For a large chunk of Saturday and Sunday this weekend (Oc.t 5-6) SR 99 from the West Seattle Bridge to Battery Street Tunnel will be closed to all traffic so the Washington State Department of Transportation can perform their semi-annual safety check of the aging roadway.

Here are the details from WSDOT:

Semiannual Alaskan Way Viaduct inspection, utility work to close SR 99 through Seattle this weekend

The Washington State Department of Transportation will close the SR 99 Alaskan Way Viaduct for a semiannual safety inspection from 5 a.m. to 6 p.m. Saturday and 6 a.m. to 6 p.m. Sunday. Additionally, crews working on the City of Seattle’s Mercer Corridor Project will close a section of SR 99 north of downtown, including the Battery Street Tunnel, to install a sewer line from 11 p.m. Friday to 5 a.m. Monday.

The closures were scheduled on the same weekend to avoid creating backups on multiple weekends. Travelers should expect increased congestion in and near downtown Seattle and allow extra time to reach their destination.

Closure details

Friday, Oct. 4, to Monday, Oct. 7 (Mercer Corridor Project):

All lanes in both directions of SR 99/Aurora Avenue North will be closed between the south end of the Battery Street Tunnel and Valley Street from 11 p.m. Friday to 5 a.m. Monday.

Saturday, Oct. 5 (viaduct inspection):

All lanes in both directions of the Alaskan Way Viaduct will be closed between South Spokane Street and the Battery Street Tunnel from 5 a.m. to 6 p.m.

Sunday, Oct. 6 (viaduct inspection):

All lanes in both directions of the Alaskan Way Viaduct will be closed between South Spokane Street and the Battery Street Tunnel from 6 a.m. to 6 p.m.