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DAT L. NELSON AND ASSOCIATES, INC. <br />Consulting Engineering Geology <br />July 13, 1990 _ <br />Project No. 9490 <br />Page 7 <br />and stiff silty fine sands and sandy silt, structural fill or crushed rock. <br />An allowable soil bearing pressure of 4000 psf could be used for foundations <br />placed within the dense to very dense and very hard silts and sands, and <br />glacial till. The suggested soil bearing capacities use a factor of safety of <br />2 and are based on the following conditions: <br />1. All footings should be founded into the native site soils, <br />structural fill, or crushed rock, as described above. <br />2. All footing excavations should be prepared such that a <br />dense, nonyielding, uniform soil condition has been <br />established prior to placement of footing concrete. <br />3. All footings should extend through any existing loose native <br />soil, non-structural fill or modified zones and be placed <br />to bear a minimum of 18 inches below finished adjacent grade. <br />1. All footings should be sized according to the anticipated <br />wall or column loadings, and the above soil bearing values. <br />Minimum footing widths of 11 and 20 inches are recommended <br />for all continuous and isolated footings, respectively. <br />5. All footings should be free of ponded water, sloughed soils <br />and water loosened soils prior to placement of footing <br />concrete. <br />We recommend that footing areas be inspected by a geotechnical consultant <br />prior to placement of concrete to verify that bearing roil type and conditions <br />are consistent with the recommendations of this report. Ground settlements <br />due to structural loads should be less than one (1) inch total and one-half <br />(1/2) inch differential over the building area. <br />During periods of wet weather or in saturated soil conditions, special <br />measures may be required to facilitate construction. Interim excavation <br />grading should be sloped to prevent pending. It should be noted that tho on - <br />site surface soils and weathered zone materials are considered highly moisture <br />sensitive, and may tend to deteriorate if worked during rainy weather or in a <br />saturated condition. Delays in construction activity may result from a <br />deteriorated soil condition. If necessary, the use of a covering of crushed <br />rock or pit run gravel over the subgrade soils is recommended to minimize <br />