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Stream Channel Parameters <br />Exhibit 55 and Changes Due to Mining-Induced Subsidence Page 7 <br />IMPACTS OF SUBSIDENCE ON STREAM CHANNELS <br />The projected subsidence under each of the 16 stream channels has been determined using the <br />output from the Comprehensive and Integrated Subsidence Prediction Ntodel (CISPIvt), Version <br />2.0 {Department of Mining Engineering, College of Mineral & Energy Resources, West Virginia <br />University), as calibrated using site-specific subsidence data and as reviewed by Mr. Richard <br />Duruvd, recognized subsidence expert. Exhibit 60 presents a detailed discussion of the <br />subsidence evaluation performed by WWE and Mr. Dunrud. <br />In utilizing the CISPM program, each stream channel reach was defined as to location by "X" <br />and "Y" coordinates. Channel slope changes along with the magnitude of the subsidence were <br />determined for relatively short stream lengths of approximately 100 feet or less. The results of <br />the computer modeling for all 16 of the potentially affected stream channels is shown in Table 4. <br />The slope change, either positive or negative, was either added to or subtracted from the existing <br />channel thalweg slope as determined from computations based upon USGS topographic maps <br />with a contour interval of 40 feet. <br />Table 4 shows that the most significant changes will occur to the south-facing tributaries to Dry <br />Fork (Basins 3, 4, and 5) due to the two-seam mining (B- and E-Seams) under these channels. <br />For these channels, the maximum changes in slope are an increase of 3.7% and a decrease of <br />5.2%. Since the pre-mining average slope of these channels ranged from 8.8% to 18%, the slope <br />changes due to subsidence do not create any reaches with negative or flat slopes. This is <br />displayed graphically for Basin 3 (Horse Gulch) in Figure 19. The pre- and post-mining profiles <br />for Basin 3, shown in Figure 20, demonstrate that the overall channel slope is not significantly <br />impacted by subsidence. <br />Basins 8. 9, and I1 through I~ are subbasins within Sylvester Gulch. The subsidence from <br />mining in these areas will result in changes in the slopes of the stream channels rangine from a <br />maximum increase of l.~% to a maximum decrease of 1.4%. These slope changes will be <br />insignificant on the stream channels within the Sylvester Gulch drainage, where existing slopes <br />are in excess of 8%. Basin 14 was chosen to graphically display the effects of subsidence on the <br />