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PHASE II ENVIRONMENTAL SITE ASSESSMENT YOSEMITE SENIOR HOUSING APNs 217-210-100 and 217-210-110 309 W.YOSEMITE AVENUE AND 105 SYCAMORE AVENUE MANTECA,SAN JOAQUIN COUNTY,CALIFORNIA EXECUTIVE SUMMARY May 28,2024 Condor Earth(Condor)conducted a Phase II Environmental Site Assessment(ESA)for the property located 309 W. Yosemite Avenue and 105 Sycamore Avenue in Manteca (Site), San Joaquin County, California (Figures 1 through 3, Appendix A). The purpose of the work was to evaluate whether past use of the property, identified in the process of conducting a Phase I ESA, had adversely affected soil and/or groundwater beneath the Site. The evaluated property included two parcels designated as Assessor's Parcel Numbers (APNs) 217-210-100 and 217-210-110, totaling approximately 0.223 acres. The Phase II ESA comprised a screening of Site soils, soil gas, and groundwater for the presence of volatile organic compounds (VOCs). Condor conducted the Phase 11 ESA under contract with Housing Authority of the County of San Joaquin(Client). According to the Phase I ESA prepared by Condor,based on review of historical documents, the western Site parcel was used as a printing shop from the early 1900s until the early 1960s, when the building was replaced with the asphalt driveway and lot. The eastern Site parcel was used as a hotel and apartment from the late 1910s until the 1990s, when the building was replaced with asphalt driveways and parking lot. Condor identified one former fuel station and boiler room on the southern adjoining property (across Yosemite Avenue approximately 75 feet south)from at least the 1920s to 1940s.No documents were found pertaining to the southern adjoining property's oil and gas station or boiler room. Condor also identified a total of one former underground storage tank (UST) location and a dry-cleaning operation located approximately 550 feet west-southwest of the Site.Previous investigations related to a historical fuel release from the UST location at 420 West Yosemite Avenue identified the presence of tetrachloroethene(PCE)in groundwater at a maximum detected concentration of 2,160 microgram per liter(µg/L).Because the former UST location has no historical documented use of PCE,the Central Valley Regional Water Quality Control Board identified the dry-cleaning operation(French Cleaners) as a potential source. Condor recommended a Phase II ESA be performed to continue the due diligence process. A total of six(6) soil gas samples,three(3) soil samples, and two(2)groundwater samples were collected. Soil gas samples were analyzed for VOCs by EPA Method TO-15, and soil and groundwater samples were analyzed for VOCs by EPA Method 8260B. Concentrations of VOCs in soil were compared to the most recent U.S. Environmental Protection Agency's Regional Screening Levels for residential soil (USEPA RSLs) or the Department of Toxic Substances Control (DTSC) Human Health Risk Assessment (HHRA) Note 3 DTSC-Modified Screening Levels, June 2020, revised May 2022 (DTSC-SLs). Concentrations of VOCs in groundwater were compared to the San Francisco Bay Regional Water Quality Control Board's Tier 1 Environmental Screening Levels for groundwater, dated 2019 (SF-ESLs). Soil gas concentrations were compared with attenuated DTSC-SL or USEPA RSLs indoor air screening levels. The DTSC- recommended attenuation factor is 0.03. None of the VOC chemicals of concern (COCs) in soil gas that were detected above their respective reporting limits exceeded their respective attenuated indoor air screening levels,except for PCE in three(3) of the collected samples and in two locations.PCE was detected in all collected samples.PCE was detected ii ILA CONDOR