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SP86-009 Printing Enterprises, Inc. - 7 - March 24, 1986 filling. Thus, if fill below water is required, we recommend that it be of a clean, coarse, granular nature, with less than 10% passing the #200 sieve. The clean sand fill should be placed in the excavation to a height 1 to 2 feet above the drawn down water surface. Then, the fill should be compacted by repeated passes of a large vibratory compactor. To minimize the risk of trapped deleterious soils below the fill, the excavation should begin in the area of the shallowest depth of excavation and proceed to the deeper areas. Depending on the results of excava- tion observations, it may be necessary to take borings through the fill to provide additional evaluation of the completness of the excavation. The fill above the clean, coarse sand could con- sist of any mineral soil. Above ground water level, all fill should be compacted in thin lifts with a large vibratory compac- tor. Compaction to a minimum of 93% of modified Proctor density would produce a fill capable of supporting on-grade slabs and footings designed to exert a bearing pressure of 3000 pounds per square foot (psf). Boring B-6 was performed in a possible borrow source area. It is our opinion that the Clayey sand encountered in this boring is sui table as fill material above water level. However, if these soils are wet or should they become wet, attaining adequate com- paction may be difficult. Some disking and drying may be required. C.3. b. Pile Foundation: In view of the significant depths of excavation required and the high ground water level, a pile foun- dation may be more economical than excavating and backfilling. It may be possible to support a portion of the building on driven piles while supporting the remaining portion on spread footings lORIIUD'i