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i Extended Plume Definition:-7500 W filth St., Tracy,C.4. Page 27 "" SJC's prediction is well supported by the data obtained from the April 30, 2004 monitoring round, particularly when it is recognized that, in the low-permeability clays re sent in the strata at the depth of the water table in MW-7, it may take a long period without purging for LNAPL to seep into the well from the adjacent formation and appear as floating product on the groundwater. While we recognize that the volume of floating product previously present in the formation around MW-7 may have been of low volume, and thus may have been largely removed by the purging operations discussed above, we note that since monitoring of the groundwater quality in that well was reinitiated on January 26, 2004 (see Table 4 for data record), the concentrations of TPHd and TPHg rose from 420 µg/L to 9,800 µg/L and 1,800 µg/L to 10,000 µg/L, respectively, with associated increases in the BTEX compounds, by April 22, 2004. To evaluate whether the increased concentrations of analytes of concern in the sample recovered from MW-7 on April 22, 2004 can be attributed to typical periodic variations in r groundwater affected by elevated concentrations of components of fuel hydrocarbons or whether it represents a trend in increasing concentrations that would result in the chemicals becoming oversaturated in the groundwater, data from at least one more round of groundwater-quality monitoring is needed. The scope of the groundwater-quality monitoring round conducted prior to the April 2004 monitoring round, (i.e., the January 26, 2004 round), in accordance with the guidance provided by the SJCEHD (San Joaquin County Environmental Health Division 2003), did not include sampling from all groundwater-quality monitoring wells extant at the site at that time. When the results of the analyses of samples that were recovered from the interior of the primary plume in January 2004 (i.e., samples from MW-3, MW-4, MW-5, MW-6, MW-7, MW-10 and MW-11) are compared with the results from the April 2004 monitoring round (see Table 4), with the exception of the significant increase in the concentrations of analytes of concern in MW-7 discussed above, the minor increases or decreases are typical of the periodic variations that have been observed previously at the Navarra Site. As is also recorded in Table 4, the results of the analyses of the samples recovered from Monitoring Wells MW-3A and MW-313 on April 21, 2004, which wells are screened in " aquifers beneath the surficial aquifer at the site and which aquifers are separated from each other and the upper aquifer by clay aquitards, show that the groundwater in those aquifers continues to be free of any detectable concentrations of components of fuel hydrocarbons. 7.2 Secondary Plume ' A secondary plume of diesel and gasoline, which is also shown on Figure 11, emanates from an area to the rear of the Casa Mendoza restaurant on the 7500 West Eleventh Street property. Although no physical evidence of an underground or above-ground storage tank has been found there, it appears that, at some time in the past, there was a source of fuel hydrocarbons located in the vicinity of Monitoring Wells MW-12 and MW-12A (see Figure 2 for locations). When the 6,000 linear feet of underground piping was removed from the site - in December 1998, a disconnected pipeline was found that ran from the general area of those sic