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M. Scott Mansholt - 3 - 13 December 2006 Chevron/UPRR — TAOC Tracy fel Pits observations indicated impacted soil was greatest in the northeast part of the site, from approximately two to six feet. Within the gravel pits, visually affected soil was present generally at one to three feet. No impacted soil was observed in trenches on the southwest part of the site. Groundwater was not encountered, but according to a site assessment of the area in 2000, depth to groundwater was reportedly 55-feet with a northerly gradient. Geomatrix, 2003 & 2005 In November 2003 and August 2005, Geomatrix conducted site investigations by advancing 35 borings (GMX-1 through 35) across the site. Analysis of the samples indicated that elevated concentrations of TPH as diesel (TPHd) to 88,000 mg/kg and TPH as motor oil (TPHmo) to 250,000 mg/kg were detected in soil generally from the northeast portion of the site. It should be pointed out that TPHd and TPHmo detections do not indicate that diesel and motor oil are present rather they occur within petroleum hydrocarbon "carbon ranges" evaluated by the analytical laboratory method. In addition, polynuclear aromatic hydrocarbons (PAHs) were detected in several soil samples and the elevated results correlate with borings having high TPH concentrations. The PAH - benzo(a)pyrene (B(a)P) was present at 0.0065 to 1.7 mg/kg and the sum of the B(a)P toxic equivalency factors (TEFs) for carcinogenic PAHs ranged from 0.0049 to 3.71 mg/kg. The residential CHHSLs (California Human Health Screening Levels) for PAH in soil by OEHHA (Office of Environmental Human Health Hazard Assessment) are 0.038 mg/kg and 0.13 mg/kg for residential and commercial scenarios, respectively. The total B(a)P TEFs were above the residential and commercial CHHSLs in two locations, impacted soil in GMX-27 (0.18 to 3.71 mg/kg) and in GMX-32 (0.57 mg/kg). Eight soil samples from four borings were submitted for Title 22 metals analysis; the majority of which were not detected at the respective reporting limit. Those metals with reportable concentrations suggest that the results are consistent with background values. Forty-six soil samples were submitted for volatile organic compounds (VOCs) analysis. Naphthalene was detected in two samples and 1,2,4-trimethylbenzene in one sample; the remainder of the VOCs compounds was ND at their respective reporting limits. The detections correspond to the soil samples having elevated TPH concentrations. Similar to earlier characterizations, during the Geomatrix investigations, TPH affected soil was encountered in the northeast part of the, generally in the upper 10 to 12 feet. Groundwater was not encountered or investigated during the 2003 investigation. Four soil samples from three borings were analyzed for dioxins and furans; no furans were detected. However, two dioxins (1 ,2,3,4,6,7,8-heptachloro-p-dioxin [HpCDD] and/or octachlorodibenzodioxin [OCDD]) were detected above the laboratory reporting limits in three of the samples. HpCDD was reported at 16 picograms per gram (pg/g) dry weight and 13.8 pg/g wet weight in sample GMX-27 at 11.5-feet; OCDD was present at concentrations ranging from 5.3 to 160 pg/g dry weight and 4.6 to 138.4 pg/g wet weight in samples GMX-27- 11.5, GMX-32-1.0, and GMX-34-5.0. The highest dioxin concentrations were found in GMX27-11.5, which also contained the highest TPH values found during the investigation.