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Hydrologic Balance - Ground Water <br />Information on the occurrence and quality of ground water in the permit and surrounding area is provided <br />in Section 2.04.7(1) and in Exhibit 3 of the Hamilton Mine permit application. The hydrologic monitoring <br />plan is presented on page 2.05 -35, and is approved as proposed. <br />The only significant ground water in the permit area occurs in sandstones of the lower Burro Canyon <br />Formation. The applicant has installed 3 monitoring wells, designated BW -1, BW -2, and BW -3, in this <br />aquifer. Alluvial ground water along Naturita Creek will be monitored in four wells installed by the <br />applicant. A well has also been installed in order to monitor alluvial ground water quality in Section 33 <br />Creek. The applicant collected baseline water level and quality data, and continued to sample all wells in <br />accordance with the approved monitoring plan in section 2.05 of the permit until 1998. In July of 2009 the <br />Division approved a revision to halt ground and surface water monitoring until two years prior to a Phase <br />III bond release request. However, the monitoring plan was subsequently modified through MR -12 and <br />the operator committed to reinitiating surface and groundwater monitoring for one year prior to Phase III <br />bond release. <br />Upon re- commencement of the approved ground and surface water monitoring, the operator will perform a <br />spoil spring survey following snowmelt. The applicant will sample water quality for any spoil aquifer <br />spring that discharges at least 10 gpm. A report submitted to the Division by June 15 each year will <br />document the survey and report any analytical results. Details of the ground and surface monitoring <br />sampling scheduled and parameters can be found in the permit. <br />Ground Water Points of Compliance <br />The following comments concerning bedrock and alluvial stratigraphic units are based on previous <br />hydrologic analysis of the Hamilton Mine completed for Technical Revision No. 7 (TR -07). That <br />analysis included a hydrogeologic cross section and calculation of the restoration time of Hamilton's <br />backfill. <br />The dry climate (12 inches annual precipitation) and the relatively small land area above <br />Hamilton' s backfilled pit (59 acres), indicates a leachate plume will not form down - gradient <br />from the pit until several decades after reclamation activities are complete. The improbability <br />of a plume forming until then indicates a bedrock ground water point of compliance is <br />unwarranted for the Hamilton Mine. Although a point of compliance is unwarranted, well <br />BW -2 meets the requirements of a ground water point of compliance at the Hamilton Mine. <br />Well BW -2 is located downgradient from Hamilton' s backfilled pit, and is close enough to the <br />pit to intercept leachate should it discharge from the pit during the bond liability period. No <br />other bedrock unit warrants a ground water point of compliance because no other units are in <br />hydraulic communication with the pit. <br />Naturita Creek alluvium is located a few thousand feet downstream from the Hamilton Mine. <br />Should a spoil spring form at Hamilton Mine, it would discharge to an ephemeral drainage that <br />flows to Naturita Creek. The review completed for TR -07 predicted an 11 -gpm spoil spring to <br />April 3, 2012 <br />RN4 <br />Bedrock Stratigraphic Units <br />Alluvial Stratigraphic Units <br />6 <br />