We are making major improvements to the area where Interstate 5, SR 161 and SR 18 connect in Federal Way.
The reconstruction includes replacing two cloverleaf ramps with flyover ramps. The ultimate interchange plan includes upgrading ramps and improving connections to and from I-5, SR 18 and SR 161.
Due to limited funding, WSDOT will construct these improvements in phases with separate contracts. Construction on the first phase began in summer 2010. In the first phase crews will:
- Build a two-lane flyover ramp connecting westbound SR 18 to southbound I-5 and rebuild the westbound SR 18 to northbound I-5 ramp to accommodate the new flyover ramp.
- Construct a new exit ramp connecting the new flyover ramp to SR 161 at S. 359th Street.
- Build a new eastbound SR 18 to northbound I-5 flyover ramp and rebuild the eastbound SR 18 to southbound I-5 ramp to accommodate the new eastbound to northbound flyover ramp.
Why is WSDOT
making improvements to the I-5 - SR 161 - SR 18 Triangle?
When the Interstate 5/State Route 18 interchange in Federal Way opened to traffic in the early 1960s its cloverleaf design was the state of the art in freeway design. But that era’s light traffic volumes concealed the major flaw of the cloverleaf interchange – the weaving that occurs when traffic merges on and off the freeway. Weaving causes congestion and increases the potential for collisions.
The problem wasn’t obvious in the 1960s because I-5 and SR 18 each carried less than a quarter of the traffic they do now. Since the 60s King and Pierce counties have grown significantly, pushing the interchange beyond its limits. The existing loop ramps are substandard and two of the loop ramps are high-accident locations. These improvements will improve traffic flow and safety at this increasingly congested interchange.
The End Result
The project will modify the I-5/SR 18 interchange to eliminate weaving vehicle movements. We have selected a series of improvements that will improve existing and future traffic flow, reduce the number and severity of accidents in the vicinity of I-5, SR 161 and SR 18, and avoid or reduce the effects on the environment.
Crews also will build a new weigh-in-motion station so truck drivers have the option of bypassing the weigh station on southbound I-5 in Federal Way.
What's next?
There is no funding for future projects, but if there were, local leaders and the Legislature have indicated what they'd like to see.
Project Benefits
- Safety: Improvements to the I-5, SR 161 and SR 18 interchange will eliminate weaving vehicle movements by removing two cloverleaf loop ramps, reducing the number of side-swipe collisions.
- Congestion relief: The project will improve traffic flow at this busy interchange.
- Environmental: To manage stormwater runoff crews will build and rebuilding detention ponds. The project includes 22 wetland sites.
What is the project timeline?
March 2005: Held an open house and comment period (pdf 184 kb) to share our new design alternative with the public.
April 2005: Began environmental studies.
Spring 2005: Selected a preferred alternative.
Fall 2005: Began early project design.
January/February 2007: Completed the environmental documentation.
Summer 2007: Began final design phase of the project
March 29, 2010: Advertised project to prospective contractors.
June 21, 2010: Awarded contract to most competitive bidder, Mowat Construction Co.
August 2010: Crews began construction of the project. We expect construction of the first phase to take about two and a half years. We are building the project in phases because we do not have enough funding to build the entire project at this time.
Summer 2012: Open new ramps.
Late 2012: Expected completion.
Financial Information
This project is funded through the following fund sources.
- 2005 Gas Tax (Partnership Funding) - $100,000,000
- 2003 Gas Tax (Nickel Funding) - $3,000,000
- Existing Funds - $687,000
- Other Agency Funds - $8.8 million (federal funds)
- Total Funding From All Sources - $112.5 million
- Voters in King, Pierce and Snohomish counties did not approve Proposition 1, which included some funding for this project as part of the 2007 Regional Transportation Investment District Blueprint for Progress. Other sources of money for this project have not been identified.
How can I get more information?
Contact:
Aleta Borschowa
WSDOT Project Engineer
206-768-5862
BorschA@wsdot.wa.gov
Mike Murphy
WSDOT Communications
206-440-4699
MurphyM@wsdot.wa.gov
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