GRI supported the design and construction of the 475-foot-long bridge that spans two active railroad lines and Sullivan’s Gulch. GRI’s geotechnical investigation included completing subsurface explorations in the ODOT, City, and UPRR right-of-way, and on the steep, heavily vegetated slope below Lloyd Boulevard. This required significant coordination with the UPRR, City, and ODOT, temporary road closures, and specialized equipment to access the intermediate bent location. Both the bridge and the abutments were designed to withstand the potential Cascadia Subduction Zone earthquake, which required designing for compatibility between the potential seismically induced lateral movement of the foundations and abutments. Some of the geotechnical challenges for this project included site constraints for constructability, the presence of undocumented fill associated with historic site grading, and relatively steep sloping ground at the site. The access requirements for traditional driven or drilled piles made both options extremely costly. Therefore, the team settled on steel-cased drilled and grouted micropiles, which could be installed with much smaller equipment.

Location: Portland, OR., Multnomah County

Owner: Portland Bureau of Transportation, ODOT

Market Sector: Development

Services: Geotechnical Engineering, Seismic Engineering