Thursday, August 30, 2012

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.
Pulling Pumps?
Photo of pumps being pulled from a few months back.

* Source: A Goulds pump salesman told me that.  

NOTE: Some edits for spelling.

Wednesday, August 29, 2012

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.  

Monday, August 27, 2012


Living with Water by Noladishu
Living with Water, a photo by Noladishu on Flickr.

Stay safe.

Also, here's my suggestion for a really handy piece of hurricane gear:
It keeps your cell phones topped up. It has ~80% of the charge of my Samsung stored for emergencies.

Sunday, August 26, 2012

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).
Southwest 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.

Saturday, August 25, 2012

A Hole in the Bottom of the Bayou

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.  

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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.  

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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:
* 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.  

Political Attack Ads...

One advantage of living in Louisiana, is, since we already know where the electoral votes are going, nobody bothers running national attack ads in the state.  Here are some to keep you entertained (H/T MoJo and Pistolette ):

Wednesday, August 8, 2012

Corps-Created Sill Gives NOLA Fresh Water

Every late summer/early fall, Mississippi River levels fall.  Less snowmelt and (this year especially, given the big drought) lead to a battle between the ocean and the river.  Saltwater, which is more dense than freshwater, crawls upriver along the riverbed.  To ensure New Orleans, Belle Chasse, Chalmette, etc. have potable water, the Corps of Engineers constructs a sill.  Just north of Myrtle Grove, dredging creates a sill that is only a few feet tall and is invisible to the casual observer (it never pokes above the water).  Despite that, it acts as a dam and ensures that the salinity of the freshwater intakes in the municipalities never exceeds acceptable levels.  It's not 100% effective; some saltwater does seep past, but it's never a problem for municipalities and industrial users (like boiler make-up water) can rent reverse osmosis units to keep it to acceptable levels for their use.  

The sill may be invisible to the naked eye, but here's a sonar image of the sill (from Meselhe 2005):

Just another part of the civil engineering that keeps the world humming every day.

UPDATE: Mike Schleifstein Writeup

Sunday, August 5, 2012

"It is what it is."

Indicates that just because customer doesn't like the answer, the laws of physics must prevail.

H/T Tim.