It's been more than 10 years since the Bonnet Carre Spillway was pulled from its recreational duties to serve its original purpose - diverting the fast rising and even faster moving Mississippi River from overtaking New Orleans.

The Army Corps of Engineers has been monitoring the river levels for several weeks and had thought that an opening wouldn't be necessary. However, recent rains in the Arkansas, Ohio, and Upper Mississippi River Valley has heighten flood worries.

The opening of the spillway in St. Charles Parish, will lower river stages in New Orleans while causing a rise in Lake Pontchartrain.

Indeed, gallons of water already has sluiced through the wooden slats of the structure over the past few weeks, resulting in the closure of the recreational areas and a local road favored by residents as a short cut between Norco and Montz.

Earlier this month, about 1,900 cubic feet per second of water was rushing through the structure, a fraction of its 250,000-cubic-feet-per-second capacity.

The spillway structure was built in response to the devastating flood of 1927 that killed more than 500 people which prompted the corps to abandon its previous levees-only strategy and add spillways.

The Bonnet Carre Spillway has 350 bays equipped with 7,000 "needles" made of creosote timbers that hold back the river. It would take Corps officials about 36 hours to raise all of the wooden timbers by crane. However, if needed the timbers could be lifted 20 at a time and reduce the opening to as little as three hours, officials have said.

Under current policy, the Bonnet Carre Spillway is the first to be opened when high water threatens the structural integrity of the levees. The corps can open as many or as few of the 350 bays in the structure as it choose.

The trigger is currently a river event where more than 1.25 million cubic feet of water per second is expected to pass the Carrollton gauge, and whether that level is rising.

The Bonnet Carre Spillway structure has been opened eight times since it was completed in 1931, the last time in 1997. That year, 298 of the bays were opened. The last full opening was in 1983.

Opening the spillway is not without cost. The flood of the river's phosphate-laden water contributes to algae blooms in Lake Pontchartrain. Advocates for the lake bitterly protested the 1997 opening, saying the 17.5-foot crest wasn't serious enough to warrant the disruption.