10312 EVERGREEN WAY SONIC Geotech Report 2023-05-25

Geotechnical Engineering Report 4 January 8,2021 Glint Car Wash and Sonic Everett,Everett,Washington RGI Project No.2020-643-1 • Structures on Site Class E sites with Ss greater than or equal to 1.0,provided the site coefficient Fa is taken as equal to that of Site Class C. • Structures on Site Class D sites with Si greater than or equal to 0.2, provided that the value of the seismic response coefficient Cs is determined by Eq.12.8-2 for values of T 5 1.5Ts and taken as equal to 1.5 times the value computed in accordance with either Eq.12.8-3 for Ti z T>1.5T5 or Eq.12.8-4 for T>TL. • Structures on Site Class E sites with Si greater than or equal to 0.2, provided that T is less than or equal to Ts and the equivalent static force procedure is used for design. The above exceptions do not apply to seismically isolated structures,structures with damping systems or structures designed using the response history procedures of Chapter 16. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil's strength. RGI reviewed the soil conditions encountered during field exploration and assessed the potential for liquefaction of the site's soil during an earthquake. Because the site is underlain by glacially consolidated deposits and lacks an established groundwater table, RGI considers the potential for liquefaction of the site soils to be minimal. 4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the conditions observed on the site, RGI considers that there are no geological hazards related to the site. 5.0 Discussion and Recommendations 5.1 GEOTECHNICAL CONSIDERATIONS Based on our study, the site is suitable for the proposed construction from a geotechnical standpoint. However, the loose fill is not suitable for directly supporting the proposed building foundation and pavement. RGI recommends that the building foundations be supported on 18 inches of structural fill. Slab-on-grade and pavement can be supported on 12 inches of structural fill. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. Corporate Office 17522 Bothell Way Northeast Bothell,Washington 98011 Phone 425.415.0551• Fax 425.415.0311 1414 '.riles-group.corn