The Army Corps of Engineers says the rising Mississippi River could bring something unprecedented: reopening a historic Louisiana flood control structure.

Spokesman Rickey Boyett tells WVUE-TV there’s a real chance the Corps might have to reopen the Bonnet Carre (BAHN-ee KEHR-ee) Spillway. It was closed April 11. Boyett says it’s never been opened twice in one year.

The National Weather Service says the river’s expected to reach 16.9 feet on May 11 at a New Orleans gauge where 17 feet generally corresponds with a spillway opening.

Boyett says flow projections are expected later this week.

The spillway’s opened to relieve stress on New Orleans levees when the Mississippi flows at 1.25 million cubic feet (35,400 cubic meters) per second, fast enough to fill the Superdome in less than two minutes.