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CMC — Henderson Operations <br />DRMS Annual Water Monitoring Report <br />May 2013 <br />conditions and consistent with historic data that demonstrates a relative increase in <br />metals /nutrients and decrease in pH during low flow conditions and a reverse trend during spring <br />and summer high flow conditions. This seasonality will continued to be assessed as future <br />monitoring data becomes available. No other trends, deviations or exceedances were observed. <br />Tabular data for MNGW -1 is presented in Table 1 and provides a comparison to applicable <br />NPLs. <br />3.1.2 Surface Water Sampling Location: BG -20 <br />BG -20 is located upgradient of the Henderson Mine in Butler Gulch and serves as an indicator of <br />background surface water quality. The limited data suggest an increase in iron, sulfate and <br />specific conductance during the December 2012 monitoring event. As discussed above, this is <br />likely attributable to normal seasonal fluctuations /low flow winter conditions and will continued <br />to be assessed as future monitoring data becomes available. No other anomalies were observed. <br />Tabular data for BG -20 is presented in Table 1. <br />3.1.3 Surface Water Sampling Location: CC -10 <br />CC -10 is also located upgradient of the Henderson Mine in the West Fork of Clear Creek and <br />serves as another indicator of background surface water quality. The limited data suggest an <br />increase in iron and specific conductance during the December 2012 monitoring event. As <br />discussed above, this is likely attributable to normal seasonal fluctuations /low flow winter <br />conditions and will continued to be assessed as future monitoring data becomes available. No <br />other anomalies were observed. <br />Tabular data for CC -10 is presented in Table 1. <br />3.1.4 Surface Water Sampling Location: CC -30 <br />CC -30 is located downgradient of the Henderson Mine in the West Fork of Clear Creek. The <br />limited data suggest an increase in iron, manganese, sulfate and specific conductance during the <br />December 2012 monitoring event. As discussed above, this is likely attributable to normal <br />seasonal fluctuations /low flow winter conditions and will continued to be assessed as future <br />monitoring data becomes available. No other anomalies were observed. <br />Tabular data for CC -30 is presented in Table 1. <br />3.2 Henderson Mill <br />The Henderson Mill monitoring locations include POC well MLGW -7, and surface water <br />locations WFR -20 and WFR -40. Graphical trends are presented as Trend Evaluations 17 -28 of <br />this report. It should be noted that for the purpose of trending the analytical data, results reported <br />as below the laboratory detection limit were included as a value of zero. <br />3.2.1 Point of Compliance Sampling Location: MLGW -7 <br />No trends, deviations or exceedances of NPLs were observed at the Mill POC well MLGW -7 <br />during 2012. <br />Tabular data for MLGW -7 is presented in Table 2 and provides a comparison to applicable <br />NPLs. <br />4of5 <br />