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

Zi pperGeo Broadway Everett Expansion Geoprofessional Consultants Project No. 2601.01 July 7, 2022 CONCLUSIONS AND RECOMMENDATIONS General Considerations Based on the subsurface conditions encountered and described in previous sections, in our opinion the proposed development is feasible from a geotechnical perspective and structures can be supported on conventional shallow foundations supported as recommended in this report. Our geotechnical engineering conclusions and recommendations are presented below. The recommendations contained in this report are based upon soils encountered in our explorations, the results of field and laboratory testing(which are presented in Appendices A and B), engineering analyses, and our current understanding of the proposed project. Geologically Hazard Areas Chapter 19.37-Regulations for Environmentally Critical Areas of the Everett Municipal Code (the Code) categorizes Geologically Hazardous Areas (GHAs) as Erosion Hazard; Landslide Hazard; Seismic Hazard; and Other geological areas which the city has reason to believe are geologically hazardous. The reader is referred to the Code for specific definitions of GHAs. The GHAs are defined by the Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett, Washington: July 1, 1991 (Dames and Moore). As part of our services, we performed an evaluation of the presence or absence of GHAs at the project site. The following paragraphs present the results of our evaluation and further discussion. Erosion Hazard The Code Chapter 19.37.080(3) classifies erosion hazards using the Dames and Moore methodology as medium to very high/severe erosion hazard areas based on geologic, topographic, and other factors. Areas defined as medium risk of erosion consist of slopes of 25 to 40 percent in geologic units other than Qva or Quaternary alluvium (Qal). The Everett Erosion Hazard Map shows the slope south of the site between the site and 1-5 as a medium erosion hazard. We concur with the mapping. It is our opinion the risks associated with erosion hazards can be adequately mitigated through the preparation and execution of a properly prepared temporary erosion and sedimentation control plan and maintenance of TESC BMPs during construction. Landslide Hazard Landslide hazard areas, according to the Code, are areas defined by the Dames and Moore Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett, Washington:July 1, 1991.The Code classifies potential landslide risk from very high to medium risk based on a combination of geologic, topographic, and hydrologic factors. Based on our review of the Code and existing site conditions,the slope which borders the site to the south appears to meet the criteria for a high landslide risk GHA. However, it appears that the slope was 4