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Status Report; Robinson Seep Investigation Climax Molybdenum Company <br />2.0 2014 FIELD SUMMARY <br />Previous field investigations have identified that electrical conductivity (EC) measurements in <br />groundwater are a suitable surrogate for sulfate (a conservative tracer of Robinson Lake seepage) <br />originating from Robinson Lake (Tetra Tech, 2013). EC measurements, along with additional field <br />parameters of pH, dissolved oxygen (DO) and reduction - oxidation (redox) potential were collected <br />from the following locations in August 2014 (Figure 1): <br />• Seven boreholes installed into bedrock with an air rotary drill rig, extending to the first <br />occurrence of water; <br />• Four hand auger borings advanced within sediments downgradient of the Robinson <br />Lake seep collection system, extending to the first occurrence of water; <br />• Two 1" stainless steel temporary drive points installed within sediments <br />downgradient of the Robinson Lake seep collection system; and <br />• Four previously sampled locations (Tetra Tech, 2013) including piezometers RL -17 <br />and PZ -04, surface water location EVS -006, and the Robinson Lake Seep. <br />A peristaltic pump was used to obtain field measurements once pH and EC values stabilized. <br />Groundwater samples were then collected and submitted to ACZ Laboratories, Steamboat <br />Springs, Colorado for analysis of metals, anions and cations, alkalinity, and total organic carbon <br />(TOC). Due to limited water within drive point DP -1, analysis was limited to iron and manganese <br />concentrations. <br />To estimate hydraulic conductivity of the alluvial hydrostratigraphic unit downgradient of the <br />Robinson Lake seep collection system, slug testing was performed at monitoring well EVMW -1 S. <br />A total of six slug tests were performed. The tests used a slug 1.5 inches in diameter and <br />approximately 2.7 feet long (0.25- gallon displacement volume) to quickly raise or lower the water <br />level in the well. Water levels in the well were recorded at 1- second intervals before and during <br />the tests, using a pressure transducer and data logger. <br />Tetra Tech November 2014 3 <br />