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• • Services, Environmental Health Division. Riedel Environmental Services (Riedel Environmental) was subcontracted to perform all soil excavation, tank removal activities and backfilling activities. Testing and Technology performed the tank integrity test on tanks 817B-1 and 817B-3. PRC professionals oversaw all activities and collected soil samples at the site. Ms. Pam Violet from the San Joaquin County Public Health Services, Environmental Health Division, was present during tank removal and soil sampling activities. Throughout field activities, the area was secured with a chain link fence and barrier tape. The specific field activities are described below. Removal of Tank 81713-2 and Soil Sampling Field activities began on April 2, 1992. In the absence of utility site plans, underground utilities were identified using visual cues such as vents, fill pipes, and pump locations. Measurements of product amounts and depth to tank bottom of the UST were also taken at this time. The liquid level inside the tank was measured to be 57 inches from the bottom of the tank. The tank was measured by Navy personnel in early March and only 2'/z inches of liquid were reported at that time. The tank had not been filled with product since that time, as stated by Navy personnel on site, and the liquid appeared to be a water and product mixture. Riedel Environmental requested a liquid pumping truck be sent from Dillard Trucking, Inc. Excavation of the soil and asphalt pavement overlying Tank 81713-2 began. The field team removed the asphalt pavement and soil above the tank to a depth of approximately 3 feet and to a depth of approximately 5 feet on the south side of the tank using a Koehring 6620 excavator (Appendix A, Photo 1). During excavation activities, a pipe was knocked loose from the top east end of the tank. At this time photoionization detector (PID) readings began to range from 0 to > 4,000 parts per million (ppm) adjacent to the excavation. Work was stopped and ambient air concentrations were monitored for total volatile organics. High concentrations continued to register on the PID, and read as high as 6,000 ppm adjacent to the excavation. Concentrations were recorded to be as high as 200 ppm for extended periods of time near occupied buildings, therefore, all station personnel and Yield crew were evacuated from the site. The NCS Stockton fire department was called by station personnel and the excavation was sprayed with a vapor reducing foam (Appendix A, Photo 2). The PID readings of free air concentrations dropped to 0.0 ppm with only a small number of spikes. The fire department sprayed foam on the excavation a total of three times. 5