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Bicarbonate/Sulfate <br />As noted in previous annual hydrology reports, upstream of the mine on Trout Creek, bicarbonate (Figure 10) is the <br />major anion with sulfate (Figure II) concentrations increasing rapidly along the mine area to become predominating <br />downstream (Figure 12). The sulfate levels increase is most markedly noticed prior to the peak flow period of Trout Creek <br />and adjacent to where mining activity took place, as are TDS levels in general. This increase is probably caused by early <br />runoff a[ the mine site leaching pyritic and organic sulfur as flow passes over and through the spoils. Since the flow of Trout <br />Creek is low at that time, the amount of sulfur is sufficient to cause an ionic shift from a bicarbonate type water [o a sulfate <br />type. During periods of higher flow and late in [he season when runoff from the mine is small relative to total Trout Creek <br />flow, the sulfate component is less able to shift the anion balance to a sulfate type with concentrations of bicarbonate and <br />sulfate being approximately equal downstream. <br />The 2000-2002 trend shows that the topological change generally still occurs at TR-B. This is believed to be the <br />result of the spoil spring, which has developed at the base of [he West Ridge mining area. As reclamation of West Ridge <br />matures, the high levels of sulfur exhibited in [he spring are anticipated to decrease. The 2000-2002 trend showing peak <br />sulfate levels at TR-C and TR-D are expected to continue For some time as spoil springs in the Moffat area have deve]oped <br />after the completion of mining in [ha[ area. Like [he West Ridge area the sulfate sources within [he Moffat area are <br />anticipated to diminish as vegetation establishes and matures. <br />While peak levels of individual constituents may be shifting as flow proceeds past the mine, they do not seem to be <br />increasing overall. It is believed that an equalization in the sulfate-bicarbonate balance or a reversal (similar to the balance at <br />TR-A) occurs downstream as the source of available sulfate (mining areas) is unavailable and dilution by runoff from <br />undisturbed areas is introduced. <br />Manganese <br />Manganese (Figure 13) shows fairly consistent values since 1989. All the manganese values observed are consistent <br />with the baseline values. Manganese values from 1992 through 2002 appear to be developing a Vend, which may be directly <br />related to flow in Trout Creek as are the TDS concentrations. <br />14 <br />