Pontoon bridges enforce weight restrictions

LAKE CHARLES, La. (KPLC) - The Louisiana Department of Transportation and Development recently announced that the department is enforcing posted weight limit restrictions at Black Bayou and Grand Lake pontoon bridges on La. 384.

The enforcements are effective immediately because of low water levels. Black Bayou and Grand Lake moveable bridges are pontoon barges that serve as floating bridges.

“So these barges are segmented into 4 compartments and each compartment has a valve that either lets water into the barge, or they have a pump that removes water from the barge,” John Guidroz, DOTD Public Information Officer: District 7 said.

The bridge operator can adjust the bridge height based on the water level; when the tide is high, they add water to lower the barge to keep it relatively flat for safe passage of vehicles. When the tide is low, they pump water out to raise the barge.

Because of extremely low water levels, the barges are completely pumped free of water and they are at grade with the roadway, and cannot be raised any higher.

“The buoyancy is what determines a load carrying capacity, so if a vehicle is over 35 tons or that’s greater than I think 70,000 pounds, the bridge operator will raise the pontoon to accommodate that extra weight and the bridge will, the barge will remain afloat while the heavier weight is applied,” Guidroz said.

If a vehicle over 35 tons attempts to cross the bridge, it may not make it across.

“The bridge is still safe to use for vehicles that are appropriately weighted, but we can’t guarantee that vehicles that are above that 35-ton threshold will be able to pass safely until the gulf intercoastal waterway levels return to normal,” Guidroz said.

Guidroz said these bridges are essentially a floating barge (just like a boat) and you can only put so much weight inside a boat before it will capsize or sink.

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