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December 2013 <br />Mine Groundwater Quality Assessment ♦ 5 <br />• Figure 2 is a graph showing pH measurements recorded in MNGW -1 for the five <br />year period beginning in 2009. In the recent year, lower pH values appear to <br />correspond with spring runoff or summer monitoring periods. In 2013 the lowest <br />pH measurements occurred during July and August. A trend of increasing pH was <br />observed following the August sampling event and continuing until the most recent <br />sample in December. The following is a list of pH measurements collected since <br />July 2012. <br />Date <br />pH <br />7/6/2012 <br />6.8 <br />12/11/2012 <br />6.4 <br />5/28/2013 <br />6.3 <br />6/19/2013 <br />6.3 <br />7/24/2013 <br />5.9 <br />8/27/2013 <br />5.4 <br />9/11/2013 <br />6.5 <br />10/1/2013 <br />6.6 <br />11/8/2013 <br />7.2 <br />12/3/2013 <br />6.7 <br />• The four most recent water chemistry samples collected from MNGW -1 were all <br />within the 6.5 to 8.5 range defined in the GWMP. <br />• Analytical results for other indicator parameters established in the GWMP as well as <br />parameters added by Henderson to further evaluate conditions at MNGW -1 are <br />presented in Table 2. Analytical results show that all other indicator parameters were <br />well below respective NPLs defined by the GWMP. This includes all samples <br />collected in 2013, including samples corresponding to low pH measurements in <br />MNGW -1. <br />• Water chemistry results show that water in MNGW -1 is primarily a calcium sulfate <br />type with low total dissolved solids (less than 400 mg /L) and low or non - detectable <br />metals concentrations. <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 />