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�_ <br />'a ,• <br /> 2. FIELD INVESTIGATIONS <br /> 2,1 PREVIOUS INVESTIGATIONS <br /> EA Engineering,Science,ark Technology,Inc.(EA)conducted a soil vapor contaminant <br /> r <br /> survey(SVCA)at former Chevron SS 9-1918 on 18 November 1987. An SVCA Is a field <br /> method of collecting and analyzing samples of soil vapor,the samples of soil vapors arc <br /> analyzed for petroleum hydrocarbons with a portable gas chromatograph. Samples of soil <br /> vepon at Chevron SS 9.1918 were collected by driving 5/8-inch diameter steel probes into <br /> the soil at ten locations(Mg=S). A vacuum pump was used to purge several volumes of <br /> vapor from the prones,thus ensuring that the samples were not cross-contaminated, <br /> thett:by improving the representation of the vapors contained in the probes. The vapors <br /> collected with a ntictosyringe through a septum In the vacuum pump and injocted into <br /> a Photovac 1 OSSO portable gas chromatograph for analysis. The Photnvac 1OS50 is x <br /> programmable,Integrating gas chromatogrph with a photoionisation detector(PTD). The <br /> instrument was calibrated with standards consisting of 10 ppm benzene and 10 Ppm toluerr_ <br /> In a1r. <br /> Perrolcum hydrocarbons were not detected in the soil vapors sampled at Chevron SS 9- <br /> 1918, A sumnutry table of tesvlts Is attached as Table 2; a copy of EA's report is ,W <br /> attached as Appendix E. Depths of sampling were rather shallow,3 tog feet below <br /> ground surface,and wet clay was noted by the field pLrsoancl at several of the sampling <br /> points. "I'he limited depth of penentlon and the wet soils may have diminished the <br /> repr esenutdon of the samples. No further work was recommended,_ <br /> Biline Tech Soviets was pics:nt on 24 February 1988 to observe the demoNtion of the <br /> service station and the rawval of four underground storage tanks. Blaine collected the <br /> enviroarrtental samples prescribed in RWQCB guidelines. Soils containing gasoline were <br /> observed beneath the gasoline storage tanks;therefore,a repre=txtive from Snit Joaquin <br /> Envkwmental HrAlth requcsud that no samples be collected from,he tank field err til more <br /> soil was excavated. One soil sample was collected from,beneath the fill pipe of the wase <br /> oil tank on 24 Fcbn y 1988;that sample contained 26 ppm of high-boiling point <br /> - - -- ---- --hydromrbom and 10 pptm low-bWUng point bled-ocubonu cosy=tratsorts of bc.n=ie,- - ----- ---- <br /> toluene,cthylbm=be,xylems,cWodmcd solvents.and PCBs were below dao tion. <br /> 3 <br />