Spanning Pontchartrain

New Orleans Twin Spans to be completed by 2011.

By Angelle Bergeron

Work continues on the $803 million new Interstate 10 Twin Spans Bridge over Lake Pontchartrain, which connects New Orleans to points east.

Fully funded by the Federal Highway Administration, the hurricane-resilient bridge is being built higher and stronger than the old one and with special features to withstand the storm-surge uplift that damaged the existing I-10 Twin Spans during Hurricane Katrina in 2005.

Lacking any American Association of State Highway and Transportation Officials standards for hurricane wind and wave action, the Louisiana Department of Transportation and Development established its own for the new, 100-year design bridges. The resulting bridges are akin to those constructed in earthquake zones, designed to resist lateral forces, says John Horn, vice president of Volkert & Associates Inc. of Alabama, which is performing Construction, Engineering & Inspection Services for DOTD.

The bridges are 21 ft higher than the old ones and feature shear keys and reinforced steel and concrete tie-ins between the decks and caps, Horn says. “This design adds a lot of time and cost, but if the bridge lasts twice as long (as the existing 40-year-old bridge), you got your money’s worth,” he says.

The project is advancing at a feverish pace, with two contractors sharing the burden of delivery.

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Boh Bros. Construction Co. LLC of New Orleans is “way ahead of schedule” on pile driving for the $379 million contract to complete the roughly 4.5-mi low-rise portions of the new bridges, says Bryan Buckel, chief construction engineer for DOTD. Boh won the contract Aug. 29, 2006, to open the westbound span by October 22, 2009, and the eastbound by August 3, 2011. Boh stands to win a potential maximum early completion incentive of $4.5 million, or $15,000 per day for 300 days, but that would mean finishing the westbound span by this December, says G.J. Schexnayder, Boh’s project manager. “We’ve already completed the pile driving on Phase I,” Schexnayder says. “We’re hitting our pace, but it’s going to be a long haul. We are not exhaling until we finish Phase I and open that to traffic.”

Boh is working from the north and south shores of Lake Pontchartrain. “The south end is about 3.5 mi of work, and we’re about a half mile out,” Schexnayder says. “The north side is close to a mile, and we are finished driving all the pilings and are about two thirds of a mile out into the water with caps and girders.”

The bridge features many unique elements, including an overhang that is 1 ft 5 in deep, unusually thicker than the typical 8 or 9 in, to accommodate the conduit that runs the length of the bridge and supports electrical, dynamic message boards and Intelligent Transportation Systems.

“A lot of people want to know what is different about this bridge since the hurricane,” he says. The shear keys, increased span length, concrete diaphragms, high performance concrete all contribute to durability, but the main thing is the height.

The low member elevation of the low-rise portion is 30 ft., which means it is 30 ft. from the bottom of the girders to the surface of the water, Horn says.

“The deck height is 38 ft.” The “hump” portion of both bridges is a roughly 1 mi 80-ft. elevated section that will provide 200 ft horizontal and 73 ft vertical navigational channel clearance.

The joint venture of Traylor Bros. Inc. of Evansville, Ind., Kiewit Southern Company of Peachtree City, Ga., and Massman Construction Co. of Kansas City, Mo.,  won the $166.6 million contract for “hump” portion of the Twin Spans, which features a different, ship impact resistant, substructure than the rest of the bridge, says Scott Armstrong, project manager.

“It’s water line footings, crash walls and columns and caps, as opposed to a standard bent,” Armstrong says.

The TKM joint venture received the work order in January 2007 and, by the beginning of March, had completed all of the substructures for the first bridge, the westbound span and the superstructure was underway. “We will start pile driving for the eastbound span before December,” Armstrong says.

Although bridge projects are often divided, “it’s unusual to have the middle part going to a different contractor,” Armstrong says. The contract poses huge logistical challenges for TKM because the joint venture has neither land side access or the benefit of building access to the project, like Boh. “Everything we do is over water and 3 or 4 mi from the work site,” Armstrong says. “And weather on the lake is always a challenge.” Depending upon the severity of the weather, TKM may be able to anchor barges with equipment, but the contractor often has to move everything into safe harbor.

Another unusual aspect of the project is Volkert’s comprehensive CE&I contract, which DOTD awarded because the department couldn’t keep up with the increased work and dispersed staff in the aftermath of Hurricane Katrina. “If it wasn’t for Katrina, the district could have handled this,” Buckel says.

Volkert’s role as quality assurance creates a partnership environment between all the players that is a far cry from the “us and them” mentality of construction, Horn says.

“We all sit down and agree on goals before the project starts and figure out how to work together so everyone can be successful.”

Having Volkert perform CE&I has been a tremendous help in keeping up the pace on the project, because Volkert has sufficient staff to keep inspections and paperwork moving, Schexnayder says. Volkert’s role will be an integral part of marrying the TKM and Boh layout systems when it’s time to tie the bridges together within a quarter of an inch.

“We’ll have common meetings at that point and I’ll serve as middle man or mediator,” Horn says.

Safety is always a challenge when working on the water, and both TKM and Boh have increased emphasis on their safety programs.

“It’s normal bridge construction, but lots of hazards,” says Armstrong, who emphasized TKM’s 100% tie off policy and the prevailing safety cultures of all three partners.
“We always think safety first, but on this kind of job, we’ve got to be more diligent about tying off,” Schexnayder says. Boh’s workers must wear flotation devices and harnesses with double lanyards if they are within 6 ft of the leading edge of work or higher than 6 ft above the work area. Boh has also ramped up its boat operator and crane safety classes, as well as on-site job safety analysis meetings.

“Education is a big part of safety,” Schexnayder says. “If we see you not tied off when you’re supposed to be, you’re going home for the day. If we see it twice, you’re going home for good.”