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1 <br /> C706gicalTeduciraW Page 6 <br /> Groundwater Monitoring Report <br /> Pro}ect No 989 2 <br /> October 4,2004 <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 the <br /> ' new monitoring wells These constituents are no longer analyzed in groundwater samples <br /> collected at this site <br /> ' Laboratory Data Sheets are included in Appendix C Groundwater analytical data is <br /> summarized in Table 3 of Appendix A Chart 1 is a plot of TPH-G versus groundwater <br /> elevation for MW-1 Chart 2 is a plot of MtBE versus groundwater elevation for MW-6 <br /> ' Figure 5 is a contour of the MtBE plume and Figure 6 is a contour of the TPH-G plume in <br /> groundwater as generated by Surfer® 7 0 software <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 Flowcell meter During this <br /> groundwater-monitoring event, dissolved oxygen was measured in all the wells using an YSI <br /> ' dissolved oxygen meter These measurements are summarized in Table 4 of Appendix A and <br /> in the field logs of Appendix B <br /> ' 2.4 Groundwater Parameters <br /> 0 pH measurements recorded in the water table wells range between 7 24 and 7 50 This <br /> range is conducive to aerobic biodegradation activity <br /> • Temperature of the groundwater dunng the July 2004 event ranged between 68 4° and <br /> ' 73 4°Fahrenheit This range is conducive to aerobic biodegradation activity <br /> • Oxidation Reduction Potential (ORP) measurements were positive in MW-5, MW-6 and <br /> MW-9 The remaining wells had slightly negative ORP readings <br /> ' + Dissolved oxygen (DO) measurements recorded in the water table wells during the April <br /> 2004 momtonng event are low,ranging from 0 26 to 0 99 ppm <br /> • Electric Conductivity (EC) ranges between 728 and 1588 in the water table wells There <br /> ' is no significant difference between impacted and non-impacted wells <br /> 3.0 CONCLUSIONS AND RECOMAWNDATIONS <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 <br /> ' • TPH-G fluctuates with groundwater and has decreased exponentially over time as seen in <br /> Chart 1 MW-1 TPH-G vs Groundwater Elevation <br />