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Former Countryside Market,Stockton,California May 20,2013 Feasibility Study and Interim Remedial Action Plan y reagent would need to be effective at oxidizing all of the COPCs, ,including benzene and 1,2- DCA, and the potential for secondary MCL exceedences and/or other unintended impacts to groundwater quality such as compound precipitation, metals mobilization and/or the potential for metal impurities within the selected oxidant would need to be carefully evaluated. As with enhanced bioremediation, multiple injections would likely be required and the goal would be to utilize advanced subsurface characterization technologies, as feasit le, during the advancement of the initial round of borings. Important advantages of this tech ology include its speed of reaction and ability to mobilize previously sorbed contamination which is beneficial for remediation purposes but tends to result in concentration rebounds (i.e., multiple injection events/escalating costs). The collection of site-specific geochemistry data is recommended to further evaluate this technology since it has the potential to meet the remedial objectives at a moderate total cost when used in conjunction or in sequence with other viable technologies. 3) Biosparging: Biosparging is achieved via the injection of air or oxygen at low flow rates (and nutrients, if needed) into contaminated groundwater for the purpose of increasing the biological activity of the indigenous microorganisms while minimizing the ri I k of inducing lateral plume migration and the stripping of volatile organic compounds (VOCs). Biosparging can be used to reduce the concentrations of petroleum hydrocarbon constitu nts that are dissolved in groundwater, adsorbed to soil below the water table, and within the smear zone/capillary fringe. For the reasons listed above, biosparging can likely be impleme ed at the Site without SVE although feasibility testing is recommended to confirm this iE the case and verify the biodegradability of relatively recalcitrant compounds like 1,2-DCA. his technology would likely meet the remedial objectives at a moderate total cost. 4) Air Sparging: AS can also likely be implemented at the Site wi hout SVE by injecting air or oxygen into contaminated groundwater at higher flow rates relative o biosparging. The injection of air at such rates serves to promote natural biodegredation of petroleum constituents in groundwater while also helping to strip dissolved contaminants and volatilize trapped, and adsorbed phase contaminants below the water table and in the capillary fringe/smear zone for anticipated vadose zone treatment via natural attenuation processes (i.e., as recommended previously, feasibility testing is proposed to confirm that the significant bioattenuation zone above the groundwater table is sufficient to liminate the need for SVE). Air added to contaminated groundwater can also enhance the biodegradation of contaminants above the water table to facilitate the treatment of residually impact vadose zone soils beneath the Site. Sparge systems can be tested, configured and operated to maintain plume stability which can be confirmed via verification monitoring. This technology would likely meet the remedial objectives at a moderate total cost that is anticipated to be lower than that of biosparging due to the generally greater zone of influence that s achieved from injecting at higher flow rates (i.e., increased well spacing) coupled with the I'kelihood of meeting cleanup goals/objectives in a shorter overall time frame. Feasibility SbAy antl[Feasibility SdAy&IR P_Text Fine[.dx 4-3 The Source Group,Inc.