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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 11) concentrations increasing rapidly along the mine azea 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 at 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 to a sulfate <br />type. During periods of higher flow and late in the 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 2002-2004 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 [he base of the West Ridge mining area. As reclamation of West Ridge <br />matures, the high levels of sulfur exhibited in the spring are anticipated to decrease. The 2002-2004 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 developed <br />after the completion of mining in that area. Like the West Ridge area the sulfate sources within the 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 1995 through 2004 appear to be developing a trend, which may be directly <br />related to flow in Trout Creek as are the TDS concentrations. <br />14 <br />