Laserfiche WebLink
03 January 1996 <br /> AGE-NC Project No. 95-0197 <br /> Page 2 of 4 <br /> 2.3. EXISTING UNDERGROUND STORAGE TANKS <br /> Two 10,000 gallon USTs are currently operated at the site. A plan to remove or replace the <br /> remaining USTs is presently being considered by the property owner. However, a pre-removal <br /> assessment of the subsurface conditions has been requested. <br /> 2.4. 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 igneous Sierra Nevada to the east and the <br /> sedimentary and metamorphic Coast Ranges to the west. The surficial and upper several hundred feet <br /> of subsurface layers consists of a great thickness of predominantly unconsolidated alluvial and <br /> floodplain deposits(dominantly sands, silts, and clays)of Quaternary age, which are derived from the <br /> predominantly granitic mountains of the Sierra Nevada. Beneath the upper sedimentary deposits lie <br /> a thick sequence of marine deposits of Mesozoic age. These units are further underlain by a pre- <br /> Jurassic complex of igneous and metamorphic basement rock. <br /> 2.5. GROUND WATER DEPTH AND GRADIENT <br /> The water-table surface beneath the site to occur at a depth of approximately 30 to 45 feet below <br /> surface grade (bsg). The uppermost ground water flows in an unconfined aquifer. With depth, the <br /> aquifer becomes more confined due to the presence of mixed heterogeneous layers of sediments. <br /> Review of ground water surface elevation contour maps published by the San Joaquin County Flood <br /> Control and Water Conservation District suggests that regional ground water flow is towards the <br /> southwest. <br /> 3.0. SCOPE OF WORK <br /> 3.1. PROBING AND SAMPLING <br /> The proposed investigation includes initially advancing six (6) to eight (8) soil penetrations using <br /> "direct push"technology. The probings will be advanced near the former and present UST locations. <br /> Soil probing locations are illustrated on Figure 2. <br /> Soil penetrations will be advanced to maximum depths of 3 5 feet utilizing a van-mounted Geoprobe <br /> 5400 soil probing unit equipped with 1.125-inch rods. <br />