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do not seem to be increasing overall. It is believed that an equalization in the sulfate-bicarbonate <br />balance or a reversal (similar to the balance at TR-A) occurs downstream as the source of <br />available sulfate (mining areas) is unavailable and dilution by runoff from undisturbed areas is <br />introduced. The lowest bicarbonate concentration in 2009 was recorded at monitoring site TR-A <br />in April with a value of 105 mg/L and the high was recorded at monitoring site TR-C in August <br />with a value of 134 mg/L. The lowest sulfate concentration in 2009 was recorded at monitoring <br />site TR-A in August with a value of 8 mg/L and the high was recorded at monitoring site TR-C <br />in April with a value of 420 mg/L. The lowest sulfate/bicarbonate ratio in 2009 was recorded at <br />monitoring site TR-A in August with a value of 0.10 SO4 (meq)/HC03 (meq) and the high was <br />recorded at monitoring site TR-C in April with a value of 5.21 SO4 (meq)/HC03 (meq). <br />3.3.8 Surface Water Manganese <br />Chart 13 shows manganese concentrations for monitoring sites TR-A, TR-B, TR-C and TR-D for <br />the period of record. Manganese shows fairly consistent values since 1989. Most of the <br />manganese values observed are consistent with baseline values. Manganese values appear to be <br />developing a trend, which may be directly related to flow in Trout Creek as are the TDS <br />concentrations. Sampling in October of 2005, at site TR-D, produced an inconsistent spike of <br />manganese up to 0.248 mg/L. Manganese remained within historical levels at all other sites <br />along Trout Creek in October 2005. The October water quality data was re-analyzed and the <br />original values were confirmed. There is no apparent reason for this sudden rise in value. <br />Site TR-D normalized over the last few years, regarding the October 2005 spike, and <br />concentrations on average for all sites are low in comparison with the past decade. The <br />concentration trend seemed to have reversed during 2006 with higher concentrations resulting <br />during low flow in Trout Creek, however the 2007 to 2009 values fall back to the expected trend <br />of decreasing concentrations according to flow. The lowest manganese concentration in 2009 <br />was recorded at monitoring site TR-A in April with a value of 0.02 mg/L and the high was <br />recorded at monitoring site TR-D in April with a value of 0.08 mg/L. <br />3.3.9 Surface Water Aluminum <br />Chart 14 shows aluminum concentrations for monitoring sites TR-A, TR-B, TR-C and TR-D for <br />the period of record. Aluminum concentrations have been low with most being below detection <br />limits throughout the duration of monitoring. The apparent elevated aluminum levels shown in <br />1995 were due to the laboratory lower detection limit being set at 0.2 ppm instead of 0.05 ppm. <br />Aluminum was elevated at TR-C during the April 2002 sampling period. However, <br />concentrations downstream of TR-C are consistent with previous sampling results. Therefore, <br />either sample contamination or laboratory error is suspected. Aluminum was slightly elevated <br />during the 2004 and 2005 sampling periods. The 2009 sampling period shows consistent <br />sampling results with the past decade. The lowest and highest aluminum concentration in 2009 <br />was the lower detection limit of <0.03 mg/L at all sites for all events. <br />Page <br />^^_wWCENGINEERIN.