The 1918 Eighth Avenue building in downtown Seattle is a 34-story mixed-use office/retail tower with below-grade parking. The site is bounded on two sides by major downtown streets and on two sides by condominium and office structures. As a result, excavation—which ranged from 63 to 73 feet deep—had complex excavation-support needs. GeoEngineers worked with Ground Support to design a unique shoring system that was cost-effective and kept the project on schedule.
The greatest design challenge the project team faced was along the east wall of the structure. Easements could not be obtained from the adjoining condominium’s owner because the building’s foundation and shoring systems could not reasonably accommodate tieback anchors from the 1918 Eighth Avenue project. GeoEngineers and Ground Support developed an innovative two-phase approach that enabled the project to proceed.
ACEC-Washington Engineering Excellence, Gold Best in State Award for Original or Innovative Application of New or Existing Techniques, 2010
The east wall shoring system demonstrated that this two-wall approach is a viable alternative when adjacent structures cannot support tieback anchors, or if there are other obstacles to traditional shoring methods.
Luis Adan, Senior Development Manager
Schnitzer West, LLC