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Closure Documentation—7500 l Eleventh Streel, Tracy,CA. Page 6 The San Joaquin Company Inc. (2004), Report on Extended Plume Definition - Former Fueling Station at 7500 West Eleventh Street, Tracy, California. October 2004. That table includes the results of analyses for lead in soil. A compilation of the results of all groundwater sample analyses conducted on samples recovered from push probe borings, from the tank pit and from groundwater-quality monitoring wells at the 7500 West I 1 th Street site were included in Table 4 of: The San Joaquin Company Inc. (2004), Report on Extended Plume Definition - Former Fueling Station at 7500 West Eleventh Street, Tracy, California. October 2004. A compilation of the results of all groundwater sample analyses conducted on samples recovered from groundwater-quality monitoring wells were included in Table 2 of- Dietz £Dietz Engineering and Construction, Inc. (2011), Groundwater-quality Monitoring Report-July 2011, Former Fueling Station, 7500 West Eleventh Street, Tracy, California. October 2011. That table includes the results of analyses for lead in groundwater. 2.8 Concentration Contours of Contaminants Found and Those Remaining in Soil and Groundwater, and Both On-site and Off-site: Lateral and Vertical Extent of Soil Contamination and Lateral and Vertical Extent of Groundwater Contamination In DECs professional opinion, based on contaminant transport studies at a multiplicity of sites, contours (isocons) of contaminants in soil and groundwater do not provide useful information to characterize contaminant plumes in alluvial fans containing narrow high permeability channels and complexly inter-bedded lenticular deposits of highly contrasting hydraulic conductivity of radically varying dimension such as are present at the 7500 W. IIth Street site. Accordingly, in all reports submitted to the regulatory agencies the plume of contaminants affecting soil and groundwater was depicted as shown. on Figure 3. In those figures, the area of the subsurface affected by mixed components of fuel hydrocarbons and the area in its surrounding fringe where only MTBE, the transport of which is little inhibited by the cation exchange capacity of clay soils, is present are identified. In addition to the release of fuel hydrocarbons from underground storage tanks that occurred on the 7500 W. 11th Street property, over the past ninety or more years numerous small releases of a variety of hydrocarbons have affected wide areas of shallow soil beneath nearby land and the 7500 W. 11 th Street property itself. The presence of those hydrocarbons can be attributed either to hydrocarbons having a vegetative source or to minor leaks and spills from vehicles using the formerly unpaved areas of the service station and being parked on the shoulders on the sides of the adjacent streets. Evidence DEC