Laserfiche WebLink
Data Recovery Report for Three Sites at the Collom Project Colowyo Coal Company <br />The Danforth Hills are a series of uplifted folds that structurally connect the Uinta Mountains to <br />the west to the Rocky Mountains to the east. The Axial Basin is a highly eroded anticlinal trough <br />and the southernmost extent of the larger Wyoming Basin (Fennerman 1931; Thornbury 1965). <br />Project elevation ranges from 6,400 feet (1,951 m) in the north to 8,567 feet (2,611 m) in the <br />south. <br />Area geology is composed of Williams Fork sandstone, shale, and coal beds. The Iles formation <br />sandstone and shale occurs in areas along the margins of the Axial Basin. Surface sediments are <br />variable depending on the location within the project. In addition to sandstone outcrops, typical <br />upland sediments are a mix of residuum and colluvium sand loam with regolith gravels. <br />Sedimentary deposition is generally shallow in the upland areas. Lowland and drainage bottom <br />sediments are typical valley fill loams with varyingly dense pebble to boulder size gravels. The <br />lowland sediments tend to be much deeper than upland areas. <br />Climatically, the upland areas have a highland climatic regime and the lowland areas have a <br />continental steppe climatic regime. Annual precipitation exceeds 30 inches [76 centimeters (cm)] <br />in the upland areas and averages between 20 and 30 inches (50 and 76 cm) in the lowland areas. <br />Climate, precipitation, and elevation determine each areas vegetation community. The lower <br />elevation vegetation community is sagebrush, rabbitbrush, wheatgrass, wild rye, and prickly pear <br />cactus. Higher elevation communities are similar with the addition of varying densities of oak <br />brush, juniper, and aspen. Along .the drainage bottoms, natural springs, and man-made water <br />features support willow, cattail, broadleaf cottonwood, and various dense grasses. <br />Fauna in the area ranges from large and medium sized ungulates like mule deer, antelope, and <br />elk to small mammals including rabbits, porcupines, greater sage grouse, and various small <br />rodents. Coyotes, black bears, and mountain lions are reported to also inhabit the region. <br />1.1.2 Site Settings <br />The three sites are all situated in the same general area to the west of Wilson Creek on the <br />southern margin of the Axial Basin (Figures 1 and 2). Site 5MF.8393 is located on a low swale <br />on a southwest to northeast trending finger ridge extending from the base of the Danforth Hills <br />(Figure 3). The site is at an elevation of 6,453 ft (1,967 m). Site 5MF.8394 is located at the base <br />of the finger ridge on the upper terrace of Wilson Creek (Figure 4). The site is at an elevation of <br />6,421 ft (1,957 m). Site 5MF.8395 is located on the eastern toe slope of the low knoll at the <br />northern end of the finger ridge (Figure 5). The site is at an elevation of 6,411 ft (1,954 m). Jubb <br />Creek and Taylor Creek are located immediately to the west and east of the sites. Vegetation <br />across the area is a dense sagebrush community with invasive plants occurring along the Moffat <br />County Road 51. Ground coverage in the area is between 25 and 40 percent. Surface sediments <br />are a colluvial/alluvial clay sand loam mix with varying densities of subrounded to rounded, poorly <br />sorted, pebble to cobble size gravels. <br />The area has been subjected to several development projects unrelated to the Colowyo Mine. <br />Moffat County Road 51 right of way is the most significant disturbance and potentially has <br />removed portions of sites 5MF.1652, 5MF.8394, and 5MF.8395. The right of way also has a <br />collocated phone line on its western side. A decommissioned liquids pipeline crosses the finger <br />ridge roughly east to west and passes through portions of sites 5MF.8393 and 5MF.8394. The <br />pipeline had not directly impacted any of the cultural material encountered in 2017. The extent of <br />the pipeline's impact is unknown. A powerline access two -track road passed through Site <br />5MF.8394 from roughly north to south paralleling the county road. The road had not directly <br />impacted any of the cultural material encountered in 2017. The extent of the road's impact is <br />unknown. <br />Tetra Tech February 2018 <br />