6801 SEAWAY BLVD Geotech Report 2025-08-19

Seaway Commercial Center Subsurface Exploration,Geologic Hazard, 7007 Seaway Boulevard and Geotechnical Engineering Evaluation Everett, Washington Design Recommendations 9.3 Site Disturbance The existing native sediments contain a high percentage of fine-grained material. These sediments are considered to be highly moisture-sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. 9.4 Winter Construction The on-site soils contain substantial silt and are considered highly moisture-sensitive. Care should be taken to seal all earthwork areas during mass grading at the end of each workday by grading all surface to drain and sealing them with a smooth-drum roller. Stockpile soils that will be reused in structural fill applications should be covered whenever rain is possible. We recommend that project planning assume that excavated on-site soils will not be available for reuse in compacted fill except during dry summer weather when soils can be aerated and moisture contents can be reduced prior to compaction. Consideration should be given to protecting access and staging areas with an appropriate section of crushed rock or asphalt treated base (ATB). If crushed rock is considered for the access and staging areas, it should be underlain by engineering stabilization fabric (such as Mirafi 5O0X or approved equivalent) to reduce the potential of fine-grained materials pumping up through the rock during wet weather and turning the area to mud. The fabric will also aid in supporting construction equipment, thus reducing the amount of crushed rock required. We recommend that at least 10 inches of rock be placed over the fabric. Crushed rock used for access and staging areas should be of at least 2-inch size. 10.0 STRUCTURAL FILL Placement of structural fill will be necessary to establish desired grades at the site and to backfill utility trenches and around foundations. All references to structural fill in this report refer to subgrade preparation, fill type, and placement and compaction of materials as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. 10.1 Subgrade Compaction After overexcavation/stripping have been performed to the satisfaction of the geotechnical engineer or engineering geologist, the upper 12 inches of exposed ground should be recompacted to a firm and unyielding condition. If the subgrade contains too much moisture, suitable recompaction may be difficult or impossible to attain and should probably not be December 17,2021 ASSOCIATED EARTH SCIENCES,INC. PEL/Id-20200319E001-002 Page 11