2017-05-31_HYDROLOGY - M1977342

• Permit No: M1977342
• IBM Index Class Name: Hydrology
• Doc Date: 5/31/2017
• Doc Name: Water Monitoring - Groundwater
• From: Climax Molybdenum
• To: DRMS
• Email Name: PSH
• Media Type: D
• Archive: No

CMC—Henderson Operations
DRMS 2016 Annual Water Monitoring Report
May 2017
Introduction
The GWMP establishes a plan for groundwater monitoring at the Henderson Mine and Mill for
the protection of groundwater quality pursuant to Rule 3.1.7(5) of the Mineral Rules and
Regulations of the Colorado Mined Land Reclamation Board for Hard Rock, Metal, and
Designated Mining Operations and the Colorado Water Quality Control Commission (WQCC)
standards. Henderson has prepared this report in accordance with the requirements of Section 7.1
of the GWMP to summarize results of 2016 water monitoring activities.
1.0 Discussion of Annual Water Monitoring Data
This section provides a summary of the annual water monitoring data collected in 2016 in
accordance with the GWMP for each permit-identified POC well and non-POC long-term
surface water monitoring location at the Henderson Mine and Mill. Monitoring is conducted
three times per year as stipulated in the GWMP as follows:
• During the April through June spring run-off period;
• During the summer months of July and August; and
• During the September through December low-flow period.
To provide a better data set for trending purposes, historical data from triannual DRMS
monitoring and 5-Quarter Baseline Monitoring are included. Data can be seen in trend
evaluation graphs as well as in the data tables. Note that for the purpose of trending the
analytical data, results reported below the laboratory detection limit are shown as a value of zero.
All monitoring locations are depicted in Figures 1 and 2.
Outliers are identified, as needed, using either the Dixon's or Rosner's statistical method
depending on the available number of data points. Although data from prior reporting years is
presented herein for trending and discussion purposes, outlier and NPL assessments/discussions
are limited to current reporting year data.
2.1 Henderson Mine
Henderson Mine monitoring locations include POC well MNGW-1 and surface water locations
BG-20, CC-10 and CC-30. Graphical trends for MNGW-1, BG-20, CC-10 and CC-30 are
presented as Trend Evaluations 1-16 of this report.
2.1.1 Point of Compliance Sampling Location: MNGW-1
MNGW-1 is a shallow alluvial well located downgradient of the Henderson Mine operations.
Values of pH below the established NPLs was seen during monitoring events in 2016. Monthly
internal sampling was conducted throughout 2016 to further monitor the wells pH. In
accordance with the GWMP, Henderson has provided notification to the DRMS upon
reoccurring pH exceedances for POC wells, when necessary.
Following the installation of two new monitoring wells, the focus of further evaluation of the pH
exceedances has shifted to influence by a diversionary canal (No Name Gulch/NNG-50), which
picks up naturally acidic waters near the Red Mountain system, as well as other potential
contributing factors. As previously discussed with DRMS, Henderson continues with a source
evaluation to determine any contributing factors to the low pH at MNGW-1.
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