The work that will happen during the SR 99 closure

SEATTLE — The new State Route 99 tunnel itself is ready for traffic.

But roadway connections still need to be made leading to the tunnel.

That's the reason for the three-week closure.

"There's a lot of work. I know three weeks seems like a long time. This isn't just moving some traffic cones," said David Sowers of the Washington State Department of Transportation.

On the south end, crews will take away the temporary roadway built to skirt the tunnel construction site.

A wall of foam blocks that forms the base for a temporary roadway will need to be pulled out during the closure.

One of the biggest tasks will be finishing a new off ramp from northbound 99 to downtown.

The bridge is done, but the next section will have to be built where the temporary roadway is now.

That is such a big job that it will take longer than three weeks, and won't be open for seven to 10 days after traffic moves into the tunnel.

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That extra construction time will lengthen the morning traffic headaches for people who live in West Seattle or points south and work downtown.

There's also a lot of work coming to the tunnel's north portal near Seattle Center. A temporary wall will be torn down so traffic can flow directly into the tunnel.

The state hopes to open the tunnel Feb. 4th, but that could be pushed back if we get a lot of bad weather.

State officials say they built two or three days into the schedule for weather delays.

"There's a fair amount of concrete work, paving, striping, some of this is weather-sensitive so there could be some impact to our schedule if we have sustained periods of really lousy weather," Sowers said.

All of the work during the three-week closure means that when the tunnel opens,  people will use SR99 differently than they do now.

For starters, there will be no downtown exits at Seneca Street and Western Avenue.

The two-mile tunnel will basically be a downtown bypass.

Some drivers will need to double back to reach their destinations.

Unlike the viaduct where northbound traffic is on top and southbound traffic is below, directions will reverse in the new tunnel, with southbound lanes on top.

Reaching the new tunnel from downtown will probably confuse drivers at first because of all the new street connections.

That's why the DOT produced videos showing several southbound paths from the tunnel's north end and the choices for going northbound from the south end.

After  the viaduct comes down and the Battery Street tunnel is filled in, Alaskan Way will be rebuilt on a transformed waterfront.

Cox Media Group