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4 . 0 ANALYTICAL RESULTS Results of the analyses for total hydrocarbons show 2600 ,ppm at the north end and ND and 260 ppm for the samples from the south end of the excavation. Caltrans decided to excavate the contaminated soil. On January 21, 1986, OHM, following the second soil excavation, collected two more soil samples, one from the south and one from the north end of the excavation. Because BTX and PCB analyses were negative on the samples from December 12 and 13 , only analyses for total hydrocarbons were performed. Results showed 2400 ppm in the north end and 5000 ppm in the south end of the excavation. Further excavation of approximately 50 cubic yards was performed by OHM on March 3 , 1985. At this time, three more soil samples were collected by OHM personnel, from twelve to eighteen inches below the floor of the excavation. Results of analyses showed 280 ppm in the south, 29 ppm in the middle and 3200 ppm in the north end of the excavation. A summary of information including sample type, dates of collection and analysis, analyses, methods and results are found in Figure 4-1. A diagram showing locations for soil collection is found on Figure 4-2 . The numbers on Figure 4-2 correspond to the sample numbers on Figure 4-1. 5 . 0 BACKFILLING AND COMPACTION In March, 1986 the San Joaquin Local Health District and Caltrans came to an agreement and authorized OHM to backfill the excavation which had now reached a depth of approximately 720 feet. On March 28 and 31, the excavation was filled with approximately 200 tons of structural backfill. The backfill was completed to the surface of the ground and was placed in horizontal uniform layers, not exceeding eight inches in thickness before compaction, and each layer was compacted until a relative compaction of not less than 90 percent was secured. 6. 0 SUMMARY Following the State of California Department of Transportation, District 10 ' s award of Contract Number 10A514 to OHM, one 10, 000 gallon diesel tank was removed. The possibility of leakage from the tank was investigated and contaminated soil was discovered. Two additional soil excavations were made each followed by soil sample collections. With approval of the San Joaquin Local Health District, the excavation was backfilled and the backfill compacted. The excavation, removal, transportation and disposal of the tank and its contents were in compliance with all local, state, and federal regulations.