4937 EVERGREEN WAY QFC FUELING STATION Geotech Report 2023-02-17

Geotechnical Engineering Report 10 January 7,2020 QFC 852 Fuel Station,Everett, Washington RGI Project No.2019-258A the wall face. A typical retaining wall drainage detail is shown on Figure 3. The retaining wall foundation subgrade should be supported on competent native soil. With wall backfill placed and compacted as recommended, and drainage properly installed, RGI recommends using the values in the following table for design. Table 5 Retaining Wall Design Design Parameter Value Allowable Bearing Capacity— Native soil or 2,500 psf structural fil Active Earth Pressure (unrestrained walls) 35 pcf At-rest Earth Pressure (restrained walls) 50 pcf For seismic design, an additional uniform load of 7 times the wall height (H) for unrestrained walls and 14H for restrained walls should be applied to the wall surface. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in the Section 5.3. 5.6 SLAB-ON-GRADE CONSTRUCTION Once site preparation has been completed as described in Section 5.2, suitable support for slab-on-grade construction should be provided. Immediatelybelow the floor slab, RGI recommends placinga 4-inch-thick capillary break p Y layer of clean, free-draining pea gravel, washed rock, or crushed rock that has less than 5 percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter- thick plastic membrane should be placed on a 4-inch-thick layer of clean gravel or rock. For the anticipated floor slab loading, we estimate post-construction floor settlements of %- to 'A-inch. For thickness design of the slab subjected to point loading from storage racks, RGI recommends using a subgrade modulus (Ks) of 150 pounds per square inch per inch of deflection. 5.7 DRAINAGE 5.7.1 SURFACE Final exterior grades should promote free and positive drainage away from the building area. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. For non-pavement locations, RGI recommends providing a minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the II 1 IIII L- RILEYGROUP