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Interim Corrective Action Plan Frontier Transportation, Inc. ' December 20, 2005 Page 4 ' 4.1) Contaminant Mass 4 TPH-gas was identifieA/at a maximum of 2,500 ppm (mg/kg) during the May 2002 excavation in sample "Bot WNS" t�tom-west, north side The same sample identified r MTBE at a maximum of 26,000 pa s per billion (ppb) and benzene at 27,000 ppn I�d According to BEII, this sample was taken from the bottom of the groundwater-flooded excavation pit Soil samples taken above groundwater level do not We contaminant levels ? that are as elevated as groundwater samples or soil samples collected dove groundwater level Groundwater chemistry demonstrates that MTBE tends to stay in the water phase ' (Appendix A) This is apparent at the site, since elevated levels of contaminants typically begin at 10' bgs, where first water levels are seen (See Table 2 for analytical results of previous soil samples ) The previous results show that adsorbed phase is limited to the source area, which has been partially excavated in May 2002 ' During September 2005 groundwater monitoring, MW-21 identified dissolved TPH- gas at 12,000 ppb, dissolved benzene at 814 ppb and dissolved MTBE at 8,750 ppb (See Table 1 and Figures 4, 5 and 6 ) Dissolved MTBE was identified in the westernmost well, ' MW-9 (screened from 5' bgs to 20' bgs), at a maximum of 1,600 ppb in June 2005 Low levels of dis1 Ll MT$E_l pve been detected in the deeper screened wells (30' bgs to 40' bgs) MW- and Mw-1 alculations of total mass of dissolved contaminants were based ' on the September 2005 groundwater monitoring event (see Appendix B for calculations) The mass of TPH-gas dissolved in groundwater was determined to be in the range of 5,000 to 7,500 grams Dissolved benzene was at a much lower level ranging near 100 grams ' Total dissolved MTBE was calculated to be approximately 4,000 to 6,000 grams ' 4.2) Ozone Injection / Sparging Ozone sparging has been found to be effective in safe mass removal in Region 5 of the ' State Water Resources Quality Control Board In Situ Ozone sparging is described as follows Ozone sparging consists of injecting ozone (03) into the aquifer Ozone reacts with ' fuel oxygenates and oxidizes these compounds This oxidizing reaction converts MTBE to TBA to TBF to acetone Any unused ozone degrades to Oz, thereby increasing the dissolved oxygen concentration in the groundwater and stimulating ' microbial activity The ozone must be generated on-site due to its rapid degradation to oxygen (Jenkins, Kleinfelder Inc ) A typical ozone generator/compressor will cost approximately $50,000 - $80,000 depending on the pounds of ozone required for ' treatment In order to maximize the delivery of ozone, a distribution system using a timed solenoid branching system would be used I I