Re: Blue Line to Kenmore
I may be new to posting, but I've been observing this board for a while. It seems that extending the Blue Line to Kenmore via Storrow is most posters' preferred routing in various transit discussions. I'm curious how you think it should be done, and what would it look like in the end?
What alignment do you think works best? Following Storrow, or ducking into the Charles for a bit (like the Red Line at Fort Point Channel)? What about at Kenmore and the Muddy River?
Tunneled or cut and cover where it's on land? Or what about grade-level portions, for example if it consumed half of Storrow's right-of-way, to save money? Would Back Bay residents accept something like this in exchange for a downsized Storrow and less motor vehicle traffic noise?
Where stations would you include? Obviously Charles and Kenmore. But what about a Hatch Shell station, or a station at Mass Ave to connect with the 1? Would you remove Bowdown, as the T has proposed? Is it possible to keep it?
How would Kenmore look? Would you work it into the existing station, converting half of the tracks to Blue Line, or would you have a separate station, for example under Beacon Street, that's parallel to the existing station and connected via a pedestrian tunnel?
Where would you position the tracks after Kenmore for a future extension?
Perhaps this could go in the Crazy Transit Pitches thread, but I'm looking for a more in-depth discussion about implementation.
That one should be noted with an asterisk. The
only way in which there would be a subway extension there is if. . .
1) Bostonians demanded that Storrow be torn down west of Charles Circle to re-claim riverfront access;
2) There had to be some sort of transit trade-in replacing the parkway serving trips displaced from the parkway across the same neighborhood as the parkway. You would expect a modest spike in Green Line trips with elimination of the highway redundancy, so Charles-Kenmore is the area needing the transit augmentation.
If those two conditions aren't in play, then Blue to Kenmore would get kicked pretty far down the list of most-wanted extensions. So it's strictly a circumstantial build driven more by Storrow elimination.
Boston Transit Commission way back in 1900 did propose a Riverbank subway from downtown along what is now Storrow. So it isn't totally an off-the-wall fantasy build...it just has somewhat all-or-nothing conditions attached.
The way you'd do it is (bolded the types of digging involved for each step). . .
- Take the Blue Line extended to Charles/MGH as per the Red-Blue project...verbatim. Let's assume this gets built many years/decades in advance. As part of that build there would be storage tail tracks extending a couple car lengths past the wedge-shaped center platform: one curving a little ways around the MGH/Embankment Rd. side of the circle, one curving a little ways around the CVS/Charles St. side of the circle.
- Bowdoin has to go, per the state's plans. Tunnel trajectory has to slice through the westernmost end of the platform to eliminate the sharp speed-killing curve just beyond the station. No real way to preserve it.
- You would take the tail track on the Charles St. side, double it up, and start cut-and-cover digging under the Storrow EB exit ramp to Charles Circle. This would require enlarging the lower-level Blue Line station from a center island to side platforms.
- Drop a new "inbound" side platform underneath that brick sidewalk in front of CVS.
- Leave the old center platform as a somewhat absurdly large "outbound" platform. You'll no longer be using in regular service the side of the island that feeds the tail track wrapping around the MGH side of the circle. But, you can still short-turn trains there, stuff equipment there, and so on.
- Tie in the new platform's egresses to the main station. Blue level is pretty deep underground here, so there's room under-street to connect everything together.
^^The modifications to Charles station and surface disruption on the CVS side of Charles Circle are probably the messiest parts of the project. There shouldn't be any historic building impacts, though. The CVS storefront is most definitely not historic Beacon Hill construction, and the tunnel extension's trajectory will steer clear of the Jeffries House.
- Continue the cut-and-cover dig in the right lanes of what's now Storrow EB.
- There will probably be a short parkway stub for reaching the Public Gardens exit, but instead of being 6 lanes + a 1-lane frontage road w/parking it'll probably be 4 lanes + a parking row.
- The lane reduction frees up the space for the cut-and-cover dig, and you'd simply lane-shift during construction then lane-shift back after the tunnel is done to pack the road stub away from the river. Fairly non-invasive construction.
- Feed the subway into the current Storrow EB auto tunnel. Verbatim...recycle the whole thing.
- Re-waterproof it.
- Tear down the roadbed to the bare pack, because you'll need to take out the pavement + concrete layer to fit Blue trains in the tight clearances.
- In the space by the current Copley exit ramp where the tunnel is at its widest, create "Esplanade" station. 2 side platforms, straight upstairs to a headhouse. Everything should be wide enough to shiv in 6-car platforms here.
- Feed the subway out of the tunnel onto what's now the Storrow EB carriageway.
- Begin a box tunnel subway dig from here all the way to Mass Ave. A box tunnel is much shallower and cheaper to construct than cut-and-cover. With cut-and-cover, you're digging 20-25 below street level and keeping the under-street utility layer sandwiched between street and subway. More invasive, and tons of utility work. With a box tunnel, the 'sandwich' layer doesn't exist (and doesn't have to, because there are no utilities underneath Storrow) and the tunnel roof is the surface level. Best example in Boston of a box tunnel: the Green Line at Hynes where the tunnel 'rump' sticks out above the Mass Pike/Worcester Line cut at surface level.
- The Back St. retaining wall sets the surface level for the Riverbank Subway. So you would rebuild that retaining wall as one of your tunnel walls, then dig down on the Storrow EB roadbed far enough to get your full tunnel dimensions. Basically, half of the tunnel height would be below the current pavement level of Storrow EB, and half of it would reach above up to the height of the Back St. wall.
- ^^Bonus: the 'rump' that sticks 4-6 feet above the surface doubles as a flood wall from the river, so the portion of the tunnel that's a few feet below surface is protected from becoming a storm drain when the Charles floods.
- Dump dirt on top of the tunnel roof and landscape the 'rump' that sticks out into a gently rolling hill down to the Esplanade. Basically like a less-steep version of the BU Beach.
- You can even preserve Storrow WB alongside as a two-lane park access road with low speed limit, since the subway stays self-contained on ex- Storrow EB.
- Note that because of the nearby lagoon you may be constrained at putting another intermediate stop in the Dartmouth/Exeter vicinity. And, I doubt the Beacon St. residential abutters want hordes of people pouring out of their alleys from the station entrances. Not impossible, but given the constraints and very heavy residential tilt you may just want to express through here without a station.
- At Mass Ave., dip into the deep cut where all the ramps are on the eastbound side. Widen out this cut into a Mass Ave. station.
- Maybe widen out the Mass Ave. bridge right at Back St. with bus turnouts for the 1/CT1 and various campus shuttles.
- From Mass Ave. to Charlesgate, transition into a deep-bore tunnel. Or whatever type of shielded tunnel keeps it water-tight well below ground under the river silt.
- ^^Most expensive per foot tunneling segment because of the depth and waterproofing. But at least it's short.
- Curve at Charlesgate East diagonally under the Muddy River to reach the intersection of Charlesgate West and Beacon.
- ^^Again, you're pretty deep underground so there shouldn't be surface impacts to very shallow Muddy riverbed. And, the Muddy was so destroyed in this spot by past road construction there's little in the way of environmental "preservation" to do here. You could take the opportunity while digging the subway to re-shape the mouth of the river for better water flow into the Charles and general environmental remediation.
- Curve onto Beacon St., transitioning to cut-and-cover tunneling.
- This would be pretty deep cut-and-cover because it's going to slot under the Green Line level at Kenmore.
- Beacon is 3-1/2 lanes wide, and much much wider where Bay State Rd. splits off. Shouldn't be any building impacts around BU Myles Standish Hall or the back side of the funeral home.
- Kenmore Station platform (center island) starts right at the corner of Raleigh St., extends about as far as the edge of the building that houses Cornwall's Pub.
- Green Line travels directly underneath the bus station straight off the Comm Ave. Mall, so the Blue platforms end where the Green tunnel slips upstairs at a 45-degree angle.
- Egress off far end of platform ties into existing fare lobby.
- Possible Blue-only headhouse at far end of Square, but space limited so not sure where it would go (here at that sketchy little white-painted thing across the street from Myles Standish?).
- 2 tail storage tracks pass underneath the Green tunnel and dead-end.
- You absolutely have to be done with the Blue platforms and to have shrunk the tunnel dimensions back to running tracks before slipping under Green so it can underpin the Green tunnel in minimally invasive fashion.
^^Kenmore from in front of Myles Standish to end of the busway median is the next-most disruptive part of construction after immediate Charles Circle. No building impacts, but it might make a mess out of the bus station and far end of the Green platforms for a couple years while they underpin everything. Pricey.
Keep in mind, if you want to keep this relatively economical by recycling as much of the freed-up Storrow roadbed as possible you've got one and only one footprint to take to reach Kenmore (under Storrow EB + diagonal under the Muddy River + Beacon St.), one and only one location for Esplanade station (the auto tunnel), and one and only one location for Mass Ave. station (the cut right under the bridge where the maze of ramps are).
The only wiggle room to play around with is the exact configuration of Charles and Kenmore stations and how much of a mess it makes, headhouse placements, whether you bother with another intermediate stop between Esplanade and Mass Ave., and where exactly the tail tracks get positioned under Kenmore.
It's limited. But the attractiveness for a Storrow trade-in is that it's dirt cheap everywhere it sticks to the Storrow roadbed. The only invasive parts are slipping onto the roadbed from Charles, slipping off it at Charlesgate, and the final interface with Kenmore. That's like 2500 ft. of "hard" for 1.25 miles of "easy"...a pretty attractive ratio for a build of that length which has two lower-level additions to existing stops, 2-3 new intermediates, and enormous relief for the Green Line between Kenmore and Gov't Center so you rig up new routes on the west end like Urban Ring tie-ins and new branches.
