7800 EVERGREEN WAY HYUNDAI Wetland Report 2025-08-05

4.7.3.Structural Fill All fill, whether existing on -site soil or imported soil, that will support floor slabs, foundations, pavement areas, or be placed in utility trenches should generally meet the criteria for structural fill presented below. The suitability of soil for use as structural fill depends on its gradation and moisture content. 4.7.3.1. Materials Materials used to constructthe building addition and underground utility trenches, and to constructaccess roads and surface parking areas are classified as structural fill forthe purpose of this report. Structural fill material quality varies depending upon its use as described below: 1. Structural fill placed below all building elements should consistof imported Gravel Borrow, as described in Section 9-03.14(1) of the 2020 WSDOT Standard Specifications, with the additional requirement that the fines content be limited to no more than 5 percent. 2. Structural fill placed to construct at -grade parking areas and to backfill utility trenches in the dry summer months may consist of imported Common Borrow per WSDOT Section 9-03.14 (3) provided no particles are larger than 3 inches and the soil is moisture conditioned within 2 percent of the optimum moisture content for the required compaction. If structural fill is placed during wet weather, the structural fill should consist of imported gravel borrow. 3. Structural fill placed within utility trenches and below pavement and sidewalk areas may consist of suitable on -site soils, if earthwork is accomplished during the dry season (June through September). If earthwork is planned duringthe wetseason (Octoberthrough May) structural fill for trench backfill and site gradingshould meetthe requirements of Gravel Borrow, as described in Section 9-03.14(1) of the 2020 WSDOTStandard Specifications. 4. Structural fill placed around perimeter footing drains should consist of washed 3/s-inch to No. 8 pea gravel per Section 9-03.1(4)C Grading No. 8, or conform to Section 9-03.12(4) of the 2020 WSDOT Standard Specifications. 5. Structural fill placed as CSBC below pavements should conform to Section 9-03.9(3) of the 2020 WSDOT Standard Specifications. 6. Structural fill placed as capillary break below slabs should consist of 1-inch-minus clean crushed rock with negligible sand or silt in conformance with Section 9-03.1(4)C, grading No. 67 of the 2020 WSDOT Standard Specifications. 4.7.3.2 Reuse of On -site Native Soils The fill and glacial till soils contain a high percentage of fines and will be sensitive to changes in moisture content and difficultto handle and compact during wetweather. The fill and glacial till deposits should not be considered for reuse as structural fill during the wet season (September through May) or during wet weather. On -site fill and glacial till soils may be reused, if suitable, as structural fill if they can be properly compacted. Imported structural fill consistingof sand and gravel (WSDOTgravel borrow) should be planned under all building foundation elements. 4.7.3.3. Reuse of Existing Asphalt, Base and Concrete Rubble Existing asphalt pavement and PCC rubble may be reused as structural fill if properly crushed during demolition. Recycled PCC rubble and base course materials may be reused as structural fill throughoutthe project, including under the building addition slabs. Recycled asphalt may be used under new pavement GEOENGINEER� December6,2021 Page9 File No. 24 59-003-00