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Three years on, and New Orleans has far from recoveredfrom Katrina. Several hundreds of thousand inhabitants never returned after they were evacuated, leaving the neighbourhoods deserted to this day. Many companies have yet to resume operations, and tourists still feel nervous about visiting the "Crescent City".
To protect the most vulnerable areas from a similar assault, the US Congress has allocated USD 15 billion to fund a network of flood defences. Among the largest is a 2.4 kilometre long, 8 metre high concrete barrier that will rise out of the swampland at the eastern edge of New Orleans, closing two large waterways – the Gulf Intracoastal Waterway and the Mississippi River Gulf Outlet.
The huge barrier and its two lock-type gates – collectively referred to as the Inner Harbor Navigation Canal Surge Reduction Barrier – are designed to keep hurricane storm surges at bay. A consortium of companies will design and build the barrier, but the principal designer is California-based engineering company COWI MARINE North America, a member of the COWI Group.
"This project is vital because it will help to protect a number of companies that are extremely important to the US economy," explains Mike Sarimsakci, Manager of Operations and Business Development for COWI MARINE North America NOLA.
Building on a surface that is only one quarter solid material, three quarters water to a depth of 4 metres requires the barrier to be built of 1400 closely set vertical concrete “friction piles”, which are supported by a gliding resistance to the sediment in which they are driven.
The concrete piles, each one measuring 1.7 metres in diameter, will first be lowered into a temporary support template. Once in place, the pressure of their own weight will push the piles 20 metres into the soft bed. Huge hammers will then pound them to a depth of 40 metres.
The backside of the barrier will be supported by angled steel struts, which will be hammered 70 metres into the sediment.
The deadline for completion of the entire project is June 2010, but, when the 2009 hurricane season starts next June, even the partly finished barrier will afford New Orleans better protection than before Katrina.
By Henrik Larsen Published: 10.12.2008