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F <br /> 14800 Highway 99 <br /> Page 2 of <br /> • Cal Tech Environmental Laboratories, the laboratory that analyzed the soil and <br /> groundwater samples, reported detected concentrations in the gasoline range organics, <br /> and based on sample chromatograms, identified the contamination as degraded gasoline. <br /> • Current contaminant concentrations are comparable to the estimated residual mass values <br /> calculated prior to site closure in December 1998. <br /> AGE has documented that concentrations for gasoline, diesel, MTBE, and 1,2-DCA detected in <br /> groundwater at this site are well above the California Environmental Protection Agency Regional <br /> Water Quality Control Board Central Valley Region water quality numerical limits for petroleum <br /> fuel mixtures, constituents, and additives. Also, the boring logs demonstrate that soil lithology <br /> tends to be sandy with low sorption capacity. Therefore, EHD cannot support a recommendation <br /> for site closure at this time. <br /> Additional information is needed to demonstrate that contaminants of concern do not pose a <br /> health risk to the public. EHD recommends that you submit a site conceptual model (SCM) that <br /> will adequately address site assessment and meet final closure requirements. Please provide a <br /> fate and transport model of petroleum hydrocarbons released at this site. The transport of <br /> petroleum hydrocarbons, potential relevant exposure pathways, and potential receptors should be <br /> specific for this site. Please submit an SCM and fate and transport model to EHD by November <br /> 28, 2005. <br /> If you have any questions regarding this letter please contact Vicki McCartney at(209)468- 3456 <br /> or by electronic mail at vmccartncy@sjcehd.com. <br /> Donna Heran, RENS, Director <br /> Environmental Health Department <br /> Victoria L.McCartney, Senior REHS Margaret Lagorio, RENS, Supervisor <br /> Unit N-Site Mitigation Unit 1V- Site Mitigation <br /> r <br /> c: Jo'1 M. Chapman-AGE <br /> James L.L. Barton - CVRWQCB <br /> I� <br /> II <br /> f <br />