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i <br /> Workplan for Additional Assessment and Feasibility Testing 5 <br /> 7-Eleven,Inc.Store No.20632,4627 DaVinci Drive,Stockton,CA October 17,2001 <br /> Each test phase begins by sealing the observation wells, calibrating the Magnehelic gauges, and then <br /> starting the thermal unit, which is connected to the well undergoing extraction.. After completion of the <br /> warm-up cycle, the unit is set to extract at maximum vacuum from the test well. Each test phase consists <br /> of applying a vacuum to the test well until equilibrium conditions (as evidenced by steady-state flow)are <br /> attained. Observation well pressure readings, extracted flowrates, and extracted vapor concentrations are <br /> obtained during each test phase. If time permits, minimum.vacuum conditions will be tested in each well. <br /> Test duration is typically 8 hours. <br />' The groundwater monitoring wells will be used during the test based on proximity to the known area of <br /> highest MTBE/hydrocarbon concentrations (the underground storage tanks/pump islands)and access to <br /> the capillary fringe/upper saturated zone zone. Application of vapor extraction treatment to this portion of <br /> the site has the most chance to beneficially affect dissolved MTBE/hydrocarbon concentrations by <br /> removing the mass closest to the water table. <br /> Vapor samples will be submitted for analysis by EPA Method 8015/8020 for TPH-G; benzene, toluene, <br /> ethylbenzene, and total xylenes (BTEX); and by EPA Method 8260 for MTBE and other oxygenates. <br /> Test data will be used to determine if vacuum application to the referenced wells result in significant <br /> production of hydrocarbon/MTBE-containing vapor's, and what is (as applicable)the lateral radius of vapor <br /> extraction influence. <br /> Schedule/Report <br /> Feasibility testing will be conducted after installation of well MW-4R. The report will be submitted <br /> concurrently with additional assessment information. <br /> Additional Feasibility Testing <br /> i <br /> Based on SVE test data and vertical plume delineation information, oxygen/air sparging may also be <br /> evaluated as a remediation method for this site. Additional feasibility tests(including proposed treatment <br /> well locations/construction)will be proposed with SVE/additional assessment findings as an addendum to <br /> this workplan. <br /> 20632SAW.DOC <br /> I <br /> E <br />