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• � City of Everett � <br /> . • c/o Ron and Kelly Krueger <br /> August 22, 2007 <br /> Page 7 <br /> Structural fill is defined as any fill placeu under the building, behind permanent <br /> retaining or foundation walis, or in other areas where the underlying soils needs to <br /> support loads. This engineer should observe site conditions during and after excavation <br /> prior to placement of any structural fill. <br /> All structural fill should be placed in horizontal lifts with a moisture content at or <br /> near the optimum moisture cont�nt. The optimum moisture content is that moisture <br /> content which results in the greatest compacted dry density. The moisture content of fill <br /> soils is very important and must be closely controlled during the filling and c�mpaction <br /> process. <br /> The allowable thickness of the fill lift will depcnd on the material ty�e, compaction <br /> equipment, and the number of passes made to compact the lift. In no case should the <br /> lifts exceed twelve (12) inches in loose thickness. The followiny table presents <br /> recommended relative compaction for structural fill: <br /> Locatior of Fill Placement Minimum Relative <br /> Compaction <br /> Beneath footings, slabs or walkways 95% <br /> Behind retaining walls 90% <br /> Beneath pavements 95% for upper 12 ir�ches of <br /> Sub-grade, 90% below that level <br /> Where: Minimum relative compaction is the ratio, expressed in percentages, of <br /> the compacted dry density to ths maximum dry density, as determined in <br /> accordance with ASTM Test Designation D-1557-78 (Modified Proctor). <br /> Use of On-Site Soils <br /> If grading activities take place during wet weather, or when the silty, on-site soils <br /> are wet, site preparation costs may b� highe�because of delays due to rains and the <br /> potential need to import granular fill. The on-site soils are generally silty and thus are <br /> highly moisture sensitive. Grading operations will be difficult when the moisture content <br /> of these soils exceeds the optimum moisture content. <br /> Moisture sensitive soils will also be susceptible to excessive softening and <br /> "pumping" from construction equipment traffic when the moisture content is greater than <br /> the optimum moisture content <br /> '7/i L <br /> - —' <br />