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Stream Channel Parameters and Changes <br /> Exhibit 55B Due to Longwall Mining-Induced Subsidence Page 12 <br /> IMPACTS OF SUBSIDENCE ON STREAM CHANNELS <br /> The projected subsidence under each of the 8 studied stream channels in the study area was <br /> calculated using Surface Deformation Prediction System (SDPS), Version 6.2G (Department of <br /> Mining Engineering, University of Kentucky; Department of Mining and Minerals Engineering, <br /> Virginia Polytechnic Institute and State University), as calibrated using site-specific subsidence <br /> data. Exhibit 60E presents a detailed discussion of the subsidence evaluation. <br /> All longwall panels were set at an elevation of zero, with the stream channel represented above <br /> based on overburden thickness. In utilizing SDPS, each stream channel reach was represented as <br /> a series of points (spaced 200 feet apart)with X, Y, and Z coordinates. The Z value for each point <br /> is the approximate overburden depth based on 10-foot overburden contours provided by MCC. <br /> Subsidence and changes to channel slope were determined along the profile. <br /> Table 4 shows that the most significant changes will occur in the tributaries overlying a significant <br /> portion of both the B-seam and E-seam panels. The E-seam mining thickness is projected to be <br /> 143 feet at a maximum to the west, and 11 feet at a maximum to the east. The B-seam thickness <br /> is projected to be 9 feet in the most southerly panel, and 14 feet at a maximum to the north. The <br /> Sunset Trail panels mined in the E-seam are expected to have similar mining thickness values, <br /> with lower mining heights projected near the eastern end of the panels. <br /> Basin Number 3 is the Horse Gulch basin, a tributary to Minnesota Reservoir. Because the B- <br /> seam has already been mined, this basin will only be affected by proposed E-seam mining. Basin <br /> 3 channel's slope will increase by a maximum 10.6% and will decrease by a maximum 2.9% due <br /> to E-seam mining. Because the pre-mining average slope of this channel is 11.1%, the slope <br /> changes due to subsidence do not create any reaches with negative or flat slopes. Maximum <br /> subsidence along the stream profile is approximately 8.3 feet. The pre- and post-mining profiles <br /> for Basin 3 are shown in Figure 21. This figure demonstrates that the overall channel slope is not <br /> 'Practically speaking,the maximum mining height with the current longwall is 13.5 feet;therefore,WWE <br /> used a height of 13.5 in the computer modeling. <br /> 831-032.921 Wright Water Engineers, Inc. <br /> December 2020 <br />