When Hurricane Katrina ravaged New Orleans and the surrounding Gulf Coast communities in August 2005, she took with her portions of the I-10 bridge over Lake Pontchartrain, one of the port city’s most visible gateways.
One year to the day after the devastating storm ground traffic and commerce to a halt, however, work began on an $800 million replacement bridge, epitomizing the resilience of a population and the camaraderie of an attuned business community committed to revival.
“Obviously, there’s a tremendous feeling of accomplishment when you build something like this, especially in an area recovering from such devastation. This project became a symbol of the rebuilding of the city of New Orleans, ” says John Horn, project manager for Mobile-based Volkert Inc., which provided the engineering services for project.
According to the Louisiana Department of Transportation and Development’s website, wind and waves from Hurricane Katrina “battered the existing bridge and knocked more than 400 concrete deck spans out of alignment.” Illustrating the “ferocity of the storm, ” the site notes that another 58 of the 300 ton concrete spans crashed into Lake Pontchartrain.
The new bridge—known by most residents and visitors as simply the Twin Span Bridge—consists of two parallel structures, each 5.5 miles long. Both structures are 60 feet wide and accommodate three 12-foot travel lanes with 12-foot shoulders on either side of the travel lanes. The new bridge is 21 feet higher than the old Twin Span Bridge and approximately 30 feet above the water level. The bridge also features an 80-foot high-rise section to provide vertical clearance for marine traffic on Lake Pontchartrain.
With nearly 90 years’ experience as a multi-disciplinary, full-service engineering and environmental firm, Volkert provided about $30 million of construction engineering and inspection services for the project. The Mobile-based firm was ranked 116th among the Top 500 Design Firms in the United States by “Engineering News Record” in 2011.
The sheer size and scope of the project made the Twin Span Bridge a challenge from day one, Horn says, but the biggest obstacle was coordinating the bridge’s rebirth, while creating only minimal interruptions to New Orleans’ primary point of entry for not only traffic but goods and services. In addition, crews remained vulnerable to Mother Nature’s continued wrath and often-harsh conditions as the six-year project progressed.
The Louisiana DOTD oversaw design of the new bridge, with features like high-performance concrete to fend off salt water damage, interlocking spans designed to prevent lifting and slipping from wave action, and integrated spans to resist wind — creating a bridge that could stand 100 years.
“That represents a good investment of taxpayer dollars, ” Horn says.
In addition, he says the design also incorporated four different kinds of spans, ranging from 30 feet to 810 feet. The smallest spans support the deck and are poured integral with the caps, making them immovable, because they’re located in the wave action zone. The larger, 75-foot spans are restrained to the caps with reinforced walls, and the 135-foot spans are “so large the wind could not possibly move them.”
“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 DOTD site states.
In addition to the safety precautions built into the new design, Horn says the bridge also can now be relied upon as a safe evacuation route during future disasters.
For example, the new bridge accommodates three lanes each way—one more than the old bridge—with 12-foot shoulders on each side, making it more useful for evacuation and safer even for routine emergency stops.
“Considering the strength of design, it’s highly unlikely this bridge will ever be shut down during a storm event, making it a much safer means of evacuation than was available before, ” he says.
And Horn says there’s no question the bridge has become a “flagship” project for Volkert, boosting the company’s already visible profile to new heights. Since 1925 the firm has provided its services to state departments of transportation, federal agencies, local and municipal governments, as well as private industry.
“We do use (the bridge) in a lot of (recruitment) proposals. It was a tremendous success, and it’s recognized all over the country, ” he says.
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Kelli Dugan is a freelance writer for Business Alabama. She lives in Mobile.
By Kelli M. Dugan