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GROUND WATER <br />• <br />Most of the ground water in the area of the mine and plant site <br />exists as a zone of saturation in the fractures of the bedrock <br />and the pore spaces of the alluvium. The movement of ground water <br />is controlled by fracture with the greatest flows beneath stream <br />valleys where larger regional fractures exist. <br />To provide information on the hydrogeologic characteristics of <br />the site, extensive field work has been performed. Basic data <br />points were established by drilling test holes in representative <br />portions of the site. Various methods were used in the field <br />program, including downhole geophysical logging of test holes <br />and seismic refraction surveys, and formal test pumping, water <br />quality sampling and water level monitoring. <br />Recharge of water-bearing units at the site occurs by direct <br />infiltration of precipitation. Spring snowmelt is the primary <br />• source of recharge water which is absorbed through the soil <br />cover or exposed bedrock. Water migrates downward through beds <br />of sandstone and into the fracture system in the shale. Movement <br />continues downgradient in horizontal and vertical increments, <br />joining the zone of saturation, Local artesian pressures are <br />produced beneath impermeable layers. Groundwater leaves the <br />property either by migrating through the bedrock or by inter- <br />secting and joining the alluvial underflow. Groundwater leaves <br />the property either by migrating through the bedrock or by inter- <br />secting and joining the alluvial underflow. Groundwater ulti- <br />mately (1) is discharged into the streams or from the cliff faces <br />as springs or seeps; (2) is consumed by evapotranspiration pro- <br />cesses; or (3) leaves the site at the southern boundary as sub- <br />surface outflow (Metcalf S Eddy, 1975). <br /> <br />G-19 <br />