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Bulldog Mine Tailings Ponds Evaluation <br />During the tests the initial manganese concentrations decreased by greater than 97%, final lead <br />• concentrations were reduced between 75% and 97% from the starting water concentration, and <br />antimony concentrations were lowered between 47% and 76% of the initial concentration. <br />Sulfate was relatively unattenuated in the tests with concentrations decreasing between 2.4% and <br />7.4% below the starting concentration <br />The highest percent removal of lead, manganese, and antimony occurred in Lower Pond <br />Sediment Sample LPSS-I. As described above, this sample is aniron-stained, medium to coazse <br />grained sand with minor amounts of organic and clay materials (compared to the other samples). <br />The iron staining on Sediment Sample LPSS-1 is most likely composed of iron oxyhydroxides. <br />These minerals aze known to effectively adsorb metals on their surfaces (Benjamin and Leckie, <br />1980; McKenzie, 1980). The fact that this sample removed the most metals implies that metal <br />attenuation in soils and sediments in the vicinity of tailings impoundments would primarily result <br />from adsorption onto iron and manganese oxyhydroxides. <br />The blank control sample used in the tests indicate that some sorption of manganese and lead <br />• occurred on the glass walls and rubber stopper of the Erlenmeyer flask and that some antimony <br />may have been released to solution from the test vessel during the test. Alternatively, there may <br />have been a significant component of analytical noise in the measurement of the low <br />concentrations of these components that is not related to the [es[ methods. The two Upper Pond <br />Sediment Sample-1 vessels had significantly different concentrations of manganese and lead at <br />the end of the test, showing variability within individual sedimenUsoil samples. However, these <br />variations in analysis results are significantly smaller than the measured decrease in <br />concentration between the starting fluid and the attenuated fluid for lead, manganese, and <br />antimony. <br />5.4.4 Attenuation Test Interpretation <br />The results of the attenuation tests indicate that a significant proportion of the constituents of <br />concern would be attenuated by Creede Formation materials below the tailings impoundments. <br />Assuming that detectable levels of manganese, lead, and antimony were to reach ground water, <br />however, the rate of movement of these constituents relative to the rate of ground water <br />H°mestake ,Mining Company Slrrplrerd 11rller. Inc. <br />P,r-~rnm~umx w~ J4 dprrl !{. 1997 <br />