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Sulfate/Bicarbonate 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 peak flow period of Trout Creek and adjacent to mining activity, 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 unreclaimed spoils. Since the flow of Trout 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 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 sulfate type with concentrations of bicarbonate and sulfate being approximately equal downstream. As mining activities have shifted from West Ridge to Moffat, the 1993- 1995 trend shows that the topological change generally still occurs at TR-H. • This is believed to be the result of the spoil spring which has developed at the base of the West Ridge mining area. As further reclamation activities continue in West Ridge, the spring exhibiting the high levels of sulfur is anticipated to decrease in flow. Once the hydrologic reconstruction plan is completed and vegetation is completely reestablished, the majority of excess runoff not used by the reestablished vegetation will be diverted along the reconstructed surface drainage system rather than being allowed to pass through the regraded spoils as is currently the case. The 1993-1995 trend showing peak sulfate levels at TR-C and TR-D are expected to continue for the duration of mining in the Moffat Area While peak levels of individual constituents may be proceeds past the mine, they do not seem to be increasing believed that an equalization in the sulfate-bicarbonate (similar to the balance at TR-A) occurs downstream as the sulfate (active mining areas) is unavailable and dilution undisturbed areas is introduced. shifting as flow overall and it is valance or a reversal source of available by runoff from Manganese • Manganese (Figure 13) shows fairly consistent values since 1986. All the manganese values observed are consistent with the baseline values. The 16