Louisiana and federal officials watching, preparing as Mississippi River rises to flood levels _lowres

Advocate staff photo by SHERRI MILLER -- The U.S. Army Corps of Engineers, New Orleans District, performed a test in which they removed and replaced several of the wooden needles at the Bonnet Carré Spillway in Norco on Wednesday, April 8, 2015.

The U.S. Army Corps of Engineers will begin opening the Bonnet Carre Spillway on Sunday morning to head off possible flooding in the New Orleans area from the swollen Mississippi River.

Crews will begin removing some of the spillway barrier’s 7,000 wooden beams, arranged in 350 linear bays, at 10 a.m. The public can watch from the Corps’ offices on River Road in Norco.

No final decision has been made about using the Morganza Spillway, which is located upriver from Baton Rouge. Maj. Gen. Michael Wehr, commander of the Mississippi River Division of the Corps, has not given the go-ahead to open the Morganza flood control structure, which could displace some residents of the Atchafalaya River Basin. It also threatens to lower the Basin’s oyster harvests, which suffer when water salinity goes down.

The earliest that the Morganza floodgates would be opened is Wednesday, said Matt Roe, a Corps spokesman, who noted that his agency was monitoring weather and river-level forecasts before making any determination.

The Bonnet Carre Spillway is in St. Charles Parish, about 28 miles upriver from New Orleans. Built after the great river flood of 1927 as a flood-relief valve, it pulls water from the river into a 5.7-mile floodway that empties into Lake Pontchartrain and, eventually, the Gulf of Mexico.

When it’s completely open, the spillway basically unzips a 7,000-foot span of the east bank of the Mississippi River, allowing 250,000 cubic feet of water per second to bypass New Orleans and the lower portion of the river.

Sunday’s opening marks the 11th time the spillway has been used since it was completed in 1931. It was last opened in May 2011, when it remained open for 43 days.

It’s unclear how long it will remain open this year, but a Jan. 10 opening is the earliest on record.

Because river levels are typically highest in the spring after the snow melts in the Midwest, eight of the spillway’s previous 10 openings occurred in March or later. But the first opening, in 1937, also was early, on Jan. 28. And in 1950, it was opened on Feb. 10.

This year, severe wintertime flooding upriver in Illinois and Missouri was triggered by heavy December rainfall in the Midwest that caused the Mississippi and its tributaries to overflow in some areas.

That water is now headed south. The river’s crest is expected to arrive in New Orleans about Jan. 21.

On Wednesday, when the river reached 15 feet at the Carrollton gauge in New Orleans, the Corps began daily patrols of the river’s levees from Baton Rouge south to Venice. As a further precaution, any construction projects within 1,500 feet of the river also were shut down.

On Saturday, the river stood at 15.8 feet in New Orleans. Still, the Port of New Orleans was seeing steady river traffic, port spokesman Matt Gresham said.

The U.S. Coast Guard has implemented some high-river safety policies for river vessels, mandating two anchors instead of one in some areas, for instance, and limiting the number of barges per tug. Also, the river is down to one-way traffic: Only one vessel at a time can traverse the dangerous turn at Algiers Point.

Motorists crossing lift bridges over the Gulf Intracoastal Waterway at peak times also may experience delays, because the bridges are opening around the clock, whenever requested by river traffic, Gresham said.

Typically, the lift bridges at St. Claude and Florida avenues in New Orleans don’t open during morning and afternoon rush hours. But because the river is higher, it takes longer for the waterway’s locks to raise and lower boats traveling to and from the river. As a result, the bridge operators have been instructed to open the bridges whenever requested, even during rush hour, to prevent approaching vessels from backing up on the river or into the canal.

Port officials are optimistic because the state’s spillway system can divert the water that has hampered some Midwest ports, Gresham said. “We have full faith in the Corps and the Coast Guard, and we don’t anticipate any significant impact,” he said.