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1 <br /> SITE CLOSURE EVALUATION REPORT <br /> Ultramar Station No. 696 <br /> 2448 West Kettleman Lane <br /> Lodi, California <br /> Delta Project No. D093-916 <br /> Page 4 <br /> ' The approximate extent of petroleum hydrocarbons in ground water as of May 1987 is illustrated in a <br /> diagram prepared by Kleinfelder which is included in Appendix B. No ground water samples collected <br /> ' from monitoring wells MW-20, MW-34, MW-35, and MW-36 after October 1992 have contained <br /> detectable concentrations of petroleum hydrocarbons. Concentrations of petroleum hydrocarbons in <br /> ground water samples collected from monitoring wells MW-24 and MW-25 since March 1992 have <br /> typically been below or only slightly above the limits of detection. None of the ground water samples <br /> ' collected during the most recent sampling event in May 1995 contained detectable concentrations of <br /> petroleum hydrocarbons. <br /> REMEDIATION <br /> 4.0 SITE _ <br /> ' Petroleum hydrocarbons have been removed from the subsurface by pumping and treating of ground <br /> water, SVE, and excavation. A ground water pump and treat system began operating at the site in <br /> January 1986, and was in operation until approximately late 1988. Records of the operation of the pump <br /> }1 <br /> and treat system and estimates of the volume of hydrocarbons removed are not available. <br /> A SVE system was operated at the site from December 1989 until April 1994. The SVE system utilized <br /> ' a catalytic oxidizer for hydrocarbon destruction through September 1992, at which time the system was <br /> converted to activated granular carbon adsorption. During the operation of the SVE system it is estimated <br /> that approximately 1,600 gallons of gasoline hydrocarbons were removed from the subsurface. <br /> 1 <br /> 5.0 ASSESSMENT OF REMEDIATION EFFECTIVENESS <br /> ' Active remediation at the site included operation of a SVE and ground water treatment system. The j <br /> ground water treatment system operated at the site during the period of January 1986 through late 1988. <br /> ' Records of the amount of petroleum hydrocarbons removed from ground water are not available to Delta; <br /> however, ground water analytical results indicate petroleum hydrocarbon concentrations decreased <br /> significantly during operation of the ground water treatment system and subsequently continued to -- -. <br /> decrease down to non-detectable concentrations. The SVE treatment system operated at the site from <br /> ' December 1989 through April 1994. During this period approximately 1,600 gallons of gasoline were <br /> removed from the underlying soil matrix. <br /> ' RPT134.SJS <br />