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• I~ and instability of the soils. <br />4.0 STEVENS GULCH ALLUVIUM <br /> <br />4.1 ALLUVIUM EXTENT AND CHARACTER <br />The potential alluvial valley floor area in Stevens Gulch <br />contains the entire well field site and extends upstream onto <br />the adjoining property (Plate 3'.). This area covers approxi- <br />mately 20 acres of the valley bottom. Approximately one acre <br />of the alluvium is areally isolated from the main alluvial val- <br />ley and lies along another tributary of the main stream channel. <br />Man-made fills have been placed at the well field site <br />beneath the roadway and below the water storage tank. Part of <br />the roadway fill forms a dam which retains a pond in the ex- <br />treme southwest corner of the alluvium. Two small stock ponds <br />are found higher along the valley, one of which lies within <br />the alluvium. The lands within the alluvial valley are present- <br />ly used for grazing livestock, and support a groorth of short <br />native grass. <br />Two test pits (TP-3 and TP-4) were excavated in the al- <br />luvium near the well field site to investigate the character <br />of the alluvium. Logs of the test pits are presented in Ap- <br />pendix A; their locations are indicated on Plate 3. The al- <br />luvium consists of silty clay to a depth of 4.5 to 6 feet. At <br />these depths, gravels containing ground water were encountered. <br />Acccording to boring logs from previous studies, sandstone bed- <br />rock of the Mesaverde Formation lies 65 to 97 feet below the <br />- 14 _ <br />I <br />Leo-Nroao eorrsu~nn~. a+e. <br />