3620 BROADWAY VERIZON 2019-01-11

y f Geotechnical Engineering Evaluation NGA File No.983917 Stadium Flowers Addition March 10,2017 Everett,Washington Page 4 Erosion Hazard The criteria used for determination of the erosion hazard for affected areas include soil type, slope gradient, vegetation cover, and groundwater conditions. The erosion sensitivity is related to vegetative cover and the specific surface soil types,which are related to the underlying geologic soil units. The Soil Survey of the Snohomish County Area, Washington, by the Soil Conservation Service (SCS) was reviewed to determine the erosion hazard of the on-site soils. The surficial soil on site is mapped mainly as Norma loam, with nearby Alderwood-Urban land complex, 2 to 8 percent slopes. The erosion hazard for these materials are listed as slight. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion from a geotechnical standpoint that the site is compatible with the planned commercial addition development provided all recommendations provided in this report are incorporated into the development plans and strictly implemented during construction. Our explorations indicated that the site is partly underlain by surficial undocumented fill soils with medium dense or better native glacial soils at shallow depths. The competent native glacial outwash deposits were encountered at approximately 1.6 to 2.4 feet below the existing ground surface with the excavation, corresponding to depths of approximately 2.4 to 6.4 feet below the projected surface of the asphalt or concrete existing throughout the site. We should note that localized areas of deeper unsuitable soils and/or undocumented fill could be encountered at this site and exposed at the proposed foundation subgrade elevations depending on final site grading and development plans. These unsuitable soils, if exist, would likely be associated with previous grading activities and/or the installation of utilities surrounding the perimeter of the property. The underlying medium dense or better native soils should provide adequate support for the planned structure. We recommend that the structure could be designed utilizing conventional spread foundations. Footings should extend through any undocumented fill, organic soil, or loose materials, and be founded on the underlying medium dense or better native soils encountered at depth. We provide recommendations for temporary and permanent cut slopes in the Temporary and Permanent Slopes section of this report. Weshould be retained to review proposed grading plans prior to construction. NELSON GEOTECHNICAL ASSOCIATES,INC.