The 48-hour shutdown will last until 11:59 p.m. Sunday. Drivers can still go south through the Battery Street Tunnel but must immediately exit using the Western Avenue offramp.

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The southbound lanes of the Alaskan Way Viaduct are closed this weekend so concrete can be poured for the future Highway 99 tunnel Sodo interchange.

The 48-hour shutdown is from 11:59 p.m. Friday until 11:59 p.m. Sunday. Drivers may still go south through the Battery Street Tunnel but must exit immediately at the Western Avenue offramp.

Meanwhile, previously announced repaving closures were rained out for both northbound I-5 from Sodo to Lake Union and westbound Highway 2 from Snohomish to Interstate 5 in Everett.

This fall the viaduct along Seattle’s waterfront will close permanently so that end ramps at both Sodo and South Lake Union can be attached to the 1.7-mile tunnel, which bypasses downtown Seattle.

This weekend’s work is at South Atlantic Street. The new interchange will have ramps from the stadium area and a future waterfront Alaskan Way boulevard, which will be the main route for ferry traffic.

The Washington State Department of Transportation says it will issue a warning one month in advance before carrying out its “Realign 99” operation, when it will close Highway 99 through Seattle for three weeks.

After that, the four-lane tunnel will have its grand opening. The new northbound exit to Dearborn Street near the stadiums will require two more weeks of construction.