The Rainbow Bridge is an icon of Idaho. It appears on postcards, paintings, and in memories.
The Idaho Transportation Department says it is time to tear it down, leaving just those memories behind.
ITD says it plans to remove the bridge, a key link across the North Fork of the Payette River, which has ferried drivers across the canyon from one side to the other since 1933.
Bridge removal
The department has not made a public announcement about the decision, but tucked notice of it inside an online microsite seeking public feedback. A news release simply said there was “an update about the existing bridge” without noting that the update was a proposal to remove it.
“ITD is proposing to remove the existing bridge because of safety risks and future costs,” the department wrote.
“Cost is not the only consideration,” ITD wrote. “The lack of options to keep and use the bridge efficiently is driving the recommendation. The environmental process and community input will also influence the outcomes of the project.”
The bridge replacement is part of a years-long project to revamp the busy state highway through the canyon.
BoiseDev reported the department initially studied rerouting Idaho 55 away from the canyon, but claimed it would be the more expensive option. As BoiseDev reported, the project’s first phase — widening the road between the bridge and Smiths Ferry — took years longer than expected and cost tens of millions of dollars more than budgeted. Numerous landslides closed the roads for weeks on end during the project.
Now, the years-ago decision not to reroute 55 could mean the end of the bridge itself.
Last year, ITD told the public it could keep the original Rainbow Bridge as a pedestrian overlook and build a second bridge for traffic. The agency said it then undertook a study of the bridge to determine what it would take to keep it.
“Our conclusion is that the best course of action is to suggest the removal of this bridge. This isn’t something that we come to lightly, and there are multiple reasons that bring us to that decision,” Jason Brinkman, ITD District Engineer for SW Idaho said. “Cost is certainly a consideration, but it is not the primary consideration. We really have given a lot of thought of what is feasible to do, and what is a reasonable thing to ask the public to see us do.
ITD claims there is extensive deterioration on the bridge, and that the “level of corrosive elements in the concrete is significant and widespread.” The agency claims to the public that keeping the bridge would cost between $20.3 million and $50.4 million, and even with the expense, neither cars nor pedestrians could use the bridge.
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The open spandrel concrete arch bridge is listed on the US National Register of Historic Places. It is the largest single-span arch in the state.
“The fact that the bridge isn’t in use as a transportation asset means it’s just there as a landmark and for its historic purpose,” Brinkman said. “And while that’s significant, it is something that some of our stakeholders would question as far as if that’s a good use of your transportation dollar to maintain something that’s there for historic and landmark purposes.”
Replacement options
ITD is seeking public comment on its proposal to scrap the current bridge, and on replacement design options. Those concepts include a “haunched steel girder,” several arch-shaped designs and an Art Deco concept.
The department says it hopes to provide a smoother curve as traffic crosses the river, with wider travel lanes and extensive shoulders. The plan also calls for retaining walls as high as 40 feet on the approach to the bridge.
Crews are currently working on the bridge this summer – shoring up the structure ahead of its replacement by 2028. Delays are expected daily, as Valley Lookout reported.
You can comment on ITD’s plans to tear down the bridge, and on possible replacements, on this online site. Feedback will be taken until August 5th.
