Hi all! I just created an account, but I've been a lurker/non-poster here for a while. I work as a structural engineer here in town. This past week I was bored (what's new) so I wrote the Oregonian piece above. Didn't think they'd actually publish it!
Here's the rest of the plan. Fleshed out some of the details last night. Iain, I actually fully agree that a MAX tunnel should be the first priority. But it wouldn't solve the seismic connection problem, and, well, good luck getting that money from ODOT. But this morning I started wondering if it wouldn't be possible to do both.
The Alaskan way tunnel had a 52' inner diameter. If that is increased to 57', it becomes possible to add a third level at the top. See sketch at the link below. The tunnel area increases by 20%, so it is a jump, but not a huge jump. And definitely cheaper than boring a separate tunnel.
https://drive.google.com/file/d/1dFz...ew?usp=sharing
Where would the tunnel go? If there's a transit component, I think the logical station locations are Lloyd / NE 12th (at beginning of tunnel), Burnside / NE 2nd, Burnside / SW 6th, and Providence Park. The western terminus of the tunnel would be near the SW Jefferson exit ramps. The NE 2nd / Burnside station would connect to a central eastside light rail line along the waterfront.
See PDF at the link below for a sketch of the central eastside (yes, I'm aware this is quite nerdy, but I had fun making it).
https://drive.google.com/file/d/1Z30...ew?usp=sharing
The east side freeway would be removed, and only ramps would remain, lowered to run in a trench. There would be one lane and a breakdown shoulder in each direction. The freight railroad that currently runs down SE 1st St. would be rerouted and lowered to run parallel with the freeway ramps. The total width of the trench would be ~75 ft., but it would be broken into three spans. This means that ODOT wouldn't have to pay for the highway caps. The blocks could be sold off individually, with developers taking responsibility for building the caps. With 25' spans, it would be no different than building on top of an underground parking level. Of course, in this case, the developers wouldn't get the benefit of having a parking level below. But with prime riverfront property, I think it would pencil. If necessary, zoning could be adjusted to allow for more stories to compensate the developers.
All of this was inspired by my (perhaps irrational) hatred of the central eastside freeway. I've seen other proposals to do away with that section of freeway, but most of them aren't convincing. Capping the highway in its current location wouldn't work since it's at grade. Lowering it while maintaining operations would be a logistical nightmare and incredibly expensive given the width and spans. A deep bore tunnel is a non-starter because of all the ramps. Much as I'd like to believe that simply removing it is an option, I'm skeptical. Funneling all of the region's N-S traffic, E-W traffic, S-E, and N-W traffic across the Fremont bridge is, I think, unrealistic.
So, to summarize: A 57' diameter tunnel that accommodates light rail and highway. Let's round the cost up from $3.3 billion to $4 billion due to the larger diameter. It's worth noting that Trimet (those excellent stewards of public funds) were batting around a $4 billion figure for their own, separate, tunnel. Let's round up again to $5 billion for all the miscellaneous stuff. Trimet can pitch in $2 billion, Multnomah county can pitch in $1 billion, ODOT can pitch in $1.5 billion, and we're basically there!
I should note that I don't actually expect this to be taken seriously, and I did this mostly for my own entertainment. Posting it here since some of you may find it interesting. I do wish we were having more of these big-picture conversations, though.
[Iain, I recognize this is very off-topic, feel free to move as appropriate]