The Washington State Department of Transportation opened the first section of the new State Route 509 Expressway in the Puget Sound area on June 28, 2025, providing travelers with another commuting option in south King County.
The first mile of the SR 509 Completion Project stretches between Interstate 5 and 24th Avenue South in SeaTac.
Atkinson Construction was awarded a $263.9 million contract in 2020 to build 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; and
• new sidewalks and multimodal connections
Since work began in 2021, construction crews have:
• excavated 750,000 cu. yds. of soil;
• placed more than 136,000 tons of asphalt;
• installed more than 1.8 million lbs. of rebar in new bridges;
• poured more than 10,700 cu. yds. of concrete;
• planted nearly 20,000 trees and shrubs throughout the project area; and
• laid down more than 10 mi. of drainage pipe
Atkinson Construction also will build the remaining 2 mi. of the expressway between 24th Avenue South and South 188th Street in SeaTac.
In all, 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 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.
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 also will help pay for construction and ongoing maintenance.
"Opening a new highway is an exciting moment for us," said John White, Puget Sound Gateway Program administrator. "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 percent 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."
(All photos courtesy of the Washington State Department of Transportation.)
