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D°cember 1. ?_tl(73 <br />Prig, 3-a <br />3) Surface occupancy or use would be controlled on lease tract slopes between 40 and 60 percent. <br />Before any such occupancy or use on lands with such slopes, a special interdisciplinary team . <br />(IDT) analysis and mitigation plan detailing construction and mitigation techniques would be <br />required. The IDT could include specialists such as a soil scientist, hydrologist, landscape <br />architect, reclamation, and a coal mining engineer. It would be expected that the mitigation <br />measures required 6y such an IDT would be highly effective in preventing impacts fo the <br />topography of the affected area. <br />3.3 Geology <br />For geology, the project impact area is the West Flatiron LBA tract area. The cumulative impact area <br />includes the area encompassing the West Elk Mine. <br />3.3.1 EXlsting COndltlons - <br />The LBA tract lies in the Paonia-Somerset coal field. The main coal beds within this area are found in the <br />Upper Cretaceous Mesaverde Formation, which is overlain by the Tertiary Wasatch Formation and <br />underlain by the Upper Cretaceous Mancos Shate. See Figure 3-2, Typical Geologic Cross-Section. <br />The coal bearing sedimentary strata of the Mesaverde Formation are relatively flat lying with a regional <br />dip of three to four degrees to the north/northeast. Local dips can vary. There are geologic faults in the <br />area, but fault displacements are minimal, and the faults are not readily discernable on the surface. <br />The principal mineable coal seam on the LBA tract is the "B" seam. Other seams within the tract are <br />either considered too thin (less than six feet) or are too discontinuous to mine. The B seam is the seam <br />that is currently being mined at the West Elk Mine, and it is logical that planned MCC longwall panels be <br />extended into the West Flatiron LBA tract. <br />The overburden overlying the B seam is generally greater than 500 feet and reaches over 2,100 feet <br />beneath the flat-topped mesa known as the West Flatiron Mesa. See Figure 2-2, Overburden Isopach <br />Map. <br />Geologic hazards are present in the LBA tract in the form of current and historic rock falls, landslides, and <br />slumps associated with unstable moderate to steep slopes. Areas of instability are typically associated <br />with steep slopes and saturated soil conditions. Slope aspect relative to geologic structure also affects <br />stability, where dipping structure daylights on exposed slopes. <br />3.3.2 Environmental Consequences <br />Alternative 1 -Proposed Action <br />Coal would be mined by longwall techniques, and overburden would be altered due to subsidence after <br />coal recovery. See Section 2.g, Reasonably Foreseeable Development Scenario, and Section 3.2.2, <br />Environmental Consequences, Alternative 1 -Proposed Action, <br />After coal recovery, the strata overlying the LBA tract would be altered due to subsidence. Subsidence <br />would occur due to the extraction of coal on retreat from the longwall panels. There would be a gradual <br />Ern:irrnn~enta! Asshsum~sni <br />!~un,a,on County, Cglorado <br />• <br />