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0014g ual Teclucics Inc Page 4 Groundwater Monitoring Report 16 Project No 989 2 August 30,2004 ' 2.2 Groundwater Analytical Results Low concentrations of TPH-G and BTEX constituents were detected in MW-1 and MW- 4 TPH-G and BTEX constituents were not present in any other monitoring wells • Trace concentrations of MtBE were present in MW-1 ' • Low concentrations of MtBE were present in MW-4, MW-5, MW-6, MW-8 and MW-9 The levels are consistent with previous monitoring events A plot of TPH-G versus groundwater elevation for MW-1 shows that generally the ' concentrations of TPH-gasoline fluctuate with groundwater elevation and that the overall concentrations have decreased two orders of magnitude over time • Historically, the fuel oxygenates DIPE, ETBE, TAME and TBA as well as 1,2 DCA and ' EDB have not been detected in any of the site's monitoring wells This holds true for the new monitoring wells These constituents are no longer analyzed in groundwater samples collected at this site Laboratory Data Sheets are included in Appendix C The data are summarized in Table 1 of Appendix A Chart 1 is a plot of TPH-G versus groundwater elevation for MW-1 Chart2 is ' a plot of MtBE versus groundwater elevation for MW-6 During purging of the monitoring wells, field measurements of the oxidation-reduction potential (ORP) of the water were taken using an YSI 3560 Flowcell meter During this groundwater-monitoring event, dissolved oxygen was measured in all the wells using an YSI ' dissolved oxygen meter These measurements are summarized in Table 4 of Appendix A and in the field logs of Appendix B 1 3.0 CONCLUSIONS AND RECOMMENDATIONS ' The following conclusions have been drawn from the data generated from this site investigation work ' Conclusions • Concentrations of TPH-G and BTEX have progressively decreased since 1996, ' suggesting that the plume is attenuating from natural causes • TPH-G fluctuates with groundwater and has decreased exponentially over time as seen in Chart 1 MW-1 TPH-G vs Groundwater Elevation ' • MTBE plume has moved downgradient from the source, the former USTs However, MTBE concentrations are low and potential risks are negligible • Chart 2 MW-6 MTBE vs Groundwater Elevation shows that MTBE fluctuates with groundwater elevation It clearly shows a decreasing MtBE plume over time and is likely attenuating from natural causes