Crazy Transit Pitches

[KCasiglio]

I like that in a vaccum, but it seems to me theres no need to build a new tunnel under the channel when a perfectly good one already exists.

 

[Charlie_mta]

^ Looks like there would be a choke point in the existing Central Subway between Kenmore and Boylston stations. Also you'd need a turnaround at North Station where the new Green Line tunnel from the south would tie in at that point.

 

[KCasiglio]

^ Looks like there would be a choke point in the existing Central Subway between Kenmore and Boylston stations. Also you'd need a turnaround at North Station where the new Green Line tunnel from the south would tie in at that point.

My bad for not writing it in, but since the stuart street tunnel/marginal road alignments have both been discussed and drawn out at length I accept one of them as given in any world where a Congress street green line is getting built.

 

[Charlie_mta]

My bad for not writing it in, but since the stuart street tunnel/marginal road alignments have both been discussed and drawn out at length I accept one of them as given in any world where a Congress street green line is getting built.

Yes, that would make a balanced system.
Also I like the Congress Street Green tunnel route you showed, because it could be built in the same structure as the N-S rail link along that same alignment. A two level deep-bore tunnel would work, similar to the two-level highway deep-bore tunnel under downtown Seattle. One level for Green, the other level for the N-S rail link.

 

[F-Line to Dudley]

Yes, that would make a balanced system.
Also I like the Congress Street Green tunnel route you showed, because it could be built in the same structure as the N-S rail link along that same alignment. A two level deep-bore tunnel would work, similar to the two-level highway deep-bore tunnel under downtown Seattle. One level for Green, the other level for the N-S rail link.

MassDOT already said the Congress alignment can't do two bores. The insanity of that rec was that expanding NSRL by +2 tracks to 4 total required building the CA/T alignment as an entirely separate and redundant project. That they would actually run with an answer like that means Congress St. is never going to host more than 2 tracks @ 1 level. Perfect for rapid transit builds TBD, absolutely horrible for NSRL when the CA/T alignment can hold it all.

Stacking is insane anyway for the added underpinning costs. That's not a "feature"...it's the utter civil engineering last resort when nothing else is capable of getting the job done. There's a reason why Green-Transitway is ultimately looking like it's going to be a South End jog; Silver Line Phase III impaled itself on the underpinning costs plowing through Chinatown.

 

[luobo]

First post on the forum, why not start with a goofy Seaport gondola?

Unlike the other goofy Seaport gondola, this one attempts to solve an problem previously identified: it's essentially a Back Bay to Track 61 substitute. We're trying to shuttle convention attendees from the hotels in Back Bay/Copley to the Seaport/Convention Center in a reasonable amount of time without too much fuss.

Why a goofy gondola?

1. Getting DMUs across the NEC and Old Colony lines via Widett is too disruptive to other train service.
2. The huge I-90/I-93 interchange and street grid layout don't support reasonably direct bus service.
3. There's an almost uninterrupted corridor of empty air between the two termini.
4. ???????
5. Gondola!

Two of the stations will require decking over I-90. The Back Bay connection is built on a decked platform east of Clarendon St. The gondola does a straight shot eastward to the second station, which is built on a decked platform between Washington and Harrison. The gondola turns northeast at this station, floating over the highways and parking lots until it reaches the terminal station abutting the Boston Convention and Expo Center at the corner of Summer St and West Side drive (since these roads are elevated, vertical circulation is easy!).

It's goofy, but:

• the potential ridership of a Back Bay to BCEC route is probably within gondola capacity limits
• a semi-scenic gondola ride might better fit the touristy vibe of that rider niche
• gondola would likely become a tourist attraction in its own right with crazy harbor/seaport/financial district views
• at a conservative 10mph, the 1.5 mile trip takes 9 minutes (with 12 second headways!)
• the decking is pricey, but makes use of otherwise dead space
• creates a Silver Line connection at the middle station because why not
• manages to cross the Pike, 93, the NEC, and the Old Colony lines without disrupting any of them!

Anyway, had a lot of fun reading some of the stuff on this forum, figured I should add my craziness to the mix.

 

[Charlie_mta]

MassDOT already said the Congress alignment can't do two bores.

I was talking about a single bore, with two floors inside the one bore; one floor a 2-track NSRL, and the other floor a 2-track Green line. Seattle just did it with 2 traffic lanes+shoulder on each of the two levels, so this bore I'm proposing would be smaller diameter than Seattle's. Seattle's bore had to go through crappy fill on its south end, so I think fill is doable. Of course all this would require geotech exploration and an engineering study for feasibility.

 

[F-Line to Dudley]

I was talking about a single bore, with two floors inside the one bore; one floor a 2-track NSRL, and the other floor a 2-track Green line. Seattle just did it with 2 traffic lanes+shoulder on each of the two levels, so this bore I'm proposing would be smaller diameter than Seattle's. Seattle's bore had to go through crappy fill on its south end, so I think fill is doable. Of course all this would require geotech exploration and an engineering study for feasibility.

Nothing to do with Seattle (which isn't an aspirational example to rely on anyway because of all the TBM'ing construction complications and cost blowouts they had).

The fact that the idiotic "build it twice on two alignments" exception exists here in the officially-vetted NSRL plans is because the Congress alignment is very specifically constrained on what you can do with it. If stacking were possible the way you pitch it, they'd be pitching that very thing as a 4-track NSRL option instead of requiring the CA/T alignment be built separately for the extra 2 tracks. They didn't because they already did enough scoping to engineering-determine that you almost certainly cannot stack infrastructure within any reasonable cost on the Congress alignment. You won't get a more 'official' thumbs-down on stacking's viability than what they just gave.

There's absolutely nothing wrong with using Congress as a rapid transit alignment that has complete and total flexibility to do what it wants on that alignment. You just can't bootstrap it with NSRL via stacking. That is not a big demerit, because the Congress St. alignment is garbage for NSRL capacity to begin with, so any sane valuation that isn't top-down directed to tank the study like our wonderful Admin. just did is going to be building the CA/T alignment as straight-up common sense Preferred Alt. and never paying Congress St. second mind. Forget all NSRL considerations on Congress; that very not-Crazy project is doomed to begin with if it's forced down there. What you are looking at is strictly a future-considerations rapid transit bore. Pure and simple. No mixed-message bootstrapping in this proposal, because mixed-message bootstrapping is today just a political shiv to kill NSRL. Bending over backwards to accommodate it just means you're trying as hard to kill your own RT proposal as Baker/Pollack are to kill NSRL. Just build the rapid transit build clean as a rapid transit build shorn of the other considerations that never were real-world relevant to begin with. This stacking debate is an OCD wormhole that isn't and never will be relevant to the build.

 

[F-Line to Dudley]

I like that in a vaccum, but it seems to me theres no need to build a new tunnel under the channel when a perfectly good one already exists.

Yep. Transitway FTW. Dual-modeing the Transitway even makes Urban Ring SE quadrant via streetcar tracks in Haul Rd. total fair game if that's how you want to handle the route from Dudley to Southie. (Note: must be streetcar tracks in mixed truck traffic, because Track 61 has absolutely zero room to shiv a second track in the combo cut).

Plus it would be a colossal waste to not use the quad-track Tremont tunnel for everything that it's worth. Especially when a Tufts station under Eliot Norton Park and extension of the 2 x 2 tunnel under the one urban-renewal block of Tremont to Marginal ends up an easy feeder for E relocation off Copley Jct. via Back Bay Station + Marginal, an eastbound tunnel under Marginal that splits the Seaport route + the Washington St. LRT route to a portal up the Herald St. retaining wall to the Washington light, and a thru-routing wye track for alt-routing E's straight to the Seaport or Washington. Which, if Urban Ring south half has to be BRT from lack of available ROW, gives you a real Kenmore-Dudley Green Line route via augmentation of 1) cross-platform transfer @ Kenmore from Urban Ring north 2) Longwood/Brookline Village via a Kenmore Loop-terminating pattern 3) run-thru on D-to-E connecting trackage (Pearl St./Riverway surface now, full-on burial of the E later), 4) the new Back Bay routing to the Marginal St. junction, 5) passing straight through the wye onto the Washington St. split-off rather than turning inbound to Tufts/Boylston like most E's. Ditto for any alt-routed E/D/Kenmore-to-Seaport patterns...demand for which will eventually compel that full-on alt-spine'ing of the Central Subway via burial of the E under Huntington to Brookline Vill.


As for fixing northbound congestion...I don't think you need a killshot like the Congress alignment to manage the Boylston-GC chokepoint. Utilizing the Boylston-Park quad-track and contructing the inbound 'fence' track crossover as GLT plans is a biggie that takes out most of the garbage. While the E relocation off Tufts pretty much fixes Boylston-Kenmore forever and makes long-term growth off Urban Ring 'circuit' thru-routing BU to downtown slot neatly in the mix. Branch merging at Kenmore is a difficult dance in itself, which is why so much GLT emphasis is being put on signal priority and cleaning up the surface branches. But at least it's one single-point crossroads where any schedule adjusting should be able to be one-and-done when branch trains are slotted on those platforms. Not so when the E is crossing at-grade at Copley throwing a further monkey-wrench into the orderly branch procession once things are in the subway. The Boylston-Park merge off the South End routes is way, way more dynamic for handling that (as is the Tremont tunnel's quad-track layout before stuff even slots at Boylston). Relocating the E looms enormous for achieving the traffic management of their dreams, additional branch patterns and all.

Past the colossal slotting improvements with an E-free Kenmore-Boylston and the quad-track slotting thru Park, the last brittle point to target is maybe GC station itself. Now, the Park-GC tunnel really cannot be widened to 4 tracks because of the historic properties above on that Tremont St. block. But the massive GC 'wedge' platform could feasibly cut a new pair of tracks across from the Park-pointing edge of the wedge straight through onto the Brattle Loop platforms so that the wedge is chopped up into an (angle-offset) 2 x 2 island setup like Park and Boylston. It'll reduce the timing urgency of trains arriving at their near/far spots on the existing thru platforms for loop-turning vs. Haymarket-thru service by instead fileting them on separate tracks, while keeping the loop as a load-bearing part of the mix. GC has a merciful scarcity of support beams because the GL-level roof is just bare City Hall Plaza and the headhouse, so unobstructed paths do exist for throwing down a new switch and cutting new tracks across the floor to the Brattle Loop side to make it a full quad-tracker. The construction complexity of doing that is more in how it radically changes pedestrian patterns on the now discontiguous 'wedge'. I couldn't even visualize what you'd need to add in terms of ped underpasses/overpasses or widenings of the Blue underpasses so they can double as eastbound/westbound changeovers on the Green level. Spatially I'm a little orientation-unclear on exactly what changes would be required to keep the flow in balance...so that could end up being a cost-bloater in the end depending on how many touches are needed. But it is physically feasible to do that at GC, and that last addition of quad-track flex should be able to lick the last of the traffic management concerns with a max-expanded Green Line. Failing that, you can revamp Haymarket station into twin IB-OB islands (the walls should be slightly expandable, even if the resulting 2 island platforms are close to minimum width) and have yet another sorting opportunity before everything continuing north has to slot back-to-back far-end vs. near-end on the North Station platform.

Regardless of the expense involved in those Central Subway touches, as a package it is VASTLY cheaper to build the South End junction, relocate the E, mod the GC track + ped layouts, and possibly light-mod Haymarket than it is carving a whole new Congress St. routing. If augmentations to Central Subway accomplish 100% of the job for alleviating all future traffic management concerns at maximal expansion...I can't see a great big value proposition in seeking a whole other cleanroom alignment. Especially when the complementary "alt-spine" effect of burying the E to Brookline Village via easy-dig tunneling under the existing reservation is likewise going to accomplish way more good at way more cost-control plugged into the existing system than pursuing the cleanroom spine on Congress. Green can be completely 21st-centuryized just by applying tunneling tricks on its existing alignment within its existing 'mongrel' nature.


Rather, the Congress alignment seems like it's screaming for a new HRT spine to relieve Red through downtown. Because Red is the one whose loads keep projecting to grow exponentially throughout the century even as we try to blunt that problem area by infilling missing crosstown connections. NSRL, for instance, may take some types of traffic off Red but also dumps so many new sources of never-before-imagined traffic onto it that we'll forever be on our toes trying to manage RL congestion. So the fact that this Congress alignment parallels Red the whole way across Downtown seems to me to be too significant a tell to ignore. If Green 2050 is settled by other (more modular-construction) means, then what does the availability of this alignment tell us about Red 2050 congestion management? Probably the whole world! That's why I really warm up to the "Red X" scheme where all 4 legs off grade-separated Columbia Jct. can alternate patterns at full-on 3 min. mainline headways. Feeds Quincy growth after Boston starts tapping out via the headway increaser, encourages more expansion off Ashmont/Mattapan, de-clogs downtown by load-spreading onto a separate set of transfer stops on the two northern legs of the "X", encourages robust expansion past Alewife because downtown dwells won't be the limiter, and just so happens to send the Congress leg of the "X" across the Charles from North Station to a spot around BET where it can literally choose-your-adventure via routing bootstrap next to any of the northside CR mains (some riper than others) for continuing service. Tough value proposition to pass up, since the hard tunneling up Congress is amortized by all the other cogs of the system being so easily plug-and-play (and literally plug-ready on the south end with the Cabot leads + Columbia Jct.).

 

[JeffDowntown]

When we talk about the future transit potential through downtown, we always seem to assume that the idiosyncrasies of the Central Subway (Tremont Street, 1897) and the Main Line Tunnel (Washington Street, 1908) are fixed barriers.

While I am not suggesting that these tunnels be massively modified for no reason, they do have a design life. At some point they are going to need major rebuilds -- civil engineering structures simply do not last forever.

If we were faced with the opportunity to reconstruct the Central Subway or the Main Line Tunnel (because we have to structurally), what would we do differently? Likely keeping essentially the current alignment, are there major barriers to future growth that we could eliminate?

 

[Arlington]

I know that Jeff was thinking about the Green and Red tunnels, but my thoughts turned to Blue before Green.

Tunnel change priority 1: Bowdoin loop elimination = longer Blue Line cars (greater commonality with Orange) and longer trains (platform lengthening). Then, no matter where Blue goes after MGH (whether Kenmore, Cambridge, or West Station) it will be a much more significant reliever for other lines.

Change 2: more entrances at both ends of platforms. It'd be kind of a big deal to let people get off "one station early" because their current penultimate station gained better access to the street.

And what about 2 new GL tracks & platform under the Common at Park with a new entry above and Red platform access below? Imagine (in the picture below) two more tracks and an island platform. The current "westbound" platform would become a center-platform place to turn trains terminating at Park (instead of looping). The new westbound platform would be on the left (in the picture) and would be nice if it tied downstairs to the under-the-Common ends of the current Red platform, and then up to a new granite-glass-and-copper headhouse on the Common.

 

[F-Line to Dudley]

When we talk about the future transit potential through downtown, we always seem to assume that the idiosyncrasies of the Central Subway (Tremont Street, 1897) and the Main Line Tunnel (Washington Street, 1908) are fixed barriers.

While I am not suggesting that these tunnels be massively modified for no reason, they do have a design life. At some point they are going to need major rebuilds -- civil engineering structures simply do not last forever.

If we were faced with the opportunity to reconstruct the Central Subway or the Main Line Tunnel (because we have to structurally), what would we do differently? Likely keeping essentially the current alignment, are there major barriers to future growth that we could eliminate?

It's not like the bare tunnel walls have a midlife replacement due or anything where you have to start jackhammering and re-pouring wall panels. It really isn't discrete like that. The tunnel structures are continuously maintained. On the Central Subway, for instance, there were massive modifactions after the big '96 flood for active-pumping room installations. Which neutralized the #1 threat--water intrusion--to any of the lining. And in the late-70's, a big reno for tunnel ventilation to accommodate the blow from the giant HVAC units on the roofs of modern LRV's and trackbed weight reinforcements for passages underneath the tracks. Those infrastructure enhancements happened largely invisible to passengers, but they were a sea change to how things were before. GLT might do a *little* bit more to the tunnel structures if curve-easing is in-play, but otherwise it's all utility renewal with no additional pressing needs on the bores themselves. The non-station physical structures of the Central Subway are pretty much at a state of repair for 100 more years easy.

This is in marked contrast to, say, the Amtrak North River tunnels out of Penn Station that have a gun to the Gateway Project's head before they have to go offline for "major midlife overhaul". But that's because there has been decades-long continuous water intrusion actively stressing the infrastructure. The exposed concrete is all spalled, and the ceiling drips to the point where there's 24/7 icicle hazard in winter. And the inadequate drainage channel (which can't be accessed while trains are running) is still clogged two-thirds a decade later with brackish Hurricane Sandy water that's accelerating the decay to alarming pace. It needs "midlife overhaul" because of a decay stressor that's active, continuous, and very severe as active stressors go. But in the absence of Sandy and in the absence of decades of leaking...it wouldn't need any major rehab. Concrete just doesn't start disintegrating in 100 years unless something is actively stressing it. That's the difference between the Central Subway and North River Tunnels: no decay force is acting on the dry GL tunnel structure in real-time. Not only that the prior flood and air quality fortifications had the luxury of being proactive moves to head off potential problems before they chemically acted on the walls. As long as the infrastructure isn't obsolete for the SERVICE (it is...GLT proves that) the "natural" aging rate of the structure itself sans any specific active stressors is on the order of multiple centuries. This is why 2000 year old bridges in Rome are still carrying rush-hour traffic over the Tiber River and 188-year-old Canton Viaduct still carrying the Acela (with that Discovery Channel "Life After People" show pegging it as the last bridge in Eastern MA to collapse after civilization...some 400+ years from now). It's not the march of time, but what stressors are *specifically* acting on the structure on pressure-over-time. Have those stressors functionally neutralized as Boston's subways do (but the water-leaking Big Dig tunnels do NOT) and useful lifespan basically stays immortal for any foreseeable century-level planning purposes.

Our subway tunnels are in rock-solid shape. Nothing like the Sandy-addled repair bill NYC has in scores of its underground transpo infrastructure.

 

[CSTH]

Our subway tunnels are in rock-solid shape. Nothing like the Sandy-addled repair bill NYC has in scores of its underground transpo infrastructure.

Thanks for yet another informative post.

With this in mind, my crazy transit pitch is to build a harbor barrier to keep a near-future Boston Sandy (whether hurricane or blizzard) from doing to our tunnels (both road and rail) what the actual Sandy did to NYC's

 

[Arlington]

, my crazy transit pitch is to build a harbor barrier to keep a near-future Boston Sandy (whether hurricane or blizzard) from doing to our tunnels (both road and rail) what the actual Sandy did to NYC's

Turns out to be a Crazy Waterfront Parks pitch. The plan is to berm the shore with public spaces (e.g.Martins Parks @ Children's Museum). I like this better than the outer barrier (which I am sure the Dutch could design but it is a lot of money compared to berms and parks that have additional value when not holding back the tide)

Separately (and faster) the T needs to (is) raising the threshold at low lying stations and vents

 

[F-Line to Dudley]

Thanks for yet another informative post.



With this in mind, my crazy transit pitch is to build a harbor barrier to keep a near-future Boston Sandy (whether hurricane or blizzard) from doing to our tunnels (both road and rail) what the actual Sandy did to NYC's

Important to note that NYC being surrounded on all sides by rivers with flood stages triggered by a NY Harbor storm surge is why their subways and rail tunnels have nowhere to hide and are so across-board vulnerable. Boston Harbor's drainage pattern is far more limited, being linear to the Charles Basin + Mystic + Ft. Point ancestral tidal bay channels. The areas of maximum risk are discrete to the landfilled areas, not exponential like surrounded-n'-outnumbered Manhattan. Nobody in North America is as fucked on intensity and $$$ of tunnel fortifications as NYC. We, despite the scary-as-fuck flood map, have it on easy street for our subterranean infrastructure.



The D portal is the most vulnerable on the entire system, being regularly exploited by an overtopping Muddy River with the devastating '62 and '96 floods each destroying Kenmore Station and millions of dollars in utility infrastructure via a pronounced 'storm drain' effect from the steep incline. Thankfully the T has already invested in a major flood barrier upgrade at the Fenway portal, installed ~3 years ago. They can barrier the incline now much faster than the manual wood planks and sandbag berm that used to take dozens of scrambling staffers to move into place. As prior noted, the Central Subway also got major investment in pump rooms after '96 so is in superior shape to cope even with things like in-station rain leaks.



Per the flood map, next-most vulnerable portal is Orange @ Back Bay. I don't know if that has any extant flood doors, but being a modern (1967) tunnel it has active pumping and Tufts Med Ctr. vicinity is high-and-dry bedrock so intrusion probably wouldn’t get very far in. Basic upgrades prudent, but no real catastrophic problem to head off like there was with the repeat-offender D portal. Red @ Columbia Jct. is vulnerable being in the Widett/Ft. Point drainage area, but there’s not much of an incline down so an intrusion would get stopped soon after the portal and not imperil short-turning Andrew service if the tracks to JFK were severed. Don't know if there's a pump room a few feet in, but that would be worth an upgrade. SW Corridor tunnel, especially between Back Bay-Ruggles, is in the maximal flood risk area. Risk there is not flowing water because the grade is flat-as-a-board and most critical utilities are wall-mount, so flood doors are neither necessary nor all that useful. Rather, better pumps and drainage channels to keep standing water from collecting or slowly rising would be prudent. Being mid-80's construction it's already got purpose-designed drainage channels, but the sea level rise maps give enough pause for Amtrak and the T to want to kick things up a notch. None of these would be expensive investments at all, and would be implementable without riders even noticing.



Red @ Kendall, Blue @ Logan, B/C/E, Science Park, and D St./Silver Line Way portals are all high-and-dry. Orange @ Community College may have 'minor' risk per the map, but slots in the minimal 0-2 ft. flood stage risk. SW Corridor western end through Ruggles has a distended risk area for standing water, but Back Bay-end fortifications largely inoculate Roxbury. On the Blue Line they're doing the entire climate resiliency study right now for Logan-Wonderland which will likely be folded into a "Blue Line Transformation" effort for next-gen signaling that consolidates hardware a couple feet above the ground. Storm surge can inundate those tracks in Revere, which is murder on the current hardware-and-electricity heavy signal system with its manual trip-stops, signal heaters, and copper relays. Going to a solid-state signal system like CBTC would massively consolidate the amount of field hardware and base it on much consolidated bundles of resilient fiber, water-tight RFID relays, and signal houses full of generic routers you can order off Amazon instead of "thar be dragons!" old electromechanical relays like the Red Line bungaloes that got ruined in last summer's derailment. Blue is the ideal first test bed for deploying CBTC to the T because it's short with wider headways and easier to fine-tune the software-dominated signal programming before they tackle Red or Orange.



On Commuter Rail the Eastern Route through Revere is most vulnerable, although it's been running on the Rumney Marsh causeway for 172 years before any Eastie landfilling so the drainage properties are well-understood. At worst you'd be looking at topping off the embankment with another 1-2 feet of rock fill. Salem Tunnel occasionally gets hosed from the south portal with storm-drain standing water in the odd severe Nor'easter which inhibits passage for 1-2 days at a time but does no damage because the signal utilities (and any future electrification) are all mounted high on the wall. They just run a few 'rust-buster' trains back and forth on the rails before reopening. Inconvenient for temp-severing Rockburyport but not all that consequential and almost a design ‘feature’ of the tunnel to be able to flood worry-free in a Salem Harbor intrusion. Note that if Peabody Branch service initiates it's going to traverse a notoriously flood-prone downtown thanks to North River absorbing a lot of Salem Harbor storm surge. The street grid + tracks along the river flood all the fucking time. Downtown fortification funding is a high priority, but has been slow-going in the Legislature for 15+ years. Rail line flooding isn’t high-risk for a damage bill…maybe even less so than Salem Tunnel. Rehabbing the branch for passenger service includes lots of culvert work (already baked into prior cost estimates).

--------------------------------



As you can see, not a lot of big worries with the existing infrastructure. Rather, it's the NEW builds that have to take extra precautions. NSRL, having portals right in the pants-shitting-scary South End and Widett Circle flood zones and extremely long and steep inclines from each will need weapons-grade portal flood protection. Big-ass flood doors and an armada of portal pumps to stop any leaks in their tracks. Once past the portals, however, the tunnels should be OK and the Somerville portals @ BET are on a high-and-dry oasis. On the CA/T alignment the slurry walls framing the lower rail level would be capped with regular tunnel lining unlike the highway level which exposes the bare frames to achieve its lane width. The NSRL level should not leak in a neverending torrent like the I-93 level does, and should not be the long-term maint nightmare that the highway level is. Other builds that have to be on top of their game: Green Line to Seaport as the tunnel will most likely swing close to the max-risk South End flood zone. However, the new pump room at Boylston already fortifies the abandoned Tremont Tunnel so construction mainly has to ensure no wall breaches and pumps where it slides under the Orange Line. Same wall-leak considerations go for relocating the E through Back Bay to the Tremont tunnel. For Washington St. LRT service, the surface incline would have to slot on the Shawmut-Washington block bolted to the Herald St. retaining wall on NEC real estate formerly occupied by the Boston Herald's freight siding (and currently just a bunch of signal boxes). Flood doors necessary there, and (so long as it doesn't impact sightlines to the traffic light @ Washington/Herald) extending the tunnel portal framing a few feet up the incline so it's not on the floor of the NEC/swimming pool can also minimize the risk.



Other than that...not a whole lot to consider with the officially-proposed stuff. BLX-Kenmore has certain advantages recycling the Storrow Dr. EB roadpack because the box tunnel (more a capped cut than anything truly subsurface) can stick 3 ft. above current ground level along a rebuilt Back St. retaining wall topped off with higher flood barrier and be covered with water-absorbant dirt berm (sort of like a second "BU Beach" between Mass Ave. and Copley) to keep its drainage properties attractively low-priced while offering some bonus fortification for the Back Bay street grid. But obviously Storrow teardown + transit trade-in are the terms of engagement for that project, so the build is highly conditional. Things like B burial to BU Bridge for the Urban Ring hook-in, E burial to Brookline Village to 'alt-spine' the Central Subway, Red Line northwest extension, and purely surface routes like Urban Ring Cambridge & Chelsea are non-factors for water. Others like the Congress St. NSRL (or alternate HRT) builds have the same exact considerations as the CA/T alignment at needing to mind their southern portals; with rapid transit that's wholly dependent on where your portals are. And we're simply not doing Crazy-crazy stuff like burying the Grand Junction (discussed at length why that's doubleplusbad for flood protection) or building that resource-impossible cross-Mass Ave. subway.

 

[CSTH]

Thanks as always.

Seems like the focus in that post is portals not stations? What about aquarium and courthouse? The vent box next to the water on the Eastie side of the blue tunnel? The pike portal @fort point? The cat vent at the intercontinental?

I get it though, convinced that it's possible to fortify the weak points instead of turning the harbor into a lake. ..at least for the purposes of 80 years worth of storm surge defense.

Long term I think harbor barrier is non negotiable but that's a topic for a different thread

 

[F-Line to Dudley]

Thanks as always.

Seems like the focus in that post is portals not stations? What about aquarium and courthouse? The vent box next to the water on the Eastie side of the blue tunnel? The pike portal @fort point? The cat vent at the intercontinental?

I get it though, convinced that it's possible to fortify the weak points instead of turning the harbor into a lake. ..at least for the purposes of 80 years worth of storm surge defense.

Long term I think harbor barrier is non negotiable but that's a topic for a different thread

Aquarium entrance definitely needs lots of help. Not sure about Courthouse; does that headhouse become a pond during a Nor'easter like Aquarium?

Intrusion down a station egress is comparably much easier to stop. Aquarium needs better barriers around it, but if it's stopped at the front door the risk downstairs is minimal. I vividly remember the '96 flood. The ped passageway at Kenmore was completely flooded up to the stairs from the torrent washing down the sidewalks into the headhouses. However, the subway entrance from the bus station stayed passable throughout to a dry fare lobby; the ped passageway ended up sacrificable. Unfortunately, that didn't end up mattering because the D portal storm drain had already done the damage sending water up to the top step of the platform egress.

In terms of terror threat level, that's instructive. Portals >> station entrances for severity of threat and how hard it is to stop the inundation once it's got runaway momentum. Similar lessons from NYC in Sandy...station entrances dwarfed by several orders of magnitude vs. in-tunnel intrusions.

 

[JimInProv]

A question: Is it possible and/or desirable to enlarge the red line level of the Park Street Station to increase the number of tracks within the station to four, extend the station closer to Beacon Street and put a Red only headhouse adjacent to Beacon Street?

 

[KCasiglio]

A question: Is it possible and/or desirable to enlarge the red line level of the Park Street Station to increase the number of tracks within the station to four, extend the station closer to Beacon Street and put a Red only headhouse adjacent to Beacon Street?

I'm ignorant from the engineering perspective but I'm interested in what you're trying to achieve with this expansion?

 

[JimInProv]

I'm ignorant from the engineering perspective but I'm interested in what you're trying to achieve with this expansion?

Mainly to move more people through the red line station more quickly.