Oriving into New Orleans from the southeast frequently involves traveling for more than five miles across Lake Pontchartrain on the I-10 twin span bridges. That was until Aug. 29, 2005, when Hurricane Katrina’s storm surge, estimated at up to 30 ft, pushed the Gulf of Mexico into the lake, lifting the bridge deck off 58 spans and misaligning 473 others. This severe damage to the bridge has dramatically impaired travel and the delivery of materials into greater New Orleans as the area continues to recover from the most devastating hurricane to make landfall in the U.S.
The existing bridges are 5.4 miles long each and are striped for four traffic lanes. Most of the bridge is at a constant grade, with a navigational channel located near the north end of the project. With the support from the Federal Highway Administration and assistance from the transportation community, especially the Florida Department of Transportation, schematic contract plans and a proposal for the bridge emergency repairs were prepared by the Louisiana Department of Transportation and Development (LaDOT). The project was advertised, bids were received and the contractor was selected to begin the work on Sept. 9, 2005.
Low bidder for emergency repairs was Boh Bros. Construction Co. LLC, one of the largest civil contractors in the Southeast. Boh Bros. reopened the eastbound bridge in just 28 days and the westbound bridge nine days ahead of schedule on Jan. 5, 2006. The Phase III contract is now in force to maintain traffic and perform final improvements, such as better anchorage of the existing spans.
Under the direction of Secretary Johnny Bradberry, LaDOTD had quickly mustered forces and reacted to the serious damage of numerous structures in their inventory. Once temporary measures were under way, the department’s attention turned to more permanent solutions. Transportation officials understood the temporary nature of the repairs and the overall condition of the remaining structure that carries I-10 traffic. They saw the need for a bridge replacement and immediately embarked on plans for the new structures.
Six to be safe
The total project encompasses more than 11 miles of bridge with Phase I including all of the twin spans that are at a constant grade, 41,836 linear ft of bridge. Twin decks, each 62 ft 6 in. wide, total over 2.6 million sq ft of bridge, all designed on an aggressive schedule. Phase II is an additional million sq ft of deck that includes the navigational channel and transition. The new design must safely provide for six lanes of traffic, long service life and better ability to withstand storm surge and vessel collision loads.
Between demands caused by the need for expediency and costs in today’s market, construction costs could exceed $500 million.
The first order for replacement was to assemble a multidiscipline project team to accomplish various tasks, such as environmental document preparation, real estate acquisitions, utility relocations and surveys. Once the environmental document was determined to be a categorical exclusion (CE), the early teams, such as surveyors, were allowed to begin their work. Despite a lack of site facilities, several teams have completed their tasks. Topographical surveyors, for instance, took as many as 600 readings a day after driving more than 100 miles to the site every day.
Alternative designs for the bridge replacement were developed to encourage competition among contractors and suppliers and to provide users with the greatest value:
Alternative A: precast concrete beam design prepared in-house by LaDOTD.
Alternative B: precast concrete segmental design prepared by a consultant team.
The goal is to advertise the Phase I construction
project for competitive bid in spring 2006, with the high-level Phase II portion of the bridges competitively bid in a subsequent phase by summer 2006.
Requests for qualifications were issued for the precast concrete segmental design with a due date of Oct. 24, 2005, less than two months after Katrina. LaDOTD selected the Alternative B (concrete segmental design) team to be led by award-winning bridge design engineers FIGG. FIGG is responsible for the bridge superstructure and overall Alternative B project management. Alternative B subconsultants, Burk-Kleinpeter Inc. of New Orleans and SITE-Blauvelt Engineers of Baton Rouge, are focusing on the bridge substructure. Notification to the selected design team was given on Nov. 1, 2005, accompanied by an immediate notice to proceed toward an aggressive completion of Phase I design on Jan. 20, 2006, less than three months later.
In the Alternative B design for Phase I, there are no internal struts or ribs in the bridge’s precast concrete box girders in order to simplify and speed construction. Typical span lengths of 155 ft maximize the efficiency of the span-by-span erection method and minimize the number of foundation elements necessary. Kent Montgomery, P.E., S.E., technical lead bridge engineer for FIGG, said, “Construction can move quickly and we can accomplish the aggressive schedule established by Louisiana. Getting the new bridge in place will help the New Orleans area recover and prosper in the future. The entire project team is proud of being able to provide our professional skills to help New Orleans recover from Katrina.”
The LaDOTD Bridge Section is designing Alternative A, the precast beam alternative design solution. It features 135-ft typical spans of BT-78 precast concrete girders, cast-in-place decks with stay-in-place forms allowed, precast or cast-in-place caps and precast driven pile or drilled shaft foundations.
The design for Phase II includes 11,304 linear ft of bridge. This portion of the bridges includes the navigational channel with requirements of a 200-ft horizontal clearance and a 73-ft vertical clearance. This allows for the passage of significant commercial and pleasure boat traffic into Lake Pontchartrain from the Gulf of Mexico and Lake Borgne and provides access to New Orleans’ Industrial Canal.
The precast concrete segmental alternative for Phase II consists of 155-ft typical spans leading to the 251-ft main span over the navigation channel. The precast beam alternative for Phase II consists of typical BT-78 approach spans of 135 ft with a 650-ft three-span steel composite unit for the navigational crossing.
Both Alternatives A and B will connect with LaDOTD-designed Type 3 spans and flat slabs transitioning from elevation 39 to elevation 9. Both alternatives also encompass roadway approach work, two minor elevated ramps, ITS signs and cameras, communication equipment, electrical power service, emergency crossover gates and truss-mounted overhead signs.
In mid-December 2005, a contractor information meeting was held to brief interested contractors on the project schedule, general design criteria and construction project advertisement. Major contractors attended and have expressed interest in bidding on the project. Bids will be received and notice to proceed given for Phase I while the final design of Phase II is being completed. Both design alternatives will be bid in the second phase, regardless of which design receives the low bid in Phase I.
The LaDOTD purchased test piles on Jan. 12, 2006. An advance test pile and test shaft project followed, with bidding scheduled for Jan. 25, 2006. This test program will optimize the foundation design and give contractors pile order lengths at bid time.
The interstate system will continue to deliver motorists, goods and services to the area, as evidenced by the efforts of LaDOTD, their consultants and those who believe that a new bridge will provide a bright future for New Orleans.