GRI provided geotechnical services for Multnomah County’s owner’s representative team. The 1,780-foot-long steel deck arch bridge spans the Willamette River and has three main spans and a total of 10 bents. Each bent is supported by four to eight large-diameter drilled shafts. The $300 million project also included landslide stabilization, retaining structures, and significant seismic design issues. GRI completed extensive review of the in-water foundation design, and provided suggestions that resulted in the elimination of embedded pier caps and the need for cellular bulkhead structures. These design changes resulted in project savings of about $6 million. GRI worked closely with the County to review progress plans and reports, identify and evaluate the owner’s risks, and provide over-the-shoulder guidance.

Location: Portland, Oregon

Owner: Multnomah County

Market Sector: Transportation 

Services: Geotechnical Engineering, Geologic Hazards, Seismic Engineering, Construction Services