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Air Quality <br /> ,Only particulate emissions would be of concern over the larger <br /> portion of the North Fork Valley. Maximum agnual average and 24-hour <br /> average concentrations 38 ug/m and 111 ug/m (micrograms per cubic <br /> meter) would occur by 1990 due to all activities in the valley. This <br /> would not exceed -the national secondary standard of 150 ug/m3 (FWCCCES, <br /> P. 239). <br /> Geologic and Geographic Setting <br /> The 854-acre tract lies on the southern slopes of Grand Mesa. The <br /> aspect, relief, and topography of the tract are controlled by a promi- <br /> nent north-south trending ridge system which separates the Stevens Gulch <br /> drainage from the Terror Creek drainage. The eastern boundary of the <br /> tract li.es immediately west of the ridge crest. <br /> Topography of the tract is extremely rugged. Altitude varies from <br /> 7,850 feet along Stevens Gulch to over 8,700 feet along the extreme <br /> northeast boundary. Elevation continues to rise to well over 10,000 <br /> feet on Grand Mesa, 3 miles north of this tract. The greatest relief on <br /> the tract occurs along south-facing slopes where slopes may average. 60 <br /> percent. Gentler west-facing slopes average 20 percent. <br /> On this tract, the coal-bearing sedimentary strata of the Mesaverde <br /> Formation are relatively flat-lying. They strike N. 88 degrees W. and <br /> dip 6 degrees to the northeast. <br /> To date there has been no visible evidence of surface subsidence at <br /> the existing mine. As the mine develops further, and as panels are <br /> developed and then. mined on retreat, the likelihood of surface subsi- <br /> dence effects will increase. <br /> Paleontology <br /> At this time it is not known whether significant paleontologic <br /> resources exist on the site. <br /> Mineral Resources <br /> There are three major. or dominant coal seams lying on this tract. <br /> All of the seams lie in the Upper Cretaceous Mesaverde Formation. The <br /> uppermost ofthe three coal seams, designated the D seam, is presently <br /> being mined just south of this tract at the Orchard Valley Mine. In <br /> addition, the short-term lease application covers only those coal re- <br /> serves lying in the D seam. <br /> The D seam varies from a thickness of 26 feet at the outcrop to <br /> approximately 8 feet along the extreme northwest tip of the tract. <br /> Drilling data indicate that the seam thins to approximately 4 feet <br /> 8 <br />