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Page S-6 Summary February 2000 • S-3.1 Air QualitylClimate Existing Conditions -The air quality and climate in the North Fork of the Gunnison River Valley are influenced by the rugged topography and the prevailing east-southeast winds. The air quality of the region is good. The mountain valleys on the west side of the Rockies are subject to large ranges in precipitation and temperature conditions. The monthly temperature profiles at Paonia, Colorado show a range from an average daily of 24.9 degrees F in January to an average monthly value of 72.6 degrees F in July. Precipitation ranges from 0.08 inches in June to 1.61 inches in October, with an average annual precipitation al Paonia of 15.17 inches. The prevailing wind direction in the North Fork of the Gunnison River Valley near the community of Somerset is east-southeast. The daily cycle of changing up-valley and down-valley local wind directions is common in western Colorado mountain areas. The strongest winds, presumably associated with passing thunder storms and pre-frontal weather are from the south or southwest. Environmental Consequences -Due to anticipated increases in coal production from the existing coal mines in the North Fork of the Gunnison River area, emissions from mining operations in the North Fork Valley and coal trains are expected to increase for the No-Action and Action Alternatives; however, any increase in the local emissions of particulate matter and tailpipe exhaust is not expected to cause any impacts to the existing ambient air quality of the region. In addition, any incremental increases in particulate emissions and gaseous emissions resulting from the action alternatives should not cause any observable, detectable or measurable visibility impacts at the West Elk Wilderness Area or at the Black Canyon National Park. S-3.2 Topography/Physiography Existing Conditions -The topography of the area within and immediately surrounding the exploration license area and the coal lease tracts ranges from steep to relatively Flat. Elevations range from slightly over 5,600 feet in the North Fork of the Gunnison River Valley near the town of Paonia to elevations over 10,000 feet in the mountains surrounding the exploration license and lease tract areas. The topography of the area has been influenced by a wide range of mass-movement land forms and processes at work in the region, including localized natural landslides and rock falls. Environmental Consequences -Exploration activities as proposed for the Iron Point Exploration License Area would have no noticeable topographic impact. If the tracts are leased, subsequent underground longwall mining would cause subsidence and physically lower the surface over mined areas. Effects of subsidence would be most noticeable on ridges and steeper slopes, particularly cliffs, where cracks might open on the order of few inches to possibly 1-foot wide and 25 to 50 feet deep. Fewer cracks would occur in the valleys than on ridges, because the valleys are more stable and the alluvial material found in the valleys tends to be more yieldable than some of the brittle bedrock found on the ridges. Subsidence from longwall mining could aggravate the movement of existing landslides and rock falls in areas of moderate to high subsidence potential. S-3.3 Geology Existing Conditions -The exploration license area and the coal lease tracts lie in the Paonia- Somerset coal field which contains medium to high coal development potential deposits. The main coal beds within this area are found in the Upper Cretaceous Mesa Verde Formation, which is overlain by the Tertiary Wasatch Formation and underlain by the Upper Cretaceous Mancos Shale. In addition to the exposed sedimentary units, isolated igneous intrusions have been encountered in the project