SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Larry's Auto Page 2 308 North Grant Street January 30, 2015 Stockton, California 95202 at approximately fifteen feet bsg in VW-2 and thin sand units at approximately fifteen to twenty feet bsg and at thirty-five feet bsg in VW-5. AGE proposes to recover vapor using nested vapor extraction well VW-5A, screened thirteen to twenty-three feet bsg, while sparging air from VW-5C. The EHD infers that AGE proposes to recover vapor using nested vapor extraction well VW-2A, screened twenty-five to forty feet bsg, while sparging air from VW-26. Although there is some potential for the clay units to impede vertical migration of the sparged air, the close proximity of the shallow-screened nested wells VW-2A and VW-5A may overcome such interferences from the clay units. Therefore, the EHD approves a six-month pilot test and directs that a work plan be submitted to the EHD by 31 March 2015 for the incorporation of VW-26 and VW-5C into the IAS system and that describes measures to detect and monitor preferential lateral migration of sparged air. Based on the groundwater analytical results from 2nd Q-2014 Report, the EHD approves the following sampling schedule for this site: • Annually collect groundwater samples from monitoring wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-8, extraction well EW-1, and vapor extraction wells VW-2A, VW-213, VW-56 and VW-5C; • Remove monitoring wells MW-7 and MW-9 from the sampling schedule; however, continue to collect depth-to-water measurements from these wells during the annual sampling event; • Analyze the samples for total petroleum hydrocarbons as gasoline (THP-g); benzene, toluene, ethylbenzene, and total xylenes (BTEX); methyl tertiary-butyl ether (MTBE), tertiary-amyl methyl ether (TAME), and 1,2-dichloroethane (1,2-DCA); and • Include the analysis of total petroleum hydrocarbons as diesel (TPH-d) for groundwater samples collected from MW-4, MW-5 and MW-8. Please provide technical justification if changes to this sampling schedule are proposed. By letter dated 28 November 2012, the EHD had approved "In-Situ Air Sparging/Soil Vapor Extraction Remediation Work Plan Addendum (Addendum), dated 17 November 2012, prepared and submitted by AGE. The Addendum included the installation of two proposed deep IAS wells, screened between 60 and 62 feet bsg and performance of a pilot test to determine whether air sparged from these two deep wells would permeate upward toward the surface and remediate petroleum hydrocarbon contamination in the vadose zone. The approved pilot test involved sparging air separately from each deep IAS well for five days at a flow rate of two to four standard cubic feet per minute (scfm) and ten to twelve pounds per square inch (psi) of pressure while measuring dissolved oxygen concentrations from the four nearby SVE wells, VW-6 through VW-9, and two monitoring wells, MW-5 and MW-6. To date, the EHD has not received the results from this pilot study and directs that the findings be submitted in the next remediation report; in addition, include tables in future remediation reports that list the hours the IAS has operated, the air sparge flow rates, sparging pressures, and dissolved oxygen measurements collected. The Addendum has not been uploaded to GeoTracker and the EHD directs that this be done immediately.