Countdown to Construction
February 2010
- This project will be advertised to contractors on March 29, 2010.
- We expect to begin construction in summer 2010.
- The project completely transforms the I-5/SR 18/SR 161 interchange and will help people move safer and faster.
- Because of limited funding we will build the project in phases. View our folio (pdf 978 kb) to learn more about the project and what we're planning to build first.
We are designing major changes to the area where Interstate 5, SR 161 and SR 18 connect in Federal Way.
The reconstruction includes replacing two cloverleaf loop ramps with flyover ramps for westbound SR 18 to southbound I-5 traffic and eastbound SR 18 to northbound I-5 traffic. We also will provide direct access to SR 161 from southbound I-5 and westbound SR 18 by building new exit ramps at S. 356th Street and S. 359th Street.
Due to limited funding, WSDOT will construct these improvements in phases with separate contracts. Construction on the first phase will begin 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
designing 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 preferred alternative that will improve existing and future traffic circulation, 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.
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.
- Congestion relief: The selected preferred alternative will improve traffic flow while reducing the number and severity of accidents.
What is the project timeline?
March 2005: Hold 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: Advertise project to prospective contractors.
Summer 2010: Begin construction of the project. We expect construction of the first phase to take about two years. We are building the project in phases because we do not have enough funding to build the entire project at this time.
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:
Bruce Nebbitt
WSDOT Project Engineer
206-716-1170
nebbieb@wsdot.wa.gov
Mike Murphy
WSDOT Communications
206-440-4699
murphym@wsdot.wa.gov
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