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Site History and Summary of Previous Environmental Investigations Q Former ARCO Service Station No. 559 Updated July 2, 2021 anteaRgraup Antea Group submitted the Soil and Groundwater Investigation Report on February 28, 2020. Five groundwater monitoring wells were installed (MW-1, MW-2, MW-4, MW-5, and MW-6)to a depth of 45 feet bgs, and one soil boring(SB-1)was advanced to 20 feet bgs between January 6 and 10, 2020. Soil and groundwater analytical data from the Site investigation and subsequent split groundwater sampling event with the Central Valley Water Board conducted on January 21, 2020 are presented in the report. On April 9, 2020,the Central Valley Water Board issued a letter to Antea Group in response to the Soil and Groundwater Investigation Report dated February 28, 2020.The Central Valley Water Board agrees with Antea Group's findings and requested three consecutive quarters of groundwater monitoring at the Site in 2020, with an evaluation of site conditions against the State Water Resources Control Boards Low Threat Underground Storage Tank Case Closure Policy to be submitted with the fourth quarter 2020 groundwater monitoring report.The letter also states that adjacent AMRW UST case is permitted to move forward with Site closure now that the Antea Group investigation is complete.A letter issued to AMRW on April 9, 2020 authorizes the destruction of any remaining site wells and to submit a Well Destruction Report by July 10, 2020 for Case Number 392001. On February 4, 2021,the Central Valley Regional Water Quality Control Board (Central Valley Water Board) provided comments to the Fourth Quarter 2020 Groundwater Monitoring Report and Closure Assessment submitted on January 29, 2021. The Central Valley Water Board does not concur with closure at this time, due to the historically high concentrations of total petroleum hydrocarbons as gasoline (TPHg), ethylbenzene,total xylenes, and naphthalene in samples collected from MW-1 during the November 2020 sampling event. Given these increased concentrations, the Central Valley Water Board staff requests that two additional quarterly groundwater sampling events be performed to better evaluate concentration trends in MW-1.And suggested that the sampling events should be conducted during V and 2nd quarters of 2021. On June 22, 2021,the State Water Resources Control Board provided comments to the Fourth Quarter 2020 Groundwater Monitoring Report and Closure Assessment submitted on January 29, 2021, and the response from the Central Valley Water Board dated February 4, 2021.The State Water Resources Control Board concurred with the Central Valley Water Board staff determination that all of the Low-Threat UST Case Closure Policy criteria has not been met and suggested to continue cooperation with the Central Valley Water Board to resolve the impediment to closure. The Environmental Data Resources (EDR) Radius Map"' Report with GeoCheck° and Offsite Receptor Report (Offsite Receptor Report) identified 53 wells within 1-mile of the Site, eight within %-mile to%-mile of the Site, and two within%-mile of the Site. However,the report does not provide public water supply system information. Searches were also conducted on the GeoTracker Groundwater Ambient Monitoring Assessment(GAMA) and United States Geological Survey (USGS) National Water Information System websites for domestic, municipal, irrigation/industrial, and water supply/other wells. Six wells were identified on the websites within 1,000-feet of the Site (four monitoring wells, one municipal well, and one supply well). GAMA reported Municipal Well 3910001- 032 as being destroyed and the USGS website reported Water Supply Well 375717121154101 as being inactive. On June 8, 2020,Antea Group personnel attempted to visually confirm Wells 375717121154101 and 3910001-032 in a vacant lot at the northwest corner of the intersection between East Sonora Street and Laurel Street.The wells were not observed during the visit. Information regarding the four wells identified on the GAMA and USGS websites as being within %-mile of the Site is summarized in Table B below.