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Interwest Construction Co.-Everett Contractor Yard Site Improvements,Everett,WA March 12,2021 <br /> Geotechnical Engineering Report P2184-T20 <br /> Footing Settlements: Assuming that structural fill soils are compacted to a dense or denser state, <br /> we estimate that total post-construction settlements of properly designed footings bearing on <br /> properly prepared subgrades will not exceed 1 inch. Differential settlements for comparably <br /> loaded elements may approach one-half of the actual total settlement over horizontal distances of <br /> approximately 50 feet. <br /> Footing Backfill: To provide erosion protection and lateral load resistance,we recommend that all <br /> footing excavations be backfilled on both sides of the footings and stemwalls after the concrete has <br /> cured. Either imported structural fill or non-organic onsite soils can be used for this purpose, <br /> contingent on suitable moisture content at the time of placement. Regardless of soil type,all footing <br /> backfill soil should be compacted to a density of at least 90 percent(based on ASTM:D-1557). <br /> Lateral Resistance: Footings that have been properly backfilled as recommended above will resist <br /> lateral movements by means of passive earth pressure and base friction. We recommend using an <br /> allowable passive earth pressure of 250 psf for both the glacial outwash and fill on site and an <br /> allowable base friction coefficient of 0.35 for both soil types. <br /> 4.4 Slab-On-Grade Floors <br /> In our opinion, soil-supported slab-on-grade floors can be used in proposed scale house if the <br /> subgrades are properly prepared. We offer the following comments and recommendations <br /> concerning slab-on-grade floors. <br /> Floor Subbase: Generally,structural fill subbases do not appear to be needed under soil-supported <br /> slab-on-grade floors. Surface compaction of slab subgrades is recommended. <br /> If a subbase is required, it should be compacted to a density of at least 95 percent (based on <br /> ' ASTM:D-1557). <br /> Capillary Break and Vapor Barrier: To retard the upward wicking of moisture beneath the floor <br /> slab, we recommend that a capillary break be placed over the subgrade. Ideally, this capillary <br /> break would consist of a 4-inch-thick layer of pea gravel or other clean, uniform, well-rounded <br /> gravel, such as "Gravel Backfill for Drains" per WSDOT Standard Specification 9-03.12(4). <br /> Alternatively,angular gravel or crushed rock can be used if it is sufficiently clean and uniform to <br /> prevent capillary wicking. <br /> Vapor Barrier: We recommend that a layer of durable plastic sheeting(such as Crosstuff,Moistop, <br /> or Visqueen)be placed directly between the capillary break and the floor slab to prevent ground <br /> moisture vapors from migrating upward through the slab. During subsequent casting of the <br /> concrete slab, the contractor should exercise care to avoid puncturing this vapor barrier. <br /> Migizi Group, Inc. Page 12 of 16 <br /> N11G111 IIIIII <br />