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• The EPA currently is doing extensive monitoring of ground water sources (as stated earlier, The Big Five Tunnel <br />drainage is monitored, collected, and pumped to the Argo Tunnel Treatment Facility located in Idaho Springs). <br />Proposed Point of Compliance: <br />For pre-existing, baseline quality of ground water beneath the proposed facility please refer to "Explanation of <br />Significant Differences Big Five Tunnel Discharge", attached at the end of this Exhibit C. The Big Five Tunnel is <br />within the vicinity beneath the proposed disposal area at a depth of approximately 1,100 feet. The condition of the <br />existing ground water (Table 1.0 in this publication) is significantly worse than the mill process water (see lab <br />analysis of proposed waste stream attached). <br />TABLE 1.0 ANALYTICAL SUMMARY TABLE BIG FIVE DISCHARGE SAMPLES <br />Metals concendrations expressed in ndamgramslLiter <br />Sampling Event As Cd Cu Hg Mn Pb Zn <br />1985 Phase i RI 10 48 1710 NAF 19,700 91 9770 <br />1989 Phase U RI 10 27 690 NAF 181800 S 9100 <br />2001 CDPHE NAF 24 1500 NAF 32,200 NAF 9160 <br />2005UOSn' 2 20 2%0 0.1 191500 16 7610 <br />State Drinking Water MCL <br />State Drialdn Water MCLG 10 <br />- 5 - <br />1300 2 <br />- <br />15 - <br />- <br />State Secondary MCL <br />A F_ Life NEC/W <br />S - <br />OAl3 100 <br />517 - <br />0.01 50 <br />1OW493 - <br />UZ S00 <br />47/200 <br />NAF m Not Analyzed For <br />MCL - Maximum Contaminant Level <br />MCLG - Maximum Contaminant Level Goal <br />NEC - No Effect Concentrations are metal concentrations at which aquatic life does not suffer any toxic effects <br />(1) UOS - START contractor for EPA's Emergeaey Response Team <br />(2) WQCD - aquatic standards for Clear Cheek Segment 2 <br />In the event there is infiltration into the groundwater table the net uuality could only significantly improve. <br />A current sampling of the Big 5 Tunnel discharge also follows in this Exhibit C. <br />This sampling was done over a period of time from 1985 - 2009. It becomes apparent that the reported metals <br />concentration varies widely. Rationale for this can be explained by variation in rainfall amounts preceding the <br />sampling and the concentration of that rainfall in different areas of differing mineralization. This wide variability <br />can not be attributed to active mining operations because we are not aware of any within this drainage area over this <br />period of time. <br />13