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4~8 <br />All side valleys exhibit ephemeral streams. The character of the alluvial deposits is distinct <br />~~ from the East Salt Creek deposits. The width of the deposits is limited, the valley is dissected <br />by deep erosional gullies, and the borders of the alluvium are frequently covered with colluvial <br />soils and alluvial fans descending from deep erosional gulches in the canyon sides. <br />UPLANDS <br />The uplands of the area are formed mostly by steep sides of the valleys that were eroded in <br />the Mesaverde Formation or in the Mancos shale. The valley sides are formed either by bedrock <br />outcrops or by colluvial soils. In addition to the bedrock, several alluvial fans of important <br />dimensions have been identified on the site. They cover the alluvial deposits of the East Salt <br />Creek and would not qualify as AVF. <br />Atone location, at the west side of the East Salt Creek valley, close below the confluence of <br />the McClane Creek, a distinct remnant of an old and high river terrace was identified. It was <br />found in the road cut; it is about 20 feet high above state Highway 139 and consists of distinct <br />horizontal layers of well rounded gravel, interbedded with several layers of silty clays. <br />• In addition to these geologic formations, a large manmade fill was mapped and indicated <br />on Figure 4.1.2. It is a large earthfill dam constructed across the East Salt Creek valley close <br />below the confluence with the ephemeral channel in McClane Canyon. <br />WATER AVAILABILITY <br />EAST SALT CREEK VALLEY <br />According to pertinent regulations, the alluvial valley floors have to have a water volume <br />sufficient for subirrigation or flood irrigation. There is enough evidence that the alluvium of the <br />East Salt Creek complies with these conditions. Apart of the valley below the McClane Canyon <br />has traditionally been irrigated with a system of diversion ditches, contour ditches and graded <br />borders. The irrigated portion of the valley stretches between the irrigation dam and the mouth <br />of Munger Canyon. The valley floor below the irrigation dam has been used for alfalfa cropping. <br />The remaining parts of the valley are currently used for grazing only. <br />It can also be concluded that even the areas that are not irrigated at present have the <br />geomorphic capability of being flood irrigated. No assessment has been made as the potential <br />• success of such an activity based upon water availability or soil conditions outside of Section <br />4.1.2.5. <br />M~ Volume 1 4 ~ 29 - 96 <br />