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[Alps]

the existing tunnel is 2 lanes. they're not replacing it, they're adding a second one.

That is clearly correct for the tunnel that is being built now, Thimble Shoal,
the southern of the CBBT tunnels. Seagoing traffic headed for the Norfolk Naval
Station, the Ports of Virginia in Hampton Roads and the Port of Richmond (at the
head of navigation of the James River) all cross the CBBT by way of Thimble Shoal.

At one point early on, there was consideration given to building one new four
lane tube that would carry alll CBBT traffic and abandoning in place the existing
tunnel, but I am not sure that a four lane tube was even considered during the
EIS process that led to approval of the new bored Thimble Shoal Tunnel that is
now under construction (with some difficulty).

The north Chesapeake Tunnel is where seagoing traffic heads north toward the
Port of Baltimore.

I was not seeing anything with 4 lanes proposed for the north tunnel either.

[cpzilliacus]

I was not seeing anything with 4 lanes proposed for the north tunnel either.

I believe you are correct.  The idea of a four lane tunnel to replace the two lane tunnel sounds good, but since the CBBTD mostly exists because of the tolls it collects, I suspect that they were properly reluctant to abandon a perfectly good tunnel (that might also anger the holders of CBBTD bonds).

[froggie]

As I recall (since I was still in Norfolk at the time), a new 4-lane tunnel to replace the existing 2-lane tunnel was the primary consideration early on (talking 2013-2014 here).  At some point, it was changed to a parallel 2-lane tunnel with rehab of the existing tunnel due primarily to cost increases.

[cpzilliacus]

As I recall (since I was still in Norfolk at the time), a new 4-lane tunnel to replace the existing 2-lane tunnel was the primary consideration early on (talking 2013-2014 here).  At some point, it was changed to a parallel 2-lane tunnel with rehab of the existing tunnel due primarily to cost increases.

I think that is correct.  And there's also the matter of tunnel boring machines.  Is there one massive enough to bore a four lane tunnel?  The biggest I can think of was Bertha, which did the SR-99 tunnel in Seattle, which is two lanes on two decks.  The overhead clearance is less than 16' 0" (4.8 meters) at 15' 2" (4.6 meters).   

As a comparison, the current CBBT tunnels are restricted to no higher than 13' 6" (4.1 meters).

[D-Dey65]

I stopped there many of times and even  took photos of the signs and tunnels there.

Oh, I took them too a while back. I'm only sorry I didn't have a digital camera back then.

[kernals12]

I clinched this along with I-64 and I-664 on Tuesday. It was really cool.

I also learned at the Hampton Roads Naval Museum that barnacles that accumulate on the bridge piers make great habitat for fish.

[plain]

As I recall (since I was still in Norfolk at the time), a new 4-lane tunnel to replace the existing 2-lane tunnel was the primary consideration early on (talking 2013-2014 here).  At some point, it was changed to a parallel 2-lane tunnel with rehab of the existing tunnel due primarily to cost increases.

I'm late (not sure how I missed this before). That original 4-lane tunnel was going to be deeper to allow a better draft for vessels passing over it (basically Post-Panamax). But yeah costs were definitely the issue.

[D-Dey65]

I'm trying to refresh my memory on the Hazmat regulations on the bridge and tunnel

http://www.cbbt.com/travel-information/hazmat-regulations/

So does this mean that one of my uncles who has COPD and is on a portable breathing machine and may or may not need oxygen tanks simply can't ride along the bridge as a passenger?

[Mapmikey]

I'm trying to refresh my memory on the Hazmat regulations on the brudge and tunnel

http://www.cbbt.com/travel-information/hazmat-regulations/

So does this mean that one of my uncles who has COPD and is on a portable breathing machine and may or may not need oxygen tanks simply can't ride along the bridge as a passenger?

no


From http://www.cbbt.com/travel-information/hazmat-regulations/

(2) Class 2, division 2.1 flammable gas is permitted provided quantities do not exceed 120 gallons in 6 gallon containers or less, with exceptions for LPG, which is restricted to two 60 pound cylinders LPG capacity, approximately 141 pounds water capacity each, or any combination of cylinders less than 60 pounds LPG capacity, with a total of 120 pounds LPG capacity;

[jeffandnicole]

I'm trying to refresh my memory on the Hazmat regulations on the brudge and tunnel

http://www.cbbt.com/travel-information/hazmat-regulations/

So does this mean that one of my uncles who has COPD and is on a portable breathing machine and may or may not need oxygen tanks simply can't ride along the bridge as a passenger?

As was pointed out above, even a regular propane tank isn't banned.  The signage doesn't spell it out, but most tunnel restrictions are for mass quantities and CDL drivers, not Jane and Joe in their sedan, SUV, or even camper.

[Mapmikey]

I was surprised to see the amount of radioactive material that is allowed over the CBBT.  This may be because medical isotopes needed on the Eastern Shore come from Norfolk, etc. and it would be prohibitively expense to have to transport these (generally) short-lived materials by helicopter or plane.  Also residual radioactive waste of the longer-lived materials would be headed to locations not in the Northeast.  The limitation for them would be the 500 pounds CBBT threshold.  300 Curies is a large quantity of radioactive material (in terms of how many atoms are decaying per second, not its mass - 300 Curies of Radium-226 would be just 300 g of actual material) and medical radioactive waste is quite unlikely to be anywhere near that much.  The mass comes from objects that have/ may have come into contact with the radioactivity (gloves, gowns, tubes, etc.)

By contrast, the Baltimore tunnels disallow any amount (not sure about amounts considered exempt from DOT and/or NRC regulations) of any radionuclide.  This is overly restrictive because many of the radioactive materials that would use the tunnels (lots of hospitals that use medical isotopes) are in tiny amounts relative to any harm they could do and they often have very short half-lives.