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EXHIBIT 55B <br /> STREAM CHANNEL PARAMETERS AND CHANGES <br /> DUE TO LONGWALL MINING-INDUCED SUBSIDENCE <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. <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 /> Fork). Basin 37 is Deep Creek, a tributary to Raven Creek, which is a tributary to the North Fork. <br /> Basins 38 and 39 are within the South Prong watershed, tributary to the East Fork of Minnesota <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. <br /> 831-032.921 Wright Water Engineers, Inc. <br /> December 2020 <br />