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• approximately 3000 umhos/cm. <br />The difference between the conductivities at the upstream and downstream stations is <br />attributable primarily to spoil spring discharges related to surface mining. These <br />discharges cause increased concentrations of dissolved solids, calcium, magnesium, and <br />sulfate, and a reduction in SAR in Foidel Creek. However, the increase in SAR levels <br />during irrigation season is not sufficient to cause material damage. While the spoil <br />springs aze adding some manganese to Foidel Creek, the level at Station 8 is still below <br />the total recoverable standard of 1000 mg/1. Historically, high total recoverable <br />manganese has also been recorded in the upstream station (14), indicating that these <br />values aze also attributable to non-mining related causes. <br />The dissolved solids concentrations in the upstream station on Fish Creek (16) are <br />generally slightly lower than those in the downstream station (1002). There is also a <br />slight downstream trend of increasing sodium and sulfate concentrations while calcium, <br />magnesium and bicarbonate concentrations remain fairly consistent. The proportionally <br />higher sodium concentrations over calcium and magnesium leads to a slight <br />• downstream increase in SAR. These major ion changes aze more appazent during the <br />low-flow period. The increase in TDS could be caused to some extent by <br />evapotransporative effects, but this would not account for the major ion changes. <br />These changes are more likely attributable to discharges of waters having higher <br />sodium and sulfate concentrations than the Fish Creek water. One source of such <br />dischazge is the spoil runoff and springs associated with Mine 2. However, the very <br />low flows associated with the Mine 2 disturbed areas indicates minimal influence from <br />this source. <br />Since 1987, with the exception of a short period during 1990, the salt content of Trout <br />Creek below Middle Creek has been consistently higher than above Middle Creek. <br />There is typically approximately 100 to 200 umhos/cm increase in field conductivity <br />over this reach. The downstream increase was apparent during the 1991 spring runoff <br />period but not during the 1991 irrigation period when there was no measurable Flow in <br />both Foidel and Middle Creeks. The Trout Creek salt content increase during the <br />spring runoff is probably due to the effects of Middle Creek flows that have a higher <br />conductivity than Trout Creek flows primarily as a result of Foidel Creek flows into <br />. Middle Creek just upgradient of the Trout Creek confluence. Foidel Creek salt loads <br />- 9 - <br />