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UST Closure Report Sharpe Defense Distribution Region West Lathrop,California Page 23 7819 Crane Road, Oakdale, CA, 95361 (telephone: (209) 845-2117). The trucks transported a total of 64 loads of the soil (or about 780 cy) to the UST excavation where it was dumped, then spread with the Caterpillar DSM bulldozer. The first lift of stockpile SPD soil was compacted to a depth of 65 inches below final surface grade with the Bomag sheep's foot drum roller compactor. The two, sand cone compaction tests conducted by Kleinfelder on March 5 on the east and west sides of this lift indicated the degree of compaction of the native fill was 94.9% and 94.0%. The second lift of the stockpile SPD soil was compacted to a depth of 36 inches below surface grade. Sand cone compaction tests on the south and north sides of this lift on March 5 indicated the native material was compacted to 98.2% and 94.3%. The remainder of the UST excavation, from a depth of 65 inches to surface grade, was backfilled with about 589 tons of 3/4 inch aggregate base Class 2 fill material. The aggregate base was transported by G.C.U. Trucking from the Teichert & Son's plant in Tracy, California to the site on March 5 and 8. The aggregate base fill was placed in the excavation in a series of four compacted lifts on March 5 and 8. The Volvo frond-end loader moved the material from the temporary stockpile of aggregate base just northwest of the excavation, to the edge of the excavation. The caterpillar bulldozer was used to spread the fill and the Bomag drum roller to compact it. The top surfaces of the compacted lifts were at depths of 28, 20, 12 and 0 inches below surface grade. Two sand cone compaction tests were conducted on each lift of fill by Kleinfelder, Inc. The compaction ranged from 94.8% to 98.4%; the average of the results from the eight tests was 96.9% compaction. Two lifts of 3/4 inch aggregate base, Class 2 imported from Teichert & Sons were used on March 4 to backfill the 3 to 4 foot-deep trenches excavated to expose and remove the product and vapor return piping. The fill was placed in the trenches with the Volvo front-end loader. It was compacted with the Bomag sheep's foot drum roller by making passes with the compactor a right angles to the direction of trench elongation. The depth to the upper surface of the first lift, after compaction was 18 inches. The top of the second lift of backfill was at surface grade. Kleinfelder, Inc. conducted two, sand cone compaction tests of each lift. The first lift achieved 98.7 and 98.1% compaction, the second, 97.9 and 98.1%. The upper surfaces of the final lifts of aggregate base fill in the UST and piping excavations were graded to match the existing grades surrounding the excavation by `back-blading' in three directions with the Volvo front-end loader on March 8 and with a John Deere loader on March 12. The very fine grained soil that had accumulated on the concrete and asphalt paving in the area immediately surrounding the backfilled excavation was scraped from the pavement with a John Deere loader on March 12. The pavement was then swept with numerous passes of a Bob Cat sweeper. The sweepings were placed on the final lift of aggregate base backfill in the excavation. N:\PROJECTS\3546\Reports\3546 UST Closure Report Draft.doc March 24,1999