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_ _ _ <br /> ..trxy -rA� �.. 3. ` 0irA <br /> d � a.. �i.:' s+' .';� ��'7�-;`. `,£"..w.::.e' ^4'.. a�' .' ''�'s�s 'S" <br /> Y <br /> represents the sura of all V-stsc responses, proportioned to that <br /> for benzene. <br /> Ell <br /> The gas chromatograph is operated in backflush modo to Prevent <br /> contar4 nation of the analytical colusrn with high concentrations <br /> of Interfering compounds. Rlanko are run to ensure that the <br /> ayrttem is free of contamination. An necossaary, the .instrument is <br /> re-calibrated by injecting standards and by running ambient air <br /> blanks approximately every two hours through the day. This re- <br /> calibration ensures that the systema is operating conaiatontly and <br /> that parametric changes caused by temperature changes through the <br /> day are accounted for. These data, along with xmtsltiple standard <br /> runs, ensure systema reproducibility. <br /> Results of t'me SVCA are presented it, Table 3. No petroleum. <br /> hydrocarbons were detected in the soil vapor at the Stockton <br /> • site. It should be noted that wet clay was encountered in a <br /> number of locations. Soil moJsture can reduce roil-gas movement <br /> by blocking the soil pores. In cases where wet clay was noted <br /> (Appendix S), the SVGA sanPlea may not be representative. <br /> Monitoring Well 2 (M42) vapors die ,xhibit a low level response. <br /> The field crew believed this was possibly clue to spillage during <br /> tank filling, since one of the fill caps wets located <br /> approximately two or three feet from MW2. This type of an <br /> occurrence has been observed previously by EA personnel. <br /> Recognizing this and rioting the absence of mcasureable <br /> hydrocarbon vapors in the remaining 20 samples suggests that the <br /> Broils and ground water of this site are not significantly <br /> contaminated with Petroleum hydrocarbons. <br /> CHV1 S:811 5 <br />