PERMFILE119567

• Permit No: C1980001
• IBM Index Class Name: Permit File
• Doc Date: 1/8/2007
• Section_Exhibit Name: 2.5 Hydrology
• Media Type: D
• Archive: No

Doc Date:1 2/1 112 0 01 III'lllll'lII1lI III
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• S/G Z.5 HYDAOLOOY
1.5.1 8IIIQ111RY 7-ND COHCLU9IOH9
The proposed additions to the Edna Mine will be located in the Williams
Fork Formation and obtain coal from the Wadge seam. It is anticipated that
the hydrologic conditions that will be encountered in the proposed mine will
be very similar to those in the existing mine.
The mean annual precipitation on the study area is estimated to be 19.52
inches. Approximately 2.69 inches of the precipitation are lost during the
winter months due to evaporation and sublimation. Of the remaining 16.83
inches, evapotranspiration accounts for 14.73 inches, overland runoff for
another 0.15 inches, and the remaining 1.95 inches is subsurface runoff.
Runoff from the mine area enters Trout Creek that runs northward at the foot
of the slope.
Inflows to the pit on the down dip limit of mining in the West Ridge
area were estimated to be on the order of 65-125 gpm by D'Appolonia (1977).
• Inflows into the pit during the mining of West Ridge appeared to be less than
those predicted. Some wet spots were noticed along the low wall of the first
cut. However, this amount of inflow was insufficient to be quantified. Small
amounts of inflow to the pit from the upslope areas were encountered where
water from intercepted perched aquifers occurred, mainly in the existing
spoils. Inflows to the box cut on the Moffat Area were originally expected to
be 55-110 gpm. However, the orientation of the pit was altered from being
parallel with the hillslope to being perpendicular to the slope since the time
of the original estimate. Additionally, intercepted water from upslope areas
was estimated at about 10 gpm. Observations made since the opening of the
Moffat area have not noted any inflow from the downdip limit of mining and
only infrequent, small amounts of inflow have been noticed along the highwall
as perched aquifers have been intersected by the advancing pit. In the
absence of fractured permeability (as assumed in the above estimates), inflows
from the alluvium along Trout Creek to the pit in the West Ridge area should
have been less than 28 gpm based on the calculations in Section 2.5.3.1. The
corresponding value for the Moffat Area is anticipated to be less than 16 gpm.
Field observations regarding inflow into the pits indicate that the most
• reasonable estimate of flow from the alluvium to the pits is zero.
Mid-term '94 2.5-1 September 15, 1994