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2.0 General Environmental Setting 0 <br />The following section describes mapped and documented data on the project area, including geology, <br />hydrology, mapped soil units, and available natural vegetative community data. <br />2.1 Geology <br />"No Name Gulch" project area bedrock is primarily composed of sandstone, and secondarily by <br />shale. Both are sedimentary rocks composed of sand -sized or finer (silt or clay) minerals. The <br />geologic unit primary to the project area is Mesaverde FM, Undivided, which originated in the <br />Cretaceous period. It is noted for containing major coal beds or seams, with coal being the tertiary <br />rock underlying the sandstone and shale (USGS 1992). <br />The project area ranges in elevation from approximately 6,100 feet above mean sea level (AMSL), at <br />the northwest corner, to approximately 7,940 feet AMSL at the southeast corner, as shown in the <br />topographic map in Figure 3. The side slopes of the Gulch are very steep, averaging 40 -60° or more, <br />and extend for a distance of approximately one - quarter mile from top to bottom. The thalweg of the <br />gulch is only slightly less steep, ranging from 30 -50 °, and extends for approximately one mile, from <br />the highest crest in the south to the lowest point in the north, near the North Fork Gunnison River. <br />Photos of the east and west slopes and thalweg of "No Name Gulch" are included in Appendix A. <br />2.2 Hydrology <br />The "No Name Gulch" project area drains south to north towards the North Fork Gunnison River. <br />One 42 -inch culvert beneath Highway 133 allows for drainage from the gulch to the North Fork <br />Gunnison River. A visual inspection of the vegetation, drainage patterns, and sedimentation in the <br />culvert and connecting ditches indicates that the culvert and ditches do not appear to convey a lot of <br />water, and may even be effectively blocked by spoil side cast resulting from onsite road construction. <br />As a whole, the "No Name Gulch" project area is somewhat xeric, especially in higher reaches. The <br />most significant source of water in the gulch is most likely snowmelt. The U.S. Geological Survey <br />Quadrangle map ( "Somerset" Quad) (Figure 4) indicates that the center of the gulch is intermittently <br />flowing. It stands to reason that most of the year, the thalweg of the gulch would be mesic to dry, but <br />during the late spring and early summer, as snowmelt runs down the gulch, collecting in the thalweg, <br />the lower (northernmost) reaches of the thalweg may experience muddy conditions and seasonal <br />flow, that may or may not ultimately reach the culvert and North Fork Gunnison River. In addition to <br />rainfall, another source of hydrology, albeit very minor, includes the occasional subsurficial flow of <br />