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Bulldog Mine Tailings Ponds Evaluation <br />Based upon conservative assumptions regazding infiltration rates into the Upper and Lower <br />• Ponds and into the surrounding watershed azeas, the dilution of tailings pore water with ground <br />water downgradient from the tailings ponds is conservatively estimated to be at least 3:1. The <br />measured attenuation and estimated dilution would lower concentrations in tailings pore water <br />that may seep from the tailings mass, such that ground water downgradient from tailings ponds <br />would meet ground water quality standazds. If points farther downstream aze considered, the <br />additional dilution would further reduce the potential for impacts to ground water quality. <br />Based on the test results and calculations discussed above, there is very low potential for pore <br />water from the tailings in the Upper and Lower Tailings Ponds to impact ground water <br />downgradient from these sites. The four key points that support [his conclusion aze summarized <br />below. <br />1. The primary direction of pore water migration through the tailings is downwazd, and the rate <br />of migration is controlled by the rate of infiltration and the low vertical hydraulic <br />conductivity of the tailings. The flow rate of seepage from the tailings mass under these <br />controlling conditions is therefore very low. <br />2. If pore water does seep from the tailings mass, the water quality of this seepage would meet <br />ground water quality standazds, with the primary exceptions of manganese, lead, and <br />anttmony. <br />3. Manganese, lead, and antimony in tailings pore water is significantly attenuated by site <br />subsoils. <br />4. For chemical constituents in tailings pore water that aze not attenuated by site subsoils (such <br />as sulfate), significant dilution of tailings seepage with ground water is likely to occur. This <br />would reduce concentrations of constituents to values that meet ground water quality <br />standards downgradient from the tailings ponds. <br />• <br />Bomesrake .4lirring Company Shepherd h1i!lcr, /nc. <br />p: u--srlin„rnny.~~ 111 ,Jpri! M, 1997 <br />