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using the sulfide mass to be mined and the results of the sulfide oxidation <br />quantity and rate testing. <br />Comprehensive direct testing of the neutralization of actual leachate from sulfide <br />oxidation of the mined overburden with actual carbonate materials present in the <br />diatreme and other neutralizing agents, which produced the result that at neutral <br />pH, leachate quality is essentially identical to water quality exiting the Carlton <br />'t'unnel water quality. <br />Comprehensive evaluation of the abundance of carbonate materials in the <br />diatremal rockmass, producing the result that the carbonate present in the <br />diatremal rocks above the Carlton Tunnel level is more than 300 times greater <br />than the amount of carbonate required to neutralize all acidity that is potentially <br />produced by oxidation of sulfide in the mined overburden. <br />Detailed evaluation of the flow system that transports water and dissolved <br />constituents from the mined overburden to the regional ground water table <br />intersected by the Carlton Tunnel to demonstrate that there is a high probability <br />that there will be both time and opportunity for any acidic leachate water to be <br />neutralized by contact with the abundant carbonates in the rockmass prior to <br />arrival at the Carlton Tunnel. <br />Based on this evaluation CC&V concluded that the quality of the regional ground water <br />table intersected by the Carlton Tunnel will not deteriorate due to the proposed surface <br />mining activities, and that acid water will not occur at the Carlton Tunnel portal as a <br />result of the mining proposed in the MLE application. <br />This conclusion is supported by the history of the quality of flow from the Carlton <br />Tunnel. The tunnel caused denaturation of a significant portion of the diatreme, <br />beginning in 1941. Since that time, essentially all the material in the top 3,000 feet of the <br />diatremal rocks have been exposed to oxygen, particularly those portions of the rock in <br />and near underground workings. The sulfide in this rockmass has been progressively <br />oxidizing, producing acid rock drainage and carbon dioxide. It is not known how much <br />sulfide oxidation has occurred, but all the acid produced from sulfide oxidation in the <br />district has been neutralized by in-situ carbonate. No acid water has been identified at the <br />Carlton Tunnel portal in more than 1,100 samples taken over 20 years of monitoring, <br />typically at least monthly. The lowest pI-I ever recorded is 7.16 s.u., and the median p1l <br />is 7.83 s.u. The minimum alkalinity ever recorded was 160 mg/L, and the median <br />alkalinity is 260 mg/L. <br />DBMS states that a long-term groundwater monitoring program for the diatremal water <br />might be necessary. CC&V has responsibility for monitoring the quality of water that <br />exits the Carlton Tunnel portal under Colorado Discharge Permit System Permit Number <br />CO-0024562. In addition, CC&V has an extensive ground water monitoring plan for the <br />entire facility since 1994 and beyond, and to date the numeric protection levels set by the <br />DBMS at those sites has not been exceeded at any of those sites. Moreover, CC&V's <br />proposed continuation of mining under the MLE application is no different than that <br />reviewed and approved for the Cresson Project under prior application submittals; thus, <br />CC&V disagrees that some form of long term monitoring is needed. <br />VI M.: For the reasons stated in the Division's response to VIA above, it remains to be seen whether <br />the entire inventory of carbonate minerals in the diatreme will be available to infiltrating leas{late. If the <br />fi acture-flow scenario plays out to the worst case, then elevated concentrations of sulfate, zinc and other <br />constituents could be sustained. For that reason, long-terns water quality monitoring will be needed to <br />ensure that waste rock infiltration is indeed neutralized by the diatreme carbonates. <br />CC&V Response: