Gating the Rigolets?

This was on the cover of the paper recently:

New $1.1 billion hurricane levee proposed for New Orleans East Land Bridge 

I expected a bit better writeup on this very important project.  It's a large levee proposed stretching from New Orleans East to Slidell.  It will have gaps in the channels at the Rigolets, but will have options to install gates at a later time.  

Note that the gating of the mouth of the lake has been proposed on numerous occasions in the past.  Proposals go back at least 40 years.  It's back under discussion, partly because of Isaac's LaPlace flooding. Here's a letter to the editor shortly after Isaac calling for the gates.  

Putting in the levee along the old St. Bernard birdsfoot is a pretty low-risk, moderate-reward project.  In fact, it was even called for in the Corps' original 1962 plan for hurricane protection levees around New Orleans, but was shelved for a variety of reasons including cost.  So long as you maintain sufficient gaps for normal inflow and outflow, there's very little impact on the lake, although there's not as much of a mitigation against storm surge.  The natural tendency is to want to gate off the final gaps, but that could cause problems.  

Gates present problems risk for two main reasons: flow and backside fetch-driven-flooding.  

The first issue is flow.  Lake Pontchartrain is really more akin to a tidal mudflat than a traditional lake.  There are MASSIVE inflows and outflows in that lake on a regular basis.  Even without hurricanes, the tidal flows through the Rigolets can reach ~6-8 knots.  That's really moving.  Any gated structure will mean a choke point which will increase the flowrate much higher.  That means the structure will be very, very vulnerable to scour and undermining.  Here's an illustration of scour at the Rigolets:

Source:

McCorquodale, J. A., Georgiou, I., Retana, A. G., Barbe, D., & Guillot, M. J. (2007). Hydrodynamic Modeling of the Tidal Prism in the Pontchartrain Basin Estuary. Dept. of Civil and Environmental Engineering, University of New Orleans, New Orleans, LA.

This is a trestle bridge that supports the CSX line that runs along the Gulf Coast.  The pilings interrupt the flow and cause major scouring in the vicinity.  Note that scour very nearly destroyed the Corps-built Old River Control Structure in 1973, partly due to a design flaw:

 In 1973, a large flood tested the ORCS to its limits.  Huge scour developed underneath the large steel pilings which anchored the structure to the river bottom. The structure was almost swept away, and emergency concrete was poured into the holes as a kind of large Band-Aid.

Any gate structure in the Rigolets would have to cope with similar, powerful scour effects.  

The other problem with gating the Rigolets is backside flooding.  You'd think that if you just built a giant plug, well, that'd solve all your problems, right?  Like putting up a giant dam, no storm surge could enter and no flooding would result, right?  Not quite.  

A term used in physical oceanography is "Fetch".  Fetch describes how wind (even very weak wind) acting over a large enough surface area begins to build up waves and surge.  Isaac, despite being barely a Category 1 storm, covered a very large surface area.  Despite they eye hitting Port Fourchon, I had friends in Charleston, SC lose power from the outer bands of the storm.  Despite weak winds, they were able to act over a large area and build up a pretty impressive surge, as anyone in Braithwait or LaPlace can tell you.  

How does this relate to gating the Rigolets?  Well, let's suppose you had a continuous, 50' barrier keeping the mouth of the lake plugged up through any and all hurricanes,  you still have the surface area of Lake Pontchartrain that the wind can act upon.  The lake is ~24 miles wide by at least double that width in the other direction.  The surface area of the lake is ~630 square miles.  Even if you have a weak wind, it has enough surface area to act upon to still make a significant surge.  Even if you have gates, you'll still need levees around the edge of the lake!  Gates alone are not enough.  

Purely fetch-driven surge in Lake Pontchartrain can pile up to 6 feet+ on the Lake (Source: Ed Fleming at a presentation I attended).  Furthermore, that surge can be driven North, South, or West, depending on the direction of where the hurricane hits.  For example, a hurricane that hits Morgan City has a north-east quadrant that would drive storm surge to the Northshore.  A hurricane that hits Bay St. Louis would push surge southwards onto the lakeside levees of Jefferson and Orleans Parish.  Note that there are no Federal flood protection levees anywhere on the Northshore and, while they have been authorized for LaPlace, no funding has ever come forward to actually build them.*  Getting around to building more levees, given current rigorous standards, could be pricey.  

My main point is this is a levee project to pay particular attention to.  Especially if the gates are added later as an option.  Gates will have some tricky design challenges and are not a panacea.  

More background here from the Lake Pontchartrain Basin Foundation.

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* There was a letter to the editor by David Vitter (note: dead link) where Vitter slammed the Corps for not building the LaPlace levee that was authorized after extensive study in ~1992.  Umm... The Corps is a creature of Congress.  It does what Congress funds.  The LaPlace levee was authorized in ~1992, but wasn't funded.  Who was in charge of securing that funding?  Maybe a politician that's been there representing Louisiana for a decade plus as a Representative and Senator?

Another sidenote: We also need to kill the whole "blame New Orleans levees for Braitwhite/LaPlace flooding" thing.  This was studied and debunked before the levees were built.  They've gone back and double checked it, and sure enough, the New Orleans levee improvements had negligible effect on levees in LaPlace/Braithwhite. UPDATE- This is the link to the Corps study stating the NOLA Levee improvements had no effect.  More here: New Orleans Levees Hold, and Outsiders Want In.


UPDATE 2- I'll just add the recent Bob Marshall Op-Ed about updating the bird's foot to save the coast and help the port here.  Worth a read.

Big, Bigger, Biggest: Oil Platform

Contagion

There's a great little movie that came out a while ago called "Contagion".  It's about a modern pandemic outbreak (a la the Spanish Flu of 1919).  Turns out, the MEV-1 virus is based off a real virus:

Nipah virus is an active virus.  It's had multiple outbreaks, some with dozens of fatalities (very high mortality rate; easily communicable), and there's still no vaccine or cure today.  And it's still out there today.

Discussion of Contagion by epidemiologists 

What's interesting about epidemiology is it's a never ending battle.  You have to constantly be on your toes, because viruses mutate over time.

One of my favorite parts was where one of the scientists working on the cure talked about Dr. Barry Marshall, who drank an infectious broth to prove his theory was correct. That's a pretty amazing way to put your money where your mouth is.

Check out the movie.  Also take a look at John Barry, author of Rising Tide and The Great Influenza, writes about what's next for Swine Flu.  The Great Influenza is also worth a read.

Merry Christmas

41-0

First Saints game in person since my dad brought me when I was a little kid. Then, I got to watch the 49ers destroy the Saints.

Marques Colston is tall.
Fun game.

Rising Tide 7

Above: Rising Tide 7 Journalism Panel.

Some thoughts I want to keep and not get lost down the Tweeter tubes:

* QOTD#1: "In New Orleans, everyone has a hustle."
* The "Petri Dish" metaphor is good and applicable to both the journalism and education 'reform' initiatives.  Good job whoever came up with that one.
* Very good steering of panels.  Panel discussions were well directed and no eyes were gouged or blood was drawn.
* Great job getting more coffee early this morning.  It was sorely needed after the previous night.
* IMHO, the weakest panel was "Oil and Water".  Not a lot of new ground covered.  It could have been better and I think the parenting panel drew a lot larger crowd than they were expecting.  Also should have set out to at least discuss Bayou Corne (w/o the audience asking a question).  

* Great term: "Nuisance Complainer"
* Karnofsky and Louis Armstrong: http://t.co/jc6pdFNB
* Tulane got their butt kicked by Ole Miss http://t.co/hD5aKELV
* Here's Bob Marshall's Op-Ed about subsidence from earlier this week: http://t.co/zpfF0fuh
* Another bid issue nobody brought up is the complex litigation related to Macondo is actually limiting how much research gets published.  See here for a sample: http://t.co/G0Elc2m3
* Not mis-allocating the BP Spill money was mentioned as an afterthought.  We could have spent a panel on just that.
* Cenlamar has #standing, even when #seated.
* All this discussion about the Times-Pic is like a funeral.  I'd rather spend a little more time chatting about what The Advocate is doing.  Also, the only one with any energy is Jason, who's been up since dawn setting up and managing the webstream for Rising Tide 7.
* Nola.com writeup of the Education Panel.

Debating with my old professor.  Thanks again Susanna.  

Note: Some updates and edits.

Rising Tide 7

Schedule Here.

Storm Surge & Pumps & Albert Baldwin Wood

What it looks like, from the Corps' River Gages:

It's basically like a really, really big tidal fluctuation.  This is the lake-side of the London Ave. Canal.  

So, we've basically been dumped on and dumped on and dumped on by Isaac.  The totals are impressive (~17" at Audubon Park as of last night), but I'd say that it never really dumped all at once; it's been a slow, steady drizzle at ~0.5"/hr or less.  One interesting note to pay attention to is the outfall canal pumps.  The Lens had a report up right before the storm about how a pair of pumps were out of commission.  Matt McBride has had a series of posts tracking failure after failure of these 'temporary' (decade-plus of service by the time they're retired) pumps.  

One thing I learned as an engineer while working for a large hot sauce concern in South Louisiana is how subjective runoff calculations are.  You can have 2 systems that are rated for the same 10-year rain event, but are dramatically different.  You start by assuming how much retention the land has at the start of your design-case rain (saturated soils absorb ~nil).  They you have retention ponds built (which will actually fill up over time).  Only then do you size the pumps.  A modern drainage system tends to be very dependent on retention ponds (like New Orleans East).  The system that Albert Baldwin Wood designed in the 1910's is almost exclusively pumping power.  As designed, there was virtually no retention capacity built into the system.  Over time, the S&WB has added some retention capacity in; for example, before a storm, the canal water levels (which have a certain, nominal level, just for the stability of the canal banks) are drawn down as low as possible.  There are also relatively few, much larger pumping stations in Albert Baldwin Wood's design.  The downside of this is the feeder canals are much longer and deeper, so when there's a problem, the S&WB has to dig to China to make a repair.  On the bright side, it means that it's easier to keep power supplied to fewer stations;  Jefferson Parish has something like three times the number of lift stations as Orleans Parish*.  Wood's system was a bit more expensive to construct and maintain, but a modern system basically raises a white flag after a certain amount of time (when the retention ponds are full), while Wood's system can keep chugging right along hour after hour with minimal de-rating.

Photo of pumps being pulled from a few months back.

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* Source: A Goulds pump salesman told me that.  

NOTE: Some edits for spelling.

Still here...

Have power.  No TV/Internet.  Good thing there's tethered smartphones.  Most activity we've seen so far is the neighbor's chimney lost a big chunk and dropped bricks onto the sidewalk.  

Take care and stay safe.  

Isaac

Living with Water, a photo by Noladishu on Flickr.

Stay safe.

Also, here's my suggestion for a really handy piece of hurricane gear:
http://www.amazon.com/Motorola-Universal-Dual-Charging-Portable-Power/dp/B00486MH80
It keeps your cell phones topped up. It has ~80% of the charge of my Samsung stored for emergencies.

One Small Step...

 Armstrong offered the following self-portrait: “I am, and ever will be, a white-socks, pocket-protector, nerdy engineer, born under the second law of thermodynamics, steeped in steam tables, in love with free-body diagrams, transformed by Laplace and propelled by compressible flow.” - The Economist Obit

Head of Passes

I want to tie a few different threads together here.  We have the release of Louisiana's 2012 Coastal Master Plan (Large PDF), the expansion of the Panama Canal, the struggles of the Port of New Orleans during low water levels, the BP spill fines, and Louisiana politics.

Mississippi River levels are now so low, barges are grounding (note: this article talks about barges upriver of Baton Rouge).  You can notice all sorts of other signs: if you drive across the CCC bridge, you'll notice extra barges around Algiers Point for lightening the load of freighters coming up the river.  If you taste the tap water right now, they're putting extra chlorine to combat the low levels.  These ultra-low levels happen about once ever 10 years and they are a pain for the Port of New Orleans.  The fall, for whatever reason, tends to be the busiest time of year.  That's also when river levels are the lowest.  Meanwhile, Congress funds the Corps' dredging and asks them to meet 40' depth (which they almost never reach, due to lack of funds).  They allocate ~$500 million dredging (don't worry too much about cost; it more than pays for itself in commercial activity).  The Port kicks in some extra, but in times like this, they always end up ~$50-100 million short of what they really should have to keep the port completely busy.  The other thing is much of that dredging money isn't spent on Southwest Pass (photo below), but instead at Pass a Loutre (a smaller, shallower channel, that, if you ever did a proper economic analysis, it'd say 'dredge more at SW Pass).


The capacity of the Panama Canal will double when the expansion project is complete.  Sometime in 2014 (or shortly after), ports that want to recieve traffic will need channels at least 50' deep.  After being caught up in Tea Party politics for years (note: dead link), Florida is finally pushing forward with the Deep Dredge project.  The Port of New Orleans had a great opportunity to leapfrog Miami and now their window of opportunity may be closing.  Meanwhile, Boss Hogg's plan to renovate Gulfport into a Superport has fallen apart (note: dead link).  Fortunately, Slabbed has been on the case.

It would be great to kill 3 birds with one stone: restore the coast, promote shipping, and protect New Orleans from hurricanes.  There's coalescing around a plan to abandon the lower Bird's Foot, divert the river, and also have a newer, shorter route to the sea for shipping.  Dr. Renfro's got an article along those lines here (also, congrats on finishing the PhD; I saw her present at a past TEF as just a PhD student).  The diversions will also continue to work, even without constant infusions of major cash (unlike dredging).  So, that's what we NEED to be doing.  What are we doing instead?

Well, first, we're fighting over the BP spill money.  There's also a fight to chip away at the few wetland protection laws there are.  Louisiana Legislators want to raid the BP money for use on their own pet projects instead of spending it on coastal projects.  Fortunately, we seem to be doing OK at beating that idea back.

Fishers and dredgers oppose Coastal Master Plan.  Unfortunately, I see a drift away from the "Engineered Avulsion" idea and towards dredged sediment restoration.  What's so bad about dredged sediment diversion?  Well, first off, what is it?  It's when you dredge a bunch of sediment, put it in a particular place, and it promotes further land growth.  Here's an example:

One of the problems with dredged sediment restoration is that it actually does work.  The reason that's a problem is it's expensive, it's a one-shot thing (you have to do it over and over) and it only works for a limited area.  

Dr. Bahr liked to call the dredging industry, "Louisiana's Military-Industrial Complex."  He has a point.  They donate tons of money to politicos, have a protected market that's not open to free trade, and just sort of sit there and make money with no innovation.  The dredgers love dredged sediment restoration, because it's money in their pocket.  The fishermen love it, because it has no impact on fisheries.  The problem is it's just not going to be enough.  It's a proverbial band-aid on a gunshot wound.  I'd hate to see the initial billions go to dredging, none to restoration, and then having to come up with remaining dough ourselves.

So, we have a fight between doing what's needed to save the state from sliding into the ocean (and making the Port of New Orleans a Superport) or in the short-term putting a few nickels in a politically-connected pocket and continuing with business as usual.  Which way will it go?

UPDATE- gCaptain article about keeping the MS River dredged.

MegaStructures: Independence Hub

When Independence Hub came on line, domestic gas production increased by >10% with a single facility.

A Hole in the Bottom of the Bayou

Assumption Parish Sinkhole (CNN)

So, once again we have someone digging a hole in the ground and they make an oopsie.  I also happen to know a bit about storage caverns.  Here's some background.

Louisiana is dotted with salt domes (Avery Island is the most famous one).  They are extensions of the massive Louann Formation that exists under much of the Gulf Coast.  They can be bored out to make enormous caverns (most of the Strategic Petroleum Reserve [SPR] is salt dome storage).  Because natural gas prices fluctuate so much, there are a variety of companies that operate caverns to store gas at low prices and sell it at high prices.  DOE has a nice page on salt cavern storage.

The way it basically works is you drill a traditional well into the salt dome, with the bottom open.  You have two areas: the center of the well and the annulus.  You pump fresh water down one hole, it dissolves the salt, and saturated brine is returned up the other hole.  The saturated brine is up to ~25% saline (seawater is only about 3% saline).  By alternating which direction you pump (and also pumping in a little diesel here and there) you can actually control the size and shape of the cavity you create.  The saturated brine can be injected into disposal wells or the salt can be separated and sold to industrial users (the diesel generally contaminates it for human consumption).  If the salt dome is big enough, you can have multiple storage caverns in a single dome.  Some of these individual caverns can be HUGE (size of the interior of the Superdome).

So, what can go wrong?  Well, according to this book, about 30% of storage caverns are lost within the first 5 years of operation, primarily due to leaching the cavern too fast.  Depending on the local geology, the subsidence may be barely noticeable spread over a large area, or massive sinkholes can form.  

LA-DNR Sketch of Texas Brine cavern.

Texas Brine abandoned the cavern in questions, but then came back and tried to use the existing wellbore to make a second cavern.  During the initial investigation on leaching a second cavern, issues started to develop ("Cavern Known to Have Problems").  A sinkhole formed nearby, gas and diesel started spilling into the wetlands, and now they've evacuated residents.  One of these caverns can store a hole hell of a lot of gas.  As long as the cavern stays full, it's actually very safe.  Without oxygen, no fire/explosion can happen.  It's once it starts to leak and you get a combustible air/fuel mixture that things get interesting.  Depending on the leak rate, you could roast quite a few marshmallows.  


Plan view of nearby areas of interest - via LEAN.  

One of the safety systems usually installed in these storage caverns is one ore more relief wells, pre-drilled.  These relief wells don't serve the same function as the Macondo relief well did (pump mud/cement down to stop the problem).  The relief well(s) are there to draw down the well as quickly as possible (generally going straight to a flare stack, burning up all the valuable product; imagine emptying a bank vault by setting the cash on fire).   The goal is a controlled release instead of a uncontrolled relief.  

The dangers of a cavern collapse aren't quite like Macondo.  There's generally very little diesel (~10,000 gallons, max), but once the gas releases, you could have a vapour cloud, and there can be significant subsidence.  

18-Aug flyover of sinkhole.  Note the pickup trucks for scale.  

Here's the relief well plan for Bayou Corne:

Actual casing plan of the relief well in Bayou Corne cavern.  Via LA-DNR.

Note that the relief well just had to stop drilling in order to case the well.  

Interesting resources for anyone wanting to know more about the Bayou Corne Sinkhole:

* LA-DNR webpage on the Bayou Corne Sinkhole

* Times-Pic Overview article from Monday.  I miss David Hammer's excellent reporting of Macondo.  Too bad he left a sinking ship and was replaced by someone with 2 years experience.  
* ABC's of the Sinkhole

"All this has happened before, and all this will happen again."

There are almost always historical parrallels for engineering disasters.  Here's a few off the top of my head:

* Weeks Island, LA, SPR The only SPR cavern that WASN'T a leached salt dome collapsed.  SPR had to sell off a massive amount of inventory very quickly and spent a while cleaning it up.  Fortunately, they just sold more oil and nobody really noticed.  Since then, the Feds have had PhD's cranking out paper after paper on salt tectonics to make sure they never lose another SPR cavern.  

* Lake Peigneur disaster:

The Iberia Parish Sheriff called the disaster, "The Coonass Mount Saint Helens" to the assembled throng of national media.  No fatalities, amazingly.  What was a ~6' deep freshwater lake became a several-hundred foot deep saltwater lake with excellent fishing (or so I'm informed).  There's also 2 barges that have never been accounted for.  

UPDATE- Minor formatting glitches fixed.