SITE INFORMATION AND CORRESPONDENCE_FILE 2

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6eoHydrologic Consultants, Inc. ■ In soils—3.3 mg/kg GRO; no benzene, MTBE or fuel oxygenates were detected. ■ In groundwater— 120 mg/L GRO, 23 mg/L benzene, and 430 ug/L MTBE; no other fuel oxygenates were detected. Cr(VI)was not detected in the soil or groundwater samples above the MDL of<0.001 mg/kg, and <0.001 mg/L, respectively. Total Cr was present in the soil sample at 24 mg/kg. Bromate was not detected in groundwater, but bromide, the potential precursor, was present at 0.47 mg/L. The concentrations of COCs and other parameters in soil and groundwater are shown in Table 4 of the Prima Report located in Appendix B. 4.3.2 COC Removal - Ozone Test Ozone was shown to be very effective in COC removal during the bench scale test. At an application of 1,600 mg ozone, the results were complete removal of GRO, benzene, ethylbenzene, and xylenes, and near complete removal of toluene and MTBE; a small amount of TBA at 51 ug/L was observed in this application. Since the TBA groundwater sample result from MW-1 1 was below the MDL(<2,000 ug/L), it is unclear as to whether the TBA was an intermediate of MTBE oxidation or masked by the high concentrations of non-target analytes. At an application of 2,600 mg ozone, the results were complete removal of all compounds. Further, TBA was not found above the MDL, showing that this compound is susceptible to ozone oxidation. The results of the removal COC test from soil and groundwater are shown in Table 5 of the Prima Report located in Appendix B. 4.3.3 COC Removal - Volatilization vs. Ozone Destruction The results of the removal COC by ozone destruction vs. volatilization confirmed that COC removal was primarily due to ozone destruction rather than volatilization in soil and groundwater and results are shown in Table 6 of the Prima Report located in Appendix B. Less than 1% of the COCs remained in the aqueous phase after treatment. Since none of the COCl except benzene were detected in the off-gases and since the amount of benzene volatilized in the 1,600 mg ozone test was only 0.086%, therefore most of the COCs lost from the aqueous phase were destroyed. 4.3.4 COC Removal - Effect on Secondary Water Quality Secondary water quality parameters were not significantly affected by treatment. Up to 0.31 mg/L of bromate was generated by ozone treatment of soil and groundwater. The amount of bromate increased when increasing the amount of ozone from 1,600 mg to 2,600 mg of ozone, and was accompanied by a decrease in bromide. Up to 0.219 mg/L of Cr(VI) was generated, and as with bromate, the amount of Cr(VI) formed increased with increased exposure to ozone. The concentration of total chromium was consistent with the amount of Cr(VI). TOC W2 Bench Scale Test Page 13