June 2009
- The SR 509/518 Safety Improvements Project is under construction and is anticipated to be complete by summer 2008.
- A Determination of Non-Significance has been issued for the project under the State Environmental Policy Act.
- Design work continues on the SR 509/518 Flyover project.
The SR 509/SR 518 Interchange Improvement Projects consist of:
Safety Improvement Project
Safety improvements that include reconfiguring the number of through and turning lanes, revised signal timing, landscaping and improved signing.
The SR 509/518 Safety Improvements project was awarded along with the SR 518 SeaTac Airport to I-5 / I-405 Interchange project, a suite of projects that will improve safety, congestion relief, and provide environmental benefits along the SR 518 corridor.
Flyover Project
Construction of a new SR 509 southbound to SR 518 eastbound freeway-to-freeway "flyover" (elevated) ramp.
The Flyover Project recently received approval from the Federal Highway Administration on the Documented Categorical Exclusion (DCE) under the National Environmental Policy Act (NEPA). Design work is proceeding on the Flyover.
Why is WSDOT
pursuing these projects?
Under current conditions, the southbound SR 509 connection to eastbound SR 518 goes through a series of signalized intersections. Many accidents have occurred at this location.
Additionally, forecasts call for strong air travel growth over the coming years. This will dramatically intensify traffic on travelers heading from Seattle on SR 509 and accessing the airport on SR 518.
The interchange improvements will address the safety problems and provide for anticipated growth.
Our Partners
WSDOT is working closely with the city of Burien to coordinate construction of these improvements.
The End Result
- Safety Improvement Project – Reconfigures the existing interchange with improved lane configurations, signal timing, traffic calming features, and signing. The improvements will better define the city of Burien’s entryway.
- Flyover Project - Builds a southbound to eastbound freeway-to-freeway connection. The connection would be made with a new elevated structure that crosses over the existing interchange. The structure would begin just south of the South 146th Street bridge and extend over SR 509 and connect to the eastbound SR 518 lanes.
Project Benefits
- Safety. There are a lot of accidents at the intersection of SR 509 and SR 518. Changing the lane configurations, signal timing, and signing will reduce the number of accidents and improve traffic movements.
- Congestion Relief. The new flyover ramp will make it easier to get to the airport and provide more direct access to the city of Burien. The flyover will allow a true freeway-to freeway connection and eliminate many of the existing backups currently experienced at the interchange.
What is the project timeline?
Spring 2008
- Continuing construction of the Interchange Safety Improvements project.
- Design work will continue on the Flyover project.
Financial Information
The current cost estimate for the SR 518 Interchange Improvements Project is:
- Flyover Project - $45 million (2005 CEVP)
To date, the SR 518 Interchange Improvements Project has received:
- $5 million from State and Local Funding
- $2.8 million from federal funding sources
Total funding available from all sources - $7.8 million
Total amount not funded - $37.2 million
How can I get more information?
Contact:
Mark Sawyer, PE
SR 509/518 Safety Inprovements Construction Projects Engineer
WSDOT, Urban Corridors Office
Phone: 425-649-4429
Jason Biggs, PE
Project Engineer
WSDOT, Urban Corridors Office
Phone: 206-768-5803
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