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0 Former Countryside Market,Stockton,California Feasibility Study and Interim Remedial Action Plan May 20,2013 Tank Case Closure Policy, dated August 17, 2012) at the Site is significant and any further impacts to groundwater from residually impacted vadose zone soils will be limited (based on the available soil data and due to the fact that the former USTs were removed from the vacant gross covered lot approximately two decades ago). As detailed in Section 5.0, this will be confirmed via the collection of soil data within the former UST area, as well as by installing and assessing vapor pha a concentrations of COPCs during proposed groundwater feasibility testing activities. Should the resuts indicate soil remediation is necessary, vadose zone feasibility testing will also be conducted per Section 5.3 with all of the findings/conclusions being presented in a subsequent report for CRWQCB reviewlapproval. Table 4 presents the list of in-situ remedial technologies that were initially cc nsidered along with no action and institutional control options. The rationale for dismissing a technology Is clearly presented in Table 4. As indicated, a total of four groundwater treatment technologies were retained after meeting all of the above initial screening criteria, and conforming with the site-specific conditions/remedial objectives. Additionally, bioventing and SVE were retained pending the collection of data to determine if soil remediation within the vadose zone is required per Section 5.0. Following s a detailed evaluation of the retained groundwater treatment technologies that are the final candidates for potential implementation. 4.2 Detailed Analysis of Remedial Alternatives The four alternatives described in the following sections were identified for f?rther detailed evaluation: 1) Enhanced Bioremediation: Enhanced biodegradation is typically accomplished by the injection of a compound within the saturated zone that will provide a SL bstrate for naturally existing bacteria capable of degrading the COPCs. This causes a significant increase in the natural population of the degrading bacteria and/or in biodegradatior rates. Injections can be accomplished through the completion of temporary injection borings and/or permanently installed injection wells. Based on the type and distribution of COPCs in the groundwater, aerobic injections would most likely be required to remediate the plume Ithough anaerobic injections could prove more effective for a portion of the plume. The potenti I exists for multiple injections to be required using this technology such that the installation f permanent injection points spaced close together would likely be part of a final implementatio i plan with the initial round of injections being achieved via CPT technology, as feasible, n an effort to obtain high resolution/targeted Site characterization data (i.e., via a combination of membrane interface probes and hydraulic profiling sampling/electro-conductivity detectors). While this technology appears to have the ability to meet the remedial objectives, the a sociated cost would likely be moderate compared to other options although it may be more cost-effective when used in conjunction and/or in sequence with another viable technology. 2) Chemical Oxidation: In-Situ chemical oxidation may be an efliactive remedial option in the former UST area if the Site geochemistry is favorable. The two most critical factors to successfully implementing this technology are effectively distributin the reagents in the treatment zone and the reactivity of the oxidant with the contamination preset (ITRC, 2005). The selected Feasbly S"aMFeabity Study a innP-T�R.Ldw 4-2 The Source Group,Inc.