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Chevron Environmental Management Company Soil and Groundwater Investigation Report Tracy Byron Road Project project can be compared and correlated with observations made during the installation of borings SB-8 through SB-16. SAIC borings SB-8 through SB-16 correlate with dewatering wells#99 through#120 along West Byron Road. Residual petroleum affected dewatering wells#109 through#117 correspond to the study area represented by SAIC's borings SB-8 through SB-12, in which petroleum affected soil was also encountered. Concentrations of TPHc in these borings ranged from 6.5 mg/kg to 3,900 mg/kg. Grab groundwater samples were collected from companion borings adjacent to borings SB-8, SB-10, and SB-12 using a Hydropunch tool. As previously stated,BTEX compounds were not detected in any groundwater samples analyzed during this investigation. Furthermore, concentrations of TPHd were below the 100 µg/L Taste and Odor Thresholds in groundwater samples GW-10-15 (SB-10) and GW-12- 13 (SB-12). Laboratory results indicate concentrations of TPHd are present in groundwater sample GW-8-13 (SB-8) at 8,900 µg/L. A silica gel cleanup preparation did not significantly reduce the concentration of TPHd in the sample. Several PAHs were detected in sample GW-8-13 at concentrations slightly above the laboratory detection limits. Based on this data, soil and groundwater in the vicinity of borings SB-8 through SB-12 is not fully characterized and the lateral extent of residual petroleum is not known. The presence of affected soil in the WSCO dewatering well borings#99 through#108 and trench excavation logs was limited. Data collected from SAIC's borings SB-13 through SB-16(adjacent to dewatering well borings#99 through#108)was also limited. SAIC's investigation results for borings SB-13 through SB-16 support the findings of limited petroleum impact observed at the former Nicholaw property. Laboratory reports did not indicate concentrations of TPHc above 100 mg/kg present in samples collected from borings SB-13 through SB-16. Groundwater samples collected from Hydropunch borings advanced adjacent to SB-14 (GW-14-15.5) and SB-16 (GW-16-16) did not contain concentrations of TPHd above the 100 µg/L Taste and Odor Thresholds. PAHs were not detected in groundwater samples GW-14-15.5 and GW-16-16. SAIC did not advance any borings between locations for SB-16 and SB-17. The former Nicholaw property is located in this area. Soil samples collected from previous borings advanced during investigation of the former Nicholaw property did not contain concentrations of residual petroleum. In May 1997, SJCEHD granted a"No Further Action" status for the Nicholaw property. SAIC recommends that additional investigation in the vicinity of borings SB-13 and SB-16 is not warranted. Concentrations of residual petroleum in soil are presented on Figure 3b. Concentrations of petroleum constituents in groundwater are presented on Figure 4a. 6.3 SECTION SB-17 THROUGH SB-26-AREA BETWEEN FORMER NICHOLAW AND CALDRON'S STORE Eleven borings (SB-17 through SB-26 and SB-36)were advanced along the southern easement of West Byron Road,just north of the parcels located between the former Nicholaw and McCormack properties. The heaviest petroleum-affected soil intervals observed during the installation of the dewatering wells and the excavation of the WSCO occurred between dewatering wells#54 through#77. Locations of borings SB-17 through SB-26 and SB-36 correspond to this interval of dewatering wells. Petroleum hydrocarbons were detected in boring SB-17 through SB-26 and SB-36 at concentrations greater than 100 mg/kg in eight of 11 borings. Concentrations of TPHc in excess of 1,000 mg/kg were reported in borings SB-19, SB-22 through SB-26, and SB-36. Soil affected by residual petroleum does not appear to be defined through this section(SB-19, SB-22 through SB-26, and SB-36) and the lateral extent is not known. Soil borings SB-17, SB-20, and SB-21 represent areas with soil concentrations of TPHc below 100 mg/kg. Because SPO was observed in several borings within this section, only four Hydropunch borings were advanced to collect groundwater samples within this section(GW-18, GW-20, GW-24, and GW-26). Sample GW-26 was also used for vertical groundwater delineation as requested by the RWQCB. Two grab groundwater samples, GW-20 and GW-26, contained TPHd concentrations of 120 µg/L and 110 9