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fff Santa Fe Pacific Pipeline Partners, L.P. J-6075.03 L� January 6, 1994 STOCKTON WORK PLAN Page 2 detected in the subsurface. Floating hydrocarbon product up to six inches thick was detected in several test pits during LF's investigation. However, based on product analysis and pipeline testing, LF concluded that the hydrocarbons in the subsurface did not originate from a SPPL pipeline leak. Results of the Levine-Fricke investigation are presented in a report titled: "Investigation of Subsurface Fuel Hydrocarbons, Southern Pacific Pipelines", dated March 23, 1988. In March 1989, Hydro-Search, Inc. conducted a subsurface soil and groundwater quality investigation at the SPPL Stockton Terminal to evaluate: regional and site specific hydrologic conditions; the impact and extent of hydrocarbons in the subsurface; and the potential movement of the identified hydrocarbons. The Hydro-Search investigation identified aromatic hydrocarbons, diesel and gasoline in the soils and groundwater beneath the site. Groundwater monitoring wells M-1 through M-4 were installed at that time. Results of the Hydro-Search investigation are presented in a report titled: "Groundwater Investigation and Environmental Assessment, Stockton Terminal, Stockton, California", dated April 28, 1989. In July 1992, Hart Crowser conducted a preliminary subsurface investigation to further characterize the horizontal and vertical extent of the dissolved hydrocarbons beneath the site and to determine the presence of a potential onsite source of hydrocarbons. The results of the investigation indicated that: ■ It is possible that an offsite, upgradient source of petroleum hydrocarbons is impacting the groundwater beneath the site. ■ The soils in the vicinity and downgradient of the manifold/prover loop area had been impacted by hydrocarbons and some downgradient migration of the hydrocarbons had occurred. The details of the preliminary subsurface assessment are presented in a report titled, "Preliminary Site Assessment, Santa Fe Pacific Pipeline Partners, Stockton Terminal, Stockton, California", dated September 3, 1992. In November 1992, RWQCB requested that SFPP install a monitoring well into the lower groundwater bearing zone (B-zone) to assess the vertical groundwater gradient and to determine the quality of groundwater. On February 11, 1993, Hart Crowser submitted an addendum to the Additional Site Assessment work plan for the well installation to the RWQCB. The well was installed during the last week of April 1993.