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Geological?-CC CS Inc Page 4 <br /> ' Groundwater Monitoring Report <br /> Project No 723 2 <br /> May 15, 2002 <br /> 1 <br /> ' 0 Oxygenated Fuel Compounds (MTBE, DIPE, ETBE, TAME & TBA) by EPA method <br /> 8260 <br /> • 1,2 DCA & EDB by EPA method 8260 <br /> ' • Methanol & Ethanol by EPA method 8015 <br /> The detection limits for the above analyses are listed in Table 2 of Appendix A, while the <br /> ' lab analytical results are presented in Appendix B <br /> As required under AB2886, the laboratory data were submitted electronically to GeoTracker <br /> ' on April 26, 2002 - confirmation number 3392832458 <br /> 2.0 FINDINGS AND DISCUSSION <br />' The results of the groundwater sample analysis show the following <br /> • The concentrations of BTEX and TPH-G continue to fluctuate in individual monitoring <br /> wells from one sampling event to the next <br /> • Deep well MW-201 contained a higher level of contaminant concentrations than <br /> intermediate well MW-101 for the second consecutive event The contamination may <br /> be a drilling artifact created by the use of mud rotary drilling, therefore additional <br /> monitoring is needed to confirm this situation It is noted that the contaminant <br /> concentrations in MW-201 have declined by an order of magnitude since the first <br /> monitoring event in December 2001, which supports the conclusion that the high <br /> concentrations were from a drilling artifact <br /> • The wells did not contain MTBE, DIPE, ETBE, TAME, TBA, 1,2-DCA, EDB, or <br /> Methanol above the laboratory reporting limits <br /> • Wells MW-2, MW-3 and MW-201 contained Ethanol during the previous event but <br /> were non-detect in February 2002 We believe this is from the weighted bentonite <br />' pellets used in the construction of the annular seal of well MW-201 Additional <br /> monitoring for ethanol is not warranted as historically the compound rapidly degrades in <br /> groundwater and does not represent a threat to human health or to the environment <br /> • Figure 4 illustrates TPH-G and Benzene concentrations versus elevation in well MW-3, <br /> which lies near the core of the plume There appears to be a direct relationship between <br /> the water table and the TPH-G concentrations Benzene concentrations have stabilized <br />' in the well <br /> • Figure 5 illustrates TPH-G and Benzene concentrations versus elevation in well MW-4, <br /> which lies up gradient of the core of the plume The contaminant concentrations have <br /> stabilized in this well <br />