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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 permit area occurs in sandstones of the lower <br />Burro Canyon Formation. The applicant has installed 3 monitoring wells, designated BW-1, 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 parameters twice per <br />year, until a Division approved revision to halt ground and surface water monitoring until two years <br />prior to a phase 3 bond release request. <br />Upon re-commencemnt of the approved ground and surface water monitoring, the applicant will <br />perform a spoil spring survey following snowmelt. The applicant will sample water quality for any <br />spoil aquifer spring that discharges at least 10 gpm. A. report submitted to the Division by June 15 <br />each year 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 are based on <br />previous hydrologic analysis of the Hamilton Mine completed for TR-7. That analysis included a <br />hydrogeologic cross-section and calculation of the resaturation time of Hamilton's backfill. <br />Bedrock stratigraphic units <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 <br />down-gradient from the pit until several decades after reclamation activities are 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. Designation of BW-2 as a compliance point at this time would, <br />however, be preliminary because the Division has not yet finalized its guidelines for <br />establishing ground water points of compliance. Well BW-2 is located downgradient <br />from Hamilton's backfilled pit, and is close enough to the pit to intercept leachate should <br />it discharge from the pit during the bond liability period. No other bedrock unit warrants a <br />ground water point of compliance because no other units are in hydraulic communication <br />with the pit. <br />Alluvial stratigraphic units <br />Naturita Creek alluvium is located a few thousand feet downstream from the Hamilton <br />4