Idaho 55 will be reduced to one lane north of Smiths Ferry starting Monday, according to the Idaho Transportation Department.
The lane closures will continue Monday through Thursday through the fall as crews complete maintenance on the historic Rainbow Bridge over the North Fork Payette River. A temporary traffic signal will direct traffic.
No lane closures will be in place on holidays or from 7 a.m. to 10 p.m. on Fridays, Saturdays, and Sundays after Memorial Day. Complete road closures are not currently planned, but could be required for brief periods, according to ITD.
Flaggers will be staged on the river as needed to direct rafters while overhead bridge work is in progress. Updated information regarding the project will be posted here.
Maintenance work
Work this summer involves repairing concrete supports on the bridge and repairing the roadway surface. The work is expected to extend the life of the bridge through 2029, when ITD expects to complete a new bridge to replace the Rainbow Bridge.
Load restrictions over the bridge would be required if the maintenance were not completed, according to ITD, which conducts annual safety inspections on the bridge.
However, the agency’s engineers determined that maintenance is not a long-term solution for the bridge, which does not meet standards for state highway bridges.
The cost of the maintenance project is unclear. ITD had not responded to Valley Lookout’s request for comment as of deadline for this story.
Last year, ITD began preliminary design work for the replacement bridge by drilling 18 holes around the site to test the soil and rock around the bridge.
Designs are still being developed, but the new bridge is expected to be built adjacent to the existing bridge. The new bridge could cost about $60 million to build, according to preliminary estimates by ITD.
Historic significance
Major maintenance was last completed in 2006 on the Rainbow Bridge, which was built in 1933 and was added to the National Register of Historic Places in 1999.
The Rainbow Bridge spans 410 feet across the North Fork, making it the longest single-span concrete arch bridge in Idaho. It cost $74,000 to build, or about $1.8 million in today’s dollars.
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It has not been determined what will happen to the Rainbow Bridge once the new bridge is completed. Public comments regarding the project can be submitted to ITD here.
