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December 1, '2003 Page 3-4 3) Surface occupancy or use would be controlled on lease tract slopes between 40 and 60 percent. Before any such occupancy or use on lands with such slopes, a special interdisciplinary team (IDT) analysis and mitigation plan detailing construction and mitigation techniques would be required. The IDT could include specialists such as a soil scientist, hydrologist, landscape architect, reclamation, and a coal mining engineer. It would be expected that the mitigation measures required by such an IDT would be highly effective in preventing impacts to the topography of the affected area. 3.3 Geology For geology, the project impact area is the West Flatiron LBA tract area. The cumulative impact area includes the area encompassing the West Elk Mine. 3.3.1 Existing Conditions The LBA tract lies in the Paonia-Somerset coal field. The main coal beds within this area are found in the Upper Cretaceous Mesaverde Formation, which is overlain by the Tertiary Wasatch Formation and underlain by the Upper Cretaceous Mancos Shale. See Figure 3-2, Typical Geologic Cross-Section. The coal bearing sedimentary strata of the Mesaverde Formation are relatively flat lying with a regional dip of three to four degrees to the northlnortheast. Local dips can vary. There are geologic faults in the area, but fault displacements are minimal, and the faults are not readily discernable on the surtace. The principal mineable coal seam on the LBA tract is the "B" seam. Other seams within the tract are either considered too thin (less than six feet) or are too discontinuous to mine. The B seam is the seam that is currently being mined at the West Elk Mine, and it is logical that planned MCC longwall panels be extended into the West Flatiron LBA tract. The overburden overlying the B seam is generally greater than 500 feet and reaches over 2,100 feet beneath the flat-topped mesa known as the West Flatiron Mesa. See Figure 2-2, Overburden Isopach Map. Geologic hazards are present in the LBA tract in the form of current and historic rock falls, landslides, and slumps associated with unstable moderate to steep slopes. Areas of instability are typically associated with steep slopes and saturated soil conditions. Slope aspect relative to geologic structure also affects stability, where dipping structure daylights on exposed slopes. 3.3.2 Environmental Consequences Alternative 1 -Proposed Action Coal would be mined by longwall techniques, and overburden would be altered due to subsidence after coal recovery. See Section 2.9, Reasonably Foreseeable Development Scenario, and Section 3.2.2, Environmental Consequences, Alternative 1 -Proposed Action. After coal recovery, the strata overlying the LBA tract would be altered due to subsidence. Subsidence would occur due to the extraction of coal on retreat from the longwall panels. There would be a gradual Envircnn~enia! Assessment Ndest F=latiron LQA Tr~]ci Cunr:isan County, Calc~rado