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Phase II Environmental Site Assessment Report Satellite Apartments 530 N.Stanislaus Street APN 139-224-090 Page 5 5.2 ORGANOCHLORINE PESTICIDES(OOPS) OCP concentrations in the collected soil samples were compared to either the USEPA RSLs for residential soil or the DTSC-SLs for residential soil.None of the OCP COCs exceeded their respective screening levels except for chlordane and dieldrin in soil samples collected at SS-IS, SS-2E, and SS-3N. Furthermore, chlordane concentrations exceeded Federal and State Title 22 Hazardous Waste Criteria's Total Threshold Limit Concentration(TTLC) for chlordane at 2.5 mg/kg. Chlordane and dieldrin concentrations compared to their respective screening levels and TTLC are included in Table 1,below: Table 1: Chlordane and Dieldrin Concentrations Compared to Screening Levels and Hazardous Waste Criteria COC SS-1S SS-2E SS-3N USEPA RSL TTLC Chlordane 8.9 5.5 18 1.7 2.5 Dieldrin 0.34 0.35 0.45 0.034 8.0 Notes: Concentrations are reported in milligrams per kilogram (mg/kg); TTLC: Total Threshold Limit Concentration; USEPA RSL: U.S Environmental Protection Agency's Regional Screening Levels;COC:Chemical of Concern The exposure pathway associated with OCPs is ingestion. The alternative method of isolating the exposure pathway when the remediation of hazardous chemicals (i.e. removal and proper disposal of contaminated soil) is not practical or safe is by encapsulating the material in place (i.e. asphalt/concrete cap, hardscape landscaping). 6.0 SUMMARY AND CONCLUSIONS The Site comprises approximately 0.55 acres designated as APN 139-224-090, located at 530 North Stanislaus Street, Stockton, San Joaquin County, California. In a Phase I ESA dated March 27, 2024, Condor identified at least five high-risk off-Site properties including automotive repair and dry-cleaning operations in close proximity to the Site. Due to the likelihood of chlorinated solvent and petroleum products use, a vapor encroachment condition could not be ruled out for the Site without further investigation. Condor recommended further due diligence with a subsurface soil gas and surface soil investigation to evaluate whether historical uses of on-Site and off-Site properties pose a risk to human health of current and future occupants at the Site. On May 13,2024, Condor collected two(2)soil gas samples at two locations within the parking lot at five feet bgs and two (2) soil gas samples beneath the sub slab of the existing apartment complex for analysis of VOCs. Additionally, Condor collected surface soil samples from four (4) locations at each side of the existing apartment complex to be analyzed for OCPs. Groundwater beneath the Site is anticipated to range from approximately 15 to 18 feet bgs and flows toward the east-northeast. None of the VOCs in soil gas samples collected from the parking lot exceeded their respective calculated soil vapor screening levels except for benzene in ASG-1 at 5 feet bgs (13 µg/m3). BTEX was detected in both ASG-1 and ASG-2 at 5 feet bgs,with concentrations decreasing towards the west,which is the opposite direction from Grant Street and the adjoining motor vehicle repair complex to the east. It is likely the that automotive complex is the source of BTEX contamination in soil gas. For this reason, Condor compared the benzene concentration to the State Water Board's LTCP no bioattenuation zone soil gas criteria for future construction to evaluate the human health risk associated with benzene for future occupants at the Site. Assuming no bioattenuation is applicable to Site conditions (the more conservative assumption), the screening level assigned to benzene is 85 µg/m3 for residential use, which exceeds the maximum benzene concentration reported during this investigation(13 µg/m3). ow k444_;� to CONDOR