2011-09-26_PERMIT FILE - C1981012 ‎(24)‎

• Permit No: C1981012
• IBM Index Class Name: Permit File
• Doc Date: 9/26/2011
• Section_Exhibit Name: EXHIBIT 08 HYDROLOGY AND GEOLOGY INFORMATION
• Media Type: D
• Archive: No

58
A permanent depression in the piezometric surface will exist in the •
vicinity of the flooded mine workings. This depression will exist because
of the high permeability region of the mine and not because of any continued
discharge from the aquifer. The magnitude of the depression will not be
large, but may extend to a distance (measured from the center of the mine}
equal to a times the equivalent radius of the mine.
The water passing through the flooded mine will be of modified quality
relative to that in the undisturbed coal seam fora period of time. The
difference between the quality of the current discharge from the Allen
Mine and that for well LA 221A may be indicative of the change that ran be
anticipated, although the small difference is within the range of variation
observed. The water of modified quality will spread in a plume downgradient
of the mine. Based on structural contours of the coal seam, water passing
through the flooded mine will move in a northeasterly direction. The theory
of flow through a region of modified permeability predicts that the plume
of modified water quality may spread to a maximum total width of about 4
times the equivalent radius of the mine. The period of time over which
waters passing through the flooded workings will continue to pick uo dis-
solved species in addition to those already present is difficult to even
estimate. It is anticipated that soluble materials will be readily flushed,
but flow rates will be very slaw, causing the flushing action to persist
over a long time period.
Stream And Near Surface Ground Waters
Our best estimate of the effective vertical permeability of the over-
burden is 0.00021 ft/d, as determined previously in this report. By lower-
' ing the piezometric surface to the roof of the mine, mining beneath the
valley could cause the vertical hydraulic gradient to be a maximum of unity.
In this case, the vertical discharge per unit area is equal to the offective
permeability in the vertical direction (i.e., 0.00021 ft/d). The width,
measured normal to the axis of the valley, of saturated alluvium is conserva-
tively estimated to average 350 ft. in the vicinity of the Maxwell !•tine.
The distance between the east and west ends of the study area is 0000 ft.
which yields a horizontal surface area of saturated alluvium equal to