Whoops, that was supposed to go above, but my Internet connection is crap, so it put it here when I tried to add a comment to this comment.

Now back to 35W and Washington:

It is not really that wide. Sure the area looks wide, but the freeway is not that wide, and that is what you are covering. By adding a bridge that connects 3rd to the West Bank, you eliminate the need for all those ramps connecting the Wash trench to the freeway. That leaves a lot of space to build and a narrower area to cover. That is land squeezed between downtown and the University, right next to a new stadium, and it is half dug out, i.e. it is valuable.