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i <br /> Workplan for Additional Assessment and Feasibility Testing 4 <br /> 7-Eleven,Inc.Store No.20632,4627 DaVinci Drive,Stockton,CA October 17,2001 <br /> i <br /> Groundwater samples from each new well will be analyzed by a State-certified.analytical.laboratory for <br /> BTEX and TPH-G by EPA methods 8020/8015 modified, and the oxygenates, TBA, MTBE, DIPE, ETRE, <br /> i <br /> TAME by EPA Method 8260. <br /> Schedule/Report <br /> Drilling will commence within 6 months of receipt of written approval of this workplan, pending permit <br /> approval. Report preparation will be completed within 6-8 weeks of well installation. <br /> WORKPLAN FOR PROPOSED INITIAL FEASIBILITY TESTING <br /> Soil Vapor Extraction Testing <br /> Soil vapor extraction (SVE)can be used to remove the soil source of the dissolved hydrocarbon plume <br /> and supply additional oxygen to the subsurface to enhance intrinsic biodegradation,with the anticipated <br /> goal of reduction of dissolved gasoline constituents. <br /> Compared with other gasoline constituents, MTBE:is both more hydrophilic and adsorbs much less. <br /> These properties result in decreased extraction potential in moist soils, but increased vapor mobility in dry . <br /> soils. Given the site's current active status, and the relative low cost of vapor extraction as.a remediation <br /> technique, it is considered prudent to test the site for venting capability. <br /> The extraction test will be performed by applying a.vacuum to wells MW-4R and MW-2 on an individual, <br /> basis using a mobile 150-cubic feet per minute (cfm)thermal oxidizer. During the test, extracted air will be <br /> channeled to the unit after passing through a moisture knockout device and an air filter. Soil vapors will <br /> then be treated by passing them through the unit prior to discharge to the atmosphere. Observation wells <br /> (all wells not undergoing extraction)will be fitted with caps and Magnehelic gauges to monitor vacuum <br /> pressure changes during the test. Extracted vapor concentrations will be measured using a photo-or <br /> flame-ionization detector. Samples of extracted vapors will also be collected from each test well into j <br /> Tedlar bags or SUMMA canisters, for laboratory analysis and permitting purposes.. <br /> i <br /> I <br /> i <br /> 20632SAW.DOC <br /> I <br /> I <br />