5200 EVERGREEN WAY SEPA 017 - 010 Geotech Report 2025-04-23

Subsurface Exploration, Geologic Hazards, and Former Brien Ford Preliminary Geotechnical Engineering Report Everett, Washington Geologic Hazards and Mitigations rupture is considered to be low, and no mitigation efforts beyond complying with the current (2015) International Building Code (IBC) are recommended. 6.2 Seismically Induced Landslides The site does not contain substantial slopes, and does not appear to have significant risk of seismically induced landslides, in our opinion. We did not complete a quantitative slope stability analysis as part of this study, and none is warranted for the currently proposed project, in our opinion. 6.3 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibrations, such as those which occur during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of overlying structures. Areas most susceptible to liquefaction include those areas underlain by non-cohesive silt and sand with low relative densities, accompanied by a shallow water table. The native sediments encountered at the site pose a low risk of liquefaction-induced settlements due to the relative densities and lack of free ground water. No quantitative liquefaction analysis was completed as part of this study, and none is warranted, in our opinion. 6.4 Ground Motion Structural design for the project should follow 2015 IBC standards using Site Class "D" as defined in Table 20.3-1 of American Society of Civil Engineers (ASCE) 7- Minimum Design Loads for Buildings and Other Structures. 7.0 EROSION HAZARDS AND MITIGATIONS Project plans will include implementation of temporary erosion controls in accordance with local standards of practice. Control methods will include but are not limited to, use of a perimeter asphalt containment berm, properly surfaced construction entrance, Baker Tanks, silt socks in existing catch basins, construction fencing, continual sweeping of asphalt and concrete surfaces where potential track-out is possible, and straw mulch in exposed areas. During construction, surface water should be collected as close as possible to the source to minimize May 16,2017 ASSOCIATED EARTH SCIENCES,INC. AWR/Id-160594V003-2-Projects\201605941KV1WP Page 7