The Coastal Bridge Company crew knew something wasn’t quite right when it started to remove portions of the Chef Menteur Pass Bridge on U.S. 90 east of New Orleans.
Bobby Overall, president of the Baton Rouge-based contractor, said workers noticed a tension crack in the ground that had not yet allowed the dirt to settle under its western side.
Wave action caused by hurricanes Rita and Katrina caused a significant scour problem around the bridge piles, lowering its capacity and forcing officials to close the structure.
Initially, Coastal took on a $1.3-million emergency contract from the Louisiana Department of Transportation and Development (DOTD) to replace 125 ft. of smaller approach spans with a single 125-ft. span on each end.
But the instability of the dirt called for a change of plans that more than doubled the contract price.
It now calls for a 200-ft. span on the west end to reach more stable ground. The smaller span had already been constructed, but Overall said it likely won’t go to waste, as the DOTD will probably design it into a future project.
“This is a very deep channel, and the material at the top of the slope is very susceptible to scouring,” said Kim Garlington, DOTD pavement and geotechnical design services engineer.
Work was initially set for completion April 15, but now, the $2.9-million project won’t be ready until mid-summer, Overall said. The additional cost covers the longer spans, heftier bents, additional stone and additional demolition.
“When you go from shorter spans to longer spans, your costs go up exponentially,” Overall said.
This isn’t the first time a crew from Coastal Bridge has worked the Chef Pass Bridge. In 1975, it added the spans on the approaches they are in the process of removing.
“The west side has always been a problem,” Overall said.
This time around, the contractor has been directed by the DOTD to place 7,600 tons of riprap in the area to assist with the earth’s stability. The original contract called for 400 tons. Overall said the crew also will degrade the banks, removing 4,000 to 5,000 cu. yds. of dirt.
Progress continues on the eastern end of the bridge, but the scheduling on the western end rests on the timely completion of the steel girder. Overall expects it to arrive at the job site in mid-June. Should it arrive as scheduled, he said the work should be finished by the end of July.
Anywhere from 15 to 20 people are working at the site each day. The primary pieces of equipment on-site are two American cranes, both floating on barges — a 998 and a 9299.
Even before the scouring occurred, Brian Buckel, DOTD District 2 construction engineer, said the agency began planning to replace the bridge. He said it is still in the design stage and construction could be eight years away, depending on the result of the coming public hearings. CEG