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Groundwater Assessment Report ARCO Facility No 2186 Stockton,California Page 6 to be towards the east-northeast at an average gradient of 0 004 ft/ft Groundwater elevation contours for September 13, 2001 are illustrated on Figure 5 Analytical Results Soil and groundwater samples were forwarded to Sequoia Analytical Inc in Sacramento, a California state-certified laboratory(FLAP #1624), for chemical analysis under strict chain- of-custody procedures The soil and groundwater samples were analyzed for TPHG and BTEX using USEPA Method 8015/8020 DHS/LUFT, and for MTBE, ethyl tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), tertiary amyl methyl ether (TAME), tertiary butyl alcohol (TBA), and 1,2-dichloroethane (1,2-DCA) using USEPA Method 8260 Soil analytical results are summarized in Table 2, and groundwater analytical results are summanzed in Table 3 Copies of the laboratory report and chain-of-custody documentation are included in Appendix F Xylenes were detected in soil samples collected from boring MW-7 at 41 feet (0 026 mg/kg) and 81 feet bgs (0 025 mg/kg) No petroleum hydrocarbons or fuel oxygenates were detected in soil samples collected from bonngs MW-5 or MW-6 Petroleum hydrocarbons or fuel oxygenates were not detected in groundwater samples collected from wells MW-5 through MW-7 SUMMARY The findings of this phase of the investigation are summarized below • Xylenes were detected in soil samples collected from boring MW-7 (41 feet bgs and 81 feet bgs) at concentrations just above laboratory reporting limits Fuel oxygenates or other petroleum hydrocarbons were not detected in soil samples from boring MW-7, • Petroleum hydrocarbons or fuel oxygenates were not detected in soil samples collected from borings MW-5 or MW-6, • Petroleum hydrocarbons or fuel oxygenates were not detected in groundwater samples collected from wells MW-5 through MW-7, and • The groundwater flow direction for September 13, 2001 was towards the east- northeast at an average gradient of 0 004 ft/fl LIMITATIONS This report was prepared in general accordance with accepted standards of care that existed at the time this work was performed No other warranty, expressed or implied is made . Conclusions and recommendations are based on field observations and data obtained from this work and previous investigations It should be recognized that definition and P\ARCO\2186\REPORTS\2186report doc