Corps Releases General Re-evaluation Reports For NOLA-Area Levee Lifts
In early August, the New Orleans Engineer District released the final version of the Lake Pontchartrain & Vicinity (LPV) and the West Bank & Vicinity (WBV) General Re-evaluation Reports, which detail the Corps’ plan to raise New Orleans-area levees and floodwalls now through the year 2078.
The levee lifts and new floodwalls are needed to ensure the Hurricane and Storm Damage Risk Reduction System (HSDRRS)—the levee system shielding the New Orleans area from inundating hurricanes—continues to provide protection from storm surge that has a 1 percent chance of occurring in any given year. That level of protection is needed for the region to qualify for the Federal Emergency Management Agency’s National Flood Insurance Program.
According to the LPV report, the Corps is recommending 50 miles of levee lifts, 1 mile of rebuilt floodwall and 2.2 miles of new floodwalls to be built over the next 50-plus years at a cost of $1.1 billion. That work is primarily along the shore of Lake Pontchartrain and includes foreshore armoring and dredging, although the plan also calls for Mississippi River levee lifts on the east bank in St. Bernard Parish.
The WBV report calls for lifting 49 miles of earthen levees, replacing 268 feet of floodwall and building 1 mile of new floodwall over the next 50-plus years at an estimated cost of $602 million. Much of the levee lifts would occur along the west bank of the Mississippi River in Orleans and Plaquemines parishes, the west bank of the Harvey Canal and along portions of both banks of the Gulf Intracoastal Waterway leading to Algiers Lock.
“Through both reports, existing levees would be lifted as needed before the combined effects of consolidation, settlement, subsidence and sea level rise reduce the levee elevations below the required design heights,” the announcement from the Corps said. “In some reaches, levee lifts may need to occur more than once. Floodwalls that will need to be higher in the future, to address those same effects, will either be modified or replaced.”
The total area included in the reports covers St. Charles, Jefferson, Orleans, St. Bernard and Plaquemines parishes. The cost-share for the projects is 65 percent from the federal government and 35 percent from the non-federal sponsor, which is the Coastal Protection and Restoration Authority Board of Louisiana (CPRA). In some instances, parish governing authorities or flood protection authorities may cover portions of the non-federal cost-share.
The HSDRRS was first authorized in the aftermath of Hurricane Katrina in 2005 and built in the years that followed at a cost of more than $14 billion. Besides the miles of levees and floodwalls that encircle the New Orleans area (and double as river levees in some instances), the system includes the largest pumping station and largest surge barrier in the world. The Gulf Intracoastal Waterway West Closure Complex is a massive gate and pumping station near the confluence of the Harvey and Algiers canals, while the Inner Harbor Navigation Canal-Lake Borgne Surge Barrier acts as an impediment to storm surge at the eastern end of the region.
The reports are available on the New Orleans District’s website, www.mvn.usace.army.mil. For the Lake Pontchartrain & Vicinity report, search “LPV-GRR.” For the West Bank & Vicinity report, search “WBV-GRR.”