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Interim Soil Remediation Work Plan STALLWORTH AUTO SALES 602 North California Street, Stockton, California 1 .0. INTRODUCTION On behalf of Mr. Gary Stallworth, Advanced GeoEnvironmental has prepared this Interim Soil Remediation Work Plan for the property located at 602 North California Street, Stockton, California (site). The scope ofwork includes installation of an interim soil vapor extraction (SVE) remediation system and a schedule for remediation at the site. The location of the site and the surrounding area are illustrated on Figure 1 ; a plan of the site is illustrated on Figure 2 . This work plan has been prepared in accordance with guidelines issued by the Central Valley Regional Water Quality Control Board (CVRWQCB) for investigation ofunderground storage tank (UST) sites. A summary of previous investigation at the site is included in Appendix A. Based on the results of soil vapor extraction (SVE) pilot tests performed at the site on 17 and 18 July 2007, AGE concluded that operation of an SVE system at the site should effectively reduce adsorbed hydrocarbon concentrations in vadose zone soils (upper 30 feet of soil) through the use of a vacuum that creates a negative pressure gradient to cause movement of vapors toward the extraction wells. Also based upon results of the SVE pilot tests, AGE recommended performance of a dual-phase extraction (DPE) pilot study using wells MW4A and VW- I . The DPE pilot test was recommended due to the hydrocarbon-impacted, fnc-grained sediments which comprised the upper 40 to 50 feet (saturated zone) of the lithology at the site. At the request of the San Joaquin County Environmental Health Department (EHD), AGE followed the dual-phase (DPE) pilot study recommendation with electronic mail correspondence on 26 October 2007 providing additional technical justification for the recommendation. In the aforementioned correspondence, AGE noted that the recommendation for DPE was presented to more effectivelyremediate contaminated ground water and soil within the saturated zone (beginning at approximately 30 feet bsg). Wells MW- IAB appear suitable wells for performance ofaDPE pilot study; MW- 1A is screened between 20 and 40 feet bsg; MW-1B is screened between 30 and 50 feet bsg. is Near the proposed location of the DPE pilot test, free product was observed during the drilling of well MW-8. If drawdown is achieved, DPE using MW- 1A/13 would likely reach soil contamination within the saturated zone. SVE would be effective in remediating the upper 30 feet of soil (vadose zone), butwould have little effect on the deeper contamination within the saturated zone. In addition, the current SVE wells could be utilized for a DPE system; essentially the SVE wells would be plumbed into the DPE system, vapor and a small volume of water would be extracted from these wells. Therefore, DPE has the potential to more effectively remediate both shallow and deep soil contamination while treating the upper zone ground water contamination. The EHD did not concur with AGE's recommendation and justification for performance of a DPE Advanced GeoEnvironmental, Ina I