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Phase II Environmental Site Assessment Report Yosemite Senior Housing 309 W.Yosemite Avenue and 105 Sycamore Avenue APNs 217-210-100 and 217-210-110 Page 3 sand(SW)layer where groundwater was encountered. Groundwater was encountered at 28 feet bgs during drilling. Static groundwater was measured in the field at 19 feet bgs. DP-2 was advanced to 32 feet bgs; from beneath 4-inches of asphalt to 20 feet bgs was fine to medium coarse sand(SP/SW); from 20 feet to 28 feet bgs was lean clay(CL),and from 28 feet to 32 feet bgs was fine to medium sand(SW).Groundwater was encountered at 28 feet bgs and static groundwater was measured at approximately 20 feet bgs. DP-3 was advanced to 20 feet bgs and comprised primarily of fine to medium coarse sand (SP/SW) beneath 4-inches of asphalt. Refusal was encountered in DP-3 at 20 feet bgs. No groundwater was encountered in DP-3. No staining or odors were observed during field activities. No significant PID readings were observed in any boring; the maximum detected PID reading was 0.2 parts per million (ppm) at approximately 15 feet in boring DP-2. Appendix D contains copies of soil boring logs and PID readings. 3.4 ACTIVE SOIL GAS SAMPLING PROCEDURES Condor installed vapor implants at three locations at depths of 5.5 feet bgs and 15 feet bgs. ASG-1 was installed near the southwest corner of the Site,at the location of the former print shop.ASG-2 was installed near the southeast corner of the Site, and ASG-3 was installed near the northeast corner of the site, in the downgradient direction with respect to groundwater flow(Figure 3,Appendix A).The vapor implants were installed by advancing a 1-inch diameter stainless steel rod to the respective sampling depths using the Direct Push rig and lowering 1/8-inch diameter Nylaflow tubing with the implant probe at the tip. The annular space was then constructed with 1-foot of sand pack around the sample probe followed by 0.5-inches of dry bentonite, then hydrated bentonite to surface. Prior to purging and sampling, the wells were allowed to sit undisturbed for at least two hours to equilibrate. Shut-in tests were performed to confirm that no leaks were present in the sample train. The wells were then purged of three void volumes (tubing and sandpack) and sampled using a 200 milliliter(mL) syringe at a flow rate no greater than 200 milliliters per minute(mL/minute). During the collection of each soil vapor sample, a leak detection test was conducted to evaluate whether there was intrusion of ambient air into the vapor sample. During the collection of each vapor sample, 1,1-difluoroethane(DFA)was applied within a shroud placed directly around the sampling interface at the surface.DFA was included in the laboratory analyses. 3.4.1 Numbers of Samples and Laboratory Analyses A total of six(6)soil gas samples,three(3)soil samples,and two(2)groundwater samples were transported by courier under chain-of-custody procedures for laboratory analysis. 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. Detected 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 attenuation factor for soil gas to indoor air is discussed in Section 4.0. All soil gas, soil and groundwater laboratory analytical reports and chain of custody forms are included in Appendix E. Ntw_ 10 coNooR