CA-24 Caldecott Tunnel Rehab & Ventilation Project

[jdbx]

It looks like Caltrans has started the public outreach phase of an upcoming project to rehabilitate the oldest 3 bores of the Caldecott Tunnel.  I took a look at the draft environmental document, and from what I can see, they are still evaluating whether to install jet fans or saccardo nozzles in bores 1 and 2, bore 3 will get jet fans.  The project will also involve repair of the tunnel walls, pavement rehabilitation, and lighting upgrades.

This is going to involve extended nighttime closures for about 3 years, which will narrow things down to 2 lanes per-direction, along with some 55-hour closures.  Options being considered also include re-implementing a reversible traffic configuration, similar to what was in place prior to the opening of the 4th bore.

The original 2 bores are nearly 90 years old, and this is one of the largest rehab projects that I can recall in my lifetime at least. 

Project information is available here: https://dot.ca.gov/caltrans-near-me/district-4/d4-projects/d4-caldecott-tunnel-upgrade

[The Ghostbuster]

Even though CA 24 will never become an extension of Interstate 980 (assuming 980 isn't demolished in the future), how close to meeting Interstate Standards is CA 24?

[Max Rockatansky]

Not close given the early tunnels are still a thing.  The rest of the freeway corridor is fine and probably is close to design Interstate standards.   

[Rothman]

I just remember my old boss saying he would be dead before the "new" 24 WB to 13 SB ramp would be completed (very late 1990s).  He was almost right.

[jdbx]

I just remember my old boss saying he would be dead before the "new" 24 WB to 13 SB ramp would be completed (very late 1990s).  He was almost right.

The hairpin on that ramp is awful.  There are many times that it causes traffic to back up onto mainline 24 WB, enough so that I avoid those right 2 lanes until I am past that exit, even if I need to exit for Broadway.

[Rothman]

I just remember my old boss saying he would be dead before the "new" 24 WB to 13 SB ramp would be completed (very late 1990s).  He was almost right.

The hairpin on that ramp is awful.  There are many times that it causes traffic to back up onto mainline 24 WB, enough so that I avoid those right 2 lanes until I am past that exit, even if I need to exit for Broadway.

...and that's after the lengthy project intended to have "improved" it. 

Congested before, congested now, congested forever...

[jdbx]

I just remember my old boss saying he would be dead before the "new" 24 WB to 13 SB ramp would be completed (very late 1990s).  He was almost right.

The hairpin on that ramp is awful.  There are many times that it causes traffic to back up onto mainline 24 WB, enough so that I avoid those right 2 lanes until I am past that exit, even if I need to exit for Broadway.

...and that's after the lengthy project intended to have "improved" it. 

Congested before, congested now, congested forever...

The way in which that interchange is squeezed in, there is no easy fix.  Terrain is the primary factor.  The opposite movement from 13 NB -> 24 EB is also rather hazardous, the exit being on the inside of a blind curve.  You will often suddenly encounter stopped traffic backed-up into the right lane, requiring the need to rapidly slow down while you hope that traffic behind you is also paying attention.

[The Ghostbuster]

Would adding a northbound exit-only lane on CA 13 between Broadway Terrace and CA 24 help matters any?

[jdbx]

Would adding a northbound exit-only lane on CA 13 between Broadway Terrace and CA 24 help matters any?

I don't think so, most of the traffic in the right lane is bound for the exit anyway, the greater issue is the lack of visibility around the inside of the curve, which is snugged up against a steep hillside with houses at the top.  The real issue is the bottleneck upstream where traffic has a short merge ahead of the tunnel immediately prior to more traffic merging from 13 SB via Broadway.  I'm not sure that there is any reasonable fix for that.

[jeffe]

Would adding a northbound exit-only lane on CA 13 between Broadway Terrace and CA 24 help matters any?

I don't think so, most of the traffic in the right lane is bound for the exit anyway, the greater issue is the lack of visibility around the inside of the curve, which is snugged up against a steep hillside with houses at the top.  The real issue is the bottleneck upstream where traffic has a short merge ahead of the tunnel immediately prior to more traffic merging from 13 SB via Broadway.  I'm not sure that there is any reasonable fix for that.

Adding an exit only lane would help add storage for cars backing up on the ramp and help keep the mainline lanes of 13 free flowing. As you noted, visibility is difficult on this curve. Pushing back the retaining wall to allow for a wide right shoulder would help with this. A similar design is used on the curve on eastbound I-580 at the Richmond Parkway exit.

Regarding the short merge on 24 and the extra traffic entering from the Broadway onramp, one possible fix would be to move the Broadway offramp west so it is before the merge from 13 and then the Broadway on-ramp would be integrated in with the N-13 to E-24 connector ramp.

[jeffe]

The project will also involve repair of the tunnel walls, pavement rehabilitation, and lighting upgrades.

The project will also add fire sprinklers to the tunnels. A tunnel doesn't need fire sprinklers if the traffic is always free flowing. The thinking is with a free flowing tunnel it can be quickly cleared of traffic. If a tunnel is subject to slow moving or even stop and go traffic, then it needs fire sprinklers.

There are three cross passages between bores 1 and 2. These will be upgraded to be used as emergency exits, similar to the cross passages between bores 3 and 4.

A project is also in the works to add jet fans to the Posey and Webster tubes.

[Rothman]

The project will also involve repair of the tunnel walls, pavement rehabilitation, and lighting upgrades.

The project will also add fire sprinklers to the tunnels. A tunnel doesn't need fire sprinklers if the traffic is always free flowing.

I agree with the engineers that insisted on the former.  Given how busy these tunnels are and will be, the idea that they will be constantly free-flowing defies reality.

(Going to be driving around the Bay Area in April again; ah, back to my old stomping grounds...back to traffic that may haunt my plans...)

[jeffe]

I agree with the engineers that insisted on the former.  Given how busy these tunnels are and will be, the idea that they will be constantly free-flowing defies reality.

Yeah, when bore 3 was opened in 1964 the sprinkler requirement didn't exist. But when bore 4 was completed in 2013 it is interesting that it didn't include sprinklers given how traffic can back up in it.

As far as I know, the only sprinklered tunnels in the Bay Area are Main Post and Battery tunnels along Presidio Parkway.

I haven't seen a lot of info on the jet fan project for the Posey and Webster tubes, but that project might add sprinklers as well seeing how those tunnels are almost always backed up.

[jdbx]

I agree with the engineers that insisted on the former.  Given how busy these tunnels are and will be, the idea that they will be constantly free-flowing defies reality.

Yeah, when bore 3 was opened in 1964 the sprinkler requirement didn't exist. But when bore 4 was completed in 2013 it is interesting that it didn't include sprinklers given how traffic can back up in it.

As far as I know, the only sprinklered tunnels in the Bay Area are Main Post and Battery tunnels along Presidio Parkway.

I haven't seen a lot of info on the jet fan project for the Posey and Webster tubes, but that project might add sprinklers as well seeing how those tunnels are almost always backed up.

I don't often see backups in the tunnels heading westbound, but they're pretty common in the eastbound direction.  Regardless, sprinklers seem like a worthwhile upgrade, particularly with the greater prevalence of EV's lately.  While EV's have no greater tendency towards fire than an ICE, when they *do* catch fire, they tend to burn a lot hotter and for a longer period than an an ICE would.

One element I am looking forward to is them addressing the pavement undulations in Bore 3, which have gotten pretty bad over time.