Seattle viaduct to close for 3 weeks this fall before new tunnel opens

Seattle's Alaskan Way Viaduct (KOMO Photo)

SEATTLE - The Alaskan Way Viaduct and Battery Street Tunnel will be closed for three weeks before the opening of the new Highway 99 tunnel this fall, forcing north-south traffic onto alternate routes through downtown Seattle, state transportation officials say.

The closure, from the Battery Street Tunnel to South Spokane Street, will be needed to realign Highway 99 from the viaduct to the tunnel.

Laura Newborn of the state Department of Transportation says officials don't yet know the exact dates of the viaduct closure, since it will depend on how long it takes to get the new tunnel ready to open. They hope to give motorists at least one month's advance notice of the viaduct closure.

Ramps at the tunnel’s south end will close earlier than the viaduct and open later to accommodate the large amount of work involved in connecting Highway 99 to the new tunnel.

The southbound off-ramp to South Atlantic Street will close approximately one week before the main closure begins. The new northbound off-ramp to South Dearborn Street will open one to two weeks after the tunnel opens to drivers.

When the viaduct closure ends, the new tunnel will open and Highway 99 drivers will have a direct route from the stadiums to the Space Needle. The viaduct and Battery Street Tunnel will then be permanently closed in preparation for the start of the demolition project.

Meanwhile, work is proceeding on the new two-mile tunnel itself, which is the largest double-deck highway tunnel of its kind in the country.

The tunnel will have two lanes in each direction, plus an eight-foot safety shoulder, with no mid-tunnel exits or entrances.

The tunnel will not be tolled when it opens. Tolling will start in 2019 on a date to be determined.

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