Reasonable Transit Pitches

http://www.bostongroundwater.org/ceprep.html

Concurrent with the filling, a sea wall was constructed along the Charles River to create Back Street that parallels Beacon Street on the water side. The top of this wall is clearly visible from Storrow Drive. A similar wall was constructed in about 1865 behind homes on the water side of Brimmer Street on Beacon Hill. Both walls were composed of dry-laid granite placed on a timber platform and supported on wood piles. It is probable the walls were ballasted with stone or gravel, similar to the Mill Dam walls.
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Still unsure if you could tunnel under Back Street, though.
 
You can tunnel anywhere between Storrow and Beacon.

Tunneling under Beacon gets you the maximum possible bang for your buck.
 
Commuting Boston Student said:
You can tunnel anywhere between Storrow and Beacon.

Tunneling under Beacon gets you the maximum possible bang for your buck.
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No, it isn't. The Boylston St. subway has an entire army of pumps keeping it dry and keeping the water level between it and abutting properties in-check. It's a very robust...but also very intricate and interconnected system. Dig under-street and under-utilities with a traditional cut and cover job a few hundred feet away and you're changing the equilibrium of that whole pump system. It'll need many pumps of its own. Other existing places will need more pumps. Pump rooms here will have to be load-balanced with pump rooms there. And the impacts zone for engineering/historical/EIS studies of how all this hidden 19th century infrastructure reacts to itself will pretty much cover the whole space between Beacon and Boylston. It doesn't matter if Beacon is a wide street and the tunnel footprint avoids building foundation. The extracurricular infrastructure and the contingency costs that'll have to be added onto the tunnel because of the water table in the landfill make it instantly cost-prohibitive.

The only reason Riverbank/Storrow is buildable while nobody has ever considered Beacon lies is the difference between tunneling depth. Even if under-Storrow is technically under the grass/pavement if you're standing on Back St. it's a box tunnel sitting on the bottom pack of the Storrow roadbed and up against that Back St. seawall, wholly outside the influence of groundwater. That construction has been done here before...on the Storrow auto tunnel, and on the deep cut for the Bowker ramps under Mass Ave. Basic air rights type work. If you're on Beacon...or even behind the wall under Back St. it's the difference of +25 ft. in depth to sandwich the (ancient) street utilities between, and no hard pack to use as a foundation. One block's distance...but it's the depth that makes all the difference between an inocuous job that doesn't technically breach the current surface pack and a Big Back Bay Dig costing ten times more with very complex hidden impacts.


There's no either/or routes here. Either it's the Storrow roadbed or nothing at all. And, no, I don't think that allows for cut-and-cover under Storrow either unless it's outright stealing away half the roadbed for transit + a calm 2-4 lane boulevard where the parkway used to be.
 
...not to mention the difference between a Beacon and Storrow line in terms of coverage would be negligible at best. We're basically talking about an area that amounts to the space between Newbury and Boylston: not a drastic difference by any stretch of the word.
 
And you'd have to deal with Back Bay NIMBYs on Beacon to boot...
 
omaja said:
...not to mention the difference between a Beacon and Storrow line in terms of coverage would be negligible at best. We're basically talking about an area that amounts to the space between Newbury and Boylston: not a drastic difference by any stretch of the word.
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Fair enough.

My other concern would be getting from the Riverbank Subway to Government Center. Deep bore looks neater, but sacrifices Park Street.

On a more philosophical level, I'd much rather see the studies happen for a Beacon Street Subway, even if the study result is 'there's no fucking way we can ever build this thing,' because F-Line's post reads to me an awful lot like nobody knows precisely how all the utilities etc. under Back Bay actually interact, nor where everything is - and the more I think about that, the less happy I am about it.

Is it really okay for us to leave everything hidden/undocumented like that?
 
^ It will get to the river via Cambridge St and Charles/MGH as a BLUE LINE extension, not a Green Line one...
 
I'm not talking about the Blue Line. (To be quite frank, the only Blue Line extensions I care about and the only two that matter are Blue Line to Charles/MGH and Blue Line to Lynn. Talking about Blue on Riverbank when we can't even get Red-Blue done is stupid, and conflating the two is even stupider. But I digress...)

Beacon Street Subway would have put Green Line Heavy Rail back on the table without disrupting the existing light rail services, all of which go up in smoke if you take the two tracks Park-GC for heavy rail. There's no room to expand because of the burial grounds on either side. Riverbank Subway also puts Green Line Heavy Rail on the table.

Kenmore - Riverbank - Government Center for Green Line Heavy Rail rather neatly side-steps every single problem area for a heavy rail conversion except for North Station at zero cost to any of the Green Line branches, and doesn't lock us in to what might not be the best way to move forward with the Blue Line.
 
Commuting Boston Student said:
Fair enough.

My other concern would be getting from the Riverbank Subway to Government Center. Deep bore looks neater, but sacrifices Park Street.

On a more philosophical level, I'd much rather see the studies happen for a Beacon Street Subway, even if the study result is 'there's no fucking way we can ever build this thing,' because F-Line's post reads to me an awful lot like nobody knows precisely how all the utilities etc. under Back Bay actually interact, nor where everything is - and the more I think about that, the less happy I am about it.

Is it really okay for us to leave everything hidden/undocumented like that?
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Back Bay isn't too badly documented since it's just over 100 years old and built on a grid. I think the word hidden meant "not in the public conscious" and not "we don't know where stuff is." FLine's point is more about the very complex system that keeps basements and the T dry. Dryish. Groundwater recharge stabilized decaying wood piles but resaturated the ground. I can think of a half dozen buildings where the water table is higher than the basement or sub-basement.

So now the the Back Bay exists in a delicate balance. Digging it Beacon St up, constructing a water-proof tunnel and load-balancing the distribution of the existing and new pumping stations is mathematically easy. Paying for it is not.
 
Commuting Boston Student said:
I'm not talking about the Blue Line. (To be quite frank, the only Blue Line extensions I care about and the only two that matter are Blue Line to Charles/MGH and Blue Line to Lynn. Talking about Blue on Riverbank when we can't even get Red-Blue done is stupid, and conflating the two is even stupider. But I digress...)

Beacon Street Subway would have put Green Line Heavy Rail back on the table without disrupting the existing light rail services, all of which go up in smoke if you take the two tracks Park-GC for heavy rail. There's no room to expand because of the burial grounds on either side. Riverbank Subway also puts Green Line Heavy Rail on the table.

Kenmore - Riverbank - Government Center for Green Line Heavy Rail rather neatly side-steps every single problem area for a heavy rail conversion except for North Station at zero cost to any of the Green Line branches, and doesn't lock us in to what might not be the best way to move forward with the Blue Line.
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This proposal does nothing to address the most overburdened stretch of the system, Park Street - Government Center. In fact it adds to the problem. This is why a Blue Line tunnel through Back Bay is necessary in the first place.
 
bigeman312 said:
This proposal does nothing to address the most overburdened stretch of the system, Park Street - Government Center. In fact it adds to the problem. This is why a Blue Line tunnel through Back Bay is necessary in the first place.
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The reason that stretch is the single most overburdened part of the system owes to a combination of factors including the lack of a direct Red-Blue Connection (which means all in-system transfers Red-Blue need to go through either Park-GC or State-DTX) and a two-track tunnel that needs to be quad-tracked but can never be (due to the burial grounds on either side of it.)

A Blue Line Tunnel through Back Bay solves neither of these problems, but a Green Line tunnel through Back Bay provides another option where you could route D-branch trains even without a heavy rail conversion through it instead, reducing the demand on the Park-GC tunnel to more manageable levels. Just because it puts the option for Green Line Heavy Rail on the table doesn't mean that it only works if packaged with a Green Line Heavy Rail conversion. In fact, assuming you leave it as a light rail tunnel, the demand mitigation on the Park-GC stretch is even better - take whichever two branches are going to use GLX and send them through the Riverbank subway, leaving the existing tracks for branches which aren't destined for GLX.
 
^ So do an E/D alternate routing via Tremont to Marginal Way along the NEC to BBY, joining the current E routing on Huntington, and allowing a connection to the D Brookline Village.
 
BussesAin'tTrains said:
^ So do an E/D alternate routing via Tremont to Marginal Way along the NEC to BBY, joining the current E routing on Huntington, and allowing a connection to the D Brookline Village.
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Also doesn't solve the problem. You're still coming into Park from the south and having to go through the Park-GC choke point tunnel.

If you're willing to dump Park/GC for South Station and Aquarium, you could alt route along Essex Street, then up the Greenway to North Station. Not sure how reasonable the Greenway Trolley really is even before you factor in tunneling under Chinatown, but that does create a direct line BBY - BOS - BON and that's somewhat huge.
 
A Blue Line tunnel to Kenmore via Charles/MGH would serve anybody coming from Kenmore and points west and at least half of the Back Bay with destinations on the northern half of the Red Line and anywhere on the current Blue Line, including Government Center, and vice versa. It would also serve as a Blue/Red Connector at Charles/MGH. I'm sure this is a sizable number of people.

Forgive me if I'm missing something, but your proposal is to have the green line branch, going westbound, after Park Street, without touching the Park Street-North Station stretch of the tunnel. This would certainly not decrease ridership on the green line (which is not a bad thing) but would still send those same riders, and maybe more, through the same Park Street-Government Center tunnel (which is a bad thing).
 
How would a Blue Line Kenmore-Government Center via Charles/MGH and Riverbank not relieve the Green Line? Currently the only way Red and Blue passengers can head west is by transferring at Park and Government Center; extend the Blue Line to Kenmore (and eventually choose a route to head further west), and you'll eliminate the Blue demand that the Green is carrying as they'll be able to go single-seat. That would also put a big dent in Red-Green transfers considering the alternate transfer point at Charles/MGH.

Edit: Looks like I was too slow at typing. :D
 
Commuting Boston Student said:
On a more philosophical level, I'd much rather see the studies happen for a Beacon Street Subway, even if the study result is 'there's no fucking way we can ever build this thing,' because F-Line's post reads to me an awful lot like nobody knows precisely how all the utilities etc. under Back Bay actually interact, nor where everything is - and the more I think about that, the less happy I am about it.

Is it really okay for us to leave everything hidden/undocumented like that?
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Simple answer: it's impossible to document it all without ripping the street open. Yes, they can easily see electrical/telecom wires and water/gas/sewer mains and whatnot by climbing down into a manhole. But what else is under there after 125 years of development? When they did the Big Dig they turned up shitloads of undocumented live utilities and redundant lines in strange places off the known utility trenches, plus stuff like old city trash landfills, groundwater culverts nobody knew existed, historical artifacts, gigantic-ass rocks somebody buried underground in some forgotten landfilling project, and other totally off-the-wall crap. On land that was already razed once in the 50's for the Central Artery.

Beacon has been pretty much undisturbed since it was first laid out...never widened at all in the 20th century like, say, Cambridge St. on the Red-Blue extension ROW. It's almost certainly got bizarre stuff under it laid out willy-nilly. Plus the Back Bay's signature wood pilings holding up the surface and buildings like rebar. Utility documentation was virtually nonexistent in the early days, spotty at best until the 50's, and not resembling comprehensive until it started getting documented for posterity on computers. And there are hundreds of those original BB support pilings still unmapped or with location only approximately known.



Honestly, these are the only places in town where new subway construction has any sort of real-world engineering feasibility:

-- Under active RR lines (NEC, Southampton Yard, BET for N-S Link + portals; Red-under-Red to fix the Savin Hill space crunch). Advantages: few opportunities historically to string underground utilities because of the active ROW's; all crisscrossing utilities had to have negotiated property easements with the RR fully documented for taxation.
-- Under trolley reservations (e.g. B and E burial). Advantages: similarly few opportunities to string underground utilities on century-active lines.
-- Cuts and air rights (e.g. Storrow/Riverbank; Green Line from Tremont to Back Bay under Marginal St.). Advantages: subterranean, but not breaching subsurface.
-- Urban renewal areas (e.g. West End/Cambridge St. for Red-Blue; under I-93 for N-S Link). Advantages: it's where all surrounding structures were leveled in recent decades, the ground was cleaned and documented for hidden infrastructure before anything new went up, and the adjacent streets were widened and had mass utility cleanup before new structures went up.
-- Outer neighborhoods, around low-density properties, in non-landfill soil (e.g. Mattapan-Fairmount ROW connecting subway for the Red Line). Advantages: fewer utilities feeding 1-2 story residential, few abutting structures when most properties have decent-size yards.
-- Deep-bore, in hard bedrock (e.g. Porter-Davis). Advantages: too far underground to disrupt surface structures, can cut across property lines, no utilities once you descend far enough to hit the bedrock. Bummer: most of the places in Boston-proper with a need for subways are the places where the solid bedrock ain't (e.g. not downtown, not along Mass Ave.).


That's about it. You can maybe justify a disruptive under-street dig like Brigham Circle-Brookline Village when it's a manageably short (< 1/2 mile) gap in an otherwise 'clean'-dig subway and lies outside the landfill zone. I'm at a loss to think of any beyond that E-burial stretch that provide any significant connectivity inside a tolerable pain threshold.
 
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