2009-05-22_PERMIT FILE - C1981044A (7)

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portions of the permit area. Outcrops occur in the valley walls of [he Yampa and Williams Fork Rivers. The Twentymile Sandstone dips gently to the north-northwest at approximately 8 [0 10 degrees and may lie at depths of up to 1400 feet in the northern portions of the permit area. There have been three (3) wells completed in the Twentymile Sandstone within the permit boundary. These wells are: 1) the No. 9 Mine Well 2) well 259, and 3) well 84-O1. Locations of these wells are shown on the Hydrologic Monitoring Program Location Map (Map 11). All three (3) wells are available for water level measurement. Well 259 and the No. 9 Mine Well are available for water quality sampling. Historical water levels for all three (3) wells are shown on Figure 18, Plot of Water Level Data - No. 9 Mine Well, Figure 19, Plot of Water Level Data -Well 259, and Figure 2Q, Plot of Water Level Data -Well 84-O1. The piezometric surface of the Twentymile Sandstone is presented on the Piezometric Surface - Twentymile Sandstone (Map 15). Water levels have remained essentially constant for the period of record. Ground water elevations indicate that the aquifer is artesian over much of the permit area. In the eastern portion of the permit area (the Utah Tract, in particular), the aquifer is unsaturated to partially saturated. During the 1984 drilling program, instructions were given to the drilling supervisor to be aware of any drill holes, which included those on the Utah Trach, making significantly more water than what was used in the circulation medium. Observations indicate that none of the drill holes made significant amounts of water. However, those drill holes on the northern end of the Utah Trach, produced more water than those to the south; again, water production was not significant. There is no site-specific hydrologic property data available for the Twentymile Sandstone. However, hydrologic properties are inferced to be similar to those described for the underlying Middle Sandstone based on the similar lithologies of the two (2) units, their similar stmctural position, and the close agreement of their water level elevations. Recharge to the Twentymile Sandstone is expected to be in the outcrop. Discharge is expected to be generally to the north toward the center of the stmctural basin. As with the Middle Sandstone, minor recharge and discharge may occur as vertical leakage. Discharge may also occur as leakage to and eventually discharged to, the underground workings. However, there is no evidence of this occurring. White Sandstone The White Sandstone lies approximately 130 feet above the "P" coal seam (previously mined in the now abandoned No. 9 mine). The White Sandstone is estimated to be approximately 350 feet thick within the permit area. The sandstone consists of three (3) fine to very fine grained calcium cazbonate, cemented sandstone benches. The structure and attitude of the White Sandstone is expected to be similar to that of the underlying Twentymile Sandstone, both dipping gently to the north- northwest. There have been three (3) hydrologic monitoring wells completed in the White Sandstone. These wells are: 1) 81-03A, 2) 81-04A, and 3) 81-19. Locations of these wells can be found on the Hydrologic Monitoring Program Location Map (Map 11}. Wells 81-03A and 81-04A replaced wells 81-03 and 81-04 respectively in June 1982. Information from wells 81-03 and 81-04 has not been used in this permit. (For more information on the White Sandstone, refer to the "Hydrologic Annual Report - 1985, Eagle No. 5 and No. 9 mines" -Empire Energy, 1985.) Ground water levels and water quality have been collected from these wells. Graphs of historical water level evaluations suggest that the No. 5 and No. 9 Mines have not affected the While Sandstone. Consequently, the deeper No. 6 Mine is not expected to affect it either. Hvdrologv of Coal Units There have been three (3) coal seams mined to date at EC. These are 1) the "P" coal seam which was mined at the now abandoned No. 9 Mine and 2) the "F" coal seam which was mined at the No. 5 Mine, and 3) the "E" coal seam, Permit Revision 04-34 2.04-14 Revised 7/2/04