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QEOMATRIX low Road (Figure 2). These pipelines, which carried crude oil and Bunker C oil, were buried at a ' depth of approximately 3 feet bgs. i�. A soil and groundwater investigation was conducted at the Dobler property in October 1998. . The field investigation revealed limited amounts of petroleum hydrocarbons in subsurface soil along the southern edge of the property that fronts Byron Road. The petroleum hydrocarbons appear similar to those found at the Dividend property(APNs 238-02-10/13/14), which is west of and adjacent to the Dobler parcel. The petroleum likely is degraded crude oil and/or Bunker C oil. Total petroleum hydrocarbons (TPH) were reported at a concentration of 2,100 parts per L. million(ppm) in 1 of 3 soil samples collected in 1998. Pyrene and chrysene were detected at concentrations of 0.035 and 0.053 milligrams per kilogram(mg/kg), respectively, in the same soil sample. The oil-affected soil was encountered between depths of approximately 8.5 and 9.5 feet bgs. The lateral distribution of petroleum hydrocarbons in soil appears to extend no more than 150 feet north of the property boundary. Figure 2 shows the sample locations and the Aw location where oil-affected soil was encountered at the Dobler property. Details regarding the ' soil and groundwater investigations on the Dobler property are presented in Geomatrix's letter 'mw report of February 17, 1999: "Soil and Groundwater Investigation Report and Site Closure Request, Dobler Property(San Joaquin County APN 209-270-26), 13588 West Grant Line Road, Tracy, California." The subsurface soil in the project area is predominantly silt and clay, with isolated sandy lenses, to a depth of at least 15 feet. The water table is approximately 7 to 9 feet bgs. It should be noted that shallow groundwater beneath the project area is prohibited for use as domestic or L municipal supply by the City of Tracy Municipal Code (Section 11.1.16) for reasons unrelated to the presence of degraded crude oil. r� Subsurface soil at a nearby property known as the Dividend property is affected by the same degraded petroleum as that found at the Dobler property. Geomatrix performed a human health risk assessment for the Dividend property, dated May 24, 1995, that was submitted to the State of California Department of Toxic Substances Control (DTSC). The purpose of the health risk assessment was to evaluate the potential health risks to future site residents associated with residual crude oil/Bunker C oil in subsurface soil along the southern boundary of the Dividend LN property. The health risk assessment was conducted in accordance with the DTSC's Human Health Screening Evaluation described in the Preliminary Endangerment Assessment Guidance LN NLSt3kdeptdata\Doc_Safe130DOs1349953499.0051soil mngnt piao.doc 2 LN