Bridge Description

on I-10 over Lake Pontchartrain in southern Louisiana between the cities of New Orleans and Slidell

Tier 1 (within 1 day)

ABC: less than 24 hours

• reduced traffic impacts – prefabrication enabled LaDOTD to minimize closure of I-10, the main artery into New Orleans and the Gulf coast
• reduced onsite construction time
• minimized environmental impacts
• improved constructability – prefabrication enabled the contractor to complete the work on the span in less than 24 hours

65-ft-long and 45.5-ft-wide prestressed concrete girder bridge span; 300-ton self-weight

48000

Traffic management alternative, if constructed conventionally: the designated alternate detour for westbound traffic to New Orleans was approximately 100 miles

The replacement span was part of the original two-lane westbound I-10 Twin Spans that consisted of 433 spans that were each 65 ft long with a typical 8.5-ft vertical clearance above lake level. Completed in 1965, the bridge cross-section consisted of six AASHTO Type III girders at 7.58-ft-spacing, with a 7.5-inch-thick composite concrete deck. The Louisiana Department of Transportation and Development (LaDOTD) removed and replaced existing Span #232L as part of a project that included construction of several emergency crossovers between existing twin spans, realignment of nine existing spans, and replacement of end spans and approach slabs. The replacement span consisted of girders and deck identical to the damaged span.

The original Twin Spans were damaged during Hurricane Katrina in 2005 and required significant repair. Because the bridge was vulnerable to storm surge due in large part to its low clearance, the LaDOTD built new higher and wider Twin Spans which opened in 2009-2010. The original Twin Spans were closed to traffic in 2010.

Prior to beginning the span removal, the replacement span complete with diaphragms, deck, and railing was required to be on a nearby barge ready for lifting into place. The new span was prefabricated on a barge on the north shore of Lake Pontchartrain and then moved to the bridge site.

The contract required the damaged span to be removed with no debris from the span removal allowed to fall into Lake Pontchartrain. The contractor removed the damaged span and erected the new span with a barge-mounted crane. The closure joints at the ends of the span were then cast.

The contract required that all work to complete the removal and replacement of the span be accomplished on a Saturday within 24 consecutive hours. The contract included an incentive of $5,000 for every hour the westbound bridge was closed less than 24 hours, up to a maximum of $20,000. It also included a disincentive of $5,000 for every hour greater than 24 hours the westbound bridge remained closed to traffic, with no maximum. The contractor completed the work on the span in less than 24 hours and earned the maximum $20,000 incentive award.