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------------ Report,Groundwater-quality Monitoring-November 28,2000; 7500 West Eleventh Street,Tracy, CA. Page 9 ,.: The results of the analyses of samples of groundwater are presented in Table 2, which also includes the results of analyses of groundwater samples recovered from the ' monitoring wells during the first sampling round on May 11, 2000. By inspection of the data in Table 2, it can be seen that the lateral and vertical distribution of components of fuel hydrocarbons found on November 28, 2000 in the subsurface beneath the 7500 West Eleventh Street site is compatible with the interpretation made from the data obtained from the site characterization program conducted in April and May 2000. That interpretation is shown graphically on Figures 2, 3, 4 and 5, which show, =' in plan view and sectional views along section lines A-A', B-B' and C-C', respectively, the locations and geometry of a primary and secondary plume of diesel and gasoline g affectin the subsurface. Comparing results of analyses of samples of groundwater recovered on November 28, 2000 with those from samples recovered on May 11, 2000, it can be seen that the traces of benzene, ethyl benzene and toluene in the sample recovered from MW-1 and the traces of benzene, ethyl benzene, xylene isomers and MTBE in the sample from MW-2 on May 11, 2000 are no longer present in the samples from those wells recovered on November 28, 2000. The samples recovered on the latter date no longer contained any detectable concentrations of any analytes of concern. The sample of groundwater from MW-5 also contained no detectable concentrations of analytes of concern, as was the case for the earlier sample from that well. _ There were minor variations in the concentrations of analytes of concern detected in the sample from MW-4 compared to the sample from that well on May 11, 2000. There were reductions in the trace concentrations of benzene, toluene, ethyl benzene and total xylene isomers (the BTEX compounds) in the samples from this well, but the concentration of gasoline rose from 52 p,glL to 370 µg/L, the concentration of MTBE rose from 990 µg/L to 1,400 pg/L, and the concentration of diesel increased slightly - from 300 µg/L to 320 Pg/L. As was the case for the sample recovered on May 11, 2000, the sample from MW-6 recovered on November 28, 2000 contained no measurable concentrations of diesel, gasoline or any of the BTEX compounds; however, it did contain MTBE at 160 Ag/L, which is little changed from the 150 µg/L that was measured in the sample recovered - from that well on May 11, 2000. The presence of that fuel oxygenate in MW-6, which is located across West Eleventh Street from the area on the 7500 West Eleventh Street property at which fuel hydrocarbons had leaked into the subsurface, is interpreted to represent a leading edge of a plume of affected groundwater emanating from that source. The absence of other analytes of concern in the sample can be accounted for by the propensity of MTBE to flow more rapidly than other fuel components through a given ` hydrostratigraphic environment, (The San Joaquin Company Inc. 2001.) The most noteworthy differences between the two rounds of groundwater sampling and analysis can be seen by inspection of the results of analyses on samples recovered from 1 monitoring wells MW-3 and MW-7. The sample recovered from MW-3 on November 28, sic