Days are numbered for only original I-84 overpass in Boise still standing. This is why
More than 139,000 drivers a day travel under Interstate 84’s Five Mile Road overpass. In a few years, those drivers could see construction and a new overpass.
The early stages of preparation to revamp the Five Mile Road overpass are beginning as two agencies plot future steps. The Ada County Highway District approved an agreement Wednesday with the Idaho Transportation Department to work together and share the costs of the project.
Five Mile Road in West Boise runs from Chinden Boulevard in the north to the New York Canal in the south.
ACHD and ITD are partnering to design a replacement of the overpass and improvements to Five Mile Road from Overland Road, which is half a mile south of the overpass, to Franklin Road, which is half a mile north.
The overpass was built in 1966 and is the last original I-84 overpass in urbanized Ada County, according to ACHD. It was constructed with two lanes and no pedestrian or bicycle facilities.
This replacement would be similar to work that was completed on the overpass at Cloverdale Road after a 2018 crash that killed four people. The crash and subsequent fire so damaged the overpass that the two highway agencies moved quickly to replace it. ACHD cited the success of that replacement in its new agreement to work with ITD.
ITD owns both overpasses, but ACHD owns the north-south roads that cross the freeway, so collaboration is necessary.
Five Mile Road, between Overland and Franklin roads, carries 19,000 vehicle trips and fewer than 20 pedestrians and cyclists per day.
ACHD and ITD estimate the Five Mile Road overpass and widening project will cost $22 million.
The first phase, which includes planning and design work and the right-of-way, is estimated to cost $4,247,000, according to the agreement that was approved Wednesday to pay for it. For the design portion, ACHD is paying 70% and ITD 30%.
The agencies are also pursuing federal aid to help cover the costs.
The next step is for the agencies to hire a design consultant and begin the design and environmental study phases. ACHD anticipates taking public comment during the design process in the next few years.
Another agreement for construction will have to be made later on in the process.
This story was originally published February 27, 2022 at 4:00 AM.
