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Bu!ldoR Mine Tailings Ponds Eva[uanal Geochemical testing included: (1) acid base accounting analyses and mineralogic analyses of • tailings solids, (2) chemical analysis of tailings pore water, and (3) attenuation testing using tailings pore water and soils from the tailings pond areas. Geotechnical testing included: (1) consolidation tests (2) permeability tests, and (3) index property tests (including moisture content, density, specific gravity, Atterberg limits, and sieve analyses). The geotechnical test results indicate that the tailings in both ponds aze saturated or nearly saturated and aze still consolidating. Based on these conditions, the volume of pore water produced from remaining consolidation is expected to be small and will occur at a very slow rate. Although the primary direction of pore water migration through the tailings in both the Upper and Lower Ponds is downwazd, the low vertical hydraulic conductivity of the tailings indicates that the rate of migration is very low and saturated conditions will be maintained within the tailings mass. The results of chemical analyses conducted on two tailings pore water and six batch leach test extract samples indicate that concentrations aze slightly above ground water quality standards for • manganese (in four of eight samples), lead (in six of eight samples), and antimony (in five of eight samples). Minor exceedances of ground water quality were also measured for fluoride, sulfate and thallium (in one or two of the eight samples). Cyanide (as weak-acid dissociable cyanide) was not detected in any tailings pore water or leachate samples, indicating that the degradation of residual cyanide related to the milling operations is complete. Acid base accounting and mineralogic analyses show the tailings are composed of 1 - 2% sulfide minerals. However, the pore water chemistry, mineralogic evaluations, and oxygen consumption/ profile measurements indicate that the sulfides have been chemically stable since their deposition in the impoundments. The low vertical hydraulic conductivity relative to the estimated infiltration into the tailings indicates that the tailings will remain saturated or nearly saturated in the future. Therefore, future oxidation of sulfides is not likely. Attenuation testing using tailings pore water and site soils shows that these materials have high retardation capacities for manganese, lead, and antimony, and that these constituents would be significantly immobilized . by sorption if tailings pore water was to seep from the tailings mass. H°mesrake Mmmg Company ShrpLrrd ,46ller. /nc. pVf-llnbu!l~.ry, it .-Ipril lJ. l99"