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<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />L <br /> <br /> <br /> <br /> <br /> <br />December of 1985 appears to be an anomaly, perhaps the result of a laboratory <br />analytical error as TR-D does not reflect an influx of TDS. <br />Calcium/Magno9;,~di_m <br />Calcium is the dominant cation in Trout Creek with magnesium and sodium <br />occurring in lesser concentrations (Figure 3). While the relative proportions <br />of these parameters change slightly between the sampling points, all show peak <br />concentrations coinciding with spring runoff, as would be expected. As with <br />TDS, all three cations show general increases in concentration as the water <br />passes active mining areas. While trends in their subsequent dilution <br />downstream have yet to form a consistent pattern, little or no dilution in <br />the calcium and magnesium concentrations have occurred between sampling points <br />TR-C and TR-D, except a calcium reading in mid-1988, since 1987. For 1990- <br />1992, it is believed that this is due to the Moffat area mining activities <br />and, as the Moffat area mining activities initiated in 1990 are directly <br />adjacent to TR-C, it is expected this pattern will continue. However, as this <br />occurrence existed prior to these activities, the trend may also suggest that <br />inflow from undisturbed areas downstream of TR-C contains approximately the <br />same concentrations of these parameters as runoff from the mine. <br />Sulfate/Bicarbonate <br />As noted in previous annual hydrology reports, upstream of the mine on Trout <br />Creek, bicarbonate is the major anion with sulfate concentrations increasing <br />rapidly along the mine area to become predominating downstream (Figure 4). <br />The sulfate levels inczease is most markedly noticed prior to the peak flow <br />period of Trout Creek and adjacent to mining activity, as are TDS levels in <br />general. This increase is probably caused by early runoff at the mine site <br />leaching pyritic and organic sulfur as flow passes over and through the <br />spoils. Since the flow of Trout Creek is low at that time, the amount of <br />sulfur is sufficient to cause an ionic shift from a bicarbonate type water to <br />a sulfate type. During periods of higher flow the input of sulfate is <br />generally insufficient to shift the anion component to a sulfate type with <br />concentrations of bicarbonate and sulfate being approximately equal <br />downstream. As mining activities have shifted from the West Ridge area to the <br />7 <br />1 <br />