2014-06-09_HYDROLOGY - M1977342

• Permit No: M1977342
• IBM Index Class Name: Hydrology
• Doc Date: 6/9/2014
• Doc Name: Submittal of Annual Water Monitoring Report
• From: Climax
• To: DRMS
• Permit Index Doc Type: Hydrology Report
• Email Name: PSH
• Media Type: D
• Archive: No

CMC—Henderson Operations
DRMS 2013 Annual Water Monitoring Report
June 2014
3.2.1 Point of Compliance Sampling Location: MLGW-7
' Deviations below the NPL of 6.5-8.5 pH were observed at well location MLGW-7 in July,
August and December of 2013. These pH values were 6.1, 6.2 and 6.4, respectively. Accelerated
monthly monitoring was established in September, 2013 to better identify trends and assess
water quality. A further summary of groundwater trends at MLGW-7 can be seen in the
Groundwater Quality Assessment for MLGW-7, Technical Memorandum (AJAX and Clear
Creek Associates, 2014).
Tabular data for MLGW-7 is presented in Table 2 and provides a comparison to applicable
NPLs. It should be noted that a new NPL of 5.9-8.5 pH for all Mill POC wells was proposed in
' the 5-Quarters Report (Aquionix, 2014). No other trends, deviations or exceedances were
observed at MLGW-7 during 2013. Trend Evaluations 17-20 are included for MLGW-7.
' 3.2.2 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. Data suggests no apparent anomalies were
' observed in 2013.
The specific conductivity value of 680.5 µS/cm, for the October 2012 monitoring event, has been
identified as a statistical outlier based upon analysis via Dixon's method.
Tabular data for WFR-20 is presented in Table 2 with accompanying Trend Evaluations 21-24.
t 3.2.3 Surface Water Sampling Location: WFR-40
WFR-40 is located downgradient of the Henderson Mill in the Williams Fork River. Data
suggests no apparent anomalies were observed in 2013.
' Tabular data for WFR-40 is presented in Table 2 with accompanying Trend Evaluations 25-28.
' 4.0 Groundwater Studies at the Mill
An initial Groundwater Monitoring Point of Compliance (POC)Technical Memorandum(AJAX
and Clear Creek Associates, May 2013)was completed and submitted to the DRMS in
' accordance with Section 3.2.6.1 of the Henderson Operations GWMP. The memo presented
several preliminary recommendations, including completion of additional monitoring to provide
data to support final determinations on potential POC locations,particularly below 1-Dam and 3-
' Dam in the Potato Gulch drainage area. The memorandum recommends that a POC location be
established at MLGW-15 in addition to existing GWMP approved POC location MLGW-7 and
MLGW-ACR.
' As previously mentioned, a Groundwater Quality Assessment for MLGW-7, Technical
Memorandum(AJAX and Clear Creek Associates, 2014) was also prepared and submitted to the
' DRMS. This report was prepared in response to pH deviations at MLGW-7.
A final report, 5-Quarter Water Quality Data and Baseline Parameters Report (Aquionix, 2014),
was recently submitted to the DRMS in accordance with Section 4.2 of the Henderson GWMP.
The purpose of the report was to establish MLGW-17 as a potential POC well, propose new pH
NPL ranges for all POC well locations at the Mill, and summarize all 5-quarter baseline data for
' MLGW-15, MLGW-17 and MLGW-ACR. Upon approval of the proposed POC locations,
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