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i d Dual Phase Extraction Pilot Study Work Plan QUICK N SAVE #1 1901 South El Dorado Street, Stockton, California 1.0. INTRODUCTION At the request of Mr. Mohamad Matar and as directed by the San Joaquin County Environmental Health Department (EHD) letter dated 30 May 2008 , Advanced GeoEnvironmental, Inc. (AGE) has prepared the enclosed Dual Phase Extraction Pilot Study Work Plan (work plan) for 1901 South El Dorado Street, Stockton, California (site). The location of the site is illustrated on Figure 1 ; a plan view of the site is illustrated on Figure 2. Additional site background information is provided in Appendix A; a copy of the aforementioned EHD directive letter is included as Appendix B. The work plan includes procedures for the performance of a dual phase extraction (DPE; high vacuum ground water extraction) pilot study, to evaluate more enhanced methods to mitigate petroleum hydrocarbons in saturated zone soils and ground water. The plan was prepared in accordance with Central ValleyRegional Water Quality Control Board (CVRWQCB) guidelines for the investigation of underground storage tank (UST) sites. 2.0. PRINCIPLES OF DUAL-PHASE EXTRACTION Recovery of hydrocarbons from the saturated subsurface is often difficult due to the fact that hydrocarbons can exist in the vapor-; dissolved- and liquid-phase. Liquid-phase hydrocarbons both dissolve into ground water and vaporize into pore spaces between sediment grains. Dissolved phase hydrocarbons also vaporize into pore spaces until equilibrium is established between the liquid, dissolved and vapor phases. Remediation methods effective in treating one phase may not be efficient for remediation of other hydrocarbon phases . High-vacuum (vacuum pump capable ofproducing 25 to 28 inches ofinercury) dual-phase extraction systems are capable of removing both hydrocarbon vapors and, depending on-site soil type, stratification, laid and dissolved phase hydrocarbons. Extracted vapors may be treated by incineration in catalytic oxidation, thermal oxidation orby carbon bed filtration. Co-produced ground water can be treated on-site and discharged into either the sanitary sewer, storm drain system (not typically available) or disposed off-site (cost prohibitive) . DPE system design specifications are discussed in Section 4. 1 . DPE is also categorized as high-vacuum ground water extraction, which aggravates the bounding of petroleum to subsurface soil and readily removed the mobilized hydrocarbons. Normal ground water "extraction" depends on water present in the well casing, above the pump inlet to supply a head pressure on the intake of the pump. DPE does not require water in the well casing for remediation. This DPE action of recovery is effective vert �irally, across the well screen and under the ground water table; however the lateral influence of the single DPE point is minimal. Advanced GeoEnvironmental, Inc