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EALVe <br /> Ms Margaret Lagorio <br /> April 12, 2004 <br /> Page 3 <br /> ' Effectiveness of Ozone Microsparge System <br /> Groundwater samples were submitted for analyses of BTEX by EPA Method 8021, TPHg by <br /> EPA Method 8015 Modified, and fuel oxygenate compounds MtBE, TAME, TBA, DIPS, and <br /> ETBE using EPA Method 8260B Additionally, groundwater samples were analyzed for lead <br /> scavengers, EDB, and 1,2-DCA, using EPA Method 8260B Concentrations of MtBE were not <br /> reported at or above laboratory reporting limits to any of the groundwater samples submitted for <br /> analysis during the first quarter 2004 <br /> ' TPHg Concentrations <br /> • Concentrations of TPHg decreased since November 2003 in wells MW-2 and MW-10 <br /> • Concentrations of TPHg increased since November 2003 in well MW-11 <br /> • Concentration of TPHg in well NP-1 was not reported at or above laboratory reporting <br /> limits since October 2002 <br /> ' Benzene Concentrations <br /> • Concentrations of benzene decreased since November 2003 in wells MW-10 and <br /> MW-11 <br /> • Concentrations of benzene increased since November 2003 in well MW-2 <br /> • Concentration of benzene in well NP-1 was not reported at or above laboratory reporting <br /> limits since November 2000 <br /> 1,2 DCA Concentrations <br /> Concentrations of 1,2-DCA, ranged between 3 3 ug/L (MW-5) and 150 ug/L (MW-17), and were <br /> reported to wells MW-4, MW-5, MW-7, MW-10, MW-11 MW-17, MW-18, and MW-19 during the <br /> first quarter 2004 <br /> Discussion <br /> ' Analytical results from well MW-10 indicate that the ozone microsparge system appears to be <br /> effective as evidenced by the decreasing petroleum hydrocarbon concentrations Increases <br /> were observed in petroleum hydrocarbon concentrations to wells MW-2 and MW-11 These <br /> ' increases to hydrocarbon concentrations are most likely due to desorption of hydrocarbons from <br /> soil caused by the microsparge bubbles Hydrocarbon concentrations in well NP-1 have <br /> remained below laboratory reporting limits during the test period with the exception of four <br /> sampling events The four detections of petroleum hydrocarbons in well NP-1 may be due to <br /> the desorption mechanism mentioned previously ENSR will continue to monitor well NP-1 to <br /> assess whether or not this is occurring <br /> J kProjects10694012859-357TinallReportskl st otr 2004 QMR RSR doc <br /> 35 Years of Excellence in Environmental Services <br />