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PHASE H ENVIRONMENTAL SITE ASSESSMENT WORK PLAN YOSEMITE SENIOR HOUSING APNS 217-210-100 AND 217-210-110 309 W.YOSEMITE AVE AND 105 SYCAMORE AVE MANTECA,SAN JOAQUIN COUNTY,CALIFORNIA April 12,2024 1.0 INTRODUCTION This work plan was prepared by Condor Earth(Condor)to describe proposed Phase II Environmental Site Assessment (ESA) investigation activities at 309 W. Yosemite Avenue and 105 Sycamore Avenue in Manteca, San Joaquin County, California (Figures 1, Appendix A, Site). Condor Earth (Condor) conducted a Phase I Environmental Site Assessment(ESA) on the Site, dated March 6, 2024. During the Phase I ESA investigation, it was identified that the western Site parcel was used as a printing shop from the early 20th Century 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 the 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 from the Site) from at least the 1920s to 1940s. No documents were located pertaining to the southern adjoining properties 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 tetrachlorethylene (PCE) in groundwater at a maximum detected concentration of 2,160 micrograms per liter (µg/L). Since the former UST location has no historical documented use of PCE, the Central Valley Regional Water Quality Control Board identified the French Cleaners location as a potential source. These off-site properties may pose a risk to the Site groundwater due to proximity and/or upgradient locations. The Phase I ESA reveal the following recognized environmental conditions (REC) in connection with the Site: - The former printing operation on the western portion of the Site from the early 20th Century until the early 1960s constitutes a REC pursuant to the ASTM Standard. Historical printing operations typically included the use and disposal of inks, coatings, varnish, and solvents known to contain chemicals that pose a material threat to human health and the environment. - The former oil and gas station and boiler room that was present on the southern adjoining property (across Yosemite Ave) from the early 1920s until at least the 1940s constitutes a REC pursuant to the ASTM Standard. No documentation was found during the file reviews pertaining to this property. - The PCE plume located approximately 550 feet west-southwest of the Site constitutes a REC pursuant to the ASTM Standard. The release may pose a future health risk to Site occupants due to proximity and upgradient groundwater direction from a subsurface vapor intrusion standpoint. i CONDOR