3620 36TH PL NE 2018-01-02 MF Import

impossible to compact as structural fill. The on -site native soils should not be planned for use as structural fill under the compost system pads or other structural areas. Significant drying during the dry summer months will be needed if they are being considered elsewhere as structural fill, such as for enhancing the flood protection berms. Currently, the moisture content of the native soils is significantly over optimum and will require long hot days to dry sufficiently. If significant quantities of existing granular fill, such as sand/gravel and/or quarry spalls, are encountered and the contractor is able to separate this material during grading, then these granular fill soils may be reused as structural fill provided that they can be properly compacted. These materials should be covered with plastic sheeting if they are stockpiled for later use. Fill soils contaminated with wood chips, other organic debris, or significant fine-grained soils should not be planned for reuse as structural fill. 4.2.7 Fill Placement and Compaction Criteria Structural fill should be mechanically compacted to a firm, non -yielding condition. The structural fill should be placed in lifts. The lift thickness should be sufficiently thin so that following compaction, the entire lift meets the compaction criteria recommended below. Each loose lift thickness should not exceed 1 foot. Each lift should be conditioned to the proper moisture content and compacted to the specified density before placing subsequent lifts. Thinner loose lifts may be needed :o achieve compaction depending on the actual compaction equipment. Structural fill should be compacted to the following criteria: • Structural fill placed to raise site grades in areas where no proposed structures are planned should be compacted to at least 90 percent of the maximum dry density (iVIDD) per ASTM D1557. • Structural fill placed below proposed structures should be compacted to at least 95 percent of the MDD per ASTM D1557. • Structural fill placed for crushed surfacing base course below paveme,as should be compacted to at least 95 percent of the MDD per ASTM D1557. a Structural fill placed within 2 feet of the pavement section subgrade elevation should be compacted to at least 95 percent of the IvIDD per ASTM D1557. • Structural fill placed as slab on grade capillary break material should be compacted to at least 95 percent of the IvIDD per ASTIVI D1557. • Structural fill placed to construct the flood control berms around the site should be compacted to at least 90 percent of the MDD per ASTM D1557. • Fill placed as preload fill should be compacted to the extent necessary to allow access for construction equipment. • Fill placed in landscape areas and other areas where no settlement sensitive improvements will be located should be compacted to at least 85 percent of the MDD per ASTM D1557. The recommendations presented in this section are for the placement of structural fill during the dry season. See the Section 4.2.8 for recommendations for performing work during the wet season or periods of wet weather. 77 G e 0 E n g i n e e r s 12 File No. 10625-001-02/123003