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The Army Corps of Engineers pull pins to open bays of the Bonnet Carre Spillway to deal with a rapidly rising Mississippi River in Norco, La. Wednesday, Feb. 27, 2019. The spillway reroutes water from the Mississippi into Lake Pontchartrain, where it then flows into Mississippi Sound and the Gulf of Mexico. The Army Corps of Engineers opened 28 bays of the spillway.

The U.S. Army Corps of Engineers closed the final bays of the Bonnet Carre Spillway on Thursday, ending a 43-day opening that marked the first time in history the facility has been used two years in a row.

The gradual closure, which began just over two weeks ago, came as the Mississippi River was falling in the New Orleans area.

The spillway is used to divert water from the river into Lake Pontchartrain to keep its level low enough to avoid causing problems for the levees in New Orleans and other areas below the spillway, which is in St. Charles Parish. 

The Corps began opening the spillway in late February, after the river's level began to rise due to heavy storms in the upper Midwest and Ohio River Valley, basins which feed into the Mississippi. The opening involves crews pulling large wooden "needles" from some of the 350 bays in its control structure.

This year's opening was the 13th in the spillway's nearly 90-year history and was the fifth-longest. 

At the river's peak this year, 206 of the bays were open to divert roughly 213,000 cubic feet of water per second into the lake.

On Thursday, the river was at about 16.1 feet above sea level at the Carrollton gauge in New Orleans. That's about a foot below the level the spillway is intended to keep the river at, and about 4 feet lower than the tops of the levees that line its banks.

The National Weather Service forecasts the river level will continue to fall over the next month, reaching about 14.3 feet in early May. 

Bonnet Carre Spillway opens along Mississippi River for third time in four years

The Corps will continue to conduct daily inspections of the levees and enforce restrictions on construction and excavation near the river while the water level remains above 11 feet.


Follow Jeff Adelson on Twitter, @jadelson.​