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BulGloq Mine Tailings Ponds Evaluation <br />6.0 CONCLUSIONS <br />• Based on the results of the geotechnical and geochemical tailings evaluation presented in this <br />report, there is very low potential for tailings seepage from the Upper and Lower Tailings Ponds <br />to impact ground water downgradient from these sites. This conclusion is based on the <br />combination of flow and geochemical and geotechnical chazacteristics of the Bulldog tailings and <br />underlying subsoils, as outlined below. <br />6.1 Physical Conditions <br />Drilling, sampling, and geochemical laboratory testing indicate that the tailings in both the Upper <br />and Lower Ponds aze saturated. Although the tailings aze still consolidating, the volume of pore <br />water expelled during remaining consolidation is expected to be relatively small and would occur <br />at a very slow rate. The primary direction of pore water migration in both the Upper and Lower <br />Ponds should be downwazd due to the vertical gradients for flow and infiltration of precipitation <br />into the top surface of the ponds. The flow rate of seepage from the tailings mass under these <br />controlling conditions would be very low. <br />u <br />6.2 Acid Generation Potential <br />The geochemical test results show that sulfides aze present in the tailings. However, pore water <br />chemistry, mineralogic evidence, and oxygen consumption/profile measurements all indicate that <br />sulfides have been stable since their deposition in the impoundments. The low vertical hydraulic <br />conductivity relative to the estimated infiltration into the tailings indicates that the tailings will <br />remain saturated or nearly saturated in the future. Future oxidation of the tailings is not likely <br />given the evidence for future saturated or neaz saturated conditions. <br />6.3 Tailings Pore Water and Leachate Chemistry <br />Analysis of tailings pore water and batch leach test extract samples show that these fluids meet <br />ground water quality standards for all pazameters except manganese, lead, and antimony. <br />• <br />Nomesrake Mirtrng Company Shepherd Ari(ler. /nc. <br />o~~rrsrne.rctx..rr 49 Aprif 1J, 1997 <br />