Corps closes Bonnet Carré

• By JOE GYAN JR.
• Advocate New Orleans bureau
• Published: May 9, 2008 - Page: 15A - UPDATED: 12:05 a.m.

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NORCO — Less than four weeks after it was partially opened to relieve pressure on downriver levees, the U.S. Army Corps of Engineers on Thursday closed the last 30 open bays of the Bonnet Carré Spillway control structure in St. Charles Parish.

The corps began opening the 1.3-mile-long weir April 11 and eventually opened 160 of the structure’s 350 bays over a nine-day span, diverting water from the swollen Mississippi River through the 8,000-acre floodway and into Lake Pontchartrain and then to the Gulf of Mexico.

The corps started closing the bays April 30, citing river levels that were returning to normal.

The latest Bonnet Carré opening, only the ninth since 1937 and the first since 1997, was prompted by heavy rain and melting snowfall in the Ohio and upper Mississippi River valleys that pushed a large volume of water into the lower Mississippi River basin.

Eric Hughes, a spokesman for the corps’ New Orleans district, said the closing of the control structure signals that New Orleans — about 30 miles below the spillway — is “basically out of the woods’’ when it comes to potential flooding from the river.

“It’s a good sign that we are closing the spillway. The city is safe. The threat is relatively over,’’ he said.

Hughes noted that the corps will continue to closely monitor the river’s flows and stages as part of the agency’s flood-fight activation.

The corps says it probably will take several weeks for the spillway to be usable again for crawfishing and other recreational activities.

“We will give folks the all-clear’’ when that time comes, Hughes said, adding that it may take more than a month for the spillway to totally drain.

The fertilizer-laden river water is expected to create an algae bloom in the lake this summer when the water heats up, which could kill seafood and fish in the lake.

The corps is working with its partners on various studies — new and ongoing — to understand and address the impacts that the spillway’s opening will have on the local environment and economy.

The corps also stresses that spillway openings are strongly associated with increased oyster, crab and other fisheries production in lakes Pontchartrain and Borgne for several years after flood events.

The last time the structure was used was 11 years ago when 298 bays were opened.