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BicarbonatelSulfate Bicarbonate (Figure 28) and sulfate (Figure 29) concentrations show a consistent topological trend over the last three years. The sulfate/bicarbonate ratio (Figure 30) during much of the previous decade showed the alluvial waters at TR-1.5, TR-3 and TR-4 and the backfill water at WR-1 to be sulfate type. Waters at TR-1.5 WR-1 and TR-3 have become slightly more sulfate over the period of record. During 1997-2006, the sulfate/bicazbonate ratio at TR-1.5 was very similar to that found in WR-1 providing further evidence that the source of sulfate may be from a sulfur rich source such as leakage from an old abandoned underground mine. Bicarbonate levels in TR-4 rose from 2003 to 2005 driving the sulfate/bicazbonate ratio lower, and shifting the water from a sulfate type to a bicarbonate type. This maybe due to the well repairs performed in the spring of 2003. The bicarbonate concentrations at TR-4 seem to have peaked in 2004 and look as if they have stabilized and/or decreased in the past few years. Sulfate concentrations exhibited the same trends in 2006 as found during previous yeazs of monitoring. Bicarbonate and sulfate analyzed values are provided in tabular format in Appendix B. Dissolved Iron/Manganese Overall, dissolved iron (Figure 31) and manganese (Figure 32) levels for the three alluvial wells TR-1.5, TR-3 and TR-4, and backfill well WR-1 remained low during 2006 as in previous years. In 2006 at well TR-1.5 dissolved iron concentrations rose compared with the past few years data, but are still within historical concentrations of previous sampling events. Manganese concentrations in TR-4 rose from 2003 to 2005 and decreased slightly during the 2006 sampling season. Once again, this may be due to the well repairs conducted in the spring of 2003. Dissolved iron and manganese analyzed values are provided in tabular format in Appendix B. 42