NEW ORLEANS - The U.S. Army Corps of Engineers' New Orleans District began construction oversight July 11 of an underwater sill across the bed of the Mississippi River channel to prevent further upriver progression of salt water from the Gulf of Mexico.
USACE awarded the contract to Weeks Marine for construction of the saltwater sill at around mile marker 64 near Myrtle Grove, La.
The initial phase of construction will build the sill to an elevation of -55 feet. At that height, USACE will monitor progression of the saltwater wedge to determine if additional height is needed to meet the saltwater intrusion mitigation requirements.
The construction of the sill is a mitigation feature required as part of the effort to deepen the shipping channel from 40 feet to 45 feet and subsequently to 50 feet. The sill is designed to create a large reservoir to collect and hold saltwater for a period of time equal to the increase in duration of the saltwater intrusion caused by the channel deepening.
USACE constructed a similar underwater sill in 1988, 1999, 2012 and 2022 at mile marker 64 to arrest the progression of saltwater intrusion. The sill will naturally erode when the Mississippi river returns to the flow levels required to push the saltwater wedge back down the river to the Gulf. (USACE New Orleans 07/11/23) USACE begins construction of Mississippi River saltwater barrier > New Orleans District > News Releases (army.mil)
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