Say they did somehow find this to be worth the $$ and they built it as the Silver line tunnel. Everything I've seen shows that they would construct the silver line loop somewhere underneath the boylston station. Would that preclude them from eventually converting the silver line tunnel into a green line tunnel? I thought the original idea was that the tunnel could easily be converted for later use by the green line.
I agree, it certainly seems cost prohibitive for the forseeable future, but the track 61 proposal, and DMU service, along with whatever silver line service is planned, just seem like they won't meet the long term needs of the area. There is still a lot of space to be filled in in the seaport, and given that it is a clean slate of sorts, could wind up being one of the best areas in town for work/live/play. I would think that direct service, via the green line from back bay and beyond would be best. That all being said, i think the idea of routing through the tremont street tunnel is a viable option, that wouldn't add much for time and really needs to be explored by the state as an alternative to the essex street tunnel (at least I haven't seen anything on it other than what's posted here).
1) The biggest contributor to the price soaring like it did was Boylston and all the design changes they had to file to accommodate a South End portal. The original plan involved outright tearing down the abandoned trolley tunnel and putting a wider one in its place. Structurally infeasible with the buildings, and ran afoul with the Historical Register. Lots more $$$ right there with that eliminated.
2) Then they revised it to build the BRT tunnel under the trolley tunnel, which required lowering the level of Boylston Under. More $$$. Bigger bloat potential structurally underpinning the entire length of the trolley tunnel.
3) Then the tunnel underpin proved equally infeasible to Tremont building foundations, and Tremont St. became a moot argument. So they started having to go to Plan B alignments. More tunneling involved for different blocks, lots more $$$.
4) Nearly all of those alternatives had unacceptable abutter impacts. So they revised, revised, revised again and eventually got one that back-tracked several blocks out of the way to Charles St. Ext. and portal on corner of Tremont/Marginal. More $$$ because the tunnel length has now increased an entire third of a mile from the original proposal. This was the only doable BRT alignment they could find after burning through every conceivable shorter route, so this ended up being the biggest % jump in cost.
5) In the midst of all that...major issues on the Common with the Boylston Under loop impacting the Central Burying Ground. Lots more $$$ for that mitigation, and I'm not sure they had even completely solved that issue by the time they pulled the plug.
6) Add in increases for invasive changes to Boylston upper level to get access down to an extremely deep lower-level station (elevators, escalators, full ADA everywhere). More $$$.
7) And add in fudge factor padding for what they feared they were going to find under Essex and Chinatown station. This was when "Copley Elevator Syndrome" was wreaking structural havoc with Old South Church during the Copley ADA project, so every estimate on Essex building impacts had to get revised up for safety.
A little bit of creep here, a lot of creep there, a little creep there, a full re-route there...that's how you get from ~$750M to $2.1B and rising in the course of 10 years of design revisions. And since final EIS has not taken place, every block of under-street digging had chance to bloat further when they started doing detail surveys. Including the Plan B portal alignment(s) that came late in the game as the best-studied alignments all got eliminated one-by-one as infeasible.
Now...a lot of time got wasted here sticking stubbornly to the BRT mode hell or high water. You can see that all except #7 were cost increases driven largely by their choice of mode, and that enough red flags had piled up that LRT scoping should've re-entered the picture or else the bodies were going to pile up enough that they had little choice but full cancellation. Which, lo and behold, is exactly what happened.
LRT would've had to have taken a different alignment because of the trajectory of the Tremont tunnel. So would've required studying of a whole new set under-street impacts any which way you did it...the more-tunneling ones that still had to hit Chinatown or the less-tunneling ones that opted for Tufts + a southerly jog. While we're having a productive time in this thread spitballing stuff there's still no guarantee a $700M starting point won't ultimately exceed $1B on LRT when the impacts get studied in depth.
But these things you can say with total certainty:
1) No need for Boylston Station impacts at all (except for simple elevators next to the headhouses and associated relocation of the 2 electrical substations on the far west side of the platform; + reinstatement of the old platform underpass with its own elevators on the far Park St. end). No Boylston Lower, no space-invasive loop, no need for tough/space-invasive access from upper level to lower level. All those associated costs come off the table
2) No Common impacts at all. All those mitigation costs come off the table.
3) No need for extra tunneling blocks out of the way on Charles Ext. or Tremont/Marginal to find an viable BRT trajectory. All those extra costs that were the biggest chunk of the bloat come off the table.
4) Narrower-profile under-street tunneling. *Modest* reduction in potential for "Copley Elevator Syndrome" on Essex and less need to over-pad those estimates. But emphasis on "modest"...80% of the bloat potential is still there on the ancient street grid.
That right there is about $1.5B in reductions that are
not going to creep back in any way, shape, or form with the mode switch to LRT...because they were BRT-specific impacts or tunneling that would only be built for BRT and none of those impact areas are touched
at all by LRT. Probably more than $1.5B in savings in the end because the upper bounds of further bloat on these BRT-only pieces had not been established yet by a final EIS. This was the highest potential for pushing the BRT build ultimately in range of $3B.
You do have potential impacts on the revised routing on un-studied streets. "Copley Elevator Syndrome"-like creep can come into the picture on any side street, and at whatever point (such as Kneeland to Chinatown Park, amongst others) you get back on alignment to where the BRT hook-in was going to be.
-- However, if the routings steer clear of under-pinning Chinatown station with a Chinatown Under it would sidestep the biggest single remaining bloat point. This is where the Tufts station under Eliot Norton Park wholly separate from the OL station structure looks most attractive because it reduces the Orange Line impacts to just a connecting walkway across the block to the OL fare lobby. And underpinning the between-station OL tunnel @ Shawmut/Marginal under the 1967-construction tunnel instead of the 1908-construction tunnel at a 1908-construction station. Both of those routing changes sharply limit the areas of impact and have firm and limited ceilings on how much OL tunnel or station impacts can complicate things. Weigh the lesser impacts accordingly vs. mapmaker's perfection.
-- If the routings steer clear of just blasting clear through the Boylston Station wall with a (shitty) at-grade junction all potential Boylston Station impacts disappear. So that last block of Boylston to Washington is unlikely diggable in a straight mapmaker's-perfect line. You can consider an earlier around-the-horn fork off the Tremont Tunnel to try to get on Stuart instead if Chinatown transfer is an ironclad requirement, but that brings structural impacts to the 1898 Tremont tunnel and Chinatown station back on the table. So the offset Tufts option has the most cost estimate certainty touching no ancient infrastructure.
-- As previously noted, sticking to urban renewal streets and 1965-makeover Pike canyon abutting, circa-2000 Big Dig abutting, taking chances along new-construction buildings like One Greenway instead of pre-war or early 20th century construction, and sticking to wider streets (Marginal, the pre-Kneeland blocks of Hudson with the One Greenway promenade) reduces the mitigation bloat potential and isolates the bad blocks to single structures. Your choice whether you prefer straight-line and Chinatown routings, but if the goal is to keep the absolute ceiling on this project's cost bloat at $1B-$1.2B from a $750M starting point...weigh the paths of least resistance accordingly or you have to allow for up bloat up to the $1.5B level and blow any chance of a favorable result keeping it in 9 figures.
But any which way you slice it, $2.1B to $3B if off the table entirely with BRT switching to LRT. It eliminates that much extra new construction to slash 50-60% or more off the final price tag. So the demarcation point between "Crazy Transit Pitches" and "Batshit Insane Transit Pitches" is with the mode choice. You can go "crazier" with LRT aiming for too much perfection on the build, but it's almost impossible to come up with something so stark-raving mad as the BRT
least-impactful options.
