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I-5 - SB S 320th St to Duwamish River Bridge - Concrete Pavement Rehab

The southbound Interstate 5 concrete pavement rehab project is located along 12.86 miles of freeway from Duwamish River Bridge in Tukwila to South 320th Street in Federal Way. View larger map

A small photo showing the condition of I-5, along with asphalt patches, between Federal Way and the Duwamish River Bridge.
There are more than 200 cracked and patched concrete panels on southbound I-5 from Tukwila to Federal Way.


March 2017

  • This project has stopped work for the winter due to weather conditions. Work will resume in late winter and be completed as scheduled in summer 2017.
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Contractor crews are rehabilitating nearly 13 miles of southbound Interstate 5 between the Duwamish River Bridge in Tukwila and South 320th Street in Federal Way. Crews will:

  • Replace 238 broken concrete panels and grind out cracks and bumps.
  • Repave 2.7 miles of concrete roadway across five lanes with new asphalt.
  • Repave five on-and off-ramps.
  • Replace aging and worn expansion joints on the Duwamish River Bridge.

Why is WSDOT rehabilitating this section of southbound I-5?
These lanes of the interstate carry approximately 200,000 vehicles each day. The interstate was built in 1965. The concrete roadway was only intended to last 25 years, but has now doubled its lifespan.

In addition to its age, the increasing number of cars and heavy trucks on the road, along with freeze/thaw cycles, have contributed to the deterioration of the highway. Drivers can notice this in the tell-tale "thump, thump, thump" of their vehicle's wheels. That's the sign of a broken concrete panel that is rocking back and forth, and beyond its lifespan.

Other problems in the southbound lanes that must be addressed include potholes, wheel ruts and worn expansion joints.  

Concrete panel replacement
Crews will remove 238 concrete panels throughout the length of the project. These panels are cracked beyond repair. After the panels are removed, the roadbed will be repaired as necessary with new gravel and then new concrete panels poured.

Throughout the project, crews will repave multiple lanes in various locations.

Repaving requires the removal of the top 1.5 to 2 inches of the existing pavement by grinding it off. This can be unavoidably noisy work. After the asphalt removal is complete, the roadbed will be repaired as needed by excavating deep potholes and cracks and then placing new fill and gravel. Once repairs are complete, a new layer of asphalt will be placed. Crews will also repave the asphalt on ramps located at SR 516, South 188th and South 200th streets.
Crack and seat
Crews will resurface a 2.7-mile section of southbound I-5 between South 188th Street and South 219th Street. The existing concrete will be replaced with asphalt using a process called "crack and seat."

This process allows crews pave over existing concrete roadway. To do this, crews use heavy machinery to break up (crack) the concrete panels that make up the roadway. Next, more heavy machinery is used to compact (seat) the broken concrete into the existing roadbed. Finally, an 8-inch thick layer of asphalt is then placed to create a new driving surface.

Roadway grinding
Roadway grinding is one of the most cost-efficient and effective ways to improve the driving surface of aging concrete.

Grinding removes a very thin layer of the concrete to reveal a new surface. This new surface improves traction for drivers and removes wheel ruts where water can pool.

Grinding work will be performed throughout the length of the project in areas that have not been repaved. 
Expansion joint replacement
Four deteriorating 20-year-old expansion joints on the southbound Duwamish River Bridge will be replaced.

Expansion joints are critical to the safe operation of bridges. They allow a bridge to bend and flex as the concrete on the bridge expands and contracts with changing traffic and freeze/thaw cycles. An expansion joint that fails can pop up into traffic.

Groundwater repair
Crews will repair an area just north of the I-405/SR 518 interchange where groundwater is not draining properly. Crews will remove the pavement on I-5, replace the fill as necessary and install drainage and then pour new concrete panels.

What are the challenges we face?

  • Weather - Paving work must be done when the weather is dry and the ground temperature is at least 45 degrees. This generally limits the times of year when the work can be performed to the summer and early fall.
  • Road and ramp closure planning - Keeping traffic and the economy moving during construction are some of our top priorities. Our engineers work with local cities, agencies and transit providers when planning closures. They also consider traffic volumes, local business needs and special events while balancing that against the time necessary to complete the work. Work hours may still inconvenience some drivers, but WSDOT tries to strike a balance between both the needs of drivers and completing the work successfully.
  • Noise - Roadway grinding and the crack and seat work is noisy and can cause vibration. People who live or work nearby may hear or feel it.

What should drivers expect?
To successfully complete the work, it will require the following closures:

  • Nighttime lane and ramp closures throughout the duration of the project.
  • Generally, no closures will be allowed on Friday and Saturday nights. There will be a few weekends with extended overnight closures, when lanes will begin to reopen at about 9 a.m.
  • At no time will all lanes of southbound I-5 be closed. 

The End Result
This preservation and improvement work will extend the useful life of the interstate for years to come, creating safer and improved driving conditions for the thousands of travelers who use it each day.

Project Benefits

  • Preservation
    • Replacing broken concrete panels, repaving, and grinding the roadway improves the driving surface and extends the life of I-5.
    • Replacing bridge expansion joints on the Duwamish River Bridge ensures the bridge will remain open and operational.
  • Safety
    • Improving the highway surface eliminates and helps prevent future potholes, cracks and wheel ruts, making for a smoother, safer ride for drivers.
    • Replacing the Duwamish River Bridge expansion joints creates safer driving conditions by reducing the chances that an aging expansion joint could become dislodged or fail, creating a hazard to drivers and forcing an emergency closure of the bridge.
  • Economic - Replacing broken concrete panels, repaving and replacing bridge expansion joints reduces the need for emergency repairs, which are costly to taxpayers and can cause additional congestion during peak commute hours. In addition, removing all the concrete at between South 219th and South 188th Street and placing new asphalt is less expensive than placing all new concrete.

What is the project timeline?

  • October 2015 - The project was advertised for competitive bidding.
  • December 2015 - Project was awarded to Midmountain Contractors, Inc.
  • March 2016 - Construction started
  • Summer 2017 - Operational completion is expected. Operationally complete means the majority of the work is complete and the roadway is open to traffic.

Financial Information

Financial Data for PIN 100504B
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $27,275
CWA $0
Total $27,275

How can I get more information?
Tom Pearce
WSDOT Communications
Phone: 206-440-4696

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