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. Mr. George Takemori Project OF90-002.07 <br /> April 30, 1999 <br /> Page 3 <br /> Analytical Methods and Results <br /> Groundwater samples collected from wells MW-3 through MW-5 and MW-9 through <br /> MW-14 were analyzed for TPHG using modified U.S. Environmental Protection Agency <br /> (USEPA) Method 5030/DHS LUFT; for BTEX using USEPA Method 5030/8020; and <br /> for methyl tert-butyl ether (MTBE) using USEPA Method 8260. The samples were <br /> analyzed at Columbia Analytical Services, Inc., in San Jose, California (California <br /> Department of Health Services Hazardous Waste Testing Laboratory Certification <br /> No. 1426). Copies of the chain-of-custody records and laboratory analysis reports are <br /> presented in Appendix B. <br /> The results of Iaboratory analyses indicate that TPHG and BTEX were not detected in <br /> groundwater samples collected from wells MW-3 through MW-5 and MW-9 through <br /> MW-12. TPHG, benzene, toluene, ethylbenzene, and total xylenes were detected in MW- <br /> 13 at concentrations of 5,100 ppb, 55 ppb, 370 ppb, 100 ppb, and 1,000 ppb, respectively. <br /> TPHG and total xylenes were detected in MW-14 at concentrations of 1,100 ppb and 6 <br /> . ppb, respectively. Benzene, toluene, and ethylbenzene were below laboratory detection <br /> limits in MW-14. MTBE was detected in wells MW-5 and MW-13 at 0.8 ppb and 4 ppb, <br /> respectively. All remaining wells sampled were below laboratory detection limits for <br /> MTBE. Analytical results are summarized in Table 1. Concentrations of TPHG and <br /> benzene are shown on Figure 3. <br /> Groundwater <br /> Analytical results of groundwater samples collected during the previous nine quarters <br /> indicate that TPHG and BTEX were not present in groundwater in monitoring wells <br /> MW-9, MW-10, and MW-12. Additionally, monitoring wells MW-3, MW-4, MW-5 and <br /> MW-11 do not have detectable levels of petroleum hydrocarbons. Dissolved <br /> hydrocarbons have been detected in monitoring wells MW-13 and MW-14. Current <br /> TPHG concentrations ranged from 1,100 to 5,100 ppb. In general, TPHG concentrations <br /> in groundwater have declined since the last monitoring event. Benzene concentrations <br /> within the last seven sampling events have shown a significant decline. Current benzene <br /> levels ranged from below laboratory detection limits to 55 ppb. Figure 2 presents the <br /> extent of current dissolved hydrocarbons beneath the site. Results of groundwater <br /> analyses are presented in Table 1. <br /> CR1E:ITEICI IERTISTOCKTONMQTRLYISTKNQ 199.DOC-95\lsg:I {3}[KstCiC� <br />