2008-08-15_PERMIT FILE - C1982056A (4)

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feet. The subsidence projections and evaluation of potential related effects on the designated Fish Creek AVF are documented in Exhibits 7B, 7C, 45, and 46. During initial mining of Panel 6, Well GWB-2 was subsided, as predicted, and the well was damaged and subsequently replaced. A replacement well (GWB-2R) was installed adjacent to the existing well. Well GWB-2R was constructed adjacent to the existing well as a two-inch well with Schedule 80 PVC. The well completion report was forwarded to the Division. The two wells were monitored for water levels twice per week for atwo- weekperiod, thereafter only Well GWB-2R will be monitored per the schedule presented on Table C of Exhibit 14. Well GWB-2 was sealed with Volclay and permanently abandoned. Prior to permanently abandoning well GWB-2, the Division. inspected the well and provided Twentymile Coal Company with approval for well abandonment. Originally, it was anticipated that room and pillar mining would be required to augment longwall production. Given, however, the productivity, efficiency, and higher recovery for the longwall mining system, the need no longer exists to identify a room and pillar area on the east side of the North Mains. As shown on Maps 23, and 23A, an additional longwall panel is planned to the east of the North Mains. Approximately 60,000 feet of mains are expected to be driven during the life-of--mine. Areal Extent The permit area of the underground mine, totals approximately 21,720 acres, of which approximately 9,000 acres have been affected, with approximately another 1,700 acres to be affected under the currently approved mine plan (2007). These areas contain all mineable coal reserves bordered by the 15 percent gradient cutoff line to the east and west and the property line to the south. At the conclusion of mining, approximately 65 percent of all the coal contained within the mineable reserve area will have been extracted (see Maps 7, 8, 9, 9a and Figure 1, Geologic Cross-Sections A-A' through E-E'). S Minim Layout The underground mine layout was designed with the objective of rapid development, optimum access to outlying reserves and maximizing recovery and safety. Numerous physical, geotechnical and operational variables influenced design of the mining layout. Mining activities are bordered on the east and west by lease boundaries, to the south by a lease boundary and mined-out reserves, and to the north by a 15 percent seam gradient cutoff limit. Reserve access is by a network of main entries oriented primarily north-south and east-west. Longwall panels are planned wherever geologically possible and consistent with safe and prudent mining practices. The following factors influenced the layout of the underground mine: Lease Boundaries -Limits the extent of mining extension Geotechnical Characteristics -Including rock and coal strengths, jointing, cleating and quality Structural Features -Major fault zones and steep gradients are avoided or crossed selectively Reserve Access -Minimal development and capital cost and optimum men and materials transport Orientation -Mains, sub-mains and panels are oriented to avoid directions that have the potential for instability Water -Inflow and control has been considered through sump location and up-dip development Subsidence -Controlled subsidence is planned over areas of full seam coal extraction • TR07-63 2.05-13 09/14/07