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AET #94-1805 - Page 5 <br /> For the soil correction method, clean granular fill soils are recommended for the entire depth <br /> of the fill sequence, due to the saturation which will occur after the fill has been placed. The <br /> granular fill should contain no more than 5% material finer than a #200 sieve and should <br /> preferably medium to coarse grained. We recommend compaction to a minimum 95% of <br /> standard Proctor density (ASTM:D698). <br /> After the building pad is brought to grade with compacted fill, the foundations can be supported <br /> at normal depth on the fill. All exterior foundations should be extended to a depth of at least <br /> 42" below exterior grade for frost protection. Interior footings in heated areas can be supported <br /> at minimum depth below the floor slab. In unheated building areas, foundations should extend <br /> to a minimum depth of 60" below grade. <br /> Based on the soil conditions encountered at the boring location, and on the minimum fill <br /> compaction levels recommended, it is our opinion the foundations can be designed based on a <br /> maximum allowable soil bearing pressure of 2,000 psf. It is our judgment this design will <br /> include a factor of safety of greater than three against sheer or base failure. It is also our <br /> judgment that total building settlement should be less than 1", and differential settlement should <br /> be less than lh". <br /> Pile Foundation <br /> An alternate foundation method will be to support the structure on a deep foundation system <br /> extending into the underlying clay soils. Considering the relatively low structural loads typical <br /> of construction of this type, driven timber piling may be the most practical deep foundation <br /> system. Such piling would derive their resistance by a combination of end bearing and side <br /> friction in the underlying clay till soils. If a deep foundation system is used, there will be <br /> additional load placed on the foundations due to subsidence and down drag of the compressible <br /> soils along the surfaces of the deep foundations above the underlying stiffer clay soils. For <br /> timber piling, we recommend that you allow at least 10 tons per pile for a drag load of this type. <br />