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December 2013 <br />Mine Groundwater Quality Assessment ♦ 6 <br />• Preliminary trend analyses of key indicator parameters appear to show that low pH <br />values correlate with lower total dissolved solids and lower metals concentrations in <br />groundwater at MNGW -1. For example, Figure 3 is a graph of pH and specific <br />conductance, an indicator of total dissolved solids, for the 2012 and 2013 period. <br />The graph shows that lower specific conductance values were measured during <br />periods of low pH. A similar correlation (lower pH = lower concentration) is <br />observed for the indicator parameter sulfate (see Figure 4). Concentrations of other <br />indicator parameters, including iron, manganese, and zinc, were too low to discern <br />reliable correlations. These observations suggest that the low pH values observed in <br />MNGW -1 do not appear to correlate with increased solute or metals concentrations <br />in groundwater. <br />• As noted above in 2013, the lowest pH values in MNGW -1 occurred during the <br />spring runoff and summer periods, suggesting a potential relationship between <br />aquifer recharge and groundwater chemistry. However, historical low pH values also <br />have been recorded during low flow /winter conditions. Figure 5 is a graph of pH <br />versus water level in MNGW -1. The graph shows some recent correlation between <br />shallow water levels, indicating recharge conditions, and low pH. The nearest <br />drainage to MNGW -1 is the so -called No Name Gulch, which originates to the West <br />of Red Mountain and is diverted around the south side of Henderson's surface <br />operations. Preliminary analyses indicate naturally low pH waters occur in this <br />drainage and that the recharge of this water during runoff periods may be effecting <br />water chemistry at MNGW -1. <br />AJAX Ltd ♦ 28828 Cedar Circle ♦ Evergreen, CO 80439 ♦ (303) 241 -2057 <br />Clear Creek Associates* 6155 E. Indian School Rd. ♦ Scottsdale, AZ 85251 ♦ (480) 659 -7131 <br />