Dredge J. S. Chatry constructing underwater sill in the Mississippi River

The U.S. Army Corps of Engineers started augmenting the underwater sill in the Mississippi River to slow progression of salt water upstream.

Photo courtesy of USACE

The New Orleans District contracted for a dredge, the J. S. Chatry, to build up the current sill from its initial depth of -55 feet to -30 feet, while leaving a 620-foot-wide navigation channel open for passage of deep-water vessels.

The dredge pulls sediment from the bottom of the river and pumps it through a series of floating pipes for deposit on top of the already-existing sill.

The sill, which was completed initially 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.

Sill augmentation began September 24, 2023, and is expected to be completed within 24 days.