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Status Report; Robinson Seep Investigation Climax Molybdenum Company <br />2.0 MONITORING DATA AND TREND ANALYSIS <br />Increasing trends were only observed in well EVMWA S and in no other monitoring wells in the <br />area. Therefore the evaluation and analyses presented in this section focuses on water quality <br />in the vicinity of Robinson Lake (EVMS -1 S, EVMW -1 D, and EVMW -004; the point of compliance <br />well near Eagle Park Reservoir). <br />2.1 Short Term Constituent Trends <br />Figure 2.1 graphically presents the observed concentrations of sulfate, TDS, and dissolved <br />manganese, iron, calcium, magnesium, molybdenum and zinc in all monitoring wells in the <br />Eagle River basin (EVMW -1 S, EVMW -1 D, EVMW -002, EVMW -3S, EVMW -3D, and EVMW -004) <br />over the period October 2011 through November 2013. EVMW -004 was constructed and first <br />sampled in December 2012. As stated previously, all wells were sampled quarterly through <br />March 2013 and beginning in April 2013 the sampling frequency of EVMW -1S, EVMW -1 D, and <br />EVMW -004 increased to monthly. <br />As illustrated in these graphs, concentrations of indicator parameters sulfate (SOA TDS, iron <br />(Fe), and manganese (Mn), and additional baseline monitoring parameters calcium (Ca) and <br />magnesium (Mg) indicate an increasing trend through April 2013 in EVMW -1 S. With the <br />exception of iron and manganese, concentrations have generally decreased since April 2013. <br />Iron and manganese concentrations appeared to be stabilizing over the period of April to <br />September, but have increased again in October and November. <br />No increases have been observed in the concentrations of cadmium, copper, lead, <br />molybdenum, or zinc over the period of record for these wells, and with the exception of <br />molybdenum, concentrations of these constituents are typically not detected above the PQL or <br />MDL. Results for molybdenum (Mo) which is measured at detectable concentrations in well <br />EVMWA S, but which show a slight decreasing trend are presented for illustration. Dissolved <br />zinc was detected in deep bedrock monitoring wells EVMWA D and EVMW -004 in November <br />2013, however these samples were collected for the first time using recently installed dedicated <br />pumps in these wells. Elevated zinc concentrations have not been observed at any <br />groundwater monitoring location below Robinson Lake. It is therefore believed that these <br />anomalous concentrations may be related to the materials of the new pumps and piping <br />systems. <br />Since April 2013, as part of the enhanced monitoring program, water quality samples are also <br />being collected monthly from Robinson Lake and the Robinson Lake Seep. Periodic sampling <br />of the Robinson Lake Seep has been conducted since early 2011, but data are not available <br />from Robinson Lake prior to April 2013. The sampling location for Robinson Lake Seep is the <br />pump station sump within the collection pond formed by the concrete cut -off wall. This additional <br />data has allowed a more complete evaluation of the influence of seepage from Robinson Lake <br />on groundwater quality and consideration of a hydrogeochemical model for this area of the mine <br />site. A summary of field parameters and analytical data for the monitoring wells and surface <br />sampling locations Robinson Lake and Robinson Lake Seep is presented in Appendix A. Figure <br />2.2 graphically presents the observed concentrations of sulfate, TDS, and dissolved <br />manganese, iron, calcium, magnesium, molybdenum and zinc in Robinson Lake, Robinson <br />Lake Seep, and monitoring well EVMW -1 S over the period September 2011 through November <br />2013. <br />Tetra Tech, Inc. November 2013 <br />