It looks like the "artists" rendition does not include the rail yard just south of Colorado and Atlantic nor the Coast Guard base. The Coast Guard Base used to use the Atlantic entrance, but has shifted to the Massachusetts entrance.
So, if the rail yard does not have the extension going under the current Alaskan Way viaduct, then how will it operate when making and breaking up trains?
There is a street car rail line between the "tunnel" and the container yard, but who knows what is up with this.
Seattle Times Artist Rendition
[
seattletimes.nwsource.com]
Google Map (switch to Satellite view)
[
maps.google.com]