NEW ORLEANS (AP) — Federal authorities say they may have to open up a major flood control project on the Mississippi River to ease pressure on New Orleans levees.

The U.S. Army Corps of Engineers said Tuesday that the river is expected to crest above 17 feet at a key New Orleans gauge as early as Friday. That would likely lead to the opening of a structure that diverts water through the Bonnet Carre spillway. It would be the first time the structure has been used three years in a row.

Extended openings last year were blamed by Mississippi authorities for feeding toxic algae blooms and killing oysters, dolphins and other sea life.