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probably indicates groundwater mounding to the north and east in the <br /> area of the California aqueduct/Delta Mendota canal complex (3). <br /> Shallow perched groundwater beneath the landfill flows to the northeast <br /> toward the San Joaquin River. This perched water appears to be confined <br /> to the eastern half otthe landfill. In addition, the shallow aquifer <br /> in the vicinity of CHSL also deviates slightly from the regional norm by <br /> flowing to the northwest and the southeast, a probable result of <br /> groundwater mounding. The shallow perched aquifer in the vicinity of <br /> the landfill does not contain reliable quantities of drinking water and, <br /> consequently, is not used as a drinking water source (3). <br /> Recharge to the upper water-bearing zones occurs primarily by direct <br /> infiltration of water from precipitation, irrigation, and seepage from <br /> canals and streams. The deep regional aquifer is overlain by <br /> approximately 200 feet of unsaturated, low permeability sediments that <br /> would restrict vertical infiltration of groundwater from the shallow <br /> perched aquifer to the usable deep aquifer. More permeable sections, <br /> however, may occur between the two aquifers (3). <br /> The deep regional aquifer (254 feet below ground surface at CHSL) is a <br /> principal source of drinking water for the City of Tracy and its <br /> environs. The City of Tracy operates a municipal well approximately 1.5 <br /> miles northeast of CHSL. The water from this well is blended through <br /> the municipal water system, which serves a population of approximately <br /> 29,000. The closest well to the site is a domestic well at the Carnegie <br /> Truck Stop, located approximately 2000 feet north of the site on Corral <br /> Hollow Road. This well is screened from 306 to 365 feet in the lower <br /> aquifer. There are an additional 60 private domestic wells within a <br /> 3-mile radius of the facility. The net annual precipitation for the <br /> Tracy area is 8.1 inches (14). <br /> 3.4 SURFACE WATER <br /> The closest surface water to the landfill is Corral Hollow Creek, an <br /> ephemeral stream that runs parallel to the site's southeastern boundary <br /> and lies within 200 feet of the site. Although the facility is located <br /> 3-9 <br /> sa/tm/chl/si <br />