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-r1'a 'Fx+3rt.:a +%3Gt-at <br />.:..r.... ... .. .... - <br /> ,,..='K,w�....v......-.. .+. -:i`— �.Y"wr-::'�'__.._..-..:.»d....�.r '•+.•. .--.. ...%:;bw+�i.uv+ u4 �''s--��...�,.-.,-"�'a:^sr*e�T^Tr�.LHx� -,v� ate. .�m "e����� �w.�.�..�.�'�;a... <br /> Fg?s <br /> 2. <br /> FIELD IIM::STIGATZOI:i <br /> 2.1 PREVIOUS INVFSTIGATIONS <br /> The nubsurface at tormf:r Chevron SS 9-1910 has boon investigated <br /> four times since november 1907. EA sampled and analyzed scil <br /> vapors with a soil vapor contaminant assessment (SVCA) on 17 <br /> November 1987. During the SVCA, samples of soil vapors at Chevron <br /> SS 9-1918 were collected by driving 518-inch diameter steel <br /> probes <br /> into the soil at ten locations. The vnpora were sampled with a <br /> " microsyringe purging the steel sampling probes; the vapors were <br /> analyzed using a Photovac 10S50 portable gas chromatograph, The <br /> Photovac 10550 is a programmable, integrating gas chromatograph <br /> � = with a photoionization detector (PID) . The instrument was <br /> calibrated with standards consintJnq of 10 ppm benzene and 10 pp.m <br /> i <br /> � j toluene in air. No concentrations of petroleum hydrocarbons <br /> greater than 1 ppm of benzene, toluene, or total detected <br /> hydrocarbons were treasured in the soil vapors sampled at Chevron <br /> SS 9-1918. <br /> F <br /> i <br /> j Blaine Tech Services oversaw the tank pull on 24 February1986 <br /> when four underground storage tanks were removed. Blaine <br /> • collected the environmental samples prescribed in RhQCB <br /> guidelines. One soil sample collected from beneath the fill pipe <br /> r ti of the waste oil tank on 24 February 1988 contained 26 ppm of <br /> 1 � F <br /> high-boiling point hydrocarbons and 10 ppm low-boiling point <br /> hydrocarbons; concentrations of benzene, toluene, ethylbenzene, <br /> xylenes, chlorinated solvents, and PCBs greater than the detections <br /> limits were not measured. Soils in and around the tank field were <br /> excavated and stockpiled onsite. Two samples of the stockpiles <br /> contained 55 ppm high boiling point hydrocarbons, 340 ppm low- <br /> -- — - boiling point hydrocarbons, 28 ppm toluene► 26 gpta xylenes, and T� - <br /> 1.2 ppm ethylbenze:ne and 490 ppm low boiling point hydrocarbons, <br /> respectively. <br />