re: Storm Watch- Gulf- Tropical Depression- Northward Miss. Valley

quote:

---

The gates at all three outfall canal structures - at the 17th Street canal, the Orleans Avenue Canal, and the London Avenue canal - have been closed ahead of tropical storm Cristobal. This is done to protect the walls and levees along the outfall canals, which despite two rounds of multimillion dollar upgrades in 2011 and 2014, still require protection from storm surge in Lake Pontchartrain.

Currently, the lake is 3.8 feet above mean lake level and rising. I don't know what the exact trigger for closure of the lakefront gates is, but I'm guessing it's three feet. That's based on the fact the gates at each lakefront station are "capable of passing the total outfall canal’s discharge with Lake Pontchartrain’s stage at 4’, 4’, and 3’ for 17th St., Orleans Ave., and London Ave, respectively without violating the prescribed maximum operating water level (MOWL)." That section in quotes is taken from the Corps' own most recent reports on the outfall canals (the so-called 2017 "reevaluation reports," which I don't mind saying the publication of which I pushed for over a span of literally years; link to the reports can be found in the comments)

The impact on drainage is this: the agency in control of the lakefront stations - the Southeast Louisiana Flood Protection Authority - East, or SLFPA-E - must coordinate their lakefront with the Sewerage and Water Board at their inland drainage pump stations to ensure levels within the canals do not rise too high.

Theoretically, the walls along the canals are rated up to 8 feet for most of their length, the Corps' so-called "MOWL" mentioned above. They used to call it the "safe water level," but got away from doing so when they decided to stop giving people the impression they could protect them. That was around the same time they rechristened the "Hurricane Protection System" as the mouthful "Hurricane and Storm Damage Risk Reduction System" or "HSDRRS."

Here's the MOWL details for each canal, working from the lake back into the city:

17th Street canal: 8 feet from the lakefront back to about Locust Court (that's a street in Jefferson Parish), then 10 feet from Locust Court back to S&WB drainage pump station (DPS) 6

Orleans Avenue canal: 8 feet for the whole length from the lakefront back to S&WB DPS 7

London Avenue canal: 8 feet from the lakefront back to between Sere and Lafrienere Street, then 9 feet from there back to S&WB DPS 3

Coordination between the two agencies is a requirement since the Corps refused to do the right thing about ten years ago and turn the outfall canals into strictly drainage channels like they have in Jefferson Parish. The plan, dubbed Option 1, would have demolished the three pump stations at the south end of each canal and deepened and channelized the canals, getting rid of the weakened levees and I-walls and leaving drainage pumping only at the lakefront. Instead, the Corps rigged the information given to the public on costs, fundamentally disobeyed congressional legislation, and offered a lesser alternative called option 2. Option 2 is what we have now, a fundamentally less safe relay system of pumping stormwater out which, unlike what was originally promised way back when, requires the lakefront gates to drop even when the lake is only elevated by 3 feet.

Even today, there is still work happening along the outfall canals due to their weakness. The SLFPA-E embarked on a project this year - delayed for six years by the Corps - to reinforce eroded sections of canal bank along the 17th Street canal by driving sheet pile and dumping rocks. Similar projects are to follow along the other two canals. None of that expense would have been necessary had Option 1 been built, but the Corps exerted their muscle and left New Orleans less safe.

None of that is a knock on those left to operate the system. They have been training for this for two years, and have been given pretty good tools. The data systems for each agency have been interlinked more robustly than was originally planned, thanks to the July and August, 2017 floods.

After those events, Veolia was given an extensive contract to perform a condition assessment of the entire S&WB drainage and power system. But as part of that contract, they were also told to install an extensive data acquisition and visibility system that gives instant feedback on what is happening with every pump, turbine, frequency changer, and most generators. It is called simply the visibility platform, and it is insanely easy to use.

The system is extensive, with thousands of data points measuring electrical and mechanical attributes of every pump, electrical feeder, and tons of other equipment. Aspects like power, voltage, vibration, on/off status for breakers and even direction of pump rotation, along with rainfall totals and rates and local water pressure at drainage pumping stations at ten fire stations are measured, archived, and (hopefully) used for decision-making on a daily basis, and especially during major events like the current one.

As to the coordination aspect, the data from the S&WB visibility system is sent out to SLFPA-E, and Jefferson Parish (only for pump station 6, which JP pays 25% of the operating cost for). The S&WB also gets back the data from the SLFPA-E. Those data chains contain multiple links. Here's how Veolia described it in 2018:

"The SLFPA-E collects data from their three stations and feeds it to the S&WB via the Modbus protocol from their VTSCADA system over an encrypted network tunnel over the internet. When the data arrives at the S&WB it is captured by a software product called KEPWare, translated to the OPC DA protocol and then fed into Pi. There are many links in this chain and the two organizations need to back up this system with a manual failsafe plan should one of the links in the chain break during an emergency situation."

Hopefully, S&WB and SLFPA-E have indeed come up with a manual backup plan as Veolia recommended. I wouldn't be surprised if there were actually multiple such plans. When the Corps of Engineers ran the show during tropical events, data was transmitted primarily by fiberoptic cable, with a primary backup via microwave via the towers at each end of the canals, and secondary backup via Iridium satellite phone.

---

quote:

---

Not a single person asked for it

---