Three new rail bridges were constructed in Sandpoint, Idaho to add a second mainline track that spanned more than four miles.
Bridge 3.9, the longest of the new bridges, is a 4,875-foot structure that stretches across Lake Pend Oreille. Built adjacent to the existing mainline track, the second mainline eliminates a railway chokepoint by enabling trains to run in both directions.
About 60 trains cross the lake each day. Prior to this project, these trains would often have to wait to cross the lake on a single track, slowing rail service. Idling trains would also block intersections where streets and roads crossed the rail tracks.
The Sandpoint Junction Connector project seems simple in theory. However, unique solutions had to be applied to a variety of constraints due to the location.
The project team consisted of owner BNSF Railway, contractor Ames Construction, design and structural engineer Hanson Professional Services and numerous subcontractors.
This project team came together and built a long bridge that spans a beautiful lake into the Rockies of Northern Idaho. A highway bridge parallels the project site, and because this is a rail bridge that will last for 150 years, it will be a landmark witnessed by generations of Americans.
For these reasons, the Sandpoint Junction Connector project is the No. 8 bridge of 2024.
The project was done in two phases. The first phase constructed the three bridges for the second mainline track. The second phase reconstructed the existing bridge.
A construction entrance was set up for material delivery on the north end of the bridge over Lake Pend Oreille and rail traffic was not disrupted. A tunnel was incorporated into the entrance for pedestrians to travel underneath.
Span lengths were doubled to reduce obstructions in the lake for boat traffic. It also minimized the impact on fish populations.
Barges were used in place of trestle and span-by-span construction for the new bridge.
A pile driving template designed to pinpoint accuracy at any water depth was used. This reduced setup time and provided greater quality control. Pile driving in the ground was inconsistent, and the team developed a plan to deal with the known pile driving results.
To speed up the splicing process, a working platform for welding access was integrated into the pile driving template.
A barge-mounted crane was used to accelerate timing for the installation and decking process of the five 104-foot bridge spans. The team averaged installation of 2.7 spans per week.
Two permanent piers were built at a time. Crews then erected temporary girders and decking to continue advancing the crane out to the next set of newly built piers.
Once all the piers were built, precast box girders were erected in the reverse order or pier construction. Crews removed the temporary girders and decking with each completion.
Materials were sourced within a 70-mile radius of the project site. This boosted the work for local facilities and provided them with the experience to expand their business into heavy bridge construction.
Crew members were given a safe work environment, and custom access was installed that allowed for quick setup and teardown for the construction of the piers.
Most of the work was kept on the ground. When work could not be done on the ground, custom work platforms were made that could be installed and removed via crane quickly.
The second mainline opened 14 months ahead of schedule in 2022 with the reconstructed bridge opening in late 2023. The second mainline improves the flow of freight and passenger trains in the region, eliminating the need for trains to idle and block traffic.
This project increased mobility in the region and reduced traffic due to rail service. Now motorists can travel through the area more efficiently.
Project: Sandpoint Junction Connector
Location: Sandpoint, Idaho
Owners: BNSF Railway
Designer: Hanson Professional Services, Inc.
Contractor: Ames Construction
Cost: Confidential
Length: 4,873 Feet
