2018-05-18_PERMIT FILE - C2009087A ‎(3)‎

• Permit No: C2009087A
• IBM Index Class Name: Permit File
• Doc Date: 5/18/2018
• Doc Name: Mitigation of the Impacts of Mining Operations
• Section_Exhibit Name: 2.05.6 Mitigation of the Impacts of Mining Operations
• Media Type: D
• Archive: Yes

RULE 2- PERMITS
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Time since mine.,e.e (month.)
Figure 2.05.642.1 Predicted Groundwater Inflow Rates, 0 -420 Months
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A cone of depression in the potentiometric surface around the mine workings will develop because
of mine dewatering activities. The drawdown related to mine dewatering was estimated using
analytical line -sink methods and a variation of the Stallman equation shown above. The drawdown
varies with time since dewatering started and with distance from the mine. Drawdown around the
mine was calculated using the following equation:
s = snD(u)h
where: s = drawdown at time r and distance r from the line sink
so = initial constant drawdown
D(u)n = drain function of u for the constant -head situation (approximated by
the complementary error function of u)
u = (r
S = storage coefficient
T = transmissivity
t = time since head was lowered
The results of the calculations are summarized in Figure 2.05.6 -F3 which shows a graph of
drawdown versus distance from the mine for 26, 60 and 420 months after the start of mining. Close
to the mine, the drawdown is equal to the difference between the elevations of the pre - mining
potentiometric surface and the Wadge coal, which will increase because of the geologic structure
from about 200 feet at the start of mining to about 900 feet by the end of the first 12 months and to
about 1200 feet by the 26th month of mining. The calculations indicate that the drawdown will
decrease rapidly with distance from the mine and will be less than five feet within about 900 feet of
PSCM Permit App.
2.05 -74
Revision 03/05/10