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• Bicarbonate/Sulfate As noted in previous annual hydrology reports, upstream of the mine on Trout Creek, bicarbonate (Figure 10) is the major anion with sulfate (Figure 11) concentrations increasing rapidly along the mine area to become predominating downstream (Figure 12). The sulfate levels increase is most markedly noticed prior to the peat flow period of Trout Creek and adjacent to where mining activity took place, as are TDS levels in general. This increase is probably caused by early runoff at the mine site leaching pyritic and organic sulfur as flow passes over and through the spoils. Since the flow of Trout Creek is low at that time, the amount of sulfur .s sufficient to cause an ionic shift from a bicarbonate type water to a sulfate type. During periods of higher flow and late in the season when runoff from the mine is small relative to total Trout Creek flow, the sulfate component is less able to shift the anion balance to a sulfa*_e type with concentrations of bicarbonate and sulfate being approximately equal downstream. The 1995-1997 trend shows that the topological change generally still occurs at TR-B. This is believed to be the result of the spoil spring which has developed at the base of the West Ridge mining area. As reclamation of West Ridge matures, the high levels of sulfur exhibited in the spring are anticipated to decrease. The 1995-1997 trend showing peak sulfate levels at TR-C and TR-D are expected to continue for some time as spoil springs in the Moffat area have developed after the • completion of mining in that area. Like the West Ridge area the sulfate sources within the Moffat area are anticipated to diminish as vegetation establishes and matures. While peak levels of individual constituents may be shifting as flow proceeds past the mine, they do not seem to be increasing overall and it is believed that an equalization in the sulfate-bicarbonate balance or a reversal (similar to the balance at TR-A) occurs downstream as the source of available sulfate (mining areas) is unavailable and dilution by runoff from undisturbed areas is introduced. Manganese Manganese (Figure 13) shows fairly consistent values since 1988. All the manganese values observed are consistent with the baseline values. The relatively high values of manganese observed at TR-C (0.13 mg/1) and TR-D (0.16 mg/1) during May of 1988 did not appear to be related to mining activity as an elevated concentration was not observed at TR-B (0.09 mg/1) which was immediately downstream of the active mining area. Manganese values from 1992 through 1997 appear to be developing a trend which may be directly related to flow in Trout Creek as are the TDS concentrations. • 15