GENERAL46036

• Permit No: C1981025
• IBM Index Class Name: General Documents
• Doc Date: 7/14/1983
• Doc Name: Amended Proposed Decision and Findings of Compliance
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

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Cumulative Ground Water Impacts
During this five-year permit period, the impacts of the Sunlight Mine,
the North Thompson Creek Mines and the Coal Basin Mines on ground water
quality and quantity will be localized in areas adjacent to the
disturbances. During the life of the North Thompson Creek Mines and the
Coal Basin Mines, the areas affected by these mines will eventually
join. When these two mines eventually join, the North Thompson Creek and
Coal Basin mines will both impact the ground water in the aquifers in the
Coal Creek Basin. The Sunlight Mine will not produce a cumulative ground
water impact with any other mine in the Roaring Fork Drainage during its
life-of-mine.
The three underground mines along the Roaring Fork River may impact
ground water quantity by one or more of the following:
induced inflows into the mines through faults and fractures
which provide communication between the mine and overlying and
underlying aquifers, and overlying surface waters;
dewatering of the coal, roof and floor with the advance of
mining; and
subsidence-induced flows into the mines.
faults and fractures which cut the bedrock strata produce a localized
increase in porosity within the strata. If the faults and fractures do
not become sealed by clays, they may become conduits for the flow of
ground and surface water. When encountered within the mine, faults and
fractures will dewater. The amount of water flowing Into the mine from
these sources depends on porosity and permeability of faults or
fractures, and on the open vertical connection within the faults and
fractures between the coal seam and sources of ground or surface water.
The impacts of subsidence due to mining can be expected to vary in
magnitude and extent. This variation will result from a combination of
numerous natural phenomenon and from the effects induced by underground
mining. Surface water and ground water can both be influenced by
differences in timing of mining and the physical environment. It is
assumed that all mining will result in subsidence at some future point in
time, although surface manifestation may require many years to occur.
Therefore, control and prediction of subsidence are critical, necessary
measures, which should be implemented before and during any mining
activity.
Natural phenomena which influence subsidence are:
- Thickness of overburden;
- Topography (variations in overburden thickness);
- Stratigraphy and lithology of the overburden;
- Thickness of the coal seam;
- Lithology of the floor strata; and
- Geologic structure (faulting and folding) of the strata.