Louisiana - New Orleans prepares for saltwater intrusion

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Salt water not expected to reach New Orleans until late November with improved Mississippi River forecast
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By Emilee Speck
Source FOX Weather

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.
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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 estimates.

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.
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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, 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."
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https://www.foxweather.com/weather-news/salt-water-new-orleans-november-mississippi-river-forecast

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2023 Saltwater Wedge





https://www.mvn.usace.army.mil/Missions/Engineering/Stage-and-Hydrologic-Data/SaltwaterWedge/

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USACE underway with sill augmentation to delay upriver progression of saltwater

USACE NEW ORLEANS DISTRICT
Published Sept. 25, 2023

NEW ORLEANS – The U.S. Army Corps of Engineers, New Orleans District is working to delay upriver progression of salt water from the Gulf of Mexico by augmenting the sill initially constructed in July 2023.

Construction is underway to increase the existing underwater sill from a depth of -55 feet to a depth of -30 feet. A 620-foot-wide navigation lane will be kept to a depth of -55 feet to ensure deep-draft shipping continues along the nation’s busiest inland waterway.

USACE initially constructed the underwater barrier sill in July 2023 to create an artificial basin to delay the ingress of salt water beyond river mile 64 above Head of Passes. As a result of the river’s prolonged extreme low-flow rate, the underwater sill was overtopped Sept. 20, 2023.

“As a result of continued falling conditions, this existing sill was overtopped and the toe of the saltwater wedge has reached River Mile 69, near the community of Jesuit Bend,” said Col. Cullen Jones, USACE New Orleans District commander. “Our modeling indicates that by augmenting the existing sill, we can support state and local preparedness and response efforts by delaying further upriver progression of the salt water by approximately 10 to 15 days.”

In addition to the sill augmentation, USACE is preparing to transport fresh water to impacted areas. During previous low-water events, such as 1988 and 2012, barging was used to transport fresh water to treatment facilities downriver of the saltwater toe.

“The Corps is securing water barges that will support impacted water treatment facilities by transporting water collected from portions of the river that do not have salinity readings,” said Jones. “This water can then be combined with water at the municipal facility to create a mixture that is safe for treatment.”

The intrusion of salt water into the river is a naturally occurring phenomenon because the bottom of the riverbed between Natchez, Miss., and the Gulf of Mexico is below sea level. Denser salt water moves upriver along the bottom of the river beneath the less dense fresh water flowing downstream. Under normal conditions, the downstream flow of the river prevents significant upriver progression of the salt water. However, in times of extreme low volume water flow, such as what has been occurring this year, unimpeded salt water can travel upriver and threaten municipal drinking water and industrial water supplies. An underwater sill was constructed on four previous occasions in 1988, 1999, 2012 and last year in 2022.

“As new information becomes available, we will reevaluate the projected movement of the salt water and share this information with our partners and the public for their preparedness, readiness, and response,” said Jones.

https://www.mvn.usace.army.mil/Media/News-Releases/Article/3536186/usace-underway-with-sill-augmentation-to-delay-upriver-progression-of-saltwater/

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New Orleans preparing for three months of salt water in drinking water supply

By MIKE SMITH | Staff writer Sep 27, 2023

New Orleans may need to deal with salt threatening local drinking water supplies for as long as three months, meaning through January according to current forecasts, a top city official said Wednesday.

Collin Arnold, New Orleans' homeland security chief, said that timeframe was based on advice from the Army Corps of Engineers.

The city, in cooperation with the surrounding region, is hoping to build a pipeline further upriver to pump water that would dilute the salt at treatment plants — an expensive plan, but one that could potentially be converted into a permanent solution.
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The current forecast shows salt reaching the intakes for New Orleans' Carrollton water plant, which supplies water to the city's east bank, around Oct. 28.

Arnold said New Orleans and Jefferson Parish were now focusing on building a pipeline for the east bank in both parishes because barges delivering water would not provide sufficient capacity.
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https://www.nola.com/news/environment/new-orleans-prepares-for-three-months-of-salt-intrusion/article_03452ac2-5d64-11ee-ba66-2fb982d2b7c1.html

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Where is the Saltwater Wedge Now?

DATE OF PREDICTION	River Miles Above Head of Passes (AHP) in the Mississippi River
20 SEPTEMBER 2023
TOE OF WEDGE ESTIMATED LOCATION
River Mile 66.0 AHP
DATE AND LOCATION OF LAST FIELD MEASUREMENT
20 SEPTEMBER 2023 River Mile 66.0 AHP

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https://www.mvn.usace.army.mil/Missi...waterWedgeNow/

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New Orleans prepares for saltwater intrusion

by: Rick Gogreve

Posted: Sep 20, 2023 / 10:11 PM CDT
Updated: Sep 21, 2023 / 09:31 AM CDT

NEW ORLEANS (WGNO) — Efforts are being made to slow down the saltwater wedge making its way up the Mississippi River, but it seems at this point that it’s inevitable that the intrusion will make its way to New Orleans, possibly contaminating water systems and affecting residents’ daily lives.

“At a certain limit, it’s unhealthy to drink obviously. Also, the land. It could be a problem for freshwater plants and aquatic species, but we’re mostly concerned about the freshwater supply,” David Ramirez said.

Sewerage and Water Board officials say while the water supply is currently clean, they are preparing for possible impacts. Something many local businesses are also doing.

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https://wgno.com/news/louisiana/orleans-parish/new-orleans-prepares-for-saltwater-intrusion/

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Sources: City of New Orleans could take precautionary action in response to Mississippi River saltwater intrusion

Experts believe saltwater from the Gulf of Mexico could reach the metro area in October, sources say

WDSU
Updated: 9:49 PM CDT Sep 19, 2023

NEW ORLEANS —

The city of New Orleans could soon be taking action in response to the Mississippi River saltwater intrusion emergency.

A source told WDSU on Tuesday that city leaders plan on taking precautionary measures in the coming days. Those measures could come in the form of issuing a state of emergency. Experts blame the low water levels and flow on the extended drought conditions. This has allowed a saltwater wedge to make its way towards the New Orleans metro area from the Gulf of Mexico.
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The Army Corps of Engineers has taken precautionary measures, building an underwater sill to prevent further upriver progression. However, due to the lack of rain, the Army Corps predicts the saltwater could reach the metro area in late October, according to the memo received by WDSU sources.

The saltwater could have an impact on drinking water since New Orleans and other area parishes rely on the river for its municipal water supply. We're told leaders across multiple parishes upriver are working together on the best solutions to address any potential issues. Although there is a lot of uncertainty, experts said if things progress, normal river flow will not return until January.
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https://www.wdsu.com/article/sources...river/45213441