Im thinking due to the river right there, they would have to swing out towards mlk and that would be an extremely expensive thing to do. Plus going from the marcum to then a tunnel? The grade is likely not safe or practical.
Much bigger city to be able to handle that and much flatter in that area than the zone of portland we are speaking of. I just dont see it from an engineering standpoint unless were speaking of an express lane without exits. In order to fit under the river on the west side it would have to start way back and with the slope, i just don't see it happening. The costs would far exceed the benefit l, due to how much would have to be torn down on the west side to make room for all the shoring up, etc., i think.
I'm no highway engineer, but I've seen tunnels built in much tougher spots. Whether it's worth the money or not is of course a value judgement. barfo
From the article you posted: “ It lies at an average of 150 feet (46 m) below the surface along the east bank of the Willamette River from the intersection of Southeast 17th Avenue and McLoughlin Boulevard to Swan Island. The pipe in the tunnel has an inside diameter of 22 feet (6.7 m).[3]” Keep in mind this is for a two lane highway. We would need three. https://en.m.wikipedia.org/wiki/Interstate_Highway_standards From this article: “The Bobby Hopper Tunnel on I-49in Arkansas was built with a 25 ft (7.6 m) height total clearance, leaving plenty of room for lighting and signs hanging from the ceiling and still exceeding the 16 ft (4.9 m) minimum for rural highways“ Again for a two lane highway. We would need three That is quite a difference in size. And to get 150ft down leaves little to zero Ability to have any exits.
