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- a <br /> • 03 July 1997 <br /> AGE-NC Project No 97-0343 <br /> Page 2 of 5 <br /> 0 010 ppm Based upon results of the soil sample analysis, the PHS-EHD is requiring assessment <br /> of the lateral and vertical extent of hydrocarbon-impacted soil and/or ground water in the area of the <br /> former UST <br /> 23 REGIONAL GEOLOGIC SETTING <br /> The site is located in the eastern portion of the Great Valley geomorphic province of California The <br /> valley is a nearly flat, elongate trough trending northwest and southeast for approximately 450 miles <br /> The valley is enclosed by the granitic Sierra Nevada on the east and the sedimentary and <br /> metamorphic Coast Ranges on the west The surficial and upper several hundred feet of subsui face <br /> layers consist primarily of unconsolidated alluvial and floodplain deposits (predominantly sand, silt, <br /> and clay) of Quaternary age, which were derived from the mountains of the Sierra Nevada Beneath <br /> the upper sedimentary deposits lie a thick sequence of marine deposits of Mesozoic age, which in <br /> turn are underlain by a pre-Juiassic complex of igneous and metamorphic basement rock <br /> . 2 4 GROUND WATER DEPTH AND FLOW DIRECTION <br /> The estimated depth to ground watcr at the site is between 70 and 80 feet below surface grade (bsg) <br /> based on information from Livres of Equal Depth of Water Wells Fall 1993, published by the San <br /> Joaquin County Flood Control District and Water Conservation District However, with significant <br /> ground water recharge between 1994 and 1996, ground water depth at the site may have deceased <br /> to 50 feet bsg <br /> Based upon flow directions at nearby sites, prevailing ground water flow direction is estimated to <br /> be southeast at the former Fisco Warehouse property However, flow directions may be both locally <br /> and seasonably variable The uppermost ground water flows in an unconfined aquifer With <br /> increasing depth, the aquifer becomes semi-confined, due to the presence of mixed heterogeneous <br /> layers of sediments <br /> The Stockton Diverting Canal is located adjacent to the site However, the Canal usually contains <br /> little water and does not appear to have a significant effect upon ground water depth or flow <br /> direction in the area <br /> 3 0. SCOPE OF WORK <br /> • The scope of work includes the collection and analysis of subsurface soil samples from the former <br /> UST area AGE proposes to collect soil samples using direct push technology (DPT) Initially, one <br /> Advanced GeoEnvironmenta 1,1nc <br />