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zone on the northwest side of the building. Results from both assessments conducted in 2017 showed that concentrations of TPHg and benzene increase significantly with distance from the location of the former USTs and groundwater impacts do not appear to be originating from the property's former USTs. In August 20181 ATC oversaw hydropunch borings HP -10 and HP -11 advanced along the eastern side of North San Joaquin Street, east of the site in the downgradient direction. TPHg was not detected in the groundwater sample collected from boring HP -10 at a depth of approximately 45 feet bgs. No water was encountered in boring HP -11 at this depth. TPHg was detected in both groundwater samples collected from borings HP -10 and HP -11 at 65 feet bgs at concentrations of 3,900 ug/L and 27,000 ug/L, respectively. Benzene, toluene, ethylbenzene and total xylenes were not detected in the groundwater sample collected from boring HP40 at 45 feet bgs. Benzene was detected in both groundwater samples collected from borings HP -10 and HP41 at 65 feet bgs at concentrations of 110 ug/L and 4,700 ug/L, respectively. Toluene, ethylbenzene and total xylenes were detected in both groundwater samples collected from borings HP -10 and HP41 at 65 feet bgs but were reported at concentrations below their respective MCLS. MTBE, ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA), tertiary amyl ether (TAME), di - isopropyl ether (DIPE), 1,24chloroethane (1,2 -DCA), and ethyl dibromide (EDB) were not detected in the groundwater sample collected from boring HP40 at 45 feet bgs. In correspondence dated June 18, 2020, the RWQCB requested a workplan to propose a scope of work to collect additional evidentiary data to support the conclusions in ATC's Supplemental Subsurface Investigation Report, dated October 1, 2018. ATC submitted a Workplan for Additional Off-site Groundwater Delineation and Monitoring Well Installation, dated September 4, 2020. The workplan proposed the installation of one on-site and two off- site monitoring wells. In correspondence dated September 18, 2020, the RWQCB approved the September 4, 2020 Workplan for Additional Off-site Groundwater Delineation and Monitoring Well Installation. Due to delays in obtaining encroachment permits, field work was performed in April 2021. In April 2021, groundwater monitoring wells MW11 through MW13 were installed in a deeper water bearing zone to evaluate groundwater quality at approximately 55 to 60 feet below the potentiometric surface, downgradient of the source area. Wells MW11 and MW12 were installed off site to the east and northeast, respectively, and MW13 was installed on site. The highest concentrations of petroleum hydrocarbons were reported in the groundwater sample collected from MW12. Low petroleum hydrocarbon concentrations were reported in the samples collected from MW11 and MW13. SCOPE OF WORK Health and Safety Plan As required by the Occupational Safety and Health Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120), and by the California Occupational Safety and Health Administration (CakOSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), Atlas will prepare a Site -Specific Health and Safety Plan (HASP) prior to the commencement of fieldwork. The Site -Specific HASP will be reviewed and signed by field staff and contractors before beginning field operations at the site. 4I Page