Personnel from the U.S. Army Corps of Engineers, New Orleans District, and their construction partners worked to augment an underwater sill in the Mississippi River Sept. 26, 2023, to help fight saltwater intrusion into the river from the Gulf of Mexico.
USACE built up the current sill to an elevation of -30 feet while maintaining a 620-foot-wide navigation lane at -55 feet to allow for deep draft navigation.
The initial sill, which was completed in July 2023, was constructed to an elevation of -55 feet, which means the top of the sill was 55 feet below the surface of the river.
Saltwater intrusion is a naturally occurring phenomenon when the river flows fall below 300,000 cubic feet per second (cfs) because the mass of fresh water is no longer capable of preventing saltwater from moving into the below-sea-level river channel.
Sill augmentation was completed Oct. 12, 2023.