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n l~ inflow from undisturbed areas downstream of TR-C contain approximately the same concentrations of these parameters as runoff from the mine. As noted in previous annual hydrology reports, upstream of the mine on Trout Creek, bicarbonate (Figure 5) is the major anion with sulfate (Figure 5) concentrations increasing rapidly along the mine area to become predominating downstream. The sulfate levels increase is most markedly noticed prior to the peak flow period of Trout Creek 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 is sufficient to cause ' an ionic shift from a bicarbonate type water to a sulfate type. An equalization in the sulfate-bicarbonate balance occurs downstream as the ' source of the sulfate (mined areas) is unavailable and dilution by runoff from undisturbed areas is introduced. During periods of higher flow the input of sulfate is insufficient to shift the anion component to a sulfate type with ' concentrations of bicarbonate and sulfate being approximately equal at TR-D. Manganese (Figure 6) shows fairly consistent values since the fall of 1981, except during 1984. At that time, a dramatic increase occurred upstream of TR-A with significant dilution being observed at each successive monitoring point along the mine area. The dilution was caused by the low concentrations present in water exiting from the mine vicinity. All the manganese values ' observed, except May, 1984, 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 (0.04 mq/1) which is immediately downstream of the active mine. Orthophosphate (Figure 7), nitrite (Figure 7), unionized ammonia (Figure 8), and dissolved aluminum (Figure 8) were added to the monitoring program in ' 1988. All values obtained during 1988, 1989, and 1990 for these parameters were low with most being below detection limits (Appendix 1). Orthophosphate and unionized ammonia showed some perturbation during the 1990 sampling ' period. These values, however, are low at slightly above detection limits.