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i !.. Page 4 Ceologlcal reclutics lnc. Groundwater Monitoring Report Lt%4 Project No. 723.2 March 10, 2003 • Oxygenated Fuel Compounds (MTBE, DIPS, ETBE, TAME & TBA) by method 82.60 Due to a GTI error in communication, MW-201 was analyzed for oxygenates only. The well will continue to be analyzed for TPH-G and BTEX for future events. are listed in Table 2 of A The detection limits for the above analysesppendix A, while the lab analytical results are presented in Appendix B. LAs required under AB2886, the laboratory data were submitted electronically to GeoTracker on January 10, 2003 - confirmation number 1718882977. 2.0 FINDINGS AND DISCUSSION The results of the groundwater sample analysis show the following: • Review of the historic groundwater elevations show that groundwater levels raised each ' season from the raid 1990s to spring 2000 and have been decreasing steadily with each seasonal cycle since spring 2000. l 4—, • The concentrations of BTEX and TPH-G continue to fluctuate in individual monitoring wells from one sampling event to the next. • Intermediate well MW-101 continues to contain stable TPH-G concentrations, but i benzene and toluene concentrations continue to fluctuate at levels just above the laboratory reporting limits. • Contaminant concentrations in deep well MW-201 are fluctuating from event to event. Although analysis for TPH-G and BTEX were not performed as stated above, MTBE I and the other gasoline oxygenates are not present. The previously noted contamination i is probably a drilling artifact created by the use of mud rotary drilling. It is noted that the contaminant concentrations in MW-201 have declined by an order of magnitude since the first monitoring event in December 2001, which supports the conclusion that the high concentrations were from a drilling artifact. However, the continued presence Lof low concentration of the contaminants suggests that this may be near the vertical extent of the plume. �: �: • Figure 4 illustrates TPH-G and Benzene concentrations versus elevation in well MW-3, which lies near the core of the plume. There appears to be a direct relationship between the water table and the TPH-G concentrations. Benzene concentrations have stabilized in the well. L • Figure 5 illustrates TPH-G and Benzene concentrations versus elevation in well MW-4, which lies up gradient of the core of the plume. The contaminant concentrations have Ll stabilized in this well. • Figure 6 illustrates TPH-G and Benzene concentrations versus elevation in deep well MW-101., which lies near the core of the plume. The concentrations are approaching i L i