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3. 2021 Soil Vapor Sampling Results Analytical laboratory reports and data usability summary reports for soil vapor samples collected in 2021 are included in Appendix B.Analytical data were validated by a Haley&Aldrich data specialist.Table 1 presents the analytical results from soil vapor sampling conducted between 2019 and 2021 for COCs and tetrachloroethene (PCE),with the soil vapor environmental screening levels (SV-ESL)for residential/public and commercial/industrial land use provided for comparison (San Francisco Bay Regional Water Quality Control Board, (RWQCB, 2019).As described in the Water Board letter dated 21 June 2021, PCE is not a Site COC but has been associated with historical dry-cleaning operations in the downtown area (Water Board, 2021). Figure 2 presents the soil vapor sampling locations and identifies the locations of soil vapor samples with TCE concentrations reported above the applicable SV-ESL(regardless of probe depth) during the most recent sampling event. Consistent with sampling results from 2019 and 2020, PCE and chloroform were detected in the majority of soil vapor samples. PCE is not a Site COC because it was not used at the former Nestle facility. Chloroform is a Nestle COC, however chloroform was not detected in co-located shallow groundwater samples, and the highest concentration of chloroform in soil vapor was detected in the sampling point located farthest from the Site(SV-124).This indicates that other potential sources of chloroform, including landscape irrigation and/or sanitary sewer exfiltration, are likely causes of the widespread detections of chloroform in soil vapor. Further discussion on potential alternative sources of chloroform in soil vapor is presented in the Third Interim Report. During the 2021 sampling events,TCE exceeded the industrial/commercial SV-ESL at the following locations zoned for industrial/commercial land use (results are presented in Table 1 and sampling locations are shown on Figure 2): Q12021 Q3 2021 SV-110-10.0 SV-122-15.0 SV-110-15.0 SV-123-15.0 SV-110-20.0 SV-110-24.5 SV-122-15.0 SV-123-15.0 During the 2021 sampling events,TCE exceeded the residential SV-ESL at the following locations zoned for residential or public land use (results are presented in Table 1 and sampling locations are shown on Figure 2): Q12021 Q3 2021 SV-107-10.0 SV-107-10.0 SV-107-15.0 SV-107-15.0 SV-113-15.0 SV-112-15.0 SV-127-10.0 SV-113-15.0 SV-127-15.0 SV-127-15.0 Note that the results from location SV-124 at 5 feet bgs during the Q1 2021 sampling indicated TCE concentrations above the residential SV-ESL; however,the results were inconsistent with prior sampling 3 �DRICH