8407 BROADWAY SECURE SPACE STORAGE Geotech Report 2025-04-24

ZipperGeo Broadway Everett Expansion GeoprofessionalConsultants Project No. 2601.01 July 7, 2022 constructed through previous legal grading activities associated with construction of the I-5/SR526 offramp. Additionally, we observed no obvious signs of instability on this slope and this slope will not be disturbed during construction. The Code requires a buffer and building setback between the face of footings and the top of landslide GHAs. The Code indicates that the buffer should be the minimum stated in the IBC. However, the Code allows for a lesser buffer provided that a specific rationale and basis for the reduced buffer is clearly articulated in a geological assessment. Assuming the maximum slope height of the landslide GHA is about 30 feet, the minimum buffer per IBC would be about 10 feet (the smaller of H/3 or 40 feet). The Code requires a minimum 10 foot building setback from the edges of critical area buffers. As such, the total minimum buffer plus setback to the face of building would be about 20 feet. As currently proposed, the south face of the building will be setback from the top of the landslide hazard GHA a distance of about 45 to 50 feet. The currently proposed building location meets the minimum buffer and setback requirements outline in the Code. Additionally, it is our opinion the proposed project will not adversely impact the stability of the landslide hazard GHA provided that the project is designed and constructed in accordance with the recommendations presented in this report. Seismic Hazards Seismic Hazards include soil liquefaction and ground surface fault rupture. The EMC defines seismic/liquefaction hazards per Dames and Moore, 1991, and those mapped as high and moderate to high liquefaction susceptibility on the Liquefaction Susceptibility Map of Snohomish County, Washington, Washington State Department of Natural Resources, Palmer, Stephen, et al., September, 2004. Fault Ground Surface Rupture: Based on our review of the USGS Quaternary age fault database for Washington State, an inferred fault trace of the Southern Whidbey Island fault zone is located approximately 2.8 miles southwest of the project site.As the fault zone does not appear to cross the site, it is our opinion that the risk of ground surface rupture at the site is low. Soil Liquefaction: Liquefaction is a phenomenon wherein cohesionless soils below the groundwater table build up excess pore water pressure during earthquake loading. Liquefaction typically occurs in loose, cohesionless soils located below the groundwater table. The potential hazardous impacts of liquefaction include liquefaction-induced settlement and lateral spreading. Seismic Hazard areas as defined by Dames and Moore in the EMC are mapped on the Critical Areas Map 4, Liquefaction (Seismic) Susceptibility.The site is mapped as not having liquefaction potential. Based on soil and groundwater conditions observed in our borings,we concur with the EMC mapping. IBC Seismic Site Class Definition We understand the City of Everett currently adopts the 2018 International Building Code (IBC). Determination of IBC seismic design parameters requires a Site Class Definition determined in accordance with Chapter 20 of ASCE 7. Based on soil conditions observed in our borings and mapped geologic conditions, we recommend Site Class C be used for determination of IBC seismic design parameters. 5