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<br />002lhJ2 <br /> <br />Initial Infonnation Package <br />Williams Fork Hydroelectric Project <br />FERC Project No. 2204 <br /> <br />completed there in 1941. It was subsequently raised to its current height in ] 959.8 <br />Below the dam, the Williams Fork River flows northeast approximately two miles <br />downstream to its confluence with the Colorado River near Parshall, Colorado. <br /> <br />Cedar Ridge is a massive outcrop of biotite gneiss of Precambrian age that was <br />upthrust by folding and faulting. The gneiss typically has foliated bands <br />predominantly composed of quartz, calcic oligoclase, and biotite and muscovite <br />mica. Differential weathering of the gneiss has left a scattering of rounded <br />boulders and tabular slabs surrounded by gravelly soils. Izett suggests that the <br />Williams Fork Valley southwest of the ridge is floored at a shallow depth by <br />. 9 <br />gneiss. <br /> <br />.I <br />i <br /> <br />Mesozoic sediments are represented by a sequence of Morrison Formation and <br />Dakota Sandstone that are exposed on the north shoulder of Cedar Ridge where <br />they uncomformably overlie the biotite gneiss. The Dakota Sandstone is resistant <br />to weathering and forms cliffs that partially bound both sides of the deep valley <br />below the Williams Fork dam. <br /> <br />Tertiary sediments are represented by the widespread silty facies of the Miocene <br />age Troublesome Formation. This formation blankets parts of the Morrison <br />Formation and Dakota Sandstone northeast of Cedar Ridge and is the basal <br />sediment exposed in road cuts in the Williams Fork Valley. <br /> <br />I <br />".l <br /> <br />In the Williams Fork Valley, the Troublesome Formation is covered by varying <br />thicknesses of Pleistocene alluvium and a thin mantle of Holocene sediments. <br />Izett (1966) describes a sequence of four Pleistocene terraces on the east side of <br />the Williams Fork Reservoir that are approximately 50 feet, 190 feet, 300 feet, <br />and 540 feet above the reservoir level. A fifth terrace level, believed to be the T I <br />(youngest) terrace, is marked by flats adjoining the southeast end of the reservoir, <br />about 15 feet above the reservoir level. Road cuts through the 50-foot and 190- <br />foot terraces, older T2 and T3 terraces, expose sediments composed primarily of <br />unconsolidated, poorly sorted gravels and f1uvially rounded cobbles in a matrix of <br />silt and sand. The 50-foot terrace is particularly well-defined and slopes towards <br />the canyon through Cedar Ridge. <br /> <br />~ <br /> <br />2.4 <br /> <br />Climate <br /> <br />The closest weather station to the Project area is at Kremmling, Colorado, <br />approximately 10 miles to the west-northwest. This station is representative of <br />the sagebrush steppe environment in the central part of the Middle Park basin. <br /> <br />8 Grand County Historical Association <br />1995 What's Up on the Williams Fork River. Grand County Historical Association Journal 13(1). <br /> <br />9 <br />1zett,G. A. <br />1966 Tertiary Exlrusive Volcanic Rocks in Middle Park. Grand COl/llly. Colorado. In Geological Survey <br />Research, pp. B42-B46, U.S. Geological Survey Professional Paper 550-B. <br /> <br />9 <br />