The Washington State Dept. of Transportation calls it the “Rest of the West” when talking about State Route 520 improvements in Seattle. And right now it remains an unfunded portion.

But even still, the transportation department unveiled updated designs and plans for the section of the $4.47 billion project that also includes a completely redone 520 east of the floating bridge and a completely new floating bridge, the longest in the world. But it is that section west of the floating bridge toward Interstate 5 that has been placed as the third and final segment of the corridor improvements.

Included in the project is the Portage Bay Bridge, which was the most significant reveal by the state on the update. Gone is the cable-stayed version deemed too expensive and unwanted by neighbors, replaced with a lower-profile six-lane concrete-girder option with seven supports in the water and three on land. It would be built next to the existing four-lane bridge.

Also key in the west side story are new HOV lanes from I-5 to Montlake, highway lids at two locations to help reconnect neighborhoods and provide transit facilities, the south half of a new west approach bridge, mobility improvements that include undercrossings and an extension of regional bicycle and pedestrian paths with connections to local trails and transit.

“These improvements will address two key segments of SR 520 that remain vulnerable to earthquakes: the Portage bay Bridge and the existing west approach bridge,” says Julie Meredith, WSDOT’s SR 520 program administrator, in a statement. “With these design concepts, we are ready to go when additional funding is available to complete this modern, safer, multimodal corridor that is vital to this region.”

The entire package is estimated to cost $1.57 billion, up from a 2012 estimate of $1.4 billion. The increase is due to rising construction costs.

The entire project’s budget of $4.47 billion hovers $180 million under the cap set by the Legisslature in 2009, but the final west portion is currently unfunded. 

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.