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Site Background Infonnation <br /> Eckert Cold Storage,Manteca,CA <br /> March 31,2005 <br /> Page 6 of 6 <br /> • 30, 2004 monitoring event for monitoring wells MW-4 and MW-7 were generally consistent with <br /> historical laboratory analytical results. However, the laboratory analytical resuIts of the groundwater <br /> sample collected from MW-5 indicated higher concentrations of benzene and TPH-G than in historic <br /> results for that well. Conversely, the laboratory analytical results of the groundwater sample collected <br /> from MW-8 indicated gasoline constituents at lower concentrations than in historic results for that well. <br /> Upon initial review of the MW-5 and MW-8 data, it appeared that the samples might have been switched <br /> and mislabeled in the field or at the laboratory. Therefore, monitoring wells MW-5 and MW-8 were re- <br /> sampled on January 10, 2005. The data from the re-sampling indicated that there was no field or <br /> laboratory mistake and that the groundwater contaminant conditions in the location of the-wells had <br /> changed. <br /> Water levels were collected from all eight of the sites monitoring wells. The average groundwater <br /> elevation was approximately 4.32 feet higher on December 30, 2004 than the previous sampling event <br /> conducted on September 7, 2004. The groundwater gradient estimated with a three-point construction <br /> using wells MW-3, MW-4, and MW-6 was approximately 0.003 ft/ft towards the north-northwest. <br /> Historically,the groundwater gradient is variable,but generally to the northwest. <br /> P:\3000_prj\3471 Eckert Cold Storage\3471 E 2005 Quarterly groundwater monitoringlReports\Mar-20051Site Background.doc <br />