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- <br /> 1 <br /> { <br /> July 8, 1988 AGS Job No. 38432-2 <br /> UNOCAL service Station No. 6981, Stockton, California <br /> d� <br /> collected in a vial at the sampled depth by a vacuum process. <br /> The samples are then analyzed using a portable gas chromatograph. <br /> The vapor probe is pushed or driven to the desired depth, and the <br /> sampling assembly containing an evacuated sample vial is lowered <br /> through the hollow center of the probe rod to collect a sample. <br /> After allowing sufficient time for collection, the sample <br /> assembly is withdrawn from the probe rod. The sampls vial is <br /> removed from the sampling assembly, and a gas sample is withdrawn <br /> with a syringe and injected into the Photovac gas chromatograph. <br /> This procedure can be repeated at multiple depth points at euL�i- <br /> sampling location. <br /> Sampling locations are based in an appropr,ate grid pattern on <br /> the surface with appropriate. spacings that allow data to be <br /> reasonably interpreted. Alternatively, locations are selected <br /> based on available information relating to plume migration. <br /> Initial samples are generally collected at the: perimeter of the . <br /> property; subsequent locations are chosen based on the results of <br /> earlier sample analyses. Analytical results are evaluated at the <br /> time of collection with computer assistance to allow field <br /> ----------;-------- - -.----interpretation-and--decisions---for-locatin subse -- -- =---- -- --- ------ <br /> -- g- quant_sampling <br /> points. This real-time analytical procedure significantly <br /> t.J <br /> A)Qj011040F GOOSyStefl?S <br />