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Geotechnical Engineering Evaluation <br />Lyashenko Accessory Dwelling Unit Development <br />Everett, Washington <br />Table 1— 2018 IBC Seismic Design Parameters <br />NGA File No. 1165620 <br />April 10, 2020 <br />Page 4 <br />Site Class <br />Spectral Acceleration <br />Spectral Acceleration <br />Site Coefficients <br />Design Spectral <br />at 0.2 sec. (g) <br />at 1.0 sec. (g) <br />Response <br />SS <br />Si <br />Parameters <br />Fa <br />F, <br />SDS <br />SDI <br />D <br />1.355 <br />0.515 <br />1.000 <br />1.50 <br />0.903 <br />0.515 <br />The spectral response accelerations were obtained from the USGS Earthquake Hazards Program <br />Interpolated Probabilistic Ground Motion website (2008 data) for the project latitude and longitude. <br />Hazards associated with seismic activity include liquefaction potential and amplification of ground <br />motion. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the <br />groundwater table. It is our opinion that the medium dense or better native glacial deposits interpreted <br />to underlie the site have a low potential for liquefaction or amplification of ground motion. <br />Erosion Hazard <br />The criteria used for determination of erosion hazard areas include soil type, slope gradient, vegetation <br />cover, and groundwater conditions. The erosion sensitivity is related to the vegetative cover and the <br />specific surface soil types, which are related to the underlying geologic soil units. The Soil Survey of <br />Snohomish County Area, Washington, by the Natural Resources Conservation Service (NRCS), was <br />reviewed to determine the erosion hazard of the on -site soils. The site surface soils were classified using <br />the NRCS classification system as Everett very gravelly sandy loam, 0 to 8 percent slopes. These soils are <br />listed as having a slight erosion hazard. It is our opinion that the erosion hazard should be low to <br />moderate in areas with vegetated, undisturbed soil. <br />LABORATORY ANALYSIS <br />We performed two grain -size analyses on representative native soil samples obtained from the site. The <br />laboratory tests were performed on samples taken from Test Pit 1 and Test Pit 3 at respective depths of <br />7.5 and 4.5 feet below the existing ground surface. The soil samples tested are classified as loamy sand <br />and sand for Test Pits 1 and 3, respectively, per the USDA Textural Triangle. The result of the sieve <br />analyses are presented in Figures 5 and 6. <br />NELSON GEOTECHNICAL ASSOCIATES, INC. <br />