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=Walsh <br />Environmental Scientists and Engineers, 1.LC <br />3.4 Minerals <br />3.4.1 Coal <br />The coal seams at the ColoWyo Mine and the proposed Collom Mine are contained <br />within the Williams Fork Formation (WMC 2005). Economically, recognized coal seams <br />include the X, B, C, D, E, F, and G seams, which are composed of high - quality, low - <br />sulfur coal. This formation conformably overlies the Trout Creek Sandstone Member of <br />the Iles Formation. Rocks of the Cretaceous Williams Fork and Iles Formations constitute <br />the Mesaverde Group. Local occurrences of Quaternary alluvium, colluvium, alluvial fan <br />deposits, and landslide deposits unconformably overlie the Williams Fork Formation in <br />the study area, particularly in the stream valleys. A generalized stratigraphic column is <br />shown on Figure 5. <br />The Williams Fork and Iles Formations comprise a sedimentary rock sequence that <br />originated from a deltaic and marginal marine depositional environment. The Trout Creek <br />Sandstone Member consists of thick marine sandstone that represents the marine facies <br />(beach) of the delta front. The lithology of the Williams Fork Formation is variable in <br />character and thickness. Individual lithologic units are most often discontinuous. The <br />formation consists predominantly of shale, sandy shale, and sandstone with subordinate <br />amounts of coal and carbonaceous shale (Brownfield and Johnson 1986). Aside from <br />volcanic ash beds, the coal seams are the most laterally persistent units in the Williams <br />Fork Formation. <br />3.4.2 Oil and Gas <br />There are no pending or approved oil and gas leases in the proposed lease area. Several <br />small oil fields, which are currently active or have been active during the past 20 years, <br />are located to the southwest of the proposed lease area. <br />3.5 Soil and Alluvial Valley Floor Resources <br />3.5.1 Soil <br />Soils within the proposed lease area are variable, depending on the combination of parent <br />materials, slope, microclimate, aspect, location and stability of slopes, age, and their <br />history of utilization (Figure 6). The dominant soil types were formed primarily from <br />alluvium, colluvium, or in -place residuum of sandy, silty or clayey bedrock. Alluvial <br />soils are located in drainages derived from the transport of upslope materials by water <br />processes. Colluvial . soils are derived from materials transported from upslope positions <br />by gravity. Relatively unweathered bedrock exposures also are observed, where soil <br />development processes do not keep up with the tendency of the rock to erode from water <br />or wind action. <br />The soils of the Collom lease area are typical of soils found in the cold, semi -arid region <br />of northwest Colorado. The soils range from shallow (less than 20 inches to bedrock) and <br />moderately deep (20 to 40 inches) to deep (greater than 40 inches thick) and are <br />P PROJECTS Co10,cco6188' FA Finol BIM-, -EA Collo .1 08 1 06 . do. <br />19 <br />