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w MF-r LEEDSH II,L•HERKENHOFF.INC. - —� PROJECT SITE BACKGROUND 2.1 SITE INFORMATION - Weber Point, located at 141 North El Dorado Street, Stockton California, is the site of an automotive maintenance repair garage and the former site of underground storage tanks (USTs) used to dispense leaded and unleaded gasoline. The site is located at the end of the Stockton Deep Water Channel (see Figure 1). The northern channel bulkhead wall runs east-west beneath a portion of the garage, before turning south near the east pump island (see Figur= 2). The ground surface of the property is approximately 10 feet above the channel water 'w surface and is paved with concrete and asphalt. Surface drainage from much of the downtown Stockton area appears to drain toward the southern boundary of the site and is discharged directly into the channel from storm drains. From 1955 to 1984, the property was operated as a gasoline and service station by the Shell Oil Company. From 1955 to 1981, four 4,000-gallon USTs were used to store and dispense leaded gasoline. In 1981, one of the 4,000-gallon USTs was ' removed and two 1,500-gallon USTs were installed to store and dispense unleaded gasoline. In 1984, gasoline sales were discontinued and all five USTs were removed and disposed of off-site. No soil samples were taken for analysis for - possible hydrocarbon contamination during either of the UST removal operations. The former UST excavation was located just west and south of the northern pump islan, (see Figure 2). An asphalt patch indicates the former excavation and is approximately 40 feet wide by 53 feet long. The actual depth of the excavation is unknown; however, most excavations to remove USTs of this size are approximately ten to twelve feet deep. The pumps at the northern pump island were apparently connected to the UST by pipelines within the former excavation. The pumps at the eastern pump island were apparantly connected to the UST by I-, underground pipelines buried in a trench from the east end of the northern pump island, to the north end of the east pump island (see Figure 2). According to the:armsent garage manager, the connecting pipelines between the two pump islands were cut and left in place during the tank excavation. The pumps at both of the i ; pump islands have been removed. One of the operations of the garage at this site is to change crankcase oil. The used waste oil was temporarily stored in an UST which was originally installed in 1955 near the west corner of the garage (see Figure 2). On June 1, 1990, the waste oil 'UST failed to pass a precision tank test, an indication that the tank may be leaking. The contents of the waste oil tank were pumped from the UST on June 5, 1990 and properly disposed of off-site. The inlet to the waste oil UST was capped and the tank is no longer being used to store waste oil. No soil samples were taken at that time to determine if the waste oil from the UST has impacted the soil, and there were no records found than could indicate how long the leak may have existed. , t J