"The Boring Company" Tunnels: A Solution Atlanta Urbanists and Suburbanists Both Can Support? (Tucker: roofing, costs)

[bu2]

Originally Posted by arjay57

Cobb did a 5 mile, 24 foot diameter, concrete-lined tunnel through hard rock for $300 million. And that included a number of large accessory tunnels and shafts.

That was a water tunnel, right? That's different.

[arjay57]

Originally Posted by bu2

That was a water tunnel, right? That's different.

Yes, they're water tunnels.

What's the diff in terms of excavating and lining? Not challenging you, just asking.

[fourthwarden]

Originally Posted by arjay57

Yes, they're water tunnels.

What's the diff in terms of excavating and lining? Not challenging you, just asking.

Depth, extent of lining, plus all the actual rail hardware, and the power cables, and drainage, and evacuation routes.

[arjay57]

Originally Posted by fourthwarden

Depth, extent of lining, plus all the actual rail hardware, and the power cables, and drainage, and evacuation routes.

Well, obviously you've got different hardware inside.

But that's why I asked the differences in excavation and tunnel lining.

For example, the Cobb tunnel was bored to a diameter of 27 feet, and then given a cast-in-place concrete lining to bring it down to an inside diameter of 24 ft. What sort of lining would be required for a transit tunnel?

[fourthwarden]

Originally Posted by arjay57

Well, obviously you've got different hardware inside.

But that's why I asked the differences in excavation and tunnel lining.

For example, the Cobb tunnel was bored to a diameter of 27 feet, and then given a cast-in-place concrete lining to bring it down to an inside diameter of 24 ft. What sort of lining would be required for a transit tunnel?

It would be something similar, though more specialized for the shape needed for mounting all the internal hardware.

[bu2]

Originally Posted by arjay57

Well, obviously you've got different hardware inside.

But that's why I asked the differences in excavation and tunnel lining.

For example, the Cobb tunnel was bored to a diameter of 27 feet, and then given a cast-in-place concrete lining to bring it down to an inside diameter of 24 ft. What sort of lining would be required for a transit tunnel?

I don't know. But I imagine it would have to be "over-engineered" because people would be in it and not just water. For one thing, you don't have to worry about a water tunnel flooding.

[primaltech]

There's another option for connecting Cumberland that I also like, that would be super cheap, and get huge bang for buck.

Convert the HOV lanes on ITP I-75 to managed HOT lanes (which I think they eventually plan to do anyway). Build the 15th St bridge (also planned by GDOT), with HOT ramps, which would be right next to Arts Center station. Build a new bus transit center (with commuter parking) at that previously referenced empty lot on Akers Mill @ 75 at the Galleria. Then run an all-day, direct, high-frequency, high-capacity BRT shuttle loop service between Arts Center and Cumberland, via all-HOT lanes.

I don't like that nearly as much as rail, obviously, but it would certainly be something, way better than what exists now.

[LTCM]

Originally Posted by bu2

I don't know. But I imagine it would have to be "over-engineered" because people would be in it and not just water. For one thing, you don't have to worry about a water tunnel flooding.

You do kind of have to worry about a water tunnel flooding. If water is getting in that means raw sewage could be getting out. Leaking sewer lines are a big deal and will get you in major trouble with the EPA. Probably one of the most commonly applied fines by the EPA.

Sewer tunnels are pretty heavily engineered. It's all the equipment inside, and the mounting of this equipment, that raises the cost of transit.

[arjay57]

Again, I'm thinking of this in terms of the excellent route suggested in primaltech's map.

Not all of this would have to be tunnel. Some areas would be fine at grade.

[samiwas1]

Originally Posted by primaltech

There's another option for connecting Cumberland that I also like, that would be super cheap, and get huge bang for buck.

Convert the HOV lanes on ITP I-75 to managed HOT lanes (which I think they eventually plan to do anyway). Build the 15th St bridge (also planned by GDOT), with HOT ramps, which would be right next to Arts Center station. Build a new bus transit center (with commuter parking) at that previously referenced empty lot on Akers Mill @ 75 at the Galleria. Then run an all-day, direct, high-frequency, high-capacity BRT shuttle loop service between Arts Center and Cumberland, via all-HOT lanes.

I don't like that nearly as much as rail, obviously, but it would certainly be something, way better than what exists now.

How does HOT connect more so than existing HOV? It doesn't change anything but that you're paying to use the lane now. Or, by "managed HOT" do you mean barrier-separated, in which case one direction would lose the lane for part of the day?

And what is the point of the 15th street bridge? What does it connect to?