Twin Span Bridge
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A Bridge Over the Bayou

After Hurricane Katrina's devastating effect on Louisiana's infrastructure, rebuilding the Twin Span Bridge was a two part project: First to restore the existing bridge, then to completely rebuild a bigger and better bridge.

By Dani Smith

Hurricane Katrina was one of the most damaging, natural disasters in U.S. history. Its effects to Florida, Mississippi and especially Louisiana were devastating to both residents of these states and the nation as a whole.

It claimed the lives of roughly 1,800 people and caused damages of upwards to $ 81 billion, making it clear that this natural disaster's wrath was one to be reckoned with, as six years later the cleanup is ongoing. Upon some of the major damages in Louisiana was the Interstate 10 freeway, named Twin Span Bridge. Spanning 2, 460 miles from Santa Monica, Calif., through Jacksonville, Fla., the Interstate 10 freeway is an integral part of the nation's transcontinental highway system and connecting New Orleans, La., to Slidell, La., across Lake Pontchartrain. Two parallel trestle bridges raised nine feet above water, the original bridge carried 55,00 daily commuters. Therefore, when Hurricane Katrina hit on Aug. 29, 2005, severely damaging both of the 5.5 mile long parallel structures, misaligning over 400 bridge decks and destroying 58 decks, it was imperative that Louisiana not waste any time in getting these roads in traveling condition as quickly as possible. "The bridge was totally impassable, so the decision was swiftly made to first repair the existing bridge to allow traffic to return to the I-10, and then to construct a new Twin Span Bridge," explained Walter Bruce Perdue, assistant district administrator of engineering for the Louisiana Department of Transportation and Development (LDOTD).

Getting the I-10 freeway up and running was a twopart process. Restoring the original bridge, constructed in 1965, was the first order of business, starting with the least damaged bridge -- the eastbound bridge -- by turning it into a two-way traffic pass in only 40 days. "The eastbound bridge was temporarily repaired using segments from the more heavily-damaged, westbound bridge, and a single lane of traffic in each direction was placed on the bridge in October 2005," explained John Horn of Volkert, Inc., who served as project engineer for the construction engineering and inspection component of the project. He added, "The construction team used temporary metal acrow bridge components to repair the westbound bridge." The Twin Span Bridge was completely restored to four lanes of traffic on January 6, 2006.

The next order of business for the Twin Span Bridge was completing a new and improved Twin Span Bridge adjacent to the original bridge. The idea was to have the original bridge as a temporary fix and use the new and improved bridge as the new route of the I-10 freeway. As Louisiana Governor, Bobby Jindal stated, "We knew it wasn't enough to just rebuild what Katrina destroyed. We were determined to build back bigger and better than ever before." Using a high-performance concrete that is stronger, denser and less porous than regular concrete, the bridge-designed for a 100-year lifespan, is more resistant to saltwater-induced corrosion. "The traditional design allowed the construction to be repeatable and swift from bent to bent. Highperformance concrete was used to obtain higher strength, lower permeability and increased durability," said Perdue.

Horn explained, "The innovative design of the bridge makes use of reinforced concrete walls that act as restraining walls to prevent the bridge girders from moving laterally or lifting, or lifting upward." He added that this increases the bridge's system storm surge resistance and will help minimize damage in the event of a barge collision." The new Twin Span Bridge is also equipped with state-of-the-art, fiber optic technology to support Intelligent Transportation System (ITS) tools including video cameras and dynamic message boards. "The ITS tools will allow DOTD personnel to rapidly and efficiently monitor and manage traffic conditions on the bridge," Perdue mentioned.

Funded by federal tax dollars from the Federal Highway Administration, on June 1, 2006, construction on the new bridge began. By April 7, 2010, the first of the new structures was completed and by September 8, 2011, the second structure was completed. A project spanning over six years from restoring and rebuilding, in a town crippled by the aftermath of a hurricane, these new bridges had many challenges associated with it. "The first challenge was establishing and maintaining traffic to and from New Orleans to support the massive recovery and reconstruction efforts within the city. The existing bridges required constant inspection and maintenance to withstand the very heavy truck traffic supplying services and materials to New Orleans," explained the project's engineer for construction engineering. Because the original bridges were only to be used as a temporary fix, their condition was such that it was necessary to rebuild the Twin Span Bridge as quickly as possible, creating for a tight construction schedule that required two separate construction contracts and as many as 500 workers. Horn also explained that the design and bid portion of the project was accelerated as well, resulting in geotechnical exploration continuing into the construction of the new bridges. "Keeping pile production ahead of schedule was a constant challenge that required significant coordination between the geotechnical staff, the contractor and fabricator," he said. Glenn Schexnayder, the project's manager for the contractor, Boh Bros. Construction, said that his challenges were faced by way of water and transport.

"Challenges associated with construction of the bridge were the marine access to the work, concrete delivery over water and working next to the interstate traffic were just a few faced on the project." He continued, "Having sufficient marine transport equipment, barges and tug boats to ensure that material deliveries were made to work on time. An onsite traffic control manager helped ensure all traffic control devices were in place and functioning as per plan." While each team member on this project had its own set of problems and solutions, Perdue's analysis sums it up best. "In a word, I think the biggest challenge was coordination. Several sections within DOTD were involved (bridge design, road design, geotechnical design, fabrication, construction and others). A consultant (Volkert, Inc.) was hired by DOTD to perform construction engineering and inspection, and there were three, prime contractors on six, separate DOTD contracts," explained Perdue. "While there were issues to be resolved on all contracts, there was a strong partnering effort by all parties and the issues were resolved one by one with no major delays."

The new $803 million Twin Span Bridge opened on Sept. 8, 2011, at which time the original twin span bridge was retired and all traffic on the I-10 was redirected to the new bridge. Standing at 30 feet above the water of the lakes, compared to only nine feet for the old structure, the new Twin Span Bridge also has a high-rise navigational section that provides 80 feet of navigational clearance for marine traffic. According to Horn, like its predecessor, the new Twin Span Bridge consists of two parallel bridge structures across Lake Pontchartrain. The bridges are approximately 5.5 miles long and 60 feet wide. Each accommodates three 12-foot travel lanes in addition to two 12-foot shoulders.

"The new bridge is taller, wider and stronger than the original bridge. The new bridge will not only be able to better withstand the forces of Mother Nature, but it also increases vehicle capacity and improves traffic flow between New Orleans and Slidell," mentioned Perdue. "The new Twin Span Bridge is one of the largest public works projects in Louisiana history. It's completion marked a significant milestone in the recovery of the Gulf Coast region in the aftermath of Hurricane Katrina."

While the old bridge is no longer used for traffic, it is still being put to good use. According to Perdue, a section of on the Slidell side of the bridge was purchased by St. Tammany Parish and is being converted into a fishing pier, two artificial reefs are being constructed in Lake Pontchartrain by the Louisiana Department of Wildlife and Fisheries, and the remainder of the old bridge is being used for a shoreline protection project by the Louisiana Office of Coastal Protection and Restoration. In the spring of 2012, the old bridge will be demolished, making the project a total of a seven years including: Repair of the original bridge, construction of the new bridge and demolition of the old bridge. "The goal was to quickly replace the existing Twin Span Bridge that was all but destroyed by Hurricane Katrina and restore this crucial link along the I-10 corridor in and out of New Orleans," said Perdue. "I think our goal was met and we were also able to make beneficial use of the original structures by providing a fishing pier, two artificial reefs and shoreline protection." He added, "Mother Nature dealt the Gulf Coast a severe blow with Hurricane Katrina, but countless people worked together to not only replace this critical link of !-10, but to make it better."

Dani Smith is editor of American Infrastructure. She may be contacted at dsmith@penpubinc.com





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