Green Line Reconfiguration

a_tortoise

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The stilts of the building are 4 tracks wide, because it bowlegs over the ancestral ROW which was quad all the way through Belmont Center. The tunnel footprint would only be somewhat wider than the island platform here, with staging not needing to touch the building stilts. The only question is whether you do some manner of delicate construction staging so 1 temp track of the Fitchburg can stay in-service through the duration, or sever the whole works for a year with "rip the band-aid" approach and alternate shuttle routes for the outbound stops.

Some additional space on the extension gets saved by the Green Line's electrical being tied into the existing Red Line/TT substation in that overhang building (the vent windows seen on the photo), meaning you can anchor the power draw for the extension with distributed power upgrades to the Porter + Alewife RL sub power rooms and the next-nearest GLX sub rather than needing to construct an all-new substation. That's a significant cost saver for this particular extension being able to span existing 600V interconnects rather than create all-new substation sources like the current GLX has had to.

It's also potentially feasible to have the tunnel construction intentionally lower the level of the Fitchburg trackbed a couple feet before reconstructing it on the roof, making the Porter-Beacon St. canyon here able to be capped over at sidewalk level for an air rights park (and, crucially, a direct Somerville Ave. driveway for Lesley U./Porter Exchange so inadequate Roseland St. no longer has to be tasked with acting like a thoroughfare between Beacon & Mass).
So, in this configuration, would the Green Line run at grade next to the Fitchburg Line in a four track right of way from Union Square to Beacon Street, where it would then enter a tunnel between Beacon Street and the Porter Square station under the commuter rail tracks? It seems as though a lot of bridge work and building demolitions would be required along the at-grade 4 track right of way between Union Square and Beacon Street, given the zero-setback footprints of many of the old buildings. Is this in fact the case, or is there enough clearance to run four tracks at grade up to Beacon Street?
 

F-Line to Dudley

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So, in this configuration, would the Green Line run at grade next to the Fitchburg Line in a four track right of way from Union Square to Beacon Street, where it would then enter a tunnel between Beacon Street and the Porter Square station under the commuter rail tracks? It seems as though a lot of bridge work and building demolitions would be required along the at-grade 4 track right of way between Union Square and Beacon Street, given the zero-setback footprints of many of the old buildings. Is this in fact the case, or is there enough clearance to run four tracks at grade up to Beacon Street?
At Union you would punch archways through the retaining wall holding back the gravel fill of the Prospect St. bridge, but there would be no mods to the actual span. Webster is TBD for widening; it handled 4 Fitchburg tracks back in the day but GLX tracks would still be returning from the Union Sq. turnout so few more feet may be needed. The current span is way past replacement age and weight-restricted. MassDOT doesn't have anything planned there, but span replacement and pre-provisioning would likely predate GLX-Porter by a few years so would be a separate self-contained budget. At the Eversource substation, transformer equipment would then have to be jacked up and moved 10 ft. back because they infringe on the clearance envelope. Space and equipment for that maneuver exists, and it wouldn't be expensive.

That's it for clearances until the CR platform starts pinching out the room past Beacon forcing the duckunder. All of it, including new bridges replaced on former abutments, used to handle quad-track to the late-50's.

The only other ROW touch is eliminating the Park St. grade crossing with a road overpass, because 6 min. GL frequencies overlaid with 15-30 min. CR frequencies is a bit stiff. But Park has a pronounced 'dip' in the road and no immediately adjacent driveways so wouldn't be a big production as a road bridge.
 

F-Line to Dudley

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There’s a center pier on the Mass Ave bridge to contend with, unless you are expecting the tunnel box to stop short of it.
Mass Ave. is past the would-be station platform, so you split the bores for the stub tracks that run 1-2 trainsets past the platform before stubbing out at a wall. Assuming it's a center island platform the bores are going to slightly split any which way.

No biggie.
 

ceo

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Building underground stations is still kind of expensive, particularly for a one-station extension to a location that already has a T station. There's a good half dozen projects I'd consider higher priority.
 

F-Line to Dudley

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Building underground stations is still kind of expensive, particularly for a one-station extension to a location that already has a T station. There's a good half dozen projects I'd consider higher priority.
You didn't claim it was "kind of expensive".
Also, a station at Porter would be incredibly expensive, since it would have to be under the commuter rail station.
These are very different statements. Which is it?

It also wouldn't be a one-station extension. There'd be at least one intermediate (Conway Park, where the 83 bus diverges)...maybe two (Wilson Sq., where the 87 converges). The bus ridership on the Somerville Ave. corridor fully merits the augmentation, as the 87 (35th in systemwide ridership) with its 20 min. frequencies and 83 (58th in systemwide ridership) with its 25 min. frequencies tag team to move a lot of people around this strip. And the major selling point of the extension is the radial interconnect to the existing Red + Purple + 77/77A superstation...particularly where it leverages the contraflow direction on the Red transfer to help overstuffed Cambridge commutes.

Your argument against this is completely incoherent and self-contradictory. The things you're nitpicking for being high-end costing by nature do not have that nature, and the things you're citing for lack of demand actually show very strong demand for it. And citing "a good half dozen projects" you'd consider more worthy by comparison isn't relevant when you won't even name what any of them are to make it a real comparison. We get it; you personally ain't feeling it with this one. But if you're trying to show for argument's sake why that holds true to a neutral observer, you...uhh...have to remember first the "show us" part. These claims ain't it.
 
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jass

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The benefit of going to Porter is then having one branch continue along the Minuteman path to Arlington Heights (old commuter line) and the second branch continue to Belmont, replacing the commuter rail stop there
 

Charlie_mta

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The benefit of going to Porter is then having one branch continue along the Minuteman path to Arlington Heights (old commuter line) and the second branch continue to Belmont, replacing the commuter rail stop there
And another option is to Watertown via the old Watertown Branch RR.
 

F-Line to Dudley

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The benefit of going to Porter is then having one branch continue along the Minuteman path to Arlington Heights (old commuter line) and the second branch continue to Belmont, replacing the commuter rail stop there
And another option is to Watertown via the old Watertown Branch RR.
It's gotta be Red if you are going to do that.
Getting a little beyond "GLX" here, as Porter is self-contained within the "Why wasn't Porter considered from Day 1?" Q&A that spawned this tangent. But, yes...
  • 1 future LRT extension to Watertown via de-landbanked H2O Branch with short stretch of median-running on Arsenal St. rates very high on bang-for-buck.
  • 1 much further-future branch to Waltham using the extra Fitchburg main track berths to Clematis Brook and flipping the Purple Line to the Central Mass so it can take over Waltham Ctr./Brandeis. Quad-track used to run thru Belmont Ctr., tri-track to Clematis Brook (excepting widening of the Waverley cut, which was a 1955 grade crossing elimination). Frequencies servable simultaneous to here and Watertown by doubling-up Union-Porter Branch from 6 mins. to 3 min. headways, making more liberal use of downtown Brattle Loop turnback, etc. This is probably not an immediate need, but you can indeed prognosticate a future universe where :15 Purple Line urban rail to 128 via Waltham & Belmont Centers is not going to be enough for demand and when that time comes rapid transit is build-feasible here.
  • Red to Arlington Heights, because the Red tunnel already points in that direction and the bus transfer loads at the 2 extension stops are going to be very large meriting the Red-level capacity. Green...which duplicates a little too much infrastructure in the process...would suffer a little bit more on toplines being only half the frequency and capacity. Remember that all of the current MA 2 frontage road bus routes would vacate Alewife altogether and retrench at Arlington Heights, plus there would be massive-potential route redraws and new route potential to string out of the new stops + backfill of the Alewife slack in the ensuing Yellow Line reboot.
Green-Porter complements Red-AH nicely by providing a sizeable amount of contraflow-direction loading relief for Cambridge so the NW 'burbs and 128 have slack to backfill. You probably need GLX-Porter to work together with RLX-AH to get optimal benefit out of that end of Red in the end. Watertown has a major Cambridge commute component with the 71 TT, and some vexing broken links to North Cambridge ripe for a backfill. Waltham has large growth to tap just running Purple Line urban rail frequencies bi-directionally every :15, in which case Porter RL/GL transfer looms huge for its prospects. And then after a few decades of sauteeing up to the limits of that :15 Purple frequency there's probably a vector for full rapid transitization to 6 mins. with stop densification. They're all fellow travelers in a related future universe, and all strategically feast on Porter being scaled up beforehand to much bigger diverging node than it currently is.


This probably isn't the thread to handicap the relative odds of those further-flung extensions...but S.T.E.P.'s advocacy plank for doing Union-Porter in the first place absolutely does bake into account that any/all of them are future attractions that could very greatly enhance the value of complete rapid transit coverage across the Somerville Ave. corridor. It's a jumping-off point to excellently buff future scalability, which is why they don't want us to forget about doing Porter sooner rather than later.
 
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dhawkins

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Could there be potential savings with an elevated Greenline structure after Dane St up to Porter? Would an elevated structure with sound barriers cost as much as new retaining walls to accommodate four tracks at grade ? The end of the line could potentially be at Somerville Ave grade which would provide a roof over the commuter stop. Would it be a mistake to not rip up and restore the existing rail bed with updated systems because it hasn't been addressed for the last hundred years or so? The retaining wall work and underground drainage (and bridge extensions) of the current extension seems to be a significant amount of cost and time.
 

fattony

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Could there be potential savings with an elevated Greenline structure after Dane St up to Porter? Would an elevated structure with sound barriers cost as much as new retaining walls to accommodate four tracks at grade ? The end of the line could potentially be at Somerville Ave grade which would provide a roof over the commuter stop. Would it be a mistake to not rip up and restore the existing rail bed with updated systems because it hasn't been addressed for the last hundred years or so? The retaining wall work and underground drainage (and bridge extensions) of the current extension seems to be a significant amount of cost and time.
Not a bad idea, if and only if you want Porter to be the end of the line forever.
 

RandomWalk

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That would make any development of the trench impossible.

Returning to the current project: They poured the top of the pedestrian bridge support at Magoun Square on Thursday. Installation of the bridge shouldn’t be too far behind.
 

bigeman312

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Crazy idea, what if you gave Somerville Ave some approximation of this treatment: MAX Light Rail, Portland, OR.

Green Line meets surface Somerville Ave somewhere in the vicinity of Beacon Street. From Beacon to White Street, Somerville Ave could be a low-speed, one-way, single-lane, westbound, local-access road on the northern side of the right-of-way.

The southern side of the right-of-way could carry the 83 and Green Line in a mixed bus / light rail reservation. The bus/GL station could be right next to Porter across from White Street, where the street ROW gets wider.
 

F-Line to Dudley

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Could there be potential savings with an elevated Greenline structure after Dane St up to Porter? Would an elevated structure with sound barriers cost as much as new retaining walls to accommodate four tracks at grade ? The end of the line could potentially be at Somerville Ave grade which would provide a roof over the commuter stop. Would it be a mistake to not rip up and restore the existing rail bed with updated systems because it hasn't been addressed for the last hundred years or so? The retaining wall work and underground drainage (and bridge extensions) of the current extension seems to be a significant amount of cost and time.
Large and unlikely assumption that the residential around here would tolerate an El structure, for one. But also more inefficient on cost. If you're folding the Park crossing elimination into the same structure, that's way too much El structure for the cost accrual to work in your favor. 0.9-1 miles of steel-and-concrete if you're starting past Dane, with a really weird sky-high section where it has to pass over the Beacon St. overpass, up to 2 intermediate stations with pronounced elevator/escalator access in the sky, and a Porter level that may have to awkwardly be up on stilts because of how high the Beacon St. overpass-of-the-overpass is. All while still needing to do the most expensive at-grade punchlist items abutting Union of getting from the station turnout back onto the running ROW, and tapping none of the benefits of the existing quad-track ROW in between. Compared to .2 miles max in tunneling @ Porter and all at-grade everywhere between Webster and Beacon.

There seems to be a few assumptions at work here: (1) tunneling is always equally extremely expensive choice between cut-and-cover vs. deep bore, so Red-Blue's recently disclosed $850M figure is being misconstrued as a likely "floor" cost to run with; (2) the ROW doesn't have room or needs major earthworks retrofitting + total vertical station access because that's how it went with the main GLX; (3) Park St. crossing elimination is going to be some ungainly blowout. I'll address each.
  1. Cut-and-cover tunneling the likes of which Red-Blue is attempting is always pretty expensive. That's entirely because of the under-street utility 'sandwich' layer and needing to relocate all utilities in it. This is considerable cost on a big-building fronted thoroughfare like Cambridge St. Red-Blue also arrives at its $850M by doing a fairly large HRT-length platform addendum, adding additional egresses to Charles station, and doing a substantial amount of under-street demolition work at Bowdoin Loop to straighten the alignment. When I say there are "no utilities" under the Fitchburg trackbed...there are no utilities, just dirt. No drains, no water, no telecom, no electrical trunks, no nothing. Those all trawl under Somerville Ave.--which we explicitly do not touch--instead, because Somerville Ave. has the "manhole-level" sandwich layer appropriate for installing utilities, while the RR ROW doesn't. The tunnel you dig here is not a cut-and-cover "subway" in the traditional sense; it's a box-tunnel facsimile of the Orange Line Wellington duckunder of Medford Jct., or the collection of Columbia Jct. Red Line duckunders near JFK. A glorified train-sized culvert you dig for the sole purpose of being able to grade separate tracks that run on the roof from tracks that run underneath. In tunneling feet the Porter cost accrual would track like the similar-length 1975 Wellington box tunnel indexed to inflation...plus the Porter platform bulb-out (which, again, only includes the single egress attachment to the CR door of the wholly pre-existing lobby)...and minus the second incline because it's a stub-end. That's an extreme lot less expensive than what Red-Blue is doing. I have a hard time seeing the glorified culvert with outfitted station bulb and CR-level reconstruction exceeding $200M in a "shitty T accounting" universe. It could potentially be in the middle-low $100M+ range under a project team that well-policed its cost controls.
  2. The ROW has complete quad-track room. If you outright got rid of the CR platform at Porter, it would also have complete at-grade room thru Porter itself. But since this build rakes the hardest on toplines being a Red+Green+Purple+bus integrated transfer, the cost of preserving the CR berth ends up generating a lot of the high-ridership ROI and ends up fully worth doing. You also have side room for the intermediates. If the Conway Park intermediate directly faces the back of Conway Park, there's adequate fan-out room for platforms, at-grade egress straight into the park, and ramp egress to the new Park St. overpass for catching the 83. If the Wilson Sq. intermediate takes the car wash on eminent domain, you have all the room in the world to shave the retaining wall at that property to bulb out for platforms, plunk a Somerville Ave.-facing headhouse, and snake a platform ramp down to the Sacramento St. underpass for accessing the Beacon side of the neighborhood. There's no massive earthworks required to pre-prep the embankment, fit everything in a deep cut, and find room for the Community Path like there is with current GLX. It's largely real-deal pre-existing quad ROW and very close to at-grade everywhere between the Union and Porter cuts, with no Community Path complications.
  3. Park St. is not a huge crossing elimination production. The only reason it was not eliminated like Dane was mid-20th century is because the ex-warehouse on Tyler St. that it abuts had an active freight siding (track remnants still there) until the early-90's where the switching activity needed back-of-building worker access via the crossing. Were it not for that customer, B&M planned to zap it along with all other Somerville residuals in the mid-50's. Its would-be elimination would be a mirror-image to Dane's 'hump' overpass, inclines, and driveway treatments around the inclines. Could likely be blitz-constructed with an outright road shutdown to save costs because there are adequate paralleling streets for temp-absorbing the volumes for 6 months to a year.
Crazy idea, what if you gave Somerville Ave some approximation of this treatment: MAX Light Rail, Portland, OR.

Green Line meets surface Somerville Ave somewhere in the vicinity of Beacon Street. From Beacon to White Street, Somerville Ave could be a low-speed, one-way, single-lane, westbound, local-access road on the northern side of the right-of-way.

The southern side of the right-of-way could carry the 83 and Green Line in a mixed bus / light rail reservation. The bus/GL station could be right next to Porter across from White Street, where the street ROW gets wider.
No, never. Somerville Ave. is one of the biggest load-bearing crosstown thoroughfares in all of Somerville. No possible way you can squirrel the native loads off of it. Part of the reason you ever would consider leveraging the Porter tunnel for air rights featuring is that Roseland St. is already this narrow alleyway being overtasked with masquerading as a thoroughfare for the Lesley/Porter Exchange parking lot and traffic loading profile of Somerville Ave. on the Beacon-Mass Ave. block. And that situation is fucked enough as-is. I don't know where you expect those thoroughfare loads to migrate to for this transit plaza but for creating another 2-3 additional totally inappropriate Roselands around the neighborhood in the process and set the whole neighborhood back a large degree on general livability.

Again...this seems to rely on an assumption that we're doing cut-and-cover tunneling at typical cut-and-cover costs. It's not a cut-and-cover; it's a box culvert. And assumes that it accrues station costs equivalent to building whole new stations like GLX and/or adding-on whole new egresses like Red-Blue is doing at Charles. It's not that, either. This is a de facto "adding a room" to full-existing Porter off the same mezzanine, off the same Commuter Rail doorway, with no further adds. Coming down the main-entrance escalators in a GLX universe, you'd simply see the Charlie gates rearranged to put the CR door behind prepayment. Then there'd be a short ramp down at the existing door for the GLX level, a short ramp up for the replacement CR level. That's the sum-total change in station access unless you want to go all optionally hyper-completist with new adds around the neighborhood.
 
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RandomWalk

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At the risk of continuing this tangent even further, would it be worth doing a limited cut/boat for the rail ROW at Park St, to reduce the incline for the bridge over the ROW?

Mods: Should this tangent be moved to Reasonable Transit Pitches?
 

F-Line to Dudley

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At the risk of continuing this tangent even further, would it be worth doing a limited cut/boat for the rail ROW at Park St, to reduce the incline for the bridge over the ROW?

Mods: Should this tangent be moved to Reasonable Transit Pitches?
No. The geometry is there for doing a straight-up Dane clone, and the rush-hour traffic on the street already gets hosed pretty bad when the Fitchburg gates are down. Plans for scaling up Waltham/128 turns to :15 bi-directional urban rail spec is only going to make that crossing suck a lot worse, so it's already a well-wanted grade separation candidate. It'll already be creaking under a trigger threshold for elimination just with the Rail Vision; GL-Porter simply pushes it to "duh-obvious" status. Half-elimination wouldn't solve for the Fitchburg-under-Rail Vision suckitude, and custom-designed boat sections are going to pile on design costs in a way that extremely generic Dane-copycat road overpass would not.

This one really, really isn't an overthinking vector for the GL project. Somerville is prolly gonna be self-debating whether to fund Park crossing elimination any which way after Fitchburg frequencies pulse way higher.
 

ceo

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You didn't claim it was "kind of expensive".

These are very different statements. Which is it?
Maybe I'm a little tired of people talking about the Porter extension as a cheap no-brainer. Which it's not, and I disagree that it's as straightforward as you claim. Be happy to be proven wrong.
It also wouldn't be a one-station extension. There'd be at least one intermediate (Conway Park, where the 83 bus diverges)...maybe two (Wilson Sq., where the 87 converges). The bus ridership on the Somerville Ave. corridor fully merits the augmentation, as the 87 (35th in systemwide ridership) with its 20 min. frequencies and 83 (58th in systemwide ridership) with its 25 min. frequencies tag team to move a lot of people around this strip. And the major selling point of the extension is the radial interconnect to the existing Red + Purple + 77/77A superstation...particularly where it leverages the contraflow direction on the Red transfer to help overstuffed Cambridge commutes.
Conway I can see, but Wilson is barely a quarter mile from there, and less than half a mile from Porter. Making the commuter rail connection easier is a good point, though.
And citing "a good half dozen projects" you'd consider more worthy by comparison isn't relevant when you won't even name what any of them are to make it a real comparison. We get it; you personally ain't feeling it with this one. But if you're trying to show for argument's sake why that holds true to a neutral observer, you...uhh...have to remember first the "show us" part. These claims ain't it.
In no particular order, Green Line to MVP, Blue Line to Lynn, Orange Line to Needham, Green Line likewise, Urban Ring LRT West Station to Logan, Green Line to the Seaport via the Transitway. Are you happy now?
Most of these are a hell of a lot more expensive than Green to Porter, granted, but in my opinion offer considerably greater benefit for the cost. I'm not saying it's a terrible idea, all I'm saying is I think it's not as simple as is being claimed.
 

themissinglink

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Maybe I'm a little tired of people talking about the Porter extension as a cheap no-brainer. Which it's not, and I disagree that it's as straightforward as you claim. Be happy to be proven wrong.
Not only would GLX to Porter be beneficial to the Red Line by offering an alternative route into the city resulting in less crowding on the Red Line, it's a clear prerequisite to building further GLX phases to Watertown or Waltham. For those two reasons, I'd consider it to be somewhat high-priority.
 

Blackbird

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Not only would GLX to Porter be beneficial to the Red Line by offering an alternative route into the city resulting in less crowding on the Red Line, it's a clear prerequisite to building further GLX phases to Watertown or Waltham. For those two reasons, I'd consider it to be somewhat high-priority.
Do people in Waltham and Watertown really like the idea of having to swing wide through Belmont, Porter, and Union to get to downtown Boston? A much straighter route from those cities goes through West Station/Boston Landing/Kenmore.
 

NoShJFK

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I haven’t read this thread in great detail but I have a fairly simple question:

What would it take to turn the Green Line from a Trolley to a TRUE Light Rail similar to say LA’s LRT. Or where they can at least use the longer (and admittedly more modern looking) LRT rolling stock as opposed the trolley looking rolling stock and I would think increase the capacity of the lines
 
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