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By January 1996, the continued dramatic rise in the groundwater table elevation had exceeded the top of the screen interval in all five groundwater monitoring wells and had entered the screen interval of the two deeper soil vapor extraction wells (VW-1D and VW-21D) Coincidentally, from July 1995 to April 1996, groundwater samples collected on four quarterly occasions from the five monitoring wells did not contain detectable concentrations of TPH-as-gasoline In August 1996, sampling of the five original monitoring wells was discontinued and the sampling of the two deeper vapor extraction wells (VW-1 D and VW-21D) was initiated Groundwater samples collected from VW-1 D and VW-21D contained detectable concentrations of TPH-as- gasoline (up to 12,000 µg/1), benzene (up to 1,300 µg/l) and Methyl tertiary butyl ether(MTBE) (up to 1,800 µg11) On November 14, 1997, Ramage Environmental collected groundwater samples from the five original groundwater monitoring wells and the two deeper sod vapor extraction wells (VW-1 D and VW-2D) To confirm the presence and concentration of MTBE and inspect for the possible presence of other alcohol- or ether-based oxygenate compounds, each of the groundwater samples was analyzed for volatile organic compounds by EPA Method 8260 Concentrations of MTBE were detected in VW-2D at 1,700 µg11, in MW-3 at 1,400 µg11, in MW-2 at 230 µg/I and in VW-1 D at 60 µg11 No other oxygenate compounds were detected, However, the volatile organic compound 1,2-Dichloroethane was detected in four wells at concentrations of up to 230 µg/I Based on the elevated concentrations of gasoline hydrocarbons (i e , benzene and MTBE) in groundwater beneath the site, proximity of the irrigation well and previous installation and pilot testing of the sod vapor extraction well network, Ramage Environmental recommended that active remediation be evaluated and designed � 5 c�