2023-02-09_REPORT - C1981044

• Permit No: C1981044
• IBM Index Class Name: Report
• Doc Date: 2/9/2023
• Doc Name: Annual Hydrology Report Adequacy Review
• From: DRMS
• To: File
• Annual Report Year: 2021
• Email Name: RAR
• Email Name: JLE
• Media Type: D
• Archive: No

Well AVF-5 exhibited sulfate concentrations above basic
standards for groundwater and within historical ranges. In
2020 Manganese concentrations were the highest(2000 UG/L),
measured in AVF-5. In 2021 the highest reading was 1030
UG/L. Only manganese was found to be above the basic
standard for groundwater. However,the baseline levels were
also above the standard. Well AVF-6 water quality was within
historic concentration ranges. The MCM report states that no
impact on alluvial water quality or water levels has occurred.
MCM did not provide an explanation for any of the higher
concentrations observed in the wells mentioned above and the
cause of the elevated concentrations remains unclear.
Additional analysis may be warranted by MCM in the future
to determine if they are mine related
Section 4.05.13(1)of the Regulations requires the
establishment of one or more ground water points of
compliance(wells),for an operation possessing the potential to
negatively impact ground water quality. It does not appear
ground water points of compliance wells have been established
for this site. However,the Middle Sandstone(well TR-7a),and
the Williams Fork alluvium(well AVF-5), are monitored. Well
TR-7a is within the expected bedrock flow path of mine
leachate, should the mine discharge leachate to bedrock units.
The AVF-5 well is within the expected alluvial flow path of
CWQCC leachate, should the mine discharge leachate to Williams Fork
19. Basic Standards for regulations River alluvium. Both wells meet the qualifications of a
Ground Water 41.4 and 41.5 compliance point as per qualifications listed in Section
4.05.13(1)(b)of the Rules.
Monitoring data from both wells indicate the mine has likely
not caused an exceedance of the Basic Standards for Ground
Water. According to section 2.04.7 of the permit, for the
Williams Fork Alluvium; dissolved solids, iron, lead,
manganese and sulfate often exceed the drinking water
standards naturally. Monitoring data does indicate that
manganese levels in AVF-5 often exceed the drinking water
limit.
MCM turned off the mine pumps in July of 2013. Some wells
reacted to the pumps being turned off. Water levels increased
or have remained stable in recent years. However,water levels
in well 83-03 continue to decrease.
20. Restoration of CDRMS
ground water recharge regulation Water levels in Middle Sandstone formation are measured in
to approximate pre- 4.05.12(3) wells TR-4,TR-7,TR-7A, 81-01, 83-01, 83-02,and 83-03 and
mining rate show a general rising trend,with the exception of well 83-03,
although over time fluctuations have been recorded in all wells.
Seasonal fluctuations are also noted.
Twenty Mile Sandstone exhibited no apparent change in water
levels attributable to mining as per the Annual Hydrology
Report. Water levels in Well 84-01, #9 Mine Well appeared
stable since monitoring began.
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