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Closure.Documentation-7500�Prlel Eleventh Street, Tracy, CA. Page 7 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. There were also releases of hydrocarbon from underground storage tanks formerly located on property adjacent to and nearby 7500 W. 1 I th Street. Areas so affected are shown on Figure 18 in: The San Joaquin Company Inc. (2004), Report on Extended Plume Definition - Former Fueling Station at 7500 West Eleventh Street, Tracy, California. October 2004. For the purpose of satisfying the requirements of the Table 1- Checklist of Required Data for No Further Action Request at Underground Tank Sites, isocons of contaminants in groundwater are presented on the following figures: Figure 4: Isocons of TPHd in Groundwater July 2009 Figure 5: Isocons of TPHg in Groundwater July 2009 Figure 6: Isocons of Benzene in Groundwater July 2009 Figure 7: Isocons of Toluene in Groundwater July 2009 Figure 8: Isocons of Ethyl Benzene in Groundwater July 2009 Figure 9: Isocons of Total Xylenes in Groundwater July 2009 Figure 10: Isocons of Total MTBE in Groundwater July 2009 The groundwater-quality data from July 2009 was used to construct the isocons because the monitoring program, which was conducted in compliance with the directives issued by the SJCEHD, did not provide data for contaminant concentrations in all of the installed wells from later monitoring rounds. However, in many cases contaminant concentrations decreased very significantly between July 2009 and July 2011. For example the concentration of benzene in groundwater in Monitoring Well MW-13 fell from 1400 gg/L to 220 liglL over that period. Where comparable data is available, with inconsequential minor exceptions, the concentrations of contaminants detected in groundwater recovered from other wells at the time of the last monitoring round conducted in July 2011 were also less that those detected in July 2009. With respect to isocons of contaminants in soil, DEC used the highest concentrations of the contaminant of concern in the zone around the depth of the water table which, as expected was found to be the most heavily affected zone, The isocons of contaminants in soil constructed in the manner described are presented on the following figures: DEC