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KLEINFELDER • 2 BACKGROUND The Unocal Stockton Terminal site is located at 2835 Navy Drive in Stockton, California (Plate 1). Unocal has leased this property from Southern Pack Pipelines (SPPL) since 1974 Unocal records indicate that Unocal installed two underground tanks under the loading dock on the western part of the property in 1974: a 20,000-gallon diesel tank and a 10,000-gallon stoddard solvent tank No other tanks were installed by Unocal at the facility,with the exception of above ground oil tanks installed in 1988, and gasoline has not been sold at the facility In 1979, Unocal subleased the northeast corner of the site to ST Services An ST Services incinerator is currently located on the property leased from Unocal and a small underground tank was removed from this property by ST Services in August 1987 The RWQCB was present during the tank removal and RWQCB photographs refer to the tank as Tank #2 The RWQCB representative noted paint peeling from the tank. Samples were apparently not collected from the tank excavation • During the summer of 1988, Kleinfelder performed a soil and ground water assessment at the Unocal facility Seven ground water monitoring wells were installed at the facility during the investigation The locations of the seven onsite monitoring wells are shown on Plate 2 One of the wells, MW-5, is located northeast of the Unocal Terminal facilities, on the portion of the property subleased by ST Services The ground water flow direction in June and July 1988 was to the east-southeast The highest concentrations of total petroleum hydrocarbons (TPH) and benzene detected during July 1988 were in the sample from MW-5 The TPH in MW-5 was quantified as gasoline by the analytical laboratory Low concentrations of TPH, quantified as diesel, were detected in MW-3 and MW-b, which are located in and around the Unocal facilities on the west part of the site The results of this investigation are presented in Kleinfelder's "Problem Assessment Report, Unocal Corporation, Unocal Stockton Terminal," dated September 1, 1988. The Regional Water Quality Control Board (RWQCB) has reviewed the past work performed at the Unocal facility and on the neighboring Port of Stockton properties In a letter dated May 3, 1989, the RWQCB requested the Port of Stockton Technical Committee to submit a comprehensive report of all work performed to date at the various 194-89-1112 3