200 W MARINE VIEW DR Geotech Report 2025-08-07

October 16,2020 Project No. T-8221 The results of the analysis indicate that lateral displacement towards the Snohomish River channel approaching one to two inches is possible to a horizontal distance of about 120 feet from the crest of the shoreline. In our opinion, this amount of displacement would not structurally impair the building but could result in damage of a cosmetic nature similar to the liquefaction induced settlements. Seismic Site Class Based on the soil conditions encountered and the local geology and because the buildings natural frequency is .5 seconds or less,the 2015 International Building Code(IBC)indicates that site class"D"should be used in structural design. 5.0 DISCUSSION AND RECOMMENDATIONS 5.1 General Based on our study,in our opinion,development of the site as proposed is feasible from a geotechnical engineering standpoint. The existing fills at the site consist mostly of silty sand and sand soils with varying amounts of gravel and minor amounts of organics and construction debris. CPT data noted the fill to be in a medium dense to dense condition in most site areas and, in its current condition, appears suitable for support of new fill, pavements, or building elements. Some areas showed the fill to be in a loose condition,which will require removal to a minimum depth of two feet below base-of-footing elevation and replacing with compacted structural fill. The need for overexcavation will require confirmation by geotechnical observation and testing at the time of grading as outlined in the following Site Preparation and Grading Section. The existing fill and underlying native soils are moisture sensitive and close moisture control will be required to facilitate structural compaction of the soils if used as fill from site excavations. Detailed recommendations regarding these issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 Site Preparation and Grading To prepare the site for construction existing vegetation should be cleared and removed from the site. Once cleared and grubbed, in the building area where three-to three-and one-half feet of fill will be required to achieve finished floor grade, the upper sparse grass and moss should be tilled into the sand fills and recompacted to structural fill requirements outlined below. In the pavement areas, where grades will be near existing, this upper organic layer should be stripped and removed. Stripping depth of two inches and less would be expected to remove this upper vegetative mat. Page No. 4