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KEI-J92-0205.R4 <br /> July 6, 1994 <br /> Page 2 <br /> The former Unocal site is surrounded by several large-scale <br /> petroleum storage and distribution facilities. It is KEI ' s <br /> understanding that several documented unauthorized releases have <br /> occurred at these sites. It is further KEI ' s understanding that <br /> the responsible parties for these sites have combined to perform an <br /> extensive regional soil and ground water contaminant investigation <br /> (piezometers P14 and P15, located at the rear of the former Unocal- <br /> leased site, were apparently part of this investigation) . The <br /> extent of the contaminant plume caused by the operation of the <br /> adjacent sites is currently unknown to KEI, but it appears that the <br /> eastern portion of the former Unocal-leased property has been <br /> impacted by this plume. <br /> The sub)ect site is owned by the Port of Stockton, and has been <br /> leased by Southern Pacific Pipelines, Inc. Unocal entered into a <br /> sublease agreement with Southern Pacific in 1974-1975, and began <br /> operation of the former facility in 1975. In approximately 1979, <br /> Unocal subleased the northeast portion of the subject site to <br /> Standard Transmission (ST) Services (Figure 1) . The Unocal <br /> facility was operated between 1975 and 1992, when the master lease <br /> between the Port of Stockton and Southern Pacific (and therefore <br /> the sublease between Unocal and Southern Pacific) was terminated. <br /> During the construction of the Unocal facility in the mid-1970 ' s, <br /> two underground storage tanks were installed at the site (10, 000 <br /> gallon and 20, 000 gallon capacity, respectively) . Based on <br /> background information gathered by Unocal, these tanks were <br /> predominantly used to store diesel for use as fuel by the distribu- <br /> tion fleet at the site. According to records researched by Unocal, <br /> the refined products (i. e. , super unleaded gasoline, unleaded <br /> gasoline, and diesel fuel #2) that were distributed to commercial <br /> accounts were stored at the nearby ST Services pipeline facilities <br /> and were withdrawn for distribution from their loading rack. <br /> In 1988 Kleinfelder installed seven monitoring wells and two <br /> exploratory borings during a soil and ground water assessment at <br /> the Unocal site. Documentation of the sample collection techniques <br /> and analytical results are presented in Kleinfelder's "Problem <br /> Assessment Report" (Kleinfelder Job No. 24-2059-01) dated September <br /> 1, 1988 . The locations of the monitoring wells and borings <br /> installed by Kleinfelder are shown on the attached Figure 1. The <br /> analytical results of the soil samples collected during well <br /> installation are summarized in the attached Tables 4 and 5. <br /> KEI ' s field work at the subject site began on April 22 , 1992 , when <br /> two underground diesel storage tanks (with capacities of 10, 000 and <br /> 20 , 000 gallons, respectively) were removed from the site. The <br /> • tanks were made of steel , and no apparent holes or cracks were <br /> observed in the tanks. Ms. Pamela Violett of the San Joaquin <br />