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Technical Memorandum <br /> Review of Work Plan for Additional Investigation <br /> 2546 French Camp Turnpike,Stockton,CA 95206 <br /> Page 2 of 2 <br /> depth of 5 feet below ground surface (bgs) to install temporary soil vapor wells. Soil vapor analyses will <br /> include total petroleum hydrocarbons as diesel range organics (TPH-DRO), soil vapor sampling will be <br /> performed utilizing sorbent tubes and shall be analyzed by McCampbell Analytical of Pittsburg,California <br /> for volatile organic compounds(VOCs)and TPH-DRO by EPA Method TO-17.Soil vapor well installation <br /> and sampling will be conducted in general accordance with the Advisory—Active Soil Gas Investigations, <br /> California Department of Toxic Substances Control(DTSC),July 2015. <br /> After sampling is complete, the soil vapor well tubing will be pulled out of the ground by hand, and the <br /> boreholes with be abandoned with neat cement and patched at the surface to substantially match original <br /> ground conditions. <br /> The results of the additional soil vapor sampling will be submitted to the EHD for review within 30 days <br /> of completion of field activities. Analytical results will be evaluated relative to the SFBRWQCB <br /> Environmental Screening Levels (ESLs) published in January 2019, and the screening levels established <br /> by the California Department of Toxic Substances Control, Human and Ecological Risk Office (HERO), <br /> Human Health Risk Assessment(HHRA),Note No. 3,June 2020. <br /> RECOMMENDATIONS <br /> Based on a review of the Work Plan,Condor concurs that the proposed additional investigation is adequate <br /> to evaluate potential off-site vapor encroachment risks to nearby sensitive receptors. Please ensure that the <br /> selected analytical laboratory maintains the appropriate accreditation for the proposed analyses to prevent <br /> potential delays or resampling requests due to data reliability concerns. Coordinate with EHD to obtain the <br /> necessary drilling permits prior to initiating field activities. Following completion of sampling activities, <br /> ensure that all temporary soil vapor wells are destroyed pursuant to EHD's Well Standards (San Joaquin <br /> County Ordinance Code Section 9-1115.6). Upon receipt of analytical results, submit a revised Site <br /> Characterization and Closure Report incorporating the updated risk evaluation. <br /> Respectfully, <br /> CONDOR EARTH �S\pNAL OFO NG y;L GF <br /> Q� !O �F.D�N P (.q,�!O <br /> dLUKE 8�( CL� <br /> N No.9945 I N0.6795 ;i <br /> SOF CA0, 0 F Or ; <br /> Luke Castle,PG No. 9945 October 13,2025 John P.Lane,PG No. 6795 October 13,2025 <br /> Associate Geologist Environmental Services Manager <br /> https://condorearth.sharepoint.com/sites/Project/Shared Documents/8000_pd/8845 SJCERD Geologist Support/8845 Site Mitigation <br /> Support/SR0086563 2546 French Camp/20251010-Further Action/L 20251013 French Camp Tumpike.docx <br /> �i� CONDOR <br />