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14 <br /> Site Background Information <br /> Eckert Cold Storage,Manteca,CA <br /> February 27,2006 <br /> Page 6 of 8 <br /> monitoring event for monitoring wells MW-4 and MW-7 were generally consistent with historical <br /> laboratory analytical results However, the laboratory analytical results of the groundwater sample <br /> collected from MW-5 indicated higher concentrations of benzene and TPH-G than in historic results for <br /> that well Conversely, the laboratory analytical results of the groundwater sample collected from MW-8 <br /> Indicated gasoline constituents at lower concentrations than in historic results for that well Upon Initial <br /> review of the MW-5 and MW-8 data, It appeared that the samples might have been switched and <br /> 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 /> Condor conducted the first quarter 2005 groundwater monitoring event at the site on March 9, 2005 <br /> Because of the change in site groundwater conditions indicated by the fourth quarter 2004 monitoring <br /> described above, Condor recommended the sampling of MW-5 on a quarterly basis in addition to <br /> regularly scheduled quarterly monitoring of MW-4 and MW-8 Harlin Knoll of the SJCEHD agreed but <br /> indicated that MW-1 should also be sampled to update contaminant concentrations in the site source area <br /> Groundwater samples, therefore, were collected and submitted for laboratory analyses from monitoring <br /> wells MW-1, MW4, MW-5, and MW-8 <br /> No separate phase petroleum was noted in the wells, but petroleum sheen and a moderate petroleum odor <br /> were noted in the groundwater inspection sample recovered from MW-8 The groundwater samples <br /> collected from the four monitoring wells were analyzed for BTEX, TPH-G, and selected gasoline <br /> oxygenates/additives including MTBE Laboratory analytical results of the sample collected from MW-1 <br /> during the March 9, 2005 monitoring event indicated that contaminant concentrations were generally an <br /> order of magnitude less than for historic monitoring results The MW-4 sample results were generally <br /> consistent with historic laboratory analytical results <br /> Prior to the December 2004 monitoring event, historic laboratory analytical results of groundwater <br /> samples collected from MW-5 Indicated generally very low contaminant concentrations Laboratory <br /> analytical results of samples collected from MW-5 in December 2004, January 2005, and March 2005 <br /> indicated higher contaminant concentrations (but with a decreasing trend in contaminant concentrations) <br /> Conversely, prior to the December 2004 monitoring event, historic laboratory analytical results of <br /> groundwater samples collected from MW-8 indicated generally elevated contaminant concentrations <br /> Laboratory analytical results of samples collected from MW-8 in December 2004, January 2005, and <br /> March 2005 indicated lower contaminant concentrations relative to the historic results <br /> Water levels were collected from all eight of the site monitoring wells on March 9, 2005 The average <br /> groundwater elevation was approximately 2 25 feet higher than the previous sampling event conducted on <br /> December 30, 2004 The groundwater gradient estimated with a three-point construction using wells <br /> MW-3, MW-4, and MW-6 was approximately 0 0033 ft/ft towards the northwest Historically, the <br /> groundwater gradient had been variable, but generally to the northwest, so the groundwater gradient <br /> direction on March 9, 2005 was generally consistent with historic groundwater gradient directions <br />