2022-06-03_HYDROLOGY - M1977342

• Permit No: M1977342
• IBM Index Class Name: Hydrology
• Doc Date: 6/3/2022
• Doc Name Note: Annual Report
• Doc Name: Water Monitoring - Groundwater
• From: Climax Molybdenum
• To: DRMS
• Annual Report Year: 2021
• Email Name: PSH
• Email Name: JLE
• Media Type: D
• Archive: No

CMC—Henderson Operations
DRMS 2021 Annual Water Monitoring Report
May 2022
2.2.3 Proposed Point of Compliance Sampling Location: MLGW-17
MLGW-17 is a shallow alluvial well located downgradient of 3-Dam. No new trends, deviations,
or exceedances were observed in 2021.
Tabular data for MLGW-17 along with applicable NPLs are presented in Table 2. Accompanying
graphs are provided in Trend Evaluations 25-28.
2.2.4 Point of Compliance Sampling Location: MLGW-ACR
MLGW-ACR is a drinking water parameter POC well located in the Aspen Canyon Ranch area.
Beginning in the third trimester of 2019 Triannual sampling, changes to the MLGW-ACR
sampling method likely caused disturbances to the solid-wall well construction indicated by the
increase in iron and sulfate concentrations starting in August 2019 and established the need for the
well to undergo rehabilitation. The current results presented are not believed to be representative
of formation water quality. Well rehabilitation will be conducted per an agreement between ACR
land ownership and Henderson.
Altogether,this has been an effort to establish an accurate representation of ambient water quality
conditions for water supply downstream from Henderson operations. Henderson will continue to
evaluate the data collected at MLGW-ACR following future sampling events to better understand
these data.
Tabular data for MLGW-ACR along with applicable NPLs are 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. Fluctuations in specific conductivity and sulfate
may correlate with land disturbance from the Williams Fork wildfire activity.Although an increase
in pH and metal concentrations was not observed, WFR-20 will continue to be monitored while
the recently burned area remains susceptible to increased erosion.
Tabular data for WFR-20 are presented in Table 2 with accompanying Trend Evaluations 33-36.
2.2.6 Surface Water Sampling Location: WFR-40
WFR-40 is located downgradient of the Henderson Mill in the Williams Fork River.Although still
within historical measurements, recent pH and sulfate fluctuations may relate to destabilization
from the Williams Fork wildfire activity. Increased pH in adjacent surface water is a common
response from runoff interacting with a recently burned area. WFR-40 will continue to be
monitored to determine potential influences from the recent wildfire activity.
Tabular data for WFR-40 are presented in Table 2 with accompanying Trend Evaluations 37-40.
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