This private family foundation funds education, health and development programs around the world. The family envisioned building a new world headquarters for the foundation on urban land in Seattle, Washington. GeoEngineers was fortunate to be involved from the very beginning—long before a site was selected—and remained on the project through the environmental cleanup, building design and construction phases.
GeoEngineers’ geotechnical engineers collaborated with the integrated project team from the conceptual phases to final design for the foundation’s campus development. The final design for the 12-acre site consisted of a parking garage and three six-story office buildings that will offer a combined 1.3 million square feet of office space once the third building is finished.
GeoEngineers’ environmental studies, analyses, and extensive experience with brownfields projects were also a critical part of the site-selection and design process. For a full discussion of the GeoEngineers’ environmental work on the Foundation project, see the related project profile.
The Fifth Avenue North garage—encompassed a full city block and extended 45 feet below existing site grades. Excavation was shored with an innovative temporary soil nail shoring system.
The Phase I campus below-grade excavation—required a soldier pile and tieback temporary shoring system comprised of more than 335 soldier piles and more than 600 tiebacks. These extended to depths of 50 feet below existing site grades. The foundation design was tailored to the variable soil conditions present at the site. Our efforts resulted in a design in which the campus facilities all bear on cost effective shallow foundations.
The 100-year-old, 6-foot-diameter brick sewer—was located 40 to 50 feet below the planned basement level of the buildings. In order to assess the potential impact to the sewer, GeoEngineers used sophisticated numerical modeling of the planned excavation sequence to estimate how much the sewer would rebound during the deep excavation for the campus basement. This modeling was used by the project team to assess the potential impact to the sewer and to facilitate permitting of the project.
A 1 million gallon rainwater storage tank—allows rainwater harvesting for landscape irrigation and non-potable reuse within the building. The rainwater storage tank was situated in an area with soils of variable compressibility and above a settlement-sensitive storm sewer. GeoEngineers developed foundation solutions for the rainwater storage tank that limited differential settlements to tolerable levels and protected the underlying storm sewer from localized settlement.
The thermal energy storage (TES) tank—optimizes the campus cooling system and required a cylindrical excavation 70 feet deep and 50 feet in diameter. GeoEngineers collaborated with the project structural engineers to develop a highly efficient compression ring shoring system (without ground anchors) to construct the tank. GeoEngineers completed the geotechnical design of the TES tank using a three-dimensional finite element model that modeled structural elements of the tank, soil and groundwater and construction sequence. The tank was constructed top-down in a series of 6-foot-high permanent reinforced shotcrete lifts. GeoEngineers monitored tank displacements throughout construction, using highly sensitive geotechnical instrumentation to confirm that the tank was performing as anticipated.