NEW ORLEANS – Residents in Louisiana received good news on Thursday as officials say the forecast has improved on the lower Mississippi River, delaying the salt water from the Gulf of Mexico moving further upriver.
Drought and low water levels in the lower Mississippi River have allowed salt water from the Gulf of Mexico to win the battle and push farther up the river, impacting local water treatment centers.
The new saltwater wedge timeline from the U.S. Army Corps of Engineers New Orleans District released on Thursday shows efforts to augment a sill, or underwater levee, in the river, and the flow-level forecast has improved, delaying the seawater reaching additional water treatment facilities by about a month compared to the previous forecast.
Based on the new timeline, the salt water will be at the Algiers Water Treatment Plant in late November, and it’s possible the salt water may not reach the Carrolton Water Treatment Plant on the Eastbank of New Orleans. The previous timeline put the salt water at the Algiers plant by the end of October.
Two water plants serve the New Orleans area. The Carrolton Water Treatment Plant treats about 150 million gallons of water daily, and the Algiers Water Treatment Plant treats about 12.5 million gallons of water daily.
The U.S. Army Corps of Engineers New Orleans District began work more than a week ago to raise the sill by an additional 25 feet. The sill is designed to delay the salt water from the Gulf of Mexico from moving up the river, and engineers say it appears to be working already.
Col. Colin Jones, 65th Commander and district engineer for the USACE New Orleans District, said the saltwater wedge has remained stationary since Sept. 24 at river mile 69.4, which is the same day the construction of the augmented sill started about six miles away.
“Our daily river surveys show that the salt water that overtops the sill has less salinity and density than that behind the wedge. And what that means is it makes it very sensitive to upticks in flow in the river, which we’ve seen through the month of September,” Jones said. “This benefit coupled with the better forecasted flows in September and the updated 28-day National Weather Service forecast going into October has enabled us to update our models and projections for the saltwater impacts.”
The sill is about 62% complete and is expected to be finished by Oct. 12, Jones said.
On Sunday, the U.S. Army Corps of Engineers began barging fresh water from an upstream location to water treatment facilities in Plaquemines Parish to dilute the salinity content to levels safe for water treatment.
The initial barge load of 500,000 gallons was delivered to Port Sulphur Water Treatment Facility.
“As barges arrive at water treatment facilities, the fresh water will be transferred to storage or reservoir tanks and then mixed with salt water from the river to bring the chloride levels down below the threshold for treatment,” the USACE said.
The USACE is working on the capability to deliver up to 36 million gallons of water per day if the saltwater intrusion impacts additional facilities on the Mississippi River. Those plans remain in place even with the improved forecast.
An emergency declaration remains in place for four parishes threatened by the advancing salt water.