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Vapor extraction wells VW-1 and VW-2 were purged of at least three well volumes using a <br /> decontaminated Teflon bailer Groundwater Sampling Forms documenting well monitoring, <br /> purging and sampling data are included as Appendix A <br /> ' Groundwater samples were collected from the five wells using a disposable Teflon sampling <br /> bailer, packed in an iced cooler, and transported under Chain-of-Custody manifest to Sparger <br /> Technology, Inc , a California-certified analytical laboratory located in Sacramento, California <br /> The laboratory analyzed each field sample for benzene, toluene, ethylbenzene, xylenes (BTEX) <br /> ' and Total Petroleum Hydrocarbons as gasoline (TPH-gasolme) using EPA Method 8015/8020 <br /> The laboratory reports and chain-of-custody documents are included as Appendix B <br /> ' Analytical results of the first quarter 1997 sampling event indicate that petroleum hydrocarbons <br /> are present in the groundwater beneath the site Total Petroleum Hydrocarbons as gasoline was <br /> detected in groundwater samples collected from VW-1 at 140 micrograms per inter(/cg/L) and in <br /> VW-2 at 1,400 ,ug/L Benzene was detected in the groundwater sampled collected from VW-1 at <br /> ' 0 72 ug/L and in VW-2 at 350 µg/L Toluene, ethylbenzene, and xylenes were also present in <br /> groundwater samples collect from VW-2 The current and historical laboratory results and their <br /> detection limits are summarized in Table 2 <br /> 4.4 Conclusions <br /> Since May 1992, the groundwater surface has risen an average of 20 55 feet Thus extreme rise <br /> ' in the groundwater table has resulted in groundwater elevations above the screened interval of <br /> the groundwater monitoring wells This condition has probably resulted in inconsistent <br /> groundwater flow direction and gradient interpretations and unrepresentative groundwater <br /> sample collection and analytical results To obtain data that better represents groundwater <br /> ' conditions, groundwater samples were collected from two vapor extraction wells, which are <br /> screened across the current groundwater table <br /> Groundwater samples collected this quarter from vapor extraction wells VW-I and VW-2 <br /> indicate a decrease in gasoline hydrocarbon concentration since the last sampling event on <br /> September 20, 1995 <br /> 2 <br />