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Tailings Disposal Area Geochemistry <br />Supplemental Information <br />Introduction and History <br />Abatement Items 8 and 10 of the Notice of Violation issued to Battle Mountain Resources, Inc. <br />(BMRI) in 1992 required that BMRI investigate the impact of disposal of tailings treated with <br />various detoxification methods on the long term reclamation plans for the facility tmd determine the <br />need for adjustments to the financial warranty as a result of the investigation. <br />In late 1992, BMRI began such an investigation with drilling and collection of sarc:pies from the <br />upper and lower tailings disposal areas. The drilling program included thirteen hoes, six in the <br />upper disposal area and seven in the lower disposal area. The drilling was conducted to collect <br />samples of tailings material and pore water through the tailings deposited after treartment with the <br />acidification-volatilization and recovery (AVR) system. as well as subsequent detoxification <br />systems (Cytox, hydrogen peroxide and fNCO). This investigation and subsequen: investigations <br />on the geotechnical characteristics of the deposited tailings also allowed predictior, of the <br />movement of the potential "cyanide plume" through the tailings material and an updated evaluation <br />of the long-term seepage to the collection pond. <br />The results of the drilling program and other information on tailings disposal and compaction were <br />presented in a document entitled San Luis Mine Reclamation Evaluation dated May 1993. The <br />report focused in part on geochemical evaluation of the tailings collected through the drilling <br />program. The results indicated that the tailings had not undergone a significant ge~xhemical <br />change rendering [hem either acid generating or capable of leaching potentially hasnnful quantities <br />of metals or other constituents as a result of the addition of any of the detoxification chemicals. In <br />addition, the tests indicated that there were no significant quantities of cyanide pre:>ent in the pore <br />waters of any portion of the disposed tailings. That information combined with they geotechnical <br />information on the permeability of the tailings and results of an evaluation of the draindown of the <br />tailings over time allowed BtvlRl to reach the following conclusions in the Reclamation Evaluation. <br />'...none of the comprehensive information gathered for the evaluation indicated that the <br />characterization of the tailings material as non-toxic and chemically inert is inappropriate. In <br />addition, the assumptions of long-term tailings geochemistry, consolidations and underdrain <br />performance which were utilized to develop the approved reclamation plan have not changed as a <br />result of the changes in tailings detoxification." <br />The Division had some questions about the report and these were forwarded to BN(RI. Comments <br />from other interested parties were also forwarded to BMRI. A meeting was held to discuss the <br />comments and at that time BMRI indicated that they were going to drill several additional holes to <br />verify that cyanide was indeed not present in pore water at depth in the tailings fac.lity. BMRI <br />indicated that they would also run geochemical analyses on the new samples to verify that the new <br />samples were similar to the previous information presented in the Reclamation Evaluation. <br />On October 1, 1993, BMRI submitted detailed responses to the Division's concerns: on the <br />Reclamation Evaluation report and indicated that the additional holes had been drilled and data was <br />