This weekend, the Viaduct closes down entirely for its twice-yearly checkup, part of routine maintenance since the 2001 Nisqually quake.
Saturday, March 4 and Sunday, March 5, SR 99 will be closed at least from 6 a.m. to 6 p.m. from Spokane Street to the Battery Street Tunnel.
Each day has unique bonus closures, though, so it might be best to avoid 99 altogether. On Saturday, road maintenance extends the closure in the southbound lanes north to Valley Street; on Sunday morning, the Hot Chocolate Run is closing 99 north all the way to 45th.
The damaged viaduct will eventually be replaced by the SR 99 tunnel. Bertha, the boring machine digging the tunnel, is around 88 percent complete, and as of Thursday is somewhere around 6th Avenue and Wall Street in Belltown.
Current estimates by Seattle Tunnel Partners, contracted by WSDOT to build the tunnel, put the opening date in early 2019. The original estimated completion date was December 2015.