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Geological Teckaics l Page 4 Groundwater Monitoring Report j Project No. 750.2 August 16,2002 f ' s I The purge water was placed in a properly labeled 55 gallon DOT approved container and stored on site until its proper disposition can be arranged. Groundwater monitoring field logs are included in Appendix C. 1.3 Laboratory Analyses The groundwater samples collected on June 28, 2002, were delivered to Sherwood Labs of Hilmar, California(Department of Health Services Certification No. 1400), for analysis. The groundwater samples were analyzed for: • Benzene,Toluene, Ethyl Benzene, and Xylene (BTEX)by EPA method 8020/8015 • i'Total Petroleum Hydrocarbons as Gasoline,(TPH-G)by EPA method 5030/8015(M) Additional samples were sent to Entech Analytical Labs, Inc. from Sherwood Labs for the analysis o£ a • "Fuel oxygenated compounds (MTBE, DIP,E, ETBE, TAME & TBA) by EPA method 8260 The detection limits for the above analyses are listed in Table 2 of Appendix A and the lab data are presented in Appendix B. s As°required under AB2886, the laboratory data was submitted electronically to GeoTracker on July 23,X002,with confirmation number 4955119967. i 1.0 FINDINGS AND DISCUSSION The results of theg roundwater sample analyses show the following: • °Well MW-1 has consistently contained low concentrations of gasoline range petroleum hydrocarbons (TPH-G, BTEX). The concentrations of TPH-G recorded for this event showed a small increase over the March 2002 event but the concentration was still slightly below the mean value. �,` • ' The remaining wells were found to be free of contaminants, which is consistent with other events. • ' Figure 4 illustrates groundwater elevations and TPH-G concentrations in MW-1 versus time. • Figure 5 illustrates groundwater elevation) and MTBE concentrations in MW-1 versus time. After an initial high of 220 µg/L, the concentrations of MTBE have fallen to non- detect(<5 µg/L).