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I-5 - Reconstruction Projects - King County

This project is in the planning phase
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I-5 thru downtown Seattle
Interstate 5 passing through downtown Seattle.


April 2014

WSDOT is developing a list of coordinated and prioritized projects to replace 16 miles of deteriorating pavement between Tukwila and Northgate while also looking at options to make traffic flow better.

Replacing the pavement on I-5 offers a unique opportunity to fix long-standing traffic bottlenecks, so we are evaluating ways to improve traffic flow that can be implemented during pavement reconstruction.

The I-5 work requires close coordination with several WSDOT departments, cities, counties and transit agencies within the corridor, and with other projects: the Alaskan Way Viaduct, the SR 520 Bridge Replacement and HOV Project, SR 519 and Sound Transit North Link Light Rail.

Why is WSDOT improving this stretch of I-5?
Every day 250,000 vehicles travel through Seattle on I-5, the main north-south interstate freeway in Washington state. It is the busiest freeway in the state with 70 percent of the state’s population living within 16 miles.

Closing lanes of I-5 for maintenance repairs is disruptive, costly and provides a temporary bandage for a worsening condition. The original concrete pavement is deteriorating to the point where it needs to be removed and replaced to preserve the freeway and provide a safer, smoother ride for thousands of drivers.

The End Result
This project is in the early stages of design. We are looking at removing the existing nine inch-thick pavement on the freeway and replacing it with thicker pavement reinforced with steel bars at the joints.

The thicker concrete would ensure at least another 40 years of service, and the bars would help the roadway behave like a single unit rather than like individual concrete panels. This would minimize the rough "thump, thump, thump" motorists now hear and feel as they drive on I-5 through Seattle.

Project Benefits
Safety. The new, smoother road surface will improve driver safety and will eliminate drivers having to avoid holes and cracks in the roadway.

Road surface. The reconstructed lanes will improve the roadway surface and provide a smoother ride for drivers.

Pavement lifespan. This project extends the freeway's lifespan and puts an end to costly and inconvenient temporary repairs.

Traffic flow. The project will reduce traffic bottlenecks and chokepoints where possible, improving the flow of people and goods through the heart of Seattle.

What is the project timeline?

  • 2004 - 2008. Identify and prioritize the list of pavement replacement projects that may include operational improvements.
  • 2009. The I-5 Pavement Repair project from Tukwila to Shoreline. This project addresses the most urgent pavement repairs until pavement replacement can be done.
  • 2012 - Start work on King County projects to grind existing pavement and replace dozens of cracked concrete panels.
  • 2017 - beyond. Construction of pavement replacement and operational improvements. (Assuming funds are available.)

Financial Information

Financial Data for PIN 800515B, 800515C
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $108,244
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $54,965
Total $163,209

Project signage will reflect the cost of construction engineering, project bid award and sales tax.

The legislature appropriated the following funds for this project. These funds are anticipated to only cover the first of many projects needed to replace the worn pavement on I-5 between Tukwila and Northgate.

Analysis and Preliminary Design
- $10.3 Million
Design and Construction - $21 Million (Available starting in 2009) and $114 Million (Available starting in 2017 and beyond)

For more information about the Cost Estimate Validation Process and the cost estimate ranges, please visit the CEVP Web site.

How can I get more information?
Carol Hunter, Project Manager

401 Second Avenue South, Suite 300
Seattle, WA 98104

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