Best Water/Environment: LPV-3.2 West Return Floodwall
The LPV-3.2 West Return Floodwall is a key piece of the U.S. Army Corps of Engineers' $14-billion mission to build the Greater New Orleans Hurricane and Storm Damage Risk Reduction System. The joint venture Odebrecht-Johnson Bros. led construction of the $94-million project.
Located on the east bank of the Mississippi River in Jefferson Parish, the West Return Floodwall runs along the St. Charles and Jefferson Parish line from Louis Armstrong New Orleans International Airport to Lake Pontchartrain. The project constructed a three-mile-long concrete T-wall on the Jefferson Parish lake front.
Traveling north to south along the Jefferson Parish line, the T- wall reduces flooding risks for residences and businesses from a storm surge in Lake Pontchartrain and the LaBranche wetlands as part of a 100-year storm. The majority of the materials and equipment were transported to the site via barges along Lake Pontchartrain and the Mississippi River.
Work consisted of clearing and grubbing, driving H-piles and sheet piles, excavating, building embankments, demolishing old floodwalls and building new ones, modifying pump station discharge pipes, laying asphalt pavement, establishing turf and doing maintenance.
The floodwall required 453,900 sq ft of sheet pile, 54,000 cu yd of concrete, 126,000 cu yd of excavation and embankment and 3,600 tons of reinforcement.
One of the challenges was working with the poor soils in the foundations of the levees and floodwalls. Permeable sand, existing peat and weak soil conditions 60 ft below existing ground contributed to levee failures during Katrina.
Construction of the floodwall took place entirely over water. To maintain the schedule, the team used bolted tension connectors in lieu of welded, specialized sheet-piling equipment and utilized nine 150-ton to 300-ton cranes.
Fifty barges were used, all contained in a canal only 100 ft wide by 6 ft deep. The site included almost two miles of temporary sheeting and 200-plus crew members.
One of the biggest design challenges was to maintain existing flood protection from the original wall during construction of the new floodwall. It was built only 20 ft to 30 ft away from the face of the existing wall. Designers had to carefully weave the H-piles for the new floodwall between reinforced concrete piles that were stabilizing the existing floodwall.
The original contract required a section of the floodwall to be entirely demolished and replaced with a temporary retaining structure. But in place of this, Odebrecht-Johnson Bros. was able to design a layout that would leave the existing wall in place during the construction, greatly reducing the risk to the city and creating substantial savings for the owner.
The project team also had to be prepared during hurricane season to close, on short notice, four breaches in the existing wall used for construction access. The construction team designed a temporary gate that could be closed within minutes if necessary.
The West Return Floodwall was delivered on time, under budget and with almost no disruption to the community.
Owner U.S. Army Corps of Engineers, Harahan, La.
General Contractor Odebrecht-Johnson Bros., a Joint Venture, New Orleans
Lead Design U.S. Army Corps of Engineers, New Orleans
Structural/Civil/MEP U.S. Army Corps of Engineers