2011-04-26_PERMIT FILE - C1981018A (2)

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C7 III.A.7 Subsidence III.A.7.a Subsidence Area Survey. BME intends to mine coal from Federal Leases C-023703, D-047201, C-0126669, C-8424, C-8425, C-44693 and COC-51551. Map 1 shows the proposed permit boundary and surface facilities. Map 2 shows the mineral and surface ownership in and adjacent to the permit boundary. The surface within the permit area lies within a semiarid region whose main use is winter livestock grazing and wildlife habitat. A detailed pre-construction survey of the property found that six building structures and a county road existed within the permit boundary.. These structures were located adjacent to the abandoned Staley Gordon Mine. The structures were a mine tipple, barn, change house, power house, fan house and scale. The change house and power house were demolished as part of the Ventilation Entry construction. The other four structures were demolished in 1986. Rio Blanco County Road 65 crosses the permit area from SE to NW. During construction, numerous structures and facilities were built within the permit area. These facilities are shown on Map 1. Surface facilities are discussed in Sections III.B and III.C. Portions of reconstructed County Road 65 and 96, the Refuse Haul Road and the 138-kV powerline cross above areas that have been or are expected to experience subsidence from longwall mining. • During the active subsidence, these facilities are monitored and corrected as described in Section III.A.7.h, Damage Mitigation. Also, Raven Park Reservoir and Halandras Reservoir have been subsided. Damage was minimal and did not warrant repair. County Road 73, Lincoln Res., Darwin Res., Red Wash Res. No. 2 and No. 3, and Spooky Mountain Draw Check Dam No. 8 are within the permit area but will not be subsided under the current permit. III.A.7.b Subsidence Control. BME intends to plan and control the surface subsidence by employing the latest technology of ground control. Subsidence is anticipated and its magnitude and extent have been predicted. The magnitude, extent and duration will be minimized to the greatest extent possible by an efficient mine layout, barrier and chain pillars, and a rapid and effective mining system and sequence. Longwall mining will produce the most subsidence, but the subsidence will be (relatively) short-lived, lasting less than 5 years after mining. Room and pillar mining will minimize initial surface subsidence during room advances and lower the surface an almost undetectable 0.025 feet or less. However, wherever chain pillars are not extracted upon the retreat from a panel the so-called "permanent" pillars • Permit Renewal #5 (4/2009) III-9