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Geosyntec <br /> 2.3 Geology and Hydrogeology <br /> The Site is located in the San Joaquin Valley Groundwater Basin and is underlain by the Corcoran <br /> Clay at a depth of approximately 270 feet below ground surface, which is a former lake deposit <br /> that forms a regionally extensive aquitard in the San Joaquin Valley (Department of Water <br /> Resources [DWR], 1981).Overlying the Corcoran Clay are alluvial deposits made up of sands and <br /> gravels with smaller amounts of silts and clays. The alluvial deposits overlying the Corcoran Clay <br /> have been previously divided into four zones: Water Table (-0-50 feet below the ground surface <br /> [bgs]), Shallow (-50-100 feet bgs), Intermediate (-100 to 150 feet bgs), and Deep (-150 feet bgs <br /> to top of the Corcoran Clay). A Site characterization field investigation is currently being <br /> conducted and an updated Conceptual Site Model will be provided in the Site Characterization <br /> Report. <br /> The depth to first groundwater in the vicinity of the planned aeration system has ranged from <br /> approximately 5 to 25 feet bgs between 1983 and 2019 based on the groundwater levels measured <br /> at nearby monitoring well PW06-080. In 2018,the depth to water in PW06-080 ranged from 11.57 <br /> feet bgs in February to 13.29 feet bgs in November 2018. <br /> The regional groundwater flow direction at the Site is to the northwest; however, the groundwater <br /> flow direction is locally influenced by groundwater pumping from the remedy extraction wells and <br /> water supply wells. Within the Deep Zone, where the Simplot and LWD water supply wells are <br /> screened, the groundwater flow direction from the Site is towards the water supply wells that are <br /> operating. <br /> Pre-Design Data Collection Work Plan 3 July 22,2019 <br />