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Stream Channel Parameters <br />Exhibit 558 and Changes Due to Mining - Induced Subsidence Page 8 <br />IMPACTS OF SUBSIDENCE ON STREAM CHANNELS <br />The projected subsidence under each of the 12 stream channels in the South of Divide mining area <br />has been determined using the output from the Comprehensive and Integrated Subsidence <br />Prediction Model ( CISPM), Version 2.0 (Department of Mining Engineering, College of Mineral <br />& Energy Resources, West Virginia University), as calibrated using site - specific subsidence data <br />and as reviewed by Mr. Richard Dunrud, recognized subsidence expert. Exhibit 60E presents a <br />detailed discussion of the subsidence evaluation. <br />In utilizing the CISPM program, each stream channel reach was defined as to location by "X" and <br />"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 the <br />computer modeling for all 12 of the potentially affected stream channels are 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 in the tributaries overlying the southern <br />portion of the mined permit area where E -seam mining thickness is projected to be at a maximum <br />(14 feet). For these channels, the maximum changes m i slope are an increase of 2.5 percent and a <br />decrease of 2.5 percent. Since the pre - mining average slope of these channels ranged from 8.5 <br />percent to 19.5 percent, the slope changes due to subsidence do not create any reaches with <br />negative or flat slopes. Slope impacts magnitudes are greatest in the lower reaches of Basins 29 <br />and 32, where the pre - mining slopes are approximately 4.8 percent and 4.0 percent, respectively. <br />The pre- and post - mining profiles for Basins 29, 32 and 36, shown in Figures 15, 16, and 18 <br />respectively, demonstrate that the overall channel slope is not significantly impacted by <br />subsidence. <br />Basins 5, 6, 26 and 31 generally overlie mining panels with mineable coal thicknesses ranging <br />from 9 to 14 feet. The subsidence from mining in these areas will result in changes in the slopes <br />• of the stream channels ranging from a maximum increase of 1.9 percent to a maximum decrease <br />831 - 032.810 Wright Water Engineers, Inc. <br />