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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 <br />provided in Section 2.04.7(1) and in Exhibit 3 of the Hamilton Mine permit application. The <br />hydrologic monitoring plan is presented on page 2.05-35, and is approved as proposed. <br />The only significant ground water in the pemut azea occurs in sandstones of the lower <br />Burro Canyon Formation. The applicant has installed 3 monitoring wells, designated BW-l, BW-2, <br />and BW-3, in this aquifer. Alluvial ground water along Naturita Creek will be monitored in four <br />wells installed by the applicant. A well has also been installed in order to monitor alluvial ground <br />water quality in Section 33 Creek. The applicant collected baseline water level and quality data, <br />and continued to sample all wells quarterly for field parameters and full-suite pazameters twice per <br />year. The Division approved a revision to halt ground and surface water monitoring until two years <br />prior to a phase 3 bond release request. <br />Upon re-commencement of the approved ground and surface water monitoring, the operator will <br />perform a spoil spring survey following snowmelt. The applicant will sample water quality for any <br />spoil aquifer spring that dischazges at least 10 gpm. A report submitted to the Division by June 15 <br />each yeaz will document the survey and report any analytical results. Details of the ground and <br />surface monitoring 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 aze based on <br />previous hydrologic analysis of the Hamilton Mine completed for Technical Revision No. 7 (TR- <br />07). That analysis included a hydrogeologic cross-section and calculation of the resaturation time <br />of Hamilton's backfill. <br />Bedrock Stratigraphic Units <br />The dry climate (]2 inches annual precipitation) and the relatively small land azea above <br />Hamilton's backfilled pit (59 acres), indicates a leachate plume will not form <br />down-gradient from the pit until several decades after reclamation activities aze complete. <br />The improbability of a plume forming until then indicates a bedrock ground water point <br />of compliance is unwarranted for the Hamilton Mine. Although a point of compliance is <br />unwarranted, well BW-2 meets the requirements of a ground water point of compliance at <br />the Hamilton Mine. Well BW-2 is located downgradient from Hamilton's backfilled pit, <br />and is close enough to the pit to intercept leachate should it discharge from the pit during <br />the bond liability period. No other bedrock unit warrants a ground water point of <br />compliance because no other units aze in hydraulic communication with the pit. <br />Alluvial Stratigraphic Units <br />Naturita Creek alluvium is located a few thousand feet downstream from the Hamilton <br />Mine. Should a spoil spring form at Hamilton Mine, it would dischazge to an ephemeral <br />drainage that flows to Naturita Creek. The review completed for TR-07 predicted an <br />4 <br />