The Jefferson (12th & Jefferson Workforce Housing)

Expo Apartments (100 Republican Apartments)
April 28, 2017
One Convention Place
April 28, 2017
Location: Seattle, Washington

The Jefferson workforce housing apartments are located in Seattle’s Central District near Seattle University. This five-story mixed-use development consists of 40 one-bedroom and two-bedroom apartments. It also includes 4,500 square feet of commercial space designed for local businesses. The building is five stories of wood-framed bearing walls over two levels of post-tensioned concrete. The building meets the Washington State Evergreen Sustainable Development Standards.

ORA was engaged as the geotechnical and structural special inspection firm of record for this project. We completed a subsurface investigation with two borings and prepared a geotechnical report for the project. Detailed design recommendations were developed for a temporary shoring system, conventional foundation support, and below-grade wall design. Our testing and inspection scope of work included the following:


  • Tieback anchor installation and testing
  • Soil bearing verification
  • Shoring installation/perform monitoring
  • Installation of internal bracing and rakers
  • Monitor adjacent building settlement
  • Erosion control – temporary
  • Observe and monitor excavation
  • Verify fill and compaction
  • Soldier pile installation (including vibration monitoring)


  • Post-tensioned prestressed concrete
  • Reinforced concrete – cast-in-place
  • Shoring system welding
  • Structural steel fabrication and erection
  • Tieback grout strength
  • Shotcrete
  • Epoxy grouting of rebar dowels