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• Mr George Takemori Project OF90-002 05 November 16, 1998 Page 3 Analytical Methods and Results Groundwater samples collected from wells MW-9 through MW-11, MW-14 and AS-1 were analyzed for TPHG using modified US Environmental Protection Agency (USEPA) Method 5030/DHS LUFT and for BTEX using USEPA Method 5030/8020 The samples were analyzed at Columbia Analytical Services, Inc , in San .lose, California (California Department of Health Services Hazardous Waste Testing Laboratory Certification No 1426) Copies of the chain-of-custody records and laboratory analysis reports are presented in Appendix B The results of laboratory analyses indicate that TPHG and BTEX were not detected in groundwater samples collected from wells MW-9 and MW-10 Dissolved hydrocarbons were detected in wells MW-11, MW-14 and AS-1 TPHG concentrations ranged from below lab detection limits in wells MW-9 and MW-10 to 500 ppb in well MW-14 Benzene concentrations ranged from below laboratory detection limits in wells MW-9, . MW-10, MW-11, and MW-14 to 0 6 ppb in well AS-1 Analytical results are summarized in Table 1 Concentrations of TPHG and benzene are shown on Figure 3 Groundwaier Analytical results of groundwater samples collected during the previous nine quarters indicate that TPHG and BTEX were not present in groundwater in monitoring wells MW-9, MW-10, and MW-12 Dissolved hydrocarbons have been detected in monitoring wells MW-11 and MW-14 Current TPHG concentrations ranged from below laboratory detection limits to 500 ppb In general, TPHG concentrations in groundwater have declined since the last monitoring event Benzene concentrations have historically ranged from below laboratory detection limits to 580 ppb Benzene concentrations within the last seven sampling events have shown a significant decline Current benzene ,levels ranged from below laboratory detection limits to 0 6 ppb Figure 2 presents the extent of current dissolved hydrocarbons beneath the site Results of groundwater analyses are presented in Table 1 CONCLUSIONS AND RECOMMENDATIONS The results of the groundwater sampling events indicate that dissolved hydrocarbons have been delineated and appear to be isolated beneath the former USTs and dispenser islands iWithin the last seven sampling events, benzene has not been detected in groundwater monitoring wells, with the exception of well AS-1, which contains a relatively low CRE ITEICHERT\QTRLY\.STOCKfiW DOC 959sg I