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CHRONOLOGY Unocal #0123 (former) 1034 Central Ave., 'Tracy CA., 95376 LOP Site RO#: 0000616 PE: 35.26 1921 to Site was operating Unocal service station, with three (3) underground 1962 storage tanks (UST) located beneath the sidewalk, northwest boundary of site at 11th street. Unocal real estate files indicate that these were two 550-gallon steel and one 1,000-'gallon steel leaded gasoline USTs. Unocal files call these "First generation USTs". 1935 to Site undergoes remodel. Four (4) new USTs installed. These referred to 1950 as "Second generationUSTs." Unocal records indicate three, steel, leaded gasoline USTs were installed in a common excavation in the central portion of the site, south' of the "First generation USTs. These were a 2,600-gallon, a 4,000-gallon, and a 6,000-gallon and were identified as three of the four new, "Second generation USTs'. The fourth UST installed during this period was an unknown size waste oil UST south of the building. Plans showed the First generation USTs as "abandoned". During this period, fuel-dispensing islands were relocated also and product lines were moved. 1962 Site purchase by Bank of America. 1 09/30/65 Site closes down operations, equipment moved, and building demolished. Unocal notes indicate, "all subsurface and aboveground facilities were demolished and removed from the site." 03/29/94 A report of a limited subsurface investigation conducted by L. M. Swift for Wells Fargo Bank was issued. The investigation included an underground electronic survey of the parking lot to verify if any UST existed beneath the site, 4 exploratory soil borings (B-1 to B-4) to collect soil and groundwater samples, and three exploratory(,trenches. This was 'first' B'-4 boring and installed at waste oil UST area,jand is the "134" included in the 1994 tables. The report stated that "no large metal anomalies were detected", but did report that "hydrocarbon-impacted groundwater was detected in the northern portion of the site."i This work was conducted under permit and oversight of San Joaquin County PHS-EHD. 05/25/94 UAR #94-U29 generated for petroleum contamination in groundwater. I 07/06/94 Site placed in LOP.