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
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, the residents of Aspen Canyon Ranch vacated the property for
several months which resulted in the regular use and pumping of MLGW-ACR to cease. In the
past, Aspen Canyon Ranch has been operated year round resulting in regular use of the well. The
samples taken during the vacancy were noted as red in color and resulted in significantly higher
than usual dissolved iron and dissolved manganese concentrations, which are not representative
of typical conditions. Specifically, samples taken on November 23, 2015, during the vacated
time period, produced results containing outlier data for dissolved iron, at a value of 2920 ug/L,
and dissolved manganese, at a value of 1100 ug/L. These outliers were established using the
Rosner's statistical method. There are currently no established NPLs for iron and manganese at
MLGW-ACR. Henderson plans to engage the State Water Quality Control Division to clarify
the regulatory disposition of MLGW-ACR, which is directly referenced in regulation (5 CCR
1002-33.32(F), and whether it's replacement, in close proximity, would transfer or if additional
steps would be necessary. Henderson also intends to continue working with the Aspen Canyon
Ranch operators to assess the possibilities of replacement or repair of the well. In a meeting with
DRMS on May 20, 2016, DRMS suggested that Henderson should consider both replacement of
the well or aggressive rehabilitation of the well to early construction state to evaluate progression
of Fe and Mn contamination. Both approaches will be taken under advisement. No other
apparent trends, deviations or exceedances were observed in 2015.
Tabular data for MLGW-ACR along with applicable NPLs is presented in Table 2.
Accompanying graphs are provided in Trend Evaluations 21-24.
2.2.3 Point of Compliance Sampling Location: MLGW-15
MLGW-15 is a deeper well nested with MLGW-7 located just downgradient of 1-Dam. No
apparent trends, deviations or exceedances were observed in 2015.
Tabular data for MLGW-15 along with applicable NPLs is presented in Table 2. Accompanying
graphs are provided in Trend Evaluations 25-28.
2.2.4 Point of Compliance Sampling Location: MLGW-17
MLGW-17 is a shallow alluvial well located downgradient of 3-Dam. No apparent trends,
deviations or exceedances were observed in 2015.
Tabular data for MLGW-17 along with applicable NPLs is presented in Table 2. Accompanying
graphs are provided in Trend Evaluations 29-32.
2.2.5 Surface Water Sampling Location: WFR-20
WFR-20 is located upgradient of the Henderson Mill in the Williams Fork River and serves as an
indicator of background surface water quality. In the 2014 Annual Report we found an error
with the WFR-20 data set from 10/16/2012. Upon further review of the field sheets, and the final
data report, the values for specific conductivity and pH has been updated to reflect the correct
values. No apparent trends or anomalies were observed in 2015.
Tabular data for WFR-20 is presented in Table 2 with accompanying Trend Evaluations 33-36.
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