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• Unocal Corporation • <br /> Diversified Businesses <br /> 2000 Crow Canyon Place,Suite 400 <br /> San Ramon,California 94583 <br /> Telephone(510)867-0760 - <br /> Facsimile(510)277-2309 <br /> UNOCALO <br /> May 22, 1996 <br /> Mr. Michael Infurna <br /> West Region San Joaquin County <br /> Environmental Remediation Services <br /> Public Health Services <br /> 304 E. Weber Avenue, 3rd Floor <br /> Stockton, California 95201-0388 <br /> SUBJECT: Site Code 2162 <br /> FORMER UNOCAL SS 95098 <br /> 5606 Pacific Avenue <br /> Stockton, California <br /> Dear Mr. Infuma: <br /> Thank you for taking the time to discuss the subject location with me today. This letter <br /> documents our discussion and proposes changes to the groundwater monitoring and <br /> sampling frequency for the site. <br /> The basis for our request is discussed below: <br /> o UNOCAL contends that soil remediation has been completed. This <br /> is substantiated by the August 25, 1989 letter from the California RWQCB <br /> whereby they confirm impacted soils have been adequately cleaned up. <br /> o Quarterly groundwater monitoring data has been generated since June 1992, <br /> enabling determination of the groundwater gradient and flow direction. <br /> o Residual hydrocarbons remain in the capillary fringe and groundwater system <br /> at the site. TPH-gasoline and BTEX levels remain elevated in wells <br /> MWA 1 and MW-12. However, analysis of hydrocarbon concentrations in <br /> these wells show reducing trends from the late 1992 levels, as illustrated on <br /> the attached plots, Figures 1 and 2. <br />