SITE INFORMATION AND CORRESPONDENCE_FILE 2

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San Joaquin County .� Environmental Health Department DIRECTOR .O Donna Heron, REHS Z. 1868 East Hazelton Avenue PROGRAM COORDINATORS < Stockton, California 95205-6232 Robert McClellon,REHS Jeff Carruesco,RENS, RDI Kasey cq•. :° Website: www.sjgov.org/ehd Linda Foley,RENS Linda Turkatte,REHS Phone: (209)468-3420 Fax: (209)464-0138 June 22, 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 (work plan), dated 07 June 2012, prepared and submitted by your consulting firm, Advanced Geo Environmental, Inc. (AGE), on your behalf for the above-referenced site. In the work plan, AGE proposed installing an in-situ air sparging (IAS) system to remediate groundwater and adding to the existing soil vapor extraction (SVE) system to remediate soil as an interim remediation measure. In the north underground storage tank (UST) area, designated UST Area #1, AGE proposed installing an in-situ air sparging (IAS) system to inject air into existing soil vapor extraction wells VW-5C, screened 45 to 55 feet below surface grade (bsg), and VW-2B, screened 44 to 54 feet bsg. AGE also proposed modifying the SVE system to apply a vacuum to VW2A, screened 25 to 40 feet bsg, and VW5A/B, screened 13 to 23 feet, and 26.5 to 41.5 feet bsg, respectively. In the south UST area, designated UST Area #2, AGE proposed installing four SVE wells, screened 10 to 35 feet bsg, two IAS wells screened 45 to 50 feet bsg, and two IAS wells screened 68 to 70 feet bsg. AGE proposed incorporating these newly-installed wells into the same IAS/SVE system used to remediate UST Area #1. The EHD has reviewed the logs for cone penetration test (CPT) boring CPT-2 and monitoring well MW-8, both advanced in the UST Area #2. Mainly clay and silt were reported from approximately 53 to 68 feet bsg with silty sand reported for MW-8 at 68 to 70 feet bsg, and stiff fine grained reported for CPT-2 at this same depth interval. There was also a high pore pressure interval reported for CPT-2 between 50 and 68 feet. Because of the soil Rhology and high pore pressure, the EHD does not believe the proposed deep IAS wells will produce significant reductions in petroleum hydrocarbon concentrations in groundwater; therefore, the EHD does not approve the two proposed deep IAS wells screened between 68 and 70 feet bsg. Instead, the EHD recommends that these two wells be installed with screen intervals between 45 and 50 feet bsg, just as the other two proposed IAS wells.