Big trip

Bayou Lafourche lock to be floated 80 mi. for installation

By Mark Friedman

When the water elevation rises in Bayou Lafourche in south Louisiana, the South Lafourche Levee District is forced to shut the floodgates. That prevents flooding, but it also wreaks havoc on fishing, boating and barge transportation.

"Once they close the gates, they can't open them again until the storm is gone and the tide goes down," said Tom Charrier, lead superintendent for levee district engineer Picciola & Associates Inc. of Cut Off, La.

Sometimes the Leon Theriot Floodgate, which is just south of Golden Meadow, La., is closed for several days.

"It's critical that the gates stay open between the Intracoastal Waterway and Port Fourchon," said Windell Curole, general manager of the South Lafourche Levee District, which operates and maintains the floodgate. "Port Fourchon supports about 75 percent of all deep offshore oil in the Gulf of Mexico."

So the levee district decided to turn the Leon Theriot Floodgate into a lock that will allow boat traffic at all times except during a hurricane. Boats will enter one side of the lock, the gate will shut and the water level inside the locked gate will be raised or lowered to allow the boat to travel to the next waterway.

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Curole said the price tag of the project is between $12 million and $14 million. The final cost isn't known because Curole doesn't yet know what it will cost for the final installation.

"We have to let it go out for bid when we're ready to put it into place," he added.

The South Lafourche Levee District couldn't acquire enough right-of-way for the project, so Cajun Constructors Inc. of Baton Rouge is building the lock in Morgan City, which is about 80 mi. by water from the floodgate. Upon completion, the contractor will float the lock to the site.

Typically, the lock would be built in place and a bypass channel constructed to allow ship traffic to go around the construction site.

Construction of the lock began in April 2005 and should be in completed in June.

Before Cajun Constructors began construction, it dammed off a 175- by 400-ft. marine slip at a New Offshore Inc. shipyard in Morgan City.

"We dug all the loose material out (from the slip) with a bucket," Charrier said. "We pumped it out, got all the fish and trash out." Workers then placed about 3,000 cu. yds. of sand and limestone to level off the bottom of the slip and poured concrete to create a 57- by 205-ft., 15-in.-thick work surface.

"A 150-ton crane operating from the work surface then began lifting and placing all the lock casings and put them into place," Charrier added. There were 60 casings made of 36-in.-diameter steel pipe reaching 30 ft. tall.

"The casings were assembled into a structure that's similar to an offshore oil platform with light framing," Charrier said. The casings were separated into six, 70,000-lb. sections. In each section, the casings were welded together with interconnecting bracing.

The casings will support the lock once it's in place at the Leon Theriot Floodgate.

"It's going in the middle of the bayou and will have pilings to support it," Charrier said. The structure will be 136 ft. long, 55 ft. wide and 30 ft. high.

"They (the contractor awarded the final phase of the project) are going to drive pilings through the casings to anchor it in place," said Paul Nola, project manager for Cajun Constructors. "So (the casings) are open to the bottom."

Cajun Constructors built 48 concrete compartments to create the lightweight cement wall that surrounds the casings.

"The 48 compartments give it its floatation," Charrier said. "It's like an inner tube made out of concrete." The compartments vary in size, with the largest measuring 15 ft. by 11.5 ft. by 7 ft..

Charrier said all the plywood compartment forms were built by hand and the lightweight concrete was poured around them.

When the project is complete, the slip will be flooded and the lock will float, Nola said.

"(We can) float it out through the bayou and tug it to Golden Meadow," he said.