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On October 16 and 17, 2012, a mobile ozone injection system was re-installed at the site and ozone injection into MW1,AS1, and AS2 commenced on November 8, 2012. The ozone sparge system was shut down on June 6, 2013. In March and April 2017, additional assessment activities were performed at the site including the advancement of direct push borings and hydropunch and cone penetration testing(CPT) borings. Soil and groundwater samples were collected for analysis. Results of soil data collected during the Marchand April 2017 assessment activities indicated that total petroleum hydrocarbons quantified as gasoline (TPHg), benzene, ethylbenzene, toluene, xylenes (BTEX), methyl tertiary butyl ether (MTBE), and naphthalene were not detected in the near surface soils at the property. Groundwater impacts from TPHg and benzene were limited to the deeper groundwater zone and to the northern side of the property nearest the neighboring property, indicating groundwater contamination in the shallow groundwater zone was delineated. ATC recommended collecting additional groundwater samples at the site to definitively show that the former USTs are not the source of petroleum hydrocarbons detected in the deeper groundwater zone on the northern portion of the property. On August 4, 2017, ATC submitted a Workplan for Additional Groundwater Delineation. The workplan was approved by the RWQCB in correspondence dated August 10, 2017. On November 22, 2017,the workplan was implemented to delineate petroleum hydrocarbons in deeper groundwater. Hydropunch borings HP-7, HP-8, and HP-9 were advanced along the eastern and northern sides of the on-site building and groundwater samples were collected at depths of 45 and 65 feet bgs in each boring. Only TPHg was detected in the 65 foot sample in boring HP-8 located near the northwest corner of the building. Based on the results, ATC recommended no further assessment. The RWQCB requested another workplan for additional groundwater delineation to determine if elevated concentrations of petroleum hydrocarbons are present in the groundwater off site near the eastern property boundary. ATC submitted a Workplan for Additional Off-site Groundwater Delineation, dated March 7, 2018. On August 6, 2018, hydropunch borings HP-10 and HP-11 were advanced along the eastern side of North San Joaquin Street, east of the site in the downgradient direction. Groundwater samples were collected at 45 and 65 feet bgs in boring HP-10 and at 65 feet bgs in boring HP-11. TPHg and benzene were detected in the groundwater samples collected from the deeper water-bearing zone. Based on an evaluation of the data,ATC recommended no further groundwater or soil assessment and proceeding with site closure activities. ATC submitted a Supplemental Subsurface Investigation Report, dated October 1, 2018. 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.