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Geotechnical Engineering Evaluation NGA File No. 1322621 Clark Garage Slope February 4,2022 Everett,Washington Page 5 ""Landslide hazard areas" means areas potentially subject to mass earth movement based on a combination of geologic, topographic, and hydrologic factors, with a vertical height of 10 feet or more. These include the following: (1) Areas of historic landslides as evidenced by landslide deposits, avalanche tracks, and areas susceptible to basal undercutting by streams, rivers or waves; (2) Areas with slopes steeper than 33 percent which intersect geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock, and which contain springs or ground water seeps; (3) Areas located in a canyon or an active alluvial fan, susceptible to inundation by debris flows or catastrophic flooding." Based on the findings of our explorations it is our opinion that the steep slopes within this site do not meet the above criteria for classification as a landslide hazard area. Our explorations and observations indicate that the core of the site slopes consists primarily of medium dense or better native glacial till soils at depth. Inclinations up to 31 degrees on the site slopes indicate high strength and internal friction angle within the underlying soils. Relatively shallow failures as well as surficial erosion are natural processes and should be expected on the steeper site slopes especially within the loose surficial soils and/or undocumented fill soils on the slopes. It is our opinion that while there is potential for on-going sloughing, soil creep, and shallow failures within the loose surficial and undocumented fill soils on the steeper site slopes, there is not a significant potential for deep-seated rotational slope failures under current site conditions. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the planned garage addition within the site is feasible from a geotechnical standpoint. It is also our opinion that the soils that underlie the site and form the core of the site slopes should be stable with respect to deep-seated earth movements, due to their inherent strength and slope geometry. Relatively shallow failures as well as surficial erosion are natural processes and should be expected on the steeper site slopes especially within the loose surficial soils and/or undocumented fill soils on the slopes. Proper erosion and drainage control measures as recommended in this report should reduce this potential. Our explorations indicated that the site is underlain by surficial undocumented fill soils with medium dense or better glacial till soils at relatively shallow depths. We should note that localized areas of deeper unsuitable soils and/or undocumented fill could be encountered at this site. NELSON GEOTECHNICAL ASSOCIATES, INC.