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Stream Channel Parameters and Changes <br /> Exhibit 55B Due to Longwall Mining-Induced Subsidence Page 13 <br /> projected to be significantly impacted by subsidence. <br /> Basins 29 (Poison Gulch) and Basin 32 (Deer Creek) are tributary to Basin 35 (Dry Fork of <br /> Minnesota Creek). These three basins will be affected by both B-seam and E-seam mining. E- <br /> seam mining in the lower reaches of these drainage basins has already occurred without any <br /> noticeable adverse impacts. Within these three basins, the maximum changes in slope are an <br /> increase of 3.5%and a decrease of 5.1%. Because the pre-mining average slope of these channels <br /> ranged from 5.3% to 9.7%, the slope changes due to subsidence do not create any reaches with <br /> negative or flat slopes. Maximum subsidence along the stream profile of Basins 29, 32, and 35 is <br /> approximately 14.7 feet, 14.3 feet, and 15.2 feet, respectively. The pre- and post-mining profiles <br /> for Basins 29, 32, and 35, are shown in Figures 22, 23, and 24; these figures demonstrate that the <br /> overall channel slope is not projected to be significantly impacted by subsidence. There may be <br /> localized reaches within Deer Creek (Basin 32) where the post-mining slope flattens to roughly <br /> 1%. <br /> Basin Number 36 is the Lick Creek basin, a tributary to East Fork Minnesota Creek. This basin <br /> will only be affected by E-seam mining. The Basin 36 channel's slope will increase by a maximum <br /> of 2.3% and will decrease by a maximum 4.4%. However, since the pre-mining average slope of <br /> this channel is 7.1%, the slope changes due to subsidence do not create any reaches with negative <br /> or flat slopes. Maximum subsidence along the stream profile is approximately 6.5 feet. The pre- <br /> and post-mining profiles for Basin 36 are shown in Figure 25. This figure demonstrates that the <br /> overall channel slope is not projected to be significantly impacted by subsidence. <br /> Basin Number 37 is the Deep Creek basin, tributary to Raven Gulch. This basin will be affected <br /> by both B-seam and E-seam mining. The Basin 37 channel's slope will increase by a maximum <br /> 1.7% and will decrease by a maximum 3.0%. However, because the pre-mining average slope of <br /> this channel is 8.3%, the slope changes due to subsidence do not create any reaches with negative <br /> or flat slopes. Maximum subsidence along the stream profile is approximately 13.4 feet. The pre- <br /> and post-mining profiles for Basin 37 are shown in Figure 26. This figure demonstrates that the <br /> overall channel slope is not projected to be significantly impacted by subsidence. <br /> 831-032.921 Wright Water Engineers, Inc. <br /> December 2020 <br />