The centerpiece of the TriMet PMLR transit project was the Tilikum Bridge, a cable-stayed bridge crossing the Willamette River. The project encompassed approximately six miles and consisted of 10 bridges, ranging between less than 100 feet long (single-span) to more than 1,600 feet long (11 spans); 45 cut-and-fill retaining walls more than a mile long and up to 32 feet high; and underground utility relocations, including up to 40-foot-deep excavations with shoring and dewatering.

The route featured extremely variable geologic conditions, and the project required heavy construction in a highly developed urban corridor. These design challenges were set against the backdrop of a very intricate construction sequence and aggressive Design/Build schedule. Shannon & Wilson evaluated site-specific seismic hazards, developed foundation design alternatives, completed final foundation design, and reviewed construction drawings and specifications. We completed a large-scale geotechnical investigation program of 169 field exploration points and performed laboratory testing. During construction, we continued as the owner’s representative and provided construction consultation and observation as the geotechnical engineer of record.