11-year project to improve Route 16/Interstate 5 interchange almost finished, state says

The end is near for the 11-year project to rebuild the Nalley Valley Viaduct, the interchange that connects State Route 16 and Interstate 5 in Tacoma.

The Washington State Department of Transportation said Tuesday that by the middle of this month, it will open connected high-occupancy vehicle lanes between the two highways.

When that happens, vehicles carrying two or more people, vanpools, carpools and school buses can use HOV lanes between Route 16 and I-5.

WSDOT has a video (see above) to show motorists how those connections will work, and it has some important pointers.

For example, HOV users traveling on northbound I-5 past the Tacoma Mall to Route 16 will have an HOV lane to use between the two highways. They will need to be in the far left lane of northbound I-5, just past the South 48th Street overpass, to access the dedicated HOV exit to westbound Route 16 HOV.

“Travelers should note that there is no connection to Sprague or Union Avenue from the HOV lane,” the video says.

Connecting the HOV lanes is the third and final project that rebuilt the interchange at an estimated cost of $441 million.

Why did it take 11 years?

“The projects were built as funding was allocated,” WSDOT spokesman Doug Adamson said in an email. “Enhancing existing highways also is no small feat. It requires in-depth planning, expertise, and elbow grease.

“All this is done while keeping tens of thousands of travelers moving every day. In the case of I-5, it’s hundreds of thousands of travelers every day,” Adamson added.

But that doesn’t mean it’s the end of work on HOV lanes in Tacoma/Pierce County.

WSDOT said the I-5/Portland Avenue to Port of Tacoma Road/Southbound HOV project consists of a new southbound I-5 Puyallup River bridge and connecting HOV lanes currently under construction between Tacoma and Fife.

When the HOV connections open at the I-5 and Route 16 interchange, motorists who use the northbound I-5 HOV lane temporarily will need to merge into mainline traffic near the Yakima Avenue overpass, said WSDOT spokeswoman Cara Mitchell.

This temporary arrangement will continue until the southbound I-5 Puyallup River Bridge project is complete, in late 2021.

That’s when the entire HOV system will be open, with HOV lanes extending from Gig Harbor on Route 16, onto I-5 through Tacoma and Fife and continuing through King County, Mitchell said.

About $1.6 billion has been spent over the past 20 years on the Tacoma/Pierce County HOV program.

The Nalley Valley Viaduct opened in 1971. Since then, the average number of vehicles using the interchange has more than tripled, from 40,000 to 133,000.

WSDOT said the original interchange was too narrow to carry additional lanes and the structure was not suitable for widening.

The design and construction efforts began in 2008 to bring additional capacity to the viaduct through three separate projects over 11 years:

Route 16 Westbound Nalley Valley project, completed in 2011

Route 16 Eastbound Nalley Valley project, completed in 2014

I-5 and Route 16 Realignment — HOV connections, completed this fall.

In a written statement, WSDOT Regional Administrator John Wynands said of the HOV lanes: “They are a key transportation component that keeps people moving and improves trip reliability for those who choose to share the ride. At the end of the day, that is what this project is all about.”

James Drew covers the state Legislature and state government for McClatchy’s Washington papers: The News Tribune, The Olympian, The Bellingham Herald and The Tri-City Herald.