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Bicarbonate/Sulfate <br />Bicarbonate (Figure 28) and sulfate (Figure 29) show a trend of topological change similar to that observed in the <br />surface waters. The bicarbonate/sulfate ratio (Figure 30) during much of the previous decade showed the alluvial waters at <br />TR-1.5 to be of a bicarbonate type while the alluvial waters at TR-3 and TR-4 were of a sulfate type. However, waters at TR- <br />1.5 have been tending to become more sulfate over the period of record. During 1996-2003, the bicarbonate/sulfate ratio at <br />TR-1.5 was very similar to that found in WR-1 providing further evidence that the source of sulfate maybe from a sulfur rich <br />source such as leakage from an old abandoned underground mine. Bicarbonate levels in TR-4 rose in 2003 driving the <br />sulfate bicarbonate ratio lower. This may be due to the well repairs performed in the spring of 2003. <br />Dissolved Iron/Manganese <br />Overall, dissolved iron (Figure 31) and manganese (Figure 32) levels for the three alluvial wells remained low during <br />2003 as in previous years. However, in August 2003, the iron and manganese concentrations in TR-4 spiked. The values <br />returned to historical levels in October 2003. Once again, this maybe due to the well repairs conducted in the spring of 2003. <br />37 <br />