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dv. ♦y S S .�'e f '�� � �'��A <br /> f <br /> r "1 <br /> 4 .0 AVAILABLE CONTAMINATION, DATA <br /> Of the two underground tanks, the west tank contained gasoline <br /> f and was operable through 1986. However, the eastern tank, <br /> which also previously contained gasoline, had been . <br /> k ' decommissioned and subsequentll Billed with sand. The fill <br /> tubes were located in the center of the tank. Both tanks had <br /> f been resting at 12 ft below the surface and were not in <br /> contact with ground water. <br /> t� <br /> Testing other than inventory reconciliation had not been done <br /> F_ prior to December 1986. Until that time no presence of a leak <br /> had been ,indicated. However, in accordance with new laws and <br /> }'3 regulations, hydrostatic tests were conducted at the end of <br /> December, 1986 and as a result of this testing, a leak was <br /> , . suspected in the west tank. The volume of gas which leaked <br /> # ,. <br /> was conzidcrad to be minimal (based on inventory records and <br /> subsequent soil sampling data) . <br /> Soil borings performed following leak testing indicated soil <br /> ;i _ <br /> z }# contamination with benzene, toluene, xylene, and lead centered <br /> # under both tanks ( see Table 4-1 ) and was found in highest <br /> IT concentration 14 to 15 ft down from the ground surface, <br /> although slight contamination was also detected at a depth of <br /> 28 ft (directly below the tanks ) . Approximately 120 cubic <br /> yards of soil was found to be contaminated with volatile <br /> hydrocarbon concentrations greater than 357 parts per million. <br /> ' When the leak was detected, abandonment and excavation <br /> procedures began. Gas was pumped out of the west tank prior <br /> to excavation. The east tank was opened and emptied of sand <br /> (approximately 20 cubic yards) while still in place. The sand <br /> from the east tank was spread evenly in a thin layer on the <br /> t■ northwest property the of edge g p y per San Joaquin Air Pollution <br /> Control District (APCD) requirements, to enhance <br /> 4-1 <br />