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<br />i • <br />~~ <br />alluvium seems to vary locally in size and character, and <br />generally consists of clayey silts, silty clays, and sands <br />containing rounded gravel, cobbles and boulders. Ground water <br />was seen to occur in gravelly layers at 4.5 to 5 feet below the <br />ground surface. No boring logs were available which penetrated <br />to bedrock beneath the alluvium; however, a geophysical sur- <br />vey performed by the Willis and Paul Corporation (1976) in- <br />dicated that Mancos Shale bedrock lies in excess of 150 feet <br />below the ground surface. <br />5.2 UPLANDS <br />Geomorphic units outside the boundaries of the alluvium <br />include high river terraces, hillslope colluvium and upland <br />outwash (pediment) deposits. One alluvial fan deposit is ident- <br />ified on the southeast side of the river. Outwash (pediment) <br />deposits are areally continuous with the alluvium on either <br />side of the river through most of the study area. The outwash <br />slopes grade continuously upslope to bedrock outcrops or col- <br />luvial slopes. Colluvial soils mantle the steeper hillslopes. <br />Older terraces are found high above the valley floor and are <br />not areally continuous with the alluvium. <br />Some of the upland areas described as outwash are used <br />as orchard lands, and are flood irrigated via man-made ditches <br />on either side of the river. It is unlikely that these areas <br />have any potential for sub irrigation. <br />Test borings drilled through the pediment deposits show <br />that this material is found at depths of up to 83 feet in the <br />loadout area, and is intertongued with alluvium at depth (Willis <br />and Paul, 1976). <br />- 17' - <br />GEOIiVDRO CONSULIING,INC. <br />