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<br />beaver ponds. Several long stretches of the creek between TR-B and TR-D <br />have also become marshes due to numerous beaver dams. <br />Snecific Conductivity <br />Specific conductivity levels (Figure 5) from September 1992 through the end <br />of the report period were similar to values obtained prior to October 1990. <br />Data taken between October 1990 and August 1992 are believed to be invalid <br />due to instrument errors. All four sites exhibited a marked increase in <br />specific conductivity for the October 1990 and August-October 1991 <br />readings. TDS values obtained during these same periods do not reflect the <br />increases, therefore it is believed that the data excursions can be <br />attributed to errors with the instrumentation rather than a reflection of <br /> actual field conditions. After the October 1990 reading, the equipment was <br /> repaired and used until July 1991, when a mechanical malfunction required <br /> switching to alternate instrumentation. It is believed that the alternate <br /> equipment was improperly calibrated or defective, resulting in inaccurate <br /> readings. New field equipment has been used since September 1992 along <br /> with laboratory verification. The values shown in Figure 5 are the <br /> laboratory values. <br /> i <br />i <br /> Total D <br />ssolved Sol <br />ds <br /> Total Dissolved Solids (TDS) concentrations (Figure 6) in Trout Creek <br /> show the expected pattern of levels increasing as stream flow passes the <br /> mine area and then beginning to decrease downstream with the introduction <br /> ~ of inflow from undisturbed areas downstream of the active mine. Peak TDS <br /> <br /> ~ levels in Trout Creek occur in early spring prior to the period of peak <br /> n <br />~~ ( flow. This is caused by the uptake of dissolved solids during the spring <br /> ~ <br /> ~ runoff from the portion of the watershed in which the Edna Mine is located. <br /> Although TDS concentrations in the mine runoff may be quite high when <br /> compared to concentrations occurring above the mine, the discharge of this <br /> runoff is small relative to that of Trout Creek so a large increase in <br /> Trout Creek waters is not observed. A comparison of the TDS and Flow <br /> indicates that TDS concentrations appear to be directly related to flow <br /> volume. <br /> As previously noted, sampling resumed at TR-C in April 1985. The TDS <br />_ concentrations in Trout Creek reach the highest levels at this point along <br /> 9 <br />