ARCHIVED REPORTS_XR0006914- CASE 2

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. Site Background Information Five Star Marina ' Page 2 of 3 UST Hydrocarbon odors were not observed in soil above 11 feet bsg Approximately 5 cubic yards ' of hydrocarbon-impacted soil were removed and stockpiled during the UST excavation Soil samples were collected 2 feet below the UST, at depths of 12 feet bsg The overburden soil was used to backfill the lowest portion of the excavation Analytical results of soil samples collected from the UST excavation indicated that an unauthonzed release of hydrocarbons had occurred at the western edge of the UST Total petroleum hydrocarbons ' quantified as gasoline (TPH-g) were detected in sample T1-W at 690 mg/kg TPH-g was not detected in the soil sample collected from the eastern end of the UST ' PREVIOUS SITE INVESTIGATION On 14 November 1996 and 16 January 1997, a total of fifteen soil probe borings(PI through P15) 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 Locations of the soil probe borings are illustrated on Figure 2 TPH-g,BTEX,and methyl tertiary-butyl ether(MTBE) were detected 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 detected in four often grab ground water samples collected from the West UST area at concentrations ranging from ' 84 micrograms per liter(µg/1)to 44,000 µg/1 Various BTEX compounds were detected in six of ten samples analyzed at concentrations ranging from 0 60 µg11 to 7,800 µg11 Hydrocarbon-impacted soil in the vadose (unsaturated) zone, associated with the West UST area 1 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 bonng P I indicated the release of gasoline to be relatively recent,possibly within the past 20 years 1 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 detected at concentrations up to 6,600 µg11 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 1