2023-04-19_PERMIT FILE - C1981010 ‎(126)‎

• Permit No: C1981010
• IBM Index Class Name: Permit File
• Doc Date: 4/19/2023
• Doc Name: pages 2-523a to 2-576u
• Section_Exhibit Name: 2.7 Hydrology Part 4
• Media Type: D
• Archive: No

2.7.5.4b Ground Water Use, I and J Pits, including the PR-11 Expansion Area

Trapper’s permit contains an updated inventory of water wells within one mile of the permit area.
Design information for these wells is provided in Tables 2.7-22b and 2.7-22c. This inventory
indicates a number of water wells are present in the area. Map M-31 shows the locations and
permit numbers of the wells. Only wells completed in the First, Second and Third White Sandstone
aquifers of the Upper Williams Fork formation and located within one mile of the I and J Pits area
are believed to have any potential to be affected by these pits due to the very small permeabilities
of the aquifers. Higher permeabilities (see Table 2-1 in the 1990 Trapper Annual Report) in the
Second or Third White Sandstone, such as those observed in monitoring wells P-5 and P-8, could
extend the potential of drawdowns in these aquifers to a slightly longer distance. The small
measured permeability of 0.03 ft/day and transmissivity of 25 gal/day/ft for the First White
Sandstone at well GLUX-1 will limit drawdowns to very near the highwall mining (HWM) mine area.

The Lux Well, 1 W1406-78 otherwise known as (153235), may be impacted by mining upgradient
in the F coal seam which exists on the top of the Second White Sandstone. HWM may come within
1,900 feet of this well in the I West Pit. If the Lux Well is completed in only the First White
Sandstone, it will likely not be impacted by the I pit mining but if its completion extends down into
the Second White Sandstone some drawdown is possible during the I pit mining. Well 81159 is
not anticipated to be impacted due to distance from highwall mining and its completion in the Third
White Sandstone. Well 85775 is also not expected to be impacted in the Second White Sandstone
due to a distance of 5,260 feet from disturbance and highwall mining in the F seam.

Wells 151991 and 93848 exist greater than one mile west of the western planned edge of the J
West Pit 1 HWM in the G coal seams which exists on the top of the Third White Sandstone. HWM
in the J pit will cause drawdowns in the Third White Sandstone aquifer but drawdowns greater than
a few feet are not expected to extend to the two western permitted wells.

Backfill aquifers at Trapper can be characterized by higher major constituent concentrations such
as TDS in some areas. These higher TDS concentrations might persist for an extended period of
time. The higher concentrations from the backfill aquifers in the I and J Pits area may recharge the
First, Second or Third White Sandstone aquifers and, therefore, eventually increase major
constituent levels in these aquifers.

2-524i