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PROpLFM ASSESSMENT REPORT <br /> Shell Scryka Station <br /> -. 7910 Lower Sacramento Load,Stockton,Cnlifornia <br /> Shell WIC No.2134-7524.0808 <br /> Delia Proicct No.40.88.147 <br /> Page 7 <br /> r" <br /> k � <br /> 3.0 PROJECT SITE IIYDROGEOLOGIC DESCRIPTION AND ANAI.Y-l'ICAL RESULTS <br /> This section presents a description of soils underlying the site, monitoring well construction information, <br /> j ground water level measurments.and soil and ground water sample analytical results. <br /> 3.1 Site Sails and Geolaev <br /> A total of six soil borings were drilled during August 1989 in order to characterize the subsurface geology <br /> F and to evaluate the presence of petroleum constituents in soils beneath the site. <br /> F...'' In order to evaluate the extent of petroleum constituents detected during tank removal in December 1%8, <br /> soil and monitoring well borings were advanced in the vicinity of soil samptirg locations where TPH <br /> eonrentrations had previously been detected Soil boring SB-1 was advanced near pump island sampling <br /> location T-3. Sail boring SB-2 was located near pump island sample T-1. Sboring SBI-3 was advanced <br /> f oil - <br /> u*.e,� through the former tank excavation backfill in the vicinity of tank samples T-5, T-6, T-7, and T-8. <br /> t. Monitoring well beyings MW-1,MW-2,and MW-3 were located around the perimeter of ti a former tank <br /> w avation to the southwest, northeast, and northwest, respectively. Locations of the soil borings and . <br /> { monitoring wells are shown:n Figure 2 <br /> Soil borings SB-1, SB-2,and SB-3 were advanced to depths ranging from 41.5 to 56.5 feet below ground <br /> surface using 8-inch4ameter hollow-stem augers. The monitoring well soil botiags were advanced to 68 <br /> t feet below grade using 10-inch-diameter hollow-stem augers. Soil boring logs and monitoring well <br /> construction reports are presented in Appendix A. <br /> Two cross-sections were generated to illustrate the subsurface geology- Figure 3 shows the surface trace of <br /> i, cross-sections A-A'and B-B'which are presented in Figures 4 and 5. Silty clays to clayey silts predominate <br /> beneath the site. A 16.5-foot-thick silty sand layer was encountered from 13.5 to 30 feet below grade in soil ` <br /> boring SB-I (Figure 4). An 1&foot-thick silty sand layer was encountered from 33 to 51 feet below grade <br /> in soil baring SB-3(Figure 5). Minor Iayers of sandy silt,smy sand,and sand are interbedded with the silty <br /> r <br /> cis+and clayey <br /> _silt layers beneath the site. Clay,silty clay,and_clayey_silt surround the backfill of the former__ <br /> T € <br /> + 3 tatticiexca-pttVSw <br /> k A _ <br />