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r a R & 5 G 4. 0 AVAILABLE CONTAMINATION DATA Of the two underground tanks, the west tank contained gasoline and was operable through 1986. However, the eastern tank, € which also previously contained gasoline, had been decommissioned and subsequently filled with sand. The fill ` tubes were located in the center of the tank. Both tanks had been resting at 12 ft below the surface and were not in t� contact with ground water. Testing other than inventory reconciliation had not been done prior to December 1966 . Until that time no presence of a leak had been indicated. However, in accordance with new laws and regulations, hydrostatic tests were conduce-ed at the end of December, 1986 and as a result of this testing, a leak was suspected in the west tan?c. The volume of gas which leaked was considered to be minimal (based on inventory records and subsequent soil sampling data ) . It is Soil borings performed following leak testing indicated soil !: contamination with benzene, toluene, xylene, and lead centered tinder both tanks (see Table 4-1 ) and was found in highest jD ,i concentration 14 to 15 ft down from the ground surface, although slight contamination was also detected at a depth of ' a 28 ft (directly below the tanks ) . Approximately 120 cubic E-a t ) ' yards of soil was found to be contaminated with volatile hydrocarbon concentrations of an average of 375 parte; per million. When the leak was detected, abandon men-'.-,i rod excavation procedures began. Gas was pumped out of the west tank prior to excavation_ The east tank was opened and ;. emptied of sand (approximately 20 cubic yards ) while still in place. The sand from the east tank was spread evenly in a thin layer on the northwest edge of the property per San Joaquin Air Pollution Control District (APCD) requirements, to enhance volatilization and biodegradation of any residual 4-1