No plans to open Bonnet Carre Spillway despite rising Mississippi

The river is rising in the Crescent City, at least until the end of the month.

The National Weather Service reports heavy rainfall in the central United States and along the Ohio River resulting in the swelling of the banks of Big Muddy to where restrictions on construction jobs within 1,500 feet of the levees will need to be enforced.

However, Renee Simpson, public information officer for St. Charles Parish, said there are no construction projects underway in St. Charles Parish that will be affected by the restriction.

By Tuesday, the parish announced Bonnet Carre Spillway Road connecting Norco and Montz had been closed that evening because of water over the roadway. Traffic was being rerouted to Airline Highway.

The National Weather Service Lower Mississippi River Forecast Center estimates heavy rains will top the river up to nearly 13 feet at Carrollton gauge by March 29.

Rising water will cause the wooden slats and gates in the lower section of the spillway to leak once the level exceeds  11.5 to 12 feet, although the top portion of the bays are up higher and don’t start leaking until the gauge reaches 13.5 feet.

There are 350 bays,of differing sizes that can be opened to maintain a safe flow rate for the spillway. If the water level gets to an unsafe level, the U.S. Army Corps of Engineers will determine how many of them to open to maintain flow and route water 5.7 miles to Lake Pontchartrain.

There is no indication at this time that opening the spillway will be necessary, said Mike Stack, chief of emergency management for the Army Corps of Engineers, New Orleans District office.

“We are in Phase 1,’” Stack said. “This phase only warrants inspections twice a week.

If the water were to rise to 17 feet we’d go to Phase II and all construction would stop. Also, a decision would be made about opening bays to maintain the water flow at that time.”The spillway has been opened 10 times since 1937; the last time in 2011. The Corps of Engineers began opening bays in 2011 to divert water and maintain the 1.25 million cubic feet per second water flow that runs through New Orleans. The April and May flooding of the Mississippi that year, caused by excessive rainfall, were the largest and most threatening floods recorded in the last 100 years.

Of the 350 bays available, the Bonnet Carre Spillway opened 330 bays channeling water to Lake Pontchartrain and eventually the Gulf of Mexico.

They began to close the bays on June 12 as the water flow rate resumed to normal; the last bay was closed on June 20.

 

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