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kn KLEINFELDER <br /> File No. 20-2182-24 <br /> February 20, 1990 <br /> and be recompacted to between 85 and 95 percent of the maximum dry <br /> density as determined by the ASTM D-1557 test procedure at optimum <br /> moisture content. We caution that overcompaction can cause <br /> difficulty in moisture conditioning due to reduced permeability. <br /> Just prior to placing floor slabs or placing nonexpansive <br /> Engineered Fill, the soils should be moisture conditioned to <br /> between 3 to 5 percent over optimum to the depths recommended in <br /> the previous section. Subgrade soils beneath all paving areas <br /> should be compacted to a minimum of 95 percent of the above test <br /> dry density. If any soft soils or pockets of debris are found in <br /> the site stripping or recompaction process, they should be <br /> overexcavated and recompacted, free of debris . <br /> If an imported granular nonexpansive soil is used beneath slabs, <br /> we recommend that the material have a maximum percentage passing <br /> the #200 Sieve of 40, a maximum Plasticity Index of 8, and a <br /> minimum Resistance-Value of 40 . Such imported fill should be <br /> compacted at a moisture content at or near optimum. We recommend <br /> that samples of any proposed imported fill soils be submitted to <br /> the soils engineer for approval prior to being taken to the site. <br /> Engineered Fill should be placed in horizontal layers a maximum of <br /> 8 inches in loose thickness and be compacted to a minimum of 90 <br /> percent of the maximum dry density as determined by the ASTM D- <br /> 1557 test procedure and at a moisture content near optimum. <br /> We recommend that structural and trench backfill be placed in the <br /> same manner as Engineered Fill. In our opinion, trench backfills <br /> 10 <br />