2007-10-31_GENERAL DOCUMENTS - C1984063

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There were no detectable impacts to surface water at the Eastside Mine, as documented in the mine's annual hydrology reports from 1984 through 2002 (monitoring ceased in 2002.) This historical record and the limited runoff from the site indicates that pollution of surface water from mining at Eastside is unlikely. This conclusion is consistent with the Probable Hydrologic Consequences section of the permit application which predicted negligible impacts to surface water. Impacts to Alluvial Valley Floors (AVFs) The Alluvial Valley Floor (AVF) nearest the Eastside Mine is approximately one mile downstream from the permit area. The mine did not interrupt this AVF and has not discharged significant volumes of water to the AVF; therefore, the essential hydrologic functions of the AVF have been preserved by maintaining the geologic, hydrologic, and biologic characteristics that support those functions. Evaluation of Subsidence Impacts Subsidence monitoring had previously been conducted dating as far back to the 1980's. The applicant revised its approved subsidence monitoring program in 1995. The results of the monitoring program were submitted to the Division semi-annually. In 2000, the Division eliminated the requirement for the subsidence monitoring program, with a condition that monitoring of the subsidence monuments be conducted one final time prior to a Phase III (Final) Bond Release. This final subsidence report was submitted to the Division August 17, 2007. The final subsidence report indicates that there is no measurable indication of subsidence occurring over the underground mine workings. The report's conclusion was confirmed during the Final Bond Release inspection conducted by the Division. There have been no reports of adverse impacts from subsidence in the area undermined. Numerous aerial inspections of the site over the years have identified no adverse impacts from subsidence. No subsidence impacts were found in the former portal area during the bond release inspection. Completion of the Hydrologic Reclamation Plan All ditches, the single sedimentation pond, and all monitoring wells have been reclaimed. The only hydrologic structure remaining on the site is a portal drainpipe. Findings on Protection of Hydrologic Balance All hydrologic structures have been reclaimed (with the exception of the portal drainpipe), and there is no water pollution occurring. All of the observed hydrologic impacts are consistent with those predicted in the Division's Colorado River Cumulative Hydrologic Impact Assessment. Based on the foregoing observations, the Division finds that the Eastside Mine has minimized disturbance of the hydrologic balance in the mine plan and adjacent areas, and prevented material damage outside the permit area. The Division also finds that the Eastside Mine has not caused Eastside Mine Page 10 October 31, 2007 Phase III Bond Release