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CMC—Henderson Operations <br /> DRMS 2013 Annual Water Monitoring Report <br /> ' June 2014 <br /> Executive Summary <br /> ' This report provides a summary of 2013 water monitoring data collected pursuant to the Climax <br /> Molybdenum Company (CMC) — Henderson Operations (Henderson) Technical Revision 16 <br /> ' (TR-16) to Permit M-1977-342 Groundwater Management Plan (GWMP). The Henderson <br /> GWMP was approved by the Division of Reclamation, Mining and Safety (DRMS) in July 2012 <br /> and, as such, this is the second submittal of this report. Data is limited to the 2012 and 2013 <br /> ' monitoring periods. Sampling was conducted at the required locations in accordance with the <br /> GWMP and each sample was analyzed for the required parameters. Baseline monitoring for <br /> additional proposed point of compliance (POC) locations has been completed and data provided <br /> to the DRMS in the recently submitted 5-Quarter Water Quality Data and Baseline Parameters <br /> Report(Aquionix, 2014). <br /> ' Mine Water Monitoring <br /> Deviations below the numeric protection limit (NPL) of 6.5-8.5 pH were observed at the Mine <br /> POC well MNGW-1 during monitoring events in December 2012 and May-August of 2013. In <br /> ' 2013,the Henderson Mine conducted investigations to evaluate groundwater quality at POC well <br /> MNGW-1. As such, a Groundwater Quality Assessment, Technical Memorandum (AJAX and <br /> Clear Creek Associates, December 2013) was submitted to DRMS with detailed <br /> ' recommendations for future assessment and monitoring. A summary of the recommendations <br /> include: <br /> ' • Continue monthly monitoring of MNGW-1 through 2014 <br /> • Install shallow monitoring wells in the glacial/alluvial deposits to the north and west <br /> of MNGW-1 to better define groundwater flow and water quality and assess source of <br /> ' low pH waters; and <br /> • Assess impact from No-Name Gulch on the water quality at MNGW-1 <br /> ' Mine water monitoring data for POC well MNGW-1 and non-POC long-term surface water <br /> locations BG-20, CC-10 and CC-30 are included in this report and presented both in a table and <br /> trend evaluation graphs. <br /> Mill Water Monitoring <br /> Deviations below the NPL of 6.5-8.5 pH were observed at well location MLGW-7 during the <br /> ' July, August and December 2013 monitoring events. Acknowledging the limited data set, <br /> accelerated monthly monitoring was established in September, 2013 to better underline trends <br /> and assess water quality. A subsequent Groundwater Quality Assessment for MLGW-7, <br /> ' Technical Memorandum (AJAX and Clear Creek Associates, 2014) was submitted to DRMS. A <br /> summary of the recommendations include: <br /> ' • Establish pH NPLs at MLGW-7, MLGW-ACR and other proposed POC wells <br /> that appropriately bracket naturally occurring conditions using statistical methods <br /> consistent with those utilized in the development of past ambient NPLs. <br /> • Return to the triannual monitoring frequency and indicator parameter list <br /> specified in the GWMP. <br /> ' 1 of 7 <br />