2023-01-10_PERMIT FILE - M2023001 ‎(12)‎

• Permit No: M2023001
• IBM Index Class Name: Permit File
• Doc Date: 1/10/2023
• Doc Name Note: Exhibit G - Water Information
• Doc Name: Application
• From: J-2 Contracting Company
• To: DRMS
• Email Name: PSH
• Email Name: JLE
• Media Type: D
• Archive: No

Fair Meadows Pit Groundwater Evaluation
November 19, 2022 Page 9 of 28
The total aquifer inflow and outflow balance at 19 cfs. The Poudre river gains approximately 12.8
cfs (17.7- 4.9) within the model area. The mass balance error is 0.0% based on the difference
between inflows and outflows. This indicates that the model has a high level of precision as well
as accuracy as shown in the calibration statistics.
Water Level Changes Caused by the Fair Meadows Slurry Wall
In model run<FMpit4>,we turned off the model cells within the Fair Meadows pit to simulate the
effect of the slurry wall. Figure A9 is the contoured"difference" in model output heads between
the post-pit run minus pre-pit run determined using GIS grid-math techniques. Positive values on
the north and west sides of the pit reflect mounding and negative values on the south and east side
of the pit reflect lower water levels in the "shadow" of the pit. The maximum change in water
level is approximately +2.5 ft in the northwest corner and slightly more than -1.5 ft of decline
(shadowing) between the south side of the pit and the Poudre River.
There are no registered production (non-monitoring) wells that are within the area where we
predict over +/- 1 foot change. Well permit no. 28964 registered to Robert Davis is located in
the northwest corner of the Mine property. According to J&T, Mr. Davis' property is now owned
by the mine and they intend to abandon it.
There are 16 registered wells that have reported water level depths (when drilled) to be less than
10 feet deep. Of these, only well permit 2020-F, belonging to the Summit Group of Southern
Wisconsin, is within the zone of expected water level rise of between 0.5 and 1 ft. There are six
registered wells that are currently being monitored by BAI that are within the area of expected
mounding of 0.5 to 1.0 ft. None of these wells have measured water levels above 10 ft so no
impact is expected. Well 374-WCB (Davis Farms) is the only other up-gradient well with an
expected rise between 0.5 and 1.0 ft. The Davis well is reportedly 86 ft deep, with a measured
water level of 31 ft when drilled. It reportedly can pump approximately 1200 gpm, one of the
highest within the model area. The expected rise in water level will likely increase the yield in
this well by increasing the saturated aquifer thickness and available drawdown.
Considering that the seasonal water table fluctuates approximately 2-4 feet, and there are no
registered wells located within the predicted water level change of+/- 1 ft, we believe the overall
impact of the mine slurry wall will be insignificant.
Model Sensitivity
The modeled mound and"shadow" impacts are insensitive to the hydraulic conductivity(K)of the
aquifer. An increase in K causes a proportional increase in model inflows, but also increases the
hydraulic connection with the Poudre River which offsets any additional mounding or shadow
effects. Therefore, we did not spend excessive time trying to match modeled verses observed
heads by changing K values.
The model results are very sensitive to the presence of surface water, but there is no realistic chance
that the Poudre River is going away. Model results are also insensitive to streambed leakance.
Even using a conservatively low Ksb value of 36 ft/day, the Poudre River is large enough and the
McGrane Water Engineering,LLC
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