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INTERNATIONAL <br /> TECHNOLOGY <br /> CORPORATION RECEIVEU <br /> F E 8 2 6 1993 <br /> February 18, 1993 ENVIRONMENTAL HEALTH <br /> PERKIT/SERVICES <br /> IT Job No. 190916 <br /> Mary Maeys <br /> San Joaquin County Health <br /> P.Q. Box 2009 <br /> Stockton,_CA 95201 <br /> re: QA/QC Anomalies <br /> Pacific Bell Facility UE042 <br /> 345 N. San Joaquin Street <br /> Stockton, CA <br /> Dear Ms. Maeys: <br /> Recently you requested a review of QA/QC anomalies which_occurred during:the analysis of <br /> a soil sample collected from monitoring well MW-3, located at the above referenced site. <br /> The sample in question.(#MW3-4) was collected at 20 feet below grade during installation of <br /> monitoring well MW-3 on December 8, 1991. The sample was analyzed for gasoline, diesel <br /> and BTEX using EPA methods modified 8015 and 8020. Upon analysis, 7.4 ppm gasoline, <br /> 0.006 ppm ethyl benzene and. 0.013 ppm xylenes were detected. It was noted on the <br /> laboratory report that the compounds detected and calculated as low boiling hydrocarbons <br /> (gasoline) are due to a petroleum mixture other than gasoline This was noted since the <br /> chromatographic pattern did not match the gasoline standard pattern used for chromatographic <br /> interpretation. <br /> The surrogate recovery percentages achieved during analysis of this sample were outside of <br /> acceptable criteria; therefore, although the recovery percentages do not warrant rejection of <br /> these results, the results achieved must be considered as estimates (qualitative, not <br /> quantitative). As the sample analyzed was a soil sample collected during well installation, it <br /> is a one-time collection point and is not repeatable. Furthermore, no petroleum hydrocarbons <br /> have ever been encountered in groundwater samples collected from this well, which appears <br /> to indicate that the hydrocarbons originally detected in the soil may have been anomalies due <br /> to organic hydrocarbon impact, lab contamination or a highly limited area of impact which <br /> has naturally attenuated. The hydrocarbon levels encountered were so low that it does not <br /> appear that any further investigative actions are warranted.in this area. <br /> Regional Office <br /> 4585 Pacheco Boulevard .Martinez, California 94553 .510-372-9100 <br /> IT Corporation is a wholly owned subsidiary of International Technology Corporation <br />