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• Bicarbonate/Sulfate <br />As noted in previous annual hydrology reports, upstream of the mine on Trout <br />Creek, bicarbonate (Figure 10) is the major anion with sulfate (Figure 11) <br />concentrations increasing rapidly along the mine area to become predominating <br />downstream (Figure 12). The sulfate levels increase is most markedly noticed prior <br />to the peak flow period of Trout Creek and adjacent to where mining activity took <br />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 <br />through the spoils. Since the flow of Trout Creek is low at that time, the amount <br />of sulfur is sufficient to cause an ionic shift from a bicarbonate type water to a <br />sulfate type. During periods of higher flow and late in the season when runoff from <br />the mine is small relative to total Trout Creek flow, the sulfate component is less <br />able to shift the anion balance to a sulfate type with concentrations of bicarbonate <br />and sulfate being approximately equal downstream. <br />The 1996-1998 trend shows that the topological change generally still occurs <br />at TR-B. This is believed to be the result of the spoil spring which has developed <br />at the base of the West Ridge mining area. As reclamation of West Ridge matures, <br />the high levels of sulfur exhibited in the spring are anticipated to decrease. The <br />1996-1998 trend showing peak sulfate levels at TR-C and TR-D are expected to <br />continue for some time as spoil springs in the Moffat area have developed after the <br />• completion of mining in that area. Like the West Ridge area the sulfate sources <br />within the Moffat area are anticipated to diminish as vegetation establishes and <br />matures. <br />While peak levels of individual constituents may be shifting as flow proceeds <br />past the mine, they do not seem to be increasing overall and it is believed that an <br />equalization in the sulfate-bicarbonate balance or a reversal (similar to the <br />balance at TR-A) occurs downstream as the source of available sulfate (mining areas) <br />is unavailable and dilution by runoff from undisturbed areas is introduced. <br />Manganese <br />Manganese (Figure 13) shows fairly consistent values since 1988. All the <br />manganese values observed are consistent with the baseline values. Manganese values <br />from 1992 through 1996 appear to be developing a trend which may be directly related <br />to flow in Trout Creek as are the TDS concentrations. <br /> <br />15 <br />