To get through the downtown area of Seattle in a motor vehicle, you currently have three options:
1) city streets
2) Freeway (I-5)
3) Alaskan Way Viaduct -- an elevated arterial, six lanes.
Option 3 is the issue. In the 90's after an earthquake they did some structural testing and discovered that the viaduct is in danger of collapsing. That would be a huge disaster. The city and state have spent the last 15 years or so debating on what the best fix would be, and came up with three options:
1) Replace the viaduct with a new one.
2) Remove the viaduct with no replacement.
3) Remove the viaduct and build a deep-bore tunnel under the city for the through traffic.
At one point in the mess the public got to vote on these three options and if I recall correctly the people voted to repair/replace the viaduct. Last year the government decided to go with the deep bore option instead. There are many many details that make this whole thing controversial:
1) Building the tunnel is the only option that will keep the viaduct open during construction/repair -- very important for freight, since the Port of Seattle
connects with the viaduct.
2) In the agreement/law/whatever stage this is in; the cost is conservatively projected to be 4.2 billion dollars, and the city of Seattle will pay for
*any/all* cost overruns.
3) The tunnel has an entrance and an exit, and as such is basically only for thru traffic. The viaduct has several entrances and exits throughout the
downtown area.
4) The viaduct could collapse any day. No, really. It borders the waterfront/boardwalk area, underneath it is a street and parking, and the other side is
mere feet from many many very very old buildings, which may not be structurally sound enough to withstand the reverberations of a collapse of this
size. And the six lanes? Well, the viaduct is two levels -- three south-bound lanes on top, and three northbound lanes under that, and then that street
below and the parking.
5) The viaduct will stay open until the tunnel is completed -- 2016 at the earliest. If it stays up that long.
6) People/govt have been arguing over these same three options for the past *nine* years.
So when the govt said that the tunnel was the final decision citizens felt "good riddance!" even though the general public did not prefer that option, it was still better than nothing. That is sort of where we are now.