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e <br />Harmon 3 Associates � W-4545 , <br />lh April 1985 Page 7 <br />southwest building is relocated directly north on the order of 50-100 feet, <br />contingent an the recortunended site preparation procEdures outlined herein. <br />_ conventional spread footings at higher elevations can•be used for foundation <br />support of the planned liyht to moderately loaded buildings. Spread footings may <br />be founded on stri�ctural fill or medium dense to very dense glacial t�ill <br />(described in Section 4.0). Based on the test pits excavated for this study, we <br />recommend that an allowable bearing pressure of 2500 psf be used for weathered <br />giacial till or gtructural fill compacted to 90 percent of the modified Proctor <br />value. A value of 6000 psf may be used for the very dense, grey, unweathered, <br />glacial till. A one-third increase of the allowable bearing capacity values <br />would be�available to accommodate seismic or transient loads. <br />All footinys should have a minimum width of 18 inches. Foundations should extend <br />at least 18 inches below adjacent ground or slab surfaces (whichever is lower) <br />for frost protection. Interior footings need only be 12 inches below slab <br />surface"s. No footings should be founded in, or above, loose/soft native soils. <br />organic-rich material. or any existiny or uncompacted fill. If such materials <br />are present at or below footing grade. they should be removed and replaced with <br />properly compacted structural fill. Failure to remove such material may result <br />in exces�ive foundation settlement. <br />Based on the above allowable beariny pressures. future settlements may be on the <br />order of 1/2 inch with differential settlements equal to that total. Considering <br />the total load.associated with a four-story building, we recommend placing all <br />footinys for the northeast buildiny upon material with the same load bearing •-�. <br />capacity. Thts is a precautionary measure which should help minimize <br />differential settlement of the foundation. If loose or soft materiats are left <br />►vithin the foundation area prior to concrete placement. settlements may be <br />inGreased. Therefore. it would be appropriate to have all footing conditions �f <br />� the subgrade observed by ttie soils engineer or his representative immediately <br />prior to concrete placement. Because the onsite soiis are moisture-sensitive. it <br />may be expedient to provide a layer of rocks. quarry spalls or a lean concrete <br />