Updated SR520 designs unveiled for final portion

The Washington State Department of Transportation (WSDOT) has recently updated the design and cost for completing “Rest of the West” state Route 520 improvements in Seattle.

In collaboration with the City of Seattle and local stakeholders, WSDOT incorporated community recommendations into its updated draft of design concepts for rebuilding the highway between Interstate 5 and Lake Washington.

Key west-side design features include:

•A new Portage Bay Bridge between I-5 and Montlake;

•New HOV lanes from I-5 to Montlake;

•Highway lids at Montlake Boulevard and 10th Avenue East/Delmar Drive East, with transit facilities;

•The south half of a new west-approach bridge built to modern seismic standards, for carrying eastbound traffic from Montlake to the new floating bridge;

•Mobility improvements such as bicycle, pedestrian and transit connections and networks to and from SR 520 to existing and planned city networks, including safer undercrossings; and

•An extension to I-5 of a regional bicycle and pedestrian path from Seattle to the Eastside, with connections to local trails and transit stops.

Along with the new design plans, WSDOT updated its cost estimate of $4.47 billion for rebuilding the full SR 520 corridor from I-5 to Interstate 405; that figure is $180 million lower than the $4.65 billion budget cap set by the Legislature in 2009.

The new estimate includes a cost of $1.57 billion to construct SR 520’s unfunded western segment; a 2012 estimate put that cost at $1.40 billion.