existence of the underground mine workings provide a direct hydraulic conduit for groundwater beneath the site. The Big Five tunnel, the major drainage for the area, lies 1,000 feet directly below the site. The Big Five Tunnel drainage is monitored, collected, and pumped to the Argo Tunnel Treatment Facility located in Idaho Springs. It produces on average, 35 gallons per minute. According to the most current FEMA :Flood Plain Map (reference FEMA Map #08019C0093D effective March 19, 2007) the proposed disposal site is in Zone X. Zone X is defined as follows: Areas of 0.2% of annual chance flood; areas of 1.0% annual chance flood with average depths of less than. 1 foot or with drainage areas of less than 1 square mile; and areas protected by levees from 1% annual chance flood. There is no surface water present directly at the site. The potential impacts to surface waters are managed through • the Stormwater and BMP plan described above (attached in this appendix), and the structures of the Tailings Impoundment Design (Exhibit E). The proposed processing of the existing waste rock dumps in the Clear Creek watershed will significant) lower the potential for pollution to surface waters and groundwater in the vicinity of the facili . For existing quality of ground water beneath the proposed facility please refer to "Explanation of Significant Differences Big Five Tunnel Discharge", attached at the end of this Exhibit C. The Big Five Tunnel is within the vicinity beneath the proposed disposal area at a depth of approximately 1,100 feet. The condition of the existing ground water (Table 1.0 in this reference) is significantly worse than the mill process water (see lab analysis of proposed waste stream attached). In the event there is infiltration into the groundwater table the net quality could only significantly improve. Despite this, however, the DRMS has determined that practice based ground water protection be applied to this operation through the implementation of a composite liner system. Numeric protection limits will not be applicable. 6.3.3(1)(j) Ground water quality will be indirectly monitored, on a quarterly basis, at a well located both up- and down-gradient of the impoundment as shown in the Tailings Impoundment Design, Exhibit E. The down-gradient monitoring well actually is in place to detect any leaks or seepages from the Tailings Impoundment liner. These wells were installed at a depth of 20' (twenty feet) into solid bedrock. The wells were drilled at 2.375" diameter and cased with nominal 2" perforated HDPE plastic pipe to allow for any leakage and/or seepage to be measured and/or collected. The pipe was grouted at the ground surface interface to prevent surface water inclusion. A lockable cap has been installed. There was no groundwater detected at the time of installation. See the figure that follows for an illustrative schematic of this installation: Page 6 of 35