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Former Countryside Market,Stockton, California Feasibility Study and Interim Remedial Action Plan May 20,2013 5.0 PROPOSED FEASIBILITY TESTING AND DATA COLLECTION PLAN Based on the technology screening evaluation presented in Section 4.0 and SGI's experience at similar sites, SGI has determined that AS and/or possibly biosparging is the most feasible remedial technology for the cleanup of the dissolved hydrocarbon plume beneath the Site and surrounding area. The potential benefits of sparging include: 1) enhanced dissolved residual plume stabilization; 2) increased available subsurface oxygen to promote natural attenuation/biodegradation (for both soil and groundwater); and 3) hydrocarbon constituent volatilization/removal from the soil and groundwater into the vapor phase for treatment within the vadose zone via natural attenuation processes. To confirm the feasibility of sparging at the Site, SGI proposes to conduct testing that will include the installation of various wells (injection, observation and vapor) within the former UST/dispenser island area, and the collection of key bioremediation and geochemical indicator data. The testing results will be utilized to help: 1) verify that sparging can be implemented on a full-scale basis; 2) provide the technical basis by which to design, install and implement the full-scale system; and 3) determine if one or more of the other final alternative technologies requires closer consideration for potential incorporation into a final RAP (i.e., in the unexpected event that the feasibility test results are not favorable and/or if the data collected indicates the use of such alternative technologies in conjunction Dr in sequence with sparging would be optimal). Activities associated with the proposed feasibility testing and bioremediation/ geochemical indicator data collection plan are detailed in the following sections. 5.1 Sparge Testing Sparge testing will be completed to determine proper injection well spacing, ideal injection air flow rates that will not require an active soil vapor recovery system, and to finalize the design of the full-scale treatment system. Following is a summary of the proposed feasibility testing activities: ➢ Sparge Pilot Testing; ➢ Sparge System Implementation and Engineering Design; ➢ Soil Gas Monitoring; ➢ Groundwater Monitoring and Sampling; and ➢ Operations and Maintenance The testing will include the installation of two injection wells (AS-1 and AS-2), one observation well (OBS-1) and one vapor well (VW-1), as shown on Figure 4. These well locations were specifically selected to help maximize data acquisition during both sparge testing and as a means to verify that no further action is necessary for vadose zone soils beneath the Site (and to potentially test/implement former UST area remediation in the event the soil data collected during wall installation activities and/or the soil gas data collected during sparge testing indicates such treatment may be required) as this general area showed the highest concentrations of VOCs in soil (Table 3) and groundwater(Table 1). Feasibility Study and lFeasi Ifty Study B lRP-Te FnaLtloc 5-1 The Source Group,Inc.