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JN 90016 <br /> Roth Quality Homes Paqe 10 <br /> January 25 . 1990 <br /> twelve ( 12) inches in loose thickness . The following table <br /> presents recommended relative compaction for structural fill : <br /> Minimum Relative <br /> f F; 11 placement Comoaction <br /> Beneath footings, slabs or 95° <br /> walkways <br /> Behind retaining walls 900 <br /> Beneath pavements 95% for upper 12 inches <br /> of subgrade, 90% below <br /> that level <br /> Where : Minimum Relative Compaction is the ratio . <br /> expressed in percentages , of the compacted <br /> dry density to the maximum dry �density, as <br /> determined in accordance with ASTM Test <br /> Designation D-1557-78 (Modified Proctor ) <br /> Use of On-Site Soils <br /> If grading activities take place during wet weather , site <br /> preparation costs may be higher because of delays due to <br /> rains. The on-site soils are �redominantly silts and <br /> thus are moisture sensitive. Grading operations in the <br /> moisture sensitive site soils will be difficult when the <br /> soil moisture content exceeds the optimum moisture <br /> content. <br /> Because the on-site soils are silts , it is our opinion <br /> that they cannot be reused as structural fill or <br /> retaining wall backfill . Imported granular fill will <br /> therefore be needed for backfill around and under the <br /> residence. <br /> Moisture sensitive soils can also fromsusconstruction <br /> excessive softening and "pumping" <br /> equipment trafEic when the moisture content is qreater <br /> than the optimum moisture content. <br /> Ideally, structural fill which is to be placed in wet weather <br /> should consist of a granular soil having no more than five ( 5 ) <br /> percent silt or clay.particles . The percentage of particles <br /> passing the No.200 sieve should be measured from that portion <br /> of the soil passinq the three-quarter i.nch sieve. <br /> GEOTECH CONSULTANTS , INC. <br />