Bonneville Old Navigation Lock (NL1) Swing Bridge

Summary (Newest Update)

Background The Bonneville Old Navigation Lock (NL1) Swing Bridge is located at Bonneville Lock and Dam, approximately 40 miles east of Portland, OR, near Cascade Locks, OR and North Bonneville, WA. Originally constructed in 1935 as a rail bridge for heavy transformers and modified in 1950, the bridge has been deemed seismically and operationally inadequate. The USACE Portland District has developed design documents to replace the existing bridge with a new fixed bridge on a new alignment while also providing for partial demolition of the existing structure. Work Details The project involves constructing a new single-span steel girder bridge with a concrete deck. Key specifications include: - Bridge width: 34’4½” out-to-out - Two travel lanes of 11’0” each - Two shoulders of 2’0” each - A sidewalk of 5’0” - Superstructure consisting of four built-up steel plate girders. The new bridge will be located downstream of the existing bridge and will provide greater under clearance over the navigation channel. Construction will require a concrete stub abutment with spread footing anchored into rock for the north abutment and a concrete abutment supported by drilled shafts for the south abutment. Portions of the existing bridge must be removed to mitigate seismic hazards while maintaining critical vehicular access throughout construction. The project will also involve lead and asbestos removal, adherence to environmental restrictions, and barge crane operations near high voltage power lines. The anticipated construction cost is between $10 million and $25 million. Period of Performance Construction work is expected to be carried out from October 2026 to October 2028. Place of Performance Bonneville Lock and Dam area, approximately 40 miles east of Portland, OR.