An example of the diverging diamond to be used in the new S.R. 18 and I-90 interchange is illustrated in a video on Snoqualmie’s website. (Courtesy Photo)

I-90/S.R. 18 interchange fixes moved up on state schedule; construction to start in 2019

Good news for Valley drivers, the problematic interchange between I-90 and State Route 18 has had its project timeline moved up seven years.

Thanks to work from State Senator Mark Mullet and State Representatives Jay Rodne and Paul Graves, the project, which was originally slated to begin in July 2023 and be completed by 2028, is now starting this year. Snoqualmie Mayor Matt Larson said the funding will be available when the state Legislature’s next fiscal year begins in July.

The new plan begins with the Washington State Department of Transportation putting out a Request for Proposal (RFP) to find a consultant to create an improved interchange design. In August, the bidding will close and a consultant will be selected.

The design process will begin in September. Design, environmental reviews and Federal Highway Administration reviews will extend into 2019, when construction is scheduled to begin. The substantial completion of the project is projected to be in 2022.

In 2015, the project received an allocation of $150 million from the state Legislature as part of that year’s $16 billion transportation package. Access to that funding, which was set to become available in 2023, was moved up because Reps. Rodne and Graves were able to get a new source of funding to speed up the process.

Larson said that there was some left-over funding from improvement work done on S.R. 18 and access to that funding is what helped push the project forward. Being able to source funding from that leftover S.R. 18 improvement project allowed more transportation funding to be available for other projects around the state.

As for the redesign of the interchange, Larson said the city came up with an unusual design that could address all of the conflicts at the interchange. The design is called the diverging diamond, which is currently implemented in 86 locations across the country.

Larson said the diverging diamond will lower the amount of conflict points at the intersection from 26 to 14 and will address them all at the same time, meaning that the project is not broken up into separate phases. The design is also cheaper than a standard flyover ramp, which would allow some of the $150 million in funding to be used by WSDOT to fund improvements along the S.R. 18 corridor.

The city of Snoqualmie has produced a video on its official YouTube channel detailing the new schedule for the interchange as well as an illustration of how the diverging diamond design will work.

Find the video at www.youtube.com/watch?v=_ZGL31BJ2gM.

More in News

Snoqualmie worker left with broken legs after being hit by a truck

A miscommunication between co-workers led to an injury resulting two broken legs… Continue reading

Carnation hires Amy Arrington as new City Manager

The city of Carnation welcomed its newest addition to the administration in… Continue reading

The Tolt Hill Bridge near Carnation will be closed Monday morning for an inspection of the steel truss connections, part of the design work for needed repairs to the structure. (File Photo)
Tolt Hill Bridge to close Monday for half-day inspection

The Tolt Hill Bridge will be closed Monday, but only for a… Continue reading

Blotter: Car hits teenage bicyclist; driver rolls over on snowy freeway

Police and fire agencies in the Snoqualmie Valley responded to the following calls:

State Patrol IDs North Bend area as preferred site for new weigh station; city, residents object at Nov. 7 town hall meeting

The Washington State Patrol, like everyone else who lives in North Bend, thinks the city will be the perfect spot to locate a future weigh station, but the plans have not received a warm welcome so far.

A group of new teachers hired in 2013 pose in front of the Snoqualmie Valley School District Office. (File Photo)
School board moves ahead with levy plans, finds funding for 40 teachers to expand programming, reduce class sizes

Two weeks ago, the Snoqualmie Valley School Board was considering the implications… Continue reading

Most incumbents ahead in election results, except Snoqualmie Valley School Board and one Snoqualmie City Council seat

Snoqualmie’s contentious election season may result in very little change on the city council, but big changes on the Snoqualmie Valley School Board.

Maleng Regional Justice Center in Kent. (Photo courtesy King County)
King County Could Ban Solitary Confinement for Youth in Detention

Last week, a lawsuit was filed over the practice; this week, King County scrambled to respond.

Most Read