BNSF Bridge 66.4 over Little White Salmon River

A 2.7-million-pound rail bridge replacement spanning over Little White Salmon River in Washington State is providing renewed and reliable connection for a critical grain export route.

As part of BNSF Railway’s Heavy Bridge Replacement program — an initiative to upgrade and improve Washington’s statewide rail network — HNTB helped replace the previous, century-old rail bridge. Services on the project included preliminary and final design, construction management and inspection, and coordination with subconsultants for geotechnical investigations, underwater inspection, surveying and permitting. HNTB designed this in-line replacement to utilize Accelerated Bridge Construction (ABC) techniques to limit track closure, ensuring that the construction sequence was executed in just 36 hours.

Design and Adaptability

The replacement bridge is a 336-foot through-truss span with 49-foot, prestressed concrete, double-cell box beam approaches. The design allows for a wider waterway opening, increased clearances and higher weight limits, and new piers on the land allow for easier access for inspection and maintenance.

Adapting to unavoidable site constraints caused by the bridge’s close proximity to an existing highway bridge, HNTB developed an innovative pier design utilizing micropiles. During construction, HNTB collaborated with the contractor to adjust the micropile layout to align with the contractor's proposed means and methods.

An Accelerated Delivery

To ensure minimal closures for railway operations, the project team collaborated to remove the old span, deliver and install its replacement, and reopen the track in under 36 hours. This accelerated delivery was made possible by first constructing the bridge off-site and 60 miles downriver, then utilizing self-propelled and float-in methods to bring the bridge on-site and into position. Once there, crews installed the two prefabricated approach spans and new track panels were laid across the deck.

Designed and delivered to support BNSF Railway initiatives, the replacement bridge now not only improves overall rail operations but also directly supports the movement of goods and the communities and regions that benefit from them.