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QeologiulTeCh9&slnc. Page 4 <br /> Groundwater Monitoring Report <br /> Project No.989.2 <br /> July 24,2003 <br /> ' As required under AB2886, the depth to groundwater data was submitted electronically to <br /> GeoTracker on July 1, 2003, with confirmation number 1574375748. <br /> 2.2 Groundwater Analytical Results <br /> ' + Low concentrations of BTEX constituents were present in MW-I and MW-4. <br /> + No constituent of BTEX was found in the remaining monitoring wells. <br /> + Low concentrations of TPH-G were detected in MW-1 and MW-4. TPH-G was not <br /> ' present in any other monitoring wells. <br /> + Low concentrations of MTBE were present in MW-1, MW-4, MW-5, MW-6, MW-8 and <br /> ' MW-9. The levels are consistent with previous monitoring events. <br /> + Concentrations of MTBE in MW-5, MW-6, MW-8 and MW-9 decreased since the last <br /> groundwater-monitoring event. <br /> ' + A plot of TPH-G versus groundwater elevation for MW-1 shows that generally the <br /> concentrations of TPH-gasoline fluctuate with groundwater elevation and that the <br /> ' overall concentrations are decreasing over time. <br /> + Historically, the fuel oxygenates DIPE, ETBE, TAME and TBA as well as 1,2 DCA and <br /> EDB have not been detected in any of the site's monitoring wells. This holds true for <br /> Mthe new monitoring wells. <br /> Laboratory Data Sheets are included in Appendix C. The data are summarized in Table 2 of <br /> ' Appendix A. Chart 1 is a plot of TPH-G versus groundwater elevation for MW-1. <br /> During purging of the monitoring wells, field measurements of the oxidation-reduction <br /> ' potential (ORP) of the water were taken using an YSI 3560 l;lowcell meter. During this <br /> groundwater-monitoring event, dissolved oxygen was measured in all the wells using an <br /> YSI dissolved oxygen meter. These measurements are summarized in Table 3 of Appendix <br /> ' A and in the field logs of Appendix B. <br /> 3.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The following conclusions have been drawn from the data generated from this site <br /> investigation work: <br /> ' Conclusions <br /> + Concentrations of TPH-G and BTEX have progressively decreased since 1996, <br /> suggesting that the plume is attenuating from natural causes. The May 2003 monitoring <br /> events shows that only two of the sites ten groundwater-monitoring wells show <br /> detectable concentrations of TPH-G and BTEX. <br /> i <br />