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Several cultural resource inventories have been conducted within the lease <br />areas. They include: "An Archeological Clearance of BLM Lands for the <br />Cambridge Mining Company" (Conner 1975); "Antiquities Inventory for Cambridge <br />Mining Company: Coal Mine Portal and Area for Coal Mine Debris Disposed in <br />Coal Canyon and Coal Gulch, Cameo, Colorado" (Wignall and Conner 1977); and <br />portions of an inventory entitled "Final Report of an Archeological Survey of <br />the West Central Colorado Coal Leases" (Hibbets et al. 1979). All total, over <br />10% of the lands in the lease areas have been inventoried for cultural <br />resources at a class III level. <br />No sites were identified in the areas inventoried by Conner and Wignall and <br />Conner. A total of 28 sites and 38 isolated finds were identified by Hibbets <br />in coal leases C-029889 and C-024998. <br />According to the mine plan submitted by Powderhorn Coal Company, there will be <br />no direct surface disturbance within the lease areas. All proposed activity <br />will be in the form of underground coal mining operations. Therefore, there <br />will be no direct adverse impacts on any sites that are eligible for listing <br />on the National Register of Historic Places within the lease areas. <br />There is a potential for some indirect impact to occur to sites eligible for <br />listing on the National Register from subsidence in areas where underground <br />mining will take place. <br />Because it is not possible to determine with any certainty the exact extent to <br />which, or location where, subsidence may occur, requirements were stipulated <br />as a result of the BLM's mine plan review in the decision package issued by <br />the Office of Surface Mining. The reader is refered to OSM's orginal mine <br />plan approval for a detailed discussion of these stipulations. <br />Since the proposed operation will not affect any sites listed on the National <br />Register of Historic Places, the proposed operation is in compliance with the <br />requirements of this section. <br />IV. Geology (2.04.5, 2.04.6) <br />The area to be affected over the life of the operation is part of the <br />Bookcliffs coal field which is an outcropping of the Mesaverde Group. The <br />Bookcliffs coal field is situated on the southern rim of the Uinta Basin. The <br />structural rim of the basin falls along the crest line of the Umcompahgre <br />uplift, some 30 miles to the south. The coal seams of the project area occur <br />in the Mount Garfield Formation of the Mesaverde Group. For purposes of <br />description of the localized structure in the general vicinity of the permit <br />area, the Bookcliffs coal field is characterized by a monoclinic al structure <br />with the strata dipping gently to the northeast. The surface geology of the <br />project area is mapped in Exhibit 13 of the application. The general <br />stratigraphy and structure is depicted in the cross-section and geologic <br />column of Exhibit 14 of the application. <br />-10- <br />