Laserfiche WebLink
15 January 1997 <br /> AGE-NC Project No 96-0229 <br /> Page 2 of 6 <br /> 23 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 estimated depth to ground water at the property is approximately forty feet bsg, based on the <br /> map entitled Lines Of Equal Depth Of Water Wells-Fall 1993, published by the San oaquin County <br /> Flood Control and Water Conservation District The prevailing ground water flow direction in <br /> northwestern Stockton is generally toward the northeast, although flow directions may be both locally <br /> and seasonably variable The uppermost ground w_ate ows in an unconfined aquifer With increasing <br /> depth, the aquifer becomes semi-confined due to the presence of mixed heterogeneous layers of <br /> sediments <br /> 3 0. PROCEDURES <br /> 3 1 SCOPE OF WORK <br /> The scope of work for preliminary site assessment included advancement of nine soil probe borings, <br /> and collection of both soil and "grab" ground water samples <br /> r 3 2 ADVANCEMENT OF SOIL PROBE BORINGS <br /> On 30 July, 02 August, 26 September and 28 October 1996, nine soil probe borings (P-1 through <br /> P-9) were advanced to depths of approximately 40 feet bsg both on-site and off-site Advancement <br /> of all probings was accomplished utilizing AGE's van-mounted Geoprobe 5400 The Geoprobe was <br /> equipped with 1 125-inch diameter probe rods with an attached 2 15-inch diameter soil sampler <br /> Soil probe borings P-1 through P-4 were advanced near the UST and dispenser areas, probe borings <br /> P-5 and P-9 were advanced upgradient of the UST and dispenser areas, probe borings P-6 through <br />