8525 EVERGREEN WAY BURGER KING 2021-05-10

Geotechnical Engineering Evaluation NGA File No. 998317 Burger King Restaurant Development August 2,2017 Everett,Washington Page 3 In general, all of our borings encountered approximately 2-inhces of surficial asphalt underlain by approximately six to eight inches of loose, dark brown silty fine to medium sand that we interpreted as undocumented fill soils. Directly underlying in all of our explorations, we encountered medium dense to very dense,gray silty fine to medium sand with fine gravel that we interpreted as native glacial till soils. . In Boring 2 at depth, blue-gray silt with fine to coarse sand and gravel was encountered at a depth of approximately 20 feet below the surface. All of our borings were terminated within the native glacial soils at a depth of 20.2 feet below the existing ground surface. Hydrogeologic Conditions Groundwater seepage was not encountered in any exploration, although increased moisture conditions were noted at depth. We interpreted this water to be a perched water condition. Perched water occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of relatively low permeability materials. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched groundwater to decrease during drier times of the year and increase during wetter periods. SENSITIVE AREA EVALUATION Seismic Hazard We reviewed the 2015 International Building Code (IBC) for seismic site classification for this project. Since dense glacially-derived soils are interpreted to underlie the site at depth, the site best fits the IBC description for Site Class D. Table 1 below provides seismic design parameters for the site that are in conformance with the 2015 IBC, which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. Table 1 —2015 IBC Seismic Design Parameters Site Class Spectral Acceleration Spectral Acceleration Site Coefficients Design Spectral at 0.2 sec. (g) at 1.0 sec. (g) Response SS Si Parameters(g) Fa F„ SDS SDI D 1.422 0.546 1.0 1.5 0.948 0.546 The spectral response accelerations were obtained from the USGS Earthquake Hazards Program Interpolated Probabilistic Ground Motion website(2008 data)for the project latitude and longitude. NELSON GEOTECHNICAL ASSOCIATES, INC.