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CHAPTER III <br />• THE AFFECTED ENVIRONMENT <br />A. General Setting <br />The Bear No. 3 Mine is located at the southwestern extremity <br />of the Piceance Creek Basin in the Paonia Coal Field. The <br />coal is mined from the Upper Cretaceous Mesaverde Formation. <br />The formation is overlain by the Ohio Creek Conglomerate, <br />then the Wasatch Formation of early Tertiary age and Quartz <br />Monzonite porphyry of Tertiary age. The Mesaverde Formation <br />is underlain by a 2000 to 3000 foot sequence of Mancos <br />shale, a result of the Cretaceous Mancos seas. The coal is <br />mined from the C and B seams of the lower coal member or <br />"Paonia Member" of the Mesaverde Formation. The lower coal <br />member averages some 270 feet thick and bears three minable <br />coal seams. The strata in the mine area dips from 3 to 5 <br />degrees in a north-northeast direction. The C seam ranges <br />from 4 feet to 9 feet in thickness while the B seam averages <br />around 25 feet thick. The coal is a low sulfur, low ash, <br />moderate BTU, and is classified as a bituminous coal <br />considered excellent for steam and domestic uses. <br />The area is characterized by deeply dissected terrain with <br />steep slopes in the drainage of the North fork of the <br />Gunnison River. Much of the area is overlain with colluvial <br />• sand deposits from various types of mass wasting, including <br />a large landslide in Section 17. The facilities area is on <br />a 500 year flood plain terrace of the North fork of the <br />Gunnison. <br />Climatic conditions in West-Central Colorado are variable <br />due to the extreme topographic changes in the region; <br />consequently, many extremes are prevalent. The town of <br />Somerset, next to the Bear Mine, receives about 25 inches of <br />precipitation yearly, mainly occurring in the fall and <br />winter months. The mean annual temperature for Paonia the <br />nearest meteorological station for which data is available <br />is about 50°F, the climate is generally favorable for fruit <br />growing (apples and cherries). Winds generally are <br />channelized by the North Fork Valley that runs east/west. <br />Particulate air quality in the study area ranges from 20 to <br />132 micrograms per cubic meter (ug/m') annual geometric mean <br />as recorded at sixteen state, municipal, and private <br />operated particulate sampling sites. In undeveloped <br />sections, particulate concentrations range for 20 to 40 <br />ug/m3. There has been no measurement of carbon monoxide, <br />Hydrocarbon, nitrogen oxides, sulfur dioxide, or other <br />gaseous pollutants near the proposed site. Since no major <br />sources of these pollutants exist in the surrounding area, <br />• 5 <br />