7200 HARDESON RD 2016-01-01 MF Import

� CNA Architecture Group 12 April 1991 � W-7352 Page 8 compaction. Structural fili :;iiould be placed in lifts not exceeding 8 inches in loose thickness. Individual lifts should be mechanically compacted to a uniform density of at least 95 percent of tl;e modified Proctor maximum dry density (ASTM:D-1557). The suitability of soil for structural fill use depends primarily on the gradation and moisture of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 Sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. Soils containing more than about 5 percent fines by weight, such as the bulk of the site soils, cannot be consistently compacted to a firm, dense, nonyielding condition if the moisture content is more than a few percent above the ootimura� moisture content. Structural fill should consist of a predominantly granular soil, free of organics and other deleterious material, with a maximum size of about 6 inches. Most fill soils encountered in the test pits contained more ti�an 5 percent fines and possessed elevated moisture contents relative to their possible reuse as structural fill. Therefore, in order to reuse existing fill material, considerable drying and moisture conditioning prior to use as a structural fill may be required. If grading must take place when onsite materials are too wet to compact, the soils should be permitted to dry, prior to placement of additional structural fill. This may require scarification, aeration or windrowing the material such that the moisture content can be Iowered. If, owing to moisture or wet weather conditions, the site soils cannot be dried back adequately, they should be removed and replaced with import fill. In order to expedite filling in w•et site conditions, if the onsitc; silty materials cannot be used, imported fill should contain no more than 5 percent by weight passing the No. 200 Sieve, when measure on the U.S. No. 4 Sieve fraction. Soilc of this gradation may be successfully compacted under a wider range of weather conditions. However, even with material of this type, delays in grading due to inclement weather can still occur. i