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regional ground water flow within that unit. Structural dip of the Trout Creek in the permit area of the Eagle No. 5 and No. 6 Mines is primarily to- the north and northeast. The configuration of the potentiometric surfaces mapped by the operator for the Middle, Twentymile, and White sandstones indicates ground water flow in the aquifer is to the west and northwest. The potentiometric maps for the Middle and Twentymile sandstones also suggest they may discharge locally at their subcrops beneath the Yampa and Williams Fork Valleys. The White sandstone may also do this, but potentiometric mapping of the available control is somewhat less supportive of this interpretation. Faulting within the permit area may provide a vehicle for ground water flow between overlying and underlying bedrock aquifers; between aquifers and mine workings; and between bedrock aquifers and the overlying surface stream/alluvial systems. Faulting and attendant fracturing result in increased, localized permeability between as well as within the individual rock aquifers. Depending on the relative magnitude of the static heads of the zones in fault communication, vertical movement of water can be upward thru the fault systems from deeper aquifers into the mine workings, or to recharge shallower aquifers, either bedrock or alluvial. Downward movement of water by means of fault zones may also take place from shallow aquifers into underlying open mine workings. Water movement into the western portions of the Eagle No. 5 Mine is presently occurring at a rate in excess of 300 gpm by means of at least two fault zones. Nearly half of the present inflow into the No, 5 Mine occurs from these fault zones. The Taw Creek sandstone is confined by the underlying Mancos Shale and the thick middle shale of the Iles Formation. Little information is available on the Tow Creek sandstone in the general area of the Eagle No. 5 and No. 6 and Trapper Mines. These mines, however, are not expected to impact the quantity or quality of water in the Tow Creek sandstone. The Tow Creek outcrops are located well outside of the permit areas and there is, within the permit area, significant stratigraphic separation between the levels of the mining operations and the Tow Creek sandstone. The Trout Creek sandstone averages about 78 feet in thickness in the permit area and crops out in the valley walls of the Williams Fork and Yampa Rivers to the south and west, The Trout Creek sandstone is confined by the underlying shales of the Iles Formation and overlying interbedded and lenticular shales, sandy shales, coals, and sandstones of the Lower Williams Fork Formation (See Figure 4), The Eagle No. 6 Mine, proposed for the "E" seam, will be separated from the Trout Creek sandstone by about 2U0 to 300 feet of interburden. The Eagle No. 5 Mine, in the "F" seam, wil], be some 40 to 100 feet stratigraphicaiiy higher than the No, 6. Empire Energy Corporation has drilled three water supply wells into the Trout Creek sandstone, the No. 5 and 5A near the No 5 Mine portal and the Okie Plaza well. The No 5 and Okie Plaza wells have been added to the proposed ground water monitoring plan. Well yields from this aquifer are highly variable and range from 10 to 100 gpm. A permeability of 0.071 gpd/ft2. for the Trout Creek sandstone was calculated from tests of the No. 5A well. The Trout Creek sandstone in an important regional aquifer used primarily for industrial and domestic purposes. -24-