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� , <br />. � • <br />' Page 7 - #4220 92-4026 <br /> Fill to replace the excavated soils must consist of a relatively ciean sand with less than 5�9 fines if it is <br />' to be placed below the water tabie. This clean type of sand should be used up to at least 2' above the <br /> groundwater level. Additional fill, as.required, should preferably consist of a relatively clean sand with <br /> less than 12% fines. This would consist of a soil classified as an SP or SP-SM sand. This fill should <br /> be placed in thin lifts for approximately 6" to 9" and compacted to at least 95% of the Standard Proctor <br /> density. A soil containing more fines could be used above the clean sand, but wouid be more di�cult � <br />� to place and compact and it would be necessary to control the moisture content. The fill should be <br /> compacted to at least 95% of the Standard Proctor density within 29'a of the optimum moisture content. <br /> Based on the finished floor elevations and the estimated excavation depths, approximately 7' of fill will _ <br />� be required on the average in the building pad azeas. <br /> 3.4 Foundation Recommendations <br /> Based on the soil conditions encountered at the boring locations, we judge that a spread footing <br /> foundation system would be the most economical method of foundation support. In our opinion, the <br /> natural soils encountered at the minimum excavation depth of footings placed�on a controlled eompacted <br /> fill placed as previousiy indicated, are competent for an allowable bearing pressure of up to 2000 pounds <br /> per square foot. Minimum footing width should be 16" and 24" for continuous and isolated column � <br /> footings, respectively. This minimum footing width should be provided even if this resuits in a bearing <br /> pressure on the soil of less than the recommended 2000 pounds per square foot maximum. Minimum <br /> footing burial depth should be 3-1/2' below exterior grade for the perimeter footings. For unheated areas <br /> and buildings, this minimum burial depth should be increased to at least 5'. Interior footings may be <br />� place� at a minimai depth below the finished floor siab oc to frost depth�if winter constructiot� is � <br />� proposed. _ . � . . <br /> twin cit� test�nq <br />' � --------.__ <br />