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<br />n <br />L~ <br />reasonable when large areas of fractured bedrock are considered. R~~mero (1970) <br />further explains that fractured bedrock openings close rapidly with depths <br />greater than 200 ft.; an upper limit of 0.1 gpd/ft. is reasonable bfayond a <br />depth of 200 ft. These authors indicate that the specific yield in this rock <br />type is usually in the range of 10%. <br />The alluvial aquifer is generally composed of sand, gravel and boulders <br />that are found in discontinuous deposits in the valley along the Ralston <br />Creek stream bed. Additionally, an alluvial aquifer usually has a higher <br />storage capacity and more stable water levels than a fractured bedrock aquifer. <br />This is due to the fact that an alluvial aquifer contains more void space <br />and is supported by both surface runoff and ground water discharge from the <br />water bearing void space. <br />• Groundwater was encountered in all of the bore holes except bore hole 5. <br />This groundwater, which flows through waste rock fill material and R,ilston <br />Creek alluvium, ranged in depth from 3 to 6 feet in bore holes 1, 2, and 3. <br />In bore hole 4, groundwater was encountered at 33 feet, which is the top of <br />the original ground surface at this location. (See Figures 2.1-1 through 2.1-5) <br />2.2.2 Surface Water Hydrology <br />The only tributary water course located in the vicinity of tf~e ore <br />sorter is Ralston Creek. The Ralston Creek basin drains easterly toward the <br />South Platte River. The drainage basin upstream from the ore sorter and the <br />western boundary of section 25 comprises an area of approximately 38 square <br />miles. Topographically, the drainage basin rises from approximately 6,800 <br />feet to 10,G00 feet, and about 70% of the drainage basin is above 8,600 feet. <br />• The length of the Ralston Creek basin is about 16.5 miles, with an average <br />basin slope of 220 feet per mile. <br />2-4 <br />