File:Sill Construction on Lower Mississippi River, July 2023 - 1.jpg

English: Sill Construction, Saltwater Wedge 07.13.2023 The U.S. Army Corps of Engineers, New Orleans District, began construction of an underwater sill July 12, 2023, across the bed of the Mississippi River channel to prevent further upriver progression of salt water from the Gulf of Mexico. To stop the salt water from moving upriver and reduce the risk to freshwater intakes, the New Orleans District constructed the underwater barrier sill near river mile 64, which is near Myrtle Grove, Louisiana. The sill was created using sediment dredged from a designated area just upstream for this purpose. The greatest risk associated with the saltwater intrusion is the appearance of unsafe salinity levels at the intakes of municipal drinking water intakes in Plaquemines Parish. Throughout the construction phase, the Corps continued to test salinity levels in the river to determine where the saltwater wedge was and how high the sill needed to be built. The Corps constructed a separate sill in the same location less than a year ago, in October 2022, to halt saltwater creeping up the Mississippi River from the Gulf of Mexico. That sill eroded away once fresh water from the river pushed the saltwater wedge back toward the gulf.