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S E C O R <br /> . Mr Jim Barton <br /> February 23, 2006 <br /> Page 4 <br /> is unlikely that the source of the MtBE detected in well GEW-007A is located beneath the <br /> Chevron site <br /> GC-FID analyses were performed on groundwater samples collected from wells MW-2, <br /> MW-3, MW-4, MW-5, MW-6, MW-7, MWA 1 D, GEW-005A, GEW-006A, GEW-007A, GEW- <br /> 008A, GEW-022B, and GEW-023B for the petroleum-hydrocarbon compounds TPHg, <br /> diesel #2 fuel, kerosene, mineral spirits, fuel oil, and coal-tar oil None of these compounds <br /> were detected at or above their respective method detection limits (MDLs) in any of the <br /> groundwater samples submitted for chemical analysis by this method <br /> The GC-FID chromatograms of petroleum hydrocarbon fuels are typically comprised of a <br /> series of peaks, each peak representing a specific petroleum hydrocarbon Since <br /> petroleum-hydrocarbon fuels are often composed of several hundred specific compounds, <br /> their "fingerprints" are normally comprised of a series of peaks spread over a range of <br /> retention (elution) times, indicative of the fuel present in the sample The TPH <br /> chromatograms for groundwater samples collected from sampled wells did not exhibit a <br /> pattern of peaks characteristic of petroleum hydrocarbon fuels, indicating petroleum <br /> hydrocarbon fuels were not present in groundwater samples Based on chromatograms for <br /> • the 4Q2005, it appears gasoline-range petroleum hydrocarbons are not present at <br /> concentrations above detection limits in groundwater beneath the site Copies of the <br /> chromatograms are included in Attachment A <br /> Groundwater samples collected from the thirteen wells sampled during the 4Q2005 <br /> sampling event were analyzed for PCE and TCE by EPA Method 8260 The results of <br /> these analyses are summarized in Table 5 PCE was detected in wells MW-2, MW-3, MW- <br /> 4, MW-5, MW-6, MW-7, MWA 1 D, GEW-005A, GEW-006A, GEW-007A, GEW-008A, GEW- <br /> 022B, and GEW-0238 at concentrations ranging from 14,000 ,ug/L in MW-3 to 26 NgIL in <br /> GEW-005A An isoconcentration map of PCE concentrations is presented as Figure 4 <br /> TCE was detected in all wells sampled at concentrations ranging from 1 NgIL in MW-4 to 28 <br /> NgIL in MW-3 <br /> N 1FiteslProlectslChevronlRetatA#9-61711Penodtc Monrtonng1200514QMR14Q2005QMR doc <br />