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Historical soil and soil vapor sample laboratory analytical results for the Site are summarized in the tables presented in Appendix B. Appendix B also includes historical groundwater monitoring and sampling data for groundwater monitoring and sampling events conducted on and prior to November 5, 2018. Appendix C includes relevant boring logs. Groundwater monitoring and sampling data for the most recent groundwater sampling event, conducted on June 2, 2021, is summarized in Tables 1 and 2. Historical groundwater grab sample laboratory analytical results are summarized in Table 3. Groundwater monitoring well and soil vapor probe construction details are summarized in Table 4. Note that Figure 3 shows proposed cone penetrometer test (CPT) borings and proposed groundwater monitoring wells which were proposed in a recent work plan prepared by FREY dated May 31, 2022 that was submitted to the RWQCB (FREY, 2022). The RWQCB has not yet responded to that work plan. POTENTIAL VAPOR INTRUSION RISK TO INDOOR AIR On September 15, 2017, AGE advanced soil borings SV-1 and SV-2 to final depths of 6.5 feet bgs with a hand auger inside the Site building at the locations shown on Figure 3. Soil vapor probes SV-1 and SV-2 were installed as permanent probes using a neat cement seal in their respective borings. Each soil vapor probe was constructed with 0.25-inch diameter Teflon tubing and a vapor probe implant installed at approximately 6 feet bgs (AGE, 2019). AGE purged and sampled the soil vapor probes on September 15, 2017, April 8, 2018 and February 25, 2019. Total petroleum hydrocarbons gasoline (TPHg) and benzene were detected in the soil vapor probes at maximum concentrations of greater than 29,000,000 micrograms per cubic meter (ug/m3) and 4,800 ug/m3, respectively. Measured oxygen concentrations ranged from 0.5 to 2.1 percent (AGE, 2019). Relatively high concentrations of cyclohexane, hexane and heptane, which were believed to be from a natural gas leak, were present in the soil vapor samples and were the cause of the elevated TPHg concentrations (AGE, 2019). Based on the results of the soil vapor probe sampling conducted by AGE, benzene was present in soil vapor at 6 feet bgs that exceeds the State Water Resources Control Board (SWRCB) Low Threat Underground Storage Tank Case Closure Policy (LTCP)threshold value for benzene of 85 ug/m3 for a site with no bioattenuation zone (oxygen less that 4 percent)(Appendix B). AGE collected an indoor air sample at the Site on February 28, 2019. The sample was collected over an 8-hour period from the central portion of the Site building in an area without public access. Relatively low concentrations of thirty-four different volatile organic compounds (VOCs) were detected in the sample, including benzene at a concentration of 0.70 ug/m3 (AGE, 2019, Appendix B). The detected benzene concentration exceeds the San Francisco Bay Regional Water Quality Control Board(SFBRWQCB) Environmental Screening Level (ESL) for benzene in indoor air for a commercial/industrial setting of 0.42 ug/m3(SFBRWQCB, 2019).