Corps balancing levee repairs on Missouri, Illinois sides of Mississippi
This article first appeared in the St. Louis Beacon, Jan. 11, 2012 - WASHINGTON - As a record deluge surged toward the confluence of the Mississippi and Ohio rivers last spring, officials had to decide whether to save the town of Cairo, Ill., by flooding 130,000 acres of Missouri farmland and its small communities.
With Cairo evacuated, sinkholes opening on Main Street and sand boils showing weakness in the levee system, the head of the Mississippi River Commission made the calllate on May 2 to blast three holes in the Missouri levees and flood the Birds Point-New Madrid floodway for the first time in 74 years.
Eight months, millions of dollars in repairs and a season of political debates later, the Corps is now engaged in a "balancing act" in repairing the damage to Cairo's shaky flood-control system at the same time that it plugs the gaps in the Birds Point-New Madrid levee system, which has been partially repaired but remains vulnerable to floods.
"There is a fine balancing act because we have to ensure that we've put in place enough protective measures [on both sides] should the river go to a higher level," says Corps flood manager Scott D. Whitney, who is in charge of the massive program to repair the flood damage to the Lower Mississippi system. The danger in merely restoring the Birds Point-New Madrid levee would be that "suddenly everything from Cairo down to Hickman, Kentucky, fails because of the pressure points that are there."
The good news is that the Corps has finally received $802 million in emergency Mississippi River flood-repair funding. In an interview, Whitney told the Beacon that his group has submitted 143 high-priority projects to headquarters on repairing levees, fixing river channels and repairing other flood-control projects in response to last spring's flood, which set records from Cairo to the Gulf of Mexico.
"The [Mississippi/Ohio river] confluence area is one of the highest priorities because of the nature of the damages there, the consequences that were suffered, and the need to restore that life safety and preserve peoples' livelihoods," he said.
The "No. 1 priority" in this fall's phase -- which the Corps paid for by shifting $120 million from other accounts -- was the "Make Safe/Make Stable" project to plug gaps in the Birds Point levees and bring them up to 55 feet on the Cairo gauge. The Corps spent about $25 million in that initial phase, which was suspended after winter weather hit.
A final decision is expected soon on whether to rebuild the Birds Point levee exactly as before -- at 62.5 feet on the Cairo gauge, with pipes that can be filled with explosives to blast open the floodway when necessary -- or to redesign it as a levee that would be naturally "overtopped" by floodwaters when the river reaches a certain level. The cost estimates for that additional work range between $20 million and $25 million.
"To bring the levee to 62 feet obviously falls a little farther down that [priority] list because one needs to recognize the system perspective," Whitney said, citing Cairo. "Bringing one area completely back to full restoration exerts additional pressure on other parts of the system -- especially across the river and immediately down river."
Another alternative for Birds Point -- building sluice gates in the levees that could be opened to let in floodwaters -- appears unlikely because of its high cost and intense local opposition. Local officials fear that such gates would be opened too often in the future.
While the decision nears on the Birds Point repairs, a Corps investigation continues into the partial failure of an "outflow crevasse" blast hole at the southern end of the 35-mile long Birds Point-New Madrid floodway.
The main blast at the northernmost point of the floodway was successful on the night of May 2, a later blast at a "lower crevasse" site -- which was supposed to let the floodwater flow out and back to the river relatively quickly -- did not work as planned. "It did not activate to the full extent that it should have," said Whitney. The result: "We have a huge, gaping crater there now because that water was concentrated."
Added Whitney: "We had some detonation issues that are still being investigated to determine what happened and why. The evidence is clear that it didn't activate to the full extent it was supposed to," slowing the exit of water from the floodway.
Cairo's Current Levee Safety in Question
Across the river, Corps officials are working to stabilize Cairo's shaky flood-control system, which Whitney described as being stressed "at its worst" during last year's flood. While Cairo's system survived the deluge, he said, "I don't know how many of us believe that it would perform again to the same extent."
The Cairo project levee is on both sides of the confluence -- the Mississippi and Ohio river sides. "That little peninsula [at the tip] has the Ohio trying to merge with the Mississippi at a higher point, and you have a spit of land with a number of residents and businesses there that need to be preserved," Whitney said.
"During and after the flood, there was about a 20-foot deep and 50-foot wide sinkhole caved in right on Main Street. That's a further indication that the entire area has significant under-pressures that are causing some pretty strange things to happen there."
Calling the sand boils that appeared in Cairo "probably one of the most extreme that anybody has seen in the history of levees," Whitney said Corps officials had been in the process of studying the weaknesses of the system -- including seepage in cutoff walls -- at the time the flood struck last spring.
Fixing the sand boil and related problems in Cairo is a complex task. "There is a number of complicating things going on in Cairo, with sand-boil seepage one of the major ones because they have the ability to undermine and cause a levee to fail," he said. Also, erosion along levees and shorelines needs to be repaired.
In October, the Corps allocated $6.6 million to address seepage in the Cairo levee, with work starting this fall to build 28 "relief wells" to contain the seepage and lessen the impact of the water on levees. A "slurry trench" also is being built to reinforce the wells.
Whitney said the Cairo sand boils and sinkholes "represent the conduit that is formed under the levee system" -- threatening the town. Repairing such boils can be complex, with the possible approaches including relief wells, seepage berms, and cutoff walls, which involve digging a big trench and adding clay grout to cut off the leak.
Does the Cairo work need to be completed before the Corps raises the Birds Point levees on the Missouri side back to 62.5 feet? "We're looking at that very carefully now," said Whitney, noting that numerous other flood-control problems between Cairo and the Gulf need to be addressed.
Corps Plans Priority List by Month's End
Much has changed since last spring's flooding, both along the river and at the Corps itself.
For one, the official who made the decision to blast the Birds Point levee -- Maj. Gen. Michael J. Walsh, then president of the Mississippi River Commission -- was promoted to the fifth highest post at Corps headquarters in Washington, in charge of civil works.
Walsh's portfolio includes the repairs of the massive Mississippi River and Tributaries Project (MR&T). Billed as the world's largest flood-control project, the MR&T is designed to protect the 36,000-square-mile lower Mississippi valley. It is operated by the Corps under the system's governing body, the Mississippi River Commission.
Last month, Congress approved $802 million for repairs to the MR&T, including the work at Cairo and the Birds Point-New Madrid floodway, one of four major floodways in the system.
Because much of that construction had to be suspended over the winter months, some damaged levees and other flood-control structures won't be fully repaired by the spring flood season, resulting in increased risks in some areas.
In mid-December, the Corps asked a Regional 2012 Flood Preparedness Team to develop plans to manage, mitigate and communicate flood risks throughout the MR&T system. A workshop will be held in Memphis in late February to discuss the team's findings and offer recommendations on how to lessen flood risks in the spring.
Whitney said that with the $802 million, the Corps "should have adequate funding to fully attack all of our critical areas." His group is now working with engineers "to put together that aggressive implementation strategy that will involve extensive contracting throughout the region, to bring to bear on these projects as quickly as possible."
He added: "Having the money now in hand is going to give us a much stronger position to be able to attack these problems systemically, to ensure that we are providing that level protection throughout the system," including some major projects in Louisiana.
While it may not be at the top of the new priority list, deciding on the design and then completing repairs on the Birds Point-New Madrid floodway levees are major issues. "We are looking at different possible alternatives," said Whitney, noting that he met with about 70 local levee district folks a couple months ago who argued for floodway levees that would be naturally overtopped, rather than blasted in an emergency.
"That decision has not yet been made," said Whitney. "I have a system performance evaluation team that has been working specifically on that. They are working with some of the Corps' best experts" on the best way to proceed.
Farmers and local officials argue that "activating" the floodway by the natural overtopping of levees would cause far less damage to the crops and structures in the 130,000-acre floodway. But Whitney cautions that allowing levees to overtop -- rather than blasting them -- could lead to unpredictable and possibly unsatisfactory results.
The last time the Birds Point floodway was activated, in 1937, the levee failed to overtop as planned, "so they ended up having to run out there at the last second with dynamite and try to blow the thing," said Whitney.
The current system -- equipping mile-long segments of the levees with special tubes that could be filled quickly with explosives when necessary -- "was a response to what we learned from the 1937 event. And subsequently we learned from last year's event and are thinking through the possibilities, including new technologies that we may employ."
The ideal for Corps engineers and for the MR&T system as a whole, he said, is "that the levee crevasse would open up the full, one-mile length. That's what the activation with the detonation performed."
Having studied levee overtopping during the 2008 Mississippi flood, Whitney said that "when a levee overtops, it's going to see the weakest point. And that weakest point is going to give way rather quickly" -- leading to sometimes unpredictable results. "Allowing a levee to overtop, and presuming that it's going to 'equally' activate is somewhat presumptuous, from an engineering perspective," he said.
Despite the problem with the lower crevasse, Whitney said the Birds Point-New Madrid floodway functioned as planned during last spring's flooding -- so well, in fact, that some areas in Mississippi have asked about building new floodways there.
"In fact, we've had other states to the south . . . asking, 'What about floodways in our area? Why don't we have the same relief valve?'" said Whitney. "If you look back at the history, there were actually two floodways designed between Morganza [La.] and Birds Point-New Madrid. But due to political and legal wranglings," those floodways were never built.
"Floodways are not a real popular topic when it involves giving up highly productive land and homes .... But in an event like [the flood of 2011], it does provide a sense of security and protection to areas" outside of the floodway itself.
So, barring an act of Congress, the Birds Point floodway will remain as such -- available for use every few decades, when an extreme flood strikes.
"At the end of the day, that floodway needs to be readily accessible to activate in a very quick fashion -- like we did this time," said Whitney. "We pushed that right to the last second, and had that not performed . . . we would have been in a pretty difficult situation."