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MEMORANDUM <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION <br /> 3343 Routier Road. Suite A Phone: (916) 255-3000 <br /> Sacramento, CA 95827-3098 CALNET: 8-494-3000 <br /> TO: Wendy L. CohenFROM: Philip S. Isorena <br /> Senior Engineer Associate Engineer <br /> DATE: 6 June 1994 SIGNATURE: <br /> SUBJECT: SITE STATUS REVIEW, FORMER UNOCAL BULK PLANT, PORT OF STOCKTON, <br /> SAN JOAQUIN COUNTY <br /> Background <br /> Mr. Robert Boust of Unocal requested in his 20 December 1993 and 18 February 1994 letters <br /> closure of their former bulk fuel terminal at the Port of Stockton. The facility operated from 1975 <br /> to 1992 predominantly as a truck dispatching and bulk lube oil warehousing facility. In 1975, two <br /> underground tanks with capacities of 10,000 and 20,000 gallons were installed for diesel storage. <br /> According to Mr. Boust, Unocal distributed unleaded and super unleaded gasoline and diesel fuel #2 <br /> to its commercial accounts but these products were stored and distributed at the ST Services <br /> facilities next door. <br /> Investigations <br /> In 1988 and 1989, Unocal performed investigations in response to Board requests to Port of <br /> Stockton fuel terminals to investigate their individual sites to assess the impacts of their operation on <br /> soil and ground water. The results of ground water and soil samples obtained during these <br /> investigations are summarized in Tables 1 and 2, respectively. The soil and ground water sampling <br /> locations are shown in Figures 1 and 2, respectively. <br /> Following removal of the two underground diesel storage tanks in April 1992, Unocal collected five <br /> soil samples (SW 1-5) and one ground water sample in the tank pit (W-1). In July 1992, Unocal <br /> collected ground water samples from MWs 1-7 and four additional soil samples (SW2 A-D) in the <br /> vicinity of SW 2, which had shown 120 ppm TPHD in the previous sampling. <br /> Chlorinated Hydrocarbon Assessment <br /> Due to the one-time detection (no confirmation sample was taken) of 20 ppb 1,2-dichloroethane <br /> (1,2-DCA) during the July 1988 sampling and alleged storage of stoddard solvent in Unocal's USTs, <br /> during the 1994 first quarter sampling event I requested Emcon to collect ground water samples for <br /> U. S. EPA Method 601 analysis by our in-house certified laboratory. The results showed the <br /> presence of chlorinated hydrocarbons in PS/MW-1M [1.5 ppb 1,2-DCA and 15 ppb cis-1,2- <br /> dichloroethylene (cis-1,2-DCE)), PS/MW-20 (0.4 ppb 1,2-DCA), UP/MW-1 (1.0 ppb 1,l-DCA ), <br /> and SP/WC-1M (0.1 ppb 1,2-DCA). As shown in Figure 3, only UP/MW-1 is proximal to Unocal. <br /> Figure 3 also shows that Unocal's MW 5 (UO/MW-5) is closer to PS/P-14, PS/MW-15, and other <br />