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Closure Documentation—7500 Wwleventh Street, Tracy,CA. Page 14 Letter from Dai Watkins, PhD, PE (The San Joaquin Company Inc.) to Rebecca Setliff REHS (San Joaquin County Public Health Services, Environmental Health Division. November 2, 2001. Characterization: Navarra Property, 7500 - Eleventh Street, Tracy, California 95376 Letter from Dai Watkins, PhD, PE (The San Joaquin Company Inc.) to Rebecca Setliff RENS, San Joaquin County Public Health Services, Environmental Health Division. November 29, 2001. The San Joaquin Company Inc. (2008), Recommendations for Closure - Former Fueling Station, 7500 West Eleventh Street, Tracy, California (Global ID T0607700606. Letter from D. J. Watkins to Nuel Henderson, San Joaquin County Environmental Health Department. December 17, 2008, 2.11 Best Available Technology (BAT) Used or an Explanation for Not Using BAT The best available technology for remediation of sites affected by releases of fuel hydrocarbons can be determined only by a site-specific evaluation with consideration of any economic constraints that inhibit application of some otherwise viable technologies. In the case of the 7500 W 11th Street site, key site-specific issues controlling selection of a best available technology were: soil and groundwater were affected by both diesel and gasoline fuels, light non-aqueous phase liquids (LNAPL) were present on the surface of the groundwater beneath some areas of the site, the site is located on an alluvial fan composed of highly complex sediments that included lenticular and channel-type deposits of permeable faces separated by low permeability clays and silty clays, the minimum elementary volume of the subsurface formations is very large, vigorous attenuation of contaminants in groundwater was occurring under the cation of aerobic and, initially, anaerobic natural attenuation (aerobic natural bioremediation is now active over the whole area of the site), and there are no septic sewers, storm-water sewers or natural streams or bodies of water at, or in the vicinity of, the site to which discharge from groundwater treatment facilities could be routed. The professional engineer in responsible charge of the work conducted a comprehensive, site-specific evaluation, that included detailed designs and cost analyses supported by technical and analytic element modeling and extensive citation to regulatory guidance documents and engineering literature to demonstrate that the best available technology for remediating the 7500 W. 11 th Street site was excavation and disposal of heavily contaminated soil, extraction of LNAPL and groundwater containing high concentration of contaminant by using vacuum trucks to suction LNAPL and highly contaminated groundwater from the surface of quiescent groundwater in large open pits followed by natural attenuation of groundwater contaminants under aerobic conditions. Those evaluations, analyses, and modeling studies were presented in the following reports, which also demonstrated that the recommended technology was capable of remediating the site at a cost greatly less than alternative technology. DEC