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8 <br /> E <br /> NO <br /> e <br /> 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 Fiver and its tributaries. Groundwater <br /> . <br /> recharge occur.-,-. 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-Ra_cent alluvial sediments. <br /> The geology of the Stoc;cton area 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 /> p 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 3O <br /> .: feet below rade and flows west to southwest based on San <br /> Joaquin Flood Control and Conservation District data (1989). <br /> r " 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 ujg <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 /> t 3.1 Drilling <br /> On November 11 1Lj89, 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 /> I log of the material encountered using the Unified Soil <br /> _-Classification__System-(Appendix_ I) . -- The threeboringswere -- - - <br /> located: as close as possible to the area of highest soil <br /> r contamination for each tank: The location of the: three <br /> 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 anasphalt surface <br /> adjacent to the borings and covered with plastic sheeting. <br /> 2 <br /> 6: <br /> Nit <br />