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20 February 1996 <br /> AGE-NC Project No. 95-0197 <br /> ' Page 2 of-5 <br /> ' upon review of PHS-EHD records, no report or laboratory analysis from the investigation was <br /> located. <br /> 2.3. REGIONAL GEOLOGIC SETTING <br /> ' The subject site is located in the eastern portion of the Great Valley geomorphic province of <br /> California. The valley is a nearly flat, elongate trough trending northwest and southeast for <br /> approximately 450 miles. The valley is enclosed by the granitic Sierra Nevada on the east and the <br /> sedimentary and metamorphic Coast Ranges on the west. The surficial and upper several hundred feet <br /> of subsurface layers consist primarily of unconsolidated alluvial and floodplain deposits <br /> (predominantly sand, silt, and clay)of Quaternary age,which were derived from the mountains of the <br /> ' Sierra Nevada. Beneath the upper sedimentary deposits lie a thick sequence of marine deposits of <br /> Mesozoic age, which in turn are underlain by a pre-Jurassic complex of igneous and metamorphic <br /> ' basement rock. <br /> 2.4. GROUND WATER DEPTH AND GRADIENT <br /> The water-table surface beneath the site occurs at a depth of approximately 27 feet below surface <br /> grade(bsg). The uppermost ground water flows in an unconfined aquifer. With increasing depth, the <br /> aquifer becomes semi-confined due to the presence of mixed heterogeneous layers of sediments. <br /> ' Ground water surface elevation contour maps published by the San Joaquin County Flood Control <br /> and Water Conservation District indicate that regional ground water flow is towards the northeast. <br /> 3.0. PROCEDURES <br /> 3.1. SOIL PROBING <br /> On 23 and 26 January 1996, six probings (B 1 - 136) were advanced to depths of approximately 30 <br /> ' bsg at the site. Advancement of probings was accomplished utilizing a van-mounted Geoprobe 5400 <br /> equipped with probe rods with an attached 1.125-inch diameter soil sampler, using "direct push" <br /> ' technology (DPT). Probings B1 through B3 were advanced along the southern portion of the <br /> property;probings B4 and B5 were advanced along the eastern portion of the property; and probing <br /> B6 was advanced near the southeast corner of the property. The probing locations are depicted on <br /> Figure 2. <br /> 1 <br />