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i Quarterly SummaryReport Second Quarter 1996 Former Unocal Bulk Plant 0788 8203 East 1 1 th Street Tracy, California City/County ID 4: Unknown County: San Joaquin BACKGROUND A partially buried 5,000-gallon transmission fluid storage tank was removed on Decem- ber 13, 1989, and analysis of soil samples indicated low levels of petroleum hydrocarbons. The San Joaquin County Public Health Services Department requested additional investi- gation on January 30, 1990. Since 1990, ten groundwater monitoring wells have been installed to assess soil and groundwater conditions. A Remedial Action Plan (RAP) rec- ommending soil vapor extraction and air sparging was submitted on March 18, 19933, A work plan for implementation of the RAP was submitted on July 13, 1993. The bulk plant was permanently closed and all related activities ceased on December 1, 1993. The above- ground tanks, loading racks, and garage structure were removed from the site in September 1994. In December 1994, Unocal proposed a site remedial strategy which in- cluded soil vapor extraction and enhanced biodegradation. Groundwater monitoring and sampling are performed on a semiannual schedule. Semiannual groundwater monitoring and sampling were performed in February 1996. Due to continued low-to-nondetect con- centrations of dissolved hydrocarbons in site wells, Unocal reevaluated remedial alterna- tives for the site, based on the"interim guidance" issued by the State Water Resources Control Board. In a letter dated January 23, 1996, PACIFIC, on behalf of Unocal, rec- ommended a site remedial strategy that includes passive bioremediation, continued groundwater monitoring, and offsite assessment to delineate the lateral extent of dissolved hydrocarbons in groundwater. RECENT QUARTER ACTIVITIES No activities were performed at this site. NEXT QUARTER,ACTi aMS Semiannual monitoring will take place in August 1996, and a report will be issued. 3100011 F12QSR96 1 July 19. 1996