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14. Invasive, Non-native Species Prevention, eazly detection, control and eradication of small noxious weed patches remain the most pracvcal, economical and effective means of weed management. 'deeds will be treated on an as needed basis. Signature of specialist: Mary Lendman 2r'27/Ol NON-CRITICAL ELEMENTS Soils Since only minimal active surface disturbance is proposed, soil impacts from these impacts would be minimal. Subsidence could occur, which could result in some low-volume, localized soil erosion. At the time that support pillars are removed, a cumulative impact from subsidence could occur throughout the mined area. However, in light of the requiremerit in State regulations to conduct operations in such a manner as to control orprevent effects of subsidence, this is not expected to be a major concern. 2. Geology and Mineral Resources • S ubsidence fractures could impact topography and surface features in the area of the proposed lease. The DMG rules require that "underground mining activities shall be planned and conducted so as to prevent subsidence from causing material damage to the surface." Material damage is defined with respect to subsidence as changes which prevent restoration of affected structures and with respect to renewable resource lands; changes which disrupt an aquifer, or a rechazge area to an aquifer, which serves as a beneficial use of water, or changes which prevent restoration of productivity for agricultural lands. In addition, National King CoaPs permits to mine coal from Colorado DMG and OSM require Cabal the company monitor subsidence on a quarterly basis. Some monitoring is also preformed periodically by the various regulating agencies (OSM and DMG) during inspections. Evidence of subsidence fractures following pillar extraction in 1979 has been noted on National King Coal's Federal lease P-058300 in an azea approximately 300 feet north of the lease boundary and on the east limb of the lease above the western edge of pillazs that were extracted. Subsidence fractures have also been observed in the 100-acre portion of the existing mine located on Ute Mountain Ute owned land. Specifically, monitoring has found that some subsidence a~actures appeared about 6 months after piliaz extraction began. Cracks ran for a distance of about 200 vet where overburden depths ranged from 100 feet (drainage ways) up to 300 feet (ridge tops) and tended to follow the contour of the surface topography. They opened as much as 6 to 12 inches wide and 9 feet deep with most evident cracks being on Cue side slopes. i TvSt-1:.°•a:iP.s 3 nd S.°.d:ment • deposition reduced crack size to 1 to 2 inches within 12 months after they first appeazed. There was no apparent change in ground elevation or land use. 14