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I I I I I I I I I I I I I I I I I I I Transport Tire, Inc. -8- March 1, .1983 The fill materials should be placed in loose lifts not exceeding 6 to 12 inches in thickness, depending on the type of compaction equipment used. The lifts should be mechanically compacted to at least 95% of the maximum laboratory Modified Proctor dry density (ASTM D-1557). The moisture content of the fill material should be within +2% of the optimum moisture as determined by ASTM D-1557 in order to obtain the best compaction characteristics. Compacted fill beneath footings should extend laterally beyond the edges of the footings a minimum horizontal distance of 1 foot for each vertical foot of fill placed beneath the footings. This lateral fill placement is required to provide sufficient lateral support for compacted fill. This means that, if 4 ft of fill is replaced over the natural fine sand and silt at approximately +895 and assuming a footing width of 2 ft, the lateral width of the footing trench should be on the order of 10 ft at the base of the excavation (i.e. +895). A net allowable soil bearing pressure of 3,000 psf may be used to proportion spread footings bearing in properly placed and compacted backfill. Alternative 4 - Alternative deep foundation systems such as driven piling or drilled piers could be used. Additional recommendations for deep foundation design can be provided if so desired. The cost of a deep foundation alternative may be prohibitive. STS Consultants, Ltd.