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<br />sites exhibited a marked increase in specific conductivity in October 1990 and <br />August-October 1991 readings. As TDS values do not reflect these increases, it <br />is believed that these data excursions can be attributed to equipment errors <br />with the Horiba instrument rather than a reflection of actual field <br />' conditions. After the October 1990 reading, the equipment was repaired and <br />used until July 1991, when a mechanical malfunction required switching to <br />another Horiba instrument. It is believed that the second Horiba was <br />improperly calibrated, resulting in inaccurate readings. A new Horiba was <br />implemented late summer 1992 and the September and October readings seem to <br />indicate that the problem has been amended. <br />' Total Dissolved Solids <br />Total Dissolved Solids (TDS) concentrations (Figure 2) in Trout Creek show the <br />expected pattern of levels increasing as stream flow passes the mine area and <br />then beginning to decrease downstream with the introduction of inflow from <br />undisturbed areas downstream of the active mine. Peak TDS levels in Trout <br />Creek occur in early spring prior to the period of peak flow. This is caused <br />by the uptake of dissolved solids during the spring runoff from the portion of <br />' the watershed in which the Edna Mine is located. Although TDS concentrations <br />in the mine runoff may be quite high when compared to concentrations occurring <br />above the mine, the discharge of this runoff is small relative to that of <br />Trout Creek so a large increase in the Trout Creek discharge is not observed. <br />' As previously noted, sampling resumed at TR-C in April 1985. The TDS <br />concentrations in Trout Creek along the mine reach the highest levels at this <br />' point. This is not unexpected, for, as mentioned in the baseline study, the <br />cause for the higher TDS levels occurring at TR-C is related to the relative <br />positions of TR-C and TR-D to the active mining area. The dilution of TDS <br />' concentrations in the stream flow since 1988 has not been as pronounced as in <br />previous years. The reason for this is not clearly understood, for active <br />mining directly above TR-C did not begin until 1990. It is possible that the <br />trend prior to 1990, therefore, was reflecting an increase in disturbance <br />' activities such as farming along the western side of Trout Creek in the <br />vicinity of the Edna Mine. All values for TDS, except one, are consistent <br />with the baseline samples. The sample taken at TR-C (TDS = 1658 mg/1) in <br />6 <br />L~ <br />