Traffic shifts to new bridge 

All traffic has been removed from the old Twin Span Bridge.  East and westbound drivers are now crossing Lake Pontchartrain entirely on the new bridge.  Traffic on either end of the bridge are sharing the eastbound approaches until the old structure can be demolished and the westbound approaches constructed.  The approaches currently accommodate two lanes of traffic in each direction, while the mainline sections of the bridge have three lanes of traffic each. 

Demolition of the old bridge and construction of the westbound approaches is on-schedule for completion before the mid-2012 contract deadline.

(Click the graphic for a closer look at the traffic alignment.) 

Old Twin Spans get new life

 As the new Twin Span bridges begin reaching across Lake Pontchartrain, parts of the old bridges are finding a new lease on life - under the water. 

Workers are taking pieces of concrete, that once made up the old bridges, and are placing them into Lake Pontchartrain to create an artificial reef, between the U.S. 11 bridge and the new Twin Span. It is part of a new initiative to use old construction material for new coastal projects.

Over the years, Lake Pontchartrain lost a lot of its hard bottom habitat. The artificial reef could help begin restoring some of it, by enhancing the environment and increasing the diversity of the habitat available to marine life. There are plans to build a second artificial reef closer to the north shore, once crews finish demolishing other portions of the old Twin Span Bridge. 

When completed, the artificial reef will cover several acres along the lake bottom. 

New bridges will be taller, stronger 

The new Twin Span Bridge will be taller, stronger and more hurricane-resistant than its predecessor.  Wind and wave action from Hurricane Katrina battered the existing bridge and knocked more than 400 concrete deck spans out of alignment.  Fifty-eight other concrete spans were toppled into Lake Pontchartrain.  To illustrate the ferocity of the storm, each of the concrete deck spans weighed in excess of 300 tons.   

In designing the new bridge the Louisiana DOTD established rigorous standards for combating hurricane wind and wave action.  The new standards result in bridges that are better able to resist lateral forces and in some ways resemble those built in earthquake zones. 

“The new bridge is 21 feet higher than the old one (30 feet versus 9 feet), but that’s only part of the difference,” said John Horn of Volkert Construction Services.  “Included in the design are shear keys and reinforced steel and concrete tie-ins between the bridge decks and caps that will help prevent misalignment and toppling due to storm surge.  In addition, the entire bridge is being constructed using high-performance concrete.”

These innovations are adding some time and cost to the project, but Horn says they will result in a more robust bridge.  

“The estimated lifespan of the existing bridge was 40 years, the new bridge will have a lifespan of 100 years.  That represents a good investment of taxpayer dollars.” 

Interactive graphics illustrate Twin Span Bridge
damage and reconstruction 

The New Orleans Times-Picayune created a series of interactive graphics to illustrate Hurricane Katrina’s impacts on the Twin Span Bridge and highlight special features of the new bridge.

The graphics are available here courtesy of the New Orleans Times-Picayune and NOLA.com. 

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