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Four other releases have occurred at the Facility: • A release of gasoline from AST No. 3301 was identified in March 2002 (Figure 2). The tank was taken out of service immediately upon discovery of the release. Fuel stored in the tank was transferred to other ASTs at the Facility, and absorbent pads were placed in the spill area to contain and remove visible product. A cracked weld in the base was identified and repaired. • A second release of gasoline was identified in April 2002 from AST No. 3302. The tank was taken out of service immediately upon discovery of the release. Fuel stored in the tank was transferred to other ASTs at the Facility and absorbent pads were placed in the spill area. A double bottom was installed on the tank to mitigate future releases. Six months after the release was discovered and the tank repaired, SPH in well ST/MW-1 were observed at a thickness of approximately 2.3 feet. • A release of diesel was reported from AST No. 1503 in June 2002. During a pipeline delivery, the capacity of the tank was miscalculated, resulting in an estimated 1,000-gallon release of diesel fuel. Absorbent pads were placed around the tank. Philip Transportation and Remediation, Inc. (Philip Services)was contracted to excavate and dispose of fuel-impacted soil around the tank. • Approximately 155 gallons of gasoline were released onto asphalt pavement in the northern truck rack area in July 2006. About 100 gallons of the product were collected into a containment sump which was emptied and cleaned. The remaining product evaporated, absorbed into the asphalt, or was removed via absorbent pads and powder. Two confirmation soil samples were subsequently collected in the upper 6 inches of soil beneath the asphalt and base rock to verify that the release had not migrated into the subsurface. One of the samples contained total petroleum hydrocarbons as gasoline (TPHg) and as diesel (TPHd) concentrations of 47 and 45 milligrams per kilogram (mg/kg), respectively, and trace concentrations of ethylbenzene (0.11 mg/kg) and total xylenes (0.062 mg/kg). The concentrations were below applicable screening levels and indicated that the release was successfully captured before it could adversely affect the underlying soil. 2.5 Previous Investigations The following describes the investigations that have been performed within the leasehold since 1992, including at and downgradient of the Facility. 2.5.1 Leasehold Investigations, 1992 to 2002 STTC Investigations. Investigations of subsurface conditions within the leasehold were initiated in the northern leasehold in the early 1980s. In 1992, the STTC formed to assess conditions downgradient of the each of the distribution facilities within the leasehold. NuStar participated in these investigations and was a member of the STTC until 2004. Section 2.3 of the Feasibility Study Report prepared for the STTC provides Revised Cleanup Plan Page 4 NuStar Stockton Terminal-Stockton California November 7,2012 1014-12