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Former Chevron Station #9-8632 - 2 - 19 March 2019 575 W. Grant Line Rd Tracy, San Joaquin County were fiberglass and were installed in 1984 to replace an unknown number of steel tanks. San Joaquin County Environmental Health Department (SJCEHD) filed an Unauthorized Release Report (URR) in June 1994 following the UST removals. Between May 1995 and February 2018, Chevron installed eight groundwater monitoring wells, four soil gas wells, and twenty soil and groundwater borings. Chevron conducted routine groundwater monitoring from 1995 through 2011. Historically, groundwater flow at the Site has been toward the northwest. In February 2018, GHD advanced five soil borings to assess for the presence of petroleum hydrocarbons in the vicinity of the former fuel USTs and WOT. GHD detected up to 45 milligrams per kilogram (mg/kg) total petroleum hydrocarbons as gasoline (TPHg), 0.0006 mg/kg benzene, and 1.6 mg/kg naphthalene in soil samples collected from the Site. During removal of the fuel USTs and WOT in May 1994, Chevron removed approximately 100 cubic yards of impacted soil from the excavation of the WOT and disposed of off-site. In August 1994, Chevron excavated an additional approximately 200 cubic yards of impacted soil from the former fuel UST and WOT areas and disposed of off-site. The 300 total cubic yards of removed soil contained approximately 500 pounds of hydrocarbons. Chevron has not conducted other active remediation at the Site; however, remaining petroleum hydrocarbons in soil and groundwater do not warrant further remedial activities. CONSTITUENT DATA Soil - The highest historical hydrocarbon concentrations detected in soil beneath the Site are shown in Table 1. Table 1 - Maximum Petroleum Hydrocarbons in Soil concentrations in milli rams per kilo ram Fmcilk TPHg TPHd Benzene Toluene Ethyl- benzene Xylenes MTBE 7,600 30,000 24 77 180 560 0.74 TPHg=total petroleum hydrocarbons as gasoline; TPHd=TPH as diesel; MTBE=methyl tertiary butyl ether Groundwater - The highest historical hydrocarbon concentrations detected in groundwater beneath the Site are shown in Table 2, and the results of the most recent groundwater sampling event, completed September 2017, are shown in Table 3. Table 2 - Maximum Petroleum Hydrocarbons in Groundwater concentrations in micro rams per liter /L TPHg TPHd Benzene Toluene Ethyl- benzene Xylenes MTBE 54,000 4,700 7,700 2,400 2,900 3,500 3,100 TPHg=total petroleum hydrocarbons as gasoline; TPHd=TPH as diesel; MTBE=methyl tertiary butyl ether