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
An outlier for dissolved iron was determined for the sample taken on December 7, 2016 based on
Rosner's statistical method. This data point was well within the established NPLs.
Tabular data for MNGW-1, along with applicable NPLs, is presented in Table 1. Accompanying
graphs are provided in Trend Evaluations 1-4.
2.1.2 Surface Water Sampling Location: BG-20
BG-20 is located upgradient of the Henderson Mine in Butler Gulch and serves as an indicator of
background surface water quality. No apparent trends or anomalies were observed in 2016.
Tabular data for BG-20 is presented in Table 1 with accompanying Trend Evaluations 5-8.
2.1.3 Surface Water Sampling Location: CC-10
CC-10 is also located upgradient of the Henderson Mine in the West Fork of Clear Creek and
serves as another indicator of background surface water quality. No apparent trends or anomalies
were observed in 2016.
Tabular data for CC-10 is presented in Table 1 with accompanying Trend Evaluations 9-12.
2.1.4 Surface Water Sampling Location: CC-30
CC-30 is located downgradient of the Henderson Mine in the West Fork of Clear Creek. No
apparent trends or anomalies were observed in 2016.
Tabular data for CC-30 is presented in Table 1 with accompanying Trend Evaluations 13-16
2.2 Henderson Mill
The Henderson Mill monitoring locations include POC wells MLGW-7, MLGW-ACR, MLGW-
15, and MLGW-17, as well as non-POC surface water locations WFR-20 and WFR-40.
Graphical trends are presented as Trend Evaluations 17-40 of this report.
2.2.1 Point of Compliance Sampling Location: MLGW-7
MLGW-7 is a shallow alluvial well nested with MLGW-15 located downgradient of 1-Dam.
Monthly monitoring conducted at MLGW-7 for an expanded parameter set as part of
groundwater quality assessment concluded at the end of 2014. Field parameters continued to be
measured on a monthly basis until terminated in July, 2015 after DRMS granted preliminary
approval of revised NPLs for pH at Mill POCs. Henderson continues to note a slight decreasing
trend in sulfate. No other apparent trends, deviations or exceedances were observed in 2016.
Tabular data for MLGW-7 along with applicable NPLs is presented in Table 2. Accompanying
graphs are provided in Trend Evaluations 17-20.
2.2.2 Point of Compliance Sampling Location: MLGW-ACR
MLGW-ACR is a drinking water parameter POC well located in the Aspen Canyon Ranch area.
Results for iron and manganese exceeded the secondary aesthetic standards. Henderson believes
that these elevated concentrations may be due to the poor condition of the well itself. As such,
Henderson has continued to conduct triannual monitoring and additional research to explore this
possibility. Beginning in October of 2015, and through the early months of 2016,the residents of
Aspen Canyon Ranch vacated the property which resulted in the regular use and pumping of
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