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r y .., Quality assurance/quality control (QA/QC) procedures will be performed during the field exploration activities. These procedures will include pressure washing drilling equipment, cleansing/rinsing of the sampling equipment between soil sampling intervals and providing chain-of-custody documentation for each sample submitted to the laboratory. The soil sampling equipment will be cleansed between each sampling point by washing the equipment with an AlconoxO solution followed by a double rinse with potable and distilled water. The augers and other down-hole drilling equipment used in advancing the borings will be pressure washed before and after each boring. Excess soil remaining from the well installation activities and the decontamination fluids generated during the field activities will be temporarily stored onsite in Department of Transportation-approved, 17-H, 55-gallon drums pending analytical results and disposal in accordance with regulatory guidelines. `" SVE Well Installation Three soil borings will be advanced to depths of approximately AQ_11EL usin; a HSA drill rig. N' Sampling, soil logging and QA/QC procedures for the SVE borings and their associated soil samples will follow the same procedures used with the AS borings and samples described above. b+ Each SVE well will be constructed using 4-inch-diameter Schedule 40 PVC well casing and perforated screen. The well screen will consist of a 30-foot section of 0.10-inch-slotted screen placed from approximately one half foot off the bottom of the boring. A filter pack consisting of clean pea gravel r will be placed from the bottom of the boring to approximately one foot above the top of the well screen. A well seal consisting of at least 3 feet of granular bentonite will be placed above the filter pack. The remaining annular space will be grouted to the surface with a Portland cement/bentonite bad slurry and the well secured with a 12-inch-diameter, traffic-rated well box set in concrete. Typical SVE well construction and SVE wellhead detail diagrams are shown on Figure 6. low Laboratory Analyses The soil samples collected from the soil borings will be analyzed under a standard 10-day turn-around- time for the following: rr • TPHg and TPHd by the United States Environmental Protection Agency (EPA) Test Method 8015M. y • BTEX, fuel oxygenate compounds (FOCs) including methyl tert-butyl ether, tert-butanol, tert amyl-methyl ether, di-isopropyl ether and ethyl tert-butyl ether, 1,2-DCA and EDB by EPA Test Method 8260B. REMEDIATION SYSTEM INSTALLATION y General Process Description Based on the findings summarized in the 2010 Pilot Test Report and the vapor extraction pilot test performed in 1996, installation of an AS/SVE system targeting the remaining soil and groundwater impacts in the vicinity of the former 10,000-gallon gasoline UST in the northwestern corner of the Site has been proposed. Air sparging is an in-situ remedial technology that reduces concentrations of r volatile constituents in petroleum products that are adsorbed to soils and dissolved in groundwater. This technology involves the injection of contaminant-free air into the subsurface saturated zone, y Stockton Maintenance Station,Task Order No.05 Caltrans Contract No.06A1141,EA 10-ON8300 Project No.S9200-06-05A - 5 - December 28,2010 r