2009-08-01_HYDROLOGY - M1981112 - Laserfiche WebLink

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5 horseweed (Conyza canadensis), common sunflower (Helianthus annuus), Russian thistle (Salsola australis), and tumble mustard (Sisymbrium altissimum). Plains cottonwood trees are sparsely represented in some areas. Table 3 provides a list of the major plants on the project site. 2.7 Soils The soils of the project site were mapped by the U.S. Soil Conservation Service (1968). Figure 10 illustrates the major soils on these properties, which are described below. 2.7.1 Bankard Series These soils are sandy or loamy soils in alluvium recently deposited on bottomlands along the River. Two Bankard soils are present on the project site. Bankard Sandy Loam (Ba). This soil occurs on the bottom lands along the River on slopes of 1 percent or less. Bankard sandy loam is a well to excessively drained sandy loamy textured soil developed on bottomlands derived from mixed alluvium sediments. The surface layer is light brownish-gray sandy loam. The underlying material is a light yellowish-brown gravelly sand. Permeability is rapid and available water capacity is medium. The effective rooting zone is 17 inches. The hazard of soil blowing is moderate and water erosion hazard is slight. Bankard Soils (Bk). These soils occur mainly on bottom lands along the River. The Bankard soil is a well to excessively drained loamy sand textured soil developed on bottomlands derived from mixed alluvium sediments. The surface layer is light brownish-gray sandy loam. The underlying material is a light yellowish-brown gravelly sand. Permeability is rapid and available water capacity is medium. The effective rooting zone is 17 inches. The rate of water intake is more rapid than that of Bankard sandy loam, and the water-holding capacity is lower. The hazard of soil blowing is severe and the hazard to water erosion is moderate. 2.7.2 Riverwash Riverwash (Rv) occurs along and in the channels of the River. It consists primarily of sandbars, which are often flooded and unstable. Riverwash is the first land to be covered by water when the stream overflows. Some areas of Riverwash have a sparse plant cover. In places on islands or along the shorelines, there are a few small clumps of grasses and a dense growth of small and large willows. Floods bring in sandy or silty deposits that cover the close-growing vegetation. 2.7.3 Wet Alluvial Land Wet alluvial land (Wt) consists of dark-colored soils on the flood plains of the larger streams. This poorly drained, loamy and sandy soil is on low terraces and flood plains derived from stratified alluvial. It lies in nearly level areas that have slight depressions. Flooding is likely, and the water table normally is within three feet of the surface. Slopes range from 0 to 1 percent. The surface layer of this land is a dark gray fine sandy loam about 8 to 10 inches thick and is somewhat similar to the surface layer of Wann clay loam, saline. Also similar is the substratum. Between the surface layer and the substratum, however, the soil material of this land is finer textured and less permeable than the subsoil of Wann clay loam, saline. Sand or sand and gravel are 24 to 40 inches below the surface of Wet alluvial land. The native vegetation consists of rushes, sedges, salt-grass, and other plants that are tolerant of water and salt. Permeability is slow and the available water holding capacity is medium. The effective rooting zone is 40 inches. The hazard of soil blowing is slight and water erosion hazard is slight. 2.8 Mining Operation Builders Aggregate Company, Inc. has a 112 Permit from the Colorado Division of Reclamation, Mining & Safety to mine sand and gravel on the Builders Aggregate Company property. The sand and gravel is mined by the hydro dredging method. Specifically, a small pond (1-1½ acre) is excavated and a floating dredge is placed on the pond. Materials are dredged from the pond edge and poured over a series of screens to size and separate the materials into the desired gradations