Operations - Mine inflow would not begin to increase appreciably until project
year 5 and would not
be fully developed until project years 6 or 7. The groundwater drawdown would
continue to slowly
expand until a steady state condition was reached later in the project. Modeling
of steady state
groundwater drawdown was chosen for project year 28. Figures 3-3 and 3-4
present the predicted
water table decline at year 28 for the moderate recharge case. The greatest
predicted groundwater
drawdown (58 feet) would occur directly above the mine. The maximum predicted
extent of the cone
of depression is indicated by the outermost contour representing the one
foot drawdown (Figure 3-3).
The water table decline predicted for the other recharge cases (low and high
recharge cases) are
similar to those for the moderate recharge case.

The cone of depression shown in Figure 3-3 would be asymmetrical because
the higher permeability
and greater thickness of the outwash south of the mine would provide the
greatest flow toward the
mine. North of the mine, the aquifer thins and a greater proportion of the
aquifer consists of low
permeability glacial till. This low permeability till reduces the potential
impacts of groundwater
drawdown on Swamp Creek.

During mining, weathered rocks with relatively high permeabilities, especially
during the massive ore
phase, would be removed and replaced with cemented backfill. This backfill
would have a lower
permeability, hence inflow to the mine might be reduced. In addition, grouting
of active water
courses may reduce inflows. The net result of these activities should be
to lower mine inflow. The
reduction in mine inflows, however, is not predictable, so decreasing inflow
was not evaluated during
modeling.

Closure - After mine pumping ceases, the water table level would rebound
to within a few meters at
the mine in three years and would be within about 1 meter of preconstruction
conditions within 6
years. Groundwater modeling indicates the water table would rebound to original
levels within 30
years of mine closure.

The recovery of the groundwater table and the resulting resaturation of the
glacial aquifer sediments
would not be expected to alter groundwater quality. Seasonal variations in
groundwater levels and
quality occur naturally, but these seasonal fluctuations do not significantly
change groundwater
quality. While the magnitude of the water level changes due to mine pumping
and recovery would be
greater than natural seasonal fluctuations, the mine-related drawdown recovery
should not produce a
greater impact on water quality than the existing fluctuations.

Resaturation of soils beneath a reagent, fuel, concentrate or other spill
or leak could release
contaminants to the groundwater. However, removal of the contaminated soil
in accordance with the
spill prevention counter-measure and control plan would minimize to the extent
possible such sources
of contamination. Also, since the majority of the groundwater level recovery
is predicted to occur
within the first 6 years, monitoring during the remaining long-term care
period should identify any
potential contamination problems. If necessary the Department could continue
monitoring beyond
the long-term care period.

Impacts on Water Wells
A water well inventory conducted by Exxon identified 27 privately owned water
wells which would be
replaced or deepened to mitigate the groundwater drawdown impacts on these
wells. These wells are
northwest of or around Little Sand Lake (Fig. 1-19). If other water wells
were affected they would
be replaced or deepened as appropriate. Section 144.855, Wisconsin Statutes,
provides relief for
private water wells impacted by mining activities. Beyond the area of greatest
drawdown, however,
negligible impacts should occur to water wells.

The closest public utility water wells are 2 miles west (Mole Lake community)
and 8 miles north (City
of Crandon). No impacts would be expected from the predicted groundwater
drawdown on either
water supply.

The water table decline and resulting changes in groundwater flow would not
be expected to
significantly affect the water quality of the area wells. The lowering of
the water table would
provide increased unsaturated soils for purification of water percolating
from local contamination



sources. In addition, any potential contamination from the mine/mill, but
not the MWDF, would flow
toward the mine.



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