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load to Trout Creek water. The increase in sulfate concentration between these two <br />locations is usually more than 50 %, sometimes resulting in the sulfate concentration in <br />Trout Creek exceeding the secondary drinking water standard of 250 mg /l, although this <br />standard is not applicable to this segment of Trout Creek. <br />The CDPS and DRMS sample data from the Edna Mine 2002 through 2008 support a <br />finding that the mine is not causing exceedances of the instream standards. <br />Permit Requirements of Colorado Discharge Permit System (CDPS) <br />As previously mentioned, Chevron Mining Inc. has sampled discharges from two outfalls in <br />the Trout Creek drainage that are monitored under the Colorado Discharge Permit System <br />(CDPS). Sample data has been collected for the following eight parameters: pH, total <br />suspended solids, settleable solids, total recoverable iron, potentially dissolved manganese, <br />oil and grease, flow, and total dissolved solids. Sample analysis has included testing for <br />Whole Effluent Toxicity. Sample data has been reported monthly in discharge monitoring <br />reports filed with the Colorado Water Quality Control Division and DRMS. The reports <br />indicate that for the time period January 2002 through June 2009, the only exceedances of <br />CDPS permit requirements were one exceedance at one outfall in 2008 and one exceedance <br />at two outfalls in 2008 of the flow limitation established in 2007. There were no <br />exceedences of CDPS permit requirements in 2007 or in 2009. <br />Clean Water Act Effluent Limitations (40 CFR Part 434) <br />Monitoring data in the Edna Mine's annual hydrology reports from 2002 through 2008 <br />indicate the mine has not caused exceedances of either limitation identified in 40 CFR Part <br />434 that is applicable to reclamation areas on coal mines (settleable solids of 0.5 ml /l and <br />pH of 6.0 to 9.0). <br />Impacts to Alluvial Valley Floors (AVFs) <br />The Trout Creek Alluvial Valley Floor is located approximately two miles downstream <br />from the western part of the Edna Mine. Monitoring data in the Edna Mine's annual <br />hydrology reports from 2002 through 2008 indicate the mine has not caused exceedances of <br />the 1000 µmhos /cm level that DRMS considers to be a potential material damage threshold <br />for irrigation water in the Trout Creek AVF during irrigation season (June through <br />September). <br />Agreement of observed hydrologic impacts with "probable hydrologic consequences" <br />WHO protected in mining permit <br />The Probable Hydrologic Consequences section of the Edna Mine permit ( "the PHC") <br />predicts minimal impacts to bedrock and alluvial ground water. As described above in the <br />discussion of ground water impacts, no significant impacts from mining have been found in <br />bedrock or alluvial ground water. <br />Edna Mine Page 24 April 12, 2013 <br />Phase II. and III Bond Release <br />