My opinion: we should replace the Key Bridge and Bay Bridge with tunnels

[bus man]

I think that, instead of rebuilding the Key Bridge as a bridge, we should replace it with a twin bore tunnel, offering two lanes of traffic in both directions (i.e. same capacity as the former bridge). Also, given that we're starting to talk about what to do with the obsolescent Bay Bridge, I think we should replace it with a three-bore tunnel, offering a total of 6 lanes (one more than exists today).

Just think: if these crossings were served by tunnels instead of bridges, there would be no danger of ship collisions. Vertical clearance would no longer be an issue, so even the tallest ships (including the latest generation of cruise ships) could operate into Baltimore. There would be no need to worry about wind warnings or restrictions; no white-knuckle drives in heavy rainstorms; no worries about snow removal; and probably fewer scared drivers trying to cross. (Though there are probably some who are afraid of tunnels, so they'd be out of luck.)

But what about hazmats? Surely we don't want hazmat trucks sharing a tunnel with regular traffic. So here's how we handle that. On the Key Bridge, each bore is open to regular traffic (i.e. two lanes in each direction) between 5:00 a.m. and 10:00 a.m., and again between 2:00 p.m. and 8:00 p.m. During those hours, hazmats are not allowed but regular trucks would be. We'd probably need to build some kind of waiting area, like a rest area for trucks, so they can wait during those hours. During other hours, one bore is used for two-way traffic just for cars, while the other one is used for alternating two-way traffic for all trucks, hazmat and otherwise. Northbound trucks enter the tunnel from the top of the hour to 20 minutes past; 10 minutes to clear them out; then southbound trucks enter the tunnel from the bottom of the hour to 50 minutes past; then 10 minutes to clear them out. Repeat hourly. Having trucks go only one way at a time eliminates the possibility of head-on collisions.

For the Bay Bridge, the three bores would be used like this: one bore for westbound traffic and one bore for eastbound traffic at all times. The middle bore would operate westbound in the morning (say 5:00 a.m. to 10:00 a.m.) and eastbound in the afternoon (2:00 p.m. to 8:00 p.m.) to handle peak-hour directional flows. Would probably need to be different on summer weekends to account for beach traffic flows. During the off hours, trucks would use the middle bore in a similar fashion to the Bay Bridge.

What do you think?

[Quick Enough]

Originally Posted by bus man

I think that, instead of rebuilding the Key Bridge as a bridge, we should replace it with a twin bore tunnel, offering two lanes of traffic in both directions (i.e. same capacity as the former bridge). Also, given that we're starting to talk about what to do with the obsolescent Bay Bridge, I think we should replace it with a three-bore tunnel, offering a total of 6 lanes (one more than exists today).

Just think: if these crossings were served by tunnels instead of bridges, there would be no danger of ship collisions. Vertical clearance would no longer be an issue, so even the tallest ships (including the latest generation of cruise ships) could operate into Baltimore. There would be no need to worry about wind warnings or restrictions; no white-knuckle drives in heavy rainstorms; no worries about snow removal; and probably fewer scared drivers trying to cross. (Though there are probably some who are afraid of tunnels, so they'd be out of luck.)

But what about hazmats? Surely we don't want hazmat trucks sharing a tunnel with regular traffic. So here's how we handle that. On the Key Bridge, each bore is open to regular traffic (i.e. two lanes in each direction) between 5:00 a.m. and 10:00 a.m., and again between 2:00 p.m. and 8:00 p.m. During those hours, hazmats are not allowed but regular trucks would be. We'd probably need to build some kind of waiting area, like a rest area for trucks, so they can wait during those hours. During other hours, one bore is used for two-way traffic just for cars, while the other one is used for alternating two-way traffic for all trucks, hazmat and otherwise. Northbound trucks enter the tunnel from the top of the hour to 20 minutes past; 10 minutes to clear them out; then southbound trucks enter the tunnel from the bottom of the hour to 50 minutes past; then 10 minutes to clear them out. Repeat hourly. Having trucks go only one way at a time eliminates the possibility of head-on collisions.

For the Bay Bridge, the three bores would be used like this: one bore for westbound traffic and one bore for eastbound traffic at all times. The middle bore would operate westbound in the morning (say 5:00 a.m. to 10:00 a.m.) and eastbound in the afternoon (2:00 p.m. to 8:00 p.m.) to handle peak-hour directional flows. Would probably need to be different on summer weekends to account for beach traffic flows. During the off hours, trucks would use the middle bore in a similar fashion to the Bay Bridge.

What do you think?

All you have to do is to sign a legitimate check!

[Igor Blevin]

The replacement will be whatever can be constructed fastest. This is an emergency situtation. Unless tunnels can be constructed faster than a bridge, I don't think they will be considered.

Also Biden has said that the federal government is paying the tab to replace the Key bridge. I doubt they will go to bat for tunneling.

[DaveinMtAiry]

Let's not overreact to some freak accident. Tunnels cost more money than any jurisdiction can afford and will screw up traffic for years. There are no tankers on the Potomac River, the Bay bridge is fortified but it could use more. So do that.

[bus man]

Originally Posted by DaveinMtAiry

Let's not overreact to some freak accident. Tunnels cost more money than any jurisdiction can afford and will screw up traffic for years. There are no tankers on the Potomac River, the Bay bridge is fortified but it could use more. So do that.

When I look at pictures of the Bay Bridge, I don't see any barriers protecting the support towers. Granted that what brought down the Key Bridge was a freak accident, but it's one that could just as easily befall the Bay Bridge.

In any case, it's not just about a freak accident, though that's part of it. It's also about ship clearances and wind restrictions and issues of traffic flow. It's about possibly losing business (and thus economic activity) at the Port of Baltimore. It's about admitting that Maryland has grown considerably in the past 50 years, and the solutions that worked back when the bridge was built may not be adequate now, much less in the future.

The Bay Bridge is functionally obsolete. That doesn't mean it's about to collapse, but it does mean that it is inadequate to meet the demands placed upon it. Like it or not, we're going to need a new crossing. I'd rather spend more money up front and get a better, more functional, safer crossing out of it.

[bus man]

Originally Posted by Igor Blevin

The replacement will be whatever can be constructed fastest. This is an emergency situtation. Unless tunnels can be constructed faster than a bridge, I don't think they will be considered.

Also Biden has said that the federal government is paying the tab to replace the Key bridge. I doubt they will go to bat for tunneling.

The Key Bridge was almost exactly the same length as the Fort McHenry Tunnel. Both of them took five years to build. Underwater tunnels can be built much more rapidly than tunnels through mountains.

As for how much We the People, via the federal government, are going to be willing to spend on a new crossing, obviously that remains to be seen.

[Joakim3]

Originally Posted by bus man

The Key Bridge was almost exactly the same length as the Fort McHenry Tunnel. Both of them took five years to build. Underwater tunnels can be built much more rapidly than tunnels through mountains.

As for how much We the People, via the federal government, are going to be willing to spend on a new crossing, obviously that remains to be seen.

The Fort McHenry Tunnel would also cost $2.8 billion dollars in 2024 vs. $735 million for the Key Bridge. Underwater tunnels cannot be built faster than modern bridges though so the underwater vs. mountain is moot especially since any tunnel under the harbor would necessitate a TBM.

The Key Bridge replacement will be almost undoubtedly be a design-build contract cable-stayed bridge with pre-cast concrete segments.

[bus man]

Originally Posted by Joakim3

The Fort McHenry Tunnel would also cost $2.8 billion dollars in 2024 vs. $735 million for the Key Bridge. Underwater tunnels cannot be built faster than modern bridges though so the underwater vs. mountain is moot especially since any tunnel under the harbor would necessitate a TBM.

The Key Bridge replacement will be almost undoubtedly be a design-build contract cable-stayed bridge with pre-cast concrete segments.

The Fort McHenry Tunnel was built with the "immersed tube method," under which various segments of the tunnel are built on land, floated out to their position, and lowered into place. The segments are then joined together and the end "caps" are removed to complete the tunnel. A TBM would not be needed for most of the tunnel's length, though it probably would be needed for the transition segments from the surface into the tunnel.

https://en.wikipedia.org/wiki/Fort_M...d_construction

If we do go with a bridge instead of a tunnel (which, I admit, is the more likely scenario), it will need to be taller by 30 feet or so, in order to accommodate the largest cruise ships and container ships that are in operation today. And yes, the same would need to be done with the Bay Bridge.

[Mathguy]

Re: Bay Bridge.

I think that in the short term you could possibly install "dolphins" aka cement islands in front of the main supports.

Considering that there is already big budget needs on the table that may be a cheaper, practical short term remedy.

I think a lot of places may be considering the same thing for vulnerable bridges.

[jetgraphics]

I favor anything that improves the navigability of American waterways.
Perhaps it might be wise to increase the lanes and add a rail right of way - just in case.