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28 December 1999 AGE-NC Project No. 97-0351_ Page 2 of 7 Approximately five cubic yards of hydrocarbon-impacted soil were removed and stockpiled during the UST removal sampling. Soil samples were collected from two feet below the UST, at depths of twelve feet bsg. The overburden soil was used to back fill the lowest portion of the excavation. Analytical results of soil samples collected-from UST excavation indicated that an unauthorized release of hydrocarbons had occurred at the western edge of the UST. Total petroleum hydrocarbons quantified as gasoline were-detected in sample Tl-W at 690 mg/Kg(milligrams per kilogram or parts per million: ppm). TPH-g was not detected in the soil sample collected from the eastern end of the UST. 2.3. 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 PHS-EHD. Soil probe borings were advanced in the vicinity of the West UST area, removed in 1986 from in the City of Stockton right-of-way; at the western edge of the site and in the vicinity of the plating shop on the site. Locations of the soil probe borings are illustrated on Figure 2. Hydrocarbon-impacted soil in the vadose zone, associated with the West UST area within San Jose Street was limited to a narrow zone from depths of approximately 5 to 15 feet bsg, immediately surrounding the UST. The detection of MTBE in soil samples collected from probe boring.Pl indicate the release of gasoline to be relatively recent, possibly within the past twenty 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. 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, soil probe borings were advanced at the site under the supervision of the PHS-EHD. On 14 November 1996 and 16 January 1997 a total of fifteen soil borings were advanced at the site. Probe boring P1.to.P5 and.P10 to P14 were established,surrounding-the West UST area and along the boundary of the subject property with the Texaco facility. Total petroleum hydrocarbons as gasoline (TPH-g), benzene, toluene, ethyl benzene and xylenes (BTE&X), methyl tertiary butyl ether (MTBE) were detected in soil samples collected from the probe boring advanced in the area of the West UST excavation at concentrations as high as 3,700 mg/kg (milligrams per kilograms or parts per million: ppm). Hydrocarbon-impacted soil associated Advanced GeoEnvironmental,Inc.