Project Facts
- 80% of traffic to Sea-Tac International Airport travels on SR 518
- Due to airport traffic, SR 518 carries more traffic than the SR 520 Bridge.
- Airport passenger growth is projected to increase from 29 million annual passengers today to 44 million by 2020.
May 2008
- Construction is underway on the SR 509/518 interchange including preliminary environmental work, erosion control and traffic control.
- WSDOT awarded the contracts for the SR 518 – SeaTac Airport to I-5 / I-405 Interchange and the SR 509/518 Interchange Improvement projects to Tri-State Construction, Inc.
- The Port of Seattle is contributing an additional $5 million to the project. The Federal Government has contributed an additional $4.8 million to the project.
Why is WSDOT
undertaking the SR 518 Sea-Tac Airport to I-5/I-405 Interchange Project?
SR 518 is becoming a progressively more popular connection between SR 509 and I-5/I-405. This increase in traffic, combined with forecasts calling for significant air travel growth over the coming years, will dramatically impact SR 518. If improvements aren't made to eastbound SR 518, drivers traveling the corridor will encounter difficult merge conditions, and drivers leaving Sea-Tac Airport can experience more than 30-minute delays, with lines of cars projected to back up nearly to the airport garage.
The End Result
The SR 518 Sea-Tac Airport to I-5/I-405 Interchange Project improves existing mobility and safety and accommodates projected airport traffic by adding a third eastbound lane on SR 518 between the North Airport Expressway and the I-5/I-405 Interchange.
The project also provides for further regional improvements, including Sound Transit's LINK light rail line extension to the airport and the Airport traffic and parking enhancements slated for completion in 2006, which are both dependent on the SR 518 improvements.
Project Benefits
• Congestion Relief
The project will reduce airport congestion and delays. Adding a third lane on SR 518 will allow better traffic flow during airport and freeway rush hours and will yield travel time savings at the airport ramps that currently experience backups.
• Safety
Adding a third eastbound lane on SR 518 will improve and simplify the merging from the North Airport Expressway on the west end of the project as well as access to the entrances to I-5 and I-405 on the east end of the project.
• Environmental Benefits
The proposed project will make beneficial improvements to existing conditions. Noise walls will be installed to reduce traffic noise for neighborhoods. Runoff from the highway will be treated to enhance overall water quality conditions. Detention facilities and stormwater treatment will be provided to protect Gilliam Creek.
What is the project timeline?
Spring 2006
The Environmental Assessment (EA) was published on May 30, 2006.
Summer 2006
The Environmental Assessment (EA) and Finding of No Significant Impact (FONSI) were approved by the Federal Highway Administration (FHWA).
Spring 2007
Project design completed.
The EA and FONSI were issued under the National Environmental Policy Act (NEPA) and adopted under the State Environmental Policy Act (SEPA) rules.
Summer 2007
Construction begins.
WSDOT has awarded the contracts for the SR 518 – SeaTac Airport to I-5 / I-405 Interchange and the SR 509/518 Interchange Improvement projects to Tri-State Construction, Inc.
Construction has begun at the SR 509/518 interchange including preliminary environmental work, erosion control and traffic control.
Fall 2009
Project opens to traffic.
Public Involvement
Your involvement throughout this project is important. It ensures that problems and concerns regarding alternatives and foreseeable disruptions are addressed.
Please send your thoughts or questions directly to our project office by filling out the Contact Us form.
Environmental Protection
The Environmental Assessment (EA) has identified and evaluated potential effects of the project. An environmental assessment is a document that identifies and evaluates potential environmental effects of the proposed project and describes the transportation or other needs that the proposed project will satisfy.
In the case of the SR 518 Sea-Tac Airport to I-5/I-405 Interchange Project, improvements result in congestion relief and improved safety. Additionally, the project environmental assessment lists and analyzes proposed alternatives as well as describes the impacts and mitigation measures for the alternatives.
Finally, an environmental assessment addresses concerns submitted by agencies and the general public during the public scoping period.
Please visit the WSDOT Environmental
Services Web site for more information.
Increasing safety is one of our priorities
Please read our "Projects Benefits" section above for more information on the project's safety improvements.
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.
Financial Information
The project is funded through the following sources:
- 2005 Gas Tax - $20 Million
- The Port of Seattle - $10 Million
- The Federal Government - $4.8 Million
- Other - $1.0 Million
Total Funding Available from all sources - $30.8 Million
How can I get more information?
Contact:
Joshua Cheatham, P.E.
Construction Project Engineer
WSDOT Urban Corridors Office
Phone: 253-872-2958
Paul E. Johnson, P.E.
Design Project Engineer
WSDOT Urban Corridors Office
Phone: 206-768-5680
Noel S. Brady
Public Information Officer
401 2nd Ave. S, Suite 200
Seattle, WA 98104
Phone: 206-464-1183
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