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Technical Memorandum Review of Work Plan for Additional Investigation 2546 French Camp Turnpike,Stockton,CA 95206 Page 2 of 3 Based on the analytical results,a release of petroleum constituents was suspected on-Site proximate to soil vapor sample location SVP-3. The vertical and lateral extent of the potential significant impact to soil,soil vapor,and/or groundwater proximate to SVP-3 is currently unknown.Additionally,based on the soil vapor results at SVP-3 for ethylbenzene (57,000 micrograms per cubic meter [ug/m3]) and xylenes (320,000 ug/m3),a VEC relative to the northern adjoining residential dwellings cannot be ruled out. PROPOSED SITE WORK PLAN FOR ADDITIONAL INFORMATION The Work Plan proposed the advancement of a total of four(4) soil borings at the locations depicted on Figure 1 in the Work Plan. The soil borings (B-1 through B-4) will be advanced to a terminal depth of approximately 15 to 20 feet below ground surface(bgs)utilizing direct-push technology. B-1: Proposed at the location of SVP-3, the boring would be advanced to a depth of approximately 15 to 20 feet bgs, depending on the depth to groundwater, with soil samples collected at depths of 2, 5, 10 and 15 feet bgs,and low-flow groundwater sampling.A temporary soil vapor probe would be installed at 5 feet bgs.Blew proposed to analyze soil,soil vapor,and groundwater samples for benzene,toluene,ethylbenzene and xylenes(BTEX)only. B-2 through B-4: Proposed laterally approximately 15 feet to the east,south,and west of B-1,they would be advanced to a depth of approximately 15 to 20 feet bgs,with soil samples collected at depth intervals of 2, 5, 10 and 15 feet bgs, depending on the depth to groundwater. Temporary soil vapor probes would be installed at 5 feet bgs. Soil and soil vapor samples would be analyzed for BTEX. Indoor air sampling is proposed at the following addresses: 594, 582, 568, 556, 534, and 522 Buena Vida Court. Indoor air sampling is contingent upon timely receipt of access agreements. Two(2) indoor air samples are proposed within each primary dwelling at each address (total of 12 indoor air samples). Four(4)outdoor/ambient air samples are also proposed.Air samples will be collected within 6-liter individually certified Summa canisters with in-line 24-hour flow regulators over a sampling period of 24-hours.Prior to sampling,Blew will complete the California Department of Toxic Substances Control (DTSC)Air Sampling Building Survey form.Air samples will be delivered under standard chain of custody protocols to a state of California certified laboratory, with proposed analysis for BTEX by EPA Method TO-15-SIM. Investigative derived waste (IDW) will be contained in a sealed and labeled 55-gallon steel drum for subsequent profiling and disposal. Representative samples will be collected, composited, and analyzed by a California-certified laboratory for VOCs via Environmental Protection Agency (EPA) Method 8260B, total petroleum hydrocarbons (TPH) via EPA Method 8015B, and CAM17 Metals via EPA Method 601013/7470/7471.A waste profile will then be prepared to determine proper disposal.IDW documentation and laboratory analytical reports will be included with each report submittal,as relevant/applicable. Reporting will combine the results of the soil vapor sampling performed in November 2025 with the results of the additional investigation outlined in this Work Plan. The report will be submitted to the EHD for review within 30 days of completion of field activities. Analytical results will be evaluated relative to the SFBRWQCB Environmental Screening Levels(ESLs)published in January 2019,and the screening levels established by the DTSC, Human and Ecological Risk Office (HERO), Human Health Risk Assessment (HHRA), Note No. 3, June 2020. Should analytical results indicate significant impact requiring remedial action,an updated work plan will be submitted. 84. ttl;� �i� CONDOR