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View 18/90 interchange concept

Project Facts

• We opened the Issaquah Hobart Road to I-90 segment of SR 18 in 1965.
• WSDOT built the westbound  I-90 bridge over SR SR 18 in 1963.
• We built the eastbound I-90 bridge in 1975.

We are developing plans to widen SR 18 to two lanes in each direction between Issaquah Hobart Road and I-90 and to rebuild the I-90/SR 18 interchange.

Why is WSDOT improving the I-90/SR 18 interchange and widening seven miles of SR 18 from Issaquah Hobart Road to I-90?

Issaquah Hobart Road to I-90 is the last segment of a multi-phase project to widen 21 miles of SR 18 to four lanes from Auburn to I-90. The widening is necessary to increase safety and improve mobility through the entire SR 18 corridor.

This segment of the project will include an expanded I-90/SR 18 interchange and a new interchange at the Tiger Mountain Summit.

We are focusing our efforts on expanding the I-90 interchange first, followed by SR 18 widening.

Additional improvements include extending truck climbing lanes, realigning sharp curves to improve driver sight distance and to help them safely maintain their speed, improving fish passage at stream crossings, new drainage facilities, and improving accommodations for wildlife crossings.

The End Result
When this project is complete, drivers will travel on an expanded I-90/SR 18 interchange and a four-lane divided highway with truck climbing lanes between Issaquah Hobart Road and I-90.

Project Benefits
•  Safety – This project will reduce the likelihood of head-on collisions by building a 51-foot median to divide opposing directions of traffic. Where the mountainous terrain and/or significant environmental impacts make the addition of the full median too costly, we will use median barrier to separate traffic. 

Find out how previous SR 18 widening projects are improving safety (pdf 343kb). 

•  Congestion Relief – We will increase the capacity of the highway by adding one lane in each direction. Truck climbing lanes will speed travel over the Tiger Mountain Summit by providing a separate lane for slow moving traffic. An improved I-90/SR 18 interchange will enhance traffic flow in a rapidly growing area.

•  Environment – This project will build drainage facilities to capture and clean highway runoff, and replace narrow culverts with wider culverts or bridges to help fish swim up and down streams. WSDOT will strive to avoid excessive impacts to wetlands and other sensitive areas. When wetlands cannot be avoided, WSDOT will create new wetlands or enhance existing ones to compensate for the impact. WSDOT will also be studying ways to protect wildlife in the area, including the construction of new wildlife crossings.

•  Freight Mobility – SR 18 is an important regional and national truck route between Eastern Washington and beyond and Sea-Tac Airport and the Port of Tacoma.  The increased capacity of the highway will help keep freight moving.

What is the project timeline?
The Nickel Funding Package passed by the 2003 Legislature provided $6 million to complete the environmental review and preliminary design for the I-90/SR 18 interchange and early design for SR 18 widening.  During this process we chose a preferred route for the highway and preferred design for the expanded interchange. 

Full project design and construction is currently unfunded.  If funding becomes available and work progresses without interruption, we expect to complete the expanded I-90/SR 18 interchange about four to five years after we receive funding.

Public Involvement
Your thoughts and opinions are important to us. Public participation opportunities will be presented throughout the design process.  Several public meetings will be held during the environmental documentation process.  As the dates for these meetings are set more information will be provided on this website and through project mailings and fliers.  Please contact the Project Engineer for more information.

Environmental Protection
Salmon an other fish are an important resource in our state.  We will build facilities to capture and clean highway runoff, and replace narrow culverts with wider culverts or bridges to help fish swim up and down streams.  WSDOT will take care to avoid excessive effects on wetlands and other sensitive areas.  When wetlands cannot be avoided, we will create new wetlands or enhance existing ones to compensate for the effect.  We also will study ways to protect wildlife in the area, including the construction of new wildlife crossings. 

Please visit the WSDOT Environmental Services Web site for more information.

Increasing safety is one of our priorities
Crews will construction a 51-foot-wide median to divide opposing directions of traffic and reduce the likelihood of head-on collisions.  Where the mountainous terrain and/or significant environmental effects make the addition of a full median too costly, we will use median barrier to separate traffic.

Will this project impact tribal resources?
At WSDOT we seek to address the concerns of the tribal nations using the process outlined in Section 106 of The National Historic Preservation Act and the WSDOT Tribal Consultation Policy adopted in 2003 by the Transportation Commission as part of the WSDOT Centennial Accord Plan.

WSDOT has continuously coordinated with the various Indian tribes in the area throughout the design and construction of the SR 18 corridor. WSDOT will continue this coordination as plans are developed for the widening from Issaquah/Hobart Rd to I90.

Financial Information

The Nickel Funding Package passed by the 2003 Legislature provided $6 million to complete the environmental review and preliminary design for the I-90/SR 18 interchange and early design for SR 18 widening from Issaquah Hobart Road to I-90. 

This project is funded through the following fund sources:

How can I get more information?
Contact:
Design Project Engineer Gary L. McKee
WSDOT Project Office
15700 Dayton Avenue North
PO Box 330310
Seattle, WA  98133-9710
Phone:  206.440.4612
E-mail: McKeeG@wsdot.wa.gov

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