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Bulldog Mine Tailings Ponds Evaluation <br />the site reclamation effort (Figure 5.3a). These results indicate that the majority of oxygen <br />• consumption in the neaz-surface materials of the tailings impoundment is related to organic <br />processes and that oxygen consumption due to sulfide mineral oxidation is negligible. <br />The results of the rate of oxygen consumption using the flux cells (shown in Table 5.3) validates <br />the previous conclusion. During the first few hours of the flux cell tests, the concentration of <br />oxygen within the head space of the flux cell decreased to the concentration of oxygen at the <br />bottom of the cell. After the cell reached equal values between the top and bottom of the device, <br />the percent oxygen in the pore spaces remained constant over a period of 17 hours (the limit of <br />the upper pond test) to more than 72 hours in the lower pond test. These results indicate that the <br />initial reduction of the concentration of oxygen in the head space of the flux cell was a iesult of <br />diffusion gradients within the cell, and the amount (and rate) of oxygen consumption due to <br />sulfide oxidation was immeasurable. <br />5.3 Chemical Analysis of Tailings Pore Water and SPLP Testing <br />• As mentioned in Section 3.2, two samples of tailings pore water were collected from the Upper <br />Pond during the initial drilling program. The pore water samples from the exploratory borings <br />were chemically analyzed for a complete list of analytes which are regulated by the State of <br />Colorado (shown in Table 5.3), and compazed to standazds (based on human health) summarized <br />by the Colorado Department of Health, Water Quality Control Commission (March l3, 1996). <br />In addition, SPLP tests using EPA method 1312 were conducted to determine if the tailings <br />release significant concentrations of dissolved constituents from simulated precipitation leaching. <br />The results of the chemical analyses of the Upper Pond pore waters (summarized in Table 5.4) <br />show that the average concentrations of lead (0.26 mg/L), antimony (0.04 mg/L), and thallium <br />(0.003 mg/L) in the pore waters exceed the Colorado human health standazds by an average <br />factor of 5.3, 6.7, and 1.5, respectively. Concentrations of sulfate and manganese aze also above <br />secondary state standards, and fluoride exceeded the state standard by a factor of 1.07 in one of <br />the pore water samples. The results of the SPLP tests on tailings from the Upper and Lower <br />Ponds are consistent with the results of the pore water analyses from the Upper Pond (Table 5.4); <br />• slight exceedances of the state guidelines occurred for lead in four of six tests, antimony in three <br />Hornesloke M1limng Company ShepHerd Stiller. lnc. <br />p.u--llnn„ud~.p,rv 29 April !4. 1991 <br />