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I I I I I 'I I I I I I I I I I I I I I SECTION II SITE CONDITIONS AND HYDROLOGY A. LOCATION OF THE PROJECT The Project is located on the Colorado River between the towns of De Beque and Parachute. It is approximately 35 miles northeast of Grand Junc- tion in Mesa and Garfield Counties. Figure S-1 is a general area map of the Project. The Project is located on the western slope of the Rocky Mountains and is accessible from Interstate Route 70 (1-70). The dam and powerhouse are located on the Colorado Ri ver in Mesa County just west of the Garfield County line and approximately 40 miles up- stream of the confluence with the Gunnison River. The dam would create a reservoir situated almost entirely in Garfield County, and which would be ap- proximately 9.7 miles long with a nonnal maximum pool at El 5070. B. TOPOGRAPHY Elevations in the drainage basin of the Colorado River vary from 14000 feet on high peaks of the headwaters to 4900 feet at the ri ver near De Beque. About 40% of the drainage basin upstream of the Una dam si te lies above 9,000 feet. The drainage basin upstream of Grand Junction and the Una dam site is characterized by high peaks, steep-walled canyons, narrow valleys and mesas. These characteristics result in numerous drainage paths with steep gradients, short channel lengths and small watershed areas. Government Creek and Parachute Creek are the larger tributaries in the reservoir vicinity above the dam site and Roan Creek and Plateau Creek are the largest below the dam site, upstream of Grand Junction. The Roan Cliffs with Mount Logan (El 8400) on the north side of the reservoir and Battlement Mesa on the south side are the dominant geologic fonnations in the vicinity. The dam site is situated between a low flat mesa on the north side of the river locally known as Negro Hill, and Sampson Mesa on the south.