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1 Geologica[Teclsnics/nc. Page 11 ' IRAP-Pilot Test Project No. 425.2 March 21,2005 1 5.0 ASSESSMENT OF REMEDIAL EFFECTIVENESS ' Pre-test soil and water quality parameter data are needed because the injection of ozone will be causing a chemical reaction in the subsurface. The chemical reaction is intended to ' destroy gasoline constituents but it can have negative affects such as increasing the solubility of metals as stated above. Water samples from all the shallow monitoring wells will be analyzed for the following constituents: • pH, EC,DO& ORP-weekly for first month, thereafter monthly • TBA,TBF, acetone (MTBE breakdown by-products)-monthly • TPH-g, BTEX and MTBE-monthly ' Hexavalent Chromium and Iron - monthly ' Above mentioned parameters will be compared with the initial concentrations on a monthly basis. After six months of operation of the system, the system will be turned off for at least 15 days before testing for the above mentioned parameters. This will provide an estimate for ' the overall effectiveness of the system in removing gasoline contamination. 5.1 Radius of Influence Determination The sparge wells are located near of monitoring wells. All the monitoring wells will be monitored to determine how long the ozone takes to affect the wells and to estimate the ' radius of influence. The concentration of dissolved oxygen (DO) in an aquifer is used as an indicator of air sparging effectiveness (source: "Analysis of Selected Enhancements for Soil Vapor Extraction", US EPA document EPA-542-R-97-007, September, 1997). This also ' applies to ozone usage as elevated DO in the wells will be an indicator that the ozone is oxidizing the subsurface with the 02 reaction byproduct present in the aquifer. ' 5.2 Plume Degradation Analysis In-situ chemical oxidation technologies generally require determining the amount of ' contaminant present and then calculating the quantity of oxidant to destroy the contaminant on a mass or weight percentage basis. The amount of TPH-g calculated to be in the ground was 6700 lbs after excavation in July 2001. In an ideal situation each molecule of ozone would react with and destroy one molecule of hydrocarbon. But other factors impede the ozone oxidation reaction including: • Micro-channeling (preferential pathways) that prevent the ozone from reaching the ' hydrocarbons that are located away from the micro-channels. • Natural organic carbon in soils that is preferentially oxidized by the ozone. • The presence of other organic and inorganic chemicals that will react with the ozone and/or oxygen.