Cities
Head’s up, south King County. Nighttime lane and ramp closures will continue on State Route 509 in SeaTac and Burien from Monday, Feb. 9 through the morning of Thursday, Feb. 12, as crews install guardrails and signage ahead of Valentine’s Day travel.
The work is part of the Washington State Department of Transportation (WSDOT) SR 509 Completion Project. Expect reduced capacity overnight and allow extra time.
Lane Closures
Overnight, 8 p.m. to 5 a.m.
- Monday night, Feb. 9 → Tuesday morning, Feb. 10
- Wednesday night, Feb. 11 → Thursday morning, Feb. 12
What to expect:
- One lane closed in each direction of SR 509 between South 176th Street and South 188th Street.
Ramp Closures
Monday night, Feb. 9 → Tuesday morning, Feb. 10
- 7 p.m. to 5 a.m. – Northbound SR 509 off-ramp to South 160th Street closed
- 10 p.m. to 5 a.m. – South 160th Street on-ramp to southbound SR 509 closed
- Signed detours will be in place
Wednesday night, Feb. 11 → Thursday morning, Feb. 12
- 7 p.m. to 5 a.m. – Northbound SR 509 off-ramp to South 160th Street closed
- 10 p.m. to 5 a.m. – South 160th Street on-ramp to southbound SR 509 closed
- Signed detours will be in place
Project Background
The SR 509 Completion Project is building three miles of new tolled highway connecting I-5 to South 188th Street near the south end of Seattle-Tacoma International Airport. Construction is being delivered in stages:
- I-5 to 24th Avenue South opened June 28, 2025
- New tunnel under I-5 at the SR 516 interchange opened July 16, 2025
- The final two miles (24th Ave S to S 188th St) are under construction, with full completion planned by 2029
The project is part of WSDOT’s broader Puget Sound Gateway Program, which also includes the SR 167 Completion Project in Pierce County.
Travel tips:
- Plan for overnight delays, especially near South 160th Street.
- Follow posted detours and watch for crews.
- If you can, shift trips earlier in the evening or use alternate routes.
We’ll keep Highline Journal readers posted if schedules change.
Images courtesy of WSDOT:
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