LA - Wedge no longer poses threat to New Orleans, latest forecast says
New Orleans’ water treatment plant in Algiers is no longer expected to be affected by the saltwater wedge moving up the Mississippi River.
The U.S. Army Corps of Engineers says salt levels should be within the safe-drinking threshold set by the Environmental Protection Agency when — and if — the wedge reaches New Orleans.
The change in forecast is largely thanks to two mitigation efforts: a newly raised barrier in the Mississippi is slowing the wedge. And less water is being diverted from the Mississippi into the Red River. That, coupled with recent rain in the Midwest, has increased the flow of fresh water toward the Gulf of Mexico.
“Over the past few forecasts we’ve released, the actual flows have been higher on the river, so we’ve been seeing a favorable trend,” the U.S. Army Corps of Engineers’ Matt Roe said in an interview with All Things Considered host Bob Pavlovich on Thursday.
The forecast also pushes back the wedge’s arrival at Belle Chasse and Dalcour water treatment plants in Plaquemines Parish by two weeks — to Oct. 27 and Nov. 1, respectively. Plans are in place to barge freshwater to both communities and provide Dalcour with a reverse osmosis filtration system, Roe said.
The wedge could reach St. Bernard Parish by Nov. 8, though the date is just outside the National Weather Service’s 28-day forecast for the lower Mississippi River.
Thanks to increased river flow, the wedge retreated more than five miles last week, according to the latest field measurement.
Flows have hovered at around 150,000 cubic feet per second over recent months, said Roe, and will need to double to push the wedge back out to the Gulf of Mexico.
Ron Spooner, interim head of the New Orleans Sewerage and Water Board, told city council members Tuesday that rain in the Midwest increased the Mississippi’s flow, pushing the wedge south.
“That is very good news for the entire region,” Spooner said.
The wedge of dense, salty water was at river mile 63.9 on Monday, according to the Army Corps of Engineers. It had been at river mile 69.4, about six miles south of Belle Chasse in Plaquemines Parish, on Oct. 2.
