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04 June 1997 <br /> AGE-NC Project No 95-0130 <br /> Page 3 of 4 <br /> Benzene was detected in ground water samples from wells MW-2, MW-3, MW-5, and VW-IC at <br /> concentrations ranging between 4 9 µg11 and 56,000 µg/l Other volatile aromatic compounds <br /> (toluene, ethylbenzene and xylenes)were detected in samples from wells MW-2, MW-3, MW-5, and <br /> VW-1C at concentrations as high as 52,000,ug/1 <br /> MTBE was detected in ground water samples from MW-3 and VW-IC at concentrations between <br /> 12 and 3,000 mg/l Analytical results of ground water samples are summarized in Table 2 -Analytical <br /> Results of Ground Water Samples The laboratory report (Castle Analytical Laboratories Reference <br /> No 1049) and chain-of-custody forms are presented in Appendix B <br /> 4.0. CONCLUSIONS & RECOMMENDATIONS <br /> 41 CONCLUSIONS <br />' Between January and March 1997, ground water flow direction and gradient remained <br /> relatively constant at the site <br /> • The ground water surface elevation at the site continues to remain above the slotted screened <br /> intervals in wells MW-1 through MW-5 Therefore, samples collected from these wells may <br /> not be representative of shallower ground water conditions at the site <br /> Q Based on the consistently high concentrations of petroleum hydrocarbons in MW-5 and the <br /> prevailing ground water flow direction, it appears quite possible that the hydrocarbon <br /> compounds detected in MW-5 are related to the operation of former USTs at the Wells Fargo <br /> Bank property <br /> • Concentrations of benzene detected in MW-2, MW-3, MW-5 and VW-1 C exceeded the State <br /> of California Maximum Contaminant Levels (MCLS) for drinking water of i 0 pg/l <br /> • Concentrations of toluene detected in VW-1C exceeded the State of California MCLs for <br /> drinking water of 150 pg/l <br /> Concentrations of ethylbenzene detected in VW-1C exceeded the State of California MCLS <br /> I for drinking water of 700 pg/l <br /> • Concentrations of xylenes detected in VW-1C exceeded the State of California MCLs for <br /> drinking water of 1,750µg/1 <br /> • Concentrations of MTBE were detected in MW-3 and VW-1C MTBE is a widely used <br /> gasoline additive (octane enhancer) that began use in California during the late 1970's and <br /> early 1980's MTBE is highly water soluble, and appears to have very slow biodegradation <br /> rates in ground water The detection of MTBE is suggestive that a leak source may have <br /> occurred within the last 20 years <br />