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• periodically by the various regulating agencies (OSM and DMG) during inspections. <br />Evidence of subsidence fractures following pillar extraction in 1979 has been noted on National <br />King Coal's Federal lease P-058300 in an azea approximately 300 feet north ofthe lease boundary <br />and onthe east limb ofthe lease above the western edge ofpillars that were extracted. Subsidence <br />fractures have also been observed in the 100-acre portion of the mine located on the Ute <br />Mountain Ute Reservation. Specifically, monitoring has found that some subsidence fractures <br />appeazed about 6 months after pillar extraction began. Cracks ran for a distance ofabout 200 feet <br />where overburden depths ranged from 100 feet (drainage ways) up to 300 feet (ridgetops) and <br />tended to follow the contour of the surface topography. They opened as much as 6 to 12 inches <br />wide and 9 feet deep with most evident cracks being on the side slopes. Frost-heaving and <br />sediment deposition reduced crack size to 1 to 2 inches within 12 months after they first <br />appeazed. There was no apparent change in ground elevation or land use. <br />Subsidence could also occur during the extraction of 4.5 to 5.7-foot coal seam pillazs on the <br />retreat in the proposed 160-acre lease area. While a maximum subsidence of 6 feet could occur, <br />the most likely showing on the surface would be tension cracks such as the ones discussed above. <br />The greater thiclmess of overburden in this area (i.e., 300 to 400 feet), however, suggests that <br />subsidence will not be as evident as it has been in those azeas. <br />Subsidence fractures could also allow the escape ofinethane gas to the surface and could increase <br />• the hazard of underground and surface fires, although this is not likely due to low liberation of <br />methane from the Menefee coal. <br />3. Vegetation <br />Direct Impacts -Some minimal impacts to vegetation would result if subsidence occurs. <br />Indirect Impacts - No impacts have been identified. <br />Cumulative Impacts - No impacts have been identified. <br />4. Wildlife <br />Direct Impacts -Since the proposed action is for subsurface mining, no direct impacts to big <br />game are anticipated. There aze no anticipated impacts to wildlife due to the possible subsidence <br />that may occur. <br />Indirect Impacts - No indirect impacts to area wildlife are expected from development of the <br />,, ~ 14 <br />t <br />