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Field Sampling Report for San Joaquin County Underground Tank Area Sampling Stockton, California On April 14, 1988, WESTON and their subcontractor, Erickson, Inc., in conjunction with Evans Brothers Inc., removed five undergro4nd fuel storage tanks and gathered soil samples from the bottom of the tank areas. The ROY F. WESTON representative (Erik A. Friedrich) arrived at the sit at 9:30 am. On site were three workers for Evan's Brothers, Inc. (EBI) and two representatives of Erickson, Inc. The EBI crew had excavated a portion of the north west 10,000 gallon unleaded gasoline tank. It was discovered that EBI had not made provisions to obtain the required dry ice. Provisions were made to obtain the ice and it arrived at 11:05 am. The tanks were filled with approximately 15 pounds per 1000 gallon capacity with dry ice. Once filled with dry ice, 02 readings were obtained. By this time both the local health district official and the fire department official were on-site to oversee the tank removal and sampling. At 11:50 am, the 02 reading for tanks T-4 and T-5 (Note: for tank designation, refer to Figure 1) were 11% and 12% respectively. The excavation equipment moved to the location of these two tanks and began removal. At 12:15 pm, tank T-4 was removed and loaded onto the waiting truck. The tank had no visible signs of leakage but a strong solvent odor emanated from the excavation area. At 12:30 pm, tank T-5 was removed and loaded onto the truck. This tank exhibited no visible leakage. The backhoe operator then broke up and removed the bottom con- crete pad and at 12:50 pm. Samples were taken from the tank bottom area. Two soil samples were gathered from each bottom of the tank area. These samples were gathered by driving a thin walled :)rass tube into the soil underneath the fill spout bottom area and center of the tank bottom area. Once the samples were obtained, the tubes were sealed with aluminum foil and plastic end caps. The samples were labeled T-4, T -4b, T-5 and T -5b. The b designation for the sample label signified middle to end of tank area. The samples were to be analyzed or BTX, TPH, EDB and Oroanol6ad. At 12:0 pm, 02 reading for tanks T-2 and T-3 were obtained. Their ovaen levels were 13.9% and 13.6% respectively. At 12:517 pm, an 02 reading was taken for tank T-1. The 02 level was 10.5%. At 1:10 pm, removal of tank T-2 began. During the excavation, noticeable product was observed near the fill spout area and the the bottom sands were gray. At 2:20 pm, samples were taken 17' from the surface underneath the end of tank area