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1 <br /> Quarter Monitoring Report <br />' January through March 2005 <br /> • 8200 N Highway 99, Stockton,CA <br /> Page 7 of 8 <br /> t <br /> 6.0 CONCLUSIONS <br />' Dissolved MTBE in the shallow aquifer beneath the site does not extend to the nearby <br /> residences, as evidenced by non-detect results in wells MW 15, MW 16, and the nearby domestic <br />' wells <br /> Groundwater extraction appears to be reducing the concentration of gasoline constituents in well <br />' MW1 and nearby monitoring wells MW3 and MW4, which are located approximately 51 feet <br /> and 56 feet, respectively, from the extraction well, although MTBE levels in the source area <br /> appeared to rebound when pumping from the extraction wells was suspended due to a scaling <br />' issue in the treatment system <br /> MTBE has been detected at relatively low levels in C Zone monitoring well MW13C, which is <br />' completed to a depth of approximately 222 feet bgs, but has not been detected in B Zone well <br /> MW14B, which is completed to a depth of approximately 124 feet bgs Well MW9B, completed <br /> to a depth of approximately 110 feet bgs, also contains no petroleum hydrocarbons <br />' Based upon analytical results of influent and effluent samples collected at the site, no <br /> carcinogenic PAHs are present in groundwater beneath the site Although concentrations of the <br />' inorganic constituents chloride, nitrate, sulfate, total dissolved solids (TDS), and specific <br /> conductance (EC) have increased since extraction well EW2 was brought online, they still are <br /> within acceptable ranges <br /> 7.0 RECOMMENDATIONS <br />' Based upon consistent non-detect results in B Zone wells MW9B and MW 14B, Ground Zero <br /> recommends that these wells be destroyed under permit from EHD These wells have <br /> demonstrated that the B Zone aquifer beneath the site (approximately 105-125 feet bgs) has not <br /> been impacted by the dissolved contaminant plume <br />' Ground Zero expects to begin vapor extraction at the site during the second quarter of 2005 The <br /> thermal oxidizer is expected to be delivered by the manufacturer during the first week of May <br /> 1 <br /> 1 <br /> • <br /> aG 1GROUNDZEITULEBURGIReporrs\QMR1200511QM2005 doc <br />