SITE INFORMATION AND CORRESPONDENCE

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DRAFT r Stockton, is about 2,000 feet to the west. Shallow groundwater at the site flows in a general easterly direction with a gradient of about 0.002. In January 1988, analyses of soil samples from five soil borings drilled to depths of 20 to 30 feet indicated that a release had occurred at the site. In February 1988, three groundwater monitor wells were installed to assess site groundwater conditions. The initial groundwater samples from the three wells revealed an absence of gasoline constituents in groundwater near the location of the two gasoline UST s,high concentrations (99,000 ppb TPH-g and 5,700-ppb benzene) to the vicinity of the easterly PUMP island, and low concentrations (170 ppb TPH-g and 1 ppb benzene) in the vicinity of the waste oil UST. Data gained from the well installations also indicated that the groundwater was confined and that it flowed in an easterly direction.Tthe waste oil UST, In March 1988,the two 10,000-gallon capacity gasoline Us and the dispensers and associated piping were removed from the site. Visual inspection of the bottom and side-walls of the gasoline UST excavation revealed that soil cubic ands affected by a release prompting petitioner to over-excavate an estimated 850 Y of soil to a final depth of 28 to 30 feee. Soil samples collected from the bottom and side wall of the excavation indicated TPH-g and benzene concentrations ranged from 3 to 18 ppm and less than 0.05 to 1.7 ppm, respectively. In August 1989,two additional groundwater monitor wells were constructed off- site f-site approximately 100 feet east and northeasterly of the former pump island where high constituent concentrations had previously been detected in groundwater. Analyses of groundwater samples from these wells revealed low concentrations of TPH-g (15 and 240 ppb), xylene (1.4 and 1.9 ppb), and ethylbenzene (less than 0.5 and 8.1 ppb),benzene and toluene were not detected. traction wells and two more groundwater monitor In February 1992, three vapor ex well were installed. Two of the vapor extraction wells were located where the easterly icates in its site z The volume of soil excavated ubi p°int of ards of oil contention.ere excavated while the County contendsrthat osummary 350 report that an estimated 1,100 c y 1491 letters petitioner, e cubic yards are documented to have been excavated. However, in a March 12, County states that;`...approximately 1300-1400 e h have ards ofcontam850 cubic yards. were excavated. Based on the reported dimensions of the excavation, 5