The Viaduct closes down entirely for its twice-yearly checkup this weekend, part of routine maintenance since the roadway suffered damage in the 2001 Nisqually earthquake.
Parts of the closure will last longer than usual due to some work being completed on its replacement, the State Route 99 tunnel.
The northbound roadway will be closed entirely from 11 p.m. the night of Friday, October 6 through 5 a.m. the morning of Monday, October 9 to allow for Seattle Tunnel Partners to complete work on the future northbound on-ramp.
The southbound roadway, as usual, will be closed during the day on Saturday, October 7 and Sunday, October 8, from 5 a.m. through 6 p.m.
The closures affect State Route 99 from Spokane Street to the north end of the Battery Street Tunnel.
The damaged viaduct will eventually be replaced by the SR 99 tunnel. Since the last closure in March, Seattle Tunnel Partners completed digging the tunnel—Bertha the tunnel-boring machine broke through in April.
Current estimates by Seattle Tunnel Partners, contracted by WSDOT to build the tunnel, put the opening date in early 2019—at which point the viaduct will be demolished. The original estimated completion date was December 2015.