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• Moffat area mining activities and, as such, the pattern is anticipated to continue. <br />However, since this occurrence existed prior to the initiation of Moffat mining <br />activity, the trend may also suggest that inflow from undisturbed areas upstream and <br />downstream of TR-C contains approximately the same concentrations of these <br />parameters as runoff from the mine. <br />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 mining activity, as are TDS <br />levels in general. This increase is probably caused by early runoff at the mine <br />site leaching pyritic and organic sulfur as flow passes over and through the spoils. <br />Since the flow of Trout Creek is low at that time, the amount of sulfuz is <br />sufficient to cause an ionic shift from a bicarbonate type water to a sulfate type. <br />During periods of higher flow and late in the season when runoff from the mine is <br />small relative to total Trout Creek flow, the sulfate component is less able to <br />shift the anion balance to a sulfate type with concentrations of bicarbonate and <br />sulfate being approximately equal downstream. <br />• As mining activities have shifted from West Ridge to Moffat, the 1994-1996 <br />trend shows that the topological change generally still occurs at TR-B. This is <br />believed to be the result of the spoil spring which has developed at the base of the <br />West Ridge mining area. As further reclamation activities continue in West Ridge, <br />the spring exhibiting the high levels of sulfur is anticipated to decrease in flow. <br />Once the hydrologic reconstruction plan is completed and vegetation is completely <br />reestablished, the majority of excess runoff not used by the reestablished <br />vegetation will be diverted along the reconstructed surface drainage system rather <br />than being allowed to pass through the regraded spoils as is currently the case. <br />The 1994-1996 trend showing peak sulfate levels at TR-C and TR-D are expected to <br />continue for some time even though mining has been completed in the Moffat Area. <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 1987. All the <br />• manganese values observed are consistent with the baseline values. The relatively <br />high values of manganese observed at TR-C (0.13 mg/1) and TR-D (0.16 mg/1) during <br />15 <br /> <br />