101 E MARINE VIEW DR SEPA 018 - 011 Geotech Report 2025-04-15

Geotechnical Engineering Evaluation NGA File No.988017 East Marine View Drive Warehouse May 19,2017 Everett,Washington Page 4 dense to very dense sand with some silty zones below the water table, therefore, we consider the liquefaction potential for this site to be low to moderate. The recommendations provided for site improvements in the form of stone columns will greatly reduce the liquefaction potential and associated distress to the structure. 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 Snohomish County Area, Washington,by the Soil Conservation Service(SCS)was reviewed to determine the erosion hazard of the on-site soils. The site surface soils were classified using the SCS classification system as Urban Land. This unit is does not have an erosion hazard listed. In our opinion, the site soils would have a low to moderate hazard for erosion where exposed. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion that the site is compatible with the planned improvements from a geotechnical standpoint. Our explorations indicated that the site is underlain by very loose/very soft to very dense/hard younger alluvial soils. Due to the very loose/soft nature of the upper site soils, we recommend that support for the proposed structure and improvements to the surficial soils be accomplished with ground modifications in the form of compacted rock aggregate piers. This type of ground modification includes augered or vibratory ramming of aggregates within the foundation and slab areas extending through the upper loose/soft soils. Compacted crushed rock fill is placed within the excavations to further densify the upper loose/soft soils to provide adequate support for the proposed structures and reducing the potential for future settlement within the building elements. The building foundations and slab are then supported directly on the compacted rock aggregate piers. This is further discussed in the Foundations and the Site Preparations and Grading subsections of this report. We also recommend that the proposed slabs-on-grade also be supported directly on the compacted rock aggregate piers. The slabs should be additionally reinforced, and cold joints incorporated in the slab design to further reduce the effects of differential settlement. In our opinion, slabs supported on compacted rock aggregate piers should experience minimal cracking and settlement. NELSON GEOTECHNICAL ASSOCIATES, INC.