Updated projection of saltwater intrusion’s arrival in New Orleans released

NEW ORLEANS (WGNO) — The New Orleans District of the United States Army Corps of Engineers released an updated timeline for the arrival of the saltwater intrusion in New Orleans on Thursday, Oct. 12.

Using the National Weather Service 28-day Lower Mississippi River forecast, the USACE’s latest projection to reach multiple water treatment facilities along the river are as follows:

• Boothville: No change
• Port Sulphur: No change
• Pointe A La Hache: No change
• Belle Chasse: Oct. 27 (previously Oct. 13)
• Dalcour: Nov. 1 (previously Oct. 17)
• St. Bernard: Nov. 8 (previously Oct. 28)
• New Orleans Algiers: Not anticipated to experience chloride levels exceeding 250 ppm (previously Nov. 23)
• Gretna: Not anticipated to experience chloride levels exceeding 250 ppm (previously Nov. 26)
• West Jefferson: No change
• New Orleans Carrollton: No change
• East Jefferson: No change

The change could possibly be due to the existing underwater sill increasing the flow of the Red River, requiring less diversion at the Old River Control Structure. Augmentation on the sill began in September and the construction brought its elevation of 55 feet below sea level to 33 feet.

Rainfall in the Red River Basin has also been listed as a contributing factor in increasing its flow. The combined flow of the Mississippi and Red Rivers is used to calculate the 70/30 distribution.

“The combination of the sill augmentation and increased river flows has led to a regression of the saltwater wedge upriver from the sill. The toe of the saltwater wedge was measured Oct. 9 at river mile 63.9, the approximate location of the sill,” said officials with the USACE.

Officials said the new forecast exhibits a delayed impact at upriver facilities but those in Plaquemines Parish will still be impacted.

To date, the corps delivered more than 9 million gallons of water to treatment facilities to blend and lower the chloride levels.

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