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-9~- <br />• tcry borings during drilling or when checked several days <br />follouic;g drilling. The soils are generally slightly moist to <br />n~oist. <br />Results of the swell-consolidation tests shown on Figs. 6 <br />through 14 indicate erratic volume change potential under condi- <br />tions of loading and wetting. The lower density soils generally <br />showed moderate to high compressibility and the higher density <br />clays showed a nil to moderate expansion. The shear testing, <br />Figs. 15 and 16, indicate the soils have moderate shear <br />strength. Results of gradation analyses performed on shall <br />diameter drive samples of the subsoils (minus 1 1/2-inch <br />fraction) are shown on Figs. 1j, 18 and 19. Atterberg limit <br />testing indicates the fine-grained portion of the subsoils is <br />• typically a silty clay witk~ loiJ to medium plasticity. Results of <br />the permeability tests and percolation tests, presented on <br />Table I and Table II, indicate t".e soil has a relatively low to <br />moderate infiltration rate. The percentage oC water soluble <br />sulfates determined on several samples is relatively low. <br />FOUPIDATION RECOt•Ih1END.ATIONS <br />Several types of possible foundation systems have been con- <br />sidered for support of the dewatering structure and thickener. <br />The natural soils encountered near proposed construction pad <br />level consist of a combination of sandy clay and clayey sand and <br />gravel that generally have moderate strength but erratic volume <br />change characteristics, especially when wetted. In their natural <br />. relatively low moisture condition the soils tested exhibit low <br />Chen &;lssociates <br />