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7-Eleven Store#14117 <br /> Results of Oxygen Injection Feasibility Pilot Study <br /> May 9, 2006 <br /> Page 3 <br /> Potassium Mercury <br /> Sodium Molybdenum <br /> Copper Nickel <br /> Iron total Lead <br /> Manganese Antimony <br /> Zinc Selenium <br /> Chloride Thallium <br /> Conductivity Vanadium <br /> Total Dissolved Solids Zinc <br /> The analytical methods are listed in Attachment C with specific sample container and <br /> preservative requirements for each analyte. <br /> SECOR personnel visited the site twice to conduct oxygen injection on December 2 and 16, <br /> 2005. Oxygen injection was completed using bottled oxygen transported to the site by <br /> SECOR. Approximately 150 ft3 of oxygen was injected into 1-1 during both phases of the <br /> pilot study. Per the request of the RWQCB, a data logger was installed in well MW-1 to <br /> record changes in dissolved oxygen (DO), pH, specific conductance, and temperature <br /> during the Pilot Study. Ferrous iron and dissolved oxygen concentrations were also <br /> measured in the field in 1-1 and MW-1 prior to and immediately following oxygen injection. <br /> Three casing volumes of water were then purged from the two wells as outlined previously <br /> and groundwater samples were then collected from the wells and analyzed for the same <br /> suite of inorganic constituents listed above. These data provide an understanding of <br /> potential immediate effects to groundwater chemistry from injection of oxygen. <br /> DATA EVALUATION AND INTERPRETATION <br /> The analytical values and field measurements evaluated below are summarized in Tables 1 <br /> and 2. The certified laboratory reports summarizing the groundwater sample analytical <br /> results are in Attachment D. <br /> Metal Speciation <br /> In reviewing the available data on the pilot study injections, it is clear that the oxygenation, <br /> because it was only operated briefly, had a limited impact on general groundwater <br /> conditions. As predicted, metal concentrations in groundwater were not significantly <br /> impacted by oxygenation (Table 1). Oxygenation did not increase metal dissolution. <br /> Selenium and lead appeared to decrease in MW-1 after oxygen injection, but the <br /> concentrations detected were near the limits of detection and the changes in concentration <br /> within the analytical error for trace level concentrations. Total and ferrous iron decreased <br /> as a result of oxygenation, indicating that the treatment had the desired effect of oxidizing <br /> redox sensitive metals, which are used by microbes to degrade hydrocarbons. <br /> Arsenic is present in the MW-1 groundwater sample near the limit of detection, and appears <br /> to increase after oxygenation, but that contradicts groundwater treatment theory which <br /> 14117 02 Pilot Study Report 04-18-06.doc SECOR International Incorporated <br />