ARCHIVED REPORTS_SITE CHARACTERIZATION WORK PLAN

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1983 Unleaded Gasoline Spill: A spill of approximately 21,000 gallons (500 barrels) of regular unleaded gasoline occurred in September 1983 during a product transfer at Tank 7701 (Time Oil, 1988). The majority of the gasoline spilled was reportedly recovered using a vacuum truck. Additional product was reportedly recovered using 8-inch diameter recovery wells TO/R-1 through TO/R-5 (Figure 3). The volume of product recovered is unknown. 1988 Leaded Gasoline Spill: Time Oil personnel noticed a wet soil area at the header connecting the Time Oil terminal to the SPPL underground product supply pipeline in February 1988. Gasoline was discovered in the soil at about two feet bgs. Time Oil and SPPL excavated a series of test pits and trench excavations (SP-1 through SP-5 and TO/T-1 through TONT-17) to determine the source and extent of the spill, and installed wells to recover product from the groundwater surface. Approximately 7,500 gallons of regular leaded gasoline were recovered from the wells in February and March 1988. Product supply and distribution pipelines and gasoline ASTs were tightness tested in February and March 1988, but the source of the spill was not determined (Levine-Fricke, 1988 and Time Oil, 1988). A tracer test of the SPPL product supply line and the Time Oil header and product supply lines conducted in 1988 indicated possible leaks near the Time Oil header, but the tests were deemed to be inconclusive because no leaks in the buried pipelines could be found and tracer chemicals were also detected along and near aboveground pipeline sections, which indicated possible accidental tracer chemical surface spillage during the testing period (Tracer Research, 1988). Follow-up testing was not conducted. 2.4 Historical Investigations Numerous activities have been performed to investigate and remediate petroleum hydrocarbon impacted soil and groundwater at the site since at least 1983. The following site history information was obtained from Time Oil-specific site assessment reports, and from STTC area-wide work plans, feasibility studies, corrective action plans, and monitoring reports. 1983: Recovery wells TO/R-1 through TO/R-6 were installed in the A Zone to 10 feet bgs in the tank farm using 8-inch diameter metal casings slotted/perforated from 3 to 10 feet bgs (EMCON, 1993). The wells were reportedly installed as recovery wells in response to the 1981 and 1983 gasoline spills in the tank farm (Time Oil, 1988). Time Oil reported that product was recovered from all wells except TO/R-6 until sometime in 1984. Separate phase hydrocarbon (SPH)thickness measurements in the wells beginning in 1988 were included in several reports(Time Oil, 1988 and EMCON, 1993). 1987: Woodward Clyde Consultants (WCC) installed thirty-two (32) 1-inch diameter polyvinyl chloride (PVC) piezometers (PS/P-1 through PS/P-32) in the A Zone around the perimeter of the petroleum terminals for the Port of Stockton in January 1987 (WCC, 1987). The piezometers were driven to 10 feet bgs using a post pounder, and screened Site Characterization Work Plan,Final, May 18,2012 1007-012.002 2-6