2016-11-23_PERMIT FILE - C1981019 (2)

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Cultural Resource Site Assessments for Collom Expansion Project Colowyo 1.1 Environmental Setting Colowyo's Collom project area is situated in the Southern Rocky Mountain physiographic province (Fennerman 1931; Thornbury 1965). The province is described as a series of uplifts that formed between 300 million years ago and 60 million years ago. The project area is among a series of long broad northeast/southwest-trending ridges that originate in the Danforth Hills to the south and end at the Axial Basin in the north (Figure 2 and 3). Elevations range from 6,500 feet (1,981 m) in the north to 8,567 feet (2,611 m) in the south. The Danforth Hills are a series of uplifted folds that structurally connect the Uinta Mountains to the west with the Rocky Mountains to the east (Fennerman 1931; Thornbury 1965). The Axial Basin is a highly eroded anticlinal trough and the southernmost extent of the larger Wyoming Basin. The project area geology is composed of Williams Fork sandstone, shale, and coal beds. Iles formation sandstone and shale occurs along the margin of the Axial Basin. Surface sediments are variable depending on the location within the project. In addition to sandstone outcrops, upland sediments are typically a mix of residuum and colluvium sand loam with regolith gravels. Sedimentary deposition is generally shallow in the upland areas. Lowland and drainage bottom sediments are typically alluvial silt loams with varyingly dense pebble to boulder size gravels. The lowland sediments tend to be much deeper than upland areas. Climatically, the upland areas have a highland climatic regime and the lowland areas have a continental steppe climate. Annual precipitation exceeds 30 inches (76 cm) in the upland areas and averages between 20 and 30 inches (50 and 76 cm) in the lowland areas. Climate, precipitation, and elevation determine vegetation communities. The dominant vegetation community is sagebrush, rabbitbrush, wheatgrass, wild rye, and prickly pear cactus. Higher elevation communities are similar with varying densities of oak brush and aspen. Riparian vegetation communities are the second most common within the project. Along the drainage bottoms, natural springs, and man-made water features are willow, cattail, broadleaf cottonwood, and various grasses. Fauna in the project area ranges from large ungulates like mule deer, antelope, and elk to small mammals including rabbits, porcupines, greater sage grouse, and various small rodents. Coyotes, black bears, and mountain lions are also reported to inhabit the region. 1.2 Present Built Environmental Setting The Collom project and vicinity has been utilized for various activities associated with recreation, homesteading, hay farming, coal mining, and livestock grazing. During the historical -era, numerous homesteads and small coal mining operations existing within and around the project area. In the modern -era, the private lands within the Collom area are owned and managed by Colowyo. Colowyo permits various levels of livestock grazing and hunting on the land. Any other land use within this area is in support of Colowyo's current mining operations and/or toward the development of the Collom area. As such, the project area is largely undeveloped land with bladed roads, fences, and abandoned homesteads that has changed little since Colowyo's acquisition. Tetra Tech July 25, 2016 For Official Use Only: Disclosure of Site Locations Prohibited (43 CFR 7 18)