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*ftwov %Woe. Yr /*s� GEOMATRIX 2.0 BACKGROUND ,r The Burns and Pombo properties are bounded to the south by West 11 th Street, to the west by Corral Hollow Road and to the northeast by the UPRC ROW. Pipelines, operated by Chevron and Texaco from approximately the early 1900s to the mid-1960s, ran parallel to the northeastern edge of the Burns and Pombo properties (Figure 2). These pipelines, which carried crude oil and Bunker C oil, were buried at a depth of approximately 3 feet bgs. 6.. Soil and groundwater investigations were conducted at the Burns and Pombo properties in July L and September 1999. Details regarding these soil and groundwater investigations are presented in the Geomatrix reports Soil and Groundwater Investigation Report and Human Health Screening Evaluation, Burns Property (San Joaquin County APN 232-170-05), 1881 Rustan `w Road, Tracy, California (January 2000) and Soil and Groundwater Investigation Report and Human Health Screening Evaluation, Pombo Property (San Joaquin County APN 232-170-07), '" 1755 West IPh Street, Tracy, California (January 2000). The field investigation revealed limited amounts of petroleum hydrocarbons in subsurface soil primarily along the northeastern 6W edge of the properties that front the UPRC ROW. MW Total petroleum hydrocarbons (TPH) were reported at concentrations varying between 22 and 18,000 milligrams per kilogram(mg/kg) in 14 of 22 soil samples collected in 1999. Benzene, toluene, ethylbenzene, and xylenes were either not detected or were detected sporadically at 6" low concentrations (up to 7.5 mg/kg). In these same borings, various combinations of eight polynuclear aromatic hydrocarbons (PAHs; acenaphthene,benzo(a)anthracene, chrysene, 4 fluorene, fluoranthene, naphthalene, phenanthrene, and pyrene) were detected at individual concentrations up to 6.8 mg/kg. Figure 2 shows the sample locations and the location where oil-affected soil was encountered at the Burns and Pombo properties. The oil-affected soil was encountered between depths of tow approximately 6 and 19 feet bgs. The lateral distribution of petroleum hydrocarbons in soil appears to extend no more than 100 feet south of the northeastern property boundary on the Burns property. The Pombo property, which is triangular in shape,has two areas where petroleum hydrocarbons have been detected in soil; the first is located in the northwestern portion of the property and extends laterally approximately 140 feet south of the northeastern property boundary; the second is located in the eastern corner of the property and extends from the northern property boundary to the southern property boundary. V V \\sf3\deptdata\Doc_Safe\6000s\6115.014\SMP.doc 2 V