Corps to build underwater sill to stop salt water from moving up the Mississippi River

The U.S. Army Corps of Engineers said Friday that it will build an underwater sill to keep saltwater from moving up the Mississippi River, the fourth-straight year in which the structure has been needed to protect upriver water systems.

The sill, a barrier that the Corps will build at the bottom of the river to keep saltwater from moving upriver, will be consturcted near Myrtle Grove in Plaquemines Parish. Due to a deepening drought, the Mississippi's flow rate has fallen and that is allowing saltwater from the Gulf of Mexico to travel north.

The Corps has built the sill every year since 2022. Prior to that year, the agency had only built a sill in the river three times: in 1988, 1999, and 2022.

Under normal conditions, the freshwater flowing down the river keeps saltwater in the Gulf.