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l r., <br /> ..cr <br /> X> <br /> �u <br /> rot <br /> ., <br /> EXECUTIVE SUMNWRY <br /> FA <br /> This report.has been prepared by Pacific Environmental Group, Inc. (PACIFIC) to <br /> document the findings of a soil and groundwater investigation performed at UNOCAL <br /> Bulk Plant 0788 located at 8203 East lith Street in Tracy, California. A summary of <br /> investigative findings is presented below: ; <br /> i <br /> I o A partially buried 5,000-gallon transmission fluid storage tank was <br /> 1 removed from the southeastern portion of the site on <br /> December 13, 1989. Analytical results indicated that low levels of <br /> ' ,.. petroleum hydrocarbons remained ir.the soils adjac,2nt to the <br /> ! excavation. <br /> 1. c The San Joaquin County Public Health Services Department issued an <br /> "Uziauthoriaed Storage Tank Release/Contamination Site Report"on <br /> ,. January 30, 1990, and requested additional investigation. <br /> o PACIFIC installed Groundwater Monitoring Wells U-1 through U-3 <br /> on October 24 and 25, 1990. Three additional groundwater monitoring <br /> wells designated U-4 through U-6,and three exploratory soil borings, <br /> U-A through U-C,were installed onsite on May 9, 1991. <br /> i <br /> o The site is underlain primarily by silts and clays to the maximum depth <br /> r I explored of 27 feet. Surficial sands were observed in the northwestern a <br /> y and southeastern portions of the site,at an approximate thickness of 5 ! <br /> k: to 8 feet. Significant subsurface sands were observed at approximate <br /> depths of 6 feet in U-6,8-1/2 feet in U-B, 16-1/2 feet in U-C,and i <br /> t 20 feet in U-4. Thnse sands ranee from approximately 1 toot to 5 feet <br /> +­" in thickness, but appear not to be laterally continuous across the site. <br /> u <br /> o Hydrocarbon concentrations in soil samples collected during October ! <br /> ' + ` 1990 and May 1991 ranged from none-detected to 1,800 parts per <br /> �. million(ppm)TPH-gasoline, and from none-detected to 4,900 ppm <br /> TPH-diesel. Hydrocarbon concentrations were ata maximum at 3 <br /> depths between 5 and 8-1/2 feet,with the maximum TPH-gasoline } <br /> concentration occurring in U-1, and the maximum TPH-diesel { <br /> 3100101/REPORT= i Scptcmber 30, 1991 <br /> t <br /> 1 <br />