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Based on this evidence, we consider that all mining areas • where total extraction is practiced and where less than 800 feet of overburden overlies the coal seam should be considered to have a high risk of subsidence cracks developing at the surface. 8.2 PREDICTED IMPACTS ON RESOURCES, STRUCTURES AND FACILITIES Most of the land under which mining will occur is currently used for relatively low intensity agricultural purposes such as forestland, rangeland and grazing, with limited local hay production. These activities should not be sensitive to the effects of subsidence and are unlikely to be adversely affected directly. However, to the extent that these activities depend on water, there will be a negative impact on them if necessary water sources aye disrupted. Subsidence cracks, while open, would pose a c:anger to the cattle or wildlife before they are filled and healed by natural processes. Surface water resources consist of stock ponds and surface streams. These should be unaffected by changes in surface gradients or total subsidence resulting from development of a subsidence profile. The ponds could be • damaged and drained by a subsidence crack that would occur directly below the pond. The probability of such an event is very low and the pond could be easily repaired. The streams could be disrupted by the subsidence cracks; such disruption could occur at any of the North Fork tributaries. Obviously, East Roatcap Creek and Stevens Gulch are the two important drainages that are endangered by such a possibility. Ground water within the Mesaverde Formation has been found to be of limited extent, occurring only as isolated perched water bearing zones. These zones are not currently exploited and, because of their limited extent, have no potential for future development. Disruption of local, perched water bearing zones may occur due to mining where they lie in the immediate vicinity of the mine roof, although, because of the nature of this ground water, this will not constitute an impact on the area's resources. The most significant ground water resour:e identified consists of the alluvial deposits of Stevens Gulch, which supplies water to CwI and other users. There is the potential that subsidence cracks due to mining could drain this aquifer; its protectior. would probably require adequate changes in mining mathods below the area. J: