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Extended Plume Definition:-7500 W 11th St.,Tracy,CA, Page 28 monitoring wells toward the West Eleventh Street frontage of the property where the underground storage tanks that were removed at that time were located. As is also shown on Figure 2, underground fuel tanks were formerly located on the property at 24195 Chrisman Road, which adjoins the 7500 West Eleventh Street site to the south. They had contained diesel but were removed in December 1998. Although no additional investigation of the 24195 Chrisman Road site has been performed, SJC believes that because samples recovered from the bottom of the tank pit at the time of removal contained only low concentrations of diesel (Dietz Irrigation 1999b), it is likely that any contribution made by diesel migrating from the 24195 Chrisman Road site to the subject property would have had little, if any, deleterious affect on the environmental condition of the subsurface beneath the subject property. ` There were no detectable concentrations of analytes of concern in the groundwater sample recovered on April 21, 2004 from Monitoring Well MW-12, which is located in the interior of the secondary plume. This finding is consistent with the trend of the data recorded in V5Table 4, which shows that analytes of concern in samples recovered from that well have reduced significantly since it was installed in April 2002. Consistent with its being screened in an aquifer that is below a clay aquitard that separates '4W that aquifer from the near surface one, the groundwater sample recovered from Monitoring Well MW-12A on April 21, 2004, as has been the case throughout the history of sampling from that well, again contained no detectable concentrations of analytes of concern. 7.3 Dispersed Low Concentrations of Hydrocarbons in Shallow Soils In addition to the well-defined primary plumes of affected soil and groundwater, the aerially extensive subsurface investigations conducted during the early phases of site characterization conducted at the Navarra Site found dispersed, low concentrations of a variety of hydrocarbons affecting wide areas of shallow soil beneath nearby land and the Navarra property itself. The presence of these hydrocarbons can be attributed either to hydrocarbons 4� having a vegetative source or to minor leaks and spills from vehicles using unpaved areas of the former service station and being parked on the shoulders of the streets over past decades. Evidence has also been found that fill used to bring West Eleventh Street, Chrisman Road and some of the adjoining sites to their present grade included some debris from bituminous macadam paving(The San Joaquin Company 2002c). The areas affected by low concentrations of hydrocarbons in shallow soil are shown on Figure 18. However, to provide for clarity of the presentation of the primary and secondary plumes of affected groundwater emanating from the 7500 West Eleventh Street site, these dispersed areas of affected soil,which are of less than minor significance, were omitted from Figures 11-17. SJC