SEATTLE – It’s about time for people who use the State Route 99 tunnel under downtown Seattle to get a grip.
Beginning Monday night, Aug. 18, contractor crews working for the Washington State Department of Transportation will texturize lanes in the tunnels to improve traction for vehicles.
The quick-moving project requires up to five nightly closures in each the northbound and southbound tunnels. Work is expected to wrap up before Labor Day weekend.
A blast back to the past
Since opening in February 2019, the driving surface of the 2-mile, double-decker tunnel has become worn. More than 47,000 vehicles used the tunnels daily in 2023.
The $1.5 million project will restore the tire grip the northbound and southbound tunnels had when they opened more than six years ago.
A technique called shot-blasting will rehabilitate the driving surface, using high-velocity particle grains. This blasting will change the roadway’s coarseness. Trucks will tow machines that blast the grains and vacuum any dust created from the process so that the tunnels’ air filtration systems and storm drains will not clog.
What to expect
Work begins with all northbound SR 99 lanes closing Monday night, Aug. 18. From 11 p.m. to 4:30 a.m. nightly for up to five nights, all northbound SR 99 traffic will need to exit to South Dearborn Street. The Colorado Avenue South on-ramp to northbound SR 99 will close an hour earlier each night at 10 p.m.
Once crews finish texturing northbound lanes, they will switch and close the southbound tunnel for up to five nights. From 10 p.m. to 5 a.m. nightly, all southbound SR 99 traffic must exit at the Denny Way off-ramp. The Sixth Avenue South on-ramp to southbound SR 99 will close at the same time.
Signed detours will guide people around the tunnel closures using city streets and northbound and southbound Interstate 5. Nightly closures will not begin until two hours after the last pitch for Seattle Mariners games at T-Mobile Park or completion of Seattle Regin and Sounders games at Lumen Field.