SITE INFORMATION AND CORRESPONDENCE_FILE 2

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San Joaquin County Environmental Health Department DIRECTOR M Donna Heran,REHS 1868 East Hazelton Avenue PROGRAM COORDINATORS m: r Stockton, California 95205-6232 Robert McClellon,REHS Jeff Carruesco,REHS,RDI Kasey• 6' ., �P Website: wwws' ov.or 1ehd Linda Foley,REHS q�iF pRi� �g 9 Linda Turkatte, REHS Phone: (209)468-3420 Fax: (209) 464-0138 November 28, 2012 Mr. Charles Skobrak 9947 East Highway 26 Stockton, California 95215 Subject: Larry's Auto 308 North Grant Street Stockton, California 95202 Dear Mr. Skobrak: The San Joaquin County Environmental Health Department (EHD) has received and reviewed In-situ Air Sparging/Soil Vapor Extraction Remediation Work Plan Addendum (addendum), dated 17 November 2012, prepared and submitted by your consulting firm, Advanced GeoEnvironmental, Inc. (AGE), on your behalf for the above-referenced site. The addendum was submitted in response to the EHD letter dated 22 June 2012 in which the EHD recommended screening the two proposed "deep" in-situ air sparging (IAS) wells between 45 and 50 feet below surface grade (bsg) instead of 68 to 70 feet bsg, as proposed by AGE. In the addendum, AGE proposed screening the two "deep' IAS wells between 60 and 62 feet bsg instead of 45 to 50 feet, as recommended by the EHD. Following the installation of the two proposed "deep" wells, AGE proposed performing a pilot test to determine whether air sparged from these two deep wells would permeate upward toward the surface, thus rermediating petroleum hydrocarbon contamination in the vadose zone. To evaluate this hyp sis, proposed sparging air separately from each "deep' AS well for five days at a flow ra standard cubic feet per minute (scfm) and 10 to 12 pounds per square inch (psi) of pressure. Each day, dissolved oxygen concentrations would be measured from the four nearby soil vapor extraction (SVE) wells and monitoring wells MW-5 and MW-6. Assuming an increase of oxygen concentrations in groundwater collected from the nearby wells listed above during the two pilot tests, AGE proposed initiating the start up and operation of the SVE/IAS system, incorporating the four proposed SVE wells and four proposed IAS wells into the current SVE/IAS system. The EHD approves the installation of the two proposed "deep" IAS wells, screened between 60 and 62 feet bsg, and performance of the pilot test as presented above. Care should be taken to avoid encountering the sand unit modeled as occurring between approximately 67 and 70 feet bsg; if encountered, the bottom of the boring should be grouted and the screen interval set higher in the boring to minimize the potential for sparging air to enter the sand unit. Submit the report of findings to the EHD within sixty days of completing the pilot test. The EHD will determine whether the two "deep' IAS wells should be incorporated into the SVE/IAS system based on the pilot test results.