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George's Service Remedial Action Work Plan Project No.425.2 June 30,2011 Hydrogen peroxide, while having a lower reduction potential than ozone, can be effectively used to treat hydrocarbon contamination in the subsurface. An advantage of hydrogen peroxide is that the volumes and concentrations can be adjusted based on subsurface conditions. Hydrogen peroxide is considered more stable, in that losses through the delivery system are typically less than those associated with ozone generation and delivery. While the basics of the Redox reaction have been discussed above, stoichiometry has not been developed to estimate quantitative relationships between reactants and products. As oxygen is introduced to the subsurface, it is expected that aerobic microbial populations will begin to flourish. The chemical breakdown of the hydrocarbon contamination in the subsurface will be augmented by the aerobic biodegradation, so mass of oxidation components required is difficult to estimate and would tend to overestimate the actual mass needed. Oxygen Releasing Compounds (ORC) can be added to the groundwater to create favorable conditions for microorganisms, thus enhancing biological degradation of contaminants. The addition of ORC to groundwater can be an effective treatment technology capable of reducing the levels of contaminants in groundwater and soil as the dormant biological populations in the subsurface will begin to thrive. ORC generally consists of magnesium peroxide, calcium peroxide, hydrogen peroxide, permanganates,or other similar compounds. All the compounds are applied to aid in the remediation of petroleum hydrocarbons and other similar contaminants found in groundwater. Oxygen Releasing Compounds(ORC)have been shown to aid in the natural attenuation degradation of petroleum hydrocarbons in the soil and groundwater. The addition of any ORC to groundwater may result in unintended secondary impacts to water quality. Any potential adverse water quality impacts are localized, short term, and do not impact any current or perspective uses of groundwater. Groundwater quality is typically tested before addition of the ORC, during treatment, and after treatment is completed to verify no adverse impact to water quality. General Waste Discharge Requirements for addition of ORC, hydrogen peroxide, ozone (or any other oxidant to the subsurface) will need to be obtained from California Regional Water Quality Control Board (CRWQCB) prior to implementation. Concerns and Limitations • Dissolved contaminant concentrations may rebound weeks or months following chemical oxidation treatment. • Significant losses of chemical oxidants may occur as they react with soil material rather than contaminants. • May significantly alter aquifer geochemistry, typically influence is temporary and only exists in the immediate area of the injection. • Higher overall costs relative to other source area solutions. Qeologica!reckgics Inc, 10 4252 RAP.docx