New Orleans Engineer District starts barging fresh water to treatment plants

With Mississippi River water levels low and salt water creeping upriver, USACE has started barging fresh water to Plaquemines Parish, La., water treatment facilities. [Photo: USACE]

As low water level conditions on the Mississippi River persist, the USACE has started barging fresh river water to Plaquemines Parish, La., water treatment facilities. This water can be mixed with water at the intake to dilute salinity content to levels safe for water 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.

To delay the upwater progression of the salt water, the New Orleans Engineer District has been building an underwater barrier sill near Myrtle Grove, La., using sediment dredged from an area designated for this purpose. Since Sunday Sept. 24, it has been working to augment the sill. Meantime, the amount of water barged daily will depend on the amount required by a requesting facility at any given time. USACE is currently acquiring the capability of delivering 36 million gallons of water per day in the event additional facilities are impacted by the saltwater intrusion in the Mississippi River.

An underwater sill was constructed on four previous occasions in 1988, 1999, 2012 and last year in 2022. Fresh water barging has also been used during previous low-water events, including 1988 and 2012, to transport fresh water to treatment facilities downriver of the saltwater toe.