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Ms Jennifer C Sedlachek 24 June 2005 ExxonMobil Refining and Supply Company Page 2 40 concentration of vapor phase hydrocarbons Sn Pari g with nitrogen(an inert gas) also significantly P P Y reduced the amount of hydrocarbons in groundwater, but the removal appears to have been due to volatilization, not destruction of hydrocarbons The volatilization of some hydrocarbons from the ozone and peroxone tests was expected It should be noted that concentrations of volatilized hydrocarbons in the field should be lower than in laboratory tests due to sorption, subsequent oxidation, or biodegradation in the vadose zone, and other factors which could not be reproduced in laboratory studies Most water quality parameters were not significantly affected by nitrogen, ozone, or peroxone treatment when compared to untreated groundwater Constituents that were affected were aluminum, arsenic, banum, bromide, manganese, molybdenum, nickel, vanadium, and Cr(VI) Of these, concentrations of arsenic, manganese, and nickel decreased after all three treatments Bromide decreased after treatment with ozone and peroxone When water that contains bromide is treated with ozone, a number of oxidation byproducts can be formed, including bromate Although the concentration of bromide decreased over time during testing,it does not appear that it was converted to bromate Bromate was not detected above the detection limit of S µg/L in either the ozone or peroxone tests Aluminum, barium, molybdenum, vanadium, and Cr(VI) concentrations increased in groundwater samples in most cases The increase in aluminum concentrations occurred after the nitrogen and ozone tests(but not the peroxone test) for reasons that are unclear The increased level of aluminum remained below the California maximum contaminant level (MCL) The concentrations of molybdenum responded similarly to both nitrogen(an inert gas)and the oxidants, suggesting that the changes in concentrations were not due to oxidation There is no MCL for molybdenum Barium, vanadium, and Cr(VI) significantly changed only in the ozone and/or peroxone tests, indicating that the changes were due to oxidation Ban urn concentrations increased but to levels below the California MCL Vanadium concentrations increased to 350 gg/L, which exceeds the California State Action Level for Drinking Water of 50 gg/L There is no MCL for vanadium Treatment with ozone and peroxone generated Cr(VI),but tests indicate that this Cr(VI)should revert to Cr(III)upon exposure to untreated soil The amount of Cr(VI)produced varied from <6 µg/L to a maximum of 570 µg/L The cause of the variability is unknown,but probably is associated with the amount or concentration of applied ozone and/or the presence of manganese in the soil or groundwater When present, manganese appears to be oxidized into permanganate (MnOa), which was present in all tests showing high Cr(VI) concentrations, but not in tests generating low concentrations of Cr(VI) Formation of Mn04" from soil manganese during ozonation is known to occur, and the ability of Mn04`to oxidize soil chromium is well-established Tests indicated that untreated soil can reduce Cr(VI) back to Cr(III) and that on a weight basis, the amount of Cr(VI)reduced is greater than the amount formed by oxidation Tests designed to quantify over time the ability of untreated soil to reduce any hexavalent chromium [Cr(VI)] that may be generated during the infection of peroxone indicated that hexavalent chromium generated by this iremedial technique will reduce back to Cr(III) within 27 days Gp.ysull)p)tpUgLlCamne pytlropm psmxtle•[hoalapY$mh of p.dl^]WZ g�lucak wm�ry>ae•+b