SmashMouth

Saltwater creeping up the Mississippi River reached Chalmette Wednesday, forcing Plaquemines Parish President Billy Nungesser to declare a state of emergency and sign a deal with New Orleans to send millions of gallons of drinking water to its downriver neighbor. Slowing currents amid one of the most widespread droughts in recent memory has allowed water from the Gulf of Mexico to breach Plaquemines' water plants and come within six river miles of New Orleans' own water supply points.

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"It could take out the water supply for all of us if we're not careful," New Orleans Deputy Mayor Cedric Grant told the Sewerage & Water Board's other members Wednesday, moments before they approved the Plaquemines deal.
To combat the saltwater, a contractor with the Army Corps of Engineers will construct a $5.8 million underwater dam meant to block the denser Gulf water from moving farther upriver. Great Lakes Dredge & Dock Co. of Oak Ridge, Ill. will build the 1,700-foot-long sediment pile, known as a sill, at Alliance in Plaquemines, where similar sills were built in 1988 and 1999.
On Monday, corps New Orleans District commander Col. Edward Fleming said the project will take about six weeks, but that the leading edge of the saltwater should retreat behind the sill within the next two weeks. Three miles of the Mississippi were closed Wednesday to allow Great Lakes to install a pipeline needed to build the sill.
Nungesser issued a drinking water advisory as saltwater contaminated water supplies at Dalcour, Belle Chasse, Pointe a la Hache and Port Sulphur. Plaquemines recorded sodium levels in some places as high as 200 milligrams per liter, or 10 times the recommended concentration for potable water.

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Halo

Corp of engineers already doing some work on this on the river.