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NMD and WMD (Panels 17-Right through 25-Right and 12-Left through 17-Left, PR 03-06 and PR06-07) Mining will continue to the northern limit of the NMD and development will be initiated in the WIvID. Mining in • the NMD will result in subsiding Fish Creek and designated Alluvial Valley Floor areas, various stock ponds, the Twentymile Sandstone, powerlines (located over the 19-Right Pane]), and the Union Pacific Raikoad Track. Each of these affected surface structures or resource values aze discussed in the following sections. Initial development in the WMD will belimited to main and sub-main entries, with retention of support and barrier pillars, with no subsidence over these areas. Land Use 'Pastureland and rangeland aze the dominant land uses in this remaining section of the Northern Mining District. The land-use patterns aze presented in Map 3, Premining Land Use. i ExisHne Structures A ui ers ' The Twentymile Sandstone outcrops along sections of the Foidel and Middle Creek drainages. The Twentymile Sandstone is a marginal regional aquifer which extends throughout much of Northwest Colorado. There are no known water supply wells completed in the Twentymile Sandstone in the vicinity of the mine. Powerline The powerlines located to the north of the 18-Right gateroad and within the 19-Right Panel, will be subsided during mining in this section of the Northern Mining District The powerline is adjacent to the gateroad, however, TCC's extensive mining experience indicates that the powerline will not be negatively impacted. "The subsidence report for the powerlines is presented in Exhibit 7e-7. . Railroad The Union Pacific Railroad spur traverses over Panels 17-Right and '18-Right and their associated gateroad during the current five-yeaz permit term (2003- 2008). Overburden thickness vanes from 1,100 to 1,200 feet in the corridor where the railroad passes over the mine workings. The location of the rail line is shown on Map 23B, Structures and Renewable Resowces The worst-case impacts, due to subsiding the railroad track, could result in a train derailment. In the unlikely event that this should occur, the coal spilled From the cazs would be cleaned-up to the extent practical. The coal would be either returned to the caz or hauled back to Twentymile's facility. In the event this occurred during an inclement period and ground conditions did not allow for the clean up, the coal would be cleaned-up during the next favorable period. Twentymile does not plan to construct any permanent roads to facilitate possible clean-up. The required mobile equipment (i.e, trucks and loaders) would drive over the tracks or immediately adjacent to the track-bed. The potential clean-up would be limited to periods of favorable field conditions, thereby reducing the chance that a road will have to be constructed into the clean-up site. A copy of the subsidence agreement between TCC and the railroad is incorporated into Exhibit 7D-1. Any additional agreement letters from different parties will also be incorporated into this exhibit (7D-1). There are two locations where the track crosses Fish Creek which will require placement of additional fill at these crossings. It is anticipated that periodic clean-up of materials from the UP's normal track maintenance activities maybe required. This work will be coordinated through the UP. During mining of the 9, 8, 7, 12, 13 and 14-Right panels, the railroad track was subsided, without causing any derailments or other material damage. The track subsided as predicted and the agreed upon repair/maintenance plan was carried out without any significant problems. The track will be subsided during the mining of Panels 17- iRight and 18-Right. It is anticipated that no problems will result from undermining and subsiding the track, given the knowledge and experience gained through the previous similar activities. PR06-07 2.05-181.9 11/07/06