In a possible change of plans, the Idaho Transportation Department is now proposing the existing Rainbow Bridge be removed. Valley Lookout/BoiseDev first reported the news.
Rainbow Bridge was constructed in 1933, spanning the North Fork of the Payette River. As Boise State Public Radio previously reported, ITD said the bridge no longer meets industry standards, with narrow lanes and shoulders, as well as limited sightlines.
A feasibility study completed in 2021 said the existing Rainbow Bridge could be used as a scenic overlook for pedestrians. ITD evaluated the bridge’s condition in 2024, which included testing concrete samples in a lab to determine the extent of deterioration, reviewing 10 years of inspection reports and exploring options and costs to keep the bridge.
According to the evaluation, ITD says the rehabilitation methods from 2006 are no longer effective and the deterioration is extensive and “will continue at an increasing rate.” The department went on to write that keeping the bridge will require significant effort and investment.
On the website for Rainbow Bridge, ITD has created three different scenarios to keep the bridge. It says in all scenarios, vehicle traffic would not be able to use the bridge and there would be no safe access for pedestrians.
- Scenario 1 ($20.3 million): Completely replace everything but the historic arches. Complete additional repairs in 2070.
- Scenario 2 ($50.4 million): Retain as much of the historic structure as practical. Continue repairs every 25 years.
- Scenario 3 ($48.4 million): Only repair the elements in the worst condition. Continue repairing every 10–15 years as the bridge deteriorates.
The new bridge will be built slightly west of the existing one, with two 12-foot lanes and 14-foot shoulders. There will also be retaining walls near the new bridge, to stabilize the canyon slopes and allow for room to keep the existing bridge open during construction.
ITD has nine designs available for public comment. The designs are based on several factors, including maintenance, costs, community input and aesthetics, and more.
You can provide input until Aug. 5, 2025. After the community engagement period, the final design will be completed and construction on the new bridge will start in 2028 or 2029.
