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• verification. The values shown in Figure 5 from 1992 through 1999 are the laboratory values. Since the field values and laboratory values have been in close agreement since 1992, values provided beginning in 1995 are field values. Total Dissolved Solids Total Dissolved Solids (TDS) concentrations (Figure 6) in Trout Creek exhibit an expected pattern. As stream flow passes the mine, TDS levels increase while adjacent to the mined areas and then begin to decline downstream due to inflow from undisturbed lands below the active mine. Peak TDS levels in Trout Creek occur in early spring prior to the period of peak flow. This is caused by the uptake of dissolved solids during the spring runoff from the portion of the watershed in which the Edna Mine is located. Although TDS concentrations in the mine runoff may be quite high when compared to concentrations occurring above the mine, the mine runoff is small relative to Trout Creek's total flow. Therefore, a large increase in Trout Creek TDS levels is not observed. A comparison of the TDS and Flow indicates that TDS concentrations appear to be directly related to flow volume. Prior to 1991, the TDS concentrations in Trout Creek reached the highest levels at TR-C. This is not unexpected. As mentioned in the baseline study, the cause for the highest TDS levels occurring at TR-C is related to the relative positions of TR-C and TR-D to the active mining area. The dilution of TDS • concentrations in the stream flow since 1988 has not been as pronounced as in previous years. The reason for this is not clearly understood since active mining directly above TR-C did not begin until 1990. It is possible that the trend exhibited from 1988 to 1990 was reflecting an increase in disturbance activities such as farming along the western side of Trout Creek in the vicinity of the Edna Mine. Since 1990, active mining has been in close proximity to TR-C with dilution of TDS concentrations occurring downstream of TR-D. Although elevated TDS concentrations have moved downstream in conjunction with the active mining, all values for TDS are consistent with the initial hydrology study projections. ~( •L'a ~.~ Z'S ti~ Calcium/Mag esium/Sodium Calcium (Figure 7) is the dominant cation in Trout Creek with magnesium (Figure 8) and sodium (Figure 9) occurring in lesser concentrations. While the relative proportions of these parameters change slightly between the sampling points, all show peak concentrations coinciding with spring runoff, as would be expected. As with TDS, all three cations show general increases in concentration as the water passes active mining areas. Additionally, the relative proportion of each constituent remains constant to the other constituents. While trends in their subsequent dilution downstream have yet to form a consistent pattern, little or no dilution in any of the concentrations have occurred between sampling points TR-C and TR-D since 1986. For 1990-1995, it is believed that this was due in part to the 10