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The final area to be impacted by subsidence is associated with mining of the 16-Right Panel. The State of Colorado is the surface owner of the parcel to be undemuned and subsided. As presented above, a total of'4 acres will be flooded by the mining of this panel. As is the case for all the lands along Fish Creek to be undermined and • subsided, no flood irrigation system has been established to increase the productivity •of the ]and nor aze management practices established for haying this area. The land is treated as unimproved rangeland utilized for grazing by TCC's grazing lessee. Ashlev Impoundment and Irritation Ditch ' The Ashley impoundment is located in the SW/4 SW/4 of Section'IS, TSN, R86W. This'impoiindment is of earthen construction, and typically holds water throughout the yeaz. The headgate foY the irrigation ditch is located in the SE/4 NE/4 of .Section 19, TSN, R86W. TCC has undermined and subsided sediment ponds during the ~minitig of reserves located in the west part of the permit area. No material damage to the ponds resulted from the mining activity. ~ It is anticipated that the Ashley impoundment will react in the same manner. If cracks develop in the embankment, they can be repaued and regraded to maintain the integrity of the impoundment. In reference to the smaller impoundment, TCC does not plan on any maintenance due to its current condition. If the owner maintains it prior to mining, then TCC will perform repairs as needed. NMD and WMD (Panels 17-Right through 25-Right and 12-Left through 17-Left, PR 03-06 and PR06-07) Proposed mining in the remaining portion of the NMD, and initial development in the WMD should not result in material damage or diminution of reasonably foreseeable use of structures or resources in the five-yeaz mine plan. The structures which will be subsided within the five-year mine plan area include stock ponds, powerlines (Public Service, Western Area Power Association and Tri-State), the Twentymile Sandstone, Union Pacific Railroad Track (formerly Southern Pacific), and Fish Creek and associated Alluvial Valley Floor areas. Stock Ponds There aze a number of small stock ponds located throughout the NMD and WMD, as shown on Map 23B. The ponds aze constructed of earthern materials and aze typically fed by spring runoff or rain storms. TCC has undermined and subsided similaz stock ponds during mining of reserves located in the northern and eastern part of the permit azea. No material damage to the ponds resulted from the mining activity. It is anticipated that the stock ponds will react in the same manner. If cracks develop in the embankments, they can be repaired and regraded to maintain the integrity of the ponds. Similarly, if differential subsidence results in changes in the elevation of the pond embankments relative to the containment basins, minor repairs/reconstruction may be necessary to maintain water storage capacity and assure the integrity of the embankments. Powerlines Twentymile successfully undermined and subsided a series of powerlines during the mining of Panels 9, 6, 5, 4, 3 and 2-Right. The powerlines were monitored per the approved plan and the resulting data was presented in semi- annual subsidence reports. The results of the monitoring show that the lines subsided, but they did not fail or experience foundation failure. This verified the contention that no impacts will be realized due to undermining and subsiding the lines. This same reasoning will be applied to the lines to be undermined by Panel 19-Right. The subsidence prediction for the powerlines is presented in Exhibit 7e-7, Twentymile Coal Company, 19-Right Powerline Study, fmal Report, prepared by SubTerra, Inc. in May 2003. As is shown, the subsidence will vary from 36 to 48 inches over the panel. The powerlines aze located closer to the 18-Right gateroad, which is the reason for the lower subsidence predictions, i.e. centerline of panel versus actual location. u PR06-07 2.05-184.7 1 I/07/06