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-11- Sandstone and the Upper Sandstone, both of which are similar to the Rollins Sandstone. These units are in turn overlain by 2000 feet of undifferentiated Mesa Verde Group. This member is typical of upper deltaic formations consisting of channel sandstones, siltstone, shale and lenticular thin coal beds. The Grand Hogback is the major structural feature within the area, forming much of the eastern edge of the Piceance Creek Basin. The Grand Hogback is a monoclinal feature with beds dipping steeply to the south and southwest. Within the mine area, the dip at the surface is approximately 50° to 60°. The outcrop of the resistant sandstone units of the Mesa Verde Formation form a topographic high along the Grand Hogback. The major movement of ground water within the area is controlled by the steep dip, with movement southward toward the central Piceance Basin. Cross communication of ground water between the sandstones and the coal units is limited by the thick inter-bedded shales present throughout the section. The deep basinal system inhibits ground water development in much of the area because of the associated high drilling and pumping costs. Four bedrock zones which are either water-bearing or potentially water-bearing have been identified in the permit area. These units are the Rollins Sandstone, the Wheeler Coal, and the Upper and Middle Sandstones. Several wells were drilled through these zones in the mine area by the applicant to evaluate the ground water resources. Ground water was not identified in the Middle and Upper Sandstones in the permit area. These sandstones are composed of medium-grained, well-indurated silica and are only occasionally calcareous. These sandstones appear to be unsaturated throughout the permit area. The Wheeler Coal was found to be saturated in only the deepest portions of the permit area, below an elevation of 6080 feet. The groundwater yield in the Wheeler Seam was estimated to be less than a few gpm, with a transmissivity estimated at less than 100 gpd/ft. The Rollins Sandstone was described as being between 80 and 150 feet thick in the permit area and composed of alight gray, moderately indurated, massive, quartz sandstone. A minimum of fractures were identified in core. In the permit area, this unit was saturated below an elevation of 6040 feet. The yield at one well was 4 gpm, with a transmissivity of 50 gpd/ft. Due to minor fracturing within the Wheeler Coal Seam and the Rollins Sandstone, there is some potential that ground water could cross-communicate between these two seams. However, neither of these rock units are utilized for ground water within the vicinity of the mine, and, due to the extreme dip on the bedrock, development of water from these seams outside the permit area would be economically prohibitive. For these reasons, significant impacts to ground water quality and quantity in bedrock from mining at the Coal Ridge #1 Mine is not expected to occur.