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Former Countryside Market,Stockton,California Feasibility Study and Interim Remedial Action Plan May 20,2013 The above data coupled with ongoing VOC results (i.e. groundwater monitoring and sampling events per Section 7.5) will allow for a comprehensive assessment of the existing electron acceptors and geochemistry within and beyond the plume core. The information will b utilized in conjunction with soil physical properties data (Section 5.1.2) to determine such factors as be aerobic and anaerobic conditions predominate prior to the advent of sparging at the Site, if bioremediation activities are fully degrading the parent compounds to nontoxic end products downgradient, and the extent to which sparging serves to alter the existing geochemistry and augment naturally occurring biodegradation rates. 5.3 Potential Vapor Extraction Testing As discussed above, soil data will be collected in the former UST area durir g sparge test well installation activities. Should the overall average of the analytical results be above the cleanup criteria presented in Section 8.0, vapor extraction testing (VET) activities will also be conducted utilizing well VW-1. Additionally, a VET would be conducted in the unlikely event that the soil gas monitoring data collected during sparge testing indicates fugitive emissions is an issue. In either qase, appropriately sized and permitted rental equipment would be mobilized to the Site as the sparge +testing is being conducted or shortly thereafter. Given the known lithology in the former UST; , a liquip ring or equivalent extraction blower would be utilized for the VET to help ensure that the testing could be conducted up to maximum feasible applied vacuums. It is estimated that the VET could be completed within 1-2 days. Flow versus vacuum step testing for the portable vapor extraction system (VES) would first be performed utilizing a Dwyer® DS-300 in-line flow sensor/averaging pitot tube, as well as magnehelic differential pressures gauges. At a minimum, observation well OBS-1 will be used for a monitoring point. Based on depth to water data collected at the time the VET is conducted, monitoring well MW-2 may also be utilized for this purpose. To record induced vacuums in the monitoring point(s), a valve will be installed at the sealed well cap(s) for connection of m gnehelic gauges of various ranges. To confirm advective airflow corresponding with measured interved ed vacuums, Tedlar bag deflation rates will additionally be determined at the monitoring point(s). advective airflow is an indication that vapors are being conveyed in the vadose zone toward the extraction well. At a minimum, two vapor samples will be collected (one at the start and end of the VET) for laboratory analysis from well VW-1. The analyses will be used to estimate both Hydrocarbon mass extraction rates and the total hydrocarbon mass removed. The vapor samples will be submitted under proper chain-of-custody protocol to a State-certified laboratory for analysis by EPA Method 8260M for TPHg, BTEX compounds and oxygenates (TAME, TBA, EDB, 1,2-DCA or EDC, DIPE, ETBE and MTBE). The end sample may also be analyzed for fixed gases (N2, 02, CO2 and CH . Soil gas will be monitored periodically throughout the testing with a PID. Feasibility Study and lFeasibilay Study&IRAP_TW Flnaldoc 5-8 the Source Group,Inc.