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[Mapmikey]

Virginia has lined up all the financing required to build the parallel tunnel at the Thimble shoal location...

Only about $47M of the $756M comes from the Tunnel District General Fund...the rest is bonds of one sort or another.

Construction to start fall 2017 and finish in fall 2022...

https://governor.virginia.gov/newsroom/newsarticle?articleId=18324

http://www.cbbt.com/ptst-project-timeline-2/

[Tom958]

"What's the point of building a second tunnel at Thimble Shoals when there'll still be only one under the main channel?" wondered Captain Obvious.

[Mapmikey]

Same principle that had them twin all the bridges but not the tunnels...?

[hbelkins]

"What's the point of building a second tunnel at Thimble Shoals when there'll still be only one under the main channel?" wondered Captain Obvious.

Funding issues? Build what you can when you can?

Maybe I haven't traveled that route at the right time, but I've never really seen that much of a bottleneck at the tunnels. I'm not sure how necessary the second tunnels are.

[jeffandnicole]

"What's the point of building a second tunnel at Thimble Shoals when there'll still be only one under the main channel?" wondered Captain Obvious.

Funding issues? Build what you can when you can?

Maybe I haven't traveled that route at the right time, but I've never really seen that much of a bottleneck at the tunnels. I'm not sure how necessary the second tunnels are.

I think the safety issue is pretty substantial here.

[Mapmikey]

AADT on the CBBT north of the pier was 8800 for 2015...

For comparison, US 301's AADT at the Virginia end of the Nice Bridge is 26000, although that segment goes all the way back to VA 206 so not all of this is traffic merging onto the bridge (AADT at VA 3 is 14000, so the true number is somewhere in between).  I know there are backups sometimes on 301 at this merge.

I don't know what the lifespan of a tunnel like these is supposed to be but the original tunnels will be nearing 60 years old when this parallel tunnel is opened, so having a new tunnel in place is an ok idea even if traffic and safety weren't issues...

[cpzilliacus]

I don't know what the lifespan of a tunnel like these is supposed to be but the original tunnels will be nearing 60 years old when this parallel tunnel is opened, so having a new tunnel in place is an ok idea even if traffic and safety weren't issues...

When the Fort McHenry Tunnel (I-95) in Baltimore opened to traffic in 1985, one of Baltimore Harbor Tunnel  (I-895) tubes was immediately closed for total reconstruction, followed by the other tube. Both tubes needed it badly as the traffic there was pretty heavy from the time it opened in 1957, and the state could never do a long-term closure.

There is a similar dynamic at the CBBT.  When the overwater trestled roadways were twinned, all traffic was moved to the new structures so significant work could be done on the "old" (now usually northbound) trestles (not sure how long that took, as I did not cross it during that work).

Once the new Thimble Shoal Tunnel is open, the existing Thimble Shoal tube can be shut-down for thorough rehabilitation and repair work.  Presumably at some point in the future, the CBBTD will twin the  Chesapeake Channel Tunnel (north tube) as well, so that existing tube can also receive the rehabilitation and repair work that it needs.

[cpzilliacus]

For comparison, US 301's AADT at the Virginia end of the Nice Bridge is 26000, although that segment goes all the way back to VA 206 so not all of this is traffic merging onto the bridge (AADT at VA 3 is 14000, so the true number is somewhere in between).  I know there are backups sometimes on 301 at this merge.

According to the 2015 State Highway Administration's Highway Location Reference, AADT on the crossing  itself is 18,576.

Even though that part of 301 is toll (MDTA) maintenance, SHA still publishes the traffic volumes for it, as they do for all MDTA-maintained roads in the state.

[froggie]

Part of it is safety-driven, which was the primary reason for the twinning of the bridge portions.  Another part of it is condition...the Thimble Shoals portals have had some cracking.  Lastly, parameters have changed from the previous plan for a parallel Thimble Shoals tunnel to a brand new 4-lane tunnel there because of a desire from the Navy for a deeper Thimble Shoals channel.  The current tunnel plan would support a deeper channel.

Regarding bottlenecks at the tunnels....they aren't significant, but in my (extensive) experience, there are two things that can happen that are technically considered bottlenecks:  A) platoons of traffic lining up behind someone driving slow through the tunnels.  I've personally been stuck behind timid drivers who will barely go 30 through the tunnel, and by the time we clear, there's a few dozen vehicles (including trucks) lined up behind the lead vehicle;  B)  incidents, whether a crash, maintenance inside the tunnel, or the need to stop traffic in both directions for an oversize/permit vehicle, can easily stop traffic for a half hour or more.

[epzik8]

So does this mean the tunnel portions will no longer be a two-way single bore? There will be two bores with one for each direction?

[jeffandnicole]

So does this mean the tunnel portions will no longer be a two-way single bore? There will be two bores with one for each direction?

Just one tunnel will have a dual tunnel (or, as mentioned above, a 4 lane tunnel).  The other will still be a single bore.

[cpzilliacus]

So does this mean the tunnel portions will no longer be a two-way single bore? There will be two bores with one for each direction?

Just one tunnel will have a dual tunnel (or, as mentioned above, a 4 lane tunnel).  The other will still be a single bore.

That's not what the CBBTD Web site says (here), though it had been discussed in the past as a possible total replacement for the existing 1960's tunnel; as well as making the tunnel four lanes wide instead of two lanes.

The Parallel Thimble Shoal Tunnel Project will construct a new two-lane tunnel under Thimble Shoal Channel.  When complete, the new tunnel will carry two lanes of traffic southbound and the existing tunnel will carry two lanes of traffic northbound.

[jeffandnicole]

So does this mean the tunnel portions will no longer be a two-way single bore? There will be two bores with one for each direction?

Just one tunnel will have a dual tunnel (or, as mentioned above, a 4 lane tunnel).  The other will still be a single bore.

That's not what the CBBTD Web site says (here), though it had been discussed in the past as a possible total replacement for the existing 1960's tunnel; as well as making the tunnel four lanes wide instead of two lanes.

The Parallel Thimble Shoal Tunnel Project will construct a new two-lane tunnel under Thimble Shoal Channel.  When complete, the new tunnel will carry two lanes of traffic southbound and the existing tunnel will carry two lanes of traffic northbound.

I was going based on what Froggie said a few posts above, which if correct simply means the website hasn't been updated yet.

[froggie]

Website's correct...I was in error and was alluding to an earlier proposal for a new tunnel.  Guessing a 4-lane replacement was dropped due to cost.

[cpzilliacus]

Website's correct...I was in error and was alluding to an earlier proposal for a new tunnel.  Guessing a 4-lane replacement was dropped due to cost.

I think it might have been discussed in the JLARC audit and study of the CBBTD and CBBT which was done in the early 2000's and  is available online here (.pdf, 3 MB).

[hubcity]

Regarding bottlenecks at the tunnels....they aren't significant, but in my (extensive) experience, there are two things that can happen that are technically considered bottlenecks:  A) platoons of traffic lining up behind someone driving slow through the tunnels.  I've personally been stuck behind timid drivers who will barely go 30 through the tunnel, and by the time we clear, there's a few dozen vehicles (including trucks) lined up behind the lead vehicle;  B)  incidents, whether a crash, maintenance inside the tunnel, or the need to stop traffic in both directions for an oversize/permit vehicle, can easily stop traffic for a half hour or more.

There's a summertime bottleneck corresponding to northern states' exodus to the Outer Banks, and vice versa, on Saturday mornings, too. (If you time it well, you can see the opposite direction's bottleneck while cruising past in the non-bottlenecked direction. If you don't time it well, you can experience the bottleneck first-hand.)

[epzik8]

So I drove across the bridge-tunnel last week. It's a fun drive.

[plain]

I just hate to see the restaurant go. I was hoping they expanded the island enough to where there's enough room for a new one but I guess there's not enough funds for it (hard to imagine though given the amount of money being thrown around) but at least they're rebuilding the fishing pier afterwards.

"What's the point of building a second tunnel at Thimble Shoals when there'll still be only one under the main channel?" wondered Captain Obvious.

I'm pretty sure the Thimble Shoals channel IS the main one. While there are obviously plenty of ships going to Baltimore (and to a much less extent D.C.), I think you're underestimating the amount of marine traffic bound for Hampton Roads... one can stand on the beach at night and see ships lining up to cross over this tunnel. Plus a lot of Baltimore bound ships also use the C&D Canal instead

[cpzilliacus]

I just hate to see the restaurant go. I was hoping they expanded the island enough to where there's enough room for a new one but I guess there's not enough funds for it (hard to imagine though given the amount of money being thrown around) but at least they're rebuilding the fishing pier afterwards.

"What's the point of building a second tunnel at Thimble Shoals when there'll still be only one under the main channel?" wondered Captain Obvious.

I'm pretty sure the Thimble Shoals channel IS the main one. While there are obviously plenty of ships going to Baltimore (and to a much less extent D.C.), I think you're underestimating the amount of marine traffic bound for Hampton Roads... one can stand on the beach at night and see ships lining up to cross over this tunnel. Plus a lot of Baltimore bound ships also use the C&D Canal instead

I am not sure that ship access to Baltimore is possible for Panamax-dimensioned vessels via the C&D Canal.  It is possible coming up the Chesapeake Bay.

[plain]

I am not sure that ship access to Baltimore is possible for Panamax-dimensioned vessels via the C&D Canal.  It is possible coming up the Chesapeake Bay.

I don't think so either. The smaller vessels can still use the C&D though. The newer Post-Panamax ships won't be able to use either port (Baltimore or Hampton Roads) though because of the depth of the tunnels.

[ixnay]

I am not sure that ship access to Baltimore is possible for Panamax-dimensioned vessels via the C&D Canal.  It is possible coming up the Chesapeake Bay.

I don't think so either. The smaller vessels can still use the C&D though. The newer Post-Panamax ships won't be able to use either port (Baltimore or Hampton Roads) though because of the depth of the tunnels.

IOW the drafts of the post-Panamax ships mean the keels or hulls would scrape the roofs of *all* the tunnels (CBBT, HRBT, *and* Interstates 895 and 95 in Baltimore)?

ixnay

[DeaconG]

I am not sure that ship access to Baltimore is possible for Panamax-dimensioned vessels via the C&D Canal.  It is possible coming up the Chesapeake Bay.

I don't think so either. The smaller vessels can still use the C&D though. The newer Post-Panamax ships won't be able to use either port (Baltimore or Hampton Roads) though because of the depth of the tunnels.

IOW the drafts of the post-Panamax ships mean the keels or hulls would scrape the roofs of *all* the tunnels (CBBT, HRBT, *and* Interstates 895 and 95 in Baltimore)?

ixnay

The drafts for New Panamax vessels are between 50 and 60 feet, so I don't think there will be an issue.

https://en.wikipedia.org/wiki/Panamax

[cpzilliacus]

IOW the drafts of the post-Panamax ships mean the keels or hulls would scrape the roofs of *all* the tunnels (CBBT, HRBT, *and* Interstates 895 and 95 in Baltimore)?

I cannot speak to the HRBT (by implication, these large vessels can pass the CBBT), but the I-95 (FMT) and I-895 (BHT) tunnels in Baltimore are upstream from the marine terminals where the large container ships (including  Panamax and post-Panamax) will tie up at the Seagirt and Dundalk docks, on the east side of Baltimore Harbor between I-695 (F.S. Key Bridge) and I-895 (BHT).

See map here.

[froggie]

What I read of the New Panamax ships is a draft around 50ft.  HRBT isn't an issue with that depth, but both CBBT tunnels and the channels into/out of Norfolk would be.

[cpzilliacus]

What I read of the New Panamax ships is a draft around 50ft.  HRBT isn't an issue with that depth, but both CBBT tunnels and the channels into/out of Norfolk would be.

The Maryland Port Administration (MPA) seems to imply on their Maryland Manual Web page that they can handle Panamax and post-Panamax cargo ships.