2009-02-20_REPORT - C1980001 (4)

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concentration in 2008 was recorded at monitoring well TCS-1 in October with a value of 9.8 mg/L and the high was recorded at monitoring well TR-1.5 in May with a value of 468 mg/L. The lowest sodium concentration in 2008 was recorded at monitoring well TR-3 in May with a value of 9.5 mg/L and the high was recorded at monitoring well TCS-1 in October with a value of 320 mg/L. 4.2.5 Ground Water Bicarbonate and Sulfate Charts 29, 30 and 31 show bicarbonate, sulfate and sodium concentrations and the sulfate/bicarbonate ratio for monitoring wells TR-1.5, TR-3, TR-4, AIR-1 and TCS-1 for the period of record. Bicarbonate and sulfate concentrations show a consistent topological trend over the last 5 years. The sulfate/bicarbonate ratio 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. The sulfate/bicarbonate ratio at TR-4 has resulted in a bicarbonate type over the last 5 years, differing from the period of record. During the last decade the sulfate/bicarbonate 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/bicarbonate ratio lower, and shifting the water from a sulfate type to a bicarbonate type. This may be 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 2008 as found during previous years of monitoring. The lowest bicarbonate concentration in 2008 was recorded at monitoring well TR-3 in October with a value of 123 mg/L and the high was recorded at monitoring well TR-4 in August with a value of 561 mg/L. The lowest sulfate concentration in 2008 was recorded at monitoring well TR-4 in August with a value of 106 mg/L and the high was recorded at monitoring site TR-1.5 in May with a value of 2990 mg/L. The lowest sulfate/bicarbonate ratio in 2008 was calculated for monitoring well TR-4 in August with a value of 0.3 SO4 (meq)/HC03 (meq) and the high was calculated for monitoring well TR-1.5 in October with a value of 18.0 SO4 (meq)/HC03 (meq). 4.2.6 Ground Water Dissolved Iron and Manganese Charts 32 and 33 show dissolved iron and manganese concentrations for monitoring wells TR- 1.5, TR-3, TR-4, WR-1 and TCS-1 for the period of record. Overall, dissolved iron and manganese levels for the three alluvial wells TR-1.5, TR-3 and TR-4, and backfill well WR-1 remained low during 2008 as in previous years. The past few years at well TR-1.5 dissolved iron concentrations have risen compared with prior data, but are still within historical concentrations of previous sampling events. Manganese concentrations in TR-4 have risen from 2003 to the 2008 sampling season. Once again, this may be due to the well repairs conducted in the spring of 2003. The lowest dissolved iron concentration in 2008 was recorded at monitoring wells TR-3, WR-1 and TCS-1 in May with a value of <0.02 mg/L and 12