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<br /> <br />831-032.923 Wright Water Engineers, Inc. <br />December 2021 <br /> <br />EXHIBIT 55B <br />STREAM CHANNEL PARAMETERS AND CHANGES <br />DUE TO LONGWALL MINING-INDUCED SUBSIDENCE <br /> <br /> <br />INTRODUCTION TO STUDY <br />Wright Water Engineers, Inc. (WWE) and Ernest Pemberton, P.E.1 determined the extent to which <br />projected subsidence due to longwall mining would impact stream channel stability and sediment <br />transport at Mountain Coal Company, LLC's (MCC) West Elk Mine. Exhibit 55 was originally <br />prepared for the B-seam longwall panels in the Apache Rocks and Box Canyon mining areas in <br />May 1995, with revisions in November 1997 and November 1999. Exhibit 55A was prepared to <br />address the E-seam longwall panels in the South of Divide mining area in April 2004, with a <br />revision in November 2004. Subsequent to Exhibit 55A, MCC obtained the coal lease to the <br />adjacent Dry Fork mining area. Tetra Tech prepared Exhibit 55B in September 2007, using Exhibit <br />55A as a base and incorporating the Dry Fork mining area. The December 2020 update was <br />performed in order to reflect the most current information regarding the layout for the Sunset Trail <br />longwall panels and panel E14 and the projected overburden thickness in these areas. The <br />December 2021 update addressed the replacement of longwall panel E9 with panels E15, E16, and <br />E17. <br />Figure 1 shows the drainage basins and stream channels in the vicinity of the Southern Panels <br />(South of Divide and Dry Fork), Apache Rocks West, and Sunset Trail longwall panels study areas. <br />Although Figure 1 also shows the layout of the development mining, this exhibit only addresses <br />potential impacts due to longwall mining of the panels. Each basin has an identification number <br />that will be used throughout this discussion of stream channel parameters and subsequent changes. <br />As shown on Figure 1, Basins 3 through 6 and 26 through 35 are located in the Dry Fork of <br />Minnesota Creek (Dry Fork) drainage; Basin 36, Lick Creek, is a tributary to the East Fork of <br />Minnesota Creek. Minnesota Creek is a tributary to the North Fork of the Gunnison River (North <br /> <br />1 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.