2025-06-30_PERMIT FILE - C1981019

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RULE 2 PERMITS Rule 2 Permits 2.04-10 Revision Date: 6/4/25 Revision No.: MR-264 by dips from nearly horizontal to as much as 20 ° to the north. As the mine advances southward, the structure is influenced by the Elkhorn Syncline and a change in attitude of the structure occurs resulting in an eastward dip and nearly north-south strike. Local deviations in this general trend are the result of discontinuous minor folds resulting from differential compaction. During geologic mapping, there was no evidence of faulting in the rock units within the mining area; however, some linear features that may be fault controlled were observed on aerial photographs of the property. Such lineations may also be related to joints (fractures without appreciable movement) in the rock. Three major joint trends that generally coincide with these lineations were observed within the permit area. These are nearly vertical or vertical and strike approximately north 70° west, north 45° west, and north 30° east. In surface exposures, sandstone exhibits joints more readily than highly oxidized and weathered coal beds do; however, both have undergone similar stresses and have developed similar readjustment features that are apparent in the subsurface. The site specific stratigraphy is described in Exhibit 6, Geological Information, and is graphically shown on the Geologic Cross Section A-A’ (Map 8) and the Geologic Cross Section B-B' (Map 9). Three additional geologic cross sections (C-C', D-D', and E-E') that show the coal seam geometry and pit limits are provided in Map 9A. The topographic locations of the geological cross sections are found on the Geology Map (Map 7A). The coal seams to be mined at the Colowyo operation are the “Y3“,“Y2“,“X“,“A2“,“A3“,“B1“, “C“, “D“, “E“, and “F“ coal seams. These coal seams are found in the Williams Fork Formation and lie within a sequence of sedimentary rocks characterized by sandstones, claystones, siltstones, shales and carbonous and silty shales. This sedimentary sequence is typical of cyclothems deposited along the linear clastic shoreline located at the western edge of an epicontinental seaway which was located in interior western North America during most of Late Cretaceous time. The analyses of the various coal seams to be mined are shown in Table 2.04.6-1, Typical Coal Seam Analyses. Exploration test borings have been conducted within the permit area and have been utilized for the following purposes: Location of Subsurface Water - Since the holes were generally dry, the primary circulation medium for most exploration bore holes drilled within the mine plan area was either compressed air or drilling mud when fractures were encountered. Several drill holes throughout the area encountered minor amounts of ground water; however, all of the data obtained to date by Colowyo and the USGS have indicated that groundwater occurrences in the are not continuous but rather are a series of perched systems. Information on groundwater occurrence is set forth under Section 2.04.7. Drill Hole Logs - Exhibit 6, Geological Information, contains numerous lithologic logs which show and describe the lithologic characteristics and thickness of each strata and each coal seam. The location of each drill hole presented in Exhibit 6, Geological Information, is shown on the Geology Map (Map 7A).