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Stantec \..� w No Further Action Request Report Chevron and ARCO Commingled Plume No. CP0034 April 10, 2012 groundwater in the nearby wells was reported during subsequent groundwater monitoring and sampling events. ARCO 2133 Facility In May 1984, free hydrocarbon product was identified in the groundwater after a leak occurred in one of the UST. The leaking tank and surrounding soil were removed after approximately 2,000 gallons of fuel were lost. New tanks were installed in the same area in June 1984. Additionally, a product recovery system including a subsurface tank was installed on the eastern side of the site. Approximately 500 gallons of product were recovered during tank removal and an additional 600 gallons of product was reported to be recovered by bailing floating product from wells and by the product recovery system (B&C 1987a). In August 1987, one 550-gallon steel waste oil UST was excavated and removed from the site. One soil sample (WO-1) was collected from the bottom of the UST pit at an approximate depth of ten ft bgs. DRO was detected in the soil sample at a concentration of 3,719 mg/kgs. GRO and motor oil were not detected above laboratory MRLs (B&C 1987b). In September 1991, a product recovery tank was removed from the eastern boundary of the site and a new waste oil UST was installed at the southwestern corner of the station building. Two soils samples (T-North and T-South) were collected from the bottom of the recovery tank excavation and one soil sample (WO-Pit) was collected from the bottom of the excavation for the new waste-oil UST. GRO was detected at concentrations up to 1,500 mg/kg in the soil samples collected from the bottom of the product recovery tank pit. GRO was detected at 14 mg/kg in the sample collected from the new waste-oil pit (B&C 1992). An unknown quantity of fuel was released at the northern dispenser island in 1995 and in 1998. During the installation of a pay-quick machine, a contractor at the site broke a fiberglass product line beneath the southern dispenser island. The broken line was repaired immediately and approximately three cubic yards of soil were excavated from beneath the broken product line. Soil samples collected after the excavation of the soil contained low levels of petroleum hydrocarbons. In 1999, one 10,000-gallon, fiberglass gasoline UST, product lines, vapor lines, and dispenser islands were removed from the site. Small cracks that appeared to have been created during excavation activities were observed in the tank. Soil samples collected from beneath the USTs contained maximum GRO, benzene, and MTBE concentrations of 690 mg/kg, 0.692 mg/kg, and 0.156 mg/kg, respectively. Soil samples collected beneath the product lines and dispenser islands contained maximum GRO, benzene, and MTBE concentrations of 102 mg/kg, 0.298 94275 NFAR 2012.doc 6