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Former Unocal Service Station #5098 5606 Pacific Avenue Stockton, California SITE DESCRIPTION AND BACKGROUND The subject site formerly contained a Unocal service station facility. The site occupies €lat terrain and is located at the northeast corner of the intersection of Pacific Avenue and Robinhood Drive in Stockton, California. The site is also situated approximately 3, 500 feet northwest of the Mokelumne Aqueduct, and 5, 000 feet northwest of the Calaveras River. A Location Map is attached to this report. The site has been under investigation since mid-1985, when the station was closed and two 10, 000 gallon fuel storage tanks and one waste oil tank were removed from the site. The location of the former tanks and pump islands are shown on the attached Figures 2 , 3 , and 4 . Soil contamination was discovered after the tanks were removed. Between mid-August 1985 and March 1988, at least 19 soil borings (seven of which were apparently converted into vapor extraction wells) and ten monitoring wells were installed by Kleinfelder and Associates, as shown on the attached Figures 3 and 4 . The vapor extraction wells reportedly were never operated. These soil borings and wells apparently delineated the zone of soil • contamination that was then present at the site. The extent of ground water contamination at the site, however, had not yet been completely defined. On January 19, 1988, and again on July 26, 1988 , KEI submitted proposals for soil and ground water remediation at the site. The January 19 , 1988, proposal was revised on September 7, 1988, as recommended by the San Joaquin County Public Health Service (SJCPHS) in a letter dated August 9, 1988 . On September 9 , 1988, the SJCPHS approved the revised proposal which included excavation of contaminated soil and issuance of a Problem Assessment Report (PAR) once the extent of soil and ground water contamination was defined. Additionally, the proposal included the submittal of a Final Remediation Plan if the PAR indicated remediation was warranted. Soil remediation excavation began on September 19, 1988, and was completed on December 12 , 1988. The area excavated in relationship to the KI -infold- And ASaor" aces so l borings 1 on the attached Figure 4. A total of 28 soil samples were collected and analyzed from the excavation sidewalls and bottom. These samples were used to further delineate the zone of contamination and guide soil excavation. The excavation was terminated at the water table (at a depth of 53 feet) or at a shallower depth if pit bottom sample analyses indicated no detectable contaminant concentrations. Soil was excavated to a maximum depth of 53 feet • KEI-P88-1013.APA