2009-09-25_PERMIT FILE - M2009076 (22)

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• 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. r ? L J 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, 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 significantly lower the potential for pollution to surface waters and groundwater in the vicinity of the facility. 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 sienificantly improve. n _...:. rV ...J;....,.e t ;.,,+, no-A nn Aietnrir Rr (`nrrPnt Ria 5 Timnel Dkeharoe* Metal Limit, Ug/l micro iter Limit mg/l milli ams/liter Justification Arsenic, As 10 0.01 Historic Big 5 Barium, Ba 2000 2 Domestic Water Std. Cadmium, Cd 48 0.048 Historic Big 5 Chromium, Cr 100 0.1 Domestic Water Std. Copper, Cu 2960 2.96 Historic Big 5 Lead, Pb 91 0.091 Historic Big 5 Manganese, Mn 32,200 32.2 Historic Big 5 Mercury, H 2 0.002 Domestic Water Std. Selenium, Se 50 0.05 Domestic Water Std. Silver, A 50 0.05 Domestic Water Std. Zinc, Zn 9770 9.77 Historic Big 5 *Note: It is necessary to apply a dilution factor of l:s to iau analysis or pilot piam sampim ?n urutx w wnv,um u.v data to proposed Mobile Mill operations. Refer to the explanation in the attached Waste Stream Characterization. See 6.3.3(2)(b) for a detailed explanation of Points of Compliance. 6.3.3(1)(1) Ground water quality will be monitored quarterly at a well located both up- and down-gradient of the impoundment as shown in the Tailings Impoundment Design, Exhibit E. A monitoring well has been installed up-gradient and down-gradient of the impoundment. 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 recharge 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. The EPA currently is doing extensive monitoring of ground water sources (as stated earlier, The Big Five Tunnel drainage is monitored, collected, and pumped to the Argo Tunnel Treatment Facility located in Idaho Springs). As a part of normal mill operations, mill process water will be continuously monitored. A pH monitor and data recorder will be installed at the tailings pump location within the mill. Should the pH reach a state outside of the 7.5-9 range that is necessary to precipitate the heavy metals, alarm notification will be activated for the operations personnel. The submittal notes on this Serfilco Model 432 monitor/recorder can be found attached in this Exhibit C. If the pH falls outside of the 7.5-9 range, the operators are instructed to shut down the operation that delivers waste to the impoundment. Once the source of the problem is corrected upstream in the process, waste can then be • continued to be discharged to the impoundment.