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Site Background Information: Five Star Marina Page 2 of 4 Part I In May 1986, one 550-gallon gasoline underground storage tank (UST; West UST Area) was removed from the City of Stockton right-of-way in San Jose Street. Total volatile hydrocarbons (TVH) and volatile aromatics benzene, toluene, ethylbenzene, and xylenes (BTEX) were reported at concentrations as high as 2,000 mg/kg(milligrams per kilogram)in a single soil sample collected from the UST excavation (Table A l).Analytical results of soil samples collected from the UST excavation indicated that an unauthorized release of hydrocarbons had occurred at the western edge of the UST. Total petroleum hydrocarbons quantified as gasoline(TPH-g)were reported in sample T1-W at 690 mg/kg. TPH-g was not reported in the soil sample collected from the eastern end of the UST (Table Al). On 14 November 1996 and 16 January 1997,a total of fifteen soil probe borings(P 1 through P 15) were advanced at the site under the supervision of the EHD. Soil probe borings were advanced in the vicinity of the West UST area at the western edge of the site and in the vicinity of the on-site plating shop. TPH-g,BTEX,and methyl tertiary-butyl ether(MTBE)were reported in soil samples collected from the probe borings at concentrations as high as 3,700 mg/kg. Hydrocarbon-impacted soil associated with the West UST area appeared to be of limited lateral extent. TPH-g was reported in four of ten grab ground water samples collected from the West UST area at concentrations ranging from 84 micrograms per liter(µg/1)to 44,000 pg/1.Various BTEX compounds were reported in six of ten samples analyzed at concentrations ranging from 0.60 Vg/1 to 7,800 µg/1. Hydrocarbon-impacted soil in the vadose (unsaturated) zone, associated with the West UST area within San Jose Street,was limited to a narrow zone from depths of approximately 5 feet to 15 feet bsg immediately surrounding the UST.The detection of MTBE in soil samples collected from probe boring P 1 indicated the release of gasoline to be relatively recent,possibly within the past 20 years. Gasoline-impacted ground water is present around the West UST area.The dissolved gasoline plume appears to extend to approximately 50 feet northeast and 50 feet southwest from the former West UST area, and has an approximate width of 40 feet. Total petroleum hydrocarbons quantified as diesel (TPH-d) was reported at concentrations up to 6,600 µg/1 from four of five grab ground water samples analyzed from the western property boundary. The subject property has no documented use of TPH-d. To determine the lateral extent of the hydrocarbon impact to soil and ground water associated with the West UST, and the potential impact from the Texaco facility to the subject property,additional soil probe borings were advanced at the site under the supervision of the EHD. Hydrocarbon- impacted water associated with the West UST was limited to vicinity of the former tank location, Advanced GeoEnvironmental,Inc.