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' 'fogk'l'Techmcs Inc Page 4 Gi oundwater Monitoring Report Project No 723 2 July 17,2003 ' 1.3 Laboratory Analyses The groundwater samples collected on June 20, 2003, were delivered to Sherwood Labs of Hilmar, California (certification #1400) for analyses of ' • Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX), MTBE, by EPA method 8020 • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015(M) ' Sherwood forwarded well MW-201 samples to Castle Analytical Laboratory (Department of Health Services Certification No 2480) of Atwater, California, for analysis of • Oxygenated Fuel Compounds (MTBE, DIPE, ETBE, TAME & TBA) by method 8260 The detection limits for the above analyses are listed in Table 2 of Appendix A, while the lab analytical results are presented in Appendix B ' As required under AB2886, groundwater elevation and laboratory data were submitted electronically to GeoTracker on July 15, 2003 - confirmation numbers 8576732456 & ' 1922917008 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 mid 1990s to spring 2000 and have been decreasing steadily with each seasonal cycle since spring 2000 • 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 BTEX & TPH-G concentrations, but benzene and toluene concentrations have fallen to below the laboratory reporting limits 1 • Deep well MW-201 contained xylene at a concentration (0 4 ug/1) dust above the laboratory reporting Inuit The previously noted contamination 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 ' • 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