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for several years at a CDPS outfall in the Oak Creek drainage located at the outlet of the <br />farthest downstream Tipple Pond (CDPS outfall 001). There were no exceedences of <br />discharge limitations at outfall 001 for the 5 years immediately prior to removal of the <br />Tipple Ponds in 2004. Discharge limitations for outfall 001 were based on which chemical <br />constituents were likely to be present in discharge effluent, and did not include all of the <br />constituents for which there are instream standards in Oak Creek. It is unlikely, however, <br />that the influent would have contained these other constituents in significant amounts; <br />therefore, it is reasonable to conclude that operations in the bond release are in compliance <br />with the instream standards. Monitoring data in the Edna Mine's annual hydrology report <br />for outfall 001 prior to 2004 indicate the mine has not caused exceedences of either <br />limitation identified in 40 CFR Part 434 that is applicable to reclamation areas on coal <br />mines (settleable solids of 0.5 ml/1 and pH of 6.0 to 9.0). <br />Imbacts to Alluvial Vallev Floors (AVFs) <br />Surface runoff from the eastern side of the Edna Mine flows to Oak Creek. This stream does <br />not meet the regulatory definition of an Alluvial Valley Floor (AVF) within the permit area. <br />Oak Creek has, however, been designated an AVF immediately north of the permit area, <br />approximately one mile downstream from the bond release area. Mining operations at the <br />Edna Mine did not disturb the alluvium of the Oak Creek AVF. The previously described <br />absence of adverse hydrologic impacts to Oak Creek surface water and alluvium indicate the <br />essential hydrologic functions have been preserved by maintaining the geologic, hydrologic, <br />and biologic characteristics that support those functions. <br />Agreement of observed hydrologic impacts with "Probable hydrologic consequences" <br />(PHC) Projected in mining permit <br />The Probable Hydrologic Consequences (PHC) section of the Edna Mine permit application <br />predicts minimal impacts to bedrock and alluvial ground water. As described above in the <br />discussion of ground water and surface water impacts, no significant impacts from mining <br />have been found in ground water or surface water. <br />Findings on Protection of Hydrologic Balance <br />The observed hydrologic impacts at the Edna Mine are consistent with those predicted in the <br />Probable Hydrologic Consequences (PHC) section of the permit application and the <br />Division's Yampa River Cumulative Hydrologic Impact Assessment. Water pollution is not <br />occurring at the Edna Mine in the bond release area, and there is no potential for future water <br />pollution in this area. Aquifer recharge has not been diminished (infiltration of meteoric <br />waters into the ground surface has not been reduced), and the permittee has not caused <br />adverse impacts to ground water that impair the postmining land use. Based on the foregoing <br />observations regarding hydrologic impacts, the Division finds the operator of the Edna Mine <br />has minimized disturbance of the hydrologic balance in the mine plan and adjacent areas of <br />the bond release area, and prevented material damage outside the permit area. <br />Edna Mine Page 10 December 11, 2009 <br />Phase I, II, and III Bond Release