2010-02-19_REPORT - C1980001 (4)

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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, WR-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 2009 as found during previous years of monitoring. The lowest bicarbonate concentration in 2009 was recorded at monitoring well TR-3 in May with a value of 111 mg/L and the high was recorded at monitoring well TR-4 in August with a value of 571 mg/L. The lowest sulfate concentration in 2009 was recorded at monitoring well TCS-1 in May with a value of 91 mg/L and the high was recorded at monitoring sites TR-1.5 and WR-1 in May with a value of 2700 mg/L. The lowest sulfate/bicarbonate ratio in 2009 was calculated for monitoring well TR-4 in May with a value of 0.25 SO4 (meq)/HC03 (meq) and the high was calculated for monitoring well WR-1 in May with a value of 15.13 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 2009 as in previous years. Monitoring wells TR-1.5 and TR-3 showed spikes in May of 2009 that are uncharacteristic of the sites. The reason for these outliers is unknown. However, both sites returned to historic: levels in August of 2009. Manganese concentrations in TR-4 have risen from 2003 to the 2009 sampling season. Once again, this may be due to the well repairs conducted in the spring of 2003. The lowest dissolved iron concentration in 2009 was recorded at monitoring wells WR-1 in August with a value of 0.02 mg/L and the high was recorded at monitoring well TR-1.5 in May with a value of 30.7 mg/L. The lowest manganese concentration in 2009 was recorded at monitoring well TCS-1 in August with a value of 0.015 mg/L and the high was recorded at monitoring well TR-4 in August with a value of 2.86 mg/L. Page 14 ??'-WWC...WEER...