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�'U Vf9 m 82B groundwater were detected along the south subject property boundary with much lower concentrations reported in grab-groundwater samples collected farther east and north on the subject property, indicating the more distal portion of the PCE plume is to the east and that the source area is upgradient to the west or southwest. Typical degradation products for PCE were also found in all of the analyzed grab-groundwater samples, including TCE, cis-1,2-DCE, and 1,2-DCA. Although the concentrations of these chlorinated compounds in groundwater were reported at concentrations that exceed an established MCL; no further action or investigation appears warranted because these detected compounds appear to be associated with an off-site release most likely the adjacent dry cleaning facility to the southwest. • In addition, reported concentrations of PCE in the analyzed soil vapor samples appear to indicate an upgradient and off site source. PCE concentrations were reported at much higher concentrations in the deeper(15 foot vapor samples)of the two vapor samples collected in borings BV-4 and BV-5, which would indicate that the PCE is migrating in groundwater with no indicated on-site shallow source. • Soil vapor samples were reported to contain 16 VOCs; however, the concentrations are below the CHHSLs, where established, except for PCE and TCE. The shallow soil gas concentrations(collected at a depth of 5 feet bgs)for PCE had a maximum reported concentration of 630 pg/m3 with a maximum concentration of 42,000 pg/m3 in the deeper 15 foot samples. These concentrations exceed the established CHHSL for PCE of 603 pg/m3. TCE in a deep vapor sample also exceeded the CHHSL of 1,770 Ng/m3. CHHSLs are not regulatory cleanup standards and are intended to be overly conservative. The presence of chemicals at concentrations above applicable CHHSLs does not necessarily indicate that a significant exposure risk exists. According to Cal EPA's Use of CHHSLs in Evaluation of Contamination Properties(January 2005), the thresholds of concern to develop CHHSLs are an excess lifetime cancer risk factor of one-in-a-million (10-6)and a hazard quotient of 1.0 for non-cancer health effects. Based on the soil vapor analytical data and in accordance with DTSC guidance, Bureau Veritas recommends performing a site-specific health risk assessment for vapor intrusion potential at the subject property to determine the potential for vapor intrusion at the Walgreen store. Based on the findings of this LSI, releases of petroleum hydrocarbons and chlorinated solvents have impacted the groundwater and soil vapor at the subject property. The findings from this LSI should be forwarded to SJCEHD, as a condition of the drilling permit, for their review and direction. Bureau Veritas recommends that the subject property owner and/or responsible party respond to and abide by any requests for information or additional investigation/characterization related to the subject property. If impacted groundwater is encountered during invasive subsurface activities(e.g., utility trenching, construction activities, etc.)additional measures may be necessary to mitigate exposure of construction workers and/or contractors. In addition, if dewatering activities are necessary at the subject property and impacted groundwater is encountered, the groundwater should be handled and managed in accordance with applicable regulations and guidelines. Should future plans involve construction of a new building or building addition, Bureau Veritas recommends that pre-development planning should be performed to mitigate possible vapor intrusion from impacted groundwater at the subject property into a new building. ii Project Number 99007-000526.03