ARCHIVED REPORTS_XR0006881- CASE 2

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' odors were not observed in soil above eleven feet below surface grade (bsg) 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 unauthoi ized release of hydrocarbons had occurred at the western edge of the UST Total petroleum hydrocarbons quantified as gasoline were detected in sample T I-W at 690 mg/Kg(milligrams per kilogram or parts per rrulhon ppm) TPH--g was not detected in the soil sample collected from the eastern end of the UST i ' PREVIOUS SITE INVESTIGATION 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 PHS-EHD Soil probe borings wei e advanced in the vicinity of the West UST area,removed in 1986 from in the City of Stockton right-of-way, at i ' the western edge of the site and in the vicinity of the plating shop on the site Locations of the soil probe borings are illusti ated on Figure 2 ' Hydi ocaibon-impacted soil in the vadose zone, associated with the West UST area within San Jose Stn eet was limited to a nan ow zone fi om depths of approximately 5 to 15 feet bsg, immediately surrounding the UST The detection of MTBE in soil samples collected froimprobe boring P 1 indicate lie the i elease of gasoline to be relatively recent, possibly within the past twenty years Gasoline-impacted ground watei is present around the West UST area The dissolved gasoline plume ' appears to extend to appioximately 50 feet northeast and 50 feet southwest from the former West UST area, and has an appi oximate width of 40 feet To determine the lateral extent of the hydrocarbon impact to soil and gi ound water associated with the West UST and the potential impact from the Texaco facility to the subject pi operty, soil probe boiings were advanced at the site under the supervision of the PHS-EHD ' On 14 November 1996 and 16 Jams 1997 a total of fifteen soil borings were advanced at the site � g 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 peti oleum hydrocarbons as gasoline (TPH-g), benzene, toluene, ethyl benzene and xylenes (BTEX),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 ' (milhgi ams per kilograms or parts per nullion ppm) Hydrocarbon-impacted soil associated with the West UST area appeared to be of limited lateral extent TPH-g was detected in four of ten grab gi ound water samples collected fi om the West UST area at concentrations ranging from 84 to 44,000 pg/l (micrograms per liter or parts per billion ppb) Various BTE&X compounds were detected in . six of ten samples analyzed at concentrations ranging from 0 60 to 7,800 ppb