Protecting MBTA Subways from Floods & Tidal Surges

Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

Moderators: CRail, sery2831

Protecting MBTA Subways from Floods & Tidal Surges

Postby Arlington » Tue Oct 30, 2012 12:23 pm

With NYC grappling with something like 7 cross-river tunnels flooded, I'd like to discuss what the MBTA has done to keep floodwaters out of the system, particularly if it is coming in the form of a tidal surge from harbor. I'm aware of two mechanisms:

Floodgates, such as keeps a tunnel's water from filling a station, or a station's water from filling a tunnel. There appears to be one of these at the "downhill" (outbound) end of the South Station platform. (Is it there to protect the station from a tunnel failure or the tunnel from a Station flood?)

Levees: (Sandbags and planking) such as keep the Muddy River out of the D-Line at Fenway Station.

If a 13' storm surge were coming to the Boston/East Boston harbor, what has been (or can be) done to keep water from entering via what I estimate to be the large, low apertures in the system:

Airport
Maverick
Aquarium

Broadway
South Station
(Courthouse...if the silver line floods it can carry water to South Station)

North Station
Community College
"Trying to solve congestion by making roadways wider is like trying to solve obesity by buying bigger pants."--Charles Marohn
Arlington
 
Posts: 3208
Joined: Wed Jun 02, 2004 7:51 am
Location: Medford MA (was Arlington MA and Arlington VA)

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby octr202 » Tue Oct 30, 2012 12:31 pm

The Red Line flood gates were designed to prevent the spread of a tunnel flood during the Big Dig construction. I believe where the I-90 connector tunnels cross the Red Line is near or under the Fort Point Channel. There was a fear that any accident in constructing the highway tunnels could breach the subway tunnels, and the doors were to prevent the flood from spreading further (and possibly into stations and other lines).
Wondering if I'll see the Haverhill double-tracking finished before I retire...
Photo: Melbourne W7 No. 1019 on Route 78, Bridge & Church Streets, Richmond, Victoria. 10/21/2010
User avatar
octr202
 
Posts: 4142
Joined: Fri Mar 12, 2004 8:13 am
Location: In the land of the once and future 73 trackless trolley.

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby Arlington » Tue Oct 30, 2012 12:38 pm

octr202 wrote:The Red Line flood gates were designed to prevent the spread of a tunnel flood during the Big Dig construction. I believe where the I-90 connector tunnels cross the Red Line is near or under the Fort Point Channel. There was a fear that any accident in constructing the highway tunnels could breach the subway tunnels, and the doors were to prevent the flood from spreading further (and possibly into stations and other lines).

That sounds right: since there was a lot of digging and casting (of I-90 sections) and flooding and floating and sinking, there was going to be ample opportunity for things to screw up the tunnel between Broadway and South Station.

Does this imply that they are "braced" to hold back water coming "up" the Dorchester Ave tunnel, but not to keep South Station water from flooding toward Broadway?
"Trying to solve congestion by making roadways wider is like trying to solve obesity by buying bigger pants."--Charles Marohn
Arlington
 
Posts: 3208
Joined: Wed Jun 02, 2004 7:51 am
Location: Medford MA (was Arlington MA and Arlington VA)

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby jbvb » Mon Nov 05, 2012 11:41 am

The big question about a storm surge would be whether it would overtop the Charles and Mystic River dams. If it does, then the problem gets a lot bigger - given the number of vents and openings it would likely be impossible to avoid flooding both the Red and Green lines.
jbvb
 
Posts: 1285
Joined: Mon Nov 12, 2007 3:50 pm
Location: Rockingham Co., NH

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby Rbts Stn » Mon Nov 05, 2012 3:15 pm

Based on driving over bridges over the Charles in Newton, Needham, and Waltham about 10 days ago, it looked like they had anticipated the storm and had lowered the level of the river by a couple of feet ahead of time, to help avoid flooding caused by the storm.
User avatar
Rbts Stn
 
Posts: 587
Joined: Thu Feb 09, 2012 2:09 pm
Location: waiting for an "A" train to Watertown

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby kwf » Mon Nov 05, 2012 3:19 pm

You can see the flood gates from the South Station platforms....
kwf
 
Posts: 166
Joined: Fri Mar 12, 2004 9:54 am
Location: Belmont Ma.

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby Arlington » Mon Nov 05, 2012 4:41 pm

kwf wrote:You can see the flood gates from the South Station platforms....

I believe they only prevent an "inbound" flood (from Broadway).

Seems to me it is time for Boston to look into the same "5 things" that the Atlantic listed here:

http://www.theatlanticcities.com/techno ... york/3754/
"Trying to solve congestion by making roadways wider is like trying to solve obesity by buying bigger pants."--Charles Marohn
Arlington
 
Posts: 3208
Joined: Wed Jun 02, 2004 7:51 am
Location: Medford MA (was Arlington MA and Arlington VA)

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby R36 Combine Coach » Tue Nov 06, 2012 1:43 am

One major city, Venice has considered sophisticated system such as floodgates and tidal barriers. Venice suffers from tidal flooding and faces similar issues as New York does.
Since my friend continues to chain smoke nonstop, she is probably an Alco.
User avatar
R36 Combine Coach
 
Posts: 4848
Joined: Mon Jun 09, 2008 8:51 pm

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby sery2831 » Tue Nov 06, 2012 2:35 am

Arlington wrote:
kwf wrote:You can see the flood gates from the South Station platforms....

I believe they only prevent an "inbound" flood (from Broadway).


There are doors on the Broadway end as well.
Moderator: MBTA Rail Operations
User avatar
sery2831
 
Posts: 5127
Joined: Fri Mar 12, 2004 2:15 pm
Location: Manchester, NH

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby Arlington » Tue Nov 06, 2012 8:47 am

So which do you suppose costs more? (where costs includes the costs of periodic, catastrophic flooding, if that's what we're willing to suffer rather than spend on prevention)

1) Doing nothing and waiting for a flood (costs = damage to buildings, electric and subway in low-lying areas)
2) Placing doors to keep tunnels from flooding (but permitting water to come into any station it "finds")
3) Raising entrances and street grates to keep water from getting into stations & tunnels?
4) An outer harbor barrier (like Venice or St Peterburg Russia) that also protects all of the city
"Trying to solve congestion by making roadways wider is like trying to solve obesity by buying bigger pants."--Charles Marohn
Arlington
 
Posts: 3208
Joined: Wed Jun 02, 2004 7:51 am
Location: Medford MA (was Arlington MA and Arlington VA)

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby MarkB » Tue Nov 06, 2012 1:02 pm

To protect the system from flooding, you'd have to raise all entrances and vents to a safe level, as well as seal all tunnel entrances. And backwash from drains may also be a problem.

First, I'd like to know what has happened in previous storms. The geometry of the New York Bight caused much higher surges than we'd see here in Boston with the same storm conditions. The coasts of New Jersey and Long Island funnel water straight to NYC. Boston Harbor is totally different. So while Sandy wasn't even a hurricane at landfall, Boston has seen Cat 3 storms without serious flooding.
MarkB
 
Posts: 105
Joined: Mon May 30, 2011 11:16 am

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby ferroequinologist » Tue Nov 06, 2012 5:55 pm

MarkB wrote:To protect the system from flooding, you'd have to raise all entrances and vents to a safe level, as well as seal all tunnel entrances. And backwash from drains may also be a problem.


Yeah, sealing all those vents would be a challenge. That's a logical point for flooding for all the subway lines through downtown, really.

MarkB wrote:First, I'd like to know what has happened in previous storms. The geometry of the New York Bight caused much higher surges than we'd see here in Boston with the same storm conditions. The coasts of New Jersey and Long Island funnel water straight to NYC. Boston Harbor is totally different. So while Sandy wasn't even a hurricane at landfall, Boston has seen Cat 3 storms without serious flooding.


Not only do NJ and LI funnel water towards NYC, but Boston has barrier islands and is protected by Cape Cod. IIRC Sandy was a hurricane when it hit, but due to Boston's position it's extremely unlikely to be hit by a hurricane, since it's farther north and has lots of land between it and the direction hurricanes come from. I doubt it'd be worth the expense of building an elaborate flood prevention system when a flood of the magnitude NY is facing is so unlikely.
ferroequinologist
 
Posts: 118
Joined: Mon Dec 26, 2011 11:24 pm

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby F-line to Dudley via Park » Wed Nov 07, 2012 1:41 pm

ferroequinologist wrote:
MarkB wrote:To protect the system from flooding, you'd have to raise all entrances and vents to a safe level, as well as seal all tunnel entrances. And backwash from drains may also be a problem.


Yeah, sealing all those vents would be a challenge. That's a logical point for flooding for all the subway lines through downtown, really.

MarkB wrote:First, I'd like to know what has happened in previous storms. The geometry of the New York Bight caused much higher surges than we'd see here in Boston with the same storm conditions. The coasts of New Jersey and Long Island funnel water straight to NYC. Boston Harbor is totally different. So while Sandy wasn't even a hurricane at landfall, Boston has seen Cat 3 storms without serious flooding.


Not only do NJ and LI funnel water towards NYC, but Boston has barrier islands and is protected by Cape Cod. IIRC Sandy was a hurricane when it hit, but due to Boston's position it's extremely unlikely to be hit by a hurricane, since it's farther north and has lots of land between it and the direction hurricanes come from. I doubt it'd be worth the expense of building an elaborate flood prevention system when a flood of the magnitude NY is facing is so unlikely.


And it is not in a harbor that has drainage issues between tides. Sandy was a killshot for NYC because Long Island Sound acts a funnel with storm surge and winds coming out of due-east. It was the second high tide that overwhelmed all the infrastructure, because the first high tide never had a chance to recede with the inflow being constant. There was no low tide. There was a day-long high tide that then got another high tide piled on top of it. Boston Harbor is physically impossible to double up like that. The opening to open ocean is too wide and too closeby.

As noted, the Cape does a superlative job chopping up the inflow from the direction hurricanes circulate, the South Shore from Marshfield to Hull takes most of the edge off the rest...and Winthrop, Nahant, and the Harbor Islands chop up most of the last. The most flood-prone area is Ft. Point Channel, which of course isn't dammed. That often overtops its banks over the Southie side (but less often the Dot Ave. side). There's no wind direction that's a straight, unimpeded killshot. It can definitely flood and cause damage. But a total inundation is extremely unlikely.


Boston's flood risk is from rain, ground saturation, and snowmelt. The soil is so poor it turns to jello when oversaturated, and it is tough to control river runoff when everything upstream and every tributary is swollen. 1996- and 2010- type rain flood events, not storm surge. And while those can FUBAR things up good and cause flash floods on an overflowing river, it is not an apocalyptic ocean inundation. But we do have to be better-prepared for them, because winter weather wild mood swings are going to have us dealing with more frequent oversaturation floods than before. Apples-oranges with what happened in Sandy, though.
F-line to Dudley via Park
 
Posts: 7112
Joined: Fri Mar 11, 2005 7:26 pm
Location: North Cambridge

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby ferroequinologist » Wed Nov 07, 2012 3:20 pm

F-line to Dudley via Park wrote:Boston's flood risk is from rain, ground saturation, and snowmelt. The soil is so poor it turns to jello when oversaturated, and it is tough to control river runoff when everything upstream and every tributary is swollen. 1996- and 2010- type rain flood events, not storm surge. And while those can FUBAR things up good and cause flash floods on an overflowing river, it is not an apocalyptic ocean inundation. But we do have to be better-prepared for them, because winter weather wild mood swings are going to have us dealing with more frequent oversaturation floods than before. Apples-oranges with what happened in Sandy, though.


Perhaps, then, it'd be worthwhile to talk about protecting the T from river flooding. Outside the issues with the Muddy River and Kenmore the T has had before, it doesn't look so bad. All the places the B&A main is near the Charles it's a good ways above it, and Riverside is pretty high up, too. Are there points along the Mystic river where there's risk of flooding? I suspect the wetlands through Revere and Lynn might cause some issues for CR as well. Has the T had issues with rain/snow drainage for the parts of the system that are below-grade? I seem to remember there being some flooding in the Southwest Corridor a few years ago, but I don't remember its effect (edit: Maybe that's the 2010 event you're talking about?)
ferroequinologist
 
Posts: 118
Joined: Mon Dec 26, 2011 11:24 pm

Re: Protecting MBTA Subways from Floods & Tidal Surges

Postby jbvb » Fri Nov 09, 2012 12:26 pm

Boston is very much at the head of the funnel that is Massachusetts Bay. A 1938-like storm on a track that brought the eye in from Provincetown to Quincy could do to Boston what the 1938 storm did to Providence. The probability is low, but not zero.
jbvb
 
Posts: 1285
Joined: Mon Nov 12, 2007 3:50 pm
Location: Rockingham Co., NH

Next

Return to Massachusetts Bay Transportation Authority (MBTA)

Who is online

Users browsing this forum: StefanW and 5 guests