The operational trigger has been met for USACE to construct an underwater sill across the bed of the Mississippi River channel to arrest further upriver progression of salt water from the Gulf of Mexico.
The Mississippi River’s volume of water has fallen to a level that allows salt water to intrude upstream.
Salt water from the Gulf of Mexico moves upriver in a wedge shape that may stretch up approximately 20 miles from the bottom to the surface of the river.
Based on current river conditions and forecasts, the toe of the saltwater wedge is expected to reach River Mile 80 Above Head of Passes within the next 28 days, triggering construction of the underwater sill, said USACE.
The underwater barrier sill, built to arrest the upriver movement of the salt water and reduce the risk to freshwater intakes along the river, will be constructed near Myrtle Grove, La., using sediment dredged from an area designated for this purpose.
The sill will take approximately two weeks to complete once the contract has been awarded and the dredge mobilized, but it will demonstrate benefits in advance of completion, said USACE.