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letter and revised permit materials received on July 29, August 9 and August 13, 1991. These materials have satisfied Division adequacy review concerns. Description of the Environment Introduction The proposed Hamilton Mine permit area encompasses 677 acres. The proposed permit area is situated atop a gently north sloping mesa overlooking Naturita Creek and the San Miguel River. The mesa is part of an extensive flat-land area whtch extends southeast to the San Juan Mountains. The area was formed from the resistant. Cretaceous-age Dakota Sandstone and Burro Canyon Formation. The Dakota Sandstone is the bedrock of the mine area and contains the coat to be mined. The mesa to be mined is bounded on the west by Bramiers Draw and on the east by Long Draw. The northernmost permit boundary is approximately one mile south of Naturita Canyon. The southern permit area boundary is 1.5 miles south of and parallel to the northern permit area boundary. The mine will be located within the southeast portion of the Colorado Plateau. The region is characterized by broad, fairly smooth surfaced plateaus and mesas with gently dipping slopes dissected by steep canyons. Surface elevations at the Hamilton Mine range from a high of 6,050 feet (MSL> in the southern part of the permit area to a low of 5,800 feet in the northern parts of the permit area. Total topographic relief is thus about 250 feet. Climate The regional climate of the Hamilton Mine area is typical of intermountain regions. It is characterized by cold winters, hot summers, low rainfall, and short growing seasons. The Hamilton Mine receives approximately twelve inches of precipitation in an average year. The majority of the precipitation falls between October and May. Regional Geology The Hamilton Mine is located near the axis of the Nuc1a Syncline (San Miguel Syncline) a shallow, broad synclinal fold running northwesterly for 65 miles. No evidence of faults has been observed in drill holes at the Hamilton Mine area. The Nucla Syncline is 10-15 miles southwest of the major regional geologic feature of the area, the Uncompahgre Uplift. The region lies in the Dolores River Basin. The mine is located one and one half miles south of the San Miguel River. The mine is located in the Nucla-Naturita Coal Field. The coal is found 1n Late Cretaceous sediments. The youngest Cretaceous rocks 1n the area consist of Mancos Shale, a dark gray marine shale, present only on isolated hilltops south of the town of Nucla. Two hundred feet of Dakota sandstone outcrops extensively along the axis of the Nucla Syncllne. This formation consists of a yellowish-gray, fissile sandstone and conglomeratic sandstone interbedded with dark gray shale and coal. There are nine coal seams within 100 feet of the base of the Dakota (Figure 2). The Lower Cretaceous unit in the area, the -4-