Cos Cob Bridge (Mianus River Drawbridge)

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Cos Cob Bridge (Mianus River Drawbridge)

Postby Jeff Smith » Sat Nov 05, 2016 3:26 pm

Greenwich Time

So let's have a topic on Cob, the Mianus River Drawbridge, since we do on WALK.

Cos Cob bridge sticks again
...
“We have teams of people at the bridge to ensure that it opens and closes correctly and as quickly as possible,” said Metro-North Railroad spokeswoman Nancy Gamerman, following the third bridge mishap in the past two weeks, including one on Tuesday. “In recent days, our crews have had difficulty properly seating the bridge upon closure.”
...
The bridge is opened about 300 times in a typical year, according to Metro-North, mostly in the summer.

The draw bridge in Cos Cob could be replaced at an estimated cost in the $800 million range, but it is only one of several such spans in the region that are due for replacement.
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby F-line to Dudley via Park » Sat Nov 05, 2016 5:43 pm

I thought Devon was supposed to be next in the replacement sequence set by desperation-of-condition. Or has Cos Cob now surpassed it in overall decrepitude?
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby NH2060 » Sat Nov 05, 2016 5:58 pm

"COB" is the new "WALK" ;-)
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby Jeff Smith » Sun Nov 06, 2016 3:16 pm

Haven't they done deck replacement at Devon? I don't believe that one is opened nearly as much. And Cob, given it's position WEST of Stamford, is very crucial indeed.
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby kitn1mcc » Tue Nov 08, 2016 7:05 pm

The Devon bridge is not as old as well
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby Ridgefielder » Mon Nov 14, 2016 12:43 pm

That's technically true. However, in the grand scheme of things, I don't think there's much difference between a bridge built in 1906 and one built in 1904. :wink:
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby kitn1mcc » Mon Nov 14, 2016 7:35 pm

That is true Plus Devon opens less
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby Ridgefielder » Tue Nov 15, 2016 9:38 am

Joking aside-- that's probably much more relevant. There's much less boat traffic through Devon. I'm not even sure how far up the river is navigable.
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Re: Cos Cob Bridge (Mianus River Drawbridge)

Postby F-line to Dudley via Park » Tue Nov 15, 2016 10:54 am

Remembering from a Courant article last year that quoted bridge openings and failures-per-opening. . .

Cos Cob alone is 50% of the total annual bridge openings on the whole New Haven Line. Walk is #2 at 25% because of the cement barges downtown. Saga, Peck, and Devon divvy up the scraps. Devon somewhat more than the other two with Peck (go figure...the one barely old enough to shave!) being really, really bereft of boat traffic with annual openings you can count on your own fingers and toes. Though Saga seems to be the most pain-in-butt to manually open and Devon a hope-and-pray that the mechanism works, so the replacement pecking order need not necessarily go by frequency of openings. Busy Walk just happened to be the one most in most danger of outright keeling over.


Devon could--feds willing--be plausibly replaced by a taller fixed bridge. Not nearly as tall as I-95 because...probably more split-the-difference height like the Sikorsky/Merrit Parkway bridge upstream since lower Housatonic boat raffic is pretty limited. Less bulky deck thickness should help offset the boat clearances a little more. You'd have to take Naugatuck Ave. temporarily out of commission and change the level of the street so it goes below both I-95 and the NEC instead of steeply changing grades to go under 95 but over the tracks. And you'd have to change the grade on the westbound wye to rise up at 1% to the level of the slightly raised fixed bridge, which requires taking the driveway overpass to the power station out-of-commission (I guess you could ditch altogether since they've got a grade-crossing driveway at the opposite end). But overall there's plenty of runup room on both sides to raise it a few feet without introducing a noticeable grade. 1% grade on the west side gives you +18 feet before the E. Main St. curve. You don't need anywhere near that much; 0.5% or less will do it. East you've got 3/4 mile of tangent track before the I-95 overpass, so it's just a matter of finding a tolerably gentle grade for the Waterbury wye to factor how much you can raise it.

CDOT definitely can't pay for that enhancement go-it-alone. They simply can't swing any wider project area to incorporate the grade change that nets a fixed bridge, no matter how engineering-feasible it is. They can only afford in-situ trade of old movable for new. Fixed has to be a federal value proposition. How much does it matter to Amtrak to reduce the movable bridge count from 5 to 4 for service reliability's sake, especially when they're whacking all the movables on their own property Pelham Bay to Gunpowder, save for Dock in NJ which opens like once every 5 years. They're going to have to be the deciders on whether it's worth going for and up their funding share accordingly. It sure would help to have the line west of NHV to Barnum and Bridgeport Yard completely fixed-span for all the SLE and Hartford Line service that's likely to terminate there. But...again, that's Fed value proposition on whether above-and-beyond cost is worth going for.
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