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2.0 SITE SETTING <br /> 2.1 Hydrogeology <br /> The project site is located within the Eastern San <br /> Joaquin County Groundwater Basin. The basin is drained by <br /> the San Joaquin River and its tributaries. Groundwater <br /> recharge occurs principally along the San Joaquin River and <br /> Sacramento River Delta north of Stockton with contributions <br /> from numerous smaller rivers/creeks. The nearest surface <br /> water body to the site is McLoed Lake located approximately <br /> 3/4 miles west of the site. The site is situated on level <br /> terrain comprised of Quaternary-Recent alluvial sediments. <br /> The geology of the Stockton arra consists of a thick <br /> sequence of river channel and flood plain deposits. These <br /> sequences contain embedded sand, gravel, silt and clay <br /> layers. As is typical of alluvial environments, higher <br /> permeability zones representing former stream channels may <br /> occur as sinuous or lenticular features. Local groundwater <br /> gradients generally parallel the westerly flowing surface <br /> drainage trends. The water table lies at approximately 30 <br /> feet below grade and flows west to southwest based on San <br /> Joaquin Flood Control and Conservation District data (1989). <br /> 2.2 Additional Sources <br /> The adjacent property located north of the De Rollo Mazda <br /> site, owned by Mr. Charles Skobrak, previously had two u/g <br /> tanks for storage of paint thinner. These tanks, located <br /> directly adjacent -to the north side of Tank A, were removed <br /> in 1989 (Figure 2) . We have been informed by the property <br /> owner that no contamination was detected in soils samples <br /> collected beneath either tank. <br /> £ ' 3.0 INVESTIGATION PROCEDURES <br /> 3.1 Drilling <br /> On November 11, 1989, three soil borings were drilled to <br /> depths ranging from 17.5 to 35 feet below grade. Drilling <br /> was conducted with a B-61 rig using eight inch (O.D. ) <br /> hollow-stem augers. The drilling was performed under the <br /> direction of a field geologist who maintained a continuous <br /> log of the material encountered using the Unified Soil <br /> - ClassificationSystem (Appendix 1). The three boringswere - - - - <br /> located as close as possible to the area of highest soil <br /> contamination . for each tank. The location of the three <br /> s borings are shown on Figure 2. Subsequent to completion, a <br /> two foot bentonite seal was placed in the bottom of each <br /> boring prior to surface sealing to grade with neat cement. <br /> The . drill cuttings were stored on an asphalt surface <br /> adjacent to the borings and covered with .plastic sheeting. <br /> 2 <br />