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Clleotogccat rechnas Inc Page 4 1 2nd Quarter 2002 Groundwater Monitonng Report Project No 507 2 • October 15,2002 1.3 Laboratory Analyses ' The groundwater samples collected on June 20, 2002, were delivered to Sherwood Labs Corporation, Department of Health Services Certification No 1400, of Hilmar, California, for analysis Sherwood Labs analyzed the groundwater samples for • Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX)by EPA method 8020 • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015 ' + MTBE by EPA Metho 8020 A e-ed The results and detection limits for the above analyses are listed in Table 3 of Appendix A ' while the lab analytical results are presented in Appendix B As required under AB2886, the laboratory data was submitted electronically to GeoTracker on September 11, 2002 - confirmation number 7703834891 2.0 FINDINGS AND DISCUSSION The results of the groundwater sample analyses indicate the following o Wells MW-1, MW-2 and MW-3 remain free of detectable contamination O MW-4, MW-5 and MW-9 have significant BTEX and TPH-G contamination ' + MW-6 and MW-8 have minor TPH-G or BTEX contamination • Water table well MW-7 did not contain contaminant concentrations above the laboratory ' reporting limits The well has intermittently contained MTBE since its installation in May 2001 The source of this contamination may be surface infiltration from unpaved areas and from the open ditch traversing the front of the parcel ' • Water table well MW-10 did not contain contaminant concentrations above the laboratory reporting limits The well has previously contained xylene at levels Just above the laboratory reporting limit of 0 3 pg/1 - ' • Deep well MW-109 did not contain contaminant concentrations above the laboratory reporting limits The well has contained minor BTEX contamination for four 1 consecutive events The reduction in contaminant concentrations from the first sampling event was noted, however sufficient monitoring has been performed to conclude that it is probably a drilling artifact or the bottom of the groundwater plume • Figures 4 and 5 indicate a previously inverse relationship between groundwater elevation and contaminant concentrations in wells MW-9 and MW-5 respectively These two parameters have demonstrated parallel slopes for recent events In Figure 4, the inverse trend was consistent for well MW-9 for the first four monitoring events, but