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The difference between the conductivities at the upstream and downstream stations is attributable <br />primarily to spoil spring discharges related to surface mining. These dischazges cause increased <br />• concentrations of dissolved solids, calcium, magnesium, and sulfate, and a reduction in SAR in <br />Foidel Creek. However, the increase in TDS levels during imgation season is not sufficient to <br />cause material damage. While the spoil springs aze adding some manganese to Foidel Creek, <br />the level at Station 8 is still below the total recoverable standard of 1000 ug/1. Historically, high <br />total recoverable manganese has also been recorded in the upstream station (14), indicating that <br />these values are also attributable to non-mining related causes. <br />The dissolved solids concentrations in the upstream station of Fish Creek (16) aze generally <br />slightly lower than those in the downstream station (1002). There is also a slight downstream <br />trend of increasing sodium and sulfate concentrations while calcium, magnesium and bicarbonate <br />concentrations remain fairly consistent. The proportionally higher sodium concentrations over <br />calcium and magnesium leads to a slight downstream increase in SAR. These major ion changes <br />aze more apparent during the low-flow period. The increase in TDS could be caused to some <br />extent by evapotransporative effects, but this would not account for the major ion changes. <br />These changes aze more likely attributable to dischazges of waters having higher sodium and <br />sulfate concentrations than the Fish Creek water. One source of such dischazge is the spoil <br />runoff and springs associated with Mine 2. However, the very-]ow ftda~s-25~6CfattxY with the -- = - - <br />Mine 2 disturbed areas indicates minimal influence from this source. - <br />Since 1987, with the exception of a short period during 1990, the salt content of Trout Creek <br />below Middle Creek has been consistently higher than above Middle Creek. There is typically <br />approximately 100 to 200 umhos/cm increase in field conductivity over this reach. The <br />downstream increase was apparent during the 1992 spring runoff period. The Trout Creek salt <br />content increase during the spring runoff is probably due to the effects of Middle Creek flows <br />that have a higher conductivity than Trout Creek Flows primarily as a result of Foidel Creek <br />flows into Middle Creek just upgradient of the Trout Creek confluence. Foidel Creek sal[ loads <br />during the Spring runoff are primarily due to the impact of surface mine dischazges. However, <br />the Trout Creek salt content increase has not caused any material damage, nor is there any <br />increase in trace metal levels. <br />~' <br />9 <br />