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Environmental Assessment Report 2 Chevron U S A Products Company,45 East Harding Way,Stockton CA July 1b 1995 23 Soil Sampling Soil samples were collected from boreholes SB-10, SB-11, SB-12 AND SB-13 at 5-foot intervals during drilling, beginning at approximately 5 feet BGS Samples were collected using a 2 5-Inch O D split-spoon sampler, lined with three 2-inch-diameter by 6-inch-long brass sample tubes The sampler was driven 18 inches ahead of the augers at each sample point Soil samples were field screened for hydrocarbon vapors using a photo-ionization detector(PID) Sal was logged using the Unified Soil Classification System by a Groundwater Technology field geologist working under the supervision of a California registered geologist(Appendix B) One sample tube from each 5-foot interval was sealed, labeled and placed on ice in an insulated container for transport under chain-of-custody manifest to Sequoia Analytical (Sequoia), a California state-certified analytical lab in Sacramento Soil samples collected at each sampling interval from 15-through 50-feet BGS from each boring were selected for laboratory analyses (Tables 1 and 2) Samples were analyzed for benzene,toluene, ethylbenzene and total xylenes (BTEX), and total petroleum hydrocarbons-as-gasoline (TPH-G), using U S Environmental Protection Agency (EPA) methods 5030/8020/modified 8015 Based on results from the above analyses,the two samples having the greatest TPH-G concentration from each boring were selected for Toxicity Characteristic Leaching Procedure (TCLP) analyses of BTEX using EPA method 8020, one sample with non-detectable levels of BTEX and TPH-G from each boring was selected for Total Organic Carbon (TOC) analysis using EPA method 9060 modified, and one • additional sample with non-detectable levels of BTEX and TPH-G from each boring was selected for dry bulk density analysis using method MSA 13-2 (see Appendix C for details) Upon completion of drilling and sampling, all four borings were backfilled with a neat cement grout to surface on June 2, 1995 30 RESULTS OF SOIL SAMPLE ANALYSES Tables 1 and 2 summarize the laboratory analytical results for sod samples collected on June 1 and 2, 1995 Table 1 presents data on BTEX and TPH-G The highest benzene concentration was reported in sample SB13-50 0 at a concentration of 0 76 milligrams per kilogram (mg/kg),while the greatest concentration of TPH-G was reported at 10,000 mg/kg in sample SB13-25 0 The highest levels of ethylbenzene and total xylenes detected in the TCLP analyses were at respective concentrations of 460 and 4,000 micrograms per liter(µg/L), concentrations of benzene and toluene were below minimum detection limits for all samples analyzed for TCLP BTEX The highest level of TOC was detected in sample SB13-40 Oat a concentration of 370 mg/kg Sample SBI 3-35 0 yielded the highest dry bulk density value of 2 35 grams per cubic centimeter(g/cm3), reported for the clay portion of the sample core 0139EAR rptiChv 35] ❑®GttOUNDWATm ❑❑❑TECHNOLOGY. I