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4.7.3.Structural Fill <br /> All fill, whether existing on-site soil or imported soil, that will support floor slabs, foundations, pavement <br /> areas, or be placed in utility trenches should generally meet the criteria for structural fill presented below. <br /> The suitability of soil for use as structural fill depends on its gradation and moisture content. <br /> 4.7.3.1.Materials <br /> Materials used to construct the building addition and underground utility trenches,and to construct access <br /> roads and surface parking areas are classified as structural fill for the purpose of this report. Structural fill <br /> material quality varies depending upon its use as described below: <br /> 1. Structural fill placed below all building elements should consist(,-)" (ported Gravel Borrow,as described <br /> in Section 9-03.14(1) of the 2020 WSDOT Standard Spen;I-I,› ions, with the additional requirement <br /> that the fines content be limited to no more than 5 percr,o . <br /> 2. Structural fill placed to construct at-grade parkin . ,iieas and to kfill utility trenches in the dry <br /> summer months may consist of imported Comm.cli 'arrow per WSDOT ,-i lion 9-03.14(3) provided no <br /> particles are larger than 3 inches and the soil I r'oisture conditioned within 2 percent of the optimum <br /> moisture content for the required compaction. li ;tructural fill is placed chi,ing wet weather, the <br /> structural fill should consist of imported gravel borru',. <br /> 3. Structural fill placed within utility t and below p: ,,;silent and sidewalk areas may consist of <br /> suitable on-site soils, if earthwork is a, nil ;!red during th Iry season (June through September). If <br /> earthwork is planned during the wet se& n (Oui ;H'r through M a !structural fill for trench backfill and <br /> site grading should meet the requirement of Gravel isms row, as db :1!bed in Section 9-03.14(1) of the <br /> 2020 WSDOT Stands etions. <br /> 4. Structural fill plact..I wound perurl>ter footing drains should consist of washed 3/8-inch to No. 8 pea <br /> gravel per Section 9-0 - l(4)C Grz -ling No. 8, or conform to Section 9-03.12(4) of the 2020 WSDOT <br /> Standard Specifications. <br /> 5. Struct, CSBC below should conform to Section 9-03.9(3) of the 2020 <br /> Wsouf Standard Spe ‘icil;etions. <br /> 6. Structu. 11 fill placed as cap;iLwy break fk low slabs should consist of 1-inch-minus clean crushed rock <br /> with neglibiiil sand or silt in c orlformanc.- .:ith Section 9-03.1(4)C,grading No. 67 of the 2020 WSDOT <br /> Standard Spc -.ations. <br /> 4.7.3.2.Reuse of On-site i\t,ltive Soils <br /> The fill and glacial till soilb ,: ,nt liri .1 high percentage of fines and will be sensitive to changes in moisture <br /> content and difficult to handle lnd compact during wet weather.The fill and glacial till deposits should not <br /> be considered for reuse as structural fill during the wet season (September through May) or during wet <br /> weather. On-site fill and glacial till soils may be reused, if suitable, as structural fill if they can be properly <br /> compacted. Imported structural fill consisting of sand and gravel (WSDOT gravel borrow)should be planned <br /> under all building foundation elements. <br /> 4.7.3.3.Reuse of Existing Asphalt,Base and Concrete Rubble <br /> Existing asphalt pavement and PCC rubble may be reused as structural fill if properly crushed during <br /> demolition. Recycled PCC rubble and base course materials may be reused as structural fill throughout the <br /> project, including under the building addition slabs. Recycled asphalt may be used under new pavement <br /> GEOENGINEERSI December6,2021 Page9 <br /> File No.24459-003-00 <br />