For the next 18 months, Washington State Department of Transportation contractors will rehabilitate nearly 13 miles of interstate on southbound I-5 between the Duwamish River and S. 320th St. in Federal Way.

Crews will start work Monday, March 21, and will replace four expansion joints on the Duwamish River Bridge, resurface sections to remove ruts and cracks and repave a 2.7-mile section between S. 188th St. and S. 219th St. They’ll also replace about 235 concrete panels and repave five ramps.

This $27.3 million project will require the crews to reduce southbound I-5 to two lanes for five weekends in July and August 2016. The work will also require frequent overnight lane reductions.

“This section of southbound I-5 is more than 50 years old, and it’s showing its age,” said Department of Transportation project engineer Mike Askarian. “It’s time to restore it. With several months of work, we can keep traffic moving on our region’s main highway for decades to come.”

To renew this section of the interstate, contractor crews from MidMountain Construction will:

• Replace 235 concrete panels that are damaged beyond repair and the expansion joints on the southbound I-5 Duwamish River Bridge.
• Repave southbound I-5 between South 188th Street in SeaTac and South 219th Street in Des Moines, as well as shoulders, lanes and several on- and off-ramps in SeaTac and Des Moines.
• Resurface the freeway by grinding out ruts and cracks in several sections, leaving a smoother driving surface.

Most of the work will be done during overnight lane reductions, mostly between 8 p.m. and 6 a.m. Sunday nights to Friday mornings.

On five weekends in July and August, southbound I-5 will be reduced to two lanes for about 3.5 miles, starting near the southbound State Route 518 onramp. The exact dates have yet to be determined.

“Southbound I-5 usually handles about 86,000 cars a day between Southcenter and Des Moines on weekends,” Askarian said. “To limit congestion, we need about 50 percent of drivers to use other routes or postpone their trip on the weekends when southbound I-5 is reduced to two lanes.”

During the lane reductions, drivers should plan to use alternate routes like State Route 167 to the east and State Routes 99 and 509 to the west, or buses or light rail.

The weekend-long lane reductions are needed to replace the expansion joints on the Duwamish River Bridge and for the paving work between South 188th Street and South 219th Street.