Saltwater Moves Up Mississippi River Towards New Orleans, USACE to Construct Barrier Sill

The USACE New Orleans gives a press conference on the construction of a barrier sill to prevent further saltwater intrusion in the Mississippi River, 9/28/2022

Saltwater intrusion in the Mississippi River has reached the US Army Corps of Engineers (USACE) trigger levels, prompting them to begin construction of a barrier sill to protect municipal drinking water intakes in Plaquemines Parish, the Corps said on Wednesday. While saltwater intrusion naturally happens periodically, droughts upriver have led to lower than usual water levels, allowing the saltwater to flow further upriver than normal. This will be the fourth time a barrier sill has been constructed – previous instances happened in 1988, 1999, and 2012.

“Once the river volume begins to fall in low water season, we regularly monitor the progression of the saltwater wedge on the Mississippi River,” said David Ramirez, chief of the New Orleans District’s Lower Mississippi River Management Branch. “This week, the projected location of wedge’s toe in combination with current National Weather Service forecasts we’ve reached our triggers for constructing the barrier sill.”

The USACE will construct the underwater barrier sill by dredging sediment from an area designated for this purpose. The process will start in about three weeks and will take around two weeks, finishing in early November. According to Heath Jones, the New Orleans Corps office emergency management director, the barrier will be constructed in five-foot increments, and construction will stop if the saltwater is blocked at a height below 45 feet. Should the barrier need to reach 45 feet, some of the largest ships that travel upriver may need to unload some cargo below New Orleans.

In order to protect the municipal drinking water intakes in Plaquemines Parish, the parish has already implemented a proactive mitigation plan.

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“We have secured two reverse osmosis machines that will run at the Boothville and East Pointe à la Hache water facilities,” said Plaquemines Parish President Kirk Lepine. “These plants will take out the chloride in the water and still produce approximately 1 million gallons of water for everyday use.”

Those machines are expected to arrive on Friday. For now, salt already in the river could affect the smell, taste, and color of drinking water in Plaquemines Parish, but shouldn’t pose a health threat. Those who are on very-low sodium diets or dialysis should check with their doctors to see if current sodium levels are safe for them to drink.

You can view the full USACE press conference on this issue here.