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-8- The climate of the region is typical of the Rocky Mountain area. The valley in which Paonia and Somerset are situated is semi-arid with annual precipitation averaging about 15 inches per year. Mean annual precipitation increases with elevation, reaching approximately 40 inches per year on the summit of Mt. Gunnison. The May-September precipitation is 5 inches for the lowlands and 13 inches for the mountain peaks. This indicates that snowfall patterns play an important part in determining the hydrology of the area. Temperature extremes at Paonia range from -28°F in January to 100°F during July and August. The average annual temperature is approximately 49°F. Snowfall averages 58 inches per year. The North Fork of the Gunnison is the major drainage for the mine site. Four ephemeral streams drain the permit area, and join the North Fork in the vicinity of Somerset. The water in the North Fork is characterized as a calcium bicarbonate type with moderate levels of sulfate. No alluvial valley floors (AVF's) exist within the permit area. Alluvial deposits along the North Fork below the town of Somerset have been found to meet the geomorphic criteria and irrigation requirements of Alluvial Valley Floor, but this area will not be affected by the operation. The coal to be mined is located in the Paonia Coal Field. The rocks exposed in the Paonia Coal Field consist of the Mancos Shale and the coal-bearing Mesa Verde Formation of Upper Cretaceous Age, the Ohio Creek Conglomerate, the Wasatch Formation of Early Tertiary Age, and the Quartz monzonite porphyry of Tertiary Age. Coal is to be produced from the Mesa Verde Formation. The Mesa Verde Formation is of Late Cretaceous Age and conformably overlies the Mancos Shale. This formation consists of approximately 2,300 feet of marine and terrestrial sedimentary rocks. The Mesa Verde Formation is the coal-bearing formation in the region and is divided into four main members: (from bottom to top) the Rollins sandstone, the Lower Coal Bearing (Bowie)member, the Upper Coal Bearing (Paonia) member, and the Barren (Undifferentiated) member (Johnson, 1948). The Rollins sandstone member is a 120 to 200 foot thick, massive, cross-bedded, medium to fine-grained, buff to white sandstone. This sandstone is regionally extensive and resistant in outcrop and forms prominent cliffs. This member is used regionally as a marker horizon to define the top of the Mancos Shale and the bottom of the coal-bearing horizons. The Lower Coal Bearing (Bowie) member consists of 260 to 350 feet of interbedded gray shales, thin to thick lenticular beds of buff-colored, fine- to medium-grained sandstones, and coals. The top of the member is usually capped by a massive buff-colored sandstone up to 90 feet in thickness. This sandstone, however, appears not to be a single persistent bed, but is actually several thick lenticular sandstones occurring at progressively lower stratigraphic horizons from east to west.