New Orleans SWB keeping eye on potential saltwater contamination in drinking water - NOLA.com

New Orleans SWB keeping eye on potential saltwater issues | Environment | nola.com

The New Orleans Sewerage & Water Board announced Wednesday that it would notify drinking water customers well in advance of any potential impacts from saltwater moving up the Mississippi River from the Gulf of Mexico, and reaffirmed that the city's water is presently safe to drink.

“The health and safety of our customers informs every decision we make at SWBNO,” Executive Director Ghassan Korban said in a news release. “We will use all resources at our disposal to both protect residents and communicate our plans to respond during this unprecedented situation.”

On Friday, officials with the New Orleans district office of the Army Corps of Engineers warned that it would have to increase the height of an underwater earthen sill built in July near Alliance in Plaquemines Parish to block the saltwater from threatening intakes in Belle Chasse, St. Bernard Parish and New Orleans as early as the second week of October.

But the extra layer on the underwater sill will include a wide notch deep enough for ocean-going vessels to travel upriver.

And on Wednesday evening, a Corps spokesperson said river surves earlier in the day found that saltwater had already overtopped the sill at river mile 63.5 above Head of Passes, and the water's leading edge was already at mile 66. The water intake for the Belle Chasse treatment plant is at mile 87.

"This overtopping is approximately two days in advance of last week’s forecasted progression," said spokesperson Ricky Boyett.

On Friday, Corps New Orleans District commander Col. Cullen Jones warned that without the elevated sill, "you potentially could see the saltwater wedge all the way up to the French Quarter." But even with the improvement, saltwater is expected to overtop it and could threaten the water supplies to the north in October, he said.

The heavier saltwater from the Gulf moving upriver is displacing freshwater moving downstream because of the lack of rainfall in the Midwest during the past two months. National Weather Service forecasters don't expect any major rainfall events upriver over the next few weeks, which will allow Gulf water to continue to move towards New Orleans.

But on Wednesday, a spokesperson for the Corps also confirmed that saltwater is moving north about 10 days faster during low-river years now than before the navigation channel in the river was deepened from 40 feet to 50 feet. The channel was deepened to 45 feet in 1986 and to 50 feet in 2022 to accommodate ever-larger ocean-going vessels. The first saltwater-limiting sill was built in 1988, a year in which saltwater traveled upriver all the way to Kenner.

The Corps is reviewing a variety of alternatives to address potential saltwater contamination, including barging in water that could be mixed with the local water supply to reduce its salt content to healthy levels, and arranging for the installation of reverse osmosis equipment that can remove saltwater as part of the treatment process for smaller facilities in Plaquemines Parish.

The saltwater contamination threat was a key focus of a Wednesday meeting of the Sewerage & Water Board’s board of directors. And SWB staffers are to meet with Corps officials on Thursday for additional discussions of alternatives, officials said.

"Once we receive an updated timeline of potential impacts to the New Orleans area based on the augmented sill and associated salinity levels, we will be able to provide more specifics," said Grace Birch, a spokesperson for the water board. "We are also actively coordinating with our downriver partners in Plaquemines and St. Bernard who are already experiencing impacts to provide as much support as possible."

"To the extent possible, in planning our response to potential impacts, we are being mindful that any infrastructure adjustments made could be more permanent to ensure we are prepared for future events," she said.

“We urge all customers to sign up to receive NOLA Ready emergency alerts to your phone or email. Text NOLAREADY to 77295 for alerts,” said the news release.

On Wednesday, a spokesperson for the Corps’ New Orleans office said officials are not concerned that immediate responses to the saltwater threat, including the sill improvements, would be affected by a potential shutdown of the federal government resulting from spending disputes in Congress. A failure to pass at least a temporary budget bill by September 30 could result in a shutdown.

“We have discussed the potential shutdown,” Boyett said. “We are moving forward with the contracting processes so the shutdown would not have an impact on our activities.”

Editor's note: This story was updated on the evening of Wednesday, Sept. 20, to indicate saltwater has crossed the sill meant to block its northward movement.