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 10.4 Structural Fill Testing The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would involve providing us with a sample of the material at least 3 business days in advance to perform a Proctor test to determine its field compaction standard. A representative from our firm should observe the stripped subgrade and be present during placement of structural fill to document the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. 11.0 FOUNDATIONS Spread footings may be used for building support when founded either directly on the medium dense to dense native sediments (lodgement till and/or ice-contact deposits) or on compacted structural fill placed over the native sediments. The existing topsoil and near-surface zones of loose weathered lodgement till are not considered suitable for foundation support due to its potential for excessive settlements. When topsoil or loose native sediments are encountered during footing excavation, we recommend undercutting to medium dense to dense native soils and replacing with structural fill compacted to 95 percent of the modified Proctor maximum dry density. 11.1 Allowable Soil Bearing Pressure Based on the current building FFE of 522 feet, we anticipate that the bottom of footing excavations will extend to about elevation 519 feet. Therefore, we anticipate the footings will bear on structural fill within the northern half of the building footprint, medium dense native sediments near the center of the building, and dense native sediments within the southern portion of the building. For footings founded either directly on the medium dense native sediments or on compacted structural fill placed over the native sediments, we recommend that an allowable bearing pressure of 3,000 pounds per square foot (psf) be used for design purposes. A higher allowable bearing pressure of 6,000 psf may be used for footings bearing on dense native sediments.The zone of foundation bearing soils suitable for 3,000 psf loading are expected to be encountered within the northern half of the site where structural fill is required to achieve final grade and within at-grade areas underlain by medium dense ice-contact deposits or weathered till. The zone of foundation bearing soils suitable for 6,000 psf loading are expected to be encountered within the southern portion of the site where the proposed grading requires approximately 5 to December 17,2021 ASSOCIATED EARTH SCIENCES,INC. PEL/Id-20200319E001-002 Page 13