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EXHIBIT 55B <br />STREAM CHANNEL PARAMETERS AND CHANGES <br />DUE TO MINING -INDUCED SUBSIDENCE <br />INTRODUCTION TO STUDY <br />Wright Water Engineers, Inc. (W WE) and Ernest Pemberton, P.E.1 determined the extent to which <br />projected subsidence would impact stream channel stability and sediment transport at Mountain <br />Coal Company, LLC's (MCC) West Elk Mine. Exhibit 55 was originally prepared for the B -seam <br />longwall panels in the Apache Rocks and Box Canyon mining areas in May 1995, with revisions <br />in November 1997 and November 1999. Exhibit 55A was prepared to address the E -seam longwall <br />panels in the South of Divide mining area in April 2004, with a revision in November 2004. <br />Subsequent to Exhibit 55A, MCC obtained the coal lease to the adjacent Dry Fork mining area. <br />Tetra Tech prepared Exhibit 55B in September 2007, using Exhibit 55A as a base and <br />incorporating the Dry Fork mining area. <br />Figure 1 shows the drainage basins of streams in the vicinity of the Southern Panels (South of <br />Divide and Dry Fork), Apache Rocks West, and Sunset Trail mining areas (study area). Each <br />basin has an identification number that will be used throughout this discussion of stream channel <br />parameters and subsequent changes. As shown on Figure 1, Basins 3 through 6 and 26 through 35 <br />are located in the Dry Fork of Minnesota Creek (Dry Fork) drainage; Basin 36, Lick Creek, is a <br />tributary to the East Fork of Minnesota Creek. Minnesota Creek is a tributary to the North Fork <br />of the Gunnison River (North Fork). Basin 37 is Deep Creek, a tributary to Raven Creek, which <br />is a tributary to the North Fork. Basins 38 through 40 are within the South Prong Creek watershed, <br />tributary to the East Fork of Minnesota Creek. Basin 41 is Lion Gulch, a tributary to Minnesota <br />Creek. <br />As of the October 2018 update of this exhibit, MCC had completed mining in E -seam longwall <br />panels LWE1 through LWE6, had completed longwall mining of the east three-quarters of <br />' Prior to his passing, adjunct Scientist with WWE, Former Head of Sedimentation and River Hydraulics <br />Section, Hydrology Department, Chief Engineer and Assistant Commissioner's Office, U.S. Bureau of Reclamation. <br />831-032.816 Wright Water Engineers, Inc. <br />October 2018 <br />