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} <br /> f <br /> l <br /> 7-Eleven Store#14117 <br /> Results of Oxygen Injection Feasibility Pilot Study <br /> May 9,2006 <br /> Page 4 <br /> predicts that arsenic would co precipitate with iron as it drops out of solution. The change <br /> in arsenic concentrations is within the error in trace level analysis. <br /> Lead concentrations decreased in 1-1 but increased in MWA as a result of treatment, but <br /> again, the change in both concentrations is within the analytical error in the measurement. <br /> Barium is typically not a metal of concern at these concentrations. All other detections of <br /> metals are at or near the limits of detection, indicating that.the detection may be a false <br /> reading. <br /> Oxygen Demand and BTEX-Oxygenates <br /> BOD measures the most labile carbon compounds that microbes can quickly degrade. <br /> BOD concentrations in 1-1 decreased after both treatment events. BOD concentrations in <br /> MWA increased, but so did COD and BTEX-Oxygenates, indicating that sparging must <br /> have locally mobilized some contaminants trapped in the soil matrix. The changes in COD <br /> reflect the change in contaminant and inorganic compounds like ferrous iron, sulfide, <br /> reduced nitrogen species etc. <br /> .SUMMARY <br /> Based on the concentrations of metals in groundwater as a result of treatment, there does <br /> not appear to be cause for concern at the site. Groundwater impacts are minimal for all <br /> compounds on the analysis list, and do not increase significantly after treatment. <br /> Fluctuations in dissolved metals or oxygen demand reflect. very minor changes in the <br /> aquifer, or variability in the low level analysis conducted for this study. <br /> BOD, COD, and BTEX-Oxygenate concentrations are indicative of low concentrations of <br /> chemicals of concern, and relatively effective induction of treatment through the addition of <br /> oxygen, as seen by the decrease in BOD in 1-1. The increase in BTEX-Oxygenate <br /> concentration in MW-1 is a short term change that the treatment is intended to treat. <br /> 14117 02 Pilot Study Report 04-18-06.doc SECOR International Incorporated <br />