2018-09-04_PERMIT FILE - C1980007A (44)

Home Browse Search

West Elk Mine • to the cliff faces along Minnesota, Dry Fork, and Lick Creeks and on the perimeter of West Flatiron Mesa. About 1 ] percent of the mine area would be defined as steep topography. The greatest effect of topography should be in the northern and eastern one-third of the property, where topography is generally the steepest. Thickness of overburden is closely related to steep topography. Steep topography is of greatest significance where overburden is the thickest. Maximum cover over the E Seam where mineably thick on the permit area is about 1,200 feet. Maximum cover over the B Seam, however, may attain thicknesses of up to 2,300 feet beneath West Flatiron Mesa. Mining conditions have been observed at the Sanborn Creek and Elk Creek Mines (Oxbow Mining, LLC) and Bowie No. 1 Mine (Bowie Resources, Ltd.) in their D Seam (stratigraphic equivalent to MCC's E Seam) where overburden thicknesses aze similaz at 800 to 1,200 feet. The gate road orientations and coal pillaz dimensions do not coincide exactly with those at the West Elk Mine, but some general inferences can be drawn. Both the Elk Creek and Bowie No. 1 mines exhibited good to excellent roof and rib stability. E Seam rib stability should not present excessive problems and can be controlled via standazd mechanical methods. Roof control measures, pillaz configuration, and mining horizons will be evaluated on an ongoing basis to optimize design of the entries. Although mining in the B Seam in the South of Divide permit revision area may be limited or precluded by seam conditions, MCC does have experience with mining in areas of overburden in excess of 2,000 feet. Where the depth of cover is greater than 1,000 feet, rib sloughage has been more common. Roof conditions in general, appeaz to be moderately affected where thick overburden and rapid changes in topography combine. E Seam overburden thicknesses are signi£cantly less in the permit area (Map 19); therefore steep topography is not anticipated to affect future E Seam mining. Pillar design modifications to the B Seam mine plan have been implemented to assure roof and rib stability and mine safety when mining under deeper cover. Geoloeic Hazards and Slope Stability In order to evaluate the geologic hazazds in the West Elk Mine coal lease azea, the definition and the concept of geologic hazazds should be reviewed. The legal definition in the Colorado Revised Statutes 24-65.1-103 is "Geologic Hazard means a geologic phenomenon which is so adverse to past, current, or foreseeable construction or land use as to constitute a significant hazard to public health and safety or to property." In other words, this applies to normal geological processes that constitute a hazazd to health, safety, or to property. Therefore, as the geologic hazazds in the West Elk coal lease azea and the pemut azea aze reviewed, the lack of structures or habitation, and the negligible public visitation must be considered. In western Colorado in the azeas of Mesaverde outcrop, landslides and slope stability processes are widespread. These conditions apply whether or not the azea has ever been mined. The stability conditions aze often exacerbated by man's activities involving excavation, construction and fills. Fortunately, MCC conducts underground mining activities in the permit area. Most related surface activities can be conducted with the existing network of primitive roads. 2.04-37 Revised November 2004 PRIO