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i <br />2005 sampling period compared with those of the last decade. However, the sodium <br />concentration levels remain within historical levels found in Trout Creek. <br />Calcium, magnesium and sodium concentrations exhibited the same trends in 2007 as <br />found during previous years of monitoring. The lowest calcium concentration in 2007 was <br />recorded at monitoring well TCS-1 in October with a value of 20.8 mg/L and the high was <br />recorded at monitoring well TR-1.5 in July with a value of 565 mg/I.. The lowest magnesium <br />concentration in 2007 was recorded at monitoring well TCS-1 in October with a value of 7.5 <br />mg/L and the high was recorded at monitoring well TR-1.5 in July with a value of 470 mg/L.. <br />The lowest sodium concentration in 2007 was recorded at monitoring well TR-3 in October <br />with a value of 10.8 mg/L and the high was recorded at monitoring well TCS-1 in October <br />with a value of 294 mg/L. <br />4.2.5 Ground Water Bicarbonate and Sulfate <br />Charts 29, 30 and 31 show bicarbonate, sulfate and sodium concentrations and the <br />sulfate/bicarbonate ratio for monitoring wells TR-1.5, TR-3, TR-4, WR-1 and TCS-1 for the <br />period of record. Bicarbonate and sulfate concentrations show a consistent topological trend <br />over the last 4 years. The sulfate bicarbonate ratio during much of the previous decade <br />showed the alluvial waters at TR-1.5, TR-3 and TR-4 and the backfill water at WR-1 to be <br />sulfate type. Waters at TR-1.5 WR-1 and TR-3 have become slightly more sulfate over the <br />period of record. During the last decade the sulfate/bicarbonate ratio at TR-1.5 was very <br />similar to that found in WR-1 providing further evidence that the source of sulfate may be <br />from a sulfur rich source such as leakage from an old abandoned underground mine. <br />Bicarbonate levels in TR-4 rose from 2003 to 2005 driving the sulfate bicarbonate <br />ratio lower, and shifting the water from a sulfate type to a bicarbonate type. This may be due <br />to the well repairs performed in the spring of 2003. The bicarbonate concentrations at TR-4 <br />seem to have peaked in 2004 and look as if they have stabilized and/or decreased in the past <br />few years. Sulfate concentrations exhibited the same trends in 2007 as found during previous <br />years of monitoring. The lowest bicarbonate concentration in 2007 was recorded at monitoring <br />well TR-3 in May with a value of 126 mg/L and the high was recorded at monitoring well TR- <br />4 in July with a value of 644 mg/L. The lowest sulfate concentration in 2007 was recorded at <br />monitoring well TCS-1 in May with a value of 100 mg/L and the high was recorded at <br />monitoring site TR-1.5 in July with a value of 3100 mg/L. The lowest sulfate bicarbonate <br />ratio in 2007 was calculated for monitoring well TR-4 in July with a value of 0.29 SO4 <br />(meq)/HCO3 (meq) and the high was calculated for monitoring well TR-1.5 in May with a <br />value of 15.59 SO4 (meq)/HCO3 (meq). <br />4.2.6 Ground Water Dissolved Iron and Manganese <br />Charts 32 and 33 show dissolved iron and manganese concentrations for monitoring <br />wells TR-1.5, TR-3, TR-4, WR-1 and TCS-1 for the period of record. Overall, dissolved iron <br />and manganese levels for the three alluvial wells TR-1.5, TR-3 and TR-4, and backfill well <br />WR-1 remained low during 2007 as in previous years. The past few years at well TR-1.5 <br />12 <br />