2009-06-22_GENERAL DOCUMENTS - C1981033 (2)

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In 1986 a debris flow at the site displaced the Bear No. 3 Mine fan. In 1993 the area of the access road immediately below the fan slid, dropping the upper road approximately six feet. It is not known if the debris flows were reactivated by mining activity. Bear Coal Company has performed subsidence monitoring quarterly with reports submitted semi- annually. As provided for in the permit application, monitoring stopped two years after the reclamation of the road. The study by Rocky Mountain Geotechnical indicates that mining of the C-Seam would result in propagation of fractures upward through the geologic section for approximately 360 feet. Strata between the C-Seam and the massive sandstone at the top of the lower coal bearing member would be rubbilized to some degree. No rubbilization of the overlying E- and F-Seams was expected to occur. Subsidence of the land surface was expected to a maximum of six to eight feet in the northwestern part of the mine. The permit application required that the operator conduct subsidence monitoring of each mined panel, beginning just prior to retreat mining of that panel. Subsidence monitoring of that panel would continue for a period of two years after retreat mining had occurred. The concern was that the subsidence effects might cause landslides or reinitiate historic landslides. With the cessation of mining in 1996, there was no more subsidence monitoring above mined panels at the Bear No. 3 Mine. The subsidence monitoring results confirmed the conclusions of the subsidence predictions. The maximum and minimum predicted subsidence values corresponded satisfactorily with the maximum and minimum observed subsidence values. Observed subsidence values ranged from negligible to about 6 feet. Shortly after retreat mining underneath the subsidence monuments began, subsidence commenced. The elevations of most of the subsidence monuments decreased steadily although, for a few stations, the rate of change in elevation varied. Subsidence of the monuments generally stopped within about a year or so after retreat mining stopped under that monument. It was predicted that subsidence would have, at most, a small effect on landslides in the area but that there would not be any long term impacts. The subsidence monitoring observations demonstrated that landslides were not initiated by the effects of subsidence and that there were no long term impacts. The mining operation is in compliance with the provisions of this section with the stipulations. XVI. Concurrent Surface and Underground Mining This section does not apply to the Bear Coal Company permit. XVII. Operations on Alluvial Valley Floors Information describing alluvial valley floors (AVFs) in the study area is located in Section 2.06.8 of the Bear No. 3 permit application. The alluvial valley floor findings made by the Division for the Mountain Coal Company's West Elk Mine are directly applicable to the Bear No. 3 Mine. The Bear No. 3 Mine permit area and hydrologically adjacent areas were included in the Mountain Coal Company AVF survey area. No AVFs are located within the Bear No. 3 Mine permit boundary. The only part of the permit or hydrologically adjacent area identified as alluvial deposits are adjacent to the 25