The first mile of the expressway extends from I-5 to South 24th Street
SEATAC – The first section of a new expressway is about to open in the Puget Sound area, providing travelers with another commuting option in south King County.
At 5:09 a.m. on Saturday, June 28, the Washington State Department of Transportation will open the first mile of the State Route 509 Expressway. The first mile of the SR 509 Completion Project stretches between Interstate 5 and 24th Avenue South in SeaTac.
“Opening a new highway is an exciting moment for us,” said Puget Sound Gateway Program Administrator John White. “Completing this section is a critical step toward delivering the entire SR 509 Completion Project to help reduce congestion and finish a vital freight link between the Port of Seattle and industrial areas in south King County.”
“Approximately 40% of jobs in Washington are tied to trade, and our economy depends on reliable, efficient connections between farms, ports, manufacturers and markets,” said Rep. Jake Fey, chair of the House Transportation Committee. “The SR 509 Expressway is more than just a new road — it’s a critical freight and commuter link that will ease congestion, improve safety and support good-paying jobs across the region. This is the kind of smart, long-term investment that helps every corner of our state thrive.”
The first mile and other improvements
The new highway is being built in stages. The first mile features two lanes in each direction between I-5 and 24th Avenue South. Northbound I-5 drivers will exit to a large fly-over ramp that connects to the expressway. Until the next section of the expressway opens, drivers will exit at 24th Avenue South. Travelers can also enter the expressway from 24th Avenue South and travel southeast to merge onto southbound I-5.
Besides the first mile, this stage of the SR 509 Completion Project features many other improvements:
- Extension of Veterans Drive, linking to a new tunnel under I-5.
- A wider South 216th Street bridge over I-5.
- A realigned southbound I-5 exit to SR 516.
- An improved eastbound SR 516 on-ramp to northbound I-5.
- New sidewalks and multimodal connections.
By the numbers
Atkinson Construction was awarded a $263.9 million contract in 2020 to build the first mile and other improvements. Since work began in 2021, construction crews have:
- Excavated 750,000 cubic yards of soil.
- Placed more than 136,000 tons of asphalt.
- Installed more than 1.8 million pounds of rebar in new bridges.
- Poured more than 10,700 cubic yards of concrete.
- Planted nearly 20,000 trees and shrubs throughout the project area.
- Laid down more than 10 miles of drainage pipe.
Atkinson Construction will also build the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street in SeaTac.
Tolling begins in the fall
The new expressway will be tolled beginning in the fall. Tolling based on time of day will be used to help manage congestion on the new corridor. Toll funding will also help pay for construction and ongoing maintenance.
Tolling will only apply to the new expressway. The existing section of SR 509 between the First Avenue South Bridge in Seattle and South 188th Street in SeaTac will not be tolled. The Washington State Transportation Commission adopted the toll rates for SR 509 on June 17. The expressway will remain free through the summer, but drivers are encouraged to set up Good To Go! accounts before tolling begins.
SR 509 Completion Project information
The SR 509 Completion Project builds 3 miles of new tolled highway between I-5 and South 188th Street near the south end of Seattle-Tacoma International Airport. It also includes improvements on I-5 between South 212th Street in SeaTac and South 272nd Street in Federal Way. The final stage of the project to build the remaining 2 miles of expressway is under construction and scheduled for completion in 2029.
Photos of construction work are available on the project’s Flickr page. A 3D video tour is also available on WSDOT’s YouTube page.
Puget Sound Gateway Program overview
The SR 509 Completion Project is part of WSDOT’s Puget Sound Gateway Program, which also includes the SR 167 Completion Project in Pierce County. Together, the two completion projects finish critical missing links in Washington’s highway and freight network.