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I-5 - S. 272nd St. to S. Rose St. Seismic Retrofit

Project map of the work area.
Click here for larger version of map.

Existing bridge columns to be retrofitted.  Beginning spring 2014, eight sections of I-5, from Federal Way to south Seattle, will be seismically retrofitted.

A closeup of columns supporting the bridge girders.
Columns and cross beams hold up the bridge girders and bridge deck under I-5.

Columns will be fitted with steel jackets to make them stronger.
Crews will strengthen columns against earthquakes by installing steel jackets around them.


February 2016

  • This project is operationally complete. Operationally complete means the majority of work is done and no additional lane closures are expected.
  • Learn more about WSDOT's seismic retrofit program.
  • Sign up to receive email updates about this project and other South King County topics.


Starting in early spring 2014, crews began seismically retrofitting eight bridged sections of Interstate 5 between South 272nd Street in Kent to South Rose Street near South Seattle. This project helps reduce damage to I-5 bridges in the event of an earthquake by strengthening the columns and crossbeams that support the bridged sections.

What can drivers expect?

• There will be no lane closures of mainline I-5. However, drivers can expect weeknight lane closure on roads and highways that pass under the elevated section of I-5. At times, crews also may work during the day.
• Crews will post easy to navigate detours directing traffic and pedestrians around the work zone when necessary.

Work will be done under northbound and southbound I-5 at:
• Military Road South near Star Lake in the Federal Way/Kent area
• South 272nd Street in Kent
• South 259th Place in Kent
• South Kent-Des Moines Road in Kent
• South 188th Street in SeaTac
• State Route 518/I-405 in Tukwila
• Klickitat Drive in Tukwila
• South Rose Street in South Seattle

Why is WSDOT seismically retrofitting eight sections of I-5 from S. 272nd Street to S. Rose Street?

I-5 was built more than 50 years ago to seismic standards that are now out of date. As a result, sections of I-5 in the Puget Sound area are vulnerable to earthquake damage. This project is part of our seismic retrofit program established in 1991 to help make bridges safer by bringing them up to current seismic standards.

As of late 2013, WSDOT has 913 bridges in the program, of which 284 have been completely retrofitted.

The End Result

WSDOT will make several types of safety improvements to the columns supporting elevated sections of I-5. Improvements include:
• Installing large steel sheets, called column jackets, around existing columns. This will help prevent them from crumbling during a sizeable earthquake.
• Adding supports to the crossbeams which hold up the bridges. The added supports are called bolsters, which create a wider base for the bridge girders to lie on.
• Installing girder stops. Girder stops are similar to bolsters. They add strength to the bridges and prevent the bridge girders from sliding around on the crossbeams.

Project Benefits

– Strengthening bridge columns, crossbeams and girders helps keep drivers safer by reducing the risk of damage during an earthquake. Concrete columns are less likely to crumble and bridge girders are less likely to slide off trusses and beams.

What is the project timeline?

  • December 18, 2013 – Contract advertised to contractors
  • January 2014 - Project awarded to Quigg Bros., Inc.
  • Early spring 2014 - Construction begins
  • December  2015 - The project is complete.

Financial Information

Financial Data for PIN 100506K, 100507C
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $13,507
Total $13,507

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

How can I get more information?
Mike Askarian
WSDOT Project Engineer 
Phone: (206) 768-5861

Kris Olsen
WSDOT Communications
Phone: (206) 440-4704

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