2012-03-07_PERMIT FILE - C2010088 (22)

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ALLUVIAL VALLEY FLOOR DETERMINATION CAM - COLORADO PROPOSED COAL LOADOUT NEAR FRUITA MESA COUNTY, COLORADO wash, suggesting the wash has also incised a channel into the shale, some of which is "backfilled" with silty clay sediment. The small swales that are tributary to Reed Wash, located on the west side of Reed Wash, appear to be natural drainageways that currently drain irrigation return flows from upstream irrigated fields (Figure 2). The swales are narrow (generally 10 to 15 feet wide) and shallow (1 foot or less lower than adjacent land) and do not have active flow channels. The flow of water through these swales is either as general surface flow or as shallow perched ground water. Given the depth to ground water in the area, any water in the saturated low permeability soils along these swales is most likely perched above the water table and not hydraulically connected to the water table, other than percolation of infiltrated water. AVF Determination The proposed loadout is along the Colorado River at the western end of the Grand Valley, just before the river leaves the valley and flows southwest into the Ruby and Horsethief canyons. Based on the proximity of the property to the Colorado River, it was anticipated that the area may qualify as an AVE However, because of both natural and man -made features, the area does not appear to currently have the typical hydrologic function or geomorphic characteristics of an AVF. The following are the known characteristics of the property with respect to whether it functions as an AVF: 1. The upper 15 to 23 feet of material beneath the surface is comprised of a combination of windblown and sheet flow deposits. This layer is typically a low permeability silty clay. 2. The surface soils are not considered suitable for agricultural purposes by the NRCS and there are no records indicating the area has ever been irrigated or cultivated. 3. There are 19 to 25 feet of river - deposited alluvium between the Mancos Shale and the upper silty clay layer. 4. Land west and north (and outside) of the project area is currently used for agricultural purposes. 5. The water table is generally at the top of the alluvium or bottommost part of the silty clay, which is too deep to provide subirrigation. 6. The ground water flow direction is toward the Colorado River from upland areas to the north and toward Reed Wash, locally. 3