The plans for a massive overhaul of the Donald-Aurora interchange on Interstate 5 go before Marion County commissioners next week.
The Marion County Board of Commissioners will hear the matter at 9:30 a.m. Wednesday, Sept. 30. The meeting comes on the heels of news that engineers have completed the in-depth comprehensive Interchange Area Management Plan for the project, available here.
The plan documents the traffic volumes and interchange performance needed to define appropriate levels of service, and establishes an agreement with local government and stakeholders on the transportation solutions, policies, and actions needed to improve the interchange.
The existing interchange was built 60 years ago and designed to handle the traffic of that day, when its closest neighbors were a handful of quiet farms. Today, it is the access point for three busy truck stops, as well as an RV park, and sees approximately 32,000 vehicles per day.
ODOT officials admit the interchange has been over capacity at peak times for many years. The project summary puts it this way: “It has significant safety issues and does not operate like a busy interchange should.”
The project is in the preliminary stages, with engineers documenting current traffic volumes, interchange performance and desired levels of service. Officials don’t want to get in the same situation with the new interchange, where it is at capacity almost as soon as it opens. They want the revamped exit to be able to handle current traffic levels, as well as future growth.
The concept engineers prefer would utilize what’s called a “diverging diamond interchange.” Originally pioneered in France, this unusual design actually requires overpass traffic to briefly switch over to the wrong side of the road, the upside being that it improves safety by eliminating the need for any left turns.
It’s not quite as confusing as it may sound, and was previously used by ODOT in 2016 at the Fern Valley I-5 interchange in southern Oregon.
The design phase is planned for next year, with a bid letting in 2021 and construction for the first phase of the project in 2022. The project has currently been allocated a total of $28.3 million, most of it coming from House Bill 2017, the so-called “Keep Oregon Moving” package.
$28 million certainly seems like a lot, but not when it comes to highway projects. This would only carry the project through design and Phase 1. ODOT says funding is not currently available for construction of a full interchange.