2010-02-19_REPORT - C1980001 (4)

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as found during baseline studies and previous years monitoring. The lowest specific conductivity concentration in 2009 was recorded at monitoring site TR-A in June with a reading of 100 umhos/cm @ 25 °C and the high was recorded at monitoring site TR-C in April with a reading of 1010 umhos/cm @ 25 °C. 3.3.5 Surface Water Total Dissolved Solids Chart 6 shows total dissolved solids (TDS) concentrations for monitoring sites TR-A, TR-B, TR- C and TR-D for the period of record. TDS concentrations 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 adjacent to the mine occur in early spring prior to the period of peak flow. This is caused by 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, generally the mine runoff is small relative to Trout Creek's total flow. Therefore, a significant increase in Trout Creek TDS levels is observed only during the initial stages of spring runoff. A comparison of the TDS and flow data indicate that TDS concentrations appear to be directly related to flow volume. The dilution of TDS concentrations in downstream flow for the past decade has not been as pronounced as in the previous decade. Beginning in 1990, mining and reclamation occurred in close proximity to TR-C. As such, dilution of TDS concentrations probably occurs farther downstream of TR-D as runoff from undisturbed areas enters into Trout Creek. Although elevated TDS concentrations have moved downstream in conjunction with mining and reclamation activities, all values for TDS are consistent with the probable hydrologic consequences projections. TDS concentrations seem to have peaked during the 1996 sampling season and have been steadily decreasing to the current year of sampling. TDS concentrations exhibited the same trends in 2009 as found during previous years monitoring. The lowest TDS concentration in 2009 was recorded at monitoring site TR-A in June with a value of 80 mg/L and the high was recorded at monitoring site TR-C in April with a value of 740 mg/L. 3.3.6 Surface Water Calcium, Magnesium and Sodium Charts 7, 8 and 9 show calcium, magnesium and sodium concentrations for monitoring sites TR- A, TR-B, TR-C and TR-D for the period of record. Calcium is the dominant cation in Trout Creek with magnesium and sodium 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 the mine area. 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 1989. For the last decade, it is believed that this was due in part to the Moffat area mining Page 6 ^?wWCENGINEERING