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<br />1.0 SOPII~fARY <br />1. This report presents the findings of an alluvial valley floor (AVF) <br />investigation in the Rapid and Cottonwood Creeks area in western <br />Colorado. The presence of an AVF is defined by the occurrence oP <br />streamlaid deposits and the presence of sufficient water to support <br />agricultural activities. <br />2. The surficial geology of the area is comprised mostly of unconsolidated <br />fan deposits Prom Grand Mesa to the east. Large angular boulders in <br />the deposits and poor sorting of material indicate mud and/or gravity <br />transport. The Colorado River has eroded the fan material and formed <br />PI <br />several upland terraces. Remnant river alluvium is found in a few <br />areas on the terrace surfaces. Rapid Creek is downcutting its charnel, <br />and no evidence exists of current sediment reworking and depositior. by <br />the creek. <br />3• Limited subirrigation occurs along Rapid Creek as evidenced by the <br />presence of phreatophytes. The subirrigated area is seldom greater <br />than 20 feet wide on either side of the creek and is on steep sloping <br />stream banks which would not support agricultural activities. The <br />• <br />water source for the subirrigation is not known, but could•be temporary <br />bank storage from high flow periods. A monitoring well completed in <br />the underlying coal has potentiometric surface at least 15 feet below <br />the creek elevation, indicating no bedrock-related ground-water <br />discharge. <br />1 <br />Hydro-Search, InC. Reno • Denver • Austin <br />cornu~nrc Hvoao~oc~sis•cEa~acisrs <br />