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Status Report' Robinson Seep Investigation Climax Molybdenum Company <br />weather and site conditions allow safe access, to continue monitoring trends and confirm the <br />observed relationships and correlations. The results of the more frequent monitoring of the <br />bedrock wells EVMW -1D and EVMW -004 have not indicated any changes relative to the <br />variations in water quality in the shallow system. However, monthly monitoring through the end <br />of 2014 should also continue to enable detection should any changes occur. At this time, <br />continued monitoring should provide adequate protection of downgradient resources. <br />As discussed throughout this report, trends of dissolved iron, and perhaps to a lesser degree <br />manganese, may not be following the same pattern as other constituents. The following <br />additional investigation and data analysis should be considered to further the evaluation and <br />understanding of iron and manganese within the system: <br />• Sample EVMW -1 S to identify types of iron bacteria present; <br />• Implementation of monthly sampling of toe drain piezometers RL -17 and PZ -04 to more <br />closely monitor trends of iron and manganese in groundwater nearer Robinson Lake; <br />• Iron speciation to further delineate flow paths; <br />If Climax observes resumed and continued increasing concentration trends for other parameters <br />(e.g., sulfate, TDS, and other metals), additional response actions should be evaluated for <br />potential future implementation as follows: <br />• Reduce and maintain lower water levels in the Robinson Lake seepage collection pond <br />to decrease the hydraulic gradient and seepage between the pond and the downgradient <br />well EVMW -1 S; <br />• Improvements to the Robinson Lake Dam toe drain extending along the toe of the dam <br />to the right (east) abutment. It may be possible to expand or deepen the existing toe <br />drain system to improve the capture of seepage from a wider, or deeper, area; <br />• Construct additional groundwater monitoring wells along the eastern and western flank <br />of the Robinson Seep cut -off wall to more closely monitor temporal water quality trends; <br />and /or <br />• Identify suitable locations and complete preliminary designs for seepage extraction <br />wells /collection drains to capture and return intercepted groundwater to either the <br />seepage collection pond or Robinson Lake directly. <br />Tetra Tech, Inc. November 2013 41 <br />