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Battle Mountain Resources <br />November I, 2000 <br />Page 5 <br />3.0 ANALYSIS OF CURRENT INFORMATION <br />The groundwater table in the West Pit backfill has been lowered to an elevation o1' approximately <br />8580 feet above mean sea level (amsl) through the implementation of the TR-26 water <br />management plan. Both water quality and water quantity data, as related to the groundwater <br />pumping from the West Pit, have been collected on a monthly basis. The available information <br />regarding the observed groundwater quality in the West Pit backfill indicated the possibility that <br />backfill Flushing might be occurring at a more rapid rate than had been previously predicted. <br />Specifically, the concentration of sulfate in West Pit groundwater has declined such that the <br />average concentration is approximately 400 mg1L. Based on the observed changes in <br />concentration, an updated analysis of backfill flushing was undertaken as described in the <br />following sub-sections of this technical memorandum. The resu]ts from the current analysis are <br />different from previous results in that the current calculations reported in this technical <br />memorandum were based solely on field information (groundwater quality and pumping volumes). <br />The field-based results are considered more representative of the actual flushing n;sponse of the <br />West Pit backfill material. <br />3.1 West Pit Hydrology <br />The previous estimates of West Pit hydrology were based, in part, on the reported amount of <br />backfill material placed in the West Pit (TR-IS Response Plan, Appendix B). An estimated <br />5,779,207 tons of material were used to backfill the West Pit. Subsequent discussions with site <br />personnel clarified that the total amount of material placed as backfill applied not on y to the West <br />Pit, but to the Pink Gneiss Pit as well. Thus, the estimated total amount of material backfilled in <br />the West Pit needs to be modified downward from the value reported in the TR-15 Iesponse Plan <br />for the calculation of the West Pit saturated pore volume. <br />As noted previously, the total amount of taterial placed as backfill in the West Pit should be <br />modified downward from the value reported in TR-26 to reflect that portion of the total that was <br />placed in the Pink Gneiss Pit The total amount of backfill material can be apporti~>ned between <br />2G3G Midponr! Dr., S'aile B, Fort Collirxc, Colorndo 80525 <br />"!'elephone (970) 4b'4-7704 /FAX (970) 484-7789 <br />