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Chapter 3 Affected Environment and Environmental Consequences effects analysis area includes the existing West Elk Mine leases and permit area (see Figure 3-1). Information on geology and subsidence came primarily from the draft subsidence report (Agapito 2005, see Appendix B), where more detail on subsidence and calculations can be found. Geologic information contained in MCC's West Elk Mine permits and other published data was also used. Information related to the soil resources within the LBA tract area was obtained from the Interim Soil Survey of Grand Mesa -West Elk Area, Colorado (fryer and Hughes 1997). This survey delineated associations, complexes, and undifferentiated groups throughout the survey area. The survey report provides quantitative and qualitative descriptions of the soils and identifies hazards and considerations for soil use and management. Information related to Geologic hazards was compiled from aerial photo interpretation, personal knowledge, and field mapping. 3.2.3 Affected Environment Topography and Geography The elevations on the LBA tract range from approximately 8,000 feet on the north boundary to just under 9,000 feet on the southeast boundary. The topography in the LBA tract consists of small mesas dissected by deep, incised channels of perennial and intermittent streams. The drainage slopes are typified by cliff and shelf topography, where sandstone outcrops are common along the mesa tops and flanks. The regional topography has been influenced by a wide range of mass movement Landforms and processes within the North Fork of Gunnison River Valley. These included localized natural landslides and fallen rock. Landslides in this region are usually preceded, accompanied, and followed by perceptible creep along the surface or with the slide mass. Areas of instability are typically associated with steep slopes and saturated soil conditions. Much of the LBA tract area contains moderate (40 to 60 percent) and steep (greater than 60 percent) slope areas. Many of the areas identified that are mapped as steep slope areas are exposed bedrock outcrop and cliffs that may have rock-fall potential depending on bedrock integrity. Geologic hazards and steep slope areas within the LBA tract are shown on Figure 3-2, Geologic Hazards Map (compilation of aerial photo interpretations, personal knowledge and third-party accounts). Geology The LBA tract lies in the Paonia-Somerset coalfield. The main coal beds within this area are found in the Upper Cretaceous Mesaverde Formation, which is overlain by the Tertiary Wasatch Formation, Ohio Creek conglomerate and underlain by the Upper Cretaceous Mancos Shale. Surficial deposits consist of colluvial and alluvial material deposited on bedrock surfaces. The coal- bearing sedimentary strata of the Mesaverde Formation are relatively flat lying with a regional dip of three [o four degrees to the north/northeast. Local dips can vary. Coal-bearing strata in the West Elk Mine region consist of interbedded sandstones and shales, with a few massive sandstone beds. Coal is primarily extracted from the E Seam within the Upper Coal Member and the B Seam in the Lower Coal Member of the Mesaverde Formation. The Upper Coal Member also contains two other coal seams (B and F Seams) as well as approximately 220 feet of shales, siltstones, and sandstones. The Lower Coal Member also includes the A and C Seams, has similar lithology to the Upper Member, and is about 270 feet thick (Agapito 2005, see Appendix B). Sandstone channel deposits are occasionally encountered within the Upper and Lower Coal Members (Agapito 2005). The extraction height of previous B and E Seam mining in the West Elk Mine averages 8 to 12 feet and about 10 feet (USDA Forest Service 2004). E Seam overburden ranges from about 1,000 feet in the northwest portion of the tract to about 2,000 feet in the southeast portion of the tract. B Seam cover varies from 1,000 feet to about 2,400 feet from the northwest to southeast (Agapito 2005). Dry Fork Lease-By-Application FEIS 3-5