2016-06-02_HYDROLOGY - M1977342

• Permit No: M1977342
• IBM Index Class Name: Hydrology
• Doc Date: 6/2/2016
• Doc Name: Annual Watering Report - Groundwater Management Plan
• From: Climax Molybdenum
• To: DRMS
• Email Name: PSH
• Media Type: D
• Archive: No

CMC—Henderson Operations
DRMS 2015 Annual Water Monitoring Report
May 2016
Executive Summary
This report provides a summary of the 2015 water monitoring data collected pursuant to the
Climax Molybdenum Company (CMC) — Henderson Operations (Henderson) Technical
Revision 16 (TR-16) to Permit M-1977-342 Groundwater Management Plan (GWMP). The
Henderson GWMP was approved by the Division of Reclamation, Mining and Safety(DRMS) in
July 2012. The focus of this report is 2015 data, however, historical data is included from the
2012-2014 monitoring periods to allow for the assessment of trends over time. Sampling was
conducted at the required locations in accordance with the GWMP and each sample was
analyzed for the required parameters.
In a memorandum dated April 14, 2015, the DRMS preliminarily accepted new proposed
Numeric Protection Limits (NPLs) for indicator parameters at Mill Point of Compliance (POC)
locations. As such, this report takes into consideration these new NPLs.
Mine Water Monitoring
While no deviations were seen in the regularly scheduled triannual DRMS sampling efforts,
Henderson did receive pH values below the NPL limits in December of 2015 during monthly
monitoring. On December 29th, 2015, in accordance with Section 5.3 of the Henderson
Groundwater Management Plan, a letter (CMC, December 2015) was sent to the DRMS
explaining the details of this groundwater NPL exceedance. Henderson will be submitting a
separate Mine Groundwater Quality Assessment Update Memo to provide more detail on the
2015 monthly sampling efforts and plans for continued evaluations of the groundwater system
dynamics in the area of the MNGW-1 well. Henderson anticipates submitting this memorandum
to DRMS in June, 2016.
Aside from the low pH level described above, there were no other deviations from established
NPLs observed at the Mine POC well.
Mine water monitoring data for POC well MNGW-1 and non-POC long-term surface water
locations BG-20, CC-10 and CC-30 are included in this report and presented both in a table and
trend evaluation graphs.
Mill Water Monitoring
There were no deviations from established NPLs observed at Mill POC wells.
Mill water monitoring data for POC wells MLGW-ACR, MLGW-7, MLGW-15 and MLGW-17
and non-POC long-term surface water monitoring locations WFR-20 and WFR-40 are included
in this report and presented both in a table and trend evaluation graphs.
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