2023-01-05_REVISION - C1981019 (13)

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The East Pit, West Pit and Section 16 Pit mining sites lie just west of the northward flowing Good Spring Creek, which is paralleled by Colorado Highway 13. The area is gently sloping and upland ranging from about 7,640 feet near the southwest corner to 6,560 feet near the northeast corner of the permit area. Valleys that cut into the upland surface are generally narrow (V- shaped) and approximately 250 feet to 500 feet deep. The topographic surface north of the East Pit, West Pit and Section 16 Pit mining sites is dominated by two ridges approximately two miles long, trending northnortheast and bounded by Good Spring Creek, Taylor Creek and Wilson Creek. The South Taylor mining area lies north and west of the northward flowing Good Spring Creek and south-southwest of the other pits. The area is also just south of the northeastward flowing Taylor Creek, which runs adjacent to the Section 16 Pit and West Pit. Much of the area was gently sloping upland rangeland, but the valleys were steeply sloping, with slopes in excess of 20 percent in some areas. The Collom area occupies the south-central headwaters of the synclinal axial basin along the Danforth Hills and drains to the northeast, eventually into the Yampa River. Elevations range from just below 6,400 feet to approximately 8,550 feet. Upland side slopes range from moderately steep to steep (>35 percent) whereas the areas between drainages generally exhibit flatter slopes with a northeasterly aspect between 1 and 5 percent. 4.5 Geology Geologic information is found in Sections 2.04.6, Maps 7 through 9A, and Exhibit 6 of the PAP. The permit area lies approximately six miles south of the axis of the Axial Basin Anticline, a large northwesttrending fold found in the southern Uinta region of the Piceance Basin. The anticline structure and corresponding Collom Syncline to the south consist of thousands of feet of marine-deposited sediments of Cretaceous age. To the south of the anticline, the axis of the Collom Syncline, a downward fold, passes directly through the permit area, trending north 70 degrees west and plunging from 0 to 20 degrees to the north. In the southeastern corner of the permit area near the Streeter Fill, the Collom Syncline is influenced by the Elkhorn Syncline which results in strata having an eastward dip and northsouth strike (see Map 7 and Figure 1 in the PAP). There appears to be no evidence of faulting in the permit area; however, linear features that may be faultrelated have been observed from aerial photographs. These linear features trend approximately north 70 degrees west, north 45 degrees west and north 30 degrees east, with near vertical inclinations. The coal-bearing strata of interest to the Colowyo operation are stratigraphically located in the Mesaverde Group within the Williams Fork Formation of the upper Cretaceous age. The Williams Fork consists of alternating beds of sandstone, sandy shale, carbonaceous shale and Proposed Decision and Findings of Compliance January 5,2023 Permit Renewal No. 8 Page 117