Market Matters Blog           10/20 16:46

   USACE Completes Underwater Sill as Mississippi River Levels Fall

   The U.S. Army Corps of Engineers, New Orleans District, finished 
construction of an underwater sill across the bed of the Mississippi River 
channel near Myrtle Grove, Louisiana.

Mary Kennedy
DTN Basis Analyst

   On Sept. 28, the U.S. Army Corps of Engineers, New Orleans District, began 
construction of an underwater sill across the bed of the Mississippi River 
channel to arrest further upriver progression of salt water from the Gulf. The 
sill was completed on Oct. 10.

   In a press release on its website, USACE said, "Mississippi River's volume 
of water has fallen to a level that allows salt water from the Gulf of America 
to intrude upstream. The intrusion of salt water into the river is a naturally 
occurring periodic condition because the bottom of the riverbed between 
Natchez, Miss., and the Gulf of America 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, unimpeded salt 
water can travel upriver and threaten municipal drinking water and industrial 
water supplies," stated USACE.

   The construction of the sill is a mitigation feature required as part of the 
effort to deepen the shipping channel from 40 feet to 45 feet and subsequently 
to 50 feet. The sill is designed to create a large reservoir to collect and 
hold salt water for a period of time equal to the increase in duration of the 
saltwater intrusion caused by the channel deepening, noted the Corps. Here is a 
link to the location of the wedge as of Oct. 14 and will update if the toe 
moves upriver: 
https://www.mvn.usace.army.mil/Missions/Engineering/Stage-and-Hydrologic-Data/Sa
ltwaterWedge/SaltwaterWedgeNow/.

   USACE constructed a similar underwater sill in 1988, 1999, 2012, 2022, 2023 
and 2024 at river mile 64, near Myrtle Grove, Louisiana, to arrest the 
progression of saltwater intrusion during that year's low water season. In 
2023, USACE augmented the underwater sill from a depth of minus 55 feet to a 
depth of minus 30 feet when the initial sill was overtopped by salt water 
moving upriver. A 620-foot-wide navigation lane was kept on the sill at a depth 
of minus 55 feet to ensure deep-draft shipping continued along the nation's 
busiest inland waterway, noted the press release.

   On Oct. 19, the Mississippi River at New Orleans was at 3 feet above zero 
gauge. When the river gets low there, off-loading barges to waiting ships can 
be difficult.

   Elsewhere on the Lower Mississippi River, the river level in St. Louis on 
Oct. 19 is at 0.34 feet above zero gauge and at Memphis, the river is at 8.72 
below zero gauge. The USCG will lower drafts on barges and tow sizes if the 
river keeps falling. This means that shippers have to load less grain in a 
barge headed to the Gulf but still pay the same freight, which could affect 
their basis paid to a farmer. Also, cutting back on tow sizes may mean that 
shippers will have to load more barges to be sure to make contract specs at the 
Gulf.

   As of Oct. 16, CIF (Cost, Insurance, and Freight) corn basis was firm, while 
CIF soybean basis was weaker. Because of the continued government shutdown, 
there are no weekly exports sales and shipment reports. However, USDA is still 
publishing weekly inspections which continues to show strong corn inspections, 
while soybean inspections have been down, mainly due to China snubbing U.S. 
soybeans because of the tariff fight with the U.S.

   Mississippi River gauge St. Louis: https://water.noaa.gov/gauges/eadm7

   Mississippi River gauge at Memphis: https://water.noaa.gov/gauges/memt1

   Mary Kennedy can be reached at mary.kennedy@dtn.com

   Follow her on social platform X @MaryCKenn




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