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IV. ENVIRONMENTAL AND LAND USE CONSEQUENCES ALTERNATIVE A -- PROPOSED .4CTION It•1PACTS AND CONSEQUENCES OF ALTERNATIVE A There will be no significant impacts to the climate, visual resources, recreation, cultural resources, and .the present land use. Air Quality There should be an insignificant impact to the air quality of the area as a result of t~e proposed action. Regional TSP levels may increase less than 1 ug/m (AGM). The TSP levels at the proposed lease site may increase less than 2 ug/m3 (AGt~1). CAAQS and NAAQS and the federal and Colorado PSD increments will not be, exceeded. There should be no impact on the air quality (as measured by the TSP levels) in the t•lesa Verde National Park as a result of the proposed action. Visibility in the region will be unaffected. Geology and Geographic Setting Evidence of possible subsidence fractures is present on the existing lease tract P-058300. The fractures were obs erved in an area approxi- mately 300 feet north of the emergency lease boundary. The area of possible subsidence is above the western edge of the pillars that were extracted in the mine approximately one year ago. The above evidence suggests that subsidence could occur due to extrac- tion of the 6-foot coal seam and pillars on retreat in the application area. Although a maximum subsidence of 6 feet could occur, the most -likely showing on the surface would be extension cracks such as, the ones identified on the existing lease. This would especially be the case in the SE';SW'< of section 32 (T. 35 N., R. 11 W., NM PM) where overburden thickness is approximately 50 feet in the bottom of Pine Gulch. Exten- sion cracks and other subsidence features would show on the surface at any time from one year to any number of years after pillar extraction. - . Subsidence fractures could allow the escape of methane gas to the surface and could Increase the hazard of underground and surface fires.' Although this is not likely due to the low liberation of methane in the mine (less than 1`6), the potential of causing surface impacts i~s present. Regulations in 30 CFR 211.31 and 817.121 require that underground mining activities be planned and conducted to control or prevent subsidence and 19