PCCP Constructors, a joint venture of Kiewit Louisiana Co., Traylor Bros. Inc., and the M.R. Pittman Group LLC, have constructed three permanent canal closure and pump station structures to block hurricane storm surges at the Lake Pontchartrain mouths of the 17th Street, Orleans Avenue and London Avenue drainage canals in New Orleans. The structures are the final major post-Katrina improvements to the New Orleans area levee system and will block storm surges from Lake Pontchartrain caused by a hurricane with a 1-percent chance of occurring in any year, commonly referred to as a 100-year storm. The structures account for expected increases in the height of Lake Pontchartrain’s water level during the next 50 years, to account for sea level rise caused by global warming and local subsidence. Each station can pump rainwater from each canal into the lake at a rate that will keep the water levels in the canals low enough to avoid overtopping or damage to the floodwalls.
Innovative OpenCell cofferdams were built at each site. Next, a total of 992 each 24- and 30-inch-diameter steel pipe piles were driven to support the concrete foundations at each pump station. The operation involved driving plumb and batter piles in a flooded cofferdam to a depth of 44 feet below the surface of Lake Pontchartrain. Three large tremie placements accounted for roughly 20 percent of the 100,000 cubic yards of concrete required for the project. Pump station concrete work, major pump equipment installation, and generator mechanical and electrical installation completed the project.
When the surge closures are operated during storms, the pumps move 12,500 cubic feet per second of water from the 17th Street Canal into Lake Pontchartrain; 2,700 cubic feet per second from the Orleans Avenue Canal, and 9,000 cubic feet per second from the London Avenue Canal.