In the aftermath of Hurricane Katrina, as part of its plan to prevent future levee failures, the U.S. Army Corps of Engineers authorized the design and construction of a series of isolating gate structures, more than 15 feet in height, across the northern end of two particularly vulnerable canals. A team was assembled to design, test and construct the gates as well as pumping stations housing 33 huge direct-drive pumps. Total capacity of all pumps running together is 5.4 billion gallons per day over the gates into Lake Pontchartrain.
The U.S. Army Corps of Engineers’ (USACE) project was managed by Weston Solutions, Inc., of West Chester, Pennsylvania, and the Engineering Research and Development Center (ERDC) in Vicksburg, Mississippi. The GS&P team, lead by Mike Barry, P.E., consisted of a group of engineers who would design two of the pumping stations and produce plans and specifications for civil-site, civil-process and structural aspects of the project. Their responsibilities included work at the 17th Street Canal and London Avenue Canal.
Even larger than the tasks of the project were the doubts of the public. Project Manager Mike Barry explained that at the start of the project, the team made a commitment to the people of New Orleans, the entire U.S. Senate, the House of Representatives and to each other that the pumps would be up and running before the height of the 2009 hurricane season. The pressure was enormous. Crews of 50-100 worked 24-hours a day seven days a week for six months straight, getting only one day off during the entire time—Father’s Day. But Barry said, “Everyone understood that this was the project of a lifetime.”
Lake Pontchartrain is not actually a lake at all. It opens into the Gulf of Mexico and is therefore subject to the same tides as the Gulf. Thus, the lake is also affected by storm surges. Surges of five feet or higher cause the lake to back feed into the canals and force the gates to be closed. After the gates are shut, the canal pumps must be started to remove the initial storm surge and the storm water being pumped into the canals by the City of New Orleans.
During Hurricane Katrina, the storm surges were between 12 and 15 feet high. With the canals already overflowing, water poured over the dry side of the levees. The storm surge, as well as the movement of the water, degraded the materials in the levees, leading to several collapses. New Orleans filled up with an endless, unstoppable flow of water coming directly from the sea, causing the unbelievable devastation that the outside world watched on TV screens in August 2005. It was believed that the 15-foot-high gates mandated by the USACE, which would be closed during a storm surge, would provide the best benefit/cost ratio for future hurricane events.
Early in the design phase there were concerns, which modeling later confirmed, that the original concept would not allow the huge volume of water to enter the pump intakes without cavitation and vortexing. This refers to the possible rapid formation and collapse of vapor pockets as well as violent whirlpools during intake that would compromise pump efficiency and possibly cause serious structural damage to the equipment. ERDC’s modeling efforts defined the necessary intake modifications, and the GS&P engineers immediately incorporated them into the final designs. Construction proceeded on schedule. Later, full-scale testing proved that vortexing and cavitation would not be issues.
“In addition,” noted Mark Markham, P.E., GS&P’s team project professional, “our hydraulic modeling efforts and pump discharge header design helped optimize pump performance and exceed the pumping rate objective by over 15%. This enhanced the ability of the stations to meet near-term and future City of New Orleans’ and USACE’s storm water control objectives.”
Matthew Beatty, Vice President, Mid-Atlantic Division of Weston Solutions, said, about GS&P’s work, “It is truly remarkable how you were able to completely shift gears on day one with the modeling redesign and still keep the critical path for materials procurement and construction moving forward. To not have one claim from our…subcontractors for delays is a miracle.”
On May 13, 2008, the Corps of Engineers put the gates to the test during a simulated hurricane named “Zeus.” As the residents of New Orleans looked on, the symbol of teamwork and unshakable commitment performed flawlessly. A New Orleans resident, who was in the city during Hurricane Katrina, said of the team, “They worked unbelievably hard. We know there will be other hurricanes, but we feel safer thanks to those people.”
On September 1, 2008 the pumps were tested again by Hurricane Gustav. Although the brunt of the storm was felt in areas west of New Orleans, the gate structures and pumps at 17th Street and London Avenue canals performed as expected. Col. Al Lee, USACE District Engineer in New Orleans, was responsible for operating the gates and pumps, and reported that the emergency structures functioned at a high level. “All the pumps worked, all the gates locked in place, all of it worked,” Lee said.
For Barry and his team, there was never any doubt.