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�J GealogicaITerhnicslnc. Page 4 1 Groundwater Monitoring Report 1 Project No. 750.2 December 20,2001 1.3 Laboratory Analyses The groundwater samples collected on November 16, 2001, were delivered to Sherwood Labs Corporation of Hilmar, California (Department of Health Services Certification No. 1400), for analysis. i The groundwater samples were analyzed for: • Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX) by EPA method 8020/8015 • Total Petroleum Hydrocarbons as Gasoline(TPH-G)by EPA method 5030/8015(M) I h Additional samples were sent to Entech Analytical Labs, Inc. from Sherwood Labs for the analysis of: • Fuel oxygenated compounds (MTBE, DIPE, 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 1i data is presented in Appendix B. {'I As required under AB2886, the laboratory data was submitted electronically to GeoTracker on December 14, 2001- confirmation number 7775261580. { 2.0 FINDINGS AND DISCUSSION { The results of the groundwater sample analyses show the following: • Well MW-1 has consistently contained low concentrations of gasoline range petroleum hydrocarbons (TPH-G, BTEX). The concentration of TPH-G recorded for this event are slightly higher than those recorded during the August 2001 event. • Figure 6 illustrates groundwater elevation and TPH-G concentrations in MW-1 versus time. The graph had suggested a fairly direct relationship between groundwater elevation changes and contaminant concentrations. An inverse relationship was noted I for the November 2001 event, coinciding with the lowest groundwater elevation noted to date. • Figure 7 illustrates groundwater elevation and MTBE concentrations in MW-1 versus time. After an initial high of 220 4gll the concentrations of MTBE have fallen to 6.2 ug/l. • The discretely screened deep well MW-101 did not contain contaminant concentrations above the laboratory reporting limits for the third consecutive event. This suggests that the previously recorded contamination was a drilling artifact. • MW-5 was found to be free of contaminants except a low concentration of MTBE.