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LA 1 Sinking, Elevated Replacement Under Construction

Started by Brian556, September 25, 2019, 10:34:34 PM

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Brian556

Google Maps and Street View show the LA 1 elevated highway that serves Port Fourchon and Grand Isle is being extended north. Looks like this project was very urgently needed given that the water level is so close to the current highway already. The land is sinking in this area. That is the primary contributor to this problem, but sea level rise may be contribution slightly to it as well. My though on this is: If the land is sinking, how long will the land that this expensive elevated highway serves last? Is it even worth it to build this if the land that it serves sinks beneath the water in the future.

I don't remember where I saw this, but a source stated existing elevated highway has already sank by something like 10 or 20 Ft in just 10 years
Looking at GSV, this doesn't look like the typical bridge construction project. You can see that construction is limited to a very small area at the end of the current elevated roadway.

GSV of bridge ext const: https://www.google.com/maps/@29.2528261,-90.2234201,3a,62.5y,338.12h,86.95t/data=!3m5!1e1!3m3!1sCoCy1OjI3sbvN4arDzOjcA!2e0!6s%2F%2Fgeo0.ggpht.com%2Fcbk%3Fpanoid%3DCoCy1OjI3sbvN4arDzOjcA%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D52.116974%26pitch%3D0%26thumbfov%3D100

Water level close to current hwy: https://www.google.com/maps/@29.3014424,-90.2350169,3a,15.2y,19.55h,87.92t/data=!3m5!1e1!3m3!1sbDEnWf67qIAtagiQsUeQoQ!2e0!6s%2F%2Fgeo1.ggpht.com%2Fcbk%3Fpanoid%3DbDEnWf67qIAtagiQsUeQoQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D176.66867%26pitch%3D0%26thumbfov%3D100

Article with dates when existing roadway expected to become unusable: https://www.businessreport.com/industry/shortcomings-roadway-built-bring-vacationers-grand-isle-model-t-fords-now-major-implications-nations-oil-supply#close-olyticsmodal

Project Page LADOTD: http://www8.dotd.la.gov/La1Project/


index

I'm wondering if they built that flat, 90 degree turn in the bridge with a possible future extension in mind? It seems like a logical thing to do.
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Chris

From what I've read, the economic rationale behind the project is Port Fourchon. This industrial site services 90% of the oil production in the Gulf of Mexico. Unavailability of LA 1 would have great economic impact. There are no alternative ports in that area. According to Wikipedia there are 600 oil platforms within 40 miles of Port Fourchon.

Anthony_JK

Quote from: index on September 26, 2019, 09:17:35 AM
I'm wondering if they built that flat, 90 degree turn in the bridge with a possible future extension in mind? It seems like a logical thing to do.

Phase 2 of the LA 1 project does include an elevated 2-lane extension from there to Golden Meadow...so, I'd say that's an affirmative.

If they really wanted to, though, they need to twin that span across Leeville and build the tollway all the way to US 90/Future I-49 South.

707

I had no idea this stuff was happening. Is anything like this threatening US 1 down the Florida keys as well?

VS988


Brian556

Quote from: 707 on September 26, 2019, 04:08:02 PM
I had no idea this stuff was happening. Is anything like this threatening US 1 down the Florida keys as well?

VS988



I have not heard of any subsidence in the Keys, so their only threat is sea-level rise, which is much slower

triplemultiplex

Quote from: 707 on September 26, 2019, 04:08:02 PM
I had no idea this stuff was happening. Is anything like this threatening US 1 down the Florida keys as well?

Just the sea level rise component.  The Keys aren't a giant delta like all of southern Louisiana is, so they don't have subsidence issues.  The Keys are the tops of a large reef system so that's relatively hard limestone compared to the largely unconsolidated silts and sands of the Mississippi Delta system.
"That's just like... your opinion, man."

Brian556

Just visited the area. There is no trace of construction on the section of LA 1 elevated expressway from Leeville to Golden Meadow.

While the water level is getting close to the section south of Golden Meadow, it is nowhere near as bad as in Golden Meadow and Galliano. In some areas, the water in Bayou Lefourche is level with LA 1, and a low concrete wall is all that is separating it from the highway and the structures across from it.
DSC_0409 by Brian Kosich, on Flickr
In other areas without the concrete wall, the bayou's waters are only inches below the grade of the highway.
DSC_0343 by Brian Kosich, on Flickr
Bayou Lafourche used to be a distributary of the Mississippi river, but was disconnected from the river at Donaldsonville long ago. They do pump limited amounts of river water into the Bayou from the river to give it some flow, to prevent water stagnation. Just imagine if Bayou Lafourche had not been disconnected from the Mississippi. This area would not be habitable due to constant flooding.

An interesting aspect of this area is all the ships parked along Bayou Lefourche. Where else can you drive this close to a ship? I'm wondering if the ship's wakes shove water over the highway.
DSC_0422 by Brian Kosich, on Flickr

wriddle082

Any chance that LA 3134 ever gets extended from Jean Lafitte to LA 1?  I can't remember if the reason it isn't built is money or the environment.

Brian556

Quote from: wriddle082 on July 10, 2020, 02:55:19 AM
Any chance that LA 3134 ever gets extended from Jean Lafitte to LA 1?  I can't remember if the reason it isn't built is money or the environment.


Haven't heard anything about this. I don't see any good reason to do this. If i remember correctly, Jean Lefitte is the first community to be evacuated due to subsidence / rising sea levels. Also, it would not be practical to build a new highway in this area for those two reasons. Cant believe they are even considering blowing money on such a thing.

wriddle082

Quote from: Brian556 on July 10, 2020, 06:31:03 PM
Quote from: wriddle082 on July 10, 2020, 02:55:19 AM
Any chance that LA 3134 ever gets extended from Jean Lafitte to LA 1?  I can't remember if the reason it isn't built is money or the environment.


Haven't heard anything about this. I don't see any good reason to do this. If i remember correctly, Jean Lefitte is the first community to be evacuated due to subsidence / rising sea levels. Also, it would not be practical to build a new highway in this area for those two reasons. Cant believe they are even considering blowing money on such a thing.

The stub ending of LA 3134 at LA 303 was constructed that way in anticipation of a future extension to LA 1.  At least that's what a local co-worker told me back in 2005 when I worked in that area not long after Katrina.

DeaconG

The latest Google Earth shows they're building a pass-through lane there, so at the very least they're setting up.
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triplemultiplex

Quote from: Brian556 on July 09, 2020, 10:26:09 PM
Just imagine if Bayou Lafourche had not been disconnected from the Mississippi. This area would not be habitable due to constant flooding.

Or the replenishment of new sediment from the periodic floods would be off-setting or even exceeding the rate of subsidence and make it more habitable for us.  When the bayou was artificial severed from the main stem of the Mississippi, that choked off the sediment load it once carried and distributed through that region of the delta.  With deposition cut off, there remains only subsidence as the dominant force in the area.

It's very interesting to pan around on Google Earth and see all these island labels in Terrebonne Bay with no land to be seen.
"That's just like... your opinion, man."

Brian556

Quote from: triplemultiplex on August 12, 2020, 02:46:17 PM
Quote from: Brian556 on July 09, 2020, 10:26:09 PM
Just imagine if Bayou Lafourche had not been disconnected from the Mississippi. This area would not be habitable due to constant flooding.

Or the replenishment of new sediment from the periodic floods would be off-setting or even exceeding the rate of subsidence and make it more habitable for us.  When the bayou was artificial severed from the main stem of the Mississippi, that choked off the sediment load it once carried and distributed through that region of the delta.  With deposition cut off, there remains only subsidence as the dominant force in the area.

It's very interesting to pan around on Google Earth and see all these island labels in Terrebonne Bay with no land to be seen.

Sediment replenishment would only work on uninhabited land. If it were to happen on inhabited land, roads would be covered, and would continue to sink. Houses, roads, and buildings would sink just like they do today, only it would be worse because they would be slowly inundated by the new sediment.



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