The State Route 99 tunnel in Seattle will experience a complete closure in both directions from 10 p. m. on February 21 to 6 a. m. on February 22, as announced by the Washington State Department of Transportation (WSDOT).

Maintenance work will start at 9 p. m. , with closures of northbound and southbound lanes to ensure safety during critical tasks. Key activities planned include fire suppression testing, drain cleaning, and light repairs, which are essential for maintaining the tunnel's infrastructure. Southbound drivers will need to divert at the Harrison Street off-ramp, while those traveling north should exit at Alaskan Way.

Furthermore, the Sixth Avenue and Royal Brougham Way on-ramps will close by 9 p. m. to facilitate the maintenance process. Commuters and travelers in downtown Seattle are strongly advised to seek alternate routes during this period. For real-time updates and traffic information, users can rely on the WSDOT mobile app and the agency's travel map.

This closure underscores the importance of infrastructure upkeep for public safety and efficient transportation in the region.