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Closure Appeal, • <br /> Flag City Chevron,6421 Capitol Avenue,Lodi,California <br /> Page 2 of 5 <br /> During the five years of operation of the groundwater pumping and treatment system at the <br /> Subject Property, neither TPHg nor benzene were detected in any groundwater samples collected <br /> (123 samples collected and analyzed from the extraction wells). These data suggest that neither <br /> TPHg nor benzene were removed from the aquifer during pumping and treatment operations. <br /> During the first quarter 2006 monitoring event conducted at the Subject Property, TPHg was <br /> detected at two on-site wells and benzene was not analyzed. <br /> Apex recommends advancement of borings in the P-30-W and the UST locations to collect <br /> soil and grab groundwater samples. Analysis should include TPHg, benzene, and MTBE. <br /> 2) The mass of MTBE remaining in soil was incorrectly calculated, vertical definition of <br /> MTBE in soil was not established, and the result was a gross underestimation of MTBE <br /> remaining in soil at the site. This underestimated mass calculation was used in the fate and <br /> transport model to close the Subject Property. <br /> The Closure Summary Report prepared by AGE dated August 31, 2005 calculates the mass of <br /> MTBE remaining in soil at the subject site at 1.54 pounds (Appendix L). There are multiple <br /> problems with this mass calculation. <br /> In nine of 15 boring locations where MTBE was detected in soil, soil sample MTBE <br /> concentrations increased with depth and were not vertically defined. In two sample locations, <br /> MTBE was detected, was not defined, and only one sample was analyzed. In one of 15 <br /> locations, MTBE was not vertically defined but did decrease with depth. Below is a summary of <br /> soil samples with detections: <br />