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FINAL REPORT--MID-CAL LEASING 1634 E. Channel 8t*CXton, Ca 95205 TANK REMOVAL One underground 300-gallon waste oil, tank was removed from inside the premises of Mid-Cal Leasing by Thorpe Oil Co. in January, 1989 . This tank had been used to collect and store used oil drained from delivery and freight trucks operated by Mid-Cal. Soil samples collected at the time of tank removal had total petroleum hydrocarbon concentrations as high as 8500 ppm. An estimated 3 . 5 cu. yds, of contan3_nated soil were returned to the tank cavity after removal of the tank. SITE ASSESSMENT This site was subsequently placed in the San Joaquin County Local Oversight Program, and San Joaquin EHD requested Mid-Cal to submit a workplan for site assessment. On 2 May 1991, Geological Audit Services submitted to EHD a Site Contamination Workplan to reexcavate the tank cavity, remove and dispose of the contaminated soil, and replace it with clean fill. The workplan was approved by Mr. Stephen Schneider of EHD in early June. Excavation took place in four phases and was performed by Falcon Energy under the supervision of Geological Audit Services, who also performed the soil sampling. Initial excavation took place on 21 June 7991, utilizing a backhoe to excavate a cavity measuring approximately 12 ft long x 10 ft wide x 16 ft deep. An excavator was used in the second phase to deepen the cavity to 21 ft on 27 June. In the third phase, which took place on 16 July, the backhoe enlarged the cavity to approximately 15 ft long x 12 ft wide. The rr final phase occurred on 2 August, when the excavator was used co remove additional soil from the western corner of the excavation. In total, approximately 180 cu. yds. of soil were removed and stockpiled in two piles adjacent to the tank cavity. A total of 13 soil samples were collected and analyzed fol contamination during the site assessment. These are listed beled: Phase I--Sample GOT-1 was collected from a depth of approx1rdtely 9 ft and was sent to NET Pacific under chain of custody for analysis of aquatic toxicity using the 96-hour €ath,ad minnow test. Phase II--Sample MCT-1 was collected from the floor of the excavation at a depth of approximately 21 ft and sent to Western Environmental Science and Technology (WEST) for analysis of TPH-g, TPH-d, motor oil, BTE&X, chlorinated hydrocarbons, PCB's, and five priority metals, in accordance with Tri-Regional Board recommendations for waste all tanks.